Engineered nanomaterials exert sublethal bacterial stress at very low doses: Effects of concentration, light, and media on cell membrane permeability.

Engineered nanomaterials (ENMs) can alter surface properties of cells and disturb cellular functions and gene expression through direct and indirect contact, exerting unintended impacts on human and ecological health. However, the effects of interactions among environmental factors, such as light, surrounding media, and ENM mixtures, on the mechanisms of ENM toxicity, especially at sublethal concentrations, are much less explored and understood. Therefore, we evaluated cell viability and outer membrane permeability of E. coli as a function of exposure to environmentally relevant concentrations of ENMs, including metal (n-Ag) and metal oxide (n-TiO2, n-Al2O3, n-ZnO, n-CuO, and n-SiO2) nanoparticles under dark and simulated sunlight illumination in MOPS, a synthetic buffer, and Lake Michigan Water (LMW), a freshwater medium. We found that light activates the phototoxicity of n-TiO2 and n-Ag by inducing significant increases in bacterial outer membrane permeability at sublethal doses (< 1 mg/L). Other ENMs, including n-ZnO, n-CuO, n-Al2O3, and n-SiO2, have small to minimal impacts. Toxicities of ENMs were greater in LMW than MOPS due to their different ionic strength and chemical composition. Physical and chemical interactions between n-TiO2 and n-Ag lead to amplified toxic effects of the ENM mixtures that are greater than the additive effects of individual ENMs acting alone. Our results revealed the significant sublethal bacterial stress exerted by ENMs and ENM mixtures at the cell surface in natural environments at low doses, which can potentially lead to further cellular damage and eventually impact overall ecological health.

A robust self-regenerating graphene-based adsorbent for pharmaceutical removal in various water environments.

The presence of active pharmaceutical ingredients (APIs) in wastewater effluents and natural aquatic systems threatens ecological and human health. While activated carbon-based adsorbents, such as GAC and PAC, are widely used for API removal, they exhibit certain deficiencies, including reduced performance due to the presence of natural organic macromolecules (NOMs) and high regeneration costs. There is growing demand for a robust, stable, and self-regenerative adsorbent designed for API removal in various environments. In this study, we synthesized a self-generating metal oxide nano-composite (S-MGC) containing titanium dioxide (TiO2) and silicon dioxide (SiO2) combined with 3D graphene oxide (GO) to adsorb APIs and undergo regeneration via light illumination. We determined optimal TiO2:SiO2:GO compositions for the S-MGCs through experiments using a model contaminant, methylene blue. The physical and chemical properties of S-MGCs were characterized, and their adsorption and photodegradation capabilities were studied using five model APIs, including sulfamethoxazole, carbamazepine, ketoprofen, valsartan, and diclofenac, both in single-component and multi-component mixtures. In the absence of TiO2/SiO2, 3D graphene oxide (CGB) displayed better adsorption performance compared to GAC, and S-MGCs further improve CGB's adsorption capacity. This performance remained consistent in two complex water environments: aqueous solutions at varying NOM levels and artificial urine. TiO2 supported on the GO surface exhibits similar photocatalytic activity to suspended TiO2. In a continuous fixed-bed column test, S-MGCs demonstrated robust API adsorption performance that is maintained in the presence of NOM or urine, and can be regenerated through multiple cycles of adsorption and light illumination.

Polyaniline-metal oxide coatings for biocidal applications: Mechanisms of activation and deactivation.

Metal oxide (MO) coatings (e.g. TiO2, ZnO, and CuO) have shown great promise to inactivate pathogenic bacteria, maintain self-cleaning surfaces, and prevent infectious diseases spread via surface contact. Under light illumination, the antibacterial performance of photoactive MO coatings is determined by reactive oxygen species (ROS) generation. However, several drawbacks, such as photo-corrosion and rapid electron-hole recombination, hinder the ROS production of MO coatings and diminish their antibacterial efficiency. In this study, we employed polyaniline (PANI), an inexpensive and easy-to-synthesize conductive polymer, to fabricate polyaniline-metal oxide composite (PMC) films. The antibacterial performance of PMC films was tested using E. coli as the model bacterium and Lake Michigan water (LMW) as the background medium and revealed enhanced antibacterial performance relative to MO coatings alone (approximately 75-90 % kill of E. coli by PMC coatings in comparison to 20-40 % kill by MO coatings), which is explained by an increase in the ROS yields of PMC. However, with repeated use, the antibacterial performance of the PMC coatings is diminished due to deprotonation of the PANI in the neutral/slightly basic aqueous environment of LMW. Overall, PANI can enhance the antibacterial performance of MO coatings, but efforts need to be directed to preserve or regenerate PMC stability under environmental conditions and applications.

