Nanosponges: As a Dynamic Drug Delivery Approach for Targeted Delivery

Recent advancements in nanotechnology have resulted in improved medicine delivery to the target site. Nanosponges are three-dimensional drug delivery systems that are nanoscale in size and created by cross-linking polymers. The introduction of Nanosponges has been a significant step toward overcoming issues such as drug toxicity, low bioavailability, and predictable medication release. Using a new way of nanotechnology, nanosponges, which are porous with small sponges (below one microm) flowing throughout the body, have demonstrated excellent results in delivering drugs. As a result, they reach the target place, attach to the skin's surface, and slowly release the medicine. Nanosponges can be used to encapsulate a wide range of medicines, including both hydrophilic and lipophilic pharmaceuticals. The medication delivery method using nanosponges is one of the most promising fields in pharmacy. It can be used as a biocatalyst carrier for vaccines, antibodies, enzymes, and proteins to be released. The existing study enlightens on the preparation method, evaluation, and prospective application in a medication delivery system and also focuses on patents filed in the field of nanosponges.Copyright © 2023 The Authors.

Dual-Action Effect of Gallium and Silver Providing Osseointegration and Antibacterial Properties to Calcium Titanate Coatings on Porous Titanium Implants.

Previously, functional coatings on 3D-printed titanium implants were developed to improve their biointegration by separately incorporating Ga and Ag on the biomaterial surface. Now, a thermochemical treatment modification is proposed to study the effect of their simultaneous incorporation. Different concentrations of AgNO3 and Ga(NO3)3 are evaluated, and the obtained surfaces are completely characterized. Ion release, cytotoxicity, and bioactivity studies complement the characterization. The provided antibacterial effect of the surfaces is analyzed, and cell response is assessed by the study of SaOS-2 cell adhesion, proliferation, and differentiation. The Ti surface doping is confirmed by the formation of Ga-containing Ca titanates and nanoparticles of metallic Ag within the titanate coating. The surfaces generated with all combinations of AgNO3 and Ga(NO3)3 concentrations show bioactivity. The bacterial assay confirms a strong bactericidal impact achieved by the effect of both Ga and Ag present on the surface, especially for Pseudomonas aeruginosa, one of the main pathogens involved in orthopedic implant failures. SaOS-2 cells adhere and proliferate on the Ga/Ag-doped Ti surfaces, and the presence of gallium favors cell differentiation. The dual effect of both metallic agents doping the titanium surface provides bioactivity while protecting the biomaterial from the most frequent pathogens in implantology.

Emerging membrane technologies and disinfection methods for efficient removal of waterborne pathogens during the COVID-19 pandemic and post-pandemic

Viruses and other microorganisms can enter water sources from different routes and cause pollution and irreparable damage. So, cost-effective and efficient systems for providing safe water are necessary. Efficient filtration systems based on antimicrobial materials have received a lot of attention in this regard. A wide range of materials play an important role in the production of efficient water filtration systems. Metal and metal oxide particles with anti-viral and antimicrobial properties comprising Cu, Cu2O, Ag, TiO2, and ZnO play a valuable role in the preparation of water filtration systems. Biopolymers such as cellulose or carbon nanomaterials like graphene or its derivatives have been reported to provide safe water. In this review, we summarize the use of diverse materials in the preparation of efficient filtration-based systems like membranes and paper filters for water treatment. Pathogen-containing water samples were effectively disinfected using the prepared water disinfection systems.Copyright © 2023 The Royal Society of Chemistry.

Identification of microplastic fibres released from COVID-19 test swabs with Raman imaging.

