The use of metal and metal oxide nanoparticles is frequently regarded as a potential solution to the issue of bacterial antibiotic resistance. Among the proposed range of nanoparticles with antibacterial properties, copper oxide nanoparticles are of particular interest. Although the antibacterial properties of copper have been known for a considerable period of time, studies on the effects of copper oxide nanomaterials with respect to biological systems have attracted considerable attention in recent years. This review presents a summary of the antibacterial properties of copper oxide nanoparticles, the mechanisms by which the antibacterial effect is realized, and the key reported methods of modifying these nanoparticles to improve their antibacterial activity. A comparative analysis of the effectiveness of these nanoparticles is presented depending on the type of microorganism, the shape of the nanoparticles, and the Gram classification of bacteria based on data from published sources. In addition, the review addresses the biological activities of copper oxide nanoparticles, including their antifungal and cytotoxic properties, as well as their “antioxidant” activity. According to the conducted analysis of the literature data, it can be concluded that copper oxide nanoparticles have a significant bacteriostatic potential with respect to a wide range of microorganisms and, in some cases, contribute to the inhibition of fungal growth. At the same time, the sensitivity of Gram-positive bacteria to the effect of copper oxide nanoparticles was often higher than that of Gram-negative bacteria.

The development of biodegradable, biocompatible materials with inherent antibacterial properties, suitable for 3D printing, is a key challenge in modern materials science. Composites based on PLA and copper nanoparticles (NPs) are promising candidates for such a material. A protocol of the low-temperature incorporation of 0.1% Cu NPs or 0.1% CuO NPs into a PLA was developed. The dependence of the materials’ physicochemical properties on nanoparticle composition was evaluated. Cu and CuO NPs were synthesized via liquid-phase laser ablation and had sizes of 25 and 80 nm, with modal zeta potential values of +31 and +42 mV, respectively. The incorporation of Cu NPs enhances the tensile strength and Young’s modulus of PLA, and improves antibacterial properties. The PLA + 0.1% CuO or PLA + 0.1% Cu nanoparticles inhibited the growth of E. coli by ~60% and >80%, respectively. PLA + 0.1% Cu NPs destructed of bacterial cell walls. The antibacterial action mechanisms are an 8-oxoguanine and LRPS generations. The obtained materials did not exhibit cytotoxic effects against normal human fibroblasts, did not alter the pH or redox potential of water, and did not release of Cu²⁺ in concentrations toxic to humans. The material PLA + 0.1% Cu NPs is the most optimal. This material may find applications in food production and biomedical applications.

Photoluminescence from the surface of Nafion polymer membrane upon swelling in water under irradiation by electromagnetic waves at a frequency of 100 MHz was studied. In these experiments, natural deionized (DI) water with a deuterium content of 157 ppm and deuterium-depleted water (DDW, deuterium content is 1 ppm) were explored. We have studied for the first time the effect of linearly and randomly polarized low-frequency electromagnetic radiation on the luminescence excitation. To obtain low-frequency electromagnetic radiation with random polarizations, anisotropic solid submicron-sized particles, which result in depolarization effects upon scattering of the initially linearly polarized radiation, were used. We compared two types of colloidal particles: spherically symmetric (isotropic) and elongated (anisotropic). If the radiation is linearly polarized, the intensity of luminescence from the Nafion surface decreases exponentially as the polymer is soaked, and such a behavior is observed both in natural DI water and DDW. When spherically symmetric submicron-sized particles are added to a liquid sample, the luminescence intensity also decreases exponentially upon swelling in both natural DI water and DDW. At the same time, when anisotropic submicron-sized particles are added to DI water, random jumps in the luminescence intensity appear during swelling. At the same time, the exponential decrease in the luminescence intensity is retained upon swelling in DDW. A qualitative theoretical model for the occurrence of random jumps in the luminescence intensity is presented.

Polycaprolactone (PCL) is a promising polymer in the medical field and is already being used in the creation of suture materials and tissue engineering. Due to the limited properties of PCL, in many medical tasks it is necessary to modify it, for example, the addition of antimicrobial properties to reduce the risk of infection in tissue repair processes. In this work, the effect of the introduction of nanoparticles of titanium oxide (NPs-TiO₂) and zinc (NPs-ZnO) into the polycaprolactone matrix on its antibacterial activity and biocompatibility was studied. The studied concentrations of NPs ranged from 0.001 to 0.5 wt. %, and the final composites were obtained by casting from a solution. An investigation into the antibacterial activity against the Gram-negative bacterium Escherichia coli revealed high efficacy of the PCL/NPs-TiO₂ composites, which increased with rising nanoparticle concentration to 27.6% at a nanoparticle content of 0.5 wt. %. PCL/NPs-ZnO composites did not show such activity. The results obtained demonstrate that the key factor determining the biological activity of a composite is not only the nature of the nanoparticles but also their ability to maintain a nanoscale state during the manufacture of the final composite. PCL/NPs-TiO₂ composites may be a promising candidate for the creation of antibacterial materials for medical purposes, for absorbable scaffolds or sutures.