Paper Title
Tribological and Mechanical Properties of the Selected Polymer/Ceramic Bio- Composites

Abstract
Biomaterials composites based on combination of polymers and ceramics becoming attractive in such medical areas as tissue engineering or bone regeneration. Modification phases based on hydroxyapatite (HAP) and collagen (COL)contribute to bioactivity of the composites. HAp, due tothe formation of apatite deposits on the bone/tissue surface, which is desirable features especially for orthopaedics. Moreover collagen phase affect the elasticity and boost regeneration processes in diverse tissues.Despite that thetribological and mechanical properties of the synthetized biomaterials, has attracted so far very little attention. For this reason in our studies we have focused on influence of HAp and collagen on diverse bio composites based on PVP/PEG and PVP/PVA polymers. The first composites series consist of polyvinylpyrrolidone (PVP) and poly(vinyl alcohol) (PVA) modified with hydroxyapatite (HAp, 10 wt.%) and collagen (30 wt.%), crosslinking agent PEGDA (poly (ethylene glycol) diacrylate)differing in the average molecular weight (575 g/mol i 700 g/mol). The second series involved polymerspolyvinylpyrrolidone (PVP)/polyethylene glycol (PEG) coatings deposited on polylactide (PLA) plates. Moreover the PVP/PEG was modified with 5wt.% and 15wt.%HAp, 2wt.% COL and glutathione (GSH), the components ofhigh biological value. The results showed that the implementation of the collagen in the diverse composites matrix can tailor demanding tribological performance, e.g., anti-wear and friction reduction.It was proved that collagen-modified composites showed higher swellingability (even 25% more) compared to unmodified ones, surface roughness, biocompatibility towardssimulated physiological liquids and hydrophilicity (contact angles lower than 90◦). Theaddition of the ceramic phase in too high a content (10-15wt.%) leads to the decreased swelling ability ofmaterials and slower liquid medium absorption by composite coatings, as well as strong surfaceroughening and loosening tribological properties. In consequence, small particles of HA from thevery rough composite crumble, having a strong abrasive effect on the sample surface.Moreover, it was observed that all samples prepared using a crosslinking agent with an average molecular weight 700 g/mol showed higher tensile strength, mechanical and anti-wear performance, although the coefficient of friction was higher. In conclusion,PVP/PEG and PVP/PVA modified with collagen and small amount (5wt.% - 10wt.%) of ceramic phase HApexhibits high bioactivity, strong mechanicaland tribological properties, the highest free surface energy, porosity, and accepted roughness to beimplemented as a material for bone regeneration. The “Multifunctional biologically active composites for applicationsin bone regenerative medicine” project is carried out within the TEAM-NET program of the Foundation for Polish Science (POIR.04.04.00-00-16D7/18)financed by the European Union under the European Regional Development Fund.