Background: COVID-19 pandemic is not yet over, and it has been generating lots of plastic wastes that become a big concern. To catch the virus, for example, no matter via antigen or PCR test, swab is generally used for sampling. Unfortunately, the swab tip is commonly made of plastics, and thus it can be a potential source of microplastics. This study aims to propose and optimise several Raman imaging to identify the microplastic fibres released from different COVID-19 test swabs. Results: The results show that Raman imaging can effectively identify and visualise the microplastic fibres released from the swabs. In the meantime, on the surface of the fibres, additives such as titanium oxide particles are also captured for some brands of swabs. To increase the result certainty, scanning electron microscope (SEM) is first employed to get the morphology of the released microplastic fibres, along with Energy-dispersive X-ray spectroscopy (EDS) to confirm the presence of titanium element. Then, Raman imaging is advanced to identify and visualise the microplastics and titanium oxide particles, from different characteristic peaks in the scanning spectrum matrix. To further increase the imaging certainty, these images can be merged and cross-checked using algorithms, or the raw data from the scanning spectrum matrix can be analysed and decoded via chemometrics, such as principal component analysis (PCA). Beyond the advantages, the disadvantages of the confocal Raman imaging (affected by focal height) and algorithms (non-supervised calculation) are also discussed and intentionally corrected. In brief, the imaging analysis (particularly the combined SEM with Raman) is recommended to avoid the possible result bias that might be generated from the single spectrum analysis at a selective but random position. Conclusions: Overall, the results indicate that Raman imaging can be a useful tool to detect microplastics. The results also send us a strong warning that, if we worry about the potential microplastics contamination, we should be cautious to select the suitable COVID-19 testing kits. Supplementary Information: The online version contains supplementary material available at 10.1186/s12302-023-00737-0.

Photocatalytic-treated asphalt road in Copenhagen for urban NO x removal.

Atmospheric nitrogen oxides ( NO x = NO + NO 2 ) are key pollutants and short-lived climate forcers contributing to acid rain, photochemical smog, aerosol formation and climate change. Exposure to nitrogen dioxide ( NO 2 ) emitted mainly from transportation, causes adverse health effects associated with respiratory illnesses and increased mortality even at low concentration. Application of titanium dioxide ( TiO 2 )-based photocatalysis in urban environment is a new air cleaning solution, activated by sunlight and water vapour to produce OH radicals, able to remove NO x and other pollutants from the planetary boundary layer. This study is a large-scale evaluation of NO x removal efficiency at a near-road environment with applied photocatalytic NOxOFF™ technology on an urban road west of Copenhagen, thus supporting local municipality in meeting their clean-air Agenda 2030. The photocatalytic NOxOFF™ granulate containing TiO 2 nanoparticles was applied on an asphalt road in July 2020 and ambient NO x was measured during a six-month monitoring campaign. It is the first NO x monitoring campaign carried out at this road and specific efforts have been devoted to evaluate the reduction in ambient NO x levels with NOxOFF™-treated asphalt. Several methods were used to evaluate the photocatalytic effect, taking into account analysis limitations such as the short reference period prior to application and the highly uncertain measurement period during which SARS-CoV-2 lockdown measures impacted air quality. There was no statistically significant difference in NO x concentrations between the reference period and the photocatalytic active period and NO removal efficiency resulted in - 0.17 (± 1.27). An upper limit removal of 17.5% NO x was estimated using a kinetic tunnel model. While NO 2 comparison with COPERT V street traffic model projection was roughly estimated to decrease by 39% (± 38%), although this estimate is subject to high uncertainty. The observed annual mean NO 2 concentration complies with Frederiksberg clean-air Agenda 2030 and air quality standards. Graphical abstract: A graphical abstract illustrating the air cleaning properties of TiO 2 -based photocatalytic-treated asphalt.

Research progress on photocatalysis systems for inactivation of microbial aerosol

Now in the context of the novel coronavirus pneumonia outbreak, the control and removal of microbial aerosols has once again attracted academic attention, while conventional air purification methods such as filtration, chemical agents and UV have their own defects and deficiencies. With the advantages of high efficiency, wide spectrum, green, no residue, dynamic continuous disinfection, photocatalysis has broad application prospects. In this paper, the research on the inactivation of microbial aerosols with photocatalysis system is summarized and analyzed from the aspects of the types of photocatalysts, the load of photocatalysts, the light source and the structure and operation of reactors. TiO2 or its derivative materials are selected as photocatalysts in most studies, and more novel and efficient photocatalysts should be applied. Porous, multi-channel and large surface area catalyst carriers can effectively improve the efficiency of photocatalysis system. The light source still depends on UV light, and the application of visible light needs more research. There are few studies on improving the photocatalysis system by optimizing the reactor structure, and the most commonly used is the ring reactor. Researchers have developed photocatalytic air purifiers or combined photocatalysis systems with indoor air duct systems. In the future, photocatalysis system will become an important means for indoor microbial aerosol control. © 2023 Chemical Industry Press. All rights reserved.

