Lengthening the aptamer to hybridize with a stem-loop DNA assistant probe for the electrochemical detection of kanamycin with improved sensitivity

Study on the photo/electrochemical bi-functional properties of a coupling interface of Ru[dcbpy]32+-AMT/Au by SECM imaging-based joint analytical method

A photo/electrochemical coupling interface of Ru[dcbpy]32+-AMT/Au (AMT; 5-Amino-1,3,4-thiadiazole-2-thiol) was fabricated using a dehydration condensation sulfhydrating method. For the interface functional properties, a combined dual-signal recording (CDSR) method was applied to characterize the response characteristics, and a scanning electrochemical microscopy-electrochemiluminescence (SECM-ECL) imaging was developed to assess the interface distribution uniformity. The interface biosensing compatibility was validated by constructing a simple DNA sensor. The research results show that the interaction between the two functional parameters follows a synergistic effect mechanism in the coupling conditions and an interference effect mechanism in the detection condition. Under optimized conditions, the saturation dual-signal response values are 156.0 and 86.8 μA, respectively. The statistics and imaging comparison analysis validate good interface distribution uniformity and stability performance. The DNA sensor's dual-signal detection limits to the signal probe (SP) are ∼30 fM and 0.3 pM with linear ranges of 100.0 fM ∼ 1.0 nM and 1.0 pM ∼ 10.0 nM, respectively. The fabricated interface exhibits an effective bi-functional response performance compatible with biosensing. The proposed imaging method has a high technical fit for studying photo/electrochemical coupling interfaces and can also provide a reference for other similar coupling interface analyses.

Target-mediated competitive hybridization of hairpin probes for kanamycin detection based on exonuclease III cleavage and DNAzyme catalysis

Based on aptamer recognition and target-mediated competitive hybridization of hairpin probes, we developed a fluorescence sensor for kanamycin (KAN) detection. The aptamer and KAN binding will open hairpin H1 to release the trigger DNA fragment, which can initiate the competitive hybridization between hairpins H2 and H3. Then, exonuclease III (Exo III) can cleave H2 and H3 to produce numerous DNA3 and DNA4. Through the synergetic hybridization among DNA1, DNA2, DNA3, and DNA4, an active Mg²⁺-DNAzyme can be formed. The cleavage reaction toward FAM-BHQ-modified DNA2 will produce a high fluorescence signal for KAN assay. Through Exo III-guided cleavage and Mg²⁺-DNAzyme-based catalysis, the sensor exhibits high sensitivity, with a detection limit of 3.1 fM. This method is robust and has been applied to the detection of KAN in milk and water samples with good accuracy and reliability. Our developed fluorescence sensor exhibits the advantages of simple operation, high sensitivity, and good robustness, which are beneficial for KAN detection in food samples.

Advances in Design Strategies of Multiplex Electrochemical Aptasensors

In recent years, the need for simple, fast, and economical detection of food and environmental contaminants, and the necessity to monitor biomarkers of different diseases have considerably accelerated the development of biosensor technology. However, designing biosensors capable of simultaneous determination of two or more analytes in a single measurement, for example on a single working electrode in single solution, is still a great challenge. On the other hand, such analysis offers many advantages compared to single analyte tests, such as cost per test, labor, throughput, and convenience. Because of the high sensitivity and scalability of the electrochemical detection systems on the one hand and the specificity of aptamers on the other, the electrochemical aptasensors are considered to be highly effective devices for simultaneous detection of multiple-target analytes. In this review, we describe and evaluate multi-label approaches based on (1) metal quantum dots and metal ions, (2) redox labels, and (3) enzyme labels. We focus on recently developed strategies for multiplex sensing using electrochemical aptasensors. Furthermore, we emphasize the use of different nanomaterials in the construction of these aptasensors. Based on examples from the existing literature, we highlight recent applications of multiplexed detection platforms in clinical diagnostics, food control, and environmental monitoring. Finally, we discuss the advantages and disadvantages of the aptasensors developed so far, and debate possible challenges and prospects.

Regulating Valence States of Gold Nanocluster as a New Strategy for the Ultrasensitive Electrochemiluminescence Detection of Kanamycin

Monitoring of kanamycin residue has attracted considerable attention owing to the potential harm caused by the abuse of kanamycin. However, the detection of kanamycin has been limited owing to its electrochemical and optical inertness. Herein, we report a facile and highly efficient electrochemiluminescence (ECL) strategy for the detection of kanamycin based on the valence state effect of gold nanocluster (AuNC) probes. It is proven that Au⁰ in chemically reduced AuNCs (CR-AuNCs) could be oxidized to Au^I via the redox reaction between kanamycin and CR-AuNCs in the presence of H₂O₂, resulting in ECL quenching due to the valence state change of CR-AuNCs. Because the ECL of the AuNC probes is sensitively affected by the valence state, excellent sensitivity for kanamycin was achieved without any signal amplification operation and aptamers. A preferable linear-dependent curve was acquired in the detection range from 1.0 × 10^-11 to 3.3 × 10^-5 M with an extremely low detection limit of 1.5 × 10^-12 M. The proposed kanamycin sensing platform is very simple and shows high selectivity and an extremely broad linear range detection of kanamycin. Furthermore, the proposed sensing platform can detect kanamycin in milk samples with excellent recoveries. Therefore, this sensing strategy provides an effective and facile way to detect kanamycin and can help promote the understanding of the constructed mechanism of the AuNC-based ECL system, thus greatly broadening its potential application in ECL fields.

Impedimetric Determination of Kanamycin in Milk with Aptasensor Based on Carbon Black-Oligolactide Composite

The determination of antibiotics in food is important due to their negative effect on human health related to antimicrobial resistance problem, renal toxicity, and allergic effects. We propose an impedimetric aptasensor for the determination of kanamycin A (KANA), which was assembled on the glassy carbon electrode by the deposition of carbon black in a chitosan matrix followed by carbodiimide binding of aminated aptamer mixed with oligolactide derivative of thiacalix[4]arene in a cone configuration. The assembling was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. In the presence of the KANA, the charge transfer resistance of the inner interface surprisingly decreased with the analyte concentration within 0.7 and 50 nM (limit of detection 0.3 nM). This was attributed to the partial shielding of the negative charge of the aptamer and of its support, a highly porous 3D structure of the surface layer caused by a macrocyclic core of the carrier. The use of electrostatic assembling in the presence of cationic polyelectrolyte decreased tenfold the detectable concentration of KANA. The aptasensor was successfully tested in the determination of KANA in spiked milk and yogurt with recoveries within 95% and 115%.