New synthesis method of HA/P(D,L)LA composites: study of fibronectin adsorption and their effects in osteoblastic behavior for bone tissue engineering

A novel synthetic method to synthesize hydroxyapatite/poly (D,L) lactic acid biocomposite is presented in this study by mixing only the precursors hydroxyapatite and (D,L) LA monomer without adding neither solvent nor catalyst. Three compositions were successfully synthesized with the weight ratios of 1/1, 1/3, and 3/5 (hydroxyapatite/(D,L) lactic acid), and the grafting efficiency of poly (D,L) lactic acid on hydroxyapatite surface reaches up to 84 %. Scanning electron microscopy and Fourier transform infrared spectroscopy showed that the hydroxyapatite particles were successfully incorporated into the poly (D,L) lactic acid polymer and X ray diffraction analysis showed that hydroxyapatite preserved its crystallinity after poly (D,L) lactic acid grafting. Differential scanning calorimetry shows that Tg of hydroxyapatite/poly (D,L) lactic acid composite is less than Tg of pure poly (D,L) lactic acid, which facilitates the shaping of the composite obtained. The addition of poly (D,L) lactic acid improves the adsorption properties of hydroxyapatite for fibronectin extracellular matrix protein. Furthermore, the presence of poly (D,L) lactic acid on hydroxyapatite surface coated with fibronectin enhanced pre-osteoblast STRO-1 adhesion and cell spreading. These results show the promising potential of hydroxyapatite/poly (D,L) lactic acid composite as a bone substitute material for orthopedic applications and bone tissue engineering.