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The toxicity of nanomaterials can sometimes be attributed to photogenerated reactive oxygen species (ROS), but these ROS can also be scavenged by nanomaterials, yielding opportunities for crossover between the properties. The morphology of nanomaterials also influences such features due to defect-induced properties. Here we report morphology-induced crossover between pro-oxidant activity (ROS generation) and antioxidant activity (ROS scavenging) of MgO. To study this process in detail, we prepared three different nanostructures of MgO (nanoparticles, nanoplates, and nanorods) and characterized them by HRTEM. These three nanostructures effectively generate superoxide anions (O2 •–) and hydroxyl radicals (•OH) at higher concentrations (>500 μg/mL) but scavenge O2 •– at lower concentrations (40 μg/mL) with successful crossover at 200 μg/mL. Nanorods of MgO generate the highest levels of O2 •–, whereas nanoparticles scavenge O2 •– to the highest extent (60%). Photoluminescence studies reveal that such crossover is based on the suppression of F2+ and the evolution of F+, F2 +, and F2 3+ defect centers. The evolution of these defect centers reflects the antibacterial activity of MgO nanostructures which is initiated at 200 μg/mL against Gram-positive S. aureus ATCC 29737 and among different bacterial strains including Gram-positive B. subtilis ATCC 6633 and M. luteus ATCC 10240 and Gram-negative E. coli ATCC K88 and K. pneumoniae ATCC 10031. Nanoparticles exhibited the highest antibacterial (92%) and antibiofilm activity (17%) against B. subtilis ATCC 6633 in the dark. Interestingly, the nitrogen-centered free radical DPPH is scavenged (100%) by nanoplates due to its large surface area (342.2 m2/g) and the presence of the F2 + defect state. The concentration-dependent interaction with an antioxidant defense system (ascorbic acid (AA)) highlights nanoparticles as potent scavengers of O2 •– in the dark. Thus, our findings establish guidelines for the selection of MgO nanostructures for diverse therapeutic applications.

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This paper investigates the design of novel polyelectrolyte complex (PEC) coacervates of chitosan (Ch) with gum Odina (GO) as potential candidates for colon targeting. Potentiometric titration experiments established that 1:1 charge stoichiometry occurred at a Ch/GO weight ratio of 1:5. The coacervate formed at pH 4.5 displayed the highest storage modulus (G′) values. FTIR, XPS, WAXS, TGA, and DSC results suggested the strong ionic (NH3 +···COO–) bond formation between these two biopolymers. Through in vitro viability tests, the pH-induced PECs were shown to be nontoxic. In vitro biodegradation rates of their microspheres revealed insolubility in simulated gastric fluid and simulated intestinal fluid and degradation by cell-associated portions of rat cecal and colonic enzymes rather than the extracellular portions. The microsphere of pH 3.0 showed the highest degradation, and LVSEM micrographs revealed notably high amount of macropores in cell-associated enzymes, in contrast to extracellular enzymes.

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The antidepressant drug amitriptyline hydrochloride was obtained in a dry powder form and was screened against 253 strains of bacteria which included 72 Gram positive and 181 Gram negative bacteria and against 5 fungal strains. The minimum inhibitory concentration (MIC) was determined by inoculating a loopful of an overnight peptone water culture of the organism on nutrient agar plates containing increasing concentrations of amitriptyline hydrochloride (0, 10 µg/mL, 25 µg/mL, 50 µg/mL, 100 µg/mL, 200 µg/mL). Amitriptyline hydrochloride exhibited significant action against both Gram positive and Gram negative bacteria at 25-200 µg/mL. In the in vivo studies it was seen that amitriptyline hydrochloride at a concentration of 25 µg/g and 30 µg/g body weight of mouse offered significant protection to Swiss strain of white mice when challenged with 50 median lethal dose (MLD) of a virulent strain of Salmonella typhimurium NCTC 74. The in vivo data were highly significant (p<0.001) according to the chi-square test.

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