Influence of Surface Chemistry and Nanomechanical Properties of Methacrylate-Based Copolymer Thin Films on Keratocyte Cell Adhesion

Keratoprosthesis is an alternative treatment for visual impairment caused by corneal diseases. However, due to the recognized postoperative complications in available Kpros, there is an exigency to explore potential alternative skirt materials for corneal implants. This study aims to investigate the suitability of poly(2-methoxyethyl methacrylate-<i>co</i>-2-hydroxyethyl methacrylate) (15% MEMA: 85% HEMA), and poly(2-phenoxyethyl methacrylate-<i>co</i>-2-hydroxyethyl methacrylate) (15% PhEMA: 85% HEMA) copolymers as a corneal implant material by evaluating their ability to adhere human keratocytes. The effect of chemical and mechanical properties of copolymers on the keratocyte cell adhesion was investigated. These copolymers are thermally stable with a glass transition temperature between 75 and 80 °C, and thermogravimetric analysis showed that the copolymers do not degrade until 190 °C. Sum frequency generation spectroscopy (SFG) and atomic force microscopy (AFM) were employed to evaluate the surface chemical and mechanical properties of the polymer thin films. SFG spectra showed the contributions of methylene (CH₂) and α-methyl (α-CH₃) functional groups at the air/polymer interface. Moreover, the signature vibrational modes of methoxy (-OCH₃) and phenoxy (-OPh) groups were detected at the 15% MEMA: 85% HEMA and 15% PhEMA: 85% HEMA copolymer surfaces that contribute to chemical composition surface analysis. Meanwhile, the analysis of the AFM topographical images showed that the 15% MEMA: 85% HEMA copolymer is relatively rougher with a root-mean-square value of 56 nm but was found to be more elastic than the 15% PhEMA: 85% HEMA copolymer with a Young's modulus value of 0.39 GPa. Fluorescence microscopy images showed visible F-actin filaments on stiffer substrates, demonstrating the ability to regulate cell adhesion and migration behavior based on the nanomechanical characteristics of implants. The results show that substrate stiffness can regulate keratocyte cell adhesion as keratocytes preferred to adhere on a stiffer 15% PhEMA: 85% HEMA copolymer surface than the 15% MEMA: 85% HEMA copolymer surface.