A RECALCITRANT SKIN LESION AND SUBSEQUENT INFECTION IN A RECREATIONAL INTRAMURAL MALE ATHLETE: A CASE REPORT.

A 35-year-old intramural male athlete presented to the athletic training staff with a 4.5cm x 2.2cm itchy, painful, swollen, and infected insidious skin lesion on his right lateral malleolus due to an underlying dermatological deficiency. Suspecting infection, the patient was referred to his nurse practitioner and was diagnosed with atopic dermatitis caused by a ceramide deficiency. He was placed on Cefalexin and Mupirocin 2% ointment but returned due to the lesion increasing to 8.5cm x 6cm although infection seemed controlled. He was instructed to use Ceravé™ topical cream, Clobetasol propionate 5%, and consume foods rich in healthy oils (omega-3s, olive oil). Unmitigated, this lesion could have resulted in severe infection and tissue damage. Atopic dermatitis is relatively common in the general population but the appearance in healthy athletes highlights that athletic trainers need to be well-versed in not just apparent causes of skin ailments (i.e., infection), but also root causes.

Effect of molecular structure on the adsorption behavior of sulfanilamide antibiotics on crumpled graphene balls.

Since the 1930s, sulfonamide(SA)-based antibiotics have served as important pharmaceuticals, but their widespread detection in water systems threatens aquatic organisms and human health. Adsorption via graphene, its modified form (graphene oxide, GO), and related nanocomposites is a promising method to remove SAs, owing to the strong and selective surface affinity of graphene/GO with aromatic compounds. However, a deeper understanding of the mechanisms of interaction between the chemical structure of SAs and the GO surface is required to predict the performance of GO-based nanostructured materials to adsorb the individual chemicals making up this large class of pharmaceuticals. In this research, we studied the adsorptive performance of 3D crumpled graphene balls (CGBs) to remove 10 SAs and 13 structural analogs from water. The maximum adsorption capacity qm of SAs on CGB increased with the number of (1) aromatic rings; (2) electron-donating functional groups; (3) hydrogen bonding acceptor sites. Furthermore, the CGB surface displayed a preference for homocyclic relative to heterocyclic aromatic structures. A leading mechanism, π-π electron-donor-acceptor interaction, combined with hydrogen bonding, explains these trends. We developed a multiple linear regression model capable of predicting the qm as a function of SA chemical structure and properties and the oxidation level of CGB. The model predicted the adsorptive behaviors of SAs well with the exception of a chlorinated/fluorinated SA. The insights afforded by these experiments and modeling will aid in tailoring graphene-based adsorbents to remove micropollutants from water and reduce the growing public health threats associated with antibiotic resistance and endocrine-disrupting chemicals.

Creating anti-viral high-touch surfaces using photocatalytic transparent films.

