Quantification of tumor fluorescence during intraoperative optical cancer imaging

PubMed Central

Judy, Ryan P.; Keating, Jane J.; DeJesus, Elizabeth M.; Jiang, Jack X.; Okusanya, Olugbenga T.; Nie, Shuming; Holt, David E.; Arlauckas, Sean P.; Low, Phillip S.; Delikatny, E. James; Singhal, Sunil

2015-01-01

Intraoperative optical cancer imaging is an emerging technology in which surgeons employ fluorophores to visualize tumors, identify tumor-positive margins and lymph nodes containing metastases. This study compares instrumentation to measure tumor fluorescence. Three imaging systems (Spectropen, Glomax, Flocam) measured and quantified fluorescent signal-to-background ratios (SBR) in vitro, murine xenografts, tissue phantoms and clinically. Evaluation criteria included the detection of small changes in fluorescence, sensitivity of signal detection at increasing depths and practicality of use. In vitro, spectroscopy was superior in detecting incremental differences in fluorescence than luminescence and digital imaging (Ln[SBR] = 6.8 ± 0.6, 2.4 ± 0.3, 2.6 ± 0.1, p = 0.0001). In fluorescent tumor cells, digital imaging measured higher SBRs than luminescence (6.1 ± 0.2 vs. 4.3 ± 0.4, p = 0.001). Spectroscopy was more sensitive than luminometry and digital imaging in identifying murine tumor fluorescence (SBR = 41.7 ± 11.5, 5.1 ± 1.8, 4.1 ± 0.9, p = 0.0001), and more sensitive than digital imaging at detecting fluorescence at increasing depths (SBR = 7.0 ± 3.4 vs. 2.4 ± 0.5, p = 0.03). Lastly, digital imaging was the most practical and least time-consuming. All methods detected incremental differences in fluorescence. Spectroscopy was the most sensitive for small changes in fluorescence. Digital imaging was the most practical considering its wide field of view, background noise filtering capability, and sensitivity to increasing depth. PMID:26563091

The development of simple and sensitive small-molecule fluorescent probes for the detection of serum proteins after native polyacrylamide gel electrophoresis.

PubMed

Wang, Fangfang; Huang, Lingyun; Na, Na; He, Dacheng; Sun, Dezhi; Ouyang, Jin

2012-05-21

In this paper, a simple and sensitive small-molecule fluorescent probe, 2,5-dihydroxy-4'-dimethylaminochalcone (DHDMAC), was designed and synthesized for the detection of human serum proteins via hydrophobic interactions after polyacrylamide gel electrophoresis (PAGE). This probe produced lower fluorescence emission in the absence of proteins, and the emission intensity was significantly increased after the interaction with serum proteins. To demonstrate the imaging performance of this probe as a fluorescent dye, a series of experiments was conducted that included sensitivity comparison and 2D-PAGE. The results indicated that the sensitivity of DHDMAC staining is comparable to that of the most widely used fluorescent dye, SYPRO Ruby, and more protein spots (including thyroxine-binding globulin, angiotensinogen, afamin, zinc-α-2-glycoprotein and α-1-antichymotrypsin) were detected after 2D-PAGE. Therefore, DHDMAC is a good protein reporter due to its fast staining procedure, low detection limits and high resolution.

A novel fluorescent aptasensor for the highly sensitive and selective detection of cardiac troponin I based on a graphene oxide platform.

PubMed

Liu, Dongkui; Lu, Xing; Yang, Yiwen; Zhai, Yunyun; Zhang, Jian; Li, Lei

2018-05-04

Acute myocardial infarction (AMI) is one of the leading risks to global health. Thus, the rapid, accurate early diagnosis of AMI is highly critical. Human cardiac troponin I (cTnI) has been regarded as a golden biomarker for AMI due to its excellent selectivity. In this work, a novel fluorescent aptasensor based on a graphene oxide (GO) platform was developed for the highly sensitive and selective detection of cTnI. GO binds to the fluorescent anti-cTnI aptamer and quenches its fluorescence. In the presence of cTnI, the fluorescent anti-cTnI aptamer leaves the surface of GO, combines with cTnI because of the powerful affinity of the fluorescent anti-cTnI aptamer and cTnI, and then restores the fluorescence of the fluorescent anti-cTnI aptamer. Fluorescence-enhanced detection is highly sensitive and selective to cTnI. The method exhibited good analytical performance with a reasonable dynamic linearity at the concentration range of 0.10-6.0 ng/mL and a low detection limit of 0.07 ng/mL (S/N = 3). The fluorescent aptasensor also exhibited high selectivity toward cTnI compared with other interference proteins. The proposed method may be a potentially useful tool for cTnI determination in human serum. Graphical abstract A novel fluorescent aptasensor for the highly sensitive and selective detection of cardiac troponin I based on a graphene oxide platform.

Molecularly imprinted fluorescent hollow nanoparticles as sensors for rapid and efficient detection λ-cyhalothrin in environmental water.

PubMed

Wang, Jixiang; Qiu, Hao; Shen, Hongqiang; Pan, Jianming; Dai, Xiaohui; Yan, Yongsheng; Pan, Guoqing; Sellergren, Börje

2016-11-15

Molecularly imprinted fluorescent polymers have shown great promise in biological or chemical separations and detections, due to their high stability, selectivity and sensitivity. In this work, molecularly imprinted fluorescent hollow nanoparticles, which could rapidly and efficiently detect λ-cyhalothrin (a toxic insecticide) in water samples, was reported. The molecularly imprinted fluorescent sensor showed excellent sensitivity (the limit of detection low to 10.26nM), rapid detection rate (quantitative detection of λ-cyhalothrin within 8min), regeneration ability (maintaining good fluorescence properties after 8 cycling operation) and appreciable selectivity over several structural analogs. Moreover, the fluorescent sensor was further used to detect λ-cyhalothrin in real samples form the Beijing-Hangzhou Grand Canal Water. Despite the relatively complex components of the environmental water, the molecularly imprinted fluorescent hollow nanosensor still showed good recovery, clearly demonstrating the potential value of this smart sensor nanomaterial in environmental monitoring. Copyright © 2016 Elsevier B.V. All rights reserved.

Reactive chromophores for sensitive and selective detection of chemical warfare agents and toxic industrial chemicals

NASA Astrophysics Data System (ADS)

Frye-Mason, Greg; Leuschen, Martin; Wald, Lara; Paul, Kateri; Hancock, Lawrence F.

2005-05-01

A reactive chromophore developed at MIT exhibits sensitive and selective detection of surrogates for G-class nerve agents. This reporter acts by reacting with the agent to form an intermediate that goes through an internal cyclization reaction. The reaction locks the molecule into a form that provides a strong fluorescent signal. Using a fluorescent sensor platform, Nomadics has demonstrated rapid and sensitive detection of reactive simulants such as diethyl chloro-phosphate (simulant for sarin, soman, and related agents) and diethyl cyanophosphate (simulant for tabun). Since the unreacted chromophore does not fluoresce at the excitation wavelength used for the cyclized reporter, the onset of fluo-rescence can be easily detected. This fluorescence-based detection method provides very high sensitivity and could enable rapid detection at permissible exposure levels. Tests with potential interferents show that the reporter is very selective, with responses from only a few highly toxic, electrophilic chemicals such as phosgene, thionyl chloride, and strong acids such as HF, HCl, and nitric acid. Dimethyl methyl phosphonate (DMMP), a common and inactive simu-lant for other CW detectors, is not reactive enough to generate a signal. The unique selectivity to chemical reactivity means that a highly toxic and hazardous chemical is present when the reporter responds and illustrates that this sensor can provide very low false alarm rates. Current efforts focus on demonstrating the sensitivity and range of agents and toxic industrial chemicals detected with this reporter as well as developing additional fluorescent reporters for a range of chemical reactivity classes. The goal is to produce a hand-held sensor that can sensitively detect a broad range of chemical warfare agent and toxic industrial chemical threats.

DNA-stabilized silver nanoclusters and carbon nanoparticles oxide: A sensitive platform for label-free fluorescence turn-on detection of HIV-DNA sequences.

PubMed

Ye, Yu-Dan; Xia, Li; Xu, Dang-Dang; Xing, Xiao-Jing; Pang, Dai-Wen; Tang, Hong-Wu

2016-11-15

Based on the remarkable difference between the interactions of carbon nanoparticles (CNPs) oxide with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), and the fact that fluorescence of DNA-stabilized silver nanoclusters (AgNCs) can be quenched by CNPs oxide, DNA-functionalized AgNCs were applied as label-free fluorescence probes and a novel fluorescence resonance energy transfer (FRET) sensor was successfully constructed for the detection of human immunodeficiency virus (HIV) DNA sequences. CNPs oxide were prepared with the oxidation of candle soot, hence it is simple, time-saving and low-cost. The strategy of dual AgNCs probes was applied to improve the detection sensitivity by using dual- probe capturing the same target DNA in a sandwich mode and as the fluorescence donor, and using CNPs oxide as the acceptor. In the presence of target DNA, a dsDNA hybrid forms, leading to the desorption of the ssDNA-AgNCs probes from CNPs oxide, and the recovering of fluorescence of the AgNCs in a HIV-DNA concentration-dependent manner. The results show that HIV-DNA can be detected in the range of 1-50nM with a detection limit of 0.40nM in aqueous buffer. The method is simple, rapid and sensitive with no need of labeled fluorescent probes, and moreover, the design of fluorescent dual-probe makes full use of the excellent fluorescence property of AgNCs and further improves the detection sensitivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Turn-on fluorescence sensor based on single-walled-carbon-nanohorn-peptide complex for the detection of thrombin.

PubMed

Zhu, Shuyun; Liu, Zhongyuan; Hu, Lianzhe; Yuan, Yali; Xu, Guobao

2012-12-14

Proteases play a central role in several widespread diseases. Thus, there is a great need for the fast and sensitive detection of various proteolytic enzymes. Herein, we have developed a carbon nanotube (CNT)-based protease biosensing platform that uses peptides as a fluorescence probe for the first time. Single-walled carbon nanohorns (SWCNHs) and thrombin were used to demonstrate this detection strategy. SWCNHs can adsorb a fluorescein-based dye (FAM)-labeled peptide (FAM-pep) and quench the fluorescence of FAM. In contrast, thrombin can cleave FAM-pep on SWCNHs and recover the fluorescence of FAM, which allows the sensitive detection of thrombin. This biosensor has a high sensitivity and selectivity toward thrombin, with a detection limit of 100 pM. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorescence ELISA based on glucose oxidase-mediated fluorescence quenching of quantum dots for highly sensitive detection of Hepatitis B.

PubMed

Wu, Yunqing; Zeng, Lifeng; Xiong, Ying; Leng, Yuankui; Wang, Hui; Xiong, Yonghua

2018-05-01

Herein, we present a novel sandwich fluorescence enzyme linked immunosorbent assay (ELISA) for highly sensitive detection of Hepatitis B virus surface antigen (HBsAg) based on glucose oxidase (GOx)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (MPA-QDs). In this system, hydrogen peroxide (H 2 O 2 ) sensitive MPA-QDs was used as a signal output, and glucose oxidase (GOx) was used as label which can generate H 2 O 2 via catalytic oxidation of glucose. The proposed method showed dynamic linear detection of HBsAg both in the range of 47pgmL -1 ~ 380pgmL -1 and 0.75ngmL -1 ~ 12.12ngmL -1 . The detection limit of the proposed fluorescence ELISA was 1.16pgmL -1 , which was approximately 430-fold lower than that of horseradish peroxidase (HRP)-based conventional ELISA. The average recoveries for HBsAg-spiked serum samples ranged from 98.0% to 126.8% with the relative standard derivation below 10%, thus indicating acceptable precision and high reproducibility of the proposed fluorescence ELISA for HBsAg detection. Additionally, the developed method showed no false positive results analyzing 35 real HBsAg-negative serum samples, and exhibited excellent agreement (R 2 =0.9907) with a commercial time-resolved fluorescence immunoassay (TRFIA) kit for detecting 31 HBsAg-positive serum samples. In summary, the proposed method based on fluorescence quenching of H 2 O 2 sensitive QDs is considerably to be an excellent biodetection platform with ultrahigh sensitivity, good accuracy and excellent reliability. Copyright © 2018 Elsevier B.V. All rights reserved.

Microgels for multiplex and direct fluorescence detection

NASA Astrophysics Data System (ADS)

Causa, Filippo; Aliberti, Anna; Cusano, Angela M.; Battista, Edmondo; Netti, Paolo A.

2015-05-01

Blood borne oligonucleotides fragments contain useful clinical information whose detection and monitoring represent the new frontier in liquid biopsy as they can transform the current diagnosis procedure. For instance, recent studies have identified a new class of circulating biomarkers such as s miRNAs, and demonstrated that changes in their concentration are closely associated with the development of cancer and other pathologies. However, direct detection of miRNAs in body fluids is particularly challenging and demands high sensitivity -concentration range between atto to femtomolarspecificity, and multiplexing Here we report on engineered multifunctional microgels and innovative probe design for a direct and multiplex detection of relevant clinical miRNAs in fluorescence by single particle assay. Polyethyleneglycol-based microgels have a coreshell architecture with two spectrally encoded fluorescent dyes for multiplex analyses and are endowed with fluorescent probes for miRNA detection. Encoding and detection fluorescence signals are distinguishable by not overlapping emission spectra. Tuneable fluorescence probe conjugation and corresponding emission confinement on single microgel allows for enhanced target detection. Such suspension array has indeed high selectivity and sensitivity with a detection limit of 10-15 M and a dynamic range from 10-9 to 10-15 M. We believe that sensitivity in the fM concentration range, signal background minimization, multiplexed capability and direct measurement of such microgels will translate into diagnostic benefits opening up new roots toward liquid biopsy in the context of point-of-care testing through an easy and fast detection of sensitive diagnostic biomarkers directly in serum.

Highly selective and sensitive detection of Cu2+ with lysine enhancing bovine serum albumin modified-carbon dots fluorescent probe.

PubMed

Liu, Jia-Ming; Lin, Li-ping; Wang, Xin-Xing; Lin, Shao-Qin; Cai, Wen-Lian; Zhang, Li-Hong; Zheng, Zhi-Yong

2012-06-07

Based on the ability of lysine (Lys) to enhance the fluorescence intensity of bovine serum albumin modified-carbon dots (CDs-BSA) to decrease surface defects and quench fluorescence of the CDs-BSA-Lys system in the presence of Cu(2+) under conditions of phosphate buffer (PBS, pH = 5.0) at 45 °C for 10 min, a sensitive Lys enhancing CDs-BSA fluorescent probe was designed. The environment-friendly, simple, rapid, selective and sensitive fluorescent probe has been utilized to detect Cu(2+) in hair and tap water samples and it achieved consistent results with those obtained by inductively coupled plasma mass spectroscopy (ICP-MS). The mechanism of the proposed assay for the detection of Cu(2+) is discussed.

Exciton-controlled fluorescence: application to hybridization-sensitive fluorescent DNA probe.

PubMed

Okamoto, Akimitsu; Ikeda, Shuji; Kubota, Takeshi; Yuki, Mizue; Yanagisawa, Hiroyuki

2009-01-01

A hybridization-sensitive fluorescent probe has been designed for nucleic acid detection, using the concept of fluorescence quenching caused by the intramolecular excitonic interaction of fluorescence dyes. We synthesized a doubly thiazole orange-labeled nucleotide showing high fluorescence intensity for a hybrid with the target nucleic acid and effective quenching for the single-stranded state. This exciton-controlled fluorescent probe was applied to living HeLa cells using microinjection to visualize intracellular mRNA localization. Immediately after injection of the probe into the cell, fluorescence was observed from the probe hybridizing with the target RNA. This fluorescence rapidly decreased upon addition of a competitor DNA. Multicoloring of this probe resulted in the simple simultaneous detection of plural target nucleic acid sequences. This probe realized a large, rapid, reversible change in fluorescence intensity in sensitive response to the amount of target nucleic acid, and facilitated spatiotemporal monitoring of the behavior of intracellular RNA.

Fluorescence background subtraction technique for hybrid fluorescence molecular tomography/x-ray computed tomography imaging of a mouse model of early stage lung cancer.

PubMed

Ale, Angelique; Ermolayev, Vladimir; Deliolanis, Nikolaos C; Ntziachristos, Vasilis

2013-05-01

The ability to visualize early stage lung cancer is important in the study of biomarkers and targeting agents that could lead to earlier diagnosis. The recent development of hybrid free-space 360-deg fluorescence molecular tomography (FMT) and x-ray computed tomography (XCT) imaging yields a superior optical imaging modality for three-dimensional small animal fluorescence imaging over stand-alone optical systems. Imaging accuracy was improved by using XCT information in the fluorescence reconstruction method. Despite this progress, the detection sensitivity of targeted fluorescence agents remains limited by nonspecific background accumulation of the fluorochrome employed, which complicates early detection of murine cancers. Therefore we examine whether x-ray CT information and bulk fluorescence detection can be combined to increase detection sensitivity. Correspondingly, we research the performance of a data-driven fluorescence background estimator employed for subtraction of background fluorescence from acquisition data. Using mice containing known fluorochromes ex vivo, we demonstrate the reduction of background signals from reconstructed images and sensitivity improvements. Finally, by applying the method to in vivo data from K-ras transgenic mice developing lung cancer, we find small tumors at an early stage compared with reconstructions performed using raw data. We conclude with the benefits of employing fluorescence subtraction in hybrid FMT-XCT for early detection studies.

Hybridization chain reaction amplification for highly sensitive fluorescence detection of DNA with dextran coated microarrays.

PubMed

Chao, Jie; Li, Zhenhua; Li, Jing; Peng, Hongzhen; Su, Shao; Li, Qian; Zhu, Changfeng; Zuo, Xiaolei; Song, Shiping; Wang, Lianhui; Wang, Lihua

2016-07-15

Microarrays of biomolecules hold great promise in the fields of genomics, proteomics, and clinical assays on account of their remarkably parallel and high-throughput assay capability. However, the fluorescence detection used in most conventional DNA microarrays is still limited by sensitivity. In this study, we have demonstrated a novel universal and highly sensitive platform for fluorescent detection of sequence specific DNA at the femtomolar level by combining dextran-coated microarrays with hybridization chain reaction (HCR) signal amplification. Three-dimensional dextran matrix was covalently coated on glass surface as the scaffold to immobilize DNA recognition probes to increase the surface binding capacity and accessibility. DNA nanowire tentacles were formed on the matrix surface for efficient signal amplification by capturing multiple fluorescent molecules in a highly ordered way. By quantifying microscopic fluorescent signals, the synergetic effects of dextran and HCR greatly improved sensitivity of DNA microarrays, with a detection limit of 10fM (1×10(5) molecules). This detection assay could recognize one-base mismatch with fluorescence signals dropped down to ~20%. This cost-effective microarray platform also worked well with samples in serum and thus shows great potential for clinical diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis of molecularly imprinted dye-silica nanocomposites with high selectivity and sensitivity: Fluorescent imprinted sensor for rapid and efficient detection of τ-fluvalinate in vodka.

PubMed

Wang, Yunyun; Wang, Jixiang; Cheng, Rujia; Sun, Lin; Dai, Xiaohui; Yan, Yongsheng

2018-04-01

An imprinted fluorescent sensor was fabricated based on SiO 2 nanoparticles encapsulated with a molecularly imprinted polymer containing allyl fluorescein. High fluorine cypermethirin as template molecules, methyl methacrylate as functional monomer, and allyl fluorescein as optical materials synthesized a core-shell fluorescent molecular imprinted sensor, which showed a high and rapid sensitivity and selectivity for the detection of τ-fluvalinate. The sensor presented appreciable sensitivity with a limit of 13.251 nM, rapid detection that reached to equilibrium within 3 min, great linear relationship in the relevant concentration range from 0 to 150 nM, and excellent selectivity over structural analogues. In addition, the fluorescent sensor demonstrated desirable regeneration ability (eight cycling operations). The molecularly imprinted polymers ensured specificity, while the fluorescent dyes provided the stabile sensitivity. Finally, an effective application of the sensor was implemented by the detection of τ-fluvalinate in real samples from vodka. The molecularly imprinted fluorescent sensor showed a promising potential in environmental monitoring and food safety. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a H2 O2 -sensitive quantum dots-based fluorescent sandwich ELISA for sensitive detection of bovine β-lactoglobulin by monoclonal antibody.

PubMed

He, Shengfa; Li, Xin; Gao, Jinyan; Tong, Ping; Chen, Hongbing

2018-01-01

Bovine β-lactoglobulin (BLG) is the major allergen in cows' milk, and the specific epitope plays a key role in food allergy. Developing a method specifically bind to the IgE epitope is necessary for testing BLG and its allergenic residues. The monoclonal antibody (1G9) specific to the IgE linear epitope for BLG was identified as high affinity and specificity. Based on 1G9, a sensitive fluorescent sandwich enzyme-linked immunosorbent assay (sELISA) was successfully developed using catalase-mediated fluorescence quenching of thiolated CdTe quantum dots in the presence of hydrogen peroxide as fluorescent signal output. The fluorescent sELISA showed high sensitivity and specificity, the limit of detection was 0.49 ng mL -1 , which was 16-fold lower than horseradish peroxidase (HRP)-based sELISA. The linear range for BLG detection were 125-4000 ng mL -1 (r = 0.9939) and 0.48-62.5 ng mL -1 (r = 0.9919). The recoveries and coefficients of variation were 94.25-109.83% and 4.38-20.29%, respectively. Allergenic residues were also detected in hydrolysed infant formulas. The results of fluorescent sELISA showed good performance as HRP-based sELISA and commercial sELISA kit. This proposed fluorescent sELISA could be employed to detect BLG and its allergenic residues in food with highly sensitivity, reliability, and recovery. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Molecular imprinting ratiometric fluorescence sensor for highly selective and sensitive detection of phycocyanin.

PubMed

Wang, Xiaoyan; Yu, Jialuo; Kang, Qi; Shen, Dazhong; Li, Jinhua; Chen, Lingxin

2016-03-15

A facile strategy was developed to prepare molecular imprinting ratiometric fluorescence sensor for highly selective and sensitive detection of phycocyanin (PC) based on fluorescence resonance energy transfer (FRET), via a sol-gel polymerization process using nitrobenzoxadiazole (NBD) as fluorescent signal source. The ratio of two fluorescence peak emission intensities of NBD and PC was utilized to determine the concentration of PC, which could effectively reduce the background interference and fluctuation of diverse conditions. As a result, this sensor obtained high sensitivity with a low detection limit of 0.14 nM within 6 min, and excellent recognition specificity for PC over its analogues with a high imprinting factor of 9.1. Furthermore, the sensor attained high recoveries in the range of 93.8-110.2% at three spiking levels of PC, with precisions below 4.7% in seawater and lake water samples. The developed sensor strategy demonstrated simplicity, reliability, rapidity, high selectivity and high sensitivity, proving to be a feasible way to develop high efficient fluorescence sensors and thus potentially applicable for ultratrace analysis of complicated matrices. Copyright © 2015 Elsevier B.V. All rights reserved.

Water-Soluble Nonconjugated Polymer Nanoparticles with Strong Fluorescence Emission for Selective and Sensitive Detection of Nitro-Explosive Picric Acid in Aqueous Medium.

PubMed

Liu, Shi Gang; Luo, Dan; Li, Na; Zhang, Wei; Lei, Jing Lei; Li, Nian Bing; Luo, Hong Qun

2016-08-24

Water-soluble nonconjugated polymer nanoparticles (PNPs) with strong fluorescence emission were prepared from hyperbranched poly(ethylenimine) (PEI) and d-glucose via Schiff base reaction and self-assembly in aqueous phase. Preparation of the PEI-d-glucose (PEI-G) PNPs was facile (one-pot reaction) and environmentally friendly under mild conditions. Also, PEI-G PNPs showed a high fluorescence quantum yield in aqueous solution, and the fluorescence properties (such as concentration- and solvent-dependent fluorescence) and origin of intrinsic fluorescence were investigated and discussed. PEI-G PNPs were then used to develop a fluorescent probe for fast, selective, and sensitive detection of nitro-explosive picric acid (PA) in aqueous medium, because the fluorescence can be easily quenched by PA whereas other nitro-explosives and structurally similar compounds only caused negligible quenching. A wide linear range (0.05-70 μM) and a low detection limit (26 nM) were obtained. The fluorescence quenching mechanism was carefully explored, and it was due to a combined effect of electron transfer, resonance energy transfer, and inner filter effect between PA and PEI-G PNPs, which resulted in good selectivity and sensitivity for PA. Finally, the developed sensor was successfully applied to detection of PA in environmental water samples.

Ability of various materials to detect explosive vapors by fluorescent technologies: a comparative study.

PubMed

Bouhadid, Myriam; Caron, Thomas; Veignal, Florian; Pasquinet, Eric; Ratsimihety, Amédée; Ganachaud, François; Montméat, Pierre

2012-10-15

For the development of fluorescent sensors, one of the key points is choosing the sensitive material. In this article, we aim at evaluating, under strictly identical experimental conditions, the performance of three materials for the detection of dinitrotoluene (a volatile marker of trinitrotoluene) through different parameters: response time, fluorescence intensity, sensitivity, reversibility, reaction after successive exposures and long-term stability. The results are discussed according to the nature of the sensitive materials. This first study rendered it possible to select a conjugated molecule as the best sensitive material for the development of a lab-made prototype. In a second part, the selectivity of this particular sensitive material was studied and its ability to detect TNT could be demonstrated. Copyright © 2012. Published by Elsevier B.V.

Interpenetrated Binary Supramolecular Nanofibers for Sensitive Fluorescence Detection of Six Classes of Explosives.

PubMed

Xiong, Wei; Zhu, Qijian; Gong, Yanjun; Wang, Chen; Che, Yanke; Zhao, Jincai

2018-04-03

In this work, we develop a sequential self-assembly approach to fabricate interpenetrated binary supramolecular nanofibers consisting of carbazole oligomer 1-cobalt(II) (1-Co 2+ ) coordination nanofibers and oligomer 2 nanofibers for the sensitive detection of six classes of explosives. When exposed to peroxide explosives (e.g., H 2 O 2 ), Co 2+ in 1-Co 2+ coordination nanofibers can be reduced to Co + that can transfer an electron to the excited 2 nanofibers and thereby quench their fluorescence. On the other hand, when exposed to the other five classes of explosives, the excited 2 nanofibers can transfer an electron to explosives to quench their fluorescence. On the basis of the distinct fluorescence quenching mechanisms, six classes of explosives can be sensitively detected. Herein, we provide a new strategy to design broad-band fluorescence sensors for a rich identification of threats.

A ratiometric fluorescent probe for rapid and sensitive detection of biothiols in fetal bovine serum.

PubMed

Wang, Fengyang; Feng, Chongchong; Lu, Linlin; Xu, Zhiai; Zhang, Wen

2017-07-01

Herein, a ratiometric turn-on fluorescent probe for sensitive detection of biothiols was designed. The probe consisted of two parts: one was rhodamine B serving as a fluorescence reference, and the other was coumarin derivative as the responsive fluorophore with an acrylate group for biothiols recognition. The response was based on the mechanism of Michael addition and intramolecular cyclization reaction, and the probe showed ratiometric and sensitive response to biothiols. Especially, the detection limit of this probe for cysteine was found to be 0.13μΜ. More importantly, the probe showed the advantage of fast response, of which the fluorescence intensity can reach the maximum within 10min. The ratiometric fluorescent probe has been successfully applied for the determination of biothiols in fetal bovine serum samples and the result was in good agreement with that tested by Ellman method. Copyright © 2017. Published by Elsevier B.V.

A new dual-channel optical signal probe for Cu2+ detection based on morin and boric acid.

PubMed

Wang, Peng; Yuan, Bin Fang; Li, Nian Bing; Luo, Hong Qun

2014-01-01

In this work we utilized the common analytical reagent morin to develop a new a dual-channel, cost-effective, and sensitive method for determination of Cu(2+). It is found that morin is only weakly fluorescent by itself, but forms highly fluorescent complexes with boric acid. Moreover, the fluorescence of complexes of morin with boric acid is quenched linearly by Cu(2+) in a certain concentration range. Under optimum conditions, the fluorescence quenching efficiency was linearly proportional to the concentration of cupric ions in the range of 0.5-25 μM with high sensitivity, and the detection limit for Cu(2+) was 0.38 μM. The linear range was 1-25 μM determined by spectrophotometry, and the detection limit for cupric ions was 0.8 μM. Furthermore, the mechanism of sensitive fluorescence quenching response of morin to Cu(2+) is discussed.

Synergistic electron transfer effect-based signal amplification strategy for the ultrasensitive detection of dopamine.

PubMed

Lu, Qiujun; Chen, Xiaogen; Liu, Dan; Wu, Cuiyan; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

2018-05-15

The selective and sensitive detection of dopamine (DA) is of great significance for the identification of schizophrenia, Huntington's disease, and Parkinson's disease from the perspective of molecular diagnostics. So far, most of DA fluorescence sensors are based on the electron transfer from the fluorescence nanomaterials to DA-quinone. However, the limited electron transfer ability of the DA-quinone affects the level of detection sensitivity of these sensors. In this work, based on the DA can reduce Ag + into AgNPs followed by oxidized to DA-quinone, we developed a novel silicon nanoparticles-based electron transfer fluorescent sensor for the detection of DA. As electron transfer acceptor, the AgNPs and DA-quinone can quench the fluorescence of silicon nanoparticles effectively through the synergistic electron transfer effect. Compared with traditional fluorescence DA sensors, the proposed synergistic electron transfer-based sensor improves the detection sensitivity to a great extent (at least 10-fold improvement). The proposed sensor shows a low detection limit of DA, which is as low as 0.1 nM under the optimal conditions. This sensor has potential applicability for the detection of DA in practical sample. This work has been demonstrated to contribute to a substantial improvement in the sensitivity of the sensors. It also gives new insight into design electron transfer-based sensors. Copyright © 2018. Published by Elsevier B.V.

Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine.

PubMed

Jiang, Hu; Li, Xiangmin; Xiong, Ying; Pei, Ke; Nie, Lijuan; Xiong, Yonghua

2017-02-28

A silver nanoparticle (AgNP)-based fluorescence-quenching lateral flow immunoassay with competitive format (cLFIA) was developed for sensitive detection of ochratoxin A (OTA) in grape juice and wine samples in the present study. The Ru(phen) 3 2 + -doped silica nanoparticles (RuNPs) were sprayed on the test and control line zones as background fluorescence signals. The AgNPs were designed as the fluorescence quenchers of RuNPs because they can block the exciting light transferring to the RuNP molecules. The proposed method exhibited high sensitivity for OTA detection, with a detection limit of 0.06 µg/L under optimized conditions. The method also exhibited a good linear range for OTA quantitative analysis from 0.08 µg/L to 5.0 µg/L. The reliability of the fluorescence-quenching cLFIA method was evaluated through analysis of the OTA-spiked red grape wine and juice samples. The average recoveries ranged from 88.0% to 110.0% in red grape wine and from 92.0% to 110.0% in grape juice. Meanwhile, less than a 10% coefficient variation indicated an acceptable precision of the cLFIA method. In summary, the new AgNP-based fluorescence-quenching cLFIA is a simple, rapid, sensitive, and accurate method for quantitative detection of OTA in grape juice and wine or other foodstuffs.

Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine

PubMed Central

Jiang, Hu; Li, Xiangmin; Xiong, Ying; Pei, Ke; Nie, Lijuan; Xiong, Yonghua

2017-01-01

A silver nanoparticle (AgNP)-based fluorescence-quenching lateral flow immunoassay with competitive format (cLFIA) was developed for sensitive detection of ochratoxin A (OTA) in grape juice and wine samples in the present study. The Ru(phen)32+-doped silica nanoparticles (RuNPs) were sprayed on the test and control line zones as background fluorescence signals. The AgNPs were designed as the fluorescence quenchers of RuNPs because they can block the exciting light transferring to the RuNP molecules. The proposed method exhibited high sensitivity for OTA detection, with a detection limit of 0.06 µg/L under optimized conditions. The method also exhibited a good linear range for OTA quantitative analysis from 0.08 µg/L to 5.0 µg/L. The reliability of the fluorescence-quenching cLFIA method was evaluated through analysis of the OTA-spiked red grape wine and juice samples. The average recoveries ranged from 88.0% to 110.0% in red grape wine and from 92.0% to 110.0% in grape juice. Meanwhile, less than a 10% coefficient variation indicated an acceptable precision of the cLFIA method. In summary, the new AgNP-based fluorescence-quenching cLFIA is a simple, rapid, sensitive, and accurate method for quantitative detection of OTA in grape juice and wine or other foodstuffs. PMID:28264472

Sensitive detection of alkaline phosphatase by switching on gold nanoclusters fluorescence quenched by pyridoxal phosphate.

PubMed

Halawa, Mohamed Ibrahim; Gao, Wenyue; Saqib, Muhammad; Kitte, Shimeles Addisu; Wu, Fengxia; Xu, Guobao

2017-09-15

In this work, we designed highly sensitive and selective luminescent detection method for alkaline phosphatase using bovine serum albumin functionalized gold nanoclusters (BSA-AuNCs) as the nanosensor probe and pyridoxal phosphate as the substrate of alkaline phosphatase. We found that pyridoxal phosphate can quench the fluorescence of BSA-AuNCs and pyridoxal has little effect on the fluorescence of BSA-AuNCs. The proposed mechanism of fluorescence quenching by PLP was explored on the basis of data obtained from high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), UV-vis spectrophotometry, fluorescence spectroscopy, fluorescence decay time measurements and circular dichroism (CD) spectroscopy. Alkaline phosphatase catalyzes the hydrolysis of pyridoxal phosphate to generate pyridoxal, restoring the fluorescence of BSA-AuNCs. Therefore, a recovery type approach has been developed for the sensitive detection of alkaline phosphatase in the range of 1.0-200.0U/L (R 2 =0.995) with a detection limit of 0.05U/L. The proposed sensor exhibit excellent selectivity among various enzymes, such as glucose oxidase, lysozyme, trypsin, papain, and pepsin. The present switch-on fluorescence sensing strategy for alkaline phosphatase was successfully applied in human serum plasma with good recoveries (100.60-104.46%), revealing that this nanosensor probe is a promising tool for ALP detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Strategies of molecular imprinting-based fluorescence sensors for chemical and biological analysis.

PubMed

Yang, Qian; Li, Jinhua; Wang, Xiaoyan; Peng, Hailong; Xiong, Hua; Chen, Lingxin

2018-07-30

One pressing concern today is to construct sensors that can withstand various disturbances for highly selective and sensitive detecting trace analytes in complicated samples. Molecularly imprinted polymers (MIPs) with tailor-made binding sites are preferred to be recognition elements in sensors for effective targets detection, and fluorescence measurement assists in highly sensitive detection and user-friendly control. Accordingly, molecular imprinting-based fluorescence sensors (MI-FL sensors) have attracted great research interest in many fields such as chemical and biological analysis. Herein, we comprehensively review the recent advances in MI-FL sensors construction and applications, giving insights on sensing principles and signal transduction mechanisms, focusing on general construction strategies for intrinsically fluorescent or nonfluorescent analytes and improvement strategies in sensing performance, particularly in sensitivity. Construction strategies are well overviewed, mainly including the traditional indirect methods of competitive binding against pre-bound fluorescent indicators, employment of fluorescent functional monomers and embedding of fluorescence substances, and novel rational designs of hierarchical architecture (core-shell/hollow and mesoporous structures), post-imprinting modification, and ratiometric fluorescence detection. Furthermore, MI-FL sensor based microdevices are discussed, involving micromotors, test strips and microfluidics, which are more portable for rapid point-of-care detection and in-field diagnosing. Finally, the current challenges and future perspectives of MI-FL sensors are proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

Ultra-sensitive and selective Hg{sup 2+} detection based on fluorescent carbon dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ruihua; Li, Haitao; Kong, Weiqian

2013-07-15

Graphical abstract: Fluorescent carbon dots were efficiently synthesized by one-step sodium hydroxide-assisted reflux method from PEG and demonstrated to show high selectivity toward Hg2+ ions detection. - Highlights: • FCDs were synthesized by one-step sodium hydroxide-assisted reflux method from PEG. • The FCDs emit blue photoluminescence and have upconversion fluorescent property. • The FCDs show ultra-sensitive detective ability for Hg{sup 2+} ions. - Abstract: Fluorescent carbon dots (FCDs) were efficiently synthesized by one-step sodium hydroxide-assisted reflux method from poly(ethylene glycol) (PEG). The obtained FCDs exhibit excellent water-solubility and high stability. Under the UV irradiation, the FCDs could emit bright bluemore » photoluminescence, and also they were found to show excellent up-conversion fluorescence. It was further demonstrated that such FCDs can serve as effective fluorescent sensing platform for Hg{sup 2+} ions detection with ultra-sensitivity and selectivity. The sensing system achieved a limit of detection as low as 1 fM, which is much lower than all the previous reported sensing systems for Hg{sup 2+} ions detection. This FCDs sensing system has been successfully applied for the analysis of Hg{sup 2+} ions in water samples from river, lake, and tap water, showing good practical feasibility.« less

Dual-Reactable Fluorescent Probes for Highly Selective and Sensitive Detection of Biological H2 S.

PubMed

Wei, Chao; Wang, Runyu; Zhang, Changyu; Xu, Guoce; Li, Yanyan; Zhang, Qiang-Zhe; Li, Lu-Yuan; Yi, Long; Xi, Zhen

2016-05-06

Hydrogen sulfide (H2 S) is an important endogenous signaling molecule with a variety of biological functions. Development of fluorescent probes for highly selective and sensitive detection of H2 S is necessary. We show here that dual-reactable fluorescent H2 S probes could react with higher selectivity than single-reactable probes. One of the dual-reactable probes gives more than 4000-fold turn-on response when reacting with H2 S, the largest response among fluorescent H2 S probes reported thus far. In addition, the probe could be used for high-throughput enzymatic assays and for the detection of Cys-induced H2 S in cells and in zebrafish. These dual-reactable probes hold potential for highly selective and sensitive detection of H2 S in biological systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A highly sensitive protocol for microscopy of alkyne lipids and fluorescently tagged or immunostained proteins[S

PubMed Central

Gaebler, Anne; Penno, Anke; Kuerschner, Lars; Thiele, Christoph

2016-01-01

The demand to study the cellular localization of specific lipids has led to recent advances in lipid probes and microscopy. Alkyne lipids bear a small, noninterfering tag and can be detected upon click reaction with an azide-coupled reporter. Fluorescent alkyne lipid imaging crucially depends on appropriate azide reporters and labeling protocols that allow for an efficient click reaction and therefore a sensitive detection. We synthesized several azide reporters with different spacer components and tested their suitability for alkyne lipid imaging in fixed cells. The implementation of a copper-chelating picolyl moiety into fluorescent or biotin-based azide reagents strongly increased the sensitivity of the imaging routine. We demonstrate the applicability and evaluate the performance of this approach using different lipid classes and experimental setups. As azide picolyl reporters allow for reduced copper catalyst concentrations, they also enable coimaging of alkyne lipids with multiple fluorescent proteins including enhanced green fluorescent protein. Alternatively, and as we also show, microscopy of alkyne lipids can be combined with protein detection by immunocytochemistry. In summary, we present a robust, sensitive, and highly versatile protocol for the labeling of alkyne lipids with azide-coupled reporters for fluorescence microscopy that can be combined with different protein detection and imaging techniques. PMID:27565170

Novel strategy combining SYBR Green I with carbon nanotubes for highly sensitive detection of Salmonella typhimurium DNA.

PubMed

Mao, Pingdao; Ning, Yi; Li, Wenkai; Peng, Zhihui; Chen, Yongzhe; Deng, Le

2014-01-10

A simple, selective, sensitive and label-free fluorescent method for detecting trpS-harboring Salmonella typhimurium was developed in this study. This assay used the non-covalent interaction of single-stranded DNA (ssDNA) probes with SWNTs, since SWNTs can quench fluorescence. Fluorescence recovery (78% with 1.8 nM target DNA) was detected in the presence of target DNA as ssDNA probes detached from SWNTs hybridized with target DNA, and the resulting double-stranded DNA (dsDNA) intercalated with SYBR Green I (SG) dyes. The increasing fluorescence intensity reached 4.54-fold. In contrast, mismatched oligonucleotides (1- or 3-nt difference to the target DNA) did not contribute to significant fluorescent recovery, which demonstrated the specificity of the assay. The increasing fluorescence intensity increased 3.15-fold when purified PCR products containing complementary sequences of trpS gene were detected. These results confirmed the ability to use this assay for detecting real samples. Copyright © 2013 Elsevier Inc. All rights reserved.

Fluorescent Metal-Organic Framework (MOF) as a Highly Sensitive and Quickly Responsive Chemical Sensor for the Detection of Antibiotics in Simulated Wastewater.

PubMed

Zhu, Xian-Dong; Zhang, Kun; Wang, Yu; Long, Wei-Wei; Sa, Rong-Jian; Liu, Tian-Fu; Lü, Jian

2018-02-05

A Zn(II)-based fluorescent metal-organic framework (MOF) was synthesized and applied as a highly sensitive and quickly responsive chemical sensor for antibiotic detection in simulated wastewater. The fluorescent chemical sensor, denoted FCS-1, exhibited enhanced fluorescence derived from its highly ordered, 3D MOF structure as well as excellent water stability in the practical pH range of simulated antibiotic wastewater (pH = 3.0-9.0). Remarkably, FCS-1 was able to effectively detect a series of sulfonamide antibiotics via photoinduced electron transfer that caused detectable fluorescence quenching, with fairly low detection limits. Two influences impacting measurements related to wastewater treatment and water quality monitoring, the presence of heavy-metal ions and the pH of solutions, were studied in terms of fluorescence quenching, which was nearly unaffected in sulfonamide-antibiotic detection. Additionally, the effective detection of sulfonamide antibiotics was rationalized by the theoretical computation of the energy bands of sulfonamide antibiotics, which revealed a good match between the energy bands of FCS-1 and sulfonamide antibiotics, in connection with fluorescence quenching in this system.

The detection of T-Nos, a genetic element present in GMOs, by cross-priming isothermal amplification with real-time fluorescence.

PubMed

Zhang, Fang; Wang, Liu; Fan, Kai; Wu, Jian; Ying, Yibin

2014-05-01

An isothermal cross-priming amplification (CPA) assay for Agrobacterium tumefaciens nopaline synthase terminator (T-Nos) was established and investigated in this work. A set of six specific primers, recognizing eight distinct regions on the T-Nos sequence, was designed. The CPA assay was performed at a constant temperature, 63 °C, and detected by real-time fluorescence. The results indicated that real-time fluorescent CPA had high specificity, and the limit of detection was 1.06 × 10(3) copies of rice genomic DNA, which could be detected in 40 min. Comparison of real-time fluorescent CPA and conventional polymerase chain reaction (PCR) was also performed. Results revealed that real-time fluorescent CPA had a comparable sensitivity to conventional real-time PCR and had taken a shorter time. In addition, different contents of genetically modified (GM)-contaminated rice seed powder samples were detected for practical application. The result showed real-time fluorescent CPA could detect 0.5 % GM-contaminated samples at least, and the whole reaction could be finished in 35 min. Real-time fluorescent CPA is sensitive enough to monitor labeling systems and provides an attractive method for the detection of GMO.

Sensitivity and accuracy of hybrid fluorescence-mediated tomography in deep tissue regions.

PubMed

Rosenhain, Stefanie; Al Rawashdeh, Wa'el; Kiessling, Fabian; Gremse, Felix

2017-09-01

Fluorescence-mediated tomography (FMT) enables noninvasive assessment of the three-dimensional distribution of near-infrared fluorescence in mice. The combination with micro-computed tomography (µCT) provides anatomical data, enabling improved fluorescence reconstruction and image analysis. The aim of our study was to assess sensitivity and accuracy of µCT-FMT under realistic in vivo conditions in deeply-seated regions. Accordingly, we acquired fluorescence reflectance images (FRI) and µCT-FMT scans of mice which were prepared with rectal insertions with different amounts of fluorescent dye. Default and high-sensitivity scans were acquired and background signal was analyzed for three FMT channels (670 nm, 745 nm, and 790 nm). Analysis was performed for the original and an improved FMT reconstruction using the µCT data. While FRI and the original FMT reconstruction could detect 100 pmol, the improved FMT reconstruction could detect 10 pmol and significantly improved signal localization. By using a finer sampling grid and increasing the exposure time, the sensitivity could be further improved to detect 0.5 pmol. Background signal was highest in the 670 nm channel and most prominent in the gastro-intestinal tract and in organs with high relative amounts of blood. In conclusion, we show that µCT-FMT allows sensitive and accurate assessment of fluorescence in deep tissue regions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Listening to membrane potential: photoacoustic voltage-sensitive dye recording.

PubMed

Zhang, Haichong K; Yan, Ping; Kang, Jeeun; Abou, Diane S; Le, Hanh N D; Jha, Abhinav K; Thorek, Daniel L J; Kang, Jin U; Rahmim, Arman; Wong, Dean F; Boctor, Emad M; Loew, Leslie M

2017-04-01

Voltage-sensitive dyes (VSDs) are designed to monitor membrane potential by detecting fluorescence changes in response to neuronal or muscle electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. By contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near-infrared light excitation and ultrasound detection. Here, we show that voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. We synthesized a near-infrared photoacoustic VSD (PA-VSD), whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model. A theoretical model accounts for how the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate PA voltage sensing but also emphasize the interplay of both fluorescence and absorbance properties in the design of optimized PA probes. Together, our results demonstrate PA sensing as a potential new modality for recording and external imaging of electrophysiological and neurochemical events in the brain.

Listening to membrane potential: photoacoustic voltage-sensitive dye recording

NASA Astrophysics Data System (ADS)

Zhang, Haichong K.; Yan, Ping; Kang, Jeeun; Abou, Diane S.; Le, Hanh N. D.; Jha, Abhinav K.; Thorek, Daniel L. J.; Kang, Jin U.; Rahmim, Arman; Wong, Dean F.; Boctor, Emad M.; Loew, Leslie M.

2017-04-01

Voltage-sensitive dyes (VSDs) are designed to monitor membrane potential by detecting fluorescence changes in response to neuronal or muscle electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. By contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near-infrared light excitation and ultrasound detection. Here, we show that voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. We synthesized a near-infrared photoacoustic VSD (PA-VSD), whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model. A theoretical model accounts for how the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate PA voltage sensing but also emphasize the interplay of both fluorescence and absorbance properties in the design of optimized PA probes. Together, our results demonstrate PA sensing as a potential new modality for recording and external imaging of electrophysiological and neurochemical events in the brain.

Intraoperative Detection of Superficial Liver Tumors by Fluorescence Imaging Using Indocyanine Green and 5-aminolevulinic Acid.

PubMed

Kaibori, Masaki; Matsui, Kosuke; Ishizaki, Morihiko; Iida, Hiroya; Okumura, Tadayoshi; Sakaguchi, Tatsuma; Inoue, Kentaro; Ikeura, Tsukasa; Asano, Hiroaki; Kon, Masanori

2016-04-01

Indocyanine green (ICG) and the porphyrin precursor 5-aminolevulinic acid (5-ALA) have been approved as fluorescence imaging agents in the clinical setting. This study evaluated the usefulness of fluorescence imaging with both ICG and 5-ALA for intraoperative identification of latent small liver tumors. There were 48 patients who had main tumors within 5 mm of the liver surface. 5-ALA hydrochloride was orally administered to patients 3 h before surgery. ICG had been intravenously injected within 14 days prior to surgery. Intraoperatively, after visual inspection, manual palpation and ultrasonography fluorescence images of the liver surface were obtained with ICG and 5-ALA prior to resection. With ICG, the sensitivity, specificity and accuracy for detecting the preoperatively identified main tumors were 96%, 50% and 94%, respectively. Twelve latent small tumors were newly detected on the liver surface using ICG, five of which proved to be carcinomas. With 5-ALA, the sensitivity, specificity and accuracy for detecting the main tumors were 57%, 100% and 58%, respectively. Five latent small tumors were newly detected using 5-ALA; all were carcinomas. Overall, five new tumors were detected by both ICG and 5-ALA fluorescence imaging; two were hepatocellular carcinomas (HCCs) and three were metastases of colorectal cancer. The sensitivity and specificity of ICG fluorescence imaging for main tumor detection were relatively high and low, respectively, but the opposite was true of 5-ALA imaging. Fluorescence imaging using 5-ALA may provide greater specificity in the detection of surface-invisible malignant liver tumors than using ICG fluorescence imaging alone. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Aptamer-based microspheres for highly sensitive protein detection using fluorescently-labeled DNA nanostructures.

PubMed

Han, Daehoon; Hong, Jinkee; Kim, Hyun Cheol; Sung, Jong Hwan; Lee, Jong Bum

2013-11-01

Many highly sensitive protein detection techniques have been developed and have played an important role in the analysis of proteins. Herein, we report a novel technique that can detect proteins sensitively and effectively using aptamer-based DNA nanostructures. Thrombin was used as a target protein and aptamer was used to capture fluorescent dye-labeled DNA nanobarcodes or thrombin on a microsphere. The captured DNA nanobarcodes were replaced by a thrombin and aptamer interaction. The detection ability of this approach was confirmed by flow cytometry with different concentrations of thrombin. Our detection method has great potential for rapid and simple protein detection with a variety of aptamers.

Highly Sensitive Ratiometric Fluorescent Sensor for Trinitrotoluene Based on the Inner Filter Effect between Gold Nanoparticles and Fluorescent Nanoparticles.

PubMed

Lu, Hongzhi; Quan, Shuai; Xu, Shoufang

2017-11-08

In this work, we developed a simple and sensitive ratiometric fluorescent assay for sensing trinitrotoluene (TNT) based on the inner filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent nanoparticles (RFNs), which was designed by hybridizing green emissive carbon dots (CDs) and red emissive quantum dots (QDs) into a silica sphere as a fluorophore pair. AuNPs in their dispersion state can be a powerful absorber to quench CDs, while the aggregated AuNPs can quench QDs in the IFE-based fluorescent assays as a result of complementary overlap between the absorption spectrum of AuNPs and emission spectrum of RFNs. As a result of the fact that TNT can induce the aggregation of AuNPs, with the addition of TNT, the fluorescent of QDs can be quenched, while the fluorescent of CDs would be recovered. Then, ratiometric fluorescent detection of TNT is feasible. The present IFE-based ratiometric fluorescent sensor can detect TNT ranging from 0.1 to 270 nM, with a detection limit of 0.029 nM. In addition, the developed method was successfully applied to investigate TNT in water and soil samples with satisfactory recoveries ranging from 95 to 103%, with precision below 4.5%. The simple sensing approach proposed here could improve the sensitivity of colorimetric analysis by changing the ultraviolet analysis to ratiometric fluorescent analysis and promote the development of a dual-mode detection system.

Ultra-sensitive fluorescent imaging-biosensing using biological photonic crystals

NASA Astrophysics Data System (ADS)

Squire, Kenny; Kong, Xianming; Wu, Bo; Rorrer, Gregory; Wang, Alan X.

2018-02-01

Optical biosensing is a growing area of research known for its low limits of detection. Among optical sensing techniques, fluorescence detection is among the most established and prevalent. Fluorescence imaging is an optical biosensing modality that exploits the sensitivity of fluorescence in an easy-to-use process. Fluorescence imaging allows a user to place a sample on a sensor and use an imager, such as a camera, to collect the results. The image can then be processed to determine the presence of the analyte. Fluorescence imaging is appealing because it can be performed with as little as a light source, a camera and a data processor thus being ideal for nontrained personnel without any expensive equipment. Fluorescence imaging sensors generally employ an immunoassay procedure to selectively trap analytes such as antigens or antibodies. When the analyte is present, the sensor fluoresces thus transducing the chemical reaction into an optical signal capable of imaging. Enhancement of this fluorescence leads to an enhancement in the detection capabilities of the sensor. Diatoms are unicellular algae with a biosilica shell called a frustule. The frustule is porous with periodic nanopores making them biological photonic crystals. Additionally, the porous nature of the frustule allows for large surface area capable of multiple analyte binding sites. In this paper, we fabricate a diatom based ultra-sensitive fluorescence imaging biosensor capable of detecting the antibody mouse immunoglobulin down to a concentration of 1 nM. The measured signal has an enhancement of 6× when compared to sensors fabricated without diatoms.

Spectroscopic quantification of 5-hydroxymethylcytosine in genomic DNA using boric acid-functionalized nano-microsphere fluorescent probes.

PubMed

Chen, Hua-Yan; Wei, Jing-Ru; Pan, Jiong-Xiu; Zhang, Wei; Dang, Fu-Quan; Zhang, Zhi-Qi; Zhang, Jing

2017-05-15

5-hydroxymethylcytosine (5hmC) is the sixth base of DNA. It is involved in active DNA demethylation and can be a marker of diseases such as cancer. In this study, we developed a simple and sensitive 2-(4-boronophenyl)quinoline-4-carboxylic acid modified poly (glycidyl methacrylate (PBAQA-PGMA) fluorescent probe to detect the 5hmC content of genomic DNA based on T4 β-glucosyltransferase-catalyzed glucosylation of 5hmC. The fluorescence-enhanced intensity recorded from the DNA sample was proportional to its 5-hydroxymethylcytosine content and could be quantified by fluorescence spectrophotometry. The developed probe showed good detection sensitivity and selectivity and a good linear relationship between the fluorescence intensity and the concentration of 5 hmC within a 0-100nM range. Compared with other fluorescence detection methods, this method not only could determine trace amounts of 5 hmC from genomic DNA but also could eliminate the interference of fluorescent dyes and the need for purification. It also could avoid multiple labeling. Because the PBAQA-PGMA probe could enrich the content of glycosyl-5-hydroxymethyl-2-deoxycytidine from a complex ground substance, it will broaden the linear detection range and improve sensitivity. The limit of detection was calculated to be 0.167nM after enrichment. Furthermore, the method was successfully used to detect 5-hydroxymethylcytosine from mouse tissues. Copyright © 2016 Elsevier B.V. All rights reserved.

Sensitivity enhancement of fluorescence detection in CE by coupling and conducting excitation light with tapered optical fiber.

PubMed

Yang, Xiupei; Huo, Feng; Yuan, Hongyan; Zhang, Bo; Xiao, Dan; Choi, Martin M F

2011-01-01

This paper reports the enhancement of sensitivity of detection for in-column fiber optic-induced fluorescence detection system in CE by tapered optical fiber (TOF). Two types of optical fiber, TOF and conventional cylindrical optical fiber (COF), were employed to construct the CE (TOF-CE and COF-CE) and were compared for sensitivity to riboflavin (RF). The fluorescence intensities from a RF sample with excitation light sources and fibers at various coupling angles were investigated. The fluorescence signal from TOF-CE was ca. ten times that of COF-CE. In addition, the detection performance of four excitation light source-fiber configurations including Laser-TOF, Laser-COF, LED-TOF, and LED-COF were compared. The LODs for RF were 0.21, 0.82, 0.80, and 7.5 nM, respectively, for the four excitation light source-fiber configurations. The results demonstrate that the sensitivity obtained by LED-TOF is close to that of Laser-COF. Both Laser-TOF and LED-TOF can greatly improve the sensitivity of detection in CE. TOF has the major attribute of collecting and focusing the excitation light intensity. Thus, the sensitivity obtained by LED-TOF without focusing lens is just same as that of LED-COF with a focusing lens. This demonstrates that the CE system can be further simplified by eliminating the focusing lens for excitation light. LED-TOF-CE and LED-COF-CE system were applied to the separation and determination of RF in real sample (green tea), respectively. The tapered fiber optic-induced fluorescence detection system in CE is an ideal tool for trace analysis. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanozyme-based bio-barcode assay for high sensitive and logic-controlled specific detection of multiple DNAs.

PubMed

Lin, Xiaodong; Liu, Yaqing; Tao, Zhanhui; Gao, Jinting; Deng, Jiankang; Yin, Jinjin; Wang, Shuo

2017-08-15

Since HCV and HIV share a common transmission path, high sensitive detection of HIV and HCV gene is of significant importance to improve diagnosis accuracy and cure rate at early stage for HIV virus-infected patients. In our investigation, a novel nanozyme-based bio-barcode fluorescence amplified assay is successfully developed for simultaneous detection of HIV and HCV DNAs with excellent sensitivity in an enzyme-free and label-free condition. Here, bimetallic nanoparticles, PtAu NPs , present outstanding peroxidase-like activity and act as barcode to catalyze oxidation of nonfluorescent substrate of amplex red (AR) into fluorescent resorufin generating stable and sensitive "Turn On" fluorescent output signal, which is for the first time to be integrated with bio-barcode strategy for fluorescence detection DNA. Furthermore, the provided strategy presents excellent specificity and can distinguish single-base mismatched mutant from target DNA. What interesting is that cascaded INHIBIT-OR logic gate is integrated with biosensors for the first time to distinguish individual target DNA from each other under logic function control, which presents great application in development of rapid and intelligent detection. Copyright © 2017. Published by Elsevier B.V.

Photonic crystal enhanced fluorescence immunoassay on diatom biosilica.

PubMed

Squire, Kenneth; Kong, Xianming; LeDuff, Paul; Rorrer, Gregory L; Wang, Alan X

2018-05-16

Fluorescence biosensing is one of the most established biosensing methods, particularly fluorescence spectroscopy and microscopy. These are two highly sensitive techniques but require high grade electronics and optics to achieve the desired sensitivity. Efforts have been made to implement these methods using consumer grade electronics and simple optical setups for applications such as point-of-care diagnostics, but the sensitivity inherently suffers. Sensing substrates, capable of enhancing fluorescence are thus needed to achieve high sensitivity for such applications. In this paper, we demonstrate a photonic crystal-enhanced fluorescence immunoassay biosensor using diatom biosilica, which consists of silica frustules with sub-100 nm periodic pores. Utilizing the enhanced local optical field, the Purcell effect and increased surface area from the diatom photonic crystals, we create ultrasensitive immunoassay biosensors that can significantly enhance fluorescence spectroscopy as well as fluorescence imaging. Using standard antibody-antigen-labeled antibody immunoassay protocol, we experimentally achieved 100× and 10× better detection limit with fluorescence spectroscopy and fluorescence imaging respectively. The limit of detection of the mouse IgG goes down to 10 -16 M (14 fg/mL) and 10 -15 M (140 fg/mL) for the two respective detection modalities, virtually sensing a single mouse IgG molecule on each diatom frustule. The effectively enhanced fluorescence imaging in conjunction with the simple hot-spot counting analysis method used in this paper proves the great potential of diatom fluorescence immunoassay for point-of-care biosensing. Scanning electron microscope image of biosilica diatom frustule that enables significant enhancement of fluorescence spectroscopy and fluorescence image. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

A highly sensitive protocol for microscopy of alkyne lipids and fluorescently tagged or immunostained proteins.

PubMed

Gaebler, Anne; Penno, Anke; Kuerschner, Lars; Thiele, Christoph

2016-10-01

The demand to study the cellular localization of specific lipids has led to recent advances in lipid probes and microscopy. Alkyne lipids bear a small, noninterfering tag and can be detected upon click reaction with an azide-coupled reporter. Fluorescent alkyne lipid imaging crucially depends on appropriate azide reporters and labeling protocols that allow for an efficient click reaction and therefore a sensitive detection. We synthesized several azide reporters with different spacer components and tested their suitability for alkyne lipid imaging in fixed cells. The implementation of a copper-chelating picolyl moiety into fluorescent or biotin-based azide reagents strongly increased the sensitivity of the imaging routine. We demonstrate the applicability and evaluate the performance of this approach using different lipid classes and experimental setups. As azide picolyl reporters allow for reduced copper catalyst concentrations, they also enable coimaging of alkyne lipids with multiple fluorescent proteins including enhanced green fluorescent protein. Alternatively, and as we also show, microscopy of alkyne lipids can be combined with protein detection by immunocytochemistry. In summary, we present a robust, sensitive, and highly versatile protocol for the labeling of alkyne lipids with azide-coupled reporters for fluorescence microscopy that can be combined with different protein detection and imaging techniques. Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.

Label free selective detection of estriol using graphene oxide-based fluorescence sensor

NASA Astrophysics Data System (ADS)

Kushwaha, H. S.; Sao, Reshma; Vaish, Rahul

2014-07-01

Water-soluble and fluorescent Graphene oxide (GO) is biocompatible, easy, and economical to synthesize. Interestingly, GO is also capable of quenching fluorescence. On the basis of its fluorescence and quenching abilities, GO has been reported to serve as an energy acceptor in a fluorescence resonance energy transfer (FRET) sensor. GO-based FRET biosensors have been widely reported for sensing of proteins, nucleic acid, ATP (Adenosine triphosphate), etc. GO complexes with fluorescent dyes and enzymes have been used to sense metal ions. Graphene derivatives have been used for sensing endocrine-disrupting chemicals like bisphenols and chlorophenols with high sensitivity and good reproducibility. On this basis, a novel GO based fluorescent sensor has been successfully designed to detect estriol with remarkable selectivity and sensitivity. Estriol is one of the three estrogens in women and is considered to be medically important. Estriol content of maternal urine or plasma acts as an important screening marker for estimating foetal growth and development. In addition, estriol is also used as diagnostic marker for diseases like breast cancer, osteoporosis, neurodegenerative and cardiovascular diseases, insulin resistance, lupus erythematosus, endometriosis, etc. In this present study, we report for the first time a rapid, sensitive with detection limit of 1.3 nM, selective and highly biocompatible method for label free detection of estriol under physiological conditions using fluorescence assay.

Detection of glucose-6-phosphate dehydrogenase deficiency in erythrocytes: a spectrophotometric assay and a fluorescent spot test compared with a cytochemical method.

PubMed

Wolf, B H; Weening, R S; Schutgens, R B; van Noorden, C J; Vogels, I M; Nagelkerke, N J

1987-09-30

The results of a quantitative spectrophotometric enzyme assay, a fluorescent spot test and a cytochemical assay for glucose-6-phosphate dehydrogenase deficiency were compared systematically. The high sensitivity of the spectrophotometric assay and the fluorescent spot test in the detection of severely deficient individuals was confirmed. For the detection of heterozygote females, however both tests were unreliable; the sensitivities of the fluorescent spot test and the spectrophotometric assay being 32% and 11% respectively. Specificities for both tests were high (99%). Introduction of the ratio of glucose-6-phosphate dehydrogenase and pyruvate kinase (G-6-PD/PK ratio) activities increased the sensitivity of the spectrophotometric assay to nearly 100%. It is concluded that the fluorescent spot test should be used for the diagnosis of G-6-PD deficiency in developing countries; whereas if spectrophotometric enzyme assays are available, the G-6-PD/PK ratio should always be performed. In cases where the ratio is less than 0.70, cytochemical analysis is indicated.

A practical and highly sensitive C3N4-TYR fluorescent probe for convenient detection of dopamine

NASA Astrophysics Data System (ADS)

Li, Hao; Yang, Manman; Liu, Juan; Zhang, Yalin; Yang, Yanmei; Huang, Hui; Liu, Yang; Kang, Zhenhui

2015-07-01

The C3N4-tyrosinase (TYR) hybrid is a highly accurate, sensitive and simple fluorescent probe for the detection of dopamine (DOPA). Under optimized conditions, the relative fluorescence intensity of C3N4-TYR is proportional to the DOPA concentration in the range from 1 × 10-3 to 3 × 10-8 mol L-1 with a correlation coefficient of 0.995. In the present system, the detection limit achieved is as low as 3 × 10-8 mol L-1. Notably, these quantitative detection results for clinical samples are comparable to those of high performance liquid chromatography. Moreover, the enzyme-encapsulated C3N4 sensing arrays on both glass slide and test paper were evaluated, which revealed sensitive detection and excellent stability. The results reported here provide a new approach for the design of a multifunctional nanosensor for the detection of bio-molecules.The C3N4-tyrosinase (TYR) hybrid is a highly accurate, sensitive and simple fluorescent probe for the detection of dopamine (DOPA). Under optimized conditions, the relative fluorescence intensity of C3N4-TYR is proportional to the DOPA concentration in the range from 1 × 10-3 to 3 × 10-8 mol L-1 with a correlation coefficient of 0.995. In the present system, the detection limit achieved is as low as 3 × 10-8 mol L-1. Notably, these quantitative detection results for clinical samples are comparable to those of high performance liquid chromatography. Moreover, the enzyme-encapsulated C3N4 sensing arrays on both glass slide and test paper were evaluated, which revealed sensitive detection and excellent stability. The results reported here provide a new approach for the design of a multifunctional nanosensor for the detection of bio-molecules. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03316k

A new high selective and sensitive turn-on fluorescent and ratiometric absorption chemosensor for Cu2+ based on benzimidazole in aqueous solution and its application in live cell.

PubMed

Bing, Qijing; Wang, Lin; Li, Donglin; Wang, Guang

2018-09-05

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu 2+ was designed and synthesized. Fluorescence and UV-vis spectra studies demonstrated that L can detect Cu 2+ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu 2+ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu 2+ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu 2+ displayed L had cell permeability and detection ability for Cu 2+ in live cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Thickness dependence of polydopamine thin films on detection sensitivity of surface plasmon-enhanced fluorescence biosensors

NASA Astrophysics Data System (ADS)

Toma, Mana; Tawa, Keiko

2018-03-01

A bioinspired polydopamine (PDA) coating is a good candidate for the rapid and cheap chemical modification of biosensor surfaces. Herein, we report the effect of PDA thickness on the detection sensitivity of a fluorescence biosensor utilizing surface plasmon-enhanced fluorescence. The thickness of PDA films was tuned by the incubation time of the dopamine solution and varied from 1 to 17 nm. The detection sensitivity was evaluated as the limit of detection (LOD) of a fluorescently labelled target analyte by a model immunoassay. The LOD was determined to be 1.6 pM for the thickest PDA film and was improved to 1.0 pM by reducing the thickness to the range from 1 to 5 nm, corresponding to the incubation time of 10 to 60 min. The experimental results indicate that the PDA coating is suitable for the surface functionalization of biosensors in mass production as it does not require precise control of the incubation time.

Highly selective and sensitive fluorescent paper sensor for nitroaromatic explosive detection.

PubMed

Ma, Yingxin; Li, Hao; Peng, Shan; Wang, Leyu

2012-10-02

Rapid, sensitive, and selective detection of explosives such as 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP), especially using a facile paper sensor, is in high demand for homeland security and public safety. Although many strategies have been successfully developed for the detection of TNT, it is not easy to differentiate the influence from TNP. Also, few methods were demonstrated for the selective detection of TNP. In this work, via a facile and versatile method, 8-hydroxyquinoline aluminum (Alq(3))-based bluish green fluorescent composite nanospheres were successfully synthesized through self-assembly under vigorous stirring and ultrasonic treatment. These polymer-coated nanocomposites are not only water-stable but also highly luminescent. Based on the dramatic and selective fluorescence quenching of the nanocomposites via adding TNP into the aqueous solution, a sensitive and robust platform was developed for visual detection of TNP in the mixture of nitroaromatics including TNT, 2,4-dinitrotoluene (DNT), and nitrobenzene (NB). Meanwhile, the fluorescence intensity is proportional to the concentration of TNP in the range of 0.05-7.0 μg/mL with the 3σ limit of detection of 32.3 ng/mL. By handwriting or finger printing with TNP solution as ink on the filter paper soaked with the fluorescent nanocomposites, the bluish green fluorescence was instantly and dramatically quenched and the dark patterns were left on the paper. Therefore, a convenient and rapid paper sensor for TNP-selective detection was fabricated.

A PDMS-based cylindrical hybrid lens for enhanced fluorescence detection in microfluidic systems.

PubMed

Lin, Bor-Shyh; Yang, Yu-Ching; Ho, Chong-Yi; Yang, Han-Yu; Wang, Hsiang-Yu

2014-02-13

Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of fluorescence detection. However, these strategies encounter common issues of complex manufacturing processes and high costs. In this study; a miniature, cylindrical and hybrid lens made of polydimethylsiloxane (PDMS) to improve the fluorescence detection in microfluidic systems is proposed. The hybrid lens integrates a laser focusing lens and a fluorescence collecting lens to achieve dual functions and simplify optical setup. Moreover, PDMS has advantages of low-cost and straightforward fabrication compared with conventional optical components. The performance of the proposed lens is first examined with two fluorescent dyes and the results show that the lens provides satisfactory enhancement for fluorescence detection of Rhodamine 6G and Nile Red. The overall increments in collected fluorescence signal and detection sensitivity are more than 220% of those without lens, and the detection limits of Rhodamine 6G and Nile red are lowered to 0.01 μg/mL and 0.05 μg/mL, respectively. The hybrid lens is further applied to the detection of Nile red-labeled Chlorella vulgaris cells and it increases both signal intensity and detection sensitivity by more than 520%. The proposed hybrid lens also dramatically reduces the variation in detected signal caused by the deviation in incident angle of excitation light.

Detection of reactive oxygen species in mainstream cigarette smoke by a fluorescent probe

NASA Astrophysics Data System (ADS)

Liu, Li; Xu, Shi-jie; Li, Song-zhan

2009-07-01

A mass of reactive oxygen species(ROS) are produced in the process of smoking. Superfluous ROS can induce the oxidative stress in organism, which will cause irreversible damage to cells. Fluorescent probe is taken as a marker of oxidative stress in biology and has been applied to ROS detection in the field of biology and chemistry for high sensitivity, high simplicity of data collection and high resolution. As one type of fluorescent probe, dihydrorhodamine 6G (dR6G) will be oxidized to the fluorescent rhodamine 6G, which could be used to detect ROS in mainstream cigarette smoke. We investigated the action mechanism of ROS on dR6G, built up the standard curve of R6G fluorescence intensity with its content, achieved the variation pattern of R6G fluorescence intensity with ROS content in mainstream cigarette smoke and detected the contents of ROS from the 4 types of cigarettes purchased in market. The result shows that the amount of ROS has close relationship with the types of tobacco and cigarette production technology. Compared with other detecting methods such as electronic spin resonance(ESR), chromatography and mass spectrometry, this detection method by the fluorescent probe has higher efficiency and sensitivity and will have wide applications in the ROS detection field.

Differential fluorescent staining method for detection of bacteria in blood cultures, cerebrospinal fluid and other clinical specimens.

PubMed

Fazii, P; Ciancaglini, E; Riario Sforza, G

2002-05-01

The aim of this study was to evaluate a differential staining method to distinguish gram-positive from gram-negative bacteria in fluorescence. The method is based on two fluorochromes, one acting in the wavelength of red, i.e. the acridine orange, and another acting in the wavelength of green, i.e. the fluorescein. With this method, gram-positive bacteria appear yellow and gram-negative bacteria appear green. In view of the importance of a rapid aetiological diagnosis in cases of septicaemia, the differential staining method in fluorescence was compared with Gram stain for the detection of bacteria in blood. Of 5,820 blood cultures entered into the study and identified by the Bactec 9120 fluorescent series instrument (Becton Dickinson Europe, France), 774 were positive. Of the 774 positive cultures, 689 yielded only a single organism. The differential staining method in fluorescence detected 626 of the 689 cultures, while Gram stain detected 468. On the basis of these results, the sensitivity of the differential staining method in fluorescence was 90.9%, while that of Gram stain was 67.9%. The difference between the two methods was statistically significant ( P<0.001). The differential fluorescent staining method was more sensitive than Gram stain in the detection of bacteria in blood cultures during the incubation period. This technique provides a rapid, simple and highly sensitive staining method that can be used in conjunction with subculture methods. Whereas subculture requires an incubation period of 18-24 h, the fluorescent staining technique can detect bacteria on the same day that smears are prepared and examined. The differential fluorescent staining method was also evaluated for its ability to detect microorganisms in cerebrospinal fluid and other clinical specimens. The microorganisms were easily detected, even when bacterial counts in the specimens were low.

Status of miniature integrated UV resonance fluorescence and Raman sensors for detection and identification of biochemical warfare agents

NASA Astrophysics Data System (ADS)

Hug, William F.; Bhartia, Rohit; Taspin, Alexandre; Lane, Arthur; Conrad, Pamela; Sijapati, Kripa; Reid, Ray D.

2005-11-01

Laser induced native fluorescence (LINF) is the most sensitive method of detection of biological material including microorganisms, virus', and cellular residues. LINF is also a sensitive method of detection for many non-biological materials as well. The specificity with which these materials can be classified depends on the excitation wavelength and the number and location of observation wavelengths. Higher levels of specificity can be obtained using Raman spectroscopy but a much lower levels of sensitivity. Raman spectroscopy has traditionally been employed in the IR to avoid fluorescence. Fluorescence rarely occurs at wavelength below about 270nm. Therefore, when excitation occurs at a wavelength below 250nm, no fluorescence background occurs within the Raman fingerprint region for biological materials. When excitation occurs within electronic resonance bands of the biological target materials, Raman signal enhancement over one million typically occurs. Raman sensitivity within several hundred times fluorescence are possible in the deep UV where most biological materials have strong absorption. Since the Raman and fluorescence emissions occur at different wavelength, both spectra can be observed simultaneously, thereby providing a sensor with unique sensitivity and specificity capability. We will present data on our integrated, deep ultraviolet, LINF/Raman instruments that are being developed for several applications including life detection on Mars as well as biochemical warfare agents on Earth. We will demonstrate the ability to discriminate organic materials based on LINF alone. Together with UV resonance Raman, higher levels of specificity will be demonstrated. In addition, these instruments are being developed as on-line chemical sensors for industrial and municipal waste streams and product quality applications.

Towards sensitive, high-throughput, biomolecular assays based on fluorescence lifetime

NASA Astrophysics Data System (ADS)

Ioanna Skilitsi, Anastasia; Turko, Timothé; Cianfarani, Damien; Barre, Sophie; Uhring, Wilfried; Hassiepen, Ulrich; Léonard, Jérémie

2017-09-01

Time-resolved fluorescence detection for robust sensing of biomolecular interactions is developed by implementing time-correlated single photon counting in high-throughput conditions. Droplet microfluidics is used as a promising platform for the very fast handling of low-volume samples. We illustrate the potential of this very sensitive and cost-effective technology in the context of an enzymatic activity assay based on fluorescently-labeled biomolecules. Fluorescence lifetime detection by time-correlated single photon counting is shown to enable reliable discrimination between positive and negative control samples at a throughput as high as several hundred samples per second.

Synchronous fluorescence based biosensor for albumin determination by cooperative binding of fluorescence probe in a supra-biomolecular host-protein assembly.

PubMed

Patra, Digambara

2010-01-15

A synchronous fluorescence probe based biosensor for estimation of albumin with high sensitivity and selectivity was developed. Unlike conventional fluorescence emission or excitation spectral measurements, synchronous fluorescence measurement offered exclusively a new synchronous fluorescence peak in the shorter wavelength range upon binding of chrysene with protein making it an easy identification tool for albumin determination. The cooperative binding of a fluorescence probe, chrysene, in a supramolecular host-protein assembly during various albumin assessments was investigated. The presence of supramolecular host molecules such as beta-cyclodextrin, curucurbit[6]uril or curucurbit[7]uril have little influence on sensitivity or limit of detection during albumin determination but reduced dramatically interference from various coexisting metal ion quenchers/enhancers. Using the present method the limit of detection for BSA and gamma-Globulin was found to be 0.005 microM which is more sensitive than reported values. Copyright 2009 Elsevier B.V. All rights reserved.

NIR-induced highly sensitive detection of latent finger-marks by NaYF4:Yb,Er upconversion nanoparticles in a dry powder state

PubMed Central

Wang, Meng; Li, Ming; Yang, Mingying; Zhang, Xiaomei; Yu, Aoyang; Zhu, Ye; Qiu, Penghe; Mao, Chuanbin

2016-01-01

The most commonly found fingermarks at crime scenes are latent and, thus, an efficient method for detecting latent fingermarks is very important. However, traditional developing techniques have drawbacks such as low detection sensitivity, high background interference, complicated operation, and high toxicity. To tackle this challenge, we employed fluorescent NaYF4:Yb,Er upconversion nanoparticles (UCNPs), which can fluoresce visible light when excited by 980 nm human-safe near-infrared light, to stain the latent fingermarks on various substrate surfaces. The UCNPs were successfully used as a novel fluorescent label for the detection of latent fingermarks with high sensitivity, low background, high efficiency, and low toxicity on various substrates including non-infiltrating materials (glass, marble, aluminum alloy sheets, stainless steel sheets, aluminum foils, and plastic cards), semi-infiltrating materials (floor leathers, ceramic tiles, wood floor, and painted wood), and infiltrating materials such as various types of papers. This work shows that UCNPs are a versatile fluorescent label for the facile detection of fingermarks on virtually any material, enabling their practical applications in forensic sciences. PMID:27818741

Ultra-Sensitive Detection of Prion Protein in Blood Using Isothermal Amplification Technology

DTIC Science & Technology

2005-12-01

cattle products are admitted into the food chain, the Western Blot or ELISA in an antigen detection format are used to test the bovine brain stems...the most sensitive fluorescent dye (SYBR Green I, SYBR Green II, or SYBR Gold) detection of transcription products using real-time technology...RNA products from ug quantities of DNA template. Figure 3 shows that SYBR Green II exhibited higher relative fluorescence units (RFU) than SYBR

A highly sensitive and selective aptasensor based on graphene oxide fluorescence resonance energy transfer for the rapid determination of oncoprotein PDGF-BB.

