Photocatalytic, self-cleaning and antibacterial properties of Cu(II) doped TiO2

Review on sterilization techniques, and the application potential of phage lyase and lyase immobilization in fighting drug-resistant bacteria

Many human health problems and property losses caused by pathogenic contamination cannot be underestimated. Bactericidal techniques have been extensively studied to address this issue of public health and economy. Bacterial resistance develops as a result of the extensive use of single or multiple but persistent usage of sterilizing drugs, and the emergence of super-resistant bacteria brings new challenges. Therefore, it is crucial to control pathogen contamination by applying innovative and effective sterilization techniques. As organisms that exist in nature and can specifically kill bacteria, phages have become the focus as an alternative to antibacterial agents. Furthermore, phage-encoded lyases are proteins that play important roles in phage sterilization. The in vitro sterilization of phage lyase has been developed as a novel biosterilization technique to reduce bacterial resistance and is more environmentally friendly than conventional sterilization treatments. For the shortcomings of enzyme applications, this review discusses the enzyme immobilization methods and the application potential of immobilized lyases for sterilization. Although some techniques provide effective solutions, immobilized lyase sterilization technology has been proven to be a more effective innovation for efficient pathogen killing and reducing bacterial resistance. We hope that this review can provide new insights for the development of sterilization techniques.

Highly hydrophilic and dispersed TiO2 nano-system with enhanced photocatalytic antibacterial activities and accelerated tissue regeneration under visible light

Titanium dioxide (TiO2)-based photodynamic antibacterial (PDA) agents present a novel approach for addressing drug-resistant bacterial infections and the associated tissue damage. However, the suboptimal dispersibility, negative charge, and weak photocatalytic activity under visible light of TiO2 hinder its practical applications. This study aimed to address these limitations by developing a highly hydrophilic and dispersed Zn-TiO2/reduced graphene oxide (rGO) (HTGZ) nano-system with exceptional visible light catalytic activity and tissue repair ability. HTGZ produced an antibacterial ratio over 98% within a short time, likely due to the enhanced production of reactive oxygen species under visible light. After being co-cultured for 4 days, L929 cells and BMSCs maintained over 90% activity, indicating that HTGZ had no significant cytotoxicity. Furthermore, the transcriptomic and metabolic analyses revealed that the antibacterial mechanism mainly came from the destruction of cell membranes and the disruption of various metabolic processes, such as purine metabolism and fatty acid biosynthesis. Critically, results of in vivo experiments had authenticated that HTGZ significantly promoted infected tissue regeneration by slaughtering bacteria and release Zn2+. After 14 days, the wound area was only one-third that of the control group. Overall, the enhanced antibacterial efficacy and wound-healing potential position HTGZ as a promising nano-antibacterial medication for the clinical treatment of infectious bacterial diseases.

Hybrid nanostructures exhibiting both photocatalytic and antibacterial activity-a review

The most vital issues of the modern world for a sustainable future are "health" and "the environment." Scientific endeavors to tackle these two major concerns for mankind need serious attention. The photocatalytic activity toward curbing environmental pollution and antibacterial performance toward a healthy society are two directions that have been emphasized for decades. Recently, materials engineering, in their nanodimension, has shown tremendous possibilities to integrate these functionalities within the same materials. In particular, hybrid nanostructures have shown magnificent prospects to combat both crucial challenges. Many researchers are separately engaged in this important field of research but the collective knowledge on this domain which can facilitate them to excel is badly missing. The present article integrates the development of different hybrid nanostructures which exhibit both photocatalytic degradations of environmental pollutants and antibacterial efficiency. Various synthesis techniques of those hybrid nanomaterials have been discussed. Hybrid nanosystems based on several successful materials have been categorically discussed for better insight into the research advancement in this direction. In particular, Ag-based, metal oxides-based, layered carbon material-based, and Mexene- and self-cleaning-based materials have been chosen for detailing their performance as anti-pollutant and antibacterial materials. Those hybrid systems along with some miscellaneous booming nanostructured materials have been discussed comprehensively with their success and limitations toward their bifunctionality as antipollutant and antibacterial agents.

Functional Fiber Membranes with Antibacterial Properties for Face Masks

Reusable face masks are an important alternative for minimizing costs of disposable and surgical face masks during pandemics. Often complementary to washing, a prolonged lifetime of face masks relies on the incorporation of self-cleaning materials. The development of self-cleaning face mask materials requires the presence of a durable catalyst to deactivate contaminants and microbes after long-term use without reducing filtration efficiency. Herein, we generate self-cleaning fibers by functionalizing silicone-based (polydimethylsiloxane, PDMS) fibrous membranes with a photocatalyst. Coaxial electrospinning is performed to fabricate fibers with a non-crosslinked silicone core within a supporting shell scaffold, followed by thermal crosslinking and removal of the water-soluble shell. Photocatalytic zinc oxide nanoparticles (ZnO NPs) are immobilized on the PDMS fibers by colloid-electrospinning or post-functionalization procedures. The fibers functionalized with ZnO NPs can degrade a photo-sensitive dye and display antibacterial properties against Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) due to the generation of reactive oxygen species upon irradiation with UV light. Furthermore, a single layer of functionalized fibrous membrane shows an air permeability in the range of 80-180 L/m2s and 65% filtration efficiency against fine particulate matter with a diameter less than 1.0 µm (PM1.0).

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42765-023-00291-7.

