Antibacterial, Redox, Cytotoxic, and Ecotoxic Properties of New Sol–Gel Silica-Copper-Based Materials

<b>Objective:</b> The objective of our study was to synthesize and characterize silica-copper nanomaterials and to evaluate their biological properties (antibacterial, redox, cytotoxic, and ecotoxic) for potential applications. <b>Methods and Results:</b> Si/Cu-based materials were prepared by a sol-gel method. They were characterized by XRD, UV-Vis, and SEM-EDS. The antibacterial activity of the materials was evaluated against Gram-positive bacteria (<i>Staphylococcus aureus</i>, <i>Bacillus cereus</i>), Gram-negative bacteria (<i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, <i>Salmonella typhimurium</i>), and yeasts (<i>Candida albicans</i>, <i>Saccharomyces cerevisiae</i>). The nanomaterial that was calcined at 500 °C exhibited greater antibacterial efficacy compared to the gel form. <i>S. typhimurium</i> demonstrated the highest susceptibility, whereas <i>S. aureus</i> and <i>P. aeruginosa</i> were the most resistant of the tested bacteria. Both yeasts exhibited comparable sensitivity (MBC = 1.0 mg/mL). The redox activity of both nanomaterials was tested at pH 7.4 (physiological) and 8.5 (optimal) by the activated chemiluminescent method. The nanocomposites significantly inhibited the free-radical and ROS generation. This presents them as redox regulators in living systems. The cytotoxic effects in normal BEAS-2B and tumor A549 human cell lines were assessed microscopically and by the cell viability neutral red uptake assay, CC₅₀ being evaluated. The observed effects suggest moderate, similar cytotoxicity in both cell lines. The ecotoxicity study using <i>Daphnia magna</i> showed an LC₅₀ of ~7-8 mg/L about Si/Cu/500. The LC₅₀ for Si/Cu (gel) was lower than 0.25 mg/L, indicating an increase in toxicity with increased exposure time. <b>Conclusions:</b> Possible applications of the newly synthesized nanomaterials include antimicrobial coatings, drug delivery systems, antioxidant additives in various formulations, and water purification.