Selective Aptasensor Research Articles

Selective aptasensor for trinitrotoluene detection: Comparison of the detecting performances from liquid and vapor phases

In general, chromatographic and sensor analyses have been utilized for explosive detection. The main interest on those systems is to develop a method to selectively detect explosives at a single step as well as from vapor phase if possible. Moreover, on-site and real-time detection with portable systems is another challenge for the researchers. On the other hand, the detection of 2,4,6-trinitrotoluene (TNT) vapor at the crime scene, preferably before the explosion is highly demanded in order to prevent the negative effects of terrorism and to ensure the safety of the civilian population. In this study, initially, Quartz Crystal Microbalance (QCM) sensor was prepared for real-time monitoring of TNT in aqueous solution, through the attachment of TNT peptide aptamer on the gold surface of QCM sensor. Secondly, after providing optimum conditions, TNT detection was investigated even from vapor phase through the QCM aptasensor. According to results, the selectivity coefficient of QCM-based aptasensor was calculated as 6.78 for TNT in respect to DNT whereas that was calculated as 9.02 for TNT in respect to TNB. In addition, the evaluation of the reusability and storage stability emphasized that the sensor could be used repeatedly without significant reduction in dissipation (∆D) values. The linearity coefficient (R2) was found to be 0.9965. The limit of detection (LOD) and the limit of quantitation (LOQ) were determined as 0.0238 and 0.0739 nM, respectively. The studies demonstrated that the portable QCM sensor decorated with the aptamer selective for TNT molecules could be classified as a promising alternative, selective, cost-friendly, easy-to-prepare, ready-to-use, and applicable for on-site and real-time explosive measurements (even from vapor phase).

Hollow carbon spheres decorated by silver nanocubes as the advanced aptasensing interface for sensitive and selective tracing of methamphetamine in human biofluids

This study presents a sensitive and selective aptasensor for the detection of trace amounts of MAMP. The aptasensing principle relies on modifying the planar screen-printed carbon electrode (SPCE) with the synthesized nanostructures of N-doped hollow carbon spheres (N-HCSs) and silver nanocubes (AgNCs). The nanocomposite has presented high active surface area and more electron transfer ability than bare SPCE surface. Furthermore, AgNCs in the nanocomposite acts as a linker to load high amounts of aptamer (Apt) biocaptures on the modified SPCE surface. By MAMP incubation on the embedded interface sensing, Apt arm wrapped around MAMP and the more space barrier induced on the surface and reduced the electrochemical signal of ferro/ferri cyanide as the anion redox probe. The aptasensor affinity toward MAMP led to a wide linear dynamic range (LDR) value from 1.00 pM to 50.00 mM with a low limit of detection (LOD) value of 3.33 × 10−4 pM compared to other electrochemical sensors with no significant interference from other common species. The aptasensor efficiency for MAMP measurement was satisfactory evaluated in some spiked and non-spiked serum, urine and saliva samples from a healthy and addicted person for MAMP. These acceptable results may promise the reliability of the proposed methodology for routine MAMP tests, especially saliva monitoring as the non-invasive analysis. The sensitivity and selectivity of the aptasensor, which is a bonus to accurate and valid discrimination of MAMP, holds great promise to provide technical support for routine analysis of real-world clinical samples.

Preparation of a Highly Sensitive Electrochemical Aptasensor for Measuring Epirubicin Based on a Gold Electrode Boosted with Carbon Nano-Onions and MB.

Epirubicin is prescribed as an essential drug for treating breast, prostate, uterine, and gastrointestinal cancers. It has many side effects, such as heart failure, mouth inflammation, abdominal pain, fever, and shortness of breath. Its measurement is necessary by straightforward and cheap methods. The application of aptamer-based electrochemical sensors is accounted as a selective option for measuring different compounds. In this work, a thiol-modified aptamer was self-assembled on the surface of the gold electrode (AuE) boosted with carbon nano-onions (CNOs), and coupled with methylene blue (MB) as an electroactive tracker to achieve a sensitive and selective aptasensor. In the absence of the epirubicin, CNOs binds to the aptamer through a π-π interaction enhancing the MB electrochemical signal. When epirubicin binds to the aptamer, the adsorption of CNOs and MB to the aptamer is not well established, so the electrochemical signal is reduced, consequently, the epirubicin value can be measured. The prepared aptasensor demonstrated an excellent sensitivity with a curve slope of 0.36 μI/nM, and 3 nM limit of detection in the linear concentration range of 1-75 nM. The prepared aptasensor was accurately capable of measuring epirubicin in blood serum samples.

