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A “turn-on” fluorometric assay for kanamycin detection by using silver nanoclusters and surface plasmon enhanced energy transfer
摘要： A rapid method is described for the determination of the antibiotic kanamycin. It integrates a kanamycin-binding aptamer and surface plasmon enhanced energy transfer (SPEET) between DNA-templated silver nanoclusters (AgNCs) and gold nanoparticles (AuNPs). The AgNCs and AuNPs were selected as energy donor and energy acceptor, respectively. The aptamer was designed to regulate the energy transfer between AgNCs and AuNPs. The aptamer was adsorbed on the AuNPs. Upon addition of kanamycin, the aptamer-kanamycin complex is formed, and this results in the aggregation of the AuNPs in high salt concentration, the formation of a blue coloration, and in the suppression of the SPEET process. The fluorescence of the AgNCs (with excitation/emission peaks at 560/600 nm) is quenched by the aptamer protected AuNPs in absence of kanamycin. The fluorescence on addition of kanamycin increases linearly in the 5 to 50 nM concentration range, with a lower detection limit of 1.0 nM (at S/N = 3). The assay can be performed within 30 min. It was successfully applied to the determination of kanamycin in spiked milk samples, and recoveries ranged between 90.2 and 95.4%. Conceivably, the strategy has a wide potential for screening by simply changing the aptamer.
关键词： Ag NCs,Milk analysis,Antibiotics detection,Au NPs,Food safety,Aptasensor
更新于2025-11-19 16:46:39
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Zero background and triple-signal amplified fluorescence aptasensor for antibiotics detection in foods
摘要： It's important to eliminate matrix interference for accurate detecting antibiotic residues in complex food samples. In this study, we designed a zero-backgrounded fluorescence aptasensor to achieve on-site detection of antibiotic residues, with chloramphenicol (CAP) as representative analyte. Moreover, a three stir-bars assisted target recycling system (TSBTR) was designed to achieve triple signal amplification and increase the sensitivity. The bars included one magnetic stir-bar modified with two kinds of long DNA chains, and two gold stir-bars modified with Y shape-duplex DNA probes respectively. In the presence of CAP, the target could recurrently react with the probes on the bars and replace a large amount of long DNA chains into supernatant. After then, the bars were taken out and SYBR green dye was added to the solution. The dye can specifically intercalate into the duplex structures of DNA chains to emit fluorescence while not emitting a signal in its free state. Under the optimized experimental conditions, a wide linear response range of 5 orders of magnitude from 0.001 ng mL?1 to 10 ng mL?1 was achieved with a detection limit of 0.033 pg mL?1 CAP. The assay was successfully employed to detect CAP in food samples (milk & fish) with consistent results with ELISA's. High selectivity and sensitivity were attributed to the zero background signal and triple signal-amplification strategy. Moreover, the detection time can be shortened to 40 min due to that three signal amplified process can occur simultaneously. The fluorescent aptasensor was also label- and enzyme-free. All these ensure the platform to be rapid, cost-effective, easily-used, and is especially appropriate for detection antibiotics in food safety.
关键词： Three stir-bars assisted target recycling,Triple signal amplification,Zero background signal,Fluorescence aptasensor,Antibiotics
更新于2025-11-19 16:46:39
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Quenched Sandwich-type Photoelectrochemical Aptasensor forProtein Detection based on Exciton Energy Transfer
摘要： This work proposes a quenched photoelectrochemical sensing method for highly selective and sensitive detection of protein via Energy Transfer (ET) effect between the AuNPs and CdS:Mn quantum dots. This detection was performed on a sandwich-type aptamer sensing interface. Chitosan modified CdS:Mn/TiO2/ITO electrode was used to immobilize capture DNA (S1) via -CONH- bond. In the presence of target protein, AuNPs labeled DNA (AuNPs-S2) was further bonded to the protein to fabricate sandwich sensing platform, which forced the AuNPs away from the electrode surface. In this state, the photocurrent was greatly depressed, mainly due to two factors: (a) the ET effect produced by interparticle distance between CdS:Mn and AuNPs; (b) the steric hindrance of AuNPs-S2 partly obstructs the diffusion of the electron donor. The photocurrent decreased with the increasing concentration of the target protein. Using thrombin as a target, this sensitized method showed a detectable range of 0.1 pM to 8 nM and a detection limit of 30 fM. It possessed high selectivity and good stability for detection of thrombin. This method is extremely flexible and can be extended to varieties of protein targets.
