Polymethyl methacrylate-co-methacrylic acid coatings with controllable concentration of surface carboxyl groups: A novel approach in fabrication of polymeric platforms for potential bio-diagnostic devices

The generally accepted strategy in development of bio-diagnostic devices is to immobilize proteins on polymeric surfaces as a part of detection process for diseases and viruses through antibody/antigen coupling. In that perspective, polymer surface properties such as concentration of functional groups must be closely controlled in order to preserve the protein activity. In order to improve the surface characteristics of transparent polymethacrylate plastics that are used for diagnostic devices, we have developed an effective fabrication procedure of polymethylmetacrylate-co-metacrylic acid (PMMA-co-MAA) coatings with controlled number of surface carboxyl groups. The polymers were processed effectively with the spin-coating technique and the detailed control over surface properties is here by demonstrated through the variation of a single synthesis reaction parameter. The chemical structure of synthesized and processed co-polymers has been investigated with nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS). The surface morphology of polymer coatings have been analyzed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). We demonstrate that the surface morphology and the concentration of surface -COOH groups (determined with UV-vis surface titration) on the processed PMMA-co-MAA coatings can be precisely controlled by variation of initial molar ratio of reactants in the free-radical polymerization reaction. The wettability of developed polymer surfaces also varies with macromolecular structure.