Photocatalytic Degradation of Paracetamol under Simulated Sunlight by Four TiO2 Commercial Powders: An Insight into the Performance of Two Sub-Micrometric Anatase and Rutile Powders and a Nanometric Brookite Powder

The photocatalytic degradation of the emerging contaminant paracetamol in aqueous solution has been studied under 1 SUN (~1000 W m−2) in the presence of four commercial TiO2 powders, namely sub-micrometric anatase and rutile, and nanometric brookite and P25 (the popular anatase/rutile mixture used as a benchmark in most papers). The rutile powder showed low activity, whereas, interestingly, the anatase and the brookite powders outperformed P25 in terms of total paracetamol conversion to carboxylic acids, which, according to the literature, are the final products of its degradation. To explain such results, the physicochemical properties of the powders were studied by applying a multi-technique approach. Among the physicochemical properties usually affecting the photocatalytic performance of TiO2, the presence of some surface impurities likely deriving from K3PO4 (used as crystallization agent) was found to significantly affect the percentage of paracetamol degradation obtained with the sub-micrometric anatase powder. To confirm the role of phosphate, a sample of anatase, obtained by a lab synthesis procedure and having a "clean” surface, was used as a control, though characterized by nanometric particles and higher surface area. The sample was less active than the commercial anatase, but it was more active after impregnation with K3PO4. Conversely, the presence of Cl at the surface of the rutile did not sizably affect the (overall poor) photocatalytic activity of the powder. The remarkable photocatalytic activity of the brookite nanometric powder was ascribed to a combination of several physicochemical properties, including its band structure and nanoparticles size.

Inactivation of SARS-CoV-2 variants by nitrogen-doped titanium dioxide loaded with metals as visible-light photocatalysts.

PURPOSE: We examined the inactivation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by a nitrogen-doped titanium dioxide (N-TiO2) visible-light photocatalyst that was activated via light irradiation in the natural environment and was safe for human use as a coating material. METHODS: The photocatalytic activity of glass slides coated with three types of N-TiO2 without metal or loaded with copper or silver and copper was investigated by measuring acetaldehyde degradation. The titer levels of infectious SARS-CoV-2 were measured using cell culture after exposing photocatalytically active coated glass slides to visible light for up to 60 min. RESULTS: N-TiO2 photoirradiation inactivated the SARS-CoV-2 Wuhan strain and this effect was enhanced by copper loading and further by the addition of silver. Hence, visible-light irradiation using silver and copper-loaded N-TiO2 inactivated the Delta, Omicron, and Wuhan strains. CONCLUSION: N-TiO2 could be used to inactivate SARS-CoV-2 variants, including emerging variants, in the environment.

Synthesis and application of titanium dioxide photocatalysis for energy, decontamination and viral disinfection: a review.

Global pollution is calling for advanced methods to remove contaminants from water and wastewater, such as TiO2-assisted photocatalysis.  The environmental applications of titanium dioxide have started after the initial TiO2 application for water splitting by Fujishima and Honda in 1972. TiO2 is now used for self-cleaning surfaces, air and water purification systems, microbial inactivation and selective organic conversion. The synthesis of titanium dioxide nanomaterials with high photocatalytic activity is actually a major challenge. Here we review titanium dioxide photocatalysis with focus on mechanims, synthesis, and applications. Synthetic methods include sol-gel, sonochemical, microwave, oxidation, deposition, hydro/solvothermal, and biological techniques. Applications comprise the production of energy, petroleum recovery, and the removal of microplastics, pharmaceuticals, metals, dyes, pesticides, and of viruses such as the severe acute respiratory syndrome coronavirus 2.

