Surface tethering of stem cells with HO-responsive anti-oxidizing colloidal particles for protection against oxidation-induced death.

Mesenchymal stem cells are the new generation of medicine for treating numerous vascular diseases and tissue defects because of their ability to secrete therapeutic factors. Poor cellular survival in an oxidative diseased tissue, however, hinders the therapeutic efficacy. To this end, we hypothesized that tethering the surface of stem cells with colloidal particles capable of discharging antioxidant cargos in response to elevated levels of hydrogen peroxide (HO) would maintain survival and therapeutic activity of the stem cells. We examined this hypothesis by encapsulating epigallocatechin gallate (EGCG) and manganese oxide (MnO) nanocatalysts into particles comprising poly(d,l-lactide-co-glycolide)-block-hyaluronic acid. The MnO nanocatalysts catalyzed the decomposition of HO into oxygen gas, which increased the internal pressure of particles and accelerated the release of EGCG by 1.5-fold. Consequently, stem cells exhibited 1.2-fold higher metabolic activity and 2.8-fold higher secretion level of pro-angiogenic factor in sub-lethal HO concentrations. These stem cells, in turn, performed a greater angiogenic potential with doubled number of newly formed mature blood vessels. We envisage that the results of this study will contribute to improving the therapeutic efficacy of a wide array of stem cells.