Aptamer Biosensor Research Articles

The research of aptamer biosensor technologies for detection of microorganism.

The activities and transmissions of microorganisms are closely related to human, and all kinds of diseases caused by pathogenic microorganisms have attracted attention in the world and brought many challenges to human health and public health. The traditional microbial detection technologies have characteristics of longer detection cycle and complicated processes, therefore, which can no longer meet the detection requirements in the field of public health. At present, it is the focus to develop and design a novel, rapid, and simple microbial detection method in the field of public health. Herein, this article summarized the development of aptamer biosensor technologies for detection of microorganism in the aspect of bacteria, viruses, and toxins in detail, including optical aptamer sensors such as fluorometry and colorimetry, electrochemical aptamer sensors, and other technologies combined with aptamer. KEY POINTS: • Aptamer biosensor is a good platform for microbial detection. • Aptamer biosensors include optical sensors and electrochemical sensors. • Aptamer sensors have been widely used in the detection of bacteria, viruses, and other microorganisms.

An electrochemical impedimetric sensing platform based on a peptide aptamer identified by high-throughput molecular docking for sensitive l-arginine detection

As a primary building block for protein synthesis, l-arginine (l-Arg) is also a precursor for the synthesis of important metabolites, and is involved in various physiological and pathophysiological processes. l-Arg is a potential biomarker in clinical diagnosis and nutritional status assessment, making it valuable to quantify and monitor this biomolecule. In this study, peptide aptamers that specifically interact with l-Arg were identified by high-throughput molecular docking, and the binding capacities between the synthesized peptide aptamers and l-Arg were then measured by isothermal titration calorimetry. We hypothesized that the peptide aptamer with the greatest binding capacity could be used as the recognition element in a biosensor. A chemosynthetic peptide aptamer modified with mercaptan and spacer units (thioctic acid-GGGG-FGHIHEGY) was thus used to construct label-free electrochemical impedimetric biosensors for l-Arg based on gold electrodes. The optimum biosensor showed good sensitivity to l-Arg with a linear range of 0.1 pM–0.1 mM, and the calculated limit of detection (three times the signal-to-noise ratio) was 0.01 pM. Interference studies and assays of diluted serum samples were also carried out, and satisfactory results obtained. In conclusion, a potential method of peptide aptamer screening and biosensor fabrication for detecting small biological molecules was demonstrated.

Investigation of the recognition interaction between glycated hemoglobin and its aptamer by using surface plasmon resonance

Glycated hemoglobin (HbA1c) has been widely explored as an important marker for monitoring and diagnosing diabetes. Due to the advantages of high selectivity, easy preparation, and convenient preservation of aptamers, research on glycated hemoglobin detection utilizing aptasensors has received much attention in recent years. However, factors such as the pH and the salt concentration of the solution and the structure of the aptamer could influence the interactions between HbA1c and the aptamer. In this study, the factors were evaluated using surface plasmon resonance (SPR). The results show that the pH and the salt concentration can greatly affect the formation of a complex between the aptamer and HbA1c. In the stereostructure of the aptamer, loop L1 may be an important motif for recognizing glycated hemoglobin. In addition, the best condition for detecting HbA1c was at pH 6, with a high sensitivity and a low limit of detection(LOD) (1.06 × 10−3RUnM /2.55 nM). The results also demonstrated that the use of an SPR aptamer biosensor can be a sensitive technique to improve the accuracy and correctness of HbA1c measurement.

