Surface Transient Binding-Based Fluorescence Correlation Spectroscopy (STB-FCS), a Simple and Easy-to-Implement Method to Extend the Upper Limit of the Time Window to Seconds.

PubMed

Peng, Sijia; Wang, Wenjuan; Chen, Chunlai

2018-05-10

Fluorescence correlation spectroscopy is a powerful single-molecule tool that is able to capture kinetic processes occurring at the nanosecond time scale. However, the upper limit of its time window is restricted by the dwell time of the molecule of interest in the confocal detection volume, which is usually around submilliseconds for a freely diffusing biomolecule. Here, we present a simple and easy-to-implement method, named surface transient binding-based fluorescence correlation spectroscopy (STB-FCS), which extends the upper limit of the time window to seconds. We further demonstrated that STB-FCS enables capture of both intramolecular and intermolecular kinetic processes whose time scales cross several orders of magnitude.

Simple fibre based dispersion management for two-photon excited fluorescence imaging through an endoscope

NASA Astrophysics Data System (ADS)

Dimopoulos, Konstantinos; Marti, Dominik; Andersen, Peter E.

2018-02-01

We want to implement two-photon excitation fluorescence microscopy (TPEFM) into endoscopes, since TPEFM can provide relevant biomarkers for cancer staging and grading in hollow organs, endoscopically accessible through natural orifices. However, many obstacles must be overcome, among others the delivery of short laser pulses to the distal end of the endoscope. To this avail, we present imaging results using an all-fibre dispersion management scheme in a TPEFM setup. The scheme has been conceived by Jespersen et al. in 20101 and relies on the combination of a single mode fibre with normal and a higher order mode fibre with anomalous dispersion properties, fused in series using a long period grating. We show that using this fibre assembly, a simple and robust pulsed laser delivery system without any free-space optics, which is thus suitable for clinical use, can be realised.

A new simple phthalimide-based fluorescent probe for highly selective cysteine and bioimaging for living cells

NASA Astrophysics Data System (ADS)

Shen, Youming; Zhang, Xiangyang; Zhang, Youyu; Zhang, Chunxiang; Jin, Junling; Li, Haitao

2017-10-01

A new turn-on phthalimide fluorescent probe has designed and synthesized for sensing cysteine (Cys) based on excited state intramolecular proton transfer (ESIPT) process. It is consisted of a 3-hydroxyphthalimide derivative moiety as the fluorophore and an acrylic ester group as a recognition receptor. The acrylic ester acts as an ESIPT blocking agent. Upon addition of cystein, intermolecular nucleophilic attack of cysteine on acrylic ester releases the fluorescent 3-hydroxyphthalimide derivative, thereby enabling the ESIPT process and leading to enhancement of fluorescence. The probe displays high sensitivity, excellent selectivity and with large Stokes shift toward cysteine. The linear interval range of the fluorescence titration ranged from 0 to 1.0 × 10- 5 M and detection limit is low (6 × 10- 8 M). In addition, the probe could be used for bio-imaging in living cells.

A synthesis of fluorescent starch based on carbon nanoparticles for fingerprints detection

NASA Astrophysics Data System (ADS)

Li, Hongren; Guo, Xingjia; Liu, Jun; Li, Feng

2016-10-01

A pyrolysis method for synthesizing carbon nanoparticles (CNPs) were developed by using malic acid and ammonium oxalate as raw materials. The incorporation of a minor amount of carbon nanoparticles into starch powder imparts remarkable color-tunability. Based on this phenomenon, an environment friendly fluorescent starch powder for detecting latent fingerprints in non-porous surfaces was prepared. The fingerprints on different non-porous surfaces developed with this powder showed very good fluorescent images under ultraviolet excitation. The method using fluorescent starch powder as fluorescent marks is simple, rapid and green. Experimental results illustrated the effectiveness of proposed methods, enabling its practical applications in forensic sciences.

Nonmydriatic fluorescence-based quantitative imaging of human macular pigment distributions

NASA Astrophysics Data System (ADS)

Sharifzadeh, Mohsen; Bernstein, Paul S.; Gellermann, Werner

2006-10-01

We have developed a CCD-camera-based nonmydriatic instrument that detects fluorescence from retinal lipofuscin chromophores ("autofluorescence") as a means to indirectly quantify and spatially image the distribution of macular pigment (MP). The lipofuscin fluorescence intensity is reduced at all retinal locations containing MP, since MP has a competing absorption in the blue-green wavelength region. Projecting a large diameter, 488 nm excitation spot onto the retina, centered on the fovea, but extending into the macular periphery, and comparing lipofuscin fluorescence intensities outside and inside the foveal area, it is possible to spatially map out the distribution of MP. Spectrally selective detection of the lipofuscin fluorescence reveals an important wavelength dependence of the obtainable image contrast and deduced MP optical density levels, showing that it is important to block out interfering fluorescence contributions in the detection setup originating from ocular media such as the lens. Measuring 70 healthy human volunteer subjects with no ocular pathologies, we find widely varying spatial extent of MP, distinctly differing distribution patterns of MP, and strongly differing absolute MP levels among individuals. Our population study suggests that MP imaging based on lipofuscin fluorescence is useful as a relatively simple, objective, and quantitative noninvasive optical technique suitable to rapidly screen MP levels and distributions in healthy humans with undilated pupils.

A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE INDUCED BY STYRENE OXIDE

EPA Science Inventory

A rapid and simple assay to detect DNA damage to calf thymus DNA caused by styrene oxide (SO) is reported. This assay is based on changes observed in the melting and annealing behavior of the damaged DNA. The melting annealing process was monitored using a fluorescence indicat...

Simple process of hybrid white quantum dot/organic light-emitting diodes by using quantum dot plate and fluorescence

NASA Astrophysics Data System (ADS)

Lee, Ho Won; Lee, Ki-Heon; Lee, Jae Woo; Kim, Jong-Hoon; Yang, Heesun; Kim, Young Kwan

2015-02-01

In this work, the simple process of hybrid quantum dot (QD)/organic light-emitting diode (OLED) was proposed to apply a white illumination light by using QD plate and organic fluorescence. Conventional blue fluorescent OLEDs were firstly fabricated and then QD plates of various concentrations, which can be controlled of UV-vis absorption and photoluminescence spectrum, were attached under glass substrate of completed blue devices. The suggested process indicates that we could fabricate the white device through very simple process without any deposition of orange or red organic emitters. Therefore, this work would be demonstrated that the potential simple process for white applications can be applied and also can be extended to additional research on light applications.

A facile fluorescent "turn-off" method for sensing paraquat based on pyranine-paraquat interaction

NASA Astrophysics Data System (ADS)

Zhao, Zuzhi; Zhang, Fengwei; Zhang, Zipin

2018-06-01

Development of a technically simple yet effective method for paraquat (PQ) detection is of great importance due to its high clinical and environmental relevance. In this study, we developed a pyranine-based fluorescent "turn-off" method for PQ sensing based on pyranine-PQ interaction. We investigated the dependence of analytical performance of this method on the experimental conditions, such as the ion strength, medium pH, and so on. Under the optimized conditions, the method is sensitive and selective, and could be used for PQ detection in real-world sample. This study essentially provides a readily accessible fluorescent system for PQ sensing which is cheap, robust, and technically simple, and it is envisaged to find more interesting clinical and environmental applications.

Plant genotyping using fluorescently tagged inter-simple sequence repeats (ISSRs): basic principles and methodology.

PubMed

Prince, Linda M

2015-01-01

Inter-simple sequence repeat PCR (ISSR-PCR) is a fast, inexpensive genotyping technique based on length variation in the regions between microsatellites. The method requires no species-specific prior knowledge of microsatellite location or composition. Very small amounts of DNA are required, making this method ideal for organisms of conservation concern, or where the quantity of DNA is extremely limited due to organism size. ISSR-PCR can be highly reproducible but requires careful attention to detail. Optimization of DNA extraction, fragment amplification, and normalization of fragment peak heights during fluorescent detection are critical steps to minimizing the downstream time spent verifying and scoring the data.

An aptamer-based fluorescence bio-sensor for chiral recognition of arginine enantiomers

NASA Astrophysics Data System (ADS)

Yuan, Haiyan; Huang, Yunmei; Yang, Jidong; Guo, Yuan; Zeng, Xiaoqing; Zhou, Shang; Cheng, Jiawei; Zhang, Yuhui

2018-07-01

In this study, a novel aptamer - based fluorescence bio-sensor (aptamer-AuNps) was developed for chiral recognition of arginine (Arg) enantiomers based on aptamer and gold nanoparticles (AuNps). Carboxyfluorescein (FAM) labeled aptamers (Apt) were absorbed on AuNps and their fluorescence intensity could be significantly quenched by AuNps based on fluorescence resonance energy transfer (FRET). Once D-Arg or L-Arg were added into the above solution, the aptamer specifically bind to Arg enantiomers and released from AuNps, so the fluorescence intensity of D-Arg system and L-Arg system were all enhanced. The affinity of Apt to L-Arg is tighter to D-Arg, so the enhanced fluorescence signals of L-Arg system was stronger than D-Arg system. What's more, the enhanced fluorescence were directly proportional to the concentration of D-Arg and L-Arg ranging from 0-300 nM and 0-400 nM with related coefficients of 0.9939 and 0.9952, respectively. Furthermore, the method was successfully applied to detection L-Arg in human urine samples with satisfactory results. Eventually, a simple "OR" logic gate with D-Arg &L-Arg as inputs and AuNps aggregation state as outputs was fabricated, which can help us understand the chiral recognition process deeply.

Eco-friendly carbon-nanodot-based fluorescent paints for advanced photocatalytic systems

PubMed Central

Young Park, So; Uk Lee, Hyun; Lee, Young-Chul; Choi, Saehae; Hyun Cho, Dae; Sik Kim, Hee; Bang, Sunghee; Seo, Soonjoo; Chang Lee, Soon; Won, Jonghan; Son, Byung-Chul; Yang, Mino; Lee, Jouhahn

2015-01-01

Fluorescent carbon nanomaterials, especially zero-dimensional (0D) carbon nanodots (CDs), are widely used in broad biological and optoelectronic applications. CDs have unique characteristics such as strong fluorescence, biocompatibility, sun-light response, and capability of mass-production. Beyond the previous green CD obtained from harmful natural substances, we report a new type of fluid-based fluorescent CD paints (C-paints) derived from polyethylene glycol (PEG; via simple ultrasound irradiation at room temperatures) and produced in quantum yields of up to ~14%. Additionally, C-paints possess a strong, UV- and visible-light-responsive photoluminescent (PL) property. Most especially, C-paints, by incorporation into a photocatalytic system, show additional roles in the emission of fluorescent light for activation of TiO2 nanoparticles (NPs) and the resultant detoxification of most organic dyes, thus further enabling embarkation in advanced water purification. PMID:26201431

Eco-friendly carbon-nanodot-based fluorescent paints for advanced photocatalytic systems.

PubMed

Park, So Young; Lee, Hyun Uk; Lee, Young-Chul; Choi, Saehae; Cho, Dae Hyun; Kim, Hee Sik; Bang, Sunghee; Seo, Soonjoo; Lee, Soon Chang; Won, Jonghan; Son, Byung-Chul; Yang, Mino; Lee, Jouhahn

2015-07-23

Fluorescent carbon nanomaterials, especially zero-dimensional (0D) carbon nanodots (CDs), are widely used in broad biological and optoelectronic applications. CDs have unique characteristics such as strong fluorescence, biocompatibility, sun-light response, and capability of mass-production. Beyond the previous green CD obtained from harmful natural substances, we report a new type of fluid-based fluorescent CD paints (C-paints) derived from polyethylene glycol (PEG; via simple ultrasound irradiation at room temperatures) and produced in quantum yields of up to ~14%. Additionally, C-paints possess a strong, UV- and visible-light-responsive photoluminescent (PL) property. Most especially, C-paints, by incorporation into a photocatalytic system, show additional roles in the emission of fluorescent light for activation of TiO2 nanoparticles (NPs) and the resultant detoxification of most organic dyes, thus further enabling embarkation in advanced water purification.

Multistage Spatial Property Based Segmentation for Quantification of Fluorescence Distribution in Cells

NASA Astrophysics Data System (ADS)

Zhang, Guangyun; Jia, Xiuping; Pham, Tuan D.; Crane, Denis I.

2010-01-01

The interpretation of the distribution of fluorescence in cells is often by simple visualization of microscope-derived images for qualitative studies. In other cases, however, it is desirable to be able to quantify the distribution of fluorescence using digital image processing techniques. In this paper, the challenges of fluorescence segmentation due to the noise present in the data are addressed. We report that intensity measurements alone do not allow separation of overlapping data between target and background. Consequently, spatial properties derived from neighborhood profile were included. Mathematical Morphological operations were implemented for cell boundary extraction and a window based contrast measure was developed for fluorescence puncta identification. All of these operations were applied in the proposed multistage processing scheme. The testing results show that the spatial measures effectively enhance the target separability.

Compound parabolic concentrator optical fiber tip for FRET-based fluorescent sensors

NASA Astrophysics Data System (ADS)

Ul Hassan, Hafeez; Nielsen, Kristian; Aasmul, Soren; Bang, Ole

2015-09-01

The Compound Parabolic Concentrator (CPC) optical fiber tip shape has been proposed for intensity based fluorescent sensors working on the principle of FRET (Förster Resonance Energy Transfer). A simple numerical Zemax model has been used to optimize the CPC tip geometry for a step-index multimode polymer optical fiber for an excitation and emission wavelength of 550 nm and 650nm, respectively. The model suggests an increase of a factor of 1.6 to 4 in the collected fluorescent power for an ideal CPC tip, as compared to the plane-cut fiber tip for fiber lengths between 5 and 45mm.

Innovative molecular-based fluorescent nanoparticles for multicolor single particle tracking in cells

NASA Astrophysics Data System (ADS)

Daniel, Jonathan; Godin, Antoine G.; Palayret, Matthieu; Lounis, Brahim; Cognet, Laurent; Blanchard-Desce, Mireille

2016-03-01

Based on an original molecular-based design, we present bright and photostable fluorescent organic nanoparticles (FONs) showing excellent colloidal stability in various aqueous environments. Complementary near-infrared emitting and green emitting FONs were prepared using a simple, fast and robust protocol. Both types of FONs could be simultaneously imaged at the single-particle level in solution as well as in biological environments using a monochromatic excitation and a dual-color fluorescence microscope. No evidence of acute cytotoxicity was found upon incubation of live cells with mixed solutions of FONs, and both types of nanoparticles were found internalized in the cells where their motion could be simultaneously tracked at video-rate up to minutes. These fluorescent organic nanoparticles open a novel non-toxic alternative to existing nanoparticles for imaging biological structures, compatible with live-cell experiments and specially fitted for multicolor single particle tracking.

An aptamer-based fluorescence bio-sensor for chiral recognition of arginine enantiomers.

PubMed

Yuan, Haiyan; Huang, Yunmei; Yang, Jidong; Guo, Yuan; Zeng, Xiaoqing; Zhou, Shang; Cheng, Jiawei; Zhang, Yuhui

2018-07-05

In this study, a novel aptamer - based fluorescence bio-sensor (aptamer-AuNps) was developed for chiral recognition of arginine (Arg) enantiomers based on aptamer and gold nanoparticles (AuNps). Carboxyfluorescein (FAM) labeled aptamers (Apt) were absorbed on AuNps and their fluorescence intensity could be significantly quenched by AuNps based on fluorescence resonance energy transfer (FRET). Once d-Arg or l-Arg were added into the above solution, the aptamer specifically bind to Arg enantiomers and released from AuNps, so the fluorescence intensity of d-Arg system and l-Arg system were all enhanced. The affinity of Apt to l-Arg is tighter to d-Arg, so the enhanced fluorescence signals of l-Arg system was stronger than d-Arg system. What's more, the enhanced fluorescence were directly proportional to the concentration of d-Arg and l-Arg ranging from 0-300 nM and 0-400 nM with related coefficients of 0.9939 and 0.9952, respectively. Furthermore, the method was successfully applied to detection l-Arg in human urine samples with satisfactory results. Eventually, a simple "OR" logic gate with d-Arg &l-Arg as inputs and AuNps aggregation state as outputs was fabricated, which can help us understand the chiral recognition process deeply. Copyright © 2018 Elsevier B.V. All rights reserved.

A simple dental caries detection system using full spectrum of laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Rocha-Cabral, Renata Maciel; Mendes, Fausto Medeiros; Maldonado, Edison Puig; Zezell, Denise Maria

2015-06-01

Objectives: to develop an apparatus for the detection of early caries lesions in enamel using the full extent of the tooth fluorescence spectrum, through the integration of a laser diode, fiber optics, filters and one portable spectrometer connected to a computer, all commercially available; to evaluate the developed device in clinical and laboratory tests, and compare its performance with commercial equipment. Methods: clinical examinations were performed in patients with indication for exodontics of premolars. After examinations, the patients underwent surgery and the teeth were stored individually. The optical measurements were repeated approximately two months after extraction, on the same sites previously examined, then histological analysis was carried out. Results: the spectral detector has presented high specificity and moderate sensitivity when applied to differentiate between healthy and damaged tissues, with no significant differences from the performance of the commercial equipment. The developed device is able to detect initial damages in enamel, with depth of approximately 300 μm. Conclusions: we successfully demonstrated the development of a simple and portable system based in laser-induced fluorescence for caries detection, assembled from common commercial parts. As the spectral detector acquires a complete recording of the spectrum from each tissue, it is possible to use it for monitoring developments of caries lesions.

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.

Teaching about photosynthesis with simple equipment: analysis of light-induced changes in fluorescence and reflectance of plant leaves.

PubMed

Björn, Lars Olof; Li, Shaoshan

2013-10-01

Solar energy absorbed by plants results in either reflection or absorption. The latter results in photosynthesis, fluorescence, or heat. Measurements of fluorescence changes have been used for monitoring processes associated with photosynthesis. A simple method to follow changes in leaf fluorescence and leaf reflectance associated with nonphotochemical quenching and light acclimation of leaves is described. The main equipment needed consists of a green-light emitting laser pointer, a digital camera, and a personal computer equipped with the camera acquisition software and the programs ImageJ and Excel. Otherwise, only commonly available cheap materials are required.

A rapid-screening approach to detect and quantify microplastics based on fluorescent tagging with Nile Red

NASA Astrophysics Data System (ADS)

Maes, Thomas; Jessop, Rebecca; Wellner, Nikolaus; Haupt, Karsten; Mayes, Andrew G.

2017-03-01

A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy.

A rapid-screening approach to detect and quantify microplastics based on fluorescent tagging with Nile Red

PubMed Central

Maes, Thomas; Jessop, Rebecca; Wellner, Nikolaus; Haupt, Karsten; Mayes, Andrew G.

2017-01-01

A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy. PMID:28300146

A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE INDUCED BY RADIATION, CHEMICAL MUTAGENS AND ENZYMES

EPA Science Inventory

A simple and rapid assay to detect DNA damage is reported. This novel assay is based on changes in melting/annealing behavior and facilitated using certain dyes that increase their fluorescence upon association with double stranded (ds)DNA. Damage caused by ultraviolet (UV) ra...

Design and development of a simple UV fluorescence multi-spectral imaging system

NASA Astrophysics Data System (ADS)

Tovar, Carlos; Coker, Zachary; Yakovlev, Vladislav V.

2018-02-01

Healthcare access in low-resource settings is compromised by the availability of affordable and accurate diagnostic equipment. The four primary poverty-related diseases - AIDS, pneumonia, malaria, and tuberculosis - account for approximately 400 million annual deaths worldwide as of 2016 estimates. Current diagnostic procedures for these diseases are prolonged and can become unreliable under various conditions. We present the development of a simple low-cost UV fluorescence multi-spectral imaging system geared towards low resource settings for a variety of biological and in-vitro applications. Fluorescence microscopy serves as a useful diagnostic indicator and imaging tool. The addition of a multi-spectral imaging modality allows for the detection of fluorophores within specific wavelength bands, as well as the distinction between fluorophores possessing overlapping spectra. The developed instrument has the potential for a very diverse range of diagnostic applications in basic biomedical science and biomedical diagnostics and imaging. Performance assessment of the microscope will be validated with a variety of samples ranging from organic compounds to biological samples.

Fluorescent and colorimetric ion probes based on conjugated oligopyrroles.

PubMed

Ding, Yubin; Tang, Yunyu; Zhu, Weihong; Xie, Yongshu

2015-03-07

Metal ions and anions play important roles in many industrial and biochemical processes, and thus it is highly desired to detect them in the relevant systems. Small organic molecule based sensors for selective and sensitive detection of target ions show the advantages of low cost, high sensitivity and convenient implementation. In this area, pyrrole has incomparable advantages. It can be easily incorporated into linear and macrocyclic conjugated structures such as dipyrrins, porphyrins, and N-confused porphyrins, which may utilize the imino N and amino NH moieties for binding metal ions and anions, respectively. In this tutorial review, we focus on representative examples to describe the design, syntheses, sensing mechanisms, and applications of the conjugated oligopyrroles. These compounds could be used as colorimetric or fluorescent ion probes, with the advantages of vivid colour and fluorescence changes, easy structural modification and functionalization, and tunable emission wavelengths. Compared with normal porphyrins, simple di- and tripyrrins, as well as some porphyrinoids are more suitable for designing fluorescence "turn-on" metal probes, because they may exhibit flexible confirmations, and metal coordination will improve the rigidity, resulting in vivid fluorescence enhancement. It is noteworthy that the oligopyrrolic moieties may simultaneously act as the binding unit as well as the reporting moiety, which simplifies the design and syntheses of the probes.

How To Characterize Individual Nanosize Liposomes with Simple Self-Calibrating Fluorescence Microscopy.

PubMed

Mortensen, Kim I; Tassone, Chiara; Ehrlich, Nicky; Andresen, Thomas L; Flyvbjerg, Henrik

2018-05-09

Nanosize lipid vesicles are used extensively at the interface between nanotechnology and biology, e.g., as containers for chemical reactions at minute concentrations and vehicles for targeted delivery of pharmaceuticals. Typically, vesicle samples are heterogeneous as regards vesicle size and structural properties. Consequently, vesicles must be characterized individually to ensure correct interpretation of experimental results. Here we do that using dual-color fluorescence labeling of vesicles-of their lipid bilayers and lumens, separately. A vesicle then images as two spots, one in each color channel. A simple image analysis determines the total intensity and width of each spot. These four data all depend on the vesicle radius in a simple manner for vesicles that are spherical, unilamellar, and optimal encapsulators of molecular cargo. This permits identification of such ideal vesicles. They in turn enable calibration of the dual-color fluorescence microscopy images they appear in. Since this calibration is not a separate experiment but an analysis of images of vesicles to be characterized, it eliminates the potential source of error that a separate calibration experiment would have been. Nonideal vesicles in the same images were characterized by how their four data violate the calibrated relationship established for ideal vesicles. In this way, our method yields size, shape, lamellarity, and encapsulation efficiency of each imaged vesicle. Applying this procedure to extruded samples of vesicles, we found that, contrary to common assumptions, only a fraction of vesicles are ideal.

Ion Sensor Properties of Fluorescent Schiff Bases Carrying Dipicolylamine Groups. A Simple Spectrofluorimetric Method to Determine Cu (II) in Water Samples.

PubMed

Vanlı, Elvan; Mısır, Miraç Nedim; Alp, Hakan; Ak, Tuğba; Özbek, Nurhayat; Ocak, Ümmühan; Ocak, Miraç

2017-09-01

Four fluorescent Schiff bases carrying dipicolylamine groups were designed and synthesized to determine their ion sensor properties in partial aqueous solution. The corresponding amine compound and the aldehyde compounds such as 1-naphthaldehyde, 9-anthraldehyde, phenanthrene-9-carboxaldehyde and 1-pyrenecarboxaldehyde were used to prepare the new Schiff bases. The influence of many metal cations and anions on the spectroscopic properties of the ligands was investigated in ethanol-water (1:1) by means of emission spectrometry. From the spectrofluorimetric titrations, the complexation stoichiometry and complex stability constants of the ligands with Cd 2+ , Zn 2+ , Cu 2+ and Hg 2+ ions were determined. The ligands did not interact with the anions. However, the Schiff base derived from phenanthrene-9-carboxaldehyde showed sensitivity for Cu 2+ among the tested metal ions. The phenanthrene-based Schiff base was used as analytical ligand for the simple and fast determination of Cu 2+ ion in water samples. A modified standard addition method was used to eliminate matrix effect. The linear range was from 0.3 mg/L to 3.8 μg/L. Detection and quantification limits were 0.14 and 0.43 mg/L, respectively. Maximum contaminant level goal (MCLG) for copper in drinking water according to EPA is 1.3 mg/L. The proposed method has high sensitivity to determine copper in drinking waters.

Characterization of flavin-based fluorescent proteins: an emerging class of fluorescent reporters.

PubMed

Mukherjee, Arnab; Walker, Joshua; Weyant, Kevin B; Schroeder, Charles M

2013-01-01

Fluorescent reporter proteins based on flavin-binding photosensors were recently developed as a new class of genetically encoded probes characterized by small size and oxygen-independent maturation of fluorescence. Flavin-based fluorescent proteins (FbFPs) address two major limitations associated with existing fluorescent reporters derived from the green fluorescent protein (GFP)-namely, the overall large size and oxygen-dependent maturation of fluorescence of GFP. However, FbFPs are at a nascent stage of development and have been utilized in only a handful of biological studies. Importantly, a full understanding of the performance and properties of FbFPs as a practical set of biological probes is lacking. In this work, we extensively characterize three FbFPs isolated from Pseudomonas putida, Bacillus subtilis, and Arabidopsis thaliana, using in vitro studies to assess probe brightness, oligomeric state, maturation time, fraction of fluorescent holoprotein, pH tolerance, redox sensitivity, and thermal stability. Furthermore, we validate FbFPs as stable molecular tags using in vivo studies by constructing a series of FbFP-based transcriptional constructs to probe promoter activity in Escherichia coli. Overall, FbFPs show key advantages as broad-spectrum biological reporters including robust pH tolerance (4-11), thermal stability (up to 60°C), and rapid maturation of fluorescence (<3 min.). In addition, the FbFP derived from Arabidopsis thaliana (iLOV) emerged as a stable and nonperturbative reporter of promoter activity in Escherichia coli. Our results demonstrate that FbFP-based reporters have the potential to address key limitations associated with the use of GFP, such as pH-sensitive fluorescence and slow kinetics of fluorescence maturation (10-40 minutes for half maximal fluorescence recovery). From this view, FbFPs represent a useful new addition to the fluorescent reporter protein palette, and our results constitute an important framework to enable

Simple determination of aflatoxins in rice by ultra-high performance liquid chromatography coupled to chemical post-column derivatization and fluorescence detection.

PubMed

Huertas-Pérez, José Fernando; Arroyo-Manzanares, Natalia; Hitzler, Dominik; Castro-Guerrero, Francisco Germán; Gámiz-Gracia, Laura; García-Campaña, Ana M

2018-04-15

A fast and simple analytical method was developed and characterized for the determination of aflatoxins (B 1 , B 2 , G 1 and G 2 ) in rice. The procedure is based on a simple solid-liquid extraction without further clean-up, and analysis by ultra-high performance liquid chromatography coupled with fluorescence detection. Fluorescence emission of aflatoxins B 1 and G 1 was enhanced by post-column chemical derivatization using pyridinium bromide perbromide. The analytical method was satisfactorily characterized in white and brown rice. Under optimum conditions, external calibration in solvent could be used for quantification purposes and limits of quantification were below the maximum contents established by the European Union regulation for these contaminants/commodity group combination (0.07-0.14 µg/kg for white rice and 0.20-0.28 µg/kg for brown rice). Recovery studies carried out at three different concentration levels (0.5, 2 and 5 µg/kg) showed values in the range of 84.5-105.3%, and RSDs ≤ 5%. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Simple and Selective Fluorescent Sensor Chip for Indole-3-Butyric Acid in Mung Bean Sprouts Based on Molecularly Imprinted Polymer Coatings

PubMed Central

Chang, Jiahua; Bahethan, Bota; Muhammad, Turghun; Yakup, Burabiye; Abbas, Mamatimin

2017-01-01

In this paper, we report the preparation of molecularly imprinted polymer coatings on quartz chips for selective solid-phase microextraction and fluorescence sensing of the auxin, indole-3-butyric acid. The multiple copolymerization method was used to prepare polymer coatings on silylated quartz chips. The polymer preparation conditions (e.g., the solvent, monomer, and cross-linker) were investigated systemically to enhance the binding performance of the imprinted coatings. Direct solid-phase fluorescence measurements on the chips facilitated monitoring changes in coating performance. The average binding capacity of an imprinted polymer coated chip was approximately 152.9 µg, which was higher than that of a non-imprinted polymer coated chip (60.8 µg); the imprinted coatings showed the highest binding to IBA among the structural analogues, indicating that the coatings possess high selectivity toward the template molecule. The developed method was used for the determination of the auxin in mung bean extraction, and the recovery was found to be in the range of 91.5% to 97.5%, with an RSD (n = 3) of less than 7.4%. Thus, the present study provides a simple method for fabricating a fluorescent sensor chip for selective analysis. PMID:28837081

A base-modified PNA-graphene oxide platform as a turn-on fluorescence sensor for the detection of human telomeric repeats

NASA Astrophysics Data System (ADS)

Sabale, Pramod M.; George, Jerrin Thomas; Srivatsan, Seergazhi G.

2014-08-01

Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures.Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures. Electronic supplementary information (ESI

Note: A portable, light-emitting diode-based ruby fluorescence spectrometer for high-pressure calibration

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

Feng Yejun

2011-04-15

Ruby (Al{sub 2}O{sub 3}, with {approx}0.5 wt. % Cr doping) is one of the most widely used manometers at the giga-Pascal scale. Traditionally, its fluorescence is excited with intense laser sources. Here, I present a simple, robust, and portable design that employs light-emitting diodes (LEDs) instead. This LED-based system is safer in comparison with laser-based ones.

Handheld Fluorescence Microscopy based Flow Analyzer.

PubMed

Saxena, Manish; Jayakumar, Nitin; Gorthi, Sai Siva

2016-03-01

Fluorescence microscopy has the intrinsic advantages of favourable contrast characteristics and high degree of specificity. Consequently, it has been a mainstay in modern biological inquiry and clinical diagnostics. Despite its reliable nature, fluorescence based clinical microscopy and diagnostics is a manual, labour intensive and time consuming procedure. The article outlines a cost-effective, high throughput alternative to conventional fluorescence imaging techniques. With system level integration of custom-designed microfluidics and optics, we demonstrate fluorescence microscopy based imaging flow analyzer. Using this system we have imaged more than 2900 FITC labeled fluorescent beads per minute. This demonstrates high-throughput characteristics of our flow analyzer in comparison to conventional fluorescence microscopy. The issue of motion blur at high flow rates limits the achievable throughput in image based flow analyzers. Here we address the issue by computationally deblurring the images and show that this restores the morphological features otherwise affected by motion blur. By further optimizing concentration of the sample solution and flow speeds, along with imaging multiple channels simultaneously, the system is capable of providing throughput of about 480 beads per second.

Simple Elimination of Background Fluorescence in Formalin-Fixed Human Brain Tissue for Immunofluorescence Microscopy.

PubMed

Sun, Yulong; Ip, Philbert; Chakrabartty, Avijit

2017-09-03

Immunofluorescence is a common method used to visualize subcellular compartments and to determine the localization of specific proteins within a tissue sample. A great hindrance to the acquisition of high quality immunofluorescence images is endogenous autofluorescence of the tissue caused by aging pigments such as lipofuscin or by common sample preparation processes such as aldehyde fixation. This protocol describes how background fluorescence can be greatly reduced through photobleaching using white phosphor light emitting diode (LED) arrays prior to treatment with fluorescent probes. The broad-spectrum emission of white phosphor LEDs allow for bleaching of fluorophores across a range of emission peaks. The photobleaching apparatus can be constructed from off-the-shelf components at very low cost and offers an accessible alternative to commercially available chemical quenchers. A photobleaching pre-treatment of the tissue followed by conventional immunofluorescence staining generates images free of background autofluorescence. Compared to established chemical quenchers which reduced probe as well as background signals, photobleaching treatment had no effect on probe fluorescence intensity while it effectively reduced background and lipofuscin fluorescence. Although photobleaching requires more time for pre-treatment, higher intensity LED arrays may be used to reduce photobleaching time. This simple method can potentially be applied to a variety of tissues, particularly postmitotic tissues that accumulate lipofuscin such as the brain and cardiac or skeletal muscles.

Oral cancer detection based on fluorescence polarization of blood plasma at excitation wavelength 405 nm

NASA Astrophysics Data System (ADS)

Pachaiappan, Rekha; Prakasarao, Aruna; Manoharan, Yuvaraj; Dornadula, Koteeswaran; Singaravelu, Ganesan

2017-02-01

During metabolism the metabolites such as hormones, proteins and enzymes were released in to the blood stream by the cells. These metabolites reflect any change that occurs due to any disturbances in normal metabolic function of the human system. This was well observed with the altered spectral signatures observed with fluorescence spectroscopic technique. Previously many have reported on the significance of native fluorescence spectroscopic method in the diagnosis of cancer. As fluorescence spectroscopy is sensitive and simple, it has complementary techniques such as excitation-emission matrix, synchronous and polarization. The fluorescence polarization measurement provides details about any association or binding reactions and denaturing effects that occurs due to change in the micro environment of cells and tissues. In this study, we have made an attempt in the diagnosis of oral cancer at 405 nm excitation using fluorescence polarization measurement. The fluorescence anisotropic values calculated from polarized fluorescence spectral data of normal and oral cancer subjects yielded a good accuracy when analyzed with linear discriminant analysis based artificial neural network. The results will be discussed in detail.

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.

Fluorescence-based visualization of autophagic activity predicts mouse embryo viability

NASA Astrophysics Data System (ADS)

Tsukamoto, Satoshi; Hara, Taichi; Yamamoto, Atsushi; Kito, Seiji; Minami, Naojiro; Kubota, Toshiro; Sato, Ken; Kokubo, Toshiaki

2014-03-01

Embryo quality is a critical parameter in assisted reproductive technologies. Although embryo quality can be evaluated morphologically, embryo morphology does not correlate perfectly with embryo viability. To improve this, it is important to understand which molecular mechanisms are involved in embryo quality control. Autophagy is an evolutionarily conserved catabolic process in which cytoplasmic materials sequestered by autophagosomes are degraded in lysosomes. We previously demonstrated that autophagy is highly activated after fertilization and is essential for further embryonic development. Here, we developed a simple fluorescence-based method for visualizing autophagic activity in live mouse embryos. Our method is based on imaging of the fluorescence intensity of GFP-LC3, a versatile marker for autophagy, which is microinjected into the embryos. Using this method, we show that embryonic autophagic activity declines with advancing maternal age, probably due to a decline in the activity of lysosomal hydrolases. We also demonstrate that embryonic autophagic activity is associated with the developmental viability of the embryo. Our results suggest that embryonic autophagic activity can be utilized as a novel indicator of embryo quality.

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.

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

A virus-MIPs fluorescent sensor based on FRET for highly sensitive detection of JEV.

PubMed

Liang, Caishuang; Wang, Huan; He, Kui; Chen, Chunyan; Chen, Xiaoming; Gong, Hang; Cai, Changqun

2016-11-01

Major stumbling blocks in the recognition and detection of virus are the unstable biological recognition element or the complex detection means. Here a fluorescent sensor based on virus-molecular imprinted polymers (virus-MIPs) was designed for specific recognition and highly sensitive detection of Japanese encephalitis virus (JEV). The virus-MIPs were anchored on the surface of silica microspheres modified by fluorescent dye, pyrene-1-carboxaldehyde (PC). The fluorescence intensity of PC can be enhanced by the principle of fluorescence resonance energy transfer (FRET), where virus acted as energy donor and PC acted as energy acceptor. The enhanced fluorescence intensity was proportional to the concentration of virus in the range of 24-960pM, with a limit of detection (LOD, 3σ) of 9.6pM, and the relative standard deviation was 1.99%. In additional, the specificity study confirmed the resultant MIPs has high-selectivity for JEV. This sensor would become a new key for the detection of virus because of its high sensitive, simple operation, high stability and low cost. Copyright © 2016. Published by Elsevier B.V.

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.

Antigen detection based on background fluorescence quenching immunochromatographic assay.

PubMed

Chen, Xiangjun; Xu, Yangyang; Yu, Jinsheng; Li, Jiutong; Zhou, Xuelei; Wu, Chuanyong; Ji, Qiuliang; Ren, Yuan; Wang, Liqun; Huang, Zhengyi; Zhuang, Hanling; Piao, Long; Head, Richard; Wang, Yajie; Lou, Jiatao

2014-09-02

Gold immunochromatographic assay (GICA) has been around for quite a while, but it is qualitative in the vast majority of applications. A fast, simple and quantitative GICA is in call for better medicine. In the current study, we have established a novel, quantitative GICA based on fluorescence quenching and nitrocellulose membrane background signals, called background fluorescence quenching immunochromatographic assay (bFQICA). Using model analyte alpha-fetoprotein (AFP), the present study assessed the performance of bFQICA in numerous assay aspects. With serial dilutions of the international AFP standard, standard curves for the calculation of AFP concentration were successfully established. At 10 and 100ngmL(-1) of the international AFP standard, the assay variability was defined with a coefficient of variance at 10.4% and 15.2%, respectively. For samples with extended range of AFP levels, bFQICA was able to detect AFP at as low as 1ngmL(-1). Fluorescence in bFQICA strips stayed constant over months. A good correlation between the results from bFQICA and from a well-established Roche electrochemiluminescence immunoassay was observed in 27 serum samples (r=0.98, p<0.001). In conclusion, our study has demonstrated distinctive features of bFQICA over conventional GICA, including utilization of a unique fluorescence ratio between nitrocellulose membrane background and specific signals (F1/F2) to ensure accurate measurements, combined qualitative and quantitative capabilities, and exceptionally high sensitivity for detection of very low levels of antigens. All of these features could make bFQICA attractive as a model for antigen-antibody complex based GICA, and could promote bFQICA to a broad range of applications for investigation of a variety of diseases. Copyright © 2014 Elsevier B.V. All rights reserved.

Fluorescent carbon dots nanosensor for label-free determination of vitamin B12 based on inner filter effect

NASA Astrophysics Data System (ADS)

Ding, Longhua; Yang, Hongmei; Ge, Shenguang; Yu, Jinghua

2018-03-01

A simple and effective fluorescent assay for the determination of vitamin B12 was developed. In this study, carbon dots (CDs) were prepared by one-pot hydrothermal method and directly used as a fluorophore in the inner filter effect (IFE). Both of the maximum absorption peak of vitamin B12 and excitation maxima of CDs are located at 360 nm, hence, the excited light of CDs can be absorbed by vitamin B12, resulting in the fluorescence reduction of CDs. And the fluorescence intensity of CDs decreases with the increasing concentration of vitamin B12. This IFE-based sensing strategy shows a good linear relationship between the normalized fluorescence intensity and the concentration of vitamin B12 ranging from 0 to 60 μM, with a limit of detection (LOD) of 0.1 μM at a signal-to-noise ratio of 3. Furthermore, this proposed approach was successfully applied to vitamin B12 sensing in injections. This IFE sensing platform based on various fluorescent nanomaterials has a high promise for the detection of other biomolecules due to its inherent convenience.

A label-free amplified fluorescence DNA detection based on isothermal circular strand-displacement polymerization reaction and graphene oxide.

PubMed

Li, Zhen; Zhu, Wenping; Zhang, Jinwen; Jiang, Jianhui; Shen, Guoli; Yu, Ruqin

2013-07-07

A label-free fluorescent DNA biosensor has been presented based on isothermal circular strand-displacement polymerization reaction (ICSDPR) combined with graphene oxide (GO) binding. The proposed method is simple and cost-effective with a low detection limit of 4 pM, which compares favorably with other GO-based homogenous DNA detection methods.

Fluorescence turn-on detection of target sequence DNA based on silicon nanodot-mediated quenching.

PubMed

Zhang, Yanan; Ning, Xinping; Mao, Guobin; Ji, Xinghu; He, Zhike

2018-05-01

We have developed a new enzyme-free method for target sequence DNA detection based on the dynamic quenching of fluorescent silicon nanodots (SiNDs) toward Cy5-tagged DNA probe. Fascinatingly, the water-soluble SiNDs can quench the fluorescence of cyanine (Cy5) in Cy5-tagged DNA probe in homogeneous solution, and the fluorescence of Cy5-tagged DNA probe can be restored in the presence of target sequence DNA (the synthetic target miRNA-27a). Based on this phenomenon, a SiND-featured fluorescent sensor has been constructed for "turn-on" detection of the synthetic target miRNA-27a for the first time. This newly developed approach possesses the merits of low cost, simple design, and convenient operation since no enzymatic reaction, toxic reagents, or separation procedures are involved. The established method achieves a detection limit of 0.16 nM, and the relative standard deviation of this method is 9% (1 nM, n = 5). The linear range is 0.5-20 nM, and the recoveries in spiked human fluids are in the range of 90-122%. This protocol provides a new tactic in the development of the nonenzymic miRNA biosensors and opens a promising avenue for early diagnosis of miRNA-associated disease. Graphical abstract The SiND-based fluorescent sensor for detection of S-miR-27a.

A simple one-step method to prepare fluorescent carbon dots and their potential application in non-invasive glioma imaging

NASA Astrophysics Data System (ADS)

Ruan, Shaobo; Qian, Jun; Shen, Shun; Zhu, Jianhua; Jiang, Xinguo; He, Qin; Gao, Huile

2014-08-01

Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging. Additionally, several experiments demonstrated that CD possessed good serum stability and low cytotoxicity. In vitro, CD could be taken up into C6 glioma cells in a time- and concentration-dependent manner, with both endosomes and mitochondria involved. In vivo, CD could be used for non-invasive glioma imaging because of its high accumulation in the glioma site of the brain, which was demonstrated by both in vivo imaging and ex vivo tissue imaging. Furthermore, the fluorescent distribution in tissue slices also showed CD distributed in glioma with high intensity, while with a low intensity in normal brain tissue. In conclusion, CD were prepared using a simple method with relatively long excitation and emission wavelengths and could be used for non-invasive glioma imaging.Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging

Field portable mobile phone based fluorescence microscopy for detection of Giardia lamblia cysts in water samples

NASA Astrophysics Data System (ADS)

Ceylan Koydemir, Hatice; Gorocs, Zoltan; McLeod, Euan; Tseng, Derek; Ozcan, Aydogan

2015-03-01

Giardia lamblia is a waterborne parasite that causes an intestinal infection, known as giardiasis, and it is found not only in countries with inadequate sanitation and unsafe water but also streams and lakes of developed countries. Simple, sensitive, and rapid detection of this pathogen is important for monitoring of drinking water. Here we present a cost-effective and field portable mobile-phone based fluorescence microscopy platform designed for automated detection of Giardia lamblia cysts in large volume water samples (i.e., 10 ml) to be used in low-resource field settings. This fluorescence microscope is integrated with a disposable water-sampling cassette, which is based on a flow-through porous polycarbonate membrane and provides a wide surface area for fluorescence imaging and enumeration of the captured Giardia cysts on the membrane. Water sample of interest, containing fluorescently labeled Giardia cysts, is introduced into the absorbent pads that are in contact with the membrane in the cassette by capillary action, which eliminates the need for electrically driven flow for sample processing. Our fluorescence microscope weighs ~170 grams in total and has all the components of a regular microscope, capable of detecting individual fluorescently labeled cysts under light-emitting-diode (LED) based excitation. Including all the sample preparation, labeling and imaging steps, the entire measurement takes less than one hour for a sample volume of 10 ml. This mobile phone based compact and cost-effective fluorescent imaging platform together with its machine learning based cyst counting interface is easy to use and can even work in resource limited and field settings for spatio-temporal monitoring of water quality.

A ratiometric fluorescent quantum dots based biosensor for organophosphorus pesticides detection by inner-filter effect.

PubMed

Yan, Xu; Li, Hongxia; Han, Xiaosong; Su, Xingguang

2015-12-15

In this work, we develop a novel and sensitive sensor for the detection of organophosphorus pesticides based on the inner-filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent quantum dots (RF-QDs). The RF-QDs has been designed by hybridizing two differently colored CdTe QDs, in which the red emissive QDs entrapped in the silica sphere acting as the reference signal, and the green emissive QDs covalently attached on the silica surface serving as the response signal.The fluorescence of RF-QDs could be quenched by AuNPs based on IFE. Protamine could effectively turn on the fluorescence due to the electrostatic attraction between protamine and AuNPs. Trypsin can easily hydrolyze protamine, leading to the quench of the fluorescence. Then, the fluorescence could be recovered again by the addition of parathion-methyl (PM) which could inhibit the activity of trypsin. By measuring the fluorescence of RF-QDs, the inhibition efficiency of PM to trypsin activity was evaluated. Under the optimized conditions, the inhibition efficiency was proportional to the logarithm of PM concentration in the range of 0.04-400 ng mL(-1), with a detection limit of 0.018 ng mL(-1). Furthermore, the simple and convenient method had been used for PM detection in environmental and agricultural samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel and simple fluorescence probe for detecting main group magnesium ion in HeLa cells and Arabidopsis.

PubMed

Yu, Tingting; Sun, Ping; Hu, Yijie; Ji, Yinggang; Zhou, Hongping; Zhang, Baowei; Tian, Yupeng; Wu, Jieying

2016-12-15

A simple-molecule fluorescence probe L has been designed, synthesized and characterized, which shows high selectivity and sensitivity for the main group magnesium ion through fluorescence "turn-on" response in ethanol solution, and no interference from calcium ion in particular. Detection limit of probe L is 1.47×10(-6) M and the rapid response could reach about 15-20s. The recognition mechanism has been established by fluorescence spectra, (1)H NMR study. Moreover, probe L presents a great photostability, low toxicity and cellular permeability, then we have carried out fluorescent bio-imaging of the probe L for magnesium ions in HeLa cells, which showed that probe L could be utilized to detect the intracellular magnesium ion. Furthermore, it is successfully used as a magnesium ion developer in plant tissues, which shows that it not only can be well tracking the transport of magnesium ion but also make a corresponding fluorescence response to different concentrations magnesium ion. These results would make this probe a great potential application for detecting Mg(2+) in biological system. Copyright © 2016 Elsevier B.V. All rights reserved.

Cytotoxicity Test Based on Human Cells Labeled with Fluorescent Proteins: Fluorimetry, Photography, and Scanning for High-Throughput Assay.

PubMed

Kalinina, Marina A; Skvortsov, Dmitry A; Rubtsova, Maria P; Komarova, Ekaterina S; Dontsova, Olga A

2018-06-01

High- and medium-throughput assays are now routine methods for drug screening and toxicology investigations on mammalian cells. However, a simple and cost-effective analysis of cytotoxicity that can be carried out with commonly used laboratory equipment is still required. The developed cytotoxicity assays are based on human cell lines stably expressing eGFP, tdTomato, mCherry, or Katushka2S fluorescent proteins. Red fluorescent proteins exhibit a higher signal-to-noise ratio, due to less interference by medium autofluorescence, in comparison to green fluorescent protein. Measurements have been performed on a fluorescence scanner, a plate fluorimeter, and a camera photodocumentation system. For a 96-well plate assay, the sensitivity per well and the measurement duration were 250 cells and 15 min for the scanner, 500 cells and 2 min for the plate fluorimeter, and 1000 cells and less than 1 min for the camera detection. These sensitivities are similar to commonly used MTT (tetrazolium dye) assays. The used scanner and the camera had not been previously applied for cytotoxicity evaluation. An image processing scheme for the high-resolution scanner is proposed that significantly diminishes the number of control wells, even for a library containing fluorescent substances. The suggested cytotoxicity assay has been verified by measurements of the cytotoxicity of several well-known cytotoxic drugs and further applied to test a set of novel bacteriotoxic compounds in a medium-throughput format. The fluorescent signal of living cells is detected without disturbing them and adding any reagents, thus allowing to investigate time-dependent cytotoxicity effects on the same sample of cells. A fast, simple and cost-effective assay is suggested for cytotoxicity evaluation based on mammalian cells expressing fluorescent proteins and commonly used laboratory equipment.

Recent Advances in Silicon Nanomaterial-Based Fluorescent Sensors.

PubMed

Wang, Houyu; He, Yao

2017-02-03

During the past decades, owing to silicon nanomaterials' unique optical properties, benign biocompatibility, and abundant surface chemistry, different dimensional silicon nanostructures have been widely employed for rationally designing and fabricating high-performance fluorescent sensors for the detection of various chemical and biological species. Among of these, zero-dimensional silicon nanoparticles (SiNPs) and one-dimensional silicon nanowires (SiNWs) are of particular interest. Herein, we focus on reviewing recent advances in silicon nanomaterials-based fluorescent sensors from a broad perspective and discuss possible future directions. Firstly, we introduce the latest achievement of zero-dimensional SiNP-based fluorescent sensors. Next, we present recent advances of one-dimensional SiNW-based fluorescent sensors. Finally, we discuss the major challenges and prospects for the development of silicon-based fluorescent sensors.

Recent Advances in Silicon Nanomaterial-Based Fluorescent Sensors

PubMed Central

Wang, Houyu; He, Yao

2017-01-01

During the past decades, owing to silicon nanomaterials’ unique optical properties, benign biocompatibility, and abundant surface chemistry, different dimensional silicon nanostructures have been widely employed for rationally designing and fabricating high-performance fluorescent sensors for the detection of various chemical and biological species. Among of these, zero-dimensional silicon nanoparticles (SiNPs) and one-dimensional silicon nanowires (SiNWs) are of particular interest. Herein, we focus on reviewing recent advances in silicon nanomaterials-based fluorescent sensors from a broad perspective and discuss possible future directions. Firstly, we introduce the latest achievement of zero-dimensional SiNP-based fluorescent sensors. Next, we present recent advances of one-dimensional SiNW-based fluorescent sensors. Finally, we discuss the major challenges and prospects for the development of silicon-based fluorescent sensors. PMID:28165357

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for Bisphenol A

NASA Astrophysics Data System (ADS)

Xiang, Guo-Qiang; Ren, Yue; Xia, Yin; Mao, Wenjie; Fan, Chao; Guo, Si-Yu; Wang, Pan-Pan; Yang, Deng-Hui; He, Lijun; Jiang, Xiuming

2017-04-01

A simple and effective strategy for designing a ratiometric fluorescent nanosensor is described in this work. A carbon dots (CDs) based dual-emission nanosensor for Bisphenol A (BPA) was prepared by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of dual-emission silica nanoparticles was quenched in hydrochloric acid by potassium bromate (KBrO3) oxidation; BPA inhibited KBrO3 oxidation, resulting in the ratiometric fluorescence response of dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80 ng mL- 1 with a linear range from 10 to 500 ng mL- 1. This was applied successfully to determine BPA in the leached solution of different plastic products with satisfactory results.

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.

Fluorescence based Aptasensors for the determination of hepatitis B virus e antigen.

PubMed

Huang, Rongrong; Xi, Zhijiang; Deng, Yan; He, Nongyue

2016-08-08

This research is aimed at selecting specific aptamer of hepatitis B e antigen by SELEX and its applications. Hepatitis B e antigen (HBeAg) seroconversion is used as an indicator of virological response when treating patients suffering from chronic hepatitis B. HBeAg also indicates a high viremia and high infectivity in untreated patients. With HBeAg modified magnetic beads as targets, three groups of aptamers are successfully selected. These are the first reported DNA aptamers that can specifically bind to HBeAg. Based on the property that the conformation changes upon binding to its target, aptamer has emerged as ideal candidate in a variety of sensing applications. In this study, we present a simple strategy for aptamer-based fluorescence biosensors for the quantitative detection of HBeAg, in which a fluorescence labeled HBeAg aptamer serves as the molecular recognition element and a short DNA molecule that is complementary to the aptamer serves as the competitor. The LOD for HBeAg is 609 ng/mL. Later, the fluorescence system is deployed in HBeAg positive and negative blood serum (p < 0.05). The total detection assay could be completed in 2 min. These newly isolated aptamers could assist the diagnosis of chronic hepatitis B.