关键词： CdS:Mn,Photoelectrochemical aptasensor,Thrombin,Energy transfer,AuNPs
更新于2025-11-14 15:15:56
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Electrochemical surface plasmon resonance (EC-SPR) aptasensor for ampicillin detection
摘要： Surface plasmon resonance technique is highly sensitive to various processes taking place on a metal film and it has emerged as a powerful label-free method to study molecular binding processes taking place on a surface. Another important but less explored area of applications is the use of hybrid methods which combine electrochemistry with optical methods for better monitoring and understanding of biochemical processes. A detection method based on surface plasmon resonance was developed for ampicillin, applying electrochemical techniques for the elaboration and characterization of the aptasensing platform used in this study. Ampicillin is a broad-spectrum β-lactam antibiotic, used both in human and veterinary medicine for the treatment and prevention of primary respiratory, gastrointestinal, urogenital, and skin bacterial infections. It is widely used because of its broad spectrum and low cost. This widespread use can result in the presence of residues in the environment and in food leading to health problems for individuals who are hypersensitive to penicillins. The gold chip was functionalized through potential-assisted immobilization, using multipulse amperometry, first with a thiol-terminated aptamer, as a specific ligand and secondly, using the same procedure, with mercaptohexanol, used to cover the unoccupied binding sites on the gold surface in order to prevent the nonspecific adsorption of ampicillin molecules. After establishing the optimal conditions for the chip functionalization, different concentrations of ampicillin were detected in real time, in the range of 2.5–1000 μmol L?1, with a limit of detection of 1 μmol L?1, monitoring the surface plasmon resonance response. The selectivity of the aptasensor was proven in the presence of other antibiotics and drugs, and the method was successfully applied for the detection of ampicillin from river water.
关键词： Multipulse amperometry,Electrochemical surface plasmon resonance (EC-SPR),Ampicillin,QCM,Antibiotic detection,SPR aptasensor
更新于2025-09-23 15:23:52
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Building a Fluorescent Aptasensor Based on Exonuclease-Assisted Target Recycling Strategy for One-Step Detection of T-2 Toxin
摘要： In this work, a rapid and accurate assay was successfully developed for T-2 toxin detection based on exonuclease-catalyzed target recycling strategy. Upconversion nanoparticles (UCNPs) were conjugated with T-2 aptamer and used as signal probes, while magnetic nanoparticles (MNPs) were conjugated with the complementary DNA of T-2 aptamer (cDNA) and used as capture probes. The results reveled that good linear correlation (R2 = 0.9988) was achieved for T-2 toxin detection over the concentration range of 0.1–100 ng/mL with a detection limit as low as 0.035 ng/mL (S/N = 3). In addition, the reliability of the proposed method was also applied to the determination of T-2 toxin contents in real food samples and the average recoveries ranged from 95.97 to 104.00%. The sensing platform developed in our study demonstrated great potential for simple and sensitive detection of T-2 toxin contents in food samples.
关键词： T-2 toxin,Food safety,Fluorescence,Aptasensor,Target recycling strategy
更新于2025-09-23 15:23:52
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An fluorescent aptasensor for sensitive detection of tumor marker based on the FRET of a sandwich structured QDs-AFP-AuNPs
摘要： The detection of alpha-fetoprotein (AFP) is of great importance for hepatocellular carcinoma (HCC) diagnosis, but it needs to be further improved because of poor sensitivity and complicated operating steps. In this paper, a simple and sensitive homogeneous aptasensor for AFP has been developed based on F?rster resonance energy transfer (FRET) where the AFP aptamer labeled luminescent CdTe quantum dots (QDs) as a donor and anti-AFP antibody functional gold nanoparticles (AuNPs) as an acceptor. In the presence of AFP, the bio-affinity between aptamer, target, and antibody made the QDs and AuNPs close enough, thus the fluorescence of CdTe QDs quenched though the FRET between QD and AuNP. The fluorescent aptasensor for AFP showed a concentration-dependent decrease of fluorescence intensity in the low nanomolar range and a detecting linear range of 0.5-45 ng mL?1, with a detection limit of 400 pg mL?1. Moreover, this homogeneous aptasensor is simple and reliable, and obtained satisfying results for the detection of AFP in human serum samples. With more and more aptamers for biomarkers have been selected gradually, this approach could be easily extended to detection of a wide range of biomarkers. The proposed aptasensor has great potential for carcinoma screening in point-of-care testing and even in field use.
关键词： alpha fetoprotein (AFP),fluorescent aptasensor,biomarker,hepatocellular carcinoma,F?rster resonance energy transfer (FRET)
更新于2025-09-23 15:23:52
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Comparison of turn-on and ratiometric fluorescent G-quadruplex aptasensor approaches for the detection of ATP
摘要： Two fluorescent aptasensor methods were developed for the detection of ATP in biochemical systems. The first method consisted of a label-free fluorescent Bturn-on^ approach using a guanine-rich ATP aptamer sequence and the DNA-binding agent berberine complex. In the presence of ATP, the ATP preferentially binds with its aptamer and conformationally changes into a G-quadruplex structure. The association of berberine with the G-quadruplex results in the enhancement of the fluorescence signal of the former. The detection limit of ATP was found to be 3.5 μM. Fluorescence, circular dichroism and melting temperature (Tm) experiments were carried out to confirm the binding specificity and structural changes. The second method employs the ratiometric fluorescent approach based on the Forster resonance energy transfer (FRET) for the detection of ATP using berberine along with a quencher (AuNRs, AgNPs) and a fluorophore (red quantum dots (RQDs), carbon dots (CDs)) labeled at 5′ and 3′ termini of the ATP-binding aptamer sequence. Upon addition of ATP and berberine, ATP specifically binds with its aptamer leading to the formation of G-quadruplex, and similarly, berberine also binds to the G-quadruplex. This leads to an enhancement of fluorescence of berberine while that of RQD and CDs were significantly quenched via FRET. The respective detection limits calculated were 3.6 μM and 3.8 μM, indicating these fluorescent aptasensor methods may be used for a wide variety of small molecules.