A simple yet highly sensitive and selective aptasensor architecture for rapid and portable miRNA detection

Electrochemical aptasensors are a versatile tool for detecting miRNA biomarkers associated with several diseases. However, most aptasensors require complex surface and probe modifications to achieve sufficiently high sensitivity and selectivity. Here, we introduce a simple yet ultrasensitive electrochemical aptasensor architecture for the rapid and portable detection of miRNA over a broad linear range of 109 orders of magnitude in concentration with a low limit of detection of 0.28 aM. We demonstrate sensing of miR-124 as a representative biomarker in light of its association with retinal diseases and in particular age-related macular degeneration. Unlike most of the existing miRNA biosensors, we use a short capture probe and establish a dual passivation and equilibration strategy of the biosensor surface before target miRNA sensing. This approach results in high sensitivity, selectivity, and reproducibility, minimizing cross-sensitivity to other miRNAs such as miR-155, miR-182, miR-183 and a scrambled miRNA sequence. The analytical utility of our aptasensor architecture is validated in mouse serum indicating immediate potential for clinical applications such as macular degeneration screening. Overall, these insights on the engineering of reproducible and stable electrochemical surfaces for miRNA detection provide directions for the design of a family of small footprint miRNA sensing devices.

A versatile fluorometric aptasensing scheme based on the use of a hybrid material composed of polypyrrole nanoparticles and DNA-silver nanoclusters: application to the determination of adenosine, thrombin, or interferon-gamma.

The authors describe a versatile aptasensing scheme based on the use of polypyrrole nanoparticles (PPyNPs) and DNA-silver nanoclusters (DNA-AgNCs) for multiple target detection. The DNA-AgNCs consist of two functional domains, viz. (a) a nucleation domain for attaching the metal core of the nanoclusters, and (b) a recognition domain which consists of a single-stranded aptamer. In the absence of analytes, the single-strand recognition domain will be absorbed onto the surface of the PPyNPs through π stacking and hydrophobic interactions. As a result, the red fluorescence of the DNA-AgNCs (with excitation/emission peaks at 535/625nm) is quenched by the PPyNPs. On introducing the analytes, the DNA-AgNCs will bind them. This leads to the desorption of DNA-AgNCs and the recovery of the red fluorescence. Based on the above strategy, a versatile, sensitive and selective aptasensor was established for detection of adenosine, thrombin and interferon-gamma. The method was applied to the detection of the above targets in (spiked) serum samples and gave satisfactory results, with detection limit of 0.58nM for IFN-γ, 0.39nM for adenosine, and 2.2nM for thrombin. The use of PPyNPs results in uniquely low non-specific absorption and in improved analytical results in case of real-sample analysis when compared to previously reported methods. Graphical abstract Schematic illustration of DNA-silver nanoclusters and polypyrrole nanoparticlesin an aptasensor for detection of multiple targets.

Impedimetric aptasensor for the label-free and selective detection of Interleukin-6 for colorectal cancer screening

Despite the fact that cancer research has experienced important advances and remarkable improvement in the curing processes during the last decades, this disease still occupies a leading position among the causes of death worldwide. It has been demonstrated that there is an interconnection between the overexpression of interleukin-6 cytokine and the tumor growth, metastasis, and therapeutic resistance in several types of malignancies. Herein, a highly sensitive and selective aptasensor for quantitative detection of interleukin-6 was developed by using a glassy carbon electrode modified with p-aminobenzoic acid, p-aminothiophenol and gold nanoparticles. A thio-terminated aptamer specific for interleukin-6 was immobilized on the surface of the modified electrode via the formation of gold-sulfur bonds. This DNA oligonucleotide was then used as a detection probe to capture the target protein at the biosensor surface allowing label-free detection by electrochemical impedance spectroscopy. The developed aptasensor showed a good linear response from 5 pgmL-1 to 100 ngmL-1 with a detection limit of 1.6 pgmL-1, within the range of physiological concentration of the protein. The biosensor exhibited high selectivity and has been successfully used to detect interleukin-6 in blood samples collected from patients suffering of colorectal cancer, with excellent recoveries after the addition of known amount of the target protein.

