Controlled silanization–amination reactions on the Ti6Al4V surface for biomedical applications

Formation of thin films on titanium alloys incorporating bioactive small molecules or macromolecules is a route to improve their biocompatibility. Aminoalkylsilanes are commonly employed as interface reagents that combine good adhesion properties with an amino tail group susceptible of further functionalization. This article introduces a reproducible methodology to obtain a cross-linked polymer-type brush structure of covalently-bonded aminoalkylsiloxane chains on Ti6Al4V. The experimental protocol can be fine-tuned to provide a high density of surface-coated amino groups (threshold value: 2.1 ± 0.1 × 10−8 mol cm−2) as proven by chemical and spectrophotometric analyses. Using a model reaction involving the condensation of 3-aminopropyltrimethoxysilane (APTMS) on Ti6Al4V alloy, we herein show the effects of reaction temperature, reaction time and solvent humidity on the composition and structure of the film. The stability of the resulting coating under physiological-like conditions as well as the possibility of surface re-silanization has also been evaluated. To verify if detrimental effects on the biological performance of the Ti6Al4V alloy were induced by this coverage, human primary osteoblasts behavior, Staphylococci adhesion and biofilm formation have been tested and compared to the Ti6Al4V oxidized surface. Reaction with trans-cinnamaldehyde has used in order to determine useful amino groups at aminosilanized surface, XPS and UV analyses of imino derivatives generated reveal that almost a 50% of these groups are actually available at the siloxane chains.