Prussian Blue@Zeolitic imidazolate framework composite toward solar-triggered biodecontamination

Metal-organic frameworks (MOFs) featuring composition and bandstructure diversity, are an emerging class of photoresponsive disinfectants. In this study, we demonstrated the superiority of core–shell arranged photoactive MOFs (prussian blue (PB) and zeolitic imidazolate framework (ZIF-8)) for pathogen inactivation in terms of biocidal efficiency and broad-spectrum sensitivity. Reactive oxygen species (ROS) production was significantly promoted after the integration of PB due to the photosensitization effect and initiation of in situ Fenton reaction. Favorably, another inactivation channel was also opened owing to the unique photothermal effect of PB. Attributed to the facilitated ROS intracellular penetration by heat, the composite outperforms not only individual component but anatase TiO2 in pathogen elimination. Specifically, the Staphylococcus aureus (S. aureus) inactivation efficiency of the composite (6.6 log) is 2, 1.8 and 5.1 times higher than that of PB (3.3 log), ZIF-8 (3.7 log) and TiO2 (1.3 log) over 45 min of simulated sunlight illumination. Significantly, the infectivity of Bacillus anthracis and murine coronavirus in droplets on composite-coated filter surface could be greatly reduced (approximately 3 log reduction in colony number/coronavirus titer) within few minutes of solar exposure, indicative of the great potential of MOF composites toward life-threatening microbial infection prevention. © 2022 Elsevier B.V.

Nanostructured coatings based on metallic nanoparticles as viral entry inhibitor to combat COVID-19

The rapid transmission of contagious viruses responsible for global pandemic and various extraordinary risk to precious human life including death. For instance, the current ongoing worldwide COVID-19 pandemic caused by novel coronavirus (SARS-CoV-2) is a communicable disease which is transmitted via touching the contaminated surfaces and then nosocomial route. In absence of effective vaccines and therapies, antiviral coatings are essential in order to prevent or slowdown rapid transmission of viruses. In this prospective, sustainable nanotechnology and material engineering have provided substantial contribution in development of engineered nanomaterial based antiviral coated surfaces to the humanity. In the recent past, nanomaterials based on silver (Ag), titanium oxide (TiO2), copper sulfide (CuS) and copper oxide (CuO) have been modified in the form of engineered nanomaterials with effective antiviral efficacy against SARS-CoV-2. In this review, various recent fundamental aspects for fabrication of metallic nanoparticles (Ag, Ti, Cu etc.) based coated surfaces on various substrates and their antiviral efficacy to inhibit viral transmission of SARS-CoV-2 are discussed along with their respective conceptual mechanisms. The antiviral mechanism based on chemistry of engineered nanomaterials is the key outcome of this review that would be useful for future research in designing and development of more advance antiviral materials and coated surfaces in order to control of future epidemics. © 2022 Elsevier B.V.

Surgical staples: Current state-of-the-art and future prospective

Wound closing is one of the widely performed and prominent clinical practices in the surgical intervention process. A physician or surgeon has several options ranging from surgical sutures and adhesive strips to fibrin glue for effective wound closure to close the commonly occurring surgical cuts and deep skin tissue injuries. However, all the commercially available wound closure devices have some limitations in each and another perspective. From the beginning of the late 90s, surgical staples got tremendous attention as efficient wound closure devices for their time-effective and sufficient mechanical strength, performance feasibility, fewer chances of surgical site infection and require minimal expertise characteristics in consideration of remote location. Even in the context of the recent COVID19 pandemic, the clinical acceptance and patient compliance for the staples have increased due to minimizing the chances of prolonged interaction between the patient and physicians. The surgical staples application is extensive and diversified, ranging from common external cuts to highly complex surgery procedures like laparoscopic appendectomy, intestinal anastomosis, etc. Thus, in this literature review, we try to give a comprehensive glimpse of the development and current state-of-the-art surgical staples in consideration with research from a commercial point of view. On a special note, this review also describes a very brief outline of the regulatory aspects and some common internationally acceptable 'de jure standards for the development of commercially viable surgical staples. Copyright © 2022 The Author(s)

Nafion Modified Titanium Nitride pH Sensor for Future Biomedical Applications.

