Cell-based therapy is one of the major potential therapeutic strategies for cardiovascular, neuronal and degenerative diseases in recent years. The aims of this study is to develop a novel biomimic polymeric materials which will facilitate the delivery cells, control cell bioactivities and enhance the focal integration of graft cells with host tissues. We synthesized a novel tri-block copolymer, methoxy-terminated poly (ethylene glycol) (MPEG)-polyL-lactide (PLLA)-polylysine (PLL) via sequential polymerization of PLLA onto MPEG, followed by ring opening polymerization of PLL onto the functionalized chain end. The triblock copolymer (5%) was then mixed with high molecular weight PLLA (95%) to form cell-delivery membranes. The spectra of copolymers were determined by NMR and ATR-FTIR spectroscopy. Human osteoblasts were used for testing biocompatibility and initial cellular reaction. It was noted that no cytotoxicity was detectable in our synthesized copolymers. Compared with pure PLLA and diblock copolymers, the triblock copolymers showed significantly better cell adhesion and proliferation. Interestingly we identified that cellular activity (attachment, proliferation and differentiation) could be regulated by the molecular weight and composition of the triblock copolymers. In conclusion controllable synthetic copolymers can be designed and synthesized to modulate cellular function in facilitating tissue repair and regeneration.