The interaction between metal nanoparticles and bacteria belongs to the central issues in a dynamically growing bionanotechnological research. Herein, we investigated the adhesion efficiency of gold nanoparticles (30 nm) for various bacterial strains, both Gram-positive (Bacillus subtilis, Staphylococcus carnosus) and Gram-negative (Neisseria subflava, Stenotrophomonas maltophilia). The thorough microscopic (SEM/TEM) observations revealed that the nanoparticles do not penetrate into the bacterial cells but adhere to the walls. Large differences in the adhered nanoparticles amount were observed for the investigated strains (B. subtilis >> S. carnosus > N. subflava > S. maltophilia). A direct correlation between the number of the attached nanoparticles and the ζ-potential of the bacterial strains was found, and the results were rationalized in terms of the DLVO model. The calculated DLVO energy profiles revealed that the activation barriers for the adhesion process are rather small (1.45–1.55 kT), and the primary energy minima of 120–170 kT are favorable for the effective adsorption process. The established linear correlation between the nanoparticles adhered to the cell surface and the size of the critical volume around the bacterial cell, where the attraction forces dominate, implies that the observed dramatic differences in the attachment efficiency result from the availability of the nanoparticles in the critical volume of the surrounding suspensions. Owing to non-specific interactions governed by the ζ-potential mainly, the obtained results can be readily extended for the other bacteria–nanoparticle systems, providing a rational background for future advances in bacteria detection and thorough characterization via SERS method as well as for nanoparticles assemblies towards nanoelectronics. Graphical abstract

In this work, polymeric and bioactive glass (BG)-modified composite films were successfully loaded with polyphenols (PPh) extracted from sage. It was hypothesized that PPh, alone and in combination with BGs particles, would affect physicochemical and biological properties of the films. Furthermore, sol-gel-derived BG particles would serve as an agent for control the release of the polyphenolic compounds, and other important properties related to the presence of PPh. The results showed that polyphenolic compounds significantly modified numerous material properties and also acted as biologically active substances. On the one hand, PPh can be considered as plasticizers for PCL, on the other hand, they can act as coupling agent in composite materials, improving their mechanical performance. The presence of PPh in materials improved their hydrophilicity and apatite-forming ability, and also provided antioxidant activity. What is important is that the aforementioned properties and kinetics of PPh release can be modulated by the use of various concentrations of PPh, and by the modification of PCL matrix with sol-gel-derived BG particles, capable of binding PPh. The films containing the lowest concentration of PPh exhibited cytocompatibility, significantly increased alkaline phosphatase activity and the expression of bone extracellular matrix proteins (osteocalcin and osteopontin) in human normal osteoblasts, while they reduced intracellular reactive oxygen species production in macrophages. Furthermore, materials loaded with PPh showed antibiofilm properties against Gram positive and Gram negative bacteria. The results suggest that obtained materials represent potential multifunctional biomaterials for bone tissue engineering with a wide range of tunable properties.