Antimicrobial and self-cleaning surface coatings are promising tools to combat the growing global threat of infectious diseases and related healthcare-associated infections (HAIs). Although many engineered TiO2-based coating technologies are reporting antibacterial performance, the antiviral performance of these coatings has not been explored. Furthermore, previous studies have underscored the importance of the "transparency" of the coating for surfaces such as the touch screens of medical devices. Hence, in this study, we fabricated a variety of nanoscale TiO2-based transparent thin films (anatase TiO2, anatase/rutile mixed phase TiO2, silver-anatase TiO2 composite, and carbon nanotube-anatase TiO2 composite) via dipping and airbrush spray coating technologies and evaluated their antiviral performance (Bacteriophage MS2 as the model) under dark and illuminated conditions. The thin films showed high surface coverage (ranging from 40 to 85%), low surface roughness (maximum average roughness 70 nm), super-hydrophilicity (water contact angle 6-38.4°), and high transparency (70-80% transmittance under visible light). Antiviral performance of the coatings revealed that silver-anatase TiO2 composite (nAg/nTiO2) coated samples achieved the highest antiviral efficacy (5-6 log reduction) while the other TiO2 coated samples showed fair antiviral results (1.5-3.5 log reduction) after 90 min LED irradiation at 365 nm. Those findings indicate that TiO2-based composite coatings are effective in creating antiviral high-touch surfaces with the potential to control infectious diseases and HAIs.

Metal oxide encapsulated by 3D graphene oxide creates a nanocomposite with enhanced organic adsorption in aqueous solution.

The presence of organic contaminants (OCs) in aquatic systems is a threat to ecological and human health. Adsorption by graphene-based adsorbent is a promising technique for OC removal and we previously fabricated crumpled graphene balls (CGBs), via a novel nano-spray drying technique, which show robust adsorptive performance. Yet, since CGBs contain non-accessible surface area due to 2D graphene stacking, the goal of this research was to investigate the efficacy of maximizing the accessible CGB surface by synthesizing a nanocomposite composed of metal oxide nanoparticles encapsulated by crumpled graphene oxide (MGC). The metal oxides reduce graphene oxide stacking, expand the internal adsorptive surface area, and boost the adsorptive capacity of the MGC. MGC (fumed SiO2 or SiO2) exhibit an enhanced Langmuir adsorption capacity (qm, normalized by the % carbon) for an OC model, methylene blue (MB), achieving improvements of 60-86% compared to CGB, 3-4 fold compared to powder activated carbon (PAC) and 6-7 fold compared to granular activated carbon (GAC). MGCs display rapid adsorption reaching equilibrium after 9-12 min of contact and remaining stable in wastewater effluent /surface water. A cost-efficiency comparison reveals MGCs achieve one ton of MB removal at similar or lower material costs than that of PAC/GAC.

TiO2 (Core)/Crumpled Graphene Oxide (Shell) Nanocomposites Show Enhanced Photodegradation of Carbamazepine.

The presence of pharmaceuticals and personal care products (PPCPs) in aquatic systems is a serious threat to human and ecological health. The photocatalytic degradation of PPCPs via titanium oxide (TiO2) is a well-researched potential solution, but its efficacy is limited by a variety of environmental conditions, such as the presence of natural organic macromolecules (NOM). In this study, we investigate the synthesis and performance of a novel photoreactive composite: a three-dimensional (3D) core (TiO2)-shell (crumpled graphene oxide) composite (TiGC) used as a powerful tool for PPCP removal and degradation in complex aqueous environments. TiGC exhibited a high adsorption capacity (maximum capacity 11.2 mg/g, 100 times larger than bare TiO2) and a 30% enhancement of photodegradation (compared to bare TiO2) in experiments with a persistent PPCP model, carbamazepine (CBZ). Furthermore, the TiGC performance was tested under various conditions of NOM concentration, light intensity, CBZ initial concentration, and multiple cycles of CBZ addition, in order to illustrate that TiGC performance is stable over a range of field conditions (including NOM). The enhanced and stable performance of TiCG to adsorb and degrade CBZ in water extends from its core-shell composite nanostructure: the crumpled graphene oxide shell provides an adsorptive surface that favors CBZ sorption over NOM, and optical and electronic interactions between TiO2 and graphene oxide result in higher hydroxyl radical (•OH) yields than bare TiO2.

The impacts of metal-based engineered nanomaterial mixtures on microbial systems: A review.

