In this study, hybrid carbon dots–plasmonic nanostructures including carbon dots/polyethyleneimine/gold (C-dots/PEI/Au), and carbon dots/polyethyleneimine/silver (C-dots/PEI/Ag) have been prepared using a microwave irradiation method. The prepared hybrid nanostructures have been characterized via optical spectroscopy, high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). A remarkable enhancement in the optical parameters, such as absorptivity and quantum yield (QY), has been observed for the hybrid nanostructure compared to pure carbon dots. This plasmonic enhancement was more pronounced in the presence of silver (C-dots/PEI/Ag nanohybrid) than that of gold (C-dots/PEI/Au nanohybrid). This is referred to the low intrinsic loss and the degree of the overlap between the absorption spectra of silver nanoparticles and carbon dots. Furthermore, the bio-compatibility assay and cellular response on epithelial kidney (Vero) normal cell has been investigated. The results showed that the optimal dose of treatment is about ∼200 μg ml⁻¹ using both C-dots/PEI/Au or C-dots/PEI/Ag, nano-hybrids could be used safely in diagnostic bioimaging applications.

The increase in antibiotic resistance related to microbial biofilms creates an urgent need to search for an alternative and active antimicrobial agent. Recently, nanoparticles have gained considerable attention from scientists due to their potent antimicrobial activity. In the present study, two endosymbiotic actinomycete strains were isolated from marine sponge Crella cyathophora by surface sterilization and incubation of sponge pieces on culture media selective for actinobacteria. The culture filtrate extracts, including the bacterial supernatants (F) and cell filtrate (C) of the two actinomycete strains, were used as the reducing agent for the green biosynthesis of silver nanoparticles. The as-prepared silver nanoparticles were characterized using dynamic light scattering, zeta-potential, UV-Vis spectroscopy, and transmission electron microscopy. The average particle size for synthesized silver nanoparticles was about ∼8.66 ± 2 to 35 ± 2 nm with monodisperse spherical-like shapes and polydispersed shapes, respectively. The synthesized silver nanoparticles exhibited significant antimicrobial activity toward pathogenic microbes, especially with P. aeruginosa and E. cloacae. The effect of silver nanoparticles on the growth curve dynamics of P. aeruginosa and E. cloacae showed that the slope of the bacterial growth curve continuously decreased with increasing nanoparticle concentration. Moreover, the antibiofilm activity of the silver nanoparticles was measured, and the results showed that the silver nanoparticles displayed high biofilm inhibition activity against P. aeruginosa, B. subtilis, and S. aureus. Furthermore, silver nanoparticles exhibited a low to moderate cytotoxic effect against hepatocellular carcinoma cancerous cells, which reflect its possible use in the biomedical field.

According to WHO warnings, the antibiotic resistance crisis is a severe health issue in the 21st century, attributed to the overuse and misuse of these medications. Consequently, the dramatic spreading rate of the drug-resistant microbial pathogens strains. The microbiological, biochemical tests and antibiotic sensitivity identified the bacteria's multi-drug resistance (MDR). About 150 different clinical samples were taken from hospitalized patients, both males, and females, ranging from 9 to 68 years. Gram-negative strains were (70.0%), while Gram-positive isolates were (30.0%). Among sixteen antibiotics, antibiotic susceptibility of imipenem was found to be the most efficient drug against most of the Gram-negative and Gram-positive isolates, followed by meropenem, depending on the culture and sensitivity results. All the experimental bacteria showed multidrug-resistant phenomena. In this study, green synthesized silver (Cur-Ag NPs) and zinc oxide (Cur-ZnO NPs) nanoparticles in the presence of curcumin extract. In addition, their physicochemical properties have been characterized using different techniques such as UV-Vis spectroscopy, transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and colloidal properties techniques. Furthermore, curcumin-capped silver nanoparticles (AgNPs) exhibited solid antimicrobial action against the experimental bacterial isolates, except Proteus vulgaris (i.e., P. vulgaris). Curcumin-capped zinc oxide nanoparticles (ZnO NPs) found antimicrobial activity against all tested strains. Finally, the minimum inhibitory concentration exhibited values from 3.9 to 15.6 μg ml⁻¹, which is too small compared to other traditional antibiotics. In addition, the green-synthesized Cur-Ag NPs and Cur-ZnO NPs showed good biocompatibility.