关键词： Aptasensor,Adenosine-5′-triphosphate,Gold nanorods,Fluorescence,FRET,Berberine
更新于2025-09-23 15:22:29
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Colorimetric detection and typing of E. coli lipopolysaccharides based on a?dual aptamer-functionalized gold nanoparticle probe
摘要： A rapid method for identification and typing of lipopolysaccharides (LPS) was developed by utilizing the different binding affinities between two kinds of gold nanoparticles (AuNPs) functionalized with two aptamers. Aptamers against ethanolamine and E. coli O111:B4 LPS were used to functionalize the AuNPs. The AuNPs functionalized with ethanolamine aptamer can bind to ethanolamine and are termed general probe (G-probe). The G-probe can recognize any type of LPS because ethanolamine is a component of every type of LPS. This causes a sandwich-mediated aggregation of the AuNPs and a color change from red to blue. The AuNPs functionalized with aptamer against the LPS of E. coli O111:B4 specifically bind to O111:B4 LPS and are termed specific probe (S-probe). By using these two probes, a logic typing method was developed. It can detect LPS in concentrations between 2.5 and 20 μg·mL?1 and with a 1 μg·mL?1 detection limit. In the authors’ perception, the use of a dual aptamer-based colorimetric method has a large potential in terms of selective detection of microorganisms.
关键词： Logic typing,O55:B5,Aptasensor,O111:B4,Visible,Ethanolamine
更新于2025-09-23 15:22:29
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2D-Porphrinic Covalent Organic Framework-Based Aptasensor with Enhanced Photoelectrochemical Response for the Detection of C-Reactive Protein
摘要： In this study, a novel photoelectrochemical (PEC) aptasensor based on two-dimensional (2D) porphyrinic covalent organic frameworks (p-COFs) for the label-free detection of C-reactive protein (CRP) is presented. The obtained p-COFs possess high conductivity and an improved stability due to strong and rigid covalent linkages. The introduction of p-COFs hinder the recombination of electrons and holes, decreasing their band gap (Eg), thereby which improved the photocurrent conversion efficiency. Compared with pure porphyrin, p-COFs exhibited enhanced photocurrent intensity. An amplified photocurrent conversion efficiency and enhanced photocurrent results from H2O2, which act as active molecules and electron donors. As an unprecedented application of COFs in PEC bioanalysis, the detection of CRP with a PEC aptasensor is presented. The assembly of a CRP aptamer on the surface of Ag nanoparticles hinders the electron transfer, resulting in the decrease of the photocurrent response. This PEC aptasensor exhibits good analytical performances such as a rapid response, high stability, wide linear range and excellent selectivity, making COFs promising candidates for PEC bioanalysis.
关键词： C-reactive protein,Porphyrinic covalent organic framework,High photocurrent conversion efficiency,Photoelectrochemical aptasensor,Enhanced photocurrent
更新于2025-09-23 15:22:29
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Graphene quantum dot-gold hybrid nanoparticles integrated aptasensor for ultra-sensitive detection of vitamin D3 towards point-of-care application
摘要： Vitamin D is a sunshine vitamin required by the body for various physiological activities. Deficiency of vitamin D (≤ 29 ng mL-1) can cause dental diseases, sarcopenia, osteoporosis, depression, type 2 diabetes, cancer, etc. Additionally, elevated levels of vitamin D (>150 ng mL-1) can result in numerous infirmities such as anorexia, irregular heartbeat, hypercalcemia, fatigue, etc. Hence, periodic detection can help maintain an appropriate level (≥ 30 ng mL-1) of vitamin D in blood serum. Conventional techniques used for the detection of vitamin D are expensive, time consuming, require skilled work force and a specialised laboratory. Herein, we report a portable electrochemical aptasensor for the detection of vitamin D3 using graphene quantum dot-gold (GQD-Au) hybrid nanoparticles. The developed aptasensor has a linear range of 1 nM – 500 nM, limit of detection (LOD) of 0.70 nM (0.28 ng mL-1), limit of quantification (LOQ) of 2.09 nM (0.84 ng mL-1), sensitivity of 0.90 Ω nM-1 mm-2 and a response time <1 minute. The sensor shows high specificity towards vitamin D3, a good stability, shelf life of over 35 days and nearly 98% recovery with serum samples. The developed sensor has been integrated with controlled electronics, thus establishing a portable prototype.
关键词： electrochemical,graphene quantum dot-gold hybrid,aptasensor,Vitamin D3,nanoparticles
更新于2025-09-23 15:21:01