pH sensors are increasingly being utilized in the biomedical field and have been implicated in health applications that aim to improve the monitoring and treatment of patients. In this work, a previously developed Titanium Nitride (TiN) solid-state pH sensor is further enhanced, with the potential to be used for pH regulation inside the human body and for other biomedical, industrial, and environmental applications. One of the main limitations of existing solid-state pH sensors is their reduced performance in high redox mediums. The potential shift E0 value of the previously developed TiN pH electrode in the presence of oxidizing or reducing agents is 30 mV. To minimize this redox shift, a Nafion-modified TiN electrode was developed, tested, and evaluated in various mediums. The Nafion-modified electrode has been shown to shift the E0 value by only 2 mV, providing increased accuracy in highly redox samples while maintaining acceptable reaction times. Overcoming the redox interference for pH measurement enables several advantages of the Nafion-modified TiN electrode over the standard pH glass electrode, implicating its use in medical diagnosis, real-time health monitoring, and further development of miniaturized smart sensors.

MXene-Based Nanomaterials for Biomedical Applications: Healthier Substitute Materials for the Future

MXene-based nanomaterial is a revolution 2D material achieving outstanding scientific attention owing to its universal characteristics for different applications (such as electronic appliances, power production, sensors, drug transfer, and biomedical). Although, the cytotoxic consequences of MXene have a considerable circumstance. Thus, rigorous investigation of the biocompatibility of MXene is a crucial prerequisite, formerly the preface to the human biological approach. Literature reveals functional outcomes wherever MXenes are used in vitro and in vivo cancer representatives. It affects drug transfer methods, sensoring electrodes, and assisting mechanisms for photothermal treatment and hyperthermy techniques. In this review, the synthesis process (such as top-down and bottom-up approaches) and properties (such as mechanical, electrical, optical, oxidative/thermal stability, and magnetic) of MXene-based nanomaterials (NMs) are discussed. In addition, the different applications (such as tissue engineering, cancer theranostic, and other biomedical [such as drug delivery biosensors and surface-enhanced Raman spectroscopy substrates for biomedical applications], antiviral, and immunomodulatory properties against SARS-CoV-2) of MXene-based NMs are discussed in detail. Finally, the conclusion, existing challenges, and future outlooks are highlighted for more scope in this field.

Comparing Bone Graft Techniques for Interbody Fusion through a Posterior Approach for Treating Mid-Thoracic Spinal Tuberculosis: A Retrospective Analysis.

OBJECTIVE: Mid-thoracic spinal tuberculosis is prone to kyphotic deformities and neurologic impairment. Posterior approach can effectively restore the spinal stability by reconstructing the anterior and middle spinal columns. Titanium mesh cages (TMC), allogeneic bone (ALB), and autogenous bone (AUB) are three main bone graft struts. We aimed to compare the therapeutic efficacy of three bone graft struts, for anterior and middle column reconstruction through a posterior approach in cases of mid-thoracic spinal tuberculosis. METHODS: Hundred and thirty seven patients with thoracic spinal tuberculosis who had undergone a posterior approach from June 2010 to December 2018 were enrolled. Of them, 46 patients were treated using a titanium mesh cage (TMC group), 44 with allogenic bone grafts (ALB group), and 47 using autogenous bone grafts (AUB group). The following were analyzed to evaluate clinical efficacy: visual analogue scale (VAS) values, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, kyphotic Cobb's angle, operation duration, intraoperative blood loss, improvement in American Spinal Injury Association (ASIA) grade and in the mental component summary (MCS) and physical component summary (PCS) of Short Form-36 (SF-36), duration of bone graft fusion. The data of the three groups were compared by way of variance analysis, followed by the LSD⁃t test to compare each group. A repeated measures ANOVA was used to analyze the dates of pre-, postoperative and final follow-up. RESULTS: The follow-up duration was at least 3 years. All patients achieved a complete cure for spinal TB. Neurological performance and quality of life were remarkably improved at the final follow-up. The intraoperative blood loss, operation time and VAS values 1 day postoperatively for TMC group and ALB group were significantly lower than those in AUB group (P < 0.05). The duration of bone graft fusion in ALB group (18.1 ± 3.7 months) was longer than that in TMC group and AUB group (9.5 ± 2.8 and 9.2 ± 1.9 months) (P < 0.05). No significant intergroup differences were observed in terms of age or preoperative, 3-months postoperative, and final follow-up indices of ESR and CRP among the three groups (P > 0.05). At the final follow-up, the correction loss was mild (2.1 ± 0.9, 2.2 ± 1.0, 2.1 ± 0.8) and Cobb's angles of the three groups were 20.1 ± 2.9, 20.5 ± 3.2, 20.9 ± 3.4, respectively, which were remarkably rectified in comparison with the preoperative measurements (P < 0.05). CONCLUSIONS: In terms of postoperative recovery and successful fusion rate of bone graft, it seems that posterior instrumentation, debridement, and interbody fusion with titanium mesh cages are more effective and appropriate surgical methods for mid-thoracic spinal tuberculosis.

