A Novel Paper-Based Electrochemical Biosensor Based on N,O-Rich Covalent Organic Frameworks for Carbaryl Detection

A new N,O-rich covalent organic framework (COFDHNDA-BTH) was synthesized by an amine-aldehyde condensation reaction between 2,6-dialdehyde-1,5-dihydroxynaphthalene (DHNDA) and 1,3,5-phenyltriformylhydrazine (BTH) for carbaryl detection. The free NH, OH, and C=O groups of COFDHNDA-BTH not only covalently couples with acetylcholinesterase (AChE) into the pores of COFDHNDA-BTH, but also greatly improves the catalytic activity of AChE in the constrained environment of COFDHNDA-BTH's pore. Under the catalysis of AChE, the acetylthiocholine (ATCl) was decomposed into positively charged thiocholine (TCl), which was captured on the COFDHNDA-BTH modified electrode. The positive charges of TCl can attract anionic probe [Fe(CN)(6)](3-/4-) on the COFDHNDA-BTH-modified electrode to show a good oxidation peak at 0.25 V (versus a saturated calomel electrode). The carbaryl detection can inhibit the activity of AChE, resulting in the decrease in the oxidation peak. Therefore, a turn-off electrochemical carbaryl biosensor based on a flexible carbon paper electrode loaded with COFDHNDA-BTH and AChE was constructed using the oxidation peak of an anionic probe [Fe(CN)(6)](3-/4-) as the detection signal. The detection limit was 0.16 mu M (S/N = 3), and the linear range was 0.48 similar to 35.0 mu M. The sensor has good selectivity, repeatability, and stability, and has a good application prospect in pesticide detection.

Automated summary

A new N,O-rich covalent organic framework (COFDHNDA-BTH) was synthesized and used for the detection of carbaryl. The framework not only improves the catalytic activity of acetylcholinesterase (AChE), but also serves as the basis for the detection signal. The modified COFDHNDA-BTH electrode shows good detection performance for carbaryl.