The role of transition metals in the formation and aging of secondary organic aerosol (SOA) from aliphatic and aromatic precursors in heterogeneous/multiphase reactions is not well understood. The reactivity of soluble Fe(III) toward known benzene photooxidation products that include fumaric (trans-butenedioic) and muconic (trans,trans-2,4-hexadienedioic) acids was investigated. Efficient formation of brightly colored nanoparticles was observed that are mostly rod- or irregular-shaped depending on the structure of the organic precursor. The particles were characterized for their optical properties, growth rate, elemental composition, iron content, and oxidation state. Results indicate that these particles have mass absorption coefficients on the same order as black carbon and larger than that of biomass burning aerosols. The particles are also amorphous in nature and consist of polymeric chains of Fe centers complexed to carboxylate groups. The oxidation state of Fe was found to be in between Fe(III) and Fe(II) in standard compounds. The organic reactant to iron molar ratio and pH were found to affect the particle growth rate. Control experiments using maleic acid (cis-butenedioic acid) and succinic acid (butanedioic acid) produced no particles. The formation of particles reported herein could account for new pathways that lead to SOA and brown carbon formation mediated by transition metals. In addition, the multiple chemically active components in these particles (iron, organics, and acidic groups) may have an effect on their chemical reactivity (enhanced uptake of trace gases, catalysis, and production of reactive oxygen species) and their likely poor cloud/ice nucleation properties.
Background Ovarian cancer is a leading cause of cancer mortality in women, and only a small percentage of cases are caught at an early stage. Novel treatments with improved efficacy are needed to fight ovarian cancer and to overcome resistance to traditional therapies. Double-stranded (ds) RNA, including the synthetic polyinosinic cytidylic acid (poly (I:C), has shown promise as a cancer therapeutic. Two ovarian cancer cell lines were tested for their ability to produce an immune response to poly (I:C) delivered using a nanoparticle carrier, a biodegradable phytoglycogen derived from sweet corn, called nanodendrix (NDX). SKOV-3 and OVCAR-3 have been previously identified as dsRNA-resistant and dsRNA-sensitive, respectively. Results Firstly, NDX was found to effectively bind poly (I:C), at a w/w ratio of 2:1 NDX:poly (I:C), the resulting particles, poly (I:C)-NDX, were tested for biological activity through uptake and two therapeutic modes of action, cytotoxicity and stimulation of the innate immune response. Both cell lines bound poly (I:C)-NDX, as observed using immunocytochemistry. In OVCAR-3 poly (I:C)-NDX caused significant cell death, even at concentrations as low as 62.5ng/mL, measured using the cell viability indicator dye alamarBlue; no cell death was observed with poly (I:C) alone across all concentrations, up to 5µg/mL in SKOV-3 and 0.5µg/mL in OVCAR-3. In both OVCAR-3 and SKOV-3, poly (I:C)-NDX stimulated the production of an innate immune chemokine, CXCL10, at the transcript and protein levels, at significantly higher levels than poly (I:C) alone. Interestingly, in response to poly (I:C)-NDX SKOV-3 produced a more robust immune response compared and higher levels of capase-3/-7 activation compared to OVCAR-3, despite showing no significant cell death. Conclusions Poly (I:C)-NDX represents a robust and multifunctional therapy with demonstrated efficacy against a range of ovarian tumour cells, potentiating poly (I:C) and sensitizing resistant cells. Additionally, the SKOV-3 and OVCAR-3 combination represents a powerful comparative model to help unravel dsRNA-mediated immune responses in ovarian cancer cells.
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