Nanoslit-concentration-chip integrated microbead-based protein assay system for sensitive and quantitative detection

A nanoslit-concentration-chip (NC-chip) integrated microbead assay system was fabricated to overcome the assay limits of the conventional microbead-based protein assay. The proposed assay system was composed of a microbead-trapping-chip (MT-chip) and a NC-chip as a protein-capturing device and a quantitative and sensitive protein detection device, respectively. Microbeads trapped in the MT-chip formed a three-dimensional microbead packed column leading to efficient protein capturing. The NC-chip was used to trap and concentrate nanoparticle (NP) probes that were specifically captured in the microbead bed of the MT-chip. Furthermore, the nanoslit-patterned membrane of the NC-chip enabled both signal enhancement and quantification of the amount of the trapped NPs. The NC-chip integrated microbead assay system was successfully applied to a protein assay. The sensitivity and reliability of streptavidin detection by HPQ motif containing peptide ligands were compared to those of other reported assay systems. This novel protein assay system could be applied to various microbead-based bioassays, and integration of the NC-chip could further improve their sensitivity and reliability.