Funzionalizzazioni chimiche ottenute con tecnologia plasma jet a pressione atmosferica, al fine di migliorare le proprietà osteointegranti di superfici in titanio

Modern studies on prosthetic biomaterials focus on surface characteristics of the material itself that influence the biological response, in order to find the right conditions to ensure an optimal osseointegration, osteoinduction, rapid bone tissue healing, prevent bone resorption and avoid bacterial infections. Currently it is known that various factors may enhance or inhibit the osseointegration processes. Factors that enhance osseointegration processes involve several implant-related features such as implant design, surface chemical composition, topography, type of material, shape, length, diameter, roughness, presence of coatings, etcetera. Titanium is one of the most used biomaterials in orthopaedic surgery and in other clinical applications due to its high osteocompatibility, resistance to corrosion and lack of toxicity. Therefore, many studies regard surface modifications of titanium and its alloys, in order to improve or enhance their prosthetic properties. The purpose of this work was to evaluate the biological effect of two different titanium chemical functionalizations, obtained through a radio frequency atmospheric pressure plasma jet device (RF-APPJ mini-torch). The two plasma surface modifications involved amine (Ti-NH₂) and carboxylic/esteric (Ti-COOH/R) functionalities, obtained respectively from aminopropyltriethoxysilane (APTES) and methylmethacrylate (MMA) precursors. A pre-osteoblastic murine cell line MC3T3-E1 was used for in vitro assays, in order to investigate the biological response variations. A large amount of adsorbed proteins and an improvement of osteoblast adhesion were detected on titanium treated samples. In particular, the COOH/R-Ti sample led to a nearly two-fold improvement of cell adhesion, compared with control sample (titanium functionalization-free). COOH/R-Ti sample and pristine titanium sample showed a comparable proliferation rate at 48h and showed a proliferation rate higher than NH₂-Ti sample. However, MC3T3-E1 seeded on titanium NH₂-Ti sample, reported a rapid morphologic change and a rapid osteocalcin release at 14 days. Experimental results showed that both functionalizations positively affected titanium osteocompatibility. However, because osteocalcin release is a marker of differentiation and osteogenic activity, titanium with amine functionalizations has been suggested to be a good biomaterial useful to obtain a rapid osseointegration and a rapid osteoinduction.