Green synthesis of silver nanoparticles using curcumin: A comparative study of antimicrobial and antibiofilm effects on Acinetobacter baumannii against chemical conventional methods

Acinetobacter baumannii (A. baumannii) is an important pathogen that causes hospital-acquired illnesses worldwide. The biofilm-forming activity of the organism enhances its capacity to acquire significant levels of antibiotic resistance, hence necessitating the development of novel and effective antibacterial drugs. Nevertheless, nanoparticles have been documented as highly effective agents against bacterial growth and biofilm formation. So, the purpose of this work was to study the antibacterial and antibiofilm capabilities of silver nanoparticles synthesized by facile green method using curcumin (GS-AgNPs) on A. baumannii compared to the chemical method (CS-AgNPs) in vitro. Moreover, twenty-four clinical isolates of A. baumannii were collected and characterized by standard microbiological techniques. The results showed that all isolates of A. baumanii exhibited a significant degree of resistance to a wide range of antimicrobials. On the other hand, the minimum inhibitory concentration (MIC) for GS-AgNPs sample fell between 250 and 7.8 μg/ml. While the CS-AgNPs sample had MIC values that fell between 500 and 1000 µg/ml. Twenty out of 24 strains were biofilm producers. The lowest MIC of the tested AgNPs was mainly observed in the strains that produce weak biofilm. GS-AgNPs significantly inhibited the biofilm production by the tested isolates than AgNPs synthesized chemically and biofilm inhibition reached to 57.43 ± 9.50 %, and 50.57 ± 3.91 % of controls for strong producers, respectively. The results of the research suggest that GS-AgNPs demonstrate notable effectiveness as a secure and powerful antibacterial and antibiofilm agent against multidrug-resistant A. baumannii strains

Highly Selective Photocatalytic Reduction of o-Dinitrobenzene to o-Phenylenediamine over Non-Metal-Doped TiO2 under Simulated Solar Light Irradiation.

Photocatalytic reduction and hydrogenation reaction of o-dinitrobenzene in the presence of oxalic acid over anatase-brookite biphasic TiO2 and non-metal-doped anatase-brookite biphasic TiO2 photocatalysts under solar simulated light was investigated. Compared with commercial P25 TiO2, the prepared un-doped and doped anatase-brookite biphasic TiO2 exhibited a high selectivity towards the formation of o-nitroaniline (85.5%) and o-phenylenediamine ~97%, respectively. The doped anatase-brookite biphasic TiO2 has promoted photocatalytic reduction of the two-nitro groups of o-dinitrobenzene to the corresponding o-phenylenediamine with very high yield ~97%. Electron paramagnetic resonance analysis, Transient Absorption Spectroscopy (TAS) and Photoluminescence analysis (PL) were performed to determine the distribution of defects and the fluorescence lifetime of the charge carriers for un-doped and doped photocatalysts. The superiority of the doped TiO2 photocatalysts is accredited to the creation of new dopants (C, N, and S) as hole traps, the formation of long-lived Ti3+ defects which leads to an increase in the fluorescence lifetime of the formed charge carriers. The schematic diagram of the photocatalytic reduction of o-dinitrobenzene using the doped TiO2 under solar light was also illustrated in detail