Fluorescence based Aptasensors for the determination of hepatitis B virus e antigen

PubMed Central

Huang, Rongrong; Xi, Zhijiang; Deng, Yan; He, Nongyue

2016-01-01

This research is aimed at selecting specific aptamer of hepatitis B e antigen by SELEX and its applications. Hepatitis B e antigen (HBeAg) seroconversion is used as an indicator of virological response when treating patients suffering from chronic hepatitis B. HBeAg also indicates a high viremia and high infectivity in untreated patients. With HBeAg modified magnetic beads as targets, three groups of aptamers are successfully selected. These are the first reported DNA aptamers that can specifically bind to HBeAg. Based on the property that the conformation changes upon binding to its target, aptamer has emerged as ideal candidate in a variety of sensing applications. In this study, we present a simple strategy for aptamer-based fluorescence biosensors for the quantitative detection of HBeAg, in which a fluorescence labeled HBeAg aptamer serves as the molecular recognition element and a short DNA molecule that is complementary to the aptamer serves as the competitor. The LOD for HBeAg is 609 ng/mL. Later, the fluorescence system is deployed in HBeAg positive and negative blood serum (p < 0.05). The total detection assay could be completed in 2 min. These newly isolated aptamers could assist the diagnosis of chronic hepatitis B. PMID:27499342

A label-free fluorescent aptamer sensor based on regulation of malachite green fluorescence

PubMed Central

Xu, Weichen; Lu, Yi

2009-01-01

We report a label-free fluorescent aptamer sensor for adenosine based on the regulation of malachite green (MG) fluorescence, with comparable sensitivity and selectivity to other labeled adenosine aptamer-based sensors. The sensor consists of free MG, an aptamer strand containing an adenosine aptamer next to an MG aptamer, and a bridging strand that partially hybridizes to the aptamer strand. Such a hybridization prevents MG from binding to MG aptamer, resulting in low fluorescence of MG in the absence of adenosine. Addition of adenosine causes the adenosine aptamer to bind adenosine, weakening the hybridization of the aptamer strand with the bridging strand, making it possible for MG to bind to the aptamer strand and exhibits high fluorescence intensity. Since this design is based purely on nucleic acid hybridization, it can be generally applied to other aptamers for the label-free detection of a broad range of analytes. PMID:20017558

Validation of a simple and fast method to quantify in vitro mineralization with fluorescent probes used in molecular imaging of bone

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

Moester, Martiene J.C.; Schoeman, Monique A.E.; Oudshoorn, Ineke B.

2014-01-03

Highlights: •We validate a simple and fast method of quantification of in vitro mineralization. •Fluorescently labeled agents can detect calcium deposits in the mineralized matrix of cell cultures. •Fluorescent signals of the probes correlated with Alizarin Red S staining. -- Abstract: Alizarin Red S staining is the standard method to indicate and quantify matrix mineralization during differentiation of osteoblast cultures. KS483 cells are multipotent mouse mesenchymal progenitor cells that can differentiate into chondrocytes, adipocytes and osteoblasts and are a well-characterized model for the study of bone formation. Matrix mineralization is the last step of differentiation of bone cells and ismore » therefore a very important outcome measure in bone research. Fluorescently labelled calcium chelating agents, e.g. BoneTag and OsteoSense, are currently used for in vivo imaging of bone. The aim of the present study was to validate these probes for fast and simple detection and quantification of in vitro matrix mineralization by KS483 cells and thus enabling high-throughput screening experiments. KS483 cells were cultured under osteogenic conditions in the presence of compounds that either stimulate or inhibit osteoblast differentiation and thereby matrix mineralization. After 21 days of differentiation, fluorescence of stained cultures was quantified with a near-infrared imager and compared to Alizarin Red S quantification. Fluorescence of both probes closely correlated to Alizarin Red S staining in both inhibiting and stimulating conditions. In addition, both compounds displayed specificity for mineralized nodules. We therefore conclude that this method of quantification of bone mineralization using fluorescent compounds is a good alternative for the Alizarin Red S staining.« less

Fast-Response Turn-on Fluorescent Probes Based on Thiolysis of NBD Amine for H2 S Bioimaging.

PubMed

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

2016-05-17

Hydrogen sulfide (H2 S) is an important endogenous signaling molecule with multiple biological functions. New selective fluorescent turn-on probes based on fast thiolyling of NBD (7-nitro-1,2,3-benzoxadiazole) amine were explored for sensing H2 S in aqueous buffer and in living cells. The syntheses of both probes are simple and quite straightforward. The probes are highly sensitive and selective toward H2 S over other biologically relevant species. The fluorescein-NBD-based probe showed 65-fold green fluorescent increase upon H2 S activation. The rhodamine-NBD-based probe reacted rapidly with H2 S (t1/2 ≈1 min) to give a 4.5-fold increase in red fluorescence. Moreover, both probes were successfully used for monitoring H2 S in living cells and in mice. Based on such probe-based tools, we could observe H2 O2 -induced H2 S biogenesis in a concentration-dependent and time-dependent fashion in living cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

First fluorescent sensor for fluoride based on 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded AADD supramolecular assembly.

PubMed

Zhao, Yao-Peng; Zhao, Chun-Chang; Wu, Li-Zhu; Zhang, Li-Ping; Tung, Chen-Ho; Pan, Yuan-Jiang

2006-03-03

A simple, highly selective, neutral, fluorescent sensor for fluoride anions is reported. It is based on 2-ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded AADD supramolecular assembly, and its assembling and disassembling processes are also able to respond to external stimuli reversibly.

Fluorescent-protein-based probes: general principles and practices.

PubMed

Ai, Hui-Wang

2015-01-01

An important application of fluorescent proteins is to derive genetically encoded fluorescent probes that can actively respond to cellular dynamics such as pH change, redox signaling, calcium oscillation, enzyme activities, and membrane potential. Despite the large diverse group of fluorescent-protein-based probes, a few basic principles have been established and are shared by most of these probes. In this article, the focus is on these general principles and strategies that guide the development of fluorescent-protein-based probes. A few examples are provided in each category to illustrate the corresponding principles. Since these principles are quite straightforward, others may adapt them to create fluorescent probes for their own interest. Hopefully, the development of the ever-growing family of fluorescent-protein-based probes will no longer be limited to a small number of laboratories specialized in senor development, leading to the situation that biological studies will be bettered assisted by genetically encoded sensors.

Real-time monitoring of endogenous cysteine levels in living cells using a CD-based ratiometric fluorescent nanoprobe.

PubMed

Wang, Hong; Zhang, Peisheng; Tian, Yong; Zhang, Yuan; Yang, Heping; Chen, Shu; Zeng, Rongjin; Long, Yunfei; Chen, Jian

2018-04-30

A simple and readily available fluorescent probe is needed for the real-time monitoring of endogenous cysteine (Cys) levels in living cells, as such a probe could be used to study the role of Cys in related diseases. Herein, we report the first fluorescent probe based on carbon dots (CDs-FITA) for the selective and ratiometric imaging of endogenous Cys in live cells. In this ratiometric fluorescent probe, a fluorescein derivative (FITA) that recognizes Cys is covalently linked to the surfaces of carbon dots (CDs); employing CDs greatly improves the water solubility of the probe. Acrylate on FITA is selectively cleaved by Cys in aqueous solution under mild conditions, leading to a dramatic increase in the fluorescence from fluorescein. The probe therefore allows the highly selective ratiometric fluorescent detection of Cys even in the presence of various interferents. The as-prepared CDs-FITA showed excellent performance when applied to detect Cys in blood serum. In addition, due to its negligible cytotoxicity, the CDs-FITA can also be utilized for the real-time monitoring of endogenous cysteine (Cys) levels in living cells. Graphical abstract Illustration of the CD-based probe for Cys imaging in living cells.

Fluorescent nanoparticles based on AIE fluorogens for bioimaging.

PubMed

Yan, Lulin; Zhang, Yan; Xu, Bin; Tian, Wenjing

2016-02-07

Fluorescent nanoparticles (FNPs) have recently attracted increasing attention in the biomedical field because of their unique optical properties, easy fabrication and outstanding performance in imaging. Compared with conventional molecular probes including small organic dyes and fluorescent proteins, FNPs based on aggregation-induced emission (AIE) fluorogens have shown significant advantages in tunable emission and brightness, good biocompatibility, superb photo- and physical stability, potential biodegradability and facile surface functionalization. In this review, we summarize the latest advances in the development of fluorescent nanoparticles based on AIE fluorogens including polymer nanoparticles and silica nanoparticles over the past few years, and the various biomedical applications based on these fluorescent nanoparticles are also elaborated.

Complexation induced fluorescence and acid-base properties of dapoxyl dye with γ-cyclodextrin: a drug-binding application using displacement assays.

PubMed

Pal, Kaushik; Mallick, Suman; Koner, Apurba L

2015-06-28

Host-guest complexation of dapoxyl sodium sulphonate (DSS), an intramolecular charge transfer dye with water-soluble and non-toxic macrocycle γ-cyclodextrin (γ-CD), has been investigated in a wide pH range. Steady-state absorption, fluorescence and time-resolved fluorescence measurements confirm the positioning of DSS into the hydrophobic cavity of γ-CD. A large fluorescence enhancement ca. 30 times, due to 1 : 2 complex formation and host-assisted guest-protonation have been utilised for developing a method for the utilisation of CD based drug-delivery applications. A simple fluorescence-displacement based approach is implemented at physiological pH for the assessment of binding strength of pharmaceutically useful small drug molecules (ibuprofen, paracetamol, methyl salicylate, salicylic acid, aspirin, and piroxicam) and six important antibiotic drugs (resazurin, thiamphenicol, chloramphenicol, ampicillin, kanamycin, and sorbic acid) with γ-CD.

Complete suppression of the fluorophore fluorescence by combined effect of multiple fluorescence quenching groups: A fluorescent sensor for Cu²⁺ with zero background signals.

PubMed

Long, Lingliang; Wu, Yanjun; Wang, Lin; Gong, Aihua; Hu, Rongfeng; Zhang, Chi

2016-02-18

The reaction-based fluorescent sensors have attracted increasing attention in the past decades. However, the application of these sensors for accurate sensing was significantly retarded by the background fluorescence from the sensors themselves. In this work, we demonstrated a novel strategy that the background fluorescence of the sensor could be completely eliminated by the combined effect of multiple fluorescence quenching groups. Based on this new strategy, as proof-of-principle study, a fluorescent sensor (CuFS) for Cu(2+) was judiciously developed. In CuFS, three types of fluorescence quenching groups were directly tethered to a commonly used coumarin fluorophore. The fluorescence of coumarin fluorophore in CuFS was completely suppressed by the combined effect of these fluorescence quenching groups. Upon treatment with 22 μM Cu(2+), sensor CuFS achieved a dramatic fluorescence enhancement (fluorescence intensity enhanced up to 811-fold) centered at 469 nm. The detection limits was determined to be 12.3 nM. The fluorescence intensity enhancement also showed a good linearity with the Cu(2+) concentration in the range of 12.3 nM to 2 μM. By fabricating test strips, sensor CuFS can be utilized as a simple tool to detect Cu(2+) in water samples. Furthermore, the fluorescent sensor was successfully applied in detecting different concentration of Cu(2+) in living cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Fluorescence lifetime based bioassays

NASA Astrophysics Data System (ADS)

Meyer-Almes, Franz-Josef

2017-12-01

Fluorescence lifetime (FLT) is a robust intrinsic property and material constant of fluorescent matter. Measuring this important physical indicator has evolved from a laboratory curiosity to a powerful and established technique for a variety of applications in drug discovery, medical diagnostics and basic biological research. This distinct trend was mainly driven by improved and meanwhile affordable laser and detection instrumentation on the one hand, and the development of suitable FLT probes and biological assays on the other. In this process two essential working approaches emerged. The first one is primarily focused on high throughput applications employing biochemical in vitro assays with no requirement for high spatial resolution. The second even more dynamic trend is the significant expansion of assay methods combining highly time and spatially resolved fluorescence data by fluorescence lifetime imaging. The latter approach is currently pursued to enable not only the investigation of immortal tumor cell lines, but also specific tissues or even organs in living animals. This review tries to give an actual overview about the current status of FLT based bioassays and the wide range of application opportunities in biomedical and life science areas. In addition, future trends of FLT technologies will be discussed.

Evaluating Sense Codon Reassignment with a Simple Fluorescence Screen.

PubMed

Biddle, Wil; Schmitt, Margaret A; Fisk, John D

2015-12-22

Understanding the interactions that drive the fidelity of the genetic code and the limits to which modifications can be made without breaking the translational system has practical implications for understanding the molecular mechanisms of evolution as well as expanding the set of encodable amino acids, particularly those with chemistries not provided by Nature. Because 61 sense codons encode 20 amino acids, reassigning the meaning of sense codons provides an avenue for biosynthetic modification of proteins, furthering both fundamental and applied biochemical research. We developed a simple screen that exploits the absolute requirement for fluorescence of an active site tyrosine in green fluorescent protein (GFP) to probe the pliability of the degeneracy of the genetic code. Our screen monitors the restoration of the fluorophore of GFP by incorporation of a tyrosine in response to a sense codon typically assigned another meaning in the genetic code. We evaluated sense codon reassignment at four of the 21 sense codons read through wobble interactions in Escherichia coli using the Methanocaldococcus jannaschii orthogonal tRNA/aminoacyl tRNA synthetase pair originally developed and commonly used for amber stop codon suppression. By changing only the anticodon of the orthogonal tRNA, we achieved sense codon reassignment efficiencies between 1% (Phe UUU) and 6% (Lys AAG). Each of the orthogonal tRNAs preferentially decoded the codon traditionally read via a wobble interaction in E. coli with the exception of the orthogonal tRNA with an AUG anticodon, which incorporated tyrosine in response to both the His CAU and His CAC codons with approximately equal frequencies. We applied our screen in a high-throughput manner to evaluate a 10(9)-member combined tRNA/aminoacyl tRNA synthetase library to identify improved sense codon reassigning variants for the Lys AAG codon. A single rapid screen with the ability to broadly evaluate reassignable codons will facilitate

Introducing a fluorescence-based standard to quantify protein partitioning into membranes.

PubMed

Thomas, Franziska A; Visco, Ilaria; Petrášek, Zdeněk; Heinemann, Fabian; Schwille, Petra

2015-11-01

The affinity of peripheral membrane proteins for a lipid bilayer can be described using the partition coefficient (KP). Although several methods to determine KP are known, all possess limitations. To address some of these issues, we developed both: a versatile method based on single molecule detection and fluorescence imaging for determining KP, and a simple measurement standard employing hexahistidine-tagged enhanced green fluorescent protein (eGFP-His6) and free standing membranes of giant unilamellar vesicles (GUVs) functionalized with NTA(Ni) lipids as binding sites. To ensure intrinsic control, our method features two measurement modes. In the single molecule mode, fluorescence correlation spectroscopy (FCS) is applied to quantify free and membrane associated protein concentrations at equilibrium and calculate KP. In the imaging mode, confocal fluorescence images of GUVs are recorded and analyzed with semi-automated software to extract protein mean concentrations used to derive KP. Both modes were compared by determining the affinity of our standard, resulting in equivalent KP values. As observed in other systems, eGFP-His6 affinity for membranes containing increasing amounts of NTA(Ni) lipids rises in a stronger-than-linear fashion. We compared our dual approach with a FCS-based assay that uses large unilamellar vesicles (LUVs), which however fails to capture the stronger-than-linear trend for our NTA(Ni)-His6 standard. Hence, we determined the KP of the MARCKS effector domain with our FCS approach on GUVs, whose results are consistent with previously published data using LUVs. We finally provide a practical manual on how to measure KP and understand it in terms of molecules per lipid surface. Copyright © 2015. Published by Elsevier B.V.

A CTRW-based model of time-resolved fluorescence lifetime imaging in a turbid medium

NASA Astrophysics Data System (ADS)

Chernomordik, Victor; Gandjbakhche, Amir H.; Hassan, Moinuddin; Pajevic, Sinisa; Weiss, George H.

2010-12-01

We develop an analytic model of time-resolved fluorescent imaging of photons migrating through a semi-infinite turbid medium bounded by an infinite plane in the presence of a single stationary point fluorophore embedded in the medium. In contrast to earlier models of fluorescent imaging in which photon motion is assumed to be some form of continuous diffusion process, the present analysis is based on a continuous-time random walk (CTRW) on a simple cubic lattice, the objective being to estimate the position and lifetime of the fluorophore. This can provide information related to local variations in pH and temperature with potential medical significance. Aspects of the theory were tested using time-resolved measurements of the fluorescence from small inclusions inside tissue-like phantoms. The experimental results were found to be in good agreement with theoretical predictions provided that the fluorophore was not located too close to the planar boundary, a common problem in many diffusive systems.

A simple fluorescence-based assay for quantification of the Toll-Like Receptor agonist E6020 in vaccine formulations.

PubMed

Pollet, Jeroen; Versteeg, Leroy; Rezende, Wanderson; Strych, Ulrich; Gusovsky, Fabian; Hotez, Peter J; Bottazzi, Maria Elena

2017-03-07

Despite the generally accepted immunostimulatory effect of Toll-Like Receptor 4 (TLR4) agonists and their value as vaccine adjuvants, there remains a demand for fast and easy quantification assays for these TLR4 agonists in order to accelerate and improve vaccine formulation studies. A new medium-throughput method was developed for the quantification of the TLR4 agonist, E6020, independent of the formulation composition. The assay uses a fluorescent hydrazide (DCCH) to label the synthetic lipopolysaccharide (LPS) analog E6020 through its diketone groups. This novel, low-cost, and fluorescence based assay may obviate the need for traditional approaches that primarily rely on Fourier transform infrared spectroscopy (FTIR) or mass spectrometry. The experiments were performed in a wide diversity of vaccine formulations containing E6020 to assess method robustness and accuracy. The assay was also expanded to evaluate the loading efficiency of E6020 in poly(lactic-co-glycolic acid) (PLGA) micro-particles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Simple and robust diagnosis of early, small and AFP-negative primary hepatic carcinomas: an integrative approach of serum fluorescence and conventional blood tests.

PubMed

Wang, Ting; Zhang, Kun-He; Hu, Piao-Ping; Huang, Zeng-Yong; Zhang, Pan; Wan, Qin-Si; Huang, De-Qiang; Lv, Nong-Hua

2016-09-27

The diagnosis of early, small and alpha-fetoprotein (AFP)-negative primary hepatic carcinomas (PHCs) remains a significant challenge. We developed a simple and robust approach to noninvasively detect these PHCs. A rapid, high-throughput and single-tube method was firstly developed to measure serum autofluorescence and cell-free DNA (cfDNA)-related fluorescence using a real-time PCR system, and both types of serum fluorescence were measured and routine laboratory data were collected in 1229 subjects, including 353 PHC patients, 331 liver cirrhosis (LC) patients, 213 chronic hepatitis (CH) patients and 332 normal controls (NC). The results showed that fluorescence indicators of PHC differed from those of NC, CH and LC to various extents, and all of them were not associated with age, gender, or AFP level. The logistic regression models established with the fluorescence indicators alone and combined with AFP, hepatic function tests and blood cell analyses were valuable for distinguishing early, small, AFP-negative and all PHC from LC, CH, NC and all non-PHC, with areas under the receiver operating characteristic curves 0.857-0.993 and diagnostic accuracies 80.2-97.7%. Conclusively, serum autofluorescence and cfDNA-related fluorescence are able to be rapidly and simultaneously measured by our simple method and valuable for diagnosing early, small and AFP-negative PHCs, especially integrating with AFP and conventional blood tests.

Carbon dots-based fluorescent probe for "off-on" sensing of Hg(II) and I⁻.

PubMed

He, Jiangling; Zhang, Haoran; Zou, Jinliang; Liu, Yingliang; Zhuang, Jianle; Xiao, Yong; Lei, Bingfu

2016-05-15

Herein, we report a simple, one-step reflux method for synthesis of photoluminescent carbon dots (CDs) using citric acid as the carbon source and diethylenetriamine (DETA) as the surface passivation reagent along with a high quantum yield (82.40%), the fluorescence intensity of the CDs was found to be effectively quenched by Hg(II) ions. Upon addition of I(-) to the CDs/Hg(II) complex dispersion, the fluorescence intensity of the CDs was significantly recovered. Furthermore, we developed an "off-on" fluorescence assay for the detection of I(-) using CDs/Hg(II) as a fluorescence probe. This probe enables the selective detection of Hg(II) with a linear range of 0-80 μM and a limit of detection is 0.201 µM and a limit of detection about I(-) is 0.234 µM with a linear range of 0-70 μM. Most importantly, the sensors can be successfully applied to the determination of Hg(II) and I(-) in real lake water and urine of cattles, the "off-on" sensor demonstrates high selectivity, repeatability, stability, which offer this CDs-based "off-on" fluorescent sensor a promising platform for environmental and biological sensing applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of adenine based on the fluorescence recovery of the L-Tryptophan-Cu(2+) complex.

PubMed

Duan, Ruilin; Li, Chunyan; Liu, Shaopu; Liu, Zhongfang; Li, Yuanfang; Yuan, Yusheng; Hu, Xiaoli

2016-01-05

A simple and sensitive method for determination of adenine was developed based on fluorescence quenching and recovery of L-Tryptophan (L-Trp). The fluorescence of L-Trp could efficiently quenched by copper ion compared with other common metal ions. Upon addition of adenine (Ade) in L-Trp-Cu(II) system, the fluorescence was reoccurred. Under the optimum conditions, the recovery fluorescence intensity was linearly correlated with the concentration of adenine in the range from 0.34 to 25.0μmolL(-1), with a correlation coefficient (R(2)) of 0.9994. The detection limit (3σ/k) was 0.046μmolL(-1), indicating that this method could applied to detect trace adenine. In this study, amino acids including L-Trp, D-Trp, L-Tyr, D-Tyr, L-Phe, D-Phe were investigated and only L-Trp could well chelated copper ion. Additionally, the mechanism of quench and recovery also were discussed and the method was successfully applied to detect the adenine in DNA with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

Ionic calcium determination in skim milk with molecular probes and front-face fluorescence spectroscopy: simple linear regression.

PubMed

Gangidi, R R; Metzger, L E

2006-11-01

The purpose of this study was to determine if the ionic calcium content of skim milk could be determined using molecular probes and front-face fluorescence spectroscopy. Current methods for determining ionic calcium are not sensitive, overestimate ionic calcium, or require complex procedures. Molecular probes designed specifically for measuring ionic calcium could potentially be used to determine the ionic calcium content of skim milk. The goal of the current study was to develop foundation methods for future studies to determine ionic calcium directly in skim milk and other dairy products with molecular probes and fluorescence spectroscopy. In this study, the effect of pH on calcium-sensitive fluorescent probe (Rhod-5N and Fluo-5N) performance using various concentrations of skim milk was determined. The pH of diluted skim milk (1.9 to 8.9% skim milk), was adjusted to either 6.2 or 7.0, after which the samples were analyzed with fluorescent probes (1 microM) and front-face fluorescence spectroscopy. The ionic calcium content of each sample was also determined using a calcium ion-selective electrode. The results demonstrated that the ionic calcium content of each sample was highly correlated (R2 > 0.989) with the fluorescence intensities of the probe-calcium adduct using simple linear regression. Higher than suggested ionic calcium contents of 1,207 and 1,973 microM were determined with the probes (Fluo-5N and Rhod-5N) in diluted skim milk with pH 7.0 and 6.2, respectively. The fluorescence intensity of the probe-calcium adduct decreased with a decrease in pH for the same ionic calcium concentration. This study demonstrates that Fluo-5N and Rhod-5N can be used to determine the ionic-calcium content of diluted milk with front-face fluorescence spectroscopy. Furthermore, these probes may also have the potential to determine the ionic calcium content of undiluted skim milk.

Carbon dots based dual-emission silica nanoparticles as ratiometric fluorescent probe for nitrite determination in food samples.

PubMed

Xiang, Guoqiang; Wang, Yule; Zhang, Heng; Fan, Huanhuan; Fan, Lu; He, Lijun; Jiang, Xiuming; Zhao, Wenjie

2018-09-15

In this work, a simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for nitrite was prepared by coating the CDs on to dye-doped silica nanoparticles. Dual-emission silica nanoparticles fluorescence was quenched in sulfuric acid using potassium bromate (KBrO 3 ). The nitrite present catalyzed the KBrO 3 oxidation, resulting in ratiometric fluorescence response of the dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated. Under optimized conditions, the limit of detection was 1.0 ng mL -1 and the linear range 10-160 ng mL -1 . Furthermore, the sensor was suitable for nitrite determination in different food samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

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.

Accurate quantification of fluorescent targets within turbid media based on a decoupled fluorescence Monte Carlo model.

PubMed

Deng, Yong; Luo, Zhaoyang; Jiang, Xu; Xie, Wenhao; Luo, Qingming

2015-07-01

We propose a method based on a decoupled fluorescence Monte Carlo model for constructing fluorescence Jacobians to enable accurate quantification of fluorescence targets within turbid media. The effectiveness of the proposed method is validated using two cylindrical phantoms enclosing fluorescent targets within homogeneous and heterogeneous background media. The results demonstrate that our method can recover relative concentrations of the fluorescent targets with higher accuracy than the perturbation fluorescence Monte Carlo method. This suggests that our method is suitable for quantitative fluorescence diffuse optical tomography, especially for in vivo imaging of fluorophore targets for diagnosis of different diseases and abnormalities.

A highly selective colorimetric and fluorescent chemosensor for Al(III) based-on simple naphthol in aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Zhaodi; Xu, Huajie; Sheng, Liangquan; Chen, Shuisheng; Huang, Deqian; Liu, Jie

2016-03-01

A colorimetric and fluorescent chemosensor (L) for Al(III) was synthesized and fully characterized. L could be both used as a colorimetric and fluorescent chemosensor for the detection of Al3 + ions with low detection limit (8.87 × 10- 7 M) in CH3CN-H2O (1:1, v/v) solution. The binding ratio of L-Al3 + was determined from the Job plot (absorption and fluorescence spectra) and MALDI-TOF MS data to be 1:1. The binding constant (Ka) of Al3 + binding to L was calculated to be 4.8 × 105 M- 1 from a Benesi-Hildebrand plot. Moreover, the binding site of L with Al3 + was determined by 1H NMR titration experiment.

A simple and general route for monofunctionalization of fluorescent and magnetic nanoparticles using peptides

NASA Astrophysics Data System (ADS)

Clarke, Samuel; Tamang, Sudarsan; Reiss, Peter; Dahan, Maxime

2011-04-01

Nanoparticles are now utilized in many diverse biological and medical applications. Despite this, it remains challenging to tailor their surface for specific molecular targeting while maintaining high biocompatibility. To address this problem, we evaluate a phytochelatin-related peptide surface coating to produce functional and biocompatible nanoparticles (NPs) based on fluorescent InP/ZnS and CdSe/ZnS or superparamagnetic FePt and Fe3O4. Using a combination of transmission electron microscopy, size-exclusion chromatography and gel electrophoresis (GE), we demonstrate the excellent colloidal properties of the peptide-coated NPs (pNPs) and the compact nature of the coating (~4 nm thickness). We develop a simple protocol for the monofunctionalization of the pNPs with targeting biomolecules, by combining covalent conjugation with GE purification. We then employ functionalized InP/ZnS pNPs in a live-cell, single-molecule imaging application to specifically target and detect individual proteins in the cell membrane. These findings showcase the versatility of the peptides for preparing compact NPs of various compositions and sizes, which are easily functionalized, and suitable for a broad range of biomedical applications.

A simple and general route for monofunctionalization of fluorescent and magnetic nanoparticles using peptides.

PubMed

Clarke, Samuel; Tamang, Sudarsan; Reiss, Peter; Dahan, Maxime

2011-04-29

Nanoparticles are now utilized in many diverse biological and medical applications. Despite this, it remains challenging to tailor their surface for specific molecular targeting while maintaining high biocompatibility. To address this problem, we evaluate a phytochelatin-related peptide surface coating to produce functional and biocompatible nanoparticles (NPs) based on fluorescent InP/ZnS and CdSe/ZnS or superparamagnetic FePt and Fe(3)O(4). Using a combination of transmission electron microscopy, size-exclusion chromatography and gel electrophoresis (GE), we demonstrate the excellent colloidal properties of the peptide-coated NPs (pNPs) and the compact nature of the coating (∼4 nm thickness). We develop a simple protocol for the monofunctionalization of the pNPs with targeting biomolecules, by combining covalent conjugation with GE purification. We then employ functionalized InP/ZnS pNPs in a live-cell, single-molecule imaging application to specifically target and detect individual proteins in the cell membrane. These findings showcase the versatility of the peptides for preparing compact NPs of various compositions and sizes, which are easily functionalized, and suitable for a broad range of biomedical applications.

Red Fluorescent Carbon Nanoparticle-Based Cell Imaging Probe.

PubMed

Ali, Haydar; Bhunia, Susanta Kumar; Dalal, Chumki; Jana, Nikhil R

2016-04-13

Fluorescent carbon nanoparticle-based probes with tunable visible emission are biocompatible, environment friendly and most suitable for various biomedical applications. However, synthesis of red fluorescent carbon nanoparticles and their transformation into functional nanoparticles are very challenging. Here we report red fluorescent carbon nanoparticle-based nanobioconjugates of <25 nm hydrodynamic size and their application as fluorescent cell labels. Hydrophobic carbon nanoparticles are synthesized via high temperature colloid-chemical approach and transformed into water-soluble functional nanoparticles via coating with amphiphilic polymer followed by covalent linking with desired biomolecules. Following this approach, carbon nanoparticles are functionalized with polyethylene glycol, primary amine, glucose, arginine, histidine, biotin and folic acid. These functional nanoparticles can be excited with blue/green light (i.e., 400-550 nm) to capture their emission spanning from 550 to 750 nm. Arginine and folic acid functionalized nanoparticles have been demonstrated as fluorescent cell labels where blue and green excitation has been used for imaging of labeled cells. The presented method can be extended for the development of carbon nanoparticle-based other bioimaging probes.

Sensitive spectrofluorometry of cellular prion protein based on the on-off interaction between fluorescent dye-labelled aptamers and multi-walled carbon nanotubes.

PubMed

Zhan, Lei; Peng, Li; Yu, Yan; Zhen, Shu Jun; Huang, Cheng Zhi

2012-11-07

The very simple and general spectrofluorometry of cellular prion protein (PrP(C)) is reported in this contribution based on the on-off noncovalent interaction of fluorescent dye-labelled PrP(C) DNA aptamers with multi-walled carbon nanotubes (MWCNTs). Due to the π-π stacking interaction between the DNA bases of the aptamer and the carbon nanotubes, the fluorescent dye and the MWCNTs are brought into close proximity, which leads to fluorescence quenching with a ratio of up to 87%. However, further addition of PrP(C), which disturbs the π-π interaction owing to the strong and specific binding of the aptamer to PrP(C), driving the aptamer away from the surface of the MWCNTs, restored the quenched fluorescence. This recovered fluorescence intensity was found to be in linear proportion to the PrP(C) concentration in the range of 8.2 to 81.7 nM, which builds the basis of the spectrofluorometry of the cellular prion protein.

A simple and highly selective 2,2-diferrocenylpropane-based multi-channel ion pair receptor for Pb(2+) and HSO4(-).

PubMed

Wan, Qian; Zhuo, Ji-Bin; Wang, Xiao-Xue; Lin, Cai-Xia; Yuan, Yao-Feng

2015-03-28

A structurally simple, 2,2-diferrocenylpropane-based ion pair receptor 1 was synthesized and characterized by (1)H NMR, (13)C NMR, HRMS, elemental analyses, and single-crystal X-ray diffraction. The ion pair receptor 1 showed excellent selectivity and sensitivity towards Pb(2+) with multi-channel responses: a fluorescence enhancement (more than 42-fold), a notable color change from yellow to red, redox anodic shift (ΔE1/2 = 151 mV), while HSO4(-) promoted fluorescence enhancement when Pb(2+) or Zn(2+) was bonded to the cation binding-site. (1)H NMR titration and density functional theory were performed to reveal the sensing mechanism based on photo-induced electron transfer (PET).

A Novel Mechanism for Chemical Sensing Based on Solvent-Fluorophore-Substrate Interaction: Highly Selective Alcohol and Water Sensor with Large Fluorescence Signal Contrast.

PubMed

Chung, Kyeongwoon; Yang, Da Seul; Jung, Jaehun; Seo, Deokwon; Kwon, Min Sang; Kim, Jinsang

2016-10-06

Differentiation of solvents having similar physicochemical properties, such as ethanol and methanol, is an important issue of interest. However, without performing chemical analyses, discrimination between methanol and ethanol is highly challenging due to their similarity in chemical structure as well as properties. Here, we present a novel type of alcohol and water sensor based on the subtle differences in interaction among solvent analytes, fluorescent organic molecules, and a mesoporous silica gel substrate. A gradual change in the chemical structure of the fluorescent diketopyrrolopyrrole (DPP) derivatives alters their interaction with the substrate and solvent analyte, which creates a distinct intermolecular aggregation of the DPP derivatives on the silica gel substrate depending on the solvent environment and produces a change in the fluorescence color and intensity as a sensory signal. The devised sensor device, which is fabricated with simple drop-casting of the DPP derivative solutions onto a silica gel substrate, exhibited a completely reversible fluorescence signal change with large fluorescence signal contrast, which allows selective solvent detection by simple optical observation with the naked eye under UV light. Superior selectivity of the alcohol and water sensor system, which can clearly distinguish among ethanol, methanol, ethylene glycol, and water, is demonstrated.

Motor Oil Classification Based on Time-Resolved Fluorescence

PubMed Central

Mu, Taotao; Chen, Siying; Zhang, Yinchao; Guo, Pan; Chen, He; Meng, Fandong

2014-01-01

A time-resolved fluorescence (TRF) technique is presented for classifying motor oils. The system is constructed with a third harmonic Nd:YAG laser, a spectrometer, and an intensified charge coupled device (ICCD) camera. Steady-state and time-resolved fluorescence (TRF) measurements are reported for several motor oils. It is found that steady-state fluorescence is insufficient to distinguish the motor oil samples. Then contour diagrams of TRF intensities (CDTRFIs) are acquired to serve as unique fingerprints to identify motor oils by using the distinct TRF of motor oils. CDTRFIs are preferable to steady-state fluorescence spectra for classifying different motor oils, making CDTRFIs a particularly choice for the development of fluorescence-based methods for the discrimination and characterization of motor oils. The two-dimensional fluorescence contour diagrams contain more information, not only the changing shapes of the LIF spectra but also the relative intensity. The results indicate that motor oils can be differentiated based on the new proposed method, which provides reliable methods for analyzing and classifying motor oils. PMID:24988439

Non-enzymatic Fluorescent Biosensor for Glucose Sensing Based on ZnO Nanorods

NASA Astrophysics Data System (ADS)

Mai, Hong Hanh; Pham, Van Thanh; Nguyen, Viet Tuyen; Sai, Cong Doanh; Hoang, Chi Hieu; Nguyen, The Binh

2017-06-01

We have developed a non-enzymatic fluorescent biosensor for glucose sensing based on ZnO nanorods. ZnO nanorods of high density, high crystallinity, and good alignment were grown on low-cost industrial copper substrates at low temperature. To grow them directly on the substrates without using a seed layer, we utilized a simple one-step seedless hydrothermal method, which is based on galvanic cell structure. Herein, the glucose-treated ZnO nanorods together with the ultraviolet (UV) irradiation of the sample during the photoluminescent measurement played the role of a catalyst. They decomposed glucose into hydrogen peroxide (H2O2) and gluconic acid, which is similar to the glucose oxidase enzyme (GOx) used in enzymatic sensors. Due to the formation of H2O2, the photoluminescence intensity of the UV emission peak of ZnO nanorods decreased as the glucose concentration increased from 1 mM to 100 mM. In comparison with glucose concentration of a normal human serum, which is in the range of 4.4-6.6 mM, the obtained results show potential of non-enzymatic fluorescent biosensors in medical applications.

Determination of fluoxetine in pharmaceutical and biological samples based on the silver nanoparticle enhanced fluorescence of fluoxetine-terbium complex.

PubMed

Lotfi, Ali; Manzoori, Jamshid L

2016-11-01

In this study, a simple and sensitive spectrofluorimetric method is presented for the determination of fluoxetine based on the enhancing effect of silver nanoparticles (AgNPs) on the terbium-fluoxetine fluorescence emission. The AgNPs were prepared by a simple reduction method and characterized by UV-Vis spectroscopy and transmission electron microscopy. It was indicated that these AgNPs have a remarkable amplifying effect on the terbium-sensitized fluorescence of fluoxetine. The effects of various parameters such as AgNP and Tb 3+ concentration and the pH of the media were investigated. Under obtained optimal conditions, the fluorescence intensity of the terbium-fluoxetine-AgNP system was enhanced linearly by increasing the concentration of fluoxetine in the range of 0.008 to 19 mg/L. The limit of detection (b + 3s) was 8.3 × 10 -4 mg/L. The interference effects of common species found in real samples were also studied. The method had good linearity, recovery, reproducibility and sensitivity, and was satisfactorily applied for the determination of fluoxetine in tablet formulations, human urine and plasma samples. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Homogeneous plate based antibody internalization assay using pH sensor fluorescent dye.

PubMed

Nath, Nidhi; Godat, Becky; Zimprich, Chad; Dwight, Stephen J; Corona, Cesear; McDougall, Mark; Urh, Marjeta

2016-04-01

Receptor-mediated antibody internalization is a key mechanism underlying several anti-cancer antibody therapeutics. Delivering highly toxic drugs to cancer cells, as in the case of antibody drug conjugates (ADCs), efficient removal of surface receptors from cancer cells and changing the pharmacokinetics profile of the antibody drugs are some of key ways that internalization impacts the therapeutic efficacy of the antibodies. Over the years, several techniques have been used to study antibody internalization including radiolabels, fluorescent microscopy, flow cytometry and cellular toxicity assays. While these methods allow analysis of internalization, they have limitations including a multistep process and limited throughput and are generally endpoint assays. Here, we present a new homogeneous method that enables time and concentration dependent measurements of antibody internalization. The method uses a new hydrophilic and bright pH sensor dye (pHAb dye), which is not fluorescent at neutral pH but becomes highly fluorescent at acidic pH. For receptor mediated antibody internalization studies, antibodies against receptors are conjugated with the pHAb dye and incubated with the cells expressing the receptors. Upon binding to the receptor, the dyes conjugated to the antibody are not fluorescent because of the neutral pH of the media, but upon internalization and trafficking into endosomal and lysosomal vesicles the pH drops and dyes become fluorescent. The enabling attributes of the pHAb dyes are the hydrophilic nature to minimize antibody aggregation and bright fluorescence at acidic pH which allows development of simple plate based assays using a fluorescent reader. Using two different therapeutic antibodies--Trastuzumab (anti-HER2) and Cetuximab (anti-EGFR)--we show labeling with pHAb dye using amine and thiol chemistries and impact of chemistry and dye to antibody ration on internalization. We finally present two new approaches using the pHAb dye, which will be

Novel Spectrofluorimetric Method for the Determination of Perindopril Erbumine Based on Fluorescence Quenching of Rhodamine B.

PubMed

Fael, Hanan; Sakur, Amir Al-Haj

2015-11-01

A novel, simple and specific spectrofluorimetric method was developed and validated for the determination of perindopril erbumine (PDE). The method is based on the fluorescence quenching of Rhodamine B upon adding perindopril erbumine. The quenched fluorescence was monitored at 578 nm after excitation at 500 nm. The optimization of the reaction conditions such as the solvent, reagent concentration, and reaction time were investigated. Under the optimum conditions, the fluorescence quenching was linear over a concentration range of 1.0-6.0 μg/mL. The proposed method was fully validated and successfully applied to the analysis of perindopril erbumine in pure form and tablets. Statistical comparison of the results obtained by the developed and reference methods revealed no significant differences between the methods compared in terms of accuracy and precision. The method was shown to be highly specific in the presence of indapamide, a diuretic that is commonly combined with perindopril erbumine. The mechanism of rhodamine B quenching was also discussed.

A Reaction-Based Novel Fluorescent Probe for Detection of Hydrogen Sulfide and Its Application in Wine.

PubMed

Wang, Hao; Wang, Jialin; Yang, Shaoxiang; Tian, Hongyu; Sun, Baoguo; Liu, Yongguo

2018-01-01

A new reaction-based fluorescent probe 6-cyanonaphthalen-2-yl-2,4- dinitrobenzenesulfonate (probe 1) was designed and synthesized for detection of hydrogen sulfide (H 2 S). The addition of H 2 S to a solution of probe 1 resulted in a marked fluorescence increased accompanied by a visual color change from colorless to yellow. Importantly, this distinct color response indicates that probe 1 could be used as a visual tool for detection of H 2 S. H 2 S can be detected quantitatively in the concentration range 0 to 25 μM and the detection limit was 30 nM. Moreover, probe 1 was successfully used as a sensor to determine H 2 S levels in red wine and beer. Fluorescent probe 1 could be employed as a visible sensor for H 2 S. Probe 1 could be used to detect H 2 S quantitatively in food simple. © 2017 Institute of Food Technologists®.

Fluorescent quenching-based quantitative detection of specific DNA/RNA using a BODIPY® FL-labeled probe or primer

PubMed Central

Kurata, Shinya; Kanagawa, Takahiro; Yamada, Kazutaka; Torimura, Masaki; Yokomaku, Toyokazu; Kamagata, Yoichi; Kurane, Ryuichiro

2001-01-01

We have developed a simple method for the quantitative detection of specific DNA or RNA molecules based on the finding that BODIPY® FL fluorescence was quenched by its interaction with a uniquely positioned guanine. This approach makes use of an oligonucleotide probe or primer containing a BODIPY® FL-modified cytosine at its 5′-end. When such a probe was hybridized with a target DNA, its fluorescence was quenched by the guanine in the target, complementary to the modified cytosine, and the quench rate was proportional to the amount of target DNA. This widely applicable technique will be used directly with larger samples or in conjunction with the polymerase chain reaction to quantify small DNA samples. PMID:11239011

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2 + in 100% aqueous media and application to real samples

NASA Astrophysics Data System (ADS)

Sun, Tao; Niu, Qingfen; Li, Tianduo; Guo, Zongrang; Liu, Haixia

2018-01-01

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu2 + was developed. Sensor ADA showed high selectivity and sensitivity toward Cu2 + in 100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480 nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu2 + recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8 nM, which is much lower than the allowable level of Cu2 + in drinking water set by U.S. Environmental Protection Agency ( 20 μM) and the World Health Organization ( 30 μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu2 + with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.

Robust, directed assembly of fluorescent nanodiamonds.

PubMed

Kianinia, Mehran; Shimoni, Olga; Bendavid, Avi; Schell, Andreas W; Randolph, Steven J; Toth, Milos; Aharonovich, Igor; Lobo, Charlene J

2016-10-27

Arrays of fluorescent nanoparticles are highly sought after for applications in sensing, nanophotonics and quantum communications. Here we present a simple and robust method of assembling fluorescent nanodiamonds into macroscopic arrays. Remarkably, the yield of this directed assembly process is greater than 90% and the assembled patterns withstand ultra-sonication for more than three hours. The assembly process is based on covalent bonding of carboxyl to amine functional carbon seeds and is applicable to any material, and to non-planar surfaces. Our results pave the way to directed assembly of sensors and nanophotonics devices.

DNA-Based Self-Assembly of Fluorescent Nanodiamonds.

PubMed

Zhang, Tao; Neumann, Andre; Lindlau, Jessica; Wu, Yuzhou; Pramanik, Goutam; Naydenov, Boris; Jelezko, Fedor; Schüder, Florian; Huber, Sebastian; Huber, Marinus; Stehr, Florian; Högele, Alexander; Weil, Tanja; Liedl, Tim

2015-08-12

As a step toward deterministic and scalable assembly of ordered spin arrays we here demonstrate a bottom-up approach to position fluorescent nanodiamonds (NDs) with nanometer precision on DNA origami structures. We have realized a reliable and broadly applicable surface modification strategy that results in DNA-functionalized and perfectly dispersed NDs that were then self-assembled in predefined geometries. With optical studies we show that the fluorescence properties of the nitrogen-vacancy color centers in NDs are preserved during surface modification and DNA assembly. As this method allows the nanoscale arrangement of fluorescent NDs together with other optically active components in complex geometries, applications based on self-assembled spin lattices or plasmon-enhanced spin sensors as well as improved fluorescent labeling for bioimaging could be envisioned.

A Schiff-based colorimetric fluorescent sensor with the potential for detection of fluoride ions.

PubMed

Huang, Cheng-Yin; Wan, Chin-Feng; Chir, Jiun-Ly; Wu, An-Tai

2013-11-01

A simple Schiff-based colorimetric fluorescent receptor 1 was prepared. It exhibits a "turn-on-type" mode with high sensitivity in the presence of F(-). The change in color is very easily observed by the naked eye in the presence of F(-), whereas other anions do not induce such a change. Job plot indicated a 1:2 complexation stoichiometry between receptor 1 and F(-). The association constant for 1-F(-) in CH3CN was determined as 1.32*10(5) M(-2) by a Hill plot.

A fluorescence method for detection of DNA and DNA methylation based on graphene oxide and restriction endonuclease HpaII.

PubMed

Wei, Wei; Gao, Chunyan; Xiong, Yanxiang; Zhang, Yuanjian; Liu, Songqin; Pu, Yuepu

2015-01-01

DNA methylation plays an important role in many biological events and is associated with various diseases. Most traditional methods for detection of DNA methylation are based on the complex and expensive bisulfite method. In this paper, we report a novel fluorescence method to detect DNA and DNA methylation based on graphene oxide (GO) and restriction endonuclease HpaII. The skillfully designed probe DNA labeled with 5-carboxyfluorescein (FAM) and optimized GO concentration keep the probe/target DNA still adsorbed on the GO. After the cleavage action of HpaII the labeled FAM is released from the GO surface and its fluorescence recovers, which could be used to detect DNA in the linear range of 50 pM-50 nM with a detection limit of 43 pM. DNA methylation induced by transmethylase (Mtase) or other chemical reagents prevents HpaII from recognizing and cleaving the specific site; as a result, fluorescence cannot recover. The fluorescence recovery efficiency is closely related to the DNA methylation level, which can be used to detect DNA methylation by comparing it with the fluorescence in the presence of intact target DNA. The method for detection of DNA and DNA methylation is simple, reliable and accurate. Copyright © 2014 Elsevier B.V. All rights reserved.

CINCH (confocal incoherent correlation holography) super resolution fluorescence microscopy based upon FINCH (Fresnel incoherent correlation holography).

PubMed

Siegel, Nisan; Storrie, Brian; Bruce, Marc; Brooker, Gary

2015-02-07

FINCH holographic fluorescence microscopy creates high resolution super-resolved images with enhanced depth of focus. The simple addition of a real-time Nipkow disk confocal image scanner in a conjugate plane of this incoherent holographic system is shown to reduce the depth of focus, and the combination of both techniques provides a simple way to enhance the axial resolution of FINCH in a combined method called "CINCH". An important feature of the combined system allows for the simultaneous real-time image capture of widefield and holographic images or confocal and confocal holographic images for ready comparison of each method on the exact same field of view. Additional GPU based complex deconvolution processing of the images further enhances resolution.

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.

CdTe quantum dot as a fluorescence probe for vitamin B12 in dosage form

NASA Astrophysics Data System (ADS)

Vaishnavi, E.; Renganathan, R.

2013-11-01

We here report the CdTe quantum dot (CdTe QDs)-based sensor for probing vitamin B12 derivatives in aqueous solution. In this paper, simple and sensitive fluorescence quenching measurements has been employed. The Stern-Volmer constant (KSV), quenching rate constant (kq) and binding constant (K) were rationalized from fluorescence quenching measurement. Furthermore, the fluorescence resonance energy transfer (FRET) mechanism was discussed. This method was applicable over the concentration ranging from 1 to 14 μg/mL (VB12) with correlation coefficient of 0.993. The limit of detection (LOD) of VB12 was found to be 0.15 μg/mL. Moreover, the present approach opens a simple pathway for developing cost-effective, sensitive and selective QD-based fluorescence sensors/probes for biologically significant VB12 in pharmaceutical sample with mean recoveries in the range of 100-102.1%.

DNA nanostructure-based fluorescence thermometer with silver nanoclusters.

PubMed

Bu, Congcong; Mu, Lixuan; Cao, XIngxing; Chen, Min; She, Guangwei; Shi, Wensheng

2018-04-27

Linking the fluorescent silver nanoclusters (AgNCs) and guanine-rich（G-rich）DNA chains by the thermal sensitive DNA stem-loop at teminal 5' and 3', DNA nanostructure-based fluorescence thermometers were fabricated. The variations of the temperature alter the distance between AgNCs and G-rich DNA chain, which could affect the interaction between them. As a result, the intensity of fluorescence emission from AgNCs at 636 nm can be sensitively modulated. It was found that such red emission is more sensitive to the temperature comparing with its intrinsic green emission at 543 nm, and sensitivity of -3.6%/℃ was achieved. Varying the melting temperature of the DNA stem-loop could readily adjust the response temperature range of thermometers. Novel DNA nanostructure-based fluorescence thermometers in this work could be anticipated to measure the temperature of biological system, even a single cell. © 2018 IOP Publishing Ltd.

Fluorescent biosensor for the detection of hyaluronidase: intensity-based ratiometric sensing and fluorescence lifetime-based sensing using a long lifetime azadioxatriangulenium (ADOTA) fluorophore.

PubMed

Chib, Rahul; Mummert, Mark; Bora, Ilkay; Laursen, Bo W; Shah, Sunil; Pendry, Robert; Gryczynski, Ignacy; Borejdo, Julian; Gryczynski, Zygmunt; Fudala, Rafal

2016-05-01

In this report, we have designed a rapid and sensitive, intensity-based ratiometric sensing as well as lifetime-based sensing probe for the detection of hyaluronidase activity. Hyaluronidase expression is known to be upregulated in various pathological conditions. We have developed a fluorescent probe by heavy labeling of hyaluronic acid with a new orange/red-emitting organic azadioxatriangulenium (ADOTA) fluorophore, which exhibits a long fluorescence lifetime (∼20 ns). The ADOTA fluorophore in water has a peak fluorescence lifetime of ∼20 ns and emission spectra centered at 560 nm. The heavily ADOTA-labeled hyaluronic acid (HA-ADOTA) shows a red shift in the peak emission wavelength (605 nm), a weak fluorescence signal, and a shorter fluorescence lifetime (∼4 ns) due to efficient self-quenching and formation of aggregates. In the presence of hyaluronidase, the brightness and fluorescence lifetime of the sample increase with a blue shift in the peak emission to its original wavelength at 560 nm. The ratio of the fluorescence intensity of the HA-ADOTA probe at 560 and 605 nm can be used as the sensing method for the detection of hyaluronidase. The cleavage of the hyaluronic acid macromolecule reduces the energy migration between ADOTA molecules, as well as the degree of self-quenching and aggregation. This probe can be efficiently used for both intensity-based ratiometric sensing as well as fluorescence lifetime-based sensing of hyaluronidase. The proposed method makes it a rapid and sensitive assay, useful for analyzing levels of hyaluronidase in relevant clinical samples like urine or plasma. Graphical Abstract Scheme showing cleavage of HA-ADOTA probe by hyaluronidase and the change in the emission spectrum of HA-ADOTA probe before and after cleavage by hyaluronidase.

A Simple and Sensitive Method for Auramine O Detection Based on the Binding Interaction with Bovin Serum Albumin.

