Microbead based immunoassay for tumor marker using electrical detection system

Abstract

This study presents a novel immunoassay based on bead-bed microbiochip and immunogold labelling with silver staining enhancement. in our microbiochip, we adopt the filteration method using the microbead to immobllize sample and IGSS (immunogold silver staining)method to increase the electrical singnal. The chip is composed of an inexpensive and biocompatilble Polydimethyliloxane(PDMS) layer and Pyrex glass substrate. Platinum moicroelectrodes for electric signal detection were fabricated on the substrate and microchannel and pillar-type microfilters were formed in the PDMS layer. Three tumor markers (AFP, CEA,PSA) were assayed by a sandwich immunoassay with the system coupled to multi-meter as a detecter. As a result of electrical signal detection, total time requied for an immunoassay was less than 50 min and the detection limit for the tumor markers was found to be as low 1 ng/ml. Such a bead-based electrical detection system, described in this study, can be applied to protein analysis system.