Multiplexed electrochemical protein coding based on quantum dot (QD)-bioconjugates for a clinical barcode system

An ultrasensitive imumunodiagnostic readout method based on an electrochemical analysis is presented. Different high-quality quantum dot (QD) nanocrystals (ZnS, CdS, and PbS) are tagged to antibodies for the on-site voltammetric stripping measurements of multiple antigen targets. These encoding QD tracers with distinct redox potential yield highly sensitive and selective stripping peaks at -1.11 V (Zn), -0.67 V (Cd) and - 0.52 V (Pb) at the mercury-coated glassy carbon electrode (vs. Ag/AgCI reference). The position and size of these peaks reflect the identity and level of the corresponding antigen target. The analog peaks of the QDs were converted to a digital bio-barcode system for simple and rapid medical diagnostics.