A Highly Sensitive Amperometric Aptamer Biosensor for Adenosine Triphosphate Detection on a 64 Channel Gold Multielectrode Array

Herein, an electrochemical aptamer biosensor based on a gold multielectrode array is reported for the detection of adenosine triphosphate (ATP), which is an important neurotransmitter in the central nervous system. The aptasensor possesses 64 individually addressable microelectrodes with a diameter of 24 μm, which is distributed over an area of 1 mm2. The electrodes are modified with an ATP‐specific aptamer, which is labeled with a ferrocene redox probe. It is demonstrated that the used chip fabrication and cleaning process generate microelectrode channels with similar electrochemical responses and electroactive surface areas. The immobilization of the aptamer on gold microelectrodes is optimized and the receptor density is determined to be (1.0 ± 0.44) × 1013 molecules cm−2. Concentration‐dependent alternating current voltammetry measurements exhibit a limit of detection of 0.30 × 10−9 m and a sensitivity of 2.4 nA logC. Furthermore, the sensor shows a high selectivity over analogous molecules and reproducible detection results in artificial cerebrospinal fluid. The sensor array is used to detect ATP via several channels of the same chip, showing high signal redundancy. A label‐free electrochemical, multichannel ATP aptasensor is demonstrated with high selectivity and subnanomolar sensitivity, which may be conducive to record this neurotransmitter in neuronal cell‐culture systems.

Tuning Biosensor Cross-Reactivity Using Aptamer Mixtures.

It is challenging to tune the response of biosensors to a set of ligands, for example, cross-reactivity to a given target family while maintaining high specificity against interferents, due to the lack of suitable bioreceptors. We present a novel approach for controlling the cross-reactivity of biosensors by employing defined mixtures of aptamers that have differing binding properties. As a demonstration, we develop assays for the specific detection of a family of illicit designer drugs, the synthetic cathinones, with customized responses to each target ligand and interferent. We first use a colorimetric dye-displacement assay to show that the binding spectra of dual-aptamer mixtures can be tuned by altering the molar ratio of these bioreceptors. Optimized assays achieve broad detection of synthetic cathinones with minimal response toward interferents and generally demonstrate better sensing performance than assays utilizing either aptamer alone. The generality of this strategy is demonstrated with a dual-aptamer electrochemical sensor. Our approach enables customization of biosensor responsiveness to an extent that has yet to be achieved through any previously reported aptamer engineering techniques such as sequence mutation or truncation. Since multiple aptamers for the designated target family can routinely be identified via high-throughput sequencing, we believe our strategy offers a generally applicable method for generating near-ideal aptamer biosensors for various analytical applications, including medical diagnostics, environmental monitoring, and drug detection.

A novel fluorescence aptamer biosensor for trace Pb(II) based on gold-doped carbon dots and DNAzyme synergetic catalytic amplification

Gold-doped carbon dots (CDAu) and carbon dots (CD) were quickly prepared by microwave irradiation procedure, using glucose as carbon source and HAuCl4 as doped reagent. Both CDAu and DNAzyme of Pb(II)-aptamer (Apt)-heme exhibit catalysis of the new fluorescence indicator reaction of H2O2-3,3′,5,5′-tetramethylbenzidine (TMB) to produce the oxidized TMB (TMBox) with a fluorescent peak at 404 nm. The Apt can be adsorbed on the CDAu surface to form a CDAu-Apt conjugate to inhibit the catalysis to cause the fluorescence intensity decreasing. The target for Pb(II) combined with the Apt to form stable G-quadruplex complex and free CDAu, in which G-quadruplex reacted with heme to form G-quadruplex/heme DNAzyme. Both the free CDAu and DNAzyme catalyzed in synergetic to produce TMBox, and the fluorescence enhanced greatly. Thus, a new and highly sensitive synergetic catalytic fluorescence method for the determination of 0.0005–0.46 μmol/L Pb(II) was established, with a detection limit of 0.25 nmol/L, its sensitivity is several orders of magnitude higher than most previously reported Pb2+ sensors. Compared with the CD, the CDAu has a quantum yield increase of 150%.

Multi-praseodymium-and-tungsten bridging octameric tellurotungstate and its 2D honeycomb composite film for detecting estrogen.

