Novel "turn on-off" paper sensor based on nonionic conjugated polythiophene-coated CdTe QDs for efficient visual detection of cholinesterase activity.

An increasing number of patients are living with Alzheimer's disease (AD); thus, the need for a method to detect AD early and sensitively has become urgent, and the demand for an intelligent analytical platform is growing year by year. Abnormal levels of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are known to be indicative of AD. In this work, a novel conjugated polythiophene (CP) compound was successfully combined with CdTe quantum dots (QDs) to improve their selectivity and sensitivity. The QDs successfully enabled the detection of low concentrations of AChE by turning on the fluorescence of the CdTe/CP via the interaction between CP and thiocholine produced by ATCh hydrolysis and aggregation induced emission enhancement (AIEE). Under optimal conditions, we reached a low detection limit of 0.14 U L-1, which is 7.9 times lower than that of pristine QDs. More importantly, an efficient, inexpensive, and disposable paper-based platform, which allows the efficient visual detection of AChE activity via the color variation of CdTe/CP, was designed. Moreover, the accuracy of the method was demonstrated by conducting a recovery test in human serum, in which the recoveries reached 107% and 110%, proving that CdTe/CP has considerable potential to be used for analyzing real biological samples. The advantages of this method are its simplicity, fast detection capability, affordability, and the fact that it can be used for on-site detection of AChE activity. Furthermore, it has certain guiding significance for detecting AD.