M.A. Pacha-Olivenza

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.

Antibacterial effect of novel biodegradable and bioresorbable PLDA/Mg composites.

Polylactic acid/Mg composites have been recently proposed for biodegradable osteosynthesis devices because, with regards to the neat polymer, they combine an enhanced biocompatibility and bioactivity with better mechanical properties, particularly creep strength. A question still arises about their bacterial behavior. For this purpose, composites of poly-L-D-lactic acid (PLDA) loaded with 1 and 10 wt.% of Mg microparticles were evaluated using Staphylococcus epidermidis, with special emphasis on the study of bacterial adhesion and biofilm formation. During biofilm formation the bacteria viability of the composites decreased up to 65.3% with respect to PLDA. These antibacterial properties do not compromise the cytocompatibility of the material as the composites enhanced the viability of mesenchymal stem cells and their osteogenic commitment. These findings provide an important added value to the biodegradable and biocompatible PLDA/Mg composites for the manufacture of osteosynthesis devices.

Eficacia bactericida in vivo del farnesol sobre implantes de Ti6Al4V

OBJECTIVE To evaluate the in vivo anti-staphylococcal bactericidal activity of farnesol on Ti6Al4V surfaces. MATERIAL AND METHODS An experimental model of infection in biomaterials was developed by inoculation of Staphylococcus aureus ATCC 29213 into the canal of both femurs of 15 Wistar rats. A Ti6Al4V pin impregnated with 30mM of farnesol was inserted into study femur, and a Ti6Al4V control was inserted into the control femur. To evaluate the bactericidal efficacy, a comparison was made between the median of the colony forming units recovered after inoculation in the study group and the control group for different times of euthanasia and inoculum size. RESULTS The median expressed as Log10 CFU counts obtained with farnesol titanium pin was 4.26, and in control group, it was 4.86, which was statistically significant (P=.001) on applying the Student t test for related samples. The median reduction obtained in farnesol pins relative to the control was 74%. CONCLUSIONS Treatment with farnesol 30mM on Ti6Al4V pins appears to decrease the rate of colonisation by Staphylococcus aureus.