Multiple antibiotic resistance has now become a major obstacle to the treatment of infectious diseases. In this context, the application of nanotechnology in medicine is a promising alternative for the prevention of infections with multidrug-resistant germs. The use of silver as a powerful antibacterial agent has attracted much interest. TiO2 and SiO2 thin films enhanced with Ag particles have been developed with the aim of maintaining the transparency of the polymer films. Antibacterial activity was evaluated for a Gram-negative species-Escherichia coli-in concentrations of 105 and 104 CFU/mL in different conditions-activation by UV irradiation, single layer and double layer. Increased antibacterial efficacy of TiO2-deposited foil was found for the tests that had been exposed to UV activation. In the case of bilayer tests, the efficiency was higher compared to those in a single layer, as the contact surface between the films and the bacterial suspension increased. Films can be used as a potential method to limit bacterial growth on hospital surfaces, such as telephone screens and medical equipment, given their optimized characteristics and proven antibacterial efficacy.

In the last years, nanoparticles such as TiO2, ZnO, NiO, CuO and Fe2O3 were mainly used in wastewater applications. In addition to the positive aspects concerning using nanoparticles in the advanced oxidation process of wastewater containing pollutants, the impact of these nanoparticles on the environment must also be investigated. The toxicity of nanoparticles is generally investigated by the nanomaterials’ effect on green algae, especially on Chlorella vulgaris. In this review, several aspects are reviewed: the Chlorella vulgaris culture monitoring and growth parameters, the effect of different nanoparticles on Chlorella vulgaris, the toxicity of photocatalyst nanoparticles, and the mechanism of photocatalyst during oxidative stress on the photosynthetic mechanism of Chlorella vulgaris. The Bold basal medium (BBM) is generally recognized as an excellent standard cultivation medium for Chlorella vulgaris in the known environmental conditions such as temperature in the range 20–30 °C and light intensity of around 150 μE·m2·s−1 under a 16/8 h light/dark cycle. The nanoparticles synthesis methods influence the particle size, morphology, density, surface area to generate growth inhibition and further algal deaths at the nanoparticle-dependent concentration. Moreover, the results revealed that nanoparticles caused a more potent inhibitory effect on microalgal growth and severely disrupted algal cells’ membranes.

The increasing occurrence of infections caused by pathogens found on objects of everyday use requires a variety of solutions for active disinfection. Using active materials that do not require daily maintenance has a potential advantage for their acceptance. In this contribution, transparent films, with silver as the main antimicrobial agent and a total thickness of a few tens of nm, were deposited on flexible self-adhesive polymer foils used as screen protectors. TiO2 and SiO2 were used as transparent matrix to embed the Ag nanoparticles, ensuring also their mechanical protection and controlled growth. HiPIMS (High-Power Impulse Magnetron Sputtering) was used for the sputtering of the Ag target and fine control of the Ag amount in the layer, whereas TiO2 and SiO2 were sputtered in RF (Radio Frequency) mode. The thin film surface was investigated by AFM (Atomic Force Microscopy), providing information on the topography of the coatings and their preferential growth on the textured polymer foil. XRD (X-Ray Diffraction) revealed the presence of specific Ag peaks in an amorphous oxide matrix. UV-Vis-NIR (Ultraviolet-Visible-Near Infrared) spectroscopy revealed the presence of nanostructured Ag, characterized by preferential absorption in the 400 to 500 nm spectral range. The antimicrobial properties were assessed using an antimicrobial test with the Escherichia coli strain. The highest efficiency was observed for the Ag/SiO2 combination, in the concentration range of 104–105 CFU/mL.

