Fabrication and characterisation of spin coated oxidised PMMA to provide a robust surface for on-chip assays. Issue 1 (6th November 2014)

• Record Type: Journal Article
• Authors: Rowinska, M.; Kelleher, S. M.; Soberon, F.; Ricco, A. J.; Daniels, S.
• Is Part Of: Journal of materials chemistry. Volume 3:Issue 1(2015)
• Page Start: 135
• Page End: 143
• Publication Date: 2014-11-06
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Biomedical materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c4tb01748j
• Languages: English
• ISSNs: 2050-750X

Abstract

Abstract : Smooth, thin PMMA layers have been oxidised using two methods on various surfaces. The longevity of activation and ability of the films to bind and retain biomolecules has been investigated. Abstract : A method to prepare a highly stable carboxylic acid functional surface on various substrates for use in bioassays is reported. A thin layer of a poly(methylmethacrylate) (PMMA) is achieved by spin coating dissolved PMMA onto a variety of underlying substrates at various thicknesses in a range of c . 5–27 nm. Varying the PMMA concentration, time and spinning speed controls the thickness of the spin coated layer. The root-mean-squared roughness values of the spin coated PMMA are less than 1.5 nm, resulting in smooth and uniform layer. Substrate functionalisation is carried out by either ultraviolet/ozone (UV/O3 ) or oxygen plasma oxidation. Both techniques result in initially stable, highly functional films as demonstrated by the covalent attachment of amino-modified oligonucleotides, however longevity studies comparing the stability of films attached following oxidative activation show better stability for UV/O3 activated substrates when compared to oxygen plasma activated substrates. PMMA films activated by UV/O3 yield highly stable (for up to 24 days) functional surfaces that retain immobilised biomolecules after several extended wash steps. In contrast, films attached to surfaces pre-treated with oxygen plasma discharge lose their functionality within 5 days of oxidation. Direct DNA and sandwich antibody assays were successfully demonstrated on the UV/O3 functionalised surfaces, showing a low level of non-specific binding. Furthermore, the quenching of fluorescently labelled biomolecules bound to PMMA-coated gold-coated slides is shown to be dependent on the PMMA thickness, indicating potential usage in surface-plasmon resonance-based assays.