A signal-on fluorescent aptasensor based on gold nanoparticles for kanamycin detection

Carbon Nanosheets Infused with Gold Nanoparticles as an Ultrasensitive Nose for Electrochemical Arsenic Sensing

Herein, we introduce an eco-friendly electrochemical sensor based on melamine-enriched nitrogen-doped carbon nanosheets decorated with gold nanoparticles (Au-CNSm) for arsenic sensing. An extremely facile, low-toxicity, biocompatible, and affordable hydrothermal technique was adopted for the synthesis of the Au-CNSm nanocomposite. The Au-CNSm-integrated sensing platform was optimized for electrode composition by cyclic voltammetry (CV). Owing to the synergistic effects of melamine-enriched carbon nanosheets (CNSm) and gold nanoparticles (AuNPs), the anodic peak current increased in the Au-CNSm-modified sensing electrode as compared to the CNSm-decorated platform. A wide linear range of 0.0001-100 μM and a low detection limit of 0.0001 μM were obtained. The visual signals can be measured at a very minute concentration of 0.0001 μM (0.1 ppb) on a screen-printed carbon electrode (SPCE) modified with Au-CNSm. Hence, this electrode system clearly outperformed the previously reported studies in terms of linear range, limit of detection (LOD), and electrocatalytic activity for arsenic sensing. Interestingly, the fabricated biosensor can be developed as a point-of-care device for real-time environmental monitoring for public safety. Henceforth, owing to exceptional attributes such as portability, selectivity, and sensitivity, this device offers great promise in modeling a revolutionary new class of electrochemical sensing platforms for an ultrasensitive and reliable detection strategy for arsenite (As(III)).

A fluorescent aptasensor based on gold nanoparticles quenching the fluorescence of rhodamine B to detect acetamiprid

Pesticide residue detection is one of the main safety issues in the utilization of medicinal plants. In this work, a highly selective and sensitive aptasensor for acetamiprid determination was designed. The mechanism of the proposed method is based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and rhodamine B (RB). Aptamers protect AuNPs from salt-induced aggregation, which causes fluorescence quenching of RB by the AuNPs via surface energy transfer. In the absence of acetamiprid, AuNPs were coated with aptamers on the surface and dispersed in NaCl solution. At this time, the dispersed AuNPs could perfectly quench the fluorescence intensity of RB. In contrast, in the presence of acetamiprid, aptamers specifically combine with acetamiprid to form a complex. With a high salt concentration, AuNPs would be aggregated without aptamer protection, weakening the RB quenching effect. Therefore, the concentration of acetamiprid could be obtained from the change in fluorescence intensity in the system. A fluorescent sensing method was established with a linear range from 0.1 to 3 μg mL^-1, and the LOD was 0.0285 μg mL^-1. The recoveries of acetamiprid in traditional Chinese medicine (TCM) samples were 96.23-105.75%. This method has great application value for the detection of acetamiprid in a complex sample matrix.

An ultrasensitive detection platform for cocaine: Aptasensing strategy in capillary tube

Cocaine as a detrimental addictive drug threats human health through inducing heart problem, blood pressure, anxiety, immunodeficiency, paranoia, and organ damage. Thus, the quantification of cocaine in the biological samples by a simple, high specificity, and fast method is highly urgent to decrease the harmful effect of the misuse of this drug. In this study, we constructed a novel fluorescent aptasensor by combining the fluorescein (FAM)-modified specific aptamer and AuNPs in a capillary tube as the sensing substrate for the first time. The presence of cocaine recovered the fluorescence response of the aptasensor through interaction with the aptamer and differentiation of the aptamer@AuNPs complex. By fluorescence microscopy imaging of the aptasensor substrate and its quantitative analysis, a remarkable linear range from 100 pM to 600 µM and the ultra-low limit of detection (LOD) as 0.31 pM were achieved for the target detection. Cocaine was successfully quantified in the real samples (human serum and urine) by using the aptasensor. The aptasensor is simple, easy-to-use, favorable applicability, and cost-effective; and to the best of our knowledge, it is the first use of the capillary tube as a sensing platform just by using about 3 μl of the samples. It is also an easy-to-carry tool, promising for the on-site target detection. Besides, it can be a portable device for monitoring cocaine by using a handheld single-beam fluorescence microscope. It can be an appropriate detection tool in forensic science and medicine.

