Tuneable hydrolytic degradation of poly(l-lactide) scaffolds triggered by ZnO nanoparticles

In this work we fabricate porous PLLA and PLLA/ZnO scaffolds with porosities ranging from 10 to 90% and average pore diameter of 125-250μm by solvent casting/particulate leaching method. The structural evolution of PLLA/ZnO scaffolds during their in vitro degradation in phosphate buffered saline (PBS) at physiological pH (7.4) has been studied as a function of porosity and obtained results were compared to plain PLLA scaffolds. The changes induced upon the hydrolytic degradation of scaffolds have been explored by measuring the pH changes of the medium, the mass loss, thermal transitions, crystalline structure, thermal stability and the morphological changes. It is shown that the degradation profile of scaffolds could be successfully modified by tuning both the amount of ZnO nanoparticles and by varying the scaffold porosity. Results reveal that the water dissociated on ZnO nanoparticle surfaces initiate hydrolytic degradation reactions by reducing the strength of the chemical bonds of the adjacent PLLA chains, causing them to further divide into water-soluble oligomers. Obtained results may be useful towards the development of antibacterial porous structures with tuneable degradation rates to be used as a substrate for the growth of different kind of cells and tissues.