Under coordination driving force of tungsten and rare-earth (RE) bridges, we synthesized a novel giant multi-tungsten-and-RE-bridging octameric tellurotungstate (TT) [H2N(CH3)2]16K8Na6H10[Pr8(H2O)20W16O48][B-α-TeW9O33]8·70H2O (1) in CH3CN-H2O mixed solvent. The cluster anion {[Pr8(H2O)20W16O48][B-α-TeW9O33]8}40- features sixteen WVI bridges, eight PrIII bridges and eight trivacant Keggin [B-α-TeW9O33]8- fragments, which the square {W4O12} cluster can be imagined as a seed to induce the aggregation of eight [B-α-TeW9O33]8- fragments by coordination driving force of additional twelve WVI bridges and eight PrIII ions. Furthermore, the 2D 1@DODA (dimethyldioctadecyl ammonium bromide = DODA·Br) honeycomb composite material was prepared. The honeycomb morphology of the 1@DODA composite material provides rich binding sites for electrodepositing Au nanoparticles to make Au/1@DODA electrodes. The aptamer of 17β-estradiol (E2) hormone can be grafted to the Au/1@DODA electrodes via Au-S bonding interaction to construct the Au/1@DODA aptamer biosensors. By virtue of the specific recognition interaction of aptamer and the electrochemical signal amplification function of methylene blue and cDNA, the Au/1@DODA aptamer biosensors can realize the electrochemical detection of E2. This finding not only offers an electrochemical biosensing platform for detecting E2, but also expands POM-based composite materials in the applications of clinical detection and biological analysis.

Gold nanoparticle-engineered electrochemical aptamer biosensor for ultrasensitive detection of thrombin.

In order to obtain a lower detection limit in electrochemical detection, the choice of signal amplification strategy is of great importance. In this work, we describe an electrochemical sandwich aptasensor based on a signal amplification system involving two thrombin (TB) aptamers (TBA1 and TBA2), gold nanoparticles (AuNPs) as aptamer carriers, and [Ru(NH3)6]3+ for signal conversion. In the presence of the target thrombin, TBA1 and TBA2 specifically bind to TB, and the TBA1-TB-TBA2 complexes cause the formation of a sandwich structure, meaning more [Ru(NH3)6]3+ can be adsorbed on the negatively charged phosphate backbone of the aptamers, resulting in an increase in the differential pulse voltammetry (DPV) current. Under optimal conditions, the aptasensor exhibited a linear range of 1 fM to 6 pM and a limit of detection of 0.1429 fM (S/N = 3) for TB. The proposed aptasensor displayed an excellent selectivity and reproducibility. Importantly, the aptasensor was capable of detecting TB in serum samples successfully.

Aptameric biosensor for the sensitive detection of major shrimp allergen, tropomyosin

The development of a sensitive and rapid detection approach for allergens in various food matrices is essential to assist patients in managing their allergies. The most common methods used for allergen detection are based on immunoassays, PCR and mass spectrometry. However, all of them are very complex and time-consuming. Herein, an aptamer biosensor for the detection of the major shrimp allergen tropomyosin (TM) was developed. Graphene oxide (GO) was used as a platform for screening of the minimal-length aptamer sequence required for high-affinity target binding. A fluorescein dye labeled GO quenches the truncated aptamer by π-stacking interactions. After the addition of TM, the fluorescence was restored due to the competitive binding of the aptamer to GO. One of the truncated aptamers was found to bind to TM with four-fold higher affinity (30 nM) compared to the full-length aptamer (124 nM), with a limit of detection (LOD) of 2 nM. The aptamer-based sensor demonstrates the sensitive, selective, and specific detection of TM in 30 min. The performance of the sensor was confirmed using TM spiked chicken soup, resulting in a high percentage recovery (~97 ± 10%). The association of GO and labelled aptamer sensor platform has shown the rapid detection of TM in food, which is compared to other methods very sensitive, specific and performs in high throughput application.

