Evaluation of the direct effects of poly(dopamine) on the in vitro response of human osteoblastic cells

Functional polymeric coatings have rapidly become one of the most efficient strategies to endow biomaterials with enhanced bioactive properties. Among the bio-inspired polymers used for biomedical applications, mussel-derived poly(dopamine) (PDA) has increasingly attracted considerable interest because of its unique characteristics. In this work, we carried out detailed physicochemical characterization of a PDA film deposited on nanoporous titanium. In particular, we employed spectroscopic techniques (Raman and ATR-FTIR) and Digital Pulsed Force Mode Atomic Force microscopy (DPFM-AFM) to probe the chemical makeup and the nanomechanical properties of PDA-coated surfaces. In addition, we investigated protein adsorption by ATR-FTIR and quantified it with ten different serum proteins by Liquid Chromatography Mass spectroscopy (LC-MS), aiming at elucidating their potential contribution to the subsequent cell colonization. Successively, we assessed the response of MG-63 human osteoblastic cells to PDA-coated titanium both the multiple- and single-cell levels. Results for this study demonstrate that, compared to bare and nanoporous titanium, the PDA coating positively influences the adhesion and proliferation of MG-63 cells. In addition, we focus on how the three different substrates influence cell morphology (i.e. aspect ratio and form factor), the establishment of focal adhesions and the expression of RhoA, a protein involved in cell contractility. In conclusion, our work provides a deeper insight on the in vitro response of human osteoblastic cells to poly(dopamine) by closing in on specific aspects of cell-PDA interactions, ultimately reaffirming the potential of this bio-inspired polymer as a functional coating for bone tissue engineering applications.