The last decade has witnessed tremendous growth in the commercial use of metal-based engineered nanomaterials (ENMs) for a wide range of products and processes. Consequently, direct and indirect release into environmental systems may no longer be considered negligible or insignificant. Yet, there is an active debate as to whether there are real risks to human or ecological health with environmental exposure to ENMs. Previous research has focused primarily on the acute effects of individual ENMs using pure cultures under controlled laboratory environments, which may not accurately reveal the ecological impacts of ENMs under real environmental conditions. The goal of this review is to assess our current understanding of ENM effects as we move from exposure of single to multiple ENMs or microbial species. For instance, are ENMs' impacts on microbial communities predicted by their intrinsic physical or chemical characteristics or their effects on single microbial populations; how do chronic ENM interactions compare to acute toxicity; does behavior under simplified laboratory conditions reflect that in environmental media; finally, is biological stress modified by interactions in ENM mixtures relative to that of individual ENM? This review summarizes key findings and our evolving understanding of the ecological effects of ENMs under complex environmental conditions on microbial systems, identifies the gaps in our current knowledge, and indicates the direction of future research.

Patient experiences of pharmacist independent prescriber-led post-myocardial infarction left ventricular systolic dysfunction clinics.

OBJECTIVES: Left ventricular systolic dysfunction (LVSD) is common following myocardial infarction (MI). Pharmacological management of secondary prevention is known to be sub-optimal. Integration of pharmacists into clinical teams improves prescribing and quantitative outcomes. Few data have been published on patient views of pharmacist input. We aimed to explore patient experiences of attending a dedicated pharmacist independent prescriber (PIP)-led clinic. METHODS: Semi-structured face-to-face interviews. Participants were aged ≥18 years with new incident MI and echocardiographically confirmed LVSD. Patients were recruited from three pharmacist-led clinics at point of clinic discharge. Interviews were transcribed verbatim. Thematic analysis was undertaken. KEY FINDINGS: Twelve patients were recruited, median age 67.5 years and ten male. Six core themes were identified: multidisciplinary working; satisfaction; confidence in the pharmacist; comparative care; prescribing behaviours; and monitoring. Pharmacist clinics complemented other established post-MI services, and participants perceived benefits obtained through effective inter-professional working. Participants welcomed dedicated appointment time, the opportunity to ask questions and address problems. Pharmacist explanations of condition and medicines, prescribing at the point of care and monitoring were beneficial and reduced patient stress. CONCLUSIONS: This study demonstrates that a PIP-led post-MI LVSD clinic delivers a positive initial patient experience. More research is needed to understand the longer-term patient experiences, the impact of such models on medication taking behaviours and the experiences of carers and other members of the multidisciplinary team.

The key to maximizing the benefits of antimicrobial and self-cleaning coatings is to fully determine their risks.

Antimicrobial and self-cleaning nanomaterial coatings have attracted significant research attention in recent years due to the growing global threat of infectious diseases, the emergence of new diseases such as COVID-19, and increases in healthcare-associated infections. Although there are many reportedly successful coating technologies, the evaluation of antimicrobial performance is primarily conducted under simple laboratory conditions without adequate testing under real environmental conditions that reflect practical use and more importantly, reveal unintended outcomes. Furthermore, there is no standardized evaluation methodology to assess the long-term stability or the consequences associated with coating deterioration, such as the ecological impacts of nanomaterials or the proliferation of antibiotic-resistant bacteria/genes. In this review, we propose a precautionary framework that integrates a rigorous assessment of potential risks and limitations of nanomaterial coatings for antimicrobial applications as intrinsic to a comprehensive evaluation of their benefits. In addition, we summarize some emerging coating technologies as promising strategies to minimize unintended risks and enhance performance.

Prenatal air pollution exposure and neurodevelopment: A review and blueprint for a harmonized approach within ECHO.

