Evaluation of antibacterial activities of face masks coated with titanium dioxide nanoparticles

The development of nanotechnology is a promising technological trend that can have a great impact in many fields, such as physics and biology, medicine, electronics, food, water quality, textile industry , air quality and biomechanics. 1. It is defined as “science and technology that is carried out to one billionth (10−9) part meter”, i.e. in the nanometer scale (1–100 nm).

There are many types of nanoparticles, such as metallic, non-metallic, organic and inorganic nanoparticles 2. Titanium, copper and silver nanoparticles are examples of metallic nanoparticles. Titanium Dioxide (TiO2) has unique properties, such as low cost, stability, low toxicity, high refractive index, high optical properties, high ultraviolet absorption, strong redox ability, temperature difference. energy (i.e. 3.2 to 5.2 eV), and has good electrical, optical and magnetic properties 3.4. It is necessary to fully define the characteristics of nanoparticles, such as their size, shape, surface morphology, crystallinity and light absorption, using appropriate characterization techniques. 5, such as microscopy techniques (electron microscopy or scanning probe microscopy). In addition, optical techniques (spectroscopy) can be used to study the characteristics of nanoparticles, such as reflectance, transmission, photochemistry and luminescence. 6. Brunauer–Emmett–Teller (BET), X-ray diffractometry (XRD) and infrared (IR) spectroscopy are the most widely used techniques for characterization of NP structures and can be used to describe phase, particle size , the type and crystalline nature of the nanoparticles. The surface quality of nanoparticles is strongly influenced by their mechanical properties, which include stress, surface coatings, hardness, strain, friction, and adhesion. Characteristics of TiO2 include stability, low cost, non-toxicity, biocompatibility, optical and electrical properties. It mainly occurs in three distinct forms, including brookite, anatase and rutile, with different structures. Thermodynamic simulations show that during heating, anatase and brookite transform into rutile, which is more stable at all temperatures and pressures below 60 kbar seven. Nanomaterials, such as TiO2 photocatalysts, have demonstrated remarkable activity in the photodegradation of a variety of organic and inorganic pollutants. Since organic contaminants can completely degrade into harmless materials under normal conditions of temperature and pressure, it is expected that photocatalysis will soon be one of the most effective methods for treating various types of contaminants. Pollutants including herbicides, carboxylic acids and alcohols can be fully broken down into carbon dioxide, water and simple minerals 8. The photocatalyst must have specific qualities, such as the right particle size, shape, crystallinity, and anatase to rutile ratio, to be particularly effective. The most common methods used to produce TiO2 nanoparticles are electrodeposition, reverse micelles, sol-gel method, chemical vapor deposition of organo-metallics, flame combustion method, gas phase (aerosol), hydrothermal methods, wet chemical synthesis by precipitation of hydroxides from salts and processes mediated by microemulsion 9. The sol-gel process is a wet chemical technique mainly used in the fields of materials science and ceramic engineering. It can be defined as the conversion of a precursor solution into an inorganic solid by water-induced polymerization reactions ten. Hydrolysis forms a sol which is essentially a dispersion of colloidal particles in a liquid, and condensation leads to the formation of a gel. Compared to the methods described above, the sol-gel process is very promising for the synthesis and preparation of hybrid inorganic and organic‒inorganic nanomaterials because it allows the use of low processing temperatures (ten. Particle size and shape are easily controlled using the sol-gel method. The sol-gel process produces fine spherical powders of uniform size and has been widely used to synthesize TiO2 materials and normally proceeds via an acid catalyzed step of titanium(IV) alkoxides 11. One of the most attractive features of the sol-gel process is the ability to shape the resulting material into desired shapes, such as fibers, films, and monodisperse powders. Several steps and conditions are applied in a sol-gel process to control the final morphology, as suggested by Mehrotra and Singh ten. The use of TiO2 as a photocatalyst to kill microorganisms has been known for a long time 12. Antibacterial properties and mechanisms of nanotechnology have been widely discussed, including those of TiO2 nanoparticles, which have been widely applied due to their photocatalytic properties to break down and remove dirt, odors and kill bacteria. The mechanism of this technique depends on the generation of reactive superoxide radicals (O2 and OH) on the surface of TiO2 molecules during the photocatalysis process when exposed to light of an appropriate wavelength 13,14,15. Oxygen rootlets affect bacterial cells by different mechanisms, leading to their death. The two types of bacteria differ from each other in their response to antibacterial nanoparticles. Disinfection is defined as the treatment procedure used to eliminate pathogenic microorganisms, but it may not eliminate bacterial spores 16. Over the past decades, TiO2 in the form of nanoparticles has been known to have broad-spectrum antibacterial activities. 17.18. Cloth face masks are materials used to protect against respirable pathogens (bacterial or viral) 19. They are classified as full masks, half masks and quarter masks. Filtering efficiency of face masks vary from one to another depending on the density of the face mask material 20. With continued use of face masks without regular exchange, improper washing can potentially contaminate surfaces, as temperature and humidity induce moisture and therefore microbial colonization; in addition, improper use may lead to the risk of spreading pathogens 21,22,23,24,25. The disposal of face masks has led to a huge increase in waste, which is classified as “hazardous with infectious risk”, and face masks are disposed of as biohazards 26. Nanoparticles have been shown to kill a wide range of organisms, including gram-negative and gram-positive bacteria, which differ in their cell wall and envelope and therefore their resistance to disinfectants 27. Additionally, many other organisms, including viruses, fungi, algae, and protozoa, have been shown to be killed by TiO2 nanoparticles. 12. These nanoparticles have been shown to be useful for disinfection of face masks 16.17. TiO2 coated face masks are widely applied to enhance self-cleaning and antibacterial properties to control infectious diseases, such as COVID-19 28. This article aimed to evaluate the antibacterial properties of face masks coated with TiO2 nanoparticles.

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