Development of Zein/tannic acid nanoparticles as antioxidants for oxidation inhibition of blackberry seed oil emulsions.

The zein-tannic acid nanoparticles (ZTNPs) were developed as antioxidants for oxidation inhibition of blackberry seed oils. These particles were spherical with an average diameter below 200 nm. The results of structural characterization indicated that tannic acid was bound to zein by electrostatic, hydrophobic, and hydrogen bonding interactions, resulting in the conformational changes of zein. The antioxidant capacity of zein was significantly improved by binding of tannic acid, which suggested ZTNPs had a 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide (PTIO) radical scavenging rate as high as 77.5 % at pH 4. Moreover, ZTNPs at pH 7 exhibited a higher thermal stability and better resistance to emulsion lipid oxidation. They inhibited the formation of ROOH and TBARS of blackberry seed oil emulsions during storage by covering at the oil-water interface with an adsorption rate of approximately 100 %, forming a dense particle film to reduce the oxygen content and prevent the continuation of the oxidation process.

An Ultrasmall Fe3 O4 -Decorated Polydopamine Hybrid Nanozyme Enables Continuous Conversion of Oxygen into Toxic Hydroxyl Radical via GSH-Depleted Cascade Redox Reactions for Intensive Wound Disinfection.

Nanozyme-based chemodynamic therapy (CDT) for fighting bacterial infections faces several major obstacles including low hydrogen peroxide (H2 O2 ) level, over-expressed glutathione (GSH) in infected sites, and inevitable damage to healthy tissue with abundant nonlocalized nanozymes. Herein, a smart ultrasmall Fe3 O4 -decorated polydopamine (PDA/Fe3 O4 ) hybrid nanozyme is demonstrated that continuously converts oxygen into highly toxic hydroxyl radical (•OH) via GSH-depleted cascade redox reactions for CDT-mediated bacterial elimination and intensive wound disinfection. In this system, photonic hyperthermia of PDA/Fe3 O4 nanozymes can not only directly damage bacteria, but also improve the horseradish peroxidase-like activity of Fe3 O4 decorated for CDT. Surprisingly, through photothermal-enhanced cascade catalytic reactions, PDA/Fe3 O4 nanozymes can consume endogenous GSH for disrupting cellular redox homeostasis and simultaneously provide abundant H2 O2 for improving •OH generation, ultimately enhancing the antibacterial performance of CDT. Such PDA/Fe3 O4 can bind with bacterial cells, and reveals excellent antibacterial property against both Staphylococcus aureus and Escherichia coli. Most interestingly, PDA/Fe3 O4 nanozymes can be strongly retained in infected sites by an external magnet for localized long-term in vivo CDT and show minimal toxicity to healthy tissues and organs. This work presents an effective strategy to magnetically retain the therapeutic nanozymes in infected sites for highly efficient CDT with good biosafety.

Magnetically retained and glucose-fueled hydroxyl radical nanogenerators for H2O2-self-supplying chemodynamic therapy of wound infections.

Chemodynamic therapy (CDT) involving the highly toxic hydroxyl radical (OH) has exhibited tremendous potentiality in combating bacterial infection. However, its antibacterial efficacy is still unsatisfactory due to the insufficient H2O2 levels and near neutral pH at infection site. Herein, a glucose-fueled and H2O2-self-supplying OH nanogenerator (pFe3O4@GOx) based on cascade catalytic reactions is developed by immobilizing glucose oxidase (GOx) on the surface of PAA-coated Fe3O4 (pFe3O4). Magnetic pFe3O4 can act as a horseradish peroxidase-like nanozyme, catalyzing the decomposition of H2O2 into OH under acidic conditions for CDT. The immobilized GOx can continuously convert non-toxic glucose into gluconic acid and H2O2, and the former improves the catalytic activity of pFe3O4 nanozymes by decreasing pH value. The self-supplying H2O2 molecules effectively enhance the OH generation, resulting in the high antibacterial efficacy. In vitro studies demonstrate that the pFe3O4@GOx conducts well in reducing pH value and improving H2O2 level for self-enhanced CDT. Moreover, the cascade catalytic reaction of pFe3O4 and GOx effectively avoids strong toxicity caused by directly adding high concentrations of H2O2 for CDT. It is worth mentioning that the pFe3O4@GOx performs highly efficient in vivo CDT of bacteria-infected wound via the localized long-term magnetic retention at infection site and causes minimal toxicity to normal tissues at therapeutic doses. Therefore, the developed glucose-fueled OH nanogenerators are a potential nano-antibacterial agent for the treatment of wound infections.