’Smart’, Injectable, Magnetic Nanocomposite Hydrogels for Biomedical Applications with a Focus on Externally-Mediated Release

Abstract

The capability of precisely controlling the kinetics of therapeutic delivery at the optimal location and rate for a given patient would have great potential to improve health and well-being in a range of current drug therapies (insulin, chemotherapeutics, vaccines, etc.). Indeed, if successfully developed, locally administered injectable drug delivery vehicles capable of remotely-triggered release would be the gold standard for many treatments. Multiple injectable nanocomposites have been investigated for this purpose that are generally comprised of a thermosensitive polymeric material and superparamagnetic iron oxide nanoparticles (SPIONs). SPIONs generate heat when exposed remote alternating magnetic fields (AMFs), and the transfer of this heat to thermosensitive polymers can be used to control the release of therapeutics. Ideally, these systems would be capable of returning to their original state and basal release rate when the external AMF trigger is removed. Several novel injectable nanocomposite materials that explore interactions between SPIONs and thermosensitive polymers to mediate drug release, from the macroscale to the nanoscale, were developed and demonstrated to be capable of remotely-triggered, AMF-mediated enhanced release. The macroscale magnetic nanocomposites have thermosensitive hydrogel and/or microgel components that regulate release based on the heat produced from SPIONs in response to an external AMF. On the millimeter-scale, a microinjection system capable of producing thermosensitive hydrogel beads that could potentially incorporate SPIONs is described. On the nanoscale, nanoparticles with a glass transition temperature and thermosensitive microgels are combined with SPIONs and investigated for their remote, AMF-mediated release characteristics. The engineered macroscale and nanoscale systems are capable of up to ~4:1 and ~7:1 enhancements in release due to an AMF application, respectively, compared to the basal release rate. Collectively, these nanocomposites represent a promising stride towards improved remote-actuation of drug release and a stepping stone for future attempts at precisely controlling the site and kinetics of drug release.