Atomic Force Microscopy Characterization of Biomaterials Modified with Poly(styrene Sulfonate)

Polycaprolactone and polyethylene terephthalate are widely used to elaborate biomaterials and medical devices in particular for long-term implant applications but tuning their surface properties remains challenging. We investigate surface functionalization by grafting poly(sodium 4-styrene sulfonate) with the aim of enhancing protein adhesion and cellular activity. Elucidating the topography and molecular level organization of the modified surfaces is important for understanding and predicting biological activity. In this work, we explore several grafting methods including thermal grafting, thermal grafting in the presence of Mohr's salt, and UV activation. We characterize the different surfaces obtained using atomic force microscopy, contact angle and X-ray photoelectron spectroscopy. The results reveal striking differences in the properties of the modified surfaces. This work demonstrates tuning of biomaterials surface by functionalization and the capability of atomic force microscopy to provide insights into the conformation and mechanical properties of the grafted polymers.