Search

It is important to detect lysozyme (LYZ) in a simple and rapid manner because of its potential application in the treatment of diseases and in the food industry. In this study, it was observed that the strong fluorescence of LYZ-modified Quantum Dots (QDs-LYZ) could be effectively quenched by gold nanoparticle(AuNPs) modified with antibodies against LYZ (anti-LYZ) due to fluorescence resonance energy transfer (FRET) between QDs-LYZ and anti-LYZ-AuNPs. The fluorescence can be reversibly recovered by LYZ (on state) owing to specific competitive interactions between LYZ, QDs-LYZ and anti-LYZ-AuNPs. The interaction of QDs-LYZ with anti-LYZ-AuNPs was studied by absorption, fluorescence spectroscopy and transmission electron microscopy (TEM). Under optimal conditions, LYZ can be detected with a linear range of 50-1000ng/mL and a detection limit (LOD) of 33.43ng/mL. This rapid and selective QD-based sensor was successfully applied for quantitation of LYZ in actual egg products. Furthermore, the strategy described in this report could be followed conveniently to establish similar immunosensors for the rapid detection of other proteins using corresponding antibodies., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel strategy for ovotransferrin (OVT) detection by tracing the "on-off-on" fluorescence signals of quantum dots (QDs) and gold nanoparticles (AuNPs) utilizing fluorescence measurements were established in this article. The immune interaction between QDs-OVT and anti-OVT-AuNPs leads to drastic quenching (turning off) of the donor by a fluorescence resonance energy transfer (FRET) process. After the addition of free OVT, anti-OVT-AuNPs peel off from the QDs-OVT surface and bind to free OVT due to competitive immunoreactions, resulting in the restoration of the fluorescence intensity of QDs (turning on). Consequently, this process can be utilized for the selective detection of OVT via optical responses. Under optimal conditions, the fluorescence intensity of the system increased linearly with increasing concentrations of OVT from 0.05 to 3.8 μg/mL. The limit of detection of OVT was 23.55 ng/mL. This method was applied to the analysis of OVT in egg powder samples. Furthermore, the strategy provided in this work could be conveniently followed to establish similar immunosensors for the rapid detection of other proteins with corresponding antibodies., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this paper, we constructed the fluorescence resonance energy transfer (FRET) system between two multi-color quantum dots (QDs) of two sizes for rapid and sensitive detection of Staphylococcus aureus. In this system, green-emitting QDs conjugated with rabbit anti-S. aureus antibodies were used as energy donors while orange-emitting QDs conjugated with goat-anti-rabbit IgG were used as energy acceptors to form FRET system. Pre-binding of Staphylococcus aureus (S. aureus) on the donor occupied the binding sites and thus blocked resonance energy transfer between two colors QDs, leading to the quenching fluorescence of the acceptor. The fluorescence of acceptor has a linear calibration graph with the concentrations of S. aureus from 52 to 2.6×10(5) CFU mL(-1). The low detection limit was 10 CFU/mL. It was worth mentioning that the detection method of S. aureus had been applied to the analysis of apple juice and milk samples, which could potentially be developed into a sensor in the further study., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Sialic acids (SA) are widely found as components of oligosaccharide units in mucins, glycoproteins and other microbial polymers in nature food. The aim of this study is to create a new fluorimetric detection method applied for determinating SA in egg products by using a sensitive lectin-CdTe quantum dots (QDs) nanoprobe. Water-soluble and high luminescent CdTe QDs were conjugated with sambucus nigra bark lectin (SNA) as probe for SA detection. As a result of specific interaction between SA and SNA-CdTe QDs, the conjugations finally lead to the change of a fluorescent signal. Under optimal conditions, fluorescence intensity increase linearly with the increase of the concentration of SA ranging from 12 to 680 ng/mL. The low detection limit is 0.67 ng/mL. This quick and selective analysis method for SA detection has been used in synthetic samples and egg products with recovery between 97.92% and 110.42%, which demonstrates the application of this assay is feasible and practical., (© 2014 Institute of Food Technologists®)

Water-soluble and high luminescent l-glutathione-capped-ZnSe quantum dots (QDs) were applied for ultrasensitive Pb(II) detection. l-glutathione-capped-ZnSe QDs were synthesized by a facile colloid aqueous phase route. It is characterized by transmission electron microscopy, X-ray powder diffraction spectrometry, Fourier transform infrared spectrometry, Ultraviolet-visible spectrometry and fluorescence spectrometry. Quantum yields of l-glutathione-capped-ZnSe QDs could reach 50.1% without post irradiation. The fluorescence quenching of the l-glutathione-capped-ZnSe QDs depended on the concentration, pH and reaction time of the Pb(II) solution. The possible mechanism of fluorescence of l-glutathione-capped-ZnSe QDs quenched by Pb(II) was discussed in detail. Under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of Pb(II) in the range of 1.0×10(-8)∼8.0×10(-7)mol/L. The limit of detection for Pb(II) was 0.71 nmol/L. This developed method is demonstrated to contain improved sensitive and selective characteristics for the detection of trace Pb(II) in water., (Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.)