PubMed

Yan, Jingjing; Huang, Xin; Liu, Shaopu; Yang, Jidong; Yuan, Yusheng; Duan, Ruilin; Zhang, Hui; Hu, Xiaoli

2016-01-01

A simple, rapid and effective method for auramine O (AO) detection was proposed by fluorescence and UV-Vis absorption spectroscopy. In the BR buffer system (pH 7.0), AO had a strong quenching ability to the fluorescence of bovin serum albumin (BSA) by dynamic quenching. In terms of the thermodynamic parameters calculated as ΔH > 0 and ΔS > 0, the resulting binding of BSA and AO was mainly attributed to the hydrophobic interaction forces. The linearity of this method was in the concentration range from 0.16 to 50 μmol L(-1) with a detection limit of 0.05 μmol L(-1). Based on fluorescence resonance energy transfer (FRET), the distance r (1.36 nm) between donor (BSA) and acceptor (AO) was obtained. Furthermore, the effects of foreign substances and ionic strength were evaluated under the optimum reaction conditions. BSA as a selective probe could be applied to the analysis of AO in medicines with satisfactory results.

Fluorescence "turn on" detection of mercuric ion based on bis(dithiocarbamato)copper(II) complex functionalized carbon nanodots.

PubMed

Yuan, Chao; Liu, Bianhua; Liu, Fei; Han, Ming-Yong; Zhang, Zhongping

2014-01-21

A new "turn on" fluorescence nanosensor for selective Hg(2+) determination is reported based on bis(dithiocarbamato)copper(II) functionalized carbon nanodots (CuDTC2-CDs). The CuDTC2 complex was conjugated to the prepared amine-coated CDs by the condensation of carbon disulfide onto the nitrogen atoms in the surface amine groups, followed by the coordination of copper(II) to the resulting dithiocarbamate groups (DTC) and finally by the additional coordination of ammonium N-(dithicarbaxy) sarcosine (DTCS) to form the CuDTC2-complexing CDs. The CuDTC2 complex at surface strongly quenched the bright-blue fluorescence of the CDs by a combination of electron transfer and energy transfer mechanism. Hg(2+) could immediately switch on the fluorescence of the CuDTC2-CDs by promptly displacing the Cu(2+) in the CuDTC2 complex and thus shutting down the energy transfer pathway, in which the sensitive limit for Hg(2+) as low as 4 ppb was reached. Moreover, a paper-based sensor has been fabricated by printing the CuDTC2-CDs probe ink on a piece of cellulose acetate paper using a commercial inkjet printer. The fluorescence "turn on" on the paper provided the most conveniently visual detection of aqueous Hg(2+) ions by the observation with naked eye. The very simple and effective strategy reported here facilitates the development of portable and reliable fluorescence nanosensors for the determination of Hg(2+) in real samples.

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.

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.

Simple apparatus for polarization sensing of analytes

NASA Astrophysics Data System (ADS)

Gryczynski, Zygmunt; Gryczynski, Ignacy; Lakowicz, Joseph R.

2000-09-01

We describe a simple device for fluorescence sensing based on an unexpansive light source, a dual photocell and a Watson bridge. The emission is detected from two fluorescent samples, one of which changes intensity in response to the analyte. The emission from these two samples is observed through two orthogonally oriented polarizers and an analyzer polarizer. The latter polarizer is rotated to yield equal intensities from both sides of the dual photocell, as determined by a zero voltage from the Watson bridge. Using this device, we are able to measure fluorescein concentration to an accuracy near 2% at 1 (mu) M fluorescein, and pH values accurate to +/- 0.02 pH units. We also use this approach with a UV hand lamp and a glucose-sensitive protein to measure glucose concentrations near 2 (mu) M to an accuracy of +/- 0.1 (mu) M. This approach requires only simple electronics, which can be battery powered. Additionally, the method is generic, and can be applied with any fluorescent sample that displays a change in intensity. One can imagine this approach being used to develop portable point-of-care clinical devices.

Patch-based anisotropic diffusion scheme for fluorescence diffuse optical tomography--part 2: image reconstruction.

PubMed

Correia, Teresa; Koch, Maximilian; Ale, Angelique; Ntziachristos, Vasilis; Arridge, Simon

2016-02-21

Fluorescence diffuse optical tomography (fDOT) provides 3D images of fluorescence distributions in biological tissue, which represent molecular and cellular processes. The image reconstruction problem is highly ill-posed and requires regularisation techniques to stabilise and find meaningful solutions. Quadratic regularisation tends to either oversmooth or generate very noisy reconstructions, depending on the regularisation strength. Edge preserving methods, such as anisotropic diffusion regularisation (AD), can preserve important features in the fluorescence image and smooth out noise. However, AD has limited ability to distinguish an edge from noise. We propose a patch-based anisotropic diffusion regularisation (PAD), where regularisation strength is determined by a weighted average according to the similarity between patches around voxels within a search window, instead of a simple local neighbourhood strategy. However, this method has higher computational complexity and, hence, we wavelet compress the patches (PAD-WT) to speed it up, while simultaneously taking advantage of the denoising properties of wavelet thresholding. Furthermore, structural information can be incorporated into the image reconstruction with PAD-WT to improve image quality and resolution. In this case, the weights used to average voxels in the image are calculated using the structural image, instead of the fluorescence image. The regularisation strength depends on both structural and fluorescence images, which guarantees that the method can preserve fluorescence information even when it is not structurally visible in the anatomical images. In part 1, we tested the method using a denoising problem. Here, we use simulated and in vivo mouse fDOT data to assess the algorithm performance. Our results show that the proposed PAD-WT method provides high quality and noise free images, superior to those obtained using AD.

A simple, sensitive determination of ganciclovir in infant plasma by high-performance liquid chromatography with fluorescence detection.

PubMed

Yoshida, Terumitsu; Takahashi, Ryohei; Imai, Koichi; Uchida, Hiroshi; Arai, Yasutoshi; Oh-ishi, Tsutomu

2010-03-01

This study developed a simple and sensitive method using reversed-phase high-performance liquid chromatography (HPLC) for ganciclovir (GCV) plasma concentrations in cytomegalovirus infectious infants with hearing loss. The method involves a simple protein precipitation procedure that uses no solid-phase or liquid-liquid extraction. The HPLC separation was carried out on a Cadenza CD-C(18) column (3 microm, 4.6 mm x 150 mm) with phosphate buffer (pH 2.5, 25 mM) containing 1% methanol-acetonitrile mixture (4:3, v/v) as a mobile phase at a 0.7 mL/min flow rate. GCV was detected using a fluorescence detection (lambdaex/em: 265/380 nm). The quantification limit was 0.025 microg/mL for 100 microL of plasma sample at which good intra- and inter-assay coefficient of variation values (< 4.96%) and recoveries (94.9-96.5%) were established.

DNA nanostructure-based fluorescence thermometer with silver nanoclusters

NASA Astrophysics Data System (ADS)

Bu, Congcong; Mu, Lixuan; Cao, Xingxing; Chen, Min; She, Guangwei; Shi, Wensheng

2018-07-01

DNA nanostructure-based fluorescence thermometers were fabricated by linking fluorescent silver nanoclusters (AgNCs) and guanine-rich（G-rich）DNA chains via a thermally sensitive DNA stem-loop at terminals 5‧ and 3‧. Variations of temperature alter the distance between the AgNCs and G-rich DNA chain, affecting the interaction between them. As a result, the intensity of fluorescence emission from the AgNCs at 636 nm can be sensitively modulated. It was found that the intensity of such red emission is more temperature sensitive than the equivalent green emission at 543 nm; sensitivity of ‑3.6%/°C was achieved. Through variation of the melting temperature of the DNA stem-loop, the response temperature range of the thermometers could be readily adjusted. Novel DNA nanostructure-based fluorescence thermometers as described in this work are anticipated to be able to measure the temperature of biological systems at small scales—even a single cell.

Fluorescence turn-on sensing of trace cadmium ions based on EDTA-etched CdTe@CdS quantum dot.

PubMed

Wang, Si-Nan; Zhu, Jian; Li, Xin; Li, Jian-Jun; Zhao, Jun-Wu

2018-05-01

Cadmium-caused environmental pollution and diseases have always been worldwide problems. Thus it is extremely urgent to establish a cheap, rapid, simple and selective detection method for trace cadmium in drinking water. In this study, a fluorescence "turn-on" method based on ethylene diamine tetraacetic acid (EDTA)-etched CdTe@CdS quantum dots (QDs) was designed to detect Cd 2+ . High resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were utilized for chemical and structural characterization of the as-prepared QDs. Based on chemical etching of EDTA on the surface of CdTe@CdS QDs, specific Cd 2+ recognition sites were produced, and then results in fluorescence quenching. The introduction of Cd 2+ could identify these sites and restore the fluorescence of the EDTA-QDs system. Under the optimum conditions, the nanoprobe shows a linear response range from 0.05 to 9 μM with a very low detection limit of 0.032 μM. In addition, the reported fluorescence probe in this work displays a good selectivity for trace Cd 2+ over other metal ions and an admirable practicability in real water samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of Mechanical Constraint on the Performance of Fluorescent Hydrogel-based Fiber Optic Sensors

NASA Astrophysics Data System (ADS)

Jukl, Jennifer Marie

Although biosensor technology is a broad and well-studied field, the progress of many novel sensor technologies faces challenges. These challenges range from simple design considerations to fundamental issues with the concept or approach. One of the most active fields of sensor research integrates fiber optics with specially engineered fluorescent molecules. This type of sensor typically utilizes a porous polymer or porous glass substrate to entrap the fluorescent (or fluorescently-tagged) molecule. Porous polymer hydrogels are generally favored due to their ease of fabrication, low cost, adaptability, and biocompatibility. While hydrogels are ideal for both functional molecule suspension and fluid diffusion, their porosity and hydrophilicity are not always advantageous. The largest drawback of these properties is the hydrogel swelling they produce and the resulting geometric changes. This project investigated the limitations of fluorescent hydrogel-based sensors and the effects of unpredictable structural changes hydrogels undergo during typical, unrestrained swelling. The significance of covalent incorporation of the sensing fluorophore into the hydrogel matrix is also explored. Leaching tests were conducted using polyacrylamide (PAm) hydrogels which were impregnated with one of two pH sensitive fluorophores, one which bonded covalently with the hydrogel matrix during polymerization (fluorescein o-acrylate), and one which did not (fluorescein sodium). Once determined to be effective, the covalently bonding fluorophore was used to create constrained-dimension fluorescent pH sensors. These sensors were tested for effectiveness and reproducibility. All data was collected using a laboratory grade optical fibers, a USB spectrometer, and SpectraSuite software (Ocean Optics, 2010) unless otherwise specified.

Novel biosensor system model based on fluorescence quenching by a fluorescent streptavidin and carbazole-labeled biotin.

PubMed

Zhu, Xianwei; Shinohara, Hiroaki; Miyatake, Ryuta; Hohsaka, Takahiro

2016-10-01

In the present study, a novel molecular biosensor system model was designed by using a couple of the fluorescent unnatural mutant streptavidin and the carbazole-labeled biotin. BODIPY-FL-aminophenylalanine (BFLAF), a fluorescent unnatural amino acid was position-specifically incorporated into Trp120 position of streptavidin by four-base codon method. On the other hand, carbazole-labeled biotin was synthesized as a quencher for the fluorescent Trp120BFLAF mutant streptavidin. The fluorescence of fluorescent Trp120BFLAF mutant streptavidin was decreased as we expected when carbazole-labeled biotin was added into the mutant streptavidin solution. Furthermore, the fluorescence decrease of Trp120BFLAF mutant streptavidin with carbazole-labeled biotin (100 nM) was recovered by the competitive addition of natural biotin. This result demonstrated that by measuring the fluorescence quenching and recovery, a couple of the fluorescent Trp120BFLAF mutant streptavidin and the carbazole-labeled biotin were successfully applicable for quantification of free biotin as a molecular biosensor system. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Development of Highly Fluorescent Materials Based on Thiophenylimidazole Dyes

NASA Technical Reports Server (NTRS)

Santos, Javier; Bu, Xiu R.; Mintz, Eric A.; Meador, Michael A. (Technical Monitor)

2000-01-01

Organic fluorescent materials are expected to find many potential applications in optical devices and photo-functionalized materials. Although many investigations have been focused on heterocyclic compounds such as coumarins, bipyridines, rhodamines, and pyrrole derivatives, little is known for fluorescent imidazole materials. We discovered that one particular class of imidazole derivatives is highly fluorescent. A series of monomeric and polymeric based fluorescent dyes were prepared containing a thiophene unit at the second position of the imidazole ring. Dependence of fluorescence efficiency on parameters such as solvent polarity and substituent groups has been investigated. It was found that a formyl group at the 2-position of the thiophene ring dramatically enhance fluorescence properties. Ion recognition probes indicated their potential as sensor materials. These fluorophores have flexibility for introduction of versatile substituent groups that could improve the fluorescence efficiency and sensor properties.

CINCH (confocal incoherent correlation holography) super resolution fluorescence microscopy based upon FINCH (Fresnel incoherent correlation holography)

PubMed Central

Siegel, Nisan; Storrie, Brian; Bruce, Marc

2016-01-01

FINCH holographic fluorescence microscopy creates high resolution super-resolved images with enhanced depth of focus. The simple addition of a real-time Nipkow disk confocal image scanner in a conjugate plane of this incoherent holographic system is shown to reduce the depth of focus, and the combination of both techniques provides a simple way to enhance the axial resolution of FINCH in a combined method called “CINCH”. An important feature of the combined system allows for the simultaneous real-time image capture of widefield and holographic images or confocal and confocal holographic images for ready comparison of each method on the exact same field of view. Additional GPU based complex deconvolution processing of the images further enhances resolution. PMID:26839443

Fluorescent chemosensor for pyridine based on N-doped carbon dots.

PubMed

Campos, B B; Abellán, C; Zougagh, M; Jimenez-Jimenez, J; Rodríguez-Castellón, E; Esteves da Silva, J C G; Ríos, A; Algarra, M

2015-11-15

Fluorescent carbon dots (CDs) and its nitrogen doped (N-CDs) nanoparticles have been synthesized from lactose as precursor using a bottom-up hydrothermal methodology. The synthesized nanoparticles have been characterized by elemental analysis, FTIR, Raman, TEM, DLS, XPS, and steady-state and life-time fluorescence. The synthesized carbon nanoparticles, CDs and N-CDs, have a size at about 7.7±2.4 and 50±15nm, respectively, and quantum yields of 8% (CDs) and 11% (N-CDs). These techniques demonstrated the effectiveness of the synthesis procedure and the functionalization of the CDs surface with amine and amide groups in the presence of NH3 in aqueous media. The effect of excitation wavelength and pH on the luminescent properties was studied. Under the optimal conditions, the nitrogen doped nanoparticles can be used as pyridine sensor in aqueous media because they show an enhancement of its fluorescence with a good linear relationship. The analytical method is simple, reproducible and very sensitive for pyridine determination. Copyright © 2015 Elsevier Inc. All rights reserved.

Real-time label-free quantitative fluorescence microscopy-based detection of ATP using a tunable fluorescent nano-aptasensor platform

NASA Astrophysics Data System (ADS)

Shrivastava, Sajal; Sohn, Il-Yung; Son, Young-Min; Lee, Won-Il; Lee, Nae-Eung

2015-11-01

Although real-time label-free fluorescent aptasensors based on nanomaterials are increasingly recognized as a useful strategy for the detection of target biomolecules with high fidelity, the lack of an imaging-based quantitative measurement platform limits their implementation with biological samples. Here we introduce an ensemble strategy for a real-time label-free fluorescent graphene (Gr) aptasensor platform. This platform employs aptamer length-dependent tunability, thus enabling the reagentless quantitative detection of biomolecules through computational processing coupled with real-time fluorescence imaging data. We demonstrate that this strategy effectively delivers dose-dependent quantitative readouts of adenosine triphosphate (ATP) concentration on chemical vapor deposited (CVD) Gr and reduced graphene oxide (rGO) surfaces, thereby providing cytotoxicity assessment. Compared with conventional fluorescence spectrometry methods, our highly efficient, universally applicable, and rational approach will facilitate broader implementation of imaging-based biosensing platforms for the quantitative evaluation of a range of target molecules.Although real-time label-free fluorescent aptasensors based on nanomaterials are increasingly recognized as a useful strategy for the detection of target biomolecules with high fidelity, the lack of an imaging-based quantitative measurement platform limits their implementation with biological samples. Here we introduce an ensemble strategy for a real-time label-free fluorescent graphene (Gr) aptasensor platform. This platform employs aptamer length-dependent tunability, thus enabling the reagentless quantitative detection of biomolecules through computational processing coupled with real-time fluorescence imaging data. We demonstrate that this strategy effectively delivers dose-dependent quantitative readouts of adenosine triphosphate (ATP) concentration on chemical vapor deposited (CVD) Gr and reduced graphene oxide (r

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.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2+ in ~100% aqueous media and application to real samples.

PubMed

Sun, Tao; Niu, Qingfen; Li, Tianduo; Guo, Zongrang; Liu, Haixia

2018-01-05

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu 2+ was developed. Sensor ADA showed high selectivity and sensitivity toward Cu 2+ in ~100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu 2+ recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu 2+ in drinking water set by U.S. Environmental Protection Agency (~20μM) and the World Health Organization (~30μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu 2+ with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field. Copyright © 2017 Elsevier B.V. All rights reserved.

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

The fluorescence theatre: a cost-effective device using theatre gels for fluorescent protein and dye screening.

PubMed

Heil, John R; Nordeste, Ricardo F; Charles, Trevor C

2011-04-01

Here we report a simple cost-effective device for screening colonies on plates for expression of the monomeric red fluorescent protein mRFP1 and the fluorescent dye Nile red. This device can be built from any simple light source, in our case a Quebec Colony Counter, and cost-effective theatre gels. The device can be assembled in as little as 20 min, and it produces excellent results when screening a large number of colonies.

Label-Free Fluorescent DNA Dendrimers for microRNA Detection Based On Nonlinear Hybridization Chain Reaction-Mediated Multiple G-Quadruplex with Low Background Signal.

PubMed

Xue, Qingwang; Liu, Chunxue; Li, Xia; Dai, Li; Wang, Huaisheng

2018-04-18

Various fluorescent sensing systems for miRNA detection have been developed, but they mostly contain enzymatic amplification reactions and label procedures. The strict reaction conditions of tool enzymes and the high cost of labeling limit their potential applications, especially in complex biological matrices. Here, we have addressed the difficult problems and report a strategy for label-free fluorescent DNA dendrimers based on enzyme-free nonlinear hybridization chain reaction (HCR)-mediated multiple G-quadruplex for simple, sensitive, and selective detection of miRNAs with low-background signal. In the strategy, a split G-quadruplex (3:1) sequence is ingeniously designed at both ends of two double-stranded DNAs, which is exploited as building blocks for nonlinear HCR assembly, thereby acquiring a low background signal. A hairpin switch probe (HSP) was employed as recognition and transduction element. Upon sensing the target miRNA, the nonlinear HCR assembly of two blocks (blocks-A and blocks-B) was initiated with the help of two single-stranded DNA assistants, resulting in chain-branching growth of DNA dendrimers with multiple G-quadruplex incorporation. With the zinc(II)-protoporphyrin IX (ZnPPIX) selectively intercalated into the multiple G-quadruplexes, fluorescent DNA dendrimers were obtained, leading to an exponential fluorescence intensity increase. Benefiting from excellent performances of nonlinear HCR and low background signal, this strategy possesses the characteristics of a simplified reaction operation process, as well as high sensitivity. Moreover, the proposed fluorescent sensing strategy also shows preferable selectivity, and can be implemented without modified DNA blocks. Importantly, the strategy has also been tested for miRNA quantification with high confidence in breast cancer cells. Thus, this proposed strategy for label-free fluorescent DNA dendrimers based on a nonlinear HCR-mediated multiple G-quadruplex will be turned into an alternative

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.

Fluorescence multispectral imaging-based diagnostic system for atherosclerosis.

PubMed

Ho, Cassandra Su Lyn; Horiuchi, Toshikatsu; Taniguchi, Hiroaki; Umetsu, Araya; Hagisawa, Kohsuke; Iwaya, Keiichi; Nakai, Kanji; Azmi, Amalina; Zulaziz, Natasha; Azhim, Azran; Shinomiya, Nariyoshi; Morimoto, Yuji

2016-08-20

Composition of atherosclerotic arterial walls is rich in lipids such as cholesterol, unlike normal arterial walls. In this study, we aimed to utilize this difference to diagnose atherosclerosis via multispectral fluorescence imaging, which allows for identification of fluorescence originating from the substance in the arterial wall. The inner surface of extracted arteries (rabbit abdominal aorta, human coronary artery) was illuminated by 405 nm excitation light and multispectral fluorescence images were obtained. Pathological examination of human coronary artery samples were carried out and thickness of arteries were calculated by measuring combined media and intima thickness. The fluorescence spectra in atherosclerotic sites were different from those in normal sites. Multiple regions of interest (ROI) were selected within each sample and a ratio between two fluorescence intensity differences (where each intensity difference is calculated between an identifier wavelength and a base wavelength) from each ROI was determined, allowing for discrimination of atherosclerotic sites. Fluorescence intensity and thickness of artery were found to be significantly correlated. These results indicate that multispectral fluorescence imaging provides qualitative and quantitative evaluations of atherosclerosis and is therefore a viable method of diagnosing the disease.

Simple-MSSM: a simple and efficient method for simultaneous multi-site saturation mutagenesis.

PubMed

Cheng, Feng; Xu, Jian-Miao; Xiang, Chao; Liu, Zhi-Qiang; Zhao, Li-Qing; Zheng, Yu-Guo

2017-04-01

To develop a practically simple and robust multi-site saturation mutagenesis (MSSM) method that enables simultaneously recombination of amino acid positions for focused mutant library generation. A general restriction enzyme-free and ligase-free MSSM method (Simple-MSSM) based on prolonged overlap extension PCR (POE-PCR) and Simple Cloning techniques. As a proof of principle of Simple-MSSM, the gene of eGFP (enhanced green fluorescent protein) was used as a template gene for simultaneous mutagenesis of five codons. Forty-eight randomly selected clones were sequenced. Sequencing revealed that all the 48 clones showed at least one mutant codon (mutation efficiency = 100%), and 46 out of the 48 clones had mutations at all the five codons. The obtained diversities at these five codons are 27, 24, 26, 26 and 22, respectively, which correspond to 84, 75, 81, 81, 69% of the theoretical diversity offered by NNK-degeneration (32 codons; NNK, K = T or G). The enzyme-free Simple-MSSM method can simultaneously and efficiently saturate five codons within one day, and therefore avoid missing interactions between residues in interacting amino acid networks.

Label-Free Carbon-Dots-Based Ratiometric Fluorescence pH Nanoprobes for Intracellular pH Sensing.

PubMed

Shangguan, Jingfang; He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Xu, Fengzhou; Liu, Jinquan; Tang, Jinlu; Yang, Xue; Huang, Jin

2016-08-02

Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.

Fluorescence imaging of angiogenesis in green fluorescent protein-expressing tumors

NASA Astrophysics Data System (ADS)

Yang, Meng; Baranov, Eugene; Jiang, Ping; Li, Xiao-Ming; Wang, Jin W.; Li, Lingna; Yagi, Shigeo; Moossa, A. R.; Hoffman, Robert M.

2002-05-01

The development of therapeutics for the control of tumor angiogenesis requires a simple, reliable in vivo assay for tumor-induced vascularization. For this purpose, we have adapted the orthotopic implantation model of angiogenesis by using human and rodent tumors genetically tagged with Aequorea victoria green fluorescent protein (GFP) for grafting into nude mice. Genetically-fluorescent tumors can be readily imaged in vivo. The non-luminous induced capillaries are clearly visible against the bright tumor fluorescence examined either intravitally or by whole-body luminance in real time. Fluorescence shadowing replaces the laborious histological techniques for determining blood vessel density. High-level GFP-expressing tumor cell lines made it possible to acquire the high-resolution real-time fluorescent optical images of angiogenesis in both primary tumors and their metastatic lesions in various human and rodent tumor models by means of a light-based imaging system. Intravital images of angiogenesis onset and development were acquired and quantified from a GFP- expressing orthotopically-growing human prostate tumor over a 19-day period. Whole-body optical imaging visualized vessel density increasing linearly over a 20-week period in orthotopically-growing, GFP-expressing human breast tumor MDA-MB-435. Vessels in an orthotopically-growing GFP- expressing Lewis lung carcinoma tumor were visualized through the chest wall via a reversible skin flap. These clinically-relevant angiogenesis mouse models can be used for real-time in vivo evaluation of agents inhibiting or promoting tumor angiogenesis in physiological micro- environments.

Shrink-induced silica multiscale structures for enhanced fluorescence from DNA microarrays.

PubMed

Sharma, Himanshu; Wood, Jennifer B; Lin, Sophia; Corn, Robert M; Khine, Michelle

2014-09-23

We describe a manufacturable and scalable method for fabrication of multiscale wrinkled silica (SiO2) structures on shrink-wrap film to enhance fluorescence signals in DNA fluorescence microarrays. We are able to enhance the fluorescence signal of hybridized DNA by more than 120 fold relative to a planar glass slide. Notably, our substrate has improved detection sensitivity (280 pM) relative to planar glass slide (11 nM). Furthermore, this is accompanied by a 30-45 times improvement in the signal-to-noise ratio (SNR). Unlike metal enhanced fluorescence (MEF) based enhancements, this is a far-field and uniform effect based on surface concentration and photophysical effects from the nano- to microscale SiO2 structures. Notably, the photophysical effects contribute an almost 2.5 fold enhancement over the concentration effects alone. Therefore, this simple and robust method offers an efficient technique to enhance the detection capabilities of fluorescence based DNA microarrays.

Shrink-Induced Silica Multiscale Structures for Enhanced Fluorescence from DNA Microarrays

PubMed Central

2015-01-01

We describe a manufacturable and scalable method for fabrication of multiscale wrinkled silica (SiO2) structures on shrink-wrap film to enhance fluorescence signals in DNA fluorescence microarrays. We are able to enhance the fluorescence signal of hybridized DNA by more than 120 fold relative to a planar glass slide. Notably, our substrate has improved detection sensitivity (280 pM) relative to planar glass slide (11 nM). Furthermore, this is accompanied by a 30–45 times improvement in the signal-to-noise ratio (SNR). Unlike metal enhanced fluorescence (MEF) based enhancements, this is a far-field and uniform effect based on surface concentration and photophysical effects from the nano- to microscale SiO2 structures. Notably, the photophysical effects contribute an almost 2.5 fold enhancement over the concentration effects alone. Therefore, this simple and robust method offers an efficient technique to enhance the detection capabilities of fluorescence based DNA microarrays. PMID:25191785

Intermolecular G-quadruplex structure-based fluorescent DNA detection system.

PubMed

Zhou, Hui; Wu, Zai-Sheng; Shen, Guo-Li; Yu, Ru-Qin

2013-03-15

Adopting multi-donors to pair with one acceptor could improve the performance of fluorogenic detection probes. However, common dyes (e.g., fluorescein) in close proximity to each other would self-quench the fluorescence, and the fluorescence is difficult to restore. In this contribution, we constructed a novel "multi-donors-to-one acceptor" fluorescent DNA detection system by means of the intermolecular G-quadruplex (IGQ) structure-based fluorescence signal enhancement combined with the hairpin oligonucleotide. The novel IGQ-hairpin system was characterized using the p53 gene as the model target DNA. The proposed system showed an improved assay performance due to the introduction of IGQ-structure into fluorescent signaling probes, which could inhibit the background fluorescence and increase fluorescence restoration amplitude of fluoresceins upon target DNA hybridization. The proof-of-concept scheme is expected to provide new insight into the potential of G-quadruplex structure and promote the application of fluorescent oligonucleotide probes in fundamental research, diagnosis, and treatment of genetic diseases. Copyright © 2012 Elsevier B.V. All rights reserved.

Novel single-stranded DNA binding protein-assisted fluorescence aptamer switch based on FRET for homogeneous detection of antibiotics.

PubMed

Wang, Ye; Gan, Ning; Zhou, You; Li, Tianhua; Cao, Yuting; Chen, Yinji

2017-01-15

Herein, a smart single-stranded DNA binding protein (SSB)-assisted fluorescence aptamer switch based on fluorescence resonance energy transfer (FRET) was designed. The FRET switch was synthesized by connecting SSB labeled quantum dots (QDs@SSB) as donor with aptamer (apt) labeled gold nanoparticles (AuNPs@apt) as acceptor, and it was employed for detecting chloramphenicol (CAP) in a homogenous solution. In the assay, the interaction between core-shell QDs@SSB and AuNPs@apt leads to a dramatic quenching (turning off). After adding CAP in the detection system, AuNPs@apt can bind the target specifically then separate QDs@SSB with AuNPs@apt-target, resulting in restoring the fluorescence intensity of QDs (turning on). Consequently, the fluorescence intensity recovers and the recovery extent can be used for detection of CAP in homogenous phase via optical responses. Under optimal conditions, the fluorescence intensity increased linearly with increasing concentrations of CAP from 0.005 to 100ngmL -1 . The limit of this fluorescence aptamer switch was around 3pgmL -1 for CAP detection. When the analyte is changed, the assay can be applied to detect other targets only by changing relative aptamer in AuNPs@apt probe. Furthermore, it has potential to be served as a simple, sensitive and portable platform for antibiotic contaminants detection in biological and environmental samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for vanadium(V) detection in mineral water samples

NASA Astrophysics Data System (ADS)

He, Lijun; Zhang, Heng; Fan, Huanhuan; Jiang, Xiuming; Zhao, Wenjie; Xiang, Guo Qiang

2018-01-01

Herein, we propose a simple and effective strategy for designing a ratiometric fluorescent nanosensor. We designed and developed a carbon dots (CDs) based dual-emission nanosensor for vanadium(V) by coating the surface of dye-doped silica nanoparticles with CDs. The fluorescence of dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. V(V) could catalyze KBrO3 oxidation reaction process, resulting in the ratiometric fluorescence quenching of dual-emission silica nanoparticles. We investigated several important parameters affecting the performance of the nanosensor. Under the optimized conditions, the detection limit of this nanosensor reached 1.1 ng mL- 1 and the linear range from 10 to 800 ng mL- 1. Furthermore, we found that the sensor was suitable for determination of V(V) in different mineral water samples with satisfactory results.

CdTe quantum dot as a fluorescence probe for vitamin B(12) in dosage form.

PubMed

Vaishnavi, E; Renganathan, R

2013-11-01

We here report the CdTe quantum dot (CdTe QDs)-based sensor for probing vitamin B12 derivatives in aqueous solution. In this paper, simple and sensitive fluorescence quenching measurements has been employed. The Stern-Volmer constant (KSV), quenching rate constant (kq) and binding constant (K) were rationalized from fluorescence quenching measurement. Furthermore, the fluorescence resonance energy transfer (FRET) mechanism was discussed. This method was applicable over the concentration ranging from 1 to 14μg/mL (VB12) with correlation coefficient of 0.993. The limit of detection (LOD) of VB12 was found to be 0.15μg/mL. Moreover, the present approach opens a simple pathway for developing cost-effective, sensitive and selective QD-based fluorescence sensors/probes for biologically significant VB12 in pharmaceutical sample with mean recoveries in the range of 100-102.1%. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

Fluorescent Trimethoprim Conjugate Probes To Assess Drug Accumulation in Wild Type and Mutant Escherichia coli

PubMed Central

2016-01-01

Reduced susceptibility to antimicrobials in Gram-negative bacteria may result from multiple resistance mechanisms, including increased efflux pump activity or reduced porin protein expression. Up-regulation of the efflux pump system is closely associated with multidrug resistance (MDR). To help investigate the role of efflux pumps on compound accumulation, a fluorescence-based assay was developed using fluorescent derivatives of trimethoprim (TMP), a broad-spectrum synthetic antibiotic that inhibits an intracellular target, dihydrofolate reductase (DHFR). Novel fluorescent TMP probes inhibited eDHFR activity with comparable potency to TMP, but did not kill or inhibit growth of wild type Escherichia coli. However, bactericidal activity was observed against an efflux pump deficient E. coli mutant strain (ΔtolC). A simple and quick fluorescence assay was developed to measure cellular accumulation of the TMP probe using either fluorescence spectroscopy or flow cytometry, with validation by LC-MS/MS. This fluorescence assay may provide a simple method to assess efflux pump activity with standard laboratory equipment. PMID:27737551

Multivariate optical element platform for compressed detection of fluorescence markers

NASA Astrophysics Data System (ADS)

Priore, Ryan J.; Swanstrom, Joseph A.

2014-05-01

The success of a commercial fluorescent diagnostic assay is dependent on the selection of a fluorescent biomarker; due to the broad nature of fluorescence biomarker emission profiles, only a small number of fluorescence biomarkers may be discriminated from each other as a function of excitation source. Multivariate Optical Elements (MOEs) are thin-film devices that encode a broad band, spectroscopic pattern allowing a simple broadband detector to generate a highly sensitive and specific detection for a target analyte. MOEs have historically been matched 1:1 to a discrete analyte or class prediction; however, MOE filter sets are capable of sensing projections of the original sparse spectroscopic space enabling a small set of MOEs to discriminate a multitude of target analytes. This optical regression can offer real-time measurements with relatively high signal-to-noise ratios that realize the advantages of multiplexed detection and pattern recognition in a simple optical instrument. The specificity advantage of MOE-based sensors allows fluorescent biomarkers that were once incapable of discrimination from one another via optical band pass filters to be employed in a common assay panel. A simplified MOE-based sensor may ultimately reduce the requirement for highly trained operators as well as move certain life science applications like disease prognostication from the laboratory to the point of care. This presentation will summarize the design and fabrication of compressed detection MOE filter sets for detecting multiple fluorescent biomarkers simultaneously with strong spectroscopic interference as well as comparing the detection performance of the MOE sensor with traditional optical band pass filter methodologies.

Real-time label-free quantitative fluorescence microscopy-based detection of ATP using a tunable fluorescent nano-aptasensor platform.

PubMed

Shrivastava, Sajal; Sohn, Il-Yung; Son, Young-Min; Lee, Won-Il; Lee, Nae-Eung

2015-12-14

Although real-time label-free fluorescent aptasensors based on nanomaterials are increasingly recognized as a useful strategy for the detection of target biomolecules with high fidelity, the lack of an imaging-based quantitative measurement platform limits their implementation with biological samples. Here we introduce an ensemble strategy for a real-time label-free fluorescent graphene (Gr) aptasensor platform. This platform employs aptamer length-dependent tunability, thus enabling the reagentless quantitative detection of biomolecules through computational processing coupled with real-time fluorescence imaging data. We demonstrate that this strategy effectively delivers dose-dependent quantitative readouts of adenosine triphosphate (ATP) concentration on chemical vapor deposited (CVD) Gr and reduced graphene oxide (rGO) surfaces, thereby providing cytotoxicity assessment. Compared with conventional fluorescence spectrometry methods, our highly efficient, universally applicable, and rational approach will facilitate broader implementation of imaging-based biosensing platforms for the quantitative evaluation of a range of target molecules.

Real-time fluorescence ligase chain reaction for sensitive detection of single nucleotide polymorphism based on fluorescence resonance energy transfer.

PubMed

Sun, Yueying; Lu, Xiaohui; Su, Fengxia; Wang, Limei; Liu, Chenghui; Duan, Xinrui; Li, Zhengping

2015-12-15

Most of practical methods for detection of single nucleotide polymorphism (SNP) need at least two steps: amplification (usually by PCR) and detection of SNP by using the amplification products. Ligase chain reaction (LCR) can integrate the amplification and allele discrimination in one step. However, the detection of LCR products still remains a great challenge for highly sensitive and quantitative SNP detection. Herein, a simple but robust strategy for real-time fluorescence LCR has been developed for highly sensitive and quantitative SNP detection. A pair of LCR probes are firstly labeled with a fluorophore and a quencher, respectively. When the pair of LCR probes are ligated in LCR, the fluorophore will be brought close to the quencher, and thus, the fluorescence will be specifically quenched by fluorescence resonance energy transfer (FRET). The decrease of fluorescence intensity resulted from FRET can be real-time monitored in the LCR process. With the proposed real-time fluorescence LCR assay, 10 aM DNA targets or 100 pg genomic DNA can be accurately determined and as low as 0.1% mutant DNA can be detected in the presence of a large excess of wild-type DNA, indicating the high sensitivity and specificity. The real-time measuring does not require the detection step after LCR and gives a wide dynamic range for detection of DNA targets (from 10 aM to 1 pM). As LCR has been widely used for detection of SNP, DNA methylation, mRNA and microRNA, the real-time fluorescence LCR assay shows great potential for various genetic analysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Implantable fluorescence-based glucose sensor development

NASA Astrophysics Data System (ADS)

Ibey, Bennett L.; Yadavalli, Vamsi K.; Thomas, Hope R.; Rounds, Rebecca M.; Pishko, Michael V.; Cote, Gerard L.

2005-03-01

An implantable sensor is being created that allows measurement of blood glucose through fluorescent detection of an embedded chemical assay. The sensor is based on the competitive binding reaction between the protein Concanavalin A and various saccharide molecules, specifically a glycodendrimer and glucose. Previous studies have shown the ability of an embedded chemical assay using Con A and dextran with shorter wavelength dyes to both sense changes in glucose and generate sufficient fluorescent emission to pass through the dermal tissue. However, due to the chemical constituents of the assay, multivalent binding was evident resulting in poor spectral change due to glucose within the biological range. Use of a glycodendrimer and longer wavelength dyes has improved the sensor"s spectral change due to glucose and the overall signal to noise ratio of the sensor. In this work, a description of this sensor and the results obtained from it will be presented showing a large dynamic range of fluorescence with glucose.

"Turn-off" fluorescent data array sensor based on double quantum dots coupled with chemometrics for highly sensitive and selective detection of multicomponent pesticides.

PubMed

Fan, Yao; Liu, Li; Sun, Donglei; Lan, Hanyue; Fu, Haiyan; Yang, Tianming; She, Yuanbin; Ni, Chuang

2016-04-15

As a popular detection model, the fluorescence "turn-off" sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence "turn-off" model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10(-8) mol L(-1) and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs. Copyright © 2016 Elsevier B.V. All rights reserved.

Enumerating viruses by using fluorescence and the nature of the nonviral background fraction.

PubMed

Pollard, Peter C

2012-09-01

Bulk fluorescence measurements could be a faster and cheaper way of enumerating viruses than epifluorescence microscopy, flow cytometry, or transmission electron microscopy (TEM). However, since viruses are not imaged, the background fluorescence compromises the signal, and we know little about its nature. In this paper the size ranges of nucleotides that fluoresce in the presence of SYBR gold were determined for wastewater and a range of freshwater samples using a differential filtration method. Fluorescence excitation-emission matrices (FEEMs) showed that >70% of the SYBR fluorescence was in the <10-nm size fraction (background) and was not associated with intact viruses. This was confirmed using TEM. The use of FEEMs to develop a fluorescence-based method for counting viruses is an approach that is fundamentally different from the epifluorescence microscopy technique used for enumerating viruses. This high fluorescence background is currently overlooked, yet it has had a most pervasive influence on the development of a simple fluorescence-based method for quantifying viral abundance in water.

Antibody immobilization on to polystyrene substrate--on-chip immunoassay for horse IgG based on fluorescence.

PubMed

Darain, Farzana; Gan, Kai Ling; Tjin, Swee Chuan

2009-06-01

A simple microfluidic immunoassay card was developed based on polystyrene (PS) substrate for the detection of horse IgG, an inexpensive model analyte using fluorescence microscope. The primary antibody was captured onto the PS based on covalent bonding via a self-assembled monolayer (SAM) of thiol to pattern the surface chemistry on a gold-coated PS. The immunosensor chip layers were fabricated from sheets by CO(2) laser ablation. The functionalized PS surfaces after each step were characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). After the antibody-antigen interaction as a sandwich immunoassay with a fluorescein isothiocyanate (FITC)-conjugated secondary antibody, the intensity of fluorescence was measured on-chip to determine the concentration of the target analyte. The present immunosensor chip showed a linear response range for horse IgG between 1 microg/ml and 80 microg/ml (r = 0.971, n = 3). The detection limit was found to be 0.71 microg/ml. The developed microfluidic system can be extended for various applications including medical diagnostics, microarray detection and observing protein-protein interactions.

Fluorescent chemosensor based on sensitive Schiff base for selective detection of Zn2+

NASA Astrophysics Data System (ADS)

Singh, T. Sanjoy; Paul, Pradip C.; Pramanik, Harun A. R.

2014-03-01

A Schiff-base fluorescent compound - N, N‧-bis(salicylidene)-1,2 - phenylenediamine (LH2) was synthesized and evaluated as a chemoselective Zn2+ sensor. Addition of Zn2+ to ethanol solution of LH2 resulted in a red shift with a pronounced enhancement in the fluorescence intensity. Moreover, other common alkali, alkaline earth and transition metal ions failed to induce response or minimal spectral changes. Notably, this chemosensor could distinguish clearly Zn2+ from Cd2+. Fluorescence studies on free Schiff base ligand LH2 and LH2 - Zn2+ complex reveal that the quantum yield strongly increases upon coordination. The stoichiometric ratio and association constant were evaluated using Benesi - Hildebrand relation giving 1:1 stoichiometry. This further corroborated 1:1 complex formation based on Job's plot analyses.

Design and Elementary Evaluation of a Highly-Automated Fluorescence-Based Instrument System for On-Site Detection of Food-Borne Pathogens

PubMed Central

Lu, Zhan; Zhang, Jianyi; Xu, Lizhou; Li, Yanbin; Chen, Siyu; Ye, Zunzhong; Wang, Jianping

2017-01-01

A simple, highly-automated instrument system used for on-site detection of foodborne pathogens based on fluorescence was designed, fabricated, and preliminarily tested in this paper. A corresponding method has been proved effective in our previous studies. This system utilizes a light-emitting diode (LED) to excite fluorescent labels and a spectrometer to record the fluorescence signal from samples. A rotation stage for positioning and switching samples was innovatively designed for high-throughput detection, ten at most in one single run. We also developed software based on LabVIEW for data receiving, processing, and the control of the whole system. In the test of using a pure quantum dot (QD) solution as a standard sample, detection results from this home-made system were highly-relevant with that from a well-commercialized product and even slightly better reproducibility was found. And in the test of three typical kinds of food-borne pathogens, fluorescence signals recorded by this system are highly proportional to the variation of the sample concentration, with a satisfied limit of detection (LOD) (nearly 102–103 CFU·mL−1 in food samples). Additionally, this instrument system is low-cost and easy-to-use, showing a promising potential for on-site rapid detection of food-borne pathogens. PMID:28241478

Design and Elementary Evaluation of a Highly-Automated Fluorescence-Based Instrument System for On-Site Detection of Food-Borne Pathogens.

PubMed

Lu, Zhan; Zhang, Jianyi; Xu, Lizhou; Li, Yanbin; Chen, Siyu; Ye, Zunzhong; Wang, Jianping

2017-02-23

A simple, highly-automated instrument system used for on-site detection of foodborne pathogens based on fluorescence was designed, fabricated, and preliminarily tested in this paper. A corresponding method has been proved effective in our previous studies. This system utilizes a light-emitting diode (LED) to excite fluorescent labels and a spectrometer to record the fluorescence signal from samples. A rotation stage for positioning and switching samples was innovatively designed for high-throughput detection, ten at most in one single run. We also developed software based on LabVIEW for data receiving, processing, and the control of the whole system. In the test of using a pure quantum dot (QD) solution as a standard sample, detection results from this home-made system were highly-relevant with that from a well-commercialized product and even slightly better reproducibility was found. And in the test of three typical kinds of food-borne pathogens, fluorescence signals recorded by this system are highly proportional to the variation of the sample concentration, with a satisfied limit of detection (LOD) (nearly 10²-10³ CFU·mL -1 in food samples). Additionally, this instrument system is low-cost and easy-to-use, showing a promising potential for on-site rapid detection of food-borne pathogens.

Intracellular pH measurements made simple by fluorescent protein probes and the phasor approach to fluorescence lifetime imaging†

PubMed Central

Digman, Michelle A.; Gratton, Enrico; Storti, Barbara; Beltram, Fabio

2013-01-01

A versatile pH-dependent fluorescent protein was applied to intracellular pH measurements by means of the phasor approach to fluorescence lifetime imaging. By this fit-less method we obtain intracellular pH maps under resting or altered physiological conditions by single-photon confocal or two-photon microscopy. PMID:22517076

Catheter-based time-gated near-infrared fluorescence/OCT imaging system

NASA Astrophysics Data System (ADS)

Lu, Yuankang; Abran, Maxime; Cloutier, Guy; Lesage, Frédéric

2018-02-01

We developed a new dual-modality intravascular imaging system based on fast time-gated fluorescence intensity imaging and spectral domain optical coherence tomography (SD-OCT) for the purpose of interventional detection of atherosclerosis. A pulsed supercontinuum laser was used for fluorescence and OCT imaging. A double-clad fiber (DCF)- based side-firing catheter was designed and fabricated to have a 23 μm spot size at a 2.2 mm working distance for OCT imaging. Its single-mode core is used for OCT, while its inner cladding transports fluorescence excitation light and collects fluorescent photons. The combination of OCT and fluorescence imaging was achieved by using a DCF coupler. For fluorescence detection, we used a time-gated technique with a novel single-photon avalanche diode (SPAD) working in an ultra-fast gating mode. A custom-made delay chip was integrated in the system to adjust the delay between the excitation laser pulse and the SPAD gate-ON window. This technique allowed to detect fluorescent photons of interest while rejecting most of the background photons, thus leading to a significantly improved signal to noise ratio (SNR). Experiments were carried out in turbid media mimicking tissue with an indocyanine green (ICG) inclusion (1 mM and 100 μM) to compare the time-gated technique and the conventional continuous detection technique. The gating technique increased twofold depth sensitivity, and tenfold SNR at large distances. The dual-modality imaging capacity of our system was also validated with a silicone-based tissue-mimicking phantom.

Highly sensitive fluorescence and SERS detection of azide through a simple click reaction of 8-chloroquinoline and phenylacetylene.

PubMed

Zeng, Qing; Ye, Lingling; Ma, Lu; Yin, Wenqing; Li, Tingsheng; Liang, Aihui; Jiang, Zhiliang

2015-05-01

In 0.19 mol/L acetic acid (HAc), a click reaction of 8-chloroquinoline/azide/phenylacetylene take places in aqueous solution without Cu(I) as a catalyst. 8-Chloroquinoline (CQN) exhibited a strong fluorescence peak at 430 nm that was quenched linearly as the concentration of azide increased from 20 to 1000 ng/mL. This quenching was due to consumption of CQN in the click reaction and a decrease in the number of efficiently excited photons due to the presence of triazole-quinoline ramification molecules with strong hydrophobicity. Using blue nanosilver sol as the substrate, CQN absorbed onto the surface of nanosilver particles, showing a strong surface-enhanced Raman scattering (SERS) peak at 1585 cm(-1) that decreased linearly as the azide concentration increased from 8 to 500 ng/mL; the detection limit was 4 ng/mL. Thus, two new, simple and sensitive fluorescence and SERS methods have been developed for the determination of azide via the click reaction. Copyright © 2014 John Wiley & Sons, Ltd.

Fluorescence-based bioassays for the detection and evaluation of food materials.

PubMed

Nishi, Kentaro; Isobe, Shin-Ichiro; Zhu, Yun; Kiyama, Ryoiti

2015-10-13

We summarize here the recent progress in fluorescence-based bioassays for the detection and evaluation of food materials by focusing on fluorescent dyes used in bioassays and applications of these assays for food safety, quality and efficacy. Fluorescent dyes have been used in various bioassays, such as biosensing, cell assay, energy transfer-based assay, probing, protein/immunological assay and microarray/biochip assay. Among the arrays used in microarray/biochip assay, fluorescence-based microarrays/biochips, such as antibody/protein microarrays, bead/suspension arrays, capillary/sensor arrays, DNA microarrays/polymerase chain reaction (PCR)-based arrays, glycan/lectin arrays, immunoassay/enzyme-linked immunosorbent assay (ELISA)-based arrays, microfluidic chips and tissue arrays, have been developed and used for the assessment of allergy/poisoning/toxicity, contamination and efficacy/mechanism, and quality control/safety. DNA microarray assays have been used widely for food safety and quality as well as searches for active components. DNA microarray-based gene expression profiling may be useful for such purposes due to its advantages in the evaluation of pathway-based intracellular signaling in response to food materials.

Fluorescence-Based Bioassays for the Detection and Evaluation of Food Materials

PubMed Central

Nishi, Kentaro; Isobe, Shin-Ichiro; Zhu, Yun; Kiyama, Ryoiti

2015-01-01

We summarize here the recent progress in fluorescence-based bioassays for the detection and evaluation of food materials by focusing on fluorescent dyes used in bioassays and applications of these assays for food safety, quality and efficacy. Fluorescent dyes have been used in various bioassays, such as biosensing, cell assay, energy transfer-based assay, probing, protein/immunological assay and microarray/biochip assay. Among the arrays used in microarray/biochip assay, fluorescence-based microarrays/biochips, such as antibody/protein microarrays, bead/suspension arrays, capillary/sensor arrays, DNA microarrays/polymerase chain reaction (PCR)-based arrays, glycan/lectin arrays, immunoassay/enzyme-linked immunosorbent assay (ELISA)-based arrays, microfluidic chips and tissue arrays, have been developed and used for the assessment of allergy/poisoning/toxicity, contamination and efficacy/mechanism, and quality control/safety. DNA microarray assays have been used widely for food safety and quality as well as searches for active components. DNA microarray-based gene expression profiling may be useful for such purposes due to its advantages in the evaluation of pathway-based intracellular signaling in response to food materials. PMID:26473869

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.

Diketopyrrolopyrrole: brilliant red pigment dye-based fluorescent probes and their applications.

PubMed

Kaur, Matinder; Choi, Dong Hoon

2015-01-07

The development of fluorescent probes for the detection of biologically relevant species is a burgeoning topic in the field of supramolecular chemistry. A number of available dyes such as rhodamine, coumarin, fluorescein, and cyanine have been employed in the design and synthesis of new fluorescent probes. However, diketopyrrolopyrrole (DPP) and its derivatives have a distinguished role in supramolecular chemistry for the design of fluorescent dyes. DPP dyes offer distinctive advantages relative to other organic dyes, including high fluorescence quantum yields and good light and thermal stability. Significant advancements have been made in the development of new fluorescent probes based on DPP in recent years as a result of tireless research efforts by the chemistry scientific community. In this tutorial review, we highlight the recent progress in the development of DPP-based fluorescent probes for the period spanning 2009 to the present time and the applications of these probes to recognition of biologically relevant species including anions, cations, reactive oxygen species, thiols, gases and other miscellaneous applications. This review is targeted toward providing the readers with deeper understanding for the future design of DPP-based fluorogenic probes for chemical and biological applications.

Cucurbiturils: molecular nanocapsules for time-resolved fluorescence-based assays.

PubMed

Marquez, Cesar; Huang, Fang; Nau, Werner M

2004-03-01

A new fluorescent host-guest system based on the inclusion of the fluorophore 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) into the cavity of the molecular container compound cucurbit[7]uril (CB7) has been designed which possesses an exceedingly long-lived emission (690 ns in aerated water). The large binding constant of (4 +/- 1) x 10(5) M(-1) along with the resistance of the CB7.DBO complex toward external fluorescence quenchers allow the use of CB7 as an enhancer in time-resolved fluorescence-based assays, e.g., to screen enzyme activity or inhibition by using DBO-labeled peptides as substrates. The response of CB7.DBO to different environmental conditions and possible quenchers are described.