A review of spectroscopic probes constructed from aptamer-binding gold/silver nanoparticles or their dimers in environmental pollutants' detection

The issue of environmental pollutant residues has gained wide public attention all along. Therefore, it is necessary to develop simple, rapid, economical, portable, and sensitive detection techniques, which have become the focus of research in the pollutants detection field. Spectroscopy is one of the most convenient, simple, rapid, and intuitive analytical tools that can provide accurate information, such as ultraviolet spectroscopy, fluorescence spectroscopy, Raman spectroscopy, plasmon resonance spectroscopy, etc. Gold nanoparticles, silver nanoparticles, and their dimers with unique optical properties are commonly used in the construction of spectroscopic probes. As a class of oligonucleotides that can recognize specific target molecules, aptamers also have a strong ability to recognize small-molecule pollutants. The application of aptamer-binding metal nanoparticles in biosensing detection presents significant advantages for instance high sensitivity, good selectivity, and rapid analysis. And many spectroscopic probes constructed by aptamer-binding gold nanoparticles, silver nanoparticles, or their dimers have been successfully demonstrated for detecting pollutants. This review summarizes the progress, advantages, and disadvantages of aptamer sensing techniques constructed by visual colorimetric, fluorescence, Raman, and plasmon resonance spectroscopic probes combining gold/silver nanoparticles or their dimers in the field of pollutants detection, and discusses the prospects and challenges for their future.

Dual Detection of Hemagglutinin Proteins of H5N1 and H1N1 Influenza Viruses Based on FRET Combined With DNase I

Influenza A viruses (IAV) are classified based on their surface proteins hemagglutinin (HA) and neuraminidase (NA). Both pandemic H1N1 (pH1N1) and highly pathogenic avian influenza (HPAI) H5N1 viruses pose a significant threat to public health. Effective methods to simultaneously distinguish H1N1 and H5N1 are thus of great clinical value. In this study, a protocol for detection of HA proteins of both H1N1 and H5N1 was established. Specifically, we designed an aptasensor for HA using fluorescence resonance energy transfer (FRET) strategy combined with DNase I-assisted cyclic enzymatic signal amplification. HA aptamers of H1N1 and H5N1 IAVs labeled with various fluorescent dyes were used as probes. Graphene oxide (GO) acted as a FRET acceptor for quenching the fluorescence signal and protected aptamers from DNase I cleavage. The fluorescence signal was recovered owing to aptamer release from GO with HA protein. DNase I-digested free aptamers and HA proteins were able to further interact with more fluorescent aptamer probes, resulting in increased signal amplification. The limits of detection (LOD) of H5N1 HA and H1N1 HA were 0.73 and 0.43 ng/ml, respectively, which were 19 and 27 times higher than LOD values obtained with the DNase I-free system. The recovery rate of HA protein in human serum samples ranged from 88.23 to 117.86%, supporting the accuracy and stability of this method in a complex detection environment. Our rapid, sensitive, and cost-effective novel approach could be expanded to other subtypes of IAVs other than H1N1 and H5N1.

Signal Transduction Strategies for Analyte Detection Using DNA-Based Nanostructures

The use of DNA-based nanostructures as probes has led to significant advances in chemical and biological sensing, allowing the detection of analytes in complex media, the understanding of fundamental biological processes, and the ability to diagnose diseases based on molecular signatures. The utility of these structures arises both from DNA's inherent ability to selectively recognize and bind a variety of chemical species and from the unique properties observed when DNA is restructured at the nanoscale. In this Minireview, we chronicle the most commonly used signal transduction strategies that have been interfaced with various DNA-based nanostructures. We discuss the types of analytes and the detection scenarios that are sought after, delineate the advantages and disadvantages of each signaling strategy, and outline the key considerations that guide the selection of each signaling method.

