量子点荧光共振能量转移检测赭曲霉毒素A

基于量子点与荧光猝灭基团之间构成的荧光共振能量转移体系,以量子点标记赭曲霉毒素A适配体与荧光猝灭基团标记的补体杂交构成荧光传感探针,当有赭曲霉毒素A存在时,由于其适配体与赭曲霉毒素A的高度亲和作用,使传感探针上结合的荧光猝灭剂减少,荧光增强,从而建立了一种检测赭曲霉毒素A的荧光分析方法.该方法简单、快速、特异性强,在适...     

Simple chemiluminescence aptasensors based on resonance energy transfer

In the present work, two aptamer-based probes and related sensor systems were developed with chemiluminescence signaling. The detection was based on "turning-on" chemiluminescence with switching "off" of the resonance energy transfer after the aptamer's recognition of the target molecule. In this design, a DNA/aptamer duplex linked a chemiluminescence group and a gold nanoparticle together. Only low-intensity chemiluminescence was obtained due to the highly efficient resonance energy transfer. After introducting the target molecule, structure-switching took place with turning off the energy transfer; thus, a restoration and turning on of the chemiluminescence was obtained. The two designs differed in the chemiluminescence groups, since one was a covalently linked luminol molecule, while the other was a conjugated horseradish peroxidase for the catalysis of further chemiluminescence reactions. These schemes provided simple and effective sensing toward a model analyte, adenosine.     

A graphene oxide platform for the assay of biomolecules based on chemiluminescence resonance energy transfer

The bifunctionality of graphene oxide (GO) that can highly adsorb single-stranded DNA (ssDNA) and effectively quench the emission of organic dyes is reasonably utilized in a chemiluminescence resonance energy transfer (CRET) system, achieving sensitive and selective detection of DNA (H1V1) and protein (thrombin), respectively.     

Photoelectrochemical biosensor for detection of adenosine triphosphate in the extracts of cancer cells

A photoelectrochemical sensing strategy for highly sensitive detection of small molecules was developed based on the recognition interaction between aptamer and target molecule-ATP.     

Nanoplasmonic detection of adenosine triphosphate by aptamer regulated self-catalytic growth of single gold nanoparticles

We present a nanoplasmonic aptasensor for adenosine triphosphate (ATP) by using single gold nanoparticles (GNPs) as probes. The specific aptamer-ATP binding induced conformational change could modulate the surface-dependent self-catalytic growth of GNPs, which enabled the detection of ATP with ultra-sensitivity and selectivity.     

Construction of a molecular beacon based on two-photon excited fluorescence resonance energy transfer with quantum dot as donor

A new molecular beacon (MB) driven by two-photon excitation (TPE) using quantum dots as energy donor is constructed, which provides reduced direct excitation of acceptor and is free of interferences from autofluorescence or scattering light in a complicated biological matrix.     

基于锰掺杂量子点的噁喹酸荧光共振能量转移检测研究

基于噁喹酸对锰掺杂硫化锌量子点的荧光猝灭作用,建立了一种噁喹酸荧光共振能量转移检测方法.噁喹酸对量子点的荧光猝灭是由于生成了新的复合物而造成的静态猝灭,二者相互作用过程中焓变ΔH ＜ 0,熵变ΔS ＜ 0,分子间作用力为氢键或范德华力.在0～65 μg/L线性范围内,噁喹酸质量浓度与量子点荧光抑制率呈现良好的线性关系(...     

A simple strategy for quantum dot assisted selective detection of cadmium ions

Here we report a simple strategy for selective detection of cadmium ions by manipulating the electron transfer pathways of surface-engineered quantum dots.     

A highly sensitive fluorescence resonance energy transfer aptasensor for staphylococcal enterotoxin B detection based on exonuclease-catalyzed target recycling strategy

An ultrasensitive fluorescence resonance energy transfer (FRET) bioassay was developed to detect staphylococcal enterotoxin B (SEB), a low molecular exotoxin, using an aptamer-affinity method coupled with upconversion nanoparticles (UCNPs)-sensing, and the fluorescence intensity was prominently enhanced using an exonuclease-catalyzed target recycling strategy. To construct this aptasensor, both fluorescence donor probes (complementary DNA₁–UCNPs) and fluorescence quencher probes (complementary DNA₂–Black Hole Quencher₃ (BHQ₃)) were hybridized to an SEB aptamer, and double-strand oligonucleotides were fabricated, which quenched the fluorescence of the UCNPs via FRET. The formation of an aptamer–SEB complex in the presence of the SEB analyte resulted in not only the dissociation of aptamer from the double-strand DNA but also both the disruption of the FRET system and the restoration of the UCNPs fluorescence. In addition, the SEB was liberated from the aptamer–SEB complex using exonuclease I, an exonuclease specific to single-stranded DNA, for analyte recycling by selectively digesting a particular DNA (SEB aptamer). Based on this exonuclease-catalyzed target recycling strategy, an amplified fluorescence intensity could be produced using different SEB concentrations. Using optimized experimental conditions produced an ultrasensitive aptasensor for the detection of SEB, with a wide linear range of 0.001–1 ng mL⁻¹ and a lower detection limit (LOD) of 0.3 pg mL⁻¹ SEB (at 3σ). The fabricated aptasensor was used to measure SEB in a real milk samples and validated using the ELISA method. Furthermore, a novel aptasensor FRET assay was established for the first time using 30 mol% Mn²⁺ ions doped NaYF₄:Yb/Er (20/2 mol%) UCNPs as the donor probes, which suggests that UCNPs are superior fluorescence labeling materials for food safety analysis.     