Physically-based in silico light sheet microscopy for visualizing fluorescent brain models

PubMed Central

2015-01-01

Background We present a physically-based computational model of the light sheet fluorescence microscope (LSFM). Based on Monte Carlo ray tracing and geometric optics, our method simulates the operational aspects and image formation process of the LSFM. This simulated, in silico LSFM creates synthetic images of digital fluorescent specimens that can resemble those generated by a real LSFM, as opposed to established visualization methods producing visually-plausible images. We also propose an accurate fluorescence rendering model which takes into account the intrinsic characteristics of fluorescent dyes to simulate the light interaction with fluorescent biological specimen. Results We demonstrate first results of our visualization pipeline to a simplified brain tissue model reconstructed from the somatosensory cortex of a young rat. The modeling aspects of the LSFM units are qualitatively analysed, and the results of the fluorescence model were quantitatively validated against the fluorescence brightness equation and characteristic emission spectra of different fluorescent dyes. AMS subject classification Modelling and simulation PMID:26329404

Label-Free Detection of Sequence-Specific DNA Based on Fluorescent Silver Nanoclusters-Assisted Surface Plasmon-Enhanced Energy Transfer.

PubMed

Ma, Jin-Liang; Yin, Bin-Cheng; Le, Huynh-Nhu; Ye, Bang-Ce

2015-06-17

We have developed a label-free method for sequence-specific DNA detection based on surface plasmon enhanced energy transfer (SPEET) process between fluorescent DNA/AgNC string and gold nanoparticles (AuNPs). DNA/AgNC string, prepared by a single-stranded DNA template encoded two emitter-nucleation sequences at its termini and an oligo spacer in the middle, was rationally designed to produce bright fluorescence emission. The proposed method takes advantage of two strategies. The first one is the difference in binding properties of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) toward AuNPs. The second one is SPEET process between fluorescent DNA/AgNC string and AuNPs, in which fluorescent DNA/AgNC string can be spontaneously adsorbed onto the surface of AuNPs and correspondingly AuNPs serve as "nanoquencher" to quench the fluorescence of DNA/AgNC string. In the presence of target DNA, the sensing probe hybridized with target DNA to form duplex DNA, leading to a salt-induced AuNP aggregation and subsequently weakened SPEET process between fluorescent DNA/AgNC string and AuNPs. A red-to-blue color change of AuNPs and a concomitant fluorescence increase were clearly observed in the sensing system, which had a concentration dependent manner with specific DNA. The proposed method achieved a detection limit of ∼2.5 nM, offering the following merits of simple design, convenient operation, and low experimental cost because of no chemical modification, organic dye, enzymatic reaction, or separation procedure involved.

Simple and rapid determination of homozygous transgenic mice via in vivo fluorescence imaging.

PubMed

Lin, Xiaolin; Jia, Junshuang; Qin, Yujuan; Lin, Xia; Li, Wei; Xiao, Gaofang; Li, Yanqing; Xie, Raoying; Huang, Hailu; Zhong, Lin; Wu, Qinghong; Wang, Wanshan; Huang, Wenhua; Yao, Kaitai; Xiao, Dong; Sun, Yan

2015-11-17

Setting up breeding programs for transgenic mouse strains require to distinguish homozygous from the heterozygous transgenic animals. The combinational use of the fluorescence reporter transgene and small animal in-vivo imaging system might allow us to rapidly and visually determine the transgenic mice homozygous for transgene(s) by the in vivo fluorescence imaging. RLG, RCLG or Rm17LG transgenic mice ubiquitously express red fluorescent protein (RFP). To identify homozygous RLG transgenic mice, whole-body fluorescence imaging for all of newborn F2-generation littermates produced by mating of RFP-positive heterozygous transgenic mice (F1-generation) derived from the same transgenic founder was performed. Subsequently, the immediate data analysis of the in vivo fluorescence imaging was carried out, which greatly facilitated us to rapidly and readily distinguish RLG transgenic individual(s) with strong fluorescence from the rest of F2-generation littermates, followed by further determining this/these RLG individual(s) showing strong fluorescence to be homozygous, as strongly confirmed by mouse mating. Additionally, homozygous RCLG or Rm17LG transgenic mice were also rapidly and precisely distinguished by the above-mentioned optical approach. This approach allowed us within the shortest time period to obtain 10, 8 and 2 transgenic mice homozygous for RLG, RCLG and Rm17LG transgene, respectively, as verified by mouse mating, indicating the practicality and reliability of this optical method. Taken together, our findings fully demonstrate that the in vivo fluorescence imaging offers a visual, rapid and reliable alternative method to the traditional approaches (i.e., mouse mating and real-time quantitative PCR) in identifying homozygous transgenic mice harboring fluorescence reporter transgene under the control of a ubiquitous promoter in the situation mentioned in this study.

Simple and rapid determination of homozygous transgenic mice via in vivo fluorescence imaging

PubMed Central

Li, Wei; Xiao, Gaofang; Li, Yanqing; Xie, Raoying; Huang, Hailu; Zhong, Lin; Wu, Qinghong; Wang, Wanshan; Huang, Wenhua; Yao, Kaitai; Xiao, Dong; Sun, Yan

2015-01-01

Setting up breeding programs for transgenic mouse strains require to distinguish homozygous from the heterozygous transgenic animals. The combinational use of the fluorescence reporter transgene and small animal in-vivo imaging system might allow us to rapidly and visually determine the transgenic mice homozygous for transgene(s) by the in vivo fluorescence imaging. RLG, RCLG or Rm17LG transgenic mice ubiquitously express red fluorescent protein (RFP). To identify homozygous RLG transgenic mice, whole-body fluorescence imaging for all of newborn F2-generation littermates produced by mating of RFP-positive heterozygous transgenic mice (F1-generation) derived from the same transgenic founder was performed. Subsequently, the immediate data analysis of the in vivo fluorescence imaging was carried out, which greatly facilitated us to rapidly and readily distinguish RLG transgenic individual(s) with strong fluorescence from the rest of F2-generation littermates, followed by further determining this/these RLG individual(s) showing strong fluorescence to be homozygous, as strongly confirmed by mouse mating. Additionally, homozygous RCLG or Rm17LG transgenic mice were also rapidly and precisely distinguished by the above-mentioned optical approach. This approach allowed us within the shortest time period to obtain 10, 8 and 2 transgenic mice homozygous for RLG, RCLG and Rm17LG transgene, respectively, as verified by mouse mating, indicating the practicality and reliability of this optical method. Taken together, our findings fully demonstrate that the in vivo fluorescence imaging offers a visual, rapid and reliable alternative method to the traditional approaches (i.e., mouse mating and real-time quantitative PCR) in identifying homozygous transgenic mice harboring fluorescence reporter transgene under the control of a ubiquitous promoter in the situation mentioned in this study. PMID:26472024

Estimating the Biodegradability of Treated Sewage Samples Using Synchronous Fluorescence Spectra

PubMed Central

Lai, Tien M.; Shin, Jae-Ki; Hur, Jin

2011-01-01

Synchronous fluorescence spectra (SFS) and the first derivative spectra of the influent versus the effluent wastewater samples were compared and the use of fluorescence indices is suggested as a means to estimate the biodegradability of the effluent wastewater. Three distinct peaks were identified from the SFS of the effluent wastewater samples. Protein-like fluorescence (PLF) was reduced, whereas fulvic and/or humic-like fluorescence (HLF) were enhanced, suggesting that the two fluorescence characteristics may represent biodegradable and refractory components, respectively. Five fluorescence indices were selected for the biodegradability estimation based on the spectral features changing from the influent to the effluent. Among the selected indices, the relative distribution of PLF to the total fluorescence area of SFS (Index II) exhibited the highest correlation coefficient with total organic carbon (TOC)-based biodegradability, which was even higher than those obtained with the traditional oxygen demand-based parameters. A multiple regression analysis using Index II and the area ratio of PLF to HLF (Index III) demonstrated the enhancement of the correlations from 0.558 to 0.711 for TOC-based biodegradability. The multiple regression equation finally obtained was 0.148 × Index II − 4.964 × Index III − 0.001 and 0.046 × Index II − 1.128 × Index III + 0.026. The fluorescence indices proposed here are expected to be utilized for successful development of real-time monitoring using a simple fluorescence sensing device for the biodegradability of treated sewage. PMID:22164023

Estimating the biodegradability of treated sewage samples using synchronous fluorescence spectra.

PubMed

Lai, Tien M; Shin, Jae-Ki; Hur, Jin

2011-01-01

Synchronous fluorescence spectra (SFS) and the first derivative spectra of the influent versus the effluent wastewater samples were compared and the use of fluorescence indices is suggested as a means to estimate the biodegradability of the effluent wastewater. Three distinct peaks were identified from the SFS of the effluent wastewater samples. Protein-like fluorescence (PLF) was reduced, whereas fulvic and/or humic-like fluorescence (HLF) were enhanced, suggesting that the two fluorescence characteristics may represent biodegradable and refractory components, respectively. Five fluorescence indices were selected for the biodegradability estimation based on the spectral features changing from the influent to the effluent. Among the selected indices, the relative distribution of PLF to the total fluorescence area of SFS (Index II) exhibited the highest correlation coefficient with total organic carbon (TOC)-based biodegradability, which was even higher than those obtained with the traditional oxygen demand-based parameters. A multiple regression analysis using Index II and the area ratio of PLF to HLF (Index III) demonstrated the enhancement of the correlations from 0.558 to 0.711 for TOC-based biodegradability. The multiple regression equation finally obtained was 0.148 × Index II - 4.964 × Index III - 0.001 and 0.046 × Index II - 1.128 × Index III + 0.026. The fluorescence indices proposed here are expected to be utilized for successful development of real-time monitoring using a simple fluorescence sensing device for the biodegradability of treated sewage.

A novel immunoassay based on the dissociation of immunocomplex and fluorescence quenching by gold nanoparticles.

PubMed

Peng, Zhaofeng; Chen, Zhaopeng; Jiang, Jianhui; Zhang, Xiaobing; Shen, Guoli; Yu, Ruqin

2007-01-30

This study reports a novel, simple and sensitive immunoassay using fluorescence quenching caused by gold nanoparticles coated with antibody. The method is based on a non-competitive heterogeneous immunoassay of human IgG conducted by the typical procedure of sandwich immunocomplex formation. Goat anti-human IgG was first adsorbed on polystyrene microwells, and human IgG analyte was captured by the primary antibody and then sandwiched by antibody labeled with gold nanoparticles. The sandwich-type immunocomplex was subsequently dissociated by the mixed solution of sodium hydroxide and trisodium citrate, the solution obtained, which contains gold nanoparticles coated with antibody, was used to quench fluorescence. The fluorescence intensity of fluorescein at 517 nm was inversely proportional to the logarithm of the concentration of human IgG in the dynamic range of 10-5000 ng mL(-1) with a detection limit of 4.7 ng mL(-1). The electrochemical experiments and the UV-vis measurements were applied to demonstrate whether the immunogold was dissociated completely and whether the gold nanoparticles aggregated after being dissociated, respectively. The proposed system can be extended to detect target molecules such as other kinds of antigen and DNA strands, and has broad potential applications in disease diagnosis.

A Model-Based Approach for Microvasculature Structure Distortion Correction in Two-Photon Fluorescence Microscopy Images

PubMed Central

Dao, Lam; Glancy, Brian; Lucotte, Bertrand; Chang, Lin-Ching; Balaban, Robert S; Hsu, Li-Yueh

2015-01-01

SUMMARY This paper investigates a post-processing approach to correct spatial distortion in two-photon fluorescence microscopy images for vascular network reconstruction. It is aimed at in vivo imaging of large field-of-view, deep-tissue studies of vascular structures. Based on simple geometric modeling of the object-of-interest, a distortion function is directly estimated from the image volume by deconvolution analysis. Such distortion function is then applied to sub volumes of the image stack to adaptively adjust for spatially varying distortion and reduce the image blurring through blind deconvolution. The proposed technique was first evaluated in phantom imaging of fluorescent microspheres that are comparable in size to the underlying capillary vascular structures. The effectiveness of restoring three-dimensional spherical geometry of the microspheres using the estimated distortion function was compared with empirically measured point-spread function. Next, the proposed approach was applied to in vivo vascular imaging of mouse skeletal muscle to reduce the image distortion of the capillary structures. We show that the proposed method effectively improve the image quality and reduce spatially varying distortion that occurs in large field-of-view deep-tissue vascular dataset. The proposed method will help in qualitative interpretation and quantitative analysis of vascular structures from fluorescence microscopy images. PMID:26224257

Multiplex fluorescent immunoassay device based on magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Godjevargova, T. I.; Ivanov, Y. L.; Dinev, D. D.

2017-02-01

Immunofluorescent analyzer based compact disc for simultaneous detection of 3 antibiotics in the same milk sample is consisting of two parts: CD-based immunofluorescence kit and optoelectronic fluorometer. Kit consists of 2 parts: Lyophilized immobilized antibodies on supermagnetic nanoparticles in Eppendorf tubes and CD-based microfluidic disk, in which are formed five chamber systems for simultaneous detecting of 5 separate samples. Each system consists of 2 chambers connected by a special micro channel acting as a hydrophobic valve. In the first chamber lyophilised conjugates of 3 antibiotics with accordingly 3 different fluorescent dyes are placed. The second chamber is for detection of fluorescent signal. The optoelectronic fluorometer is comprising of: integrated thermostatic block; mechanical-detecting unit (fluorometer) and block with controlling and visualizing electronics.The disc gets into a second block of the analyzer, where centrifugation is performed and also reporting of the fluorescent signals. This unit comprises a rotor on which the disc is fixed, permanent electromagnet in the form of a ring inserted under the disc and module of 3 LED diodes with emission filters for the relevant wavelengths corresponding to the used fluorescent dyes and 1 integrated photodiode, in front of which is mounted filter with 3 spectral peaks.The signal from the photodiode is detected by the electronic unit which is sensitive "lock-in" amplifier, the engine rotor management, control of thermostatic device and management of periphery of the analyzer, consisting of display and communications with computer.

Wireless implantable electronic platform for chronic fluorescent-based biosensors.

PubMed

Valdastri, Pietro; Susilo, Ekawahyu; Förster, Thilo; Strohhöfer, Christof; Menciassi, Arianna; Dario, Paolo

2011-06-01

The development of a long-term wireless implantable biosensor based on fluorescence intensity measurement poses a number of technical challenges, ranging from biocompatibility to sensor stability over time. One of these challenges is the design of a power efficient and miniaturized electronics, enabling the biosensor to move from bench testing to long term validation, up to its final application in human beings. In this spirit, we present a wireless programmable electronic platform for implantable chronic monitoring of fluorescent-based autonomous biosensors. This system is able to achieve extremely low power operation with bidirectional telemetry, based on the IEEE802.15.4-2003 protocol, thus enabling over three-year battery lifetime and wireless networking of multiple sensors. During the performance of single fluorescent-based sensor measurements, the circuit drives a laser diode, for sensor excitation, and acquires the amplified signals from four different photodetectors. In vitro functionality was preliminarily tested for both glucose and calcium monitoring, simply by changing the analyte-binding protein of the biosensor. Electronics performance was assessed in terms of timing, power consumption, tissue exposure to electromagnetic fields, and in vivo wireless connectivity. The final goal of the presented platform is to be integrated in a complete system for blood glucose level monitoring that may be implanted for at least one year under the skin of diabetic patients. Results reported in this paper may be applied to a wide variety of biosensors based on fluorescence intensity measurement.

A fluorescence-based polymerase chain reaction-linked single-strand conformation polymorphism (F-PCR-SSCP) assay for the identification of Fasciola spp.

PubMed

Alasaad, Samer; Soriguer, Ramón C; Abu-Madi, Marawan; El Behairy, Ahmed; Baños, Pablo Díez; Píriz, Ana; Fickel, Joerns; Zhu, Xing-Quan

2011-06-01

The present study aimed to establish a fluorescence-based polymerase chain reaction-linked single-strand conformation polymorphism (F-PCR-SSCP) assay for the identification of Fasciola spp. Based on the sequences of the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA, we designed a set of genus-specific primers for the amplification of Fasciola ITS-2, with an estimated size of 140 bp. These primers were labelled by fluorescence dyes, and the PCR products were analyzed by capillary electrophoresis under non-denaturing conditions (F-PCR-SSCP). Capillary electrophoresis analysis of the fluorescence-labelled DNA fragments displayed three different peak profiles that allowed the accurate identification of Fasciola species: one single peak specific for either Fasciola hepatica or Fasciola gigantica and a doublet peak corresponding to the "intermediate" Fasciola. Validation of our novel method was performed using Fasciola specimens from different host animals from China, Spain, Nigeria, and Egypt. This F-PCR-SSCP assay provides a rapid, simple, and robust tool for the identification and differentiation between Fasciola spp.

Hoechst tagging: a modular strategy to design synthetic fluorescent probes for live-cell nucleus imaging.

PubMed

Nakamura, Akinobu; Takigawa, Kazumasa; Kurishita, Yasutaka; Kuwata, Keiko; Ishida, Manabu; Shimoda, Yasushi; Hamachi, Itaru; Tsukiji, Shinya

2014-06-11

We report a general strategy to create small-molecule fluorescent probes for the nucleus in living cells. Our strategy is based on the attachment of the DNA-binding Hoechst compound to a fluorophore of interest. Using this approach, simple fluorescein, BODIPY, and rhodamine dyes were readily converted to novel turn-on fluorescent nucleus-imaging probes.

Angular shaping of fluorescence from synthetic opal-based photonic crystal.

PubMed

Boiko, Vitalii; Dovbeshko, Galyna; Dolgov, Leonid; Kiisk, Valter; Sildos, Ilmo; Loot, Ardi; Gorelik, Vladimir

2015-01-01

Spectral, angular, and temporal distributions of fluorescence as well as specular reflection were investigated for silica-based artificial opals. Periodic arrangement of nanosized silica globules in the opal causes a specific dip in the defect-related fluorescence spectra and a peak in the reflectance spectrum. The spectral position of the dip coincides with the photonic stop band. The latter is dependent on the size of silica globules and the angle of observation. The spectral shape and intensity of defect-related fluorescence can be controlled by variation of detection angle. Fluorescence intensity increases up to two times at the edges of the spectral dip. Partial photobleaching of fluorescence was observed. Photonic origin of the observed effects is discussed.

Synthesis and characterization of citrate-based fluorescent small molecules and biodegradable polymers.

PubMed

Xie, Zhiwei; Kim, Jimin P; Cai, Qing; Zhang, Yi; Guo, Jinshan; Dhami, Ranjodh S; Li, Li; Kong, Bin; Su, Yixue; Schug, Kevin A; Yang, Jian

2017-03-01

Novel citric acid based photoluminescent dyes and biodegradable polymers are synthesized via a facile "one-pot" reaction. A comprehensive understanding of the fluorescence mechanisms of the resulting citric acid-based fluorophores is reported. Two distinct types of fluorophores are identified: a thiozolopyridine family with high quantum yield, long lifetime, and exceptional photostability, and a dioxopyridine family with relatively lower quantum yield, multiple lifetimes, and solvent-dependent band shifting behavior. Applications in molecular labeling and cell imaging were demonstrated. The above discoveries contribute to the field of fluorescence chemistry and have laid a solid foundation for further development of new fluorophores and materials that show promise in a diversity of fluorescence-based applications. Photoluminescent materials are pivotal for fluorescence based imaging, labeling and sensing applications. Understanding their fluorescence mechanism is challenging and imperative. We develop a new class of citric acid-derived fluorescent materials in forms of polymers and small molecular dyes by a one-step solvent free reaction. We discovered two different classes of citric acid-derived fluorophores. A two-ring thiozolopyridine structure demonstrates strong fluorescence and exceptional resistance to photo-bleaching. A one-ring dioxopyridine exhibits relative weak fluorescence but with intriguing excitation and solvent-dependent emission wavelength shifting. Our methodology of synthesizing citric acid-derived fluorophores and the understanding on their luminescence are instrumental to the design and production of a large number of new photoluminescent materials for biological and biomedical applications. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Statistical image segmentation for the detection of skin lesion borders in UV fluorescence excitation

NASA Astrophysics Data System (ADS)

Ortega-Martinez, Antonio; Padilla-Martinez, Juan Pablo; Franco, Walfre

2016-04-01

The skin contains several fluorescent molecules or fluorophores that serve as markers of structure, function and composition. UV fluorescence excitation photography is a simple and effective way to image specific intrinsic fluorophores, such as the one ascribed to tryptophan which emits at a wavelength of 345 nm upon excitation at 295 nm, and is a marker of cellular proliferation. Earlier, we built a clinical UV photography system to image cellular proliferation. In some samples, the naturally low intensity of the fluorescence can make it difficult to separate the fluorescence of cells in higher proliferation states from background fluorescence and other imaging artifacts -- like electronic noise. In this work, we describe a statistical image segmentation method to separate the fluorescence of interest. Statistical image segmentation is based on image averaging, background subtraction and pixel statistics. This method allows to better quantify the intensity and surface distributions of fluorescence, which in turn simplify the detection of borders. Using this method we delineated the borders of highly-proliferative skin conditions and diseases, in particular, allergic contact dermatitis, psoriatic lesions and basal cell carcinoma. Segmented images clearly define lesion borders. UV fluorescence excitation photography along with statistical image segmentation may serve as a quick and simple diagnostic tool for clinicians.

Fluorescence errors in integrating sphere measurements of remote phosphor type LED light sources

NASA Astrophysics Data System (ADS)

Keppens, A.; Zong, Y.; Podobedov, V. B.; Nadal, M. E.; Hanselaer, P.; Ohno, Y.

2011-05-01

The relative spectral radiant flux error caused by phosphor fluorescence during integrating sphere measurements is investigated both theoretically and experimentally. Integrating sphere and goniophotometer measurements are compared and used for model validation, while a case study provides additional clarification. Criteria for reducing fluorescence errors to a degree of negligibility as well as a fluorescence error correction method based on simple matrix algebra are presented. Only remote phosphor type LED light sources are studied because of their large phosphor surfaces and high application potential in general lighting.

High-Capacitance Hybrid Supercapacitor Based on Multi-Colored Fluorescent Carbon-Dots.

PubMed

Genc, Rukan; Alas, Melis Ozge; Harputlu, Ersan; Repp, Sergej; Kremer, Nora; Castellano, Mike; Colak, Suleyman Gokhan; Ocakoglu, Kasim; Erdem, Emre

2017-09-11

Multi-colored, water soluble fluorescent carbon nanodots (C-Dots) with quantum yield changing from 4.6 to 18.3% were synthesized in multi-gram using dated cola beverage through a simple thermal synthesis method and implemented as conductive and ion donating supercapacitor component. Various properties of C-Dots, including size, crystal structure, morphology and surface properties along with their Raman and electron paramagnetic resonance spectra were analyzed and compared by means of their fluorescence and electronic properties. α-Manganese Oxide-Polypyrrole (PPy) nanorods decorated with C-Dots were further conducted as anode materials in a supercapacitor. Reduced graphene oxide was used as cathode along with the dicationic bis-imidazolium based ionic liquid in order to enhance the charge transfer and wetting capacity of electrode surfaces. For this purpose, we used octyl-bis(3-methylimidazolium)diiodide (C8H16BImI) synthesized by N-alkylation reaction as liquid ionic membrane electrolyte. Paramagnetic resonance and impedance spectroscopy have been undertaken in order to understand the origin of the performance of hybrid capacitor in more depth. In particular, we obtained high capacitance value (C = 17.3 μF/cm 2 ) which is exceptionally related not only the quality of synthesis but also the choice of electrode and electrolyte materials. Moreover, each component used in the construction of the hybrid supercapacitor is also played a key role to achieve high capacitance value.

A simple chip free-flow electrophoresis for monosaccharide sensing via supermolecule interaction of boronic acid functionalized quencher and fluorescent dye.

PubMed

Yin, Xiao-Yang; Dong, Jing-Yu; Wang, Hou-Yu; Li, Si; Fan, Liu-Yin; Cao, Cheng-Xi

2013-08-01

Here, a simple micro free-flow electrophoresis (μFFE) was developed for fluorescence sensing of monosaccharide via supermolecule interaction of synthesized boronic acid functionalized benzyl viologen (ο-BBV) and fluorescent dye. The μFFE contained two open electrode cavities and an ion-exchange membrane was sandwiched between two polymethylmethacrylate plates. The experiments demonstrated the following merits of developed μFFE: (i) up to 90.5% of voltage efficiency due to high conductivity of ion-exchange membrane; (ii) a strong ability against influence of bubble produced in two electrodes due to open design of electrode cavities; and (iii) reusable and washable separation chamber (45 mm × 17 mm × 100 μm, 77 μL) avoiding the discard of μFFE due to blockage of solute precipitation in chamber. Remarkably, the μFFE was first designed for the sensing of monosaccharide via the supermolecule interaction of synthesized ο-BBV, fluorescent dye, and monosaccharide. Under the optimized conditions, the minimum concentration of monosaccharide that could be detected was 1 × 10(-11) M. Finally, the developed device was used for the detection of 0.3 mM glucose spiked in human urine. All of the results demonstrated the feasibility of monosaccharide detection via the μFFE. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A NBD-based simple but effective fluorescent pH probe for imaging of lysosomes in living cells.

PubMed

Cao, Xiang-Jian; Chen, Li-Na; Zhang, Xuan; Liu, Jin-Ting; Chen, Ming-Yu; Wu, Qiu-Rong; Miao, Jun-Ying; Zhao, Bao-Xiang

2016-05-12

NBDlyso with lysosome-locating morpholine moiety has been developed as a high selective and sensitive fluorescent pH probe. This probe can respond to acidic pH (2.0-7.0) in a short time (less than 1 min) and not almost change after continuously illuminated for an extended period by ultraviolet light. The fluorescence intensity of NBDlyso enhanced 100-fold in acidic solution, with very good linear relationship (R(2) = 0.996). The pKa of probe NBDlyso is 4.10. Therefore, NBDlyso was used to detect lysosomal pH changes successfully. Besides, X-ray crystallography was used to verify the structure of NBDlyso, and the recognition mechanism involving photo-induced electron transfer was interpreted theoretically by means of DFT and TDDFT calculations skillfully when NBDlyso comes into play under the acidic condition. This probe showed good ability to sense pH change in living cell image. Copyright © 2016 Elsevier B.V. All rights reserved.

Antibody-mediated fluorescence enhancement based on shifting the intramolecular dimer<-->monomer equilibrium of fluorescent dyes.

PubMed

Wei, A P; Blumenthal, D K; Herron, J N

1994-05-01

A novel concept is described for directly coupling fluorescence emission to protein-ligand binding. It is based on shifting the intramolecular monomer<-->dimer equilibrium of two fluorescent dyes linked by a short spacer. A 13-residue peptide, recognized by a monoclonal antibody against human chorionic gonadotrophin (hCG), was labeled with fluorescein (F) and tetramethylrhodamine (T) at its N- and C-terminus, respectively. Spectral evidence suggests that when the conjugate is free in solution, F and T exist as an intramolecular dimer. Fluorescence quenching of fluorescein and rhodamine is approximately 98% and approximately 90%, respectively, due to dimerization. When the double-labeled peptide is bound to anti-hCG, however, the rhodamine fluorescence increases by up to 7.8-fold, depending upon the excitation wavelength. This is attributed to the dissociation of intramolecular dimers brought about by conformational changes of the conjugate upon binding. Fluorescein fluorescence, on the other hand, was still quenched because of excited-state energy transfer and residual ground-state interactions. Antibody binding also resulted in a approximately 3.4-fold increase in fluorescence anisotropy of the peptide. These changes in intensity and anisotropy allow direct measurement of antigen-antibody binding with a fluorescence plate reader or a polarization analyzer, without the need for separation steps and labeling antibodies. Because recent advances in peptide technology have allowed rapid and economical identification of antigen-mimicking peptides, the double-labeled peptide approach offers many opportunities for developing new diagnostic assays and screening new therapeutic drugs. It also has many potential applications to techniques involving recombinant antibodies, biosensors, cell sorting, and DNA probes.

Simple fluorescence-based detection of protein kinase A activity using a molecular beacon probe.

PubMed

Ma, Changbei; Lv, Xiaoyuan; Wang, Kemin; Jin, Shunxin; Liu, Haisheng; Wu, Kefeng; Zeng, Weimin

2017-11-02

Protein kinase A was detected by quantifying the amount of ATP used after a protein kinase reaction. The ATP assay was performed using the T4 DNA ligase and a molecular beacon (MB). In the presence of ATP, DNA ligase catalyzed the ligation of short DNA. The ligation product then hybridized to MB, resulting in a fluorescence enhancement of the MB. This assay was capable of determining protein kinase A in the range of 12.5∼150 nM, with a detection limit of 1.25 nM. Furthermore, this assay could also be used to investigate the effect of genistein on protein kinase A. It was a universal, non-radioisotopic, and homogeneous method for assaying protein kinase A.

Mechanical Damage Detection of Indonesia Local Citrus Based on Fluorescence Imaging

NASA Astrophysics Data System (ADS)

Siregar, T. H.; Ahmad, U.; Sutrisno; Maddu, A.

2018-05-01

Citrus experienced physical damage in peel will produce essential oils that contain polymethoxylated flavone. Polymethoxylated flavone is fluorescence substance; thus can be detected by fluorescence imaging. This study aims to study the fluorescence spectra characteristic and to determine the damage region in citrus peel based on fluorescence image. Pulung citrus from Batu district, East Java, as a famous citrus production area in Indonesia, was used in the experiment. It was observed that the image processing could detect the mechanical damage region. Fluorescence imaging can be used to classify the citrus into two categories, sound and defect citruses.

A simple quinolone Schiff-base containing CHEF based fluorescence 'turn-on' chemosensor for distinguishing Zn2+ and Hg2+ with high sensitivity, selectivity and reversibility.

PubMed

Dong, Yuwei; Fan, Ruiqing; Chen, Wei; Wang, Ping; Yang, Yulin

2017-05-23

A new simple 'dual' chemosensor MQA ((E)-2-methoxy-N-((quinolin-2-yl)methylene)aniline) for distinguishing Zn 2+ and Hg 2+ has been designed, synthesized and characterized. The sensor showed excellent selectivity and sensitivity with a fluorescence enhancement to Zn 2+ /Hg 2+ over other commonly coexisting cations (such as Na + , Mg 2+ , Al 3+ , K + , Mn 2+ , Fe 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Ga 3+ , Cd 2+ , In 3+ and Pb 2+ ) in DMSO-H 2 O solution (1/99 v/v), which was reversible with the addition of ethylenediaminetetraacetic acid (EDTA). The detection limit for Zn 2+ /Hg 2+ by MQA both reached the 10 -8 M level. The 1 : 1 ligand-to-metal coordination patterns of the MQA-Zn2+ and MQA-Hg2+ were calculated through a Job's plot and ESI-MS spectra, and were further confirmed by X-ray crystal structures of complexes MQA-Zn2+ and MQA-Hg2+. This chemosensor can recognize similar metal ions by coherently utilizing intramolecular charge transfer (ICT) and different electronic affinities of various metal ions. DFT calculations have revealed that the energy gap between the HOMO and LUMO of MQA has decreased upon coordination with Zn(ii)/Hg(ii).

Free-radical sensing by using naphthalimide based mesoporous silica (MCM-41) nanoparticles: A combined fluorescence and cellular imaging study

NASA Astrophysics Data System (ADS)

Jha, Gaurav; Roy, Subhasis; Sahu, Prabhat Kumar; Banerjee, Somnath; Anoop, N.; Rahaman, Abdur; Sarkar, Moloy

2018-01-01

Keeping in mind the advantages of material-based systems over simple molecule-based systems, we have designed and developed three inorganic-organic hybrid systems by anchoring 1,8-naphthalimide derivatives to mesoporous silica nanoparticles for detection of free radicals. Prior to photophysical study, systems are characterized by spectroscopic, microscopic and thermo-gravimetric techniques. Steady state and time-resolved fluorescence studies demonstrate that the hydrazine based system is senstive towards detection of various free radicals. Cellular imaging study reveals cell permeability and toxicity study demonstrates the non-toxic nature of the material. These studies have suggested that present system has the potential to be used in various biological applications.

Genetic diversity analysis of sugarcane germplasm based on fluorescence-labeled simple sequence repeat markers and a capillary electrophoresis-based genotyping platform

USDA-ARS?s Scientific Manuscript database

Genetic diversity analysis, which refers to the elaboration of total extent of genetic characteristics in the genetic makeup of a certain species, constitutes a classical strategy for the study of diversity, population genetic structure, and breeding practices. In this study, fluorescence-labeled se...

Tomato seeds maturity detection system based on chlorophyll fluorescence

NASA Astrophysics Data System (ADS)

Li, Cuiling; Wang, Xiu; Meng, Zhijun

2016-10-01

Chlorophyll fluorescence intensity can be used as seed maturity and quality evaluation indicator. Chlorophyll fluorescence intensity of seed coats is tested to judge the level of chlorophyll content in seeds, and further to judge the maturity and quality of seeds. This research developed a detection system of tomato seeds maturity based on chlorophyll fluorescence spectrum technology, the system included an excitation light source unit, a fluorescent signal acquisition unit and a data processing unit. The excitation light source unit consisted of two high power LEDs, two radiators and two constant current power supplies, and it was designed to excite chlorophyll fluorescence of tomato seeds. The fluorescent signal acquisition unit was made up of a fluorescence spectrometer, an optical fiber, an optical fiber scaffolds and a narrowband filter. The data processing unit mainly included a computer. Tomato fruits of green ripe stage, discoloration stage, firm ripe stage and full ripe stage were harvested, and their seeds were collected directly. In this research, the developed tomato seeds maturity testing system was used to collect fluorescence spectrums of tomato seeds of different maturities. Principal component analysis (PCA) method was utilized to reduce the dimension of spectral data and extract principal components, and PCA was combined with linear discriminant analysis (LDA) to establish discriminant model of tomato seeds maturity, the discriminant accuracy was greater than 90%. Research results show that using chlorophyll fluorescence spectrum technology is feasible for seeds maturity detection, and the developed tomato seeds maturity testing system has high detection accuracy.

Organic Dots Based on AIEgens for Two-Photon Fluorescence Bioimaging.

PubMed

Lou, Xiaoding; Zhao, Zujin; Tang, Ben Zhong

2016-12-01

Two-photon fluorescence imaging technique is a powerful bioanalytical approach in terms of high photostability, low photodamage, high spatiotemporal resolution. Recently, fluorescent organic dots comprised of organic emissive cores and a polymeric matrix are emerging as promising contrast reagents for two-photon fluorescence imaging, owing to their numerous merits of high and tunable fluorescence, good biocompatibility, strong photobleaching resistance, and multiple surface functionality. The emissive core is crucial for organic dots to get high brightness but many conventional chromophores often encounter a severe problem of fluorescence quenching when they form aggregates. To solve this problem, fluorogens featuring aggregation-induced emission (AIE) can fluoresce strongly in aggregates, and thus become ideal candidates for fluorescent organic dots. In addition, two-photon absorption property of the dots can be readily improved by just increase loading contents of AIE fluorogen (AIEgen). Hence, organic dots based on AIEgens have exhibited excellent performances in two-photon fluorescence in vitro cellular imaging, and in vivo vascular architecture visualization of mouse skin, muscle, brain and skull bone. In view of the rapid advances in this important research field, here, we highlight representative fluorescent organic dots with an emissive core of AIEgen aggregate, and discuss their great potential in bioimaging applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Iterative Correction Scheme Based on Discrete Cosine Transform and L1 Regularization for Fluorescence Molecular Tomography With Background Fluorescence.

PubMed

Zhang, Jiulou; Shi, Junwei; Guang, Huizhi; Zuo, Simin; Liu, Fei; Bai, Jing; Luo, Jianwen

2016-06-01

High-intensity background fluorescence is generally encountered in fluorescence molecular tomography (FMT), because of the accumulation of fluorescent probes in nontarget tissues or the existence of autofluorescence in biological tissues. The reconstruction results are affected or even distorted by the background fluorescence, especially when the distribution of fluorescent targets is relatively sparse. The purpose of this paper is to reduce the negative effect of background fluorescence on FMT reconstruction. After each iteration of the Tikhonov regularization algorithm, 3-D discrete cosine transform is adopted to filter the intermediate results. And then, a sparsity constraint step based on L1 regularization is applied to restrain the energy of the objective function. Phantom experiments with different fluorescence intensities of homogeneous and heterogeneous background are carried out to validate the performance of the proposed scheme. The results show that the reconstruction quality can be improved with the proposed iterative correction scheme. The influence of background fluorescence in FMT can be reduced effectively because of the filtering of the intermediate results, the detail preservation, and noise suppression of L1 regularization.

Example-Based Super-Resolution Fluorescence Microscopy.

PubMed

Jia, Shu; Han, Boran; Kutz, J Nathan

2018-04-23

Capturing biological dynamics with high spatiotemporal resolution demands the advancement in imaging technologies. Super-resolution fluorescence microscopy offers spatial resolution surpassing the diffraction limit to resolve near-molecular-level details. While various strategies have been reported to improve the temporal resolution of super-resolution imaging, all super-resolution techniques are still fundamentally limited by the trade-off associated with the longer image acquisition time that is needed to achieve higher spatial information. Here, we demonstrated an example-based, computational method that aims to obtain super-resolution images using conventional imaging without increasing the imaging time. With a low-resolution image input, the method provides an estimate of its super-resolution image based on an example database that contains super- and low-resolution image pairs of biological structures of interest. The computational imaging of cellular microtubules agrees approximately with the experimental super-resolution STORM results. This new approach may offer potential improvements in temporal resolution for experimental super-resolution fluorescence microscopy and provide a new path for large-data aided biomedical imaging.

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.

[Development of a near-infrared fluorescence imaging system based on fluorescence properties of methylene blue].

PubMed

Huang, Lu-Mao; DU, Pei-Yan; Chen, Lan; Zhang, Sa; Zhou, Di-Fu; Chen, Chun-Lin; Xin, Xue-Gang

2018-04-20

To develop a near-infrared fluorescence imaging system based on the fluorescence properties of methylene blue. According to the optical properties of methylene blue, we used a custom-made specific LED light source and an interference filter, a CCD camera and other relevant components to construct the near-infrared fluorescence imaging system. We tested the signal-to-background ratio (SBR) of this imaging system for detecting methylene blue under different experimental conditions and analyzed the SBR in urine samples collected from 15 Wistar rats with intravenous injection of methylene blue at the doses of 0, 1.4, 1.6, 1.8, or 2.0 0 mg/kg methylene blue. The SBR of this imaging system for detecting methylene blue was affected by the concentration of methylene blue and the distance from the sample (P<0.05). In the urine samples from Wistar rats, the SBR varied with the the injection dose, and the rats injected with 1.6 mg/kg methylene blue showed the highest SBR (8.71∓0.20) in the urine (P<0.05). This near-infrared fluorescence imaging system is useful for fluorescence detection of methylene blue and can be used for real-time recognition of ureters during abdominal surgery.

Optical fiber-based fluorescent viscosity sensor

NASA Astrophysics Data System (ADS)

Haidekker, Mark A.; Akers, Walter J.; Fischer, Derek; Theodorakis, Emmanuel A.

2006-09-01

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Optical fiber-based fluorescent viscosity sensor.

PubMed

Haidekker, Mark A; Akers, Walter J; Fischer, Derek; Theodorakis, Emmanuel A

2006-09-01

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Fluorescence tomography characterization for sub-surface imaging with protoporphyrin IX

PubMed Central

Kepshire, Dax; Davis, Scott C.; Dehghani, Hamid; Paulsen, Keith D.; Pogue, Brian W.

2009-01-01

Optical imaging of fluorescent objects embedded in a tissue simulating medium was characterized using non-contact based approaches to fluorescence remittance imaging (FRI) and sub-surface fluorescence diffuse optical tomography (FDOT). Using Protoporphyrin IX as a fluorescent agent, experiments were performed on tissue phantoms comprised of typical in-vivo tumor to normal tissue contrast ratios, ranging from 3.5:1 up to 10:1. It was found that tomographic imaging was able to recover interior inclusions with high contrast relative to the background; however, simple planar fluorescence imaging provided a superior contrast to noise ratio. Overall, FRI performed optimally when the object was located on or close to the surface and, perhaps most importantly, FDOT was able to recover specific depth information about the location of embedded regions. The results indicate that an optimal system for localizing embedded fluorescent regions should combine fluorescence reflectance imaging for high sensitivity and sub-surface tomography for depth detection, thereby allowing more accurate localization in all three directions within the tissue. PMID:18545571

MATtrack: A MATLAB-Based Quantitative Image Analysis Platform for Investigating Real-Time Photo-Converted Fluorescent Signals in Live Cells

PubMed Central

Courtney, Jane; Woods, Elena; Scholz, Dimitri; Hall, William W.; Gautier, Virginie W.

2015-01-01

We introduce here MATtrack, an open source MATLAB-based computational platform developed to process multi-Tiff files produced by a photo-conversion time lapse protocol for live cell fluorescent microscopy. MATtrack automatically performs a series of steps required for image processing, including extraction and import of numerical values from Multi-Tiff files, red/green image classification using gating parameters, noise filtering, background extraction, contrast stretching and temporal smoothing. MATtrack also integrates a series of algorithms for quantitative image analysis enabling the construction of mean and standard deviation images, clustering and classification of subcellular regions and injection point approximation. In addition, MATtrack features a simple user interface, which enables monitoring of Fluorescent Signal Intensity in multiple Regions of Interest, over time. The latter encapsulates a region growing method to automatically delineate the contours of Regions of Interest selected by the user, and performs background and regional Average Fluorescence Tracking, and automatic plotting. Finally, MATtrack computes convenient visualization and exploration tools including a migration map, which provides an overview of the protein intracellular trajectories and accumulation areas. In conclusion, MATtrack is an open source MATLAB-based software package tailored to facilitate the analysis and visualization of large data files derived from real-time live cell fluorescent microscopy using photoconvertible proteins. It is flexible, user friendly, compatible with Windows, Mac, and Linux, and a wide range of data acquisition software. MATtrack is freely available for download at eleceng.dit.ie/courtney/MATtrack.zip. PMID:26485569

MATtrack: A MATLAB-Based Quantitative Image Analysis Platform for Investigating Real-Time Photo-Converted Fluorescent Signals in Live Cells.

PubMed

Courtney, Jane; Woods, Elena; Scholz, Dimitri; Hall, William W; Gautier, Virginie W

2015-01-01

We introduce here MATtrack, an open source MATLAB-based computational platform developed to process multi-Tiff files produced by a photo-conversion time lapse protocol for live cell fluorescent microscopy. MATtrack automatically performs a series of steps required for image processing, including extraction and import of numerical values from Multi-Tiff files, red/green image classification using gating parameters, noise filtering, background extraction, contrast stretching and temporal smoothing. MATtrack also integrates a series of algorithms for quantitative image analysis enabling the construction of mean and standard deviation images, clustering and classification of subcellular regions and injection point approximation. In addition, MATtrack features a simple user interface, which enables monitoring of Fluorescent Signal Intensity in multiple Regions of Interest, over time. The latter encapsulates a region growing method to automatically delineate the contours of Regions of Interest selected by the user, and performs background and regional Average Fluorescence Tracking, and automatic plotting. Finally, MATtrack computes convenient visualization and exploration tools including a migration map, which provides an overview of the protein intracellular trajectories and accumulation areas. In conclusion, MATtrack is an open source MATLAB-based software package tailored to facilitate the analysis and visualization of large data files derived from real-time live cell fluorescent microscopy using photoconvertible proteins. It is flexible, user friendly, compatible with Windows, Mac, and Linux, and a wide range of data acquisition software. MATtrack is freely available for download at eleceng.dit.ie/courtney/MATtrack.zip.

Facile synthesis of a two-photon fluorescent probe based on pyrimidine 2-isothiocyanate and its application in bioimaging.

PubMed

Yang, Jie; Hu, Wei; Li, Huirong; Hou, Hanna; Tu, Yi; Liu, Bo

2018-04-18

Two-photon microscopy imaging has been widely applied in biological imaging, but the development of two-photon absorption probes is obviously lagging behind in the development of imaging technology. In this paper, a two-photon fluorescent probe (1) based on pyrimidine 2-isothiocyanate has been designed and synthesized through a simple method for two-photon biological imaging. Probe 1 was able to couple effectively with the amino groups on biomolecules. To verify the reactivity of the isothiocyanate group on probe 1 and the amine groups on the biomolecules, d-glucosamine was chosen as a model biomolecule to conjugate with probe 1. The result showed that probe 1 could effectively conjugate with d-glucosamine to synthesize probe 2, and the yield of probe 2 was 83%. After conjugating with d-glucosamine, linear absorption spectra, single-photon fluorescence spectra, and two-photon fluorescence spectra of probes 1 and 2 did not present significant changes. Probes 1 and 2 exhibited high fluorescence quantum yields (0.71-0.79) in toluene and chloroform. They also exhibited different photo-physical properties in solvents with different polarities. The two-photon absorption cross-section of probe 1 was 953 GM in toluene. In addition, probe 1 could be effectively conjugated with transferrin, and the conjugated probe (Tf-1) could be transported into Hep G2 cells through a receptor-mediated process for biological imaging. These results demonstrate that such probes are expected to have great potential applications in two-photon fluorescence bioimaging.

Chemical biology-based approaches on fluorescent labeling of proteins in live cells.

PubMed

Jung, Deokho; Min, Kyoungmi; Jung, Juyeon; Jang, Wonhee; Kwon, Youngeun

2013-05-01

Recently, significant advances have been made in live cell imaging owing to the rapid development of selective labeling of proteins in vivo. Green fluorescent protein (GFP) was the first example of fluorescent reporters genetically introduced to protein of interest (POI). While GFP and various types of engineered fluorescent proteins (FPs) have been actively used for live cell imaging for many years, the size and the limited windows of fluorescent spectra of GFP and its variants set limits on possible applications. In order to complement FP-based labeling methods, alternative approaches that allow incorporation of synthetic fluorescent probes to target POIs were developed. Synthetic fluorescent probes are smaller than fluorescent proteins, often have improved photochemical properties, and offer a larger variety of colors. These synthetic probes can be introduced to POIs selectively by numerous approaches that can be largely categorized into chemical recognition-based labeling, which utilizes metal-chelating peptide tags and fluorophore-carrying metal complexes, and biological recognition-based labeling, such as (1) specific non-covalent binding between an enzyme tag and its fluorophore-carrying substrate, (2) self-modification of protein tags using substrate variants conjugated to fluorophores, (3) enzymatic reaction to generate a covalent binding between a small molecule substrate and a peptide tag, and (4) split-intein-based C-terminal labeling of target proteins. The chemical recognition-based labeling reaction often suffers from compromised selectivity of metal-ligand interaction in the cytosolic environment, consequently producing high background signals. Use of protein-substrate interactions or enzyme-mediated reactions generally shows improved specificity but each method has its limitations. Some examples are the presence of large linker protein, restriction on the choice of introducible probes due to the substrate specificity of enzymes, and competitive

Advances in Spiropyrans/Spirooxazines and Applications Based on Fluorescence Resonance Energy Transfer (FRET) with Fluorescent Materials.

PubMed

Xia, Hongyan; Xie, Kang; Zou, Gang

2017-12-18

Studies on the following were reviewed: (1) the structure of spiropyrans and spirooxazines (two kinds of spiro compounds) under external stimuli and (2) the construction and applications of composite systems based on fluorescence resonance energy transfer (FRET) with fluorescent materials. When treated with different stimuli (light, acids and bases, solvents, metal ions, temperature, redox potential, and so on), spiropyrans/spirooxazines undergo transformations between the ring-closed form (SP), the ring-opened merocyanine (MC) form, and the protonated ring-opened form (MCH). This is due to the breakage of the spiro C-O bond and the protonation of MC, along with a color change. Various novel, multifunctional materials based on photochromic spiropyrans and spirooxazines have been successfully developed because of the vastly differently physiochemical properties posssed by the SP, MC and MCH forms. Among the three different structural forms, the MC form has been studied most extensively. The MC form not only gives complexes with various inorganic particles, biological molecules, and organic chemicals but also acts as the energy acceptor (of energy from fluorescent molecules) during energy transfer processes that take place under proper conditions. Furthermore, spiropyran and spirooxazine compounds exhibit reversible physicochemical property changes under proper stimuli; this provides more advantages compared with other photochromic compounds. Additionally, the molecular structures of spiropyrans and spirooxazines can be easily modified and extended, so better compounds can be obtained to expand the scope of already known applications. Described in detail are: (1) the structural properties of spiropyrans and spirooxazines and related photochromic mechanisms; (2) composite systems based on spiropyrans and spirooxazines, and (3) fluorescent materials which have potential applications in sensing, probing, and a variety of optical elements.

Fluorescence intensity- and lifetime-based glucose sensing using glucose/galactose-binding protein.

PubMed

Pickup, John C; Khan, Faaizah; Zhi, Zheng-Liang; Coulter, Jonathan; Birch, David J S

2013-01-01

We review progress in our laboratories toward developing in vivo glucose sensors for diabetes that are based on fluorescence labeling of glucose/galactose-binding protein. Measurement strategies have included both monitoring glucose-induced changes in fluorescence resonance energy transfer and labeling with the environmentally sensitive fluorophore, badan. Measuring fluorescence lifetime rather than intensity has particular potential advantages for in vivo sensing. A prototype fiber-optic-based glucose sensor using this technology is being tested. © 2013 Diabetes Technology Society.

Application of normal fluorescence and stability-indicating derivative synchronous fluorescence spectroscopy for the determination of gliquidone in presence of its fluorescent alkaline degradation product

NASA Astrophysics Data System (ADS)

El-ghobashy, Mohamed R.; Yehia, Ali M.; Helmy, Aya H.; Youssef, Nadia F.

2018-01-01

Simple, smart and sensitive normal fluorescence and stability-indicating derivative synchronous spectrofluorimetric methods have been developed and validated for the determination of gliquidone in the drug substance and drug product. Normal spectrofluorimetric method of gliquidone was established in methanol at λ excitation 225 nm and λ emission 400 nm in concentration range 0.2-3 μg/ml with LOD equal 0.028. The fluorescence quantum yield of gliquidone was calculated using quinine sulfate as a reference and found to be 0.542. Stability-indicating first and third derivative synchronous fluorescence spectroscopy were successfully utilized to overcome the overlapped spectra in normal fluorescence of gliquidone and its alkaline degradation product. Derivative synchronous methods are based on using the synchronous fluorescence of gliquidone and its degradation product in methanol at Δ λ50 nm. Peak amplitude in the first derivative of synchronous fluorescence spectra was measured at 309 nm where degradation product showed zero-crossing without interference. The peak amplitudes in the third derivative of synchronous fluorescence spectra, peak to trough were measured at 316,329 nm where degradation product showed zero-crossing. The different experimental parameters affecting the normal and synchronous fluorescence intensity of gliquidone were studied and optimized. Moreover, the cited methods have been validated as per ICH guidelines. The peak amplitude-concentration plots of the derivative synchronous fluorescence were linear over the concentration range 0.05-2 μg/ml for gliquidone. Limits of detection were 0.020 and 0.022 in first and third derivative synchronous spectra, respectively. The adopted methods were successfully applied to commercial tablets and the results demonstrated that the derivative synchronous fluorescence spectroscopy is a powerful stability-indicating method, suitable for routine use with a short analysis time. Statistical comparison between

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.

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.

Colorful protein-based fluorescent probes for collagen imaging.

PubMed

Aper, Stijn J A; van Spreeuwel, Ariane C C; van Turnhout, Mark C; van der Linden, Ardjan J; Pieters, Pascal A; van der Zon, Nick L L; de la Rambelje, Sander L; Bouten, Carlijn V C; Merkx, Maarten

2014-01-01

Real-time visualization of collagen is important in studies on tissue formation and remodeling in the research fields of developmental biology and tissue engineering. Our group has previously reported on a fluorescent probe for the specific imaging of collagen in live tissue in situ, consisting of the native collagen binding protein CNA35 labeled with fluorescent dye Oregon Green 488 (CNA35-OG488). The CNA35-OG488 probe has become widely used for collagen imaging. To allow for the use of CNA35-based probes in a broader range of applications, we here present a toolbox of six genetically-encoded collagen probes which are fusions of CNA35 to fluorescent proteins that span the visible spectrum: mTurquoise2, EGFP, mAmetrine, LSSmOrange, tdTomato and mCherry. While CNA35-OG488 requires a chemical conjugation step for labeling with the fluorescent dye, these protein-based probes can be easily produced in high yields by expression in E. coli and purified in one step using Ni2+-affinity chromatography. The probes all bind specifically to collagen, both in vitro and in porcine pericardial tissue. Some first applications of the probes are shown in multicolor imaging of engineered tissue and two-photon imaging of collagen in human skin. The fully-genetic encoding of the new probes makes them easily accessible to all scientists interested in collagen formation and remodeling.