Functionalized Titanium Dioxide Nanoparticle-Based Electrochemical Immunosensor for Detection of SARS-CoV-2 Antibody.

The advancement in biosensors can overcome the challenges faced by conventional diagnostic techniques for the detection of the highly infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hence, the development of an accurate, rapid, sensitive, and selective diagnostic technique can mitigate adverse health conditions caused by SARS-CoV-2. This work proposes the development of an electrochemical immunosensor based on bio-nanocomposites for the sensitive detection of SARS-CoV-2 antibodies through the differential pulse voltammetry (DPV) electroanalytical method. The facile synthesis of chitosan-functionalized titanium dioxide nanoparticles (TiO2-CS bio-nanocomposites) is performed using the sol-gel method. Characterization of the TiO2-CS bio-nanocomposite is accomplished using UV-vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The electrochemical performance is studied using cyclic voltammetry (CV), DPV, and electrochemical impedance spectroscopy (EIS) for its electroanalytical and biosensing capabilities. The developed immunosensing platform has a high sensitivity with a wide range of detection from 50 ag mL-1 to 1 ng mL-1. The detection limit of the SARS-CoV-2 antibody in buffer media is obtained to be 3.42 ag mL-1 and the limit of quantitation (LOQ) to be 10.38 ag mL-1. The electrochemical immunosensor has high selectivity in different interfering analytes and is stable for 10 days. The results suggest that the developed electrochemical immunosensor can be applicable for real sample analysis and further high-throughput testing.

Inorganic Coatings and Films for Antibacterial and Antivirus Functionality

The global pandemic of COVID-19 has caused serious harm to people's healthy life and the normal operation of society. People have paid more attention to the prevention and control of microbial contamination such as bacteria and viruses. Blocking the spread of disease-causing microorganisms through indirect contact with humans through contaminated surfaces, or avoiding direct contact with them, is the primary way to protect us from harm. Current solutions include designing antibacterial and antiviral surface coatings and developing personal protective equipment made from self-cleaning films or fabrics. In this paper, the work of several widely studied metals, metal oxides, metal organic framework materials, etc. with antibacterial and antiviral functionality is reviewed, their microbial inactivation mechanisms as well as performance are summarized and discussed. In the end, the future perspectives on emerging research directions and challenges in the development of antibacterial and antiviral coatings and films are presented.

Rutile-TiO2/PtO2 Glass Coatings Disinfects Aquatic Legionella pneumophila via Morphology Change and Endotoxin Degradation under LED Irradiation

