Application of encoded microparticles fabricated by standard lithography on multiplexed bioassay

Suspension microarray, has become a popular candidate for multiplexed bioassay since its advent. Unlike traditional planar microarray, suspension microarray permits the probes suspended in aqueous solution while keeping their addresses, and possesses many advantages such as large available binding surface, rapid reaction rate, high multiplexing ability, and high sensitivity and specificity. Photolithography, the technology widely utilized for production of abundant microparticles as carrier in suspension microarray, was investigated by many researchers. However, there was still not a mature, efficient method to produce microparticles with low background, easily recognized identity and good hybridization capacity. To address those issues, we developed a massive coding of dissociated elements (MiCODE) technology for microparticles fabricated by standard lithography of a phototcurable polymer based on innovation of off-stoichiometry thiol-allyl, a photo-triggered free radical reaction. Every microparticles can be encoded by a specific Quick Response (QR) code. The codes were introduced by photobleaching of the fluorophores incorporated inside the polymeric microparticles. Amine-modification can be applied on the surface of microparticles for further introduction of DNA probes, leveraging the presence of excess thiol functionality on the surface. We demonstrated a multiplexed DNA hybridization using the DNA-grafted QR-encoded microparticles. MiCODE technology was further characterized by the application of microcontact printing of oligonucleotide probes on the surface of microparticles. This flexible technology take advantage of sophisticated lithography facilities for fabrication and thus is reliable to scale-up in the future, with potential functionalization in bioassays and in consumer products labeling. From the project introduced subsequently, we would prove that the well-developed standard lithography is still amenable to micropatterning, ironically it has not been developed to produce multifunctional hydrogel microparticles which are naturally compatible for bioassays. We solve this problem by developing a negative photoresist-like polymer which contain polyvinylpyrrolidone (PVP) as a rigid long-chain scaffold, interpenetrated by polyethylene glycol (PEG) triacrylate cross-linking network. This polymer can be applied to standard lithography to fabricate multilayer microparticles that are inherently hydrophilic, low-autofluorescent and chemically reactive. Microparticles can be encoded by combination of distinctive fluorescent dyes incorporated in different layers. DNA probes can be also anchored spatially for multiplexed detection after modifying the polymer composition using porogens. The resultant microparticles is demonstrated as color-encoded, pore-controllable, bioactive and potentially used as DNA sensor.