Linear Schiff-base fluorescence probe with aggregation-induced emission characteristics for Al3+ detection and its application in live cell imaging.

PubMed

Wen, Xiaoye; Fan, Zhefeng

2016-11-16

A simple Schiff-base derivative with salicylaldehyde moieties as fluorescent probe 1 was reported by aggregation-induced emission (AIE) characterization for the detection of metal ions. Spectral analysis revealed that probe 1 was highly selective and sensitive to Al 3+ . The probe 1 was also subject to minimal interference from other common competitive metal ions. The detection limit of Al 3+ was 0.4 μM, which is considerably lower than the World Health Organization standard (7.41 μM), and the acceptable level of Al 3+ (1.85 μM) in drinking water. The Job's plot and the results of 1 H-NMR and FT-IR analyses indicated that the binding stoichiometry ratio of probe 1 to Al 3+ was 1:2. Probe 1 demonstrated a fluorescence-enhanced response upon binding with Al 3+ based on AIE characterization. This response was due to the restricted molecular rotation and increased rigidity of the molecular assembly. Probe 1 exhibited good biocompatibility, and Al 3+ was detected in live cells. Therefore, probe 1 is a promising fluorescence probe for Al 3+ detection in the environment. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Fluorescence detection of dental calculus

NASA Astrophysics Data System (ADS)

Gonchukov, S.; Biryukova, T.; Sukhinina, A.; Vdovin, Yu

2010-11-01

This work is devoted to the optimization of fluorescence dental calculus diagnostics in optical spectrum. The optimal wavelengths for fluorescence excitation and registration are determined. Two spectral ranges 620 - 645 nm and 340 - 370 nm are the most convenient for supra- and subgingival calculus determination. The simple implementation of differential method free from the necessity of spectrometer using was investigated. Calculus detection reliability in the case of simple implementation is higher than in the case of spectra analysis at optimal wavelengths. The use of modulated excitation light and narrowband detection of informative signal allows us to decrease essentially its diagnostic intensity even in comparison with intensity of the low level laser dental therapy.

Acoustically levitated droplets: a contactless sampling method for fluorescence studies.

PubMed

Leiterer, Jork; Grabolle, Markus; Rurack, Knut; Resch-Genger, Ute; Ziegler, Jan; Nann, Thomas; Panne, Ulrich

2008-01-01

Acoustic levitation is used as a new tool to study concentration-dependent processes in fluorescence spectroscopy. With this technique, small amounts of liquid and solid samples can be measured without the need for sample supports or containers, which often limits signal acquisition and can even alter sample properties due to interactions with the support material. We demonstrate that, because of the small sample volume, fluorescence measurements at high concentrations of an organic dye are possible without the limitation of inner-filter effects, which hamper such experiments in conventional, cuvette-based measurements. Furthermore, we show that acoustic levitation of liquid samples provides an experimentally simple way to study distance-dependent fluorescence modulations in semiconductor nanocrystals. The evaporation of the solvent during levitation leads to a continuous increase of solute concentration and can easily be monitored by laser-induced fluorescence.

Photon upconversion in homogeneous fluorescence-based bioanalytical assays.

PubMed

Soukka, Tero; Rantanen, Terhi; Kuningas, Katri

2008-01-01

Upconverting phosphors (UCPs) are very attractive reporters for fluorescence resonance energy transfer (FRET)-based bioanalytical assays. The large anti-Stokes shift and capability to convert near-infrared to visible light via sequential absorption of multiple photons enable complete elimination of autofluorescence, which commonly impairs the performance of fluorescence-based assays. UCPs are ideal donors for FRET, because their very narrow-banded emission allows measurement of the sensitized acceptor emission, in principle, without any crosstalk from the donor emission at a wavelength just tens of nanometers from the emission peak of the donor. In addition, acceptor dyes emitting at visible wavelengths are essentially not excited by near-infrared, which further emphasizes the unique potential of upconversion FRET (UC-FRET). These characteristics result in favorable assay performance using detection instrumentation based on epifluorometer configuration and laser diode excitation. Although UC-FRET is a recently emerged technology, it has already been applied in both immunoassays and nucleic acid hybridization assays. The technology is also compatible with optically difficult biological samples, such as whole blood. Significant advances in assay performance are expected using upconverting lanthanide-doped nanocrystals, which are currently under extensive research. UC-FRET, similarly to other fluorescence techniques based on resonance energy transfer, is strongly distance dependent and may have limited applicability, for example in sandwich-type assays for large biomolecules, such as viruses. In this article, we summarize the essentials of UC-FRET, describe its current applications, and outline the expectations for its future potential.

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.

Magneto-Fluorescent Core-Shell Supernanoparticles

PubMed Central

Chen, Ou; Riedemann, Lars; Etoc, Fred; Herrmann, Hendrik; Coppey, Mathieu; Barch, Mariya; Farrar, Christian T.; Zhao, Jing; Bruns, Oliver T.; Wei, He; Guo, Peng; Cui, Jian; Jensen, Russ; Chen, Yue; Harris, Daniel K.; Cordero, Jose M.; Wang, Zhongwu; Jasanoff, Alan; Fukumura, Dai; Reimer, Rudolph; Dahan, Maxime; Jain, Rakesh K.; Bawendi, Moungi G.

2014-01-01

Magneto-fluorescent particles have been recognized as an emerging class of materials that exhibit great potential in advanced applications. However, synthesizing such magneto-fluorescent nanomaterials that simultaneously exhibit uniform and tunable sizes, high magnetic content loading, maximized fluorophore coverage at the surface, and a versatile surface functionality has proven challenging. Here we report a simple approach for co-assembling magnetic nanoparticles with fluorescent quantum dots to form colloidal magneto-fluorescent supernanoparticles. Importantly, these supernanoparticles exhibit a superstructure consisting of a close packed magnetic nanoparticle “core” which is fully surrounded by a “shell” of fluorescent quantum dots. A thin layer of silica-coating provides high colloidal stability and biocompatiblity and a versatile surface functionality. We demonstrate that after surface pegylation, these silica-coated magneto-fluorescent supernanoparticles can be magnetically manipulated inside living cells while being optically tracked. Moreover, our silica-coated magneto-fluorescent supernanoparticles can also serve as an in vivo multi-photon and magnetic resonance dual-modal imaging probe. PMID:25298155

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant.

PubMed

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-05-15

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant

NASA Astrophysics Data System (ADS)

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-05-01

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies.

Simple structured hybrid WOLEDs based on incomplete energy transfer mechanism: from blue exciplex to orange dopant

PubMed Central

Zhang, Tianyou; Zhao, Bo; Chu, Bei; Li, Wenlian; Su, Zisheng; Yan, Xingwu; Liu, Chengyuan; Wu, Hairuo; Gao, Yuan; Jin, Fangming; Hou, Fuhua

2015-01-01

Exciplex is well known as a charge transfer state formed between electron-donating and electron-accepting molecules. However, exciplex based organic light emitting diodes (OLED) often performed low efficiencies relative to pure phosphorescent OLED and could hardly be used to construct white OLED (WOLED). In this work, a new mechanism is developed to realize efficient WOLED with extremely simple structure by redistributing the energy of triplet exciplex to both singlet exciplex and the orange dopant. The micro process of energy transfer could be directly examined by detailed photoluminescence decay measurement and time resolved photoluminescence analysis. This strategy overcomes the low reverse intersystem crossing efficiency of blue exciplex and complicated device structure of traditional WOLED, enables us to achieve efficient hybrid WOLEDs. Based on this mechanism, we have successfully constructed both exciplex-fluorescence and exciplex-phosphorescence hybrid WOLEDs with remarkable efficiencies. PMID:25975371

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.

Efficient hybrid white organic light-emitting diodes for application of triplet harvesting with simple structure

NASA Astrophysics Data System (ADS)

Hwang, Kyo Min; Lee, Song Eun; Lee, Sungkyu; Yoo, Han Kyu; Baek, Hyun Jung; Kim, Young Kwan; Kim, Jwajin; Yoon, Seung Soo

2016-08-01

In this study, we fabricated hybrid white organic light-emitting diodes (WOLEDs) based on triplet harvesting with a simple structure. All the hole transporting material and host in the emitting layer (EML) of devices utilized the same material N,N'-di-1-naphthalenyl-N,N'-diphenyl [1,1':4',1″:4″,1‴-quaterphenyl]-4,4‴-diamine (4P-NPD), which is known to be blue fluorescent material. Simple hybrid WOLEDs were fabricated with blue fluorescent, green and red phosphorescent materials. We investigated the effect of triplet harvesting (TH) by an exciton generation zone on simple hybrid WOLEDs. The simple hybrid WOLEDs characteristically had a dominant hole mobility, so an exciton generation zone was expected in the EML. Additionally, the optimal the thickness of the hole transporting layer and electron transporting layer was fabricated a simple hybrid WOLEDs. The simple hybrid WOLED exhibits a maximum luminous efficiency of 29.3 cd/A and a maximum external quantum efficiency of 11.2%. The Commission Internationale de l'Éclairage (International Commission on Illumination) coordinates were (0.45, 0.43) at about 10,000 cd/m2.

Long wavelength fluorescence based biosensors for in vivo continuous monitoring of metabolites

NASA Astrophysics Data System (ADS)

Thomas, Joseph; Ambroise, Arounaguiry; Birchfield, Kara; Cai, Wensheng; Sandmann, Christian; Singh, Sarabjit; Weidemaier, Kristin; Pitner, J. Bruce

2006-02-01

The early stage development studies of novel implantable continuous metabolite sensor systems for glucose, lactate and fatty acids are discussed. These sensors utilize non-enzymatic "reagentless" sensor systems based on NIR fluorophore-labeled binding proteins. For in vivo applications, NIR fluorescence based systems (beyond 600 nm) have the added benefit of reduced interference from background scattering, tissue and serum absorption and cell auto-fluorescence. The long wavelength emission facilitates implanted sensor disks to transmit fluorescence to an external reader through wireless connections and the resulting fluorescence signals can be correlated to metabolite concentrations. We have developed a prototype optical system that uses a bifurcated optical fiber to transmit excitation and read emission at the surface of the skin. With this system, fluorescence signals were read over time through animal skin. The changes in glucose concentration were studied using immobilized sensor proteins and were compared to non-immobilized sensors in solution. For sensors in solution, no response delay was observed. For immobilized systems, the fluorescence response showed a delay corresponding to the diffusion time for the metabolite to equilibrate within the sensor.

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.

An efficient ratiometric fluorescence sensor based on metal-organic frameworks and quantum dots for highly selective detection of 6-mercaptopurine.

PubMed

Jin, Meng; Mou, Zhao-Li; Zhang, Rui-Ling; Liang, Si-Si; Zhang, Zhi-Qi

2017-05-15

The development of a simple and accurate quantitative method for the determination of 6-mercaptopurine (6-MP) is of great importance because of its serious side effects. Ratiometric fluorescence (RF) sensors are not subject to interference from environmental factors, and exhibit enhanced precision and accuracy. Therefore, a novel RF sensor for the selective detection of 6-MP was developed based on a dual-emission nanosensor. The nanosensor was fabricated by combining a blue-emission metal-organic framework (MOF) NH 2 -MIL-53(Al) (λ em =425nm) with green-emission 3-mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) (λ em =528nm) under a single excitation wavelength (335nm). Upon addition of 6-MP, the fluorescence of NH 2 -MIL-53(Al) in the nanohybrid was selectively quenched due to strong inner filter effects, while the fluorescence of the MPA-CdTe QDs was enhanced. The novel RF sensor exhibited higher selectivity towards 6-MP than CdTe QDs alone, and higher sensitivity than MOFs alone. 6-MP could be detected in the range of 0-50μM with a detection limit of 0.15μM (S/N=3). The developed sensor was applied for the determination of 6-MP in human urine samples and satisfactory results were obtained. Overall, a novel and efficient fluorescence-based method was developed for the detection of 6-MP in biosamples. Copyright © 2016 Elsevier B.V. All rights reserved.

Micro-hole array fluorescent sensor based on AC-Dielectrophoresis (DEP) for simultaneous analysis of nano-molecules

NASA Astrophysics Data System (ADS)

Kim, Hye Jin; Kang, Dong-Hoon; Lee, Eunji; Hwang, Kyo Seon; Shin, Hyun-Joon; Kim, Jinsik

2018-02-01

We propose a simple fluorescent bio-chip based on two types of alternative current-dielectrophoretic (AC-DEP) force, attractive (positive DEP) and repulsive (negative DEP) force, for simultaneous nano-molecules analysis. Various radius of micro-holes on the bio-chip are designed to apply the different AC-DEP forces, and the nano-molecules are concentrated inside the micro-hole arrays according to the intensity of the DEP force. The bio-chip was fabricated by Micro Electro Mechanical system (MEMS) technique, and was composed of two layers; a SiO2 layer and Ta/Pt layer were accomplished for an insulation layer and a top electrode with micro-hole arrays to apply electric fields for DEP force, respectively. Each SiO2 and Ta/Pt layers were deposited by thermal oxidation and sputtering, and micro-hole arrays were fabricated with Inductively Coupled Plasma (ICP) etching process. For generation of each positive and negative DEP at micro-holes, we applied two types of sine-wave AC voltage with different frequency range alternately. The intensity of the DEP force was controlled by the radius of the micro-hole and size of nano-molecule, and calculated with COMSOL multi-physics. Three types of nano-molecules labelled with different fluorescent dye were used and the intensity of nano-molecules was examined by the fluorescent optical analysis after applying the DEP force. By analyzing the fluorescent intensities of the nano-molecules, we verify the various nano-molecules in analyte are located successfully inside corresponding micro-holes with different radius according to their size.

Quantitative and qualitative 5-aminolevulinic acid–induced protoporphyrin IX fluorescence in skull base meningiomas

PubMed Central

Bekelis, Kimon; Valdés, Pablo A.; Erkmen, Kadir; Leblond, Frederic; Kim, Anthony; Wilson, Brian C.; Harris, Brent T.; Paulsen, Keith D.; Roberts, David W.

2011-01-01

Object Complete resection of skull base meningiomas provides patients with the best chance for a cure; however, surgery is frequently difficult given the proximity of lesions to vital structures, such as cranial nerves, major vessels, and venous sinuses. Accurate discrimination between tumor and normal tissue is crucial for optimal tumor resection. Qualitative assessment of protoporphyrin IX (PpIX) fluorescence following the exogenous administration of 5-aminolevulinic acid (ALA) has demonstrated utility in malignant glioma resection but limited use in meningiomas. Here the authors demonstrate the use of ALA-induced PpIX fluorescence guidance in resecting a skull base meningioma and elaborate on the advantages and disadvantages provided by both quantitative and qualitative fluorescence methodologies in skull base meningioma resection. Methods A 52-year-old patient with a sphenoid wing WHO Grade I meningioma underwent tumor resection as part of an institutional review board–approved prospective study of fluorescence-guided resection. A surgical microscope modified for fluorescence imaging was used for the qualitative assessment of visible fluorescence, and an intraoperative probe for in situ fluorescence detection was utilized for quantitative measurements of PpIX. The authors assessed the detection capabilities of both the qualitative and quantitative fluorescence approaches. Results The patient harboring a sphenoid wing meningioma with intraorbital extension underwent radical resection of the tumor with both visibly and nonvisibly fluorescent regions. The patient underwent a complete resection without any complications. Some areas of the tumor demonstrated visible fluorescence. The quantitative probe detected neoplastic tissue better than the qualitative modified surgical microscope. The intraoperative probe was particularly useful in areas that did not reveal visible fluorescence, and tissue from these areas was confirmed as tumor following histopathological

Bleaching/blinking assisted localization microscopy for superresolution imaging using standard fluorescent molecules.

PubMed

Burnette, Dylan T; Sengupta, Prabuddha; Dai, Yuhai; Lippincott-Schwartz, Jennifer; Kachar, Bechara

2011-12-27

Superresolution imaging techniques based on the precise localization of single molecules, such as photoactivated localization microscopy (PALM) and stochastic optical reconstruction microscopy (STORM), achieve high resolution by fitting images of single fluorescent molecules with a theoretical Gaussian to localize them with a precision on the order of tens of nanometers. PALM/STORM rely on photoactivated proteins or photoswitching dyes, respectively, which makes them technically challenging. We present a simple and practical way of producing point localization-based superresolution images that does not require photoactivatable or photoswitching probes. Called bleaching/blinking assisted localization microscopy (BaLM), the technique relies on the intrinsic bleaching and blinking behaviors characteristic of all commonly used fluorescent probes. To detect single fluorophores, we simply acquire a stream of fluorescence images. Fluorophore bleach or blink-off events are detected by subtracting from each image of the series the subsequent image. Similarly, blink-on events are detected by subtracting from each frame the previous one. After image subtractions, fluorescence emission signals from single fluorophores are identified and the localizations are determined by fitting the fluorescence intensity distribution with a theoretical Gaussian. We also show that BaLM works with a spectrum of fluorescent molecules in the same sample. Thus, BaLM extends single molecule-based superresolution localization to samples labeled with multiple conventional fluorescent probes.

Radiative decay engineering 5: metal-enhanced fluorescence and plasmon emission

PubMed Central

Lakowicz, Joseph R.

2009-01-01

Metallic particles and surfaces display diverse and complex optical properties. Examples include the intense colors of noble metal colloids, surface plasmon resonance absorption by thin metal films, and quenching of excited fluorophores near the metal surfaces. Recently, the interactions of fluorophores with metallic particles and surfaces (metals) have been used to obtain increased fluorescence intensities, to develop assays based on fluorescence quenching by gold colloids, and to obtain directional radiation from fluorophores near thin metal films. For metal-enhanced fluorescence it is difficult to predict whether a particular metal structure, such as a colloid, fractal, or continuous surface, will quench or enhance fluorescence. In the present report we suggest how the effects of metals on fluorescence can be explained using a simple concept, based on radiating plasmons (RPs). The underlying physics may be complex but the concept is simple to understand. According to the RP model, the emission or quenching of a fluorophore near the metal can be predicted from the optical properties of the metal structures as calculated from electrodynamics, Mie theory, and/or Maxwell’s equations. For example, according to Mie theory and the size and shape of the particle, the extinction of metal colloids can be due to either absorption or scattering. Incident energy is dissipated by absorption. Far-field radiation is created by scattering. Based on our model small colloids are expected to quench fluorescence because absorption is dominant over scattering. Larger colloids are expected to enhance fluorescence because the scattering component is dominant over absorption. The ability of a metal’s surface to absorb or reflect light is due to wavenumber matching requirements at the metal–sample interface. Wavenumber matching considerations can also be used to predict whether fluorophores at a given distance from a continuous planar surface will be emitted or quenched. These

A highly selective and simple fluorescent sensor for mercury (II) ion detection based on cysteamine-capped CdTe quantum dots synthesized by the reflux method.

PubMed

Ding, Xiaojie; Qu, Lingbo; Yang, Ran; Zhou, Yuchen; Li, Jianjun

2015-06-01

Cysteamine (CA)-capped CdTe quantum dots (QDs) (CA-CdTe QDs) were prepared by the reflux method and utilized as an efficient nano-sized fluorescent sensor to detect mercury (II) ions (Hg(2+) ). Under optimum conditions, the fluorescence quenching effect of CA-CdTe QDs was linear at Hg(2+) concentrations in the range of 6.0-450 nmol/L. The detection limit was calculated to be 4.0 nmol/L according to the 3σ IUPAC criteria. The influence of 10-fold Pb(2+) , Cu(2+) and Ag(+) on the determination of Hg(2+) was < 7% (superior to other reports based on crude QDs). Furthermore, the detection sensitivity and selectivity were much improved relative to a sensor based on the CA-CdTe QDs probe, which was prepared using a one-pot synthetic method. This CA-CdTe QDs sensor system represents a new feasibility to improve the detection performance of a QDs sensor by changing the synthesis method. Copyright © 2014 John Wiley & Sons, Ltd.

Multi-Phenotypic subtyping of circulating tumor cells using sequential fluorescent quenching and restaining

NASA Astrophysics Data System (ADS)

Adams, Daniel L.; Alpaugh, R. Katherine; Tsai, Susan; Tang, Cha-Mei; Stefansson, Steingrimur

2016-09-01

In tissue biopsies formalin fixed paraffin embedded cancer blocks are micro-sectioned producing multiple semi-identical specimens which are analyzed and subtyped proteomically, and genomically, with numerous biomarkers. In blood based biopsies (BBBs), blood is purified for circulating tumor cells (CTCs) and clinical utility is typically limited to cell enumeration, as only 2-3 positive fluorescent markers and 1 negative marker can be used. As such, increasing the number of subtyping biomarkers on each individual CTC could dramatically enhance the clinical utility of BBBs, allowing in depth interrogation of clinically relevant CTCs. We describe a simple and inexpensive method for quenching the specific fluors of fluorescently stained CTCs followed by sequential restaining with additional biomarkers. As proof of principle a CTC panel, immunosuppression panel and stem cell panel were used to sequentially subtype individual fluorescently stained patient CTCs, suggesting a simple and universal technique to analyze multiple clinically applicable immunomarkers from BBBs.

Universal Multifunctional Nanoplatform Based on Target-Induced in Situ Promoting Au Seeds Growth to Quench Fluorescence of Upconversion Nanoparticles.

PubMed

Wu, Qiongqiong; Chen, Hongyu; Fang, Aijin; Wu, Xinyang; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

2017-12-22

Construction of a new multifunctional chemo/biosensing platform for small biomolecules and tumor markers is of great importance in analytical chemistry. Herein, a novel universal multifunctional nanoplatform for biomolecules and enzyme activity detection was proposed based on fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) and target-inducing enlarged gold nanoparticles (AuNPs). The reductive molecule such as H 2 O 2 can act as the reductant to reduce HAuCl 4 , which will make the Au seeds grow. The enlarged AuNPs can effectively quench the fluorescence of UCNPs owing to the good spectral overlap between the absorption band of the AuNPs and the emission band of the UCNPs. Utilizing the FRET between the UCNPs and enlarged AuNPs, good linear relationship between the fluorescence of UCNPs and the concentration of H 2 O 2 can be found. Based on this strategy, H 2 O 2 related molecules such as l-lactate, glucose, and uric acid can also be quantified. On the basis of UCNPs and PVP/HAuCl 4 , a general strategy for other reductants such as ascorbic acid (AA), dopamine (DA), or enzyme activity can be established. Therefore, the universal multifunctional nanoplatform based on UCNPs and the target-inducing in situ enlarged Au NPs will show its potential as a simple method for the detection of some life related reductive molecules, enzyme substrates, as well as enzyme activity.

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.

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.

Widefield fluorescence microscopy with sensor-based conjugate adaptive optics using oblique back illumination

PubMed Central

Li, Jiang; Bifano, Thomas G.; Mertz, Jerome

2016-01-01

Abstract. We describe a wavefront sensor strategy for the implementation of adaptive optics (AO) in microscope applications involving thick, scattering media. The strategy is based on the exploitation of multiple scattering to provide oblique back illumination of the wavefront-sensor focal plane, enabling a simple and direct measurement of the flux-density tilt angles caused by aberrations at this plane. Advantages of the sensor are that it provides a large measurement field of view (FOV) while requiring no guide star, making it particularly adapted to a type of AO called conjugate AO, which provides a large correction FOV in cases when sample-induced aberrations arise from a single dominant plane (e.g., the sample surface). We apply conjugate AO here to widefield (i.e., nonscanning) fluorescence microscopy for the first time and demonstrate dynamic wavefront correction in a closed-loop implementation. PMID:27653793

A chromenoquinoline-based fluorescent off-on thiol probe for bioimaging.

PubMed

Kand, Dnyaneshwar; Kalle, Arunasree Marasanapalli; Varma, Sreejith Jayasree; Talukdar, Pinaki

2012-03-11

A new chromenoquinoline-based fluorescent off-on thiol probe 2 is reported. In aqueous buffer solutions at physiological pH, the probe exhibited 223-fold enhancement in fluorescence intensity by a Michael addition of cysteine to the maleimide appended to a chromenoquinoline. Cell permeability and live cell imaging of thiols are also demonstrated. This journal is © The Royal Society of Chemistry 2012

Assessment of bile fluorescence patterns in a tropical fish, Nile tilapia (Oreochromis niloticus) exposed to naphthalene, phenanthrene, pyrene and chrysene using fixed wavelength fluorescence and synchronous fluorescence spectrometry.

PubMed

Pathiratne, A; Hemachandra, C K; Pathiratne, K A S

2010-05-01

Bile fluorescence patterns in Nile tilapia, a potential fish for biomonitoring tropical water pollution were assessed following exposure to selected polycyclic aromatic hydrocarbons (PAHs): naphthalene, phenanthrene, pyrene and chrysene. Non-normalized fixed wavelength fluorescence signals in the fish exposed to these PAHs reflected dose and/or time response relationships of their metabolism. Normalizing signals to biliverdin introduced deviations to these response patterns. The optimal wavelength pairs (excitation/emission) for synchronous fluorescence scanning measurements of bile metabolites of naphthalene, phenanthrene, pyrene and chrysene were identified as 284/326, 252/357, 340/382 and 273/382 respectively. This study supports the use of bile fluorescence in Nile tilapia by fixed wavelength fluorescence and synchronous fluorescence spectrometry with non-normalized data as a simple method for screening bioavailability of these PAHs.

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.

[Determination of H2S in Rat Intestinal Perfusion Solution Based on Fluorescence Analysis].

PubMed

Hou, Jun-feng; Li, Xin-xia; Shen, Xue-ru; Huojia, Miliban; Guan, Ming

2015-08-01

Under alkaline conditions, Fluorescein mercury has strong fluorescence, however, when it met S(2-), its fluorescence would quench, in view of the above, a fluorescence method for determination of H2S in biological samples was established. In the 0.1 mol · L(-1) NaOH dilution, when the concentration of fluorescein Mercury and Na2S was 5.0 × 10(-5) and 1.0 × 10(-5) mol · L(-1) respectively, the fluorescence intensity of system was determined at 522 nm. The results showed that, at the range of 4.0 × 10(-7)~2.0 × 10(-6) mol · L(-1), the concentration decreasing of H2S and fluorescence intensity had good linear relationship, r=0.9980, the RSD of precision test was 4.59% (n=7), the detection limit was 3.5 × 10(-8) mol · L(-1), the content of H2S in the sample were 1.01 × 10(-6) and 1.15 × 10(-6) mol · L(-1), and the recovery rate was 95.8%~101.0%, the method has the advantages of simple operation, high sensitivity, good selectivity, can accurately determine of H2S in intestinal perfused solution, and provides the basis for the determination of endogenous H2S.

Coumarinocoumarin-Based Two-Photon Fluorescent Cysteine Biosensor for Targeting Lysosome.

PubMed

Chen, Chunyang; Zhou, Liuqing; Liu, Wei; Liu, Weisheng

2018-05-15

Coumarinocoumarin, one of the coumarin derivatives, is easy to synthesize and has rich modification sites. The large conjugate plane of coumarinocoumarin gives it a more excellent optical property than conventional coumarin, for example, the two-photon fluorescence property. So, the coumarinocoumarin-based probe (CCy) has been designed and synthesized, which is the first lysosomal targeting fluorescent biosensor for cysteine. This probe was prepared by a three-step procedure as a latent fluorescence probe to achieve high sensitivity and fluorescence turn-on response toward cysteine (Cys) over homocysteine (Hcy), glutathione (GSH), and other various natural amino acids under physiological conditions. Upon addition of Cys to the solution of CCy, remarkable enhancement on 520 nm of fluorescence spectra can be monitored. This probe was then successfully used for fluorescence imaging of Cys in mice organ tissues and HeLa cells, and quantitative determination has been achieved within a certain range, which proved the permeability of CCy. The concentration of Cys in animal serum was measured and the viability exceeded 80%, indicating that CCy can be a biocompatible and rapid probe for Cys in vivo. Simultaneously, its ability to detect Cys in lysosome has been validated by its lysosomal targeting.

Highly sensitive detection of target molecules using a new fluorescence-based bead assay

NASA Astrophysics Data System (ADS)

Scheffler, Silvia; Strauß, Denis; Sauer, Markus

2007-07-01

Development of immunoassays with improved sensitivity, specificity and reliability are of major interest in modern bioanalytical research. We describe the development of a new immunomagnetic fluorescence detection (IM-FD) assay based on specific antigen/antibody interactions and on accumulation of the fluorescence signal on superparamagnetic PE beads in combination with the use of extrinsic fluorescent labels. IM-FD can be easily modified by varying the order of coatings and assay conditions. Depending on the target molecule, antibodies (ABs), entire proteins, or small protein epitopes can be used as capture molecules. The presence of target molecules is detected by fluorescence microscopy using fluorescently labeled secondary or detection antibodies. Here, we demonstrate the potential of the new assay detecting the two tumor markers IGF-I and p53 antibodies in the clinically relevant concentration range. Our data show that the fluorescence-based bead assay exhibits a large dynamic range and a high sensitivity down to the subpicomolar level.

Determining absolute protein numbers by quantitative fluorescence microscopy.

PubMed

Verdaasdonk, Jolien Suzanne; Lawrimore, Josh; Bloom, Kerry

2014-01-01

Biological questions are increasingly being addressed using a wide range of quantitative analytical tools to examine protein complex composition. Knowledge of the absolute number of proteins present provides insights into organization, function, and maintenance and is used in mathematical modeling of complex cellular dynamics. In this chapter, we outline and describe three microscopy-based methods for determining absolute protein numbers--fluorescence correlation spectroscopy, stepwise photobleaching, and ratiometric comparison of fluorescence intensity to known standards. In addition, we discuss the various fluorescently labeled proteins that have been used as standards for both stepwise photobleaching and ratiometric comparison analysis. A detailed procedure for determining absolute protein number by ratiometric comparison is outlined in the second half of this chapter. Counting proteins by quantitative microscopy is a relatively simple yet very powerful analytical tool that will increase our understanding of protein complex composition. © 2014 Elsevier Inc. All rights reserved.

Red fluorescent proteins (RFPs) and RFP-based biosensors for neuronal imaging applications

PubMed Central

Shen, Yi; Lai, Tiffany; Campbell, Robert E.

2015-01-01

Abstract. The inherent advantages of red-shifted fluorescent proteins and fluorescent protein-based biosensors for the study of signaling processes in neurons and other tissues have motivated the development of a plethora of new tools. Relative to green fluorescent proteins (GFPs) and other blue-shifted alternatives, red fluorescent proteins (RFPs) provide the inherent advantages of lower phototoxicity, lower autofluorescence, and deeper tissue penetration associated with longer wavelength excitation light. All other factors being the same, the multiple benefits of using RFPs make these tools seemingly ideal candidates for use in neurons and, ultimately, the brain. However, for many applications, the practical utility of RFPs still falls short of the preferred GFPs. We present an overview of RFPs and RFP-based biosensors, with an emphasis on their reported applications in neuroscience. PMID:26158012

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.

The Statistical Value of Raw Fluorescence Signal in Luminex xMAP Based Multiplex Immunoassays

PubMed Central

Breen, Edmond J.; Tan, Woei; Khan, Alamgir

2016-01-01

Tissue samples (plasma, saliva, serum or urine) from 169 patients classified as either normal or having one of seven possible diseases are analysed across three 96-well plates for the presences of 37 analytes using cytokine inflammation multiplexed immunoassay panels. Censoring for concentration data caused problems for analysis of the low abundant analytes. Using fluorescence analysis over concentration based analysis allowed analysis of these low abundant analytes. Mixed-effects analysis on the resulting fluorescence and concentration responses reveals a combination of censoring and mapping the fluorescence responses to concentration values, through a 5PL curve, changed observed analyte concentrations. Simulation verifies this, by showing a dependence on the mean florescence response and its distribution on the observed analyte concentration levels. Differences from normality, in the fluorescence responses, can lead to differences in concentration estimates and unreliable probabilities for treatment effects. It is seen that when fluorescence responses are normally distributed, probabilities of treatment effects for fluorescence based t-tests has greater statistical power than the same probabilities from concentration based t-tests. We add evidence that the fluorescence response, unlike concentration values, doesn’t require censoring and we show with respect to differential analysis on the fluorescence responses that background correction is not required. PMID:27243383

Fluorescence-based enhanced reality (FLER) for real-time estimation of bowel perfusion in minimally invasive surgery

NASA Astrophysics Data System (ADS)

Diana, Michele

2016-03-01

Pre-anastomotic bowel perfusion is a key factor for a successful healing process. Clinical judgment has limited accuracy to evaluate intestinal microperfusion. Fluorescence videography is a promising tool for image-guided intraoperative assessment of the bowel perfusion at the future anastomotic site in the setting of minimally invasive procedures. The standard configuration for fluorescence videography includes a Near-Infrared endoscope able to detect the signal emitted by a fluorescent dye, more frequently Indocyanine Green (ICG), which is administered by intravenous injection. Fluorescence intensity is proportional to the amount of fluorescent dye diffusing in the tissue and consequently is a surrogate marker of tissue perfusion. However, fluorescence intensity alone remains a subjective approach and an integrated computer-based analysis of the over-time evolution of the fluorescence signal is required to obtain quantitative data. We have developed a solution integrating computer-based analysis for intra-operative evaluation of the optimal resection site, based on the bowel perfusion as determined by the dynamic fluorescence intensity. The software can generate a "virtual perfusion cartography", based on the "fluorescence time-to-peak". The virtual perfusion cartography can be overlapped onto real-time laparoscopic images to obtain the Enhanced Reality effect. We have defined this approach FLuorescence-based Enhanced Reality (FLER). This manuscript describes the stepwise development of the FLER concept.

A simple fluorescence quenching method for berberine determination using water-soluble CdTe quantum dots as probes

NASA Astrophysics Data System (ADS)

Cao, Ming; Liu, Meigui; Cao, Chun; Xia, Yunsheng; Bao, Linjun; Jin, Yingqiong; Yang, Song; Zhu, Changqing

2010-03-01

A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5 × 10 -8 and 8.0 × 10 -6 mol L -1 with a detection limit of 6.0 × 10 -9 mol L -1. The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.

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.

Pancreatic tumor detection using hypericin-based fluorescence spectroscopy and cytology

NASA Astrophysics Data System (ADS)

Lavu, Harish; Geary, Kevin; Fetterman, Harold R.; Saxton, Romaine E.

2005-04-01

Hypericin is a novel, highly fluorescent photosensitizer that exhibits selective tumor cell uptake properties and is particularly resistant to photobleaching. In this study, we have characterized hypericin uptake in human pancreatic tumor cells with relation to incubation time, cell number, and drug concentration. Ex vivo hypericin based fluorescence spectroscopy was performed to detect the presence of MIA PaCa-2 pancreatic tumor cells in the peritoneal cavity of BALB/c nude mice, as well as to quantify gross tumor burden. Hypericin based cytology of peritoneal lavage samples, using both one and two photon laser confocal microscopy, demonstrated more than a two-fold increase in fluorescence emission of pancreatic tumor cells as compared to control samples. In vitro treatment of pancreatic cancer cells with hypericin based photodynamic therapy showed tumor cell cytotoxicity in a drug dose, incident laser power, and time dependent manner. For these experiments, a continuous wavelength solid-state laser source (532 nm) was operated at power levels in the range of 100-400 mW. Potential applications of hypericin in tumor diagnosis, staging, and therapy will be presented.

Quencher-Free Fluorescence Method for the Detection of Mercury(II) Based on Polymerase-Aided Photoinduced Electron Transfer Strategy.

PubMed

Liu, Haisheng; Ma, Linbin; Ma, Changbei; Du, Junyan; Wang, Meilan; Wang, Kemin

2016-11-18

A new quencher-free Hg 2+ ion assay method was developed based on polymerase-assisted photoinduced electron transfer (PIET). In this approach, a probe is designed with a mercury ion recognition sequence (MRS) that is composed of two T-rich functional areas separated by a spacer of random bases at the 3'-end, and a sequence of stacked cytosines at the 5'-end, to which a fluorescein (FAM) is attached. Upon addition of Hg 2+ ions into this sensing system, the MRS folds into a hairpin structure at the 3'-end with Hg 2+ -mediated base pairs. In the presence of DNA polymerase, it will catalyze the extension reaction, resulting in the formation of stacked guanines, which will instantly quench the fluorescence of FAM through PIET. Under optimal conditions, the limit of detection for Hg 2+ ions was estimated to be 5 nM which is higher than the US Environmental Protection Agency (EPA) standard limit. In addition, no labeling with a quencher was requiring, and the present method is fairly simple, fast and low cost. It is expected that this cost-effective fluorescence method might hold considerable potential in the detection of Hg 2+ ions in real biological and environmental samples.

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.

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.

Conjugated polyelectrolyte based real-time fluorescence assay for phospholipase C.

PubMed

Liu, Yan; Ogawa, Katsu; Schanze, Kirk S

2008-01-01

A fluorescence turnoff assay for phospholipase C (PLC) from Clostridium perfringens is developed based on the reversible interaction between the natural substrate, phosphatidylcholine, and a fluorescent, water-soluble conjugated polyelectrolyte (CPE). The fluorescence intensity of the CPE in water is increased substantially by the addition of the phospholipid due to the formation of a CPE-lipid complex. Incubation of the CPE-lipid complex with the enzyme PLC causes the fluorescence intensity to decrease (turnoff sensor); the response arises due to PLC-catalyzed hydrolysis of the phosphatidylcholine, which effectively disrupts the CPE-lipid complex. The PLC assay operates with phospholipid substrate concentrations in the micromolar range, and the analytical detection limit for PLC is <1 nM. The optimized assay provides a convenient, rapid, and real-time sensor for PLC activity. The real-time fluorescence intensity from the CPE can be converted to substrate concentration by using an ex situ calibration curve, allowing PLC-catalyzed reaction rates and kinetic parameters to be determined. PLC activation by Ca2+ and inhibition by EDTA and fluoride ion are demonstrated using the optimized sensor.

One-step synthesis of nitrogen, boron co-doped fluorescent carbon nanoparticles for glucose detection.

PubMed

Liang, Meijuan; Ren, Yi; Zhang, Haijuan; Ma, Yunxia; Niu, Xiaoying; Chen, Xingguo

2017-09-01

Heteroatom-doped carbon nanoparticles (CNPs) have attracted considerable attention due to an effective improvement in their intrinsic properties. Here, a facile and simple synthesis of nitrogen, boron co-doped carbon nanoparticles (NB-CNPs) from a sole precursor, 3-aminophenylboronic acid, was performed via a one-step solid-phase approach. Because of the presence of boronic acid, NB-CNPs can be used directly as a fluorescent probe for glucose. Based on a boronic acid-triggered specific reaction, we developed a simple NB-CNP probe without surface modification for the detection of glucose. When glucose was introduced, the fluorescence of NB-CNPs was suppressed through a surface-quenching states mechanism. Obvious fluorescence quenching allowed the highly sensitive determination of glucose with a limit of detection of 1.8 μM. Moreover, the proposed method has been successfully used to detect glucose in urine from people with diabetes, suggesting potential application in sensing glucose. Copyright © 2017 John Wiley & Sons, Ltd.

Label-free detection of kanamycin based on a G-quadruplex DNA aptamer-based fluorescent intercalator displacement assay

NASA Astrophysics Data System (ADS)

Xing, Yun-Peng; Liu, Chun; Zhou, Xiao-Hong; Shi, Han-Chang

2015-01-01

This work was the first to report that the kanamycin-binding DNA aptamer (5'-TGG GGG TTG AGG CTA AGC CGA-3') can form stable parallel G-quadruplex DNA (G4-DNA) structures by themselves and that this phenomenon can be verified by nondenaturing polyacrylamide gel electrophoresis and circular dichroism spectroscopy. Based on these findings, we developed a novel label-free strategy for kanamycin detection based on the G4-DNA aptamer-based fluorescent intercalator displacement assay with thiazole orange (TO) as the fluorescence probe. In the proposed strategy, TO became strongly fluorescent upon binding to kanamycin-binding G4-DNA. However, the addition of kanamycin caused the displacement of TO from the G4-DNA-TO conjugate, thereby resulting in decreased fluorescent signal, which was inversely related to the kanamycin concentration. The detection limit of the proposed assay decreased to 59 nM with a linear working range of 0.1 μM to 20 μM for kanamycin. The cross-reactivity against six other antibiotics was negligible compared with the response to kanamycin. A satisfactory recovery of kanamycin in milk samples ranged from 80.1% to 98.0%, confirming the potential of this bioassay in the measurement of kanamycin in various applications. Our results also served as a good reference for developing similar fluorescent G4-DNA-based bioassays in the future.

Optimization-Based Approach for Joint X-Ray Fluorescence and Transmission Tomographic Inversion

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

Di, Zichao; Leyffer, Sven; Wild, Stefan M.

2016-01-01

Fluorescence tomographic reconstruction, based on the detection of photons coming from fluorescent emission, can be used for revealing the internal elemental composition of a sample. On the other hand, conventional X-ray transmission tomography can be used for reconstructing the spatial distribution of the absorption coefficient inside a sample. In this work, we integrate both X-ray fluorescence and X-ray transmission data modalities and formulate a nonlinear optimization-based approach for reconstruction of the elemental composition of a given object. This model provides a simultaneous reconstruction of both the quantitative spatial distribution of all elements and the absorption effect in the sample. Mathematicallymore » speaking, we show that compared with the single-modality inversion (i.e., the X-ray transmission or fluorescence alone), the joint inversion provides a better-posed problem, which implies a better recovery. Therefore, the challenges in X-ray fluorescence tomography arising mainly from the effects of self-absorption in the sample are partially mitigated. The use of this technique is demonstrated on the reconstruction of several synthetic samples.« less

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.

Simple and rapid quality control of sulfated glycans by a fluorescence sensor assay--exemplarily developed for the sulfated polysaccharides from red algae Delesseria sanguinea.

PubMed

Lühn, Susanne; Grimm, Juliane C; Alban, Susanne

2014-04-10

Sulfated polysaccharides (SP) from algae are of great interest due to their manifold biological activities. Obstacles to commercial (especially medical) application include considerable variability and complex chemical composition making the analysis and the quality control challenging. The aim of this study was to evaluate a simple microplate assay for screening the quality of SP. It is based on the fluorescence intensity (FI) increase of the sensor molecule Polymer-H by SP and was originally developed for direct quantification of SP. Exemplarily, 65 SP batches isolated from the red alga Delesseria sanguinea (D.s.-SP) and several other algae polysaccharides were investigated. Their FI increase in the Polymer-H assay was compared with other analytical parameters. By testing just one concentration of a D.s.-SP sample, quality deviations from the reference D.s.-SP and thus both batch-to-batch variability and stability can be detected. Further, structurally distinct SP showed to differ in their concentration-dependent FI profiles. By using corresponding reference compounds, the Polymer-H assay is therefore applicable as identification assay with high negative predictability. In conclusion, the Polymer-H assay showed to represent not only a simple method for quantification, but also for characterization identification and differentiation of SP of marine origin.

Why do aged fluorescent tubes flicker?

NASA Astrophysics Data System (ADS)

Plihon, Nicolas; Ferrand, Jérémy; Guyomar, Tristan; Museur, Flavien; Taberlet, Nicolas

2017-11-01

Our everyday experience of aged and defective fluorescent tubes or bulbs informs us that they may flicker and emit a clicking sound while struggling to light up. In this article, the physical mechanisms controlling the initial illumination of a functioning fluorescent tube are investigated using a simple and affordable experimental setup. Thermionic emission from the electrodes of the tube controls the startup of fluorescent tubes. The origin of the faulty startup of aged fluorescent tubes is discussed and flickering regimes using functional tubes are artificially produced using a dedicated setup that decreases electron emission by the thermionic effect in a controlled manner. The physical parameters controlling the occurrence of flickering light are discussed, and their temporal statistics are reported.

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.

Ratiometric fluorescent nanosensor based on carbon dots for the detection of mercury ion

NASA Astrophysics Data System (ADS)

Ma, Yusha; Mei, Jing; Bai, Jianliang; Chen, Xu; Ren, Lili

2018-05-01

A novel ratiometric fluorescent nanosensor based on carbon dots has been synthesized via bonding rhodamine B hydrazide to the carbon dots surface by an amide reaction. The ratiometric fluorescent nanosensor showed only a single blue fluorescence emission around 450 nm. While, as mercury ion was added, due to the open-ring of rhodamine moiety bonded on the CDs surface, the orange emission of the open-ring rhodamine would increase obviously according to the concentration of mercury ion, resulting in the distinguishable dual emissions at 450 nm and 575 nm under a single 360 excitation wavelength. Meanwhile, the ratiometric fluorescent nanosensor based on carbon dots we prepared is more sensitive to qualitative and semi-quantitative detection of mercury ion in the range of 0–100 μM, because fluorescence changes gradually from blue to orange emission under 365 nm lamp with the increasing of mercury ion in the tested solution.

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.

A simple turn on fluorescent sensor for the selective detection of thiamine using coconut water derived luminescent carbon dots.

PubMed

Purbia, Rahul; Paria, Santanu

2016-05-15

In this study microwave-assisted hydrothermal method was used to prepare highly luminescent carbon dots (1-6 nm size) within a minute from tender coconut (Cocos nucifera) water. The synthesized carbon dots (C-dots) exhibit emission of blue and green lights while excited at 390 and 450 nm wavelengths, respectively. As an application, these C-dots were tested for a simple "turn on" fluorescent sensor for rapid detection of thiamine (vitamin B1). The detection of thiamine in human body is very important to prevent various diseases such as beriberi, neurological disorders, optic neuropathy, etc. The fluorescence emission intensity of C-dots quenches after addition of Cu(2+) ion and then again increases selectively (turn on) after the addition of thiamine. The fluorescence emission intensity enhancement of Cu(2+) ion modified C-dots in the presence of thiamine exhibits a linear relationship within the thiamine concentration range of 10-50 μM. The limit of detection was found to be 280 nM from this study. The selectivity of the detection was also tested in the presence of different organic molecules and inorganic ions (Ca(2+), Mg(2+), Na(+), K(+), Cl(-), SO4(2-), and NO3(-)) which are present in blood serum and urine and found to be almost no interference in the detection. Finally, to see the applicability in real samples a commercial vitamin capsule was tested and found less than 3% error in the detected concentration. The C-dots were also used for bioimaging of fungus and the results show they are also suitable for this application too. Copyright © 2015 Elsevier B.V. All rights reserved.

Mosaic-Detector-Based Fluorescence Spectral Imager

NASA Technical Reports Server (NTRS)

Son, Kyung-Ah; Moon, Jeong

2007-01-01

A battery-powered, pen-sized, portable instrument for measuring molecular fluorescence spectra of chemical and biological samples in the field has been proposed. Molecular fluorescence spectroscopy is among the techniques used most frequently in laboratories to analyze compositions of chemical and biological samples. Heretofore, it has been possible to measure fluorescence spectra of molecular species at relative concentrations as low as parts per billion (ppb), with a few nm spectral resolution. The proposed instrument would include a planar array (mosaic) of detectors, onto which a fluorescence spectrum would be spatially mapped. Unlike in the larger laboratory-type molecular fluorescence spectrometers, mapping of wavelengths to spatial positions would be accomplished without use of relatively bulky optical parts. The proposed instrument is expected to be sensitive enough to enable measurement of spectra of chemical species at relative concentrations <1 ppb, with spectral resolution that could be tailored by design to be comparable to a laboratory molecular fluorescence spectrometer. The proposed instrument (see figure) would include a button-cell battery and a laser diode, which would generate the monochromatic ultraviolet light needed to excite fluorescence in a sample. The sample would be held in a cell bounded by far-ultraviolet-transparent quartz or optical glass. The detector array would be, more specifically, a complementary metal oxide/ semiconductor or charge-coupled- device imaging photodetector array, the photodetectors of which would be tailored to respond to light in the wavelength range of the fluorescence spectrum to be measured. The light-input face of the photodetector array would be covered with a matching checkerboard array of multilayer thin film interference filters, such that each pixel in the array would be sensitive only to light in a spectral band narrow enough so as not to overlap significantly with the band of an adjacent pixel. The

Design strategy for photoinduced electron transfer-based small-molecule fluorescent probes of biomacromolecules.

PubMed

Zhang, Wei; Ma, Zhao; Du, Lupei; Li, Minyong

2014-06-07

As the cardinal support of innumerable biological processes, biomacromolecules such as proteins, nucleic acids and polysaccharides are of importance to living systems. The key to understanding biological processes is to realize the role of these biomacromolecules in thte localization, distribution, conformation and interaction with other molecules. With the current development and adaptation of fluorescent technologies in biomedical and pharmaceutical fields, the fluorescence imaging (FLI) approach of using small-molecule fluorescent probes is becoming an up-to-the-minute method for the detection and monitoring of these imperative biomolecules in life sciences. However, conventional small-molecule fluorescent probes may provide undesirable results because of their intrinsic deficiencies such as low signal-to-noise ratio (SNR) and false-positive errors. Recently, small-molecule fluorescent probes with a photoinduced electron transfer (PET) "on/off" switch for biomacromolecules have been thoroughly considered. When recognized by the biomacromolecules, these probes turn on/off the PET switch and change the fluorescence intensity to present a high SNR result. It should be emphasized that these PET-based fluorescent probes could be advantageous for understanding the pathogenesis of various diseases caused by abnormal expression of biomacromolecules. The discussion of this successful strategy involved in this review will be a valuable guide for the further development of new PET-based small-molecule fluorescent probes for biomacromolecules.

Optical Characterization of Paper Aging Based on Laser-Induced Fluorescence (LIF) Spectroscopy.

PubMed

Zhang, Hao; Wang, Shun; Chang, Keke; Sun, Haifeng; Guo, Qingqian; Ma, Liuzheng; Yang, Yatao; Zou, Caihong; Wang, Ling; Hu, Jiandong

2018-06-01

Paper aging and degradation are growing concerns for those who are responsible for the conservation of documents, archives, and libraries. In this study, the paper aging was investigated using laser-induced fluorescence spectroscopy (LIFS), where the fluorescence properties of 47 paper samples with different ages were explored. The paper exhibits fluorescence in the blue-green spectral region with two peaks at about 448 nm and 480 nm under the excitation of 405 nm laser. Both fluorescence peaks changed in absolute intensities and thus the ratio of peak intensities was also influenced with the increasing ages. By applying principal component analysis (PCA) and k-means clustering algorithm, all 47 paper samples were classified into nine groups based on the differences in paper age. Then the first-derivative fluorescence spectral curves were proposed to figure out the relationship between the spectral characteristic and the paper age, and two quantitative models were established based on the changes of first-derivative spectral peak at 443 nm, where one is an exponential fitting curve with an R-squared value of 0.99 and another is a linear fitting curve with an R-squared value of 0.88. The results demonstrated that the combination of fluorescence spectroscopy and PCA can be used for the classification of paper samples with different ages. Moreover, the first-derivative fluorescence spectral curves can be used to quantitatively evaluate the age-related changes of paper samples.

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for... reflector) medium base compact fluorescent lamps; and (2) For each basic model of bare or covered (no...

Hydrogen sulfide deactivates common nitrobenzofurazan-based fluorescent thiol labeling reagents.

