Tensile strain-controlled drug delivery system based on a cracked metal structure

Recently, mechanical stimuli-responsive drug delivery systems have received much attention as they have the advantages of being easily accessible for self-administered therapeutics and requiring no additional equipment. In this study, we report a tensile strain-controlled drug delivery system based on a micro-cracked membrane. The membrane consists of a drug-loaded polyurethane polymer layer coated with a biocompatible titanium metal layer. On application of external tensile strain to the membrane, micro-sized cracks are generated and propagate in the metallic layer. The exposed crack region acts as a channel for the drug molecules to diffuse into the surrounding buffer solution. We utilized the membrane as a drug delivery system by controlling the exposed crack region, which is dependent on the applied strain. Our results indicated that the amount of released drug increased with the applied strain, and the drug release profile had a highly linear correlation with the ‘ratio of exposed region’ in both experimental and numerical results (greater than 0.9). Although the developed crack-based drug release system has limitations such as drug leakage under the 0% strain condition, we believe that this drug release system can be a useful tool as an on-demand mechanically stimulated controlled drug delivery system, especially for applications requiring continued and long-term drug delivery.