Highly sensitive microfluidic competitive enzyme immunoassay based on chemiluminescence resonance energy transfer for the detection of neuron‐specific enolase

A microfluidic competitive enzyme immunoassay based on chemiluminescence resonance energy transfer (CRET) was developed for highly sensitive detection of neuron‐specific enolase (NSE). The CRET system consisted of horseradish peroxidase (HRP)/luminol as a light donor and fluorescein isothiocyanate as an acceptor. When fluorescein isothiocyanate‐labeled antibody binds with HRP‐labeled antigen to form immunocomplex, the donor and acceptor are brought close each other and CRET occurs in the immunocomplex. In the MCE, the immunocomplex and excess HRP–NSE were separated, and the chemiluminescense intensity of immunocomplex was used to estimate NSE concentration. The calibration curve showed a linearity in the range of NSE concentrations from 9.0 to 950 pM with a correlation coefficient of 0.9964. Based on a S/N of 3, the detection limit for NSE determination was estimated to be 4.5 pM, which is two‐order magnitude lower than that of without CRET detection. This assay was applied for NSE quantification in human serum. The obtained results demonstrated that the proposed immunoassay may serve as an alternative tool for clinical analysis of NSE.     

Novel molecular recognition via fluorescent resonance energy transfer using a biotin-PEG/polyamine stabilized CdS quantum dot

A novel functionally PEGylated quantum dot (QD) was prepared by a coprecipitation method in the presence of the biotin-PEG/polyamine block copolymer. When CdCl2 and Na2S were mixed in aqueous media in the presence of the biotin-PEG-b-poly(2-(N,N-dimethylamino)ethyl methacrylate) [biotin-PEG/PAMA], a CdS QD with a size of ca. 5 nm was prepared. The polyamine segment was anchored on the surface of the formed CdS nanoparticle, whereas the PEG segment was tethered on the surface to form a hydrophilic palisade, thus improving the dispersion stability in aqueous media even under a high salt concentration condition. An effective fluorescent resonance energy transfer (FRET) was observed by the specific interaction of the biotin-PEG/PAMA stabilized CdS QD with TexasRed-labeled streptavidin of the physiological ionic strength of 0.15 M. The extent of the energy transfer was in proportion to the concentration of the TexasRed-streptavidin. This FRET system using the PEGylated CdS QD coupled with fluorescent-labeled protein can be utilized as a highly sensitive bioanalytical system.     

A label-free and high sensitive aptamer biosensor based on hyperbranched polyester microspheres for thrombin detection

In this paper, we have synthesized hyperbranched polyester microspheres with carboxylic acid functional groups (HBPE-CA) and developed a label-free electrochemical aptamer biosensor using thrombin-binding aptamer (TBA) as receptor for the measurement of thrombin in whole blood. The indium tin oxide (ITO) electrode surface modified with HBPE-CA microspheres was grafted with TBA, which has excellent binding affinity and selectivity for thrombin. Binding of the thrombin at the modified ITO electrode surface greatly restrained access of electrons for a redox probe of [Fe(CN)₆]^3−/4−. Moreover, the aptamer biosensor could be used for detection of thrombin in whole blood, a wide detection range (10 fM–100 nM) and a detection limit on the order of 0.90 fM were demonstrated. Control experiments were also carried out by using bull serum albumin (BSA) and lysozyme in the absence of thrombin. The good stability and repeatability of this aptamer biosensor were also proved. We expect that this demonstration will lead to the development of highly sensitive label-free sensors based on aptamer with lower cost than current technology. The integration of the technologies, which include anticoagulant, sensor and nanoscience, will bring significant input to high-performance biosensors relevant to diagnostics and therapy of interest for human health.     