PubMed

Liang, Junfei; Wei, Ran; He, Shuai; Liu, Yikan; Guo, Lin; Li, Lidong

2013-03-21

Oncoprotein platelet derived growth factor-BB (PDGF-BB) is one of the most critical growth factors that regulates tumor growth and division. In this work, a highly sensitive and selective fluorescence resonance energy transfer (FRET) aptasensor for PDGF-BB detection based on the assembly of dye-labeled aptamer and graphene oxide (GO) is developed for the first time. Due to the non-covalent assembly between aptamer and GO, fluorescence quenching of the dye takes place because of FRET. In the presence of PDGF-BB, the binding between aptamer and PDGF-BB will disturb the interaction between aptamer and GO, and release the dye-labeled aptamer from the GO surface, resulting in restoration of the fluorophore fluorescence. Because of the high fluorescence quenching efficiency, unique structure, and electronic properties of GO, the GO aptasensor exhibits extraordinarily high sensitivity. We also demonstrate that two highly related molecular variants of PDGF (AA, AB) can be distinguished from PDGF-BB, which indicates the aptasensor has excellent selectivity. Such an aptasensor opens a rapid, selective and sensitive route for the detection of PDGF-BB and provides a promising strategy for other cancer-related proteins detections.

Highly sensitive low-background fluorescent probes for imaging of nitric oxide in cells and tissues.

PubMed

Zhang, Hui-Xian; Chen, Jian-Bo; Guo, Xiao-Feng; Wang, Hong; Zhang, Hua-Shan

2014-03-18

Small-molecule fluorescent probes in combination with fluorescent microscopy can be a powerful tool to provide real-time detection and high spatiotemporal resolution of transient molecules in cells and bodies. For the design of fluorescent probes for transient molecule imaging, high detection sensitivity is crucial. In this report, two new fluorescent probes, 8-(3,4-diaminophenyl)-4,4-difluoro-4-bora-3a,4a-diaza-di(1,2-dihydro)naphtho[b,g]-s-indacene (DANPBO-H) and 8-(3,4-diaminophenyl)-1,7-dimethyl-4,4-difluoro-4-bora-3a,4a-diaza-di(1,2-dihydro)naphtho[b,g]-s-indacene (DANPBO-M), have been developed for nitric oxide (NO) imaging. The detection sensitivity has been efficiently improved by use of these probes through increasing NO detection signals and decreasing background fluorescence. Fluorescence in the far-red region is enhanced by 400- and 550-fold after reaction with NO is achieved and remains stable for at least 24 h under the irradiation of xenon lamp. Excitation and emission wavelengths longer than 600 nm and excellent intracellular retention of these probes and their NO products create dark background inside and outside cells and tissues. What is more, the excellent intracellular retention of these compounds is obtained by their strong lipophilicity, which is a novel design concept diametrically opposite to the traditional approaches. The high sensitivity and dark background make DANPBO-H and DANPBO-M competitive for NO imaging in cells and tissues. The lipophilicity-based intracellular retention mechanism as a design strategy has great potential in the development of fluorescent probes for bioimaging.

Sensitive spectroscopic detection of large and denatured protein aggregates in solution by use of the fluorescent dye Nile red.

PubMed

Sutter, Marc; Oliveira, Sabrina; Sanders, Niek N; Lucas, Bart; van Hoek, Arie; Hink, Mark A; Visser, Antonie J W G; De Smedt, Stefaan C; Hennink, Wim E; Jiskoot, Wim

2007-03-01

The fluorescent dye Nile red was used as a probe for the sensitive detection of large, denatured aggregates of the model protein beta-galactosidase (E. coli) in solution. Aggregates were formed by irreversible heat denaturation of beta-galactosidase below and above the protein's unfolding temperature of 57.4 degrees C, and the presence of aggregates in heated solutions was confirmed by static light scattering. Interaction of Nile red with beta-galactosidase aggregates led to a shift of the emission maximum (lambda (max)) from 660 to 611 nm, and to an increase of fluorescence intensity. Time-resolved fluorescence and fluorescence correlation spectroscopy (FCS) measurements showed that Nile red detected large aggregates with hydrodynamic radii around 130 nm. By steady-state fluorescence measurements, it was possible to detect 1 nM of denatured and aggregated beta-galactosidase in solution. The comparison with size exclusion chromatography (SEC) showed that native beta-galactosidase and small aggregates thereof had no substantial effect on the fluorescence of Nile red. Large aggregates were not detected by SEC, because they were excluded from the column. The results with beta-galactosidase demonstrate the potential of Nile red for developing complementary analytical methods that overcome the size limitations of SEC, and can detect the formation of large protein aggregates at early stages.

Dual Recognition Strategy for Specific and Sensitive Detection of Bacteria Using Aptamer-Coated Magnetic Beads and Antibiotic-Capped Gold Nanoclusters.

PubMed

Cheng, Dan; Yu, Mengqun; Fu, Fei; Han, Weiye; Li, Gan; Xie, Jianping; Song, Yang; Swihart, Mark T; Song, Erqun

2016-01-05

Food poisoning and infectious diseases caused by pathogenic bacteria such as Staphylococcus aureus (SA) are serious public health concerns. A method of specific, sensitive, and rapid detection of such bacteria is essential and important. This study presents a strategy that combines aptamer and antibiotic-based dual recognition units with magnetic enrichment and fluorescent detection to achieve specific and sensitive quantification of SA in authentic specimens and in the presence of much higher concentrations of other bacteria. Aptamer-coated magnetic beads (Apt-MB) were employed for specific capture of SA. Vancomycin-stabilized fluorescent gold nanoclusters (AuNCs@Van) were prepared by a simple one-step process and used for sensitive quantification of SA in the range of 32-10(8) cfu/mL with the detection limit of 16 cfu/mL via a fluorescence intensity measurement. And using this strategy, about 70 cfu/mL of SA in complex samples (containing 3 × 10(8) cfu/mL of other different contaminated bacteria) could be successfully detected. In comparison to prior studies, the developed strategy here not only simplifies the preparation procedure of the fluorescent probes (AuNCs@Van) to a great extent but also could sensitively quantify SA in the presence of much higher concentrations of other bacteria directly with good accuracy. Moreover, the aptamer and antibiotic used in this strategy are much less expensive and widely available compared to common-used antibodies, making it cost-effective. This general aptamer- and antibiotic-based dual recognition strategy, combined with magnetic enrichment and fluorescent detection of trace bacteria, shows great potential application in monitoring bacterial food contamination and infectious diseases.

Oligonucleotide-stabilized fluorescent silver nanoclusters for the specific and sensitive detection of biotin.

PubMed

Xiong, Xiaoli; Tang, Yan; Zhao, Jingjin; Zhao, Shulin

2016-02-21

A novel biotin fluorescent probe based on oligonucleotide-stabilized silver nanoclusters (DNA-AgNCs) was synthesized by employing a biotinylated cytosine-rich sequence as a synthesized template. The fluorescence properties of the DNA-AgNCs are related to the modified position of the DNA. When biotin is linked to the middle thymine base of the DNA sequence, the DNA-AgNCs emit the strongest fluorescence. Moreover, the stability of the DNA-AgNCs was affected by avidin through biotin-avidin binding, quenching the fluorescence of the DNA-AgNCs. In contrast, if free biotin is further introduced into this system, the quenching is apparently weakened by competition, leading to the restoration of fluorescence. This phenomenon can be utilized for the detection of biotin. Under the optimal conditions, the fluorescence recovery is linearly proportional to the concentration of biotin in the range of 10 nM-1.0 μM with a detection limit of 6.0 nM. This DNA-AgNCs probe with excellent fluorescent properties is sensitive and selective for the detection of biotin and has been applied for the determination of biotin in wheat flour.

An ATMND/SGI based label-free and fluorescence ratiometric aptasensor for rapid and highly sensitive detection of cocaine in biofluids.

PubMed

Wang, Jiamian; Song, Jie; Wang, Xiuyun; Wu, Shuo; Zhao, Yanqiu; Luo, Pinchen; Meng, Changgong

2016-12-01

A label-free ratiometric fluorescence aptasensor has been developed for the rapid and sensitive detection of cocaine in complex biofluids. The fluorescent aptasensor is composed of a non-labeled GC-38 cocaine aptamer which serves as a basic sensing unit and two fluorophores, 2-amino-5,6,7-trimethyl-1,8-naphthyridine (ATMND) and SYBR Green I (SGI) which serves as a signal reporter and a build-in reference, respectively. The detection principle is based on a specific cocaine mediated ATMND displacement reaction and the corresponding change in the fluorescence ratio of ATMND to SGI. Due to the high affinity of the non-labeled aptamer, the good precision originated from the ratiometric method, and the good fluorescence quantum yield of the fluorophore, the aptasensor shows good analytical performance with respect to cocaine detection. Under optimal conditions, the aptasensor shows a linear range of 0.10-10μM and a low limit of detection of 56nM, with a fast response of 20s. The low limit of detection is comparable to most of the fluorescent aptasensors with signal amplification strategies and much lower than all of the unamplified cocaine aptasensors. Practical sample analysis in a series of complex biofluids, including urine, saliva and serum, also indicates the good precision, stability, and high sensitivity of the aptasensor, which may have great potential for the point-of-care screening of cocaine in complex biofluids. Copyright © 2016 Elsevier B.V. All rights reserved.

An ultra-sensitive monoclonal antibody-based fluorescent microsphere immunochromatographic test strip assay for detecting aflatoxin M1 in milk

USDA-ARS?s Scientific Manuscript database

A rapid lateral flow fluorescent microspheres immunochromatography test strip (FMs-ICTS) has been developed for the detection of aflatoxin M1 (AFM1) residues in milk. For this purpose, an ultra-sensitive anti-AFM1 monoclonal antibody (MAb) 1D3 was prepared and identified. The IC50 value of the MA...

Mercaptosuccinic acid-coated NIR-emitting gold nanoparticles for the sensitive and selective detection of Hg2.

PubMed

Xiong, Xiaodong; Lai, Xiaoqi; Liu, Jinbin

2018-01-05

A sensitive fluorescent detection platform for Hg 2+ was constructed based on mercaptosuccinic acid (MSA) coated near-infrared (NIR)-emitting gold nanoparticles (AuNPs). The thiolated mercaptosuccinic acid was employed as both reducing agent and surface coating ligand in a one-step synthesis of NIR-emitting AuNPs (MSA-AuNPs), which exhibited stable fluorescence with the maximum wavelength at 800nm and a wide range of excitation (220-650nm) with the maxima at 413nm. The MSA coated NIR-emitting AuNPs showed a rapid fluorescence quenching toward Hg 2+ over other metal ions with a limit of detection (LOD, 3δ) as low as 4.8nM. The sensing mechanism investigation revealed that the AuNPs formed aggregation due to the "recognition" of Hg 2+ from the MSA, and the resultant strong coupling interaction between Hg 2+ and Au (I) to further quench the fluorescence of the AuNPs, which synergistically resulted in a highly sensitive and selective fluorescence response toward Hg 2+ . This proposed strategy was also demonstrated the possibility to be used for Hg 2+ detection in water samples. Copyright © 2017. Published by Elsevier B.V.

Mercaptosuccinic acid-coated NIR-emitting gold nanoparticles for the sensitive and selective detection of Hg2 +

NASA Astrophysics Data System (ADS)

Xiong, Xiaodong; Lai, Xiaoqi; Liu, Jinbin

2018-01-01

A sensitive fluorescent detection platform for Hg2 + was constructed based on mercaptosuccinic acid (MSA) coated near-infrared (NIR)-emitting gold nanoparticles (AuNPs). The thiolated mercaptosuccinic acid was employed as both reducing agent and surface coating ligand in a one-step synthesis of NIR-emitting AuNPs (MSA-AuNPs), which exhibited stable fluorescence with the maximum wavelength at 800 nm and a wide range of excitation (220-650 nm) with the maxima at 413 nm. The MSA coated NIR-emitting AuNPs showed a rapid fluorescence quenching toward Hg2 + over other metal ions with a limit of detection (LOD, 3δ) as low as 4.8 nM. The sensing mechanism investigation revealed that the AuNPs formed aggregation due to the "recognition" of Hg2 + from the MSA, and the resultant strong coupling interaction between Hg2 + and Au (I) to further quench the fluorescence of the AuNPs, which synergistically resulted in a highly sensitive and selective fluorescence response toward Hg2 +. This proposed strategy was also demonstrated the possibility to be used for Hg2 + detection in water samples.

A novel near-infrared fluorescent probe for sensitive detection of β-galactosidase in living cells.

PubMed

Zhang, Jingtuo; Li, Cong; Dutta, Colina; Fang, Mingxi; Zhang, Shuwei; Tiwari, Ashutosh; Werner, Thomas; Luo, Fen-Tair; Liu, Haiying

2017-05-22

A novel near-infrared fluorescent probe for β-galactosidase has been developed based on a hemicyanine skeleton, which is conjugated with a d-galactose residue via a glycosidic bond. The probe serves as a substrate of β-galactosidase and displays rapid and sensitive turn-on fluorescent responses to β-galactosidase in aqueous solution. A 12.8-fold enhancement of fluorescence intensity at 703 nm was observed after incubation of 10 nM of β-galactosidase with 5 μM probe for 10 min. The probe can sensitively detect as little as 0.1 nM of β-galactosidase and shows linear responses to the enzyme concentration below 1.4 nM. The kinetic study showed that the probe has high binding affinity to β-galactosidase with K m  = 3.6 μM. The probe was used to detect β-galactosidase in living cells by employing the premature cell senescence model. The probe exhibited strong fluorescent signals in senescent cells but not in normal cells, which demonstrates that the probe is able to detect the endogenous senescence-associated β-galactosidase in living cells. Copyright © 2017 Elsevier B.V. All rights reserved.

Sensitive, label-free protein assay using 1-ethyl-3-methylimidazolium tetrafluoroborate-supported microchip electrophoresis with laser-induced fluorescence detection.

PubMed

Xu, Yuanhong; Li, Jing; Wang, Erkang

2008-05-01

Based on the dimer-monomer equilibrium movement of the fluorescent dye Pyronin Y (PY), a rapid, simple, highly sensitive, label-free method for protein detection was developed by microchip electrophoresis with LIF detection. PY formed a nonfluorescent dimer induced by the premicellar aggregation of an anionic surfactant, SDS, however, the fluorescence intensity of the system increased dramatically when proteins such as BSA, bovine hemoglobin, cytochrome c, and trypsin were added to the solution due to the transition of dimer to fluorescent monomer. Furthermore, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) instead of PBS was applied as running buffers in microchip electrophoresis. Due to the excellent properties of EMImBF4, not only nonspecific protein adsorption was more efficiently suppressed, but also approximately ten-fold higher fluorescence intensity enhancement was obtained than that using PBS. Under the optimal conditions, detection limits for BSA, bovine hemoglobin, cytochrome c, and trypsin were 1.00x10(-6), 2x10(-6), 7x10(-7), and 5x10(-7) mg/mL, respectively. Thus, without covalent modification of the protein, a protein assay method with high sensitivity was achieved on microchips.

Fluorescence detection system for microfluidic droplets

NASA Astrophysics Data System (ADS)

Chen, Binyu; Han, Xiaoming; Su, Zhen; Liu, Quanjun

2018-05-01

In microfluidic detection technology, because of the universality of optical methods in laboratory, optical detection is an attractive solution for microfluidic chip laboratory equipment. In addition, the equipment with high stability and low cost can be realized by integrating appropriate optical detection technology on the chip. This paper reports a detection system for microfluidic droplets. Photomultiplier tubes (PMT) is used as a detection device to improve the sensitivity of detection. This system improves the signal to noise ratio by software filtering and spatial filter. The fluorescence intensity is proportional to the concentration of the fluorescence and intensity of the laser. The fluorescence micro droplets of different concentrations can be distinguished by this system.

Colorimetric and fluorescent detection of hydrazine with high sensitivity and excellent selectivity

NASA Astrophysics Data System (ADS)

Shi, Bingjie; Qi, Sujie; Yu, Mingming; Liu, Chunxia; Li, Zhanxian; Wei, Liuhe; Ni, Zhonghai

2018-01-01

It is critical to develop probes for rapid, selective, and sensitive detection of the highly toxic hydrazine in both environmental and biological science. In this work, under mild condition, a novel colorimetric and off-on fluorescent probe was synthesized for rapid recognition of hydrazine with excellent selectivity over other various species including some biological species, metal ions and anions. The limit of quantification (LOQ) value was 1.5 × 10- 4 M-3.2 × 10- 3 M (colorimetric method) and 1.5 × 10- 4 M - 3.2 × 10- 3 M (fluorescent method) with as low as detection limit of 46.2 μM.

Laser-induced fluorescence detection strategies for sodium atoms and compounds in high-pressure combustors

NASA Technical Reports Server (NTRS)

Weiland, Karen J. R.; Wise, Michael L.; Smith, Gregory P.

1993-01-01

A variety of laser-induced fluorescence schemes were examined experimentally in atmospheric pressure flames to determine their use for sodium atom and salt detection in high-pressure, optically thick environments. Collisional energy transfer plays a large role in fluorescence detection. Optimum sensitivity, at the parts in 10 exp 9 level for a single laser pulse, was obtained with the excitation of the 4p-3s transition at 330 nm and the detection of the 3d-3p fluorescence at 818 nm. Fluorescence loss processes, such as ionization and amplified spontaneous emission, were examined. A new laser-induced atomization/laser-induced fluorescence detection technique was demonstrated for NaOH and NaCl. A 248-nm excimer laser photodissociates the salt molecules present in the seeded flames prior to atom detection by laser-induced fluorescence.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Gangadhar, E-mail: gdas@rrcat.gov.in; Tiwari, M. K.; Singh, A. K.

The Compton and elastic scattering radiations are the major contributor to the spectral background of an x-ray fluorescence spectrum, which eventually limits the element detection sensitivities of the technique to µg/g (ppm) range. In the present work, we provide a detail mathematical descriptions and show that how polarization properties of the synchrotron radiation influence the spectral background in the x-ray fluorescence technique. We demonstrate our theoretical understandings through experimental observations using total x-ray fluorescence measurements on standard reference materials. Interestingly, the azimuthal anisotropy of the scattered radiation is shown to have a vital role on the significance of the x-raymore » fluorescence detection sensitivities.« less

Highly selective and sensitive nanoprobes for cyanide based on gold nanoclusters with red fluorescence emission

NASA Astrophysics Data System (ADS)

Zhang, Guomei; Qiao, Yunyun; Xu, Ting; Zhang, Caihong; Zhang, Yan; Shi, Lihong; Shuang, Shaomin; Dong, Chuan

2015-07-01

We report a novel and environmentally friendly fluorescent probe for detecting the cyanide ion (CN-) using l-amino acid oxidase (LAAOx)-protected Au nanoclusters (LAAOx@AuNCs) with red emission. The fluorescence-based sensing behaviour of LAAOx@AuNCs towards anions was investigated in buffered aqueous media. Among the anions studied, CN- was found to effectively quench the fluorescence emission of AuNCs based on CN- induced Au core decomposition. Excellent sensitivity and selectivity toward the detection of CN- in aqueous solution were observed. The CN- detection limit was determined to be approximately 180 nM, which is 15 times lower than the maximum level (2700 nM) of CN- in drinking water permitted by the World Health Organization (WHO). A linear relationship between the fluorescence intensity and CN- concentration was observed in two ranges of CN- concentration, including 3.2 × 10-6 to 3.4 × 10-5 mol L-1 and 3.81 × 10-5 to 1.04 × 10-4 mol L-1. The high sensitivity and selectivity to CN- among the 17 types of anions make the AuNCs good candidates for use in fluorescent nanoprobes of CN-.

Immuno-magnetic beads-based extraction-capillary zone electrophoresis-deep UV laser-induced fluorescence analysis of erythropoietin.

PubMed

Wang, Heye; Dou, Peng; Lü, Chenchen; Liu, Zhen

2012-07-13

Erythropoietin (EPO) is an important glycoprotein hormone. Recombinant human EPO (rhEPO) is an important therapeutic drug and can be also used as doping reagent in sports. The analysis of EPO glycoforms in pharmaceutical and sports areas greatly challenges analytical scientists from several aspects, among which sensitive detection and effective and facile sample preparation are two essential issues. Herein, we investigated new possibilities for these two aspects. Deep UV laser-induced fluorescence detection (deep UV-LIF) was established to detect the intrinsic fluorescence of EPO while an immuno-magnetic beads-based extraction (IMBE) was developed to specifically extract EPO glycoforms. Combined with capillary zone electrophoresis (CZE), CZE-deep UV-LIF allows high resolution glycoform profiling with improved sensitivity. The detection sensitivity was improved by one order of magnitude as compared with UV absorbance detection. An additional advantage is that the original glycoform distribution can be completely preserved because no fluorescent labeling is needed. By combining IMBE with CZE-deep UV-LIF, the overall detection sensitivity was 1.5 × 10⁻⁸ mol/L, which was enhanced by two orders of magnitude relative to conventional CZE with UV absorbance detection. It is applicable to the analysis of pharmaceutical preparations of EPO, but the sensitivity is insufficient for the anti-doping analysis of EPO in blood and urine. IMBE can be straightforward and effective approach for sample preparation. However, antibodies with high specificity were the key for application to urine samples because some urinary proteins can severely interfere the immuno-extraction. Copyright © 2012 Elsevier B.V. All rights reserved.

Extremely fast and highly selective detection of nitroaromatic explosive vapours using fluorescent polymer thin films.

PubMed

Demirel, Gokcen Birlik; Daglar, Bihter; Bayindir, Mehmet

2013-07-14

A novel sensing material based on pyrene doped polyethersulfone worm-like structured thin film is developed using a facile technique for detection of nitroaromatic explosive vapours. The formation of π-π stacking in the thin fluorescent film allows a highly sensitive fluorescence quenching which is detectable by the naked eye in a response time of a few seconds.

A "turn-on" fluorescent sensor for ozone detection in ambient air using protein-directed gold nanoclusters.

PubMed

Wu, Di; Qi, Wenjing; Liu, Chun; Zhang, Qing

2017-04-01

A "turn-on" fluorescent sensor for ozone using bovine serum albumin-directed gold nanoclusters (BSA-Au NCs) via energy transfer was developed. The spectral overlap of fluorescent spectrum of BSA-Au NCs with absorption spectrum of indigo carmine (IDS) was utilized. Ozone cleaves C = C bond of IDS and suppresses energy transfer from BSA-Au NCs to IDS. Therefore, this proposed fluorescent sensor is a "turn-on" detection motif. It is the first application of fluorescent nanoclusters in sensitively detecting ozone from 0.2 to 12 μM with the limit of detection of 35 nM (the volume of 500 μL, 1.68 ppb). The proposed fluorescent sensor for ozone is more sensitive and faster (within 2 min) than most methods and is with good selectivity for ozone detection against other reactive oxygen species, reactive nitrogen, or metallic ions. Besides, the proposed method is also utlized in ozone detection in ambient air by monitoring 1 h (60 min) in Qijiang district in Chongqing city. The average of concentration of ozone in ambient air ranges from 44.97 to 52.85 μg/m 3 . The results are compared with the automatic monitoring data provided by Qijiang Environmental Monitoring Station and the relative deviations range, respectively, from 2.1 to 5.6%, which suggests that it is a promising fluorescent sensor for ozone in ambient air. This study not only develops a new model of energy transfer motif using BSA-Au NCs as donor and IDS as acceptor but also expands the application of BSA-Au NCs in environmental science. Graphical abstract A "turn-on" fluorescent sensor for ozone detection using bovine serum albumin-directed gold nanoclusters (BSA-Au NCs) via energy transfer is developed. It is the first time to utilize spectral overlap of fluorescent spectrum of BSA-Au NCs with absorption spectrum of indigo carmine and to achieve fast, sensitive, and selective ozone detection with a limit of detection of down to 35 nM (the volume of 500 μL, 1.68 ppb).

Tumor detection in mice by measurement of fluorescence decay time matrices

NASA Astrophysics Data System (ADS)

Cubeddu, R.; Pifferi, A.; Taroni, P.; Valentini, G.; Canti, G.

1995-12-01

An intensified CCD video camera has been used to measure the spatial distribution of the fluorescence decay time in tumor-bearing mice sensitized with hematoporphyrin derivative. Mice were injected with five doses of sensitizer, ranging from 0.1 to 10 mg / kg body weight. For any drug dose the decay time of the exogenous fluorescence in the tumor is always significantly longer than in normal tissues. The image created by associating a gray-shade scale to the decay time matrix of each mouse permits a reliable and precise detection of the neoplasia.

Fluorescence quencher improves SCANSYSTEM for rapid bacterial detection.

PubMed

Schmidt, M; Hourfar, M K; Wahl, A; Nicol, S-B; Montag, T; Roth, W K; Seifried, E

2006-05-01

The optimized scansystem could detect contaminated platelet products within 24 h. However, the system's sensitivity was reduced by a high fluorescence background even in sterile samples, which led to the necessity of a well-trained staff for confirmation of microscope results. A new protocol of the optimized scansystem with the addition of a fluorescence quencher was evaluated. Pool platelet concentrates contaminated with five transfusion-relevant bacterial strains were tested in a blind study. In conjunction with new analysis software, the new quenching dye was able to reduce significantly unspecific background fluorescence. Sensitivity was best for Bacillus cereus and Escherichia coli (3 CFU/ml). The application of a fluorescence quencher enables automated discrimination of positive and negative test results in 60% of all analysed samples.

A dual amplification strategy for DNA detection combining bio-barcode assay and metal-enhanced fluorescence modality.

PubMed

Zhou, Zhenpeng; Li, Tian; Huang, Hongduan; Chen, Yang; Liu, Feng; Huang, Chengzhi; Li, Na

2014-11-11

Silver-enhanced fluorescence was coupled with a bio-barcode assay to facilitate a dual amplification assay to demonstrate a non-enzymatic approach for simple and sensitive detection of DNA. In the assay design, magnetic nanoparticles seeded with silver nanoparticles were modified with the capture DNA, and silver nanoparticles were modified with the binding of ssDNA and the fluorescently labeled barcode dsDNA. Upon introduction of the target DNA, a sandwich structure was formed because of the hybridization reaction. By simple magnetic separation, silver-enhanced fluorescence of barcode DNAs could be readily measured without the need of a further step to liberate barcode DNAs from silver nanoparticles, endowing the method with simplicity and high sensitivity with a detection limit of 1 pM.

Deep UV laser-induced fluorescence detection of unlabeled drugs and proteins in microchip electrophoresis.

PubMed

Schulze, Philipp; Ludwig, Martin; Kohler, Frank; Belder, Detlev

2005-03-01

Deep UV fluorescence detection at 266-nm excitation wavelength has been realized for sensitive detection in microchip electrophoresis. For this purpose, an epifluorescence setup was developed enabling the coupling of a deep UV laser into a commercial fluorescence microscope. Deep UV laser excitation utilizing a frequency quadrupled pulsed laser operating at 266 nm shows an impressive performance for native fluorescence detection of various compounds in fused-silica microfluidic devices. Aromatic low molecular weight compounds such as serotonin, propranolol, a diol, and tryptophan could be detected at low-micromolar concentrations. Deep UV fluorescence detection was also successfully employed for the detection of unlabeled basic proteins. For this purpose, fused-silica chips dynamically coated with hydroxypropylmethyl cellulose were employed to suppress analyte adsorption. Utilizing fused-silica chips permanently coated with poly(vinyl alcohol), it was also possible to separate and detect egg white chicken proteins. These data show that deep UV fluorescence detection significantly widens the application range of fluorescence detection in chip-based analysis techniques.

Fluorescence detection of a protein-bound 2Fe2S cluster.

PubMed

Hoff, Kevin G; Goodlitt, Rochelle; Li, Rui; Smolke, Christina D; Silberg, Jonathan J

2009-03-02

A fluorescent biosensor is described for 2Fe2S clusters that is composed of green fluorescent protein (GFP) fused to glutaredoxin 2 (Grx2), as illustrated here. 2Fe2S detection is based on the reduction of GFP fluorescence upon the 2Fe2S-induced dimerization of GFP-Grx2. This assay is sufficiently sensitive to detect submicromolar changes in 2Fe2S levels, thus making it suitable for high-throughput measurements of metallocluster degradation and synthesis reactions.

Horseradish peroxidase-labeled oligonucleotides and fluorescent tyramides for rapid detection of chromosome-specific repeat sequences.

PubMed

van Gijlswijk, R P; Wiegant, J; Vervenne, R; Lasan, R; Tanke, H J; Raap, A K

1996-01-01

We present a sensitive and rapid fluorescence in situ hybridization (FISH) strategy for detecting chromosome-specific repeat sequences. It uses horseradish peroxidase (HRP)-labeled oligonucleotide sequences in combination with fluorescent tyramide-based detection. After in situ hybridization, the HRP conjugated to the oligonucleotide probe is used to deposit fluorescently labeled tyramide molecules at the site of hybridization. The method features full chemical synthesis of probes, strong FISH signals, and short processing periods, as well as multicolor capabilities.

A novel fluorescent probe for rapid and sensitive detection of hydrogen sulfide in living cells

NASA Astrophysics Data System (ADS)

Pan, Jian; Xu, Junchao; Zhang, Youlai; Wang, Liang; Qin, Caiqin; Zeng, Lintao; Zhang, Yue

2016-11-01

A novel fluorescent probe for H2S was developed based on a far-red emitting indole-BODIPY, which was decorated with morpholine and 2,4-dinitrobenzenesulfonyl (DNBS) group. This probe showed rapid response (t1/2 = 3 min), high selectivity and sensitivity for H2S with significant colorimetric and fluorescence OFF-ON signals, which was triggered by cleavage of 2,4-dinitrobenzenesulfonyl group. This probe could quantitatively detect the concentrations of H2S ranging from 0 to 60 μM, and the detection of limit was found to be as low as 26 nM. Cell imaging results indicated that the probe could detect and visualize H2S in the living cells.

Fluorescent microplate assay method for high-throughput detection of lipase transesterification activity.

PubMed

Zheng, Jianyong; Wei, Wei; Lan, Xing; Zhang, Yinjun; Wang, Zhao

2018-05-15

This study describes a sensitive and fluorescent microplate assay method to detect lipase transesterification activity. Lipase-catalyzed transesterification between butyryl 4-methyl umbelliferone (Bu-4-Mu) and methanol in tert-butanol was selected as the model reaction. The release of 4-methylumbelliferone (4-Mu) in the reaction was determined by detecting the fluorescence intensity at λ ex 330 nm and λ em 390 nm. Several lipases were used to investigate the accuracy and efficiency of the proposed method. Apparent Michaelis constant (Km) was calculated for transesterification between Bu-4-Mu and methanol by the lipases. The main advantages of the assay method include high sensitivity, inexpensive reagents, and simple detection process. Copyright © 2018 Elsevier Inc. All rights reserved.

Single-molecule detection: applications to ultrasensitive biochemical analysis

NASA Astrophysics Data System (ADS)

Castro, Alonso; Shera, E. Brooks

1995-06-01

Recent developments in laser-based detection of fluorescent molecules have made possible the implementation of very sensitive techniques for biochemical analysis. We present and discuss our experiments on the applications of our recently developed technique of single-molecule detection to the analysis of molecules of biological interest. These newly developed methods are capable of detecting and identifying biomolecules at the single-molecule level of sensitivity. In one case, identification is based on measuring fluorescence brightness from single molecules. In another, molecules are classified by determining their electrophoretic velocities.

Bioconjugated fluorescent silica nanoparticles for the rapid detection of Entamoeba histolytica.

PubMed

Hemadi, Ahmad; Ekrami, Alireza; Oormazdi, Hormozd; Meamar, Ahmad Reza; Akhlaghi, Lame; Samarbaf-Zadeh, Ali Reza; Razmjou, Elham

2015-05-01

Rapid detection of Entamoeba histolytica based on fluorescent silica nanoparticle (FSNP) indirect immunofluorescence microscopy was evaluated. Silica nanoparticles were synthesized using Stöber's method, with their surface activated to covalently bind to, and immobilize, protein A. For biolabeling, FSNP was added to conjugated E. histolytica trophozoites with monoclonal anti-E. histolytica IgG1 for microscopic observation of fluorescence. Fluorescent silica nanoparticle sensitivity was determined with axenically cultured E. histolytica serially diluted to seven concentrations. Specificity was evaluated using other intestinal protozoa. Fluorescent silica nanoparticles detected E. histolytica at the lowest tested concentration with no cross-reaction with Entamoeba dispar, Entamoeba moshkovskii, Blastocystis sp., or Giardia lamblia. Visualization of E. histolytica trophozoites with anti-E. histolytica antibody labeled with fluorescein isothiocyanate (FITC) was compared with that using anti-E. histolytica antibody bioconjugated FSNP. Although FITC and FSNP produced similar results, the amount of specific antibody required for FITC to induce fluorescence of similar intensity was fivefold that for FSNP. Fluorescent silica nanoparticles delivered a rapid, simple, cost-effective, and highly sensitive and specific method of detecting E. histolytica. Further study is needed before introducing FSNP for laboratory diagnosis of amoebiasis. Copyright © 2015 Elsevier B.V. All rights reserved.

A fluorescent aptasensor for amplified label-free detection of adenosine triphosphate based on core-shell Ag@SiO2 nanoparticles.

PubMed

Song, Quanwei; Peng, Manshu; Wang, Le; He, Dacheng; Ouyang, Jin

2016-03-15

The novel, facile and universal aptamer-based methods for the highly sensitive and selective fluorescence detection of important biomolecules have attracted considerable interest. Here, we present a label-free aptasensor for adenosine triphosphate (ATP) detection in aqueous solutions by using an ultra-sensitive nucleic acid stain PicoGreen (PG) as a fluorescent indicator and core-shell Ag@SiO2 nanoparticles (NPs) as a metal-enhanced fluorescence (MEF) platform. In the presence of ATP, the complementary DNA (cDNA)/aptamer duplexes confined onto the Ag@SiO2 NPs surface can release their aptamers into the buffered solution, causing a significant reduction in fluorescence intensity. By virtue of the amplified fluorescence signal, this aptasensor toward ATP can achieve a detection limit of 14.2 nM with a wide linear range and exhibit a good assay performance in complex biological samples. This sensing approach is cost-effective and efficient because it avoids the fluorescence labeling process and the use of any enzymes. Hence, this method may offer an alternative tool for determining the concentrations of ATP in biochemical and biomedical research. Copyright © 2015 Elsevier B.V. All rights reserved.

Signal-on fluorescence biosensor for microRNA-21 detection based on DNA strand displacement reaction and Mg2+-dependent DNAzyme cleavage.

PubMed

Yin, Huan-Shun; Li, Bing-Chen; Zhou, Yun-Lei; Wang, Hai-Yan; Wang, Ming-Hui; Ai, Shi-Yun

2017-10-15

MicroRNAs have been involved into many biological processes and are regarded as disease biomarkers. Simple, rapid, sensitive and selective method for microRNA detection is crucial for early diagnosis and therapy of diseases. In this work, sensitive fluorescence assay was developed for microRNA-21 detection based on DNA polymerase induced strand displacement amplification reaction, Mg 2+ -dependent DNAzyme catalysis reaction, and magnetic separation. In the presence of target microRNA-21, amounts of trigger DNA could be produced with DNA polymerase induced strand displacement amplification reaction, and the trigger DNA could be further hybridized with signal DNA, which was labeled with biotin and AMCA dye. After introduction of Mg 2+ , trigger DNA could form DNAzyme to cleave signal DNA. After magnetic separation, the DNA fragment with AMCA dye could give fluorescence signal, which was related to microRNA-21 concentration. Based on the two efficient signal amplifications, the developed method showed high detection sensitivity with low detection limit of 0.27fM (3σ). In addition, this fluorescence strategy also possessed excellent detection specificity, and could be applied to analyze microRNA-21 expression level in serum of cancer patient. According to the obtained results, the developed fluorescence method might be a promising detection platform for microRNA-21 quantitative analysis in biomedical research and clinical diagnosis. Copyright © 2017 Elsevier B.V. All rights reserved.

Imaging of tumor hypermetabolism with near-infrared fluorescence contrast agents

NASA Astrophysics Data System (ADS)

Chen, Yu; Zheng, Gang; Zhang, Zhihong; Blessington, Dana; Intes, Xavier; Achilefu, Samuel I.; Chance, Britton

2004-08-01

We have developed a high sensitivity near-infrared (NIR) optical imaging system for non-invasive cancer detection through molecular labeled fluorescent contrast agents. Near-infrared (NIR) imaging can probe tissue deeply thus possess the potential for non-invasively detection of breast or lymph node cancer. Recent developments in molecular beacons can selectively label various pre-cancer/cancer signatures and provide high tumor to background contrast. To increase the sensitivity in detecting fluorescent photons and the accuracy of localization, phase cancellation (in- and anti-phase) device is employed. This frequency-domain system utilizes the interference-like pattern of diffuse photon density wave to achieve high detection sensitivity and localization accuracy for the fluorescent heterogeneity embedded inside the scattering media. The opto-electronic system consists of the laser sources, fiber optics, interference filter to select the fluorescent photons and the high sensitivity photon detector (photomultiplier tube). The source-detector pair scans the tissue surface in multiple directions and the two-dimensional localization image can be obtained using goniometric reconstruction. In vivo measurements with tumor-bearing mouse model using the novel Cypate-mono-2-deoxy-glucose (Cypate-2-D-Glucosamide) fluorescent contrast agent, which targets the enhanced tumor glycolysis, demonstrated the feasibility on detection of 2 cm deep subsurface tumor in the tissue-like medium, with a localization accuracy within 2 ~ 3 mm. This instrument has the potential for tumor diagnosis and imaging, and the accuracy of the localization suggests that this system could help to guide the clinical fine-needle biopsy. This portable device would be complementary to X-ray mammogram and provide add-on information on early diagnosis and localization of early breast tumor.

A novel fluorimetric sensing platform for highly sensitive detection of organophosphorus pesticides by using egg white-encapsulated gold nanoclusters.

PubMed

Yan, Xu; Li, Hongxia; Hu, Tianyu; Su, Xingguang

2017-05-15

Assays for organophosphorus pesticides (OPs) with high sensitivity as well as on-site screening have been urgently required to protect ecosystem and prevent disease. Herein, a novel fluorimetric sensing platform was constructed for quantitative detection of OPs via tyrosinase (TYR) enzyme-controlled quenching of gold nanoclusters (AuNCs). One-step green synthetic approach was developed for the synthesis of AuNCs by using chicken egg white (CEW) as template and stabilizer. Initially, TYR can catalyze the oxidation of dopamine to dopaminechrome, which can efficiently quench the fluorescence intensity of AuNCs at 630nm based on dynamic quenching process. However, with the presence of OPs, the activity of TYR was inhibited, resulting in the fluorescence recovery of AuNCs. This proposed fluorescence platform was demonstrated to enable rapid detection for OPs (paraoxon as model) and to provide excellent sensitivity with a detection limit of 0.1ngmL -1 . Significantly, the fluorescence probe was used to prepare paper-based test strips for visual detection of OPs, which validated the excellent potential for real-time and on-site application. Copyright © 2016 Elsevier B.V. All rights reserved.

Sensitive arginine sensing based on inner filter effect of Au nanoparticles on the fluorescence of CdTe quantum dots

NASA Astrophysics Data System (ADS)

Liu, Haijian; Li, Ming; Jiang, Linye; Shen, Feng; Hu, Yufeng; Ren, Xueqin

2017-02-01

Arginine plays an important role in many biological functions, whose detection is very significant. Herein, a sensitive, simple and cost-effective fluorescent method for the detection of arginine has been developed based on the inner filter effect (IFE) of citrate-stabilized gold nanoparticles (AuNPs) on the fluorescence of thioglycolic acid-capped CdTe quantum dots (QDs). When citrate-stabilized AuNPs were mixed with thioglycolic acid-capped CdTe QDs, the fluorescence of CdTe QDs was significantly quenched by AuNPs via the IFE. With the presence of arginine, arginine could induce the aggregation and corresponding absorption spectra change of AuNPs, which then IFE-decreased fluorescence could gradually recover with increasing amounts of arginine, achieving fluorescence ;turn on; sensing for arginine. The detection mechanism is clearly illustrated and various experimental conditions were also optimized. Under the optimum conditions, a decent linear relationship was obtained in the range from 16 to 121 μg L- 1 and the limit of detection was 5.6 μg L- 1. And satisfactory results were achieved in arginine analysis using arginine injection, compound amino acid injection, even blood plasma as samples. Therefore, the present assay showed various merits, such as simplicity, low cost, high sensitivity and selectivity, making it promising for sensing arginine in biological samples.

A Graphene Oxide-Based Fluorescent Aptasensor for the Turn-on Detection of CCRF-CEM.

PubMed

Tan, Jie; Lai, Zongqiang; Zhong, Liping; Zhang, Zhenghua; Zheng, Rong; Su, Jing; Huang, Yong; Huang, Panpan; Song, Hui; Yang, Nuo; Zhou, Sufang; Zhao, Yongxiang

2018-04-01

A convenient, low-cost, and highly sensitive fluorescent aptasensor for detection of leukemia has been developed based on graphene oxide-aptamer complex (GO-apt). Graphene oxide (GO) can absorb carboxyfluorescein-labeled Sgc8 aptamer (FAM-apt) by π-π stacking and quench the fluorescence through fluorescence resonance energy transfer (FRET). In the absence of Sgc8 target cell CCRF-CEM, the fluorescence is almost all quenched. Conversely, when the CCRF-CEM cells are added, the quenched fluorescence can be recovered rapidly and significantly. Therefore, based on the change of fluorescence signals, we can detect the number of CCRF-CEM cells in a wide range from 1 × 10 2 to 1 × 10 7  cells/mL with a limit of detection (LOD) of 10 cells/mL. Therefore, this strategy of graphene oxide-based fluorescent aptasensor may be promising for the detection of cancer.

A nanocluster-based fluorescent sensor for sensitive hemoglobin detection.

PubMed

Yang, Dongqin; Meng, Huijie; Tu, Yifeng; Yan, Jilin

2017-08-01

In this report, a fluorescence sensor for sensitive detection of hemoglobin was developed. Gold nanoclusters were first synthesized with bovine serum albumin. It was found that both hydrogen peroxide and hemoglobin could weakly quench the fluorescence from the gold nanoclusters, but when these two were applied onto the nanolcusters simultaneously, a much improved quenching was resulted. This enhancing effect was proved to come from the catalytic generation of hydroxyl radical by hemoglobin. Under an optimized condition, the quenching linearly related to the concentration of hemoglobin in the range of 1-250nM, and a limit of detection as low as 0.36nM could be obtained. This provided a sensitive means for the quantification of Hb. The sensor was then successfully applied for blood analyses with simple sample pretreatment. Copyright © 2017 Elsevier B.V. All rights reserved.

An intraoperative spectroscopic imaging system for quantification of Protoporphyrin IX during glioma surgery (Conference Presentation)

NASA Astrophysics Data System (ADS)

Angulo-Rodríguez, Leticia M.; Laurence, Audrey; Jermyn, Michael; Sheehy, Guillaume; Sibai, Mira; Petrecca, Kevin; Roberts, David W.; Paulsen, Keith D.; Wilson, Brian C.; Leblond, Frédéric

2016-03-01

Cancer tissue often remains after brain tumor resection due to the inability to detect the full extent of cancer during surgery, particularly near tumor boundaries. Commercial systems are available for intra-operative real-time aminolevulenic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence imaging. These are standard white-light neurosurgical microscopes adapted with optical components for fluorescence excitation and detection. However, these instruments lack sensitivity and specificity, which limits the ability to detect low levels of PpIX and distinguish it from tissue auto-fluorescence. Current systems also cannot provide repeatable and un-biased quantitative fluorophore concentration values because of the unknown and highly variable light attenuation by tissue. We present a highly sensitive spectroscopic fluorescence imaging system that is seamlessly integrated onto a neurosurgical microscope. Hardware and software were developed to achieve through-microscope spatially-modulated illumination for 3D profilometry and to use this information to extract tissue optical properties to correct for the effects of tissue light attenuation. This gives pixel-by-pixel quantified fluorescence values and improves detection of low PpIX concentrations. This is achieved using a high-sensitivity Electron Multiplying Charge Coupled Device (EMCCD) with a Liquid Crystal Tunable Filter (LCTF) whereby spectral bands are acquired sequentially; and a snapshot camera system with simultaneous acquisition of all bands is used for profilometry and optical property recovery. Sensitivity and specificity to PpIX is demonstrated using brain tissue phantoms and intraoperative human data acquired in an on-going clinical study using PpIX fluorescence to guide glioma resection.

A novel fluorescence biosensor for sensitivity detection of tyrosinase and acid phosphatase based on nitrogen-doped graphene quantum dots.

PubMed

Qu, Zhengyi; Na, Weidan; Liu, Xiaotong; Liu, Hua; Su, Xingguang

2018-01-02

In this paper, we developed a sensitive fluorescence biosensor for tyrosinase (TYR) and acid phosphatase (ACP) activity detection based on nitrogen-doped graphene quantum dots (N-GQDs). Tyrosine could be catalyzed by TYR to generate dopaquinone, which could efficiently quench the fluorescence of N-GQDs, and the degree of fluorescence quenching of N-GQDs was proportional to the concentration of TYR. In the presence of ACP, l-Ascorbic acid-2-phosphate (AAP) was hydrolyzed to generate ascorbic acid (AA), and dopaquinone was reduced to l-dopa, resulting in the fluorescence recovery of the quenched fluorescence by dopaquinone. Thus, a novel fluorescence biosensor for the detection of TYR and ACP activity based on N-GQDs was constructed. Under the optimized experimental conditions, the fluorescence intensity was linearly correlated with the concentration of TYR and ACP in the range of 0.43-3.85 U mL -1 and 0.04-0.7 mU mL -1 with a detection limit of 0.15 U mL -1 and 0.014 mU mL -1 , respectively. The feasibility of the proposed biosensor in real samples assay was also studied and satisfactory results were obtained. Copyright © 2017 Elsevier B.V. All rights reserved.

Fluorescence detection of trace PCB101 based on PITC immobilized on porous AAO membrane.

PubMed

Wang, Meiling; Meng, Guowen; Huang, Qing; Li, Mingtao; Li, Zhongbo; Tang, Chaolong

2011-01-21

A sensitive and selective fluorescent membrane for rapid detection of trace 2,2',4,5,5'-pentachlorinated biphenyl (PCB101) has been achieved by immobilizing the fluorophore phenyl isothiocyanate (PITC) onto porous anodic aluminium oxide (AAO) membrane (denoted as PITC@AAO). The fluorescence of the PITC@AAO membrane is obviously enhanced after titrating the analyte PCB101 into the membrane, being ascribed to the halogen-bonding interaction between the fluorophore PITC and the analyte PCB101. The fluorescence intensity increases with the PCB101 concentration in the low range below 1 ppm, and there exists an approximate linear relationship between the relative fluorescence intensity and the PCB101 concentration in the low range of 1-6 ppb. Moreover, the PITC@AAO membrane shows good selectivity; for example, it is insensitive to common structural analogs (polychlorinated aromatics). The mechanisms of the fluorescence enhancement and the better sensitivity and selectivity of the PITC@AAO membrane to PCB101 than that of PITC/n-hexane solution are also discussed. This work demonstrates that trace (in ppb range) PCBs can be detected by simple fluorescence measurement.

A new fluorescent enhanced probe based on (E)-9-(2-nitrovinyl)-anthracene for the detection of bisulfite anions and its practical application

NASA Astrophysics Data System (ADS)

Chao, Jianbin; Liu, Yuhong; Zhang, Yan; Zhang, Yongbin; Huo, Fangjun; Yin, Caixia; Wang, Yu; Qin, Liping

2015-07-01

A new fluorescent enhanced probe based on (E)-9-(2-nitrovinyl)-anthracene is developed, which shows high selectivity and sensitivity for the detection of bisulfite anions at Na2HPO4 citric acid buffer solutions (pH 5.0). When addition of HSO3-, the fluorescence intensity is significantly enhanced and the probe displays apparent fluorescence color changes from non-fluorescence to blue under a UV lamp illumination, the solution color also changes from yellow to colorless. The detection limit is determined to be as low as 6.30 μM. This offers another specific colorimetric and fluorescent probe for bisulfite anions detection, furthermore it is applied in detecting the level of bisulfite in sugar samples.

Readily Available Fluorescent Probe for Carbon Monoxide Imaging in Living Cells.

PubMed

Feng, Weiyong; Liu, Dandan; Feng, Shumin; Feng, Guoqiang

2016-11-01

Carbon monoxide (CO) is an important gasotransmitter in living systems and its fluorescent detection is of particular interest. However, fluorescent detection of CO in living cells is still challenging due to lack of effective probes. In this paper, a readily available fluorescein-based fluorescent probe was developed for rapid detection of CO. This probe can be used to detect CO in almost wholly aqueous solution under mild conditions and shows high selectivity and sensitivity for CO with colorimetric and remarkable fluorescent turn-on signal changes. The detection limit of this probe for CO is as low as 37 nM with a linear range of 0-30 μM. More importantly, this probe (1 μM dose) can be conveniently used for fluorescent imaging CO in living cells.

Detection of TNT using a sensitive two-photon organic dendrimer for remote sensing

NASA Astrophysics Data System (ADS)

Narayanan, Aditya; Varnavski, Oleg; Mongin, Oliver; Majoral, Jean-Pierre; Blanchard-Desce, Mireille; Goodson, Theodore, III

2008-03-01

There is currently a need for superior stand-off detection schemes for protection against explosive weapons of mass destruction. Fluorescence detection at small distances from the target has proven to be attractive. A novel unexplored route in fluorescence chemical sensing that utilizes the exceptional spectroscopic capabilities of nonlinear optical methods is two-photon excited fluorescence. This approach utilizes infra-red light for excitation of remote sensors. Infra-red light suffers less scattering in porous materials which is beneficial for vapor sensing and has greater depth of penetration through the atmosphere, and there are fewer concerns regarding eye safety in remote detection schemes. We demonstrate this method using a novel dendritic system which possesses both excellent fluorescence sensitivity to the presence of TNT with infra-red pulses of light and high two-photon absorption (TPA) response. This illustrates the use of TPA for potential stand-off detection of energetic materials in the infra-red spectral regions in a highly two-photon responsive dendrimer.

Quantum dot-fluorescence in situ hybridisation for Ectromelia virus detection based on biotin-streptavidin interactions.

PubMed

Wang, Ting; Zheng, Zhenhua; Zhang, Xian-En; Wang, Hanzhong

2016-09-01

Ectromelia virus (ECTV) is an pathogen that can lead to a lethal, acute toxic disease known as mousepox in mice. Prevention and control of ECTV infection requires the establishment of a rapid and sensitive diagnostic system for detecting the virus. In the present study, we developed a method of quantum-dot-fluorescence based in situ hybridisation for detecting ECTV genome DNA. Using biotin-dUTP to replace dTTP, biotin was incorporated into a DNA probe during polymerase chain reaction. High sensitivity and specificity of ECTV DNA detection were displayed by fluorescent quantum dots based on biotin-streptavidin interactions. ECTV DNA was then detected by streptavidin-conjugated quantum dots that bound the biotin-labelled probe. Results indicated that the established method can visualise ECTV genomic DNA in both infected cells and mouse tissues. To our knowledge, this is the first study reporting quantum-dot-fluorescence based in situ hybridisation for the detection of viral nucleic acids, providing a reference for the identification and detection of other viruses. Copyright © 2016. Published by Elsevier B.V.

Time-Resolved Fluorescent Immunochromatography of Aflatoxin B1 in Soybean Sauce: A Rapid and Sensitive Quantitative Analysis.

PubMed

Wang, Du; Zhang, Zhaowei; Li, Peiwu; Zhang, Qi; Zhang, Wen

2016-07-14

Rapid and quantitative sensing of aflatoxin B1 with high sensitivity and specificity has drawn increased attention of studies investigating soybean sauce. A sensitive and rapid quantitative immunochromatographic sensing method was developed for the detection of aflatoxin B1 based on time-resolved fluorescence. It combines the advantages of time-resolved fluorescent sensing and immunochromatography. The dynamic range of a competitive and portable immunoassay was 0.3-10.0 µg·kg(-1), with a limit of detection (LOD) of 0.1 µg·kg(-1) and recoveries of 87.2%-114.3%, within 10 min. The results showed good correlation (R² > 0.99) between time-resolved fluorescent immunochromatographic strip test and high performance liquid chromatography (HPLC). Soybean sauce samples analyzed using time-resolved fluorescent immunochromatographic strip test revealed that 64.2% of samples contained aflatoxin B1 at levels ranging from 0.31 to 12.5 µg·kg(-1). The strip test is a rapid, sensitive, quantitative, and cost-effective on-site screening technique in food safety analysis.

Fluorescent Quantum Dots for Biological Labeling

NASA Technical Reports Server (NTRS)

McDonald, Gene; Nadeau, Jay; Nealson, Kenneth; Storrie-Lomardi, Michael; Bhartia, Rohit

2003-01-01

Fluorescent semiconductor quantum dots that can serve as "on/off" labels for bacteria and other living cells are undergoing development. The "on/off" characterization of these quantum dots refers to the fact that, when properly designed and manufactured, they do not fluoresce until and unless they come into contact with viable cells of biological species that one seeks to detect. In comparison with prior fluorescence-based means of detecting biological species, fluorescent quantum dots show promise for greater speed, less complexity, greater sensitivity, and greater selectivity for species of interest. There are numerous potential applications in medicine, environmental monitoring, and detection of bioterrorism.

Fluorescent aptasensor for antibiotic detection using magnetic bead composites coated with gold nanoparticles and a nicking enzyme.

PubMed

Luo, Zewei; Wang, Yimin; Lu, Xiaoyong; Chen, Junman; Wei, Fujing; Huang, Zhijun; Zhou, Chen; Duan, Yixiang

2017-09-01

Antibiotic abuse has been bringing serious pollution in water, which is closely related to human health. It is desirable to develop a new strategy for antibiotic detection. To address this problem, a sensitive fluorescent aptasensor for antibiotic detection was developed by utilizing gold nanoparticles modified magnetic bead composites (AuNPs/MBs) and nicking enzyme. AuNPs/MBs were synthesized with the help of polyethylenimine (PEI). The prepared AuNPs/MBs acted as dual-functional scaffolds that owned excellent magnetic separation capacity and strong covalent bio-conjugation. The non-specifically absorbed aptamers in AuNPs/MBs were less than that in MBs. Hence, the fluorescent aptasensor based on AuNPs/MBs show a better signal to background ratio than that based on carboxyl modified magnetic beads (MBs). In this work, ampicillin was employed as a model analyte. In the presence of ampicillin, the specific binding between ampicillin and aptamer induced structure-switching that led to the release of partial complementary DNA (cDNA) of aptamer. Then, the released cDNA initiated the cycle of nicking enzyme assisted signal amplification (NEASA). Therefore, a large amount of taqman probes were cleaved and fluorescence signal was amplified. The prepared fluorescent aptasensor bring sensitive detection in range of 0.1-100 ng mL -1 with the limit of detection of 0.07 ng mL -1 . Furthermore, this aptasensor was also successfully applied in real sample detection with acceptable accuracy. The fluorescent aptasensor provides a promising method for efficient, rapid and sensitive antibiotic detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Toehold strand displacement-driven assembly of G-quadruplex DNA for enzyme-free and non-label sensitive fluorescent detection of thrombin.

PubMed

Xu, Yunying; Zhou, Wenjiao; Zhou, Ming; Xiang, Yun; Yuan, Ruo; Chai, Yaqin

2015-02-15

Based on a new signal amplification strategy by the toehold strand displacement-driven cyclic assembly of G-quadruplex DNA, the development of an enzyme-free and non-label aptamer sensing approach for sensitive fluorescent detection of thrombin is described. The target thrombin associates with the corresponding aptamer of the partial dsDNA probes and liberates single stranded initiation sequences, which trigger the toehold strand displacement assembly of two G-quadruplex containing hairpin DNAs. This toehold strand displacement reaction leads to the cyclic reuse of the initiation sequences and the production of DNA assemblies with numerous G-quadruplex structures. The fluorescent dye, N-Methyl mesoporphyrin IX, binds to these G-quadruplex structures and generates significantly amplified fluorescent signals to achieve highly sensitive detection of thrombin down to 5 pM. Besides, this method shows high selectivity towards the target thrombin against other control proteins. The developed thrombin sensing method herein avoids the modification of the probes and the involvement of any enzyme or nanomaterial labels for signal amplification. With the successful demonstration for thrombin detection, our approach can be easily adopted to monitor other target molecules in a simple, low-cost, sensitive and selective way by choosing appropriate aptamer/ligand pairs. Copyright © 2014 Elsevier B.V. All rights reserved.

Dopamine fluorescent sensors based on polypyrrole/graphene quantum dots core/shell hybrids.

PubMed

Zhou, Xi; Ma, Peipei; Wang, Anqi; Yu, Chenfei; Qian, Tao; Wu, Shishan; Shen, Jian

2015-02-15

A facilely prepared fluorescent sensor was developed for dopamine (DA) detection with high sensitivity and selectivity based on polypyrrole/graphene quantum dots (PPy/GQDs) core/shell hybrids. The composites exhibit strong fluorescence emission, which is dramatically enhanced as high as three times than pristine GQDs. The prepared sensor allows a highly sensitive determination of DA by fluorescent intensity decreasing with the addition of DA and presents a good linearity in range of 5-8000 nM with the detection limit of 10 pM (S/N = 3). Furthermore, the application of the proposed approach have been demonstrated in real samples and showed promise in diagnostic purposes. Copyright © 2014 Elsevier B.V. All rights reserved.

Conjugated polymer nanoparticles-based fluorescent biosensor for ultrasensitive detection of hydroquinone.

PubMed

Liu, Yuan; Wang, Yu-Min; Zhu, Wu-Yang; Zhang, Chong-Hua; Tang, Hao; Jiang, Jian-Hui

2018-07-05

This work describes a simple and sensitive fluorescent method for detection of hydroquinone utilizing conjugated polymer nanoparticles (CPNs). The CPNs serve both as a catalyst to accelerate the conversion of hydroquinone to benzoquinone and a fluorescent probe. In the presence of hydroquinone, the fluorescence of CPNs can be effectively quenched by benzoquinone. The detection limit of hydroquinone was down to 5 nM and excellent selectivity toward possible interferences was obtained. This method was successfully applied for hydroquinone detection in lake water and satisfactory results were achieved. Copyright © 2018 Elsevier B.V. All rights reserved.

Detection limits of 405 nm and 633 nm excited PpIX fluorescence for brain tumor detection during stereotactic biopsy

NASA Astrophysics Data System (ADS)

Markwardt, Niklas; Götz, Marcus; Haj-Hosseini, Neda; Hollnburger, Bastian; Sroka, Ronald; Stepp, Herbert; Zelenkov, Petr; Rühm, Adrian

2016-04-01

5-aminolevulinic-acid-(5-ALA)-induced protoporphyrin IX (PpIX) fluorescence may be used to improve stereotactic brain tumor biopsies. In this study, the sensitivity of PpIX-based tumor detection has been investigated for two potential excitation wavelengths (405 nm, 633 nm). Using a 200 μm fiber in contact with semi-infinite optical phantoms containing ink and Lipovenös, PpIX detection limits of 4.0 nM and 200 nM (relating to 1 mW excitation power) were determined for 405 nm and 633 nm excitation, respectively. Hence, typical PpIX concentrations in glioblastomas of a few μM should be well detectable with both wavelengths. Additionally, blood layers of selected thicknesses were placed between fiber and phantom. Red excitation was shown to be considerably less affected by blood interference: A 50 μm blood layer, for instance, blocked the 405- nm-excited fluorescence completely, but reduced the 633-nm-excited signal by less than 50%. Ray tracing simulations demonstrated that - without blood layer - the sensitivity advantage of 405 nm rises for decreasing fluorescent volume from 50-fold to a maximum of 100-fold. However, at a tumor volume of 1 mm3, which is a typical biopsy sample size, the 633-nm-excited fluorescence signal is only reduced by about 10%. Further simulations revealed that with increasing fiber-tumor distance, the signal drops faster for 405 nm. This reduces the risk of detecting tumor tissue outside the needle's coverage, but diminishes the overlap between optically and mechanically sampled volumes. While 405 nm generally offers a higher sensitivity, 633 nm is more sensitive to distant tumors and considerably superior in case of blood-covered tumor tissue.

Use of a capillary electrophoresis instrument with laser-induced fluorescence detection for DNA quantitation. Comparison of YO-PRO-1 and PicoGreen assays.

PubMed

Guillo, Christelle; Ferrance, Jerome P; Landers, James P

2006-04-28

Highly selective and sensitive assays are required for detection and quantitation of the small masses of DNA typically encountered in clinical and forensic settings. High detection sensitivity is achieved using fluorescent labeling dyes and detection techniques such as spectrofluorometers, microplate readers and cytometers. This work describes the use of a laser-induced fluorescence (LIF) detector in conjunction with a commercial capillary electrophoresis instrument for DNA quantitation. PicoGreen and YO-PRO-1, two fluorescent DNA labeling dyes, were used to assess the potential of the system for routine DNA analysis. Linearity, reproducibility, sensitivity, limits of detection and quantitation, and sample stability were examined for the two assays. The LIF detector response was found to be linear (R2 > 0.999) and reproducible (RSD < 9%) in both cases. The PicoGreen assay displayed lower limits of detection and quantitation (20 pg and 60 pg, respectively) than the YO-PRO-1 assay (60 pg and 260 pg, respectively). Although a small variation in fluorescence was observed for the DNA/dye complexes over time, quantitation was not significantly affected and the solutions were found to be relatively stable for 80 min. The advantages of the technique include a 4- to 40-fold reduction in the volume of sample required compared to traditional assays, a 2- to 20-fold reduction in the volume of reagents consumed, fast and automated analysis, and low cost (no specific instrumentation required).

A nano grating tunable MEMS optical filter for high-speed on-chip multispectral fluorescent detection.

PubMed

Truxal, Steven C; Huang, Nien-Tsu; Kurabayashi, Katsuo

2009-01-01

We report a microelectromechanical (MEMS) tunable optical filter and its integration in a fluorescence microscope for high speed on-chip spectral measurements. This integration allows for measurements of any fluorescence sample placed onto the microscope stage. We demonstrate the system capabilities by taking spectral measurements of multicolor fluorescent beads and fluorescently labeled cells passing through a microfluidic cytometer. The system has applications in biological studies where the measurement of multiple fluorescent peaks is restricted by the detection method's speed and sensitivity.

Photonic Crystal Enhanced Fluorescence for Early Breast Cancer Biomarker Detection

PubMed Central

Cunningham, Brian T.; Zangar, Richard C.

2013-01-01

Photonic crystal surfaces offer a compelling platform for improving the sensitivity of surface-based fluorescent assays used in disease diagnostics. Through the complementary processes of photonic crystal enhanced excitation and enhanced extraction, a periodic dielectric-based nanostructured surface can simultaneously increase the electric field intensity experienced by surface-bound fluorophores and increase the collection efficiency of emitted fluorescent photons. Through the ability to inexpensively fabricate photonic crystal surfaces over substantial surface areas, they are amenable to single-use applications in biological sensing, such as disease biomarker detection in serum. In this review, we will describe the motivation for implementing high-sensitivity, multiplexed biomarker detection in the context of breast cancer diagnosis. We will summarize recent efforts to improve the detection limits of such assays though the use of photonic crystal surfaces. Reduction of detection limits is driven by low autofluorescent substrates for photonic crystal fabrication, and detection instruments that take advantage of their unique features. PMID:22736539

Capillary Array Waveguide Amplified Fluorescence Detector for mHealth

PubMed Central

Balsam, Joshua; Bruck, Hugh Alan; Rasooly, Avraham

2013-01-01

Mobile Health (mHealth) analytical technologies are potentially useful for carrying out modern medical diagnostics in resource-poor settings. Effective mHealth devices for underserved populations need to be simple, low cost, and portable. Although cell phone cameras have been used for biodetection, their sensitivity is a limiting factor because currently it is too low to be effective for many mHealth applications, which depend on detection of weak fluorescent signals. To improve the sensitivity of portable phones, a capillary tube array was developed to amplify fluorescence signals using their waveguide properties. An array configured with 36 capillary tubes was demonstrated to have a ~100X increase in sensitivity, lowering the limit of detection (LOD) of mobile phones from 1000 nM to 10 nM for fluorescein. To confirm that the amplification was due to waveguide behavior, we coated the external surfaces of the capillaries with silver. The silver coating interfered with the waveguide behavior and diminished the fluorescence signal, thereby proving that the waveguide behavior was the main mechanism for enhancing optical sensitivity. The optical configuration described here is novel in several ways. First, the use of capillaries waveguide properties to improve detection of weak florescence signal is new. Second we describe here a three dimensional illumination system, while conventional angular laser waveguide illumination is spot (or line), which is functionally one-dimensional illumination, can illuminate only a single capillary or a single column (when a line generator is used) of capillaries and thus inherently limits the multiplexing capability of detection. The planar illumination demonstrated in this work enables illumination of a two dimensional capillary array (e.g. x columns and y rows of capillaries). In addition, the waveguide light propagation via the capillary wall provides a third dimension for illumination along the axis of the capillaries. Such an array can potentially be used for sensitive analysis of multiple fluorescent detection assays simultaneously. The simple phone based capillary array approach presented in this paper is capable of amplifying weak fluorescent signals thereby improving the sensitivity of optical detectors based on mobile phones. This may allow sensitive biological assays to be measured with low sensitivity detectors and may make mHealth practical for many diagnostics applications, especially in resource-poor and global health settings. PMID:24039345

Partially reduced graphene oxide based FRET on fiber-optic interferometer for biochemical detection

NASA Astrophysics Data System (ADS)

Yao, B. C.; Wu, Y.; Yu, C. B.; He, J. R.; Rao, Y. J.; Gong, Y.; Fu, F.; Chen, Y. F.; Li, Y. R.

2016-03-01

Fluorescent resonance energy transfer (FRET) with naturally exceptional selectivity is a powerful technique and widely used in chemical and biomedical analysis. However, it is still challenging for conventional FRET to perform as a high sensitivity compact sensor. Here we propose a novel ‘FRET on Fiber’ concept, in which a partially reduced graphene oxide (prGO) film is deposited on a fiber-optic modal interferometer, acting as both the fluorescent quencher for the FRET and the sensitive cladding for optical phase measurement due to refractive index changes in biochemical detection. The target analytes induced fluorescence recovery with good selectivity and optical phase shift with high sensitivity are measured simultaneously. The functionalized prGO film coated on the fiber-optic interferometer shows high sensitivities for the detections of metal ion, dopamine and single-stranded DNA (ssDNA), with detection limits of 1.2 nM, 1.3 μM and 1 pM, respectively. Such a prGO based ‘FRET on fiber’ configuration, bridging the FRET and the fiber-optic sensing technology, may serve as a platform for the realization of series of integrated ‘FRET on Fiber’ sensors for on-line environmental, chemical, and biomedical detection, with excellent compactness, high sensitivity, good selectivity and fast response

Partially reduced graphene oxide based FRET on fiber-optic interferometer for biochemical detection

PubMed Central

Yao, B. C.; Wu, Y.; Yu, C. B.; He, J. R.; Rao, Y. J.; Gong, Y.; Fu, F.; Chen, Y. F.; Li, Y. R.

2016-01-01

Fluorescent resonance energy transfer (FRET) with naturally exceptional selectivity is a powerful technique and widely used in chemical and biomedical analysis. However, it is still challenging for conventional FRET to perform as a high sensitivity compact sensor. Here we propose a novel ‘FRET on Fiber’ concept, in which a partially reduced graphene oxide (prGO) film is deposited on a fiber-optic modal interferometer, acting as both the fluorescent quencher for the FRET and the sensitive cladding for optical phase measurement due to refractive index changes in biochemical detection. The target analytes induced fluorescence recovery with good selectivity and optical phase shift with high sensitivity are measured simultaneously. The functionalized prGO film coated on the fiber-optic interferometer shows high sensitivities for the detections of metal ion, dopamine and single-stranded DNA (ssDNA), with detection limits of 1.2 nM, 1.3 μM and 1 pM, respectively. Such a prGO based ‘FRET on fiber’ configuration, bridging the FRET and the fiber-optic sensing technology, may serve as a platform for the realization of series of integrated ‘FRET on Fiber’ sensors for on-line environmental, chemical, and biomedical detection, with excellent compactness, high sensitivity, good selectivity and fast response PMID:27010752

Research of the absorbance detection and fluorescence detection for multifunctional nutrition analyzer

NASA Astrophysics Data System (ADS)

Ni, Zhengyuan; Yan, Huimin; Ni, Xuxiang; Zhang, Xiuda

2017-10-01

The research of the multifunctional analyzer which integrates absorbance detection, fluorescence detection, time-resolved fluorescence detection, biochemical luminescence detection methods, can make efficient detection and analysis for a variety of human body nutrients. This article focuses on the absorbance detection and fluorescence detection system. The two systems are modular in design and controlled by embedded system, to achieve automatic measurement according to user settings. In the optical path design, the application of confocal design can improve the optical signal acquisition capability, and reduce the interference. A photon counter is used for detection, and a high performance counter module is designed to measure the output of photon counter. In the experiment, we use neutral density filters and potassium dichromate solution to test the absorbance detection system, and use fluorescein isothiocyanate FITC for fluorescence detection system performance test. The experimental results show that the absorbance detection system has a detection range of 0 4OD, and has good linearity in the detection range, while the fluorescence detection system has a high sensitivity of 1pmol/L concentration.

Noninvasive detection of diabetes mellitus

NASA Astrophysics Data System (ADS)

Eppstein, Jonathan A.; Bursell, Sven-Erik

1992-05-01

Recent advances in fluorescence spectroscopy of the lens reveal the potential of a non-invasive device and methodology to sensitively measure changes in the lens of the eye associated with diabetes mellitus. The system relies on the detection of the spectrum of fluorescence emitted from a selected volume (approximately 1/10 mm3) of the lens of living human subjects using low power excitation illumination from monochromatic light sources. The sensitivity of this technique is based on the measurement of the fluorescence intensity in a selected region of the fluorescence spectrum and normalization of this fluorescence with respect to attenuation (scattering and absorption) of the incident excitation light. The amplitude of the unshifted Rayleigh line, measured as part of the fluorescence spectrum, is used as a measure of the attenuation of the excitation light in the lens. Using this methodology we have demonstrated that the normalized lens fluorescence provides a more sensitive discrimination between diabetic and non-diabetic lenses than more conventional measurements of fluorescence intensity from the lens. The existing instrumentation will be described as well as the proposed design for a commercial version of the instrument expected to be ready for FDA trials by late 1992. The results from clinical measurements are used to describe a relationship between normalized lens fluorescence and hemoglobin A1c levels in diabetic patients.

A Label-Free Aptasensor for Ochratoxin a Detection Based on the Structure Switch of Aptamer.

PubMed

Liu, Feng; Ding, Ailing; Zheng, Jiushang; Chen, Jiucun; Wang, Bin

2018-06-01

A label-free sensing platform is developed based on switching the structure of aptamer for highly sensitive and selective fluorescence detection of ochratoxin A (OTA). OTA induces the structure of aptamer, transforms into G-quadruplex and produces strong fluorescence in the presence of zinc(II)-protoporphyrin IX probe due to the specific bind to G-quadruplex. The simple method exhibits high sensitivity towards OTA with a detection limit of 0.03 nM and excellent selectivity over other mycotoxins. In addition, the successful detection of OTA in real samples represents a promising application in food safety.

Shape Engineering Boosts Magnetic Mesoporous Silica Nanoparticle-Based Isolation and Detection of Circulating Tumor Cells.

PubMed

Chang, Zhi-Min; Wang, Zheng; Shao, Dan; Yue, Juan; Xing, Hao; Li, Li; Ge, Mingfeng; Li, Mingqiang; Yan, Huize; Hu, Hanze; Xu, Qiaobing; Dong, Wen-Fei

2018-04-04

Magnetic mesoporous silica nanoparticles (M-MSNs) are attractive candidates for the immunomagnetic isolation and detection of circulating tumor cells (CTCs). Understanding of the interactions between the effects of the shape of M-MSNs and CTCs is crucial to maximize the binding capacity and capture efficiency as well as to facilitate the sensitivity and efficiency of detection. In this work, fluorescent M-MSNs were rationally designed with sphere and rod morphologies while retaining their robust fluorescence and uniform surface functionality. After conjugation with the antibody of epithelial cell adhesion molecule (EpCAM), both of the differently shaped M-MSNs-EpCAM obtained achieved efficient enrichment of CTCs and fluorescent-based detection. Importantly, rodlike M-MSNs exhibited faster immunomagnetic isolation as well as better performance in the isolation and detection of CTCs in spiked cells and real clinical blood samples than those of their spherelike counterparts. Our results showed that shape engineering contributes positively toward immunomagnetic isolation, which might open new avenues to the rational design of magnetic-fluorescent nanoprobes for the sensitive and efficient isolation and detection of CTCs.

[Rapid Detection of Adenovirus in Fecal Samples by Capillary Electrophoresis-laser Induced Fluorescence and Microchip Capillary Electrophoresis-laser Induced Fluorescence].

PubMed

Ruan, Jia; Ren, Dong-xia; Yang, Dan-ni; Long, Pin-pin; Zhao, Hong-yue; Wang, Yi-qi; Li, Yong-xin

2015-07-01

To establish a rapid and sensitive method based on polymerase chain reaction (PCR) combined with capillary electrophoresis-laser induced fluorescence (CE-LIF) and microchip capillary electrophoresis-laser induced fluorescence (MCE-LIF) for detecting adenoviruses in fecal samples. The DNA of adenovirus in fecal samples were extracted by the commercial kits and the conserved region of hexon gene was selected as the target gene and amplified by PCR reaction. After labeling highly sensitive nucleic acid fluorescent dye SYBR Gold and SYBR Orange respectively, PCR amplification products were separated by CE and MCE under the optimized condition and detected by LIF detector. PCR amplification products could be detected within 9 min by CE-LIF and 6 min by MCE-LIF under the optimized separation condition. The sequenced PCR product showed good specificity in comparison with the prototype sequences from NCBI. The intraday and inter-day relative standard deviation (RSD) of the size (bp) of the target DNA was in the range of 1.14%-1.34% and 1.27%- 2.76%, respectively, for CE-LIF, and 1.18%-1.48% and 2.85%-4.06%, respectively, for MCE-LIF. The detection limits was 2.33 x 10(2) copies/mL for CE-LIF and 2.33 x 10(3) copies/mL for MCE-LIF. The two proposed methods were applied to detect fecal samples, both showing high accuracy. The two proposed methods of PCR-CE-LIF and PCR-MCE-LIF can detect adenovirus in fecal samples rapidly, sensitively and specifically.

Fluorescent hybridization probes for nucleic acid detection.

PubMed

Guo, Jia; Ju, Jingyue; Turro, Nicholas J

2012-04-01

Due to their high sensitivity and selectivity, minimum interference with living biological systems, and ease of design and synthesis, fluorescent hybridization probes have been widely used to detect nucleic acids both in vivo and in vitro. Molecular beacons (MBs) and binary probes (BPs) are two very important hybridization probes that are designed based on well-established photophysical principles. These probes have shown particular applicability in a variety of studies, such as mRNA tracking, single nucleotide polymorphism (SNP) detection, polymerase chain reaction (PCR) monitoring, and microorganism identification. Molecular beacons are hairpin oligonucleotide probes that present distinctive fluorescent signatures in the presence and absence of their target. Binary probes consist of two fluorescently labeled oligonucleotide strands that can hybridize to adjacent regions of their target and generate distinctive fluorescence signals. These probes have been extensively studied and modified for different applications by modulating their structures or using various combinations of fluorophores, excimer-forming molecules, and metal complexes. This review describes the applicability and advantages of various hybridization probes that utilize novel and creative design to enhance their target detection sensitivity and specificity.

