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Fibrin is a protein that can be used as an ideal scaffolding material to promote tissue regeneration. In order to enhance its physical properties in this study a natural crosslinker, genipin (GP), was employed with the aim to obtain a hydrogel with tuneable properties for tissue engineering applications. The fibrin gel was crosslinked by two different methods using four concentrations of GP to get a stable hydrogel network. Crosslinking density, mechanical properties, swelling, and enzymatic degradation of the hydrogels were tested for each GP content and method employed. The method I: Crosslinking after gel formation promotes a high crosslinking and retains the gel shape for long term whilst the method II: Simultaneous gel formation and crosslinking improves the mechanical properties of the gel. This study confirms the use of GP at different concentrations as a suitable crosslinker of fibrin that promotes the cellular viability of L929 for 21 days of in vitro culture.

Short poly-L-lactic acid (PLLA) microfibers have been produced in order to disperse them into the gelatin solution and enable injection in the tissue defect prior to gel formation. Two methods for fabrication of loose fibers with submicrometric dimensions are presented in this paper. One is based on manufacturing electrospun meshes and subsequent milling (PLLA-ES) and the other involves projection of a PLLA solution into a high turbulent non-solvent medium (PLLA-HT). Composites produced with PLLA-ES show a compression Young's modulus from 2.65 kPa for the pure gelatin to 6.69 kPa for the composite with 1.5% PLLA-ES fibers. The new injectable gelatin-fiber composites are not cytotoxic.

We present a concept for a new regenerative and resorbable prosthesis for tendon and ligament and characterize the physicomechanical and biological behavior of one of its components, a hollow braid made of poly-lactide acid (PLA) which is the load-bearing part of the prosthesis concept. The prosthesis consists of a braid, microparticles in its interior serving as cell carriers, and a surface non-adherent coating, all these parts being made of biodegradable materials. The PLA braid has a nonlinear convex stress-strain behavior with a Young modulus of 1370±90 MPa in the linear, stretched state, and after 12 months of hydrolytic degradation the modulus shows a reduction by a factor of four. Different disinfection methods were tested as to their efficiency in cleansing the braid and preparing it for cell culture. Fibroblasts of L929 line were grown on the PLA braid for 14 days, showing good adherence and proliferation. These studies validate the PLA braid for the intended purpose in the regenerative prosthesis concept.

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