Luminescent carbon nanodots based aptasensors for rapid detection of kanamycin residue

Despite the success in long-term storage of food and dietary products using antibiotics as supplements, enormous levels of their residues have remained as a significant health concern, leading to severe toxicity issues on consumption. Herein, we report an ultrasensitive and highly selective aptasensor based on carbon nanoparticles (CNPs) through a fluorescence-based aptamer-linked immunosorbent assay (FALIA) for rapid detection of kanamycin (KAA) residue. The fabricated CNP-aptasensor exhibited superior selectivity with exceptional photoluminescence properties. Under the optimal conditions, the linear equation of standard KAA solution was Y = −0.2279LogX+1.3648 (R = −0.9893) ranged from 10−4 to 10−7 ppb with excellent relative standard deviations (RSD) between 3.12 and 5.59 % (n = 3). Moreover, the limit of detection (LOD) was lower than 5.0 × 10−8 ppb. Together, the excellent recovery and significant efficacy in the rapid detection of antibiotics at a low level in milk indicate that this fabricated CNP-aptasensor has a great potential in the establishment of an efficient antibiotic detector system in food and other nutraceutical industries.

Synergistic molecular assembly of an aptamer and surfactant on gold nanoparticles for the colorimetric detection of trace levels of As3+ions in real samples

A facile and selective aptasensor was developed by the synergistic molecular assembly of the Ars-3 aptamer on AuNPs for the detection of As3+ions using CTAB as a binder.

A novel aptasensor for malathion blood samples detection based on DNA–silver nanocluster

A sensitive and selective aptasensor based on DNA–silver nanocluster probes has been proposed for the simple and efficient detection of malathion in biological samples.

An electrochemical aptasensor for the highly sensitive detection of 8-hydroxy-2′-deoxyguanosine based on the hybridization chain reaction

In the present work a highly sensitive and selective aptasensor was developed for the determination of 8-hydroxy-2′-deoxyguanosine (8-OH-dG) based on the hybridization chain reaction (HCR) signal amplification. It was observed that the aptamer of 8-OH-dG could hybridize with the capture DNA immobilized on the gold electrode with a sticky tail left, which initiated the HCR and led to the formation of extended dsDNA structure on the electrode surface. Then the electroactive species ([Ru(NH3)6]3+, RuHex) intercalated into the dsDNA grooves to generate the amplified signal. However, in the presence of 8-OH-dG, the aptamer containing G-rich nucleic acid sequences would be induced to form a G-quadruplex structure, which made it impossible to continue the HCR. So the detection signal will significantly decrease. Under the optimal conditions, the peak current of RuHex was linear with the logarithm of 8-OH-dG concentration in the range from 10pM to 100μM with the detection limit of 2.5pM. By integrating the merits of enzyme-free amplification power of the HCR and the inherent high sensitivity of the electrochemical technique, the prepared aptasensor not only showed high sensitivity for the detection of 8-OH-dG, but also exhibited good selectivity against to the uric acid, an important interferent in the urine sample. Particularly, the aptasensor was applied to detect 8-OH-dG in urine samples with satisfactory results.

Highly sensitive and selective aptasensor for detection of adenosine based on fluorescence resonance energy transfer from carbon dots to nano-graphite

In this article, a novel aptasensor was fabricated by modifying carbon dots (CDs) with adenosine aptamer (CDs-aptamer) for sensitive, selective and quantitative detection of adenosine (AD). When nano-graphite (NG) as an energy acceptor was added into the CDs-aptamer (energy donor) solution, the fluorescence of CDs-aptamer was quenched due to fluorescence resonance energy transfer (FRET). When AD was present in the solution of CDs-aptamer/NG, the process of FRET was inhibited because of the specific combination between AD and AD aptamer. As a result, the fluorescence of CDs-aptamer was restored due to the dissociation of CDs-aptamer from NG and its change was proportional to the AD concentration. Under the optimized conditions, a linear range was found to be 2–50nM for the detection of AD with a detection limit of 0.63nM. Furthermore, the application of the proposed approach was demonstrated in real sample with satisfying results and it showed promise in diagnostic purpose.

A sensitive aptasensor for colorimetric detection of adenosine triphosphate based on the protective effect of ATP-aptamer complexes on unmodified gold nanoparticles

Adenosine triphosphate (ATP) is the most direct source of energy in organisms. This study is the first to demonstrate that ATP-aptamer complexes provide greater protection for unmodified gold nanoparticles (AuNPs) against salt-induced aggregation than either aptamer or ATP alone. This protective effect was confirmed using transmission electron microscopy, dynamic light scattering, Zeta potential measurement, and fluorescence polarization techniques. Utilizing controlled particle aggregation/dispersion as a gauge, a sensitive and selective aptasensor for colorimetric detection of ATP was developed using ATP-binding aptamers as the identification element and unmodified AuNPs as the probe. This aptasensor exhibited a good linear relationship between the absorbance and the logarithm concentration of ATP within a 50–1000nM range. ATP analogs such as guanosine triphosphate, uridine triphosphate and cytidine triphosphate resulted in little or no interference in the determination of ATP.