Fabrication of ultra-sensitive photoelectrochemical aptamer biosensor: Based on semiconductor/DNA interfacial multifunctional reconciliation via 2D-C3N4

In this work, we fabricate a novel bismuth vanadate/two dimensional-carbon nitride/deoxyribonucleic acid (BiVO4/2D-C3N4/DNA) aptamer photoelectrochemical (PEC) sensor, and this sensor provides a record detection sensitivity area (5 × 10−7 μg/L - 10 μg/L) for Microcystin-LR (MC-LR). Meanwhile, except for MC-LR detection, this sensor presents highly sensitivity for tumor marker, heavy metal ion, antibiotic also by changing the DNA aptamer. Photo charge dynamic and theory calculation results reveal that 2D-C3N4 is a key material for multifunctional interface reconciliation of this PEC aptamer sensor. Firstly, it can serve as photogenerated hole oriented-transfer medium from the BiVO4 photoanode to the detective target; In addition, 2D-C3N4 with large area of π electron cloud can fix the DNA aptamer parallelly by π-π bonding with the nucleic acid in the DNA aptamer to shorten the hole transfer distance from the semiconductor to target. So that, a record MC-LR detection sensitivity has been achieved by the 2D-C3N4 modified BiVO4/DNA aptamer sensor.

Challenges in Electrochemical Aptasensors and Current Sensing Architectures Using Flat Gold Surfaces

In recent years, reagentless aptamer biosensors, named aptasensors, have shown significant advancements. Particularly, electrochemical aptasensors could change the field of biosensors in this era, where digitalization seems to be a common goal of many fields. Biomedical devices are integrating electronic technologies for detecting pathogens, biomolecules, small molecules, and ions, and the physical-chemical properties of nucleic acid aptamers makes them very interesting for these devices. Aptamers can be easily synthesized and functionalized with functional groups for immobilization and with redox chemical groups that allow for the conversion of molecular interactions into electrical signals. Furthermore, non-labeled aptamers have also been utilized. This review presents the current challenges involved in aptasensor architectures based on gold electrodes as transducers.

Aptamer-Based Nanoporous Anodic Alumina Interferometric Biosensor for Real-Time Thrombin Detection.

Aptamer biosensors are one of the most powerful techniques in biosensing. Achieving the best platform to use in aptamer biosensors typically includes crucial chemical modifications that enable aptamer immobilization on the surface in the most efficient manner. These chemical modifications must be well defined. In this work we propose nanoporous anodic alumina (NAA) chemically modified with streptavidin as a platform for aptamer immobilization. The immobilization of biotinylated thrombin binding aptamer (TBA) was monitored in real time by means of reflective interferometric spectroscopy (RIfS). The study has permitted to characterize in real time the path to immobilize TBA on the inner pore walls of NAA. Furthermore, this study provides an accurate label-free method to detect thrombin in real-time with high affinity and specificity.

Reflectance aptasensor based on metal salphen label for rapid and facile determination of insulin

An optical aptasensor-based sensing platform for rapid insulin detection was fabricated. Aminated porous silica microparticles (PSiMPs) were synthesized via a facile mini-emulsion method to provide large surface area for covalent immobilization of insulin-binding DNA aptamer (IGA3) by glutaraldehyde cross-linking protocol. A Nickel-salphen type complex with piperidine side chain [Ni(II)-SP] was synthesized with a simple one-pot reaction, and functionalized as an optical label due to strong π-π interaction between aromatic carbons of G-quadruplex DNA aptamer and planar aromatic groups of Ni(II)-SP to form the immobilized IGA3-Ni(II)-SP complex, i.e. the dye-labeled aptamer, thereby bringing yellow colouration to the immobilized G-quartet plane. Optical characterization of aptasensor towards insulin binding was carried out with a fiber optic reflectance spectrophotometer. The maximum reflectance intensity of the immobilized IGA3-Ni(II)-SP complex at 656 nm decreased upon binding with insulin as aptasensor changed to brownish orange colouration in the background. This allows optical detection of insulin as the colour change of aptasensor is dependent on the insulin concentration. The linear detection range of the aptasensor is obtained from 10 to 50 μIU mL−1 (R2 = 0.9757), which conformed to the normal fasting insulin levels in human with a limit of detection (LOD) at 3.71 μIU mL−1. The aptasensor showed fast response time of 40 min and long shelf life stability of >3 weeks. Insulin detection using healthy human serums with informed consent provided by participants suggests the DNA aptamer biosensor was in good agreement with ELISA standard method using BIOMATIK Human INS (Insulin) ELISA Kit.