Fundamentals and practice for ultrasensitive laser-induced fluorescence detection in microanalytical systems.

PubMed

Johnson, Mitchell E; Landers, James P

2004-11-01

Laser-induced fluorescence is an extremely sensitive method for detection in chemical separations. In addition, it is well-suited to detection in small volumes, and as such is widely used for capillary electrophoresis and microchip-based separations. This review explores the detailed instrumental conditions required for sub-zeptomole, sub-picomolar detection limits. The key to achieving the best sensitivity is to use an excitation and emission volume that is matched to the separation system and that, simultaneously, will keep scattering and luminescence background to a minimum. We discuss how this is accomplished with confocal detection, 90 degrees on-capillary detection, and sheath-flow detection. It is shown that each of these methods have their advantages and disadvantages, but that all can be used to produce extremely sensitive detectors for capillary- or microchip-based separations. Analysis of these capabilities allows prediction of the optimal means of achieving ultrasensitive detection on microchips.

Cutaneous porphyrins exhibit anti-stokes fluorescence that is detectable in sebum (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tian, Giselle; Zeng, Haishan; Zhao, Jianhua; Wu, Zhenguo; Al Jasser, Mohammed; Lui, Harvey; Mclean, David I.

2016-02-01

Porphyrins produced by Propionibacterium acnes represent the principal fluorophore associated with acne, and appear as orange-red luminescence under the Wood's lamp. Assessment of acne based on Wood's lamp (UV) or visible light illumination is limited by photon penetration depth and has limited sensitivity for earlier stage lesions. Inducing fluorescence with near infrared (NIR) excitation may provide an alternative way to assess porphyrin-related skin disorders. We discovered that under 785 nm CW laser excitation PpIX powder exhibits fluorescence emission in the shorter wavelength range of 600-715 nm with an intensity that is linearly dependent on the excitation power. We attribute this shorter wavelength emission to anti-Stokes fluorescence. Similar anti-Stokes fluorescence was also detected focally in all skin-derived samples containing porphyrins. Regular (Stokes) fluorescence was present under UV and visible light excitation on ex vivo nasal skin and sebum from uninflamed acne, but not on nose surface smears or sebum from inflamed acne. Co-registered CW laser-excited anti-Stokes fluorescence and fs laser-excited multi-photon fluorescence images of PpIX powder showed similar features. In the skin samples because of the anti-Stokes effect, the NIR-induced fluorescence was presumably specific for porphyrins since there appeared to be no anti-Stokes emission signals from other typical skin fluorophores such as lipids, keratins and collagen. Anti-Stokes fluorescence under NIR CW excitation is more sensitive and specific for porphyrin detection than UV- or visible light-excited regular fluorescence and fs laser-excited multi-photon fluorescence. This approach also has higher image contrast compared to NIR fs laser-based multi-photon fluorescence imaging. The anti-Stokes fluorescence of porphyrins within sebum could potentially be applied to detecting and targeting acne lesions for treatment via fluorescence image guidance.

Polythiophene nanofilms for sensitive fluorescence detection of viruses in drinking water.

PubMed

Wankar, Shashwati; Turner, Nicholas W; Krupadam, Reddithota J

2016-08-15

Molecular imprints of the tobacco necrosis virus (TNV) have been formed within polythiophene nanofilms with an approximate thickness of 200nm. These films have been electrochemically deposited onto conducting Au surfaces. Upon rebinding, the TNV-polythiophene complex changes the fluorescence intensity of the nanofilm. The fluorescence intensity at 410nm was observed to be proportional to the concentration of viruses in the range of 0.1-10ngL(-1) (0.15-15pg) with the lower calculated detection limit of 2.29ngL(-1) (3.4pg). The intensity of the fluorescence emission is not affected by the thickness of the polythiophene film and the nature of TNV specific binding sites. Kinetic data analyses showed that the nanofilm responds to TNV within 2min; and cross-selectivity studies with tobacco mosaic virus (TMV) showed an excellent specificity for the targeted TNV. These binding experiments demonstrate the potential of fluorescence emission for the specific, label free and rapid detection of viruses using nanofilm sensors. Taking into account the lower limit of detection, the fluorescence sensing reported here is reliable, simple to perform, rapid, cost-effective and offers a sensitive analytical method for virus detection in water resources. Copyright © 2016 Elsevier B.V. All rights reserved.

Plasmonics Enhanced Smartphone Fluorescence Microscopy.

PubMed

Wei, Qingshan; Acuna, Guillermo; Kim, Seungkyeum; Vietz, Carolin; Tseng, Derek; Chae, Jongjae; Shir, Daniel; Luo, Wei; Tinnefeld, Philip; Ozcan, Aydogan

2017-05-18

Smartphone fluorescence microscopy has various applications in point-of-care (POC) testing and diagnostics, ranging from e.g., quantification of immunoassays, detection of microorganisms, to sensing of viruses. An important need in smartphone-based microscopy and sensing techniques is to improve the detection sensitivity to enable quantification of extremely low concentrations of target molecules. Here, we demonstrate a general strategy to enhance the detection sensitivity of a smartphone-based fluorescence microscope by using surface-enhanced fluorescence (SEF) created by a thin metal-film. In this plasmonic design, the samples are placed on a silver-coated glass slide with a thin spacer, and excited by a laser-diode from the backside through a glass hemisphere, generating surface plasmon polaritons. We optimized this mobile SEF system by tuning the metal-film thickness, spacer distance, excitation angle and polarization, and achieved ~10-fold enhancement in fluorescence intensity compared to a bare glass substrate, which enabled us to image single fluorescent particles as small as 50 nm in diameter and single quantum-dots. Furthermore, we quantified the detection limit of this platform by using DNA origami-based brightness standards, demonstrating that ~80 fluorophores per diffraction-limited spot can be readily detected by our mobile microscope, which opens up new opportunities for POC diagnostics and sensing applications in resource-limited-settings.

Rapid, Sensitive Detection of Botulinum Toxin on a Flexible Microfluidics Platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warner, Marvin G.; Dockendorff, Brian P.; Feldhaus, Michael J.

2004-10-30

In this paper we will describe how high affinity reagents and a sensor configuration enabling rapid mass transport can be combined for rapid, sensitive biodetection. The system that we have developed includes a renewable surface immunoassay, which involves on-column detection of a fluorescently labeled secondary antibody in a sandwich immunoassay. Yeast display and directed molecular evolution were used to create high affinity antibodies to the botulinum toxin heavy chain receptor binding domain, AR1 and 3D12. A rotating rod renewable surface microcolumn was used to form a microliter-sized column containing beads functionalized with the capture antibody (AR1). The column was perfusedmore » with sample, wash solutions, and a fluorescently labeled secondary antibody (3D12) while the on-column fluorescence was monitored. Detection was accomplished in less than 5 minutes, with a total processing time of about 10 minutes. On-column detection of botulinum toxin was more sensitive and much faster than flow cytometry analysis on microbeads using the same reagents.« less

[Laser induced fluorescence spectrum characteristics of common edible oil and fried cooking oil].

PubMed

Mu, Tao-tao; Chen, Si-ying; Zhang, Yin-chao; Chen, He; Guo, Pan; Ge, Xian-ying; Gao, Li-lei

2013-09-01

In order to detect the trench oil the authors built a trench oil rapid detection system based on laser induced fluorescence detection technology. This system used 355 nm laser as excitation light source. The authors collected the fluorescence spectrum of a variety of edible oil and fried cooking oil (a kind of trench oil) and then set up a fluorescence spectrum database by taking advantage of the trench oil detection system It was found that the fluorescence characteristics of fried cooking oil and common edible oil were obviously different. Then it could easily realize the oil recognition and trench oil rapid detection by using principal component analysis and BP neural network, and the overall recognition rate could reach as high as 97.5%. Experiments showed that laser induced fluorescence spectrum technology was fast, non-contact, and highly sensitive. Combined with BP neural network, it would become a new technique to detect the trench oil.

Detection of chitinase activity by 2-aminobenzoic acid labeling of chito-oligosaccharides.

PubMed

Ghauharali-van der Vlugt, Karen; Bussink, Anton P; Groener, Johanna E M; Boot, Rolf G; Aerts, Johannes M F G

2009-01-01

Chitinases are hydrolases capable of hydrolyzing the abundant natural polysaccharide chitin. Next to artificial fluorescent substrates, more physiological chito-oligomers are commonly used in chitinase assays. Analysis of chito-oligosaccharides products is generally accomplished by UV detection. However, the relatively poor sensitivity poses a serious limitation. Here we report on a novel, much more sensitive assay for the detection of chito-oligosaccharide reaction products released by chitinases, based on fluorescent detection, following chemical labeling by 2-aminobenzoic acid. Comparison with existing UV-based assays, shows that the novel assay offers the same advantages yet allows detection of chito-oligosaccharides in the low picomolar range.

Phase-sensitive flow cytometer

DOEpatents

Steinkamp, John A.

1993-01-01

A phase-sensitive flow cytometer (FCM) provides additional FCM capability to use the fluorescence lifetime of one or more fluorochromes bound to single cells to provide additional information regarding the cells. The resulting fluorescence emission can be resolved into individual fluorescence signals if two fluorochromes are present or can be converted directly to a decay lifetime from a single fluorochrome. The excitation light for the fluorochromes is modulated to produce an amplitude modulated fluorescence pulse as the fluorochrome is excited in the FCM. The modulation signal also forms a reference signal that is phase-shifted a selected amount for subsequent mixing with the output modulated fluorescence intensity signal in phase-sensitive detection circuitry. The output from the phase-sensitive circuitry is then an individual resolved fluorochrome signal or a single fluorochrome decay lifetime, depending on the applied phase shifts.

Fluorescent Probes for Sensitive and Selective Detection of pH Changes in Live Cells in Visible and Near-infrared Channels.

PubMed

Fang, Mingxi; Adhikari, Rashmi; Bi, Jianheng; Mazi, Wafa; Dorh, Nethaniah; Wang, Jianbo; Conner, Nathan; Ainsley, Jon; Karabencheva-Christova, Tatyana G; Luo, Fen-Tair; Tiwari, Ashutosh; Liu, Haiying

2017-12-28

We report five fluorescent probes based on coumarin-hybridized fluorescent dyes with spirolactam ring structures (A-E) to detect pH changes in live cell by monitoring visible and near-infrared fluorescence changes. Under physiological or basic conditions, the fluorescent probes A, B, C, D and E preserve their spirolactam ring-closed forms and only display fluorescent peaks in the visible region corresponding to coumarin moieties at 497, 483, 498, 497 and 482 nm, respectively. However, at acidic pH, the rings of the spirolactam forms of the fluorescent probes A, B, C, D and E open up, generating new near-infrared fluorescence peaks at 711, 696, 707, 715, and 697 nm, respectively, through significantly extended π-conjugation to coumarin moieties of the fluorophores. The fluorescent probes B and E can be applied to visualize pH changes by monitoring visible as well as near-infrared fluorescence changes. This helps avoid fluorescence imaging blind spots at neutral or basic pH, which typical pH fluorescent probes encounter. The probes exhibit high sensitivity to pH changes, excellent photostability, low auto-fluorescence background and good cell membrane permeability.

An ultra-small, multi-point, and multi-color photo-detection system with high sensitivity and high dynamic range.

PubMed

Anazawa, Takashi; Yamazaki, Motohiro

2017-12-05

Although multi-point, multi-color fluorescence-detection systems are widely used in various sciences, they would find wider applications if they are miniaturized. Accordingly, an ultra-small, four-emission-point and four-color fluorescence-detection system was developed. Its size (space between emission points and a detection plane) is 15 × 10 × 12 mm, which is three-orders-of-magnitude smaller than that of a conventional system. Fluorescence from four emission points with an interval of 1 mm on the same plane was respectively collimated by four lenses and split into four color fluxes by four dichroic mirrors. Then, a total of sixteen parallel color fluxes were directly input into an image sensor and simultaneously detected. The emission-point plane and the detection plane (the image-sensor surface) were parallel and separated by a distance of only 12 mm. The developed system was applied to four-capillary array electrophoresis and successfully achieved Sanger DNA sequencing. Moreover, compared with a conventional system, the developed system had equivalent high fluorescence-detection sensitivity (lower detection limit of 17 pM dROX) and 1.6-orders-of-magnitude higher dynamic range (4.3 orders of magnitude).

A reversible metal ion fueled DNA three-way junction molecular device for "turn-on and -off" fluorescence detection of mercury ions (II) and biothiols respectively with high selectivity and sensitivity.

PubMed

Ma, Long; Wu, Guanrong; Li, Yufeng; Qin, Ping; Meng, Lingpei; Liu, Haiyan; Li, Yuyin; Diao, Aipo

2015-11-21

We constructed a reversible molecular device in the nanoscale based on a DNA three-way junction (3WJ) fueled by Hg(2+) binding and sequestration. It is highly responsive to external stimuli, which brings about optically detectable global structural changes. Such a DNA device can serve as a novel "turn-on and -off" fluorescent sensor for Hg(2+) and biothiol detection with high selectivity and sensitivity.

Scanning Fiber Endoscope Improves Detection of 5-Aminolevulinic Acid-Induced Protoporphyrin IX Fluorescence at the Boundary of Infiltrative Glioma.

PubMed

Belykh, Evgenii; Miller, Eric J; Hu, Danying; Martirosyan, Nikolay L; Woolf, Eric C; Scheck, Adrienne C; Byvaltsev, Vadim A; Nakaji, Peter; Nelson, Leonard Y; Seibel, Eric J; Preul, Mark C

2018-05-01

Fluorescence-guided surgery with protoporphyrin IX (PpIX) as a photodiagnostic marker is gaining acceptance for resection of malignant gliomas. Current wide-field imaging technologies do not have sufficient sensitivity to detect low PpIX concentrations. We evaluated a scanning fiber endoscope (SFE) for detection of PpIX fluorescence in gliomas and compared it to an operating microscope (OPMI) equipped with a fluorescence module and to a benchtop confocal laser scanning microscope (CLSM). 5-Aminolevulinic acid-induced PpIX fluorescence was assessed in GL261-Luc2 cells in vitro and in vivo after implantation in mouse brains, at an invading glioma growth stage, simulating residual tumor. Intraoperative fluorescence of high and low PpIX concentrations in normal brain and tumor regions with SFE, OPMI, CLSM, and histopathology were compared. SFE imaging of PpIX correlated to CLSM at the cellular level. PpIX accumulated in normal brain cells but significantly less than in glioma cells. SFE was more sensitive to accumulated PpIX in fluorescent brain areas than OPMI (P < 0.01) and dramatically increased imaging time (>6×) before tumor-to-background contrast was diminished because of photobleaching. SFE provides new endoscopic capabilities to view PpIX-fluorescing tumor regions at cellular resolution. SFE may allow accurate imaging of 5-aminolevulinic acid labeling of gliomas and other tumor types when current detection techniques have failed to provide reliable visualization. SFE was significantly more sensitive than OPMI to low PpIX concentrations, which is relevant to identifying the leading edge or metastasizing cells of malignant glioma or to treating low-grade gliomas. This new application has the potential to benefit surgical outcomes. Copyright © 2018 Elsevier Inc. All rights reserved.

Sentinel lymph node detection in gynecologic malignancies by a handheld fluorescence camera

NASA Astrophysics Data System (ADS)

Hirsch, Ole; Szyc, Lukasz; Muallem, Mustafa Zelal; Ignat, Iulia; Chekerov, Radoslav; Macdonald, Rainer; Sehouli, Jalid; Braicu, Ioana; Grosenick, Dirk

2017-02-01

Near-infrared fluorescence imaging using indocyanine green (ICG) as a tracer is a promising technique for mapping the lymphatic system and for detecting sentinel lymph nodes (SLN) during cancer surgery. In our feasibility study we have investigated the application of a custom-made handheld fluorescence camera system for the detection of lymph nodes in gynecological malignancies. It comprises a low cost CCD camera with enhanced NIR sensitivity and two groups of LEDs emitting at wavelengths of 735 nm and 830 nm for interlaced recording of fluorescence and reflectance images of the tissue, respectively. With the help of our system, surgeons can observe fluorescent tissue structures overlaid onto the anatomical image on a monitor in real-time. We applied the camera system for intraoperative lymphatic mapping in 5 patients with vulvar cancer, 5 patients with ovarian cancer, 3 patients with cervical cancer, and 3 patients with endometrial cancer. ICG was injected at four loci around the primary malignant tumor during surgery. After a residence time of typically 15 min fluorescence images were taken in order to visualize the lymph nodes closest to the carcinomas. In cases with vulvar cancer about half of the lymph nodes detected by routinely performed radioactive SLN mapping have shown fluorescence in vivo as well. In the other types of carcinomas several lymph nodes could be detected by fluorescence during laparotomy. We conclude that our low cost camera system has sufficient sensitivity for lymphatic mapping during surgery.

A carbon dot-based "off-on" fluorescent probe for highly selective and sensitive detection of phytic acid.

PubMed

Gao, Zhao; Wang, Libing; Su, Rongxin; Huang, Renliang; Qi, Wei; He, Zhimin

2015-08-15

We herein report a facile, one-step pyrolysis synthesis of photoluminescent carbon dots (CDs) using citric acid as the carbon source and lysine as the surface passivation reagent. The as-prepared CDs show narrow size distribution, excellent blue fluorescence and good photo-stability and water dispersivity. The fluorescence of the CDs was found to be effectively quenched by ferric (Fe(III)) ions with high selectivity via a photo-induced electron transfer (PET) process. Upon addition of phytic acid (PA) to the CDs/Fe(III) complex dispersion, the fluorescence of the CDs was significantly recovered, arising from the release of Fe(III) ions from the CDs/Fe(III) complex because PA has a higher affinity for Fe(III) ions compared to CDs. Furthermore, we developed an "off-on" fluorescence assay method for the detection of phytic acid using CDs/Fe(III) as a fluorescent probe. This probe enables the selective detection of PA with a linear range of 0.68-18.69 μM and a limit of detection (signal-to-noise ratio is 3) of 0.36 μM. The assay method demonstrates high selectivity, repeatability, stability and recovery ratio in the detection of the standard and real PA samples. We believe that the facile operation, low-cost, high sensitivity and selectivity render this CD-based "off-on" fluorescent probe an ideal sensing platform for the detection of PA. Copyright © 2015 Elsevier B.V. All rights reserved.

The use of one- and two- photon induced fluorescence spectroscopy for the optical characterization of carcinogenic aflatoxins

NASA Astrophysics Data System (ADS)

Smeesters, L.; Meulebroeck, W.; Raeymaekers, S.; Thienpont, H.

2014-09-01

Carcinogenic and toxic contaminants in food and feed products are nowadays mostly detected by destructive, time-consuming chemical analyses, like HPLC and LC-MS/MS methods. However, as a consequence of the severe and growing regulations on food products by the European Union, there arose an increased demand for the ultra-fast, high-sensitive and non-destructive detection of contaminants in food and feed products. Therefore, we have investigated fluorescence spectroscopy for the characterization of carcinogenic aflatoxins. With the use of a tunable titanium-sapphire laser in combination with second and third harmonic wavelength generation, both one- and two-photon induced fluorescence excitation wavelengths could be generated using the same setup. We characterized and compared the one- and two-photon induced fluorescence spectra of pure aflatoxin powder, after excitation with 365nm and 730nm respectively. Moreover, we investigated the absolute fluorescence intensity as function of the excitation power density. Afterwards, we applied our characterization setup to the detection of aflatoxins in maize grains. The fluorescence spectra of both healthy and contaminated maize samples were experimentally characterized. In addition to the fluorescence spectrum of the pure aflatoxin, we observed an unwanted influence of the intrinsic fluorescence of the maize. Depending on the excitation wavelength, a varying contrast between the fluorescence spectra of the healthy and contaminated samples was obtained. After a comparison of the measured fluorescence signals, a detection criterion for the optical identification of the contaminated maize samples could be defined. As a result, this illustrates the use of fluorescence spectroscopy as a valuable tool for the non-destructive, real-time and high-sensitive detection of aflatoxins in maize.

A Comparison of the Capability of Sensitivity Level 3 and Sensitivity Level 4 Fluorescent Penetrants to Detect Fatigue Cracks in Aluminum

NASA Technical Reports Server (NTRS)

Parker, Bradford, H.

2009-01-01

Historically both sensitivity level 3 and sensitivity level 4 fluorescent penetrants have been used to perform NASA Standard Level inspections of aerospace hardware. In April 2008, NASA-STD-5009 established a requirement that only sensitivity level 4 penetrants were acceptable for inspections of NASA hardware. Having NASA contractors change existing processes or perform demonstration tests to certify sensitivity level 3 penetrants posed a potentially huge cost to the Agency. This study was conducted to directly compare the probability of detection sensitivity level 3 and level 4 penetrants using both Method A and Method D inspection processes. The study results strongly support the conclusion that sensitivity level 3 penetrants are acceptable for NASA Standard Level inspections

Quick and simple estimation of bacteria using a fluorescent paracetamol dimer-Au nanoparticle composite

NASA Astrophysics Data System (ADS)

Sahoo, Amaresh Kumar; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

2012-02-01

Rapid, simple and sensitive detection of bacterial contamination is critical for safeguarding public health and the environment. Herein, we report an easy method of detection as well as enumeration of the bacterial cell number on the basis of fluorescence quenching of a non-antibacterial fluorescent nanocomposite, consisting of paracetamol dimer (PD) and Au nanoparticles (NPs), in the presence of bacteria. The composite was synthesized by reaction of paracetamol (p-hydroxyacetanilide) with HAuCl4. The Au NPs of the composite were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction and selected area electron diffraction analysis. The paracetamol dimer in the composite showed emission peak at 435 nm when excited at 320 nm. The method successfully detected six bacterial strains with a sensitivity of 100 CFU mL-1. The Gram-positive and Gram-negative bacteria quenched the fluorescence of the composite differently, making it possible to distinguish between the two. The TEM analysis showed interaction of the composite with bacteria without any apparent damage to the bacteria. The chi-square test established the accuracy of the method. Quick, non-specific and highly sensitive detection of bacteria over a broad range of logarithmic dilutions within a short span of time demonstrates the potential of this method as an alternative to conventional methods.Rapid, simple and sensitive detection of bacterial contamination is critical for safeguarding public health and the environment. Herein, we report an easy method of detection as well as enumeration of the bacterial cell number on the basis of fluorescence quenching of a non-antibacterial fluorescent nanocomposite, consisting of paracetamol dimer (PD) and Au nanoparticles (NPs), in the presence of bacteria. The composite was synthesized by reaction of paracetamol (p-hydroxyacetanilide) with HAuCl4. The Au NPs of the composite were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction and selected area electron diffraction analysis. The paracetamol dimer in the composite showed emission peak at 435 nm when excited at 320 nm. The method successfully detected six bacterial strains with a sensitivity of 100 CFU mL-1. The Gram-positive and Gram-negative bacteria quenched the fluorescence of the composite differently, making it possible to distinguish between the two. The TEM analysis showed interaction of the composite with bacteria without any apparent damage to the bacteria. The chi-square test established the accuracy of the method. Quick, non-specific and highly sensitive detection of bacteria over a broad range of logarithmic dilutions within a short span of time demonstrates the potential of this method as an alternative to conventional methods. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr11837h

Optical imaging for the diagnosis of oral cancer and oral potentially malignant disorders

NASA Astrophysics Data System (ADS)

Yoshida, K.

2016-03-01

Optical Imaging is being conducted as a therapeutic non-invasive. Many kinds of the light source are selected for this purpose. Recently the oral cancer screening is conducted by using light-induced tissue autofluorescence examination such as several kinds of handheld devices. However, the mechanism of its action is still not clear. Therefore basic experimental research was conducted. One of auto fluorescence Imaging (AFI) device, VELscopeTM and near-infrared (NIR) fluorescence imaging using ICG-labeled antibody as a probe were compared using oral squamous cell carcinoma (OSCC) mouse models. The experiments revealed that intracutaneous tumor was successfully visualized as low density image by VELscopeTM and high density image by NIR image. In addition, VELscopeTM showed higher sensitivity and lower specificity than that of NIR fluorescence imaging and the sensitivity of identification of carcinoma areas with the VELscopeTM was good results. However, further more studies were needed to enhance the screening and diagnostic uses, sensitivity and specificity for detecting malignant lesions and differentiation from premalignant or benign lesions. Therefore, additional studies were conducted using a new developed near infrared (NIR) fluorescence imaging method targeting podoplanine (PDPN) which consists of indocyanine green (ICG)-labeled anti-human podoplanin antibody as a probe and IVIS imaging system or a handy realtime ICG imaging device that is overexpressed in oral malignant neoplasm to improve imaging for detection of early oral malignant neoplasm. Then evaluated for its sensitivity and specificity for detection of oral malignant neoplasm in xenografted mice model and compared with VELscopeTM. The results revealed that ICG fluorescence imaging method and VELscopeTM had the almost the same sensitivity for detection of oral malignant neoplasm. The current topics of optical imaging about oral malignant neoplasm were reviewed.

Make Caffeine Visible: a Fluorescent Caffeine “Traffic Light” Detector

NASA Astrophysics Data System (ADS)

Xu, Wang; Kim, Tae-Hyeong; Zhai, Duanting; Er, Jun Cheng; Zhang, Liyun; Kale, Anup Atul; Agrawalla, Bikram Keshari; Cho, Yoon-Kyoung; Chang, Young-Tae

2013-07-01

Caffeine has attracted abundant attention due to its extensive existence in beverages and medicines. However, to detect it sensitively and conveniently remains a challenge, especially in resource-limited regions. Here we report a novel aqueous phase fluorescent caffeine sensor named Caffeine Orange which exhibits 250-fold fluorescence enhancement upon caffeine activation and high selectivity. Nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy indicate that π-stacking and hydrogen-bonding contribute to their interactions while dynamic light scattering and transmission electron microscopy experiments demonstrate the change of Caffeine Orange ambient environment induces its fluorescence emission. To utilize this probe in real life, we developed a non-toxic caffeine detection kit and tested it for caffeine quantification in various beverages. Naked-eye sensing of various caffeine concentrations was possible based on color changes upon irradiation with a laser pointer. Lastly, we performed the whole system on a microfluidic device to make caffeine detection quick, sensitive and automated.

FRET-based quantum dot immunoassay for rapid and sensitive detection of Aspergillus amstelodami.

PubMed

Kattke, Michele D; Gao, Elizabeth J; Sapsford, Kim E; Stephenson, Larry D; Kumar, Ashok

2011-01-01

In this study, a fluorescence resonance energy transfer (FRET)-based quantum dot (QD) immunoassay for detection and identification of Aspergillus amstelodami was developed. Biosensors were formed by conjugating QDs to IgG antibodies and incubating with quencher-labeled analytes; QD energy was transferred to the quencher species through FRET, resulting in diminished fluorescence from the QD donor. During a detection event, quencher-labeled analytes are displaced by higher affinity target analytes, creating a detectable fluorescence signal increase from the QD donor. Conjugation and the resulting antibody:QD ratios were characterized with UV-Vis spectroscopy and QuantiT protein assay. The sensitivity of initial fluorescence experiments was compromised by inherent autofluorescence of mold spores, which produced low signal-to-noise and inconsistent readings. Therefore, excitation wavelength, QD, and quencher were adjusted to provide optimal signal-to-noise over spore background. Affinities of anti-Aspergillus antibody for different mold species were estimated with sandwich immunoassays, which identified A. fumigatus and A. amstelodami for use as quencher-labeled- and target-analytes, respectively. The optimized displacement immunoassay detected A. amstelodami concentrations as low as 10(3) spores/mL in five minutes or less. Additionally, baseline fluorescence was produced in the presence of 10(5) CFU/mL heat-killed E. coli O157:H7, demonstrating high specificity. This sensing modality may be useful for identification and detection of other biological threat agents, pending identification of suitable antibodies. Overall, these FRET-based QD-antibody biosensors represent a significant advancement in detection capabilities, offering sensitive and reliable detection of targets with applications in areas from biological terrorism defense to clinical analysis.

FRET-Based Quantum Dot Immunoassay for Rapid and Sensitive Detection of Aspergillus amstelodami

PubMed Central

Kattke, Michele D.; Gao, Elizabeth J.; Sapsford, Kim E.; Stephenson, Larry D.; Kumar, Ashok

2011-01-01

In this study, a fluorescence resonance energy transfer (FRET)-based quantum dot (QD) immunoassay for detection and identification of Aspergillus amstelodami was developed. Biosensors were formed by conjugating QDs to IgG antibodies and incubating with quencher-labeled analytes; QD energy was transferred to the quencher species through FRET, resulting in diminished fluorescence from the QD donor. During a detection event, quencher-labeled analytes are displaced by higher affinity target analytes, creating a detectable fluorescence signal increase from the QD donor. Conjugation and the resulting antibody:QD ratios were characterized with UV-Vis spectroscopy and QuantiT protein assay. The sensitivity of initial fluorescence experiments was compromised by inherent autofluorescence of mold spores, which produced low signal-to-noise and inconsistent readings. Therefore, excitation wavelength, QD, and quencher were adjusted to provide optimal signal-to-noise over spore background. Affinities of anti-Aspergillus antibody for different mold species were estimated with sandwich immunoassays, which identified A. fumigatus and A. amstelodami for use as quencher-labeled- and target-analytes, respectively. The optimized displacement immunoassay detected A. amstelodami concentrations as low as 103 spores/mL in five minutes or less. Additionally, baseline fluorescence was produced in the presence of 105 CFU/mL heat-killed E. coli O157:H7, demonstrating high specificity. This sensing modality may be useful for identification and detection of other biological threat agents, pending identification of suitable antibodies. Overall, these FRET-based QD-antibody biosensors represent a significant advancement in detection capabilities, offering sensitive and reliable detection of targets with applications in areas from biological terrorism defense to clinical analysis. PMID:22163961

Method Of Signal Amplification In Multi-Chromophore Luminescence Sensors

DOEpatents

Levitsky, Igor A.; Krivoshlykov, Sergei G.

2004-02-03

A fluorescence-based method for highly sensitive and selective detection of analyte molecules is proposed. The method employs the energy transfer between two or more fluorescent chromophores in a carefully selected polymer matrix. In one preferred embodiment, signal amplification has been achieved in the fluorescent sensing of dimethyl methylphosphonate (DMMP) using two dyes, 3-aminofluoranthene (AM) and Nile Red (NR), in a hydrogen bond acidic polymer matrix. The selected polymer matrix quenches the fluorescence of both dyes and shifts dye emission and absorption spectra relative to more inert matrices. Upon DMMP sorption, the AM fluorescence shifts to the red at the same time the NR absorption shifts to the blue, resulting in better band overlap and increased energy transfer between chromophores. In another preferred embodiment, the sensitive material is incorporated into an optical fiber system enabling efficient excitation of the dye and collecting the fluorescent signal form the sensitive material on the remote end of the system. The proposed method can be applied to multichromophore luminescence sensor systems incorporating N-chromophores leading to N-fold signal amplification and improved selectivity. The method can be used in all applications where highly sensitive detection of basic gases, such as dimethyl methylphosphonate (DMMP), Sarin, Soman and other chemical warfare agents having basic properties, is required, including environmental monitoring, chemical industry and medicine.

Sensitive Carbohydrate Detection using Surface Enhanced Raman Tagging

PubMed Central

Vangala, Karthikeshwar; Yanney, Michael; Hsiao, Cheng-Te; Wu, Wells W.; Shen, Rong-Fong; Zou, Sige; Sygula, Andrzej; Zhang, Dongmao

2010-01-01

Glycomic analysis is an increasingly important field in biological and biomedical research as glycosylation is one of the most important protein post-translational modifications. We have developed a new technique to detect carbohydrates using surface enhanced Raman spectroscopy (SERS) by designing and applying a Rhodamine B derivative as the SERS tag. Using a reductive amination reaction, the Rhodamine-based tag (RT) was successfully conjugated to three model carbohydrates (glucose, lactose and glucuronic acid). SERS detection limits obtained with 632 nm HeNe laser were ~1 nM in concentration for all the RT-carbohydrate conjugates and ~10 fmol in total sample consumption. The dynamic range of the SERS method is about 4 orders of magnitude, spanning from 1 nM to 5 µM. Ratiometric SERS quantification using isotope-substituted SERS internal references also allows comparative quantifications of carbohydrates labeled with RT and deuterium/hydrogen substituted RT tags, respectively. In addition to enhancing the SERS detection of the tagged carbohydrates, the Rhodamine tagging facilitates fluorescence and mass spectrometric detection of carbohydrates. Current fluorescence sensitivity of RT-carbohydrates is ~ 3 nM in concentration while the mass spectrometry (MS) sensitivity is about 1 fmol that was achieved with linear ion trap electrospray ionization (ESI)-MS instrument. Potential applications that take advantage of the high SERS, fluorescence and MS sensitivity of this SERS tagging strategy are discussed for practical glycomic analysis where carbohydrates may be quantified with a fluorescence and SERS technique, and then identified with ESI-MS techniques. PMID:21082777

Development of a fluorescent immnunochromatographic assay for the procalcitonin detection of clinical patients in China.

PubMed

Wang, Haiying; Wang, Hong; Chen, Shaopei; Dzakah, Emmanuel E; Kang, Keren; Wang, Jihua; Wang, Jufang

2015-04-15

Procalcitonin (PCT) has been recognized as a biomarker in severe inflammation, infection and sepsis. PCT detection in serum requires sensitive and specific antibodies. In this study, we generated monoclonal antibodies (mAbs) and developed fluorescent immunochromatographic assay for PCT detection. Human recombinant PCT was used as immunogen. mAbs against PCT were developed and applied to fluorescent immunochromatographic assay for PCT detection in clinical samples. Out of 35 hybridoma cell lines secreting antibodies against the recombinant PCT, five sensitive and specific cell lines were selected and designated as F6, G2, C2, D2 and E5. All these antibodies have no cross reaction with calcitonin or calcitonin gene-related peptides (CGRP). After screening for pairing, mAb F6 was labeled with fluorescent microspheres and C2 was coated on a nitrocellulose membrane for immunochromatographic test. All 35 clinical samples were detected by the mAb F6-C2 test strips and the bioMérieux PCT assay. The test strips showed high specificity and sensitivity for PCT. Good correlation was observed between our immunochromatographic test strips and the bioMérieux PCT assay (R(2):0.986). These newly developed anti-PCT mAbs and fluorescent immunochromatographic assay can serve as important diagnostic tools for a fast, reliable and point-of-care testing for easy determination of PCT in serum and diagnosis of bacterial infection, inflammation or sepsis. Copyright © 2015 Elsevier B.V. All rights reserved.

Rapid and quantitative detection of zoonotic influenza A virus infection utilizing coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT).

PubMed

Yeo, Seon-Ju; Huong, Dinh Thi; Hong, Nguyen Ngoc; Li, Chun-Ying; Choi, Kyunghan; Yu, Kyoungsik; Choi, Du-Young; Chong, Chom-Kyu; Choi, Hak Soo; Mallik, Shyam Kumar; Kim, Hak Sung; Sung, Haan Woo; Park, Hyun

2014-01-01

Great efforts have been made to develop robust signal-generating fluorescence materials which will help in improving the rapid diagnostic test (RDT) in terms of sensitivity and quantification. In this study, we developed coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT) assay with enhanced sensitivity as a quantitative diagnostic tool in typical RDT environments. The accuracy of the proposed FICT was compared with that of dot blot immunoassay techniques and conventional RDTs. Through conjugation of coumarin-derived dendrimers with latex beads, fluorescent emission covering broad output spectral ranges was obtained which provided a distinct advantage of easy discrimination of the fluorescent emission of the latex beads with a simple insertion of a long-pass optical filter away from the excitation wavelength. The newly developed FICT assay was able to detect 100 ng/10 μL of influenza A nucleoprotein (NP) antigen within 5 minutes, which corresponded to 2.5-fold higher sensitivity than that of the dot blot immunoassay or conventional RDTs. Moreover, the FICT assay was confirmed to detect at least four avian influenza A subtypes (H5N3, H7N1, H7N7, and H9N2). On applying the FICT to the clinical swab samples infected with respiratory viruses, our FICT assay was confirmed to differentiate influenza H1N1 infection from other respiratory viral diseases. These data demonstrate that the proposed FICT assay is able to detect zoonotic influenza A viruses with a high sensitivity, and it enables the quantitation of the infection intensity by providing the numerical diagnostic values; thus demonstrating enhanced detectability of influenza A viruses.

Highly sensitive oligothiophene-phenylamine-based dual-functional fluorescence "turn-on" sensor for rapid and simultaneous detection of Al3+ and Fe3+ in environment and food samples.

PubMed

Guo, Zongrang; Niu, Qingfen; Li, Tianduo

2018-07-05

Developing low-cost and efficient sensors for rapid, selective and sensitive detection of the transition metal ions in environmental and food science is very important. In this study, a novel dual-functional fluorescent "turn-on" sensor 3TP based on oligothiophene-phenylamine Schiff base has been synthesized for discrimination and simultaneous detection of both Al 3+ and Fe 3+ ions with high selectivity and anti-interference over other metal ions. Sensor 3TP displayed a very fast fluorescence-enhanced response towards Al 3+ and Fe 3+ ions with low detection limits (0.177μM for Al 3+ and 0.172μM for Fe 3+ ) and wide pH response range (4.0-12.0). The Al 3+ /Fe 3+ sensing mechanisms were investigated by fluorescence experiments, 1 H NMR titrations, FT-IR and ESI-MS spectra. Importantly, sensor 3TP was served as an efficient solid material for the highly sensitive and selective detection of Fe 3+ on TLC plates. Moreover, the sensor 3TP has been successfully used to detect trace Al 3+ and Fe 3+ in environment and food samples with satisfactory results and good recoveries, revealing a convenient, reliable and accurate method for Al 3+ and Fe 3+ analysis in real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Highly sensitive oligothiophene-phenylamine-based dual-functional fluorescence "turn-on" sensor for rapid and simultaneous detection of Al3+ and Fe3+ in environment and food samples

NASA Astrophysics Data System (ADS)

Guo, Zongrang; Niu, Qingfen; Li, Tianduo

2018-07-01

Developing low-cost and efficient sensors for rapid, selective and sensitive detection of the transition metal ions in environmental and food science is very important. In this study, a novel dual-functional fluorescent "turn-on" sensor 3TP based on oligothiophene-phenylamine Schiff base has been synthesized for discrimination and simultaneous detection of both Al3+ and Fe3+ ions with high selectivity and anti-interference over other metal ions. Sensor 3TP displayed a very fast fluorescence-enhanced response towards Al3+ and Fe3+ ions with low detection limits (0.177 μM for Al3+ and 0.172 μM for Fe3+) and wide pH response range (4.0-12.0). The Al3+/Fe3+ sensing mechanisms were investigated by fluorescence experiments, 1H NMR titrations, FT-IR and ESI-MS spectra. Importantly, sensor 3TP was served as an efficient solid material for the highly sensitive and selective detection of Fe3+ on TLC plates. Moreover, the sensor 3TP has been successfully used to detect trace Al3+ and Fe3+ in environment and food samples with satisfactory results and good recoveries, revealing a convenient, reliable and accurate method for Al3+ and Fe3+ analysis in real samples.

Improved Diffuse Fluorescence Flow Cytometer Prototype for High Sensitivity Detection of Rare Circulating Cells In Vivo

NASA Astrophysics Data System (ADS)

Pestana, Noah Benjamin

Accurate quantification of circulating cell populations is important in many areas of pre-clinical and clinical biomedical research, for example, in the study of cancer metastasis or the immune response following tissue and organ transplants. Normally this is done "ex-vivo" by drawing and purifying a small volume of blood and then analyzing it with flow cytometry, hemocytometry or microfludic devices, but the sensitivity of these techniques are poor and the process of handling samples has been shown to affect cell viability and behavior. More recently "in vivo flow cytometry" (IVFC) techniques have been developed where fluorescently-labeled cells flowing in a small blood vessel in the ear or retina are analyzed, but the sensitivity is generally poor due to the small sampling volume. To address this, our group recently developed a method known as "Diffuse Fluorescence Flow Cytometry" (DFFC) that allows detection and counting of rare circulating cells with diffuse photons, offering extremely high single cell counting sensitivity. In this thesis, an improved DFFC prototype was designed and validated. The chief improvements were three-fold, i) improved optical collection efficiency, ii) improved detection electronics, and iii) development of a method to mitigate motion artifacts during in vivo measurements. In combination, these improvements yielded an overall instrument detection sensitivity better than 1 cell/mL in vivo, which is the most sensitive IVFC system reported to date. Second, development and validation of a low-cost microfluidic device reader for analysis of ocular fluids is described. We demonstrate that this device has equivalent or better sensitivity and accuracy compared a fluorescence microscope, but at an order-of-magnitude reduced cost with simplified operation. Future improvements to both instruments are also discussed.

Highly selective and sensitive determination of Cu2+ in drink and water samples based on a 1,8-diaminonaphthalene derived fluorescent sensor

NASA Astrophysics Data System (ADS)

Sun, Tao; Li, Yang; Niu, Qingfen; Li, Tianduo; Liu, Yan

2018-04-01

A new simple and efficient fluorescent sensor L based on 1,8-diaminonaphthalene Schiff-base for highly sensitive and selective determination of Cu2+ in drink and water has been developed. This Cu2+-selective detection over other tested metal ions displayed an obvious color change from blue to colorless easily detected by naked eye. The detection limit is determined to be as low as 13.2 nM and the response time is very fast within 30 s. The 1:1 binding mechanism was well confirmed by fluorescence measurements, IR analysis and DFT calculations. Importantly, this sensor L was employed for quick detection of Cu2+ in drink and environmental water samples with satisfactory results, providing a simple, rapid, reliable and feasible Cu2+-sensing method.

Sensitive detection of mercury and copper ions by fluorescent DNA/Ag nanoclusters in guanine-rich DNA hybridization

NASA Astrophysics Data System (ADS)

Peng, Jun; Ling, Jian; Zhang, Xiu-Qing; Bai, Hui-Ping; Zheng, Liyan; Cao, Qiu-E.; Ding, Zhong-Tao

2015-02-01

In this work, we designed a new fluorescent oligonucleotides-stabilized silver nanoclusters (DNA/AgNCs) probe for sensitive detection of mercury and copper ions. This probe contains two tailored DNA sequence. One is a signal probe contains a cytosine-rich sequence template for AgNCs synthesis and link sequence at both ends. The other is a guanine-rich sequence for signal enhancement and link sequence complementary to the link sequence of the signal probe. After hybridization, the fluorescence of hybridized double-strand DNA/AgNCs is 200-fold enhanced based on the fluorescence enhancement effect of DNA/AgNCs in proximity of guanine-rich DNA sequence. The double-strand DNA/AgNCs probe is brighter and stable than that of single-strand DNA/AgNCs, and more importantly, can be used as novel fluorescent probes for detecting mercury and copper ions. Mercury and copper ions in the range of 6.0-160.0 and 6-240 nM, can be linearly detected with the detection limits of 2.1 and 3.4 nM, respectively. Our results indicated that the analytical parameters of the method for mercury and copper ions detection are much better than which using a single-strand DNA/AgNCs.

Carbon nanoparticle for highly sensitive and selective fluorescent detection of mercury(II) ion in aqueous solution.

PubMed

Li, Hailong; Zhai, Junfeng; Tian, Jingqi; Luo, Yonglan; Sun, Xuping

2011-08-15

In this article, carbon nanoparticles (CNPs) were used as a novel fluorescent sensing platform for highly sensitive and selective Hg(2+) detection. To the best of our knowledge, this is the first example of CNPs obtained from candle soot used in this type of sensor. The general concept used in this approach is based on that adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by CNP via π-π stacking interactions between DNA bases and CNP leads to substantial dye fluorescence quenching; however, in the presence of Hg(2+), T-Hg(2+)-T induced hairpin structure does not adsorb on CNP and thus retains the dye fluorescence. A detection limit as low as 10nM was achieved. The present CNP-based biosensor for Hg(2+) detection exhibits remarkable specificity against other possible metal ions. Furthermore, superior selectivity performance was observed when Hg(2+) detection was carried out in the presence of a large amount of other interference ions. Finally, in order to evaluate its potential practical application, Hg(2+) detection was conducted with the use of lake water other than pure buffer and it is believed that it holds great promise for real sample analysis upon further development. Copyright © 2011 Elsevier B.V. All rights reserved.

Active substrates improving sensitivity in biomedical fluorescence microscopy

NASA Astrophysics Data System (ADS)

Le Moal, E.; Leveque-Fort, S.; Fort, E.; Lacharme, J.-P.; Fontaine-Aupart, M.-P.; Ricolleau, C.

2005-08-01

Fluorescence is widely used as a spectroscopic tool or for biomedical imaging, in particular for DNA chips. In some cases, detection of very low molecular concentrations and precise localization of biomarkers are limited by the weakness of the fluorescence signal. We present a new method based on sample substrates that improve fluorescence detection sensitivity. These active substrates consist in glass slides covered with metal (gold or silver) and dielectric (alumina) films and can directly be used with common microscope set-up. Fluorescence enhancement affects both excitation and decay rates and is strongly dependant on the distance to the metal surface. Furthermore, fluorescence collection is improved since fluorophore emission lobes are advantageously modified close to a reflective surface. Finally, additional improvements are achieved by structuring the metallic layer. Substrates morphology was mapped by Atomic Force Microscopy (AFM). Substrates optical properties were studied using mono- and bi-photonic fluorescence microscopy with time resolution. An original set-up was implemented for spatial radiation pattern's measurement. Detection improvement was then tested on commercial devices. Several biomedical applications are presented. Enhancement by two orders of magnitude are achieved for DNA chips and signal-to-noise ratio is greatly increased for cells imaging.

Rapid and ratiometric detection of hypochlorite with real application in tap water: molecules to low cost devices (TLC sticks).

PubMed

Goswami, Shyamaprosad; Manna, Abhishek; Paul, Sima; Quah, Ching Kheng; Fun, Hoong-Kun

2013-12-25

We have designed a chemodosimeter DPNO (weak fluorescence) which can be oxidized to HPNO (strong blue fluorescence) by OCl(-) with high selectivity and sensitivity in a ratiometric approach with a noticeably lower detection limit. The sensor could be useful for the detection of hypochlorites in tap water.

Bifunctional fluorescent probes for detection of amyloid aggregates and reactive oxygen species

NASA Astrophysics Data System (ADS)

Needham, Lisa-Maria; Weber, Judith; Fyfe, James W. B.; Kabia, Omaru M.; Do, Dung T.; Klimont, Ewa; Zhang, Yu; Rodrigues, Margarida; Dobson, Christopher M.; Ghandi, Sonia; Bohndiek, Sarah E.; Snaddon, Thomas N.; Lee, Steven F.

2018-02-01

Protein aggregation into amyloid deposits and oxidative stress are key features of many neurodegenerative disorders including Parkinson's and Alzheimer's disease. We report here the creation of four highly sensitive bifunctional fluorescent probes, capable of H2O2 and/or amyloid aggregate detection. These bifunctional sensors use a benzothiazole core for amyloid localization and boronic ester oxidation to specifically detect H2O2. We characterized the optical properties of these probes using both bulk fluorescence measurements and single-aggregate fluorescence imaging, and quantify changes in their fluorescence properties upon addition of amyloid aggregates of α-synuclein and pathophysiological H2O2 concentrations. Our results indicate these new probes will be useful to detect and monitor neurodegenerative disease.

Bifunctional fluorescent probes for detection of amyloid aggregates and reactive oxygen species.

PubMed

Needham, Lisa-Maria; Weber, Judith; Fyfe, James W B; Kabia, Omaru M; Do, Dung T; Klimont, Ewa; Zhang, Yu; Rodrigues, Margarida; Dobson, Christopher M; Ghandi, Sonia; Bohndiek, Sarah E; Snaddon, Thomas N; Lee, Steven F

2018-02-01

Protein aggregation into amyloid deposits and oxidative stress are key features of many neurodegenerative disorders including Parkinson's and Alzheimer's disease. We report here the creation of four highly sensitive bifunctional fluorescent probes, capable of H 2 O 2 and/or amyloid aggregate detection. These bifunctional sensors use a benzothiazole core for amyloid localization and boronic ester oxidation to specifically detect H 2 O 2 . We characterized the optical properties of these probes using both bulk fluorescence measurements and single-aggregate fluorescence imaging, and quantify changes in their fluorescence properties upon addition of amyloid aggregates of α-synuclein and pathophysiological H 2 O 2 concentrations. Our results indicate these new probes will be useful to detect and monitor neurodegenerative disease.

Bifunctional fluorescent probes for detection of amyloid aggregates and reactive oxygen species

PubMed Central

Needham, Lisa-Maria; Weber, Judith; Fyfe, James W. B.; Kabia, Omaru M.; Do, Dung T.; Klimont, Ewa; Zhang, Yu; Rodrigues, Margarida; Dobson, Christopher M.; Ghandi, Sonia; Bohndiek, Sarah E.; Snaddon, Thomas N.

2018-01-01

Protein aggregation into amyloid deposits and oxidative stress are key features of many neurodegenerative disorders including Parkinson's and Alzheimer's disease. We report here the creation of four highly sensitive bifunctional fluorescent probes, capable of H2O2 and/or amyloid aggregate detection. These bifunctional sensors use a benzothiazole core for amyloid localization and boronic ester oxidation to specifically detect H2O2. We characterized the optical properties of these probes using both bulk fluorescence measurements and single-aggregate fluorescence imaging, and quantify changes in their fluorescence properties upon addition of amyloid aggregates of α-synuclein and pathophysiological H2O2 concentrations. Our results indicate these new probes will be useful to detect and monitor neurodegenerative disease. PMID:29515860

SISGR: Room Temperature Single-Molecule Detection and Imaging by Stimulated Emission Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Xiaoliang Sunney

Single-molecule spectroscopy has made considerable impact on many disciplines including chemistry, physics, and biology. To date, most single-molecule spectroscopy work is accomplished by detecting fluorescence. On the other hand, many naturally occurring chromophores, such as retinal, hemoglobin and cytochromes, do not have detectable fluorescence. There is an emerging need for single-molecule spectroscopy techniques that do not require fluorescence. In the last proposal period, we have successfully demonstrated stimulated emission microscopy, single molecule absorption, and stimulated Raman microscopy based on a high-frequency modulation transfer technique. These first-of-a- kind new spectroscopy/microscopy methods tremendously improved our ability to observe molecules that fluorescence weakly,more » even to the limit of single molecule detection for absorption measurement. All of these methods employ two laser beams: one (pump beam) excites a single molecule to a real or virtual excited state, and the other (probe beam) monitors the absorption/emission property of the single. We extract the intensity change of the probe beam with high sensitivity by implementing a high-frequency phase-sensitive detection scheme, which offers orders of magnitude improvement in detection sensitivity over direct absorption/emission measurement. However, single molecule detection based on fluorescence or absorption is fundamentally limited due to their broad spectral response. It is important to explore other avenues in single molecule detection and imaging which provides higher molecular specificity for studying a wide variety of heterogeneous chemical and biological systems. This proposal aimed to achieve single-molecule detection sensitivity with near resonance stimulated Raman scattering (SRS) microscopy. SRS microscopy was developed in our lab as a powerful technique for imaging heterogeneous samples based on their intrinsic vibrational contrasts, which provides much higher molecular specificity than absorption and fluorescence. Current sensitivity limit of SRS microscopy has not yet reached single molecule detection. We proposed to capitalize on our state-of-the-art SRS microscopy and develop near-resonance enhanced SRS for single molecule detection of carotenoids and heme proteins. The specific aims we pursued are: (1) building the next SRS generation microscope that utilizes near resonance enhancement to allow detection and imaging of single molecules with undetectable fluorescence, such as -carotene. (2) using near-resonance SRS as a contrast mechanism to study dye-sensitize semiconductor interface, elucidating the heterogeneous electron ejection kinetics with high spatial and temporal resolution. (3) studying the binding and unbinding of oxygen in single hemoglobin molecules in order to gain molecular level understanding of the long-standing issue of cooperativity. The new methods developed in the fund period of this grant have advanced the detection sensitivity in many aspects. Near-resonance SRS improved the signal by using shorter wavelengths for SRS microscopy. Frequency modulation and multi-color SRS target the reduction of background to improve the chemical specificity of SRS while maintaining the high imaging speed. Time-domain coherent Raman scattering microscopy targets to reduce the noise floor of coherent Raman microscopy. These methods have already demonstrated first-of-a-kind new applications in biology and medical research. However, we are still one order of magnitude away from single molecule limit. It is important to continue to improve the laser specification and develop new imaging methods to finally achieve label-free single molecule microscopy.« less

Detection of Citrus tristeza virus by using fluorescence resonance energy transfer-based biosensor

NASA Astrophysics Data System (ADS)

Shojaei, Taha Roodbar; Salleh, Mohamad Amran Mohd; Sijam, Kamaruzaman; Rahim, Raha Abdul; Mohsenifar, Afshin; Safarnejad, Reza; Tabatabaei, Meisam

2016-12-01

Due to the low titer or uneven distribution of Citrus tristeza virus (CTV) in field samples, detection of CTV by using conventional detection techniques may be difficult. Therefore, in the present work, the cadmium-telluride quantum dots (QDs) was conjugated with a specific antibody against coat protein (CP) of CTV, and the CP were immobilized on the surface of gold nanoparticles (AuNPs) to develop a specific and sensitive fluorescence resonance energy transfer (FRET)-based nanobiosensor for detecting CTV. The maximum FRET efficiency for the developed nano-biosensor was observed at 60% in AuNPs-CP/QDs-Ab ratio of 1:8.5. The designed system showed higher sensitivity and specificity over enzyme linked immunosorbent assay (ELISA) with a limit of detection of 0.13 μg mL- 1 and 93% and 94% sensitivity and specificity, respectively. As designed sensor is rapid, sensitive, specific and efficient in detecting CTV, this could be envisioned for diagnostic applications, surveillance and plant certification program.

Synthesis of yeast extract-stabilized Cu nanoclusters for sensitive fluorescent detection of sulfide ions in water.

PubMed

Jin, Lihua; Zhang, Zaihua; Tang, Anwen; Li, Cong; Shen, Yehua

2016-05-15

In this work, we have presented a novel strategy to utilize as-synthesized yeast extract-stabilized Cu nanoclusters (Cu NCs) for sensitive and selective detection of S(2-). The fluorescence intensity of Cu NCs was enhanced significantly in the presence of both Na2S2O8 and S(2-). By virtue of this specific response, a Cu NC-based fluorescent turn-on sensor was developed, which allows the detection of S(2-) in the range of 0.02-0.8 μM with a detection limit of 10nM. The enhancing mechanism was also discussed based on fluorescence decay, transmission electron microscopy (TEM) and dynamic light scattering (DLS) studies, indicating that S(2-) enhanced the Cu NCs emission mainly through sulfide-induced aggregation of Cu NCs. Furthermore, we demonstrated the usability of the present approach for the detection of S(2-) in water samples, which illustrates its great potential for the environmental monitoring and water quality inspection fields. Copyright © 2015 Elsevier B.V. All rights reserved.

A new N-imidazolyl-1,8-naphthalimide based fluorescence sensor for fluoride detection.

PubMed

Wang, Junqi; Yang, Lingyun; Hou, Chen; Cao, Haishi

2012-08-21

A chemosensor is reported with high sensitivity and selectivity for detection of fluoride anion. The recognition mechanism is attributed to a fluoride-triggered disruption of the hydrogen bond between imidazole and naphthalimide moieties, resulting in a noncoplanar geometry with low fluorescence.

A Rapid and Sensitive Strip-Based Quick Test for Nerve Agents Tabun, Sarin, and Soman Using BODIPY-Modified Silica Materials.

PubMed

Climent, Estela; Biyikal, Mustafa; Gawlitza, Kornelia; Dropa, Tomáš; Urban, Martin; Costero, Ana M; Martínez-Máñez, Ramón; Rurack, Knut

2016-08-01

Test strips that in combination with a portable fluorescence reader or digital camera can rapidly and selectively detect chemical warfare agents (CWAs) such as Tabun (GA), Sarin (GB), and Soman (GD) and their simulants in the gas phase have been developed. The strips contain spots of a hybrid indicator material consisting of a fluorescent BODIPY indicator covalently anchored into the channels of mesoporous SBA silica microparticles. The fluorescence quenching response allows the sensitive detection of CWAs in the μg m(-3) range in a few seconds. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase-sensitive flow cytometer

DOEpatents

Steinkamp, J.A.

1993-12-14

A phase-sensitive flow cytometer (FCM) provides additional FCM capability to use the fluorescence lifetime of one or more fluorochromes bound to single cells to provide additional information regarding the cells. The resulting fluorescence emission can be resolved into individual fluorescence signals if two fluorochromes are present or can be converted directly to a decay lifetime from a single fluorochrome. The excitation light for the fluorochromes is modulated to produce an amplitude modulated fluorescence pulse as the fluorochrome is excited in the FCM. The modulation signal also forms a reference signal that is phase-shifted a selected amount for subsequent mixing with the output modulated fluorescence intensity signal in phase-sensitive detection circuitry. The output from the phase-sensitive circuitry is then an individual resolved fluorochrome signal or a single fluorochrome decay lifetime, depending on the applied phase shifts. 15 figures.

pHuji, a pH-sensitive red fluorescent protein for imaging of exo- and endocytosis

PubMed Central

Shen, Yi; Rosendale, Morgane

2014-01-01

Fluorescent proteins with pH-sensitive fluorescence are valuable tools for the imaging of exocytosis and endocytosis. The Aequorea green fluorescent protein mutant superecliptic pHluorin (SEP) is particularly well suited to these applications. Here we describe pHuji, a red fluorescent protein with a pH sensitivity that approaches that of SEP, making it amenable for detection of single exocytosis and endocytosis events. To demonstrate the utility of the pHuji plus SEP pair, we perform simultaneous two-color imaging of clathrin-mediated internalization of both the transferrin receptor and the β2 adrenergic receptor. These experiments reveal that the two receptors are differentially sorted at the time of endocytic vesicle formation. PMID:25385186

Label-free fluorescence strategy for sensitive microRNA detection based on isothermal exponential amplification and graphene oxide.

PubMed

Li, Wei; Hou, Ting; Wu, Min; Li, Feng

2016-01-01

MicroRNAs (miRNAs) play an important role in many biological processes, and have been regarded as potential targets and biomarkers in cancer diagnosis and therapy. Also, to meet the big challenge imposed by the characteristics of miRNAs, such as small size and vulnerability to enzymatic digestion, it is of great importance to develop accurate, sensitive and simple miRNA assays. Herein, we developed a label-free fluorescence strategy for sensitive miRNA detection by combining isothermal exponential amplification and the unique features of SYBR Green I (SG) and graphene oxide (GO), in which SG gives significantly enhanced fluorescence upon intercalation into double-stranded DNAs (dsDNAs), and GO selectively adsorbs miRNA, single-stranded DNA and SG, to protect miRNA from enzymatic digestion, and to quench the fluorescence of the adsorbed SG. In the presence of the target miRNA, the ingeniously designed hairpin probe (HP) is unfolded and the subsequent polymerization and strand displacement reaction takes place to initiate the target recycling process. The newly formed dsDNAs are then recognized and cleaved by the nicking enzyme, generating new DNA triggers with the same sequence as the target miRNA, which hybridize with intact HPs to initiate new extension reactions. As a result, the circular exponential amplification for target miRNA is achieved and large amount of dsDNAs are formed to generate significantly enhanced fluorescence upon the intercalation of SG. Thus sensitive and selective fluorescence miRNA detection is realized, and the detection limit of 3 fM is obtained. Besides, this method exhibits additional advantages of simplicity and low cost, since expensive and tedious labeling process is avoided. Therefore, the as-proposed label-free fluorescence strategy has great potential in the applications in miRNA-related clinical practices and biochemical researches. Copyright © 2015 Elsevier B.V. All rights reserved.

Quantum dots as optical labels for ultrasensitive detection of polyphenols.

PubMed

Akshath, Uchangi Satyaprasad; Shubha, Likitha R; Bhatt, Praveena; Thakur, Munna Singh

2014-07-15

Considering the fact that polyphenols have versatile activity in-vivo, its detection and quantification is very much important for a healthy diet. Laccase enzyme can convert polyphenols to yield mono/polyquinones which can quench Quantum dots fluorescence. This phenomenon of charge transfer from quinones to QDs was exploited as optical labels to detect polyphenols. CdTe QD may undergo dipolar interaction with quinones as a result of broad spectral absorption due to multiple excitonic states resulting from quantum confinement effects. Thus, "turn-off" fluorescence method was applied for ultrasensitive detection of polyphenols by using laccase. We observed proportionate quenching of QDs fluorescence with respect to polyphenol concentration in the range of 100 µg to 1 ng/mL. Also, quenching of the photoluminescence was highly efficient and stable and could detect individual and total polyphenols with high sensitivity (LOD-1 ng/mL). Moreover, proposed method was highly efficient than any other reported methods in terms of sensitivity, specificity and selectivity. Therefore, a novel optical sensor was developed for the detection of polyphenols at a sensitive level based on the charge transfer mechanism. Copyright © 2014 Elsevier B.V. All rights reserved.

Selective detection of Co2+ by fluorescent nano probe: Diagnostic approach for analysis of environmental samples and biological activities

NASA Astrophysics Data System (ADS)

Mahajan, Prasad G.; Dige, Nilam C.; Desai, Netaji K.; Patil, Shivajirao R.; Kondalkar, Vijay V.; Hong, Seong-Karp; Lee, Ki Hwan

2018-06-01

Nowadays scientist over the world are engaging to put forth improved methods to detect metal ion in an aqueous medium based on fluorescence studies. A simple, selective and sensitive method was proposed for detection of Co2+ ion using fluorescent organic nanoparticles. We synthesized a fluorescent small molecule viz. 4,4‧-{benzene-1,4-diylbis-[(Z)methylylidenenitrilo]}dibenzoic acid (BMBA) to explore its suitability as sensor for Co2+ ion and biocompatibility in form of nanoparticles. Fluorescence nanoparticles (BMBANPs) prepared by simple reprecipitation method. Aggregation induced enhanced emission of BMBANPs exhibits the narrower particle size of 68 nm and sphere shape morphology. The selective fluorescence quenching was observed by addition of Co2+ and does not affected by presence of other coexisting ion solutions. The photo-physical properties, viz. UV-absorption, fluorescence emission, and lifetime measurements are in support of ligand-metal interaction followed by static fluorescence quenching phenomenon in emission of BMBANPs. Finally, we develop a simple analytical method for selective and sensitive determination of Co2+ ion in environmental samples. The cell culture E. coli, Bacillus sps., and M. tuberculosis H37RV strain in the vicinity of BMBANPs indicates virtuous anti-bacterial and anti-tuberculosis activity which is of additional novel application shown by prepared nanoparticles.

A K(+)-mediated G-quadruplex formation enhancement fluorescence polarization system based on quantum dots for detection of Hg2+ and biothiols.

PubMed

Zhang, Juanni; Tian, Jianniao; He, Yanlong; Zhao, Yanchun; Zhao, Shulin

2014-02-25

A fluorescence polarization homogenous system based on CdTe/CdS QDs that employed a K(+)-mediated G-quadruplex as an enhancer was identified for sensitive and selective detection of Hg(2+) and biothiols in complex samples.

Fluorescence spectroscopy approaches for the development of a real-time organophosphate detection system using an enzymatic sensor.

PubMed

Carullo, Paola; Cetrangolo, Giovanni Paolo; Mandrich, Luigi; Manco, Giuseppe; Febbraio, Ferdinando

2015-02-09

Organophosphates are organic substances that contain a phosphoryl or a thiophosphoryl bond. They are mainly used around the world as pesticides, but can also be used as chemical warfare agents. Their detection is normally entrusted to techniques like GC- and LC-MS that, although sensitive, do not allow their identification on site and in real time. We have approached their identification by exploiting the high-affinity binding of these compounds with the esterase 2 from Alicyclobacillus acidocaldarius. Using an in silico analysis to evaluate the binding affinities of the enzyme with organophosphate inhibitors, like paraoxon, and other organophosphate compounds, like parathion, chlorpyriphos, and other organophosphate thio-derivatives, we have designed fluorescence spectroscopy experiments to study the quenching of the tryptophan residues after esterase 2 binding with the organophosphate pesticides. The changes in the fluorescence signals permitted an immediate and quantitative identification of these compounds from nano- to picomolar concentrations. A fluorescence based polarity-sensitive probe (ANS) was also employed as a means to understand the extent of the interactions involved, as well as to explore other ways to detect organophosphate pesticides. Finally, we designed a framework for the development of a biosensor that exploits fluorescence technology in combination with a sensitive and very stable bio-receptor.

A Metal-Polydopamine Framework (MPDA) as an Effective Fluorescent Quencher for Highly Sensitive Detection of Hg (II) And Ag (I) ions Through Exonuclease III Activity.

PubMed

Ravikumar, Ayyanu; Panneerselvam, Perumal; Morad, Norhashimah

2018-05-24

In this paper, we propose a metal-polydopamine framework (MPDA) with specific molecular probe which appears to be the most promising approach to a strong fluorescence quencher. The MPDA framework quenching ability towards various organic fluorophore such as aminoethylcomarin acetate (AMCA), 6-carboxyfluorescein (FAM), carboxyteramethylrhodamine (TAMRA) and Cy5 are used to establish a fluorescent biosensor that can selectively recognize Hg2+ and Ag+ ion. The fluorescent quenching efficiency was sufficient to achieve more than 96%. The MPDA framework also exhibits different affinities with ssDNA and dsDNA. In addition, the FAM labelled ssDNA was adsorbed onto MPDA framework, based on their interaction with the complex formed between MPDA frameworks/ssDNA taken as a sensing platform. By taking advantage of this sensor highly sensitive and selective determination of Hg2+and Ag+ ions is achieved through Exonuclease III signal amplification activity. The detection limits of Hg2+and Ag+ achieved to be 1.2 pM and 34 pM respectively, were compared to co-existing metal ions and GO based sensors. Furthermore, the potential applications of this study establish the highly sensitive fluorescence detection targets in environmental and biological fields.

Detecting RNA/DNA hybridization using double-labeled donor probes with enhanced fluorescence resonance energy transfer signals.

PubMed

Okamura, Yukio; Watanabe, Yuichiro

2006-01-01

Fluorescence resonance energy transfer (FRET) occurs when two fluorophores are in close proximity, and the emission energy of a donor fluorophore is transferred to excite an acceptor fluorophore. Using such fluorescently labeled oligonucleotides as FRET probes, makes possible specific detection of RNA molecules even if similar sequences are present in the environment. A higher ratio of signal to background fluorescence is required for more sensitive probe detection. We found that double-labeled donor probes labeled with BODIPY dye resulted in a remarkable increase in fluorescence intensity compared to single-labeled donor probes used in conventional FRET. Application of this double-labeled donor system can improve a variety of FRET techniques.

Solid-phase single molecule biosensing using dual-color colocalization of fluorescent quantum dot nanoprobes

NASA Astrophysics Data System (ADS)

Liu, Jianbo; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Liu, Wei; Wang, Dong

2013-10-01

The development of solid-phase surface-based single molecule imaging technology has attracted significant interest during the past decades. Here we demonstrate a sandwich hybridization method for highly sensitive detection of a single thrombin protein at a solid-phase surface based on the use of dual-color colocalization of fluorescent quantum dot (QD) nanoprobes. Green QD560-modified thrombin binding aptamer I (QD560-TBA I) were deposited on a positive poly(l-lysine) assembled layer, followed by bovine serum albumin blocking. It allowed the thrombin protein to mediate the binding of the easily detectable red QD650-modified thrombin binding aptamer II (QD650-TBA II) to the QD560-TBA I substrate. Thus, the presence of the target thrombin can be determined based on fluorescent colocalization measurements of the nanoassemblies, without target amplification or probe separation. The detection limit of this assay reached 0.8 pM. This fluorescent colocalization assay has enabled single molecule recognition in a separation-free detection format, and can serve as a sensitive biosensing platform that greatly suppresses the nonspecific adsorption false-positive signal. This method can be extended to other areas such as multiplexed immunoassay, single cell analysis, and real time biomolecule interaction studies.The development of solid-phase surface-based single molecule imaging technology has attracted significant interest during the past decades. Here we demonstrate a sandwich hybridization method for highly sensitive detection of a single thrombin protein at a solid-phase surface based on the use of dual-color colocalization of fluorescent quantum dot (QD) nanoprobes. Green QD560-modified thrombin binding aptamer I (QD560-TBA I) were deposited on a positive poly(l-lysine) assembled layer, followed by bovine serum albumin blocking. It allowed the thrombin protein to mediate the binding of the easily detectable red QD650-modified thrombin binding aptamer II (QD650-TBA II) to the QD560-TBA I substrate. Thus, the presence of the target thrombin can be determined based on fluorescent colocalization measurements of the nanoassemblies, without target amplification or probe separation. The detection limit of this assay reached 0.8 pM. This fluorescent colocalization assay has enabled single molecule recognition in a separation-free detection format, and can serve as a sensitive biosensing platform that greatly suppresses the nonspecific adsorption false-positive signal. This method can be extended to other areas such as multiplexed immunoassay, single cell analysis, and real time biomolecule interaction studies. Electronic supplementary information (ESI) available: Absorbance and fluorescence spectra of quantum dot nanoprobes, electrophoresis analysis, and experimental setup for fluorescence imaging with dual channels. See DOI: 10.1039/c3nr03291d

Polydopamine Nanotubes as an Effective Fluorescent Quencher for Highly Sensitive and Selective Detection of Biomolecules Assisted with Exonuclease III Amplification.

PubMed

Fan, Daoqing; Zhu, Xiaoqing; Zhai, Qingfeng; Wang, Erkang; Dong, Shaojun

2016-09-20

In this work, the effective fluorescence quenching ability of polydopamine nanotubes (PDANTs) toward various fluorescent dyes was studied and further applied to fluorescent biosensing for the first time. The PDANTs could quench the fluorophores with different emission frequencies, aminomethylcoumarin acetate (AMCA), 6-carboxyfluorescein (FAM), 6-carboxytetramethylrhodamine (TAMRA), and Cy5. All the quenching efficiencies reached to more than 97%. Taking advantage of PDANTs' different affinities toward ssDNA and dsDNA and utilizing the complex of FAM-labeled ssDNA and PDANTs as a sensing platform, we achieved highly sensitive and selective detection of human immunodeficiency virus (HIV) DNA and adenosine triphosphate (ATP) assisted with Exonuclease III amplification. The limits of detection (LODs) of HIV DNA and ATP reached to 3.5 pM and 150 nM, respectively, which were all lower than that of previous nanoquenchers with Exo III amplification, and the platform also presented good applicability in biological samples. Fluorescent sensing applications of this nanotube enlightened other targets detection based upon it and enriched the building blocks of fluorescent sensing platforms. This polydopamine nanotube also possesses excellent biocompatibility and biodegradability, which is suitable for future drug delivery, cell imaging, and other biological applications.

Coordination ability determined transition metal ions substitution of Tb in Tb-Asp fluorescent nanocrystals and a facile ions-detection approach.

PubMed

Duan, Jiazhi; Ma, Baojin; Liu, Feng; Zhang, Shan; Wang, Shicai; Kong, Ying; Du, Min; Han, Lin; Wang, Jianjun; Sang, Yuanhua; Liu, Hong

2018-04-26

Although the synthesis and fluorescent properties of lanthanide-amino acid complex nanostructures have been investigated extensively, limited studies have been reported on metal ions' substitution ability for the lanthanide ions in the complex and their effect on the fluorescent property. In this study, taking biocompatible Tb-aspartic acid (Tb-Asp) complex nanocrystals as a model, the substitution mechanism of metal ions, particularly transition metals, for Tb ions in Tb-Asp nanocrystals and the change in the fluorescent property of the Tb-Asp nanocrystals after substitution were systematically investigated. The experimental results illustrated that metal ions with higher electronegativity, higher valence, and smaller radius possess stronger ability for Tb ions' substitution in Tb-Asp nanocrystals. Based on the effect of substituting ions' concentration on the fluorescent property of Tb-Asp, a facile method for copper ions detection with high sensitivity was proposed by measuring the fluorescent intensity of Tb-Asp nanocrystals' suspensions containing different concentrations of copper ions. The good biocompatibility, great convenience of synthesis and sensitive detection ability make Tb-Asp nanocrystals a very low cost and effective material for metal ions detection, which also opens a new door for practical applications of metal-Asp coordinated nanocrystals.

A sensitive fluorescent sensor for quantification of alpha-fetoprotein based on immunosorbent assay and click chemistry.

PubMed

Xie, Qunfang; Weng, Xiuhua; Lu, Lijun; Lin, Zhenyu; Xu, Xiongwei; Fu, Caili

2016-03-15

A novel fluoresencent immunosensor for determination of cancer biomarkers such as alpha-fetoprotein (AFP) was designed by utilizing both the high specificity of antigen-antibody sandwich structure and the high sensitivity of the click chemistry based fluorescence detection. Instead of an enzyme or fluorophore, the CuO nanoparticles are labeled on the detection antibody, which was not susceptible to the change of the external environments. The CuO nanoparticles which were modified on the sandwich structure can be dissolved to produce Cu(2+) ions with the help of HCl and then the Cu(2+) ions were reduced by sodium ascorbate to produce Cu(+) ions which triggered the Cu(+) catalyzed alkyne-azide cycloaddition (CuAAC) reaction between the weak fluorescent compound (3-azido-7-hydroxycoumarin) and propargyl alcohol to form a strong fluorescent compound. A good linear relationship was observed between the fluorescence increase factor of the system and the concentration of AFP in the range of 0.025-5.0 ng/mL with a detection limit of 12 pg/mL (S/N=3). The proposed fluorescent sensor had been applied to detect AFP in the human serum samples and gave satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

Instrument for fluorescence sensing of circulating cells with diffuse light in mice in vivo.

PubMed

Zettergren, Eric; Vickers, Dwayne; Runnels, Judith; Murthy, Shashi K; Lin, Charles P; Niedre, Mark

2012-03-01

Accurate quantification of circulating cell populations in mice is important in many areas of preclinical biomedical research. Normally, this is done either by extraction and analysis of small blood samples or, more recently, by using microscopy-based in vivo fluorescence flow cytometry. We describe a new technological approach to this problem using detection of diffuse fluorescent light from relatively large blood vessels in vivo. The diffuse fluorescence flow cytometer (DFFC) uses a laser to illuminate a mouse limb and an array of optical fibers coupled to a high-sensitivity photomultiplier tube array operating in photon counting mode to detect weak fluorescence signals from cells. We first demonstrate that the DFFC instrument is capable of detecting fluorescent microspheres and Vybrant-DiD-labeled cells in a custom-made optical flow phantom with similar size, optical properties, linear flow rates, and autofluorescence as a mouse limb. We also present preliminary data demonstrating that the DFFC is capable of detecting circulating cells in nude mice in vivo. In principle, this device would allow interrogation of the whole blood volume of a mouse in minutes, with sensitivity improvement by several orders of magnitude compared to current approaches. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).

Improving the Sensitivity and Functionality of Mobile Webcam-Based Fluorescence Detectors for Point-of-Care Diagnostics in Global Health.

PubMed

Rasooly, Reuven; Bruck, Hugh Alan; Balsam, Joshua; Prickril, Ben; Ossandon, Miguel; Rasooly, Avraham

2016-05-17

Resource-poor countries and regions require effective, low-cost diagnostic devices for accurate identification and diagnosis of health conditions. Optical detection technologies used for many types of biological and clinical analysis can play a significant role in addressing this need, but must be sufficiently affordable and portable for use in global health settings. Most current clinical optical imaging technologies are accurate and sensitive, but also expensive and difficult to adapt for use in these settings. These challenges can be mitigated by taking advantage of affordable consumer electronics mobile devices such as webcams, mobile phones, charge-coupled device (CCD) cameras, lasers, and LEDs. Low-cost, portable multi-wavelength fluorescence plate readers have been developed for many applications including detection of microbial toxins such as C. Botulinum A neurotoxin, Shiga toxin, and S. aureus enterotoxin B (SEB), and flow cytometry has been used to detect very low cell concentrations. However, the relatively low sensitivities of these devices limit their clinical utility. We have developed several approaches to improve their sensitivity presented here for webcam based fluorescence detectors, including (1) image stacking to improve signal-to-noise ratios; (2) lasers to enable fluorescence excitation for flow cytometry; and (3) streak imaging to capture the trajectory of a single cell, enabling imaging sensors with high noise levels to detect rare cell events. These approaches can also help to overcome some of the limitations of other low-cost optical detection technologies such as CCD or phone-based detectors (like high noise levels or low sensitivities), and provide for their use in low-cost medical diagnostics in resource-poor settings.

