Engineering the Ratios of Nanoparticles Dispersed in Triphasic Nanocomposites for Biomedical Applications.

Polymer/ceramic nanocomposites integrated the advantages of both polymers and ceramics for a wide range of biomedical applications, such as bone tissue repair. Here, we reported triphasic poly(lactic--glycolic acid) (PLGA, LA/GA = 90:10) nanocomposites with improved dispersion of hydroxyapatite (HA) and magnesium oxide (MgO) nanoparticles using a process that integrated the benefits of ultrasonic energy and dual asymmetric centrifugal mixing. We characterized the microstructure and composition of the nanocomposites and evaluated the effects of the HA/MgO ratios on degradation behavior and cell-material interactions. The PLGA/HA/MgO nanocomposites were composed of 70 wt % PLGA and 30 wt % nanoparticles made of 20:10, 25:5, and 29:1% by weight of HA and MgO, respectively. The results showed that the nanocomposites had a homogeneous nanoparticle distribution and as-designed elemental composition. The cell study indicated that reducing the MgO content in the triphasic nanocomposite increased the BMSC adhesion density under both direct and indirect contact conditions. Specifically, after the 24 and 48 h of culture, the PLGA/HA/MgO group with a weight ratio of 70:29:1 (P70/H29/M1) exhibited the greatest average cell adhesion density under direct and indirect contact conditions among triphasic nanocomposites. During a 28-day degradation study, the mass loss of triphasic nanocomposites was 18 ± 2% for P70/H20/M10, 9 ± 2% for P70/H25/M5, and 7 ± 1% for P70/H29/M1, demonstrating that MgO nanoparticles accelerated the degradation of the nanocomposites. Postculture analysis showed that the pH values and Mg ion concentrations in the media increased with increasing MgO content in the nanocomposites. Triphasic nanocomposites provided different degradation profiles that can be tuned for different biomedical applications, especially when a shorter or longer period of degradation would be desirable for optimal bone tissue regeneration. The concentration and ratio of nanoparticles should be adjusted and optimized when other polymers with different degradation modes and rates are used in the nanocomposites.