Construction of porous bFGF-PLGA-HAP-PLLA microsphere and its biocompatibility with bone marrow mesenchymal stem cells

Background: The innovative repair materials for the bones are still lacking. So, we synthesized a porous microsphere by using basic fibroblast growth factor (bFGF), polylactide-co-glycolide (PLGA), poly L-lactic acid (PLLA) and hydroxylapatite (HAP), and its biocompatibility with bone marrow mesenchymal stem cells (BM-MSCs) was investigated in vitro. Methods: A modified solvent extraction/evaporation double emulsion method was used to first prepare PLGA and bFGF-PLGA microspheres. The morphologies and surface characteristics of PLGA microspheres and bFGF-PLGA microspheres were observed by using laser diffraction particle size analyzer and transmission electron microscopy (TEM). Drug release patterns of bFGF-PLGA microspheres in vitro were also examined. The porous bFGF-PLGA-HAP-PLLA microspheres were then fabricated with PLLA, HAP and the bFGF-PLGA microspheres and subjected to thermal analysis, scanning electron microscope (SEM) for surface morphology detection and X-ray diffraction (XRD) analysis and fourier transform infrared spectroscopy (FT-IR) spectra analysis. The cytotoxicity and biocompatibility with BM-MSCs in vitro were also tested by measuring BMSCs viability and proliferation by using MTT assay or observed by microscope. Results: The results showed that the particle size of bFGF-PLGA microspheres was about 250 nm with a morphology of mono-disperse spherical without aggregation. The drug release profile of bFGF-PLGA microspheres exhibited the one phase release profile with an initial burst rate of 33% in the first 10 hours, then 70.5% accumulative release after 7 days. Thermal analysis suggested porous materials were decomposed between 250°C~400°C, and the mass of porous materials was reduced extremely in the range of 300°C~350°C and slowly after 400°C because of PLLA, PLGA and HAP property. SEM scanning showed that the appearance of PLGA microspheres was spherical, and the hydroxyapatite was reunited. Synthesized XRD patterns showed that strong Bragg reflections (18.5° and 32°) were seen which correspond to the PLLA and HAP. FT-IR spectra found that the PLLA+HAP+bFGF-PLGA porous material had very similar curve lines to other microspheres. MTT assay and microscopy results suggested the cytotoxicity of bFGF-PLGA+HAP+PLLA porous material met the requirements of the scaffold material in bone tissue engineering and was conducive to promote the proliferation of BM-MSCs. Conclusion: The bFGF-PLGA+HAP+PLLA porous material is successfully prepared and has good biocompatibility with BMSC.