A solid-state electrochemiluminescence sensing platform for detection of adenosine based on ferrocene-labeled structure-switching signaling aptamer

A solid-state electrochemiluminescence sensing platform based on ferrocene-labeled structure-switching signaling aptamer (Fc-aptamer) for highly sensitive detection of small molecules is developed successfully using adenosine as a model analyte. Such special sensing platform included two main parts, an electrochemiluminescence (ECL) substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Au nanoparticle and Ruthenium (II) tris-(bipyridine) (Ru(bpy)₃²⁺-AuNPs) onto Au electrode. An anti-adenosine aptamer labeled by ferrocene acted as the ECL intensity switch. A short complementary ssDNA for the aptamer was applied to hybridizing with the aptamer, yielding a double-stranded complex of the aptamer and the ssDNA on the electrode surface. The introduction of adenosine triggered structure switching of the aptamer. As a result, the ssDNA was forced to dissociate from the sensing platform. Such structural change of the aptamer resulted in an obvious ECL intensity decrease due to the increased quenching effect of Fc to the ECL substrate. The analytic results were sensitive and specific.     

Label-free detection of adenosine based on fluorescence resonance energy transfer between fluorescent silica nanoparticles and unmodified gold nanoparticles

A sensitive and convenient strategy was developed for label-free assay of adenosine. The strategy adapted the fluorescence resonance energy transfer property between Rhodamine B doped fluorescent silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs) to generate signal. The different affinities of AuNPs toward the unfolded and folded aptamers were employed for the signal transfer in the system. In the presence of adenosine, the split aptamer fragments react with adenosine to form a structured complex. The folded aptamer cannot be adsorbed on the surface of AuNPs, which induces the aggregation of AuNPs under high ionic concentration conditions, and the aggregation of AuNPs leads to the decrease of the quenching ability. Therefore, the fluorescence intensity of Rhodamine B doped fluorescent SiNPs increased along with the concentration of adenosine. Because of the highly specific recognition ability of the aptamer toward adenosine and the strong quenching ability of AuNPs, the proposed strategy demonstrated good selectivity and high sensitivity for the detection of adenosine. Under the optimum conditions in the experiments, a linear range from 98 nM to 100 μM was obtained with a detection limit of 45 nM. As this strategy is convenient, practical and sensitive, it will provide a promising potential for label-free aptamer-based protein detection.     

Rolling circle amplification based amperometric aptamer/immuno hybrid biosensor for ultrasensitive detection of Vibrio parahaemolyticus

Microchimica Acta - The authors describe an antibody-aptamer based hetero-sandwich amperometric biosensor for the foodborne pathogen Vibrio parahaemolyticus. Antibody on the surface of a gold...     

Label-free electrochemical detection of nanomolar adenosine based on target-induced aptamer displacement

In this work, a label-free electrochemical sensor based on target-induced displacement is reported with adenosine as the model analyte. The sensing substrate is prepared using a gold electrode modified with a self-assembled monolayer of 1,6-hexanedithiol that mediates the assembly of a gold nanoparticle film, which can increase the surface loading of capture probe and enhance the signal. An aptamer for adenosine is applied to hybridizing with the capture probe, yielding a double-stranded complex of the aptamer and the capture probe on the surface. The interaction of adenosine with the aptamer displaces the aptamer sequence and causes it to dissociate from the interface. This results in a decrease in the amount of aptamer/capture probe duplex form, and, accordingly, the desorption of methylene blue, an electroactive indicator bound to the duplex, from the electrode. Then, the redox current of the indicator can reflect the concentration of the analyte. The fabricated sensor is shown to exhibit high sensitivity, desirable selectivity and a three-decade wide linear range.     

Reversible modulation of quantum dot photoluminescence using a protein- bound photochromic fluorescence resonance energy transfer acceptor

Multiple copies ( approximately 20) of Escherichia coli maltose binding protein (MBP) were coordinated to luminescent semiconductor quantum dots (QDs) via a C-terminal oligohistidine segment. The MBP was labeled with a sulfo-N-hydroxysuccinimide-activated photochromic BIPS molecule (1',3-dihydro-1'-(2-carboxyethyl)-3,3-dimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indoline]) at two different dye-to-MBP ratios; D/P = 1 and 5. The ability of MBP-BIPS to modulate QD photoluminescence was tested by switching BIPS from the colorless spiropyran (SP) to the colored merocyanine (MC) using white light (>500 nm) or UV light ( approximately 365 nm), respectively. QDs surrounded by MBP-BIPS with D/P = 1 were quenched on average approximately 25% with consecutive repeated switches, while QDs surrounded by MBP-BIPS with D/P = 5 were quenched approximately 60%. This result suggests a possible use of BIPS-labeled proteins in QD-based nanostructures as part of a threshold switch or other biosensing device.     

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

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