Improving the Sensitivity and Functionality of Mobile Webcam-Based Fluorescence Detectors for Point-of-Care Diagnostics in Global Health

PubMed Central

Rasooly, Reuven; Bruck, Hugh Alan; Balsam, Joshua; Prickril, Ben; Ossandon, Miguel; Rasooly, Avraham

2016-01-01

Resource-poor countries and regions require effective, low-cost diagnostic devices for accurate identification and diagnosis of health conditions. Optical detection technologies used for many types of biological and clinical analysis can play a significant role in addressing this need, but must be sufficiently affordable and portable for use in global health settings. Most current clinical optical imaging technologies are accurate and sensitive, but also expensive and difficult to adapt for use in these settings. These challenges can be mitigated by taking advantage of affordable consumer electronics mobile devices such as webcams, mobile phones, charge-coupled device (CCD) cameras, lasers, and LEDs. Low-cost, portable multi-wavelength fluorescence plate readers have been developed for many applications including detection of microbial toxins such as C. Botulinum A neurotoxin, Shiga toxin, and S. aureus enterotoxin B (SEB), and flow cytometry has been used to detect very low cell concentrations. However, the relatively low sensitivities of these devices limit their clinical utility. We have developed several approaches to improve their sensitivity presented here for webcam based fluorescence detectors, including (1) image stacking to improve signal-to-noise ratios; (2) lasers to enable fluorescence excitation for flow cytometry; and (3) streak imaging to capture the trajectory of a single cell, enabling imaging sensors with high noise levels to detect rare cell events. These approaches can also help to overcome some of the limitations of other low-cost optical detection technologies such as CCD or phone-based detectors (like high noise levels or low sensitivities), and provide for their use in low-cost medical diagnostics in resource-poor settings. PMID:27196933

Molecularly Imprinted Core-Shell CdSe@SiO2/CDs as a Ratiometric Fluorescent Probe for 4-Nitrophenol Sensing

NASA Astrophysics Data System (ADS)

Liu, Mingyue; Gao, Zhao; Yu, Yanjun; Su, Rongxin; Huang, Renliang; Qi, Wei; He, Zhimin

2018-01-01

4-Nitrophenol (4-NP) is a priority pollutant in water and is both carcinogenic and genotoxic to humans and wildlife even at very low concentrations. Thus, we herein fabricated a novel molecularly imprinted core-shell nanohybrid as a ratiometric fluorescent sensor for the highly sensitive and selective detection of 4-NP. This sensor was functioned by the transfer of fluorescence resonance energy between photoluminescent carbon dots (CDs) and 4-NP. This sensor was synthesized by linking organosilane-functionalized CDs to silica-coated CdSe quantum dots (CdSe@SiO2) via Si-O bonds. The nanohybrids were further modified by anchoring a molecularly imprinted polymer (MIP) layer on the ratiometric fluorescent sensor through a facile sol-gel polymerization method. The morphology, chemical structure, and optical properties of the resulting molecularly imprinted dual-emission fluorescent probe were characterized by transmission electron microscopy and spectroscopic analysis. The probe was then applied in the detection of 4-NP and exhibited good linearity between 0.051 and 13.7 μg/mL, in addition to a low detection limit of 0.026 μg/mL. Furthermore, the simplicity, reliability, high selectivity, and high sensitivity of the developed sensor demonstrate that the combination of MIPs and ratiometric fluorescence allows the preparation of excellent fluorescent sensors for the detection of trace or ultra-trace analytes.

Recording membrane potential changes through photoacoustic voltage sensitive dye

NASA Astrophysics Data System (ADS)

Zhang, Haichong K.; Kang, Jeeun; Yan, Ping; Abou, Diane S.; Le, Hanh N. D.; Thorek, Daniel L. J.; Kang, Jin U.; Gjedde, Albert; Rahmim, Arman; Wong, Dean F.; Loew, Leslie M.; Boctor, Emad M.

2017-03-01

Monitoring of the membrane potential is possible using voltage sensitive dyes (VSD), where fluorescence intensity changes in response to neuronal electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. In contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near infrared light excitation and ultrasound detection. In this work, we develop the theoretical concept whereby the voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. Based on this concept, we synthesized a novel near infrared photoacoustic VSD (PA-VSD) whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model. With a 3-9 μM VSD concentration, we measured a PA signal increase in the range of 5.3 % to 18.1 %, and observed a corresponding signal reduction in fluorescence emission of 30.0 % to 48.7 %. A theoretical model successfully accounts for how the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate the voltage sensing capability of the dye, but also indicate the necessity of considering both fluorescence and absorbance spectral sensitivities in order to optimize the characteristics of improved photoacoustic probes. Together, our results demonstrate photoacoustic sensing as a potential new modality for sub-second recording and external imaging of electrophysiological and neurochemical events in the brain.

A fluorescence microplate screen assay for the detection of neurite outgrowth and neurotoxicity using an antibody against βIII-tubulin.

PubMed

Popova, Dina; Jacobsson, Stig O P

2014-04-01

The majority of environmental and commercial chemicals have not been evaluated for their potential to cause neurotoxicity. We have investigated if neuron specific anti-βIII-tubulin antibodies are useful in a microplate assay of neurite outgrowth of retinoic acid-induced neurons from mouse P19 embryonal carcinoma cells. By incubating the P19-derived neurons with the primary anti-βIII-tubulin antibody and a secondary Alexa Fluor 488-conjugated antibody, followed by measuring the fluorescence in a microplate reader, a time-dependent increase in anti-βIII-tubulin immunofluorescence was observed. The relative fluorescence units increased by 4.3-fold from 2 to 10 days in culture. The results corresponded well with those obtained by semi-automatic tracing of neurites in fluorescence microscopy images of βIII-tubulin-labeled neurons. The sensitivity of the neurite outgrowth assay using a microplate reader to detect neurotoxicity produced by nocodazole, methyl mercury chloride and okadaic acid was significantly higher than for a cell viability assay measuring intracellular fluorescence of calcein-AM. The microplate-based method to measure toxicity targeting neurites using anti-βIII-tubulin antibodies is however less sensitive than the extracellular lactate dehydrogenase activity assay to detect general cytotoxicity produced by high concentrations of clomipramine, or glutamate-induced excitotoxicity. In conclusion, the fluorescence microplate assay for the detection of neurite outgrowth by measuring changes in βIII-tubulin immunoreactivity is a rapid and sensitive method to assess chemical- or toxin-induced neurite toxicity. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fluorescence based explosive detection: from mechanisms to sensory materials.

PubMed

Sun, Xiangcheng; Wang, Ying; Lei, Yu

2015-11-21

The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large number of emissive sensing materials have been developed for the detection of explosives in vapor, solution, and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramolecular systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.

Highly sensitive and selective fluoride detection in water through fluorophore release from a metal-organic framework

PubMed Central

Hinterholzinger, Florian M.; Rühle, Bastian; Wuttke, Stefan; Karaghiosoff, Konstantin; Bein, Thomas

2013-01-01

The detection, differentiation and visualization of compounds such as gases, liquids or ions are key challenges for the design of selective optical chemosensors. Optical chemical sensors employ a transduction mechanism that converts a specific analyte recognition event into an optical signal. Here we report a novel concept for fluoride ion sensing where a porous crystalline framework serves as a host for a fluorescent reporter molecule. The detection is based on the decomposition of the host scaffold which induces the release of the fluorescent dye molecule. Specifically, the hybrid composite of the metal-organic framework NH2-MIL-101(Al) and fluorescein acting as reporter shows an exceptional turn-on fluorescence in aqueous fluoride-containing solutions. Using this novel strategy, the optical detection of fluoride is extremely sensitive and highly selective in the presence of many other anions. PMID:24008779

Cu2 + modulated nitrogen-doped grapheme quantum dots as a turn-off/on fluorescence sensor for the selective detection of histidine in biological fluid

NASA Astrophysics Data System (ADS)

Wang, Zhiyu; Fan, ZheFeng

2018-01-01

A highly sensitive sensor for detection of histidine (His) based on the nitrogen-doped graphene quantum dots (N-GQDs)-Cu2 + system has been designed. The N-GQDs were synthesized by one-step hydrothermal approach according to previous report. The fluorescence of N-GQDs can be effectively quenched by Cu2 + due to the binding between Cu2 + and functional groups on the surface of N-GQDs. The high affinity of His to Cu2 + enables Cu2 + to be dissociated from the surface of N-GQDs and recovering the fluorescence. The sensor displayed a sensitive response to His in the concentration range of 0-35 μmol L- 1, with a detection limit of 72.2 nmol L- 1. The proposed method is successfully applied to detect His in samples with a recovery range of 96-102%.

Ultra-sensitive detection using integrated waveguide technologies

USDA-ARS?s Scientific Manuscript database

There is a pressing need to detect analytes at very low concentrations, such as food- and water-borne pathogens (e.g. E. coli O157:H7) and biothreat agents (e.g., anthrax, toxins). Common fluorescence detection methods, such as 96 well plate readers, are not sufficiently sensitive for low concentra...

Visual and sensitive fluorescent sensing for ultratrace mercury ions by perovskite quantum dots.

PubMed

Lu, Li-Qiang; Tan, Tian; Tian, Xi-Ke; Li, Yong; Deng, Pan

2017-09-15

Mercury ions sensing is an important issue for human health and environmental safety. A novel fluorescence nanosensor was designed for rapid visual detection of ultratrace mercury ions (Hg 2+ ) by using CH 3 NH 3 PbBr 3 perovskite quantum dots (QDs) based on the surface ion-exchange mechanism. The synthesized CH 3 NH 3 PbBr 3 QDs can emitt intense green fluorescence with high quantum yield of 50.28%, and can be applied for Hg 2+ sensing with the detection limit of 0.124 nM (24.87 ppt) in the range of 0 nM-100 nM. Furthermore, the interfering metal ions have no any influence on the fluorescence intensity of QDs, showing the perovskite QDs possess the high selectivity and sensitivity for Hg 2+ detection. The sensing mechanism of perovskite QDs for Hg 2+ is has also been investigated by XPS, EDX studies, showing Pb 2+ on the surface of perovskite QDs has been partially replaced by Hg 2+ . Spot plate test shows that the perovskite QDs can also be used for visual detection of Hg 2+ . Our research indicated the perovskite QDs are promising candidates for the visual fluorescence detection of environmental micropollutants. Copyright © 2017 Elsevier B.V. All rights reserved.

Zinc Oxide Nanomaterials for Biomedical Fluorescence Detection

PubMed Central

Hahm, Jong-in

2014-01-01

One-dimensional zinc oxide nanomaterials have been recently developed into novel, extremely effective, optical signal-enhancing bioplatforms. Their usefulness has been demonstrated in various biomedical fluorescence assays. Fluorescence is extensively used in biology and medicine as a sensitive and noninvasive detection method for tracking and analyzing biological molecules. Achieving high sensitivity via improving signal-to-noise ratio is of paramount importance in fluorescence-based, trace-level detection. Recent advances in the development of optically superior one-dimensional materials have contributed to this important biomedical area of detection. This review article will discuss major research developments that have so far been made in this emerging and exciting topical field. The discussion will cover a broad range of subjects including synthesis of zinc oxide nanorods (ZnO NRs), various properties differentiating them as suitable optical biodetection platforms, their demonstrated applicability in DNA and protein detection, and the nanomaterial characteristics relevant for biomolecular fluorescence enhancement. This review will then summarize the current status of ZnO NR-based biodetection and further elaborate future utility of ZnO NR platforms for advanced biomedical assays, based on their proven advantages. Lastly, present challenges experienced in this topical area will be identified and focal subject areas for future research will be suggested as well. PMID:24730276

A nanoscale Zr-based fluorescent metal-organic framework for selective and sensitive detection of hydrogen sulfide

NASA Astrophysics Data System (ADS)

Li, Yanping; Zhang, Xin; Zhang, Ling; Jiang, Ke; Cui, Yuanjing; Yang, Yu; Qian, Guodong

2017-11-01

Hydrogen sulfide (H2S) has been commonly viewed as a gas signaling molecule in various physiological and pathological processes. However, the highly efficient H2S detection still remains challenging. Herein, we designed a new robust nano metal-organic framework (MOF) UiO-66-CH=CH2 as a fluorescent probe for rapid, sensitive and selective detection of biological H2S. UiO-66-CH=CH2 was prepared by heating ZrCl4 and 2-vinylterephthalic acid via a simple method. UiO-66-CH=CH2 displayed fluorescence quenching to H2S and kept excellent selectivity in the presence of biological relevant analytes especially the cysteine and glutathione. This MOF-based probe also exhibited fast response (10 s) and high sensitivity with a detection limit of 6.46 μM which was within the concentration range of biological H2S in living system. Moreover, this constructed MOF featured water-stability, nanoscale (20-30 nm) and low toxicity, which made it a promising candidate for biological H2S sensing.

Detection of tropospheric OH and HO2 by laser-induced fluorescence at low pressure using the 308nm excitation of OH

NASA Technical Reports Server (NTRS)

Hofzumahaus, Andreas; Holland, Frank

1994-01-01

Laser-induced fluorescence (LIF) spectroscopy is a highly sensitive method for the direct in situ measurement of hydroxyl concentrations in the atmosphere. Its sensitivity and selectivity relies on the intense discrete UV-absorption lines of OH which are strongest around 282nm and 308nm. We have developed a LIF-instrument based on the low-pressure experiment (FAGE). However, we use 308nm instead of 282nm as excitation wavelength for OH, a concept that is also pursued by other groups. One advantage of the longer excitation wavelength is the higher detection sensitivity due to the about 6 times larger effective OH-fluorescence cross-section. Moreover, the O3/H2O-interference (OH self-generation by the laser) is about a factor of 200 smaller at 308nm than at 282nm. This keeps the interference level well below the projected detection limit of 10(exp 5) OH/cm(exp 3). Atmospheric HO2-radicals are detected by chemical conversion of HO2 into OH with NO.

Rapid analysis of N-linked oligosaccharides in glycoproteins (ovalbumin, ribonuclease B and fetuin) by reversed-phase ultra-performance liquid chromatography with fluorescence detection and electrospray ionization time-of-flight mass spectrometry.

PubMed

Kurihara, Takamasa; Min, Jun Zhe; Hirata, Asuka; Toyo'oka, Toshimasa; Inagaki, Shinsuke

2009-05-01

Rapid, selective and sensitive determination of N-linked oligosaccharides in glycoproteins (ovalbumin, ribonuclease B and fetuin) was performed by ultra-performance liquid chromatography (UPLC) with fluorescence (FL) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). The asparaginyl-oligosaccharide moiety was first liberated from each glycoprotein by pronase E (a proteolitic enzyme). The oligosaccharide fractions separated by gel-permeation chromatography were labeled with 1-pyrenesulfonyl chloride (PSC, a fluorescence reagent), separated by UPLC in a short run time, and then detected by FL and TOF-MS. The PSC-labeled oligosaccharides were selectively identified from the FL detection and then sensitively determined by ESI-TOF-MS. As the results, 15, eight and four kinds of N-linked oligosaccharides were detected from ovalbumin, ribonuclease B and fetuin, respectively. Because the present method is rapid (within 9 min), selective and sensitive (approximate 60 fmol, S/N = 5), the determination of N-linked oligosaccharides in various glycoproteins seems to be possible.

Investigation of common fluorophores for the detection of nitrated explosives by fluorescence quenching.

PubMed

Meaney, Melissa S; McGuffin, Victoria L

2008-03-03

Previous studies have indicated that nitrated explosives may be detected by fluorescence quenching of pyrene and related compounds. The use of pyrene, however, invokes numerous health and waste disposal hazards. In the present study, ten safer fluorophores are identified for quenching detection of target nitrated compounds. Initially, Stern-Volmer constants are measured for each fluorophore with nitrobenzene and 4-nitrotoluene to determine the sensitivity of the quenching interaction. For quenching constants greater than 50 M(-1), sensitivity and selectivity are investigated further using an extended set of target quenchers. Nitromethane, nitrobenzene, 4-nitrotoluene, and 2,6-dinitrotoluene are chosen to represent nitrated explosives and their degradation products; aniline, benzoic acid, and phenol are chosen to represent potential interfering compounds. Among the fluorophores investigated, purpurin, malachite green, and phenol red demonstrate the greatest sensitivity and selectivity for nitrated compounds. Correlation of the quenching rate constants for these fluorophores to Rehm-Weller theory suggests an electron-transfer quenching mechanism. As a result of the large quenching constants, purpurin, malachite green, and phenol red are the most promising for future detection of nitrated explosives via fluorescence quenching.

Hg2+-reactive double hydrophilic block copolymer assemblies as novel multifunctional fluorescent probes with improved performance.

PubMed

Hu, Jinming; Li, Changhua; Liu, Shiyong

2010-01-19

We report on novel type of responsive double hydrophilic block copolymer (DHBC)-based multifunctional chemosensors to Hg(2+) ions, pH, and temperatures and investigate the effects of thermo-induced micellization on the detection sensitivity. Well-defined DHBCs bearing rhodamine B-based Hg(2+)-reactive moieties (RhBHA) in the thermo-responsive block, poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-RhBHA) (PEO-b-P(NIPAM-co-RhBHA)), were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Nonfluorescent RhBHA moieties are subjected to selective ring-opening reaction upon addition of Hg(2+) ions or lowering solution pH, producing highly fluorescent acyclic species. Thus, at room temperature PEO-b-P(NIPAM-co-RhBHA) DHBCs can serve as water-soluble multifunctional and efficient fluorescent chemosensors to Hg(2+) ions and pH. Upon heating above the lower critical solution temperature (approximately 36 degrees C) of the PNIPAM block, they self-assemble into micelles possessing P(NIPAM-co-RhBHA) cores and well-solvated PEO coronas, which were fully characterized by dynamic and static laser light scattering. It was found that the detection sensitivity to Hg(2+) ions and pH could be dramatically improved at elevated temperatures due to fluorescence enhancement of RhBHA residues in the acyclic form, which were embedded within hydrophobic cores of thermo-induced micellar aggregates. This work represents a proof-of-concept example of responsive DHBC-based multifunctional fluorescent chemosensors for the highly efficient detection of Hg(2+) ions, pH, and temperatures with tunable detection sensitivity. Compared to reaction-based small molecule Hg(2+) probes in previous literature reports, the integration of stimuli-responsive block copolymers with well-developed small molecule-based selective sensing moieties in the current study are expected to exhibit preferred advantages including enhanced detection sensitivity, water dispersibility, biocompatibility, facile incorporation into devices, and the ability of further functionalization for targeted imaging and detection.

Label-free imaging and spectroscopy for early detection of cervical cancer.

PubMed

Jing, Yueyue; Wang, Yulan; Wang, Xinyi; Song, Chuan; Ma, Jiong; Xie, Yonghui; Fei, Yiyan; Zhang, Qinghua; Mi, Lan

2018-05-01

The label-free imaging and spectroscopy method was studied on cervical unstained tissue sections obtained from 36 patients. The native fluorescence spectra of tissues are analyzed by the optical redox ratio (ORR), which is defined as fluorescence intensity ratio between NADH and FAD, and indicates the metabolism change with the cancer development. The ORRs of normal tissues are consistently higher than those of precancer or cancerous tissues. A criterion line of ORR at 5.0 can be used to discriminate cervical precancer/cancer from normal tissues. The sensitivity and specificity of the native fluorescence spectroscopy method for cervical cancer diagnosis are determined as 100% and 91%. Moreover, the native fluorescence spectroscopy study is much more sensitive on the healthy region of cervical precancer/cancer patients compared with the traditional clinical staining method. The results suggest label-free imaging and spectroscopy is a fast, highly sensitive and specific method on the detection of cervical cancer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sensitive Detection of Polynucleotide Kinase Activity by Paper-Based Fluorescence Assay with λ Exonuclease Assistance.

PubMed

Zhang, Hua; Zhao, Zhen; Lei, Zhen; Wang, Zhenxin

2016-12-06

The phosphorylation of nucleic acid with 5'-OH termini catalyzed by polynucleotide kinase (PNK) involves several significant cellular events. Here a paper-based fluorescence assay with λ exonuclease assistance was reported for facile detection of PNK activity through monitoring the change of fluorescence intensity on paper surface. Cy5-labeled ssDNA was first immobilized on the surface of aldehyde group modified paper, and BHQ-labeled ssDNA was then employed to quench the fluorescence of the immobilized Cy5-labeled ssDNA with the help of an adaptor ssDNA. When PNK and λ exonuclease cleavage reaction were introduced, the fluorescence quenching effect on the paper surface was blocked because of the digestion of phosphorylated dsDNA by the coupled enzymes. By using this paper-based assay, PNK activity both in pure reaction buffer and in practical biosample have been successfully measured. Highly sensitive detection of PNK activity down to 0.0001 U mL -1 and lysate of about 50 cells is achieved. The inhibition of PNK activity has also been investigated and a satisfactory result is obtained.

Poly-adenine-mediated fluorescent spherical nucleic acid probes for live-cell imaging of endogenous tumor-related mRNA.

PubMed

Zhu, Dan; Zhao, Dongxia; Huang, Jiaxuan; Zhu, Yu; Chao, Jie; Su, Shao; Li, Jiang; Wang, Lihua; Shi, Jiye; Zuo, Xiaolei; Weng, Lixing; Li, Qian; Wang, Lianhui

2018-05-16

Identification of tumor-related mRNA in living cells hold great promise for early cancer diagnosis and pathological research. Herein, we present poly-adenine (polyA)-mediated fluorescent spherical nucleic acid (FSNA) probes for intracellular mRNA detection with regulable sensitivities by programmably adjusting the loading density of DNA on gold nano-interface. Gold nanoparticles (AuNPs) functionalized with polyA-tailed recognition sequences were hybridized to fluorescent "reporter" strands to fabricate fluorescence-quenched FSNA probes. While exposed to target gene, the "reporter" strands were released from FSNA through strand displacement and fluorescence was recovered. With polyA20 tail as the attaching block, the detection limit of FSNA probes was calculated to be 0.31 nM, which is ~55 fold lower than that of thiolated probes without surface density regulation. Quantitative intracellular mRNA detection and imaging could be achieved with polyA-mediated FSNA probes within 2 hours, indicating their application potential in rapid and sensitive intracellular target imaging. Copyright © 2018. Published by Elsevier Inc.

A colorimetric and fluorescent probe for detecting intracellular biothiols.

PubMed

Chen, Chunyang; Liu, Wei; Xu, Cong; Liu, Weisheng

2016-11-15

A new rapid and highly sensitive coumarin-based probe (probe 1) has been designed and synthesized for detecting intracellular thiols. Probe 1 was prepared by a 4-step procedure as a latent fluorescence probe to achieve high sensitivity and fluorescence turn-on response toward cysteine and homocysteine over GSH and other various natural amino acids under physiological conditions. Owing to specific cyclization between thiols and aldehyde group, probe 1 displayed a highly selectivity toward cysteine and homocysteine. Above all, probe 1 was successfully used for fluorescence imaging of biothiols in Hela cells, and quantitative determination had been achieved within a certain range. Then specific fluorescence imaging of mice organ tissues was obtained for proving the permeability of probe 1. Simultaneously, the viability was measured to be more than 80%, which shows probe 1 can be a rapid and biocompatible probe for biothiols in cells. Furthermore, the measurement of thiols detection in 5 kinds of animal serum showed that probe 1 can be used in determination of biothiols in blood. Copyright © 2016 Elsevier B.V. All rights reserved.

A signal-on fluorosensor based on quench-release principle for sensitive detection of antibiotic rapamycin.

PubMed

Jeong, Hee-Jin; Itayama, Shuya; Ueda, Hiroshi

2015-03-26

An antibiotic rapamycin is one of the most commonly used immunosuppressive drugs, and also implicated for its anti-cancer activity. Hence, the determination of its blood level after organ transplantation or tumor treatment is of great concern in medicine. Although there are several rapamycin detection methods, many of them have limited sensitivity, and/or need complicated procedures and long assay time. As a novel fluorescent biosensor for rapamycin, here we propose "Q'-body", which works on the fluorescence quench-release principle inspired by the antibody-based quenchbody (Q-body) technology. We constructed rapamycin Q'-bodies by linking the two interacting domains FKBP12 and FRB, whose association is triggered by rapamycin. The fusion proteins were each incorporated position-specifically with one of fluorescence dyes ATTO520, tetramethylrhodamine, or ATTO590 using a cell-free translation system. As a result, rapid rapamycin dose-dependent fluorescence increase derived of Q'-bodies was observed, especially for those with ATTO520 with a lowest detection limit of 0.65 nM, which indicates its utility as a novel fluorescent biosensor for rapamycin.

A Signal-On Fluorosensor Based on Quench-Release Principle for Sensitive Detection of Antibiotic Rapamycin

PubMed Central

Jeong, Hee-Jin; Itayama, Shuya; Ueda, Hiroshi

2015-01-01

An antibiotic rapamycin is one of the most commonly used immunosuppressive drugs, and also implicated for its anti-cancer activity. Hence, the determination of its blood level after organ transplantation or tumor treatment is of great concern in medicine. Although there are several rapamycin detection methods, many of them have limited sensitivity, and/or need complicated procedures and long assay time. As a novel fluorescent biosensor for rapamycin, here we propose “Q’-body”, which works on the fluorescence quench-release principle inspired by the antibody-based quenchbody (Q-body) technology. We constructed rapamycin Q’-bodies by linking the two interacting domains FKBP12 and FRB, whose association is triggered by rapamycin. The fusion proteins were each incorporated position-specifically with one of fluorescence dyes ATTO520, tetramethylrhodamine, or ATTO590 using a cell-free translation system. As a result, rapid rapamycin dose-dependent fluorescence increase derived of Q’-bodies was observed, especially for those with ATTO520 with a lowest detection limit of 0.65 nM, which indicates its utility as a novel fluorescent biosensor for rapamycin. PMID:25822756

A novel dicyanoisophorone based red-emitting fluorescent probe with a large Stokes shift for detection of hydrazine in solution and living cells

NASA Astrophysics Data System (ADS)

Lv, Hongshui; Sun, Haiyan; Wang, Shoujuan; Kong, Fangong

2018-05-01

A novel dicyanoisophorone based fluorescent probe HP was developed to detect hydrazine. Upon the addition of hydrazine, probe HP displayed turn-on fluorescence in the red region with a large Stokes shift (180 nm). This probe exhibited high selectivity and high sensitivity to hydrazine in solution. The detection limit of HP was found to be 3.26 ppb, which was lower than the threshold limit value set by USEPA (10 ppb). Moreover, the probe was successfully applied to detect hydrazine in different water samples and living cells.

Highly sensitive and selective detection of dopamine using one-pot synthesized highly photoluminescent silicon nanoparticles.

PubMed

Zhang, Xiaodong; Chen, Xiaokai; Kai, Siqi; Wang, Hong-Yin; Yang, Jingjing; Wu, Fu-Gen; Chen, Zhan

2015-03-17

A simple and highly efficient method for dopamine (DA) detection using water-soluble silicon nanoparticles (SiNPs) was reported. The SiNPs with a high quantum yield of 23.6% were synthesized by using a one-pot microwave-assisted method. The fluorescence quenching capability of a variety of molecules on the synthesized SiNPs has been tested; only DA molecules were found to be able to quench the fluorescence of these SiNPs effectively. Therefore, such a quenching effect can be used to selectively detect DA. All other molecules tested have little interference with the dopamine detection, including ascorbic acid, which commonly exists in cells and can possibly affect the dopamine detection. The ratio of the fluorescence intensity difference between the quenched and unquenched cases versus the fluorescence intensity without quenching (ΔI/I) was observed to be linearly proportional to the DA analyte concentration in the range from 0.005 to 10.0 μM, with a detection limit of 0.3 nM (S/N = 3). To the best of our knowledge, this is the lowest limit for DA detection reported so far. The mechanism of fluorescence quenching is attributed to the energy transfer from the SiNPs to the oxidized dopamine molecules through Förster resonance energy transfer. The reported method of SiNP synthesis is very simple and cheap, making the above sensitive and selective DA detection approach using SiNPs practical for many applications.

Improved sensing using simultaneous deep-UV Raman and fluorescence detection-II

NASA Astrophysics Data System (ADS)

Hug, W. F.; Bhartia, R.; Sijapati, K.; Beegle, L. W.; Reid, R. D.

2014-05-01

Photon Systems in collaboration with JPL is continuing development of a new technology robot-mounted or hand-held sensor for reagentless, short-range, standoff detection and identification of trace levels chemical, biological, and explosive (CBE) materials on surfaces. This deep ultraviolet CBE sensor is the result of Army STTR and DTRA programs. The evolving 10 to 15 lb, 20 W, sensor can discriminate CBE from background clutter materials using a fusion of deep UV excited resonance Raman (RR) and laser induced native fluorescence (LINF) emissions collected is less than 1 ms. RR is a method that provides information about molecular bonds, while LINF spectroscopy is a much more sensitive method that provides information regarding the electronic configuration of target molecules. Standoff excitation of suspicious packages, vehicles, persons, and other objects that may contain hazardous materials is accomplished using excitation in the deep UV where there are four main advantages compared to near-UV, visible or near-IR counterparts. 1) Excited between 220 and 250 nm, Raman emission occur within a fluorescence-free region of the spectrum, eliminating obscuration of weak Raman signals by fluorescence from target or surrounding materials. 2) Because Raman and fluorescence occupy separate spectral regions, detection can be done simultaneously, providing an orthogonal set of information to improve both sensitivity and lower false alarm rates. 3) Rayleigh law and resonance effects increase Raman signal strength and sensitivity of detection. 4) Penetration depth into target in the deep UV is short, providing spatial/spectral separation of a target material from its background or substrate. 5) Detection in the deep UV eliminates ambient light background and enable daylight detection.

Part-per-trillion level detection of estradiol by competitive fluorescence immunoassay using DNA/dye conjugate as antibody multiple labels.

PubMed

Zhu, Shengchao; Zhang, Qin; Guo, Liang-Hong

2008-08-22

Fluorescent organic dyes are currently the standard signal-generating labels used in microarray quantification. However, new labeling strategies are needed to meet the demand for high sensitivity in the detection of low-abundance proteins and small molecules. In this report, a long-chain DNA/dye conjugate was used to attach multiple fluorescence labels on antibodies to improve signal intensity and immunoassay sensitivity. Compared with the 30 base-pair (bp) oligonucleotide used in our previous work [Q. Zhang, L.-H. Guo, Bioconjugate Chem. 18 (2007) 1668-1672], conjugation of a 219 bp DNA in solution with a fluorescent DNA binder SYBR Green I resulted in more than sixfold increase in signal intensity, consistent with the increase in bp number. In a direct immunoassay for the detection of goat anti-mouse IgG in a mouse IgG-coated 96-well plate, the long DNA conjugate label also produced higher fluorescence than the short one, accompanied by about 15-fold improvement in the detection limit. To demonstrate its advantage in real applications, the DNA/dye conjugate was employed in the competitive immunoassay of 17beta-estradiol, a clinically and environmentally important analyte. The biotin-terminated DNA was attached to biotinylated anti-estradiol antibody through the biotin/streptavidin/biotin bridge after the immuno-reaction was completed, followed by conjugation with SYBR Green I. The limit of detection for 17beta-estradiol is 1.9 pg mL(-1), which is 200-fold lower than the assay using fluorescein-labeled antibodies. The new multiple labeling strategy uses readily available reagents, and is also compatible with current biochip platform. It has great potential in the sensitive detection of protein and antibody microarrays.

Endoscopic detection of murine colonic dysplasia using a novel fluorescence-labeled peptide

NASA Astrophysics Data System (ADS)

Miller, Sharon J.; Joshi, Bishnu P.; Gaustad, Adam; Fearon, Eric R.; Wang, Thomas D.

2011-03-01

Current endoscopic screening does not detect all pre-malignant (dysplastic) colorectal mucosa, thus requiring the development of more sensitive, targeted techniques to improve detection. The presented work utilizes phage display to identify a novel peptide binder to colorectal dysplasia in a CPC;Apc mouse model. A wide-field, small animal endoscope capable of fluorescence excitation (450-475 nm) identified polyps via white light and also collected fluorescence images (510 nm barrier filter) of peptide binding. The peptide bound ~2-fold greater to the colonic adenomas when compared to the control peptide. We have imaged fluorescence-labeled peptide binding in vivo that is specific towards distal colonic adenomas.

High sensitivity fluorescent single particle and single molecule detection apparatus and method

DOEpatents

Mathies, Richard A.; Peck, Konan; Stryer, Lubert

1990-01-01

Apparatus is described for ultrasensitive detection of single fluorescent particles down to the single fluorescent molecule limit in a fluid or on a substrate comprising means for illuminating a predetermined volume of the fluid or area of the substrate whereby to emit light including background light from the fluid and burst of photons from particles residing in the area. The photon burst is detected in real time to generate output representative signal. The signal is received and the burst of energy from the fluorescent particles is distinguished from the background energy to provide an indication of the number, location or concentration of the particles or molecules.

Laser-induced fluorescence microscopic system using an optical parametric oscillator for tunable detection in microchip analysis.

PubMed

Kumemura, Momoko; Odake, Tamao; Korenaga, Takashi

2005-06-01

A laser-induced fluorescence microscopic system based on optical parametric oscillation has been constructed as a tunable detector for microchip analysis. The detection limit of sulforhodamine B (Ex. 520 nm, Em. 570 nm) was 0.2 mumol, which was approximately eight orders of magnitude better than with a conventional fluorophotometer. The system was applied to the determination of fluorescence-labeled DNA (Ex. 494 nm, Em. 519 nm) in a microchannel and the detection limit reached a single molecule. These results showed the feasibility of this system as a highly sensitive and tunable fluorescence detector for microchip analysis.

Study of experimental endometriosis using fluorescence of eosin-tamoxifen association

NASA Astrophysics Data System (ADS)

Brogniez, A.; Mordon, Serge R.; Devoisselle, Jean-Marie; Querleu, Denis; Brunetaud, Jean Marc

1993-08-01

The main problem of endometriosis is the detection of microscopic and atypical lesions. The successful destruction of these endometriotic sites depends on their detection. This study aimed to develop a spectrofluorometric method to increase the sensitivity of detection of endometriosis. A surgical-induced endometriosis was performed in ten rabbits. Five weeks later, the fluorescence of these endometriotic lesions was studied after injection of tamoxifen and local application of eosin. This fluorescence was compared with that of healthy broad ligament and that obtained without tamoxifen and without eosin. A spectral analysis showed a specific fluorescence of eosin-tamoxifen association, more intense than autofluorescence and selectively observed within endometriosis.

Ultra-sensitive in-situ detection of near-infrared persistent luminescent tracer nanoagents in crude oil-water mixtures.

PubMed

Chuang, Yen-Jun; Liu, Feng; Wang, Wei; Kanj, Mazen Y; Poitzsch, Martin E; Pan, Zhengwei

2016-06-15

Current fluorescent nanoparticles-based tracer sensing techniques for oilfield applications suffer from insufficient sensitivity, with the tracer detection limit typically at the several hundred ppm level in untreated oil/water mixtures, which is mainly caused by the interference of the background fluorescence from the organic residues in crude oil under constant external excitation. Here we report the use of a persistent luminescence phenomenon, which enables an external excitation-free and thus background fluorescence-free measurement condition, for ultrahigh-sensitivity crude oil sensing. By using LiGa5O8:Cr(3+) near-infrared persistent luminescent nanoparticles as a tracer nanoagent, we achieved a tracer detection limit at the single-digit ppb level (down to 1 ppb concentration of nanoparticles) in high oil fraction (up to 65 wt.%) oil/water mixtures via a convenient, CCD camera-based imaging technique without any pretreatment or phase separation of the fluid samples. This detection limit is about four to five orders of magnitude lower than that obtained using conventional spectral methods. This study introduces a new type of tracer nanoagents and a new detection method for water tracer sensing in oil reservoir characterization and management.

Nanostructured Surfaces and Detection Instrumentation for Photonic Crystal Enhanced Fluorescence

PubMed Central

Chaudhery, Vikram; George, Sherine; Lu, Meng; Pokhriyal, Anusha; Cunningham, Brian T.

2013-01-01

Photonic crystal (PC) surfaces have been demonstrated as a compelling platform for improving the sensitivity of surface-based fluorescent assays used in disease diagnostics and life science research. PCs can be engineered to support optical resonances at specific wavelengths at which strong electromagnetic fields are utilized to enhance the intensity of surface-bound fluorophore excitation. Meanwhile, the leaky resonant modes of PCs can be used to direct emitted photons within a narrow range of angles for more efficient collection by a fluorescence detection system. The multiplicative effects of enhanced excitation combined with enhanced photon extraction combine to provide improved signal-to-noise ratios for detection of fluorescent emitters, which in turn can be used to reduce the limits of detection of low concentration analytes, such as disease biomarker proteins. Fabrication of PCs using inexpensive manufacturing methods and materials that include replica molding on plastic, nano-imprint lithography on quartz substrates result in devices that are practical for single-use disposable applications. In this review, we will describe the motivation for implementing high-sensitivity fluorescence detection in the context of molecular diagnosis and gene expression analysis though the use of PC surfaces. Recent efforts to improve the design and fabrication of PCs and their associated detection instrumentation are summarized, including the use of PCs coupled with Fabry-Perot cavities and external cavity lasers. PMID:23624689

An ultrasensitive quantum dots fluorescent polarization immunoassay based on the antibody modified Au nanoparticles amplifying for the detection of adenosine triphosphate.

PubMed

He, Yanlong; Tian, Jianniao; Hu, Kun; Zhang, Juanni; Chen, Sheng; Jiang, Yixuan; Zhao, Yanchun; Zhao, Shulin

2013-11-13

In this work, an ultrasensitive fluorescent polarization immunoassay (FPIA) method based on the quantum dot/aptamer/antibody/gold nanoparticles ensemble has been developed for the detection of adenosine triphosphate (ATP). DNA hybridization is formed when ATP is present in the PBS solution containing the DNA-conjugated quantum dots (QDs) and antibody-AuNPs. The substantial sensitivity improvement of the antibody-AuNPs-enhanced method is mainly attributed to the slower rotation of fluorescent unit when QDs-labeled oligonucleotides hybridize with antibody modified the gold nanoparticle. As a result, the fluorescent polarization (FP) values of the system increase significantly. Under the optimal conditions, a linear response with ATP concentration is ranged from 8×10(-12) M to 2.40×10(-4) M. The detection limit reached as low as 1.8 pM. The developed work provides a sensitive and selective immunoassay protocol for ATP detection, which could be applied in more bioanalytical systems. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Sensitive fluorescence detection of mercury(ii) in aqueous solution by the fluorescence quenching effect of MoS2 with DNA functionalized carbon dots.

PubMed

Srinivasan, K; Subramanian, K; Murugan, K; Dinakaran, K

2016-10-24

A rapid and sensitive fluorescent sensor based on the MoS 2 nanosheet/DNA/carbon dot nanoassembly has been developed towards the detection of mercury(ii) present in environmental samples. Bio-carbon dots (CDs) having strong fluorescence maxima at 451 nm were synthesized via one-step treatment with honey under low temperature carbonization. These CDs were nearly spherical with good size distribution and excellent monodispersity, and the average sizes of CD were around 2-4 nm as evidenced from transmission electron microscopy. The conjugation of DNA strands on the surface of the carbon dots provided an efficient fluorescent probe. The fluorescence of the MoS 2 nanosheet/DNA/carbon dot nanoassembly enhanced gradually with the increase in the concentration of Hg 2+ ions and the detection limit was found to be 1.02 nM. Furthermore, the fluorescence intensity was found to be linear with the concentration of Hg 2+ ions in the range from 0 to 10 nM and their respective coefficient of determination was found to be 0.93676 and 0.98178. The present MoS 2 nanosheet/DNA/carbon dot nanoassembly is highly selective toward Hg 2+ ions over a wide range of metal ions tested.

Detection and Quantification of 8-Hydroxy-2′-Deoxyguanosine in Alzheimer’s Transgenic Mouse Urine using Capillary Electrophoresis

PubMed Central

Zhang, Cheng; Nestorova, Gergana; Rissman, Robert A.; Feng, June

2013-01-01

8-Hydroxy-2′-deoxyguanosine (8-OHdG) is one of the major forms of oxidative deoxyribonucleic acid (DNA) damage, and is commonly analyzed as an excellent marker of DNA lesions. The purpose of this study was to develop a sensitive method to accurately and rapidly quantify the 8-OHdG by using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). The method involved the use of specific antibody to detect DNA lesions (8-OHdG) and consecutive fluorescence labeling. Next, the urine sample with 8-OHdG fluorescently labeled along with other constituents was resolved by capillary electrophoretic system and the lesion of interest was detected using fluorescence detector. The limit of detection was 0.18 fmol, which is sufficient sensitivity for detection and quantification of 8-OHdG in untreated urine samples. The relative standard deviation (RSD) was found to be 11.32 % for migration time, and 5.52 % for peak area. To demonstrate the utility of this method, the urinary concentration of 8-OHdG in an Alzheimer’s transgenic mouse model was determined. Collectively, our results indicate that this methodology offers great advantages such as high separation efficiency, good selectivity, low limit of detection (LOD), simplicity and low cost of analysis. PMID:23712533

Rapid and sensitive detection of clenbuterol using a fluorescence nanosensor based on diazo coupling mechanism

NASA Astrophysics Data System (ADS)

Thanh Hop Tran, Thi; Huong Do, Thi Mai; Hoang, Mai Ha; Tuyen Nguyen, Duc; Le, Quang Tuan; Nghia Nguyen, Duc; Ngo, Trinh Tung

2015-01-01

In this paper, the fluorescence resonance energy transfer (FRET) effect has been used for fabrication of nanosensor for the detection of clenbuterol. In the nanosensor, the CdTe quantum dots (QDs) are the donors while the acceptor is the super-macromolecule formed by the diazoation coupling mechanism between diazo clenbuterol and naphthylethylene diamine. Changes in fluorescence intensities of nanosensor were used to determine the clenbuterol concentration. We have successfully fabricated a nanosensor for detection of clenbuterol sensible to clenbuterol concentration of 10-12 g ml-1.

Rapid, sensitive, and selective fluorescent DNA detection using iron-based metal-organic framework nanorods: Synergies of the metal center and organic linker.

PubMed

Tian, Jingqi; Liu, Qian; Shi, Jinle; Hu, Jianming; Asiri, Abdullah M; Sun, Xuping; He, Yuquan

2015-09-15

Considerable recent attention has been paid to homogeneous fluorescent DNA detection with the use of nanostructures as a universal "quencher", but it still remains a great challenge to develop such nanosensor with the benefits of low cost, high speed, sensitivity, and selectivity. In this work, we report the use of iron-based metal-organic framework nanorods as a high-efficient sensing platform for fluorescent DNA detection. It only takes about 4 min to complete the whole "mix-and-detect" process with a low detection limit of 10 pM and a strong discrimination of single point mutation. Control experiments reveal the remarkable sensing behavior is a consequence of the synergies of the metal center and organic linker. This work elucidates how composition control of nanostructures can significantly impact their sensing properties, enabling new opportunities for the rational design of functional materials for analytical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

A quick and simple FISH protocol with hybridization-sensitive fluorescent linear oligodeoxynucleotide probes

PubMed Central

Wang, Dan Ohtan; Matsuno, Hitomi; Ikeda, Shuji; Nakamura, Akiko; Yanagisawa, Hiroyuki; Hayashi, Yasunori; Okamoto, Akimitsu

2012-01-01

Fluorescence in situ hybridization (FISH) is a powerful tool used in karyotyping, cytogenotyping, cancer diagnosis, species specification, and gene-expression analysis. Although widely used, conventional FISH protocols are cumbersome and time consuming. We have now developed a FISH method using exciton-controlled hybridization-sensitive fluorescent oligodeoxynucleotide (ECHO) probes. ECHO–FISH uses a 25-min protocol from fixation to mounting that includes no stringency washing steps. We use ECHO–FISH to detect both specific DNA and RNA sequences with multicolor probes. ECHO–FISH is highly reproducible, stringent, and compatible with other fluorescent cellular labeling techniques. The resolution allows detection of intranuclear speckles of poly(A) RNA in HeLa cells and dissociated hippocampal primary cultures, and mRNAs in the distal dendrites of hippocampal neurons. We also demonstrate detection of telomeric and centromeric DNA on metaphase mouse chromosomes. The simplicity of the ECHO–FISH method will likely accelerate cytogenetic and gene-expression analysis with high resolution. PMID:22101241

Electron-rich triphenylamine-based sensors for picric acid detection.

PubMed

Chowdhury, Aniket; Mukherjee, Partha Sarathi

2015-04-17

This paper demonstrates the role of solvent in selectivity and sensitivity of a series of electron-rich compounds for the detection of trace amounts of picric acid. Two new electron-rich fluorescent esters (6, 7) containing a triphenylamine backbone as well as their analogous carboxylic acids (8, 9) have been synthesized and characterized. Fluorescent triphenylamine coupled with an ethynyl moiety constitutes π-electron-rich selective and sensitive probes for electron-deficient picric acid (PA). In solution, the high sensitivity of all the sensors toward PA can be attributed to a combined effect of the ground-state charge-transfer complex formation and resonance energy transfer between the sensor and analyte. The acids 8 and 9 also showed enhanced sensitivity for nitroaromatics in the solid state, and their enhanced sensitivity could be attributed to exciton migration due to close proximity of the neighboring acid molecules, as evident from the X-ray diffraction study. The compounds were found to be quite sensitive for the detection of trace amount of nitroaromatics in solution, solid, and contact mode.

Multispectral fluorescence imaging techniques for nondestructive food safety inspection

NASA Astrophysics Data System (ADS)

Kim, Moon S.; Lefcourt, Alan M.; Chen, Yud-Ren

2004-03-01

The use of spectral sensing has gained acceptance as a rapid means for nondestructive inspection of postharvest food produce. Current technologies generally use color or a single wavelength camera technology. The applicability and sensitivity of these techniques can be expanded through the use of multiple wavelengths. Reflectance in the Vis/NIR is the prevalent spectral technique. Fluorescence, compared to reflectance, is regarded as a more sensitive technique due to its dynamic responses to subtle changes in biological entities. Our laboratory has been exploring fluorescence as a potential means for detection of quality and wholesomeness of food products. Applications of fluorescence sensing require an understanding of the spectral characteristics emanating from constituents and potential contaminants. A number of factors affecting fluorescence emission characteristics are discussed. Because of relatively low fluorescence quantum yield from biological samples, a system with a powerful pulse light source such as a laser coupled with a gated detection device is used to harvest fluorescence, in the presence of ambient light. Several fluorescence sensor platforms developed in our laboratory, including hyperspectral imaging, and laser-induced fluorescence (LIF) and steady-state fluorescence imaging systems with multispectral capabilities are presented. We demonstrate the potential uses of recently developed fluorescence imaging platforms in food safety inspection of apples contaminated with animal feces.

Synthesis of a ratiometric fluorescent peptide sensor for the highly selective detection of Cd2+.

PubMed

Li, Yan; Li, Lianzhi; Pu, Xuewei; Ma, Guolin; Wang, Erqiong; Kong, Jinming; Liu, Zhipeng; Liu, Yangzhong

2012-06-15

A novel ratiometric fluorescent peptidyl chemosensor (Dansyl-Cys-Pro-Gly-Cys-Trp-NH(2), D-P5) for metal ions detection has been synthesized via Fmoc solid-phase peptide synthesis. The chemosensor exhibited a high selectivity for Cd(2+) over other metal ions including competitive transition and Group I and II metal ions in neutral pH. The fluorescence emission intensity of D-P5 was significantly enhanced in the presence of Cd(2+) by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The binding stoichiometry, detection limit, binding affinity, reversibility and pH sensitivity of the sensor for Cd(2+) were investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Recent developments in optical detection methods for microchip separations.

PubMed

Götz, Sebastian; Karst, Uwe

2007-01-01

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

New highly sensitive and selective fluorescent terbium complex for the detection of aluminium ions

NASA Astrophysics Data System (ADS)

Anwar, Zeinab M.; Ibrahim, Ibrahim A.; Kamel, Rasha M.; Abdel-Salam, Enas T.; El-Asfoury, Mahmoud H.

2018-02-01

A highly sensitive and selective spectrofluorimetric method has been developed for the rapid determination of aluminium ions. The method is based on the fluorescence enhancement of Tb complex with 3,4-dimetyl-thieno[2,3 b] thiophene-2,5-dicarboxylic acid (LN) after addition trace amount of aluminium ions. The fluorescence of the probe is monitored at the characteristic an emission wavelength of Tb3+ at 545 nm with excitation at 300 nm. Optimum detection was obtained in DMSO-H2O (2:8, v/v) and at pH 6.0 using MOPSO buffer. Under the optimum conditions linear calibration curves were obtained from 0.5 μ mol L-1 to 20 μ mol L-1 with detection limit of 0.1 μ mol L-1. Effect of interference of other ions was studied.

Sentinel lymph nodes fluorescence detection and imaging using Patent Blue V bound to human serum albumin

PubMed Central

Tellier, Franklin; Steibel, Jérôme; Chabrier, Renée; Blé, François Xavier; Tubaldo, Hervé; Rasata, Ravelo; Chambron, Jacques; Duportail, Guy; Simon, Hervé; Rodier, Jean-François; Poulet, Patrick

2012-01-01

Patent Blue V (PBV), a dye used clinically for sentinel lymph node detection, was mixed with human serum albumin (HSA). After binding to HSA, the fluorescence quantum yield increased from 5 × 10−4 to 1.7 × 10−2, which was enough to allow fluorescence detection and imaging of its distribution. A detection threshold, evaluated in scattering test objects, lower than 2.5 nmol × L−1 was obtained, using a single-probe setup with a 5-mW incident light power. The detection sensitivity using a fluorescence imaging device was in the µmol × L−1 range, with a noncooled CCD camera. Preclinical evaluation was performed on a rat model and permitted to observe inflamed nodes on all animals. PMID:23024922

A novel fluorescence immunoassay for the sensitive detection of Escherichia coli O157:H7 in milk based on catalase-mediated fluorescence quenching of CdTe quantum dots.

PubMed

Chen, Rui; Huang, Xiaolin; Li, Juan; Shan, Shan; Lai, Weihua; Xiong, Yonghua

2016-12-01

Immunoassay is a powerful tool for rapid detection of food borne pathogens in food safety monitoring. However, conventional immunoassay always suffers from low sensitivity when it employs enzyme-catalyzing chromogenic substrates to generate colored molecules as signal outputs. In the present study, we report a novel fluorescence immunoassay for the sensitive detection of E. coli O157:H7 through combination of the ultrahigh bioactivity of catalase to hydrogen peroxide (H 2 O 2 ) and H 2 O 2 -sensitive mercaptopropionic acid modified CdTe QDs (MPA-QDs) as a signal transduction. Various parameters, including the concentrations of anti-E. coli O157:H7 polyclonal antibody and biotinylated monoclonal antibody, the amounts of H 2 O 2 and streptavidin labeled catalase (CAT), the hydrolysis temperature and time of CAT to H 2 O 2 , as well as the incubation time between H 2 O 2 and MPA-QDs, were systematically investigated and optimized. With optimal conditions, the catalase-mediated fluorescence quenching immunoassay exhibits an excellent sensitivity for E. coli O157:H7 with a detection limit of 5 × 10 2  CFU/mL, which was approximately 140 times lower than that of horseradish peroxidase-based colorimetric immunoassay. The reliability of the proposed method was further evaluated using E. coli O157:H7 spiked milk samples. The average recoveries of E. coli O157:H7 concentrations from 1.18 × 10 3  CFU/mL to 1.18 × 10 6  CFU/mL were in the range of 65.88%-105.6%. In brief, the proposed immunoassay offers a great potential for rapid and sensitive detection of other pathogens in food quality control. Copyright © 2016 Elsevier B.V. All rights reserved.

Efficient ensemble system based on the copper binding motif for highly sensitive and selective detection of cyanide ions in 100% aqueous solutions by fluorescent and colorimetric changes.

PubMed

Jung, Kwan Ho; Lee, Keun-Hyeung

2015-09-15

A peptide-based ensemble for the detection of cyanide ions in 100% aqueous solutions was designed on the basis of the copper binding motif. 7-Nitro-2,1,3-benzoxadiazole-labeled tripeptide (NBD-SSH, NBD-SerSerHis) formed the ensemble with Cu(2+), leading to a change in the color of the solution from yellow to orange and a complete decrease of fluorescence emission. The ensemble (NBD-SSH-Cu(2+)) sensitively and selectively detected a low concentration of cyanide ions in 100% aqueous solutions by a colorimetric change as well as a fluorescent change. The addition of cyanide ions instantly removed Cu(2+) from the ensemble (NBD-SSH-Cu(2+)) in 100% aqueous solutions, resulting in a color change of the solution from orange to yellow and a "turn-on" fluorescent response. The detection limits for cyanide ions were lower than the maximum allowable level of cyanide ions in drinking water set by the World Health Organization. The peptide-based ensemble system is expected to be a potential and practical way for the detection of submicromolar concentrations of cyanide ions in 100% aqueous solutions.

A fluorescent nanosensor based on graphene quantum dots-aptamer probe and graphene oxide platform for detection of lead (II) ion.

PubMed

Qian, Zhao Sheng; Shan, Xiao Yue; Chai, Lu Jing; Chen, Jian Rong; Feng, Hui

2015-06-15

The sensitive detection of heavy metal ions in the organism and aquatic ecosystem using nanosensors based on environment friendly and biocompatible materials still remains a challenge. A fluorescent turn-on nanosensor for lead (II) detection based on biocompatible graphene quantum dots and graphene oxide by employment of Pb(2+)-induced G-quadruplex formation was reported. Graphene quantum dots with high quantum yield, good biocompatibility were prepared and served as the fluorophore of Pb(2+) probe. Fluorescence turn-off of graphene quantum dots is easily achieved through efficient photoinduced electron transfer between graphene quantum dots and graphene oxide, and subsequent fluorescence turn-on process is due to the formation of G-quadraplex aptamer-Pb(2+) complex triggered by the addition of Pb(2+). This nanosensor can distinguish Pb(2+) ion from other ions with high sensitivity and good reproducibility. The detection method based on this nanosensor possesses a fast response time of one minute, a broad linear span of up to 400.0 nM and ultralow detection limit of 0.6 nM. Copyright © 2015 Elsevier B.V. All rights reserved.

Lanthanide-functionalized silver nanoparticles for detection of an anthrax biomarker and test paper fabrication

NASA Astrophysics Data System (ADS)

Tan, Hongliang; Li, Qian; Ma, Chanjiao; Song, Yonghai; Xu, Fugang; Chen, Shouhui; Wang, Li

2014-01-01

It is highly desirable to develop a simple and sensitive analytical method for detection of anthrax biomarker (dipicolinic acid, DPA) because of its dangerous nature. In this work, we developed a fluorescent sensor for DPA detection based on terbium ion-functionalized silver nanoparticles with an average size of 6.7 nm (AgNPs-Tb3+). The fluorescent intensity of Tb-DPA complex on the surface of AgNPs was two times higher than that of Tb-DPA complex alone in a solution phase due to the metal-enhanced fluorescence (MEF) effect of AgNPs. The proposed fluorescent sensor exhibits excellent selectivity and high sensitivity for DPA. Importantly, a test paper for DPA detection was fabricated for the first time by the integration of AgNPs-Tb3+ onto the nitrocellulose membrane. Owing to the MEF effect of AgNPs, the lowest detectable concentration of the test paper-integrated AgNPs-Tb3+ for DPA by naked eyes is 10 times lower than that of the test paper-integrated Tb3+ alone. We believe that the presented strategy may open up new avenues to the development of portable and robust-sensing platforms based on functional hybrid materials.

Time-Domain Microfluidic Fluorescence Lifetime Flow Cytometry for High-Throughput Förster Resonance Energy Transfer Screening

PubMed Central

Nedbal, Jakub; Visitkul, Viput; Ortiz-Zapater, Elena; Weitsman, Gregory; Chana, Prabhjoat; Matthews, Daniel R; Ng, Tony; Ameer-Beg, Simon M

2015-01-01

Sensing ion or ligand concentrations, physico-chemical conditions, and molecular dimerization or conformation change is possible by assays involving fluorescent lifetime imaging. The inherent low throughput of imaging impedes rigorous statistical data analysis on large cell numbers. We address this limitation by developing a fluorescence lifetime-measuring flow cytometer for fast fluorescence lifetime quantification in living or fixed cell populations. The instrument combines a time-correlated single photon counting epifluorescent microscope with microfluidics cell-handling system. The associated computer software performs burst integrated fluorescence lifetime analysis to assign fluorescence lifetime, intensity, and burst duration to each passing cell. The maximum safe throughput of the instrument reaches 3,000 particles per minute. Living cells expressing spectroscopic rulers of varying peptide lengths were distinguishable by Förster resonant energy transfer measured by donor fluorescence lifetime. An epidermal growth factor (EGF)-stimulation assay demonstrated the technique's capacity to selectively quantify EGF receptor phosphorylation in cells, which was impossible by measuring sensitized emission on a standard flow cytometer. Dual-color fluorescence lifetime detection and cell-specific chemical environment sensing were exemplified using di-4-ANEPPDHQ, a lipophilic environmentally sensitive dye that exhibits changes in its fluorescence lifetime as a function of membrane lipid order. To our knowledge, this instrument opens new applications in flow cytometry which were unavailable due to technological limitations of previously reported fluorescent lifetime flow cytometers. The presented technique is sensitive to lifetimes of most popular fluorophores in the 0.5–5 ns range including fluorescent proteins and is capable of detecting multi-exponential fluorescence lifetime decays. This instrument vastly enhances the throughput of experiments involving fluorescence lifetime measurements, thereby providing statistically significant quantitative data for analysis of large cell populations. © 2014 International Society for Advancement of Cytometry PMID:25523156

(DNS)C: a fluorescent, environmentally sensitive cytidine derivative for the direct detection of GGG triad sequences.

PubMed

Kim, Ki Tae; Kim, Hyun Woo; Moon, Dohyun; Rhee, Young Min; Kim, Byeang Hyean

2013-09-14

With the goal of developing a fluorescent nucleoside sensitive to its environment, in this study we synthesized (DNS)C, a novel modified 2'-deoxycytidine bearing a 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) moiety at the N4 position, and tested its properties in monomeric and oligomeric states. (DNS)C undergoes intramolecular photoinduced electron transfer between its dansyl and cytosine units, resulting in remarkable changes in fluorescence that depend on the choice of solvent. In addition, the fluorescence behavior and thermal stability of oligonucleotides containing (DNS)C are dependent on the nature of the flanking and neighboring bases. Notably, (DNS)C exhibits fluorescence enhancement only in fully matched duplex DNA containing a GGG triad sequence. The environmental sensitivity of (DNS)C can be exploited as a fluorescence tool for monitoring the interactions of DNA with other biomolecules, including DNA, RNA, and proteins.

Triplex DNA formation-mediated strand displacement reaction for highly sensitive fluorescent detection of melamine.

PubMed

Liu, Xiaojuan; Xu, Ningning; Gai, Panpan; Li, Feng

2018-08-01

Since melamine is a strong hazard to human health, the development of new methods for highly sensitive detection of melamine is highly desirable. Herein, a novel fluorescent biosensing strategy was designed for sensitive and selective melamine assay based on the recognition ability of abasic (AP) site in triplex towards melamine and signal amplification by Mg 2+ -dependent DNAzyme. In this strategy, the melamine-induced formation of triplex DNA was employed to trigger the strand displacement reaction (SDR). The SDR process converted the specific target recognition into the release and activation of Mg 2+ -dependent DNAzyme, which could catalyze the cleavage of fluorophore/quencher labeled DNA substrate (FQ), resulting in a significantly increased fluorescent signal. Under the optimal conditions, the fluorescent signal has a linear relationship with the logarithm of the melamine concentration in a wide range of 0.005-50 μM. The detection limit was estimated to be 0.9 nM (0.1ppb), which is sufficiently sensitive for practical application. Furthermore, this strategy exhibits high selectivity against other potential interfering substances, and the practical application of this strategy for milk samples reveals that the proposed strategy works well for melamine assay in real samples. Therefore, this strategy presents a new method for the sensitive melamine assay and holds great promise for sensing applications in the environment and the food safety field. Copyright © 2018 Elsevier B.V. All rights reserved.

An optical fiber taper fluorescent probe for detection of nitro-explosives based on tetraphenylethylene with aggregation-induced emission

NASA Astrophysics Data System (ADS)

Liu, Fukun; Cui, Minxin; Ma, Jiajun; Zou, Gang; Zhang, Qijin

2017-07-01

In this work, we report a novel optical fiber taper fluorescent probe for detection of nitro-explosives. The probe was fabricated by an in-situ photo-plating through evanescent wave and transmitted light initiated thiol-ene ;click; reaction, from which a cross-linked fluorescence porous polymer film was covalently bonded on the surface of the fiber taper. The film exhibits well-organized porous structure due to the presence of polyhedral oligomeric vinylsilsesquioxane moieties, and simultaneously displays strong fluorescence from tetraphenylethylene with aggregation-induced emission property. These two characters make the probe show a remarkable sensitivity, anti-photo-bleaching and a repeatability in detection of TNT and DNT vapors by fluorescence quenching. In addition, the detection is not interfered in the presence of other volatile organic gases.

Rapid and Sensitive Detection of Protein Biomarker Using a Portable Fluorescence Biosensor based on Quantum Dots and a Lateral Flow Test Strip

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhaohui; Wang, Ying; Wang, Jun

2010-08-15

A portable fluorescence biosensor with rapid and ultrasensitive response for trace protein has been built up with quantum dots and lateral flow test strip. The superior signal brightness and high photostability of quantum dots are combined with the promising advantages of lateral flow test strip and resulted in high sensitivity, selectivity and speedy for protein detection. Nitrated ceruloplasmin, a significant biomarker for cardiovascular disease, lung cancer and stress response to smoking, was used as model protein to demonstrate the good performances of this proposed Qdot-based lateral flow test strip. Quantitative detection of nitrated ceruloplasmin was realized by recording the fluorescencemore » intensity of quantum dots captured on the test line. Under optimal conditions, this portable fluorescence biosensor displays rapid responses for nitrated ceruloplasmin in wide dynamic range with a detection limit of 0.1ng/mL (S/N=3). Furthermore, the biosensor was successfully utilized for spiked human plasma sample detection with the concentration as low as 1ng/mL. The results demonstrate that the quantum dot-based lateral flow test strip is capable for rapid, sensitive, and quantitative detection of nitrated ceruloplasmin and hold a great promise for point-of-care and in field analysis of other protein biomarkers.« less

Application of silver nanoparticles in the detection of SYBR Green I by surface enhanced Raman and surface-enhanced fluorescence

NASA Astrophysics Data System (ADS)

Guo, Wei; Wu, Jian; Wang, Chunyan; Zhang, Tian; Chen, Tao

2018-05-01

Silver nanomaterials have remarkable application in biomedical detection due to their unique surface plasmon resonance (SPR) characteristics. It can be used for surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF). Current research elaborates a technique for improvement of SYBR Green I detection obtained from surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) by silver nanoparticles with the average size about 70 nm. Primarily, SYBR Green I is an important fluorescent dye used in polymerase chain reaction (PCR). It is found that both Raman and fluorescence can be used for detection of this dye. Furthermore, the enhanced efficiency of the Raman and fluorescence by SERS and SEF is observed in this study, the enhancement factor for Raman signals is 3.2 × 103, and the fluorescence intensity bincreased two times by SEF. The quantitative detection of SYBR Green I by SERS and SEF can be achieved. The present work can be used to improve the detection of SYBR Green I by SERS and SEF. It would also be employed for high-sensitive detection of other materials in the future.

Highly sensitive strategy for Hg2+ detection in environmental water samples using long lifetime fluorescence quantum dots and gold nanoparticles.

PubMed

Huang, Dawei; Niu, Chenggang; Ruan, Min; Wang, Xiaoyu; Zeng, Guangming; Deng, Canhui

2013-05-07

The authors herein described a time-gated fluorescence resonance energy transfer (TGFRET) sensing strategy employing water-soluble long lifetime fluorescence quantum dots and gold nanoparticles to detect trace Hg(2+) ions in aqueous solution. The water-soluble long lifetime fluorescence quantum dots and gold nanoparticles were functionalized by two complementary ssDNA, except for four deliberately designed T-T mismatches. The quantum dot acted as the energy-transfer donor, and the gold nanoparticle acted as the energy-transfer acceptor. When Hg(2+) ions were present in the aqueous solution, DNA hybridization will occur because of the formation of T-Hg(2+)-T complexes. As a result, the quantum dots and gold nanoparticles are brought into close proximity, which made the energy transfer occur from quantum dots to gold nanoparticles, leading to the fluorescence intensity of quantum dots to decrease obviously. The decrement fluorescence intensity is proportional to the concentration of Hg(2+) ions. Under the optimum conditions, the sensing system exhibits the same liner range from 1 × 10(-9) to 1 × 10(-8) M for Hg(2+) ions, with the detection limits of 0.49 nM in buffer and 0.87 nM in tap water samples. This sensor was also used to detect Hg(2+) ions from samples of tap water, river water, and lake water spiked with Hg(2+) ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. In comparison to some reported colorimetric and fluorescent sensors, the proposed method displays the advantage of higher sensitivity. The TGFRET sensor also exhibits excellent selectivity and can provide promising potential for Hg(2+) ion detection.

Intravital Fluorescence Excitation in Whole-Animal Optical Imaging.

PubMed

Nooshabadi, Fatemeh; Yang, Hee-Jeong; Bixler, Joel N; Kong, Ying; Cirillo, Jeffrey D; Maitland, Kristen C

2016-01-01

Whole-animal fluorescence imaging with recombinant or fluorescently-tagged pathogens or cells enables real-time analysis of disease progression and treatment response in live animals. Tissue absorption limits penetration of fluorescence excitation light, particularly in the visible wavelength range, resulting in reduced sensitivity to deep targets. Here, we demonstrate the use of an optical fiber bundle to deliver light into the mouse lung to excite fluorescent bacteria, circumventing tissue absorption of excitation light in whole-animal imaging. We present the use of this technology to improve detection of recombinant reporter strains of tdTomato-expressing Mycobacterium bovis BCG (Bacillus Calmette Guerin) bacteria in the mouse lung. A microendoscope was integrated into a whole-animal fluorescence imager to enable intravital excitation in the mouse lung with whole-animal detection. Using this technique, the threshold of detection was measured as 103 colony forming units (CFU) during pulmonary infection. In comparison, the threshold of detection for whole-animal fluorescence imaging using standard epi-illumination was greater than 106 CFU.

Intravital Fluorescence Excitation in Whole-Animal Optical Imaging

PubMed Central

Bixler, Joel N.; Kong, Ying; Cirillo, Jeffrey D.; Maitland, Kristen C.

2016-01-01

Whole-animal fluorescence imaging with recombinant or fluorescently-tagged pathogens or cells enables real-time analysis of disease progression and treatment response in live animals. Tissue absorption limits penetration of fluorescence excitation light, particularly in the visible wavelength range, resulting in reduced sensitivity to deep targets. Here, we demonstrate the use of an optical fiber bundle to deliver light into the mouse lung to excite fluorescent bacteria, circumventing tissue absorption of excitation light in whole-animal imaging. We present the use of this technology to improve detection of recombinant reporter strains of tdTomato-expressing Mycobacterium bovis BCG (Bacillus Calmette Guerin) bacteria in the mouse lung. A microendoscope was integrated into a whole-animal fluorescence imager to enable intravital excitation in the mouse lung with whole-animal detection. Using this technique, the threshold of detection was measured as 103 colony forming units (CFU) during pulmonary infection. In comparison, the threshold of detection for whole-animal fluorescence imaging using standard epi-illumination was greater than 106 CFU. PMID:26901051

A new pyrene based highly sensitive fluorescence probe for copper(II) and fluoride with living cell application.

PubMed

Goswami, Shyamaprosad; Chakraborty, Shampa; Paul, Sima; Halder, Sandipan; Panja, Sukanya; Mukhopadhyay, Subhra Kanti

2014-05-21

A new pyrene based fluorescence probe has been synthesized for fluorogenic detection of Cu(2+) in acetonitrile-aqueous media (7 : 3 CH3CN-HEPES buffer, v/v, at pH 7.5) with bioimaging in both prokaryotic (Candida albicans cells) and eukaryotic (Tecoma stans pollen cells) living cells. The anion recognition properties of the sensor have also been studied in acetonitrile by fluorescence methods which show remarkable sensitivity toward fluoride over other anions examined.

Visible-light system for detecting doxorubicin contamination on skin and surfaces.

PubMed

Van Raalte, J; Rice, C; Moss, C E

1990-05-01

A portable system that uses fluorescence stimulated by visible light to identify doxorubicin contamination on skin and surfaces was studied. When activated by violet-blue light in the 465-nm range, doxorubicin fluoresces, emitting orange-red light in the 580-nm range. The light source to stimulate fluorescence was a slide projector with a filter to selectively pass short-wave (blue) visible light. Fluorescence was both observed visually with viewing spectacles and photographed. Solutions of doxorubicin in sterile 0.9% sodium chloride injection were prepared in nine standard concentrations ranging from 2 to 0.001 mg/mL. Droplets of each admixture were placed on stainless steel, laboratory coat cloth, pieces of latex examination glove, bench-top absorbent padding, and other materials on which antineoplastics might spill or leak. These materials then were stored for up to eight weeks and photographed weekly. The relative ability of water, household bleach, hydrogen peroxide solution, and soap solution to deactivate doxorubicin was also measured. Finally, this system was used to inspect the antineoplastic-drug preparation and administration areas of three outpatient cancer clinics for doxorubicin contamination. Doxorubicin fluorescence was easily detectable with viewing spectacles when a slide projector was used as the light source. The photographic method was sensitive for doxorubicin concentrations from 2.0 to 0.001 mg/mL. Immersion of study materials in bleach for one minute eliminated detectable fluorescence. Doxorubicin contamination is detectable for at least eight weeks in the ambient environment. Probable doxorubicin contamination was detected in two of the three clinics surveyed. A safe, portable system that uses fluorescence stimulated by visible light is a sensitive method for detecting doxorubicin on skin and surfaces.

A novel lab-on-chip platform with integrated solid phase PCR and Supercritical Angle Fluorescence (SAF) microlens array for highly sensitive and multiplexed pathogen detection.

PubMed

Hung, Tran Quang; Chin, Wai Hoe; Sun, Yi; Wolff, Anders; Bang, Dang Duong

2017-04-15

Solid-phase PCR (SP-PCR) has become increasingly popular for molecular diagnosis and there have been a few attempts to incorporate SP-PCR into lab-on-a-chip (LOC) devices. However, their applicability for on-line diagnosis is hindered by the lack of sensitive and portable on-chip optical detection technology. In this paper, we addressed this challenge by combining the SP-PCR with super critical angle fluorescence (SAF) microlens array embedded in a microchip. We fabricated miniaturized SAF microlens array as part of a microfluidic chamber in thermoplastic material and performed multiplexed SP-PCR directly on top of the SAF microlens array. Attribute to the high fluorescence collection efficiency of the SAF microlens array, the SP-PCR assay on the LOC platform demonstrated a high sensitivity of 1.6 copies/µL, comparable to off-chip detection using conventional laser scanner. The combination of SP-PCR and SAF microlens array allows for on-chip highly sensitive and multiplexed pathogen detection with low-cost and compact optical components. The LOC platform would be widely used as a high-throughput biosensor to analyze food, clinical and environmental samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Sensitive determination of carbohydrates by fluorimetric method with Ce(IV) and sodium triphosphate.

PubMed

Yang, Jinghe; Cao, Xihui; Sun, Changxia; Wu, Xia; Li, Lei

2004-05-01

A new simple and sensitive fluorimetric method for the determination of carbohydrates is described. The method is based on the reaction between carbohydrates and Ce(IV) in the presence of sulfuric acid. All the reductive carbohydrates can be detected indirectly by the fluorescence of Ce(III) produced. The addition of sodium triphate enhances the sensitivity of the method by more than 10-folds. Under optimum conditions, an excellent linear relationship was obtained between the fluorescence intensity and the concentration of carbohydrates. The limits of detection lie in the range of 9.3 x 10(-10) - 1.3 x 10(-9) mol/L. As compared to the normal fluorimetric method, the proposed method is faster and more sensitive.

Mesoporous structured MIPs@CDs fluorescence sensor for highly sensitive detection of TNT.

PubMed

Xu, Shoufang; Lu, Hongzhi

2016-11-15

A facile strategy was developed to prepare mesoporous structured molecularly imprinted polymers capped carbon dots (M-MIPs@CDs) fluorescence sensor for highly sensitive and selective determination of TNT. The strategy using amino-CDs directly as "functional monomer" for imprinting simplify the imprinting process and provide well recognition sites accessibility. The as-prepared M-MIPs@CDs sensor, using periodic mesoporous silica as imprinting matrix, and amino-CDs directly as "functional monomer", exhibited excellent selectivity and sensitivity toward TNT with detection limit of 17nM. The recycling process was sustainable for 10 times without obvious efficiency decrease. The feasibility of the developed method in real samples was successfully evaluated through the analysis of TNT in soil and water samples with satisfactory recoveries of 88.6-95.7%. The method proposed in this work was proved to be a convenient and practical way to prepare high sensitive and selective fluorescence MIPs@CDs sensors. Copyright © 2016 Elsevier B.V. All rights reserved.

Establishing and validating the fluorescent amyloid ligand h-FTAA (heptamer formyl thiophene acetic acid) to identify transthyretin amyloid deposits in carpal tunnel syndrome.

PubMed

Hahn, Katharina; Nilsson, K Peter R; Hammarström, Per; Urban, Peter; Meliss, Rolf Rüdiger; Behrens, Hans-Michael; Krüger, Sandra; Röcken, Christoph

2017-06-01

Transthyretin-derived (ATTR) amyloidosis is a frequent finding in carpal tunnel syndrome. We tested the following hypotheses: the novel fluorescent amyloid ligand heptameric formic thiophene acetic acid (h-FTAA) has a superior sensitivity for the detection of amyloid compared with Congo red-staining; Amyloid load correlates with patient gender and/or patient age. We retrieved 208 resection specimens obtained from 184 patients with ATTR amyloid in the carpal tunnel. Serial sections were stained with Congo red, h-FTAA and an antibody directed against transthyretin (TTR). Stained sections were digitalized and forwarded to computational analyses. The amount of amyloid was correlated with patient demographics. Amyloid stained intensely with h-FTAA and an anti-TTR-antibody. Congo red-staining combined with fluorescence microscopy was significantly less sensitive than h-FTAA-fluorescence and TTR-immunostaining: the highest percentage area was found in TTR-immunostained sections, followed by h-FTAA and Congo red. The Pearson correlation coefficient was .8 (Congo red vs. h-FTAA) and .9 (TTR vs. h-FTAA). Amyloid load correlated with patient gender, anatomical site and patient age. h-FTAA is a highly sensitive method to detect even small amounts of ATTR amyloid in the carpal tunnel. The staining protocol is easy and h-FTAA may be a much more sensitive procedure to detect amyloid at an earlier stage.

Sensitive and selective detection of Hg2+ and Cu2+ ions by fluorescent Ag nanoclusters synthesized via a hydrothermal method

NASA Astrophysics Data System (ADS)

Liu, Jing; Ren, Xiangling; Meng, Xianwei; Fang, Zheng; Tang, Fangqiong

2013-09-01

An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu2+. Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg2+ and Cu2+ ions sensors.An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu2+. Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg2+ and Cu2+ ions sensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03329e

A novel fluorescence-quenching immunochromatographic sensor for detection of the heavy metal chromium.

