(579d) Benchmarking the Scavenging of Reactive Oxygen Species Using Inorganic and Carbon-Based Nanoparticle Systems in Isolated Chloroplasts From Spinacia Oleracea

The chloroplast contains densely stacked arrays of light-harvesting proteins ideal for harnessing solar energy. Over time, the photoactive proteins within the chloroplast become photodamaged due to reactive oxygen species (ROS) generation. In vivo, photoautotrophs address issues of photodegradation by applying a self-repair cycle that dynamically repairs and replaces photodamaged components. Outside the cell, ROS-induced photodegradation contributes to limited chloroplast stabilities. The incorporation of chloroplasts into light-harvesting devices therefore requires regenerative ROS scavenging mechanisms to prolong chloroplast photoactivity outside the cell. For the first time, we have studied the ROS generating behavior of isolated chloroplasts directly interfaced with nanoparticles, including dextran-wrapped nanoceria (dNC) that has demonstrated remedial ROS scavenging mechanisms. We quantitatively examine the effect of dNC, along with cerium ions, fullerenol, and DNA-wrapped single-walled carbon nanotubes (SWNTs), on the ROS generation of isolated chloroplasts using the oxidative dyes, 2’,7’- dichlorodihydrofluorescein diacetate (H₂DCF-DA) and 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide sodium salt (XTT).Chloroplast photoactivity in the presence of the nanoparticle additives was also measured using chloroplast fluorescence and the artificial, photosynthetic electron accepting dye, dichloroindophenol (DCPIP). We conclude that the dNC is the most effective agent for decreasing oxidizing agent and superoxide concentrations whilst preserving chloroplast photoactivity at concentrations below 5 µM. Confocal microscopy verifies that the mechanism of remedial ROS scavenging by the dNC occurs external to the isolated chloroplast. We believe that coupled to an approach for chloroplast internalization, dNC offers a promising mechanism for maintaining regenerative chloroplast photoactviity for light harvesting applications.