Ti3C2Tx MXene and polyoxometalate nanohybrid embedded with polypyrrole: Ultra-sensitive platform for the detection of osteopontin

A nanohybrid of Ti3C2Tx MXene and phosphomolybdic acid (PMo12) embedded with polypyrrole (denoted as PPy@Ti3C2Tx/PMo12) was synthesized and used as the boost platform for strongly anchoring the osteopontin (OPN) aptamer to construct an impedimetric aptamer biosensor for the detection of OPN. The PPy@Ti3C2Tx/PMo12 hybrid not only demonstrated rich-chemical functionality, relatively high crystallinity degree, and homogeneous surface morphology but also displayed desirable electrochemical activity. These features endowed the PPy@Ti3C2Tx/PMo12 hybrid with good stability, excellent biocompatibility, and strong binding force toward OPN aptamer strands. Thus, the PPy@Ti3C2Tx/PMo12 hybrid illustrated a superior electrochemical sensing to other developed bicomponent aptasensors, such as PPy@PMo12, Ti3C2Tx@PMo12, and PPy@Ti3C2Tx hybrids. The PPy@Ti3C2Tx/PMo12-based aptasensor exhibited an extremely low detection limit of 0.98 fg mL−1, as well as high selectivity and stability, good reproducibility, acceptable regenerability, and applicability in human serum samples. This study provided a feasible, sensitive, and reliable tool for OPN detection in clinical diagnostics.

The Arsenic-Binding Aptamer Cannot Bind Arsenic: Critical Evaluation of Aptamer Selection and Binding.

An arsenic-binding aptamer named Ars-3 was reported in 2009, and it has been used for detection of As(III) in more than two dozen papers. In this work, we performed extensive binding assays using isothermal titration calorimetry, various DNA-staining dyes, and gold nanoparticles. By carefully comparing Ars-3 and a few random control DNA sequences, no specific binding of As(III) was observed in each case. Therefore, we conclude that Ars-3 cannot bind As(III). Possible reasons for some of the previously reported binding and detection were speculated to be related to the adsorption of As(III) onto gold surfaces, which were used in many related sensor designs, and As(III)/Au interactions were not considered before. The selection data in the original paper were then analyzed in terms of sequence alignment, secondary structure prediction, and dissociation constant measurement. These steps need rigorous testing before confirming specific binding of newly selected aptamers. This study calls for attention to the gap between aptamer selection and biosensor design, and the gap needs to be filled by careful binding assays to further the growth of the aptamer field.

Electrochemical aptamer biosensor for As3+ based on apta deep trapped Ag-Au alloy nanoparticles-impregnated glassy carbon electrode

ABSTRACTArsenic is toxic, so being able to detect and monitor arsenic in aqueous environments is important. Here, we report a biosensor for As3+ (Arsenic (III)) which uses a glassy carbon electrode modified with Ag-Au alloy NPs (i.e. Silver and gold alloy nanoparticles) and loaded with an aptamer. The electrode contains apta deep trapped Ag-Au alloy NPs, and the detection method employs cyclic voltammetry and differential pulse voltammetry. Captured As3+ ions undergo electrochemical reaction, producing a significant increase in the current which is observed in the voltammetry curves. This current increase is a result of the electrocatalytic properties of the NPs. The electrode is used for the determination of As3+ in real water samples. The activity curve is linear for As3+ concentrations of 0.01µg/L to 10 µg/L, and the detection limit is 0.003 × 10−3µg/L. The operation of the biosensor is reproducible, stable, and selective, and the biosensor performs well in determining As3+ in water from natural water courses, lakes, and wells.