PubMed

Fu, QiangQiang; Tang, Yong; Shi, CongYing; Zhang, XiaoLi; Xiang, JunJian; Liu, Xi

2013-11-15

A novel fluorescence quenching immunochromatographic sensor (ICS) was developed for detecting chromium (Cr(3+)) within 15 min utilizing the fluorescence quenching function of gold nanoparticles (Au-NPs). The sensor performed with a positive readout. When the low concentrations of Cr(3+) samples were applied, detection signals of the test line (T line) were quenched, whereas when higher concentration Cr(3+) samples (1.56 ng/mL) were applied, the detection signal of the T line appeared. The detection signal intensity of the T line increased with increasing concentrations of Cr(3+). The low detection limit of developed fluorescence quenching ICS was 1.56 ng/mL. The fluorescence quenching ICS has a linear range of detection of Cr(3+) comprising between 6.25 ng/mL to 800 ng/mL. The recoveries of the fluorescence quenching ICS to detect Cr(3+) in tap water ranged from 94.7% to 101.7%. This result indicated that the developed sensor gave higher sensitivity and reliable reproducibility. It could provide a general detection method for small analyte in water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Carbon dots for fluorescent detection of α-glucosidase activity using enzyme activated inner filter effect and its application to anti-diabetic drug discovery.

PubMed

Kong, Weiheng; Wu, Di; Xia, Lian; Chen, Xuefeng; Li, Guoliang; Qiu, Nannan; Chen, Guang; Sun, Zhiwei; You, Jinmao; Wu, Yongning

2017-06-22

Recently, α-glucosidase inhibitor has been widely used in clinic for diabetic therapy. In the present study, a facile and sensitive fluorescent assay based on enzyme activated inner filter effect (IFE) on nitrogen-doped carbon dots (CDs) was first developed for the detection of α-glucosidase. The N-doped CDs with green emission were prepared by a one-step hydrothermal synthesis and gave the fluorescence quantum yield of 30%, which were used as the signal output. Through α-glucosidase catalysis, 4-nitrophenol was released from 4-nitrophenyl-α-d-glucopyranoside (NGP). Interestingly, the absorption of 4-nitrophenol and the excitation of CDs were completely overlapping. Due to its great molar absorptivity, 4-nitrophenol was capable of acting as a powerful absorber to affect the fluorescent signal of CDs (i.e. IFE). By converting the absorption signals into fluorescence signals, the facile fluorescence assay strategy could be realized for α-glucosidase activity sensing, which effectively avoided the complex modification of the surface of CDs or construction of the nanoprobes. The established IFE-based sensing platform offered a low detection limit of 0.01 U/mL (S/N = 3). This proposed sensing approach has also been expanded to the inhibitor screening and showed excellent applicability. As a typical α-glucosidase inhibitor, acarbose was investigated with a low detection limit of 10 -8  M. This developed method enjoyed many merits including simplicity, lost cost, high sensitivity, good reproducibility and excellent selectivity, which also provided a new insight on the application of CDs to develop the facile and sensitive biosensor. Copyright © 2017 Elsevier B.V. All rights reserved.

Near real time, accurate, and sensitive microbiological safety monitoring using an all-fibre spectroscopic fluorescence system

NASA Astrophysics Data System (ADS)

Vanholsbeeck, F.; Swift, S.; Cheng, M.; Bogomolny, E.

2013-11-01

Enumeration of microorganisms is an essential microbiological task for many industrial sectors and research fields. Various tests for detection and counting of microorganisms are used today. However most of the current methods to enumerate bacteria require either long incubation time for limited accuracy, or use complicated protocols along with bulky equipment. We have developed an accurate, all-fibre spectroscopic system to measure fluorescence signal in-situ. In this paper, we examine the potential of this setup for near real time bacteria enumeration in aquatic environment. The concept is based on a well-known phenomenon that the fluorescence quantum yields of some nucleic acid stains significantly increase upon binding with nucleic acids of microorganisms. In addition we have used GFP labeled organisms. The fluorescence signal increase can be correlated to the amount of nucleic acid present in the sample. In addition we have used GFP labeled organisms. Our results show that we are able to detect a wide range of bacteria concentrations without dilution or filtration (1-108 CFU/ml) using different optical probes we designed. This high sensitivity is due to efficient light delivery with an appropriate collection volume and in situ fluorescence detection as well as the use of a sensitive CCD spectrometer. By monitoring the laser power, we can account for laser fluctuations while measuring the fluorescence signal which improves as well the system accuracy. A synchronized laser shutter allows us to achieve a high SNR with minimal integration time, thereby reducing the photobleaching effect. In summary, we conclude that our optical setup may offer a robust method for near real time bacterial detection in aquatic environment.

A sensitive flow-batch system for on board determination of ultra-trace ammonium in seawater: Method development and shipboard application.

PubMed

Zhu, Yong; Yuan, Dongxing; Huang, Yongming; Ma, Jian; Feng, Sichao

2013-09-10

Combining fluorescence detection with flow analysis and solid phase extraction (SPE), a highly sensitive and automatic flow system for measurement of ultra-trace ammonium in open ocean water was established. Determination was based on fluorescence detection of a typical product of o-phthaldialdehyde and ammonium. In this study, the fluorescence reaction product could be efficiently extracted onto an SPE cartridge (HLB, hydrophilic-lipophilic balance). The extracted fluorescence compounds were rapidly eluted with ethanol and directed into a flow cell for fluorescence detection. Compared with the common used fluorescence method, the proposed one offered the benefits of improved sensitivity, reduced reagent consumption, negligible salinity effect and lower cost. Experimental parameters were optimized using a univariate experimental design. Calibration curves, ranging from 1.67 to 300nM, were obtained with different reaction times. The recoveries were between 89.5 and 96.5%, and the detection limits in land-based and shipboard laboratories were 0.7 and 1.2nM, respectively. The relative standard deviation was 3.5% (n=5) for an aged seawater sample spiked with 20nM ammonium. Compared with the analytical results obtained using the indophenol blue method coupled to a long-path liquid waveguide capillary cell, the proposed method showed good agreement. The method had been applied on board during a South China Sea cruise in August 2012. A vertical profile of ammonium in the South East Asia Time-Series (SEATS, 18° N, 116° E) station was produced. The distribution of ammonium in the surface seawater of the Qiongdong upwelling in South China Sea is also presented. Copyright © 2013 Elsevier B.V. All rights reserved.

A fluorescent graphitic carbon nitride nanosheet biosensor for highly sensitive, label-free detection of alkaline phosphatase.

PubMed

Xiang, Mei-Hao; Liu, Jin-Wen; Li, Na; Tang, Hao; Yu, Ru-Qin; Jiang, Jian-Hui

2016-02-28

Graphitic C3N4 (g-C3N4) nanosheets provide an attractive option for bioprobes and bioimaging applications. Utilizing highly fluorescent and water-dispersible ultrathin g-C3N4 nanosheets, a highly sensitive, selective and label-free biosensor has been developed for ALP detection for the first time. The developed approach utilizes a natural substrate of ALP in biological systems and thus affords very high catalytic efficiency. This novel biosensor is demonstrated to enable quantitative analysis of ALP in a wide range from 0.1 to 1000 U L(-1) with a low detection limit of 0.08 U L(-1), which is among the most sensitive assays for ALP. It is expected that the developed method may provide a low-cost, convenient, rapid and highly sensitive platform for ALP-based clinical diagnostics and biomedical applications.

A novel dichromate-sensitive fluorescent nano-chemosensor using new functionalized SBA-15.

PubMed

Hosseini, Morteza; Gupta, Vinod Kumar; Ganjali, Mohammad Reza; Rafiei-Sarmazdeh, Zahra; Faridbod, Farnoush; Goldooz, Hassan; Badiei, Ali Reza; Norouzi, Parviz

2012-02-17

A novel fluorescence nano-chemosensor for Cr(2)O(7)(2-) anion has been developed by assembly of fluorescent aluminum complex of 8-hydroxyquinoline (AlQ(x)) within the channels of modified SBA-15. SBA-SPS-AlQ(x) shows a fluorescence emission at 486 nm. The observed remarkable fluorescence of SBA-SPS-AlQ(x) quenches in presence of Cr(2)O(7)(2-) anion. The results showed that this fluorescent nano-material can be a useful chemo-sensor for determination of dichromate anions in aqueous solutions. The linear detecting range of fluorescent nano-chemosensor for Cr(2)O(7)(2-) anion was 0.16-2.9 μmol L(-1). The lowest limit of detection (LDL) was also found to be 0.2 ng mL(-1) in aqueous solutions. SBA-SPS-AlQ(x) showed selectively and sensitively fluorescent quenching response toward Cr(2)O(7)(2-) ion in comparison with I(3)(-), NO(3)(-), CN(-), CO(3)(2-), Br(-), Cl(-), F(-), H(2)PO(4)(-) and SO(4)(2-) ions, which was because of the higher stability of its inorganic complex with dichromate ion. Copyright © 2011 Elsevier B.V. All rights reserved.

Enhanced fluorescence microscope and its application

NASA Astrophysics Data System (ADS)

Wang, Susheng; Li, Qin; Yu, Xin

1997-12-01

A high gain fluorescence microscope is developed to meet the needs in medical and biological research. By the help of an image intensifier with luminance gain of 4 by 104 the sensitivity of the system can achieve 10-6 1x level and be 104 times higher than ordinary fluorescence microscope. Ultra-weak fluorescence image can be detected by it. The concentration of fluorescent label and emitting light intensity of the system are decreased as much as possible, therefore, the natural environment of the detected call can be kept. The CCD image acquisition set-up controlled by computer obtains the quantitative data of each point according to the gray scale. The relation between luminous intensity and output of CCD is obtained by using a wide range weak photometry. So the system not only shows the image of ultra-weak fluorescence distribution but also gives the intensity of fluorescence of each point. Using this system, we obtained the images of distribution of hypocrellin A (HA) in Hela cell, the images of Hela cell being protected by antioxidant reagent Vit. E, SF and BHT. The images show that the digitized ultra-sensitive fluorescence microscope is a useful tool for medical and biological research.

Highly sensitive ;turn-on; fluorescent chemical sensor for trace analysis of Cr3 + using electro-synthesized poly(N-(9-fluorenylmethoxycarbonyl)-L-histidine)

NASA Astrophysics Data System (ADS)

Zhang, Hui; Zhang, Ge; Xu, Jingkun; Wen, Yangping; Ming, Shouli; Zhang, Jie; Ding, Wanchuan

2018-02-01

Trivalent chromium (Cr3 +) can cause severely environment pollution, declining quality of edible agro-products in plants and animals, and human diseases. Poly(N-(9-fluorenylmethoxycarbonyl)-L-histidine) (PFLH) synthesized by the direct electro-polymerization of its corresponding commercially available monomer in both boron trifluoride diethyl etherate and dichloromethane mixed system. The ;turn-on; type fluorescent sensor based on PFLH displayed high sensitivity and selectivity for Cr3 + detecting. The structure of PFLH was rationally proved by 1H NMR spectra, FT-IR spectra, quantum chemical calculations, and its optical properties were characterized. The electro-synthesized PFLH exhibited a ;turn-on; fluorescent response towards Cr3 +, which was employed as a sensing platform for the ;turn-on; fluorescent analysis of Cr3 + in a wide linear range from 5.1 nM to 25 μM with a low limit of detection as low as 1.7 nM. The possible mechanism of fluorescent ;turn-on; sensor based on PFLH for Cr3 + was proposed. The sensor displayed high sensitivity, good selectivity, satisfactory practicability, suggesting that PFLH has potential fluorescent application for ;turn-on; sensing Cr3 + in agricultural environments and edible agro-products of plants and animals.

Highly sensitive detection of cancer cells using femtosecond dual-wavelength near-IR two-photon imaging.

PubMed

Starkey, Jean R; Makarov, Nikolay S; Drobizhev, Mikhail; Rebane, Aleksander

2012-07-01

We describe novel imaging protocols that allow detection of small cancer cell colonies deep inside tissue phantoms with high sensitivity and specificity. We compare fluorescence excited in Styryl-9M molecules by femtosecond pulses at near IR wavelengths, where Styryl-9M shows the largest dependence of the two-photon absorption (2PA) cross section on the local environment. We show that by calculating the normalized ratio of the two-photon excited fluorescence (2PEF) intensity at 1200 nm and 1100 nm excitation wavelengths we can achieve high sensitivity and specificity for determining the location of cancer cells surrounded by normal cells. The 2PEF results showed a positive correlation with the levels of MDR1 proteins expressed by the cells, and, for high MDR1 expressors, as few as ten cancer cells could be detected. Similar high sensitivity is also demonstrated for tumor colonies induced in mouse external ears. This technique could be useful in early cancer detection, and, perhaps, also in monitoring dormant cancer deposits.

A highly sensitive peptide substrate for detecting two Aß-degrading enzymes: neprilysin and insulin-degrading enzyme.

PubMed

Chen, Po-Ting; Liao, Tai-Yan; Hu, Chaur-Jong; Wu, Shu-Ting; Wang, Steven S-S; Chen, Rita P-Y

2010-06-30

Neprilysin has been singled out as the most promising candidate for use in the degradation of Abeta as a therapy for Alzheimer's disease. In this study, a quenched fluorogenic peptide substrate containing the first seven residues of the Abeta peptide plus a C-terminal Cysteine residue was synthesized to detect neprilysin activity. A fluorophore was attached to the C-terminal Cysteine and its fluorescence was quenched by a quencher linked to the N-terminus of the peptide. When this peptide substrate was degraded by an endopeptidase, fluorescence was produced and proved to be a sensitive detection system for endopeptidase activity. Our results showed that this assay system was extremely sensitive to neprilysin and insulin-degrading enzyme, but insensitive, or much less sensitive, to other Abeta-degrading enzymes. As low as 0.1 nM of neprilysin and 0.2 nM of insulin-degrading enzyme can be detected. Copyright 2010 Elsevier B.V. All rights reserved.

A distance-dependent metal-enhanced fluorescence sensing platform based on molecular beacon design.

PubMed

Zhou, Zhenpeng; Huang, Hongduan; Chen, Yang; Liu, Feng; Huang, Cheng Zhi; Li, Na

2014-02-15

A new metal-enhanced fluorescence (MEF) based platform was developed on the basis of distance-dependent fluorescence quenching-enhancement effect, which combined the easiness of Ag-thiol chemistry with the MEF property of noble-metal structures as well as the molecular beacon design. For the given sized AgNPs, the fluorescence enhancement factor was found to increase with a d(6) dependency in agreement with fluorescence resonance energy transfer mechanism at shorter distance and decrease with a d(-3) dependency in agreement with plasmonic enhancement mechanism at longer distance between the fluorophore and the AgNP surface. As a proof of concept, the platform was demonstrated by a sensitive detection of mercuric ions, using thymine-containing molecular beacon to tune silver nanoparticle (AgNP)-enhanced fluorescence. Mercuric ions were detected via formation of a thymine-mercuric-thymine structure to open the hairpin, facilitating fluorescence recovery and AgNP enhancement to yield a limit of detection of 1 nM, which is well below the U.S. Environmental Protection Agency regulation of the Maximum Contaminant Level Goal (10nM) in drinking water. Since the AgNP functioned as not only a quencher to reduce the reagent blank signal but also an enhancement substrate to increase fluorescence of the open hairpin when target mercuric ions were present, the quenching-enhancement strategy can greatly improve the detection sensitivity and can in principle be a universal approach for various targets when combined with molecular beacon design. © 2013 Elsevier B.V. All rights reserved.

Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)

Treesearch

Kevin T. Smith; Jean Christophe Balouet; Walter C. Shortle; Michel Chalot; François Beaujard; Hakan Grudd; Don A. Vroblesky; Joel G. Burken

2014-01-01

Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to...

A simple but highly efficient multi-formyl phenol-amine system for fluorescence detection of peroxide explosive vapour.

PubMed

Xu, Wei; Fu, Yanyan; Gao, Yixun; Yao, Junjun; Fan, Tianchi; Zhu, Defeng; He, Qingguo; Cao, Huimin; Cheng, Jiangong

2015-07-11

A simple, highly stable, sensitive and selective fluorescent system for peroxide explosives was developed via an aromatic aldehyde oxidation reaction. The high efficiency arises from its higher HOMO level and multiple H-bonding. The sensitivity is obtained to be 0.1 ppt for H2O2 and 0.2 ppb for TATP.

A fluorescent sensor for selective detection of cyanide using mesoporous graphitic carbon(IV) nitride.

PubMed

Lee, Eun Zoo; Lee, Sun Uk; Heo, Nam-Su; Stucky, Galen D; Jun, Young-Si; Hong, Won Hi

2012-04-25

A turn-on fluorescence sensor, Cu(2+)-c-mpg-C(3)N(4), was developed for detection of CN(-) in aqueous solution by simply mixing cubic mesoporous graphitic carbon nitride (c-mpg-C(3)N(4)) and aqueous solution of Cu(NO(3))(2). The highly sensitive detection of CN(-) with a detection limit of 80 nM is not only possible in aqueous solution but also in human blood serum.

Fluorenone based fluorescent probe for selective "turn-on" detection of pyrophosphate and alanine

NASA Astrophysics Data System (ADS)

Daniel Thangadurai, T.; Nithya, I.; Manjubaashini, N.; Bhuvanesh, N.; Bharathi, G.; Nandhakumar, R.; Nataraj, D.

2018-06-01

To sense biologically important entities with different size and dimensions, a fluorenone based fluorescent receptor was designed and synthesized. Probe 1 displayed a distinct fluorescence enhancement emission at 565 nm for pyrophosphate and 530 nm for alanine in polar solvent. The fluorescence titration experiments confirm 1:1 stoichiometric ratio with high-binding constant and very low limit of detection (LoD) values. Receptor 1 showed a highly selective and sensitive recognition to HP2O73 - and to alanine over other competitive anions and amino acids. In addition, the fluorescence lifetime measurement and reversible binding study results support the practical importance of 1.

Fiber-optic multiphoton flow cytometry in whole blood and in vivo

NASA Astrophysics Data System (ADS)

Chang, Yu-Chung; Ye, Jing Yong; Thomas, Thommey P.; Cao, Zhengyi; Kotlyar, Alina; Tkaczyk, Eric R.; Baker, James R.; Norris, Theodore B.

2010-07-01

Circulating tumor cells in the bloodstream are sensitive indicators for metastasis and disease prognosis. Circulating cells have usually been monitored via extraction from blood, and more recently in vivo using free-space optics; however, long-term intravital monitoring of rare circulating cells remains a major challenge. We demonstrate the application of a two-photon-fluorescence optical fiber probe for the detection of cells in whole blood and in vivo. A double-clad fiber was used to enhance the detection sensitivity. Two-channel detection was employed to enable simultaneous measurement of multiple fluorescent markers. Because the fiber probe circumvents scattering and absorption from whole blood, the detected signal strength from fluorescent cells was found to be similar in phosphate-buffered saline (PBS) and in whole blood. The detection efficiency of cells labeled with the membrane-binding dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindoldicarbocyanine, 4-chlorobenzenesulfonate (DiD) was demonstrated to be the same in PBS and in whole blood. A high detection efficiency of green fluorescent protein (GFP)-expressing cells in whole blood was also demonstrated. To characterize in vivo detection, DiD-labeled untransfected and GFP-transfected cells were injected into live mice, and the cell circulation dynamics was monitored in real time. The detection efficiency of GFP-expressing cells in vivo was consistent with that observed ex vivo in whole blood.

Selective and Sensitive Detection of Cyanide Based on the Displacement Strategy Using a Water-Soluble Fluorescent Probe.

PubMed

La, Ming; Hao, Yuanqiang; Wang, Zhaoyang; Han, Guo-Cheng; Qu, Lingbo

2016-01-01

A water-soluble fluorescent probe (C-GGH) was used for the highly sensitive and selective detection of cyanide (CN(-)) in aqueous media based on the displacement strategy. Due to the presence of the recognition unit GGH (Gly-Gly-His), the probe C-GGH can coordinate with Cu(2+) and consequently display ON-OFF type fluorescence response. Furthermore, the in situ formed nonfluorescent C-GGH-Cu(2+) complex can act as an effective OFF-ON type fluorescent probe for sensing CN(-) anion. Due to the strong binding affinity of CN(-) to Cu(2+), CN(-) can extract Cu(2+) from C-GGH-Cu(2+) complex, leading to the release of C-GGH and the recovery of fluorescent emission of the system. The probe C-GGH-Cu(2+) allowed detection of CN(-) in aqueous solution with a LOD (limit of detection) of 0.017 μmol/L which is much lower than the maximum contaminant level (1.9 μmol/L) for CN(-) in drinking water set by the WHO (World Health Organization). The probe also displayed excellent specificity for CN(-) towards other anions, including F(-), Cl(-), Br(-), I(-), SCN(-), PO4 (3-), N3 (-), NO3 (-), AcO(-), SO4 (2-), and CO3 (2-).

Selective and Sensitive Detection of Cyanide Based on the Displacement Strategy Using a Water-Soluble Fluorescent Probe

PubMed Central

La, Ming; Hao, Yuanqiang; Wang, Zhaoyang; Han, Guo-Cheng; Qu, Lingbo

2016-01-01

A water-soluble fluorescent probe (C-GGH) was used for the highly sensitive and selective detection of cyanide (CN−) in aqueous media based on the displacement strategy. Due to the presence of the recognition unit GGH (Gly-Gly-His), the probe C-GGH can coordinate with Cu2+ and consequently display ON-OFF type fluorescence response. Furthermore, the in situ formed nonfluorescent C-GGH-Cu2+ complex can act as an effective OFF-ON type fluorescent probe for sensing CN− anion. Due to the strong binding affinity of CN− to Cu2+, CN− can extract Cu2+ from C-GGH-Cu2+ complex, leading to the release of C-GGH and the recovery of fluorescent emission of the system. The probe C-GGH-Cu2+ allowed detection of CN− in aqueous solution with a LOD (limit of detection) of 0.017 μmol/L which is much lower than the maximum contaminant level (1.9 μmol/L) for CN− in drinking water set by the WHO (World Health Organization). The probe also displayed excellent specificity for CN− towards other anions, including F−, Cl−, Br−, I−, SCN−, PO4 3−, N3 −, NO3 −, AcO−, SO4 2−, and CO3 2−. PMID:26881185

A highly selective fluorescent probe based on coumarin for the imaging of N2H4 in living cells

NASA Astrophysics Data System (ADS)

Chen, Song; Hou, Peng; Wang, Jing; Liu, Lei; Zhang, Qi

2017-02-01

A turn-on fluorescence probe for highly sensitive and selective detection of N2H4 was developed based on hydrazine-triggered a substitution- cyclization-elimination cascade. Upon the treatment with N2H4, probe 1, 4-methyl-coumarin-7-yl bromobutanoate, displayed a remarkable fluorescence enhancement (25-fold) with a maximum at 450 nm. This probe can quantitatively detect N2H4 with a extremely low detection limit as 7 × 10- 8 M. Moreover, cell imaging experiments have indicated that probe 1 has potential ability to detect and image N2H4 in biological systems.

Flow cytometry as a rapid test for detection of penicillin resistance directly in bacterial cells in Enterococcus faecalis and Staphylococcus aureus.

PubMed

Jarzembowski, T; Wiśniewska, K; Józwik, A; Bryl, E; Witkowski, J

2008-08-01

We studied the usefulness of flow cytometry for detection of penicillin resistance in E. faecalis and S. aureus by direct binding of commercially available fluorescent penicillin, Bocillin FL, to cells obtained from culture. There were significantly lower percentages of fluorescent cells and median and mean fluorescence values per particle in penicillin-resistant than in penicillin-sensitive strains of both species observed. The method allows rapid detection of penicillin resistance in S. aureus and E. faecalis. The results encourage further investigations on the detection of antibiotic resistance in bacteria using flow cytometry.

Multicolor fluorescent biosensor for multiplexed detection of DNA.

PubMed

Hu, Rong; Liu, Tao; Zhang, Xiao-Bing; Huan, Shuang-Yan; Wu, Cuichen; Fu, Ting; Tan, Weihong

2014-05-20

Development of efficient methods for highly sensitive and rapid screening of specific oligonucleotide sequences is essential to the early diagnosis of serious diseases. In this work, an aggregated cationic perylene diimide (PDI) derivative was found to efficiently quench the fluorescence emission of a variety of anionic oligonucleotide-labeled fluorophores that emit at wavelengths from the visible to NIR region. This broad-spectrum quencher was then adopted to develop a multicolor biosensor via a label-free approach for multiplexed fluorescent detection of DNA. The aggregated perylene derivative exhibits a very high quenching efficiency on all ssDNA-labeled dyes associated with biosensor detection, having efficiency values of 98.3 ± 0.9%, 97 ± 1.1%, and 98.2 ± 0.6% for FAM, TAMRA, and Cy5, respectively. An exonuclease-assisted autocatalytic target recycling amplification was also integrated into the sensing system. High quenching efficiency combined with autocatalytic target recycling amplification afforded the biosensor with high sensitivity toward target DNA, resulting in a detection limit of 20 pM, which is about 50-fold lower than that of traditional unamplified homogeneous fluorescent assay methods. The quencher did not interfere with the catalytic activity of nuclease, and the biosensor could be manipulated in either preaddition or postaddition manner with similar sensitivity. Moreover, the proposed sensing system allows for simultaneous and multicolor analysis of several oligonucleotides in homogeneous solution, demonstrating its potential application in the rapid screening of multiple biotargets.

Selective and sensitive fluorescent sensor for Pd2+ using coumarin 460 for real-time and biological applications.

PubMed

Ashwin, Bosco Christin Maria Arputham; Sivaraman, Gandhi; Stalin, Thambusamy; Yuvakkumar, Rathinam; Muthu Mareeswaran, Paulpandian

2018-06-01

The efficient fluorescent property of coumarin 460 (C460) is utilized to sense the Pd 2+ selectively and sensitively. Fabrication of a sensor strip using commercial adhesive tape is achieved and the detection of Pd 2+ is attempted using a handy UV torch. The naked eye detection in solution state using UV chamber is also attempted. The calculated high binding constant values support the strong stable complex formation of Pd 2+ with C460. The detection limit up to 2.5 × 10 -7  M is achieved using fluorescence spectrometer, which is considerably low from the WHO's recommendation. The response of coumarin 460 with various cations also studied. The quenching is further studied by the lifetime measurements. The binding mechanism is clearly explained by the 1 H NMR titration. The sensing mechanism is established as ICT. C460 strip's Pd 2+ quenching detection is further confirmed by solid-state PL study. The in-vitro response of Pd 2+ in a living cell is also studied using fluorescent imaging studies by means of HeLa cell lines and this probe is very compatible with biological environments. It could be applicable to sense trace amounts of a Pd 2+ ion from various industries. Compared with previous reports, this one is very cheap, sensitive, selective and suitable for biological systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Design strategies of fluorescent probes for selective detection among biothiols.

PubMed

Niu, Li-Ya; Chen, Yu-Zhe; Zheng, Hai-Rong; Wu, Li-Zhu; Tung, Chen-Ho; Yang, Qing-Zheng

2015-10-07

Simple thiol derivatives, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play key roles in biological processes, and the fluorescent probes to detect such thiols in vivo selectively with high sensitivity and fast response times are critical for understanding their numerous functions. However, the similar structures and reactivities of these thiols pose considerable challenges to the development of such probes. This review focuses on various strategies for the design of fluorescent probes for the selective detection of biothiols. We classify the fluorescent probes for discrimination among biothiols according to reaction types between the probes and thiols such as cyclization with aldehydes, conjugate addition-cyclization with acrylates, native chemical ligation, and aromatic substitution-rearrangement.

High-Collection-Efficiency Fluorescence Detection Cell

NASA Technical Reports Server (NTRS)

Hanisco, Thomas; Cazorla, Maria; Swanson, Andrew

2013-01-01

A new fluorescence cell has been developed for the laser induced fluorescence (LIF) detection of formaldehyde. The cell is used to sample a flow of air that contains trace concentrations of formaldehyde. The cell provides a hermetically sealed volume in which a flow of air containing formaldehyde can be illuminated by a laser. The cell includes the optics for transmitting the laser beam that is used to excite the formaldehyde and for collecting the resulting fluorescence. The novelty of the cell is its small size and simple design that provides a more robust and cheaper alternative to the state of the art. Despite its simplicity, the cell provides the same sensitivity to detection as larger, more complicated cells.

Functionalization of Polymers with Fluorescent and Neutron Sensitive Groups for Efficient Neutron and Gamma Detection

NASA Astrophysics Data System (ADS)

Mahl, Adam; Yemam, Henok; Remedes, Tyler; Stuntz, Jack; Koldemir, Unsal; Sellinger, Alan; Greife, Uwe

2015-10-01

This presentation will review the efforts made by an interdisciplinary development project aimed at cost-effective, thermal neutron sensitive, plastic scintillators as part of the communities efforts towards replacing 3He based detectors. Colorado School of Mines researchers with backgrounds in Physics and Chemistry have worked on the incorporation of 10B in plastics through admixture of various commercial and novel dopants developed at CSM. In addition, new fluorescent dopants have been developed for plastic scintillators in an effort towards better understanding quenching effects and scintillator response to thermal neutrons via pulse shape discrimination methods. Results on transparent samples using fluorescent spectroscopy and gamma/neutron excitation will be presented. Funded via Department of Homeland Security - Domestic Nuclear Detection Office.

Electrophoretically mediated microanalysis of leucine aminopeptidase using two-photon excited fluorescence detection on a microchip.

PubMed

Zugel, S A; Burke, B J; Regnier, F E; Lytle, F E

2000-11-15

Two-photon excited fluorescence detection was performed on a microfabricated electrophoresis chip. A calibration curve of the fluorescent tag beta-naphthylamine was performed, resulting in a sensitivity of 2.5 x 10(9) counts M(-1) corresponding to a detection limit of 60 nM. Additionally, leucine aminopeptidase was assayed on the chip using electrophoretically mediated microanalysis. The differential electroosmotic mobilities of the enzyme and substrate, L-leucine beta-naphthylamide, allowed for efficient mixing in an open channel, resulting in the detection of a 30 nM enzyme solution under constant potential. A zero potential incubation for 1 min yielded a calculated detection limit of 4 nM enzyme.

Trace vapor detection of hydrogen peroxide: An effective approach to identification of improvised explosive devices

NASA Astrophysics Data System (ADS)

Xu, Miao

Vapor detection has been proven as one of the practical, noninvasive methods suitable for explosives detection among current explosive detection technologies. Optical methods (especially colorimetric and fluorescence spectral methods) are low in cost, provide simple instrumentation alignment, while still maintaining high sensitivity and selectivity, these factors combined facilitate broad field applications. Trace vapor detection of hydrogen peroxide (H2O2) represents an effective approach to noninvasive detection of peroxide-based explosives, though development of such a sensor system with high reliability and sufficient sensitivity (reactivity) still remains challenging. Three vapor sensor systems for H2O2 were proposed and developed in this study, which exploited specific chemical reaction towards H2O2 to ensure the selectivity, and materials surface engineering to afford efficient air sampling. The combination of these features enables expedient, cost effective, reliable detection of peroxide explosives. First, an expedient colorimetric sensor for H2O2 vapor was developed, which utilized the specific interaction between Ti(oxo) and H2O2 to offer a yellow color development. The Ti(oxo) salt can be blended into a cellulose microfibril network to produce tunable interface that can react with H2O2. The vapor detection limit can reach 400 ppb. To further improve the detection sensitivity, a naphthalimide based fluorescence turn-on sensor was designed and developed. The sensor mechanism was based on H2O2-mediated oxidation of a boronate fluorophore, which is nonfluorescent in ICT band, but becomes strongly fluorescent upon conversion into the phenol state. The detection limit of this sensory material was improved to be below 10 ppb. However, some technical factors such as sensor concentration, local environment, and excitation intensity were found difficult to control to make the sensor system sufficiently reproducible. To solve the problem, we developed a ratiometric fluorescence sensor, which allows for dual-band emission monitoring and thus enhances the detection reliability. Moreover, the significant spectral overlap between the fluorescence of the pristine sensor and the absorption of the reacted state enables effective Foster Resonance Energy Transfer (FRET). This FRET process can significantly enhance the fluorescence sensing efficiency in comparison to the normal single-band sensor system, for which the sensing efficiency is solely determined by the stoichiometric conversion of sensor molecules.

Rapid and sensitive detection of ketamine in blood using novel fluorescence genosensor.

PubMed

Ding, Yanjun; Li, Xingmei; Guo, Yadong; Yan, Jie; Ling, Jiang; Li, Weichen; Lan, Lingmei; Chang, Yunfeng; Cai, Jifeng; Zha, Lagabaiyla

2017-12-01

In recent years, drug abuse has been considered as a most challenging social problem that aroused public attention. Ketamine has increased in unregulated use as a 'recreational drug' in teenagers. However, there is no suitable and maneuverable detection method for ketamine in situ at the moment. Fluorescence sensor technique, with predominant recognition and simple operation, is a good potential application in drug detection. Here, we first reported a highly sensitive and selective fluorescence genosensor for rapid detection of ketamine based on DNA-templated silver nanoclusters (DNA-AgNCs) probes, in which the DNA sequence could specially recognize ketamine with high affinity. Parameters affecting detection efficiency were investigated and optimized. Under optimum conditions, the as-prepared genosensor can allow for the determination of ketamine in the concentration range of 0.0001-20 μg/mL with two linear equations: one is y = 2.84x-7.139 (R 2 = 0.987) for 0.0001-0.1 μg/mL, and the other is y = 1.87x-0.091 (R 2 = 0.962) for 0.1-20 μg/mL, and the estimated detection limit of ketamine is 0.06 ng/mL. Moreover, the feasibility of this proposed method was also demonstrated by analyzing forensic blood samples. Compared with official gas chromatography/mass spectrometry (GC/MS), this fluorescence genosensor is simple, rapid, and accurate for quantitative determination of ketamine in blood for pharmaceutical and forensic analysis. Overall, it is the first report on a fluorescence genosensor for detecting ketamine directly in blood. This research may provide a new insight for the analyst to band fluorescence genosensor technology together with drug monitoring in the battle against drug abuse and forensic examination. Graphical abstract High selectively detection of ketamine using a novel fluorescence genosensor based on DNA-AgNCs probe.

Sensitive Detection of Protein and miRNA Cancer Biomarkers using Silicon-Based Photonic Crystals and A Resonance Coupling Laser Scanning Platform

PubMed Central

George, Sherine; Chaudhery, Vikram; Lu, Meng; Takagi, Miki; Amro, Nabil; Pokhriyal, Anusha; Tan, Yafang; Ferreira, Placid; Cunningham, Brian T.

2013-01-01

Enhancement of the fluorescent output of surface-based fluorescence assays by performing them upon nanostructured photonic crystal (PC) surfaces has been demonstrated to increase signal intensities by >8000×. Using the multiplicative effects of optical resonant coupling to the PC in increasing the electric field intensity experienced by fluorescent labels (“enhanced excitation”) and the spatially biased funneling of fluorophore emissions through coupling to PC resonances (“enhanced extraction”), PC enhanced fluorescence (PCEF) can be adapted to reduce the limits of detection of disease biomarker assays, and to reduce the size and cost of high sensitivity detection instrumentation. In this work, we demonstrate the first silicon-based PCEF detection platform for multiplexed biomarker assay. The sensor in this platform is a silicon-based PC structure, comprised of a SiO2 grating that is overcoated with a thin film of high refractive index TiO2 and is produced in a semiconductor foundry for low cost, uniform, and reproducible manufacturing. The compact detection instrument that completes this platform was designed to efficiently couples fluorescence excitation from a semiconductor laser to the resonant optical modes of the PC, resulting in elevated electric field strength that is highly concentrated within the region <100 nm from the PC surface. This instrument utilizes a cylindrically focused line to scan a microarray in <1 minute. To demonstrate the capabilities of this sensor-detector platform, microspot fluorescent sandwich immunoassays using secondary antibodies labeled with Cy5 for two cancer biomarkers (TNF-α and IL-3) were performed. Biomarkers were detected at concentrations as low as 0.1 pM. In a fluorescent microarray for detection of a breast cancer miRNA biomarker miR-21, the miRNA was detectable at a concentration of 0.6 pM. PMID:23963502

Hydrophobic-carbon-dot-based dual-emission micelle for ratiometric fluorescence biosensing and imaging of Cu2+ in liver cells.

PubMed

Lu, Linlin; Feng, Chongchong; Xu, Jie; Wang, Fengyang; Yu, Haijun; Xu, Zhiai; Zhang, Wen

2017-06-15

Copper is closely related to liver damage, therefore, it is essential to develop a simple and sensitive strategy to detect copper ions (Cu 2+ ) in liver cells. A hydrophobic carbon dots (HCDs)-based dual-emission fluorescent probe for Cu 2+ was prepared by encapsulating HCDs in micelles formed by self-assembly of amphiphilic polymer DSPE-PEG and tetrakis (4-carboxyphenyl) porphyrin (TCPP)-modified DSPE-PEG. The obtained probe showed characteristic fluorescence emissions of HCDs and TCPP with large emission shift of 170nm with single-wavelength excitation. In the presence of Cu 2+ , the fluorescence of TCPP was quenched and that of HCDs remained unchanged, displaying ratiometric fluorescence response to Cu 2+ . The developed probe exhibited high sensitivity (detection limit down to 36nM) and selectivity to Cu 2+ over other substances, and the probe was used to image the changes of Cu 2+ level in liver cells successfully. Copyright © 2017 Elsevier B.V. All rights reserved.

A fluorescent aptasensor for sensitive analysis oxytetracycline based on silver nanoclusters.

PubMed

Hosseini, Morteza; Mehrabi, Fatemeh; Ganjali, Mohammad Reza; Norouzi, Parviz

2016-11-01

A fluorescent aptasensor for detection of oxytetracycline (OTC) was presented based on fluorescence quenching of DNA aptamer-templated silver nanoclusters (AgNCs). The specific DNA scaffolds with two different nucleotides fragments were used: one was enriched with a cytosine sequence fragment (C12) that could produce DNA-AgNCs via a chemical reduction method, and another was the OTC aptamer fragment that could selectively bind to the OTC antibiotic. Thus, the as-prepared AgNCs could exhibit quenched fluorescence after binding to the target OTC. The fluorescence ratio of the DNA-AgNCs was quenched in a linearly proportional manner to the concentration of the target in the range of 0.5 nM to 100 nM with a detection limit of 0.1 nM. This proposed nanobiosensor was demonstrated to be sensitive, selective, and simple, introducing a viable alternative for rapid determination of toxin OTC in honey and water samples. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Allyl Fluorescein Ethers as Promising Fluorescent Probes for Carbon Monoxide Imaging in Living Cells.

PubMed

Feng, Shumin; Liu, Dandan; Feng, Weiyong; Feng, Guoqiang

2017-03-21

Recently, the fluorescent detection of carbon monoxide (CO) in living cells has attracted great attention. However, due to the lack of effective ways to construct fluorescent CO probes, fluorescent detection of CO in living cells is still in its infancy. In this paper, we report for the first time the use of allyl ether as a reaction site for construction of fluorescent CO probes. By this way, two readily available allyl fluorescein ethers were prepared, which were found to be highly selective and sensitive probes for CO in the presence of PdCl 2 . These probes have the merits of good stability, good water-solubility, and rapid and distinct colorimetric and remarkable fluorescent turn-on signal changes. Moreover, a very low dose of these two probes can be used to detect and track CO in living cells, indicating that these two probes could be very promising biological tools for CO detection in living systems. Overall, this work provided not only two new promising fluorescent CO probes but also a new way to devise fluorescent CO probes.

Non-Covalent Fluorescent Labeling of Hairpin DNA Probe Coupled with Hybridization Chain Reaction for Sensitive DNA Detection.

PubMed

Song, Luna; Zhang, Yonghua; Li, Junling; Gao, Qiang; Qi, Honglan; Zhang, Chengxiao

2016-04-01

An enzyme-free signal amplification-based assay for DNA detection was developed using fluorescent hairpin DNA probes coupled with hybridization chain reaction (HCR). The hairpin DNAs were designed to contain abasic sites in the stem moiety. Non-covalent labeling of the hairpin DNAs was achieved when a fluorescent ligand was bound to the abasic sites through hydrogen bonding with the orphan cytosine present on the complementary strand, accompanied by quench of ligand fluorescence. As a result, the resultant probes, the complex formed between the hairpin DNA and ligand, showed almost no fluorescence. Upon hybridization with target DNA, the probe underwent a dehybridization of the stem moiety containing an abasic site. The release of ligand from the abasic site to the solution resulted in an effective fluorescent enhancement, which can be used as a signal. Compared with a sensing system without HCR, a 20-fold increase in the sensitivity was achieved using the sensing system with HCR. The fluorescent intensity of the sensing system increased with the increase in target DNA concentration from 0.5 nM to 100 nM. A single mismatched target ss-DNA could be effectively discriminated from complementary target DNA. Genotyping of a G/C single-nucleotide polymorphism of polymerase chain reaction (PCR) products was successfully demonstrated with the sensing system. Therefore, integrating HCR strategy with non-covalent labeling of fluorescent hairpin DNA probes provides a sensitive and cost-effective DNA assay. © The Author(s) 2016.

Using fluorescence measurement of zinc ions liberated from ZnS nanoparticle labels in bioassay for Escherichia coli O157:H7

NASA Astrophysics Data System (ADS)

Cowles, Chad L.; Zhu, Xiaoshan; Pai, Chi-Yun

2011-10-01

In this study, an alternative approach using ZnS nanoparticle biolabels as fluorescence signal transducers is reported for the immunoassay of E. coli O157:H7 in tap water samples. Instead of measuring the fluorescence of ZnS nanoparticles in the assay, the fluorescence signal is generated through the binding of zinc ions released from nanoparticle labels with zinc-ion sensitive fluorescence indicator Fluozin-3. In the assay, ZnS nanoparticles around 50 nm in diameter were synthesized, bioconjugated, and applied for the detection of E. coli O157:H7. The assay shows a detection range over two orders of magnitude and a detection limit around 1000 colony-forming units (cfu) of E. coli O157:H7.

Carbon dots based fluorescent sensor for sensitive determination of hydroquinone.

PubMed

Ni, Pengjuan; Dai, Haichao; Li, Zhen; Sun, Yujing; Hu, Jingting; Jiang, Shu; Wang, Yilin; Li, Zhuang

2015-11-01

In this paper, a novel biosensor based on Carbon dots (C-dots) for sensitive detection of hydroquinone (H2Q) is reported. It is interesting to find that the fluorescence of the C-dots could be quenched by H2Q directly. The possible quenching mechanism is proposed, which shows that the quenching effect may be caused by the electron transfer from C-dots to oxidized H2Q-quinone. Based on the above principle, a novel C-dots based fluorescent probe has been successfully applied to detect H2Q. Under the optimal condition, detection limit down to 0.1 μM is obtained, which is far below U.S. Environmental Protection Agency estimated wastewater discharge limit of 0.5 mg/L. Moreover, the proposed method shows high selectivity for H2Q over a number of potential interfering species. Finally, several water samples spiked with H2Q are analyzed utilizing the sensing method with satisfactory recovery. The proposed method is simple with high sensitivity and excellent selectivity, which provides a new approach for the detection of various analytes that can be transformed into quinone. Copyright © 2015 Elsevier B.V. All rights reserved.

Fast and sensitive near-infrared fluorescent probes for ALP detection and 3d printed calcium phosphate scaffold imaging in vivo.

PubMed

Park, Chul Soon; Ha, Tai Hwan; Kim, Moonil; Raja, Naren; Yun, Hui-Suk; Sung, Mi Jeong; Kwon, Oh Seok; Yoon, Hyeonseok; Lee, Chang-Soo

2018-05-15

Alkaline phosphatase (ALP) is a critical biological marker for osteoblast activity during early osteoblast differentiation, but few biologically compatible methods are available for its detection. Here, we describe the discovery of highly sensitive and rapidly responsive novel near-infrared (NIR) fluorescent probes (NIR-Phos-1, NIR-Phos-2) for the fluorescent detection of ALP. ALP cleaves the phosphate group from the NIR skeleton and substantially alters its photophysical properties, therefore generating a large "turn-on" fluorescent signal resulted from the catalytic hydrolysis on fluorogenic moiety. Our assay quantified ALP activity from 0 to 1.0UmL -1 with a 10 -5 -10 -3 UmL -1 limit of detection (LOD), showing a response rate completed within 1.5min. A potentially powerful approach to probe ALP activity in biological systems demonstrated real-time monitoring using both concentration- and time-dependent variations of endogenous ALP in live cells and animals. Based on high binding affinity to bone tissue of phosphate moiety, bone-like scaffold-based ALP detection in vivo was accessed using NIR probe-labeled three-dimensional (3D) calcium deficient hydroxyapatite (CDHA) scaffolds. They were subcutaneously implanted into mice and monitored ALP signal changes using a confocal imaging system. Our results suggest the possibility of early-stage ALP detection during neo-bone formation inside a bone defect, by in vivo fluorescent evaluation using 3D CDHA scaffolds. Copyright © 2018 Elsevier B.V. All rights reserved.

Development of redox-sensitive red fluorescent proteins for imaging redox dynamics in cellular compartments.

PubMed

Fan, Yichong; Ai, Hui-wang

2016-04-01

We recently reported a redox-sensitive red fluorescent protein, rxRFP1, which is one of the first genetically encoded red-fluorescent probes for general redox states in living cells. As individual cellular compartments have different basal redox potentials, we hereby describe a group of rxRFP1 mutants, showing different midpoint redox potentials for detection of redox dynamics in various subcellular domains, such as mitochondria, the cell nucleus, and endoplasmic reticulum (ER). When these redox probes were expressed and subcellularly localized in human embryonic kidney (HEK) 293 T cells, they responded to membrane-permeable oxidants and reductants. In addition, a mitochondrially localized rxRFP1 mutant, Mito-rxRFP1.1, was used to detect mitochondrial oxidative stress induced by doxorubicin-a widely used cancer chemotherapy drug. Our work has expanded the fluorescent protein toolkit with new research tools for studying compartmentalized redox dynamics and oxidative stress under various pathophysiological conditions.

Detection of ultra-low oxygen concentration based on the fluorescence blinking dynamics of single molecules

NASA Astrophysics Data System (ADS)

Wu, Ruixiang; Chen, Ruiyun; Zhou, Haitao; Qin, Yaqiang; Zhang, Guofeng; Qin, Chengbing; Gao, Yan; Gao, Yajun; Xiao, Liantuan; Jia, Suotang

2018-01-01

We present a sensitive method for detection of ultra-low oxygen concentrations based on the fluorescence blinking dynamics of single molecules. The relationship between the oxygen concentration and the fraction of time spent in the off-state, stemming from the population and depopulation of triplet states and radical cationic states, can be fitted with a two-site quenching model in the Stern-Volmer plot. The oxygen sensitivity is up to 43.42 kPa-1 in the oxygen partial pressure region as low as 0.01-0.25 kPa, which is seven times higher than that of the fluorescence intensity indicator. This method avoids the limitation of the sharp and non-ignorable fluctuations that occur during the measurement of fluorescence intensity, providing potential applications in the field of low oxygen-concentration monitoring in life science and industry.

Fluorescence enhancement of quercetin complexes by silver nanoparticles and its analytical application

NASA Astrophysics Data System (ADS)

Liu, Ping; Zhao, Liangliang; Wu, Xia; Huang, Fei; Wang, Minqin; Liu, Xiaodan

2014-03-01

It is found that the plasmon effect of silver nanoparticles (AgNPs) helps to enhance the fluorescence intensity of the quercetin (Qu) and nucleic acids system. Qu exhibited strong fluorescence enhancement when it bound to nucleic acids in the presence of AgNPs. Based on this, a sensitive method for the determination of nucleic acids was developed. The detection limits for the nucleic acids (S/N = 3) were reduced to the ng mL-1 level. The interaction mechanism of the AgNPs-fish sperm DNA (fsDNA)-Qu system was also investigated in this paper. This complex system of Qu and AgNPs was also successfully used for the detection of nucleic acids in agarose gel electrophoresis analysis. Preliminary results indicated that AgNPs also helped to improve sensitivity in the fluorescence image analysis of Qu combined with cellular contents in Arabidopsis thaliana protoplasts.

Rapid and sensitive detection of early esophageal squamous cell carcinoma with fluorescence probe targeting dipeptidylpeptidase IV

PubMed Central

Onoyama, Haruna; Kamiya, Mako; Kuriki, Yugo; Komatsu, Toru; Abe, Hiroyuki; Tsuji, Yosuke; Yagi, Koichi; Yamagata, Yukinori; Aikou, Susumu; Nishida, Masato; Mori, Kazuhiko; Yamashita, Hiroharu; Fujishiro, Mitsuhiro; Nomura, Sachiyo; Shimizu, Nobuyuki; Fukayama, Masashi; Koike, Kazuhiko; Urano, Yasuteru; Seto, Yasuyuki

2016-01-01

Early detection of esophageal squamous cell carcinoma (ESCC) is an important prognosticator, but is difficult to achieve by conventional endoscopy. Conventional lugol chromoendoscopy and equipment-based image-enhanced endoscopy, such as narrow-band imaging (NBI), have various practical limitations. Since fluorescence-based visualization is considered a promising approach, we aimed to develop an activatable fluorescence probe to visualize ESCCs. First, based on the fact that various aminopeptidase activities are elevated in cancer, we screened freshly resected specimens from patients with a series of aminopeptidase-activatable fluorescence probes. The results indicated that dipeptidylpeptidase IV (DPP-IV) is specifically activated in ESCCs, and would be a suitable molecular target for detection of esophageal cancer. Therefore, we designed, synthesized and characterized a series of DPP-IV-activatable fluorescence probes. When the selected probe was topically sprayed onto endoscopic submucosal dissection (ESD) or surgical specimens, tumors were visualized within 5 min, and when the probe was sprayed on biopsy samples, the sensitivity, specificity and accuracy reached 96.9%, 85.7% and 90.5%. We believe that DPP-IV-targeted activatable fluorescence probes are practically translatable as convenient tools for clinical application to enable rapid and accurate diagnosis of early esophageal cancer during endoscopic or surgical procedures. PMID:27245876

One-step synthesis of fluorescent carbon dots for sensitive and selective detection of hyperin.

PubMed

Liu, Lizhen; Mi, Zhi; Hu, Qin; Li, Caiqing; Li, Xiaohua; Feng, Feng

2018-08-15

In this article, we presented a new rapid, sensitive and selective method for the determination of hyperin (Hyp) based on the fluorescence quenching of fluorescent carbon dots (CDs). The CDs were prepared by simply mixing an aqueous solution of citric acid with diphosphorus pentoxide. This one-step synthetic route is fast and simple with neither high temperature nor complicated synthesis steps is involved. When Hyp was added to CDs solution, the fluorescence intensity of the CDs significantly decreased. The CDs display high selectivity for Hyp over many potentially interfering substances. Under the optimized conditions, a good linear relationship between the fluorescence intensity ratio F o /F and the concentration of Hyp is obtained in a range of 0.22-55 µM with a detection limit (S/N = 3) of 78.3 nM. The method was successfully applied for the determination of Hyp in fufangmuji granules and human serum samples with recoveries in a range of 93.3-107.0%. This paper highlights the usefulness of CDs as an effective fluorescence probe for the Hyp detection due to its easy preparation, low-cost, excellent photostability, favorable biocompatibility and low cytotoxicity. Copyright © 2018 Elsevier B.V. All rights reserved.

Label-free fluorescence strategy for sensitive detection of adenosine triphosphate using a loop DNA probe with low background noise.

PubMed

Lin, Chunshui; Cai, Zhixiong; Wang, Yiru; Zhu, Zhi; Yang, Chaoyong James; Chen, Xi

2014-07-15

A simple, rapid, label-free, and ultrasensitive fluorescence strategy for adenosine triphosphate (ATP) detection was developed using a loop DNA probe with low background noise. In this strategy, a loop DNA probe, which is the substrate for both ligation and digestion enzyme reaction, was designed. SYBR green I (SG I), a double-stranded specific dye, was applied for the readout fluorescence signal. Exonuclease I (Exo I) and exonuclease III (Exo III), sequence-independent nucleases, were selected to digest the loop DNA probe in order to minimize the background fluorescence signal. As a result, in the absence of ATP, the loop DNA was completely digested by Exo I and Exo III, leading to low background fluorescence owing to the weak electrostatic interaction between SG I and mononucleotides. On the other hand, ATP induced the ligation of the nicking site, and the sealed loop DNA resisted the digestion of Exo I and ExoIII, resulting in a remarkable increase of fluorescence response. Upon background noise reduction, the sensitivity of the ATP determination was improved significantly, and the detection limitation was found to be 1.2 pM, which is much lower than that in almost all the previously reported methods. This strategy has promise for wide application in the determination of ATP.

Multi-scale silica structures for improved point of care detection

NASA Astrophysics Data System (ADS)

Lin, Sophia; Lin, Lancy; Cho, Eunbyul; Pezzani, Gaston A. O.; Khine, Michelle

2017-03-01

The need for sensitive, portable diagnostic tests at the point of care persists. We report on a simple method to obtain improved detection of biomolecules by a two-fold mechanism. Silica (SiO2) is coated on pre-stressed thermoplastic shrink-wrap film. When the film retracts, the resulting micro- and nanostructures yield far-field fluorescence signal enhancements over their planar or wrinkled counterparts. Because the film shrinks by 95% in surface area, there is also a 20x concentration effect. The SiO2 structured substrate is therefore used for improved detection of labeled proteins and DNA hybridization via both fluorescent and bright field. Through optical characterization studies, we attribute the fluorescence signal enhancements of 100x to increased surface density and light scattering from the rough SiO2 structures. Combining with our open channel self-wicking microfluidics, we can achieve extremely low cost yet sensitive point of care diagnostics.

Fabrication of valine-functionalized graphene quantum dots and its use as a novel optical probe for sensitive and selective detection of Hg2 +

NASA Astrophysics Data System (ADS)

Xiaoyan, Zhou; Zhangyi, Li; Zaijun, Li

2017-01-01

The functionalization of graphene quantum dots has become a powerful method to modulate its chemical, electronic and optical properties for various applications. In the study, we reported a facile synthesis of valine-functionalized graphene quantum dots (Val-GQDs) and its use as a novel fluorescent probe for optical detection of Hg2 +. Herein, Val-GQDs was synthesized by the thermal pyrolysis of citric acid and valine. The resulting Val-GQDs has an average size of 3 nm and the edge of graphene sheets contains the rich of hydrophilic groups, leading to a high water-solubility. Compared to the GQDs prepared by thermal pyrolysis of citric acid, Val-GQDs exhibits a stronger fluorescence (> 10-fold) and better photostability (> 4-fold). Interestingly, the existence of valine moieties in the Val-GQDs results in a more sensitive fluorescent response to Hg2 +. The fluorescent signal will linearly decrease with the increase of Hg2 + concentration in the range from 0.8 nM to 1 μM with the correlation coefficient of 0.992. The detection limit is 0.4 nM (S/N = 3), which the sensitivity is > 14-fold that of GQDs. The analytical method provides the prominent advantage of sensitivity, selectivity and stability. It has been successfully applied in the optical detection of Hg2 + in real water samples. The study also provides a promising approach for the design and synthesis of functionalized GQDs to meet the needs of further applications in sensing and catalysis.

A highly sensitive and selective detection of Cr(VI) and ascorbic acid based on nitrogen-doped carbon dots.

PubMed

Zhang, Yuhua; Fang, Xian; Zhao, Hong; Li, Zengxi

2018-05-01

A highly sensitive and selective detection of hexavalent chromium (Cr(VI)) and ascorbic acid (AA) was proposed using nitrogen-doped carbon dots (N-CDs). In the absence of AA, the quantitative detection of Cr(VI) was realized through Cr(VI) acting as a quencher to quench the fluorescence of N-CDs by inner filter effect (IFE) and static quenching effect. Under the optimal conditions, the linear range for Cr(VI) detection was from 0.01 to 250μM with a detection limit of 5nM (S/N = 3). In the presence of AA, the fluorescence intensity could be rapidly enhanced compared with the fluorescence of N-CDs/Cr(VI) system since Cr(VI) can be reduced into trivalent chromium (Cr(III)) by AA. And a wide linear range for AA detection was obtained from 1 to 750μM. The detection limit was 0.3μM (S/N = 3). More importantly, this method can be successfully applied to the detection of Cr(VI) in real water samples, and AA in vitamins C tablets and human serum sample. Copyright © 2018 Elsevier B.V. All rights reserved.

Towards the fluorogenic detection of peroxide explosives through host-guest chemistry.

PubMed

Almenar, Estefanía; Costero, Ana M; Gaviña, Pablo; Gil, Salvador; Parra, Margarita

2018-04-01

Two dansyl-modified β-cyclodextrin derivatives ( 1 and 2 ) have been synthesized as host-guest sensory systems for the direct fluorescent detection of the peroxide explosives diacetone diperoxide (DADP) and triacetone triperoxide (TATP) in aqueous media. The sensing is based on the displacement of the dansyl moiety from the cavity of the cyclodextrin by the peroxide guest resulting in a decrease of the intensity of the fluorescence of the dye. Both systems showed similar fluorescent responses and were more sensitive towards TATP than DADP.

A brief review of other notable protein detection methods on acrylamide gels.

PubMed

Kurien, Biji T; Scofield, R Hal

2012-01-01

Several methods have been described to stain proteins analyzed on acrylamide gels. These include ultrasensitive protein detection in one-dimensional and two-dimensional gel electrophoresis using a fluorescent product from the fungus Epicoccum nigrum; a fluorescence-based Coomassie Blue protein staining; visualization of proteins in acrylamide gels using ultraviolet illumination; fluorescence visualization of proteins in sodium dodecyl sulfate-polyacrylamide gels using environmentally benign, nonfixative, saline solution; and increasing the sensitivity four- to sixfold for detecting trace proteins in dye or silver stained polyacrylamide gels using polyethylene glycol 6000. All these methods are reviewed briefly in this chapter.

Selective and Sensitive Fluorescent Detection of Picric Acid by New Pyrene and Anthracene Based Copper Complexes.

PubMed

Reddy, Kumbam Lingeshwar; Kumar, Anabathula Manoj; Dhir, Abhimanew; Krishnan, Venkata

2016-11-01

New pyrene and anthracene based copper complexes 4 and 7 respectively were designed, synthesized and characterized. The fluorescence behaviour of both 4 and 7 were evaluated towards nitro aromatics and anions. Both 4 and 7 possess high selectivity for the detection of well-known explosive picric acid (PA) by showing maximum fluorescence affinity. Furthermore, complex 4 showed similar sensing efficiency towards PA at different pH ranges. It was also used for real world applications, as illustrated by the very fast detection of PA from soil samples observed directly by naked eye.

Mercury assisted fluorescent supramolecular assembly of hexaphenylbenzene derivative for femtogram detection of picric acid.

PubMed

Pramanik, Subhamay; Bhalla, Vandana; Kumar, Manoj

2013-09-02

Aggregates of hexaphenylbenzene derivatives 3, having pyrene groups form network of fluorescent nanofibres in presence of mercury ions. Further, fluorescent nanofibres of 3-Hg(2+) supramolecular ensemble exhibit sensitive and pronounced response towards the picric acid. In addition, the solution coated paper strips of 3-Hg(2+) supramolecular ensemble can detect picric acid in the range of 2.29 fg/cm(2), thus, providing a simple, portable and low cost method for detection of picric acid in solution and in contact mode. Copyright © 2013 Elsevier B.V. All rights reserved.

Simple and sensitive HPLC method with fluorescence detection for the measurement of ibuprofen in rat plasma: application to a long-lasting dosage form.

PubMed

Hassan, Ahmed Sheikh; Sapin, Anne; Ubrich, Nathalie; Maincent, Philippe; Bolzan, Claire; Leroy, Pierre

2008-10-01

A simple and sensitive high-performance liquid chromatography (HPLC) assay applied to the measurement of ibuprofen in rat plasma has been developed. Two parameters have been investigated to improve ibuprofen detectability using fluorescence detection: variation of mobile phase pH and the use of beta-cyclodextrin (beta-CD). Increasing the pH value from 2.5 to 6.5 and adding 5 mM beta-CD enhanced the fluorescence signal (lambda(exc) = 224 nm; lambda(em) = 290 nm) by 2.5 and 1.3-fold, respectively, when using standards. In the case of plasma samples, only pH variation significantly lowered detection and quantification limits, down to 10 and 35 ng/mL, respectively. Full selectivity was obtained with a single step for plasma treatment, that is, protein precipitation with acidified acetonitrile. The validated method was applied to a pharmacokinetic study of ibuprofen encapsulated in microspheres and subcutaneously administered to rats.

Hemoglobin detection using carbon dots as a fluorescence probe.

PubMed

Barati, Ali; Shamsipur, Mojtaba; Abdollahi, Hamid

2015-09-15

Herein, we have described the application of high fluorescent carbon dots (CDs) without any surface modification as a simple and fast responding fluorescence probe for sensitive and selective determination of hemoglobin (Hb) in the presence of H2O2. Although Hb itself was able to quench the fluorescence of CDs, based on the inner filter effect (IFE) of the protein that affects both excitation and emission spectra of CDs, the presence of H2O2 resulted in further improvement of the sensitivity of Hb detection. The assay is based on the reaction of Hb with H2O2 that generates reactive oxygen species including hydroxyl (OH•) and superoxide (O2(•-)) radicals under heme degradation and/or iron release from Hb and the subsequent reaction of hydroxyl radicals, as strong oxidizing agents, with CDs resulting in high fluorescence quenching. The proposed probe was used for determination of Hb in concentration range of 1-100 nM with a detection limit of 0.4 nM. The method was successfully applied to the determination of Hb in human blood samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Intrinsic fluorescence based in-vivo detection of cervical precancer with hand held prototype device

NASA Astrophysics Data System (ADS)

Meena, Bharat Lal; Raikwar, Akanksha; Pandey, Kiran; Agarwal, Asha; Pantola, Chayanika; Pradhan, Asima

2018-02-01

A prototype device (hand held probe) designed and fabricated in the lab has been tested for cervical precancer detection using intrinsic fluorescence. The intrinsic fluorescence gets strongly modulated by the interplay of scattering and absorption. This masks valuable biochemical information which is present in the intrinsic fluorescence. These distortion effects can be minimized by normalizing the polarized fluorescence spectra by the polarized elastic scattering spectra. The measurements have been made with a in-house fabricated device using a 405 nm diode laser and white light source respectively. 166 sites of different grades of cervical pre-cancer biopsy samples (CIN I and CIN II) (CIN: cervical intraepithelial neoplastic) have been discriminated from 29 sites of normal biopsy samples using principal component analysis (PCA) based linear discriminant analysis (LDA). The sensitivity and specificity for discrimination of normal samples from CIN I are found to be 99% and 96% respectively. Further the normal samples can be discriminated from CIN II samples with 96% sensitivity and 96% specificity. Based on these promising ex-vivo results an in-vivo study on patients has been initiated in the hospital. The hand held device built in-house shows promise as a useful tool for in vivo cervical precancer detection by polarized fluorescence. Preliminary in-vivo results on 10 patients indicate the efficacy of the hand held device for screening cervical precancers using intrinsic fluorescence.

Fluorescent triplex-forming DNA oligonucleotides labeled with a thiazole orange dimer unit

PubMed Central

Ikeda, Shuji; Yanagisawa, Hiroyuki; Yuki, Mizue; Okamoto, Akimitsu

2013-01-01

Fluorescent probes for the detection of a double-stranded DNA were prepared by labeling a triplex-forming DNA oligonucleotide with a thiazole orange (TO) dimer unit. They belong to ECHO (exciton-controlled hybridization-sensitive fluorescent oligonucleotide) probes which we have previously reported. The excitonic interaction between the two TO molecules was expected to effectively suppress the background fluorescence of the probes. The applicability of the ECHO probes for the detection of double-stranded DNA was confirmed by examining the thermal stability and photophysical and kinetic properties of the DNA triplexes formed by the ECHO probes. PMID:23445822

Navigation surgery for intraoperative sentinel lymph node detection using Indocyanine green (ICG) fluorescence real-time imaging in breast cancer.

PubMed

Toh, U; Iwakuma, N; Mishima, M; Okabe, M; Nakagawa, S; Akagi, Y

2015-09-01

A new sensitive fluorescence imaging system was developed for the real-time identification of sentinel lymph nodes (SLNs) in patients with early breast cancer. The purpose of this study was to evaluate the utility of a color charge-coupled device camera system for the intraoperative detection of SLNs and to determine its clinical efficacy and sensitivity in patients with operable breast cancer. We assessed a total of 168 patients diagnosed with or suspected of having early-stage breast cancer without metastasis in SLNs. The intraoperative detection of SLNs was performed using the conventional Indigo Carmine dye (indigotindisulfonate sodium) technique combined with a new Indocyanine green (ICG) imaging system (HyperEye Medical System: HEMS, MIZUHO IKAKOGYO, Japan) to map SLNs, in which the lymphatic vessels and SLNs were visualized transcutaneously with illuminating ICG fluorescence. Between January 2012 and May 2013, SLNs were successfully identified in all 168 patients (detection rate: 100%). By histopathology, the sensitivity was 93.8% for the detection of the metastatic involvement of SLNs (15 of 16 nodal-positive patients). After a median follow-up of 30.5 months, none of the patients presented with axillary recurrence. These results suggest that the HEMS imaging system is a feasible and effective method for the detection of SLNs in breast cancer. Furthermore, the HEMS device permitted the transcutaneous visualization of lymphatic vessels under light conditions, thus facilitating the identification and detection of SLNs without affecting the surgical procedure, together with a high sensitivity and specificity.

A portable smart-phone device for rapid and sensitive detection of E. coli O157:H7 in Yoghurt and Egg.

PubMed

Zeinhom, Mohamed Maarouf Ali; Wang, Yijia; Song, Yang; Zhu, Mei-Jun; Lin, Yuehe; Du, Dan

2018-01-15

The detection of E. coli O157:H7 in foods has held the attention of many researchers because of the seriousness attributed to this pathogen. In this study, we present a simple, sensitive, rapid and portable smartphone based fluorescence device for E. coli O157:H7 detection. This field-portable fluorescent imager on the smartphone involves a compact laser-diode-based photosource, a long-pass (LP) thin-film interference filter and a high-quality insert lenses. The design of the device provided a low noise to background imaging system. Based on a sandwich ELISA and the specific recognition of antibody to E. coli O157:H7, the sensitive detection of E. coli O157:H7 were realized both in standard samples and real matrix in yoghurt and egg on our device. The detection limit are 1 CFU/mL and 10 CFU/mL correspondingly. Recovery percentages of spiked yogurt and egg samples with 10 3 , 10 4 and 10 5 CFU/mL E. coli O157:H7 were 106.98, 96.52 and 102.65 (in yogurt) and 107.37, 105.64 and 93.84 (in egg) samples using our device, respectively. Most importantly, the entire process could be quickly completed within two hours. This smartphone based device provides a simple, rapid, sensitive detection platform for fluorescent imaging which applied in pathogen detection for food safety monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

Clinical evaluation of near-infrared light transillumination in approximal dentin caries detection.

PubMed

Ozkan, Gokhan; Guzel, Kadriye Gorkem Ulu

2017-08-01

The objective of this clinical study was to compare conventional caries detection techniques, pen-type laser fluorescence device, and near-infrared light transillumination method in approximal dentin caries lesions. The study included 157 patients, aged 12-18, without any cavity in the posterior teeth. Two calibrated examiners carried out the assessments of selected approximal caries sites independently. After the assessments, the unopened sites were excluded and a total of 161 approximal sites were included in the study. When both the examiners arrived at a consensus regarding the presence of dentin caries, the detected lesions were opened with a conical diamond burr, the cavity extent was examined and validated (gold standard). Sensitivity, specificity, negative predictive value, positive predictive value, accuracy, and area under the ROC curve (Az) values among the caries detection methods were calculated. Bitewing radiography and near-infrared (NIR) light transillumination methods showed the highest sensitivity (0.83-0.82) and accuracy (0.82-0.80) among the methods. Visual inspection showed the lowest sensitivity (0.54). Laser fluorescence device and visual inspection showed nearly equal performance. Near-infrared light transillumination can be used as an alternative method to approximal dentin caries detection. Visual inspection and laser fluorescence device alone should not be used for approximal dentin caries.

Fluorescent cellulose microfibrils as substrate for the detection of cellulase activity.

PubMed

Helbert, William; Chanzy, Henri; Husum, Tommy Lykke; Schülein, Martin; Ernst, Steffen

2003-01-01

To devise a sensitive cellulase assay based on substrates having most of the physical characteristics of native cellulose, 5-(4,6-dichlorotriazinyl)aminofluorescein (DTAF) was used as a grafting agent to prepare suspensions of fluorescent microfibrils from bacterial cellulose. These suspensions were digested by a series of commercially relevant cellulases from Humicola insolens origin: cloned Cel6B and Cel 45A as well as crude H. insolens complex. The digestion induced the release of fluorescent cellodextrins as well as reducing sugars. After adequate centrifugation, these soluble products were analyzed as a function of grafting content, digestion time, and cellulase characteristics. The resulting data allowed the grafting conditions to be optimized in order to maximize the quantity of soluble products and therefore to increase the sensitivity of the detection. A comparison between the amount of released fluorescence and that of released reducing sugar allowed the differentiation between processive exo and endo cellulase activities. The casting of films of DTAF-grafted microfibrils at the bottom of the microwell titer plates also led to sensitive cellulase detection. As these films kept their integrity and remained firmly glued to the well bottom during the digestion time, they are tailored made for a full automation of the cellulases testing.

PH-sensitive fluorescence detection by diffuse fluorescence tomography

NASA Astrophysics Data System (ADS)

Li, Jiao; Gao, Feng; Duan, Linjing; Wang, Xin; Zhang, Limin; Zhao, Huijuan

2012-03-01

The importance of cellular pH has been shown clearly in the study of cell activity, pathological feature, drug metabolism, etc. Monitoring pH changes of living cells and imaging the regions with abnormal pH values in vivo could provide the physiologic and pathologic information for the research of the cell biology, pharmacokinetics, diagnostics and therapeutics of certain diseases such as cancer. Thus, pH-sensitive fluorescence imaging of bulk tissues has been attracting great attention in the regime of near-infrared diffuse fluorescence tomography (DFT), an efficient small-animal imaging tool. In this paper, the feasibility of quantifying pH-sensitive fluorescence targets in turbid medium is investigated using both time-domain and steady-state DFT methods. By use of the specifically designed time-domain and continuous-wave systems and the previously proposed image reconstruction scheme, we validate the method through 2-dimensional imaging experiments on a small-animal-sized phantom with multiply targets of distinct pH values. The results show that the approach can localize the targets with reasonable accuracy and achieve quantitative reconstruction of the pH-sensitive fluorescent yield.

Research of the fluorescence detection apparatus for nutrients

NASA Astrophysics Data System (ADS)

Wang, Yu; Yan, Huimin; Ni, Xuxiang; Xu, Xiaoyi; Chen, Shibing

2015-10-01

The research of the multifunctional analyzer of Clinical Nutrition, which integrates the absorbance, luminescence, fluorescence and other optical detection methods, can overcome the functional limitations of a single technology on human nutrition analysis, and realize a rapid and accurate analysis of the nutrients. This article focuses on the design of fluorescence detection module that uses a photomultiplier tube(PMT) to detect weak fluorescence, and utilizes the single photon counting method to measure the fluorescence intensity, and then according to the relationship between the fluorescent marker and fluorescence intensity, the concentration of the analyte can be derived. Using fluorescein isothiocyanate(FITC, the most widely used fluorescein currently)to mark antibodies in the experiment, therefore, according to the maximum absorption wavelength and the maximum emission wavelength of the fluorescein isothiocyanate, to select the appropriate filters to set up the optical path. In addition, the fluorescence detection apparatus proposed in this paper uses an aspherical lens with large numerical aperture, in order to improve the capacity of signal acquisition more effectively, and the selective adoption of flexible optical fiber can realize a compact opto-mechanical structure, which is also conducive to the miniaturization of the device. The experimental results show that this apparatus has a high sensitivity, can be used for the detection and analysis of human nutrition.

Near-Infrared Fluorescent Turn-on Probe with a Remarkable Large Stokes Shift for Imaging Selenocysteine in Living Cells and Animals.

PubMed

Feng, Weiyong; Li, Meixing; Sun, Yao; Feng, Guoqiang

2017-06-06

Selenocysteine (Sec) is the 21st naturally occurring amino acid and has emerged as an important sensing target in recent years. However, fluorescent detection of Sec in living systems is challenging. To date, very few fluorescent Sec probes have been reported and most of them respond fluorescence to Sec in the visible region. In this paper, a very promising near-infrared fluorescent probe for Sec was developed. This probe works in aqueous solution over a wide pH range under mild conditions and can be used for rapid, highly selective and sensitive detection of Sec with significant near-infrared fluorescent turn-on signal changes. In addition, it features a remarkable large Stokes shift (192 nm) and a low detection limit (60 nM) for Sec with a wide linear range (0-70 μM). Moreover, this probe can be conveniently used to detect Sec in serum samples, living cells, and animals, indicating it holds great promise for biological applications.

Reaction-based small-molecule fluorescent probes for dynamic detection of ROS and transient redox changes in living cells and small animals.

PubMed

Lü, Rui

2017-09-01

Dynamic detection of transient redox changes in living cells and animals has broad implications for human health and disease diagnosis, because intracellular redox homeostasis regulated by reactive oxygen species (ROS) plays important role in cell functions, normal physiological functions and some serious human diseases (e.g., cancer, Alzheimer's disease, diabetes, etc.) usually have close relationship with the intracellular redox status. Small-molecule ROS-responsive fluorescent probes can act as powerful tools for dynamic detection of ROS and redox changes in living cells and animals through fluorescence imaging techniques; and great advances have been achieved recently in the design and synthesis of small-molecule ROS-responsive fluorescent probes. This article highlights up-to-date achievements in designing and using the reaction-based small-molecule fluorescent probes (with high sensitivity and selectivity to ROS and redox cycles) in the dynamic detection of ROS and transient redox changes in living cells and animals through fluorescence imaging. Copyright © 2017. Published by Elsevier Ltd.

Photoinduced electron transfer between Fe(III) and adenosine triphosphate-BODIPY conjugates: Application to alkaline-phosphatase-linked immunoassay.

PubMed

Lin, Jia-Hui; Yang, Ya-Chun; Shih, Ya-Chen; Hung, Szu-Ying; Lu, Chi-Yu; Tseng, Wei-Lung

2016-03-15

Fluorescent boron dipyrromethene (BODIPY) analogs are often used as sensors for detecting various species because of their relatively high extinction coefficients, outstanding fluorescence quantum yields, photostability, and pH-independent fluorescence. However, there is little-to-no information in the literature that describes the use of BODIPY analogs for detecting alkaline phosphatase (ALP) activity and inhibition. This study discovered that the fluorescence of BODIPY-conjugated adenosine triphosphate (BODIPY-ATP) was quenched by Fe(III) ions through photoinduced electron transfer. The ALP-catalyzed hydrolysis of BODIPY-ATP resulted in the formation of BODIPY-adenosine and phosphate ions. The fluorescence of the generated BODIPY-adenosine was insensitive to the change in the concentration of Fe(III) ions. Thus, the Fe(III)-induced fluorescence quenching of BODIPY-ATP can be paired with its ALP-mediated dephosphorylation to design a turn-on fluorescence probe for ALP sensing. A method detection limit at a signal-to-noise ratio of 3 for ALP was estimated to be 0.02 units/L (~6 pM; 1 ng/mL). This probe was used for the screening of ALP inhibitors, including Na3VO4, imidazole, and arginine. Because ALP is widely used in enzyme-linked immunosorbent assays, the probe was coupled to an ALP-linked immunosorbent assay for the sensitive and selective detection of immunoglobulin G (IgG). The lowest detectable concentration for IgG in this system was 5 ng/mL. Compared with the use of 3,6-fluorescein diphosphate as a signal reporter in an ALP-linked immunosorbent assay, the proposed system provided comparable sensitivity, large linear range, and high stability over temperature and pH changes. Copyright © 2015 Elsevier B.V. All rights reserved.

Highly sensitive and selective detection of Pb2+ using a turn-on fluorescent aptamer DNA silver nanoclusters sensor.

PubMed

Zhang, Baozhu; Wei, Chunying

2018-05-15

A novel turn-on fluorescent biosensor has been constructed using C-PS2.M-DNA-templated silver nanoclusters (Ag NCs) with an average diameter of about 1 nm. The proposed approach presents a low-toxic, simple, sensitive, and selective detection for Pb 2+ . The fluorescence intensity of C-PS2.M-DNA-Ag NCs enhances significantly in the presence of Pb 2+ , which is attributed to the special interaction between Pb 2+ and its aptamer DNA PS2.M. Pb 2+ induces the aptamer to form G-quadruplex and makes two darkish DNA/Ag NCs located at the 3' and 5' terminus close, resulting in the fluorescence light-up. Moreover, Pb 2+ can be detected as low as 3.0 nM within a good linear range from 5 to 50 nM (R = 0.9862). Furthermore, the application for detection of Pb 2+ in real water samples further demonstrates the reliability of the sensor. Thus, this sensor system shows a potential application for monitoring Pb 2+ in environmental samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Chemical redox modulated fluorescence of nitrogen-doped graphene quantum dots for probing the activity of alkaline phosphatase.