Nanoparticles have applications in various fields such as manufacturing and materials synthesis, the environment, electronics, energy harvesting, and medicine. Besides many applications of nanoparticles, further research is required for toxic environmental effect investigation. The toxic effect of titanium dioxide nanoparticles on the physiology of the green alga Chlorella vulgaris was studied with a widely used pesticide, imidacloprid (IMD). Chlorella vulgaris was exposed for 120 h in Bold’s basal medium to different toxic compounds, such as (i) a high concentration of TiO2 nanoparticles, 150–2000 mg/L, usually optimised in the photocatalytic degradation of wastewater, (ii) an extremely toxic pesticide for the aquatic environment, imidacloprid, in concentrations ranging from 5 to 40 mg/L, (iii) TiO2 nanoparticles combined with imidacloprid, usually used in a photocatalytic system. The results show that the TiO2 nanoparticles and IMD inhibited Chlorella vulgaris cell growth and decreased the biovolume by approximately 80% when 2 g/L TiO2 was used, meaning that the cells devised a mechanism to cope with a potentially stressful situation; 120 h of Chlorella vulgaris exposure to 40 mg/L of IMD resulted in a 16% decreased cell diameter and a 41% decrease in cell volume relative to the control sample, associated with the toxic effect of pesticides on the cells. Our study confirms the toxicity of nanoparticles through algal growth inhibition with an effective concentration (EC50) value measured after 72 h of 388.14 mg/L for TiO2 and 13 mg/L for IMD in a single-toxic system. The EC50 of TiO2 slowly decreased from 258.42 to 311.11 mg/L when IMD from 5 to 20 mg/L was added to the binary-toxic system. The concentration of TiO2 in the binary-toxic system did not change the EC50 for IMD, and its value was 0.019 g/L. The photodegradation process of imidacloprid (range of 5–40 mg/L) was also investigated in the algal medium incubated with 150–600 mg/L of titanium dioxide.

Introduction: Non-porous surfaces with antibacterial properties have begun to gain notoriety because strategies are being sought to prevent infections by methods that are as safe as possible for the human body. Objectives: Test methods can be variates, such as ISO 22196 standardized testing, inoculation testing with a sterile swab, bacteriological loop, and touch-transfer assay. The steps followed in developing and choosing the right strategy for each surface aim at the following aspects, namely: sterilization of working materials to remove the possibility of bacterial superinfection and to correctly interpret the results, selection of bacterial strains and in vitro growth conditions, selection of sampling and colony counting and choice of method for validating and reporting of results. Discussions: The advantage of the in vitro experimental technique is that it can be easily repeated and reproduced, which helps to draw conclusions about the proven efficacy of the antimicrobial property. However, there are also limitations of this test, namely the fact that the results cannot be extrapolated to in vivo conditions because the very important parameters for bacterial proliferation cannot be maintained and controlled. Conclusions: These aspects are important for evaluating the real efficiency of surfaces with antibacterial properties. Rezumat Introducere: Suprafețele neporoase cu proprietăți antibacteriene au început să capete notorietate deoarece se caută strategii de a preveni infecțiile prin metode cât mai sigure pentru organismul uman. Scop: Metodele de testare pot fi variate, precum testarea standardizată ISO 22196, testarea prin inoculare cu ajutorul tamponului steril, cu ajutorul ansei bacteriologice și prin metoda amprentării. Etapele urmărite în dezvoltarea și alegerea strategiei potrivite pentru fiecare suprafață în parte urmăresc următoarele aspecte, și anume: sterilizarea materialelor de lucru pentru a înlătura posibilitatea unei suprainfecții bacteriene și pentru a interpreta corect rezultatele, selectarea tulpinilor bacteriene și a condițiilor de creștere in vitro, selectarea modalităților de eșantionare și numărare a coloniilor și alegerea metodei de validare a raportării rezultatelor. Discuții: Avantajele tehnicilor experimentale in vitro constau în faptul că pot fi repetate și reproduse facil, aspect care ajută la obținerea de concluzii cu privire la eficiența dovedită a proprietății antimicrobiene. Însă, există și limitări ale acestei testări și anume faptul că rezultatele nu se pot extrapola la condițiile in vivo deoarece nu se pot menține și controla parametrii foarte importanți pentru proliferarea bacteriană. Concluzii: Acestea aspecte sunt importante pentru evaluarea eficienței reale a suprafețelor cu proprietăți antibacteriene.