Optical and electrochemical detection of biothiols based on aggregation of silver nanoparticles
A sensitive assay for the detection of biothiols was reported based on biothiol-induced aggregation of silver nanoparticles (Ag NPs). In the presence of biothiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), the aggregation of Ag NPs resulted in the colorimetric change of the nanoparticles, which could be observed by the naked eye and measured with UV-vis spectroscopy. More importantly, the method can be developed into a more sensitive and stable electrochemical biothiol sensing method by monitoring the electrochemical current of the Ag NPs. In the electrochemical analysis, the biothiol-induced aggregation of Ag NPs resulted in the decrease of electrochemical current. Experimental results demonstrated that for the detection of GSH, the detection limit of the electrochemical method was as low as 200 nM, which is more than 2 orders of magnitude lower than that of the colorimetric method. The developed method is simple in design and fast in operation, which can be applied to other target-induced aggregation assays and demonstrates wide applications in bio-sensing fields.