A technique for producing controlled interconnected porous structures for application as a tissue engineering scaffold is presented in this article. The technique is based on the fabrication of a template of interconnected poly(ethyl methacrylate) (PEMA) microspheres, the introduction of a biodegradable polymer, poly-epsilon-caprolactone (PCL), and the elimination of the template by a selective solvent. A series of PCL scaffolds with a porosity of 70% and pore sizes up to 200 microm were produced and characterized (both thermally and mechanically). Human chondrocytes were cultured in monolayer on bulk PCL disks or seeded into porous PCL scaffolds. Cell adhesion, viability, proliferation, and proteoglycan (PG) synthesis were tested and compared with monolayer cultures on tissue-treated polystyrene or pellet cultures as reference controls. Cells cultured on PCL disks showed an adhesion similar to that of the polystyrene control (which allowed high levels of proliferation). Stained scaffold sections showed round-shaped chondrocyte aggregates embedded into porous PCL. PG production was similar to that of the pellet cultures and higher than that obtained with monolayer postconfluence cultures. This shows that the cells are capable of attaching themselves to PCL. Furthermore, in porous PCL, cells maintain the same phenotype as the chondrocytes within the native cartilage. These results suggest that PCL scaffolds may be a suitable candidate for chondrocyte culture.

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.

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Although implants are becoming increasingly common in dental practice, before implantation strict patient selection criteria have to be implemented since the implants should have a good chance of osseointegration into the maxillary bone. Moreover, the implanted sites can become severely infected and, consequently, the implant might have to be removed. To avoid implant-related infections and to promote the osseointegration of commercial Titanium implants, different silica-chitosan matrices were synthesized using the sol-gel process. Three different alkoxysilanes were used, methyltrimethoxysilane (MTMOS), 3glycidoxypropyltrimethoxysilane (GPTMS), and tetraethoxysilane (TEOS). The network formed during the matrix synthesis gradually degrades in aqueous media, and during this hydrolytic degradation, silicon is released, inducing bone formation. Chitosan, with its high biocompatibility and strong antibacterial activity, was selected to confer antibacterial properties to the coatings. The synthesized hybrids were characterized using 29 Si-and 13 C-NMR to verify the correct formation of the network. The technique was also used to confirm the covalent union between chitosan and the silicon network. Hydrolytic degradation and silicon release studies in the aqueous media were examined, showing the effective silicon release from the hybrids. The analysis of cell cultures in vitro demonstrated that the hybrid coatings were not cytotoxic and promoted cell proliferation on their surfaces. The coatings containing 5%-10% chitosan had substantial antibacterial properties. The introduction of different amounts of chitosan and TEOS modulated the degradation of the coatings and, consequently, the Si release.

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.

Titanium dental implants are commonly used due to their biocompatibility and biochemical properties; blasted acid-etched Ti is used more frequently than smooth Ti surfaces. In this study, physicochemical characterisation revealed important differences in roughness, chemical composition and hydrophilicity, but no differences were found in cellular in vitro studies (proliferation and mineralization). On the other hand, the deposition of proteins onto the implant surface might affect in vivo osseointegration. To test that hypothesis, protein layers formed on both surface type discs after incubation with human serum were analysed.Using mass spectrometry (LC/MS/MS), 139 proteins were identified, 31 of which were associated with bone metabolism. Interestingly, Apo E, antithrombin and protein C adsorbed mostly onto blasted and acid-etched Ti, whereas the proteins of the complement system (C3) were found predominantly on smooth Ti surfaces. These results suggest that physicochemical characteristics could be responsible for the differences observed in the adsorbed protein layer.

The interactions of implanted biomaterials with the host organism determine the success or failure of an implantation. Normally, their biocompatibility is assessed using in vitro tests. Unfortunately, in vitro and in vivo results are not always concordant; new, effective methods of biomaterial characterisation are urgently needed to predict the in vivo outcome. As the first layer of proteins adsorbed onto the biomaterial surfaces might condition the host response, mass spectrometry analysis was performed to characterise these proteins. Four distinct hybrid sol-gel biomaterials were tested. The in vitro results were similar for all the materials examined here. However, in vivo, the materials behaved differently. Six of the 171 adsorbed proteins were significantly more abundant on the materials with weak biocompatibility; these proteins are associated with the complement pathway. Thus, protein analysis might be a suitable tool to predict the in vivo outcomes of implantations using newly formulated biomaterials.