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).

Clay minerals are actively used to obtain a bioactive composite. Kaolinite, as a representative of clay minerals, possesses unique properties essential for the creation of biocomposite materials. This mineral, characterized by its distinctive layered structure, is chemically inert, highly stable, thermally resistant, eco-friendly, biocompatible, and non-toxic. Kaolinite, which plays the role of a carrier in this work, has such properties and can be the basis for biologically active composites. Antibacterial composites, namely, kaolinite/chlorhexidine and kaolinite/triclosan, were synthesized by impregnation of calcined and non-calcined samples of natural kaolinite with the antibacterial agents chlorhexidine and triclosan. The structure, morphology, elemental composition, and mineralogical characteristics of the natural and synthesized kaolinite/chlorhexidine (KAO/CHX) and kaolinite/triclosan (KAO/TCS) composites were investigated by methods of analysis such as X-ray diffraction, FTIR (Fourier-transform infrared) spectroscopy, and scanning electron microscopy. The calcined kaolinite/chlorhexidine composite at 500 °C (KAO_500°C/CHX) exhibited a higher content of antiseptics compared to the non-calcined kaolinite composite. The antibacterial activities of the kaolinite/chlorhexidine and kaolinite/triclosan composites were investigated against Gram-positive Staphylococcus epidermidis and Gram-negative Klebsiella pneumoniae and Escherichia coli strains by the well diffusion method and dilution method. The highest zone of inhibition was observed against Staphylococcus epidermidis (30.00 ± 0.00 mm and 30.67 ± 0.58 mm) by applying KAO/TCS and KAO_500°C/TCS via the well diffusion method. The minimum bactericidal concentration of the kaolinite/TCS composite was 15.63 μg/mL for Staphylococcus epidermidis and Klebsiella pneumoniae.

In this study, hemolytically safe and antibacterial polyvinyl alcohol/kaolinite/chitosan (PVA/KAO/CS) hydrogels were obtained using the freeze–thaw method. The structure of the chemical bonds present in the developed hydrogels was investigated by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) and optical microscopy study results showed the morphological and structural characteristics of the hydrogels’ surface. The thermal stability and phase transitions of the obtained hydrogel samples were determined by thermogravimetric analysis (TGA). Porosity, swelling, gel fractions, and mechanical properties were also examined. Biomedical properties of the samples were evaluated using in vitro and in vivo tests such as hemolytic activity, inhibition of protein denaturation, antimicrobial activity, and hemostatic activity. The obtained hydrogels demonstrated safe hemolytic activity, pronounced hemostatic activity, the ability to prevent thermal denaturation of albumin, as well as antimicrobial activity against Gram-positive bacteria Staphylococcus aureus ATCC BAA-39 and Streptococcus pyogenes ATCC 19615 and Gram-negative bacteria Pseudomonas aeruginosa ATCC 9027 and Escherichia coli ATCC 8739. All the obtained characteristics confirmed the promising biomedical applications of the obtained hydrogels.