Selection, Characterization, and Application of High Affinity Microcystin-Targeting Aptamers in a Graphene-Based Biosensing Platform

The development of successful biosensing platforms is highly dependent upon the biorecognition properties of the recognition receptor and the sensitivity of the transducer of the binding signal. The integration of the high affinity and specificity of DNA aptamers, and the unique properties of the carbon nanomaterial graphene, offers an excellent avenue for sensitive and selective biosensing architectures. In this work, novel microcystin-targeting DNA aptamers were successfully selected using systematic evolution of ligand by exponential enrichement (SELEX). Then, highly sensitive and selective aptasensor which utilizes an unlabeled aptamer noncovalently assembled on a graphene electrode for microcystin-LR detection was developed. Assembly of the DNA aptamer on the graphene-modified electrodes caused a marked drop in the square wave voltammetric reduction signal of the [Fe(CN)6]4−/3− redox couple. The presence of microcystin-LR, on the other hand, caused a dose-responsive increase in peak current, allowing the quantification of microcystin-LR through the measurement of peak current change. Under optimal conditions, the detection limit of the developed aptasensor was 1.9 pM in buffer, a concentration much lower than those offered by previously reported biosensors for microcystin-LR. The developed aptasensor also exhibited excellent selectivity for microcystin-LR with no detectable cross-reactivity to okadaic acid, microcystin-LA and -YR. Moreover, the proposed aptasensor has been applied for the analysis of spiked tap water and fish samples showing good recovery percentages. We also demonstrated in this work that the mechanism of the detection was based on the conformation change in part of the aptamer without complete release from the graphene surface. This novel, simple, high performance and low-cost detection platform would facilitate the routine monitoring of microcystin –LR in real samples.

Non-Faradaic electrochemical impedance spectroscopy as a reliable and facile method: Determination of the potassium ion concentration using a guanine rich aptasensor.

In this article we report the application of non-Faradaic mode of electrochemical impedance spectroscopy (EIS) for determination of potassium ion (K(+)) concentration using a guanine rich K(+)-selective aptasensor (K(+)-aptasensor). This is a simple, electroactive probe free, sensitive and reproducible method allowing determination of K(+) ion concentration without any disturbance from electroactive probes used in similar works based on the Faradaic EIS method. Herein, a wide linear range of K(+) ion concentrations (1 μM-0.1mM) with a 200 nM limit of detection was achieved which is better than most of the previously reported Faradaic biosensing methods. The proposed method maintains valuable applications when it is used for K(+) determination in the presence of potentially important interferences in biological media. Thus, application of the non-Faradaic EIS method for sensing the concentration of K(+) ion with the presented K(+)-aptasensor can find an important role in clinical assay.

A novel ultrasensitive aptasensor based on silver nanoparticles measured via enhanced voltammetric response of electrochemical reduction of riboflavin as redox probe for cocaine detection

A novel, simple and selective aptasensor for ultrasensitive detection of the addictive drug, cocaine, is developed using the electrochemical transduction method. The aptasensor is constructed by covalent immobilization of aptamer-functionalized AgNPs on the MWCNTs/IL/Chit nanocomposite as the sensing interface which improves the conductivity and performance characteristics of the aptasensor and enhances the loading amount of the aptamer DNA sequence. In this study, riboflavin (RF) has been used for the first time as the redox probe in the development of the electrochemical aptasensor for the diagnosis of cocaine. AgNPs lead to the acceleration of the electron transfer kinetics related to the reduction of RF. The differential pulse voltammetric (DPV) signal of the RF linearly decreases with increased concentration of cocaine from 2nM to 2.5μM with a detection limit (S/N=3) of 150pM. By using certain analgesic drugs as the interfering agents, the excellent specificity of this sensing system for cocaine measurement is also demonstrated. Finally, the proposed aptasensor has successfully been used to detect cocaine in human serum samples.

Label-Free Voltammetric Aptasensor for the Sensitive Detection of Microcystin-LR Using Graphene-Modified Electrodes

