Label-free hairpin-like aptamer and EIS-based practical, biostable sensor for acetamiprid detection

Abstract

Acetamiprid (ACE) is a kind of broad-spectrum pesticide that has potential health risk to human beings. Aptamers (Ap-DNA (1)) have a great potential as analytical tools for pesticide detection. In this work, a label-free electrochemical sensing assay for ACE determination is presented by electrochemical impedance spectroscopy (EIS). And the specific binding model between ACE and Ap-DNA (1) was further investigated for the first time. Circular dichroism (CD) spectroscopy and EIS demonstrated that the single strand AP-DNA (1) first formed a loosely secondary structure in Tris-HClO4 (20 mM, pH = 7.4), and then transformed into a more stable hairpin-like structure when incubated in binding buffer (B-buffer). The formed stem-loop bulge provides the specific capturing sites for ACE, forming ACE/AP-DNA (1) complex, and induced the RCT (charge transfer resistance) increase between the solution-based redox probe [Fe(CN)6]3−/4− and the electrode surface. The change of ΔRCT (charge transfer resistance change, ΔRCT = RCT(after)-RCT(before)) is positively related to the ACE level. As a result, the AP-DNA (1) biosensor showed a high sensitivity with the ACE concentration range spanning from 5 nM to 200 mM and a detection limit of 1 nM. The impedimetric AP-DNA (1) sensor also showed good selectivity to ACE over other selected pesticides and exhbited excellent performance in environmental water and orange juice samples analysis, with spiked recoveries in the range of 85.8% to 93.4% in lake water and 83.7% to 89.4% in orange juice. With good performance characteristics of practicality, sensitivity and selectivity, the AP-DNA (1) sensor holds a promising application for the on-site ACE detection.

Secondary Structure of DNA Aptamer Influences Biomimetic Mineralization of Calcium Carbonate

“…Circular dichroism (CD) experiments were similarly conducted at a range of pH values. Figure B shows significant differences between aptamer G and aptamer G– secondary structures at pH 7.4, with aptamer G spectra matching a typical hybrid or 3 + 1 G-quadruplex structure and aptamer G– spectra matching a typical hairpin structure . Increasing the pH to near 10 produced no significant change in the aptamer G– spectra, suggesting that it maintains its folded structure at this pH.…”

Diagnostic Approaches For COVID-19: Lessons Learned and the Path Forward

“…This may attributed to the necessity to find the best binding protocol which can capture the target molecule in a pile of many interferences present in the sample. Examples of the capturing probes which hold a promise to address these challenges include antibodies, , aptamers, , peptides, , and molecularly imprinted polymers (MIPs) , (Figure A).…”

Electrochemically mediated multi‐modal detection strategy‐driven sensor platform to detect and quantify pesticides

“…Receptor‐free approach assay is built directly over the functionalized sensor whereas affinity‐based approach is achieved by utilizing a receptor system like an antibody to capture the target analyte. [ 27 ] Both the approaches have their advantages and disadvantages, purely depending on the physico‐chemical characteristics of the analyte and transducer. In our previous work, we have shown sensing methodologies to test water and produce groups for Glyphosate and Atrazine, respectively, using an affinity‐based biosensing mechanism that is highly specific to the target species.…”

“…[19,20] Other electrochemical detection sensor platforms for use in pesticide monitoring have been evaluated quite a bit for single analyte detection. These systems include testing based on cyclic voltammetry, [20,21] square wave voltammetry, [22] amperometry, [23] differential pulse voltammetry, [24] potentiometry and electrochemical impedance spectroscopy (EIS)-faradaic (label), [25] and non-faradaic (label-free) [26,27] modalities. As per our understanding and literature surveys, there has not been much work done in universal platforms that can be applied toward a holistic pesticide assessment system.…”

“…[34,35] For the non-affinity or no-antibody-based direct sensing, the choice of the transducing material and their interaction with the analyte is extremely critical. [27] The conducting polymer is an inevitable choice to utilize as a transducer due to its unique physico-chemical properties along with excellent electrical conductivity. Among many widely popular conducting polymers, poly (3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) is a widely popular conducting polymer, known to be one of the prime choices for environmental monitor due to less toxicity compared to other conducting polymers.…”