Targets regulated formation of boron nitride quantum dots - Gold nanoparticles nanocomposites for ultrasensitive detection of acetylcholinesterase activity and its inhibitors

A rapid, label-free, and highly sensitive fluorescence biosensing platform has been fabricated for effectively detecting acetylcholinesterase (AChE) activity via fluorescence resonance energy transfer (FRET) between boron nitride quantum dots (BNQDs) and gold nanoparticles (AuNPs). In this work, AChE hydrolyzed acetylthiocholine (ATCh) to generate thiocholine (TCh), which can reduce chloroauric acid (HAuCl4) into AuNPs and in situ formation of TCh-BNQDs/AuNPs aggregates, resulting in fluorescence quenching of BNQDs. Moreover, paraoxon, a organophosphorus pesticide, was used to lower the activity of AChE and hinder the enzymatic hydrolysis reaction, hence weakened the fluorescence quenching of BNQDs. Based on these findings, a simple 'one-pot' FRET-based biosensor has been constructed to assess AChE activity and its inhibitor by measuring the fluorescence intensity of BNQDs. The linear range toward AChE was from 0.05 to 6.0 mU/mL with the lower detection limit of 0.0212 mU/mL, indicating the biosensor out-performs most of the reported sensors. Since the activity of AChE has been connected to a number of diseases, this convenient 'mix and detect' approach has potentially extensive application in clinic diagnosis. On the other hand, the inhibition effect by paraoxon was evaluated, and the corresponding half maximal inhibitory concentration (IC50) toward AChE was estimated to be 2.987 mu g/L. As far as we known, the proposed biosensing platform based on TCh-BNQDs/AuNPs nanocomposites is the first time to demonstrate the application of BNQDs for fluormetric assays of enzyme activity and inhibiting effect. It also opens up a novel pathway of using BNQDs to develop optical biosensors for analyzing many other analytes.