Non-thiolated nucleic acid functionalized gold nanoparticle-based aptamer lateral flow assay for rapid detection of kanamycin

A novel Apt-LFA has been established for kanamycin based on non-thiolated nucleic acid-modified colloidal gold nanoprobe (AuNPs@polyA-DNA). The improvement in nucleic acid hybridization speed and efficiency was verified by modifying AuNPs with polyA-DNA strands instead of thiolated oligonucleotides (SH-DNA) strands. Moreover, the AuNPs@polyA-DNA was explored to apply in an Apt-LFA. The experimental factors including the concentration of the aptamer, the concentration of SA-DNA_T conjugate, the incubation time, and temperature were carefully investigated. In addition, the kanamycin aptamer was modified by extending several bases at its end to modulate the hybridization complementary strand, which was found to significantly improve the performance of Apt-LFA. Under optimal experimental conditions, the Apt-LFA can detect kanamycin in honey with a LOD of 250 ng mL^-1 by the naked eyes. A linear range of 50-1250 ng mL^-1 was obtained with a LOD of 15 ng mL^-1 in honey by a portable reader. The Apt-LFA was successfully applied to the detection of kanamycin in honey with recoveries of 95.1-105.2%.

Structural and photoactive properties of self-assembled peptide-based nanostructures and their optical bioapplication in food analysis

BACKGROUND

Food processing plays an important role in the modern industry because food quality and security directly affect human health, life safety, and social and economic development. Accurate, efficient, and sensitive detection technology is the basis for ensuring food quality and security. Optosensor-based technology with the advantage of fast and visual real-time detection can be used to detect pesticides, metal ions, antibiotics, and nutrients in food. As excellent optical centres, self-assembled peptide-based nanostructures possess attractive advantages, such as simple preparation methods, controllable morphology, tunable functionality, and inherent biocompatibility.

AIM OF REVIEW

Self-assembled peptide nanostructures with good fabrication yield, stability, dispersity in a complex sample matrix, biocompatibility, and environmental friendliness are ideal development goals in the future. Owing to its flexible and unique optical properties, some short peptide self-assemblies can possibly be used to achieve the purpose of rapid and sensitive detection of composition in food, agriculture, and the environment, expanding the understanding and application of peptide-based optics in analytical chemistry.

KEY SCIENTIFIC CONCEPT OF REVIEW

The self-assembly process of peptides is driven by noncovalent interactions, including hydrogen bonding, electrostatic interactions, hydrophobic interactions, and π-π stacking, which are the key factors for obtaining stable self-assembled peptide nanostructures with peptides serving as assembly units. Controllable morphology of self-assembled peptide nanostructures can be achieved through adjustment in the type, concentration, and pH of organic solvents and peptides. The highly ordered nanostructures formed by the self-assembly of peptides have been proven to be novel biological structures and can be used for the construction of optosensing platforms in biological or other systems. Optosensing platforms make use of signal changes, including optical signals and electrical signals caused by specific reactions between analytes and active substances, to determine the content or concentration of an analyte.

Sensitivity of photoelctrocehmical aptasensor using spiral nanorods for detecting antiobiotic levels in experimental and real samples

Given increasing concern regarding antibiotic environmental contamination, there is immediate need to monitor antibiotic levels to effectively control pollution. In this study, we used a photoelectrochemical aptasensor based on TiO₂@MoS₂ spiral nanoarrays to detect chloramphenicol (CAP) in antibiotics. Nanoarrays were directly grown on fluorine-doped tin oxide (FTO) conductive glass with excellent biochemical stability, while aptamer-SH were immobilized by chemical binding on a synthetic TiO₂@MoS₂ nanoarray. Results show that the photocurrents were reduced in the presence of photoelectrochemistry associated with specific selection of aptamer for CAP. When the measurement of the fabricated nanomaterial chip was carried out using a three-electrode system, we found a highly specific and stable detection of chloramphenicol that ranged between 0.1 pM and 1 μM, with the detection limit of 0.1 pM. In addition, we obtained satisfactory results when real sample were used to validate the potential of photoelectrochemical (PEC) aptasensor for detecting chloramphenicol content in milk. Our results demonstrate that photoelectrochemical aptasensor is conducive to the development of less toxic multifunctional nanomaterials, making the biosensor more robust and environmentally friendly. Therefore, photoelectrochemical aptasensor can be widely applied in the field of environmental monitoring.