Applied Surface Science 300 (2014) 43–50 Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc 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 Samira Hosseini a , Fatimah Ibrahim a , Ivan Djordjevic a,∗ , Leo H. Koole a,b a Center for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia b Department of Biomedical Engineering, Faculty of Health. Medicine & Life Science, Maastricht University, PO Box 616, NL 6200 MD Maastricht, The Netherlands a r t i c l e i n f o Article history: Received 27 November 2013 Accepted 31 January 2014 Available online 9 February 2014 Keywords: Co-polymer Spin-coating Surface functional groups Diagnostic device a b s t r a c t 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 cou- pling. 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 characteris- tics 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 pro- cessed 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 mor- phology 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 sur- face –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 polymeriza- tion reaction. The wettability of developed polymer surfaces also varies with macromolecular structure. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The development of biosensors has drawn a vital role of research interest due to the high sensitivity and selectivity in detection of diseases and viruses. Of particular interests are polymeric mate- rials used for surface protein immobilization. Those immobilized surface proteins are further engaged in detection of coupling proteins (antibody/antigen) present in diseased blood. The most commonly applied diagnostic device, based on heterogeneous antibody/antigen interaction, the enzyme-linked immunosorbent assay (ELISA), still presents a “golden standard” in clinical diag- nostic practice [1,2]. However, conventional ELISA has its own limitations such as: tedious and labor-intensive protocol, long incu- bation times between each step and inconsistency of the results ∗ Corresponding author. Tel.: +60 3 7967 7616; fax: +60 3 7967 4579. E-mail address: ivan.djordjevic@um.edu.my (I. Djordjevic). [3]. In order to overcome those serious limitations, there is a strong need for development of advanced polymer coatings with controllable surface properties such as surface chemistry and mor- phology. In that perspective, a generation of functionalities such as hydroxyl (–OH), amine (–NH 2 ) and carboxyl (–COOH) groups at the surface of polymer coatings presents the crucial step for further immobilization of proteins and subsequent effective detec- tion of diseases and viruses. Furthermore, the surface concentration of those functional groups must be closely controlled in order to avoid protein de-activation caused by either steric repulsion (over- functionalization) or protein denaturation in close proximity of the polymer surface (low surface concentration of functional groups) [4]. In recent years, polymethyl methacrylate (PMMA) has shown a great potential due to the particular properties and a wide range of applications [5]. PMMA is a low cost polymer with chemical inertness, low specific weight, high impact resistance and flexi- bility. PMMA has been successfully used for the immobilization of 0169-4332/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2014.01.203