Modulation of cell morphology and function using synthetic biodegradable polymers

Abstract

Synthetic biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) has been fabricated into thin films for use as scaffolds for cell transplantation and guided tissue regeneration. We evaluated the ability of PLGA films to provide a suitable template for directing specific cell growth and tissue formation using cells derived from retinal pigment epithelium (RPE) as an in vitro model. RPE cells were shown to attach to and proliferate on PLGA films during a 7-day culture period. Both polymer composition and initial cell seeding density affected cell growth. PLGA films were formulated with copolymer ratios of 50:50 and 75:25 and thickness levels of 10 and 100 mum. In vitro degradation of these thin films in simulated body fluid was characterized in terms of mass loss, molecular weight loss, dimensional changes, and morphology over a time course of ten weeks. The PLGA films demonstrated a pattern typical of heterogeneous bulk degradation and exhibited an autocatalytic effect. To further modulate cellular responses, biodegradable polymers of PLGA were investigated for controlled and sustained delivery of bioactive molecules. Transforming growth factor-beta1 (TGF-beta1) was incorporated into microparticles of, blends of PLGA and poly(ethylene glycol) (PEG) as a model growth factor and released in vitro in buffer solutions simulating body fluids for up to 28 days. The release of TGF-beta1 was affected by the PEG content and buffer pH. Increasing the PEG content or decreasing buffer pH resulted in accelerated PLGA degradation. The release of bioactive molecules from PLGA/PEG microparticles was governed by both diffusion and polymer degradation. The feasibility of controlling cell morphology and function by modification of substrate surface with defined hydrophobic and hydrophilic domains was assessed. We described the preparation and characterization of model surfaces consisting of glass domains with a diameter of 10 or 50 mum surrounded by octadecyltrichlorosilane self-assembled monolayers. The micropatterned surfaces were shown to affect initial RPE cell attachment and spreading, and modulate the expression of differentiated cell phenotype. A novel biodegradable polymer substrate was developed with micropatterned surfaces composed of PLGA and a block copolymer of PEG and poly(DL-lactic acid) (PDLLA). We demonstrated that engineering of surface chemistry and microstructure of substrates could induce proper cell shape and function