Electrochemical Biosensor for Acetamiprid Based on Aptamer As Captured Probe and Horseradish Peroxidase for Signal Amplification

Nowadays, people pay more attention to the environmental protection and food safety problems caused by pesticide residues. In this paper, a biosensor for sensitive detection of acetamiprid, a kind of insecticide, was fabricated based on aptamer as a captured probe of acetamiprid and horseradish peroxidase (HRP) as a biocatalyst for signal amplification. The schematic diagram of fabrication of the biosensor was shown in Fig. 1. Fig. 1 The preparation of biosensor and the detection of acetamiprid Labeled aptamer of acetamiprid and a complementary DNA strand (cDNA) of the aptamer were synthesized by Shanghai Sangon Biological Engineering Technological Co. Ltd. (China). The base sequences are as-follows:[1] aptamer: 5′-NH2-(CH2)6-TGT AAT TTG TCT GCA GCG GTT CTT GAT CGC TGA CAC CAT ATT ATG AAG A-3′; cDNA: 5′- (SH) - (CH2)6 - T CTT CAT AAT ATG GTG TCA GCG ATC AAG AAC CGC TGC AGA CAA ATT ACA -3′. A 10 mL graphene oxide (GNO) suspension of 1.0 mg/mL was uniformly coated on the surface of a glassy carbon electrode (GCE) by drop-casting and allowed it to dry naturally in the air. The modified electrode (GNO/GCE) was immersed in 0.1 mol/L PBS solution containing of 0.4 mM xanthurenic acid (Xa) and was performed cyclic voltammetry scan from 0.65 V to -1.70 V (vs.SCE) for 10 cycles. GNO as the starting material was electrochemical reduction to ERGO at cathodic potential and the electropolymerization of xanthurenic acid (PXa) was achieved at anodic potential in a simply one-step process by cyclic voltammetry (CV), simultaneously. Because of the π–π* interaction between the conjugated GNO layers and aromatic rings of Xa, GNO can serve as a strong adsorbing platform for Xa monomer and promote the electropolymerization of Xa effectively. [2] After the PXa-ERGO composite film was synthesized, the PXa-ERGO/GCE electrode was immersed in 0.1 M phosphate buffer solution (PBS) of pH 7.0 containing 5.0 mM ethyl-3-(dimethylaminopropyl) carbodiimide (EDC) and 8.0 mM N-hydroxysuccinimide (NHS) to convert the terminal carboxylic group to active NHS ester. Double-helix DNA (dsDNA) was prepared by the hybridization between aptamer and cDNA. Then the dsDNA solution was coated on the surface of the PXa-ERGO/GCE electrode and incubated for 2 hours. The rich carboxylic groups of PXa-ERGO film were applied to immobilize the dsDNA with amino groups at 5’ end of cDNA by covalent bonding. The biosensor was denoted as dsDNA/PXa-ERGO/GCE. Gold nanoparticles (AuNPs) and HRP–AuNPs conjugates were prepared. Transmission electron microscope (TEM) images and ultraviolet-visible absorption spectra were used to characterize the AuNPs. AuNPs-HRP conjugates were modified onto the dsDNA/PXa-ERGO/GCE though Au–thiol interactions. Hydroquinone (HQ) and H2O2 in solution were catalyzed by HRP to generate an anodic voltammetric peak. The aptamer biosensor was successfully applied to determine acetamiprid by differential pulse voltammetry (DPV). The analysis was based on the change in the anodic peak current (i p) before and after sample solutions were applied to the surface of the working electrode at room temperature. When the background current stabilized, the anodic peak current response was recorded as i p0. In the presence of acetamiprid, aptamers bind with acetamiprid to produce a complex on the electrode surface. The HRP–AuNP–cDNA conjugates therefore fall off from the electrode surface. The anodic peak current decreased and was recorded as i p. The change in current was given by Δi p = i p0 - i p. A 25 mL aliquot of 0.1 M PBS (pH 7.4) was placed in a voltammetric cell and the required volumes of 3.0 mM HQ and 1.5 mM H2O2 solution were added. The DPV potential scan was performed from -0.4 V to 0.6 V (vs.SCE) at pulse amplitude of 20 mV, pulse frequency of 25 Hz and increment potential of 4 mV. Under the optimal conditions, the Δi p value highly and linearly increased with the increase in the logarithm of the acetamiprid concentration (c) over a range from 0.010 to 20 μg/L, with a detection limit of 0.005 μg/L. This aptamer sensor was applied in the determination of acetamiprid in river water with high specificity, sensitivity and selectivity.

