Osteogenic Potential of Poly (l-lactic acid) Scaffolds Prepared by Thermally Controlled Methods on Human Adipose Derived Stem Cells

Abstract

Thermally Induced Phase Separation (TIPS) method was used to make porous three-dimensional PLLA scaffolds. The effect of imposed thermal profile during freezing of the PLLA in dioxane solution on the scaffold was characterized by their micro-structure, porosity (%), pore-sizes distribution and mechanical strength. The porosity (%) decreased considerably with increasing concentrations of PLLA in the solution, while a decreasing trend was observed with increasing cooling rates. The mechanical strength increases with increase in PLLA concentration and also with increase in the cooling rate for both types of solvents. Therefore, mechanical strength was increased by higher cooling rates while the porosity (%) remained relatively consistent. Scaffolds made using higher concentrations of PLLA (7% and 10% w/v) in solvent, showed better mechanical strength which improved relatively with increasing cooling rates. This phenomenon of enhanced structural integrity with increasing cooling rates was more prominent in scaffolds made from higher initial PLLA concentrations. Human adipose derived stem cells were cultured on these scaffold (7 and 10% w/v) prepared by TIPS at all cooling rates to measure the cell proliferation efficiency as a function of their micro-structural properties. Mean pore-sizes played a crucial role in the cell proliferation than % porosity since all scaffolds were > 88 % porous. The viability of human adipose tissue derived adult stem cells cultured on 7% PLLA scaffolds cooled at 10˚C/min was also shown to be comparable with corresponding culture conditions without scaffolds for a period of 42 days. Scaffolds made from 10% PLLA in dioxane and cooled at 10°C/min favored cell proliferation compared to scaffolds made from other parameters. This structurally characterized scaffolds for bio-response was used for osteogenic studies and found that PLLA scaffolds are ‘osteoinductive’ when cultured in stromal media in vitro. Osteo-conductivity of PLLA on hASCs was further enhanced with osteo-inductive media.