Development of stable and sensitive strip biosensors for the rapid detection of organophosphates and aflatoxin B1 in agricultural samples.

In this study, we present a facile and efficient method for fabricating silk fibroin hydrogel films encapsulating the acetylcholinesterase enzyme (AChE) and pH test strips (biosensor strips) for detecting organophosphorus pesticides (OPs) and aflatoxin B1 (AFB1). These biosensor strips possess several unique properties: flexibility, time efficiency, and high stability. Upon exposure to OPs or AFB1, AChE activity is inhibited, leading to a discernible color change on the pH test strip, enabling rapid and sensitive visual detection of these contaminants. The strips were effectively utilized as a practical and sensitive platform for the visual detection of OPs and AFB1. The limits of detection for paraoxon, aldicarb, and AFB1 were determined to be 6.57, 8.92, and 0.274 ng mL, respectively. Furthermore, the applicability of these biosensors for detecting OPs or AFB1 in real samples of Chinese cabbage and peanuts was successfully demonstrated. Additionally, the performance of these novel strip composites was validated through comparison with commercial pesticide rapid test papers. Notably, the encapsulated AChE enzymes retained significant sensitivity for over 18 months, even when stored at 37 °C, and the biosensor strips exhibited remarkable resistance to sensitivity loss caused by inhibitors. This work presents a highly sensitive and stable enzyme-based visual detection paper for agricultural and food safety applications. In addition to its outstanding resistance to interference, the developed biosensor ensures reliable reproducibility and maintains stability over long-term use. This new approach to OP analysis in ecological samples has also been effectively used in the determination of OPs in lake water.