No abstract

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.

The development of modern technology is also towards the use of microorganisms as microfactories of the biomaterials with unique properties. Combining the original properties of biosilica extracted from diatoms (microalgae) together with immobilised silver and cerium in nanoparticle forms, allowed to obtain a modern composite material with antibacterial activity. The synthesised composites contained heteroepitaxially growing Ag/AgCl/CeO2 complex nanoparticles were studied using a different types of instrumental analysis. SEM-EDX and XRD analysis allowed the qualitative and quantitative determination of the elements present and their forms in the composites. TEM analysis allowed to information about the shape, size and structure specificity of the created nanoparticles. The possible mechanism of nanoparticles formation was suggested. Antibacterial properties of synthesised composites were characterised using a minimum inhibitory concentration test on six selected bacterial strains. Diatomaceous biosilica containing heteroepitaxially growing silver chloride, metallic silver, and cerium (IV) oxide nanoparticles have been prepared for the first time. The proposed method for synthesising composites did not use toxic reagents, making it environmentally friendly.