New approach to improve polymer-Mg interface in biodegradable PLA/Mg composites through particle surface modification

PLA/Mg composites have been successfully proposed as biodegradable and fully bioabsorbable materials for bone repair. The present work claims the benefits of Mg particles modification throughout the adsorption of surface modifiers in the in vitro biodegradation behavior of PLA/Mg composites. Additionally, the mixture of PLA with Mg particles in a colloidal suspension replaces the thermal-melting extrusion mixing, preventing the drawbacks associated to the thermal degradation of the polymer during processing. To fulfill this requirement it is necessary to improve the interaction particle-liquid medium for the hydrophilic surface of Mg particles and the organic solvent of PLA, which will provide the maximum dispersion of the Mg in the composite. In this sense, surfaces of Mg particles were modified by the adsorption of two different stabilizers, a surfactant as cetyl-trimethylammonium bromide (CTAB) and a polyelectrolyte as polyethylenimine (PEI). The colloidal and chemical stability of Mg was studied in terms of Mg2+ dissolution, zeta-potential and rheology. A chemically stable suspension of modified Mg particles was mixed with the PLA solution in THF, and the mixture was used as feedstock to prepare films by tape casting. The characterization of the composites shows that particle surface modification determines Mg corrosion and hence governs the composite biodegradation.