PubMed

Liu, JingJing; Tang, Duosi; Chen, Zhitao; Yan, Xiaomei; Zhong, Zhou; Kang, Longtian; Yao, Jiannian

2017-08-15

Alkaline phosphatase (ALP) as an essential enzyme plays an important role in clinical diagnoses and biomedical researches. Hence, the development of convenient and sensitivity assay for monitoring ALP is extremely important. In this work, on the basis of chemical redox strategy to modulate the fluorescence of nitrogen-doped graphene quantum dots (NGQDs), a novel label-free fluorescent sensing system for the detection of alkaline phosphatase (ALP) activity has been developed. The fluorescence of NGQDs is firstly quenched by ultrathin cobalt oxyhydroxide (CoOOH) nanosheets, and then restored by ascorbic acid (AA), which can reduce CoOOH to Co 2+ , thus the ALP can be monitored based on the enzymatic hydrolysis of L-ascorbic acid-2-phosphate (AAP) by ALP to generate AA. Quantitative evaluation of ALP activity in a range from 0.1 to 5U/L with the detection limit of 0.07U/L can be realized in this sensing system. Endowed with high sensitivity and selectivity, the proposed assay is capable of detecting ALP in biological system with satisfactory results. Meanwhile, this sensing system can be easily extended to the detection of various AA-involved analytes. Copyright © 2017 Elsevier B.V. All rights reserved.

Supramolecular nano-sniffers for ultrasensitive detection of formaldehyde.

PubMed

Akshath, Uchangi Satyaprasad; Bhatt, Praveena

2018-02-15

Supramolecular nanoparticle hybrids for biosensing of analytes have been a major focus due to their tunable optical and surface properties. Quantum dots-Gold nanoparticle (QDs-GNP) based FRET probes involving turn on/off principles have gained immense interest due to their specificity and sensitivity. Recent focus is on applying these supramolecular hybrids for enzyme operated biosensors that can specifically turn-on fluorescence induced by co-factor or product formed from enzymatic reaction. The present study focuses on locking and unlocking the interaction between QD-GNP pair leading to differential fluorescent properties. Cationic GNPs efficiently quenched the anionic QD fluorescence by forming nanoparticle hybrid. Quenching interaction between QD-GNP pair was unlocked by NADH leading to QD fluorescence turn-on. This phenomenon was applied for the successful detection of formaldehyde using NAD + dependent formaldehyde dehydrogenase. The proposed nano-sniffer could successfully detect formaldehyde from 0.001 to 100000ng/mL (R 2 = 0.9339) by the turn off-turn on principle. It could also detect formaldehyde in fruit juice and wine samples indicating its stability and sensitivity in real samples. The proposed nanoprobe can have wide applications in developing enzyme biosensors in future. Copyright © 2017 Elsevier B.V. All rights reserved.

Visualizing BPA by molecularly imprinted ratiometric fluorescence sensor based on dual emission nanoparticles.

PubMed

Lu, Hongzhi; Xu, Shoufang

2017-06-15

Construction of ratiometric fluorescent probe often involved in tedious multistep preparation or complicated coupling or chemical modification process. The emergence of dual emission fluorescent nanoparticles would simplify the construction process and avoids the tedious chemical coupling. Herein, we reported a facile strategy to prepare ratiometric fluorescence molecularly imprinted sensor based on dual emission nanoparticles (d-NPs) which comprised of carbon dots and gold nanoclusters for detection of Bisphenol A (BPA). D-NPs emission at 460nm and 580nm were first prepared by seed growth co-microwave method using gold nanoparticles as seeds and glucose as precursor for carbon dots. When they were applied to propose ratiometric fluorescence molecularly imprinted sensor, the preparation process was simplified, and the sensitivity of sensor was improved with detection limit of 29nM, and visualizing BPA was feasible based on the distinguish fluorescence color change. The feasibility of the developed method in real samples was successfully evaluated through the analysis of BPA in water samples with satisfactory recoveries of 95.9-98.9% and recoveries ranging from 92.6% to 98.6% in canned food samples. When detection BPA in positive feeding bottles, the results agree well with those obtained by accredited method. The developed method proposed in this work to prepare ratiometric fluorescence molecularly imprinted sensor based on dual emission nanoparticles proved to be a convenient, reliable and practical way to prepared high sensitive and selective fluorescence sensors. Copyright © 2017 Elsevier B.V. All rights reserved.

Fluorescence and Spectral Imaging

PubMed Central

DaCosta, Ralph S.; Wilson, Brian C.; Marcon, Norman E.

2007-01-01

Early identification of dysplasia remains a critical goal for diagnostic endoscopy since early discovery directly improves patient survival because it allows endoscopic or surgical intervention with disease localized without lymph node involvement. Clinical studies have successfully used tissue autofluorescence with conventional white light endoscopy and biopsy for detecting adenomatous colonic polyps, differentiating benign hyperplastic from adenomas with acceptable sensitivity and specificity. In Barrett's esophagus, the detection of dysplasia remains problematic because of background inflammation, whereas in the squamous esophagus, autofluorescence imaging appears to be more dependable. Point fluorescence spectroscopy, although playing a crucial role in the pioneering mechanistic development of fluorescence endoscopic imaging, does not seem to have a current function in endoscopy because of its nontargeted sampling and suboptimal sensitivity and specificity. Other point spectroscopic modalities, such as Raman spectroscopy and elastic light scattering, continue to be evaluated in clinical studies, but still suffer the significant disadvantages of being random and nonimaging. A recent addition to the fluorescence endoscopic imaging arsenal is the use of confocal fluorescence endomicroscopy, which provides real-time optical biopsy for the first time. To improve detection of dysplasia in the gastrointestinal tract, a new and exciting development has been the use of exogenous fluorescence contrast probes that specifically target a variety of disease-related cellular biomarkers using conventional fluorescent dyes and novel potent fluorescent nanocrystals (i.e., quantum dots). This is an area of great promise, but still in its infancy, and preclinical studies are currently under way. PMID:18167619

Coherent nonlinear optical imaging: beyond fluorescence microscopy.

PubMed

Min, Wei; Freudiger, Christian W; Lu, Sijia; Xie, X Sunney

2011-01-01

The quest for ultrahigh detection sensitivity with spectroscopic contrasts other than fluorescence has led to various novel approaches to optical microscopy of biological systems. Coherent nonlinear optical imaging, especially the recently developed nonlinear dissipation microscopy (including stimulated Raman scattering and two-photon absorption) and pump-probe microscopy (including excited-state absorption, stimulated emission, and ground-state depletion), provides new image contrasts for nonfluorescent species. Thanks to the high-frequency modulation transfer scheme, these imaging techniques exhibit superb detection sensitivity. By directly interrogating vibrational and/or electronic energy levels of molecules, they offer high molecular specificity. Here we review the underlying principles and excitation and detection schemes, as well as exemplary biomedical applications of this emerging class of molecular imaging techniques.

Sensitive naked eye detection and quantification assay for nitrite by a fluorescence probe in various water resources

NASA Astrophysics Data System (ADS)

Zhang, Fengyuan; Zhu, Xinyue; Jiao, Zhijuan; Liu, Xiaoyan; Zhang, Haixia

2018-07-01

An uncontrolled increase of nitrite concentration in groundwater, rivers and lakes is a growing threat to public health and environment. It is important to monitor the nitrite levels in water and clinical diagnosis. Herein, we developed a switch-off fluorescence probe (PyI) for the sensitive detection of nitrite ions in the aqueous media. This probe selectively recognizes nitrite ions through a distinct visual color change from colorless to pink with a detection limit of 0.1 μM. This method has been successfully applied to the determination of nitrites in tap water, lake water and Yellow River water with recoveries in the range of 94.8%-105.4%.

A Series of Fluorescent and Colorimetric Chemodosimeters for Selective Recognition of Cyanide Based on the FRET Mechanism.

PubMed

Hua, Ying-Xi; Shao, Yongliang; Wang, Ya-Wen; Peng, Yu

2017-06-16

A series of fluorescence "turn-on" probes (PY, AN, NA, B1, and B2) have been developed and successfully applied to detect cyanide anions based on the Michael addition reaction and FRET mechanism. These probes demonstrated good selectivity, high sensitivity, and very fast recognition for CN - . In particular, the fluorescence response of probe NA finished within 3 s. Low limits of detection (down to 63 nM) are also obtained in these probes with remarkable fluorescence enhancement factors. In addition, fluorescence colors of these probes turned to blue, yellow, or orange upon sensing CN - . In UV-vis mode, all of them showed ratiometric response for CN - . 1 H NMR titration experiments and TDDFT calculations were taken to verify the mechanism of the specific reaction and fluorescence properties of the corresponding compounds. Moreover, silica gel plates with these probes were also fabricated and utilized to detect cyanide.

Optical and Electrochemical Aptasensors for Sensitive Detection of Streptomycin in Blood Serum and Milk.

PubMed

Ramezani, Mohammad; Abnous, Khalil; Taghdisi, Seyed Mohammad

2017-01-01

Detection and quantitation of antibiotic residues in blood serum and foodstuffs are in great demand. We have developed aptasensors for detection of streptomycin using electrochemical and optical methods. In the first method, an electrochemical aptasensor was developed for sensitive and selective detection of streptomycin, based on combination of exonuclease I (Exo I), complementary strand of aptamer (CS), arch shaped structure of aptamer (Apt)-CS conjugate, and gold electrode. The designed electrochemical aptasensor exhibited high selectivity toward streptomycin with a limit of detection (LOD) as low as 11.4 nM. Moreover, the developed electrochemical aptasensor was successfully used to detect streptomycin in milk and serum with LODs of 14.1 and 15.3 nM, respectively. In the second method, fluorescence quenching and colorimetric aptasensors were designed for detection of streptomycin based on aqueous gold nanoparticles (AuNPs) and double-stranded DNA (dsDNA). In the absence of streptomycin, aptamer/FAM-labeled complementary strand dsDNA is stable, resulting in the aggregation of AuNPs by salt bridge and an obvious color change from red to blue and strong emission of fluorescence. The colorimetric and fluorescence quenching aptasensors showed excellent selectivity toward streptomycin with limit of detections as low as 73.1 and 47.6 nM, respectively. The presented aptasensors were successfully used to detect streptomycin in milk and serum. For serum, LODs were determined to be 58.2 and 102.4 nM for fluorescence quenching and colorimetric aptasensors, respectively. For milk, LODs were calculated to be 56.2 and 108.7 nM for fluorescence quenching and colorimetric aptasensors, respectively.

Red Fluorescent Line Emission from Hydrogen Molecules in Diffuse Molecular Clouds

NASA Technical Reports Server (NTRS)

Neufeld, David A.; Spaans, Marco

1996-01-01

We have modeled the fluorescent pumping of electronic and vibrational emissions of molecular hydrogen (H2) within diffuse molecular clouds that are illuminated by ultraviolet continuum radiation. Fluorescent line intensities are predicted for transitions at ultraviolet, infrared, and red visible wavelengths as functions of the gas density, the visual extinction through the cloud, and the intensity of the incident UV continuum radiation. The observed intensity in each fluorescent transition is roughly proportional to the integrated rate of H2 photodissociation along the line of sight. Although the most luminous fluorescent emissions detectable from ground-based observatories lie at near-infrared wavelengths, we argue that the lower sky brightness at visible wavelengths makes the red fluorescent transitions a particularly sensitive probe. Fabry-Perot spectrographs of the type that have been designed to observe very faint diffuse Ha emissions are soon expected to yield sensitivities that will be adequate to detect H2 vibrational emissions from molecular clouds that are exposed to ultraviolet radiation no stronger than the mean radiation field within the Galaxy. Observations of red H2 fluorescent emission together with cospatial 21 cm H I observations could serve as a valuable probe of the gas density in diffuse molecular clouds.

Fluorescence detection of organic molecules in the Jovian atmosphere

NASA Technical Reports Server (NTRS)

Levine, J. S.; Rogowski, R. S.

1975-01-01

A search for fluorescent emission due to the presence of possible organic molecules in the Jovian atmosphere is described. We first consider natural Jovian fluorescent emission excited by precipitating auroral particles. Due to our lack of knowledge of the Jovian precipitating particle energies and fluxes we next consider fluorescent emission excited by a laser system aboard a Jupiter spacecraft. Laser-induced fluorescence is routinely used to monitor trace constituents and pollutants in the terrestrial atmosphere. Several spacecraft laser systems are currently under development. Our calculations indicate that laser-induced fluorescent detection is approximately two orders of magnitude more sensitive than rocket ultraviolet measurements of possible Jovian absorption features at 2600 A that have been attributed to the presence of adenine or benzene.

Detection of iron atoms by emission spectroscopy and laser-induced fluorescence in solid propellant flames.

PubMed

Vilmart, G; Dorval, N; Orain, M; Lambert, D; Devillers, R; Fabignon, Y; Attal-Tretout, B; Bresson, A

2018-05-10

Planar laser-induced fluorescence on atomic iron is investigated in this paper, and a measurement strategy is proposed to monitor the fluorescence of iron atoms with good sensitivity. A model is proposed to fit the experimental fluorescence spectra, and good agreement is found between simulated and experimental spectra. Emission and laser-induced fluorescence measurements are performed in the flames of ammonium perchlorate composite propellants containing iron-based catalysts. A fluorescence signal from iron atoms after excitation at 248 nm is observed for the first time in propellant flames. Images of the spatial distribution of iron atoms are recorded in the flame in which turbulent structures are generated. Iron fluorescence is detected up to 1.0 MPa, which opens the way to application in propellant combustion.

Use of zero order diffraction of a grating monochromator towards convenient and sensitive detection of fluorescent analytes in multi fluorophoric systems

NASA Astrophysics Data System (ADS)

Panigrahi, Suraj Kumar; Mishra, Ashok Kumar

2018-02-01

White light excitation fluorescence (WLEF) is known to possess analytical advantage in terms of enhanced sensitivity and facile capture of the entire fluorescence spectral signature of multi component fluorescence systems. Using the zero order diffraction of the grating monochromator on the excitation side of a commercial spectrofluorimeter, it has been shown that WLEF spectral measurements can be conveniently carried out. Taking analyte multi-fluorophoric systems like (i) drugs and vitamins spiked in urine sample, (ii) adulteration of extra virgin olive oil with olive pomace oil and (iii) mixture of fabric dyes, it was observed that there is a significant enhancement of measurement sensitivity. The total fluorescence spectral response could be conveniently analysed using PLS2 regression. This work brings out the ease of the use of a conventional fluorimeter for WLEF measurements.

Fluorescence-based ion-sensing with colloidal particles.

PubMed

Ashraf, Sumaira; Carrillo-Carrion, Carolina; Zhang, Qian; Soliman, Mahmoud G; Hartmann, Raimo; Pelaz, Beatriz; Del Pino, Pablo; Parak, Wolfgang J

2014-10-01

Particle-based fluorescence sensors for the quantification of specific ions can be made by coupling ion-sensitive fluorophores to carrier particles, or by using intrinsically fluorescent particles whose fluorescence properties depend on the concentration of the ions. Despite the advantages of such particle-based sensors for the quantitative detection of ions, such as the possibility to tune the surface chemistry and thus entry portal of the sensor particles to cells, they have also some associated problems. Problems involve for example crosstalk of the ion-sensitive fluorescence read-out with pH, or spectral overlap of the emission spectra of different fluorescent particles in multiplexing formats. Here the benefits of using particle-based fluorescence sensors, their limitations and strategies to overcome these limitations will be described and exemplified with selected examples. Copyright © 2014 Elsevier Ltd. All rights reserved.

Sprayable enzyme-activatable fluorescent probes: kinetic mapping using dynamic fluorescence imaging can help detecting tiny cancer foci (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kobayashi, Hisataka

2017-02-01

Optical fluorescence-guided imaging is increasingly used to guide surgery and endoscopic procedures. Sprayable enzyme-activatable probes are particularly useful because of high target-to-background ratios that increase sensitivity for tiny cancer foci. However, green fluorescent activatable probes suffers from interference from autofluorescence found in biological tissue. Dynamic imaging followed by the kinetic analysis could be detected local enzyme activity and used to differentiate specific fluorescence arising from an activated probe in a tumor from autofluorescence in background tissues especially when low concentrations of the dye are applied to detect tiny cancer foci. Serial fluorescence imaging was performed using various concentrations of γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) which was sprayed on the peritoneal surface with tiny implants of SHIN3-dsRed ovarian cancer tumors. Temporal differences in signal between specific green fluorescence in cancer foci and non-specific autofluorescence in background tissue was measured and processed into three kinetic maps reflecting maximum fluorescence signal (MF), wash-in rate (WIR), and area under the curve (AUC), respectively. Especially at lower concentrations, kinetic maps derived from dynamic fluorescence imaging were clearly superior to unprocessed images for detection small cancer foci.

Sentinel lymph nodes detection with an imaging system using Patent Blue V dye as fluorescent tracer

NASA Astrophysics Data System (ADS)

Tellier, F.; Steibel, J.; Chabrier, R.; Rodier, J. F.; Pourroy, G.; Poulet, P.

2013-03-01

Sentinel lymph node biopsy is the gold standard to detect metastatic invasion from primary breast cancer. This method can help patients avoid full axillary chain dissection, thereby decreasing the risk of morbidity. We propose an alternative to the traditional isotopic method, to detect and map the sentinel lymph nodes. Indeed, Patent Blue V is the most widely used dye in clinical routine for the visual detection of sentinel lymph nodes. A Recent study has shown the possibility of increasing the fluorescence quantum yield of Patent Blue V, when it is bound to human serum albumin. In this study we present a preclinical fluorescence imaging system to detect sentinel lymph nodes labeled with this fluorescent tracer. The setup is composed of a black and white CCD camera and two laser sources. One excitation source with a laser emitting at 635 nm and a second laser at 785 nm to illuminate the region of interest. The prototype is operated via a laptop. Preliminary experiments permitted to determine the device sensitivity in the μmol.L-1 range as regards the detection of PBV fluorescence signals. We also present a preclinical evaluation performed on Lewis rats, during which the fluorescence imaging setup detected the accumulation and fixation of the fluorescent dye on different nodes through the skin.

The enhanced cyan fluorescent protein: a sensitive pH sensor for fluorescence lifetime imaging.

PubMed

Poëa-Guyon, Sandrine; Pasquier, Hélène; Mérola, Fabienne; Morel, Nicolas; Erard, Marie

2013-05-01

pH is an important parameter that affects many functions of live cells, from protein structure or function to several crucial steps of their metabolism. Genetically encoded pH sensors based on pH-sensitive fluorescent proteins have been developed and used to monitor the pH of intracellular compartments. The quantitative analysis of pH variations can be performed either by ratiometric or fluorescence lifetime detection. However, most available genetically encoded pH sensors are based on green and yellow fluorescent proteins and are not compatible with multicolor approaches. Taking advantage of the strong pH sensitivity of enhanced cyan fluorescent protein (ECFP), we demonstrate here its suitability as a sensitive pH sensor using fluorescence lifetime imaging. The intracellular ECFP lifetime undergoes large changes (32 %) in the pH 5 to pH 7 range, which allows accurate pH measurements to better than 0.2 pH units. By fusion of ECFP with the granular chromogranin A, we successfully measured the pH in secretory granules of PC12 cells, and we performed a kinetic analysis of intragranular pH variations in living cells exposed to ammonium chloride.

TCSPC based approaches for multiparameter detection in living cells

NASA Astrophysics Data System (ADS)

Jahn, Karolina; Buschmann, Volker; Koberling, Felix; Hille, Carsten

2014-03-01

In living cells a manifold of processes take place simultaneously. This implies a precise regulation of intracellular ion homeostasis. In order to understand their spatio-temporal pattern comprehensively, the development of multiplexing concepts is essential. Due to the multidimensional characteristics of fluorescence dyes (absorption and emission spectra, decay time, anisotropy), the highly sensitive and non-invasive fluorescence microscopy is a versatile tool for realising multiplexing concepts. A prerequisite are analyte-specific fluorescence dyes with low cross-sensitivity to other dyes and analytes, respectively. Here, two approaches for multiparameter detection in living cells are presented. Insect salivary glands are well characterised secretory active tissues which were used as model systems to evaluate multiplexing concepts. Salivary glands secrete a KCl-rich or NaCl-rich fluid upon stimulation which is mainly regulated by intracellular Ca2+ as second messenger. Thus, pairwise detection of intracellular Na+, Cl- and Ca2+ with the fluorescent dyes ANG2, MQAE and ACR were tested. Therefore, the dyes were excited simultaneously (2-photon excitation) and their corresponding fluorescence decay times were recorded within two spectral ranges using time-correlated singlephoton counting (TCSPC). A second approach presented here is based on a new TCSPC-platform covering decay time detection from picoseconds to milliseconds. Thereby, nanosecond decaying cellular fluorescence and microsecond decaying phosphorescence of Ruthenium-complexes, which is quenched by oxygen, were recorded simultaneously. In both cases changes in luminescence decay times can be linked to changes in analyte concentrations. In consequence of simultaneous excitation as well as detection, it is possible to get a deeper insight into spatio-temporal pattern in living tissues.

Engineering of near IR fluorescent albumin nanoparticles for in vivo detection of colon cancer.

PubMed

Cohen, Sarit; Margel, Shlomo

2012-08-14

The use of near-infrared (NIR) fluorescence imaging techniques has gained great interest for early detection of cancer because water and other intrinsic biomolecules display negligible absorption or autofluorescence in this region. Novel fluorescent nanoparticles with potential to improve neoplasm detection sensitivity may prove to be a valuable tool in early detection of colon tumors. The present study describes the synthesis and use of NIR fluorescent albumin nanoparticles as a diagnostic tool for detection of colon cancer. These fluorescent nanoparticles were prepared by a precipitation process of human serum albumin (HSA) in aqueous solution in the presence of a carboxylic acid derivative of the NIR dye IR-783 (CANIR). Tumor-targeting ligands such as peanut agglutinin (PNA), anti-carcinoembryonic antigen antibodies (anti-CEA) and tumor associated glycoprotein-72 monoclonal antibodies (anti-TAG-72) were covalently conjugated to the albumin nanoparticles via the surface carboxylate groups by using the carbodiimide activation method. Leakage of the encapsulated dye into PBS containing 4% HSA or human bowel juice was not detected. This study also demonstrates that the encapsulation of the NIR fluorescent dye within the HSA nanoparticles reduces the photobleaching of the dye significantly. Specific colon tumor detection in a mouse model was demonstrated for PNA, anti-CEA and anti-TAG-72 conjugated NIR fluorescent HSA nanoparticles. These bioactive NIR fluorescent albumin nanoparticles also detected invisible tumors that were revealed as pathological only subsequent to histological analysis. These results may suggest a significant advantage of NIR fluorescence imaging using NIR fluorescent nanoparticles over regular colonoscopy. In future work we plan to broaden this study by encapsulating cancer drugs, such as paclitaxel and doxorubicin, within these biodegradable NIR fluorescent HSA nanoparticles, in order to use them for both detection as well as therapy of colon cancer and others.

Detection of acrylamide in potato chips using a fluorescent sensing method based on acrylamide polymerization-induced distance increase between quantum dots.

PubMed

Hu, Qinqin; Xu, Xiahong; Li, Zhanming; Zhang, Ying; Wang, Jianping; Fu, Yingchun; Li, Yanbin

2014-04-15

Acrylamide is a neurotoxin and potential carcinogen, but is found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple and sensitive methods for on-line detection of acrylamide are needed to ensure food safety. In this paper, a novel fluorescent sensing method based on acrylamide polymerization-induced distance increase between quantum dots (QDs) was proposed for detecting acrylamide in potato chips. The functional QDs were prepared by their binding with N-acryloxysuccinimide (NAS), which was characterized by Fourier transform infrared (FR-IR) spectra. The carbon-carbon double bonds of NAS modified QDs polymerized with assistance of photo initiator under UV irradiation, leading to QDs getting closer along with fluorescence intensity decreasing. Acrylamide in the sample participated in the polymerization and induced an increase of fluorescence intensity. This method possessed a linear range from 3.5×10(-5) to 3.5 g L(-1) (r(2)=0.94) and a limit of detection of 3.5×10(-5) g L(-1). Although the sensitivity and specificity cannot be compared with standard LC-MS/MS analysis, this new method requires much less time and cost, which is promising for on-line rapid detection of acrylamide in food processing. © 2013 Published by Elsevier B.V.

Surface plasmon-enhanced fluorescence on Au nanohole array for prostate-specific antigen detection

PubMed Central

Zhang, Qingwen; Wu, Lin; Wong, Ten It; Zhang, Jinling; Liu, Xiaohu; Zhou, Xiaodong; Bai, Ping; Liedberg, Bo; Wang, Yi

2017-01-01

Localized surface plasmon (LSP) has been widely applied for the enhancement of fluorescence emission for biosensing owing to its potential for strong field enhancement. However, due to its small penetration depth, LSP offers limited fluorescence enhancement over a whole sensor chip and, therefore, insufficient sensitivity for the detection of biomolecules, especially large molecules. We demonstrate the simultaneous excitation of LSP and propagating surface plasmon (PSP) on an Au nanohole array under Kretschmann configuration for the detection of prostate-specific antigen with a sandwich immunoassay. The proposed method combines the advantages of high field enhancement by LSP and large surface area probed by PSP field. The simulated results indicated that a maximum enhancement of electric field intensity up to 1,600 times can be achieved under the simultaneous excitation of LSP and PSP modes. The sandwich assay of PSA carried out on gold nanohole array substrate showed a limit of detection of 140 fM supporting coexcitation of LSP and PSP modes. The limit of detection was approximately sevenfold lower than that when only LSP was resonantly excited on the same substrate. The results of this study demonstrate high fluorescence enhancement through the coexcitation of LSP and PSP modes and pave a way for its implementation as a highly sensitive bioassay. PMID:28392689

Highly selective and sensitive near-infrared-fluorescent probes for the detection of cellular hydrogen sulfide and the imaging of H2S in mice.

PubMed

Wu, Haixia; Krishnakumar, Saarangan; Yu, Jie; Liang, Dong; Qi, Hongyi; Lee, Zheng-Wei; Deng, Lih-Wen; Huang, Dejian

2014-12-01

Herein, we report the development of two fluorescent probes for the highly selective and sensitive detection of H2S. The probes take advantage of a Cu(II)-cyclen complex, which acts as a reaction center for H2S and as a quencher of BODIPY (boron-dipyrromethene)-based fluorophores with emissions at 765 and 680 nm, respectively. These non-fluorescent probes could only be turned on by the addition of H2 S, and not by other potentially interfering biomolecules, including reactive oxygen species, cysteine, and glutathione. In a chemical system, both probes detected H2S with a detection limit of 80 nM. The probes were successfully used for the endogenous detection of H2S in HEK 293 cells, for measuring the H2S-release activity of dietary organosulfides in MCF-7 cells, and for the in vivo imaging of H2S in mice. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A robust and versatile signal-on fluorescence sensing strategy based on SYBR Green I dye and graphene oxide

PubMed Central

Qiu, Huazhang; Wu, Namei; Zheng, Yanjie; Chen, Min; Weng, Shaohuang; Chen, Yuanzhong; Lin, Xinhua

2015-01-01

A robust and versatile signal-on fluorescence sensing strategy was developed to provide label-free detection of various target analytes. The strategy used SYBR Green I dye and graphene oxide as signal reporter and signal-to-background ratio enhancer, respectively. Multidrug resistance protein 1 (MDR1) gene and mercury ion (Hg2+) were selected as target analytes to investigate the generality of the method. The linear relationship and specificity of the detections showed that the sensitive and selective analyses of target analytes could be achieved by the proposed strategy with low detection limits of 0.5 and 2.2 nM for MDR1 gene and Hg2+, respectively. Moreover, the strategy was used to detect real samples. Analytical results of MDR1 gene in the serum indicated that the developed method is a promising alternative approach for real applications in complex systems. Furthermore, the recovery of the proposed method for Hg2+ detection was acceptable. Thus, the developed label-free signal-on fluorescence sensing strategy exhibited excellent universality, sensitivity, and handling convenience. PMID:25565810

Nucleic acid in-situ hybridization detection of infectious agents

NASA Astrophysics Data System (ADS)

Thompson, Curtis T.

2000-04-01

Limitations of traditional culture methods and newer polymerase chain reaction (PCR)-based methods for detection and speciation of infectious agents demonstrate the need for more rapid and better diagnostics. Nucleic acid hybridization is a detection technology that has gained wide acceptance in cancer and prenatal cytogenetics. Using a modification of the nucleic acid hybridization technique known as fluorescence in-situ hybridization, infectious agents can be detected in a variety of specimens with high sensitivity and specificity. The specimens derive from all types of human and animal sources including body fluids, tissue aspirates and biopsy material. Nucleic acid hybridization can be performed in less than one hour. The result can be interpreted either using traditional fluorescence microscopy or automated platforms such as micro arrays. This paper demonstrates proof of concept for nucleic acid hybridization detection of different infectious agents. Interpretation within a cytologic and histologic context is possible with fluorescence microscopic analysis, thereby providing confirmatory evidence of hybridization. With careful probe selection, nucleic acid hybridization promises to be a highly sensitive and specific practical diagnostic alternative to culture, traditional staining methods, immunohistochemistry and complicated nucleic acid amplification tests.

Capillary electrophoresis hyphenated with UV-native-laser induced fluorescence detection (CE/UV-native-LIF).

PubMed

Couderc, François; Ong-Meang, Varravaddheay; Poinsot, Véréna

2017-01-01

Native laser-induced fluorescence using UV lasers associated to CE offers now a large related literature, for now 30 years. The main works have been performed using very expensive Ar-ion lasers emitting at 257 and 275 nm. They are not affordable for routine analyses, but have numerous applications such as protein, catecholamine, and indolamine analysis. Some other lasers such as HeCd 325 nm have been used but only for few applications. Diode lasers, emitting at 266 nm, cheaper, are extensively used for the same topics, even if the obtained sensitivity is lower than the one observed using the costly UV-Ar-ion lasers. This review presents various CE or microchips applications and different UV lasers used for the excitation of native fluorescence. We showed that CE/Native UV laser induced fluorescence detection is very sensitive for detection as well as small aromatic biomolecules than proteins containing Trp and Tyr amino acids. Moreover, it is a simple way to analyze biomolecules without derivatization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Benzimidazole derivatives: selective fluorescent chemosensors for the picogram detection of picric acid.

PubMed

Xiong, Jin-Feng; Li, Jian-Xiao; Mo, Guang-Zhen; Huo, Jing-Pei; Liu, Jin-Yan; Chen, Xiao-Yun; Wang, Zhao-Yang

2014-12-05

1,3,5-Tri(1H-benzo[d]imidazol-2-yl)benzene derivatives, as a new kind of fluorescent chemosensor for the detection of nitroaromatic explosives, are designed and synthesized by simple N-hydrocarbylation. Among 16 obtained compounds, compound 4g has the best capability for detection of picric acid (PA), having good selectivity and high sensitivity. The detection of PA with 4g solution-coated paper strips at the picogram level is developed. A simple, portable, and low-cost method is provided for detecting PA in solution and contact mode.

[Chromosomal localization of foreign genes in transgenic mice using dual-color fluorescence in situ hybridization].

PubMed

Lin, Dan; Gong, Xiu-li; Li, Wei; Guo, Xin-bing; Zhu, Yi-wen; Huang, Ying

2008-02-01

To establish a highly sensitive and specific dual-color fluorescence in situ hybridization (D-FISH) method used for chromosomal localization of foreign genes in double transgenic mice. Two strains of double transgenic mice were used in this experiment, one was integrated with the herpes simplex virus thymidine kinase (HSV-tk) and the enhanced green fluorescence protein (eGFP), the other was with the short hairpin RNA interference(RNAi) and beta(654). Splenic cells cultured in vitro were arrested in metaphase by colchicine and hybridized with digoxigenin-labeled and biotinylated DNA probes, then detected by rhodamine-conjugated avidin and FITC-conjugated anti-digoxigenin. Dual-color fluorescence signals were detected on the same metaphase in both transgenic mice strains. In HSV-tk/eGFP double transgenic mice, strong green fluorescence for HSV-tk and red for eGFP were observed and localized at 2E5-G3 and 8A2-A4 respectively. In beta(654)/RNAi mice, beta(654) was detected as red fluorescence on chromosome 7D3-E2, and RNAi showed random integration on chromosomes. It was detected as green fluorescence on chromosome 12B1 in one mouse, while on 1E2.3-1F and 3A3 in the other. Highly sensitive and specific D-FISH method was established using the self-prepared DNA probes, and chromosomal localization of the foreign genes was also performed in combination with G-banding in double transgenic mice. This technology will facilitate the researches in transgenic animals and gene therapy models.

In-vacuum scattered light reduction with black cupric oxide surfaces for sensitive fluorescence detection.

PubMed

Norrgard, E B; Sitaraman, N; Barry, J F; McCarron, D J; Steinecker, M H; DeMille, D

2016-05-01

We demonstrate a simple and easy method for producing low-reflectivity surfaces that are ultra-high vacuum compatible, may be baked to high temperatures, and are easily applied even on complex surface geometries. Black cupric oxide (CuO) surfaces are chemically grown in minutes on any copper surface, allowing for low-cost, rapid prototyping, and production. The reflective properties are measured to be comparable to commercially available products for creating optically black surfaces. We describe a vacuum apparatus which uses multiple blackened copper surfaces for sensitive, low-background detection of molecules using laser-induced fluorescence.

Comparison of Near-Infrared Imaging Camera Systems for Intracranial Tumor Detection.

PubMed

Cho, Steve S; Zeh, Ryan; Pierce, John T; Salinas, Ryan; Singhal, Sunil; Lee, John Y K

2018-04-01

Distinguishing neoplasm from normal brain parenchyma intraoperatively is critical for the neurosurgeon. 5-Aminolevulinic acid (5-ALA) has been shown to improve gross total resection and progression-free survival but has limited availability in the USA. Near-infrared (NIR) fluorescence has advantages over visible light fluorescence with greater tissue penetration and reduced background fluorescence. In order to prepare for the increasing number of NIR fluorophores that may be used in molecular imaging trials, we chose to compare a state-of-the-art, neurosurgical microscope (System 1) to one of the commercially available NIR visualization platforms (System 2). Serial dilutions of indocyanine green (ICG) were imaged with both systems in the same environment. Each system's sensitivity and dynamic range for NIR fluorescence were documented and analyzed. In addition, brain tumors from six patients were imaged with both systems and analyzed. In vitro, System 2 demonstrated greater ICG sensitivity and detection range (System 1 1.5-251 μg/l versus System 2 0.99-503 μg/l). Similarly, in vivo, System 2 demonstrated signal-to-background ratio (SBR) of 2.6 ± 0.63 before dura opening, 5.0 ± 1.7 after dura opening, and 6.1 ± 1.9 after tumor exposure. In contrast, System 1 could not easily detect ICG fluorescence prior to dura opening with SBR of 1.2 ± 0.15. After the dura was reflected, SBR increased to 1.4 ± 0.19 and upon exposure of the tumor SBR increased to 1.8 ± 0.26. Dedicated NIR imaging platforms can outperform conventional microscopes in intraoperative NIR detection. Future microscopes with improved NIR detection capabilities could enhance the use of NIR fluorescence to detect neoplasm and improve patient outcome.

Enumeration of Vibrio cholerae O1 in Bangladesh waters by fluorescent-antibody direct viable count.

PubMed Central

Brayton, P R; Tamplin, M L; Huq, A; Colwell, R R

1987-01-01

A field trial to enumerate Vibrio cholerae O1 in aquatic environments in Bangladesh was conducted, comparing fluorescent-antibody direct viable count with culture detection by the most-probable-number index. Specificity of a monoclonal antibody prepared against the O1 antigen was assessed and incorporated into the fluorescence staining method. All pond and water samples yielded higher counts of viable V. cholerae O1 by fluorescent-antibody direct viable count than by the most-probable-number index. Fluorescence microscopy is a more sensitive detection system than culture methods because it allows the enumeration of both culturable and nonculturable cells and therefore provides more precise monitoring of microbiological water quality. PMID:3324967

Co-registered photoacoustic and fluorescent imaging of a switchable nanoprobe based on J-aggregates of indocyanine green

NASA Astrophysics Data System (ADS)

Dumani, Diego S.; Brecht, Hans-Peter; Ivanov, Vassili; Deschner, Ryan; Harris, Justin T.; Homan, Kimberly A.; Cook, Jason R.; Emelianov, Stanislav Y.; Ermilov, Sergey A.

2018-02-01

We introduce a preclinical imaging platform - a 3D photoacoustic/fluorescence tomography (PAFT) instrument augmented with an environmentally responsive dual-contrast biocompatible nanoprobe. The PAFT instrument was designed for simultaneous acquisition of photoacoustic and fluorescence orthogonal projections at each rotational position of a biological object, enabling direct co-registration of the two imaging modalities. The nanoprobe was based on liposomes loaded with J-aggregates of indocyanine green (PAtrace). Once PAtrace interacts with the environment, a transition from J-aggregate to monomeric ICG is induced. The subsequent recovery of monomeric ICG is characterized by dramatic changes in the optical absorption spectrum and reinstated fluorescence. In the activated state, PAtrace can be simultaneously detected by both imaging modes of the PAFT instrument using 780 nm excitation and fluorescence detection at 810 nm. The fluorescence imaging component is used to boost detection sensitivity by providing lowresolution map of activated nanoprobes, which are then more precisely mapped in 3D by the photoacoustic imaging component. Activated vs non-activated particles can be distinguished based on their different optical absorption peaks, removing the requirements for complex image registration between reference and detection scans. Preliminary phantom and in vivo animal imaging results showed successful activation and visualization of PAtrace with high sensitivity and resolution. The proposed PAFT-PAtrace imaging platform could be used in various functional and molecular imaging applications including multi-point in vivo assessment of early metastasis.

Fluorescent trimethyl-substituted naphthyridine as a label-free signal reporter for one-step and highly sensitive fluorescent detection of DNA in serum samples.

PubMed

Wang, Jiamian; Wang, Xiuyun; Wu, Shuo; Che, Ruping; Luo, Pinchen; Meng, Changgong

2017-01-15

A facile label-free sensing method is developed for the one-step and highly sensitive fluorescent detection of DNA, which couples the specific C-C mismatch bonding and fluorescent quenching property of a trimethyl-substituted naphthyridine dye (ATMND) with the exonuclease III (Exo III) assisted cascade target recycling amplification strategy. In the absence of target DNA, the DNA hairpin probe with a C-C mismatch in the stem and more than 4 bases overhung at the 3' terminus could entrap and quench the fluorescence of ATMND and resist the digestion of Exo III, thus showing a low fluorescence background. In the presence of the target, however, the hybridization event between the two protruding segments and the target triggers the digestion reaction of Exo III, recycles the initial target, and simultaneously releases both the secondary target analogue and the ATMND caged in the stem. The released initial and secondary targets take part in another cycle of digestion, thus leading to the release of a huge amount of free ATMND for signal transducing. Based on the fluorescence recovery, the as-proposed label-free fluorescent sensing strategy shows very good analytical performances towards DNA detection, such as a wide linear range from 10pM to 1μM, a low limit of detection of 6pM, good selectivity, and a facile one-step operation at room temperature. Practical sample analysis in serum samples indicates the method has good precision and accuracy, which may thus have application potentials for point-of-care screening of DNA in complex clinical and environmental samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Toward a Droplet-Based Single-Cell Radiometric Assay.

PubMed

Gallina, Maria Elena; Kim, Tae Jin; Shelor, Mark; Vasquez, Jaime; Mongersun, Amy; Kim, Minkyu; Tang, Sindy K Y; Abbyad, Paul; Pratx, Guillem

2017-06-20

Radiotracers are widely used to track molecular processes, both in vitro and in vivo, with high sensitivity and specificity. However, most radionuclide detection methods have spatial resolution inadequate for single-cell analysis. A few existing methods can extract single-cell information from radioactive decays, but the stochastic nature of the process precludes high-throughput measurement (and sorting) of single cells. In this work, we introduce a new concept for translating radioactive decays occurring stochastically within radiolabeled single-cells into an integrated, long-lasting fluorescence signal. Single cells are encapsulated in radiofluorogenic droplets containing molecular probes sensitive to byproducts of ionizing radiation (primarily reactive oxygen species, or ROS). Different probes were examined in bulk solutions, and dihydrorhodamine 123 (DHRh 123) was selected as the lead candidate due to its sensitivity and reproducibility. Fluorescence intensity of DHRh 123 in bulk increased at a rate of 54% per Gy of X-ray radiation and 15% per MBq/ml of 2-deoxy-2-[ 18 F]-fluoro-d-glucose ([ 18 F]FDG). Fluorescence imaging of microfluidic droplets showed the same linear response, but droplets were less sensitive overall than the bulk ROS sensor (detection limit of 3 Gy per droplet). Finally, droplets encapsulating radiolabeled cancer cells allowed, for the first time, the detection of [ 18 F]FDG radiotracer uptake in single cells through fluorescence activation. With further improvements, we expect this technology to enable quantitative measurement and selective sorting of single cells based on the uptake of radiolabeled small molecules.

A new azine derivative colorimetric and fluorescent dual-channel probe for cyanide detection

NASA Astrophysics Data System (ADS)

Yu, Bin; Li, Chun-Yu; Sun, Yin-Xia; Jia, Hao-Ran; Guo, Jian-Qiang; Li, Jing

2017-09-01

A novel azine derivative colorimetric and fluorescent dual-channel probe salicylaldehyde hydrazine-3,5-dibromosalicylaldehyde (1) has been designed, synthesized and characterized. The probe 1 is confirmed to have especial selectivity and good sensitivity on detecting CN- via UV-vis absorption and fluorescence spectrum in aqueous solution (H2O/DMSO, 1:4, v/v). This colorimetric and fluorescent dual-channel probe response to CN- owed to the deprotonation process and established the mechanism by using 1H NMR spectroscopy. Further researches showed that the detection limit of the probe 1 to CN- anions is 8.01 × 10- 9 M, significantly lower than the maximum level 1.9 × 10- 6 M in potable water from WHO guidelines.

A reversible fluorescence "off-on-off" sensor for sequential detection of aluminum and acetate/fluoride ions.

PubMed

Gupta, Vinod Kumar; Mergu, Naveen; Kumawat, Lokesh Kumar; Singh, Ashok Kumar

2015-11-01

A new rhodamine functionalized fluorogenic Schiff base CS was synthesized and its colorimetric and fluorescence responses toward various metal ions were explored. The sensor exhibited highly selective and sensitive colorimetric and "off-on" fluorescence response towards Al(3+) in the presence of other competing metal ions. These spectral changes are large enough in the visible region of the spectrum and thus enable naked-eye detection. Studies proved that the formation of CS-Al(3+) complex is fully reversible and can sense to AcO(-)/F(-) via dissociation. The results revealed that the sensor provides fluorescence "off-on-off" strategy for the sequential detection of Al(3+) and AcO(-)/F(-). Copyright © 2015 Elsevier B.V. All rights reserved.

Nanomolar pyrophosphate detection and nucleus staining in living cells with simple terpyridine-Zn(II) complexes.

PubMed

Chao, Duobin; Ni, Shitan

2016-05-20

Great efforts have been made to develop fluorescent probes for pyrophosphate (PPi) detection. Nucleus staining with fluorescence microscopy has been also widely investigated. But fluorescent probes for PPi detection with high sensitivity in water medium and nucleus staining with low-cost non-precious metal complexes in living cells are still challenging. Herein, we report simple terpyridine-Zn(II) complexes for selective nanomolar PPi detection over ATP and ADP in water based on aggregation induced emission (AIE) and intramolecular charge transfer (ICT). In addition, these terpyridine-Zn(II) complexes were successfully employed for nucleus staining in living cells. These results demonstrated simply obtained terpyridine-Zn(II) complexes are powerful tool for PPi detection and the development of PPi-related studies.

Efficient On-Off Ratiometric Fluorescence Probe for Cyanide Ion Based on Perturbation of the Interaction between Gold Nanoclusters and a Copper(II)-Phthalocyanine Complex.

PubMed

Shojaeifard, Zahra; Hemmateenejad, Bahram; Shamsipur, Mojtaba

2016-06-22

A new ratiometric fluorescent sensor was developed for the sensitive and selective detection of cyanide ion (CN(-)) in aqueous media. The ratiometric sensing system is based on CN(-) modulated recovery of copper(II) phthalocyanine (Cu(PcTs)) fluorescence signal at the expense of diminished fluorescence intensity of gold nanoclusters (AuNCs). Preliminary experiments revealed that the AuNCs and Cu(PcTs) possess a turn-off effect on each other, the interaction of which being verified through studying their interactions by principle component analysis (PCA) and multivariate cure resolution-alternating least-squares (MCR-ALS) methods. In the presence of CN(-) anion, the AuNCs and Cu(PcTs) interaction was perturbed, so that the fluorescence of Cu (PcTs), already quenched by AuNCs, was found to be efficiently recovered, while the fluorescence intensity of AuNCs was quenched via the formation of a stable [Au(CN)2](-) species. The ratiometric variation of AuNCs and Cu(PcTs) fluorescence intensities leads to designing a highly sensitive probe for CN(-) ion detection. Under the optimal conditions, CN(-) anion was detected without needing any etching time, over the concentration range of 100 nM-220 μM, with a detection limit of 75 nM, which is much lower than the allowable level of CN(-) in water permitted by the World Health Organization (WHO). Moreover, the detection of CN(-) was developed based on the CN(-) effects on the blue and red florescent colors of Cu(PcTs) and AuNCs, respectively. The designed probe displays a continuous color change from red to blue by addition of CN(-), which can be clearly observed by the naked eye in the range of 7-350 μM, under UV lamp. The prepared AuNCs/Cu(PcTs) probe was successfully utilized for the selective and sensitive determination of CN(-) anion in two different types of natural water (Rodbal dam and rainwater) and also in blood serum as a biological sample.

A Water-Soluble Fluorescent Probe for SO2 Derivatives in Aqueous Solution and Serum Based on Phenanthroimidazole Dye.

PubMed

Zhou, Yang; Wang, Ying; Xiao, Shuzhang; He, Xiafeng; Zhang, Nuonuo; Li, Dejiang; Zheng, Kaibo

2017-05-01

A water-soluble fluorescent SO 2 derivatives probe PI-SO 2 based on a phenanthroimidazole dye, and a sensitive SO 2 recognition site, aldehyde was constructed. The probe PI-SO 2 exhibits desirable properties such as high sensitivity, high selectivity and good water-solubility. Significantly, we have demonstrated that the probe PI-SO 2 is suitable for rapidly fluorescence detecting of SO 2 derivatives in aqueous solution and serum. The application of the novel probe PI-SO 2 proved that it was not only a useful tool for the detection of SO 2 derivatives in vitro, but also a potential assay for investigating the effects of SO 2 derivatives, and demonstrating its value in practical applicationin of complex biological samples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Zongchao; Wang, Fengqin, E-mail: wangfengqin@tjpu.edu.cn; Lin, Xiangyi

Metal-organic frameworks (MOFs) are porous crystalline materials with high potential for applications in fluorescence sensors. In this work, two solvent-induced Zn(II)–based metal-organic frameworks, Zn{sub 3}L{sub 3}(DMF){sub 2} (1) and Zn{sub 3}L{sub 3}(DMA){sub 2}(H{sub 2}O){sub 3} (2) (L=4,4′-stilbenedicarboxylic acid), were investigated as selective sensing materials for detection of nitroaromatic compounds and metal ions. The sensing experiments show that 1 and 2 both exhibit selective fluorescence quenching toward nitroaniline with a low detection limit. In addition, 1 exhibits high selectivity for detection of Fe{sup 3+} and Al{sup 3+} by significant fluorescence quenching or enhancement effect. While for 2, it only exhibits significantmore » fluorescence quenching effect for Fe{sup 3+}. The results indicate that 1 and 2 are both promising fluorescence sensors for detecting and recognizing nitroaniline and metal ions with high sensitivity and selectivity. - Graphical abstract: Two MOFs have been selected as the fluorescence sensing materials for selectively sensing mitroaromatic compounds and metal ions. The high selectivity makes them promising fluorescence sensors for detecting and recognizing nitroaniline and Fe{sup 3+} or Al{sup 3+}.« less

Near-infrared laser-induced fluorescence detection in capillary electrophoresis.

PubMed

McWhorter, S; Soper, S A

2000-04-01

As capillary electrophoresis continues to focus on miniaturization, either through reducing column dimensions or situating entire electrophoresis systems on planar chips, advances in detection become necessary to meet the challenges posed by these electrophoresis platforms. The challenges result from the fact that miniaturization requires smaller load volumes, demanding highly sensitive detection. In addition, many times multiple targets must be analyzed simultaneously (multiplexed applications), further complicating detection. Near-infrared (NIR) fluorescence offers an attractive alternative to visible fluorescence for critical applications in capillary electrophoresis due to the impressive limits of detection that can be generated, in part resulting from the low background levels that are observed in the NIR. Advances in instrumentation and fluorogenic labels appropriate for NIR monitoring have led to a growing number of examples of the use of NIR fluorescence in capillary electrophoresis. In this review, we will cover instrumental components used to construct ultrasensitive NIR fluorescence detectors, including light sources and photon transducers. In addition, we will discuss various types of labeling dyes appropriate for NIR fluorescence and finally, we will present several applications that have used NIR fluorescence in capillary electrophoresis, especially for DNA sequencing and fragment analysis.

Cytidine-stabilized gold nanocluster as a fluorescence turn-on and turn-off probe for dual functional detection of Ag(+) and Hg(2+).

PubMed

Zhang, Yuanyuan; Jiang, Hui; Wang, Xuemei

2015-04-22

In this study, we have developed a label-free, dual functional detection strategy for highly selective and sensitive determination of aqueous Ag(+) and Hg(2+) by using cytidine stabilized Au NCs and AuAg NCs as fluorescent turn-on and turn off probes, respectively. The Au NCs and AuAg NCs showed a remarkably rapid response and high selectivity for Ag(+) and Hg(2+) over other metal ions, and relevant detection limit of Ag(+) and Hg(2+) is ca. 10 nM and 30 nM, respectively. Importantly, the fluorescence enhanced Au NCs by doping Ag(+) can be conveniently reusable for the detection of Hg(2+) based on the corresponding fluorescence quenching. The sensing mechanism was based on the high-affinity metallophilic Hg(2+)-Ag(+) interaction, which effectively quenched the fluorescence of AuAg NCs. Furthermore, these fluorescent nanoprobes could be readily applied to Ag(+) and Hg(2+) detection in environmental water samples, indicating their possibility to be utilized as a convenient, dual functional, rapid response, and label-free fluorescence sensor for related environmental and health monitoring. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs

NASA Astrophysics Data System (ADS)

Huang, Xiaolin; Zhan, Shengnan; Xu, Hengyi; Meng, Xianwei; Xiong, Yonghua; Chen, Xiaoyuan

2016-04-01

Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL-1 to 10 pg mL-1. The half maximal inhibitory concentration was 0.53 pg mL-1 and the limit of detection was 0.05 pg mL-1. These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring.Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL-1 to 10 pg mL-1. The half maximal inhibitory concentration was 0.53 pg mL-1 and the limit of detection was 0.05 pg mL-1. These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01136e

A facile, sensitive, and highly specific trinitrophenol assay based on target-induced synergetic effects of acid induction and electron transfer towards DNA-templated copper nanoclusters.

PubMed

Li, Haiyin; Chang, Jiafu; Hou, Ting; Ge, Lei; Li, Feng

2016-11-01

Reliable, selective and sensitive approaches for trinitrophenol (TNP) detection are highly desirable with respect to national security and environmental protection. Herein, a simple and novel fluorescent strategy for highly sensitive and specific TNP assay has been successfully developed, which is based on the quenching of the fluorescent poly(thymine)-templated copper nanoclusters (DNA-CuNCs), through the synergetic effects of acid induction and electron transfer. Upon the addition of TNP, donor-acceptor complexes between the electron-deficient nitro-groups in TNP and the electron-donating DNA templates are formed, resulting in the close proximity between TNP and CuNCs. Moreover, the acidity of TNP contributes to the pH decrease of the system. These factors combine to dramatically quench the fluorescence of DNA-CuNCs, providing a "signal-off" strategy for TNP sensing. The as-proposed strategy demonstrates high sensitivity for TNP assay, and a detection limit of 0.03μM is obtained, which is lower than those reported by using organic fluorescent materials. More significantly, this approach shows outstanding selectivity over a number of TNP analogues, such as 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitrophenol (DNP), 3-nitrophenol (NP), nitrobenzene (NB), phenol (BP), and toluene (BT). Compared with previous studies, this method does not need complex DNA sequence design, fluorescent dye labeling, or sophisticated organic reactions, rendering the strategy with additional advantages of simplicity and cost-effectiveness. In addition, the as-proposed strategy has been adopted for the detection of TNP in natural water samples, indicating its great potential to be applied in the fields of public safety and environmental monitoring. Copyright © 2016 Elsevier B.V. All rights reserved.

Molecular switch-modulated fluorescent copper nanoclusters for selective and sensitive detection of histidine and cysteine.

PubMed

Gu, Zefeng; Cao, Zhijuan

2018-06-07

A novel assay for histidine and cysteine has been constructed based on modulation of fluorescent copper nanoclusters (CuNCs) by molecular switches. In our previous work, a dumbbell DNA template with a poly-T (thymine) loop has been developed as an excellent template for the formation of strongly fluorescent CuNCs. Herein, for the first time, we established this biosensor for sensing two amino acids by using dumbbell DNA-templated CuNCs as the single probe. Among 20 natural amino acids, only histidine and cysteine can selectively quench fluorescence emission of CuNCs, because of the specific interaction of these compounds with copper ions. Furthermore, by using nickel ions (Ni 2+ ) and N-ethylmaleimide as the masking agents for histidine and cysteine respectively, an integrated logic gate system was designed by coupling with the fluorescent CuNCs and demonstrated selective and sensitive detection of cysteine and histidine. Under optimal conditions, cysteine can be detected in the concentration ranges of 0.01-10.0 μM with the detection limit (DL) of as low as 98 pM, while histidine can be detected in the ranges of 0.05-40.0 μM with DL of 1.6 nM. In addition, histidine and cysteine can be observed with the naked eye under a hand-held UV lamp (DL, 50 nM), which can be easily adapted to automated high-throughput screening. Finally, the strategy has been successfully utilized for biological fluids. The proposed system can be conducted in homogeneous solution, eliminating the need for organic cosolvents, separation processes of nanomaterials, or any chemical modifications. Overall, the assay provides an alternative method for simultaneous detection of cysteine and histidine by taking the advantages of high speed, no label and enzyme requirement, and good sensitivity and specificity, and will satisfy the great demand for determination of amino acids in fields such as food processing, biochemistry, pharmaceuticals, and clinical analysis. Graphical abstract.

An ultrasensitive alloyed near-infrared quinternary quantum dot-molecular beacon nanodiagnostic bioprobe for influenza virus RNA.

PubMed

Adegoke, Oluwasesan; Kato, Tatsuya; Park, Enoch Y

2016-06-15

Conventional techniques used to diagnose influenza virus face several challenges, such as low sensitivity, slow detection, false positive results and misinterpreted data. Hence, diagnostic probes that can offer robust detection qualities, such as high sensitivity, rapid detection, elimination of false positive data, and specificity for influenza virus, are urgently needed. The near-infrared (NIR) range is an attractive spectral window due to low photon absorption by biological tissues, hence well-constructed fluorescent biosensors that emit within the NIR window can offer an improved limit of detection (LOD). Here, we demonstrate the use of a newly synthesized NIR quinternary alloyed CdZnSeTeS quantum dots (QDs) as an ultrasensitive fluorescence reporter in a conjugated molecular beacon (MB) assay to detect extremely low concentrations of influenza virus H1N1 RNA. Under optimum conditions, two different strains of influenza virus H1N1 RNA were detected based on fluorescence enhancement signal transduction. We successfully discriminated between two different strains of influenza virus H1N1 RNA based on the number of complementary nucleotide base pairs of the MB to the target RNA sequence. The merits of our bioprobe system are rapid detection, high sensitivity (detects H1N1 viral RNA down to 2 copies/mL), specificity and versatility (detects H1N1 viral RNA in human serum). For comparison, a conventional CdSe/ZnS-MB probe could not detect the extremely low concentrations of H1N1 viral RNA detected by our NIR alloyed CdZnSeTeS-MB probe. Our bioprobe detection system produced a LOD as low as ~1 copy/mL and is more sensitive than conventional molecular tests and rapid influenza detection tests (RIDTS) probes. Copyright © 2016 Elsevier B.V. All rights reserved.

A Colorimetric and Fluorescent Probe for the Detection of Cu2+ in a Complete Aqueous Solution.

PubMed

Xu, Jing; Wang, Zuokai; Liu, Caiyun; Xu, Zhenghe; Zhu, Baocun; Wang, Ning; Wang, Kun; Wang, Jiangting

2018-01-01

The fluorescent probe has become an important method for the detection of heavy metal ions. In the present work, a new and simple fluorescent probe, Cu-P, for detecting copper ion (Cu 2+ ) was designed and synthesized. The probe has shown high sensitivity and selectivity toward Cu 2+ . The detection limit was 13 nM (based on the 3σ/slope). A significant color change from yellow to pink was observed; thus, the probe Cu-P could serve as a "naked-eye" indicator for Cu 2+ . Furthermore, the proposed probe was used to detect Cu 2+ in real water and soil extract samples, with the result being satisfactory. Therefore, our proposed probe would provide a promising method for the detection of Cu 2+ in the environment.

Detection of proteolytic activity by covalent tethering of fluorogenic substrates in zymogram gels.

PubMed

Deshmukh, Ameya A; Weist, Jessica L; Leight, Jennifer L

2018-05-01

Current zymographic techniques detect only a subset of known proteases due to the limited number of native proteins that have been optimized for incorporation into polyacrylamide gels. To address this limitation, we have developed a technique to covalently incorporate fluorescently labeled, protease-sensitive peptides using an azido-PEG3-maleimide crosslinker. Peptides incorporated into gels enabled measurement of MMP-2, -9, -14, and bacterial collagenase. Sensitivity analysis demonstrated that use of peptide functionalized gels could surpass detection limits of current techniques. Finally, electrophoresis of conditioned media from cultured cells resulted in the appearance of several proteolytic bands, some of which were undetectable by gelatin zymography. Taken together, these results demonstrate that covalent incorporation of fluorescent substrates can greatly expand the library of detectable proteases using zymographic techniques.

Fluorescence Behavior and Dural Infiltration of Meningioma Analyzed by 5-Aminolevulinic Acid-Based Fluorescence: Operating Microscope Versus Mini-Spectrometer.

PubMed

Knipps, Johannes; Beseoglu, Kerim; Kamp, Marcel; Fischer, Igor; Felsberg, Joerg; Neumann, Lisa M; Steiger, Hans-Jakob; Cornelius, Jan F

2017-12-01

To compare fluorescence intensity of tumor specimens, as measured by a fluorescence-guided surgery microscope and a spectrometer, to evaluate tumor infiltration of dura mater around meningiomas with help of these 2 different 5-aminolevulinic acid (5-ALA)-based fluorescence tools, and to correlate fluorescence intensity with histopathologic data. In a clinical series, meningiomas were resected by 5-ALA fluorescence-guided surgery. Fluorescence intensity was semiquantitatively rated by the surgeon at predefined points. Biopsies were harvested and fluorescence intensity measured by a spectrometer and histopathologically analyzed. Sampling was realized at the level of the dura in a centrifugal direction. A total of 104 biopsies (n = 13 tumors) were analyzed. Specificity and sensitivity of the microscope were 0.96 and 0.53 and of the spectrometer 0.95 and 0.93, respectively. Fluorescence intensity as measured by the spectrometer was correlated to histologically confirmed tumor burden. In a centrifugal direction, tumor burden and fluorescence intensity continuously decreased (along the dural tail). Below a threshold value of 639 arbitrary units no tumor was histologically detectable. At the level of the dura the spectrometer was highly sensitive for detection of meningioma cells. The surgical microscope showed false negative results and missed residual tumor cells in more than one half of the cases. The complementary use of both fluorescence tools may improve resection quality. Copyright © 2017 Elsevier Inc. All rights reserved.

The design and application of fluorophore–gold nanoparticle activatable probes

PubMed Central

Swierczewska, Magdalena; Lee, Seulki; Chen, Xiaoyuan

2013-01-01

Fluorescence-based assays and detection techniques are among the most highly sensitive and popular biological tests for researchers. To match the needs of research and the clinic, detection limits and specificities need to improve, however. One mechanism is to decrease non-specific background signals, which is most efficiently done by increasing fluorescence quenching abilities. Reports in the literature of theoretical and experimental work have shown that metallic gold surfaces and nanoparticles are ultra-efficient fluorescence quenchers. Based on these findings, subsequent reports have described gold nanoparticle fluorescence-based activatable probes that were designed to increase fluorescence intensity based on a range of stimuli. In this way, these probes can detect and signify assorted biomarkers and changes in environmental conditions. In this review, we explore the various factors and theoretical models that affect gold nanoparticle fluorescence quenching, explore current uses of activatable probes, and propose an engineering approach for future development of fluorescence based gold nanoparticle activatable probes. PMID:21380462

Highly sensitive optical detection of specific protein in breast cancer cells using microstructured fiber in extremely low sample volume

NASA Astrophysics Data System (ADS)

Padmanabhan, Saraswathi; Shinoj, Vengalathunadakal K.; Murukeshan, Vadakke M.; Padmanabhan, Parasuraman

2010-01-01

A simple optical method using hollow-core photonic crystal fiber for protein detection has been described. In this study, estrogen receptor (ER) from a MCF-7 breast carcinoma cell lysates immobilized inside a hollow-core photonic crystal fiber was detected using anti-ER primary antibody with either Alexa™ Fluor 488 (green fluorescent dye) or 555 (red Fluorescent dye) labeled Goat anti-rabbit IgG as the secondary antibody. The fluorescence fingerprints of the ERα protein were observed under fluorescence microscope, and its optical characteristics were analyzed. The ERα protein detection by this proposed method is based on immuno binding from sample volume as low as 50 nL. This method is expected to offer great potential as a biosensor for medical diagnostics and therapeutics applications.

An erythrosin B-based "turn on" fluorescent sensor for detecting perfluorooctane sulfonate and perfluorooctanoic acid in environmental water samples.

PubMed

Cheng, Zhen; Du, Lingling; Zhu, Panpan; Chen, Qian; Tan, Kejun

2018-05-04

Because of the serious harm to animals and the environment associated with perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), a rapid, sensitive and low-cost method for detecting PFOS and PFOA is of great importance. In this paper, a novel sensing method has been proposed for the highly sensitive detection of PFOS and PFOA in environmental water samples based on the "turn-on" switch of erythrosine B (EB)-hexadecyltrimethylammonium bromide (CTAB) system. In pH 8.55 Britton-Robinson (BR) buffer, EB can react with CTAB by electrostatic attraction, resulting in a strong fluorescence quenching of EB. With a subsequent addition of the CTAB, a red-shift occurred (11 nm), followed by a significant increase in fluorescence at high surfactant concentrations. It was found that PFOS and PFOA can obviously enhance fluorescence intensity of EB-CTAB system. The enhanced fluorescence intensity is proportional to the concentration of PFOS and PFOA in the range of 0.05-10 μM with detection limit of 12.8 nM and 11.8 nM (3σ), respectively. The presented assay has been successfully applied to sensing PFOS and PFOA in real water samples with RSD ≤ 4.3% and 2.9%, respectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Supramolecular assembly affording a ratiometric two-photon fluorescent nanoprobe for quantitative detection and bioimaging.

PubMed

Wang, Peng; Zhang, Cheng; Liu, Hong-Wen; Xiong, Mengyi; Yin, Sheng-Yan; Yang, Yue; Hu, Xiao-Xiao; Yin, Xia; Zhang, Xiao-Bing; Tan, Weihong

2017-12-01

Fluorescence quantitative analyses for vital biomolecules are in great demand in biomedical science owing to their unique detection advantages with rapid, sensitive, non-damaging and specific identification. However, available fluorescence strategies for quantitative detection are usually hard to design and achieve. Inspired by supramolecular chemistry, a two-photon-excited fluorescent supramolecular nanoplatform ( TPSNP ) was designed for quantitative analysis with three parts: host molecules (β-CD polymers), a guest fluorophore of sensing probes (Np-Ad) and a guest internal reference (NpRh-Ad). In this strategy, the TPSNP possesses the merits of (i) improved water-solubility and biocompatibility; (ii) increased tissue penetration depth for bioimaging by two-photon excitation; (iii) quantitative and tunable assembly of functional guest molecules to obtain optimized detection conditions; (iv) a common approach to avoid the limitation of complicated design by adjustment of sensing probes; and (v) accurate quantitative analysis by virtue of reference molecules. As a proof-of-concept, we utilized the two-photon fluorescent probe NHS-Ad-based TPSNP-1 to realize accurate quantitative analysis of hydrogen sulfide (H 2 S), with high sensitivity and good selectivity in live cells, deep tissues and ex vivo -dissected organs, suggesting that the TPSNP is an ideal quantitative indicator for clinical samples. What's more, TPSNP will pave the way for designing and preparing advanced supramolecular sensors for biosensing and biomedicine.

Carbon dots as fluorescent probes for "off-on" detection of Cu2+ and L-cysteine in aqueous solution.

PubMed

Zong, Jie; Yang, Xiaoling; Trinchi, Adrian; Hardin, Simon; Cole, Ivan; Zhu, Yihua; Li, Chunzhong; Muster, Tim; Wei, Gang

2014-01-15

Copper ion (Cu(2+)) and L-cysteine (L-Cys) detection is critically important since an abnormal level of Cu(2+) or L-Cys is an indicator for many diseases. In this paper, we demonstrate an "off-on" approach for highly sensitive and selective detection of Cu(2+) and L-Cys using carbon dots (CDs) as fluorescent probes. CDs were prepared by using mesoporous silica (MS) spheres as nanoreactors. The binding ability of CDs towards metal ions was examined by comparing the fluorescence intensities of CDs before and after the addition of the metal ions. The addition of Cu(2+) cations leads to their absorption on the surface of CDs and the significant fluorescence quench of CDs (turn-off). The resulting in CDs-Cu(2+) system was found to be sensitive to L-Cys. The addition of L-Cys not only serves to shelter the CDs effectively from being quenched, but also to reverse the quenching and restore the fluorescence (turn-on) due to its ability to remove Cu(2+) from the surface of CDs. This method is facile, rapid, low cost, and environment-friendly. A detection limit as low as 2.3×10(-8) M for Cu(2+) and 3.4×10(-10) M for L-Cys is obtained, which is promising for biological applications. © 2013 Elsevier B.V. All rights reserved.

Trace Detection of RDX, HMX and PETN Explosives Using a Fluorescence Spot Sensor

PubMed Central

Wang, Chen; Huang, Helin; Bunes, Benjamin R.; Wu, Na; Xu, Miao; Yang, Xiaomei; Yu, Li; Zang, Ling

2016-01-01

1,3,5-trinitroperhydro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and pentaerythritol tetranitrate (PETN), the major components in plastic explosives, pose a significant threat to public safety. A quick, sensitive, and low-cost detection method for these non-volatile explosives is eagerly demanded. Here we present a fluo-spot approach, which can be employed for in situ detection of trace amount of explosives. The sensor molecule is a charge-transfer fluorophore, DCM, which is strongly fluorescent in its pristine state, but non-fluorescent after the quick reaction with NO2· (or NO2+) generated from the UV photolysis of RDX, HMX (or PETN). When fabricated within silica gel TLC plate, the fluo-spot sensor features high sensitivity owing to the large surface area and porous structure of the substrate. The sensor reaction mechanism was verified by various experimental characterizations, including chromatography, UV-Vis absorption and fluorescence spectroscopy, MS and 1H NMR spectrometry. The fluo-spot also demonstrated high selectivity towards RDX, HMX and PETN, as no significant fluorescence quenching was observed for other chemical compounds including common nitro-aromatic explosives and inorganic oxidative compounds. The DCM sensor can also be used as an economical spray kit to directly spot the explosives by naked eyes, implying great potential for quick, low-cost trace explosives detection. PMID:27146290

Trace Detection of RDX, HMX and PETN Explosives Using a Fluorescence Spot Sensor.

PubMed

Wang, Chen; Huang, Helin; Bunes, Benjamin R; Wu, Na; Xu, Miao; Yang, Xiaomei; Yu, Li; Zang, Ling

2016-05-05

1,3,5-trinitroperhydro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and pentaerythritol tetranitrate (PETN), the major components in plastic explosives, pose a significant threat to public safety. A quick, sensitive, and low-cost detection method for these non-volatile explosives is eagerly demanded. Here we present a fluo-spot approach, which can be employed for in situ detection of trace amount of explosives. The sensor molecule is a charge-transfer fluorophore, DCM, which is strongly fluorescent in its pristine state, but non-fluorescent after the quick reaction with NO2· (or NO2(+)) generated from the UV photolysis of RDX, HMX (or PETN). When fabricated within silica gel TLC plate, the fluo-spot sensor features high sensitivity owing to the large surface area and porous structure of the substrate. The sensor reaction mechanism was verified by various experimental characterizations, including chromatography, UV-Vis absorption and fluorescence spectroscopy, MS and (1)H NMR spectrometry. The fluo-spot also demonstrated high selectivity towards RDX, HMX and PETN, as no significant fluorescence quenching was observed for other chemical compounds including common nitro-aromatic explosives and inorganic oxidative compounds. The DCM sensor can also be used as an economical spray kit to directly spot the explosives by naked eyes, implying great potential for quick, low-cost trace explosives detection.

Bead-based competitive fluorescence immunoassay for sensitive and rapid diagnosis of cyanotoxin risk in drinking water.

PubMed

Yu, Hye-Weon; Jang, Am; Kim, Lan Hee; Kim, Sung-Jo; Kim, In S

2011-09-15

Due to the increased occurrence of cyanobacterial blooms and their toxins in drinking water sources, effective management based on a sensitive and rapid analytical method is in high demand for security of safe water sources and environmental human health. Here, a competitive fluorescence immunoassay of microcystin-LR (MCYST-LR) is developed in an attempt to improve the sensitivity, analysis time, and ease-of-manipulation of analysis. To serve this aim, a bead-based suspension assay was introduced based on two major sensing elements: an antibody-conjugated quantum dot (QD) detection probe and an antigen-immobilized magnetic bead (MB) competitor. The assay was composed of three steps: the competitive immunological reaction of QD detection probes against analytes and MB competitors, magnetic separation and washing, and the optical signal generation of QDs. The fluorescence intensity was found to be inversely proportional to the MCYST-LR concentration. Under optimized conditions, the proposed assay performed well for the identification and quantitative analysis of MCYST-LR (within 30 min in the range of 0.42-25 μg/L, with a limit of detection of 0.03 μg/L). It is thus expected that this enhanced assay can contribute both to the sensitive and rapid diagnosis of cyanotoxin risk in drinking water and effective management procedures.

Electrolyte-free Amperometric Immunosensor using a Dendritic Nanotip†

PubMed Central

Kim, Jong-Hoon; Hiraiwa, Morgan; Lee, Hyun-Boo; Lee, Kyong-Hoon; Cangelosi, Gerard A.; Chung, Jae-Hyun

2013-01-01

Electric detection using a nanocomponent may lead to platforms for rapid and simple biosensing. Sensors composed of nanotips or nanodots have been described for highly sensitive amperometry enabled by confined geometry. However, both fabrication and use of nanostructured sensors remain challenging. This paper describes a dendritic nanotip used as an amperometric biosensor for highly sensitive detection of target bacteria. A dendritic nanotip is structured by Si nanowires coated with single-walled carbon nanotubes (SWCNTs) for generation of a high electric field. For reliable measurement using the dendritic structure, Si nanowires were uniformly fabricated by ultraviolet (UV) lithography and etching. The dendritic structure effectively increased the electric current density near the terminal end of the nanotip according to numerical computation. The electrical characteristics of a dendritic nanotip with additional protein layers was studied by cyclic voltammetry and I–V measurement in deionized (DI) water. When the target bacteria dielectrophoretically captured onto a nanotip were bound with fluorescence antibodies, the electric current through DI water decreased. Measurement results were consistent with fluorescence- and electron microscopy. The sensitivity of the amperometry was 10 cfu/sample volume (103 cfu/mL), which was equivalent to the more laborious fluorescence measurement method. The simple configuration of a dendritic nanotip can potentially offer an electrolyte-free detection platform for sensitive and rapid biosensors. PMID:23585927

Electrolyte-free Amperometric Immunosensor using a Dendritic Nanotip.

PubMed

Kim, Jong-Hoon; Hiraiwa, Morgan; Lee, Hyun-Boo; Lee, Kyong-Hoon; Cangelosi, Gerard A; Chung, Jae-Hyun

2013-01-01

Electric detection using a nanocomponent may lead to platforms for rapid and simple biosensing. Sensors composed of nanotips or nanodots have been described for highly sensitive amperometry enabled by confined geometry. However, both fabrication and use of nanostructured sensors remain challenging. This paper describes a dendritic nanotip used as an amperometric biosensor for highly sensitive detection of target bacteria. A dendritic nanotip is structured by Si nanowires coated with single-walled carbon nanotubes (SWCNTs) for generation of a high electric field. For reliable measurement using the dendritic structure, Si nanowires were uniformly fabricated by ultraviolet (UV) lithography and etching. The dendritic structure effectively increased the electric current density near the terminal end of the nanotip according to numerical computation. The electrical characteristics of a dendritic nanotip with additional protein layers was studied by cyclic voltammetry and I-V measurement in deionized (DI) water. When the target bacteria dielectrophoretically captured onto a nanotip were bound with fluorescence antibodies, the electric current through DI water decreased. Measurement results were consistent with fluorescence- and electron microscopy. The sensitivity of the amperometry was 10 cfu/sample volume (10 3 cfu/mL), which was equivalent to the more laborious fluorescence measurement method. The simple configuration of a dendritic nanotip can potentially offer an electrolyte-free detection platform for sensitive and rapid biosensors.

A Smart Detection System Based on Specific Magnetic and Rolling Cycle Amplification Signal-Amplified Dual-Aptamers to Accurately Monitor Minimal Residual Diseases in Patients with T-ALL.

PubMed

Li, Xa; Zhou, Bo; Zhao, Zilong; Hu, Zixi; Zhou, Sufang; Yang, Nuo; Huang, Yong; Zhang, Zhenghua; Su, Jing; Lan, Dan; Qin, Xue; Meng, Jinyu; Zheng, Duo; He, Jian; Huang, Xianing; Zhao, Jing; Zhang, Zhiyong; Tan, Weihong; Lu, Xiaoling; Zhao, Yongxiang

2016-12-01

It is a major clinical challenge for clinicians how to early find out minimal residual diseases (MRD) of leukemia. Here, we developed a smart detection system for MRD involving magnetic aptamer sgc8 probe (M-sgc8 probe) to capture CEM cells and rolling cycle amplification probe (RCA-sgc8 probe) to initiate RCA, producing a single-stranded tandem repeated copy of the circular template. The DNA products were hybridized with molecular beacon to generate the amplified fluorescence signal. An in vitro model to mimic MRD was established to evaluate the sensitivity of the smart detection system. The smart detection system was used to detect MRD in patients with T-ALL peri-chemotherapy, which could not only specifically captured T-ALL cells, but also significantly amplified fluorescence signals on them. The sensitivity was 1/20,000. These results indicate that the smart detection system with high specificity and sensitivity could more efficiently monitor the progress of T-ALL peri-chemotherapy.

Fluorescence detection of small gastrointestinal tumours: principles, technique, first clinical experience.

