Delivering regenerative cues to the heart: cardiac drug delivery by microspheres and peptide nanofibers.

Our understanding of signaling pathways and cues vital for cardiac regeneration is being refined by laboratories worldwide. As various mechanisms enabling cardiac regeneration are becoming elucidated, delivery vehicles suited for these potential therapeutics must also be developed. This review focuses on advances in two technologies, novel degradable microspheres for controlled release systems and self-assembling peptide nanofibers for cell and factor delivery. Polyketals, a new class of resorbable polymers, are well suited for treating inflammatory diseases due to biocompatible degradation products. Polyketals have been used to deliver small molecule inhibitors and antioxidant proteins to rat models of myocardial infarction with notable improvements in cardiac function. Self-assembling peptide nanofibers are a class of hydrogels that are well-defined scaffolds made up of 99% water and amenable to incorporation of a variety of bioactive cues. Work done by our laboratory and others have demonstrated functional improvements using these hydrogels as both a drug delivery vehicle for proteins as well as a defined microenvironment for transplanted cells. Combining non-inflammatory polymer microspheres for sustained release of drugs with self-assembling nanofibers yields multifunctional scaffolds that may soon drive the body's healing response following myocardial infarction towards cardiac regeneration.