Stimuli-responsive conductive hydrogel touch sensor for electrochemical and fluorescence monitoring of acetylcholinesterase activity and inhibition

In this study, we produced a stimuli-responsive electrochemical and fluorescence biosensor using carbonized diselenide-crosslinked polymer dot-loaded polydopamine nanoparticles (PDA@dsPD) incorporated into polyvinyl alcohol/chitosan hydrogel, to examine the activity and inhibition of acetylcholinesterase (AChE). The PDA@dsPD inside the hydrogels (i.e., PDA@dsPD-Hydrogel) was sensitive to AChE in the presence of acetylthiocholine, which formed thiocholine that dissolved the diselenide bonds and simultaneously released polydopamine nanoparticles; this affected the optical and electronic performance of the hydrogel. The electronic response-based pressure and strain on the PDA@dsPD-Hydrogel shifted to 23 % when the AChE concentration was 300 U/L, while in the absence of AChE, this value shifted to 46 %. The PDA@dsPD-Hydrogels were able to visualize the AChE fluorescence signal expressed by PC-12 cells, in addition to an increase in electronic conductivity after the cleavage of the diselenide bond. In contrast, no change in the electrochemical or fluorescence signals was observed in the presence of neostigmine, an AChE inhibitor. The novel PDA@dsPD-Hydrogel can even be connected to a wireless electronic device to facilitate the detection of AChE via smartphones.