Trimethyl chitosan-capped silver nanoparticles with positive surface charge: Their catalytic activity and antibacterial spectrum including multidrug-resistant strains of Acinetobacter baumannii.

We report a facile route for the green synthesis of trimethyl chitosan nitrate-capped silver nanoparticles (TMCN-AgNPs) with positive surface charge. In this synthesis, silver nitrate, glucose, and trimethyl chitosan nitrate (TMCN) were used as silver precursor, reducing agent, and stabilizer, respectively. The reaction was carried out in a stirred basic aqueous medium at room temperature without the use of energy-consuming or expensive equipment. We investigated the effects of the concentrations of NaOH, glucose, and TMCN on the particle size, zeta potential, and formation yield. The AgNPs were characterized by UV-vis spectroscopy, photon correlation spectroscopy, laser Doppler anemometry, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalytic activity of the TMCN-AgNPs was studied by the reduction of 4-nitrophenol using NaBH4 as a reducing agent. We evaluated the antibacterial effects of the TMCN-AgNPs on Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus using the broth microdilution method. The results showed that both gram-positive and gram-negative bacteria were killed by the TMCN-AgNPs at very low concentration (<6.13µg/mL). Moreover, the TMCN-AgNPs also showed high antibacterial activity against clinically isolated multidrug-resistant A. baumannii strains, and the minimum inhibitory concentration (MIC) was ≤12.25µg/mL.

Genetic variation in hypothalamic methyltrienolone (R1881) binding in male mice.

Methyltrienolone (R1881) binding to androgen receptors (AR) from combined hypothalamic-preoptic-septal cytosol was examined in CF-1, CFW, and CD-1 male mice, strains that differ in their sensitivity to the aggression-promoting property of this hormone. Both the affinity of R1881-AR binding and the number of binding sites (Bmax) significantly differed among the genotypes. The dissociation constant (Kd) was lower in CF-1 males (6.7 nM), a behaviorally responsive strain, in comparison to the insensitive CFW and CD-1 males (3.0 nM and 2.0 nM, respectively). The number of binding sites was higher in CF-1 and CFW males (9.07 and 8.81 fmol/mg protein, respectively) than in CD-1 males (5.11 fmol). The results were basically consistent with studies of neural dihydrotestosterone (DHT) binding in these genotypes, and the implications and limits of these data for understanding the androgenic regulation of intermale aggression are discussed.