Fabrication Of Alendronate Gradient On Poly(ε-caprolactone)Membrane Surface For Localized Osteogenic Differentiation Of Bone Marrow Stem Cells

Tissue engineering has broad application prospects in repairing damaged tissues and organs. Through methods including induction of localized differentiation of bone marrow stem cells (BMSCs) via fabrication of biomaterials with gradient properties, interface tissue engineering (ITE) aims at repairing interfaces of neighboring tissues. As a widely adopted surface modification method for polyesters, aminolysis could be used to fabricate gradient of amino groups which can immobilize bioactive molecules on polyester surfaces in a gradient manner and spatially modulate differentiation behaviors of BMSCs. However, as a result of deficiency in studies of kinetics of aminolysis and its effects on material properties, fabrication of gradient materials with aminolysis still lacks of scientific or technological basis. Based on thorough study of influences of reaction parameters on the aminolysis of poly(ε-caprolactone)(PCL) membranes, PCL membranes with well defined gradient amino groups were obtained. Thus, gradient density of Alendronate (Aln) was generated on PCL membrane surface and successfully induced localized osteogenic differentiation of rat BMSCs. In this thesis, following innovations were achieved:(1) The effects of reaction parameters including diamine molecular weight,1,6-hexanediamine concentration and reaction temperature on aminolysis reaction rate have been illustrated. Gradiently aminolyzed PCL membranes were obtained via injection method and gradiently grafted Aln to membrane surface with GA coupling, obtaining linear Aln density gradient surfaces.(2) It was found that rat BMSCs are able to adhere to and proliferate on PCL-Aln membranes with different Aln densities. Through binding with cell surface receptor Cx43. Aln induces BMSCs osteogenic differentiation, and its effect has positive correlation with its density. The BMSCs on the Aln gradient surfaces with spatially improved expression of osteogenic marker proteins including ALP. Collagen type1. Runx2and OCN with a Aln density dependent manner, which is a key evidence of localized differentiation.