Pyrolized Diatomaceous Biomass Doped with Epitaxially Growing Hybrid Ag/TiO2 Nanoparticles: Synthesis, Characterisation and Antibacterial Application.

In the pursuit of innovative solutions for modern technologies, particularly in the design and production of new micro/nanostructured materials, microorganisms acting as "natural microtechnologists" can serve as a valuable source of inspiration. This research focuses on harnessing the capabilities of unicellular algae (diatoms) to synthesize hybrid composites composed of AgNPs/TiO2NPs/pyrolyzed diatomaceous biomass (AgNPs/TiO2NPs/DBP). The composites were consistently fabricated through metabolic (biosynthesis) doping of diatom cells with titanium, pyrolysis of the doped diatomaceous biomass, and chemical doping of the pyrolyzed biomass with silver. To characterize the synthesized composites, their elemental and mineral composition, structure, morphology, and photoluminescent properties were analysed using techniques such as X-ray diffraction, scanning and transmission electron microscopy, and fluorescence spectroscopy. The study revealed the epitaxial growth of Ag/TiO2 nanoparticles on the surface of pyrolyzed diatom cells. The antimicrobial potential of the synthesized composites was evaluated using the minimum inhibitory concentration (MIC) method against prevalent drug-resistant microorganisms, including Staphylococcus aureus, Klebsiella pneumonia, and Escherichia coli, both from laboratory cultures and clinical isolates.

Development and characterization of antibacterial coatings on surgical sutures based on sodium carboxymethyl cellulose/chitosan/chlorhexidine.

The layer-by-layer assembly (LBL) method was used in this work to apply antibacterial coatings to the surface of sutures. The nanofilm was created using sodium carboxymethyl cellulose, chitosan, and chlorhexidine digluconate. Polyethylene terephthalate and polyamide surgical sutures were used as the substrate. At pH 5, thin, uniform coatings with the ideal number of biopolymers in the film (10 bilayers) are produced. The pH and the shape of the polyelectrolyte macromolecules determine the film's thickness and form. The morphology of the surface and the structure of the sutures after modification become homogeneous and smooth. Both treated and untreated sutures retain their mechanical strength, and there is no significant loss of tensile strength. Nanofilms obtained on the surface of the sutures showed high antimicrobial efficacy against microorganisms Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Staphylococcus epidermidis, and Streptococcus pneumoniae. Chlorhexidine incorporated into the multilayer membrane was found to have greater antimicrobial activity than sutures treated with chlorhexidine alone. Modified surgical sutures provide antibacterial qualities that last for up to 30 days in a stable, controlled manner. The results showed the prospects of applying nanofilms based on sodium carboxymethyl cellulose/chitosan/chlorhexidine to surgical sutures that can prevent the infectious consequences of surgical interventions.

Synthesis and Antimicrobial Activity of 3D Micro-Nanostructured Diatom Biosilica Coated by Epitaxially Growing Ag-AgCl Hybrid Nanoparticles.

The 3D (three-dimensional) micro-nanostructured diatom biosilica obtained from cultivated diatoms was used as a support to immobilize epitaxially growing AgCl-Ag hybrid nanoparticles ((Ag-AgCl)NPs) for the synthesis of nanocomposites with antimicrobial properties. The prepared composites that contained epitaxially grown (Ag-AgCl)NPs were investigated in terms of their morphological and structural characteristics, elemental and mineral composition, crystalline forms, zeta potential, and photoluminescence properties using a variety of instrumental methods including SEM (scanning electron microscopy), TEM (transmission electron microscopy), EDX (energy-dispersive X-ray spectroscopy), XRD (X-ray powder diffraction), zeta-potential measurement, and photoluminescence spectroscopy. The content of (AgCl-Ag)NPs in the hybrid composites amounted to 4.6 mg/g and 8.4 mg/g with AgClNPs/AgNPs ratios as a percentage of 86/14 and 51/49, respectively. Hybrid nanoparticles were evenly dispersed with a dominant size of 5 to 25 nm in composite with an amount of 8.4 mg/g of silver. The average size of the nanoparticles was 7.5 nm; also, there were nanoparticles with a size of 1-2 nm and particles that were 20-40 nm. The synthesis of (Ag-AgCl)NPs and their potential mechanism were studied. The MIC (the minimum inhibitory concentration method) approach was used to investigate the antimicrobial activity against microorganisms Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus. The nanocomposites containing (Ag-AgCl)NPs and natural diatom biosilica showed resistance to bacterial strains from the American Type Cultures Collection and clinical isolates (diabetic foot infection and wound isolates).

Synthesis, characterization of silver/kaolinite nanocomposite and studying its antibacterial activity.

In the present study, silver/kaolinite nanocomposites were synthesized by impregnation in a silver nitrate solution. Silver nanoparticles are deposited onto the surface of the kaolinite by a simple wet reduction of a silver precursor using hydrogen peroxide as a reducing agent. Elemental, mineral composition, structure and morphology of natural kaolinite and synthesized nanocomposites are characterized by X-ray diffractometry, FT-IR spectroscopy, photoluminescence (PL), zeta potential, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. The antibacterial activity of AgNPs/kaolinite nanocomposites to Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae, Escherichia coli strains was studied by the minimum inhibitory concentration method. The obtained AgNPs/kaolinite nanocomposite was shown to have antimicrobial potential.