Construction of ultrasensitive label-free aptasensor for thrombin detection using palladium nanocones boosted electrochemiluminescence system

Aptamer-based bioassay of biomarker has broad applications in clinical research and disease diagnosis. In this work, a label-free aptamer biosensor for ultrasensitive thrombin (TB) detection was constructed based on highly enhanced electrochemiluminescence (ECL) of functional palladium nanocones (Pd NCs) with tripropylamine (TPA) system. Herein, well-defined Pd NCs were initially functionalized by mercaptoethanol (MCH) as an ECL emitter and immobilized onto the glassy carbon electrode (GCE) initially grafted with amine-terminated polyamidoamine (PAMAM) via electro-oxidation reaction. Under optimal conditions, the ECL intensity of the Pd NCs/TPA system was about 2.5 times enhancement when compared to that of bare GCE. The ECL and cyclic voltammetry (CV) were synchronously employed to illustrate the enhanced ECL mechanism. By virtue of the linkage of the modified Pd NCs with specified TB aptamer (TBA) containing sulfydryl group, a label-free ECL detection platform was designed. After full coverage of the nonspecific sites with bovine serum albumin (BSA), an ECL biosensor for TB detection was constructed by taking the advantage of the steric hindrance effects, showing the wider linear range, lower detection limit of TB (even down to 6.76 fM), superb selectivity and stability. The current strategy provides a highly sensitive platform for detection of various biomolecules in bioanalysis.

A computational investigation of the interaction between As3+ and deoxynucleotides

ABSTRACTA successful aptamer biosensor for As3+ in aqueous solution indicated that deoxynucleotides could be a potential ligand for arsenic absorption. However, the interaction mechanism between aptamer and As3+ is still not clear. In this paper, a density functional method was applied to investigate the interactions between As3+ and four kinds of deoxynucleotides in different charge states. According to the binding energy, dGMP was the best monomer with four different binding modes, and dGMP3–As3+ with the O atom in the phosphate group was calculated to be the most stable one. Moreover, the interaction energy increased when the charge of deoxynucleotide was increased, suggesting that a negative charge was advantageous for deoxynucleotides to absorb As3+. The atoms in molecules (AIM), localised orbital locator (LOL) and Charge decomposition analyses (CDA) confirmed that the bond between N atoms and As3+ were covalent interactions and that between O atoms and As3+ were dominated by electrostatic interactions. As the charge grew, the bond strength of both interactions increased. At the same time, O atom in the vicinity of nucleobases began to participate in the interaction with As3+, which was originally bonded to N atoms.

A novel fluorescence aptasensor based on mesoporous silica nanoparticles for selective and sensitive detection of aflatoxin B1

Based on the mesoporous silica nanoparticles (MSN), a novel, simple and label-free aptamer biosensor was designed for the detection of aflatoxin B1 (AFB1). Here, the aptamers were used as molecular recognition probes and “gated molecules” while Rh6G was loaded into the interior of the particles as the signal probe. In the absence of AFB1, the “gate” was closed to prevent the leakage of the signal probe because of the immobilization of aptamers on the surface of MSN-NH2. With the presence of AFB1, the “gate” could be opened to release the signal probe for the specifical binding of aptamers to AFB1. Our results showed that the fluorescence intensity was positively correlated with the concentration of AFB1 (0.5–50 ng mL−1), with the detection limit as low as 0.13 ng mL−1. What's more, this design provides a new approach for rapid, sensitive and selective detection based on aptamers and it could be applied to numerous other analytes if appropriate aptamers are available.