Fabrication of electro-active nano-trans surfaces to design label free electrochemical aptasensor for ochratoxin A detection

A novel electrochemical aptasensor based on polyaniline and gold nanoparticles for ultrasensitive and selective detection of ascorbic acid

Ascorbic acid (AA) is involved in many physiological activities of the body and plays an important role in maintaining and promoting human health. It is also present in many natural and artificial foods. Therefore, the development of highly sensitive and accurate AA sensors is highly desirable for human health monitoring, as well as other commercial application fields. Herein, an ultrasensitive and selective electrochemical sensor based on an aptamer was developed for the determination of AA for the first time. The aptasensor was fabricated by modifying a composite made of polyaniline (PANI) and gold nanoparticles (AuNPs) on a glassy carbon electrode. The morphologies and electrochemical properties of the resulting electrodes were characterized by various analytical methods. The results indicated relatively good electrical conduction properties of PANI for accelerated electron transfer. The modification with AuNPs provided signal amplification, suitable for applications as novel platforms for the sensitive sensing of AA. Under optimized conditions, the proposed aptasensor displayed a wide linear response toward the detection of AA from 1.0 to 1.0 × 105 ng L-1 coupled with a low detection limit of 0.10 ng L-1. The sensor also exhibited excellent selectivity and high stability, with at least 2000-fold higher sensitivity than similar previously reported methods. Importantly, the aptasensor exhibited promising properties for the determination of AA in real fruits, vegetables, and infant milk powder, thereby showing potential for food analysis.

Ratiometric Detection of Ochratoxin A Using a Regenerable COF-Au-MB-Apt Signal Probe on a Thermal-Regulated Sensor Module

Ochratoxin A (OTA) frequently contaminates grains and consequently threatens human health. Herein, we develop a regenerable signal probe and apply it to a Au-based screen-printed electrode module (SPE) for OTA determination. The signal probe, containing a structural covalent organic framework, gold nanoparticles (AuNPs), indicative methylene blue (MB), and a highly selective aptamer, is synthesized with hydrothermal and self-assembly methods. The SPE is permanently functionalized with Prussian blue (PB), AuNPs, and semicomplementary ssDNA. The signal probe, absorbed onto this SPE via hybridization, is competitively expelled by OTA, providing a ratiometric readout of ΔIMB/IPB. Probe regeneration, to erase expired COF-Au-MB-Apt after each analysis, is established with the synergy of OTA-conducted Apt-ssDNA dissociation and on-chip thermal regulation. This advantage powerfully guarantees reduplicative analyses by avoiding irreversible Apt-OTA combination and accumulation on the sensing interface. Regenerations are performed in repetitive cycles (N = 7) with 98.5% reproduction efficiency, and IMB and IPB fluctuations are calculated as 1.45 and 1.12%. This method shows log-linear OTA response in a wide range from 0.2 pg/mL to 0.6 μg/mL, and the limit of detection is 0.12 pg/mL. During natural OTA determinations, recommended readouts match well with HPLC with less than 4.82% relative error.