Electrophoretic deposition and characterization of nanocomposites and nanoparticles on magnesium substrates.

This study introduces a triphasic design of biodegradable materials composed of nanophase hydroxyapatite (nHA), poly(lactic-co-glycolic acid) (PLGA), and magnesium (Mg) substrates for musculoskeletal implant applications. Specifically, nHA_PLGA composites and nHA nanoparticles were synthesized, deposited on three-dimensional Mg substrates using electrophoretic deposition (EPD), and characterized. The three components involved, that is, nHA, PLGA, and Mg are all biodegradable in the human body, thus promising for biodegradable implant and device applications. Mg and its alloys are attractive for musculoskeletal implant applications due to their comparable modulus and strength to cortical bone. Controlling the interface of Mg with the biological environment, however, is the key challenge that currently limits this biodegradable metal for broad applications in medical implants. This article particularly focuses on creating nanostructured interface between the biodegradable Mg and surrounding tissue for the dual purposes of (1) mediating the degradation of the Mg-based substrates and (2) potentially enhancing osteointegration. Nanophase hydroxyapatite (nHA) is an excellent candidate as a coating material due to its osteoconductivity, while the polymer phase promotes interfacial adhesion between the nHA and Mg. Moreover, the degradation products of PLGA and Mg neutralize each other. Surface characterization showed successful deposition of nHA_PLGA composite microspheres and nHA nanoparticles on Mg substrates using EPD. Mg substrates coated with nHA_PLGA composites showed greater adhesion strength when compared with nHA coating, and slower corrosion rate than nHA coated Mg and non-coated Mg. The triphasic composites of nHA, PLGA and Mg are promising as the next-generation biodegradable materials for medical applications.