The development of successful biosensing platforms is highly dependent upon the biorecognition properties of the recognition receptor and the sensitivity of the transducer of the binding signal. The integration of the high affinity and specificity of DNA aptamers with the unique properties of the carbon nanomaterial graphene offers an excellent avenue for sensitive and selective biosensing architectures. In this work, a highly sensitive and selective aptasensor which utilizes an unlabeled DNA aptamer assembled on a graphene electrode for microcystin-LR detection was developed. A facile strategy was used for the aptasensor fabrication on the basis of the noncovalent assembly of DNA aptamer on graphene-modified screen printed carbon electrodes. Assembly of the DNA aptamer on the graphene-modified electrodes caused a marked drop in the square wave voltammetric reduction signal of the [Fe(CN)6](4-/3-) redox couple. The presence of microcystin-LR, on the other hand, caused a dose-responsive increase in peak current, allowing the quantification of microcystin-LR through the measurement of peak current change. Under optimal conditions, the detection limit of the developed aptasensor was 1.9 pM in buffer, a concentration much lower than those offered by previously reported biosensors for microcystin-LR. The developed aptasensor also exhibited excellent selectivity for microcystin-LR with no detectable cross-reactivity to okadaic acid, microcystin-LA, and microcystin-YR. Moreover, the proposed aptasensor has been applied for the analysis of spiked tap water and fish samples showing good recovery percentages. This novel, simple, high-performance, and low-cost detection platform would facilitate the routine monitoring of microcystin-LR in real samples.

A highly sensitive and selective aptasensor based on fluorescence polarization for the rapid determination of oncoprotein vascular endothelial growth factor (VEGF)

Vascular endothelial growth factor (VEGF) discrimination in blood is useful for the early diagnosis, staging, and monitoring of cancers. However, effective and efficient methods are needed to improve the diagnosis and assessment of cancer. Here, we report a DNA aptasensor based on fluorescence polarization for the detection of vascular endothelial growth factor (VEGF), a predominant biomarker of cancer angiogenesis. An anti-VEGF DNA aptamer, labeled by a single fluorescent dye at its extremity, was employed as a model functional nucleic acid probe. The DNA conformational change generated by the VEGF binding was able to induce a significant increase in the fluorescence polarization signal. In the absence of VEGF, fluorescently labeled aptamer is in a flexible single strand state, and will have a low P value of the system. Upon the addition of VEGF, it binds with its aptamer, forming a G-quadruplex aptamer–VEGF complex upon its association with the protein. This leads to a significant increase of P value, which provides the quantitative basis of the detection of VEGF. The sensor is prepared in aqueous solution, without separation and washing, and essentially reagentless. We envision that our developed aptasensor holds utilities for point-of-care cancer prognostics by incorporating simplicity in detection, low-cost for test, and required small sample volumes.

A highly sensitive and selective aptasensor based on graphene oxide fluorescence resonance energy transfer for the rapid determination of oncoprotein PDGF-BB

Oncoprotein platelet derived growth factor-BB (PDGF-BB) is one of the most critical growth factors that regulates tumor growth and division. In this work, a highly sensitive and selective fluorescence resonance energy transfer (FRET) aptasensor for PDGF-BB detection based on the assembly of dye-labeled aptamer and graphene oxide (GO) is developed for the first time. Due to the non-covalent assembly between aptamer and GO, fluorescence quenching of the dye takes place because of FRET. In the presence of PDGF-BB, the binding between aptamer and PDGF-BB will disturb the interaction between aptamer and GO, and release the dye-labeled aptamer from the GO surface, resulting in restoration of the fluorophore fluorescence. Because of the high fluorescence quenching efficiency, unique structure, and electronic properties of GO, the GO aptasensor exhibits extraordinarily high sensitivity. We also demonstrate that two highly related molecular variants of PDGF (AA, AB) can be distinguished from PDGF-BB, which indicates the aptasensor has excellent selectivity. Such an aptasensor opens a rapid, selective and sensitive route for the detection of PDGF-BB and provides a promising strategy for other cancer-related proteins detections.

Detection of thrombin using electrogenerated chemiluminescence based on Ru(bpy) 32+-doped silica nanoparticle aptasensor via target protein-induced strand displacement

A sensitive and selective aptasensor using tri(2,2′-bipyridyl)ruthenium(II)-doped silica nanoparticles (Ru(bpy) 3 2+-doped SNPs) as DNA tags for detection of thrombin is developed based on the target protein-induced strand displacement of the DNA probe. For the proposed aptasensor, the aptamer was assembled on the surface of the Au electrode through Au-S binding. The hybridization event between the DNA probe labeled by the Ru(bpy) 3 2+-doped SNPs and the aptamer was evaluated by electrogenerated chemiluminescence (ECL) measurements. Then, the DNA probe was displaced by thrombin and the binding event between the thrombin and the aptamer was monitored by ECL measurements again. The difference of ECL intensity (Δ I ECL) of the two events could be used to quantify the thrombin. Other proteins, such as bovine serum albumin and bovine hemoglobin, had almost negligible Δ I ECL. Under the optimal conditions, the Δ I ECL was linearly related to the concentration of the thrombin in the range of 10 fM to 10 pM and the detection limit was down to 1.0 fM since SNPs containing a large number of Ru(bpy) 3 2+ molecules were labeled on the DNA probe.