Abstract
Composite materials composed of polylactide (PLA) and nano-hydroxyapatite (n-HA) have been recognized as excellent candidate material in bone repai The difference in hydrophilicity/hydrophobicity and poor interfacial compatibility between n-HA filler and PLA matrix leads to non-uniform dispersion of n-HA in PLA matrix and consequent poor reinforcement effect. In this study, an HA/PLA nanocomposite was designed based on the surface modification of n-HA with poly(D-lactide) (PDLA), which not only can improve the dispersion of n-HA in the poly(L-lactide) (PLLA) matrix but also could form a stereocomplex crystal with the matrix PLLA at the interface and ultimately lead to greatly enhanced mechanical performance The n-HA/PLA composites were characterized by means of scanning electron microscopy, Fourier transform infrared spectroscopy, X-Ray diffraction, thermal gravity analysis, differential scanning calorimetry, and a mechanical test; in vitro cytotoxicity of the composite material as well as its efficacy in inducing osteogenic differentiation of rat bone marrow stromal cells (rMSCs) were also evaluated. Compared with those of neat PLLA, the tensile strength, Young’s modulus, interfacial shear strength, elongation at break and crystallinity of the composites increased by 34%, 53%, 26%, 70%, and 17%, respectively. The adhesion and proliferation as well as the osteogenic differentiation of rMSCs on HA/PLA composites were clearly evidenced. Therefore, the HA/PLA composites have great potential for bone repai.
Highlights
As one of the most popular biodegradable polymers, poly(lactic acid)/polylactide (PLA) has attracted tremendous attention as a biomaterial, owing to its excellent biocompatibility and biodegradability [1,2]; efforts have been devoted to its applications as a drug delivery matrix, tissue engineering scaffold, and, in addition, orthopedic implants [3,4].In order to meet the clinical requirements of long-term orthopaedic implantation, the problems of inadequate mechanical properties and poor osseointegration of PLA need to be solved
The additional peak in the spectra of mHA1, mHA2 and mHA3 at 1750 cm−1 corresponds to the carbonyl group (C=O) and the 2900–3000 cm−1 corresponds to the alkyl groups (CH3 - and -CH2 -) of PDLA, indicating the successful grafting of D-lactid The Thermogravimetric Analysis (TGA) (Figure 1c) curves demonstrated that the decomposition of PDLA occurred at approximately 250 ◦ C, and HA was stable upon heating in N2
The mHA1 (5%)/PLA and mHA1 (10%)/PLA nanocomposite films exhibited significantly higher calcium deposition levels than other film These results demonstrate that high concentration of mHA1 can promote the mineralization of rat bone marrow stromal cells (rMSCs)
Summary
As one of the most popular biodegradable polymers, poly(lactic acid)/polylactide (PLA) has attracted tremendous attention as a biomaterial, owing to its excellent biocompatibility and biodegradability [1,2]; efforts have been devoted to its applications as a drug delivery matrix, tissue engineering scaffold, and, in addition, orthopedic implants [3,4].In order to meet the clinical requirements of long-term orthopaedic implantation, the problems of inadequate mechanical properties and poor osseointegration of PLA need to be solved. As one of the most popular biodegradable polymers, poly(lactic acid)/polylactide (PLA) has attracted tremendous attention as a biomaterial, owing to its excellent biocompatibility and biodegradability [1,2]; efforts have been devoted to its applications as a drug delivery matrix, tissue engineering scaffold, and, in addition, orthopedic implants [3,4]. Bioactive inorganic fillers can be used to effectively improve the mechanical strength and the biological activity of PLA [8,9]. The bioactivity of PLA composites with these inorganic fillers comes from the dissolution of calcium ion, phosphate ion, and, in addition, silicate ions; these ions can act as the calcium source in the mineralization and promote the proliferation and osteogenic differentiation of osteoprogenitor cells or bone marrow stromal cells (rMSCs) through different signaling pathways [13–18]. The bioactive inorganic fillers, such as HA [22] and BG [23], could induce the onset of crystallization and re-mineralization
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