Preventing and controlling the spread of multidrug-resistant (MDR) bacteria implicated in healthcare-associated infections is the greatest challenge of the health systems. In recent decades, research has shown the need for passive antibacterial protection of surfaces in order to reduce the microbial load and microbial biofilm development, frequently associated with transmission of infections. The aim of the present study is to analyze the efficiency of photocatalytic antimicrobial protection methods of surfaces using the new photocatalytic paint activated by light in the visible spectrum. The new composition is characterized by a wide range of analytical methods, such as UV-VIS spectroscopy, electron microscopy (SEM), X-ray powder diffraction (PXRD) or X-ray photoelectron spectroscopy (XPS). The photocatalytic activity in the UV-A was compared with the one in the visible light spectrum using an internal method developed on the basis of DIN 52980: 2008-10 standard and ISO 10678—2010 standard. Migration of metal ions in the composition was tested based on SR EN1186-3: 2003 standard. The new photocatalytic antimicrobial method uses a type of photocatalytic paint that is active in the visible spectral range and generates reactive oxygen species with inhibitory effect against all tested microbial strains.

The ability of TiO2 to generate reactive oxygen species under UV radiation makes it an efficient candidate in antimicrobial studies. In this context, the preparation of TiO2 microparticles coated with Ca- and Cu-based composite layers over which Cu(II), Cu(I), and Cu(0) species were identified is presented here. The obtained materials were characterized by a wide range of analytical methods, such as X-ray diffraction, electron microscopy (TEM, SEM), X-ray photoelectron (XPS), and UV-VIS spectroscopy. The antimicrobial efficiency was evaluated using qualitative and quantitative standard methods and standard clinical microbial strains. A significant aspect of this composite is that the antimicrobial properties were evidenced both in the presence and absence of the light, as result of competition between photo and electrical effects. However, the antibacterial effect was similar in darkness and light for all samples. Because no photocatalytic properties were found in the absence of copper, the results sustain the antibacterial effect of the electric field (generated by the electrostatic potential of the composite layer) both under the dark and in light conditions. In this way, the composite layers supported on the TiO2 microparticles’ surface can offer continuous antibacterial protection and do not require the presence of a permanent light source for activation. However, the antimicrobial effect in the dark is more significant and is considered to be the result of the electric field effect generated on the composite layer.

The paper describes the studies started by an inter-disciplinary team in finding a disinfection method using a coating with photocatalytically activated antimicrobial properties by visible spectrum radiation. An own method of preparation led to the obtaining of a photocatalytic pigment based on copper-doped titanium dioxide to move the activation spectrum to the visible range. The preparation method was designed so as to allow transposition into industrial production. The demonstration and measurement of the photocatalytic effect for certification as an industrial product was done based on an adapted method, starting from two existing standards. A washable paint containing the photocatalytic pigment was tested "in situ", the results demonstrating the reduction of microbial load. The paper is based on current knowledge about light-activated antimicrobiological agents (LAAs) in an attempt to further the study of visible spectrum radiation, which in combination with a series of photosensitizers excited by this radiation, have the role of generating photocatalytic reactions with disinfection effect.

An ever-increasing rate of morbidity and mortality caused by healthcare associated infections is reported annually. Air circulation mediates contact with microbial contaminated aerosols and represents a major risk of transmitting healthcare associated infections. We propose a revolutionary technique for the protection of interior surfaces based on a photocatalytic composition with doped TiO2 or ZnO type semiconductor metal oxides which exert antimicrobial effect. In principle, there is an activation of the photocatalytic coating with light from the normal lighting apparatus, which may incorporate one or more sources of photocatalytic excitation light. By studying the air circulation in the hospital, it is possible to design light fixtures with specific design of light distribution, in order to perform the disinfection of the air and surfaces and to amplify the antimicrobial effect. The disinfection process does not affect patients or healthcare professionals, it can be done in their presence and has a continuous, controllable effect. Photocatalytic paint in combination with a prototype luminaire with a precise spectrum light sources, light output and a light intensity distribution curve relative to the shape and dimensions of the rooms, shows that the proposed method may represent a successful alternative to classical methods of disinfection in hospitals. This technique can also be used in other areas of interest.