(19a) A Model of Oxidation Injury and an Antoxidant Drug Delivery Rescue Strategy

LAP is a widely used photoinitiator for hydrogel fabrication, though it can be toxic during crosslinking when encapsulating certain types of cells. The effect of NAC treatment after photoinitiated LAP injury was examined on oligodendrocyte progenitor cells (OPCs), the cells that give rise to myelinating oligodendrocytes in the central nervous system. OPCs were exposed to 0.55 mM LAP and 10 minutes of UV light (5 mW/cm^2, 365 nm). 6 hours after LAP injury, control samples exhibited a high level of processes/cell, 0.80±0.097, while injured OPCs exhibited a process/cell value of 0.39±0.0016. Treatment with 25 mM of the antioxidant NAC 15 minutes after UV/LAP exposure rescued the number of processes/cell to 0.78±0.080. By 48 hours post-injury, the NAC-treated OPCs yielded a processes/cell value of 0.59±0.077, which was significantly higher than that of both the control (0.35±0.032) and injured cells (0.36±0.093). To provide a measure of nuclear fragmentation, an indicator of apoptosis, the number of DAPI particles/cell were quantified 48 hours after LAP/UV injury and yielded values of 1.09, 1.47, and 1.28 for control, injured, and injured/NAC-treated OPCs, respectively. Thus, NAC treatment administered after photoinitiated LAP exposure can rescue OPC morphology and nuclear fragmentation from toxic photoinitiated LAP radicals.

We have previously demonstrated a method to create microparticles with high loads of NAC that protected OPCs from oxidant-induced injury. We hypothesize that a controlled, zero-order release of NAC will protect OPCs from photoinitiated LAP, but moreover, from oxidants over a longer time period. Core-shell particles have previously been shown to tune drug release over longer time frames, and results in a linear release rate, a particular challenge for delivery of small, hydrophilic drugs like NAC from polymer-based particles. Preliminary confocal images suggest that we can fabricate core-shell microparticles using an empty poly(lactic acid) shell and TRITC-BSA-loaded poly(lactic-co-glycolic acid) (PLGA) core. 2-hour BSA release of core-localized particles was half that of shell-localized particles, indicating a reduced burst release. A linear fit of cumulative BSA release profiles for one week yielded R² values of 0.74 and -0.71 for drug in core-localized and shell-localized particles, respectively, indicating a near-zero order BSA release profile for core-localized particles. Future work aims to encapsulate NAC into the core of core-shell particles and characterize their therapeutic affect on LAP-injured OPCs over time. NAC core shell particles will also be encapsulated in a physiologically relevant 3D hydrogel/OPC system to examine the particles’ therapeutic affect for longer time frames.