PubMed

Montoya, Leticia A; Pluth, Michael D

2014-06-17

Sulfhydryl-containing compounds, including thiols and hydrogen sulfide (H2S), play important but differential roles in biological structure and function. One major challenge in separating the biological roles of thiols and H2S is developing tools to effectively separate the reactivity of these sulfhydryl-containing compounds. To address this challenge, we report the differential responses of common electrophilic fluorescent thiol labeling reagents, including nitrobenzofurazan-based scaffolds, maleimides, alkylating agents, and electrophilic aldehydes, toward cysteine and H2S. Although H2S reacted with all of the investigated scaffolds, the photophysical response to each scaffold was significantly different. Maleimide-based, alkylating, and aldehydic thiol labeling reagents provided a diminished fluorescence response when treated with H2S. By contrast, nitrobenzofurazan-based labeling reagents were deactivated by H2S addition. Furthermore, the addition of H2S to thiol-activated nitrobenzofurazan-based reagents reduced the fluorescence signal, thus establishing the incompatibility of nitrobenzofurazan-based thiol labeling reagents in the presence of H2S. Taken together, these studies highlight the differential reactivity of thiols and H2S toward common thiol-labeling reagents and suggest that sufficient care must be taken when labeling or measuring thiols in cellular environments that produce H2S due to the potential for both false-positive and eroded responses.

A high-throughput direct fluorescence resonance energy transfer-based assay for analyzing apoptotic proteases using flow cytometry and fluorescence lifetime measurements.

PubMed

Suzuki, Miho; Sakata, Ichiro; Sakai, Takafumi; Tomioka, Hiroaki; Nishigaki, Koichi; Tramier, Marc; Coppey-Moisan, Maïté

2015-12-15

Cytometry is a versatile and powerful method applicable to different fields, particularly pharmacology and biomedical studies. Based on the data obtained, cytometric studies are classified into high-throughput (HTP) or high-content screening (HCS) groups. However, assays combining the advantages of both are required to facilitate research. In this study, we developed a high-throughput system to profile cellular populations in terms of time- or dose-dependent responses to apoptotic stimulations because apoptotic inducers are potent anticancer drugs. We previously established assay systems involving protease to monitor live cells for apoptosis using tunable fluorescence resonance energy transfer (FRET)-based bioprobes. These assays can be used for microscopic analyses or fluorescence-activated cell sorting. In this study, we developed FRET-based bioprobes to detect the activity of the apoptotic markers caspase-3 and caspase-9 via changes in bioprobe fluorescence lifetimes using a flow cytometer for direct estimation of FRET efficiencies. Different patterns of changes in the fluorescence lifetimes of these markers during apoptosis were observed, indicating a relationship between discrete steps in the apoptosis process. The findings demonstrate the feasibility of evaluating collective cellular dynamics during apoptosis. Copyright © 2015 Elsevier Inc. All rights reserved.

5-ALA/PpIX fluorescence detection of gastrointestinal neoplasia

NASA Astrophysics Data System (ADS)

Borisova, Ekaterina G.; Vladimirov, Borislav; Terziev, Ivan; Ivanova, Radina; Avramov, Latchezar

2009-07-01

In the recent study delta-ALA/PpIX is used as fluorescent marker for dysplasia and tumor detection in esophagus, stomach and colon. ALA is administered per os six to eight (depending on the lesion location) hours before measurements at dose 20mg/kg weight. High-power light-emitting diode at 405 nm is used as an excitation source. Special opto-mechanical device is built for the LED to use the light guide of standard video-endoscopic system. Through endoscopic instrumental channel a fiber is applied to return information about fluorescence to microspectrometer. The fluorescence detected from tumor sites has very complex spectral origins. It consists of autofluorescence, fluorescence from exogenous fluorophores and re-absorption from the chromophores accumulated in the tissue investigated. Spectral features observed during endoscopic investigations could be distinct as the next regions: 450-630 nm region, where tissue autofluorescence is observed; 630-710 nm region, where fluorescence of PpIX is clearly pronounced; 530-580 nm region, where minima in the autofluorescence signal are observed, related to re-absorption of oxy-hemoglobin in this spectral area. Endogenous and exogenous fluorescence spectra are used to develop simple but effective algorithm, based on dimensionless ratio of the signals at 560 and 635 nm, for differentiation of normal/abnormal gastrointestinal tissues. Very good correlation between fluorescence signals and histology examination of the lesions investigated is achieved.

Highly Efficient Multiple-Anchored Fluorescent Probe for the Detection of Aniline Vapor Based on Synergistic Effect: Chemical Reaction and PET.

PubMed

Jiao, Zinuo; Zhang, Yu; Xu, Wei; Zhang, Xiangtao; Jiang, Haibo; Wu, Pengcheng; Fu, Yanyan; He, Qingguo; Cao, Huimin; Cheng, Jiangong

2017-05-26

A multiple-anchored fluorescent probe ((((hexane-1,6-diylbis(2,7-bis(4-formyl)-phenyl)-9H-fluorine-9,9-diyl))-bis(hexane-6,1-diyl))-bis(9H-carbazole-9,3,6-triyl))-tetrakis(benzene-4,1-diyl))-tetraformyl-(8FP-2F) with eight aldehyde groups was designed and synthesized. The molecule has four branches and highly twisted structure. Furthermore, it tends to self-assemble into nanospheres, which is beneficial for gaseous analyte penetration and high fluorescence quantum efficiency. Among gaseous analytes, detection of aniline vapor is extraordinarily important in the control of environmental issues and human diseases. Herein, 8FP-2F was introduced to detect aniline vapor with distinguished sensitivity and selectivity via simple Schiff base reaction at room temperature. After exposure to saturate aniline vapor, the 89% fluorescence of 8FP-2F was quenched in 50 s and the detection limit was as low as 3 ppb. Further study showed the suitable HOMO/LUMO energy levels and matched orbital symmetry between probe and aniline molecules ensured chemical reaction and PET process work together. The synergistic effect resulted in a significant sensing performance and fluorescence quenching toward aniline vapor. Moreover, the multiple active sites structure of 8FP-2F means it could be applied for constructing many interesting structures and highly efficient organic optoelectronic functional materials.

Aqueous synthesis of near-infrared highly fluorescent platinum nanoclusters

NASA Astrophysics Data System (ADS)

García Fernández, Jenifer; Trapiella-Alfonso, Laura; Costa-Fernández, José M.; Pereiro, Rosario; Sanz-Medel, Alfredo

2015-05-01

A one-step synthesis of near infrared fluorescent platinum nanoclusters (PtNCs) in aqueous medium is described. The proposed optimized procedure for PtNC synthesis is rather simple, fast and it is based on the direct metal reduction with NaBH4. Bidentated thiol ligands (lipoic acid) were selected as nanoclusters stabilizers in water media. The structural characterization revealed attractive features of the PtNCs, including small size, high water solubility, near-infrared luminescence centered at 680 nm, long-term stability and the highest quantum yield in water reported so far (47%) for PtNCs. Moreover, their stability in different pH media and an ionic strength of 0.2 M NaCl was studied and no significant changes in fluorescence emission were detected. In brief, they offer a new type of fluorescent noble metal nanoprobe with a great potential to be applied in several fields, including biolabeling and imaging experiments.

Ensemble empirical mode decomposition based fluorescence spectral noise reduction for low concentration PAHs

NASA Astrophysics Data System (ADS)

Wang, Shu-tao; Yang, Xue-ying; Kong, De-ming; Wang, Yu-tian

2017-11-01

A new noise reduction method based on ensemble empirical mode decomposition (EEMD) is proposed to improve the detection effect for fluorescence spectra. Polycyclic aromatic hydrocarbons (PAHs) pollutants, as a kind of important current environmental pollution source, are highly oncogenic. Using the fluorescence spectroscopy method, the PAHs pollutants can be detected. However, instrument will produce noise in the experiment. Weak fluorescent signals can be affected by noise, so we propose a way to denoise and improve the detection effect. Firstly, we use fluorescence spectrometer to detect PAHs to obtain fluorescence spectra. Subsequently, noises are reduced by EEMD algorithm. Finally, the experiment results show the proposed method is feasible.

Highly selective rhodamine-based fluorescence turn-on chemosensor for Al3+ ion

NASA Astrophysics Data System (ADS)

Manjunath, Rangasamy; Kannan, Palaninathan

2018-05-01

A new rhodamine-based colorimetric and fluorescent turn-on chemosensor (L) has been designed and synthesized for selective and sensitive detection of Al3+ ion. The sensing behavior toward metal ion was investigated by UV/Vis and fluorescence spectroscopy. Upon addition of Al3+ ion to solution of L provided a visual color change as well as significantly fluorescent enhancement, while other metal ions including Na+, Mg2+, K+, Mn2+, Fe3+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+ ions fails to generate a distinct color and spectral changes, the distinct color change and rapid switch-on fluorescence also provide naked eye detection for Al3+ ion. The mechanism involved equilibrium between non-fluorescent spirocyclic form and highly fluorescent ring open form process was utilized and 1:2 stoichiometry for L-Al3+ complex formed with an association constant of 1.42 × 103 M-1. Moreover, chemosensor L was applied for living cell imaging and confirmed that can be used as a fluorescent probe for monitoring Al3+ ion in living cells.

Fluorescence Aggregation-Caused Quenching versus Aggregation-Induced Emission: A Visual Teaching Technology for Undergraduate Chemistry Students

ERIC Educational Resources Information Center

Ma, Xiaofeng; Sun, Rui; Cheng, Jinghui; Liu, Jiaoyan; Gou, Fei; Xiang, Haifeng; Zhou, Xiangge

2016-01-01

A laboratory experiment visually exploring two opposite basic principles of fluorescence of aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) is demonstrated. The students would prepared two salicylaldehyde-based Schiff bases through a simple one-pot condensation reaction of one equiv of 1,2-diamine with 2 equiv of…

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.

A fluorescence-based imaging approach to pharmacokinetic analysis of intracochlear drug delivery.

PubMed

Ayoob, Andrew M; Peppi, Marcello; Tandon, Vishal; Langer, Robert; Borenstein, Jeffrey T

2018-04-05

Advances in microelectromechanical systems (MEMS) technologies are enhancing the development of intracochlear delivery devices for the treatment of hearing loss with emerging pharmacological therapies. Direct intracochlear delivery addresses the limitations of systemic and intratympanic delivery. However, optimization of delivery parameters for these devices requires pharmacokinetic assessment of the spatiotemporal drug distribution inside the cochlea. Robust methods of measuring drug concentration in the perilymph have been developed, but lack spatial resolution along the tonotopic axis or require complex physiological measurements. Here we describe an approach for quantifying distribution of fluorescent drug-surrogate probe along the cochlea's sensory epithelium with high spatial resolution enabled by confocal fluorescence imaging. Fluorescence from FM 1-43 FX, a fixable endocytosis marker, was quantified using confocal fluorescence imaging of whole mount sections of the organ of Corti from cochleae resected and fixed at several time points after intracochlear delivery. Intracochlear delivery of FM 1-43 FX near the base of the cochlea produces a base-apex gradient of fluorescence in the row of inner hair cells after 1 h post-delivery that is consistent with diffusion-limited transport along the scala tympani. By 3 h post-delivery there is approximately an order of magnitude decrease in peak average fluorescence intensity, suggesting FM 1-43 FX clearance from both the perilymph and inner hair cells. The increase in fluorescence intensity at 72 h post-delivery compared to 3 h post-delivery may implicate a potential radial transport pathway into the scala media. Copyright © 2018 Elsevier B.V. All rights reserved.

Maximizing Aggregation of Organic Fluorophores to Prolong Fluorescence Lifetime for Two-Photon Fluorescence Lifetime Imaging.

PubMed

Hu, Wenbo; Guo, Lihong; Bai, Lei; Miao, Xiaofei; Ni, Yun; Wang, Qi; Zhao, Hui; Xie, Meng; Li, Lin; Lu, Xiaomei; Huang, Wei; Fan, Quli

2018-05-28

Two-photon fluorescence lifetime imaging (TP-FLIM) not only permits imaging deep inside the tissues with precise spatial manipulation but also circumvents tissue autofluorescence, holding tremendous promise in molecular imaging. However, the serious lack of suitable contrast agents with long fluorescence lifetime and efficient two-photon absorption (TPA) greatly limits the advance of TP-FLIM. This study reports a simple approach to fabricate water-soluble organic semiconducting nanoparticles [thioxanthone (TXO) NPs] with ultralong fluorescence lifetime and efficient TPA for in vivo TP-FLIM. The approach utilizes the aggregation of a specifically selected thermally activated delayed fluorescence (TADF) fluorophore to prolong its fluorescence lifetime. Encapsulating the TADF fluorophore within an amphiphilic copolymer not only maximizes its aggregation but also obtains TXO NPs with efficient TPA. Importantly, as-prepared TXO NPs exhibit a considerably long fluorescence lifetime at a magnitude of 4.2 µs, which is almost 1000 times larger than that of existing organic contrast agents. Moreover, such long fluorescence lifetime is almost oxygen-inert, readily realizing both in vitro and in vivo TP-FLIM. This work may set valuable guidance for designing organic semiconducting materials with ultralong fluorescence lifetimes to fulfill the potential of FLIM. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybrid Integrated Silicon Microfluidic Platform for Fluorescence Based Biodetection.

PubMed

Chandrasekaran, Arvind; Acharya, Ashwin; You, Jian Liang; Soo, Kim Young; Packirisamy, Muthukumaran; Stiharu, Ion; Darveau, André

2007-09-11

The desideratum to develop a fully integrated Lab-on-a-chip device capable ofrapid specimen detection for high throughput in-situ biomedical diagnoses and Point-of-Care testing applications has called for the integration of some of the novel technologiessuch as the microfluidics, microphotonics, immunoproteomics and Micro ElectroMechanical Systems (MEMS). In the present work, a silicon based microfluidic device hasbeen developed for carrying out fluorescence based immunoassay. By hybrid attachment ofthe microfluidic device with a Spectrometer-on-chip, the feasibility of synthesizing anintegrated Lab-on-a-chip type device for fluorescence based biosensing has beendemonstrated. Biodetection using the microfluidic device has been carried out usingantigen sheep IgG and Alexafluor-647 tagged antibody particles and the experimentalresults prove that silicon is a compatible material for the present application given thevarious advantages it offers such as cost-effectiveness, ease of bulk microfabrication,superior surface affinity to biomolecules, ease of disposability of the device etc., and is thussuitable for fabricating Lab-on-a-chip type devices.

Fluoromodule-based reporter/probes designed for in vivo fluorescence imaging

PubMed Central

Zhang, Ming; Chakraborty, Subhasish K.; Sampath, Padma; Rojas, Juan J.; Hou, Weizhou; Saurabh, Saumya; Thorne, Steve H.; Bruchez, Marcel P.; Waggoner, Alan S.

2015-01-01

Optical imaging of whole, living animals has proven to be a powerful tool in multiple areas of preclinical research and has allowed noninvasive monitoring of immune responses, tumor and pathogen growth, and treatment responses in longitudinal studies. However, fluorescence-based studies in animals are challenging because tissue absorbs and autofluoresces strongly in the visible light spectrum. These optical properties drive development and use of fluorescent labels that absorb and emit at longer wavelengths. Here, we present a far-red absorbing fluoromodule–based reporter/probe system and show that this system can be used for imaging in living mice. The probe we developed is a fluorogenic dye called SC1 that is dark in solution but highly fluorescent when bound to its cognate reporter, Mars1. The reporter/probe complex, or fluoromodule, produced peak emission near 730 nm. Mars1 was able to bind a variety of structurally similar probes that differ in color and membrane permeability. We demonstrated that a tool kit of multiple probes can be used to label extracellular and intracellular reporter–tagged receptor pools with 2 colors. Imaging studies may benefit from this far-red excited reporter/probe system, which features tight coupling between probe fluorescence and reporter binding and offers the option of using an expandable family of fluorogenic probes with a single reporter gene. PMID:26348895

Polymer-and glass-based fluorescence standards for the near infrared (NIR) spectral region.

PubMed

Würth, Christian; Hoffmann, Katrin; Behnke, Thomas; Ohnesorge, Marius; Resch-Genger, Ute

2011-05-01

The widespread use and acceptance of fluorescence techniques especially in regulated areas like medical diagnostics is closely linked to standardization concepts that guarantee and improve the comparability and reliability of fluorescence measurements. At the core of such concepts are dependable fluorescence standards that are preferably certified. The ever rising interest in fluorescence measurements in the near-infrared (NIR) spectral region renders the availability of spectral and intensity standards for this wavelength region increasingly important. This encouraged us to develop approaches to solid NIR standards based upon dye-doped polymers and assess their application-relevant properties in comparison to metal ion-doped glasses. The overall goal is here to provide inexpensive, easily fabricated, and robust internal and external calibration tools for a broad variety of fluorescence instruments ranging e.g. from spectrofluorometers over fluorescence microscopes to miniaturized fluorescence sensors. © Springer Science+Business Media, LLC 2010

Highly sensitive colorimetric and fluorescent sensor for cyanazine based on the inner filter effect of gold nanoparticles

NASA Astrophysics Data System (ADS)

Dong, Liang; Hou, Changjun; Yang, Mei; Fa, Huanbao; Wu, Huixiang; Shen, Caihong; Huo, Danqun

2016-06-01

Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP-CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods.

Aptamer-Functionalized Fluorescent Silica Nanoparticles for Highly Sensitive Detection of Leukemia Cells

NASA Astrophysics Data System (ADS)

Tan, Juntao; Yang, Nuo; Hu, Zixi; Su, Jing; Zhong, Jianhong; Yang, Yang; Yu, Yating; Zhu, Jianmeng; Xue, Dabin; Huang, Yingying; Lai, Zongqiang; Huang, Yong; Lu, Xiaoling; Zhao, Yongxiang

2016-06-01

A simple, highly sensitive method to detect leukemia cells has been developed based on aptamer-modified fluorescent silica nanoparticles (FSNPs). In this strategy, the amine-labeled Sgc8 aptamer was conjugated to carboxyl-modified FSNPs via amide coupling between amino and carboxyl groups. Sensitivity and specificity of Sgc8-FSNPs were assessed using flow cytometry and fluorescence microscopy. These results showed that Sgc8-FSNPs detected leukemia cells with high sensitivity and specificity. Aptamer-modified FSNPs hold promise for sensitive and specific detection of leukemia cells. Changing the aptamer may allow the FSNPs to detect other types of cancer cells.

Fluorescent biosensors enabled by graphene and graphene oxide.

PubMed

Zhang, Huan; Zhang, Honglu; Aldalbahi, Ali; Zuo, Xiaolei; Fan, Chunhai; Mi, Xianqiang

2017-03-15

During the past few years, graphene and graphene oxide (GO) have attracted numerous attentions for the potential applications in various fields from energy technology, biosensing to biomedical diagnosis and therapy due to their various functionalization, high volume surface ratio, unique physical and electrical properties. Among which, graphene and graphene oxide based fluorescent biosensors enabled by their fluorescence-quenching properties have attracted great interests. The fluorescence of fluorophore or dye labeled on probes (such as molecular beacon, aptamer, DNAzymes and so on) was quenched after adsorbed on to the surface of graphene. While in the present of the targets, due to the strong interactions between probes and targets, the probes were detached from the surface of graphene, generating dramatic fluorescence, which could be used as signals for detection of the targets. This strategy was simple and economy, together with great programmable abilities of probes; we could realize detection of different kinds of species. In this review, we first briefly introduced the history of graphene and graphene oxide, and then summarized the fluorescent biosensors enabled by graphene and GO, with a detailed account of the design mechanism and comparison with other nanomaterials (e.g. carbon nanotubes and gold nanoparticles). Following that, different sensing platforms for detection of DNAs, ions, biomolecules and pathogens or cells as well as the cytotoxicity issue of graphene and GO based in vivo biosensing were further discussed. We hope that this review would do some help to researchers who are interested in graphene related biosening research work. Copyright © 2016 Elsevier B.V. All rights reserved.

Strand displacement activated peroxidase activity of hemin for fluorescent DNA sensing.

PubMed

Wang, Quanbo; Xu, Nan; Gui, Zhen; Lei, Jianping; Ju, Huangxian; Yan, Feng

2015-10-07

To efficiently regulate the catalytic activity of the peroxidase mimic hemin, this work designs a double-stranded DNA probe containing an intermolecular dimer of hemin, whose peroxidase activity can be activated by a DNA strand displacement reaction. The double-stranded probe is prepared by annealing two strands of hemin labelled DNA oligonucleotides. Using the fluorescent oxidation product of tyramine by H2O2 as a tracing molecule, the low peroxidase activity of the hemin dimer ensures a low fluorescence background. The strand displacement reaction of the target DNA dissociates the hemin dimer and thus significantly increases the catalytic activity of hemin to produce a large amount of dityramine for fluorescence signal readout. Based on the strand displacement regulated peroxidase activity, a simple and sensitive homogeneous fluorescent DNA sensing method is proposed. The detection can conveniently be carried out in a 96-well plate within 20 min with a detection limit of 0.18 nM. This method shows high specificity, which can effectively distinguish single-base mismatched DNA from perfectly matched target DNA. The DNA strand displacement regulated catalytic activity of hemin has promising application in the determination of various DNA analytes.

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

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.

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

A coumarin based Schiff base probe for selective fluorescence detection of Al3 + and its application in live cell imaging

NASA Astrophysics Data System (ADS)

Sen, Bhaskar; Sheet, Sanjoy Kumar; Thounaojam, Romita; Jamatia, Ramen; Pal, Amarta Kumar; Aguan, Kripamoy; Khatua, Snehadrinarayan

2017-02-01

A new coumarin based Schiff base compound, CSB-1 has been synthesized to detect metal ion based on the chelation enhanced fluorescence (CHEF). The cation binding properties of CSB-1 was thoroughly examined in UV-vis and fluorescence spectroscopy. In fluorescence spectroscopy the compound showed high selectivity toward Al3 + ion and the Al3 + can be quantified in mixed aqueous buffer solution (MeOH: 0.01 M HEPES Buffer; 9:1; v/v) at pH 7.4 as well as in BSA media. The fluorescence intensity of CSB-1 was enhanced by 24 fold after addition of only five equivalents of Al3 +. The fluorescence titration of CSB-1 with Al3 + in mixed aqueous buffer afforded a binding constant, Ka = (1.06 ± 0.2) × 104 M- 1. The colour change from light yellow to colourless and the appearance of blue fluorescence, which can be observed by the naked eye, provides a real-time method for Al3 + sensing. Further the live cell imaging study indicated that the detection of intracellular Al3 + ions are also readily possible in living cell.

BODIPY-Based Fluorescent Probes for Sensing Protein Surface-Hydrophobicity.

PubMed

Dorh, Nethaniah; Zhu, Shilei; Dhungana, Kamal B; Pati, Ranjit; Luo, Fen-Tair; Liu, Haiying; Tiwari, Ashutosh

2015-12-18

Mapping surface hydrophobic interactions in proteins is key to understanding molecular recognition, biological functions, and is central to many protein misfolding diseases. Herein, we report synthesis and application of new BODIPY-based hydrophobic sensors (HPsensors) that are stable and highly fluorescent for pH values ranging from 7.0 to 9.0. Surface hydrophobic measurements of proteins (BSA, apomyoglobin, and myoglobin) by these HPsensors display much stronger signal compared to 8-anilino-1-naphthalene sulfonic acid (ANS), a commonly used hydrophobic probe; HPsensors show a 10- to 60-fold increase in signal strength for the BSA protein with affinity in the nanomolar range. This suggests that these HPsensors can be used as a sensitive indicator of protein surface hydrophobicity. A first principle approach is used to identify the molecular level mechanism for the substantial increase in the fluorescence signal strength. Our results show that conformational change and increased molecular rigidity of the dye due to its hydrophobic interaction with protein lead to fluorescence enhancement.

Maximizing fluorescence collection efficiency in multiphoton microscopy

PubMed Central

Zinter, Joseph P.; Levene, Michael J.

2011-01-01

Understanding fluorescence propagation through a multiphoton microscope is of critical importance in designing high performance systems capable of deep tissue imaging. Optical models of a scattering tissue sample and the Olympus 20X 0.95NA microscope objective were used to simulate fluorescence propagation as a function of imaging depth for physiologically relevant scattering parameters. The spatio-angular distribution of fluorescence at the objective back aperture derived from these simulations was used to design a simple, maximally efficient post-objective fluorescence collection system. Monte Carlo simulations corroborated by data from experimental tissue phantoms demonstrate collection efficiency improvements of 50% – 90% over conventional, non-optimized fluorescence collection geometries at large imaging depths. Imaging performance was verified by imaging layer V neurons in mouse cortex to a depth of 850 μm. PMID:21934897

Exploring the Dynamics of Cell Processes through Simulations of Fluorescence Microscopy Experiments

PubMed Central

Angiolini, Juan; Plachta, Nicolas; Mocskos, Esteban; Levi, Valeria

2015-01-01

Fluorescence correlation spectroscopy (FCS) methods are powerful tools for unveiling the dynamical organization of cells. For simple cases, such as molecules passively moving in a homogeneous media, FCS analysis yields analytical functions that can be fitted to the experimental data to recover the phenomenological rate parameters. Unfortunately, many dynamical processes in cells do not follow these simple models, and in many instances it is not possible to obtain an analytical function through a theoretical analysis of a more complex model. In such cases, experimental analysis can be combined with Monte Carlo simulations to aid in interpretation of the data. In response to this need, we developed a method called FERNET (Fluorescence Emission Recipes and Numerical routines Toolkit) based on Monte Carlo simulations and the MCell-Blender platform, which was designed to treat the reaction-diffusion problem under realistic scenarios. This method enables us to set complex geometries of the simulation space, distribute molecules among different compartments, and define interspecies reactions with selected kinetic constants, diffusion coefficients, and species brightness. We apply this method to simulate single- and multiple-point FCS, photon-counting histogram analysis, raster image correlation spectroscopy, and two-color fluorescence cross-correlation spectroscopy. We believe that this new program could be very useful for predicting and understanding the output of fluorescence microscopy experiments. PMID:26039162

A label-free, fluorescence based assay for microarray

NASA Astrophysics Data System (ADS)

Niu, Sanjun

DNA chip technology has drawn tremendous attention since it emerged in the mid 90's as a method that expedites gene sequencing by over 100-fold. DNA chip, also called DNA microarray, is a combinatorial technology in which different single-stranded DNA (ssDNA) molecules of known sequences are immobilized at specific spots. The immobilized ssDNA strands are called probes. In application, the chip is exposed to a solution containing ssDNA of unknown sequence, called targets, which are labeled with fluorescent dyes. Due to specific molecular recognition among the base pairs in the DNA, the binding or hybridization occurs only when the probe and target sequences are complementary. The nucleotide sequence of the target is determined by imaging the fluorescence from the spots. The uncertainty of background in signal detection and statistical error in data analysis, primarily due to the error in the DNA amplification process and statistical distribution of the tags in the target DNA, have become the fundamental barriers in bringing the technology into application for clinical diagnostics. Furthermore, the dye and tagging process are expensive, making the cost of DNA chips inhibitive for clinical testing. These limitations and challenges make it difficult to implement DNA chip methods as a diagnostic tool in a pathology laboratory. The objective of this dissertation research is to provide an alternative approach that will address the above challenges. In this research, a label-free assay is designed and studied. Polystyrene (PS), a commonly used polymeric material, serves as the fluorescence agent. Probe ssDNA is covalently immobilized on polystyrene thin film that is supported by a reflecting substrate. When this chip is exposed to excitation light, fluorescence light intensity from PS is detected as the signal. Since the optical constants and conformations of ssDNA and dsDNA (double stranded DNA) are different, the measured fluorescence from PS changes for the same

Flow Cytometric Analysis of Bimolecular Fluorescence Complementation: A High Throughput Quantitative Method to Study Protein-protein Interaction

PubMed Central

Wang, Li; Carnegie, Graeme K.

2013-01-01

Among methods to study protein-protein interaction inside cells, Bimolecular Fluorescence Complementation (BiFC) is relatively simple and sensitive. BiFC is based on the production of fluorescence using two non-fluorescent fragments of a fluorescent protein (Venus, a Yellow Fluorescent Protein variant, is used here). Non-fluorescent Venus fragments (VN and VC) are fused to two interacting proteins (in this case, AKAP-Lbc and PDE4D3), yielding fluorescence due to VN-AKAP-Lbc-VC-PDE4D3 interaction and the formation of a functional fluorescent protein inside cells. BiFC provides information on the subcellular localization of protein complexes and the strength of protein interactions based on fluorescence intensity. However, BiFC analysis using microscopy to quantify the strength of protein-protein interaction is time-consuming and somewhat subjective due to heterogeneity in protein expression and interaction. By coupling flow cytometric analysis with BiFC methodology, the fluorescent BiFC protein-protein interaction signal can be accurately measured for a large quantity of cells in a short time. Here, we demonstrate an application of this methodology to map regions in PDE4D3 that are required for the interaction with AKAP-Lbc. This high throughput methodology can be applied to screening factors that regulate protein-protein interaction. PMID:23979513

Flow cytometric analysis of bimolecular fluorescence complementation: a high throughput quantitative method to study protein-protein interaction.

PubMed

Wang, Li; Carnegie, Graeme K

2013-08-15

Among methods to study protein-protein interaction inside cells, Bimolecular Fluorescence Complementation (BiFC) is relatively simple and sensitive. BiFC is based on the production of fluorescence using two non-fluorescent fragments of a fluorescent protein (Venus, a Yellow Fluorescent Protein variant, is used here). Non-fluorescent Venus fragments (VN and VC) are fused to two interacting proteins (in this case, AKAP-Lbc and PDE4D3), yielding fluorescence due to VN-AKAP-Lbc-VC-PDE4D3 interaction and the formation of a functional fluorescent protein inside cells. BiFC provides information on the subcellular localization of protein complexes and the strength of protein interactions based on fluorescence intensity. However, BiFC analysis using microscopy to quantify the strength of protein-protein interaction is time-consuming and somewhat subjective due to heterogeneity in protein expression and interaction. By coupling flow cytometric analysis with BiFC methodology, the fluorescent BiFC protein-protein interaction signal can be accurately measured for a large quantity of cells in a short time. Here, we demonstrate an application of this methodology to map regions in PDE4D3 that are required for the interaction with AKAP-Lbc. This high throughput methodology can be applied to screening factors that regulate protein-protein interaction.

Selective detection of pyrophosphate anion by a simple Cd(II) based terpyridine complex

NASA Astrophysics Data System (ADS)

Purohit, Aditya Kumar; Ghosh, Biswa Nath; Kar, Pravin Kumar

2018-01-01

A simple ratiometric terpyridine-Cd(ll) complex was synthesized by the treatment of CdCl2 with terpyridine ligand 4‧-(4-N,N‧-dimethylaminophenyl)-2,2‧:6‧,2″-terpyridine. The synthesized complex was found to act as a selective fluorescent chemosensor for pyrophosphate P2O74 - (PPi) over other anions like F-, Cl-, Br-, CO32 -, SO32 -, AcO-, NO2-, and H2PO4-. Furthermore, the receptor probe was also successfully employed in HeLa cell for PPi detection, which indicates this can be used as a chemosensor for cells.

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.

A colorimetric and ratiometric fluorescent chemosensor for fluoride based on proton transfer.

PubMed

Jia, Chuandong; Wu, Biao; Liang, Jianjun; Huang, Xiaojuan; Yang, Xiao-Juan

2010-01-01

N-Phenyl-N'-(3-quinolinyl)urea (1) has been developed as a highly selective colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on a proton transfer mechanism. Evidences for the mechanism were provided by UV-vis and fluorescence titration and especially (1)H and (19)F NMR experiments. The sensor gave the largest ratiometric fluorescent response reported so far (R(max)/R(min) = 2620) to fluoride. Taking H(+) as the "recovering reagent", the sensor can be reversibly "used" and "recovered" for several cycles with only a slight decay of the response ability.

Advanced fluorescence imaging endoscopy using an acousto-optic tuneable filter

NASA Astrophysics Data System (ADS)

Whelan, Maurice P.; Bouhifd, Mounir; Aprahamian, Marc

2004-07-01

Two novel prototype instruments for in vivo fluorescence-based medical diagnostics are described. The devices are based on an acousto-optic tuneable filter (AOTF) and can be easily attached to the eyepiece of most commercially available endoscopes. The instruments developed offer significant advantages over typical fixed-filter or filter-wheel fluorescence imaging systems in terms of flexibility, performance and diagnostic potential. Any filtering center-wavelength in the range from 450 to 700 nm can be rapidly selected either by random access or sequential tuning using simple commands delivered over a PC serial interface. In addition, both filtered and unfiltered light can be imaged to facilitate the direct association of fluorescence signals with specific anatomical sites. To demonstrate the system in vivo, a study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on rats. The aim was to detect extremely low-levels of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response. Results show clearly that the device is effective in diagnosing mild pancreatitis in rats without the necessity of administering PpIX promoting agents such as ALA. Planning of human clinical trials is currently underway to demonstrate its potential as a tool for non-invasive early diagnosis of gastroenterological diseases.

Microwave-assisted synthesis of highly fluorescent nanoparticles of a melamine-based porous covalent organic framework for trace-level detection of nitroaromatic explosives.

PubMed

Zhang, Wang; Qiu, Ling-Guang; Yuan, Yu-Peng; Xie, An-Jian; Shen, Yu-Hua; Zhu, Jun-Fa

2012-06-30

Covalent organic frameworks (COFs) are a new generation of porous materials constructed from light elements linked by strong covalent bonds. Herein we present rapid preparation of highly fluorescent nanoparticles of a new type of COF, i.e. melamine-based porous polymeric network SNW-1, by a microwave-assisted synthesis route. Although the synthesis of SNW-1 has to be carried out at 180°C for 3d under conventional reflux conditions, SNW-1 nanoparticles could be obtained in 6h by using such a microwave-assisted method. The results obtained have clearly demonstrated that microwave-assisted synthesis is a simple yet highly efficient approach to nanoscale COFs or other porous polymeric materials. Remarkably, the as-synthesized SNW-1 nanoparticles exhibit extremely high sensitivity and selectivity, as well as fast response to nitroaromatic explosives such as 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (Tetryl) and picric acid (PA) without interference by common organic solvents, which is due to the nanoscaled size and unique hierarchical porosity of such fluorescence-based sensing material. Copyright © 2012 Elsevier B.V. All rights reserved.

Cyquant cell proliferation assay as a fluorescence-based method for in vitro screening of antimalarial activity.

PubMed

Sriwilaijaroen, Nongluk; Kelly, Jane Xu; Riscoe, Michael; Wilairat, Prapon

2004-12-01

The appearance of drug resistant parasites and the absence of an effective vaccine have resulted in the need for new effective antimalarial drugs. Consequently, a convenient method for in vitro screening of large numbers of antimalarial drug candidates has become apparent. The CyQUANT cell proliferation assay is a highly sensitive fluorescence-based method for quantitation of cell number by measuring the strong fluorescence produced when green GR dye binds to nucleic acids. We have applied the CyQUANT assay method to evaluate the growth of Plasmodium falciparum D6 strain in culture. The GR-nucleic acid fluorescence linearly correlated with percent parasitemia at both 0.75 or 1 percent hematocrit with the same correlation coefficient of r2 = 0.99. The sensitivity of P. falciparum D6 strain to chloroquine and to 3,6-bis-omega-diethylaminoamyloxyxanthone, a novel antimalarial, determined by the CyQUANT assay were comparable to those obtained by the traditional [3H]-ethanolamine assay: IC50 value of chloroquine was 54 nM and 51 nM by the CyQUANT and [3H]-ethanolamine assay, respectively; IC50 value for 3,6-bis-omega-diethylaminoamyloxyxanthone was 254 nM and 223 nM by the CyQUANT and [3H]-ethanolamine assay, respectively. This procedure requires no radioisotope, uses simple equipment, and is an easy and convenient procedure, with no washing and harvesting steps. Moreover, all procedures can be set up continuously and thus, the CyQUANT assay is suitable in automatic high through-put drug screening of antimalarial drugs.

Synthesis and biological imaging of cross-linked fluorescent polymeric nanoparticles with aggregation-induced emission characteristics based on the combination of RAFT polymerization and the Biginelli reaction.

PubMed

Dong, Jiande; Liu, Meiying; Jiang, Ruming; Huang, Hongye; Wan, Qing; Wen, Yuanqing; Tian, Jianwen; Dai, Yanfeng; Zhang, Xiaoyong; Wei, Yen

2018-05-17

Fluorescent probes have long been regarded as tools for imaging living organisms with advantages such as high sensitivity, good designability and multifunctional potential. Many fluorescent probes, especially the probes based on aggregation-induced emission (AIE) dyes, have received increasing attention since the AIE phenomenon was discovered. These AIE dye-based fluorescent probes could elegantly overcome the notorious quenching effect caused by aggregation of conventional organic dyes. However, it is still difficult to directly apply these AIE-active dyes for biomedical applications owing to their hydrophobic nature. Therefore, the development of novel and facile strategies to endow them with water dispersibility is of critical importance. In this work, we exploit an efficient and simple strategy to fabricate an AIE dye-based fluorescent copolymer through the combination of reversible addition-fragmentation chain transfer and the Biginelli reaction. Moreover, the copolymer can self-assemble to fluorescent polymeric nanoparticles (FPNs) in water solution. Hydrophilic poly(PEGMA-co-AEMA) was reacted with the AIE-active dye 4',4‴-(1,2-diphenylethene-1,2-diyl)bis([1,1'-biphenyl]-4-carbaldehyde (CHO-TPE-CHO) to form amphiphilic luminescent polymers using urea as the connection bridge. The successful synthesis of the final products (poly(PEGMA-co-AEMA-TPE) FPNs) was confirmed by various instruments. Furthermore, Transmission electron microscopy (TEM) images manifest that poly(PEGMA-co-AEMA-TPE) copolymers will self-assemble into spherical nanoparticles in aqueous environments with sizes between 100 nm and 200 nm. The cell uptake and bioimaging experiment confirm that poly(PEGMA-co-AEMA-TPE) FPNs have excellent biocompatibility and emit strong green fluorescence in a cellular environment. Thus, poly(PEGMA-co-AEMA-TPE) FPNs are excellent candidates for biomedical applications. Copyright © 2018. Published by Elsevier Inc.

Piezoresistor-equipped fluorescence-based cantilever probe for near-field scanning.

PubMed

Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

2007-08-01

Scanning near-field optical microscopes (SNOMs) with fluorescence-based probes are promising tools for evaluating the optical characteristics of nanoaperture devices used for biological investigations, and this article reports on the development of a microfabricated fluorescence-based SNOM probe with a piezoresistor. The piezoresistor was built into a two-legged root of a 160-microm-long cantilever. To improve the displacement sensitivity of the cantilever, the piezoresistor's doped area was shallowly formed on the cantilever surface. A fluorescent bead, 500 nm in diameter, was attached to the bottom of the cantilever end as a light-intensity-sensitive material in the visible-light range. The surface of the scanned sample was simply detected by the probe's end being displaced by contact with the sample. Measuring displacements piezoresistively is advantageous because it eliminates the noise arising from the use of the optical-lever method and is free of any disturbance in the absorption or the emission spectrum of the fluorescent material at the probe tip. The displacement sensitivity was estimated to be 6.1 x 10(-6) nm(-1), and the minimum measurable displacement was small enough for near-field measurement. This probe enabled clear scanning images of the light field near a 300 x 300 nm(2) aperture to be obtained in the near-field region where the tip-sample distance is much shorter than the light wavelength. This scanning result indicates that the piezoresistive way of tip-sample distance regulation is effective for characterizing nanoaperture optical devices.

Open-source do-it-yourself multi-color fluorescence smartphone microscopy

PubMed Central

Sung, Yulung; Campa, Fernando; Shih, Wei-Chuan

2017-01-01

Fluorescence microscopy is an important technique for cellular and microbiological investigations. Translating this technique onto a smartphone can enable particularly powerful applications such as on-site analysis, on-demand monitoring, and point-of-care diagnostics. Current fluorescence smartphone microscope setups require precise illumination and imaging alignment which altogether limit its broad adoption. We report a multi-color fluorescence smartphone microscope with a single contact lens-like add-on lens and slide-launched total-internal-reflection guided illumination for three common tasks in investigative fluorescence microscopy: autofluorescence, fluorescent stains, and immunofluorescence. The open-source, simple and cost-effective design has the potential for do-it-yourself fluorescence smartphone microscopy. PMID:29188104

Development of a Terbium-Sensitized Fluorescence Method for Analysis of Silibinin.

PubMed

Ershadi, Saba; Jouyban, Abolghasem; Molavi, Ommoleila; Shayanfar, Ali

2017-05-01

Silibinin is a natural flavonoid with potent anticancer properties, as shown in both in vitro and in vivo experiments. Various methods have been used for silibinin analysis. Terbium-sensitized fluorescence methods have been widely used for the determination of drugs in pharmaceutical preparations and biological samples in recent years. The present work is aimed at providing a simple analytical method for the quantitative determination of silibinin in aqueous solutions based on the formation of a fluorescent complex with terbium ion. Terbium concentration, pH, and volume of buffer, the important effective parameters for the determination of silibinin by the proposed method, were optimized using response surface methodology. The fluorescence intensity of silibinin was measured at 545 nm using λex = 334 nm. The developed method was applied for the determination of silibinin in plasma samples after protein precipitation with acetone. Under optimum conditions, the method provided a linear range between 0.10 and 0.50 mg/L, with a coefficient of determination (R2) of 0.997. The LOD and LOQ were 0.034 and 0.112 mg/L, respectively. These results indicate that the developed method is a simple, low-cost, and suitable analytical method for the quantification of silibinin in aqueous solution and plasma samples.

Naphthol-based fluorescent sensors for aluminium ion and application to bioimaging

NASA Astrophysics Data System (ADS)

Liu, Bin; Wang, Pan-feng; Chai, Jie; Hu, Xiang-quan; Gao, Tingting; Chao, Jian-bin; Chen, Ting-gui; Yang, Bin-sheng

2016-11-01

Three naphthol Schiff base-type fluorescent sensors, 1,3-Bis(2-hydroxy-1-naphthylideneamino)propane (L1), 1,3-Bis(1-naphthylideneamino)-2-hydroxypropane (L2) and 1,3-Bis(2-hydroxy-1-naphthylideneamino)-2-hydroxypropane (L3), have been synthesized. Their recognition abilities for Al3 + are studied by fluorescence spectra. Coordination with Al3 + inhibited the Cdbnd N isomerization of Schiff base which intensely increase the fluorescence of L1-L3. Possessing a suitable space coordination structure, L3 is a best selective probe for Al3 + over other metal ions in MeOH-HEPES buffer (3/7, V/V, pH = 6.6, 25 °C, λem = 435 nm). A turn-on ratio over 140-fold is triggered with the addition of 1.0 equiv. Al3 + to L3. The binding constant Ka of L3-Al3 + is found to be 1.01 × 106.5 M- 1 in a 1:1 complex mode. The detection limit for Al3 + is 0.05 μM. Theoretical calculations have also been included in support of the configuration of the L3-Al3 + complex. Importantly, the probe L3 has been successfully used for fluorescence imaging in colon cancer SW480 cells.

Enantioselective Fluorescent Recognition of Chiral Acids by Cyclohexane-1,2-diamine-Based Bisbinaphthyl Molecules

PubMed Central

Li, Zi-Bo; Lin, Jing; Sabat, Michal; Hyacinth, Marilise; Pu, Lin

2008-01-01

The cyclohexane-1,2-diamine-based bisbinaphthyl macrocycles (S)-/(R)-5 and their cyclic and acyclic analogs are synthesized. The interactions of these compounds with various chiral acids are studied. Compounds (S)-/(R)-5 exhibit highly enantioselective fluorescent responses and high fluorescent sensitivity toward α-hydroxycarboxylic acids and N-protected amino acids. Among these interactions, (S)-mandelic acid (10−3 M) led to over 20 fold fluorescence enhancement of (S)-5 (1.0 × 10−5 M in benzene/0.05% DME) at the monomer emission and (S)-hexahydromandelic acid (10−3 M) led to over 80 fold fluorescence enhancement. These results demonstrate that (S)-5 is useful as an enantioselective fluorescent sensor for the recognition of the chiral acids. On the basis of the study of the structures of (S)-5 and the previously reported 1,2-diphenylethylenediamine-based bisbinaphthyl macrocycle (S)-4, the large fluorescence enhancement of (S)-5 with achirality-matched α-hydroxycarboxylic acid is attributed to the formation of a structurally rigidified host-guest complex and the further interaction of this complex with the acid to suppress the photo-induced electron transfer fluorescent quenching caused by the nitrogens in (S)-5. PMID:17530897

Novel and remarkable enhanced-fluorescence system based on gold nanoclusters for detection of tetracycline.

PubMed

Yang, Xiaoming; Zhu, Shanshan; Dou, Yao; Zhuo, Yan; Luo, Yawen; Feng, Yuanjiao

2014-05-01

Tetracycline and Eu(3+), while coexisting, usually appear as a complex by chelating. This complex shows low fluorescence intensity, leading to its limitation of analytical goals. Gold nanoclusters (AuNCs), emerging as novel nano-material, are attracting increasing attentions in multiple fields. Herein, gold nanoclusters first function as a fluorescence-enhanced reagent rather than a conventional fluorescent-probe, and a dramatic enhanced-fluorescence system was built based on Eu(3+)-Tetracycline complex (EuTC) by introducing gold nanoclusters. Simultaneously, three types of gold nanoclusters were employed for exploring various conditions likely affecting the system, which demonstrate that no other gold nanoclusters than DNA-templated gold nanoclusters enormously caused fluorescence-enhancement of EuTC. Moreover, this enhanced-fluorescence system permitted available detection of tetracycline (TC) in a linear range of 0.01-5 μM, with a detection limit of 4 nM at a signal-to-noise ratio of 3. Significantly, the practicality of this method for detection of TC in human urine and milk samples was validated, demonstrating its advantages of simplicity, sensitivity and low cost. Interestingly, this system described here is probably promising for kinds of applications based on its dramatically enhanced-fluorescence. © 2013 Published by Elsevier B.V.

Fluorescence-based methods for detecting caries lesions: systematic review, meta-analysis and sources of heterogeneity.

PubMed

Gimenez, Thais; Braga, Mariana Minatel; Raggio, Daniela Procida; Deery, Chris; Ricketts, David N; Mendes, Fausto Medeiros

2013-01-01

Fluorescence-based methods have been proposed to aid caries lesion detection. Summarizing and analysing findings of studies about fluorescence-based methods could clarify their real benefits. We aimed to perform a comprehensive systematic review and meta-analysis to evaluate the accuracy of fluorescence-based methods in detecting caries lesions. Two independent reviewers searched PubMed, Embase and Scopus through June 2012 to identify papers/articles published. Other sources were checked to identify non-published literature. STUDY ELIGIBILITY CRITERIA, PARTICIPANTS AND DIAGNOSTIC METHODS: The eligibility criteria were studies that: (1) have assessed the accuracy of fluorescence-based methods of detecting caries lesions on occlusal, approximal or smooth surfaces, in both primary or permanent human teeth, in the laboratory or clinical setting; (2) have used a reference standard; and (3) have reported sufficient data relating to the sample size and the accuracy of methods. A diagnostic 2×2 table was extracted from included studies to calculate the pooled sensitivity, specificity and overall accuracy parameters (Diagnostic Odds Ratio and Summary Receiver-Operating curve). The analyses were performed separately for each method and different characteristics of the studies. The quality of the studies and heterogeneity were also evaluated. Seventy five studies met the inclusion criteria from the 434 articles initially identified. The search of the grey or non-published literature did not identify any further studies. In general, the analysis demonstrated that the fluorescence-based method tend to have similar accuracy for all types of teeth, dental surfaces or settings. There was a trend of better performance of fluorescence methods in detecting more advanced caries lesions. We also observed moderate to high heterogeneity and evidenced publication bias. Fluorescence-based devices have similar overall performance; however, better accuracy in detecting more advanced caries

Smartphone Cortex Controlled Real-Time Image Processing and Reprocessing for Concentration Independent LED Induced Fluorescence Detection in Capillary Electrophoresis.

PubMed

Szarka, Mate; Guttman, Andras

2017-10-17

We present the application of a smartphone anatomy based technology in the field of liquid phase bioseparations, particularly in capillary electrophoresis. A simple capillary electrophoresis system was built with LED induced fluorescence detection and a credit card sized minicomputer to prove the concept of real time fluorescent imaging (zone adjustable time-lapse fluorescence image processor) and separation controller. The system was evaluated by analyzing under- and overloaded aminopyrenetrisulfonate (APTS)-labeled oligosaccharide samples. The open source software based image processing tool allowed undistorted signal modulation (reprocessing) if the signal was inappropriate for the actual detection system settings (too low or too high). The novel smart detection tool for fluorescently labeled biomolecules greatly expands dynamic range and enables retrospective correction for injections with unsuitable signal levels without the necessity to repeat the analysis.

Fluorescence-tunable Ag-DNA biosensor with tailored cytotoxicity for live-cell applications

NASA Astrophysics Data System (ADS)

Bossert, Nelli; de Bruin, Donny; Götz, Maria; Bouwmeester, Dirk; Heinrich, Doris

2016-11-01

DNA-stabilized silver clusters (Ag-DNA) show excellent promise as a multi-functional nanoagent for molecular investigations in living cells. The unique properties of these fluorescent nanomaterials allow for intracellular optical sensors with tunable cytotoxicity based on simple modifications of the DNA sequences. Three Ag-DNA nanoagent designs are investigated, exhibiting optical responses to the intracellular environments and sensing-capability of ions, functional inside living cells. Their sequence-dependent fluorescence responses inside living cells include (1) a strong splitting of the fluorescence peak for a DNA hairpin construct, (2) an excitation and emission shift of up to 120 nm for a single-stranded DNA construct, and (3) a sequence robust in fluorescence properties. Additionally, the cytotoxicity of these Ag-DNA constructs is tunable, ranging from highly cytotoxic to biocompatible Ag-DNA, independent of their optical sensing capability. Thus, Ag-DNA represents a versatile live-cell nanoagent addressable towards anti-cancer, patient-specific and anti-bacterial applications.

Evaluation of slide based cytometry (SBC) for concentration measurements of fluorescent dyes in solution

NASA Astrophysics Data System (ADS)

Pierzchalski, Arkadiusz; Marecka, Monika; Müller, Hans-Willy; Bocsi, József; Tárnok, Attila

2009-02-01

Flow cytometers (FCM) are built for particle measurements. In principle, concentration measurement of a homogeneous solution is not possible with FCM due to the lack of a trigger signal. In contrast to FCM slide based cytometry systems could act as tools for the measurement of concentrations using volume defined cell counting chambers. These chambers enable to analyze a well defined volume. Sensovation AG (Stockach, Germany) introduced an automated imaging system that combines imaging with cytometric features analysis. Aim of this study was to apply this imaging system to quantify the fluorescent molecule concentrations. The Lumisens (Sensovation AG) slide-based technology based on fluorescence digital imaging microscopy was used. The instrument is equipped with an inverted microscope, blue and red LEDs, double band-pass filters and a high-resolution cooled 16-bit digital camera. The instrument was focussed on the bottom of 400μm deep 6 chamber slides (IBIDI GmbH, Martinsried, Germany) or flat bottom 96 well plates (Greiner Bio One GmbH, Frickenhausen, Germany). Fluorescent solutions were imaged under 90% pixel saturation in a broad concentration range (FITC: 0.0002-250 μg/ml, methylene blue (MethB): 0.0002-250 μg/ml). Exposition times were recorded. Images were analysed by the iCys (CompuCyte Corp., Cambridge, MA, USA) image analysis software with the phantom contour function. Relative fluorescence intensities were calculated from mean fluorescence intensities per phantom contours divided by the exposition time. Solution concentrations could be distinguished over a broad dynamic range of 3.5 to 5.5 decades log (range FITC: 0.0002-31.25μg/ml, MethB: 0.0076-31.25μg/ml) with a good linear relationship between dye concentration and relative fluorescence intensity. The minimal number of fluorescent molecules per pixel as determined by the mean fluorescence intensity and the molecular weight of the fluorochrome were about 800 molecules FITC and ~2.000 MethB. The

FRET-based small-molecule fluorescent probes: rational design and bioimaging applications.

