Cu Nanoclusters-Encapsulated Liposomes: Toward Sensitive Liposomal Photoelectrochemical Immunoassay.

Herein we report the strategy of liposome-mediated Cu2+-induced exciton trapping upon CdS quantum dots (QDs) for amplified photoelectrochemical (PEC) bioanalysis application. Specifically, the Cu nanoclusters (NCs)-encapsulated liposomes were first fabricated and then processed with antibodies bound to their external surfaces. After the sandwich immunocomplexing, the confined liposomal labels were subjected to sequential lysis treatments for the release of Cu NCs and numerous Cu2+ ions, which were then directed to interact with the CdS QDs electrode. The interaction of Cu2+ ions with CdS QDs could generate CuxS and form the trapping sites to block the photocurrent generation. Since the photocurrent inhibition is closely related with the Cu NCs-loaded liposomal labels, a novel and general "signal-off" PEC immunoassay could thus be tailored with high sensitivity. Meanwhile, a complementary "signal-on" fluorescent detection could be accomplished by measuring the fluorescence intensity originated from the Cu NCs. This work features the first use of Cu NCs in PEC bioanalysis and also the first NCs-loaded liposomal PEC bioanalysis. More importantly, by using other specific ions/reagents-semiconductors interactions, this protocol could serve as a common basis for the general development of a new class of liposome-mediated PEC bioanalysis.