PLA-BASED FOAMS AS SCAFFOLDS FOR TISSUE ENGINEERING APPLICATIONS

Introduction: The need for alternative solutions to meet the demand for replacement organs and tissue parts continues to drive advances in tissue engineering because no material meets all the design parameters in all applications, but a wide range of materials finds uses in different tissue engineering applications. In this research work, starting from biocomposites based on crosslinked particles of poly(acrylic acid) (SAP) and poly-L-lactic acid (PLLA), new open-pore PLLA-based foams with good physico-mechanical properties are produced in absence of organic solvents and chemical foaming agents. Materials and methods: Biocomposites based on a binary system containing crosslinked particles of (SAP), commonly used as superabsorbent polymer, and PLLA have been prepared by melt-blending in a discontinuous mixer. Components were melt-mixed in different ratios in the presence of plasticizers and fibers or blended with different biopolymers such as poly (ethylene glycol) (PEG), poly (e-caprolactone) (PCL) and polyhydroxybutyrate (PHB). All samples were recovered from the mixing chamber and hot pressed using a laboratory compression molding machine to realize 0.2 mm thick sheets from which the specimens for mechanical tests were obtained. Results: A fairly homogeneous dispersion of particles was obtained, as revealed by SEM micrographs, showed a biphasic system with a regular distribution of particles, with diameter ranging from 5 to 10 mm, within the PLLA polymeric matrix. This biphasic system also showed excellent swelling properties, demonstrating that cross-linked particles retain their superabsorbent ability even if distributed in a thermoplastic polymeric matrix. Furthermore, in aqueous environments the particles swell and are leached from PLLA matrix generating very high porosity with random and irregular open pore structure. Density and porosity were measured using liquid substitution method. As expected, reduced density and increased porosity were observed on the samples as a result of the increased amount of leached particles. The biocompatibility of all samples and the influence of the surface on cell behavior were assessed in a preliminary investigation which evidenced optimal cell viability, adhesion and proliferation. Discussion: These new open-pore PLLA-based foams, produced in absence of organic solvents and chemical foaming agents, with good physico-mechanical properties appear very promising for scaffold production technology. In fact, open porosity is a crucial point because scaffold must possess a highly porous structure with a fully interconnected geometry to provide cell ingrowth and survival and uniform cell distribution. This new methodology allows to obtain a polymeric scaffold, with a porosity that can be easily tuned by a proper choice of superabsorbent particles. Another key point are surface properties, which include both chemical and topographical characteristics and can control and affect cellular adhesion and proliferation. The scaffold surface is the initial and primary site of interaction with surrounding cells and tissue. Surface properties can be selectively modified to enhance the performance of the biomaterials. For instance, by blending PLA matrix with PCL, PHB or PEG, optimal surface, chemical, and physical properties promoting cell viability were attained