PubMed

Orth, K; Russ, D; Steiner, R; Beger, H G

2000-11-01

Photodynamic therapy (PDT) is a form of cancer treatment based on the selective accumulation of a photosensitizer in neoplastic tissue. The fluorescent properties of a photosensitizer permit diagnostic localization of primary tumours and/or metastasis. Occult lesions are hard to detect and can easily be missed during routine laparoscopy. Fluorescence observation offers additional optical information and the ability to detect these occult tumours. Clinically, we used 5-aminolevulinic acid for peritoneal staining and tumour demarcation via tumour-specific fluorescence induced by protoporphyrin IX. For laparoscopic observations, a "D-Light" system was used; the conventional white light source was equipped with an optical blocking filter that transmits at the excitation wavelength (380-450 nm) and blocks all other parts of the spectrum. With the aid of a suitable observation filter, the relevant fluorescence was detectable. With the help of this fluorescence we increased the capacity to detect occult tumours, that were missed with white-light observation (9/26). In the gastrointestinal tract, we used a krypton laser at 405 nm for PP IX fluorescence induction. Although there were high sensitivity rates for neoplasms (81% peritoneal carcinomas, 60% gastric cancer), no exact histopathological statement could be achieved at because of false-positive fluorescence, mainly caused by inflammation (6/32). Current clinical goals and the future perspectives of photodynamic diagnostic are discussed.

[Development of fluorescent probes for bone imaging in vivo ~Fluorescent probes for intravital imaging of osteoclast activity~.

PubMed

Minoshima, Masafumi; Kikuchi, Kazuya

Fluorescent molecules are widely used as a tool to directly visualize target biomolecules in vivo. Fluorescent probes have the advantage that desired function can be rendered based on rational design. For bone-imaging fluorescent probes in vivo, they should be delivered to bone tissue upon administration. Recently, a fluorescent probe for detecting osteoclast activity was developed. The fluorescent probe has acid-sensitive fluorescence property, specific delivery to bone tissue, and durability against laser irradiation, which enabled real-time intravital imaging of bone-resorbing osteoclasts for a long period of time.

Highly sensitive fluorescence detection of metastatic lymph nodes of gastric cancer with photo-oxidation of protoporphyrin IX.

PubMed

Koizumi, N; Harada, Y; Beika, M; Minamikawa, T; Yamaoka, Y; Dai, P; Murayama, Y; Yanagisawa, A; Otsuji, E; Tanaka, H; Takamatsu, T

2016-08-01

The establishment of a precise and rapid method to detect metastatic lymph nodes (LNs) is essential to perform less invasive surgery with reduced gastrectomy along with reduced lymph node dissection. We herein describe a novel imaging strategy to detect 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence in excised LNs specifically with reduced effects of tissue autofluorescence based on photo-oxidation of PpIX. We applied the method in a clinical setting, and evaluated its feasibility. To reduce the unfavorable effect of autofluorescence, we focused on photo-oxidation of PpIX: Following light irradiation, PpIX changes into another substance, photo-protoporphyrin, via an oxidative process, which has a different spectral peak, at 675 nm, whereas PpIX has its spectral peak at 635 nm. Based on the unique spectral alteration, fluorescence spectral imaging before and after light irradiation and subsequent originally-developed image processing was performed. Following in vitro study, we applied this method to a total of 662 excised LNs obtained from 30 gastric cancer patients administered 5-ALA preoperatively. Specific visualization of PpIX was achieved in in vitro study. The method allowed highly sensitive detection of metastatic LNs, with sensitivity of 91.9% and specificity of 90.8% in the in vivo clinical trial. Receiver operating characteristic analysis indicated high diagnostic accuracy, with the area under the curve of 0.926. We established a highly sensitive and specific 5-ALA-induced fluorescence imaging method applicable in clinical settings. The novel method has a potential to become a useful tool for intraoperative rapid diagnosis of LN metastasis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Multi-capillary based optical sensors for highly sensitive protein detection

NASA Astrophysics Data System (ADS)

Okuyama, Yasuhira; Katagiri, Takashi; Matsuura, Yuji

2017-04-01

A fluorescence measuring method based on glass multi-capillary for detecting trace amounts of proteins is proposed. It promises enhancement of sensitivity due to effects of the adsorption area expansion and the longitudinal excitation. The sensitivity behavior of this method was investigated by using biotin-streptavidin binding. According to experimental examinations, it was found that the sensitivity was improved by a factor of 70 from common glass wells. We also confirmed our measuring system could detect 1 pg/mL of streptavidin. These results suggest that multi-capillary has a potential as a high-sensitive biosensor.

Detection system of capillary array electrophoresis microchip based on optical fiber

NASA Astrophysics Data System (ADS)

Yang, Xiaobo; Bai, Haiming; Yan, Weiping

2009-11-01

To meet the demands of the post-genomic era study and the large parallel detections of epidemic diseases and drug screening, the high throughput micro-fluidic detection system is needed urgently. A scanning laser induced fluorescence detection system based on optical fiber has been established by using a green laser diode double-pumped solid-state laser as excitation source. It includes laser induced fluorescence detection subsystem, capillary array electrophoresis micro-chip, channel identification unit and fluorescent signal processing subsystem. V-shaped detecting probe composed with two optical fibers for transmitting the excitation light and detecting induced fluorescence were constructed. Parallel four-channel signal analysis of capillary electrophoresis was performed on this system by using Rhodamine B as the sample. The distinction of different samples and separation of samples were achieved with the constructed detection system. The lowest detected concentration is 1×10-5 mol/L for Rhodamine B. The results show that the detection system possesses some advantages, such as compact structure, better stability and higher sensitivity, which are beneficial to the development of microminiaturization and integration of capillary array electrophoresis chip.

Towards the fluorogenic detection of peroxide explosives through host–guest chemistry

PubMed Central

Almenar, Estefanía; Costero, Ana M.; Gil, Salvador; Parra, Margarita

2018-01-01

Two dansyl-modified β-cyclodextrin derivatives (1 and 2) have been synthesized as host–guest sensory systems for the direct fluorescent detection of the peroxide explosives diacetone diperoxide (DADP) and triacetone triperoxide (TATP) in aqueous media. The sensing is based on the displacement of the dansyl moiety from the cavity of the cyclodextrin by the peroxide guest resulting in a decrease of the intensity of the fluorescence of the dye. Both systems showed similar fluorescent responses and were more sensitive towards TATP than DADP. PMID:29765646

Feasibility of Using Fluorescence Spectrophotometry to Develop a Sensitive Dye Immersion Method for Container Closure Integrity Testing of Prefilled Syringes.

PubMed

Lu, Xujin; Lloyd, David K; Klohr, Steven E

2016-01-01

A feasibility study was conducted for a sensitive and robust dye immersion method for the measurement of container closure integrity of unopened prefilled syringes using fluorescence spectrophotometry as the detection method. A Varian Cary Eclipse spectrofluorometer was used with a custom-made sample holder to position the intact syringe in the sample compartment for fluorescence measurements. Methylene blue solution was initially evaluated as the fluorophore in a syringe with excitation at 607 nm and emission at 682 nm, which generated a limit of detection of 0.05 μg/mL. Further studies were conducted using rhodamine 123, a dye with stronger fluorescence. Using 480 nm excitation and 525 nm emission, the dye in the syringe could be easily detected at levels as low as 0.001 μg/mL. The relative standard deviation for 10 measurements of a sample of 0.005 μg/mL (with repositioning of the syringe after each measurement) was less than 1.1%. A number of operational parameters were optimized, including the photomultiplier tube voltage, excitation, and emission slit widths. The specificity of the testing was challenged by using marketed drug products and a protein sample, which showed no interference to the rhodamine detection. Results obtained from this study demonstrated that using rhodamine 123 for container closure integrity testing with in-situ (in-syringe) fluorescence measurements significantly enhanced the sensitivity and robustness of the testing and effectively overcame limitations of the traditional methylene blue method with visual or UV-visible absorption detection. Ensuring container closure integrity of injectable pharmaceutical products is necessary to maintain quality throughout the shelf life of a sterile drug product. Container closure integrity testing has routinely been used to evaluate closure integrity during product development and production line qualification of prefilled syringes, vials, and devices. However, container closure integrity testing has recently gained industry attention due to increased regulatory agency scrutiny regarding the analytical rigor of container closure integrity testing methods and expectations to use container closure integrity testing in lieu of sterility tests in stability programs. Methylene blue dye is often used for dye ingress testing of container closure integrity, but we found it unsuitable for reliable detection of small breaches in prefilled syringes of drug product. This work describes the suitability and advantages of using a fluorescent dye and spectroscopic detection for a robust, sensitive, and quality control-friendly container closure integrity testing method for prefilled syringes. © PDA, Inc. 2016.

Highly sensitive C-reactive protein (CRP) assay using metal-enhanced fluorescence (MEF)

NASA Astrophysics Data System (ADS)

Zhang, Yi; Keegan, Gemma L.; Stranik, Ondrej; Brennan-Fournet, Margaret E.; McDonagh, Colette

2015-07-01

Fluorescence has been extensively employed in the area of diagnostic immunoassays. A significant enhancement of fluorescence can be achieved when noble metal nanoparticles are placed in close proximity to fluorophores. This effect, referred to as metal-enhanced fluorescence (MEF), has the potential to produce immunoassays with a high sensitivity and a low limit of detection (LOD). In this study, we investigate the fluorescence enhancement effect of two different nanoparticle systems, large spherical silver nanoparticles (AgNPs) and gold edge-coated triangular silver nanoplates, and both systems were evaluated for MEF. The extinction properties and electric field enhancement of both systems were modeled, and the optimum system, spherical AgNPs, was used in a sandwich immunoassay for human C-reactive protein with a red fluorescent dye label. A significant enhancement in the fluorescence was observed, which corresponded to an LOD improvement of 19-fold compared to a control assay without AgNPs.

Ultrasensitive and Multiple Disease-Related MicroRNA Detection Based on Tetrahedral DNA Nanostructures and Duplex-Specific Nuclease-Assisted Signal Amplification.

PubMed

Xu, Fang; Dong, Haifeng; Cao, Yu; Lu, Huiting; Meng, Xiangdan; Dai, Wenhao; Zhang, Xueji; Al-Ghanim, Khalid Abdullah; Mahboob, Shahid

2016-12-14

A highly sensitive and multiple microRNA (miRNA) detection method by combining three-dimensional (3D) DNA tetrahedron-structured probes (TSPs) to increase the probe reactivity and accessibility with duplex-specific nuclease (DSN) for signal amplification for sensitive miRNA detection was proposed. Briefly, 3D DNA TSPs labeled with different fluorescent dyes for specific target miRNA recognition were modified on a gold nanoparticle (GNP) surface to increase the reactivity and accessibility. Upon hybridization with a specific target, the TSPs immobilized on the GNP surface hybridized with the corresponding target miRNA to form DNA-RNA heteroduplexes, and the DSN can recognize the formed DNA-RNA heteroduplexes to hydrolyze the DNA in the heteroduplexes to produce a specific fluorescent signal corresponding to a specific miRNA, while the released target miRNA strands can initiate another cycle, resulting in a significant signal amplification for sensitive miRNA detection. Different targets can produce different fluorescent signals, leading to the development of a sensitive detection for multiple miRNAs in a homogeneous solution. Under optimized conditions, the proposed assay can simultaneously detect three different miRNAs in a homogeneous solution with a logarithmic linear range spanning 5 magnitudes (10 -12 -10 -16 ) and achieving a limit of detection down to attomolar concentrations. Meanwhile, the proposed miRNA assay exhibited the capability of discriminating single bases (three bases mismatched miRNAs) and showed good eligibility in the analysis of miRNAs extracted from cell lysates and miRNAs in cell incubation media, which indicates its potential use in biomedical research and clinical analysis.

Assessment of drinking water quality at the tap using fluorescence spectroscopy.

PubMed

Heibati, Masoumeh; Stedmon, Colin A; Stenroth, Karolina; Rauch, Sebastien; Toljander, Jonas; Säve-Söderbergh, Melle; Murphy, Kathleen R

2017-11-15

Treated drinking water may become contaminated while travelling in the distribution system on the way to consumers. Elevated dissolved organic matter (DOM) at the tap relative to the water leaving the treatment plant is a potential indicator of contamination, and can be measured sensitively, inexpensively and potentially on-line via fluorescence and absorbance spectroscopy. Detecting elevated DOM requires potential contamination events to be distinguished from natural fluctuations in the system, but how much natural variation to expect in a stable distribution system is unknown. In this study, relationships between DOM optical properties, microbial indicator organisms and trace elements were investigated for households connected to a biologically-stable drinking water distribution system. Across the network, humic-like fluorescence intensities showed limited variation (RSD = 3.5-4.4%), with half of measured variation explained by interactions with copper. After accounting for quenching by copper, fluorescence provided a very stable background signal (RSD < 2.2%) against which a ∼2% infiltration of soil water would be detectable. Smaller infiltrations would be detectable in the case of contamination by sewage with a strong tryptophan-like fluorescence signal. These findings indicate that DOM fluorescence is a sensitive indicator of water quality changes in drinking water networks, as long as potential interferents are taken into account. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Enhancing early bladder cancer detection with fluorescence-guided endoscopic optical coherence tomography

NASA Astrophysics Data System (ADS)

Pan, Y. T.; Xie, T. Q.; Du, C. W.; Bastacky, S.; Meyers, S.; Zeidel, M. L.

2003-12-01

We report an experimental study of the possibility of enhancing early bladder cancer diagnosis with fluorescence-image-guided endoscopic optical coherence tomography (OCT). After the intravesical instillation of a 10% solution of 5-aminolevulinic acid, simultaneous fluorescence imaging (excitation of 380-420 nm, emission of 620-700 nm) and OCT are performed on rat bladders to identify the photochemical and morphological changes associated with uroepithelial tumorigenesis. The preliminary results of our ex vivo study reveal that both fluorescence and OCT can identify early uroepithelial cancers, and OCT can detect precancerous lesions (e.g., hyperplasia) that fluorescence may miss. This suggests that a cystoscope combining 5-aminolevulinic acid fluorescence and OCT imaging has the potential to enhance the efficiency and sensitivity of early bladder cancer diagnosis.

pH-sensitive fluorescent sensors based on europium(III) complexes.

PubMed

Zhang, Xiaolin; Jiao, Yang; Jing, Xu; Wu, Hongmei; He, Guangjie; Duan, Chunying

2011-03-21

New europium(III) complexes Eu(TTA)(2)-DSQ and Eu(TTA)(3)-DR1 were designed and synthesized as new fluorescent pH probes (where HDSQ = 5-(dimethylamino)-N-(4-(2-((8-hydroxyquinolin-2-yl)methylene)hydrazinecarbonyl)phenyl)naphthalene-1-sulfonamide, DR1 = N(1)-(4-(dimethylamino)benzylidene)-N(2)-(rhodamine-6G) lactamethylene-diamine and TTA = thiophentrifluoroacetone). Eu(TTA)(2)-DSQ exhibited high sensitivity in monitoring pH changes in neutral aqueous solution with negligible background fluorescence. Eu(TTA)(3)-DR1 comprised a green light emitting Rhodamine 6G fluorophore and a Eu(III) moiety as the origin of red light. These pH-sensitive emitter components have pK(a) values of 5.0 and 7.2 respectively, and exhibit isolated protonated steps within one molecule. Luminescence titrations demonstrate that Eu(TTA)(3)-DR1 was able to detect pH values at both near neutral pH and acidic pH ranges, and was also able to detect pH in both cultured cells and in vivo.

A Redox-Nucleophilic Dual-Reactable Probe for Highly Selective and Sensitive Detection of H2S: Synthesis, Spectra and Bioimaging

NASA Astrophysics Data System (ADS)

Zhang, Changyu; Wang, Runyu; Cheng, Longhuai; Li, Bingjie; Xi, Zhen; Yi, Long

2016-07-01

Hydrogen sulfide (H2S) is an important signalling molecule with multiple biological functions. The reported H2S fluorescent probes are majorly based on redox or nucleophilic reactions. The combination usage of both redox and nucleophilic reactions could improve the probe’s selectivity, sensitivity and stability. Herein we report a new dual-reactable probe with yellow turn-on fluorescence for H2S detection. The sensing mechanism of the dual-reactable probe was based on thiolysis of NBD (7-nitro-1,2,3-benzoxadiazole) amine (a nucleophilic reaction) and reduction of azide to amine (a redox reaction). Compared with its corresponding single-reactable probes, the dual-reactable probe has higher selectivity and fluorescence turn-on fold with magnitude of multiplication from that of each single-reactable probe. The highly selective and sensitive properties enabled the dual-reactable probe as a useful tool for efficiently sensing H2S in aqueous buffer and in living cells.

In Vivo Follow-up of Brain Tumor Growth via Bioluminescence Imaging and Fluorescence Tomography

PubMed Central

Genevois, Coralie; Loiseau, Hugues; Couillaud, Franck

2016-01-01

Reporter gene-based strategies are widely used in experimental oncology. Bioluminescence imaging (BLI) using the firefly luciferase (Fluc) as a reporter gene and d-luciferin as a substrate is currently the most widely employed technique. The present paper compares the performances of BLI imaging with fluorescence imaging using the near infrared fluorescent protein (iRFP) to monitor brain tumor growth in mice. Fluorescence imaging includes fluorescence reflectance imaging (FRI), fluorescence diffuse optical tomography (fDOT), and fluorescence molecular Imaging (FMT®). A U87 cell line was genetically modified for constitutive expression of both the encoding Fluc and iRFP reporter genes and assayed for cell, subcutaneous tumor and brain tumor imaging. On cultured cells, BLI was more sensitive than FRI; in vivo, tumors were first detected by BLI. Fluorescence of iRFP provided convenient tools such as flux cytometry, direct detection of the fluorescent protein on histological slices, and fluorescent tomography that allowed for 3D localization and absolute quantification of the fluorescent signal in brain tumors. PMID:27809256

In Vivo Follow-up of Brain Tumor Growth via Bioluminescence Imaging and Fluorescence Tomography.

PubMed

Genevois, Coralie; Loiseau, Hugues; Couillaud, Franck

2016-10-31

Reporter gene-based strategies are widely used in experimental oncology. Bioluminescence imaging (BLI) using the firefly luciferase (Fluc) as a reporter gene and d-luciferin as a substrate is currently the most widely employed technique. The present paper compares the performances of BLI imaging with fluorescence imaging using the near infrared fluorescent protein (iRFP) to monitor brain tumor growth in mice. Fluorescence imaging includes fluorescence reflectance imaging (FRI), fluorescence diffuse optical tomography (fDOT), and fluorescence molecular Imaging (FMT ® ). A U87 cell line was genetically modified for constitutive expression of both the encoding Fluc and iRFP reporter genes and assayed for cell, subcutaneous tumor and brain tumor imaging. On cultured cells, BLI was more sensitive than FRI; in vivo, tumors were first detected by BLI. Fluorescence of iRFP provided convenient tools such as flux cytometry, direct detection of the fluorescent protein on histological slices, and fluorescent tomography that allowed for 3D localization and absolute quantification of the fluorescent signal in brain tumors.

Portable spotter for fluorescent contaminants on surfaces

DOEpatents

Schuresko, Daniel D.

1980-01-01

A portable fluorescence-based spotter for polynuclear aromatic hydrocarbon contamination on personnel and work area surfaces under ambient lighting conditions is provided. This instrument employs beam modulation and phase sensitive detection for discriminating between fluorescence from organic materials from reflected background light and inorganic fluorescent material. The device uses excitation and emission filters to provide differentiation between classes of aromatic organic compounds. Certain inorganic fluorescent materials, including heavy metal compounds, may also be distinguished from the organic compounds, despite both having similar optical properties.

Sensitive fluorescence on-off probes for the fast detection of a chemical warfare agent mimic.

PubMed

Khan, Muhammad Shar Jhahan; Wang, Ya-Wen; Senge, Mathias O; Peng, Yu

2018-01-15

Two highly sensitive probes bearing a nucleophilic imine moiety have been utilized for the selective detection of chemical warfare agent (CWA) mimics. Diethyl chlorophosphate (DCP) was used as mimic CWAs. Both iminocoumarin-benzothiazole-based probes not only demonstrated a remarkable fluorescence ON-OFF response and good recognition, but also exhibited fast response times (10s) along with color changes upon addition of DCP. Limits of detection for the two sensors 1 and 2 were calculated as 0.065μM and 0.21μM, respectively, which are much lower than most other reported probes. These two probes not only show high sensitivity and selectivity in solution, but can also be applied for the recognition of DCP in the gas state, with significant color changes easily observed by the naked eye. Copyright © 2017 Elsevier B.V. All rights reserved.

Direct Detection of Nucleic Acid with Minimizing Background and Improving Sensitivity Based on a Conformation-Discriminating Indicator.

PubMed

Zhu, Lixuan; Qing, Zhihe; Hou, Lina; Yang, Sheng; Zou, Zhen; Cao, Zhong; Yang, Ronghua

2017-08-25

As is well-known, the nucleic acid indicator-based strategy is one of the major approaches to monitor the nucleic acid hybridization-mediated recognition events in biochemical analysis, displaying obvious advantages including simplicity, low cost, convenience, and generality. However, conventional indicators either hold strong self-fluorescence or can be lighted by both ssDNA and dsDNA, lacking absolute selectivity for a certain conformation, always with high background interference and low sensitivity in sensing; and additional processing (e.g., nanomaterial-mediated background suppression, and enzyme-catalyzed signal amplification) is generally required to improve the detection performance. In this work, a carbazole derivative, EBCB, has been synthesized and screened as a dsDNA-specific fluorescent indicator. Compared with conventional indicators under the same conditions, EBCB displayed a much higher selective coefficient for dsDNA, with little self-fluorescence and negligible effect from ssDNA. Based on its superior capability in DNA conformation-discrimination, high sensitivity with minimizing background interference was demonstrated for direct detection of nucleic acid, and monitoring nucleic acid-based circuitry with good reversibity, resulting in low detection limit and high capability for discriminating base-mismatching. Thus, we expect that this highly specific DNA conformation-discriminating indicator will hold good potential for application in biochemical sensing and molecular logic switching.

Rare Earth Fluorescent Nanomaterials for Enhanced Development of Latent Fingerprints.

PubMed

Wang, Meng; Li, Ming; Yu, Aoyang; Wu, Jian; Mao, Chuanbin

2015-12-30

The most commonly found fingerprints at crime scenes are latent and, thus, an efficient method for detecting latent fingerprints is very important. However, traditional developing techniques have drawbacks such as low developing sensitivity, high background interference, complicated operation, and high toxicity. To tackle this challenge, we have synthesized two kinds of rare earth fluorescent nanomaterials, including the fluoresce red-emitting YVO4:Eu nanocrystals and green-emitting LaPO4:Ce,Tb nanobelts, and then used them as fluorescent labels for the development of latent fingerprints with high sensitivity, high contrast, high selectivity, high efficiency, and low background interference, on various substrates including noninfiltrating materials, semi-infiltrating materials, and infiltrating materials.

Investigation of detection limits for diffuse optical tomography systems: II. Analysis of slab and cup geometry for breast imaging.

PubMed

Ziegler, Ronny; Brendel, Bernhard; Rinneberg, Herbert; Nielsen, Tim

2009-01-21

Using a statistical (chi-square) test on simulated data and a realistic noise model derived from the system's hardware we study the performance of diffuse optical tomography systems for fluorescence imaging. We compare the predicted smallest size of detectable lesions at various positions in slab and cup geometry and model how detection sensitivity depends on breast compression and lesion fluorescence contrast. Our investigation shows that lesion detection is limited by relative noise in slab geometry and by absolute noise in cup geometry.

A turn-on near-infrared fluorescent chemosensor for selective detection of lead ions based on a fluorophore-gold nanoparticle assembly.

PubMed

Wang, Shaozhen; Sun, Junyong; Gao, Feng

2015-06-21

A turn-on fluorescent chemosensor of Pb(2+) in the near-infrared (NIR) region, which is based on the Pb(2+)-tuned restored fluorescence of a weakly fluorescent fluorophore-gold nanoparticle (AuNPs) assembly, has been reported. In this fluorophore-AuNP assembly, NIR fluorescent dye brilliant cresyl blue (BCB) molecules act as fluorophores and are used for signal transduction of fluorescence, while AuNPs act as quenchers to quench the nearby fluorescent BCB molecules via electron transfer. In the presence of Pb(2+), fluorescent BCB molecules detached from AuNPs and restored their fluorescence due to the formation of a chelating complex between Pb(2+) and glutathione confined on AuNPs. Under the optimal conditions, the present BCB-AuNP assembly is capable of detecting Pb(2+) with a concentration ranging from 7.5 × 10(-10) to 1 × 10(-8) mol L(-1) (0.16-2.1 ng mL(-1)) and a detection limit of 0.51 nM (0.11 ng mL(-1)). The present BCB-AuNP assembly can be used in aqueous media for the determination of Pb(2+) unlike common organic fluorescent reagents, and also shows advantages of NIR fluorescence spectrophotometry such as less interference, lower detection limit, and higher sensitivity. Moreover, the present method was successfully applied for the detection of Pb(2+) in water samples with satisfactory results.

Interventional fluorescence spectroscopy: preliminary results to detect tumor margins during glioma resection with two fluorescence spectra of PpIX

NASA Astrophysics Data System (ADS)

Alston, L. M.; Guyotat, J.; Mahieu-Williame, L.; Hebert, M.; Kantapareddy, P.; Meyronet, D.; Rousseau, D.; Montcel, B.

2017-07-01

We show the feasibility of using an intraoperative spectroscopic device to identify tumors margins during glioma resection. The collected fluorescence spectra is fitted with two reference spectra of PpIX and the contribution of each spectrum enables to overcome the sensitivity of current techniques by seeing tumor margins and low grade gliomas.

Flexible planar microfluidic chip employing a light emitting diode and a PIN-photodiode for portable flow cytometers.

PubMed

Kettlitz, Siegfried W; Valouch, Sebastian; Sittel, Wiebke; Lemmer, Uli

2012-01-07

Detection of fluorescence particles is a key method of flow cytometry. We evaluate the performance of a design for a microfluidic fluorescence particle detection device. Due to the planar design with low layer thicknesses, we avoid optical components such as lenses or dichroic mirrors and substitute them with a shadow mask and colored film filters. A commercially available LED is used as the light source and a PIN-photodiode as detector. This design approach reduces component cost and power consumption and enables supplying the device with power from a standard USB port. From evaluation of this design, we obtain a maximum particle detection frequency of up to 600 particles per second at a sensitivity of better than 4.7 × 10(5) MESF (molecules of equivalent soluble fluorochrome) measured with particles for FITC sensitivity calibration. Lowering the flow rate increases the instrument sensitivity by an order of magnitude enabling the detection of particles with 4.5 × 10(4) MESF.

SHERLOC on Mars 2020

NASA Astrophysics Data System (ADS)

Beegle, L. W.; Bhartia, R.; DeFlores, L. P.; Abbey, W.; Asher, S. A.; Burton, A. S.; Fries, M.; Conrad, P. G.; Clegg, S. M.; Wiens, R. C.; Edgett, K. S.; Ehlmann, B. L.; Nealson, K. H.; Minitti, M. E.; Popp, J.; Langenhorst, F.; Sobron, P.; Steele, A.; Williford, K. H.; Yingst, R. A.

2017-12-01

The Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) investigation is part of the Mars 2020 integrated payload. SHERLOC enables non-contact, spatially resolved, and highly sensitivity detection and characterization of organics and minerals in the Martian surface and near subsurface. SHERLOC is an arm-mounted, Deep UV (DUV) resonance Raman and fluorescence spectrometer utilizing a 248.6-nm DUV laser. Deep UV induced native fluorescence is very sensitive to condensed carbon and aromatic organics, enabling detection at or below 10-6 w/w (1 ppm) at <100 µm spatial scales. SHERLOC's deep UV resonance Raman enables detection and classification of aromatic and aliphatic organics with sensitivities of 10-2 to below 10-4 w/w. In addition to organics, the deep UV Raman enables detection and classification of minerals relevant to aqueous chemistry with grain sizes below 20 µm. SHERLOC will be able to map the distribution of organic material with respect to visible features and minerals that are identifiable with the Raman spectrometer. These maps will enable analysis of the distribution of organics with minerals.

Determination of fatty acids in bio-samples based on the pre-column fluorescence derivatization with 1,3,5,7-tetramethyl-8-butyrethylenediamine-difluoroboradiaza-s-indacene by high performance liquid chromatography.

PubMed

Wang, Fei-Hua; Xiong, Xu-Jie; Guo, Xiao-Feng; Wang, Hong; Zhang, Hua-Shan

2013-05-24

1,3,5,7-Tetramethyl-8-butyrethylenediamine-difluoroboradiaza-s-indacene (TMBB-EDAN) has been designed and synthesized as a highly fluorescent labeling reagent for carboxylic acids. By using TMBB-EDAN, a sensitive and rapid method based on high performance liquid chromatography-fluorescence detection for the determination of twelve fatty acids (FAs) in bio-samples has been developed. Under optimized conditions, these FAs were tagged with TMBB-EDAN in the presence of 1-ethyl-3-(3-dimethyla-minopropyl) carbodiamide at 20°C for 30min and then the baseline separation was achieved on a C18 column with a linear gradient elution in 26min. With fluorescence detection at λex/λem=490nm/510nm, the linear ranges of FAs were from 3.0 to 300nM and the detection limits with a signal-to-noise ratio of 3 were in the 0.2-0.4nM range. The proposed method offers advantages of milder derivatization condition and much better sensitivity for the determination of FAs, when compared to the reported fluorescence derivatization-based methods. Copyright © 2013 Elsevier B.V. All rights reserved.

A dual-emission and large Stokes shift fluorescence probe for real-time discrimination of ROS/RNS and imaging in live cells.

PubMed

Guo, Ting; Cui, Lei; Shen, Jiaoning; Wang, Rui; Zhu, Weiping; Xu, Yufang; Qian, Xuhong

2013-03-04

A novel dual-emission fluorescence probe has been developed for specific and sensitive detection of hypochlorite (ClO(-)). Upon addition of ClO(-), significant changes in fluorescence emission intensity at two discrete wavelengths were observed. Meanwhile OONO(-) led to only a single-channel fluorescence enhancement. This feature makes it a clear advantage in distinguishing ClO(-), RNS from other ROS.

Highly selective fluorescence detection of Cu2+ in water by chiral dimeric Zn2+ complexes through direct displacement.

PubMed

Khatua, Snehadrinarayan; Choi, Shin Hei; Lee, Junseong; Huh, Jung Oh; Do, Youngkyu; Churchill, David G

2009-03-02

Fluorescent dinuclear chiral zinc complexes were synthesized in a "one-pot" method in which the lysine-based Schiff base ligand was generated in situ. This complex acts as a highly sensitive and selective fluorescent ON-OFF probe for Cu(2+) in water at physiological pH. Other metal ions such as Hg(2+), Cd(2+), and Pb(2+) gave little fluorescence change.

Silver nanoparticles-enhanced time-resolved fluorescence sensor for VEGF(165) based on Mn-doped ZnS quantum dots.

PubMed

Zhu, Dong; Li, Wei; Wen, Hong-Mei; Yu, Sheng; Miao, Zhao-Yi; Kang, An; Zhang, Aihua

2015-12-15

A silver nanoparticles (AgNPs)-enhanced time-resolved fluorescence (TR-FL) sensor based on long-lived fluorescent Mn-doped ZnS quantum dots (QDs) is developed for the sensitive detection of vascular endothelial growth factor-165 (VEGF165), a predominant cancer biomarker in cancer angiogenesis. The aptamers bond with the Mn-doped ZnS QDs and the BHQ-2 quencher-labelling strands hybridized in duplex are coupled with streptavidin (SA)-functionalized AgNPs to form the AgNPs-enhanced TR-FL sensor, showing lower fluorescence intensity in the duplex state due to the fluorescence resonance energy transfer (FRET) between the Mn-doped ZnS QDs and quenchers. Upon the addition of VEGF165, the BHQ-2 quencher-labelling strands of the duplex are displaced, leading to the disruption of the FRET. As a result, the fluorescence of the Mn-doped QDs within the proximity of the AgNPs is recovered. The FL signal can be measured free of the interference of short-lived background by setting appropriate delay time and gate time, which offers a signal with high signal-to-noise ratio in photoluminescent biodetection. Compared with the bare TR-FL sensor, the AgNPs-based TR-FL sensor showed a huge improvement in fluorescence based on metal-enhanced fluorescence (MEF) effect, and the sensitivity increased 11-fold with the detection limit of 0.08 nM. In addition, the sensor provided a wide range of linear detection from 0.1 nM to 16 nM. Copyright © 2015 Elsevier B.V. All rights reserved.

Sensitive molecular diagnostics using surface-enhanced resonance Raman scattering (SERRS)

NASA Astrophysics Data System (ADS)

Faulds, Karen; Graham, Duncan; McKenzie, Fiona; MacRae, Douglas; Ricketts, Alastair; Dougan, Jennifer

2009-02-01

Surface enhanced resonance Raman scattering (SERRS) is an analytical technique with several advantages over competitive techniques in terms of improved sensitivity and multiplexing. We have made great progress in the development of SERRS as a quantitative analytical method, in particular for the detection of DNA. SERRS is an extremely sensitive and selective technique which when applied to the detection of labelled DNA sequences allows detection limits to be obtained which rival, and in most cases, are better than fluorescence. Here the conditions are explored which will enable the successful detection of DNA using SERRS. The enhancing surface which is used is crucial and in this case suspensions of nanoparticles were used as they allow quantitative behaviour to be achieved and allow analogous systems to current fluorescence based systems to be made. The aggregation conditions required to obtain SERRS of DNA are crucial and herein we describe the use of spermine as an aggregating agent. The nature of the label which is used, be it fluorescent, positively or negatively charged also effects the SERRS response and these conditions are again explored here. We have clearly demonstrated the ability to identify the components of a mixture of 5 analytes in solution by using two different excitation wavelengths and also of a 6-plex using data analysis techniques. These conditions will allow the use of SERRS for the detection of target DNA in a meaningful diagnostic assay.

Photocatalysis-Based Nanoprobes Using Noble Metal-Semiconductor Heterostructure for Visible Light-Driven in Vivo Detection of Mercury.

PubMed

Zhi, Lihua; Zeng, Xiaofan; Wang, Hao; Hai, Jun; Yang, Xiangliang; Wang, Baodui; Zhu, Yanhong

2017-07-18

The development of sensitive and reliable methods to monitor the presence of mercuric ions in cells and organisms is of great importance to biological research and biomedical applications. In this work, we propose a strategy to construct a solar-driven nanoprobe using a 3D Au@MoS 2 heterostructure as a photocatalyst and rhodamine B (RB) as a fluorescent and color change reporter molecule for monitoring Hg 2+ in living cells and animals. The sensing mechanism is based on the photoinduced electron formation of gold amalgam in the 3D Au@MoS 2 heterostructure under visible light illumination. This formation is able to remarkably inhibit the photocatalytic activity of the heterostructure toward RB decomposition. As a result, "OFF-ON" fluorescence and color change are produced. Such characteristics enable this new sensing platform to sensitively and selectively detect Hg 2+ in water by fluorescence and colorimetric methods. The detection limits of the fluorescence assay and colorimetric assay are 0.22 and 0.038 nM for Hg 2+ , respectively; these values are well below the acceptable limits in drinking water standards (10 nM). For the first time, such photocatalysis-based sensing platform is successfully used to monitor Hg 2+ in live cells and mice. Our work therefore opens a promising photocatalysis-based analysis methodology for highly sensitive and selective in vivo Hg 2+ bioimaging studies.

Protein-templated gold nanoclusters based sensor for off-on detection of ciprofloxacin with a high selectivity.

PubMed

Chen, Zhanguang; Qian, Sihua; Chen, Junhui; Cai, Jie; Wu, Shuyan; Cai, Ziping

2012-05-30

In this contribution, bovine serum albumin stabilized gold nanoclusters as novel fluorescent probes were successfully utilized for the detection of ciprofloxacin for the first time. Our prepared gold nanoclusters exhibited strong emission with peak maximum at 635 nm. Cu(2+) was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of ciprofloxacin caused the fluorescence intensity restoration of the Cu(2+)-gold nanoclusters system. The increase in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by ciprofloxacin allows the sensitive detection of ciprofloxacin in the range of 0.4 ng mL(-1) to 50 ng mL(-1). The detection limit for ciprofloxacin is 0.3 ng mL(-1) at a signal-to-noise ratio of 3. The present sensor for ciprofloxacin detection possesses a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results. Copyright © 2012 Elsevier B.V. All rights reserved.

A fluorescence detection of D-penicillamine based on Cu(2+)-induced fluorescence quenching system of protein-stabilized gold nanoclusters.

PubMed

Wang, Peng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

2015-01-25

In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu(2+)-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0×10(-5)-2.39×10(-4) M. The detection limit for D-penicillamine was 5.4×10(-6) M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results. Copyright © 2014 Elsevier B.V. All rights reserved.

Designed to dissolve: suppression of colloidal aggregation of Cu(I)-selective fluorescent probes in aqueous buffer and in-gel detection of a metallochaperone.

PubMed

Morgan, M Thomas; Bagchi, Pritha; Fahrni, Christoph J

2011-10-12

Due to the lipophilicity of the metal-ion receptor, previously reported Cu(I)-selective fluorescent probes form colloidal aggregates, as revealed by dynamic light scattering. To address this problem, we have developed a hydrophilic triarylpyrazoline-based fluorescent probe, CTAP-2, that dissolves directly in water and shows a rapid, reversible, and highly selective 65-fold fluorescence turn-on response to Cu(I) in aqueous solution. CTAP-2 proved to be sufficiently sensitive for direct in-gel detection of Cu(I) bound to the metallochaperone Atox1, demonstrating the potential for cation-selective fluorescent probes to serve as tools in metalloproteomics for identifying proteins with readily accessible metal-binding sites.

MEH-PPV film thickness influenced fluorescent quenching of tip-coated plastic optical fiber sensors

NASA Astrophysics Data System (ADS)

Yusufu, A. M.; Noor, A. S. M.; Tamchek, N.; Abidin, Z. Z.

2017-12-01

The performance of plastic optical fiber sensors in detecting nitro aromatic explosives 1,4-dinitrobenzene (DNB) have been investigated by fluorescence spectroscopy and analyzed by using fluorescence quenching technique. The plastic optical fiber utilized is 90 degrees cut tip and dip-coated with conjugated polymer MEH-PPV poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] thin films for detection conjugants. The thicknesses of the MEH-PPV coating were varied to improvise the sensitivity whilst slowly reducing the fluorescence intensity. It was shown that fluorescence intensity from thinner film decreased by (82% in 40 s) in the presence of DNB signifying an improvement of 28% reduction with time 13 s less than that of the thicker film.

Sensitive and Selective Ratiometric Fluorescence Probes for Detection of Intracellular Endogenous Monoamine Oxidase A.

PubMed

Wu, Xiaofeng; Li, Lihong; Shi, Wen; Gong, Qiuyu; Li, Xiaohua; Ma, Huimin

2016-01-19

Monoamine oxidase A (MAO-A) is known to widely exist in most cell lines in the body, and its dysfunction (unusually high or low levels of MAO-A) is thought to be responsible for several psychiatric and neurological disorders. Thus, a sensitive and selective method for evaluating the relative MAO-A levels in different live cells is urgently needed to better understand the function of MAO-A, but to our knowledge such a method is still lacking. Herein, we rationally design two new ratiometric fluorescence probes (1 and 2) that can sensitively and selectively detect MAO-A. The probes are constructed by incorporating a recognition group of propylamine into the fluorescent skeleton of 1,8-naphthalimide, and the detection mechanism is based on amine oxidation and β-elimination to release the fluorophore (4-hydroxy-N-butyl-1,8-naphthalimide), which is verified by HPLC analysis. Reaction of the probes with MAO-A produces a remarkable fluorescence change from blue to green, and the ratio of fluorescence intensity at 550 and 454 nm is directly proportional to the concentration of MAO-A in the ranges of 0.5-1.5 and 0.5-2.5 μg/mL with detection limits of 1.1 and 10 ng/mL (k = 3) for probes 1 and 2, respectively. Surprisingly, these probes show strong fluorescence responses to MAO-A but almost none to MAO-B (one of two isoforms of MAO), indicating superior ability to distinguish MAO-A from MAO-B. The high specificity of the probes for MAO-A over MAO-B is further supported by different inhibitor experiments. Moreover, probe 1 displays higher sensitivity than probe 2 and is thus investigated to image the relative MAO-A levels in different live cells, such as HeLa and NIH-3T3 cells. It is found that the concentration of endogenous MAO-A in HeLa cells is approximately 1.8 times higher than that in NIH-3T3 cells, which is validated by the result from an ELISA kit. Additionally, the proposed probes may find more uses in the specific detection of MAO-A between the two isoforms of MAO, thereby promoting our understanding of the behavior and function of MAO-A in living biosystems.

A fluorescence high throughput screening method for the detection of reactive electrophiles as potential skin sensitizers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avonto, Cristina; Chittiboyina, Amar G.; Rua, Diego

2015-12-01

Skin sensitization is an important toxicological end-point in the risk assessment of chemical allergens. Because of the complexity of the biological mechanisms associated with skin sensitization, integrated approaches combining different chemical, biological and in silico methods are recommended to replace conventional animal tests. Chemical methods are intended to characterize the potential of a sensitizer to induce earlier molecular initiating events. The presence of an electrophilic mechanistic domain is considered one of the essential chemical features to covalently bind to the biological target and induce further haptenation processes. Current in chemico assays rely on the quantification of unreacted model nucleophiles aftermore » incubation with the candidate sensitizer. In the current study, a new fluorescence-based method, ‘HTS-DCYA assay’, is proposed. The assay aims at the identification of reactive electrophiles based on their chemical reactivity toward a model fluorescent thiol. The reaction workflow enabled the development of a High Throughput Screening (HTS) method to directly quantify the reaction adducts. The reaction conditions have been optimized to minimize solubility issues, oxidative side reactions and increase the throughput of the assay while minimizing the reaction time, which are common issues with existing methods. Thirty-six chemicals previously classified with LLNA, DPRA or KeratinoSens™ were tested as a proof of concept. Preliminary results gave an estimated 82% accuracy, 78% sensitivity, 90% specificity, comparable to other in chemico methods such as Cys-DPRA. In addition to validated chemicals, six natural products were analyzed and a prediction of their sensitization potential is presented for the first time. - Highlights: • A novel fluorescence-based method to detect electrophilic sensitizers is proposed. • A model fluorescent thiol was used to directly quantify the reaction products. • A discussion of the reaction workflow and critical parameters is presented. • The method could provide a useful tool to complement existing chemical assays.« less

A unique charge-coupled device/xenon arc lamp based imaging system for the accurate detection and quantitation of multicolour fluorescence.

PubMed

Spibey, C A; Jackson, P; Herick, K

2001-03-01

In recent years the use of fluorescent dyes in biological applications has dramatically increased. The continual improvement in the capabilities of these fluorescent dyes demands increasingly sensitive detection systems that provide accurate quantitation over a wide linear dynamic range. In the field of proteomics, the detection, quantitation and identification of very low abundance proteins are of extreme importance in understanding cellular processes. Therefore, the instrumentation used to acquire an image of such samples, for spot picking and identification by mass spectrometry, must be sensitive enough to be able, not only, to maximise the sensitivity and dynamic range of the staining dyes but, as importantly, adapt to the ever changing portfolio of fluorescent dyes as they become available. Just as the available fluorescent probes are improving and evolving so are the users application requirements. Therefore, the instrumentation chosen must be flexible to address and adapt to those changing needs. As a result, a highly competitive market for the supply and production of such dyes and the instrumentation for their detection and quantitation have emerged. The instrumentation currently available is based on either laser/photomultiplier tube (PMT) scanning or lamp/charge-coupled device (CCD) based mechanisms. This review briefly discusses the advantages and disadvantages of both System types for fluorescence imaging, gives a technical overview of CCD technology and describes in detail a unique xenon/are lamp CCD based instrument, from PerkinElmer Life Sciences. The Wallac-1442 ARTHUR is unique in its ability to scan both large areas at high resolution and give accurate selectable excitation over the whole of the UV/visible range. It operates by filtering both the excitation and emission wavelengths, providing optimal and accurate measurement and quantitation of virtually any available dye and allows excellent spectral resolution between different fluorophores. This flexibility and excitation accuracy is key to multicolour applications and future adaptation of the instrument to address the application requirements and newly emerging dyes.

Noninvasive Optical Tracking of Red Fluorescent Protein-Expressing Cancer Cells in a Model of Metastatic Breast Cancer 1*

PubMed Central

Winnard, Paul T; Kluth, Jessica B; Raman, Venu

2006-01-01

Abstract We have evaluated the use of the Xenogen IVIS 200 imaging system for real-time fluorescence protein-based optical imaging of metastatic progression in live animals. We found that green fluorescent protein-expressing cells (100 x 106) were not detectable in a mouse cadaver phantom experiment. However, a 10-fold lower number of tdTomato-expressing cells were easily detected. Mammary fat pad xenografts of stable MDA-MB-231-tdTomato cells were generated for the imaging of metastatic progression. At 2 weeks postinjection, barely palpable tumor burdens were easily detected at the sites of injection. At 8 weeks, a small contralateral mammary fat pad metastasis was imaged and, by 13 weeks, metastases to lymph nodes were detectable. Metastases with nodular composition were detectable within the rib cage region at 15 weeks. 3-D image reconstructions indicated that the detection of fluorescence extended to approximately 1 cm below the surface. A combination of intense tdTomato fluorescence, imaging at ≥ 620 nm (where autofluorescence is minimized), and the sensitivity of the Xenogen imager made this possible. This study demonstrates the utility of the noninvasive optical tracking of cancer cells during metastatic progression with endogenously expressed fluorescence protein reporters using detection wavelengths of ≥ 620 nm. PMID:17032496

Label-free and enzyme-free detection of transcription factors with graphene oxide fluorescence switch-based multifunctional G-quadruplex-hairpin probe.

PubMed

Zhu, Desong; Wang, Lei; Xu, Xiaowen; Jiang, Wei

2016-01-15

Transcription factors (TFs) play pivotal roles in the regulation of a variety of essential cellular processes and some of them have been recognized as potential diagnostic markers and therapeutic targets of some diseases. Sensitive and accurate detection of TFs is of great importance to better understanding their roles in gene regulation and evaluation of disease state. Here, we developed a simple, label-free and enzyme-free new fluorescent strategy for the detection of TFs by graphene oxide (GO) fluorescence switch-based multifunctional G-quadruplex-hairpin probe (MGHP). The MGHP possessed of three functions simultaneously, adsorbing onto GO with the loop part, binding to target with the stem part and serving as signal carrier with the terminal G-quadruplex. First, the MGHP was adsorbed quickly to GO. Next, the TF bound to the stem part of MGHP to form a huge target-MGHP complex, which led to desorption of the complex from GO. Finally, NMM was inserted into G-quadruplex in the complex to yield an enhanced fluorescence response. The GO used here, as a fluorescence switch, could quickly and efficiently quench the fluorescence of NMM inserted into the MGHP absorbed on the GO, guaranteeing a high signal-to-noise ratio. Sensitive detection of purified NF-κB p50 and HeLa cell nuclear extracts were achieved with detection limits of 0.2nM and 7.8ng/µL, respectively. Moreover, this proposed strategy could be used to screen inhibitors of NF-κB p50 activity. The strategy proposed here might offer a new potential approach for reliable quantification of TFs in clinical diagnostics and treatment research of some diseases. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel NBD-based fluorescent turn-on probe for the detection of cysteine and homocysteine in living cells

NASA Astrophysics Data System (ADS)

Wang, Jiamin; Niu, Linqiang; Huang, Jing; Yan, Zhijie; Wang, Jianhong

2018-03-01

Biothiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), are involved in a number of biological processes and play crucial roles in biological systems. Thus, the detection of biothiols is highly important for early diagnosis of diseases and evaluation of disease progression. Herein, we developed a new turn-on fluorescent probe 1 based on 7-nitro-2,1,3-benzoxadiazole (NBD) with high selectivity and sensitivity for Cys/Hcy on account of nucleophilic substitution and Smiles rearrangement reaction. The probe could sense Cys/Hcy rapidly, the intensity of fluorescence increased immediately within 1 min. Furthermore, the probe is low toxic and has been successfully applied to detect intracellular Cys/Hcy by cell fluorescence imaging in living normal and cancer cells.

Imaging Lysosomal pH Alteration in Stressed Cells with a Sensitive Ratiometric Fluorescence Sensor.

PubMed

Xue, Zhongwei; Zhao, Hu; Liu, Jian; Han, Jiahuai; Han, Shoufa

2017-03-24

The organelle-specific pH is crucial for cell homeostasis. Aberrant pH of lysosomes has been manifested in myriad diseases. To probe lysosome responses to cell stress, we herein report the detection of lysosomal pH changes with a dual colored probe (CM-ROX), featuring a coumarin domain with "always-on" blue fluorescence and a rhodamine-lactam domain activatable to lysosomal acidity to give red fluorescence. With sensitive ratiometric signals upon subtle pH changes, CM-ROX enables discernment of lysosomal pH changes in cells undergoing autophagy, cell death, and viral infection.

Automatic enhancement of skin fluorescence localization due to refractive index matching

NASA Astrophysics Data System (ADS)

Churmakov, Dmitry Y.; Meglinski, Igor V.; Piletsky, Sergey A.; Greenhalgh, Douglas A.

2004-07-01

Fluorescence diagnostic techniques are notable amongst many other optical methods, as they offer high sensitivity and non-invasive measurements of tissue properties. However, a combination of multiple scattering and physical heterogeneity of biological tissues hampers the interpretation of the fluorescence measurements. The analyses of the spatial distribution of endogenous and exogenous fluorophores excitations within tissues and their contribution to the detected signal localization are essential for many applications. We have developed a novel Monte Carlo technique that gives a graphical perception of how the excitation and fluorescence detected signal are localized in tissues. Our model takes into account spatial distribution of fluorophores and their quantum yields. We demonstrate that matching of the refractive indices of ambient medium and topical skin layer improves spatial localization of the detected fluorescence signal within the tissue. This result is consistent with the recent conclusion that administering biocompatible agents results in higher image contrast.

A new FRET ratiometric fluorescent chemosensor for Hg2+ and its application in living EC 109 cells

NASA Astrophysics Data System (ADS)

Song, Jianhua; Huai, Manxiu; Wang, Cuicui; Xu, Zhanhui; Zhao, Yufen; Ye, Yong

2015-03-01

On the basis of fluorescent resonance energy transfer, a new fluorophore dyad (L) bearing rhodamine B and naphthalimide was developed as fluorescent ratiometric chemosensor for Hg2+ in aqueous solution. L exhibited high selectivity and excellent sensitivity towards Hg2+ with a broad pH span (1.0-8.0) and the detection limit of L was 2.11 × 10-8 M. Sensor L for the detection of Hg2+ was rapid and the recognizing event could complete in 2.5 min. A significant change in the color could be used for naked-eye detection. The selective fluorescence response of L to Hg2+ is due to the Hg2+-promoted ring opening of spirolactam of rhodamine moiety, leading to a cyclization reaction of thiourea moiety. In addition, fluorescence imaging experiments of Hg2+ in living EC 109 cells demonstrated its value of practical applications in biological systems.

Multimodal Sensing Strategy Using pH Dependent Fluorescence Switchable System

NASA Astrophysics Data System (ADS)

Muthurasu, A.; Ganesh, V.

2016-12-01

Biomolecules assisted preparation of fluorescent gold nanoparticles (FL-Au NPs) has been reported in this work using glucose oxidase enzyme as both reducing and stabilizing agent and demonstrated their application through multimodal sensing strategy for selective detection of cysteine (Cys). Three different methods namely fluorescence turn OFF-ON strategy, naked eye detection and electrochemical methods are used for Cys detection by employing FL-Au NPs as a common probe. In case of fluorescence turn-OFF method a strong interaction between Au NPs and thiol results in quenching of fluorescence due to replacement of glucose oxidase by Cys at neutral pH. Second mode is based on fluorescence switch-ON strategy where initial fluorescence is significantly quenched by either excess acid or base and further addition of Cys results in appearance of rosy-red and green fluorescence respectively. Visual colour change and fluorescence emission arises due to etching of Au atoms on the surface by thiol leading to formation of Au nanoclusters. Finally, electrochemical sensing of Cys is also carried out using cyclic voltammetry in 0.1 M PBS solution. These findings provide a suitable platform for Cys detection over a wide range of pH and concentration levels and hence the sensitivity can also be tuned accordingly.

Development and application of a fluorescence protein microarray for detecting serum alpha-fetoprotein in patients with hepatocellular carcinoma.

PubMed

Zhang, Aiying; Yin, Chengzeng; Wang, Zhenshun; Zhang, Yonghong; Zhao, Yuanshun; Li, Ang; Sun, Huanqin; Lin, Dongdong; Li, Ning

2016-12-01

Objective To develop a simple, effective, time-saving and low-cost fluorescence protein microarray method for detecting serum alpha-fetoprotein (AFP) in patients with hepatocellular carcinoma (HCC). Method Non-contact piezoelectric print techniques were applied to fluorescence protein microarray to reduce the cost of prey antibody. Serum samples from patients with HCC and healthy control subjects were collected and evaluated for the presence of AFP using a novel fluorescence protein microarray. To validate the fluorescence protein microarray, serum samples were tested for AFP using an enzyme-linked immunosorbent assay (ELISA). Results A total of 110 serum samples from patients with HCC ( n = 65) and healthy control subjects ( n = 45) were analysed. When the AFP cut-off value was set at 20 ng/ml, the fluorescence protein microarray had a sensitivity of 91.67% and a specificity of 93.24% for detecting serum AFP. Serum AFP quantified via fluorescence protein microarray had a similar diagnostic performance compared with ELISA in distinguishing patients with HCC from healthy control subjects (area under receiver operating characteristic curve: 0.906 for fluorescence protein microarray; 0.880 for ELISA). Conclusion A fluorescence protein microarray method was developed for detecting serum AFP in patients with HCC.

Development and application of a fluorescence protein microarray for detecting serum alpha-fetoprotein in patients with hepatocellular carcinoma

PubMed Central

Zhang, Aiying; Yin, Chengzeng; Wang, Zhenshun; Zhang, Yonghong; Zhao, Yuanshun; Li, Ang; Sun, Huanqin; Lin, Dongdong

2016-01-01

Objective To develop a simple, effective, time-saving and low-cost fluorescence protein microarray method for detecting serum alpha-fetoprotein (AFP) in patients with hepatocellular carcinoma (HCC). Method Non-contact piezoelectric print techniques were applied to fluorescence protein microarray to reduce the cost of prey antibody. Serum samples from patients with HCC and healthy control subjects were collected and evaluated for the presence of AFP using a novel fluorescence protein microarray. To validate the fluorescence protein microarray, serum samples were tested for AFP using an enzyme-linked immunosorbent assay (ELISA). Results A total of 110 serum samples from patients with HCC (n = 65) and healthy control subjects (n = 45) were analysed. When the AFP cut-off value was set at 20 ng/ml, the fluorescence protein microarray had a sensitivity of 91.67% and a specificity of 93.24% for detecting serum AFP. Serum AFP quantified via fluorescence protein microarray had a similar diagnostic performance compared with ELISA in distinguishing patients with HCC from healthy control subjects (area under receiver operating characteristic curve: 0.906 for fluorescence protein microarray; 0.880 for ELISA). Conclusion A fluorescence protein microarray method was developed for detecting serum AFP in patients with HCC. PMID:27885040

Fluorescent probes sensitive to changes in the cholesterol-to-phospholipids molar ratio in human platelet membranes during atherosclerosis

NASA Astrophysics Data System (ADS)

Posokhov, Yevgen

2016-09-01

Environment-sensitive fluorescent probes were used for the spectroscopic visualization of pathological changes in human platelet membranes during cerebral atherosclerosis. It has been estimated that the ratiometric probes 2-(2‧-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole and 2-phenyl-phenanthr[9,10]oxazole can detect changes in the cholesterol-to-phospholipids molar ratio in human platelet membranes during the disease.

Polyethylenimine-coated Fe3O4 nanoparticles effectively quench fluorescent DNA, which can be developed as a novel platform for protein detection.

PubMed

Ma, Long; Sun, Nana; Zhang, Jinyan; Tu, Chunhao; Cao, Xiuqi; Duan, Demin; Diao, Aipo; Man, Shuli

2017-11-23

We report a novel assembly of polyethyleneimine (PEI)-coated Fe 3 O 4 nanoparticles (NPs) with single-stranded DNA (ssDNA), and the fluorescence of the dye labeled in the DNA is remarkably quenched. In the presence of a target protein, the protein-DNA aptamer mutual interaction releases the ssDNA from this assembly and hence restores the fluorescence. This feature could be adopted to develop an aptasensor for protein detection. As a proof-of-concept, for the first time, we have used this proposed sensing strategy to detect thrombin selectively and sensitively. Furthermore, simultaneous multiple detection of thrombin and lysozyme in a complex protein mixture has been proven to be possible.

Fluoride sensing by catechol-based π-electron systems.

PubMed

An, Byeong-Kwan; Wang, Xin; Burn, Paul L; Meredith, Paul

2010-11-15

We have developed new catechol-based sensors that can detect fluoride via fluorescence or optical absorption even in the presence of other halides. The level and sensitivity of detection of the sensing molecules is dependent on the chromophore length, which is controlled by the number of thiophene units (one to three) within the chromophore. The sensor with three thiophene units, (E)-2-(2,2'-terthiophen-5-yl)-3-(3,4-dihydroxyphenyl)acrylonitrile, gives the best response to fluoride. By using fluorescence measurements fluoride is detectable over the concentration range 1.7 μM to 200 μM. Importantly, when adsorbed onto a solid support the fluorescent catechol dye can be used to detect the presence of fluoride in aqueous solution.

Ultrasensitive detection of lead (II) based on fluorescent aptamer-functionalized carbon nanotubes.

PubMed

Taghdisi, Seyed Mohammad; Emrani, Somayeh Sarreshtehdar; Tabrizian, Kaveh; Ramezani, Mohammad; Abnous, Khalil; Emrani, Ahmad Sarreshtehdar

2014-05-01

Lead contamination is a serious environmental problem with toxic effects in human. Here, we developed a simple and sensitive sensing method employing ATTO 647N/aptamer-SWNT ensemble for detection of Pb(2+). This method is based on the super quenching capability of single-walled carbon nanotubes (SWNTs), high affinity of the aptamer toward Pb(2+) and different propensities of ATTO 647N-aptamer and ATTO 647N-aptamer/Pb(2+) complex for adsorption on SWNTs. In the absence of Pb(2+), the fluorescence of ATTO 647N-aptamer is efficiently quenched by SWNTs. Upon addition of Pb(2+), the aptamer binds to its target, leading to the formation of a G-quadruplex/Pb(2+) complex and does not interact with SWNTs and ATTO 647N-aptamer starts fluorescing. This sensor exhibited a high selectivity toward Pb(2+) and a limit of detection (LOD) as low as 0.42 nM was obtained. Also this sensor could be applied for detection of Pb(2+) ions in tap water and biological sample like serum with high sensitivity. Copyright © 2014 Elsevier B.V. All rights reserved.

Selective and Sensitive Detection of Heavy Metal Ions in 100% Aqueous Solution and Cells with a Fluorescence Chemosensor Based on Peptide Using Aggregation-Induced Emission.

PubMed

Neupane, Lok Nath; Oh, Eun-Taex; Park, Heon Joo; Lee, Keun-Hyeung

2016-03-15

A fluorescent peptidyl chemosensor for the detection of heavy metal ions in aqueous solution as well as in cells was synthesized on the basis of the peptide receptor for the metal ions using an aggregation-induced emission fluorophore. The peptidyl chemosensor (1) bearing tetraphenylethylene fluorophore showed an exclusively selective turn-on response to Hg(2+) among 16 metal ions in aqueous buffered solution containing NaCl. The peptidyl chemosensor complexed Hg(2+) ions and then aggregated in aqueous buffered solution, resulting in the significant enhancement (OFF-On) of emissions at around 470 nm. The fluorescent sensor showed a highly sensitive response to Hg(2+), and about 1.0 equiv of Hg(2+) was enough for the saturation of the emission intensity change. The detection limit (5.3 nM, R(2) = 0.99) of 1 for Hg(2+) ions was lower than the maximum allowable level of Hg(2+) in drinking water by EPA. Moreover, the peptidyl chemosensor penetrated live cells and detected intracellular Hg(2+) ions by the turn-on response.

Fluorescent sensing with Fresnel microlenses for optofluidic systems

NASA Astrophysics Data System (ADS)

Siudzińska, Anna; Miszczuk, Andrzej; Marczak, Jacek; Komorowska, Katarzyna

2017-05-01

The concept of fluorescent sensing in a microchannel equipped with focusing light Fresnel lenses has been demonstrated. The concept employs a line or array of Fresnel lenses generating a line or array of focused light spots within a microfluidic channel, to increase the sensitivity of fluorescent signal detection in the system. We have presented efficient methods of master mold fabrication based on the lithography method and focused ion beam milling. The flexible microchannel was fabricated by an imprint process with new thiolene-epoxy resin with a good ability to replicate even submicron-size features. For final imprinted lenses, the measured background to peak signal level shows more than nine times the increase in brightness at the center of the focal spot for the green part of the spectrum (532 nm). The effectiveness of the microlenses in fluorescent-marked Escherichia coli bacteria was confirmed in a basic fluoroscope experiment, showing the increase of the sensitivity of the detection by the order of magnitude.

A fast-response two-photon fluorescent probe for imaging endogenous H2O2 in living cells and tissues

NASA Astrophysics Data System (ADS)

Lu, Yanan; Shi, Xiaomin; Fan, Wenlong; Black, Cory A.; Lu, Zhengliang; Fan, Chunhua

2018-02-01

As a second messenger, hydrogen peroxide plays significant roles in numerous physiological and pathological processes and is related to various diseases including inflammatory disease, diabetes, neurodegenerative disorders, cardiovascular disease and Alzheimer's disease. Two-photon (TP) fluorescent probes reported for the detection of endogenous H2O2 are rare and most have drawbacks such as slow response and low sensitivity. In this report, we demonstrate a simple H2O2-specific TP fluorescent probe (TX-HP) containing a two-photon dye 6-hydroxy-2,3,4,4a-tetrahydro-1H-xanthen-1-one (TX) on the modulation of the ICT process. The probe exhibits a rapid fluorescent response to H2O2 in 9 min with both high sensitivity and selectivity. The probe can detect exogenous H2O2 in living cells. Furthermore, the probe is successfully utilized for imaging H2O2 in liver tissues.

Multicoloured fluorescent indicators for live-cell and in vivo imaging of inorganic mercury dynamics.

PubMed

Tao, Rongkun; Shi, Mei; Zou, Yejun; Cheng, Di; Wang, Qiaohui; Liu, Renmei; Wang, Aoxue; Zhu, Jiahuan; Deng, Lei; Hu, Hanyang; Chen, Xianjun; Du, Jiulin; Zhu, Weiping; Zhao, Yuzheng; Yang, Yi

2018-06-01

Engineered fluorescent indicators for visualizing mercury ion (Hg 2+ ) are powerful tools to illustrate the intracellular distribution and serious toxicity of the ion. However, the sensitive and specific detection of Hg 2+ in living cells and in vivo is challenging. This paper reported the development of fluorescent indicators for Hg 2+ in green or red color by inserting a circularly permuted fluorescent protein into a highly mercury-specific repressor. These sensors provided a rapid, sensitive, specific, and real-time read-out of Hg 2+ dynamics in solutions, bacteria, subcellular organelles of mammalian cells, and zebrafish, thereby providing a useful new method for Hg 2+ detection and bioimaging. In conjunction with the hydrogen peroxide sensor HyPer, we found mercury uptake would trigger subcellular oxidative events at the single-cell level, and provided visual evidence of the causality of mercury and oxidative damage. These sensors would paint the landscape of mercury toxicity to cell functions. Copyright © 2018 Elsevier Inc. All rights reserved.

Fluorescent Polymer Incorporating Triazolyl Coumarin Units for Cu2+ Detection via Planarization of Ict-Based Fluorophore

PubMed Central

Ngororabanga, Jean Marie Vianney; Du Plessis, Jacolien; Mama, Neliswa

2017-01-01

A novel fluorescent polymer with pendant triazolyl coumarin units was synthesized through radical polymerization. The polymer showed reasonable sensitivity and selectivity towards Cu2+ in acetonitrile in comparison to other tested metal ions with a significant quenching effect on fluorescence and blue shifting in the range of 20 nm. The blue shift was assigned to the conformation changes of the diethylamino group from the coumarin moiety which led to planarization of the triazolyl coumarin units. The possible binding modes for Cu2+ towards the polymer were determined through the comparison of the emission responses of the polymer, starting vinyl monomer and reference compound, and the triazole ring was identified as one of the possible binding sites for Cu2+. The detection limits of the polymer and vinyl monomer towards Cu2+ were determined from fluorescence titration experiments and a higher sensitivity (35 times) was observed for the polymer compared with its starting monomer. PMID:28867764

Fluorescent Polymer Incorporating Triazolyl Coumarin Units for Cu2+ Detection via Planarization of Ict-Based Fluorophore.

PubMed

Ngororabanga, Jean Marie Vianney; Du Plessis, Jacolien; Mama, Neliswa

2017-08-30

A novel fluorescent polymer with pendant triazolyl coumarin units was synthesized through radical polymerization. The polymer showed reasonable sensitivity and selectivity towards Cu 2+ in acetonitrile in comparison to other tested metal ions with a significant quenching effect on fluorescence and blue shifting in the range of 20 nm. The blue shift was assigned to the conformation changes of the diethylamino group from the coumarin moiety which led to planarization of the triazolyl coumarin units. The possible binding modes for Cu 2+ towards the polymer were determined through the comparison of the emission responses of the polymer, starting vinyl monomer and reference compound, and the triazole ring was identified as one of the possible binding sites for Cu 2+ . The detection limits of the polymer and vinyl monomer towards Cu 2+ were determined from fluorescence titration experiments and a higher sensitivity (35 times) was observed for the polymer compared with its starting monomer.

Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics.

PubMed

Davis, Caitlin M; Reddish, Michael J; Dyer, R Brian

2017-05-05

Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of <0.2mOD and a fluorescence sensitivity of 2% of the overall fluorescence intensity. Using a computer controlled QCL to rapidly tune the IR frequency it is possible to create a T-jump induced difference spectrum from 50ns to 0.5ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics. Copyright © 2017 Elsevier B.V. All rights reserved.

Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics

NASA Astrophysics Data System (ADS)

Davis, Caitlin M.; Reddish, Michael J.; Dyer, R. Brian

2017-05-01

Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of < 0.2 mOD and a fluorescence sensitivity of 2% of the overall fluorescence intensity. Using a computer controlled QCL to rapidly tune the IR frequency it is possible to create a T-jump induced difference spectrum from 50 ns to 0.5 ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics.

Rapid and reliable diagnostic method to detect Zika virus by real-time fluorescence reverse transcription loop-mediated isothermal amplification.

PubMed

Guo, Xu-Guang; Zhou, Yong-Zhuo; Li, Qin; Wang, Wei; Wen, Jin-Zhou; Zheng, Lei; Wang, Qian

2018-04-18

To detect Zika virus more rapidly and accurately, we developed a novel method that utilized a real-time fluorescence reverse transcription loop-mediated isothermal amplification (LAMP) technique. The NS5 gene was amplified by a set of six specific primers that recognized six distinct sequences. The amplification process, including 60 min of thermostatic reaction with Bst DNA polymerase following real-time fluorescence reverse transcriptase using genomic Zika virus standard strain (MR766), was conducted through fluorescent signaling. Among the six pairs of primers that we designate here, NS5 was the most efficient with a high sensitivity of up to 3.3 ng/μl and reproducible specificity on eight pathogen samples that were used as negative controls. The real-time fluorescence reverse transcription LAMP detection process can be completed within 35 min. Our study demonstrated that real-time fluorescence reverse transcription LAMP could be highly beneficial and convenient clinical application to detect Zika virus due to its high specificity and stability.

Spinach RNA aptamer detects lead (II) with high selectivity†

PubMed Central

DasGupta, Saurja; Shelke, Sandip A.; Li, Nan-sheng

2015-01-01

Spinach RNA aptamer contains a G-quadruplex motif that serves as a platform for binding and fluorescence activation of a GFP-like fluorophore. Here we show that Pb2+ induces formation of Spinach’s G-quadruplex and activates fluorescence with high selectivity and sensitivity. This device establishes the first example of an RNA-based sensor that provides a simple and inexpensive tool for Pb2+ detection. PMID:25940073

A two-step lyssavirus real-time polymerase chain reaction using degenerate primers with superior sensitivity to the fluorescent antigen test.

PubMed

Suin, Vanessa; Nazé, Florence; Francart, Aurélie; Lamoral, Sophie; De Craeye, Stéphane; Kalai, Michael; Van Gucht, Steven

2014-01-01

A generic two-step lyssavirus real-time reverse transcriptase polymerase chain reaction (qRT-PCR), based on a nested PCR strategy, was validated for the detection of different lyssavirus species. Primers with 17 to 30% of degenerate bases were used in both consecutive steps. The assay could accurately detect RABV, LBV, MOKV, DUVV, EBLV-1, EBLV-2, and ABLV. In silico sequence alignment showed a functional match with the remaining lyssavirus species. The diagnostic specificity was 100% and the sensitivity proved to be superior to that of the fluorescent antigen test. The limit of detection was ≤ 1 50% tissue culture infectious dose. The related vesicular stomatitis virus was not recognized, confirming the selectivity for lyssaviruses. The assay was applied to follow the evolution of rabies virus infection in the brain of mice from 0 to 10 days after intranasal inoculation. The obtained RNA curve corresponded well with the curves obtained by a one-step monospecific RABV-qRT-PCR, the fluorescent antigen test, and virus titration. Despite the presence of degenerate bases, the assay proved to be highly sensitive, specific, and reproducible.

A Two-Step Lyssavirus Real-Time Polymerase Chain Reaction Using Degenerate Primers with Superior Sensitivity to the Fluorescent Antigen Test

PubMed Central

Nazé, Florence; Francart, Aurélie; Lamoral, Sophie; De Craeye, Stéphane; Kalai, Michael

2014-01-01

A generic two-step lyssavirus real-time reverse transcriptase polymerase chain reaction (qRT-PCR), based on a nested PCR strategy, was validated for the detection of different lyssavirus species. Primers with 17 to 30% of degenerate bases were used in both consecutive steps. The assay could accurately detect RABV, LBV, MOKV, DUVV, EBLV-1, EBLV-2, and ABLV. In silico sequence alignment showed a functional match with the remaining lyssavirus species. The diagnostic specificity was 100% and the sensitivity proved to be superior to that of the fluorescent antigen test. The limit of detection was ≤1 50% tissue culture infectious dose. The related vesicular stomatitis virus was not recognized, confirming the selectivity for lyssaviruses. The assay was applied to follow the evolution of rabies virus infection in the brain of mice from 0 to 10 days after intranasal inoculation. The obtained RNA curve corresponded well with the curves obtained by a one-step monospecific RABV-qRT-PCR, the fluorescent antigen test, and virus titration. Despite the presence of degenerate bases, the assay proved to be highly sensitive, specific, and reproducible. PMID:24822188

Nitrogen and Phosphorus Co-Doped Carbon Nanodots as a Novel Fluorescent Probe for Highly Sensitive Detection of Fe(3+) in Human Serum and Living Cells.

PubMed

Shi, Bingfang; Su, Yubin; Zhang, Liangliang; Huang, Mengjiao; Liu, Rongjun; Zhao, Shulin

2016-05-04

Chemical doping with heteroatoms can effectively modulate physicochemical and photochemical properties of carbon dots (CDs). However, the development of multi heteroatoms codoped carbon nanodots is still in its early stage. In this work, a facile hydrothermal synthesis strategy was applied to synthesize multi heteroatoms (nitrogen and phosphorus) codoped carbon nanodots (N,P-CDs) using glucose as carbon source, and ammonia, phosphoric acid as dopant, respectively. Compared with CDs, the multi heteroatoms doped CDs resulted in dramatic improvement in the electronic characteristics and surface chemical activities. Therefore, the N,P-CDs prepared as described above exhibited a strong blue emission and a sensitive response to Fe(3+). The N,P-CDs based fluorescent sensor was then applied to sensitively determine Fe(3+) with a detection limit of 1.8 nM. Notably, the prepared N,P-CDs possessed negligible cytotoxicity, excellent biocompatibility, and high photostability. It was also applied for label-free detection of Fe(3+) in complex biological samples and the fluorescence imaging of intracellular Fe(3+), which indicated its potential applications in clinical diagnosis and other biologically related study.

Determination of aristolochic acids by high-performance liquid chromatography with fluorescence detection.

PubMed

Wang, Yinan; Chan, Wan

2014-06-25

Nephrotoxic and carcinogenic aristolochic acids (AAs) are naturally occurring nitrophenanthrene carboxylic acids in the herbal genus Aristolochia. The misuse of AA-containing herbs in preparing slimming drugs has caused hundred of cases of kidney disease in Belgium women in a slimming regime in the early 1990s. Accumulating evidence also suggested that prolong dietary intake of AA-contaminated food is one of the major causes to the Balkan endemic nephropathy that was first observed in the late 1950s. Therefore, analytical methods of high sensitivity are extremely important for safeguarding human exposure to AA-containing herbal medicines, herbal remedies, and food composites. In this paper, we describe the development of a new high-performance liquid chromatography coupled fluorescence detector (HPLC-FLD) method for the sensitive determination of AAs. The method makes use of a novel cysteine-induced denitration reaction that "turns on" the fluorescence of AAs for fluorometric detections. Our results showed that the combination of cysteine-induced denitration and HPLC-FLD analysis allows for sensitive quantification of AA-I and AA-II at detection limits of 27.1 and 25.4 ng/g, respectively. The method was validated and has been successfully applied in quantifying AAs in Chinese herbal medicines.

A highly selective and sensitive fluorescent chemosensor and its application for rapid on-site detection of Al3 +

NASA Astrophysics Data System (ADS)

Yue, Xiao-li; Wang, Zhao-qing; Li, Chao-rui; Yang, Zheng-yin

2018-03-01

In this paper, a simple naphthalene-based derivative (HL) has been designed and synthesized as a Al3 +-selective fluorescent chemosensor based on the PET mechanism. HL exhibited high selectivity and sensitivity towards Al3 + over other commonly coexisting metal ions in ethanol with a detection limit of 2.72 nM. The 1:1 binding stoichiometry of the complex (HL-Al3 +) was determined from the Job's plot based on fluorescence titrations and the ESI-MS spectrum data. Moreover, the binding site of HL with Al3 + was assured by the 1H NMR titration experiment. The binding constant (Ka) of the complex (HL-Al3 +) was calculated to be 5.06 × 104 M- 1 according to the Benesi-Hildebrand equation. In addition, the recognizing process of HL towards Al3 + was chemically reversible by adding Na2EDTA. Importantly, HL could directly and rapidly detect aluminum ion through the filter paper without resorting to additional instrumental analysis.

Highly selective and sensitive macrocycle-based dinuclear foldamer for fluorometric and colorimetric sensing of citrate in water.

PubMed

Rhaman, Md Mhahabubur; Hasan, Mohammad H; Alamgir, Azmain; Xu, Lihua; Powell, Douglas R; Wong, Bryan M; Tandon, Ritesh; Hossain, Md Alamgir

2018-01-10

The selective detection of citrate anions is essential for various biological functions in living systems. A quantitative assessment of citrate is required for the diagnosis of various diseases in the human body; however, it is extremely challenging to develop efficient fluorescence and color-detecting molecular probes for sensing citrate in water. Herein, we report a macrocycle-based dinuclear foldamer (1) assembled with eosin Y (EY) that has been studied for anion binding by fluorescence and colorimetric techniques in water at neutral pH. Results from the fluorescence titrations reveal that the 1·EY ensemble strongly binds citrate anions, showing remarkable selectivity over a wide range of inorganic and carboxylate anions. The addition of citrate anions to the 1·EY adduct led to a large fluorescence enhancement, displaying a detectable color change under both visible and UV light in water up to 2 μmol. The biocompatibility of 1·EY as an intracellular carrier in a biological system was evaluated on primary human foreskin fibroblast (HF) cells, showing an excellent cell viability. The strong binding properties of the ensemble allow it to be used as a highly sensitive, detective probe for biologically relevant citrate anions in various applications.

A novel magneto-DNA duplex probe for bacterial DNA detection based on exonuclease III-aided cycling amplification.

