Abstract: Objective　Studying the changes of structural properties and cytological behavior of these microspheres modified with different concentrations of type I collagen (COLI), to guide the preparation of scaffold conducive to bone tissue regeneration. Methods　PCL microspheres were prepared (as the control group), then modified with COLI of different concentrations (as experimental groups). The surface morphology was observed by field emission scanning electron microscope (FESEM). Water absorption rate of materials was measured by dry-wet mass method. The proliferation of BMSCs was tested by Cell counting Kit-8 (CCK-8) assay, while the adhesion of cells was estimated by confocal laser scanning microscopy (CLSM) and Alkaline phosphatase (ALP) activity of cells was measured at 3 and 7 days. Results　FESEM pictures showed that collagen fibers were crisscross arranged to wrap the surface of microspheres in collagen modified groups. The water absorption rate of collagen modified group was higher than that of control group (P<0.05). CCK-8 results showed that BMSCs in all groups were proliferating continuously within 7 days, and the proliferation rate of the 0.1% COLI group was higher than other groups (P<0.05). Cells in the 0.1% and 0.5% COLI groups spread better than the other two groups at 6 h by CLSM. ALP activity of BMSCs cells in 0.1% COLI group was higher than that of other groups (P<0.05).Conclusions　The 0.1% COLI modified microspheres prepared in this study can promote adhesion, proliferation and early osteogenic differentiation of BMSCs in vitro.

Key words: type I collagen, microspheres, surface modification, bone marrow mesenchymal stem cells