Preparation, Antimicrobial Properties under Different Light Sources, Mechanisms and Applications of TiO2: A Review

Traditional antimicrobial methods, such as antibiotics and disinfectants, may cause adverse effects, such as bacterial resistance and allergic reactions. Photocatalysts based on titanium dioxide (TiO₂) have shown great potential in the field of antimicrobials because of their high efficiency, lack of pollution, and lack of side effects. This paper focuses on the antimicrobial activity of TiO₂ under different light sources. To improve the photocatalytic efficiency of TiO₂, we can reduce electron-hole recombination and extend the photocatalytic activity to the visible light region by doping with different ions or compounds and compounding with polymers. We can also improve the surface properties of materials, increase the contact area with microorganisms, and further enhance the resistance to microorganisms. In addition, we also reviewed their main synthesis methods, related mechanisms, and main application fields to provide new ideas for the enhancement of photocatalytic microorganism performance and application popularization in the future.

Hybrid Density Functional Investigation of Cu Doping Impact on the Electronic Structures and Optical Characteristics of TiO2 for Improved Visible Light Absorption

We report a theoretical investigation of the influence of Cu doping into TiO₂ with various concentrations on crystal structure, stability, electronic structures and optical absorption coefficient using density functional theory via the hybrid formalism based on Heyd Scuseria Ernzerhof. Our findings show that oxygen-rich environments are better for fabricating Cu-doped materials and that the energy of formation for Cu doping at the Ti site is lower than for Cu doping at the O site under these environments. It is found that Cu doping introduces intermediate bands into TiO₂, narrowing the band gap. Optical absorption curves show that the Cu-doped TiO₂ can successfully harvest visible light. The presence of widely intermediate bands above the valence-band edge could explain the increase in the visible light absorption range. However, the intensity of visible light absorption rises with the increase in doping concentration.

New trends on green energy and environmental technologies, with special focus on biomass valorization, water and waste recycling: editorial of the special issue

In this editorial piece, the Editors of the Virtual Special Issue (VSI) "New Trends on Green Energy and Environmental Technologies, with Special Focus on Biomass Valorization, Water and Waste Recycling", present summarized data corresponding to the accepted submissions, as well as additional comments regarding the thematic of the VSI. Overall, 83 manuscripts were received, with final publication of those having the highest quality, accepted after peer-reviewing. The Editors think that the result is a set of very interesting papers that increase the knowledge on the matter, and which would be useful for researchers and the whole society.

Copper-containing nanoparticles: Mechanism of antimicrobial effect and application in dentistry-a narrative review

Copper has been used as an antimicrobial agent long time ago. Nowadays, copper-containing nanoparticles (NPs) with antimicrobial properties have been widely used in all aspects of our daily life. Copper-containing NPs may also be incorporated or coated on the surface of dental materials to inhibit oral pathogenic microorganisms. This review aims to detail copper-containing NPs' antimicrobial mechanism, cytotoxic effect and their application in dentistry.

Novel antibacterial polyurethane and cellulose acetate mixed matrix membrane modified with functionalized TiO2 nanoparticles for water treatment applications

Bacterial contamination is one of the leading causes of water pollution. Antibacterial polyurethane/cellulose acetate membranes modified by functionalized TiO₂ nanoparticles were processed and studied. TiO₂ nanoparticles were prepared and ultraviolet (UV) irradiated to activate their photocatalytic activity against Escherichia coli (E. Coil) and Methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Functionalized TiO₂ nanoparticles were incorporated in flat-sheet mixed matrix membranes (MMMs). These membranes were characterized for their different properties such as morphology, thermal stability, mechanical strength, surface wettability, water retention, salt rejection, water flux, and their antibacterial performance against E. Coil and MRSA was also tested. The activity of nanoparticles against MRSA and E. coli was analyzed using three different concentrations, 0.5 wt%, 1.0 wt% and 1.5 wt% of nanoparticles and 0.5 wt% of TiO₂ nanoparticles showed maximum growth of bacteria. The maximum inhibition was observed in membranes with maximum nanoparticles when compared with other membranes. All these characteristics were strongly affected by increasing the concentration of TiO₂ nanoparticles in the prepared membranes and the duration of their UV exposure. Hence, it was proved from this analysis that these TiO₂ modified membranes exhibit substantial antibacterial properties. The results are supporting the utilization of these materials for water purification purposes.

Preparation of High-Porosity B-TiO2/C3N4 Composite Materials: Adsorption-Degradation Capacity and Photo-Regeneration Properties

Adsorption can quickly remove pollutants in water, while photocatalysis can effectively decompose organic matter. B-TiO₂/g-C₃N₄ ternary composite photocatalytic materials were prepared by molten method, and their adsorption-degradation capability under visible light conditions was discussed. The morphology of the B-TiO₂/g-C₃N₄ materials was inspected by SEM, TEM, BET, and EDS, and the results showed that close interfacial connections between TiO₂ and g-C₃N₄, which are favorable for charge transfer between these two semiconductors, formed heterojunctions with suitable band structure which was contributed by the molten B₂O₃. Meanwhile, the molten B₂O₃ effectively increased the specific surface area of TiO₂/C₃N₄ materials, thereby increasing the active sites and reducing the recombination of photogenerated electron-hole pairs and improving the photocatalytic degradation abilities of TiO₂ and g-C₃N₄. Elsewhere, the crystal structure analysis (XRD, XPS, FTIR) results indicated that the polar -B=O bond formed a new structure with TiO₂ and g-C₃N₄, which is not only beneficial for inhibiting the recombination of electron holes but also improving the photocatalytic activity. By removal experiment, the adsorption and degradation performances of B-TiO₂/g-C₃N₄ composite material were found to be 8.5 times and 3.4 times higher than that of g-C₃N₄. Above all, this study prepared a material for removing water pollutants with high efficiency and provides theoretical support and experimental basis for the research on the synergistic removal of pollutants by adsorption and photocatalysis.