The aim of this paper was to demonstrate a rapid and selective fluorescence-linked immunoassay method based on quantum dots as the fluorescent marker for the detection of Salmonella Enteritidis on eggshell. Highly-fluorescent and water-soluble CdTe quantum dots were prepared by using thioglycolic acid and 1-thioglycerol as ligands and were then conjugated with anti-Salmonella antibodies. As a result of specific interaction, Salmonella Enteritidis were specifically captured by bioconjugated CdTe quantum dots which led to the detection of a fluorescent signal. The bacterial cell images were obtained using fluorescence microscopy. Under optimal conditions, the quenched fluorescence intensity increased linearly with the log total count of Salmonella Enteritidis ranging from 3 × 102 to 3 × 107 CFU/mL within 1–2 h. The low detection limit was 1 × 102 CFU/mL without sample enrichment. This method was satisfactorily applied to the analysis of egg samples, which was demonstrated as a simple scheme for quick and selective detection of Salmonella Enteritidis on eggshell. [ABSTRACT FROM AUTHOR]

The immunoglobulins, most of them are glycoprotein, play an important role on humoral immune. We herein report a triple-modenano sensor with a fluorometric readout based on CdTe quantum dots (QDs) and gold nanoparticles (AuNPs) for discriminative detection of immunoglobulin. Immunoglobulins fall into several classes, each with its own functional characteristics. In this research, we use chicken egg yolk immunoglobulin (IgY) as an example to establish the specific detection methods. IgY is the only antibody existing in chicken egg yolk, which has many significant advantages. We used anti-IgY and staphylococcal protein A (SPA) to make the detection discriminatively to IgY. The immune interaction between QDs-SPA and anti-IgY-AuNPs leads to drastic quenching (turning off) of the donor by a fluorescence resonance energy transfer (FRET) process. After the addition of IgY, anti-IgY-AuNPs peel off from the QDs-SPA surface and bind to IgY due to competitive immunoreactions, resulting in the restoration of the fluorescence intensity of QDs (turning on). Consequently, this process can be utilized for the selective detection of IgY via optical responses. This proposed assay demonstrated a favorable anti interference ability and highly selectivity toward IgY with a detection limit of 1.16 ng/mL. More importantly, the nanosensor could not only function in aqueous solution for IgY detection with high sensitivity but also exhibit sensitive responses toward IgY in complicated biological environments, demonstrating its potential in bioanalysis, which might be significant in biochemical field in the future. [ABSTRACT FROM AUTHOR]

Rapid and simultaneous detection of multiple pathogenic bacteria in foods is of great importance to ensure food safety. The aim of this study is to develop a fluoroimmunoassay method using multicolor quantum dots (QDs) as fluorescent probes for simultaneous, sensitive, and rapid detection of three species of major pathogenic bacteria, that is, Salmonella Enteritidis, Staphylococcus aureus and Escherichia coli . The multicolor QDs, with different emission wavelengths located at 504 nm, 557 nm and 604 nm, were conjugated with anti- S. Enteritidis, anti- S. aureus and anti- E. coli antibodies, respectively. Through immunological recognition, target bacteria were captured by QD-antibody conjugates selectively and rapidly. The fluorescence intensities of the final complexes (measured at 504 nm, 557 nm and 604 nm respectively) have increased regularly with the increasing cell numbers of target bacteria. The changed fluorescence intensities (Δ F ) as a function of cell number (N) have been found for the three target bacteria, respectively. This multiplex fluoroimmunoassay method has been applied to nine different kinds of food samples to prove its strong anti-interference ability and wide range of application. [ABSTRACT FROM AUTHOR]

Abstract: A novel two-step controlled basic water phase method has been developed for synthesizing size-tunable and water-soluble CdTe/Cd(OH)2 core/shell quantum dots with high quantum yield and good stability. The size of the prepared CdTe/Cd(OH)2 core/shell quantum dots can be easily manipulated by varying the concentrations of NaOH solution step by step. The maximal emission wavelengths of the series CdTe/Cd(OH)2 core/shell QDs were from 513nm to 610nm (emission colors tuned from green to red). The CdTe/Cd(OH)2 core/shell quantum dots not only possess high quantum yield (up to 83%) but also exhibit excellent photostability (being stable after being stored for more than 2 months). The CdTe/Cd(OH)2 core/shell quantum dots were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction spectrometry, ultraviolet–visible spectrometry and fluorescence spectrometry. The water-soluble nature of the CdTe/Cd(OH)2 core/shell quantum dots offers great potentiality for their chemical and biological applications. This method is easily controlled, low-cost and reproducible. So it is possible to extend this approach to the preparation of other size-tunable inorganic metal hydroxide capped core/shell quantum dots. [Copyright &y& Elsevier]

Abstract: A new method for the determination of lysozyme with high sensitivity based on Resonance Rayleigh scattering (RRS) by using Cd doped ZnSe quantum dots (QDs) as a probe was proposed in this experiment. Cd doped ZnSe QDs capped with glutathione were prepared in the water phase. Further, the RRS spectrum, transmission electron microscope, and absorption spectrum of the QDs–lysozyme system have been characterized. In addition, the effects of several factors on scattering intensities were investigated, including pH value of solution, amount of QDs, mixing sequence of each reagent and the coexisting substances. Moreover, the possible mechanism for the RRS enhancement of Cd doped ZnSe QDs–lysozyme system was preliminary discussed. The RRS method for the determination of lysozyme has good sensitivity with the detection limits 6.5×10−10 gmL−1. The contents of lysozyme were determined with recoveries of 97.1–101.6% and relativity standard deviation of 2.5–3.1%, respectively. It proved that the method established in our study is very sensitive, rapid, convenient and tolerant for the determination of lysozyme in synthetically and chicken egg white. [Copyright &y& Elsevier]