Surface modification and immunoassys on COC, cross-flow microfluid channels and FRET molecules

In an effort to manufacture a high-performance disposable microfluidic system for applications in medical diagnostics, a series of studies were carried. Surface modification on COC, nanoparticle-based immunoassays on COC, manufacturing cross flow microfluidic system, synthesis of a pair of molecules for fluorescence resonance energy transfer (FRET) and preparation of a FRET nanoparticle are presented in this report. Plastics are advantageous compared with the conventional hard materials such as glass and silicon, in the application of microfluidic devices. However most plastics lack proper functional groups or hydrophilicity, which are essential requirements for microfluidic devices that need various surface chemistry. Among the plastic materials, cyclo-olefin copolymer (COC) has been recently reported to be equipped with more superior physical and optical properties. However since the COC is synthesized by copolymerizing ethylene with norbornene based on Metallocene catalyst, COC is composed only of C and H with no unsaturation. The saturated hydrocarbon polymer provides high optical clarity, which is also the cause for inertness of the COC surface. In an effort to find effective application as a microfluidic device for diagnostic purpose, we have generated an effective functional group (-OH) on the surface of COC by treating the COC with O
₂
plasma. The surface was characterized by ESCA and the fluorescence microscopy. We further proceeded to carry out sandwich-type immunoassays using fluorescence nanoparticles. A series of nanoparticle-based immunoassays were processed on a COC plate and the results were compared with those on a glass plate. AFP was turned out to be detected as low as a few ng/ml. Microfluidic channels for cross reactions were manufactured. Two types of fluidic channels were manufactured; one for surface modification and the other immunoassays. Also a series of fluorescence molecules were synthesized to choose an optimum pair for FRET. The behavior of fluorescence and FRET of the acceptor and donor dyes were studied. The future research will concern integration of each component for a disposable microfluidic chip.