Allylamine Plasma Enhanced Cytocompatibility of Porous NiTi Bone Implants

It is generally agreed that the surface properties of biomedical implants such as surface topography, roughness, and chemical composition play a crucial in cell recognition and bone healing. In addition, the interaction between hyaluronan produced by the cells and matrix hyaluronan-binding proteins and cell-surface hyaluronan receptors significantly influences cell behavior such as cell migration, cell-cell adhesion, and cell differentiation because hyaluronan acts as a mediator and modulator during the initial steps of cellular adhesion [1, 2]. Since hyaluronan is negatively charged, a positive charge on the biomaterials surface is needed to attract hyaluronan. The introduction of amino groups is one of the important surface strategies to introduce positive charges in the aqueous environment. In this work, a thin polymeric allylamine (P-PPAAm) layer is deposited on the surface of a porous NiTi scaffold to enhance the cytocompatibility using a pulsed radio frequency (RF) plasma containing allylamine vapor and NH3 as the precursor gas. In vitro tests reveal that P-PPAAm functionalized surface enhances adhesion and proliferation of both endothelial cells and osteoblasts. This can be attributed to the formation of a high density of positively-charged amino groups on the exposed surface of the porous NiTi scaffold and it consequently promotes attachment of hyaluronan and cell adhesion.