PubMed

Yuan, Lin; Lin, Weiying; Zheng, Kaibo; Zhu, Sasa

2013-07-16

Fluorescence imaging has emerged as a powerful tool for monitoring biomolecules within the context of living systems with high spatial and temporal resolution. Researchers have constructed a large number of synthetic intensity-based fluorescent probes for bio-imaging. However, intensity-based fluorescent probes have some limitations: variations in probe concentration, probe environment, and excitation intensity may influence the fluorescence intensity measurements. In principle, the use of ratiometric fluorescent probes can alleviate this shortcoming. Förster resonance energy transfer (FRET) is one of the most widely used sensing mechanisms for ratiometric fluorescent probes. However, the development of synthetic FRET probes with favorable photophysical properties that are also suitable for biological imaging applications remains challenging. In this Account, we review the rational design and biological applications of synthetic FRET probes, focusing primarily on studies from our laboratory. To construct useful FRET probes, it is a pre-requisite to develop a FRET platform with favorable photophysical properties. The design criteria of a FRET platform include (1) well-resolved absorption spectra of the donor and acceptor, (2) well-separated emission spectra of the donor and acceptor, (3) donors and acceptors with comparable brightness, (4) rigid linkers, and (5) near-perfect efficiency in energy transfer. With an efficient FRET platform in hand, it is then necessary to modulate the donor-acceptor distance or spectral overlap integral in an analyte-dependent fashion for development of FRET probes. Herein, we emphasize our most recent progress on the development of FRET probes by spectral overlap integral, in particular by changing the molar absorption coefficient of the donor dyes such as rhodamine dyes, which undergo unique changes in the absorption profiles during the ring-opening and -closing processes. Although partial success has been obtained in design of

Utilizing hyaluronic acid as a versatile platform for fluorescence resonance energy transfer-based glucose sensing.

PubMed

Ge, Minghao; Bai, Pengli; Chen, Mingli; Tian, Jingjing; Hu, Jun; Zhi, Xu; Yin, Huancai; Yin, Jian

2018-03-01

Here, we utilized the ultrasonic emulsification technique to generate hyaluronic acid microspheres incorporating a fluorescence-based glucose biosensor. We synthesized a novel lanthanide ion luminophore based on Eu 3+ . Eu sulfosuccinimidyl dextran (Eu-dextran) and Alexa Fluor 647 sulfosuccinimidyl-ConA (Alexa Fluor 647-ConA) were encapsulated in hyaluronic acid hydrogel to generate microspheres. Glucose sensing was carried out using a fluorescence resonance energy transfer (FRET)-based assay principle. A proportional fluorescence intensity increase was found within a 0.5-10-mM glucose concentration range. The glucose-sensing strategy showed an excellent tolerance for potential interferents. Meanwhile, the fluorescent signal of hyaluronic acid microspheres was very stable after testing for 72 h in glucose solution. Overall, hyaluronic acid microspheres encapsulating sensing biomolecules offer a stable and biocompatible biosensor for a variety of applications including cell culture systems, tissue engineering, detection of blood glucose, etc. Graphical abstract We report an ingenious biosensor encapsulated in hyaluronic acid microspheres for monitoring of glucose. Glucose sensing is carried out using a fluorescence resonance energy transfer-based assay principle with a novel lanthanide ions luminophore. The glucose detection system has excellent biocompatibility and stability for monitoring of glucose.

ALA-based fluorescent diagnosis of malignant oral lesions in the presence of bacterial porphyrin formation

NASA Astrophysics Data System (ADS)

Schleier, P.; Berndt, A.; Zinner, K.; Zenk, W.; Dietel, W.; Pfister, W.

2006-02-01

The aminolevulinic acid (5-ALA) -based fluorescence diagnosis has been found to be promising for an early detection and demarcation of superficial oral squamous cell carcinomas (OSCC). This method has previously demonstrated high sensitivity, however this clinical trial showed a specificity of approximately 62 %. This specificity was mainly restricted by tumor detection in the oral cavity in the presence of bacteria. After topical ALA application in the mouth of patients with previously diagnosed OSSC, red fluorescent areas were observed which did not correlate to confirm histological findings. Swabs and plaque samples were taken from 44 patients and cultivated microbiologically. Fluorescence was investigated (OMA-system) from 32 different bacteria strains found naturally in the oral cavity. After ALA incubation, 30 of 32 strains were found to synthesize fluorescent porphyrins, mainly Protoporphyrin IX. Also multiple fluorescent spectra were obtained having peak wavelengths of 636 nm and around 618 nm - 620 nm indicating synthesis of different porphyrins, such as the lipophylic Protoporphyrin IX (PpIX) and hydrophylic porphyrins (water soluble porphyrins, wsp). Of the 32 fluorescent bacterial strains, 18 produced wsp, often in combination with PpIX, and 5 produced solely wsp. These results clarify that ALA-based fluorescence diagnosis without consideration or suppression of bacteria fluorescence may lead to false-positive findings. It is necessary to suppress bacteria fluorescence with suitable antiseptics before starting the procedure. In this study, when specific antiseptic pre-treatment was performed bacterial associated fluorescence was significantly reduced.

Quaternized magnetic nanoparticles-fluorescent polymer system for detection and identification of bacteria.

PubMed

Wan, Yi; Sun, Yan; Qi, Peng; Wang, Peng; Zhang, Dun

2014-05-15

Nanomaterial-based 'chemical nose' sensor with sufficient sensing specificity is a useful analytical tool for the detection of toxicologically important substances in complicated biological systems. A sensor array containing three quaternized magnetic nanoparticles (q-MNPs)-fluorescent polymer systems has been designed to identify and quantify bacteria. The bacterial cell membranes disrupt the q-MNP-fluorescent polymer, generating unique fluorescence response array. The response intensity of the array is dependent on the level of displacement determined by the relative q-MNP-fluorescent polymer binding strength and bacteria cells-MNP interaction. These characteristic responses show a highly repeatable bacteria cells and can be differentiated by linear discriminant analysis (LDA). Based on the array response matrix from LDA, our approach has been used to measure bacteria with an accuracy of 87.5% for 10(7) cfu mL(-1) within 20 min. Combined with UV-vis measurement, the method can be successfully performed to identify and detect eight different pathogen samples with an accuracy of 96.8%. The measurement system has a potential for further applications and provides a facile and simple method for the rapid analysis of protein, DNA, and pathogens. Copyright © 2013 Elsevier B.V. All rights reserved.

The photoluminescence of a fluorescent lamp: didactic experiments on the exponential decay

NASA Astrophysics Data System (ADS)

Onorato, Pasquale; Gratton, Luigi; Malgieri, Massimiliano; Oss, Stefano

2017-01-01

The lifetimes of the photoluminescent compounds contained in the coating of fluorescent compact lamps are usually measured using specialised instruments, including pulsed lasers and/or spectrofluorometers. Here we discuss how some low cost apparatuses, based on the use of either sensors for the educational lab or commercial digital photo cameras, can be employed to the same aim. The experiments do not require that luminescent phosphors are hazardously extracted from the compact fluorescent lamp, that also contains mercury. We obtain lifetime measurements for specific fluorescent elements of the bulb coating, in good agreement with the known values. We also address the physical mechanisms on which fluorescence lamps are based in a simplified way, suitable for undergraduate students; and we discuss in detail the physics of the lamp switch-off by analysing the time dependent spectrum, measured through a commercial fiber-optic spectrometer. Since the experiment is not hazardous in any way, requires a simple setup up with instruments which are commonly found in educational labs, and focuses on the typical features of the exponential decay, it is suitable for being performed in the undergraduate laboratory.

Highly Fluorescent Noble Metal Quantum Dots

PubMed Central

Zheng, Jie; Nicovich, Philip R.; Dickson, Robert M.

2009-01-01

Highly fluorescent, water-soluble, few-atom noble metal quantum dots have been created that behave as multi-electron artificial atoms with discrete, size-tunable electronic transitions throughout the visible and near IR. These “molecular metals” exhibit highly polarizable transitions and scale in size according to the simple relation, Efermi/N1/3, predicted by the free electron model of metallic behavior. This simple scaling indicates that fluorescence arises from intraband transitions of free electrons and that these conduction electron transitions are the low number limit of the plasmon – the collective dipole oscillations occurring when a continuous density of states is reached. Providing the “missing link” between atomic and nanoparticle behavior in noble metals, these emissive, water-soluble Au nanoclusters open new opportunities for biological labels, energy transfer pairs, and light emitting sources in nanoscale optoelectronics. PMID:17105412

Development of fluorescence based handheld imaging devices for food safety inspection

NASA Astrophysics Data System (ADS)

Lee, Hoyoung; Kim, Moon S.; Chao, Kuanglin; Lefcourt, Alan M.; Chan, Diane E.

2013-05-01

For sanitation inspection in food processing environment, fluorescence imaging can be a very useful method because many organic materials reveal unique fluorescence emissions when excited by UV or violet radiation. Although some fluorescence-based automated inspection instrumentation has been developed for food products, there remains a need for devices that can assist on-site inspectors performing visual sanitation inspection of the surfaces of food processing/handling equipment. This paper reports the development of an inexpensive handheld imaging device designed to visualize fluorescence emissions and intended to help detect the presence of fecal contaminants, organic residues, and bacterial biofilms at multispectral fluorescence emission bands. The device consists of a miniature camera, multispectral (interference) filters, and high power LED illumination. With WiFi communication, live inspection images from the device can be displayed on smartphone or tablet devices. This imaging device could be a useful tool for assessing the effectiveness of sanitation procedures and for helping processors to minimize food safety risks or determine potential problem areas. This paper presents the design and development including evaluation and optimization of the hardware components of the imaging devices.

Photobleaching correction in fluorescence microscopy images

NASA Astrophysics Data System (ADS)

Vicente, Nathalie B.; Diaz Zamboni, Javier E.; Adur, Javier F.; Paravani, Enrique V.; Casco, Víctor H.

2007-11-01

Fluorophores are used to detect molecular expression by highly specific antigen-antibody reactions in fluorescence microscopy techniques. A portion of the fluorophore emits fluorescence when irradiated with electromagnetic waves of particular wavelengths, enabling its detection. Photobleaching irreversibly destroys fluorophores stimulated by radiation within the excitation spectrum, thus eliminating potentially useful information. Since this process may not be completely prevented, techniques have been developed to slow it down or to correct resulting alterations (mainly, the decrease in fluorescent signal). In the present work, the correction by photobleaching curve was studied using E-cadherin (a cell-cell adhesion molecule) expression in Bufo arenarum embryos. Significant improvements were observed when applying this simple, inexpensive and fast technique.

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.

Micromotor-based on-off fluorescence detection of sarin and soman simulants.

PubMed

Singh, Virendra V; Kaufmann, Kevin; Orozco, Jahir; Li, Jinxing; Galarnyk, Michael; Arya, Gaurav; Wang, Joseph

2015-06-30

Self-propelled micromotor-based fluorescent "On-Off" detection of nerve agents is described. The motion-based assay utilizes Si/Pt Janus micromotors coated with fluoresceinamine toward real-time "on-the-fly" field detection of sarin and soman simulants.

Widely accessible method for superresolution fluorescence imaging of living systems

PubMed Central

Dedecker, Peter; Mo, Gary C. H.; Dertinger, Thomas; Zhang, Jin

2012-01-01

Superresolution fluorescence microscopy overcomes the diffraction resolution barrier and allows the molecular intricacies of life to be revealed with greatly enhanced detail. However, many current superresolution techniques still face limitations and their implementation is typically associated with a steep learning curve. Patterned illumination-based superresolution techniques [e.g., stimulated emission depletion (STED), reversible optically-linear fluorescence transitions (RESOLFT), and saturated structured illumination microscopy (SSIM)] require specialized equipment, whereas single-molecule–based approaches [e.g., stochastic optical reconstruction microscopy (STORM), photo-activation localization microscopy (PALM), and fluorescence-PALM (F-PALM)] involve repetitive single-molecule localization, which requires its own set of expertise and is also temporally demanding. Here we present a superresolution fluorescence imaging method, photochromic stochastic optical fluctuation imaging (pcSOFI). In this method, irradiating a reversibly photoswitching fluorescent protein at an appropriate wavelength produces robust single-molecule intensity fluctuations, from which a superresolution picture can be extracted by a statistical analysis of the fluctuations in each pixel as a function of time, as previously demonstrated in SOFI. This method, which uses off-the-shelf equipment, genetically encodable labels, and simple and rapid data acquisition, is capable of providing two- to threefold-enhanced spatial resolution, significant background rejection, markedly improved contrast, and favorable temporal resolution in living cells. Furthermore, both 3D and multicolor imaging are readily achievable. Because of its ease of use and high performance, we anticipate that pcSOFI will prove an attractive approach for superresolution imaging. PMID:22711840

Thermal precipitation fluorescence assay for protein stability screening.

PubMed

Fan, Junping; Huang, Bo; Wang, Xianping; Zhang, Xuejun C

2011-09-01

A simple and reliable method of protein stability assessment is desirable for high throughput expression screening of recombinant proteins. Here we described an assay termed thermal precipitation fluorescence (TPF) which can be used to compare thermal stabilities of recombinant protein samples directly from cell lysate supernatants. In this assay, target membrane proteins are expressed as recombinant fusions with a green fluorescence protein tag and solubilized with detergent, and the fluorescence signals are used to report the quantity of the fusion proteins in the soluble fraction of the cell lysate. After applying a heat shock, insoluble protein aggregates are removed by centrifugation. Subsequently, the amount of remaining protein in the supernatant is quantified by in-gel fluorescence analysis and compared to samples without a heat shock treatment. Over 60 recombinant membrane proteins from Escherichia coli were subject to this screening in the presence and absence of a few commonly used detergents, and the results were analyzed. Because no sophisticated protein purification is required, this TPF technique is suitable to high throughput expression screening of recombinant membrane proteins as well as soluble ones and can be used to prioritize target proteins based on their thermal stabilities for subsequent large scale expression and structural studies. Copyright © 2011 Elsevier Inc. All rights reserved.

Rapid High-Throughput Assessment of Aerobic Bacteria in Complex Samples by Fluorescence-Based Oxygen Respirometry

PubMed Central

O'Mahony, Fiach C.; Papkovsky, Dmitri B.

2006-01-01

A simple method has been developed for the analysis of aerobic bacteria in complex samples such as broth and food homogenates. It employs commercial phosphorescent oxygen-sensitive probes to monitor oxygen consumption of samples containing bacteria using standard microtiter plates and fluorescence plate readers. As bacteria grow in aqueous medium, at certain points they begin to deplete dissolved oxygen, which is seen as an increase in probe fluorescence above baseline signal. The time required to reach threshold signal is used to either enumerate bacteria based on a predetermined calibration or to assess the effects of various effectors on the growth of test bacteria by comparison with an untreated control. This method allows for the sensitive (down to a single cell), rapid (0.5 to 12 h) enumeration of aerobic bacteria without the need to conduct lengthy (48 to 72 h) and tedious colony counts on agar plates. It also allows for screening a wide range of chemical and environmental samples for their toxicity. These assays have been validated with different bacteria, including Escherichia coli, Micrococcus luteus, and Pseudomonas fluorescens, with the enumeration of total viable counts in broth and industrial food samples (packaged ham, chicken, and mince meat), and comparison with established agar plating and optical-density-at-600-nm assays has been given. PMID:16461677

Enhancing in vivo tumor boundary delineation with structured illumination fluorescence molecular imaging and spatial gradient mapping

NASA Astrophysics Data System (ADS)

Sun, Jessica; Miller, Jessica P.; Hathi, Deep; Zhou, Haiying; Achilefu, Samuel; Shokeen, Monica; Akers, Walter J.

2016-08-01

Fluorescence imaging, in combination with tumor-avid near-infrared (NIR) fluorescent molecular probes, provides high specificity and sensitivity for cancer detection in preclinical animal models, and more recently, assistance during oncologic surgery. However, conventional camera-based fluorescence imaging techniques are heavily surface-weighted such that surface reflection from skin or other nontumor tissue and nonspecific fluorescence signals dominate, obscuring true cancer-specific signals and blurring tumor boundaries. To address this challenge, we applied structured illumination fluorescence molecular imaging (SIFMI) in live animals for automated subtraction of nonspecific surface signals to better delineate accumulation of an NIR fluorescent probe targeting α4β1 integrin in mice bearing subcutaneous plasma cell xenografts. SIFMI demonstrated a fivefold improvement in tumor-to-background contrast when compared with other full-field fluorescence imaging methods and required significantly reduced scanning time compared with diffuse optical spectroscopy imaging. Furthermore, the spatial gradient mapping enhanced highlighting of tumor boundaries. Through the relatively simple hardware and software modifications described, SIFMI can be integrated with clinical fluorescence imaging systems, enhancing intraoperative tumor boundary delineation from the uninvolved tissue.

Copper nanoclusters as probes for turn-on fluorescence sensing of L-lysine.

PubMed

Zhang, Mingming; Qiao, Juan; Zhang, Shufeng; Qi, Li

2018-05-15

Herein, a unique protocol based on copper nanoclusters (CuNCs) probe for turn-on fluorescence sensing of L-lysine was developed. The fluorescent CuNCs with ovalbumin as the stabilizer was prepared by a simple, one-step and green method. When 370 nm was used as the excitation wavelength, the resultant CuNCs exhibited a pale blue fluorescence with the maximum emission at 440 nm. Interestingly, existence of L-lysine evoked the obvious fluorescence intensity increase of CuNCs. The detection limit of the proposed method for L-lysine was 5.5 μM, with a good linear range from 10.0 μM to 1.0 mM (r 2 = 0.999). Moreover, the possible mechanism for enhanced fluorescence intensity of CuNCs by addition of L-lysine was explored and discussed briefly. Further, the as-prepared fluorescent CuNCs was successfully applied in detection of L-lysine in urine. Our results demonstrated that L-lysine could be monitored by the probe, providing new path for construction of CuNCs as fluorescent probes and showing great potential in quantification of L-lysine in real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

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 novel acidic pH fluorescent probe based on a benzothiazole derivative

NASA Astrophysics Data System (ADS)

Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

2017-04-01

A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H+ in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1 min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

Fluorescence-based Western blotting for quantitation of protein biomarkers in clinical samples.

PubMed

Zellner, Maria; Babeluk, Rita; Diestinger, Michael; Pirchegger, Petra; Skeledzic, Senada; Oehler, Rudolf

2008-09-01

Since most high throughput techniques used in biomarker discovery are very time and cost intensive, highly specific and quantitative analytical alternative application methods are needed for the routine analysis. Conventional Western blotting allows detection of specific proteins to the level of single isotypes while its quantitative accuracy is rather limited. We report a novel and improved quantitative Western blotting method. The use of fluorescently labelled secondary antibodies strongly extends the dynamic range of the quantitation and improves the correlation with the protein amount (r=0.997). By an additional fluorescent staining of all proteins immediately after their transfer to the blot membrane, it is possible to visualise simultaneously the antibody binding and the total protein profile. This allows for an accurate correction for protein load. Applying this normalisation it could be demonstrated that fluorescence-based Western blotting is able to reproduce a quantitative analysis of two specific proteins in blood platelet samples from 44 subjects with different diseases as initially conducted by 2D-DIGE. These results show that the proposed fluorescence-based Western blotting is an adequate application technique for biomarker quantitation and suggest possibilities of employment that go far beyond.

Upconversion fluorescent strip sensor for rapid determination of Vibrio anguillarum

NASA Astrophysics Data System (ADS)

Zhao, Peng; Wu, Yuanyuan; Zhu, Yihua; Yang, Xiaoling; Jiang, Xin; Xiao, Jingfan; Zhang, Yuanxing; Li, Chunzhong

2014-03-01

Here, we report a simple and ultrasensitive upconversion fluorescent strip sensor based on NaYF4:Yb,Er nanoparticles (NPs) and the lateral flow immunochromatographic assay (LFIA). Carboxyl-modified β-NaYF4:Yb,Er NPs were successfully synthesized by a facile one-pot solvothermal approach, upon further coupling with monoclonal antibody, the resultant UCNPs-antibody conjugates probes were used in LFIA and served as signal vehicles for the fluorescent reporters. V. anguillarum was used as a model analyte to demonstrate the use of this strip sensor. The limit of the detection for the fluorescent strip was determined as 102 CFU mL-1, which is 100 times lower than those displayed by enzyme-linked immunosorbent assays, while the time needed for the detection was only 15 min. Furthermore, no cross-reaction with other eight pathogens was found, indicating the good specificity of the strip. This developed LFIA would offer the potential as a useful tool for the quantification of pathogens analysis in the future.

The impact of fluorescent dyes on the performances of polystyrene-based plastic scintillators

NASA Astrophysics Data System (ADS)

Zhu, Jun; Deng, Cheng; Jiang, Huimin; Zheng, Zhanlong; Gong, Rui; Bi, Yutie; Zhang, Lin; Lin, Runxiong

2016-11-01

To investigate the influence of both the first luminescent additive and the wavelength-shifter on the performance of plastic scintillator, a series of polystyrene-based scintillator had been prepared by thermal polymerization. Three first luminescent additives (PPO, p-TP and b-PBD) and four wavelength-shifters (POPOP, Bis-MSB, Me-MSB and DPA) were added to the scintillators respectively. The comparison results showed that PPO and POPOP were the most adequate fluorescent dyes for the polystyrene-based plastic scintillator. Moreover, with the increase of the concentration of PPO and POPOP, the fluorescence intensity and light yield were increased firstly and then decreased. The plastic scintillator containing 2% PPO and 0.02% POPOP had the highest fluorescence intensity and light yield.

A cell-surface-anchored ratiometric fluorescent probe for extracellular pH sensing.

PubMed

Ke, Guoliang; Zhu, Zhi; Wang, Wei; Zou, Yuan; Guan, Zhichao; Jia, Shasha; Zhang, Huimin; Wu, Xuemeng; Yang, Chaoyong James

2014-09-10

Accurate sensing of the extracellular pH is a very important yet challenging task in biological and clinical applications. This paper describes the development of an amphiphilic lipid-DNA molecule as a simple yet useful cell-surface-anchored ratiometric fluorescent probe for extracellular pH sensing. The lipid-DNA probe, which consists of a hydrophobic diacyllipid tail and a hydrophilic DNA strand, is modified with two fluorescent dyes; one is pH-sensitive as pH indicator and the other is pH-insensitive as an internal reference. The lipid-DNA probe showed sensitive and reversible response to pH change in the range of 6.0-8.0, which is suitable for most extracellular studies. In addition, based on simple hydrophobic interactions with the cell membrane, the lipid-DNA probe can be easily anchored on the cell surface with negligible cytotoxicity, excellent stability, and unique ratiometric readout, thus ensuring its accurate sensing of extracellular pH. Finally, this lipid-DNA-based ratiometric pH indicator was successfully used for extracellular pH sensing of cells in 3D culture environment, demonstrating the potential applications of the sensor in biological and medical studies.

Simple and sensitive determination of five quinolones in food by liquid chromatography with fluorescence detection.

PubMed

Ramos, Macarena; Aranda, Angela; Garcia, Elena; Reuvers, Thea; Hooghuis, Henny

2003-06-15

A simple and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of five different quinolones: enrofloxacin, ciprofloxacin, sarafloxacin, oxolinic acid and flumequine in pork and salmon muscle. The method includes one extraction and clean-up step for the five quinolones together which are detected in two separated HPLC runs by means of their fluorescence. The proposed analytical method involves homogenizing of the tissue sample with 0.05 M phosphate buffer, pH 7.4 and clean-up by Discovery DS-18 cartridges. For chromatographic separation a Symmetry C(18) column is used in two different runs: (1) ciprofloxacin, enrofloxacin and sarafloxacin with acetonitrile-0.02 M phosphate buffer pH 3.0 (18:82) as mobile phase and the detector at excitation wavelength: 280 nm and emission wavelength 450 nm; and (2) oxolinic acid and flumequine with acetonitrile-0.02 M phosphate buffer pH 3.0 (34:66) as mobile phase and excitation wavelength: 312 nm and emission wavelength: 366 nm. Detection limit was as low as 5 ng g(-1), except for sarafloxacin which had a limit of 10 ng g(-1). Standard curves using blank muscle tissues spiked at different levels showed a good linear correlation coefficient, r(2) higher than 0.999 for all quinolones.

Chromophore Isomer Stabilization Is Critical to the Efficient Fluorescence of Cyan Fluorescent Proteins.

PubMed

Gotthard, Guillaume; von Stetten, David; Clavel, Damien; Noirclerc-Savoye, Marjolaine; Royant, Antoine

2017-12-12

ECFP, the first usable cyan fluorescent protein (CFP), was obtained by adapting the tyrosine-based chromophore environment in green fluorescent protein to that of a tryptophan-based one. This first-generation CFP was superseded by the popular Cerulean, CyPet, and SCFP3A that were engineered by rational and random mutagenesis, yet the latter CFPs still exhibit suboptimal properties of pH sensitivity and reversible photobleaching behavior. These flaws were serendipitously corrected in the third-generation CFP mTurquoise and its successors without an obvious rationale. We show here that the evolution process had unexpectedly remodeled the chromophore environment in second-generation CFPs so they would accommodate a different isomer, whose formation is favored by acidic pH or light irradiation and which emits fluorescence much less efficiently. Our results illustrate how fluorescent protein engineering based solely on fluorescence efficiency optimization may affect other photophysical or physicochemical parameters and provide novel insights into the rational evolution of fluorescent proteins with a tryptophan-based chromophore.

The Mechanisms and Biomedical Applications of an NIR BODIPY-Based Switchable Fluorescent Probe

PubMed Central

Cheng, Bingbing; Bandi, Venugopal; Yu, Shuai; D’Souza, Francis; Nguyen, Kytai T.; Hong, Yi; Tang, Liping; Yuan, Baohong

2017-01-01

Highly environment-sensitive fluorophores have been desired for many biomedical applications. Because of the noninvasive operation, high sensitivity, and high specificity to the microenvironment change, they can be used as excellent probes for fluorescence sensing/imaging, cell tracking/imaging, molecular imaging for cancer, and so on (i.e., polarity, viscosity, temperature, or pH measurement). In this work, investigations of the switching mechanism of a recently reported near-infrared environment-sensitive fluorophore, ADP(CA)2, were conducted. Besides, multiple potential biomedical applications of this switchable fluorescent probe have been demonstrated, including wash-free live-cell fluorescence imaging, in vivo tissue fluorescence imaging, temperature sensing, and ultrasound-switchable fluorescence (USF) imaging. The fluorescence of the ADP(CA)2 is extremely sensitive to the microenvironment, especially polarity and viscosity. Our investigations showed that the fluorescence of ADP(CA)2 can be switched on by low polarity, high viscosity, or the presence of protein and surfactants. In wash-free live-cell imaging, the fluorescence of ADP(CA)2 inside cells was found much brighter than the dye-containing medium and was retained for at least two days. In all of the fluorescence imaging applications conducted in this study, high target-to-noise (>5-fold) was achieved. In addition, a high temperature sensitivity (73-fold per Celsius degree) of ADP(CA)2-based temperature probes was found in temperature sensing. PMID:28208666

Widespread bone-based fluorescence in chameleons.

PubMed

Prötzel, David; Heß, Martin; Scherz, Mark D; Schwager, Martina; Padje, Anouk Van't; Glaw, Frank

2018-01-15

Fluorescence is widespread in marine organisms but uncommon in terrestrial tetrapods. We here show that many chameleon species have bony tubercles protruding from the skull that are visible through their scales, and fluoresce under UV light. Tubercles arising from bones of the skull displace all dermal layers other than a thin, transparent layer of epidermis, creating a 'window' onto the bone. In the genus Calumma, the number of these tubercles is sexually dimorphic in most species, suggesting a signalling role, and also strongly reflects species groups, indicating systematic value of these features. Co-option of the known fluorescent properties of bone has never before been shown, yet it is widespread in the chameleons of Madagascar and some African chameleon genera, particularly in those genera living in forested, humid habitats known to have a higher relative component of ambient UV light. The fluorescence emits with a maximum at around 430 nm in blue colour which contrasts well to the green and brown background reflectance of forest habitats. This discovery opens new avenues in the study of signalling among chameleons and sexual selection factors driving ornamentation.

RNA-ID, a highly sensitive and robust method to identify cis-regulatory sequences using superfolder GFP and a fluorescence-based assay.

PubMed

Dean, Kimberly M; Grayhack, Elizabeth J

2012-12-01

We have developed a robust and sensitive method, called RNA-ID, to screen for cis-regulatory sequences in RNA using fluorescence-activated cell sorting (FACS) of yeast cells bearing a reporter in which expression of both superfolder green fluorescent protein (GFP) and yeast codon-optimized mCherry red fluorescent protein (RFP) is driven by the bidirectional GAL1,10 promoter. This method recapitulates previously reported progressive inhibition of translation mediated by increasing numbers of CGA codon pairs, and restoration of expression by introduction of a tRNA with an anticodon that base pairs exactly with the CGA codon. This method also reproduces effects of paromomycin and context on stop codon read-through. Five key features of this method contribute to its effectiveness as a selection for regulatory sequences: The system exhibits greater than a 250-fold dynamic range, a quantitative and dose-dependent response to known inhibitory sequences, exquisite resolution that allows nearly complete physical separation of distinct populations, and a reproducible signal between different cells transformed with the identical reporter, all of which are coupled with simple methods involving ligation-independent cloning, to create large libraries. Moreover, we provide evidence that there are sequences within a 9-nt library that cause reduced GFP fluorescence, suggesting that there are novel cis-regulatory sequences to be found even in this short sequence space. This method is widely applicable to the study of both RNA-mediated and codon-mediated effects on expression.

Instrumentation and methodology for quantifying GFP fluorescence in intact plant organs

NASA Technical Reports Server (NTRS)

Millwood, R. J.; Halfhill, M. D.; Harkins, D.; Russotti, R.; Stewart, C. N. Jr

2003-01-01

The General Fluorescence Plant Meter (GFP-Meter) is a portable spectrofluorometer that utilizes a fiber-optic cable and a leaf clip to gather spectrofluorescence data. In contrast to traditional analytical systems, this instrument allows for the rapid detection and fluorescence measurement of proteins under field conditions with no damage to plant tissue. Here we discuss the methodology of gathering and standardizing spectrofluorescence data from tobacco and canola plants expressing GFP. Furthermore, we demonstrate the accuracy and effectiveness of the GFP-Meter. We first compared GFP fluorescence measurements taken by the GFP-Meter to those taken by a standard laboratory-based spectrofluorometer, the FluoroMax-2. Spectrofluorescence measurements were taken from the same location on intact leaves. When these measurements were tested by simple linear regression analysis, we found that there was a positive functional relationship between instruments. Finally, to exhibit that the GFP-Meter recorded accurate measurements over a span of time, we completed a time-course analysis of GFP fluorescence measurements. We found that only initial measurements were accurate; however, subsequent measurements could be used for qualitative purposes.

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.

Multispectral Fluorescence Imaging During Robot-assisted Laparoscopic Sentinel Node Biopsy: A First Step Towards a Fluorescence-based Anatomic Roadmap.

PubMed

van den Berg, Nynke S; Buckle, Tessa; KleinJan, Gijs H; van der Poel, Henk G; van Leeuwen, Fijs W B

2017-07-01

During (robot-assisted) sentinel node (SN) biopsy procedures, intraoperative fluorescence imaging can be used to enhance radioguided SN excision. For this combined pre- and intraoperative SN identification was realized using the hybrid SN tracer, indocyanine green- 99m Tc-nanocolloid. Combining this dedicated SN tracer with a lymphangiographic tracer such as fluorescein may further enhance the accuracy of SN biopsy. Clinical evaluation of a multispectral fluorescence guided surgery approach using the dedicated SN tracer ICG- 99m Tc-nanocolloid, the lymphangiographic tracer fluorescein, and a commercially available fluorescence laparoscope. Pilot study in ten patients with prostate cancer. Following ICG- 99m Tc-nanocolloid administration and preoperative lymphoscintigraphy and single-photon emission computed tomograpy imaging, the number and location of SNs were determined. Fluorescein was injected intraprostatically immediately after the patient was anesthetized. A multispectral fluorescence laparoscope was used intraoperatively to identify both fluorescent signatures. Multispectral fluorescence imaging during robot-assisted radical prostatectomy with extended pelvic lymph node dissection and SN biopsy. (1) Number and location of preoperatively identified SNs. (2) Number and location of SNs intraoperatively identified via ICG- 99m Tc-nanocolloid imaging. (3) Rate of intraoperative lymphatic duct identification via fluorescein imaging. (4) Tumor status of excised (sentinel) lymph node(s). (5) Postoperative complications and follow-up. Near-infrared fluorescence imaging of ICG- 99m Tc-nanocolloid visualized 85.3% of the SNs. In 8/10 patients, fluorescein imaging allowed bright and accurate identification of lymphatic ducts, although higher background staining and tracer washout were observed. The main limitation is the small patient population. Our findings indicate that a lymphangiographic tracer can provide additional information during SN biopsy based on ICG- 99m

Impact of background on color, transmittance, and fluorescence of leucite based ceramics.

PubMed

Rafael, Caroline Freitas; Güth, Jan-Frederik; Kauling, Ana Elisa Colle; Cesar, Paulo Francisco; Volpato, Claudia Angelo Mazieiro; Liebermann, Anja

2017-07-26

This study evaluated the impact of tooth shade on differences in color (∆E), lightness (∆L), chromaticity coordinates a*/b* (∆a and ∆b), transmittance and the degree of fluorescence of CAD/CAM leucite based ceramic (LBC). Ten disks were fabricated of LBC; Empress CAD, A2, thickness of 1.5 mm and eight disks of resin-nano-ceramic (RNC; Lava Ultimate) in different colors to simulate variations in substrate shade. The associations of LBC disks with different color substrates were analyzed with a spectrophotometer; ∆E, ∆L*, ∆a*, ∆b*, and transmittance were measured and calculated. Fluorescence was evaluated with a fluorescence system (Fluorescence System, Biopdi). All substrate shades influenced the optical properties of LBC, with regard to color, luminosity, coordinate a* and b*, transmittance, and fluorescence (p<0.001). Substrate colors with high saturation (A3.5 and C2) presented highest impact, whereas colors with lowest saturations (BL, B1) showed less impact. Substrate color influenced the optical properties of ceramic restorations.

Fluorescent staining for leukocyte chemotaxis. Eosinophil-specific fluorescence with aniline blue.

PubMed

McCrone, E L; Lucey, D R; Weller, P F

1988-11-10

To overcome problems associated with the quantitation of human eosinophil chemotaxis in micropore filters, we have developed a fluorescent method of specifically staining eosinophils in chemotactic filters. A neutral solution of aniline blue yielded bright green fluorescent staining of the cytoplasmic granules of eosinophils. Other leukocytes and contaminating neutrophils potentially present with eosinophils did not fluoresce with aniline blue. The fluorescent staining eosinophils within filters provided bright, non-fading images that facilitated visual microscopic counting and were of sufficiently high contrast, unlike those with conventional eosinophil stains, to allow image analyzer based enumeration of eosinophil chemotactic responses at levels through the filters. Although not cell type-specific, congo red and ethidium bromide also provided high contrast, fluorescent images of all leukocyte types within chemotactic filters. Fluorescent staining with aniline blue constitutes a rapid, stable and eosinophil-specific stain that facilitates the visual or image analyzer-based quantitation of eosinophil chemotaxis.

In vivo fluorescent detection of Fe-S clusters coordinated by human GRX2.

PubMed

Hoff, Kevin G; Culler, Stephanie J; Nguyen, Peter Q; McGuire, Ryan M; Silberg, Jonathan J; Smolke, Christina D

2009-12-24

A major challenge to studying Fe-S cluster biosynthesis in higher eukaryotes is the lack of simple tools for imaging metallocluster binding to proteins. We describe the first fluorescent approach for in vivo detection of 2Fe2S clusters that is based upon the complementation of Venus fluorescent protein fragments via human glutaredoxin 2 (GRX2) coordination of a 2Fe2S cluster. We show that Escherichia coli and mammalian cells expressing Venus fragments fused to GRX2 exhibit greater fluorescence than cells expressing fragments fused to a C37A mutant that cannot coordinate a metallocluster. In addition, we find that maximal fluorescence in the cytosol of mammalian cells requires the iron-sulfur cluster assembly proteins ISCU and NFS1. These findings provide evidence that glutaredoxins can dimerize within mammalian cells through coordination of a 2Fe2S cluster as observed with purified recombinant proteins. Copyright 2009 Elsevier Ltd. All rights reserved.

Analysis of pre-service physics teacher skills designing simple physics experiments based technology

NASA Astrophysics Data System (ADS)

Susilawati; Huda, C.; Kurniawan, W.; Masturi; Khoiri, N.

2018-03-01

Pre-service physics teacher skill in designing simple experiment set is very important in adding understanding of student concept and practicing scientific skill in laboratory. This study describes the skills of physics students in designing simple experiments based technologicall. The experimental design stages include simple tool design and sensor modification. The research method used is descriptive method with the number of research samples 25 students and 5 variations of simple physics experimental design. Based on the results of interviews and observations obtained the results of pre-service physics teacher skill analysis in designing simple experimental physics charged technology is good. Based on observation result, pre-service physics teacher skill in designing simple experiment is good while modification and sensor application are still not good. This suggests that pre-service physics teacher still need a lot of practice and do experiments in designing physics experiments using sensor modifications. Based on the interview result, it is found that students have high enough motivation to perform laboratory activities actively and students have high curiosity to be skilled at making simple practicum tool for physics experiment.

Direct fluorescence anisotropy assay for cocaine using tetramethylrhodamine-labeled aptamer.

PubMed

Liu, Yingxiong; Zhao, Qiang

2017-06-01

Development of simple, sensitive, and rapid method for cocaine detection is important in medicine and drug abuse monitoring. Taking advantage of fluorescence anisotropy and aptamer, this study reports a direct fluorescence anisotropy (FA) assay for cocaine by employing an aptamer probe with tetramethylrhodamine (TMR) labeled on a specific position. The binding of cocaine and the aptamer causes a structure change of the TMR-labeled aptamer, leading to changes of the interaction between labeled TMR and adjacent G bases in aptamer sequence, so FA of TMR varies with increasing of cocaine. After screening different labeling positions of the aptamer, including thymine (T) bases and terminals of the aptamer, we obtained a favorable aptamer probe with TMR labeled on the 25th base T in the sequence, which exhibited sensitive and significant FA-decreasing responses upon cocaine. Under optimized assay conditions, this TMR-labeled aptamer allowed for direct FA detection of cocaine as low as 5 μM. The maximum FA change reached about 0.086. This FA method also enabled the detection of cocaine spiked in diluted serum and urine samples, showing potential for applications. Graphical Abstract The binding of cocaine to the TMR-labeled aptamer causes conformation change and alteration of the intramolecular interaction between TMR and bases of aptamer, leading to variance of fluorescence anisotropy (FA) of TMR, so direct FA analyis of cocaine is achieved.

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.

In Situ Live-Cell Nucleus Fluorescence Labeling with Bioinspired Fluorescent Probes.

PubMed

Ding, Pan; Wang, Houyu; Song, Bin; Ji, Xiaoyuan; Su, Yuanyuan; He, Yao

2017-08-01

Fluorescent imaging techniques for visualization of nuclear structure and function in live cells are fundamentally important for exploring major cellular events. The ideal cellular labeling method is capable of realizing label-free, in situ, real-time, and long-term nucleus labeling in live cells, which can fully obtain the nucleus-relative information and effectively alleviate negative effects of alien probes on cellular metabolism. However, current established fluorescent probes-based strategies (e.g., fluorescent proteins-, organic dyes-, fluorescent organic/inorganic nanoparticles-based imaging techniques) are unable to simultaneously realize label-free, in situ, long-term, and real-time nucleus labeling, resulting in inevitable difficulties in fully visualizing nuclear structure and function in live cells. To this end, we present a type of bioinspired fluorescent probes, which are highly efficacious for in situ and label-free tracking of nucleus in long-term and real-time manners. Typically, the bioinspired polydopamine (PDA) nanoparticles, served as fluorescent probes, can be readily synthesized in situ within live cell nucleus without any further modifications under physiological conditions (37 °C, pH ∼7.4). Compared with other conventional nuclear dyes (e.g., propidium iodide (PI), Hoechst), superior spectroscopic properties (e.g., quantum yield of ∼35.8% and high photostability) and low cytotoxicity of PDA-based probes enable long-term (e.g., 3 h) fluorescence tracking of nucleus. We also demonstrate the generality of this type of bioinspired fluorescent probes in different cell lines and complex biological samples.

Nontemplated Approach to Tuning the Spectral Propertiesof Cyanine-Based Fluorescent NanoGUMBOS

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

Das, Susmita; Bwambok, David; El-Zahab, Bilal

2010-01-01

Template-free controlled aggregation and spectral properties in fluorescent organic nanoparticles (FONs) is highly desirable for various applications.Herein, we report a nontemplated method for controlling the aggregation in near-infrared (NIR) cyanine-based nanoparticles derived from a group of uniformmaterials based on organic salts (GUMBOS). Cationic heptamethine cyanine dye 1,10,3,3,30,30-hexamethylindotricarbocyanine (HMT) was coupled with five different anions, viz., [NTf2 -], [BETI-], [TFPB-], [AOT-], and [TFP4B-], by an ion-exchange method to obtain the respective GUMBOS. The nanoGUMBOS obtained via a reprecipitation method were primarily amorphous and spherical (30-100 nm) as suggested by selected area electron diffraction (SAED) and transmission electron microscopy (TEM). The formationmore » of tunable self-assemblies within the nanoGUMBOS was characterized using absorption and fluorescence spectroscopy in conjunction with molecular dynamics simulations. Counterion-controlled spectral properties observed in the nanoGUMBOS were attributed to variations in J/H ratios with different anions. Association with the [AOT-] anion afforded predominant J aggregation enabling the highest fluorescence intensity, whereas [TFP4B-] disabled the fluorescence due to predominantHaggregation in the nanoparticles. Analyses of the stacking angle of the cations based on molecular dynamic simulation results in [HMT][NTf2], [HMT][BETI], and [HMT][AOT] dispersed in water and a visual analysis of the representative simulation snapshots also imply that the type of aggregation was controlled through the counterion associated with the dye cation.« less

Wireless fluorescence capsule for endoscopy using single photon-based detection

NASA Astrophysics Data System (ADS)

Al-Rawhani, Mohammed A.; Beeley, James; Cumming, David R. S.

2015-12-01

Fluorescence Imaging (FI) is a powerful technique in biological science and clinical medicine. Current FI devices that are used either for in-vivo or in-vitro studies are expensive, bulky and consume substantial power, confining the technique to laboratories and hospital examination rooms. Here we present a miniaturised wireless fluorescence endoscope capsule with low power consumption that will pave the way for future FI systems and applications. With enhanced sensitivity compared to existing technology we have demonstrated that the capsule can be successfully used to image tissue autofluorescence and targeted fluorescence via fluorophore labelling of tissues. The capsule incorporates a state-of-the-art complementary metal oxide semiconductor single photon avalanche detector imaging array, miniaturised optical isolation, wireless technology and low power design. When in use the capsule consumes only 30.9 mW, and deploys very low-level 468 nm illumination. The device has the potential to replace highly power-hungry intrusive optical fibre based endoscopes and to extend the range of clinical examination below the duodenum. To demonstrate the performance of our capsule, we imaged fluorescence phantoms incorporating principal tissue fluorophores (flavins) and absorbers (haemoglobin). We also demonstrated the utility of marker identification by imaging a 20 μM fluorescein isothiocyanate (FITC) labelling solution on mammalian tissue.

Intrinsic fluorescence of protein in turbid media using empirical relation based on Monte Carlo lookup table

NASA Astrophysics Data System (ADS)

Einstein, Gnanatheepam; Udayakumar, Kanniyappan; Aruna, Prakasarao; Ganesan, Singaravelu

2017-03-01

Fluorescence of Protein has been widely used in diagnostic oncology for characterizing cellular metabolism. However, the intensity of fluorescence emission is affected due to the absorbers and scatterers in tissue, which may lead to error in estimating exact protein content in tissue. Extraction of intrinsic fluorescence from measured fluorescence has been achieved by different methods. Among them, Monte Carlo based method yields the highest accuracy for extracting intrinsic fluorescence. In this work, we have attempted to generate a lookup table for Monte Carlo simulation of fluorescence emission by protein. Furthermore, we fitted the generated lookup table using an empirical relation. The empirical relation between measured and intrinsic fluorescence is validated using tissue phantom experiments. The proposed relation can be used for estimating intrinsic fluorescence of protein for real-time diagnostic applications and thereby improving the clinical interpretation of fluorescence spectroscopic data.

Improving sensitivity of gold nanoparticle based fluorescence quenching and colorimetric aptasensor by using water resuspended gold nanoparticle.

PubMed

Liu, Jinchuan; Guan, Zheng; Lv, Zhenzhen; Jiang, Xiaoling; Yang, Shuming; Chen, Ailiang

2014-02-15

Gold nanoparticles (AuNPs) based fluorescence quenching or colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. However, the effects of remnant non-AuNPs components in the colloid gold solution on these assays performance remain unclear. For the first time, we demonstrated that the remnant sodium citrate and the reaction products of three acids play counteractive roles in AuNPs based fluorescence quenching and colorimetric aptasensor in three ways in this study. First, the remnant sodium citrate in the colloid gold solution could increase the fluorescence intensity of FAM labeled on the aptamer that reduce the efficiency of AuNPs fluorescent quenching. Second, the reaction products of citric acid, HCl and ketoglutaric acid reduce the fluorescence recovery by quenching the fluorescence of FAM labeled on the aptamer dissociated from the surface of AuNPs upon addition of target. Lastly, the reaction products of three acids reduce the pH value of the colloid gold solution that reduce the sensitivity of AuNPs based colorimetric aptasensor by increasing the adsorption of aptamer to surface of AuNPs. With sulfadimethoxine and thrombin as model analytes, we found that water resuspended AuNPs can significantly increase the sensitivity by more than 10-fold for AuNPs based fluorescence quenching aptasensor. In the AuNPs based colorimetric aptasensor for sulfadimethoxine using the water resuspended AuNPs, the sensitivity also was increased by 10-fold compared with that of original AuNPs. The findings in this study provide theoretical guidance for further improving AuNPs based fluorescent quenching and colorimetric aptasensor by adjusting the composition of AuNPs solution. © 2013 Elsevier B.V. All rights reserved.

Enhanced fluorescence of tetrasulfonated zinc phthalocyanine by graphene quantum dots and its application in molecular sensing/imaging.

PubMed

Wang, Jian; Zhang, Yanjun; Ye, Jiqing; Jiang, Zhou

2017-06-01

When excited at 435 nm, tetra-sulfonate zinc phthalocyanine (ZnPcS 4 ) emitted dual fluorescence at 495 and 702 nm. The abnormal fluorescence at 495 nm was experimentally studied and analyzed in detail for the first time. The abnormal fluorescence at 495 nm was deduced to originate from triplet-triplet (T-T) energy transfer of excited phthalocyanine ( 3 *ZnPcS 4 ). Furthermore, graphene quantum dots (GQDs) enhanced the 495 nm fluorescence quantum yield (Q) of ZnPcS 4 . The fluorescence properties of ZnPcS 4 -GQDs conjugate were retained in a cellular environment. Based on the fluorescence of ZnPcS 4 -GQDs conjugate, we designed and prepared an Apt29/thrombin/Apt15 sandwich thrombin sensor with high specificity and affinity. This cost-saving, simple operational sensing strategy can be extended to use in sensing/imaging of other biomolecules. Copyright © 2016 John Wiley & Sons, Ltd.

Fluorescence triggering: A general strategy for enumerating and phenotyping extracellular vesicles by flow cytometry.

PubMed

Arraud, Nicolas; Gounou, Céline; Turpin, Delphine; Brisson, Alain R

2016-02-01

Plasma contains cell-derived extracellular vesicles (EVs) which participate in various physiopathological processes and have potential biomedical applications. Despite intense research activity, knowledge on EVs is limited mainly due to the difficulty of isolating and characterizing sub-micrometer particles like EVs. We have recently reported that a simple flow cytometry (FCM) approach based on triggering the detection on a fluorescence signal enabled the detection of 50× more Annexin-A5 binding EVs (Anx5+ EVs) in plasma than the conventional FCM approach based on light scattering triggering. Here, we present the application of the fluorescence triggering approach to the enumeration and phenotyping of EVs from platelet free plasma (PFP), focusing on CD41+ and CD235a+ EVs, as well as their sub-populations which bind or do not bind Anx5. Higher EV concentrations were detected by fluorescence triggering as compared to light scattering triggering, namely 40× for Anx5+ EVs, 75× for CD41+ EVs, and 15× for CD235a+ EVs. We found that about 30% of Anx5+ EVs were of platelet origin while only 3% of them were of erythrocyte origin. In addition, a majority of EVs from platelet and erythrocyte origin do not expose PS, in contrast to the classical theory of EV formation. Furthermore, the same PFP samples were analyzed fresh and after freeze-thawing, showing that freeze-thawing processes induce an increase, of about 35%, in the amount of Anx5+ EVs, while the other EV phenotypes remain unchanged. The method of EV detection and phenotyping by fluorescence triggering is simple, sensitive and reliable. We foresee that its application to EV studies will improve our understanding on the formation mechanisms and functions of EVs in health and disease and help the development of EV-based biomarkers. © 2015 International Society for Advancement of Cytometry.

Femtogram detection of explosive nitroaromatics: fluoranthene-based fluorescent chemosensors.

PubMed

Venkatramaiah, N; Kumar, Shiv; Patil, Satish

2012-11-12

Herein we report a novel fluoranthene-based fluorescent fluorophore 7,10-bis(4-bromophenyl)-8,9-bis[4-(hexyloxy)phenyl]fluoranthene (S(3)) and its remarkable properties in applications of explosive detection. The sensitivity towards the detection of nitroaromatics (NACs) was evaluated through fluorescence quenching in solution, vapor, and contact mode approaches. The contact mode approach using thin-layer silica chromatographic plates exhibited a femtogram (1.15 fg cm(-2)) detection limit for trinitrotoluene (TNT) and picric acid (PA), whereas the solution-phase quenching showed PA detection at the 2-20 ppb level. Fluorescence lifetime measurements revealed that the quenching is static in nature and the quenching process is fully reversible. Binding energies between model binding sites of the S(3) and analyte compounds reveal that analyte molecules enter into the cavity created by substituted phenyl rings of fluoranthene and are stabilized by strong intermolecular interactions with alkyl chains. It is anticipated that the sensor S(3) could be a promising material for the construction of portable optical devices for the detection of onsite explosive nitroaromatics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A rhodol-based fluorescent chemosensor for hydrazine and its application in live cell bioimaging

NASA Astrophysics Data System (ADS)

Tiensomjitr, Khomsan; Noorat, Rattha; Wechakorn, Kanokorn; Prabpai, Samran; Suksen, Kanoknetr; Kanjanasirirat, Phongthon; Pewkliang, Yongyut; Borwornpinyo, Suparerk; Kongsaeree, Palangpon

2017-10-01

A rhodol cinnamate fluorescent chemosensor (RC) has been developed for selective detection of hydrazine (N2H4). In aqueous medium, the rhodol-based probe exhibited high selectivity for hydrazine among other molecules. The addition of hydrazine triggered a fluorescence emission with 48-fold enhancement based on hydrazinolysis and a subsequent ring-opening process. The chemical probe also displayed a selective colorimetric response toward N2H4 from colorless solution to pink, readily observed by the naked eye. The detection limit of RC for hydrazine was calculated to be 300 nM (9.6 ppb). RC is membrane permeable and was successfully demonstrated to detect hydrazine in live HepG2 cells by confocal fluorescence microscopy.

Photoacoustic-fluorescence in vitro flow cytometry for quantification of absorption, scattering and fluorescence properties of the cells

NASA Astrophysics Data System (ADS)

Nedosekin, D. A.; Sarimollaoglu, M.; Foster, S.; Galanzha, E. I.; Zharov, V. P.