PubMed

Zeng, Yan; Wan, Yi; Zhang, Dun; Qi, Peng

2015-01-01

A novel magneto-DNA duplex probe for bacterial DNA detection based on exonuclease III (Exo-III) aided cycling amplification has been developed. This magneto-DNA duplex probe contains a partly hybrid fluorophore-modified capture probe and a fluorophore-modified signal probe with magnetic microparticle as carrier. In the presence of a perfectly matched target bacterial DNA, blunt 3'-terminus of the capture probe is formed, activating the Exo-III aided cycling amplification. Thus, Exo-III catalyzes the stepwise removal of mononucleotides from this terminus, releasing both fluorophore-modified signal probe, fluorescent dyes of the capture probe and target DNA. The released target DNA then starts a new cycle, while released fluorescent fragments are recovered with magnetic separation for fluorescence signal collection. This system exhibited sensitive detection of bacterial DNA, with a detection limit of 14 pM because of the unique cleavage function of Exo-III, high fluorescence intensity, and separating function of magneto-DNA duplex probes. Besides this sensitivity, this strategy exhibited excellent selectivity with mismatched bacterial DNA targets and other bacterial species targets and good applicability in real seawater samples, hence, this strategy could be potentially used for qualitative and quantitative analysis of bacteria. Copyright © 2014 Elsevier B.V. All rights reserved.

Sensitive determination of sulfonamides in environmental water by capillary electrophoresis coupled with both silvering detection window and in-capillary optical fiber light-emitting diode-induced fluorescence detector.

PubMed

Ji, Hongyun; Wu, Yu; Duan, Zhijuan; Yang, Feng; Yuan, Hongyan; Xiao, Dan

2017-02-01

A new detector, silvering detection window and in-capillary optical fiber light-emitting diode-induced fluorescence detector (SDW-ICOF-LED-IFD), is introduced for capillary electrophoresis (CE). The strategy of the work was that half surface of the detection window was coated with silver mirror, which could reflect the undetected fluorescence to the photomultiplier tube to be detected, consequently enhancing the detection sensitivity. Sulfonamides (SAs) are important antibiotics that achieved great applications in many fields. However, they pose a serious threat on the environment and human health when they enter into the environment. The SDW-ICOF-LED-IFD-CE system was used to determine fluorescein isothiocyanate (FITC)-labeled sulfadoxine (SDM), sulfaguanidine (SGD) and sulfamonomethoxine sodium (SMM-Na) in environmental water. The detection results obtained by the SDW-ICOF-LED-IFD-CE system were compared to those acquired by the CE with in-capillary optical fiber light-emitting diode-induced fluorescence detection (ICOF-LED-IFD-CE). The limits of detection (LODs) of SDW-ICOF-LED-IFD-CE and ICOF-LED-IFD-CE were 1.0-2.0 nM and 2.5-7.7 nM (S/N = 3), respectively. The intraday (n = 6) and interday (n = 6) precision of migration time and corresponding peak area for both types of CE were all less than 0.86% and 3.68%, respectively. The accuracy of the proposed method was judged by employing standard addition method, and recoveries obtained were in the range of 92.5-102.9%. The results indicated that the sensitivity of the SDW-ICOF-LED-IFD-CE system was improved, and that its reproducibility and accuracy were satisfactory. It was successfully applied to analyze SAs in environmental water. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorescent "on-off-on" switching sensor based on CdTe quantum dots coupled with multiwalled carbon nanotubes@graphene oxide nanoribbons for simultaneous monitoring of dual foreign DNAs in transgenic soybean.

PubMed

Li, Yaqi; Sun, Li; Qian, Jing; Long, Lingliang; Li, Henan; Liu, Qian; Cai, Jianrong; Wang, Kun

2017-06-15

With the increasing concern of potential health and environmental risk, it is essential to develop reliable methods for transgenic soybean detection. Herein, a simple, sensitive and selective assay was constructed based on homogeneous fluorescence resonance energy transfer (FRET) between CdTe quantum dots (QDs) and multiwalled carbon nanotubes@graphene oxide nanoribbons (MWCNTs@GONRs) to form the fluorescent "on-off-on" switching for simultaneous monitoring dual target DNAs of promoter cauliflower mosaic virus 35s (P35s) and terminator nopaline synthase (TNOS) from transgenic soybean. The capture DNAs were immobilized with corresponding QDs to obtain strong fluorescent signals (turning on). The strong π-π stacking interaction between single-stranded DNA (ssDNA) probes and MWCNTs@GONRs led to minimal background fluorescence due to the FRET process (turning off). The targets of P35s and TNOS were recognized by dual fluorescent probes to form double-stranded DNA (dsDNA) through the specific hybridization between target DNAs and ssDNA probes. And the dsDNA were released from the surface of MWCNTs@GONRs, which leaded the dual fluorescent probes to generate the strong fluorescent emissions (turning on). Therefore, this proposed homogeneous assay can be achieved to detect P35s and TNOS simultaneously by monitoring the relevant fluorescent emissions. Moreover, this assay can distinguish complementary and mismatched nucleic acid sequences with high sensitivity. The constructed approach has the potential to be a tool for daily detection of genetically modified organism with the merits of feasibility and reliability. Copyright © 2017 Elsevier B.V. All rights reserved.

First-in-human intraoperative near-infrared fluorescence imaging of glioblastoma using cetuximab-IRDye800.

PubMed

Miller, Sarah E; Tummers, Willemieke S; Teraphongphom, Nutte; van den Berg, Nynke S; Hasan, Alifia; Ertsey, Robert D; Nagpal, Seema; Recht, Lawrence D; Plowey, Edward D; Vogel, Hannes; Harsh, Griffith R; Grant, Gerald A; Li, Gordon H; Rosenthal, Eben L

2018-04-06

Maximizing extent of surgical resection with the least morbidity remains critical for survival in glioblastoma patients, and we hypothesize that it can be improved by enhancements in intraoperative tumor detection. In a clinical study, we determined if therapeutic antibodies could be repurposed for intraoperative imaging during resection. Fluorescently labeled cetuximab-IRDye800 was systemically administered to three patients 2 days prior to surgery. Near-infrared fluorescence imaging of tumor and histologically negative peri-tumoral tissue was performed intraoperatively and ex vivo. Fluorescence was measured as mean fluorescence intensity (MFI), and tumor-to-background ratios (TBRs) were calculated by comparing MFIs of tumor and histologically uninvolved tissue. The mean TBR was significantly higher in tumor tissue of contrast-enhancing (CE) tumors on preoperative imaging (4.0 ± 0.5) compared to non-CE tumors (1.2 ± 0.3; p = 0.02). The TBR was higher at a 100 mg dose than at 50 mg (4.3 vs. 3.6). The smallest detectable tumor volume in a closed-field setting was 70 mg with 50 mg of dye and 10 mg with 100 mg. On sections of paraffin embedded tissues, fluorescence positively correlated with histological evidence of tumor. Sensitivity and specificity of tumor fluorescence for viable tumor detection was calculated and fluorescence was found to be highly sensitive (73.0% for 50 mg dose, 98.2% for 100 mg dose) and specific (66.3% for 50 mg dose, 69.8% for 100 mg dose) for viable tumor tissue in CE tumors while normal peri-tumoral tissue showed minimal fluorescence. This first-in-human study demonstrates the feasibility and safety of antibody based imaging for CE glioblastomas.

Dual lanthanide-doped complexes: the development of a time-resolved ratiometric fluorescent probe for anthrax biomarker and a paper-based visual sensor.

PubMed

Wang, Qi-Xian; Xue, Shi-Fan; Chen, Zi-Han; Ma, Shi-Hui; Zhang, Shengqiang; Shi, Guoyue; Zhang, Min

2017-08-15

In this work, a novel time-resolved ratiometric fluorescent probe based on dual lanthanide (Tb: terbium, and Eu: europium)-doped complexes (Tb/DPA@SiO 2 -Eu/GMP) has been designed for detecting anthrax biomarker (dipicolinic acid, DPA), a unique and major component of anthrax spores. In such complexes-based probe, Tb/DPA@SiO 2 can serve as a stable reference signal with green fluorescence and Eu/GMP act as a sensitive response signal with red fluorescence for ratiometric fluorescent sensing DPA. Additionally, the probe exhibits long fluorescence lifetime, which can significantly reduce the autofluorescence interferences from biological samples by using time-resolved fluorescence measurement. More significantly, a paper-based visual sensor for DPA has been devised by using filter paper embedded with Tb/DPA@SiO 2 -Eu/GMP, and we have proved its utility for fluorescent detection of DPA, in which only a handheld UV lamp is used. In the presence of DPA, the paper-based visual sensor, illuminated by a handheld UV lamp, would result in an obvious fluorescence color change from green to red, which can be easily observed with naked eyes. The paper-based visual sensor is stable, portable, disposable, cost-effective and easy-to-use. The feasibility of using a smartphone with easy-to-access color-scanning APP as the detection platform for quantitative scanometric assays has been also demonstrated by coupled with our proposed paper-based visual sensor. This work unveils an effective method for accurate, sensitive and selective monitoring anthrax biomarker with backgroud-free and self-calibrating properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Increasing selectivity for TNT-based explosive detection by synchronous luminescence and derivative spectroscopy with quantum yields of selected aromatic amines.

PubMed

Sheaff, Chrystal N; Eastwood, Delyle; Wai, Chien M

2007-01-01

The detection of explosive material is at the forefront of current analytical problems. A detection method is desired that is not restricted to detecting only explosive materials, but is also capable of identifying the origin and type of explosive. It is essential that a detection method have the selectivity to distinguish among compounds in a mixture of explosives. The nitro compounds found in explosives have low fluorescent yields or are considered to be non-fluorescent; however, after reduction, the amino compounds exhibit relatively high fluorescence. We discuss how to increase selectivity of explosive detection using fluorescence; this includes synchronous luminescence and derivative spectroscopy with appropriate smoothing. By implementing synchronous luminescence and derivative spectroscopy, we were able to resolve the reduction products of one major TNT-based explosive compound, 2,4-diaminotoluene, and the reduction products of other minor TNT-based explosives in a mixture. We also report for the first time the quantum yields of these important compounds. Relative quantum yields are useful in establishing relative fluorescence intensities and are an important spectroscopic measurement of molecules. Our approach allows for rapid, sensitive, and selective detection with the discrimination necessary to distinguish among various explosives.

Designed Strategies for Fluorescence-Based Biosensors for the Detection of Mycotoxins

PubMed Central

Sharma, Atul; Khan, Reem; Catanante, Gaelle; Sherazi, Tauqir A.; Bhand, Sunil; Hayat, Akhtar; Marty, Jean Louis

2018-01-01

Small molecule toxins such as mycotoxins with low molecular weight are the most widely studied biological toxins. These biological toxins are responsible for food poisoning and have the potential to be used as biological warfare agents at the toxic dose. Due to the poisonous nature of mycotoxins, effective analysis techniques for quantifying their toxicity are indispensable. In this context, biosensors have been emerged as a powerful tool to monitors toxins at extremely low level. Recently, biosensors based on fluorescence detection have attained special interest with the incorporation of nanomaterials. This review paper will focus on the development of fluorescence-based biosensors for mycotoxin detection, with particular emphasis on their design as well as properties such as sensitivity and specificity. A number of these fluorescent biosensors have shown promising results in food samples for the detection of mycotoxins, suggesting their future potential for food applications. PMID:29751687

Highly selectively monitoring heavy and transition metal ions by a fluorescent sensor based on dipeptide.

PubMed

Neupane, Lok Nath; Thirupathi, Ponnaboina; Jang, Sujung; Jang, Min Jung; Kim, Jung Hwa; Lee, Keun-Hyeung

2011-09-15

Fluorescent sensor (DMH) based on dipeptide was efficiently synthesized in solid phase synthesis. The dipeptide sensor shows sensitive response to Ag(I), Hg(II), and Cu(II) among 14 metal ions in 100% aqueous solution. The fluorescent sensor differentiates three heavy metal ions by response type; turn on response to Ag(I), ratiometric response to Hg(II), and turn off detection of Cu(II). The detection limits of the sensor for Ag(I) and Cu(II) were much lower than the EPA's drinking water maximum contaminant levels (MCL). Specially, DMH penetrated live cells and detected intracellular Ag(+) by turn on response. We described the fluorescent change, binding affinity, detection limit for the metal ions. The study of a heavy metal-responsive sensor based on dipeptide demonstrates its potential utility in the environment field. Copyright © 2011 Elsevier B.V. All rights reserved.

Designed Strategies for Fluorescence-Based Biosensors for the Detection of Mycotoxins.

PubMed

Sharma, Atul; Khan, Reem; Catanante, Gaelle; Sherazi, Tauqir A; Bhand, Sunil; Hayat, Akhtar; Marty, Jean Louis

2018-05-11

Small molecule toxins such as mycotoxins with low molecular weight are the most widely studied biological toxins. These biological toxins are responsible for food poisoning and have the potential to be used as biological warfare agents at the toxic dose. Due to the poisonous nature of mycotoxins, effective analysis techniques for quantifying their toxicity are indispensable. In this context, biosensors have been emerged as a powerful tool to monitors toxins at extremely low level. Recently, biosensors based on fluorescence detection have attained special interest with the incorporation of nanomaterials. This review paper will focus on the development of fluorescence-based biosensors for mycotoxin detection, with particular emphasis on their design as well as properties such as sensitivity and specificity. A number of these fluorescent biosensors have shown promising results in food samples for the detection of mycotoxins, suggesting their future potential for food applications.

Fluorescent molecularly imprinted polymer based on Navicula sp. frustules for optical detection of lysozyme.

PubMed

Lim, Guat Wei; Lim, Jit Kang; Ahmad, Abdul Latif; Chan, Derek Juinn Chieh

2016-03-01

The direct correlation between disease and lysozyme (LYZ) levels in human body fluids makes the sensitive and convenient detection of LYZ the focus of scientific research. Fluorescent molecularly imprinted polymer has emerged as a new alternative for LYZ detection in order to resolve the limitation of immunoassays, which are expensive, unstable, require complex preparation, and are time consuming. In this study, a novel fluorescence molecularly imprinted polymer based on Navicula sp. frustules (FITC-MIP) has been synthesized via post-imprinting treatment for LYZ detection. Navicula sp. frustules were used as supported material because of their unique properties of moderate surface area, reproducibility, and biocompatibility, to address the drawbacks of nanoparticle core material with low adsorption capacity. The FITC acts as recognition signal and optical readout, whereas MIP provides LYZ selectivity. The synthesized FITC-MIP showed a response time as short as 5 min depending on the concentration of LYZ. It is found that the LYZ template can significantly quench the fluorescence intensity of FITC-MIP linearly within a concentration range of 0 to 0.025 mg mL(-1), which is well described by Stern-Volmer equation. The FITC-MIP can selectively and sensitively detect down to 0.0015 mg mL(-1) of LYZ concentration. The excellent sensing performance of FITC-MIP suggests that FITC-MIP is a potential biosensor in clinical diagnosis applications.

Fluorescent aptasensor for detection of four tetracycline veterinary drugs in milk based on catalytic hairpin assembly reaction and displacement of G-quadruplex.

PubMed

Zhou, Chen; Zou, Haimin; Sun, Chengjun; Ren, Dongxia; Xiong, Wei; Li, Yongxin

2018-05-01

Based on a novel signal amplification strategy by catalytic hairpin assembly and displacement of G-quadruplex DNA, an enzyme-free, non-label fluorescent aptasensing approach was established for sensitive detection of four tetracycline veterinary drugs in milk. The network consisted of a pair of partially complementary DNA hairpins (HP1 and HP2). The DNA aptamer of four tetracycline veterinary drugs was located at the sticky end of the HP1. The ring region of HP1 rich in G and C could form a stable G-quadruplex structure, which could emit specific fluorescence signal after binding with the fluorescent dye and N-methylmesoporphyrin IX (NMM). When presented in the system, the target analytes would be repeatedly used to trigger a recycling procedure between the hairpins, generating numerous HP1-HP2 duplex complexes and displacing G-quadruplex DNA. Thus, the sensitive detection of target analytes was achieved in a wide linear range (0-1000 μg/L) with the detection limit of 4.6 μg/L. Moreover, this proposed method showed high discrimination efficiency towards target analytes against other common mismatched veterinary drugs, and could be successfully applied to the analysis of milk samples. Graphical abstract Schematic of target analyte detection based on catalytic hairpin assembly reaction and displacement of G-quadruplex.

Determination of 2-alkylcyclobutanones by combining precolumn derivatization with 1-naphthalenyl hydrazine and ultra-performance liquid chromatography with fluorescence detection.

PubMed

Meng, Xiangpeng; Tong, Tong; Wang, Lianrong; Liu, Hanxia; Chan, Wan

2016-05-01

2-Alkylcyclobutanones (2-ACBs) are uniquely formed when triglycerides-containing food products are exposed to ionizing radiation. Thus, 2-ACBs have been used as marker molecules to identify irradiated food. Most methods to determine 2-ACBs involve mass spectrometric detection after chromatographic separation. The spectrofluorometer is rarely used to determine 2-ACBs because these molecules do not fluoresce. In this study, we developed an ultra-performance liquid chromatography (UPLC) method to determine 2-ACBs. 2-ACBs were converted into fluorophores after reacting with 1-naphthalenyl hydrazine to facilitate their sensitive and selective detection using a fluorescence detector (FLD). Analysis of 2-ACBs using our developed UPLC-FLD method allows sensitive determination of 2-ACBs at a detection limit of 2 ng 2-ACBs per g of fat (30 pg/injection), which is significantly lower than that of existing analytical methods. After validation for trueness and precision, the method was applied to γ-irradiated chicken samples to determine their 2-ACB content. Comparative studies employing liquid chromatography-tandem mass spectrometric method revealed no systematic difference between the two methods, thereby demonstrating that the proposed UPLC-FLD method can be suitably used to determine 2-ACBs in irradiated foodstuffs. Graphical Abstract Determination of radiation-induced food-borne 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone by combining 1-naphthalenyl hydrazine derivatization and ultra-performance liquid chromatography with fluorescence detection.

Fluorescent-Magnetic-Biotargeting Multifunctional Nanobioprobes for Detecting and Isolating Multiple Types of Tumor Cells

PubMed Central

Song, Er-Qun; Hu, Jun; Wen, Cong-Ying; Tian, Zhi-Quan; Yu, Xu; Zhang, Zhi-Ling; Shi, Yun-Bo; Pang, Dai-Wen

2011-01-01

Fluorescent-magnetic-biotargeting multifunctional nanobioprobes (FMBMNs) have attracted great attention in recent years due to their increasing, important applications in biomedical research, clinical diagnosis, and biomedicine. We have previously developed such nanobioprobes for the detection and isolation of a single kind of tumor cells. Detection and isolation of multiple tumor markers or tumor cells from complex samples sensitively and with high efficiency is critical for the early diagnosis of tumors, especially malignant tumors or cancers, which will improve clinical diagnosis outcomes and help to select effective treatment approaches. Here, we expanded the application of the monoclonal antibody (mAb)-coupled FMBMNs for multiplexed assays. Multiple types of cancer cells, such as leukemia cells and prostate cancer cells, were detected and collected from mixed samples within 25 minutes by using a magnet and an ordinary fluorescence microscope. The capture efficiencies of mAb-coupled FMBMNs for the above mentioned two types of cells were 96% and 97% respectively. Furthermore, by using the mAb-coupled FMBMNs, specific and sensitive detection and rapid separation of a small number of spiked leukemia cells and prostate cancer cells in a large population of cultured normal cells (about 0.01% were tumor cells) were achieved simply and inexpensively without any sample pretreatment before cell analysis. Therefore, mAb-coupled multicolour FMBMNs may be used for very sensitive detection and rapid isolation of multiple cancer cells in biomedical research and medical diagnostics. PMID:21250650

A catalytic and dual recycling amplification ATP sensor based on target-driven allosteric structure switching of aptamer beacons.

PubMed

Peng, Ying; Li, Daxiu; Yuan, Ruo; Xiang, Yun

2018-05-15

Abnormal concentrations of ATP are associated with many diseases and cancers, and quantitative detection of ATP is thus of great importance for disease diagnosis and prognosis. In the present work, we report a new dual recycling amplification sensor integrated with catalytic hairpin assembly (CHA) to achieve high sensitivity for fluorescent detection of ATP. The association of the target ATP with the aptamer beacons causes the allosteric structure switching of the aptamer beacons to expose the toehold regions, which hybridize with and unfold the fluorescently quenched hairpin signal probes (HP1) to recycle the target ATP and to trigger CHA between HP1 and the secondary hairpin probes (HP2) to form HP1/HP2 duplexes. Due to the recycling amplification, the presence of ATP leads to the formation of many HP1/HP2 duplexes, generating dramatically amplified fluorescent signals for sensitive detection of ATP. Under optimal experimental conditions, our sensor linearly responds to ATP in the range from 25 to 600nM with a calculated detection limit of 8.2nM. Furthermore, the sensor shows a high selectivity and can also be used to detect ATP in human serums to realize its application for real samples. With the distinct advantage of significant signal amplification without the involvement of any nanomaterial and enzyme, the developed sensor thus holds great potential for simple and sensitive detection of different small molecules and proteins. Copyright © 2018 Elsevier B.V. All rights reserved.

Whole-animal imaging of bacterial infection using endoscopic excitation of β-lactamase (BlaC)-specific fluorogenic probe

NASA Astrophysics Data System (ADS)

Nooshabadi, Fatemeh; Yang, Hee-Jeong; Cheng, Yunfeng; Xie, Hexin; Rao, Jianghong; Cirillo, Jeffrey D.; Maitland, Kristen C.

2016-03-01

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains one of the most frequent causes of death worldwide. The slow growth rate of Mtb limits progress toward understanding tuberculosis including diagnosis of infections and evaluating therapeutic efficacy. Development of near-infrared (NIR) β-lactamase (BlaC)-specific fluorogenic substrate has made a significant breakthrough in the whole-animal imaging to detect Mtb infection. The reporter enzyme fluorescence (REF) system using a BlaC-specific fluorogenic substrate has improved the detection sensitivity in whole-animal optical imaging down to ~104 colony forming units (CFU) of bacteria, about 100-fold improvement over recombinant strains. However, improvement of detection sensitivity is strongly needed for clinical diagnosis of early stage infection at greater tissue depth. In order to improve detection sensitivity, we have integrated a fiber-based microendoscpe into a whole-animal imaging system to transmit the excitation light from the fiber bundle to the fluorescent target directly and measure fluorescent level using BlaC-specific REF substrate in the mouse lung. REF substrate, CNIR800, was delivered via aerosol route to the pulmonary infected mice with M. bovis BCG strain at 24 hours post-infection and groups of mice were imaged at 1-4 hours post-administration of the substrate using the integrated imaging system. In this study we evaluated the kinetics of CNIR800 substrate using REF technology using the integrated imaging system. Integration of these technologies has great promise for improved detection sensitivity allowing pre-clinical imaging for evaluation of new therapeutic agents.

Dual channel sensitive detection of hsa-miR-21 based on rolling circle amplification and quantum dots tagging.

PubMed

Wangt, Dan-Chen; Hu, Li-Hui; Zhou, Yu-Hui; Huang, Yu-Ting; Li, Xinhua; Zhu, Jun-Jie

2014-04-01

An isothermal, highly sensitive and specific assay for the detection of hsa-miR-21 with the integration of QDs tagging and rolling circle amplification was offered. In addition, a dual channel strategy for miRNA detection was proposed: anodic stripping voltammetry (ASV) and fluorescent method were both performed for the final Cd2+ signal readout. The designed strategy exhibited good specificity to hsa-miR-21 and presented comparable detection results by detection methods.

Detection of IgG aggregation by a high throughput method based on extrinsic fluorescence.

PubMed

He, Feng; Phan, Duke H; Hogan, Sabine; Bailey, Robert; Becker, Gerald W; Narhi, Linda O; Razinkov, Vladimir I

2010-06-01

The utility of extrinsic fluorescence as a tool for high throughput detection of monoclonal antibody aggregates was explored. Several IgG molecules were thermally stressed and the high molecular weight species were fractionated using size-exclusion chromatography (SEC). The isolated aggregates and monomers were studied by following the fluorescence of an extrinsic probe, SYPRO Orange. The dye displayed high sensitivity to structurally altered, aggregated IgG structures compared to the native form, which resulted in very low fluorescence in the presence of the dye. An example of the application is presented here to demonstrate the properties of this detection method. The fluorescence assay was shown to correlate with the SEC method in quantifying IgG aggregates. The fluorescent probe method appears to have potential to detect protein particles that could not be analyzed by SEC. This method may become a powerful high throughput tool to detect IgG aggregates in pharmaceutical solutions and to study other protein properties involving aggregation. It can also be used to study the kinetics of antibody particle formation, and perhaps allow identification of the species, which are the early building blocks of protein particles. (c) 2009 Wiley-Liss, Inc. and the American Pharmacists Association

Rational synthesis of an exceptionally stable Zn(II) metal-organic framework for the highly selective and sensitive detection of picric acid.

PubMed

Hu, Yingli; Ding, Meili; Liu, Xiao-Qin; Sun, Lin-Bing; Jiang, Hai-Long

2016-04-28

Based on an organic ligand involving both carboxylate and tetrazole groups, a chemically stable Zn(II) metal-organic framework has been rationally synthesized and behaves as a fluorescence chemosensor for the highly selective and sensitive detection of picric acid, an extremely hazardous and strong explosive.

Terbium(III)/gold nanocluster conjugates: the development of a novel ratiometric fluorescent probe for mercury(II) and a paper-based visual sensor.

PubMed

Qi, Yan-Xia; Zhang, Min; Zhu, Anwei; Shi, Guoyue

2015-08-21

In this work, a novel ratiometric fluorescent probe was developed for rapid, highly accurate, sensitive and selective detection of mercury(II) (Hg(2+)) based on terbium(III)/gold nanocluster conjugates (Tb(3+)/BSA-AuNCs), in which bovine serum albumin capped gold nanoclusters (BSA-AuNCs) acted as the signal indicator and terbium(III) (Tb(3+)) was used as the build-in reference. Our proposed ratiometric fluorescent probe exhibited unique specificity toward Hg(2+) against other common environmentally and biologically important metal ions, and had high accuracy and sensitivity with a low detection limit of 1 nM. In addition, our proposed probe was effectively employed to detect Hg(2+) in the biological samples from the artificial Hg(2+)-infected rats. More significantly, an appealing paper-based visual sensor for Hg(2+) was designed by using filter paper embedded with Tb(3+)/BSA-AuNC conjugates, and we have further demonstrated its feasibility for facile fluorescent sensing of Hg(2+) in a visual format, in which only a handheld UV lamp is used. In the presence of Hg(2+), the paper-based visual sensor, illuminated by a handheld UV lamp, would undergo a distinct fluorescence color change from red to green, which can be readily observed with naked eyes even in trace Hg(2+) concentrations. The Tb(3+)/BSA-AuNC-derived paper-based visual sensor is cost-effective, portable, disposable and easy-to-use. This work unveiled a facile approach for accurate, sensitive and selective measuring of Hg(2+) with self-calibration.

Sensitive and background-free determination of thiols from wastewater samples by MOF-5 extraction coupled with high-performance liquid chromatography with fluorescence detection using a novel fluorescence probe of carbazole-9-ethyl-2-maleimide.

PubMed

Lv, Zhengxian; Sun, Zhiwei; Song, Cuihua; Lu, Shuaimin; Chen, Guang; You, Jinmao

2016-12-01

A sensitive and background-free pre-column derivatization method for the determination of thiol compounds using metal-organic framework material (MOF-5) as dispersive solid-phase extraction (DSPE) adsorbent followed by high-performance liquid chromatography fluorescence detection (HPLC-FLD) has been developed. In this paper, a novel labeling reagent, carbazole-9-ethyl-2-maleimide(CAEM), was synthesized and reacted with thiols at 40°C for 10min in the presence of PBS buffer (0.02mol/L, pH 7.5). Interestingly, CAEM itself had no fluorescence, while its derivatives exhibited intense fluorescence with an excitation maximum at λ ex 274nm and an emission maximum at λ em 363nm, which greatly reduced the background interference and improved the sensitivity of the method. Furthermore, the MOF-5 was prepared and used as DSPE adsorbent for the selective adsorption of thiols from wastewater sample. Under the optimized experimental conditions, an excellent linearity for all analytes over their concentration ranges of 0.01-1.0μmol/L (R 2 >0.9986)were obtained with the limit of detection (LOD) ranging from 8 to 17.1pmol/L for nine tested thiols. The feasibility of this method for the determination of thiols in wastewater samples had been evaluated and satisfactory average recoveries (n=3) were achieved with the range of 86.6-98.5%. Copyright © 2016 Elsevier B.V. All rights reserved.

Smartphone-Based Fluorescent Diagnostic System for Highly Pathogenic H5N1 Viruses.

PubMed

Yeo, Seon-Ju; Choi, Kyunghan; Cuc, Bui Thi; Hong, Nguyen Ngoc; Bao, Duong Tuan; Ngoc, Nguyen Minh; Le, Mai Quynh; Hang, Nguyen Le Khanh; Thach, Nguyen Co; Mallik, Shyam Kumar; Kim, Hak Sung; Chong, Chom-Kyu; Choi, Hak Soo; Sung, Haan Woo; Yu, Kyoungsik; Park, Hyun

2016-01-01

Field diagnostic tools for avian influenza (AI) are indispensable for the prevention and controlled management of highly pathogenic AI-related diseases. More accurate, faster and networked on-site monitoring is demanded to detect such AI viruses with high sensitivity as well as to maintain up-to-date information about their geographical transmission. In this work, we assessed the clinical and field-level performance of a smartphone-based fluorescent diagnostic device with an efficient reflective light collection module using a coumarin-derived dendrimer-based fluorescent lateral flow immunoassay. By application of an optimized bioconjugate, a smartphone-based diagnostic device had a two-fold higher detectability as compared to that of the table-top fluorescence strip reader for three different AI subtypes (H5N3, H7N1, and H9N2). Additionally, in a clinical study of H5N1-confirmed patients, the smartphone-based diagnostic device showed a sensitivity of 96.55% (28/29) [95% confidence interval (CI): 82.24 to 99.91] and a specificity of 98.55% (68/69) (95% CI: 92.19 to 99.96). The measurement results from the distributed individual smartphones were wirelessly transmitted via short messaging service and collected by a centralized database system for further information processing and data mining. Smartphone-based diagnosis provided highly sensitive measurement results for H5N1 detection within 15 minutes. Because of its high sensitivity, portability and automatic reporting feature, the proposed device will enable agile identification of patients and efficient control of AI dissemination.

Smartphone-Based Fluorescent Diagnostic System for Highly Pathogenic H5N1 Viruses

PubMed Central

Yeo, Seon-Ju; Choi, Kyunghan; Cuc, Bui Thi; Hong, Nguyen Ngoc; Bao, Duong Tuan; Ngoc, Nguyen Minh; Le, Mai Quynh; Hang, Nguyen Le Khanh; Thach, Nguyen Co; Mallik, Shyam Kumar; Kim, Hak Sung; Chong, Chom-Kyu; Choi, Hak Soo; Sung, Haan Woo; Yu, Kyoungsik; Park, Hyun

2016-01-01

Field diagnostic tools for avian influenza (AI) are indispensable for the prevention and controlled management of highly pathogenic AI-related diseases. More accurate, faster and networked on-site monitoring is demanded to detect such AI viruses with high sensitivity as well as to maintain up-to-date information about their geographical transmission. In this work, we assessed the clinical and field-level performance of a smartphone-based fluorescent diagnostic device with an efficient reflective light collection module using a coumarin-derived dendrimer-based fluorescent lateral flow immunoassay. By application of an optimized bioconjugate, a smartphone-based diagnostic device had a two-fold higher detectability as compared to that of the table-top fluorescence strip reader for three different AI subtypes (H5N3, H7N1, and H9N2). Additionally, in a clinical study of H5N1-confirmed patients, the smartphone-based diagnostic device showed a sensitivity of 96.55% (28/29) [95% confidence interval (CI): 82.24 to 99.91] and a specificity of 98.55% (68/69) (95% CI: 92.19 to 99.96). The measurement results from the distributed individual smartphones were wirelessly transmitted via short messaging service and collected by a centralized database system for further information processing and data mining. Smartphone-based diagnosis provided highly sensitive measurement results for H5N1 detection within 15 minutes. Because of its high sensitivity, portability and automatic reporting feature, the proposed device will enable agile identification of patients and efficient control of AI dissemination. PMID:26877781

A novel fluorescence probe based on triphenylamine Schiff base for bioimaging and responding to pH and Fe3.

PubMed

Wang, Lei; Yang, Xiaodong; Chen, Xiuli; Zhou, Yuping; Lu, Xiaodan; Yan, Chenggong; Xu, Yikai; Liu, Ruiyuan; Qu, Jinqing

2017-03-01

A novel fluorescence probe 1 based on triphenylamine was synthesized and characterized by NMR, IR, high resolution mass spectrometry and elemental analysis. Its fluorescence was quenched when pH below 2. There was a linear relationship between the fluorescence intensity and pH value ranged from 2 to 7. And its fluorescence emission was reversibility in acidic and alkaline solution. Furthermore, it exhibited remarkable selectivity and high sensitivity to Fe 3+ and was able to detect Fe 3+ in aqueous solution with low detection limit of 0.511μM. Job plot showed that the binding stoichiometry of 1 with Fe 3+ was 1:1. Further observations of 1 H NMR titration suggested that coordination interaction between Fe 3+ and nitrogen atom on CN bond promoted the intramolecular charge transfer (ICT) or energy transfer process causing fluorescence quenching. Additionally, 1 was also able to be applied for detecting Fe 3+ in living cell and bioimaging. Copyright © 2016. Published by Elsevier B.V.

Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers.

PubMed

Liu, Nan; Hao, Juan; Cai, Keying; Zeng, Mulan; Huang, Zhenzhong; Chen, Lili; Peng, Bingxian; Li, Ping; Wang, Li; Song, Yonghai

2018-02-01

A novel ratiometric fluorescence nanosensor for superoxide anion (O 2 •- ) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb 3+ and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O 2 •- . The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O 2 •- demonstrated high sensitivity and selectivity with a wide linear response range (14 nM-10 μM) and a low detection limit (4.7 nM). Copyright © 2017 John Wiley & Sons, Ltd.

One-step synthesis of fluorescein modified nano-carbon for Pd(II) detection via fluorescence quenching.

PubMed

Panchompoo, Janjira; Aldous, Leigh; Baker, Matthew; Wallace, Mark I; Compton, Richard G

2012-05-07

Carbon black (CB) nanoparticles modified with fluorescein, a highly fluorescent molecule, were prepared using a facile and efficient methodology. Simply stirring CB in aqueous solution containing fluorescein resulted in the strong physisorption of fluorescein onto the CB surface. The resulting Fluorescein/CB was then characterised by means of X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), fluorescence microscopy and fluorescence spectroscopy. The optimum experimental conditions for fluorescence of Fluorescein/CB viz. fluorescence excitation and emission wavelengths, O(2) removal and the amount of Fluorescein/CB used, were investigated. The Fluorescein/CB was used as a fluorescent probe for the sensitive detection of Pd(II) in water, based on fluorescence quenching. The results demonstrated that the fluorescence intensity of Fluorescein/CB decreased with increasing Pd(II) concentration, and the fluorescence quenching process could be described by the Stern-Volmer equation. The limit of detection (LOD) for the fluorescence quenching of Fluorescein/CB by Pd(II) in aqueous solution was found to be 1.07 μM (based on 3σ). Last, approaches were studied for the removal of Fe(III) which interferes with the fluorescence quenching of Fluorescein/CB. Complexation of Fe(III) with salicylic acid was used to enhance and control the selectivity of Fluorescein/CB sensor towards Pd(II) in the presence of Fe(III).

A graphene oxide-based fluorescent aptasensor for the turn-on detection of epithelial tumor marker mucin 1.

PubMed

He, Yue; Lin, Yi; Tang, Hongwu; Pang, Daiwen

2012-03-21

Mucin 1 (MUC1) which presents in epithelial malignancies, is a well-known tumor biomarker. In this paper, a highly sensitive and selective fluorescent aptasensor for Mucin 1 (MUC1) detection is constructed, utilizing graphene oxide (GO) as a quencher which can quench the fluorescence of single-stranded dye-labeled MUC1 specific aptamer. In the absence of MUC1, the adsorption of the dye-labeled aptamer on GO brings the dyes in close proximity to the GO surface resulting in high efficiency quenching of dye fluorescence. Therefore, the fluorescence of the designed aptasensor is completely quenched by GO, and the system shows very low background fluorescence. Conversely, and very importantly, upon the adding of MUC1, the quenched fluorescence is recovered significantly, and MUC1 can be detected in a wide range of 0.04-10 μM with a detection limit of 28 nM and good selectivity. Moreover, the results have also been verified for real sample application by testing 2% serum containing buffer solution spiked with a series of concentrations of MUC1. This journal is © The Royal Society of Chemistry 2012

Target-protecting dumbbell molecular probe against exonucleases digestion for sensitive detection of ATP and streptavidin.

PubMed

Chen, Jinyang; Liu, Yucheng; Ji, Xinghu; He, Zhike

2016-09-15

In this work, a versatile dumbbell molecular (DM) probe was designed and employed in the sensitively homogeneous bioassay. In the presence of target molecule, the DM probe was protected from the digestion of exonucleases. Subsequently, the protected DM probe specifically bound to the intercalation dye and resulted in obvious fluorescence signal which was used to determine the target molecule in return. This design allows specific and versatile detection of diverse targets with easy operation and no sophisticated fluorescence labeling. Integrating the idea of target-protecting DM probe with adenosine triphosphate (ATP) involved ligation reaction, the DM probe with 5'-end phosphorylation was successfully constructed for ATP detection, and the limitation of detection was found to be 4.8 pM. Thanks to its excellent selectivity and sensitivity, this sensing strategy was used to detect ATP spiked in human serum as well as cellular ATP. Moreover, the proposed strategy was also applied in the visual detection of ATP in droplet-based microfluidic platform with satisfactory results. Similarly, combining the principle of target-protecting DM probe with streptavidin (SA)-biotin interaction, the DM probe with 3'-end biotinylation was developed for selective and sensitive SA determination, which demonstrated the robustness and versatility of this design. Copyright © 2016 Elsevier B.V. All rights reserved.

Study on high power ultraviolet laser oil detection system

NASA Astrophysics Data System (ADS)

Jin, Qi; Cui, Zihao; Bi, Zongjie; Zhang, Yanchao; Tian, Zhaoshuo; Fu, Shiyou

2018-03-01

Laser Induce Fluorescence (LIF) is a widely used new telemetry technology. It obtains information about oil spill and oil film thickness by analyzing the characteristics of stimulated fluorescence and has an important application in the field of rapid analysis of water composition. A set of LIF detection system for marine oil pollution is designed in this paper, which uses 355nm high-energy pulsed laser as the excitation light source. A high-sensitivity image intensifier is used in the detector. The upper machine sends a digital signal through a serial port to achieve nanoseconds range-gated width control for image intensifier. The target fluorescence spectrum image is displayed on the image intensifier by adjusting the delay time and the width of the pulse signal. The spectral image is coupled to CCD by lens imaging to achieve spectral display and data analysis function by computer. The system is used to detect the surface of the floating oil film in the distance of 25m to obtain the fluorescence spectra of different oil products respectively. The fluorescence spectra of oil products are obvious. The experimental results show that the system can realize high-precision long-range fluorescence detection and reflect the fluorescence characteristics of the target accurately, with broad application prospects in marine oil pollution identification and oil film thickness detection.

Sensitivity evaluation of rhodamine B hydrazide towards nitric oxide and its application for macrophage cells imaging.

PubMed

Wu, Chi-Ming; Chen, Yen-Hao; Dayananda, Kasala; Shiue, Tsun-Wei; Hung, Chen-Hsiung; Liaw, Wen-Feng; Chen, Po-Yu; Wang, Yun-Ming

2011-12-05

A colorless and non-fluorescent rhodamine derivative, rhodamine B hydrazide (RH), is applied to detect nitric oxide and form fluorescent rhodamine B (RB). The reaction mechanism of RH with NO is proposed in this study. The probe shows good stability over a broad pH range (pH>4). Furthermore, fluorescence intensity of RH displays an excellent linearity to the NO concentration and the detection limit is as low as 20 nM. A 1000-fold fluorescence turn-on from a dark background was observed. Moreover, the selectivity study indicated that the fluorescence intensity increasing in the presence of NO was significantly higher than those of other reactive oxygen/nitrogen species. In exogenously generated NO detection study, clear intracellular red fluorescence was observed in the presence of S-nitroso-N-acetyl-D,L-penicillamine (SNAP, a kind of NO releasing agent). In endogenously generated NO detection study, increasing incubation time of RH with lipopolysaccharied (LPS) pre-treated cells could obtain a highly fluorescent cell image. These cell imaging results demonstrated that RH can efficiently penetrate into Raw 264.7 cells and be used for detection of exogenously and endogenously generated nitric oxide. Copyright © 2011 Elsevier B.V. All rights reserved.

Sensitive determination of endogenous hydroxyl radical in live cell by a BODIPY based fluorescent probe.

PubMed

Lei, Kepeng; Sun, Mingtai; Du, Libo; Zhang, Xiaojie; Yu, Huan; Wang, Suhua; Hayat, Tasawar; Alsaedi, Ahmed

2017-08-01

The sensitive and selective fluorescence probe for hydroxyl radical analysis is of significance because hydroxyl radical plays key roles in many physiological and pathological processes. In this work, a novel organic fluorescence molecular probe OHP for hydroxyl radical is synthesized by a two-step route. The probe employs 4-bora-3a,4a-diaza-s-indacene (difluoroboron dipyrromethene, BODIPY) as the fluorophore and possesses relatively high fluorescence quantum yields (77.14%). Hydroxyl radical can rapidly react with the probe and quench the fluorescence in a good linear relationship (R 2 =0.9967). The limit of detection is determined to be as low as 11nM. In addition, it has been demonstrated that the probe has a good stability against pH and light illumination, low cytotoxicity and high biocompatibility. Cell culture experimental results show that the probe OHP is sensitive and selective for imaging and tracking endogenous hydroxyl radical in live cells. Copyright © 2017 Elsevier B.V. All rights reserved.

Whole-body multicolor spectrally resolved fluorescence imaging for development of target-specific optical contrast agents using genetically engineered probes

NASA Astrophysics Data System (ADS)

Kobayashi, Hisataka; Hama, Yukihiro; Koyama, Yoshinori; Barrett, Tristan; Urano, Yasuteru; Choyke, Peter L.

2007-02-01

Target-specific contrast agents are being developed for the molecular imaging of cancer. Optically detectable target-specific agents are promising for clinical applications because of their high sensitivity and specificity. Pre clinical testing is needed, however, to validate the actual sensitivity and specificity of these agents in animal models, and involves both conventional histology and immunohistochemistry, which requires large numbers of animals and samples with costly handling. However, a superior validation tool takes advantage of genetic engineering technology whereby cell lines are transfected with genes that induce the target cell to produce fluorescent proteins with characteristic emission spectra thus, identifying them as cancer cells. Multicolor fluorescence imaging of these genetically engineered probes can provide rapid validation of newly developed exogenous probes that fluoresce at different wavelengths. For example, the plasmid containing the gene encoding red fluorescent protein (RFP) was transfected into cell lines previously developed to either express or not-express specific cell surface receptors. Various antibody-based or receptor ligand-based optical contrast agents with either green or near infrared fluorophores were developed to concurrently target and validate cancer cells and their positive and negative controls, such as β-D-galactose receptor, HER1 and HER2 in a single animal/organ. Spectrally resolved fluorescence multicolor imaging was used to detect separate fluorescent emission spectra from the exogenous agents and RFP. Therefore, using this in vivo imaging technique, we were able to demonstrate the sensitivity and specificity of the target-specific optical contrast agents, thus reducing the number of animals needed to conduct these experiments.

Intraoperative Detection of Cell Injury and Cell Death with an 800 nm Near-Infrared Fluorescent Annexin V Derivative

PubMed Central

Ohnishi, Shunsuke; Vanderheyden, Jean-Luc; Tanaka, Eiichi; Patel, Bhavesh; De Grand, Alec; Laurence, Rita G.; Yamashita, Kenichiro; Frangioni, John V.

2008-01-01

The intraoperative detection of cell injury and cell death is fundamental to human surgeries such as organ transplantation and resection. Because of low autofluorescence background and relatively high tissue penetration, invisible light in the 800 nm region provides sensitive detection of disease pathology without changing the appearance of the surgical field. In order to provide surgeons with real-time intraoperative detection of cell injury and death after ischemia/reperfusion (I/R), we have developed a bioactive derivative of human annexin V (annexin800), which fluoresces at 800 nm. Total fluorescence yield, as a function of bioactivity, was optimized in vitro, and final performance was assessed in vivo. In liver, intestine and heart animal models of I/R, an optimal signal to background ratio was obtained 30 min after intravenous injection of annexin800, and histology confirmed concordance between planar reflectance images and actual deep tissue injury. In summary, annexin800 permits sensitive, real-time detection of cell injury and cell death after I/R in the intraoperative setting, and can be used during a variety of surgeries for rapid assessment of tissue and organ status. PMID:16869796

Detection of dysplasia and carcinoma in situ by ratio fluorometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lam, S.; Hung, J.Y.; Kennedy, S.M.

1992-12-01

Fluorescence bronchoscopy was performed in 82 volunteers recruited from occupational groups at risk of exposure to asbestos and/or diesel fumes to determine whether differences in tissue autofluorescence between normal and malignant bronchial tissues can be used to improve the sensitivity of standard fiberoptic bronchoscopy in detecting dysplasic and carcinoma in situ (CIS). This study consisted of 25 nonsmokers, 40 exsmokers, and 17 current smokers with mean ages of 52, 55, and 49 yr, respectively. Tissue autofluorescence was induced by a blue light from an He-Cd laser coupled to the illumination channel of the bronchoscope and analyzed by a ratiofluorometer. Onemore » or more sites of moderate or severe dysplasia were found in 12% of the exsmokers and current smokers but in none of the nonsmoker volunteers. CIS was found in two of the exsmokers. The sensitivity of fluorescence bronchoscopy (86%) was found to be 50% better than that of conventional white-light bronchoscopy (52%) in detecting dysplasia and CIS. Pre- and post-bronchoscopy sputum cytology failed to detect these precancerous lesions. Our results suggest that fluorescence bronchoscopy may be an important new method that can improve the ability to detect and localize precancerous and/or CIS lesions.« less

Highly selective and sensitive coumarin-triazole-based fluorometric 'turn-off' sensor for detection of Pb2+ ions.

PubMed

Shaily; Kumar, Ajay; Parveen, Iram; Ahmed, Naseem

2018-06-01

Exposure to even very low concentrations of Pb 2+ is known to cause cardiovascular, neurological, developmental, and reproductive disorders, and affects children in particular more severely. Consequently, much effort has been dedicated to the development of colorimetric and fluorescent sensors that can selectively detect Pb 2+ ions. Here, we describe the development of a triazole-based fluorescent sensor L5 for Pb 2+ ion detection. The fluorescence intensity of chemosensor L5 was selectively quenched by Pb 2+ ions and a clear color change from colorless to yellow could be observed by the naked eye. Chemosensor L5 exhibited high sensitivity and selectivity towards Pb 2+ ions in phosphate-buffered solution [20 mM, 1:9 DMSO/H 2 O (v/v), pH 8.0] with a 1:1 binding stoichiometry, a detection limit of 1.9 nM and a 6.76 × 10 6  M -1 binding constant. Additionally, low-cost and easy-to-prepare test strips impregnated with chemosensor L5 were also produced for efficient of Pb 2+ detection and proved the practical use of this test. Copyright © 2018 John Wiley & Sons, Ltd.

A highly selective colorimetric and ratiometric fluorescent probe for instantaneous sensing of Hg2+ in water, soil and seafood and its application on test strips.

PubMed

Lan, Linxin; Niu, Qingfen; Li, Tianduo

2018-09-06

A new simple and efficient oligothiophene-based colorimetric and ratiometric fluorescent probe has been developed for highly sensitive and fast detection of Hg 2+ in water, soil and seafood. The probe 5-(1,3-dithiolan-2-yl)-2,2':5',2″-terthiophene 3 TS can selectively detect Hg 2+ via the Hg 2+ -promoted deprotection reaction of thioacetals, which caused a remarkable color change from colorless to yellow and a strong fluorescence enhancement with emission color varying from blue to yellow, enabling naked-eye detection of Hg 2+ . The probe shows high sensitivity with the detection limit down to 1.03 × 10 -8  M. Visual color changes of 3 TS were observed on filter paper and TLC testing strips when they were impregnated on testing strips and immersed in Hg 2+ solution. Moreover, the probe 3 TS has been successfully used to rapidly detect trace amounts of hazardous Hg 2+ ions in tap, distilled, river and lake water, cropland soil, fish, shrimp and kelp samples with acceptable results and good recoveries. Copyright © 2018 Elsevier B.V. All rights reserved.

Parallel, confocal, and complete spectrum imager for fluorescent detection of high-density microarray

NASA Astrophysics Data System (ADS)

Bogdanov, Valery L.; Boyce-Jacino, Michael

1999-05-01

Confined arrays of biochemical probes deposited on a solid support surface (analytical microarray or 'chip') provide an opportunity to analysis multiple reactions simultaneously. Microarrays are increasingly used in genetics, medicine and environment scanning as research and analytical instruments. A power of microarray technology comes from its parallelism which grows with array miniaturization, minimization of reagent volume per reaction site and reaction multiplexing. An optical detector of microarray signals should combine high sensitivity, spatial and spectral resolution. Additionally, low-cost and a high processing rate are needed to transfer microarray technology into biomedical practice. We designed an imager that provides confocal and complete spectrum detection of entire fluorescently-labeled microarray in parallel. Imager uses microlens array, non-slit spectral decomposer, and high- sensitive detector (cooled CCD). Two imaging channels provide a simultaneous detection of localization, integrated and spectral intensities for each reaction site in microarray. A dimensional matching between microarray and imager's optics eliminates all in moving parts in instrumentation, enabling highly informative, fast and low-cost microarray detection. We report theory of confocal hyperspectral imaging with microlenses array and experimental data for implementation of developed imager to detect fluorescently labeled microarray with a density approximately 103 sites per cm2.

Toehold-mediated strand displacement reaction-dependent fluorescent strategy for sensitive detection of uracil-DNA glycosylase activity.

PubMed

Wu, Yushu; Wang, Lei; Jiang, Wei

2017-03-15

Sensitive detection of uracil-DNA glycosylase (UDG) activity is beneficial for evaluating the repairing process of DNA lesions. Here, toehold-mediated strand displacement reaction (TSDR)-dependent fluorescent strategy was constructed for sensitive detection of UDG activity. A single-stranded DNA (ssDNA) probe with two uracil bases and a trigger sequence were designed. A hairpin probe with toehold domain was designed, and a reporter probe was also designed. Under the action of UDG, two uracil bases were removed from ssDNA probe, generating apurinic/apyrimidinic (AP) sites. Then, the AP sites could inhibit the TSDR between ssDNA probe and hairpin probe, leaving the trigger sequence in ssDNA probe still free. Subsequently, the trigger sequence was annealed with the reporter probe, initiating the polymerization and nicking amplification reaction. As a result, numerous G-quadruplex (G4) structures were formed, which could bind with N-methyl-mesoporphyrin IX (NMM) to generate enhanced fluorescent signal. In the absence of UDG, the ssDNA probe could hybridize with the toehold domain of the hairpin probe to initiate TSDR, blocking the trigger sequence, and then the subsequent amplification reaction would not occur. The proposed strategy was successfully implemented for detecting UDG activity with a detection limit of 2.7×10 -5 U/mL. Moreover, the strategy could distinguish UDG well from other interference enzymes. Furthermore, the strategy was also applied for detecting UDG activity in HeLa cells lysate with low effect of cellular components. These results indicated that the proposed strategy offered a promising tool for sensitive quantification of UDG activity in UDG-related function study and disease prognosis. Copyright © 2016 Elsevier B.V. All rights reserved.

A fluorescent immunochromatographic strip test using a quantum dot-antibody probe for rapid and quantitative detection of 1-aminohydantoin in edible animal tissues.

PubMed

Le, Tao; Zhang, Zhihao; Wu, Juan; Shi, Haixing; Cao, Xudong

2018-01-01

A rapid, simple, and sensitive fluorescent immunochromatographic strip test (ICST) based on quantum dots (QDs) has been developed to detect 1-aminohydantoin (AHD), a major metabolite of nitrofurantoin in animal tissues. To achieve this, QD-labeled antibody conjugates, which consist of CdSe/ZnS QDs and monoclonal antibodies, were prepared by an activated ester method. Under optimal conditions, with the nitrophenyl derivative of AHD as the target, the ICST had a linear range from 0.1 to 100 ng/mL, with a correlation coefficient of 0.9656 and a 50% inhibitory concentration of 4.51 ng/mL. The limit of detection was 0.14 ng/g, which was below the minimum required performance limit of 1 μg/kg for AHD established by the European Commission. The recoveries for AHD ranged from 81.5% to 108.2%, with coefficients of variation below 13%, based on intraday and interday analysis. Furthermore, for AHD in real samples, the ICST showed high reliability and high correlation with liquid chromatography-tandem mass spectrometry (correlation coefficient of 0.9916). To the best of our knowledge, this is the first report of a novel and sensitive method based on a fluorescent ICST to detect AHD below the minimum required performance limit. The ICST demonstrated high reliability, and could be ideally suited for rapid, simple, and on-site screening of AHD contamination in animal tissues. Graphical abstract A rapid, simple, and sensitive fluorescent immunochromatographic strip test that is based on quantum dots was developed to detect 1-aminohydantoin (AHD), a major metabolite of nitrofurantoin in animal tissues. 2-NBA 2-nitrobenzaldehyde, NP nitrophenyl.

Determination of ethambutol by a sensitive fluorescent probe

NASA Astrophysics Data System (ADS)

Wu, Wen-Ying; Yang, Ji-Yuan; Du, Li-Ming; Wu, Hao; Li, Chang-Feng

2011-08-01

The competitive reaction between ethambutol and two fluorescent probes (i.e., berberine and palmatine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by spectrofluorometry. The CB[7] reacts with these probes to form stable complexes, and the fluorescence intensity of the complexes is greatly enhanced. In addition, the excitation and emission wavelengths of their complexes moved to wavelengths of 343 nm and 495 nm, respectively. However, the addition of ethambutol dramatically quenches the fluorescence intensity of the two complexes. Accordingly, a couple of new fluorescence quenching methods for the determination of ethambutol were established. The methods can be applied for quantifying ethambutol. A linear relationship between the fluorescence quenching values (Δ F) and ethambutol concentration exists in the range of 5.0-1000.0 ng mL -1, with a correlation coefficient ( r) of 0.9997. The detection limit is 1.7 ng mL -1. The fluorescent probe of berberine has higher sensitivity than palmatine. This paper also discusses the mechanism of fluorescence indicator probes.

Contact-lens type of micromachined hydrogenated amorphous Si fluorescence detector coupled with microfluidic electrophoresis devices

NASA Astrophysics Data System (ADS)

Kamei, Toshihiro; Wada, Takehito

2006-09-01

A 5.8-μm-thick SiO2/Ta2O5 multilayer optical interference filter was monolithically integrated and micromachined on a hydrogenated amorphous Si (a-Si :H) pin photodiode to form a fluorescence detector. A microfluidic electrophoresis device was mounted on a detection platform comprising a fluorescence-collecting half-ball lens and the micromachined fluorescence detector. The central aperture of the fluorescence detector allows semiconductor laser light to pass up through the detector and to irradiate an electrophoretic separation channel. The limit of detection is as low as 7nM of the fluorescein solution, and high-speed DNA fragment sizing can be achieved with high separation efficiency. The micromachined a-Si :H fluorescence detector exhibits high sensitivity for practical fluorescent labeling dyes as well as integration flexibility on various substances, making it ideal for application to portable microfluidic bioanalysis devices.

X ray sensitive area detection device

NASA Technical Reports Server (NTRS)

Carter, Daniel C. (Inventor); Witherow, William K. (Inventor); Pusey, Marc L. (Inventor); Yost, Vaughn H. (Inventor)

1990-01-01

A radiation sensitive area detection device is disclosed which comprises a phosphor-containing film capable of receiving and storing an image formed by a pattern of incoming x rays, UV, or other radiation falling on the film. The device is capable of fluorescing in response to stimulation by a light source in a manner directly proportional to the stored radiation pattern. The device includes: (1) a light source capable of projecting light or other appropriate electromagnetic wave on the film so as to cause it to fluoresce; (2) a means to focus the fluoresced light coming from the phosphor-containing film after light stimulation; and (3) at least one charged coupled detector or other detecting element capable of receiving and digitizing the pattern of fluoresced light coming from the phosphor-containing film. The device will be able to generate superior x ray images of high resolution from a crystal or other sample and will be particularly advantageous in that instantaneous near-real-time images of rapidly deteriorating samples can be obtained. Furthermore, the device can be made compact and sturdy, thus capable of carrying out x ray or other radiation imaging under a variety of conditions, including those experienced in space.

Focus on quantum dots as potential fluorescent probes for monitoring food toxicants and foodborne pathogens.

PubMed

Vinayaka, A C; Thakur, M S

2010-06-01

Water-soluble quantum dots (QDs) are fluorescent semiconductor nanoparticles with narrow, very specific, stable emission spectra. Therefore, the bioconjugation of these QDs for biological fluorescent labeling may be of interest due to their unique physical and optical properties as compared to organic fluorescent dyes. These intrinsic properties of QDs have been used for the sensitive detection of target analytes. From the viewpoint of ensuring food safety, there is a need to develop rapid, sensitive and specific detection techniques to monitor food toxicants in food and environmental samples. Even trace levels of these toxicants can inadvertently enter the food chain, creating severe health hazards. The present review emphasizes the application of water-soluble bioconjugated QDs for the detection of food contaminants such as pesticides, pathogenic bacterial toxins such as botulinum toxin, enterotoxins produced by Staphylococcus aureus, Escherichia coli, and for the development of oligonucleotide-based microarrays. This review also emphasizes the application of a possible resonance energy transfer phenomenon resulting from nanobiomolecular interactions obtained through the bioconjugation of QDs with biomolecules. Furthermore, the utilization of significant changes in the spectral behavior of QDs (attributed to resonance energy transfer in the bioconjugate) in future nanobiosensor development is also emphasized.

mTHPC-mediated photodynamic detection for fluorescence-guided resection of brain tumors

NASA Astrophysics Data System (ADS)

Kostron, Herwig; Zimmermann, Andreas; Obwegeser, Alois

1998-06-01

A most radical resection is of great importance in the treatment of brain tumors, however they can hardly be differentiated from normal brain parenchyma by the naked eye of the neurosurgeon. Photosensitizers are highly selective taken up into malignant tissues, therefore the fluorescence properties of photosensitizers could be utilized for optical differentiation of normal and malignant tissue. Ten patients presenting with brain malignancies were sensitized for photodynamic diagnosis (PDD) and photodynamic treatment (PDT) with 0.15 mg/kg b.w. m-THPC. On day 4 intraoperative PDD and fluorescence guided tumor resection (FGR) was performed, followed by intraoperative PDT. The fluorescence was induced by a xenon lamp at an excitation wavelength ranging from 370 to 440 nm. A sensitive CCD camera was employed for imaging, equipped with a long pass filter to shut off the excitation wavelength and to improve the signal to noise ratio. The pictures are converted digitally by a standard frame grabber and processed in real time and calculated for the tissue auto fluorescence in the emission band of m-THPC at 652 nm. Out of 10 0bservations, two were false negative and 2 were false positive. Our preliminary results indicate that fluorescence guided surgery is feasible and proved to be of significant help in delineating tumor margins and in resection of residual tumor that could not be detected by the surgeon, however the sensitivity and specificity needs to be further improved.

Fluorescence detection of malignant liver tumors using 5-aminolevulinic acid-mediated photodynamic diagnosis: principles, technique, and clinical experience.

PubMed

Inoue, Yoshihiro; Tanaka, Ryo; Komeda, Koji; Hirokawa, Fumitoshi; Hayashi, Michihiro; Uchiyama, Kazuhisa

2014-07-01

Photoactive drugs selectively accumulate in malignant tissue specimens and cause drug-induced fluorescence. Photodynamic diagnosis (PDD) and fluorescence can distinguish normal from malignant tissue. From May 2012 to September 2013, a total of 70 patients underwent hepatic resections using 5-ALA-mediated PDD for liver tumors at our hospital. 5-ALA fluorescence was detected in all hepatocellular carcinoma cases with serosa invasion. In liver metastasis from colorectal cancer cases with serosa invasion, 18 patients (85.7 %) were detected, and three patients (14.2 %) whose tumors showed complete response to neoadjuvant chemotherapy showed no fluorescence. Both superficial and deep malignant liver tumors were detected with 92.5 % sensitivity. Using 5-ALA-mediated PDD, tumors remaining at the cut surface and postoperative bile leakage were less frequent than in our previous hepatic resections using conventional white-light observation. Moreover, all malignant liver tumors were completely removed with a clear microscopic margin using 5-ALA, with a significant difference in resection margin width between 5-ALA-mediated PDD (6.7 ± 6.9 mm) and white-light observation (9.2 ± 7.0 mm; p = 0.0083). With the detection of malignant liver tumors, residual tumor and bile leakage at the cut surface of the remnant liver were improved by PDD with 5-ALA. This procedure may provide greater sensitivity than the conventional procedure. Furthermore, 5-ALA-mediated PDD can ensure histological clearance regardless of the resection margin and preserve as much liver parenchyma as possible in patients with impaired liver function.

A molecular imprinting-based turn-on Ratiometric fluorescence sensor for highly selective and sensitive detection of 2,4-dichlorophenoxyacetic acid (2,4-D).

PubMed

Wang, Xiaoyan; Yu, Jialuo; Wu, Xiaqing; Fu, Junqing; Kang, Qi; Shen, Dazhong; Li, Jinhua; Chen, Lingxin

2016-07-15

A novel molecular imprinting-based turn-on ratiometric fluorescence sensor was constructed via a facile sol-gel polymerization for detection of 2,4-dichlorophenoxyacetic acid (2,4-D) on the basis of photoinduced electron transfer (PET) by using nitrobenzoxadiazole (NBD) as detection signal source and quantum dots (QDs) as reference signal source. With the presence and increase of 2,4-D, the amine groups on the surface of QDs@SiO2 could bind with 2,4-D and thereby the NBD fluorescence intensities could be significantly enhanced since the PET process was inhibited, while the QDs maintained constant intensities. Accordingly, the ratio of the dual-emission intensities of green NBD and red QDs could be utilized for turn-on fluorescent detection of 2,4-D, along with continuous color changes from orange-red to green readily observed by the naked eye. The as-prepared fluorescence sensor obtained high sensitivity with a low detection limit of 0.14μM within 5min, and distinguished recognition selectivity for 2,4-D over its analogs. Moreover, the sensor was successfully applied to determine 2,4-D in real water samples, and high recoveries at three spiking levels of 2,4-D ranged from 95.0% to 110.1% with precisions below 4.5%. The simple, rapid and reliable visual sensing strategy would not only provide potential applications for high selective ultratrace analysis of complicated matrices, but also greatly enrich the research connotations of molecularly imprinted sensors. Copyright © 2016 Elsevier B.V. All rights reserved.

Synchronous detection of ebolavirus conserved RNA sequences and ebolavirus-encoded miRNA-like fragment based on a zwitterionic copper (II) metal-organic framework.

PubMed

Qiu, Gui-Hua; Weng, Zi-Hua; Hu, Pei-Pei; Duan, Wen-Jun; Xie, Bao-Ping; Sun, Bin; Tang, Xiao-Yan; Chen, Jin-Xiang

2018-04-01

From a three-dimensional (3D) metal-organic framework (MOF) of {[Cu(Cmdcp)(phen)(H 2 O)] 2 ·9H 2 O} n (1, H 3 CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide, phen = phenanthroline), a sensitive and selective fluorescence sensor has been developed for the simultaneous detection of ebolavirus conserved RNA sequences and ebolavirus-encoded microRNA-like (miRNA-like) fragment. The results from molecular dynamics simulation confirmed that MOF 1 absorbs carboxyfluorescein (FAM)-tagged and 5(6)-carboxyrhodamine, triethylammonium salt (ROX)-tagged probe ss-DNA (probe DNA, P-DNA) by π … π stacking and hydrogen bonding, as well as additional electrostatic interactions to form a sensing platform of P-DNAs@1 with quenched FAM and ROX fluorescence. In the presence of targeted ebolavirus conserved RNA sequences or ebolavirus-encoded miRNA-like fragment, the fluorophore-labeled P-DNA hybridizes with the analyte to give a P-DNA@RNA duplex and released from MOF 1, triggering a fluorescence recovery. Simultaneous detection of two target RNAs has also been realized by single and synchronous fluorescence analysis. The formed sensing platform shows high sensitivity for ebolavirus conserved RNA sequences and ebolavirus-encoded miRNA-like fragment with detection limits at the picomolar level and high selectivity without cross-reaction between the two probes. MOF 1 thus shows the potential as an effective fluorescent sensing platform for the synchronous detection of two ebolavirus-related sequences, and offer improved diagnostic accuracy of Ebola virus disease. Copyright © 2017 Elsevier B.V. All rights reserved.

A novel method for the rapid detection of benzo(a)pyrene in liquid milk by dimethyl sulfoxide selectively enhanced synchronous fluorescence spectrometry.

PubMed

Lin, Li-Rong; Luo, He-Dong; Li, Xiu-Ying; Li, Na; Zhou, Na; Jia, Yu-Zhu; Liu, Yi-Hong; Li, Yao-Qun

2014-01-01

Based on the high solubility efficiency and strong fluorescence response of benzo(a)pyrene (BaP) in dimethyl sulfoxide in combination with the high-performance derivative constant-energy synchronous fluorescence spectroscopic (DCESFS) technique, a simple, sensitive and economic method was developed for the determination of BaP in liquid milk. This method comprises ultrasound-assisted solvent extraction, solvent replacement and DCESFS detection. No saponification or other tedious clean-up procedures were needed. The recoveries of BaP in different milk samples were greater than 82%. Detection limits in full- and low-fat milk were 0.03 and 0.04 μg kg(-1), respectively.

Rapid synthesis of N, S co-doped carbon dots and their application for Fe3+ ion detection

NASA Astrophysics Data System (ADS)

Zhang, Jian; Wang, Junbin; Fu, Jinping; Fu, Xucheng; Gan, Wei; Hao, Hequn

2018-02-01

In this study, nitrogen and sulfur co-doped carbon dots (NSCDs) were fabricated by microwave-assisted one-pot synthesis using vitamin C and thiourea as precursors. The as-prepared NSCDs demonstrated excellent properties, including aqueous dispensability, strong fluorescence emission, excellent environmental stability, high selectivity, and sensitivity toward Fe3+ ions. The NSCD-based material can be used as a "turn off" fluorescent probe for detecting Fe3+ ions at a low detection limit (4.2 nM). In addition, the "turn off" and "turn on" of NSCD fluorescent probe could be modulated by adding Fe3+ and EDTA, indicating weak interaction between the Fe3+ ions and NSCDs.

Engineering of near IR fluorescent albumin nanoparticles for in vivo detection of colon cancer

PubMed Central

2012-01-01

Background The use of near-infrared (NIR) fluorescence imaging techniques has gained great interest for early detection of cancer because water and other intrinsic biomolecules display negligible absorption or autofluorescence in this region. Novel fluorescent nanoparticles with potential to improve neoplasm detection sensitivity may prove to be a valuable tool in early detection of colon tumors. Methods The present study describes the synthesis and use of NIR fluorescent albumin nanoparticles as a diagnostic tool for detection of colon cancer. These fluorescent nanoparticles were prepared by a precipitation process of human serum albumin (HSA) in aqueous solution in the presence of a carboxylic acid derivative of the NIR dye IR-783 (CANIR). Tumor-targeting ligands such as peanut agglutinin (PNA), anti-carcinoembryonic antigen antibodies (anti-CEA) and tumor associated glycoprotein-72 monoclonal antibodies (anti-TAG-72) were covalently conjugated to the albumin nanoparticles via the surface carboxylate groups by using the carbodiimide activation method. Results and discussion Leakage of the encapsulated dye into PBS containing 4% HSA or human bowel juice was not detected. This study also demonstrates that the encapsulation of the NIR fluorescent dye within the HSA nanoparticles reduces the photobleaching of the dye significantly. Specific colon tumor detection in a mouse model was demonstrated for PNA, anti-CEA and anti-TAG-72 conjugated NIR fluorescent HSA nanoparticles. These bioactive NIR fluorescent albumin nanoparticles also detected invisible tumors that were revealed as pathological only subsequent to histological analysis. Conclusions These results may suggest a significant advantage of NIR fluorescence imaging using NIR fluorescent nanoparticles over regular colonoscopy. In future work we plan to broaden this study by encapsulating cancer drugs, such as paclitaxel and doxorubicin, within these biodegradable NIR fluorescent HSA nanoparticles, in order to use them for both detection as well as therapy of colon cancer and others. PMID:22891637

Quenching of cascade reaction between triplet and photochrome probes with nitroxide radicals. A novel labeling method in study of membranes and surface systems.

PubMed

Papper, V; Medvedeva, N; Fishov, I; Likhtenshtein, G I

2000-01-01

We proposed a new method for the study of molecular dynamics and fluidity of the living and model biomembranes and surface systems. The method is based on the measurements of the sensitized photoisomerization kinetics of a photochrome probe. The cascade triplet cis-trans photoisomerization of the excited stilbene derivative sensitized with the excited triplet Erythrosin B has been studied in a model liposome membrane. The photoisomerization reaction is depressed with nitroxide radicals quenching the excited triplet state of the sensitizer. The enhanced fluorescence polarization of the stilbene probe incorporated into liposome membranes indicates that the stilbene molecules are squeezed in a relatively viscous media of the phospholipids. Calibration of the "triple" cascade system is based on a previously proposed method that allows the measurement of the product of the quenching rate constant and the sensitizer's triplet lifetime, as well as the quantitative detection of the nitroxide radicals in the vicinity of the membrane surface. The experiment was conducted using the constant-illumination fluorescence technique. Sensitivity of the method using a standard commercial spectrofluorimeter is about 10(-12) mol of fluorescence molecules per sample and can be improved using an advanced fluorescence technique. The minimal local concentration of nitroxide radicals or any other quenchers being detected is about 10(-5) M. This method enables the investigation of any chemical and biological surface processes of microscopic scale when the minimal volume is about 10(-3) microL or less.

FITC-modified PPy nanotubes embedded in nanoporous AAO membrane can detect trace PCB20 via fluorescence ratiometric measurement.

PubMed

Wang, Meiling; Meng, Guowen; Huang, Qing; Xu, Qiaoling; Chu, Zhaoqin; Zhu, Chuhong

2011-04-07

A highly sensitive and selective fluorescence ratiometric sensor membrane for 2,3,3'-trichlorobiphenyl has been achieved, via depositing polypyrrole nanotubes (PPyNTs, the fluorescence indicator) in nano-porous anodic aluminium oxide (NPAAO) template and subsequently immobilizing fluorescein isothiocyanate (as an internal reference) onto the inner walls of the PPyNTs embedded in the NPAAO.

Near-infrared surface-enhanced fluorescence using silver nanoparticles in solution

NASA Astrophysics Data System (ADS)

Furtaw, Michael D.

Fluorescence spectroscopy is a widely used detection technology in many research and clinical assays. Further improvement to assay sensitivity may enable earlier diagnosis of disease, novel biomarker discovery, and ultimately, improved outcomes of clinical care along with reduction in costs. Near-infrared, surface-enhanced fluorescence (NIR-SEF) is a promising approach to improve assay sensitivity via simultaneous increase in signal with a reduction in background. This dissertation describes research conducted with the overall goal to determine the extent to which fluorescence in solution may be enhanced by altering specific variables involved in the formation of plasmon-active nanostructures of dye-labeled protein and silver nanoparticles in solution, with the intent of providing a simple solution that may be readily adopted by current fluorescence users in the life science research community. First, it is shown that inner-filtering, re-absorption of the emitted photons, can red-shift the optimal fluorophore spectrum away from the resonant frequency of the plasmon-active nanostructure. It is also shown that, under certain conditions, the quality factor may be a better indicator of SEF than the commonly accepted overlap of the fluorophore spectrum with the plasmon resonance of the nanostructure. Next, it is determined that streptavidin is the best choice for carrier protein, among the most commonly used dye-labeled detection antibodies, to enable the largest fluorescence enhancement when labeled with IRDye 800CW and used in combination with silver nanoparticles in solution. It is shown that the relatively small and symmetric geometry of streptavidin enables substantial electromagnetic-field confinement when bound to silver nanoparticles, leading to strong and reproducible enhancement. The role of silver nanoparticle aggregation is demonstrated in a droplet-based microfluidic chip and further optimized in a standard microtiter-plate format. A NIR-SEF technology based on aggregation with optimized salt concentration demonstrates a fluorescence signal enhancement up to 2530-fold while improving the limit-of-detection over 1000-fold. Finally, the NIR-SEF technology is applied to demonstrate 42-fold improvement in sensitivity of the clinically-relevant biomarker, alpha-fetoprotein, along with a 16-fold improvement in limit-of-detection.

In Vivo Fluorescence Imaging and Tracking of Circulating Cells and Therapeutic Nanoparticles

NASA Astrophysics Data System (ADS)

Markovic, Stacey

Noninvasive enumeration of rare circulating cells in small animals is of great importance in many areas of biomedical research, but most existing enumeration techniques involve drawing and enriching blood which is known to be problematic. Recently, small animal "in vivo flow cytometry" (IVFC) techniques have been developed, where cells flowing through small arterioles are counted continuously and noninvasively in vivo. However, higher sensitivity IVFC techniques are needed for studying low-abundance (<100/mL) circulating cells. To this end, we developed a macroscopic fluorescence imaging system and automated computer vision algorithm that allows in vivo detection, enumeration and tracking of circulating fluorescently labeled cells from multiple large blood vessels in the ear of a mouse. This technique ---"computer vision IVFC" (CV-IVFC) --- allows cell detection and enumeration at concentrations of 20 cells/mL. Performance of CV-IVFC was also characterized for low-contrast imaging scenarios, representing conditions of weak cell fluorescent labeling or high background tissue autofluorescence, and showed efficient tracking and enumeration of circulating cells with 50% sensitivity in contrast conditions degraded 2 orders of magnitude compared to in vivo testing supporting the potential utility of CV-IVFC in a range of biological models. Refinement of prior work in our lab of a separate rare-cell detection platform - "diffuse fluorescence flow cytometry" (DFFC) --- implemented a "frequency encoding" scheme by modulating two excitation lasers. Fluorescent light from both lasers can be simultaneously detected and split by frequency allowing for better discrimination of noise, sensitivity, and cell localization. The system design is described in detail and preliminary data is shown. Last, we developed a broad-field transmission fluorescence imaging system to observe nanoparticle (NP) diffusion in bulk biological tissue. Novel, implantable NP spacers allow controlled, long-term release of drugs. However, kinetics of NP (drug) diffusion over time is still poorly understood. Our imaging system allowed us to quantify diffusion of free dye and NPs of different sizes in vitro and in vivo. Subsequent analysis verified that there was continuous diffusion which could be controlled based on particle size. Continued use of this imaging system will aid optimization of NP spacers.

A Sensitive Near-Infrared Fluorescent Sensor for Mitochondrial Hydrogen Sulfide.

PubMed

Ji, Ao; Fan, Yichong; Ren, Wei; Zhang, Shen; Ai, Hui-Wang

2018-05-03

Hydrogen sulfide (H 2 S) is an important gasotransmitter. Although a large number of fluorescent probes for cellular H 2 S have been reported, only a few can detect H 2 S in mitochondria, a cellular organelle connecting H 2 S with mitochondrial function and metabolic pathways. We hereby describe a novel near-infrared fluorescent probe, nimazide, by introducing sulfonyl azide to the core structure of a QSY-21 dark quencher. Nimazide responded quickly to H 2 S, resulting in robust fluorescence turn-off changes. This conversion displayed high specificity and fast kinetics. More impressively, we observed a robust fluorescence decrease in live cells loaded with mitochondrial nimazide in response to extracellular addition of nanomolar H 2 S, and successfully imaged biologically generated mitochondrial H 2 S in live mammalian cells. Nimazide is one of the most sensitive fluorescent probes for mitochondrial H 2 S.