Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and amino-functionalized nanodiamond bionanocomposites for bone tissue defect repair.

Injection-molded nanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) with 6 % of 3-hydroxyvalerate (HV) and amino-nanodiamonds (nD-A) were produced and characterized to investigate the effect of functionalized nanodiamonds on mechanical and biological behavior to bone replacement application. To prepare mixtures of PHBHV and nD-A in different concentrations, nD-A was dispersed in chloroform by sonication with 40 % of amplitude. Three specimens were characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (DRX), differential scanning calorimetry (DSC), 3-point flexural tests, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). FTIR and TGA evidenced the existence of interactions between the nD-A and PHBHV. The crystallinity degree of PHBHV slightly reduced (~9 %) in nanocomposites and the morphology of the crystals changed. Nanocomposites achieved satisfactory dispersion and distribution of nD-A for low concentrations. Elastic modulus (E) increased from 1.96 ± 0.20 (PHBHV) to 2.59 ± 0.19 GPa (PHBHV/1.0%nD-A) (30 %). Despite the relatively limited dispersion, PHBHV/2.0 % nD-A had the best combination of E, strength, and maximum deformation. It had the highest glass transition temperature (43.1 vs 40.3 °C of PHBHV) and the best adhesion coefficient and reinforcement effectiveness. PHBHV-nD-A did not induce toxicity in 7 days and allowed cell fixation and expansion. These bionanocomposites should be considered for supplementary studies for bone tissue engineering.