Legionella pneumophila (L. pneumophila) is the causative agent of Legionnaires’ disease and Pontiac fever, collectively known as legionellosis. L. pneumophila infection occurs through inhalation of contaminated aerosols from water systems in workplaces and institutions. The development of disinfectants that can eliminate L. pneumophila in such water systems without evacuating people is needed to prevent the spread of L. pneumophila. Photocatalysts are attractive disinfectants that do not harm human health. In particular, the TiO2 photocatalyst kills L. pneumophila under various conditions, but its mode of action is unknown. Here, we confirmed the high performance of TiO2 photocatalyst containing PtO2 via the degradation of methylene blue (half-value period: 19.2 min) and bactericidal activity against Escherichia coli (half-value period: 15.1 min) in water. Using transmission electron microscopy, we demonstrate that the disinfection of L. pneumophila (half-value period: 6.7 min) by TiO2 photocatalyst in water is accompanied by remarkable cellular membrane and internal damage to L. pneumophila. Assays with limulus amebocyte lysate and silver staining showed the release of endotoxin from L. pneumophila due to membrane damage and photocatalytic degradation of this endotoxin. This is the first study to demonstrate the disinfection mechanisms of TiO2 photocatalyst, namely, via morphological changes and membrane damage of L. pneumophila. Our results suggest that TiO2 photocatalyst might be effective in controlling the spread of L. pneumophila.

Antimicrobial Activity of a Titanium Dioxide Additivated Thermoset

The transmission of pathogens via surfaces poses a major health problem, particularly in hospital environments. Antimicrobial surfaces can interrupt the path of spread, while photocatalytically active titanium dioxide (TiO2) nanoparticles have emerged as an additive for creating antimicrobial materials. Irradiation of such particles with ultraviolet (UV) light leads to the formation of reactive oxygen species that can inactivate bacteria. The aim of this research was to incorporate TiO2 nanoparticles into a cellulose-reinforced melamine-formaldehyde resin (MF) to obtain a photocatalytic antimicrobial thermoset, to be used, for example, for device enclosures or tableware. To this end, composites of MF with 5, 10, 15, and 20 wt% TiO2 were produced by ultrasonication and hot pressing. The incorporation of TiO2 resulted in a small decrease in tensile strength and little to no decrease in Shore D hardness, but a statistically significant decrease in the water contact angle. After 48 h of UV irradiation, a statistically significant decrease in tensile strength for samples with 0 and 10 wt% TiO2 was measured but with no statistically significant differences in Shore D hardness, although a statistically significant increase in surface hydrophilicity was measured. Accelerated methylene blue (MB) degradation was measured during a further 2.5 h of UV irradiation and MB concentrations of 12% or less could be achieved. Samples containing 0, 10, and 20 wt% TiO2 were investigated for long-term UV stability and antimicrobial activity. Fourier-transform infrared spectroscopy revealed no changes in the chemical structure of the polymer, due to the incorporation of TiO2, but changes were detected after 500 h of irradiation, indicating material degradation. Specimens pre-irradiated with UV for 48 h showed a total reduction in Escherichia coli when exposed to UV irradiation.

Flexible, disposable photocatalytic plastic films for the destruction of viruses.

A thin, 30 µm, flexible, robust low-density polyethylene, LDPE, film, loaded with 30 wt% P25 TiO2, is extruded and subsequently rendered highly active photocatalytically by exposing it to UVA (352 nm, 1.5 mW cm-2) for 144 h. The film was tested for anti-viral activity using four different viruses, namely, two strains of Influenza A Virus (IAV), WSN, and a recombinant PR8, encephalomyocarditis virus (EMCV), and SARS-CoV-2 (SARS2). The film was irradiated with either UVA radiation (352 nm, 1.5 mW cm-2; although only 0.25 mW cm-2 for SARS2) or with light from a cool white fluorescent lamp (UVA irradiance: 365 nm, 0.047 mW cm-2). In all cases the films exhibited an average virus inactivation rate of >1.5log/h. In the case of SARS2, the rates were > 2log/h, with the rate determined using a dedicated, low intensity UVA source (0.25 mW cm-2) only 1.3 x's faster than that for a cool white lamp (UVA irradiance = 0.047 mW cm-2), which suggests that SARS2 is particularly prone to photocatalytic inactivation even under low UV irradiation conditions, such as found in a room lit with just white fluorescent tubes. This is the first example of a flexible, very thin, photocatalytic plastic film, produced by a scalable process (extrusion), for virus inactivation. The potential of such a film for use as a disposable, self-sterilising thin plastic material alternative to the common, non-photocatalytic, inert equivalent used currently for curtains, aprons and table coverings in healthcare is discussed briefly.