Deposition of chemically reactive and repellent sites on biosensor chips for reduced non-specific binding.

The performances of new polymeric materials with excellent optical properties and good machinability have led the biomedical diagnostics industry to develop cheap disposable biosensor platforms appropriate for point of care applications. Zeonor, a type of cycloolefin polymer (COP), is one such polymer that presents an excellent platform for biosensor chips. These polymer substrates have to be modified to have suitable physico-chemical properties for immobilizing proteins. In this work, we have demonstrated the amine functionalization of COP substrates, by plasma enhanced chemical vapour deposition (PECVD), through codeposition of ethylene diamine and 3-aminopropyltriethoxysilane precursors, for building chemistries on the plastic chip. The elemental composition, adhesion, ageing and reactivity of the plasma polymerized film were examined. The Si-O functionality present in amino silane contributed for a good interfacial adhesion of the coating to COP substrates and also acted as a network building layer for plasma polymerization. Wet chemical modification was then carried out on the amine functionalized chips to create chemically reactive isothiocyanate sites and protein repellent fluorinated sites on the same chip. The density of the reactive and repellent sites was altered by choosing appropriate mixtures of homofunctional phenyldiisothiocyanate (PDITC), pentafluoroisothiocyanate (5FITC) and phenylisothiocyanate (PITC) compounds. By tailoring the density of reactive binding sites and protein repellent sites, the non-specific binding of ssDNA has been decreased to a significant extent.

Reactive amine surfaces for biosensor applications, prepared by plasma-enhanced chemical vapour modification of polyolefin materials.

Here we have demonstrated a solventless plasma-based process that integrates low-cost, high throughput, high reproducibility and ecofriendly process for the functionalization of the next-generation point-of-care device platforms. Amine functionalities were deposited by plasma-enhanced chemical vapour deposition (PECVD) using a new precursor. The influence of the plasma RF power and the deposition time on surfacial properties, as well as their effect on the reactivity and content of amino groups was investigated. The key process determinants were to have a sufficient power in the plasma to activate and partially fragment the monomer but not too much as to lose the reactive amine functionality, and sufficient deposition time to develop a reactive layer but not to consume or erode the amine reactivity. An immunoassay performed using human immunoglobulin (IgG) as a model analyte showed an improvement of the detection limit by two orders of magnitude beyond that obtained using devices activated by liquid-phase reaction.

Protein pattern transfer for biosensor applications.

This paper presents a very simple, industrially scalable method for transferring a high-resolution, biologically active protein pattern from one substrate to another. We demonstrate the transfer of a protein pattern formed initially by microcontact printing from a silicon surface (to which this form of printing is applicable) onto a glass or polymer substrate, almost independently of the surface/bulk properties of the second substrate. A very thin, spin-coated layer of a sugar is used to preserve the structure and organization of proteins during the subsequent plasma deposition of a siloxane polymer, after which the protein pattern could simply be peeled off the silicon substrate and glued onto any other desired substrate.

Plasma surface modification of cyclo-olefin polymers and its application to lateral flow bioassays.

The modification of cyclo-olefin polymer Zeonor by plasma-enhanced chemical vapor deposition to form a silica-like surface and evaluation of its application for lateral flow bioassays applications are discussed in this study. The SiOx layer was extensively characterized using contact angle measurements, atomic force microscopy, and Fourier transform infrared spectroscopy in attenuated total internal reflectance mode where the presence of a uniform SiOx film was clearly identified. The SiOx modification resulted in a surface with enhanced wettability and excellent fluidic properties when combined with a hot-embossed micropillar capillary fill-based substrate. The SiOx surface also had the ability to accelerate the clotting of human plasma, which may have application in certain types of blood coagulation assays.