Microfluidic-preparation of PLGA microcarriers with collagen patches for MSCs expansion and osteogenic differentiation

This study was aimed to develop a capillary-based microfluidic methodology for preparing poly (lactic-co-glycolic acid) (PLGA) microcarriers patterned with collagen patchy structure (PLGA-Col), which are superior in enhancing proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) seeded on them. Primary W/O emulsions were first prepared using aqueous collagen and PLGA solutions. A two-phase microfluidic device was then designed and the emulsions were used as the inner liquid phase to obtain PLGA-Col microcarriers. The content of collagen was varied to yield PLGA-Col-L (lower collagen content) and PLGA-Col-H (higher collagen content). The proliferation behavior of the cells on the microcarriers was evaluated by live/dead cell staining and CCK-8 assays, while the osteogenic differentiation behavior was evaluated by ALP and qRT-PCR assays. Pristine PLGA microcarriers were also prepared to serve as a control. Three groups, PLGA, PLGA-Col-L, and PLGA-Col-H were then obtained. PLGA-Col was asymmetric with a rough/porous collagen patchy structure. All of these microcarriers could maintain morphology integrity for at least 3 weeks in the aqueous medium before undergoing obvious swelling (5w) and further erosion (7w). It was demonstrated that PLGA-Col could not only enhance the MSCs adhesion/proliferation but also mediate their subsequent osteogenic differentiation. PLGA-Col-L was suitable for supporting the MSCs proliferation, while PLGA-Col-H was more efficient in promoting the osteogenic differentiation of MSCs. Hence, the incorporation of collagen as a patchy structure into PLGA microspheres through the current microfluidic method could be an effective strategy to provide a superior type of microcarriers with well-defined functionality.