Nanoengineered Encapsulation of Mediator Microcrystals and Their Use as a Non-metallic Label System for the Silver Enhancement Technique

Abstract

We report on the nanoengineered encapsulation and functionalization of mediator microcrystals and their use as a non-metallic bioassay label system for the silver enhancement technology. Mediator microcrystals were encapsulated and functionalized by using a Layer-by-Layer (LbL) based approach. This is a generic way to transform most low-soluble mediators (e.g., ferroceneacetic acid) into a label for electrochemical bioassays. Instead of using conventional gold particles, encapsulated mediator microcrystals are used as the primary label for the silver enhancement technique. After the biorecognition reaction the unbound labels were separated and a silver(I) ion solution was added. The mediator reduces silver ions into metallic silver and the mediator microcrystal was transformed into a silver particle. Consecutively a reducing agent was added leading to a further silver growth, representing the silver enhancement step. A large amount of silver was developed from the mediator, resulting in signal amplification. The amount of developed silver was studied in a bioassay and was found proportional to the analyte concentration.