Biological characterization of a new silicon based coating developed for dental implants.

Taking into account the influence of Si in osteoblast cell proliferation, a series of sol-gel derived silicon based coating was prepared by controlling the process parameters and varying the different Si-alkoxide precursors molar rate in order to obtain materials able to release Si compounds. For this purpose, methyltrimethoxysilane (MTMOS) and tetraethyl orthosilicate (TEOS) were hydrolysed together and the sol obtained was used to dip-coat the different substrates. The silicon release ability of the coatings was tested finding that it was dependent on the TEOS precursor content, reaching a Si amount value around ninefolds higher for coatings with TEOS than for the pure MTMOS material. To test the effect of this released Si, the in vitro performance of developed coatings was tested with human adipose mesenchymal stem cells finding a significantly higher proliferation and mineralization on the coating with the higher TEOS content. For in vivo evaluation of the biocompatibility, coated implants were placed in the tibia of the rabbit and a histological analysis was performed. The evaluation of parameters such as the bone marrow state, the presence of giant cells and the fibrous capsule proved the biocompatibility of the developed coatings. Furthermore, coated implants seemed to produce a qualitatively higher osteoblastic activity and a higher number of bone spicules than the control (uncoated commercial SLA titanium dental implant).

Hybrid structure in PCL-HAp scaffold resulting from biomimetic apatite growth.

Polymer-ceramic composites are favourite candidates when aiming to replace bone tissue. We present here scaffolds made of polycaprolactone-hydroxyapatite (PCL-HAp) composites, and investigate in vitro mineralisation of the scaffolds in SBF after or without a nucleation treatment. In vitro bioactivity is enhanced by HAp incorporation as well as by nucleation treatment, as demonstrated by simulated body fluid (SBF) mineralization. Surprisingly, we obtained a hybrid interconnected organic-inorganic structure, as a result of micropore invasion by biomimetic apatite, which results in a mechanical strengthening of the material after two weeks of immersion in SBF92. The presented scaffolds, due to their multiple qualities, are expected to be valuable supports for bone tissue engineering.

Biodegradable polycaprolactone scaffold with controlled porosity obtained by modified particle-leaching technique.

Scaffold with controlled porosity constitute a cornerstone in tissue engineering, as a physical support for cell adhesion and growth. In this work, scaffolds of polycaprolactone were synthesized by a modified particle leaching method in order to control porosity and pore interconnectivity; the aim is to observe their influence on the mechanical properties and, in the future, on cell adhesion and proliferation rates. Low molecular weight PEMA beads with an average size of 200 microm were sintered with various compression rates in order to obtain the templates (negatives of the scaffolds). Then the melt polycaprolactone was injected into the porous template under nitrogen pressure in a custom made device. After cooling and solidifying of the melt polymer, the porogen was removed by selective dissolution in ethanol. The porosity and morphology of the scaffold were studied as well as the mechanical properties. Porosities from 60% to 85% were reached; it was found that pore interconnectivity logically increases with increasing porosity, and that mechanical strength decreases with increasing porosity. Because of their interesting properties and interconnected structure, these scaffolds are expected to find useful applications as a cartilage or bone repair material.