The continued risk of death due to heart failure has spurred the advancement of biomaterials-based treatments for cardiac repair, two of which are the application of a cardiac patch or intramyocardial material injection. The inclusion of signaling molecules in these materials can improve the treatment results; however, appropriate molecule delivery is not trivial. This research presents the broad application of therapeutics from both a patch and injectable system to demonstrate how system properties influence drug delivery and how these systems may be engineered to provide added benefit in the desired application.
We demonstrated the ability to release a gene-inducing molecule, Rheoswitch ligand 1 (RSL1), from a biodegradable elastomer that has been used as a cardiac patch. Not only was bioactive RSL1 released over an extended period, the ability to differentially load scaffolds with RSL1 allowed for spatial patterning of gene expression in cells cultured on the scaffold surface, which has implications for creating complex 3D tissues in vitro. This same elastomeric material was able to release bioactive insulin-like growth factor 1 (IGF1) and hepatocyte growth factor (HGF) in vitro. The complex release behavior of IGF1 into saline was replaced by a much simpler release profile during simulated in vivo degradation, demonstrating that the implant environment must be considered when studying drug delivery behavior.
A strong, thermoresponsive and degradable hydrogel was developed for intramyocardial injection. We showed the release rates of a model protein from this gel, or from protein-loaded microparticles inside the gel, could be controlled by changing the material composition. The combination of hydrogel with microparticles delivered two proteins in a sequential manner. We further used this system to release bioactive basic fibroblast growth factor (bFGF) followed by IGF1 in vitro. Injection of the unloaded polymer into infarcted rat hearts was able to improve the remodeling process for at least 16 weeks. While increased tissue bFGF and IGF1 were demonstrated following injection of growth factor-loaded gels, there were no clear benefits seen from protein inclusion. This points to the primary ability of the hydrogel alone to benefit cardiac function and cellular environment and warrants further investigation