2013-03-01

Fluorescence flow cytometry is a well-established analytical tool that provides quantification of multiple biological parameters of cells at molecular levels, including their functional states, morphology, composition, proliferation, and protein expression. However, only the fluorescence and scattering parameters of the cells or labels are available for detection. Cell pigmentation, presence of non-fluorescent dyes or nanoparticles cannot be reliably quantified. Herewith, we present a novel photoacoustic (PA) flow cytometry design for simple integration of absorbance measurements into schematics of conventional in vitro flow cytometers. The integrated system allow simultaneous measurements of light absorbance, scattering and of multicolor fluorescence from single cells in the flow at rates up to 2 m/s. We compared various combinations of excitation laser sources for multicolor detection, including simultaneous excitation of PA and fluorescence using a single 500 kHz pulsed nanosecond laser. Multichannel detection scheme allows simultaneous detection of up to 8 labels, including 4 fluorescent tags and 4 PA colors. In vitro PA-fluorescence flow cytometer was used for studies of nanoparticles uptake and for the analysis of cell line pigmentation, including genetically encoded melanin expression in breast cancer cell line. We demonstrate that this system can be used for direct nanotoxicity studies with simultaneous quantification of nanoparticles content and assessment of cell viability using a conventional fluorescent apoptosis assays.

Studies of bio-mimetic medium of ionic and non-ionic micelles by a simple charge transfer fluorescence probe N,N-dimethylaminonapthyl-(acrylo)-nitrile

NASA Astrophysics Data System (ADS)

Samanta, Anuva; Paul, Bijan Kumar; Guchhait, N.

2011-05-01

In this report we have studied micellization process of anionic, cationic and non-ionic surfactants using N,N-dimethylaminonapthyl-(acrylo)-nitrile (DMANAN) as an external fluorescence probe. Micropolarity, microviscosity, critical micellar concentration of these micelles based on steady state absorption and fluorescence and time resolved emission spectroscopy of the probe DMANAN show that the molecule resides in the micelle-water interface for ionic micelles and in the core for the non-ionic micelle. The effect of variation of pH of the micellar solution as well as fluorescence quenching measurements of DMANAN provide further support for the location of the probe in the micelles.

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.

Fluorescence exclusion: A simple versatile technique to calculate cell volumes and local heights (Conference Presentation)

NASA Astrophysics Data System (ADS)

Thouvenin, Olivier; Fink, Mathias; Boccara, A. Claude

2017-02-01

Understanding volume regulation during mitosis is technically challenging. Indeed, a very sensitive non invasive imaging over time scales ranging from seconds to hours and over large fields is required. Therefore, Quantitative Phase Imaging (QPI) would be a perfect tool for such a project. However, because of asymmetric protein segregation during mitosis, an efficient separation of the refractive index and the height in the phase signal is required. Even though many strategies to make such a separation have been developed, they usually are difficult to implement, have poor sensitivity, or cannot be performed in living cells, or in a single shot. In this paper, we will discuss the use of a new technique called fluorescence exclusion to perform volume measurements. By coupling such technique with a simultaneous phase measurement, we were also able to recover the refractive index inside the cells. Fluorescence exclusion is a versatile and powerful technique that allows the volume measurement of many types of cells. A fluorescent dye, which cannot penetrate inside the cells, is mixed with the external medium in a confined environment. Therefore, the fluorescent signal depends on the inverse of the object's height. We could demonstrate both experimentally and theoretically that fluorescence exclusion can accurately measure cell volumes, even for cells much higher than the depth of focus of the objective. A local accurate height and RI measurement can also be obtained for smaller cells. We will also discuss the way to optimize the confinement of the observation chamber, either mechanically or optically.

Fluorescence suppression using wavelength modulated Raman spectroscopy in fiber-probe-based tissue analysis.

PubMed

Praveen, Bavishna B; Ashok, Praveen C; Mazilu, Michael; Riches, Andrew; Herrington, Simon; Dholakia, Kishan

2012-07-01

In the field of biomedical optics, Raman spectroscopy is a powerful tool for probing the chemical composition of biological samples. In particular, fiber Raman probes play a crucial role for in vivo and ex vivo tissue analysis. However, the high-fluorescence background typically contributed by the auto fluorescence from both a tissue sample and the fiber-probe interferes strongly with the relatively weak Raman signal. Here we demonstrate the implementation of wavelength-modulated Raman spectroscopy (WMRS) to suppress the fluorescence background while analyzing tissues using fiber Raman probes. We have observed a significant signal-to-noise ratio enhancement in the Raman bands of bone tissue, which have a relatively high fluorescence background. Implementation of WMRS in fiber-probe-based bone tissue study yielded usable Raman spectra in a relatively short acquisition time (∼30  s), notably without any special sample preparation stage. Finally, we have validated its capability to suppress fluorescence on other tissue samples such as adipose tissue derived from four different species.

Carbon nanosphere-based fluorescence aptasensor for targeted detection of breast cancer cell MCF-7.

PubMed

Yang, Dandan; Liu, Mei; Xu, Jing; Yang, Chao; Wang, Xiaoxiao; Lou, Yongbing; He, Nongyue; Wang, Zhifei

2018-08-01

In this work, carbon nanosphere (CNS)-based fluorescence "turn off/on" aptasensor was developed for targeted detection of breast cancer cell MCF-7 by conjugation with FAM (a dye)-labeled mucin1 (MUC1) aptamer P0 (P0-FAM), which can recognize MUC1 protein overexpressed on the surface of MCF-7. Different from other carbon based fluorescence quenching materials, CNSs prepared by the carbonization of glucose not only have the high fluorescence quenching efficiency (98.8%), but also possess negligible cytotoxicity (in the concentration range of 0-1 mg/mL, which is 10 times higher than that of traditional carbon nanotubes or graphene oxide (0-100 µg/mL)). As for the detection of the mimic of the tumor antigen MUC1, the resulting fluorescence intensity increases nearly linearly in the range of 0-6 μM with the limit of detection (LOD) of 25 nM. Copyright © 2018 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.

EDTA aggregates induce SYPRO orange-based fluorescence in thermal shift assay

PubMed Central

Kroeger, Tobias; Frieg, Benedikt; Zhang, Tao; Hansen, Finn K.; Marmann, Andreas; Proksch, Peter; Nagel-Steger, Luitgard; Groth, Georg; Smits, Sander H. J.

2017-01-01

Ethylenediaminetetraacetic acid (EDTA) is widely used in the life sciences as chelating ligand of metal ions. However, formation of supramolecular EDTA aggregates at pH > 8 has been reported, which may lead to artifactual assay results. When applied as a buffer component at pH ≈ 10 in differential scanning fluorimetry (TSA) using SYPRO Orange as fluorescent dye, we observed a sharp change in fluorescence intensity about 20°C lower than expected for the investigated protein. We hypothesized that this change results from SYPRO Orange/EDTA interactions. TSA experiments in the presence of SYPRO Orange using solutions that contain EDTA-Na+ but no protein were performed. The TSA experiments provide evidence that suggests that at pH > 9, EDTA4- interacts with SYPRO Orange in a temperature-dependent manner, leading to a fluorescence signal yielding a “denaturation temperature” of ~68°C. Titrating Ca2+ to SYPRO Orange and EDTA solutions quenched fluorescence. Ethylene glycol tetraacetic acid (EGTA) behaved similarly to EDTA. Analytical ultracentrifugation corroborated the formation of EDTA aggregates. Molecular dynamics simulations of free diffusion of EDTA-Na+ and SYPRO Orange of in total 27 μs suggested the first structural model of EDTA aggregates in which U-shaped EDTA4- arrange in an inverse bilayer-like manner, exposing ethylene moieties to the solvent, with which SYPRO Orange interacts. We conclude that EDTA aggregates induce a SYPRO Orange-based fluorescence in TSA. These results make it relevant to ascertain that future TSA results are not influenced by interference between EDTA, or EDTA-related molecules, and the fluorescent dye. PMID:28472107

Ultra-sensitive detection of kanamycin for food safety using a reduced graphene oxide-based fluorescent aptasensor

NASA Astrophysics Data System (ADS)

Ha, Na-Reum; Jung, In-Pil; La, Im-Joung; Jung, Ho-Sup; Yoon, Moon-Young

2017-01-01

Overuse of antibiotics has caused serious problems, such as appearance of super bacteria, whose accumulation in the human body through the food chain is a concern. Kanamycin is a common antibiotic used to treat diverse infections; however, residual kanamycin can cause many side effects in humans. Thus, development of an ultra-sensitive, precise, and simple detection system for residual kanamycin in food products is urgently needed for food safety. In this study, we identified kanamycin-binding aptamers via a new screening method, and truncated variants were analyzed for optimization of the minimal sequence required for target binding. We found various aptamers with high binding affinity from 34.7 to 669 nanomolar Kdapp values with good specificity against kanamycin. Furthermore, we developed a reduced graphene oxide (RGO)-based fluorescent aptasensor for kanamycin detection. In this system, kanamycin was detected at a concentration as low as 1 pM (582.6 fg/mL). In addition, this method could detect kanamycin accurately in kanamycin-spiked blood serum and milk samples. Consequently, this simple, rapid, and sensitive kanamycin detection system with newly structural and functional analysis aptamer exhibits outstanding detection compared to previous methods and provides a new possibility for point of care testing and food safety.

Toxicological evaluation of Cd-based fluorescent nanoprobes by means of in vivo studies

NASA Astrophysics Data System (ADS)

Farias, Patricia M. A.; Ma-Hock, Lan; Landsiedel, Robert; van Ravenzwaay, Bennard

2018-02-01

Cadmium still represents a stigma for many research- and/or industrial applications. Some deleterious effects are attributed to Cadmium. In the present work, highly fluorescent Cadmium sulfide quantum dots are investigated by e.g. physical-chemical characterization. Most important however is their application as fluorescent probes for bio-imaging in living cells and tissues. This work presents their toxicological evaluation by means of in vivo studies. Bio-imaging experiments are performed without any pre-treatment. The toxicological studies performed, strongly indicate that the use of Cadmium based nanoparticles as fluorescent probes may be nonhazardous and not induce side effects for cells/tissues.

Functionality-Oriented Derivatization of Naphthalene Diimide: A Molecular Gel Strategy-Based Fluorescent Film for Aniline Vapor Detection.

PubMed

Fan, Jiayun; Chang, Xingmao; He, Meixia; Shang, Congdi; Wang, Gang; Yin, Shiwei; Peng, Haonan; Fang, Yu

2016-07-20

Modification of naphthalene diimide (NDI) resulted in a photochemically stable, fluorescent 3,4,5-tris(dodecyloxy)benzamide derivative of NDI (TDBNDI), and introduction of the long alkyl chains endowed the compound with good compatibility with commonly found organic solvents and in particular superior self-assembly in the solution state. Further studies revealed that TDBNDI forms gels with nine of the 18 solvents tested at a concentration of 2.0% (w/v), and the critical gelation concentrations of five of the eight gels are lower than 1.0% (w/v), indicating the high efficiency of the compound as a low-molecular mass gelator (LMMG). Transmission electron microscopy, scanning electron microscopy, and confocal laser scanning microscopy studies revealed the networked fibrillar structure of the TDBNDI/methylcyclohexane (MCH) gel. On the basis of these findings, a fluorescent film was developed via simple spin-coating of the TDBNDI/MCH gel on a glass substrate surface. Fluorescence behavior and sensing performance studies demonstrated that this film is photochemically stable, and sensitive and selective to the presence of aniline vapor. Notably, the response is instantaneous, and the sensing process is fully and quickly reversible. This case study demonstrates that derivatization of photochemically stable fluorophores into LMMGs is a good strategy for developing high-performance fluorescent sensing films.

Probing structure and dynamics of DNA with 2-aminopurine: effects of local environment on fluorescence.

PubMed

Rachofsky, E L; Osman, R; Ross, J B

2001-01-30

2-Aminopurine (2AP) is an analogue of adenine that has been utilized widely as a fluorescence probe of protein-induced local conformational changes in DNA. Within a DNA strand, this fluorophore demonstrates characteristic decreases in quantum yield and emission decay lifetime that vary sensitively with base sequence, temperature, and helix conformation but that are accompanied by only small changes in emission wavelength. However, the molecular interactions that give rise to these spectroscopic changes have not been established. To develop a molecular model for interpreting the fluorescence measurements, we have investigated the effects of environmental polarity, hydrogen bonding, and the purine and pyrimidine bases of DNA on the emission energy, quantum yield, and intensity decay kinetics of 2AP in simple model systems. The effects of environmental polarity were examined in a series of solvents of varying dielectric constant, and hydrogen bonding was investigated in binary mixtures of water with 1,4-dioxane or N,N-dimethylformamide (DMF). The effects of the purine and pyrimidine bases were studied by titrating 2AP deoxyriboside (d2AP) with the nucleosides adenosine (rA), cytidine (rC), guanosine (rG), and deoxythymidine (dT), and the nucleoside triphosphates ATP and GTP in neutral aqueous solution. The nucleosides and NTPs each quench the fluorescence of d2AP by a combination of static (affecting only the quantum yield) and dynamic (affecting both the quantum yield and the lifetime, proportionately) mechanisms. The peak wavelength and shape of the emission spectrum are not altered by either of these effects. The static quenching is saturable and has half-maximal effect at approximately 20 mM nucleoside or NTP, consistent with an aromatic stacking interaction. The rate constant for dynamic quenching is near the diffusion limit for collisional interaction (k(q) approximately 2 x 10(9) M(-1) s(-1)). Neither of these effects varies significantly between the various

Highly selective and sensitive turn-on fluorescent sensor for detection of Al3+ based on quinoline-base Schiff base

NASA Astrophysics Data System (ADS)

Wang, Yang; Ma, Zhong-Ying; Zhang, De-Long; Deng, Jia-Li; Chen, Xiong; Xie, Cheng-Zhi; Qiao, Xin; Li, Qing-Zhong; Xu, Jing-Yuan

2018-04-01

A new aluminum ion fluorescent probe (4-(diethylamino)-2-hydroxybenzylidene)isoquinoline-1-carbohydrazide (HL1) has been conveniently synthesized and characterized. HL1 exhibited a highly selective and pronounced enhancement for Al3+ in the fluorescence emission over other common cations by forming a 2:1 complex, with a recognition mechanism based on excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT). The strong fluorescent emission can be observed even at ppm level concentration of the probe in the presence of Al3+ with 41 fold intensity enhancement at 545 nm. HL1 displays good linear relationship with Al3+ in the low concentration and the limit of detection is 8.08 × 10-8 mol/L. Similar molecules with different substituents on salicylaldehyde phenyl ring were synthesized for studying the structure-activity relationship. Density-functional theory (DFT) calculations are in agreement with the proposed mechanism. It is confirmed that HL1 could be used to detect Al3+ ions in real sample by fluorescence spectrometry and Al3+ ions in cells by bioimaging.

Diketopyrrolopyrrole Amphiphile-Based Micelle-Like Fluorescent Nanoparticles for Selective and Sensitive Detection of Mercury(II) Ions in Water.

PubMed

Nie, Kaixuan; Dong, Bo; Shi, Huanhuan; Liu, Zhengchun; Liang, Bo

2017-03-07

A technique for encapsulating fluorescent organic probes in a micelle system offers an important alternative method to manufacture water-soluble organic nanoparticles (ONPs) for use in sensing Hg 2+ . This article reports on a study of a surfactant-free micelle-like ONPs based on a 3,6-di(2-thienyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (TDPP) amphiphile, (2-(2-(2-methoxyethoxy)ethyl)-3,6-di(2-thiophyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (NDPP) fabricated to monitor Hg 2+ in water. NDPP was synthesized through a simple one-step modification of a commercially available dye TDPP with a flexible and hydrophilic alkoxy. This study reports, for the first time, that TDPP dyes can respond reversibly, sensitively, and selectively to Hg 2+ through TDPP-Hg-TDPP complexation, similar to the well-known thymine(T)-Hg-thymine(T) model and the accompanying molecular aggregation. Interestingly, transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed that, in water, NDPP forms loose micelle-like fluorescent ONPs with a hydrohobic TDPP portion encapsulated inside. These micelle-like nanoparticles offer an ideal location for TDPP-Hg complexation with a modest molecular aggregation, thereby providing both clear visual and spectroscopic signals for Hg 2+ sensing. An estimated detection limit of 11 nM for Hg 2+ sensing with this NDPP nanoparticle was obtained. In addition, NDPP ONPs show good water solubility and high selectivity to Hg 2+ in neutral or alkalescent water. It was superior to most micelle-based nanosensors, which require a complicated process in the selection or synthesis of suitable surfactants. The determinations in real samples (river water) were made and satisfactory results were achieved. This study provides a low-cost strategy for fabricating small molecule-based fluorescent nanomaterials for use in sensing Hg 2+ . Moreover, the NDPP nanoparticles show potential ability in Hg 2+ ion adsorption and recognization of cysteine

Fiber-optic fluorescence imaging

PubMed Central

Flusberg, Benjamin A; Cocker, Eric D; Piyawattanametha, Wibool; Jung, Juergen C; Cheung, Eunice L M; Schnitzer, Mark J

2010-01-01

Optical fibers guide light between separate locations and enable new types of fluorescence imaging. Fiber-optic fluorescence imaging systems include portable handheld microscopes, flexible endoscopes well suited for imaging within hollow tissue cavities and microendoscopes that allow minimally invasive high-resolution imaging deep within tissue. A challenge in the creation of such devices is the design and integration of miniaturized optical and mechanical components. Until recently, fiber-based fluorescence imaging was mainly limited to epifluorescence and scanning confocal modalities. Two new classes of photonic crystal fiber facilitate ultrashort pulse delivery for fiber-optic two-photon fluorescence imaging. An upcoming generation of fluorescence imaging devices will be based on microfabricated device components. PMID:16299479

Synthesis and validation of novel cholesterol-based fluorescent lipids designed to observe the cellular trafficking of cationic liposomes.

PubMed

Kim, Bieong-Kil; Seu, Young-Bae; Choi, Jong-Soo; Park, Jong-Won; Doh, Kyung-Oh

2015-09-15

Cholesterol-based fluorescent lipids with ether linker were synthesized using NBD (Chol-E-NBD) or Rhodamine B (Chol-E-Rh), and the usefulnesses as fluorescent probes for tracing cholesterol-based liposomes were validated. The fluorescent intensities of liposomes containing these modified lipids were measured and observed under a microscope. Neither compound interfered with the expression of GFP plasmid, and live cell images were obtained without interferences. Changes in the fluorescent intensity of liposomes containing Chol-E-NBD were followed by flow cytometry for up to 24h. These fluorescent lipids could be useful probes for trafficking of cationic liposome-mediated gene delivery. Copyright © 2015 Elsevier Ltd. All rights reserved.

Capillary Array Waveguide Amplified Fluorescence Detector for mHealth

PubMed Central

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

2013-01-01

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

Simple approach to three-color two-photon microscopy by a fiber-optic wavelength convertor.

PubMed

Li, Kuen-Che; Huang, Lynn L H; Liang, Jhih-Hao; Chan, Ming-Che

2016-11-01

A simple approach to multi-color two-photon microscopy of the red, green, and blue fluorescent indicators was reported based on an ultra-compact 1.03-μm femtosecond laser and a nonlinear fiber. Inside the nonlinear fiber, the 1.03-μm laser pulses were simultaneously blue-shifted to 0.6~0.8 μm and red-shifted to 1.2~1.4 μm region by the Cherenkov radiation and fiber Raman gain effects. The wavelength-shifted 0.6~0.8 μm and 1.2~1.4 μm radiations were co-propagated with the residual non-converted 1.03-μm pulses inside the same nonlinear fiber to form a fiber-output three-color femtosecond source. The application of the multi-wavelength sources on multi-color two-photon fluorescence microscopy were also demonstrated. Overall, due to simple system configuration, convenient wavelength conversion, easy wavelength tunability within the entire 0.7~1.35 μm bio-penetration window and less requirement for high power and bulky light sources, the simple approach to multi-color two-photon microscopy could be widely applicable as an easily implemented and excellent research tool for future biomedical and possibly even clinical applications.

Simple refractometer based on in-line fiber interferometers

NASA Astrophysics Data System (ADS)

Esteban, Ó.; Martínez Manuel, R.; Shlyagin, M. G.

2015-09-01

A very simple but accurate optical fiber refractometer based on the Fresnel reflection in the fiber tip and two in-line low-reflective mirrors for light intensity referencing is reported. Each mirror was generated by connecting together 2 fiber sections with FC/PC and FC/APC connectors using the standard FC/PC mating sleeve. For the sensor interrogation, a standard DFB diode laser pumped with a sawtooth-wave current was used. A resolution of 6 x 10-4 was experimentally demonstrated using different liquids. A simple sensor construction and the use of low cost components make the reported system interesting for many applications.

Microplate Bioassay for Nisin in Foods, Based on Nisin-Induced Green Fluorescent Protein Fluorescence

PubMed Central

Reunanen, J.; Saris, P. E. J.

2003-01-01

A plasmid coding for the nisin two-component regulatory proteins, NisK and NisR, was constructed; in this plasmid a gfp gene (encoding the green fluorescent protein) was placed under control of the nisin-inducible nisF promoter. The plasmid was transformed into non-nisin-producing Lactococcus lactis strain MG1614. The new strain could sense extracellular nisin and transduce it to green fluorescent protein fluorescence. The amount of fluorescence was dependent on the nisin concentration, and it could be measured easily. By using this strain, an assay for quantification of nisin was developed. With this method it was possible to measure as little as 2.5 ng of pure nisin per ml in culture supernatant, 45 ng of nisin per ml in milk, 0.9 μg of nisin in cheese, and 1 μg of nisin per ml in salad dressings. PMID:12839802

Chemosensors and biosensors based on polyelectrolyte microcapsules containing fluorescent dyes and enzymes.

PubMed

Kazakova, Lyubov I; Shabarchina, Lyudmila I; Anastasova, Salzitsa; Pavlov, Anton M; Vadgama, Pankaj; Skirtach, Andre G; Sukhorukov, Gleb B

2013-02-01

The concept of enzyme-assisted substrate sensing based on use of fluorescent markers to detect the products of enzymatic reaction has been investigated by fabrication of micron-scale polyelectrolyte capsules containing enzymes and dyes in one entity. Microcapsules approximately 5 μm in size entrap glucose oxidase or lactate oxidase, with peroxidase, together with the corresponding markers Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride (Ru(dpp)) complex and dihydrorhodamine 123 (DHR123), which are sensitive to oxygen and hydrogen peroxide, respectively. These capsules are produced by co-precipitation of calcium carbonate particles with the enzyme followed by layer-by-layer assembly of polyelectrolytes over the surface of the particles and incorporation of the dye in the capsule interior or in the multilayer shell. After dissolution of the calcium carbonate the enzymes and dyes remain in the multilayer capsules. In this study we produced enzyme-containing microcapsules sensitive to glucose and lactate. Calibration curves based on fluorescence intensity of Ru(dpp) and DHR123 were linearly dependent on substrate concentration, enabling reliable sensing in the millimolar range. The main advantages of using these capsules with optical recording is the possibility of building single capsule-based sensors. The response from individual capsules was observed by confocal microscopy as increasing fluorescence intensity of the capsule on addition of lactate at millimolar concentrations. Because internalization of the micron-sized multi-component capsules was feasible, they could be further optimized for in-situ intracellular sensing and metabolite monitoring on the basis of fluorescence reporting.

Intrinsic fluorescence for cervical precancer detection using polarized light based in-house fabricated portable device

NASA Astrophysics Data System (ADS)

Meena, Bharat Lal; Singh, Pankaj; Sah, Amar Nath; Pandey, Kiran; Agarwal, Asha; Pantola, Chayanika; Pradhan, Asima

2018-01-01

An in-house fabricated portable device has been tested to detect cervical precancer through the intrinsic fluorescence from human cervix of the whole uterus in a clinical setting. A previously validated technique based on simultaneously acquired polarized fluorescence and polarized elastic scattering spectra from a turbid medium is used to extract the intrinsic fluorescence. Using a diode laser at 405 nm, intrinsic fluorescence of flavin adenine dinucleotide, which is the dominant fluorophore and other contributing fluorophores in the epithelium of cervical tissue, has been extracted. Different grades of cervical precancer (cervical intraepithelial neoplasia; CIN) have been discriminated using principal component analysis-based Mahalanobis distance and linear discriminant analysis. Normal, CIN I and CIN II samples have been discriminated from one another with high sensitivity and specificity at 95% confidence level. This ex vivo study with cervix of whole uterus samples immediately after hysterectomy in a clinical environment indicates that the in-house fabricated portable device has the potential to be used as a screening tool for in vivo precancer detection using intrinsic fluorescence.

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.

A novel and sensitive fluorescence sensor for glutathione detection by controlling the surface passivation degree of carbon quantum dots.

PubMed

Pan, Jiahong; Zheng, Zengyao; Yang, Jianying; Wu, Yaoyu; Lu, Fushen; Chen, Yaowen; Gao, Wenhua

2017-05-01

A novel fluorescence sensor based on controlling the surface passivation degree of carbon quantum dots (CQDs) was developed for glutathione (GSH) detection. First, we found that the fluorescence intensity of the CQDs which was obtained by directly pyrolyzing citric acid would increased largely after the surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). In the light of this phenomenon, we designed a simple, rapid and selective fluorescence sensor based on the surface passivated CQDs. A certain and excess amount of EDC were mixed with GSH, part of EDC would form a stable complex with GSH owing to the exposed sulfhydryl group of GSH. As the synthesized CQDs were added into the above mixture solution, the fluorescence intensity of the (EDC/GSH)/CQDs mixture solution could be directly related to the amount of GSH. Compared to other fluorescence analytical methods, the fluorescence sensor we design is neither the traditional fluorescent "turn on" probes nor "turn off" probes. It is a new fluorescence analytical method that target object indirectly control the surface passivation degree of CQDs so that it can realize the detection of the target object. Moreover, the proposed method manifested great advantages including short analysis time, low cost and ease of operation. Copyright © 2017 Elsevier B.V. All rights reserved.

Fluorescence sensing and photocatalytic properties of a 2D stable and biocompatible Zn(II)-based polymer

NASA Astrophysics Data System (ADS)

Wu, Jian; Li, Bao-Hong; Zhong, Hua-Rui; Qiu, Shuo-Wen; Liang, Yi-Wen; Zhuang, Xiao-Yi; Singh, Amita; Kumar, Abhinav

2018-04-01

A biocompatible metal-organic framework (MOF) [Zn2(TPL)(FA)(OH)(H2O)] (1) (TPL = theophylline and H2FA = fumaric acid) had been chosen which offers an ideal model for the development of fluorescencent chemosensor using simple synthetic protocol. The MOF 1 have been tested as a fluorescent chemosensor against nitro-aromatics (NACs) and it displayed high selectivity for 4-NT over other NACs as evident by the emission spectroscopy. The alleviation in fluorescence intensity of 1 in presence of different NACs have been explained with the help of theoretical calculations which suggested that there is occurrence of both electron and energy transfer processes, in addition to electrostatic interaction between 1 and NACs which may be responsible for the unprecedented selective alleviation in the fluorescence intensity. Also, 1 had been deployed as a photocatalyst for the degradation of methyl violet (MV) and Rhodamine B (Rh B) in aqueous solution under UV irradiation. The photocatalytic results indicated the 1 exhibit 85% photocatalytic efficiency against Rh B in 100 min, while its efficiency against MV was only 50% under the identical experimental conditions. The possible mechanism for the photocatalytic activity has been proposed using density of states (DOS) calculations.

Fluorescent and colorimetric detection of Fe(III) and Cu(II) by a difunctional rhodamine-based probe

NASA Astrophysics Data System (ADS)

Wang, Lei; Ye, Dandan; Li, Wenxuan; Liu, Yuanyuan; Li, Longhua; Zhang, Wenli; Ni, Liang

2017-08-01

A new rhodamine B hydrazone derivative (probe L) was synthesized and characterized. The probe L had sufficiently satisfactory selective response to Fe3 + and Cu2 + ions among various interferential metal ions, and high sensitivity with the detection limit of 4.63 × 10- 9 M and 5.264 × 10- 7 M for Fe3 + and Cu2 + ions, respectively. In the presence of Fe3 +, the probe L exhibited turn-on orange fluorescence accompanied by color change from colorless to pink. Toward Cu2 +, the probe L showed significant color change from colorless to red purple. These remarkable orange fluorescence and color change made probe L suitable naked-eye identify for Fe3 + and Cu2 + ions. By means of Job's plot, Benesi-Hildebrand studies and FTIR spectra, both 1:1 binding modes (L-Fe3 + and L-Cu2 +) were confirmed. The coordination mechanism and turn on/off fluorescence for L-Fe3 + and L-Cu2 + complexes were well explained by theoretical calculations. Moreover, probe L could be used as a quick, simple, visual test strip for Fe3 + and Cu2 + detection.

Development of fluorescent probes based on protection-deprotection of the key functional groups for biological imaging.

PubMed

Tang, Yonghe; Lee, Dayoung; Wang, Jiaoliang; Li, Guanhan; Yu, Jinghua; Lin, Weiying; Yoon, Juyoung

2015-08-07

Recently, the strategy of protection-deprotection of functional groups has been widely employed to design fluorescent probes, as the protection-deprotection of functional groups often induces a marked change in electronic properties. Significant advances have been made in the development of analyte-responsive fluorescent probes based on the protection-deprotection strategy. In this tutorial review, we highlight the representative examples of small-molecule based fluorescent probes for bioimaging, which are operated via the protection-deprotection of key functional groups such as aldehyde, hydroxyl, and amino functional groups reported from 2010 to 2014. The discussion includes the general protection-deprotection methods for aldehyde, hydroxyl, or amino groups, as well as the design strategies, sensing mechanisms, and deprotection modes of the representative fluorescent imaging probes applied to bio-imaging.

Protein-Induced Fluorescence Enhancement Based Detection of Plasmodium falciparum Glutamate Dehydrogenase Using Carbon Dot Coupled Specific Aptamer.

PubMed

Singh, Naveen Kumar; Chakma, Babina; Jain, Priyamvada; Goswami, Pranab

2018-06-11

A novel 90-mer long ssDNA aptamer (NG3) covering a 40-mer random region targeting Plasmodium falciparum glutamate dehydrogenase ( PfGDH) developed through systematic evolution of ligands by exponential enrichment (SELEX) technique. The binding affinity of the aptamer to PfGDH discerned by circular dichroism (CD) was 0.5 ± 0.04 μM. The specificity of the aptamer toward the target was confirmed by gel electrophoresis and CD studies. The presence of two quadruplex forming regions, two big and four small stem loop structures with a δG of -7.99 kcal mol -1 for NG3 were deduced by computational studies. The spherical carbon dots (Cdots) of size 2-4 nm, synthesized by pyrolysis method using l-glutamate as a substrate were covalently linked to the amine modified aptamer. The Cdot with a band gap of 2.8 eV and a quantum yield of 34% produced fluorescence at ∼ λ 410 nm when excited at λ 320nm . The quantum yield of Cdot-aptamer assembly was increased up to 40% in the presence of the PfGDH in solution. A linear relationship with a dynamic range of 0.5 nM to 25 nM (R 2 = 0.98) and a limit of detection (LOD) of 0.48 nM was observed between the fluorescence intensity of the Cdots-aptamer conjugate and the concentration of PfGDH. The method could detect PfGDH with an LOD of 2.85 nM in diluted serum sample. This novel simple, sensitive and specific protein induced fluorescence enhancement based detection of PfGDH has a great potential to develop as a method for malaria detection.

A small-molecule-linked DNA-graphene oxide-based fluorescence-sensing system for detection of biotin.

PubMed

Zhang, Hao; Li, Yan; Su, Xingguang

2013-11-15

In this paper, we establish a novel fluorescence-sensing system for the detection of biotin based on the interaction between DNA and graphene oxide and on protection of the terminal of the biotinylated single-stranded DNA fluorescent probe by streptavidin. In this system, streptavidin binds to the biotinylated DNA, which protects the DNA from hydrolysis by exonuclease I. The streptavidin-DNA conjugate is then adsorbed to the graphene oxide resulting in the fluorescence being quenched. Upon the addition of free biotin, it competes with the labeled biotin for the binding sites of streptavidin and then the exonuclease I digests the unbound DNA probe from the 3' to the 5' terminal, releasing the fluorophore from the DNA. Because of the weak affinity between the fluorophore and graphene oxide, the fluorescence is recovered. Under optimal conditions, the fluorescence intensity is proportional to the concentration of biotin in the concentration range of 0.5-20nmol/L. The detection limit for biotin is 0.44nmol/L. The proposed fluorescence-sensing system was applied to the determination of biotin in some real samples with satisfactory reproducibility and accuracy. This work could provide a common platform for detecting small biomolecules based on protein-small molecule ligand binding. Copyright © 2013 Elsevier Inc. All rights reserved.

A fast reconstruction algorithm for fluorescence optical diffusion tomography based on preiteration.

PubMed

Song, Xiaolei; Xiong, Xiaoyun; Bai, Jing

2007-01-01

Fluorescence optical diffusion tomography in the near-infrared (NIR) bandwidth is considered to be one of the most promising ways for noninvasive molecular-based imaging. Many reconstructive approaches to it utilize iterative methods for data inversion. However, they are time-consuming and they are far from meeting the real-time imaging demands. In this work, a fast preiteration algorithm based on the generalized inverse matrix is proposed. This method needs only one step of matrix-vector multiplication online, by pushing the iteration process to be executed offline. In the preiteration process, the second-order iterative format is employed to exponentially accelerate the convergence. Simulations based on an analytical diffusion model show that the distribution of fluorescent yield can be well estimated by this algorithm and the reconstructed speed is remarkably increased.

Pyrimidine-based twisted donor-acceptor delayed fluorescence molecules: a new universal platform for highly efficient blue electroluminescence.

PubMed

Park, In Seob; Komiyama, Hideaki; Yasuda, Takuma

2017-02-01

Deep-blue emitters that can harvest both singlet and triplet excited states to give high electron-to-photon conversion efficiencies are highly desired for applications in full-color displays and white lighting devices based on organic light-emitting diodes (OLEDs). Thermally activated delayed fluorescence (TADF) molecules based on highly twisted donor-acceptor (D-A) configurations are promising emitting dopants for the construction of efficient deep-blue OLEDs. In this study, a simple and versatile D-A system combining acridan-based donors and pyrimidine-based acceptors has been developed as a new platform for high-efficiency deep-blue TADF emitters. The designed pre-twisted acridan-pyrimidine D-A molecules exhibit small singlet-triplet energy splitting and high photoluminescence quantum yields, functioning as efficient deep-blue TADF emitters. The OLEDs utilizing these TADF emitters display bright blue electroluminescence with external quantum efficiencies of up to 20.4%, maximum current efficiencies of 41.7 cd A -1 , maximum power efficiencies of 37.2 lm W -1 , and color coordinates of (0.16, 0.23). The design strategy featuring such acridan-pyrimidine D-A motifs can offer great prospects for further developing high-performance deep-blue TADF emitters and TADF-OLEDs.

Micelle-induced versatile sensing behavior of bispyrene-based fluorescent molecular sensor for picric acid and PYX explosives.

PubMed

Ding, Liping; Bai, Yumei; Cao, Yuan; Ren, Guijia; Blanchard, Gary J; Fang, Yu

2014-07-08

The effect of surfactant micelles on the photophysical properties of a cationic bispyrene fluorophore, Py-diIM-Py, was systemically examined. The results from series of measurements including UV-vis absorption, steady-state fluorescence emission, quantum yield, fluorescence lifetime, and time-resolved emission spectra reveal that the cationic fluorophore is only encapsulated by the anionic sodium dodecyl sulfate (SDS) surfactant micelles and not incorporated in the cationic dodecyltrimethylammonium bromide (DTAB) and neutral Triton X-100 (TX100) surfactant micelles. This different fluorophore location in the micellar solutions significantly influences its sensing behavior to various explosives. Fluorescence quenching studies reveal that the simple variation of micellar systems leads to significant changes in the sensitivity and selectivity of the fluorescent sensor to explosives. The sensor exhibits an on-off response to multiple explosives with the highest sensitivity to picric acid (PA) in the anionic SDS micelles. In the cationic DTAB micelles, it displays the highest on-off responses to PYX. Both the sensitivity and selectivity to PYX in the cationic micelles are enhanced compared with that to PA in the anionic micelles. However, the poor encapsulation in the neutral surfactant TX100 micelles leads to fluorescence instability of the fluorophore and fails to function as a sensor system. Time-resolved fluorescence decays in the presence of explosives reveal that the quenching mechanism of two micellar sensor systems to explosives is static in nature. The present work demonstrates that the electrostatic interaction between the cationic fluorophore and differently charged micelles plays a determinative role in adjusting its distribution in micellar solutions, which further influences the sensing behavior of the obtained micellar sensor systems.

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 stable lipid-encapsulation of fluorescent nanodiamonds for bioimaging applications.

PubMed

Sotoma, Shingo; Hsieh, Feng-Jen; Chen, Yen-Wei; Tsai, Pei-Chang; Chang, Huan-Cheng

2018-01-23

Highly stable lipid-encapsulated fluorescent nanodiamonds (FNDs) are produced by photo-crosslinking of diacetylene-containing lipids physically attached to the FND surface. Not only is this coating method simple and fast, but also it gives the FND-lipid hybrids favorable properties for bioapplications. The hybrids are useful as fluorescent biolabels as well as fiducial markers for correlative light and electron microscopy.

An amplified graphene oxide-based fluorescence aptasensor based on target-triggered aptamer hairpin switch and strand-displacement polymerization recycling for bioassays.

PubMed

Hu, Kun; Liu, Jinwen; Chen, Jia; Huang, Yong; Zhao, Shulin; Tian, Jianniao; Zhang, Guohai

2013-04-15

An amplified graphene oxide (GO) based fluorescence aptasensor based on target-triggered aptamer hairpin switch and strand-displacement polymerization recycling is developed for bioassays. The dye-labeled single-strand DNA (aptamer hairpin) was adsorbed on the surface of GO, which result in the fluorescence quenching of dye, and exhibiting minimal background fluorescence. Upon the target, primer and polymerase, the stem of the aptamer hairpin was opened, and binds with the primer to triggers the circular target strand-displacement polymerization reaction, which produces huge amounts of duplex helixes DNA and lead to strong fluorescence emission due to shielding of nucelobases within its double-helix structure. During the polymerization reaction, the primer was extended, and target was displaced. And the displaced target recognizes and hybridizes with another hairpin probe, triggering the next round of polymerization reaction, and the circle process induces fluorescence signal amplification for the detection of analyte. To test the feasibility of the aptasensor systems, interferon-gamma (IFN-γ) was employed as a model analyte. A detection limit as low as 1.5 fM is obtained based on the GO aptasensor with a linear range of three orders of magnitude. The present method was successfully applied for the detection of IFN-γ in human plasma. Copyright © 2012 Elsevier B.V. All rights reserved.

A simple tagging system for protein encapsulation.

PubMed

Seebeck, Florian P; Woycechowsky, Kenneth J; Zhuang, Wei; Rabe, Jürgen P; Hilvert, Donald

2006-04-12

Molecular containers that encapsulate specific cargo can be useful for many natural and non-natural processes. We report a simple system, based on charge complementarity, for the encapsulation of appropriately tagged proteins within an engineered, proteinaceous capsid. Four negative charges per monomer were added to the lumazine synthase from Aquifex aeolicus (AaLS). The capsids formed by the engineered AaLS associate with green fluorescent protein bearing a positively charged deca-arginine tag upon coproduction in Escherichia coli. Analytical ultracentrifugation and scanning force microscopy studies indicated that the engineered AaLS retains the ability to form capsids, but that their average size was substantially increased. The success of this strategy demonstrates that both the container and guest components of protein-based encapsulation systems can be convergently designed in a straightforward manner, which may help to extend their versatility.

Fluorescent marker-based and marker-free discrimination between healthy and cancerous human tissues using hyper-spectral imaging

NASA Astrophysics Data System (ADS)

Arnold, Thomas; De Biasio, Martin; Leitner, Raimund

2015-06-01

Two problems are addressed in this paper (i) the fluorescent marker-based and the (ii) marker-free discrimination between healthy and cancerous human tissues. For both applications the performance of hyper-spectral methods are quantified. Fluorescent marker-based tissue classification uses a number of fluorescent markers to dye specific parts of a human cell. The challenge is that the emission spectra of the fluorescent dyes overlap considerably. They are, furthermore disturbed by the inherent auto-fluorescence of human tissue. This results in ambiguities and decreased image contrast causing difficulties for the treatment decision. The higher spectral resolution introduced by tunable-filter-based spectral imaging in combination with spectral unmixing techniques results in an improvement of the image contrast and therefore more reliable information for the physician to choose the treatment decision. Marker-free tissue classification is based solely on the subtle spectral features of human tissue without the use of artificial markers. The challenge in this case is that the spectral differences between healthy and cancerous tissues are subtle and embedded in intra- and inter-patient variations of these features. The contributions of this paper are (i) the evaluation of hyper-spectral imaging in combination with spectral unmixing techniques for fluorescence marker-based tissue classification, (ii) the evaluation of spectral imaging for marker-free intra surgery tissue classification. Within this paper, we consider real hyper-spectral fluorescence and endoscopy data sets to emphasize the practical capability of the proposed methods. It is shown that the combination of spectral imaging with multivariate statistical methods can improve the sensitivity and specificity of the detection and the staging of cancerous tissues compared to standard procedures.

Two-photon excited fluorescence from a pseudoisocyanine-attached gold-coated tip via a thin tapered fiber under a weak continuous wave excitation.

PubMed

Ren, Fang; Takashima, Hideaki; Tanaka, Yoshito; Fujiwara, Hideki; Sasaki, Keiji

2013-11-18

A simple tapered fiber based photonic-plasmonic hybrid nanostructure composed of a thin tapered fiber and a pseudoisocyanine (PIC)-attached Au-coated tip was demonstrated. Using this simple hybrid nanostructure, we succeeded in observing two-photon excited fluorescence from the PIC dye molecules under a weak continuous wave excitation condition. From the results of the tip-fiber distance dependence and excitation polarization dependence, we found that using a thin tapered fiber and an Au-coated tip realized efficient coupling of the incident light (~95%) and LSP excitation at the Au-coated tip, suggesting the possibility of efficiently inducing two-photon excited fluorescence from the PIC dye molecules attached on the Au-coated tip. This simple photonic-plasmonic hybrid system is one of the promising tools for single photon sources, highly efficient plasmonic sensors, and integrated nonlinear plasmonic devices.

Synthesis and application of a highly selective copper ions fluorescent probe based on the coumarin group

NASA Astrophysics Data System (ADS)

He, Guangjie; Liu, Xiangli; Xu, Jinhe; Ji, Liguo; Yang, Linlin; Fan, Aiying; Wang, Songjun; Wang, Qingzhi

2018-02-01

A highly selective copper ions fluorescent probe based on the coumarin-type Schiff base derivative 1 (probe) was produced by condensation reaction between coumarin carbohydrazide and 1H-indazole-3-carbaldehyde. The UV-vis spectroscopy showed that the maximum absorption peak of compound 1 appeared at 439 nm. In the presence of Cu2 + ions, the maximum peak decreased remarkably compared with other physiological important metal ions and a new absorption peak at 500 nm appeared. The job's plot experiments showed that complexes of 1:2 binding mode were formed in CH3CN:HEPES (3:2, v/v) solution. Compound 1 exhibited a strong blue fluorescence. Upon addition of copper ions, the fluorescence gradually decreased and reached a plateau with the fluorescence quenching rate up to 98.73%. The detection limit for Cu2 + ions was estimated to 0.384 ppm. Fluorescent microscopy experiments demonstrated that probe 1 had potential to be used to investigate biological processes involving Cu2 + ions within living cells.

Computer-assisted sperm morphometry fluorescence-based analysis has potential to determine progeny sex.

PubMed

Santolaria, Pilar; Pauciullo, Alfredo; Silvestre, Miguel A; Vicente-Fiel, Sandra; Villanova, Leyre; Pinton, Alain; Viruel, Juan; Sales, Ester; Yániz, Jesús L

2016-01-01

This study was designed to determine the ability of computer-assisted sperm morphometry analysis (CASA-Morph) with fluorescence to discriminate between spermatozoa carrying different sex chromosomes from the nuclear morphometrics generated and different statistical procedures in the bovine species. The study was divided into two experiments. The first was to study the morphometric differences between X- and Y-chromosome-bearing spermatozoa (SX and SY, respectively). Spermatozoa from eight bulls were processed to assess simultaneously the sex chromosome by FISH and sperm morphometry by fluorescence-based CASA-Morph. SX cells were larger than SY cells on average (P < 0.001) although with important differences between bulls. A simultaneous evaluation of all the measured features by discriminant analysis revealed that nuclear area and average fluorescence intensity were the variables selected by stepwise discriminant function analysis as the best discriminators between SX and SY. In the second experiment, the sperm nuclear morphometric results from CASA-Morph in nonsexed (mixed SX and SY) and sexed (SX) semen samples from four bulls were compared. FISH allowed a successful classification of spermatozoa according to their sex chromosome content. X-sexed spermatozoa displayed a larger size and fluorescence intensity than nonsexed spermatozoa (P < 0.05). We conclude that the CASA-Morph fluorescence-based method has the potential to find differences between X- and Y-chromosome-bearing spermatozoa in bovine species although more studies are needed to increase the precision of sex determination by this technique.

[Molecular beacon based PNA-FISH method combined with fluorescence scanning for rapid detection of Listeria monocytogenes].

PubMed

Wu, Shan; Zhang, Xiaofeng; Shuai, Jiangbing; Li, Ke; Yu, Huizhen; Jin, Chenchen

2016-07-04

To simplify the PNA-FISH (Peptide nucleic acid-fluorescence in situ hybridization) test, molecular beacon based PNA probe combined with fluorescence scanning detection technology was applied to replace the original microscope observation to detect Listeria monocytogenes The 5′ end and 3′ end of the L. monocytogenes specific PNA probes were labeled with the fluorescent group and the quenching group respectively, to form a molecular beacon based PNA probe. When PNA probe used for fluorescence scanning and N1 treatment as the control, the false positive rate was 11.4%, and the false negative rate was 0; when N2 treatment as the control, the false positive rate decreased to 4.3%, but the false negative rate rose to 18.6%. When beacon based PNA probe used for fluorescence scanning, taken N1 treatment as blank control, the false positive rate was 8.6%, and the false negative rate was 1.4%; taken N2 treatment as blank control, the false positive rate was 5.7%, and the false negative rate was 1.4%. Compared with PNA probe, molecular beacon based PNA probe can effectively reduce false positives and false negatives. The success rates of hybridization of the two PNA probes were 83.3% and 95.2% respectively; and the rates of the two beacon based PNA probes were 91.7% and 90.5% respectively, which indicated that labeling the both ends of the PNA probe dose not decrease the hybridization rate with the target bacteria. The combination of liquid phase PNA-FISH and fluorescence scanning method, can significantly improve the detection efficiency.

Antibody incubation at 37°C improves fluorescent immunolabeling in free-floating thick tissue sections.

PubMed

Xiao, Xia; Feng, Ya-Ping; Du, Bin; Sun, Han-Ru; Ding, You-Quan; Qi, Jian-Guo

2017-03-01

Fluorescent immunolabeling and imaging in free-floating thick (50-60 μm) tissue sections is relatively simple in practice and enables design-based non-biased stereology, or 3-D reconstruction and analysis. This method is widely used for 3-D in situ quantitative biology in many areas of biological research. However, the labeling quality and efficiency of standard protocols for fluorescent immunolabeling of these tissue sections are not always satisfactory. Here, we systematically evaluate the effects of raising the conventional antibody incubation temperatures (4°C or 21°C) to mammalian body temperature (37°C) in these protocols. Our modification significantly enhances the quality (labeling sensitivity, specificity, and homogeneity) and efficiency (antibody concentration and antibody incubation duration) of fluorescent immunolabeling of free-floating thick tissue sections.

FPGA based demodulation of laser induced fluorescence in plasmas

NASA Astrophysics Data System (ADS)

Mattingly, Sean W.; Skiff, Fred

2018-04-01

We present a field programmable gate array (FPGA)-based system that counts photons from laser-induced fluorescence (LIF) on a laboratory plasma. This is accomplished with FPGA-based up/down counters that demodulate the data, giving a background-subtracted LIF signal stream that is updated with a new point as each laser amplitude modulation cycle completes. We demonstrate using the FPGA to modulate a laser at 1 MHz and demodulate the resulting LIF data stream. This data stream is used to calculate an LIF-based measurement sampled at 1 MHz of a plasma ion fluctuation spectrum.

Fluorescently labelled multiplex lateral flow immunoassay based on cadmium-free quantum dots.

PubMed

Beloglazova, Natalia V; Sobolev, Aleksander M; Tessier, Mickael D; Hens, Zeger; Goryacheva, Irina Yu; De Saeger, Sarah

2017-03-01

A sensitive tool for simultaneous qualitative detection of two mycotoxins based on use of non-cadmium quantum dots (QDs) is presented for the first time. QDs have proven themselves as promising fluorescent labels for biolabeling and chemical analysis. With an increasing global tendency to regulate and limit the use of hazardous elements, indium phosphide (InP) QDs are highlighted as environmentally-friendly alternatives to the highly efficient and well-studied, but potentially toxic Cd- and Pb-based QDs. Here, we developed water-soluble InP QDs-based fluorescent nanostructures. They consisted of core/shell InP/ZnS QDs enrobed in a silica shell that allowed the water solubility (QD@SiO 2 ). Then we applied the QD@SiO 2 as novel, silica shell-encapsulated fluorescent labels in immunoassays for rapid multiplexed screening. Two mycotoxins, zearalenone and deoxynivalenol, were simultaneously detected in maize and wheat, since the two QD@SiO 2 labelled conjugates emit at two different, individually detectable wavelengths. The cutoff values for the simultaneous determination were 50 and 500μgkg -1 for zearalenone and deoxynivalenol, respectively, in both maize and wheat. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to confirm the result. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Fluorescence Intensity- and Lifetime-Based Glucose Sensing Using Glucose/Galactose-Binding Protein

PubMed Central

Pickup, John C.; Khan, Faaizah; Zhi, Zheng-Liang; Coulter, Jonathan; Birch, David J. S.

2013-01-01

We review progress in our laboratories toward developing in vivo glucose sensors for diabetes that are based on fluorescence labeling of glucose/galactose-binding protein. Measurement strategies have included both monitoring glucose-induced changes in fluorescence resonance energy transfer and labeling with the environmentally sensitive fluorophore, badan. Measuring fluorescence lifetime rather than intensity has particular potential advantages for in vivo sensing. A prototype fiber-optic-based glucose sensor using this technology is being tested.Fluorescence technique is one of the major solutions for achieving the continuous and noninvasive glucose sensor for diabetes. In this article, a highly sensitive nanostructured sensor is developed to detect extremely small amounts of aqueous glucose by applying fluorescence energy transfer (FRET). A one-pot method is applied to produce the dextran-fluorescein isothiocyanate (FITC)-conjugating mesoporous silica nanoparticles (MSNs), which afterward interact with the tetramethylrhodamine isothiocyanate (TRITC)-labeled concanavalin A (Con A) to form the FRET nanoparticles (FITC-dextran-Con A-TRITC@MSNs). The nanostructured glucose sensor is then formed via the self-assembly of the FRET nanoparticles on a transparent, flexible, and biocompatible substrate, e.g., poly(dimethylsiloxane). Our results indicate the diameter of the MSNs is 60 ± 5 nm. The difference in the images before and after adding 20 μl of glucose (0.10 mmol/liter) on the FRET sensor can be detected in less than 2 min by the laser confocal laser scanning microscope. The correlation between the ratio of fluorescence intensity, I(donor)/I(acceptor), of the FRET sensor and the concentration of aqueous glucose in the range of 0.04–4 mmol/liter has been investigated; a linear relationship is found. Furthermore, the durability of the nanostructured FRET sensor is evaluated for 5 days. In addition, the recorded images can be converted to digital images by

Synchronous fluorescence spectroscopic study of solvatochromic curcumin dye

NASA Astrophysics Data System (ADS)

Patra, Digambara; Barakat, Christelle