Indentation Creep Reservoirs for Drug-Eluting Poly(L-Lactic Acid) Scaffolds

The indentation creep behavior of poly(L-lactic acid) (PLLA) thin and thick films was examined. The creep rate was found to be strongly dependent on applied stress, as well as on the thickness of the PLLA film with creep rates being much larger in thin films compared to thick ones at lower stresses, but the difference was minimal at high stresses. The indentation creep approach was used to create a drug-delivery device with multiple reservoirs. Managing the thickness of the diffusion barrier that was a low-molecular-weight PLLA controlled the rate of drug release and it is shown that transport of drug through the barrier is diffusion controlled and the rate of dissolution of the PLLA is slower than the rate of transport of drug. A stable release rate together with periodic pulsed release was achieved over a period of 28 days with complete transport of the drug achieved over this time frame.