BACKGROUND: Air pollution exposure is ubiquitous with demonstrated effects on morbidity and mortality. A growing literature suggests that prenatal air pollution exposure impacts neurodevelopment. We posit that the Environmental influences on Child Health Outcomes (ECHO) program will provide unique opportunities to fill critical knowledge gaps given the wide spatial and temporal variability of ECHO participants. OBJECTIVES: We briefly describe current methods for air pollution exposure assessment, summarize existing studies of air pollution and neurodevelopment, and synthesize this information as a basis for recommendations, or a blueprint, for evaluating air pollution effects on neurodevelopmental outcomes in ECHO. METHODS: We review peer-reviewed literature on prenatal air pollution exposure and neurodevelopmental outcomes, including autism spectrum disorder, attention deficit hyperactivity disorder, intelligence, general cognition, mood, and imaging measures. ECHO meta-data were compiled and evaluated to assess frequency of neurodevelopmental assessments and prenatal and infancy residential address locations. Cohort recruitment locations and enrollment years were summarized to examine potential spatial and temporal variation present in ECHO. DISCUSSION: While the literature provides compelling evidence that prenatal air pollution affects neurodevelopment, limitations in spatial and temporal exposure variation exist for current published studies. As >90% of the ECHO cohorts have collected a prenatal or infancy address, application of advanced geographic information systems-based models for common air pollutant exposures may be ideal to address limitations of published research. CONCLUSIONS: In ECHO we have the opportunity to pioneer unifying exposure assessment and evaluate effects across multiple periods of development and neurodevelopmental outcomes, setting the standard for evaluation of prenatal air pollution exposures with the goal of improving children's health.

Functionalizing a Polyelectrolyte Complex with Chitosan Derivatives to Tailor Membrane Surface Properties.

Polyelectrolyte complex (PEC) materials show promise in the development of tunable membranes for aqueous and organic solvent separations, as well as in the creation of surface layers for fouling control. In this study, we developed a polyelectrolyte complex (PEC) functionalized by negatively charged carboxymethyl chitosan (CMC-) and positively charged quaternized chitosan (QC+) to tailor its surface properties and antibacterial efficacy. CMC- and QC+ were prepared and characterized using FT-IR and 1H NMR, which confirmed the presence of the carboxymethyl group and trimethylammonium group in CMC- and QC+ with 65.6% and 83.9% substitution, respectively. The CMC- functionalized PEC (CMC-/PEC) and QC+ functionalized PEC materials (QC+/PEC) were evaluated for their stability in water, resistance to organic and inorganic adsorption, and antibacterial action against a model microorganism, Pseudomonas putida. The results showed no release of chitosan derivatives after adsorption, and CMC-/PEC and QC+/PEC exhibited charge-based, selective repulsion of model organic and inorganic substances. Moreover, the functionalized PEC surfaces displayed lower bacterial attachment due to their smoother surfaces as compared to the bare ceramic membrane and their antimicrobial properties. Among the PEC samples, CMC-/PEC had the lowest cell attachment, while QC+/PEC showed the highest attachment due to electrostatic attraction. The ceramic and bare PEC surfaces were negligibly bactericidal, while cell viability decreased to 34.4 ± 10.2% and 30.6 ± 8.2% with the CMC-/PEC and QC+/PEC surfaces, respectively. In the filtration experiments, the unmodified PEC and CMC-/PEC showed lower rates of flux decline due to organic fouling than did the bare ceramic or QC+/PEC due to electrostatic repulsion. Furthermore, PECs as protective layers promoted much higher flux recoveries than simply backwashing the uncoated membranes. This surface tunability, then, enhances the potential of PECs either as fouling resistant materials or as a method to create a sacrificial, protective layer on surfaces that once fouled can be dissolved and re-established.

Nano-enabled, antimicrobial toothbrushes - How physical and chemical properties relate to antibacterial capabilities.

Over the past two decades, Ag and Zn nanoparticles have been integrated into various consumer products as a biocide. While some nano-enabled consumer products have been shown to have antibacterial properties, their antibacterial efficacy as well as the human and environmental health outcomes are not fully known. In this study, we examine a nanoparticle-enabled product that also serves as a conduit for human exposure to bacteria: toothbrushes. We utilize a combination of chemical analyses, laboratory experiments, and microscopy to characterize the nano-enabled toothbrush bristles. Our analysis showed the majority of measured Ag and Zn particles ranged from approximately 50 to 100 nm in size and were located on the surface and within bristles. During simulated brushing, antimicrobial bristles released both Ag and Zn, the majority of which was released in particulate form. While our results demonstrate that antimicrobial bristles have enhanced bactericidal properties compared to control samples, we also show that the surface topography influences nanoparticle retention, microbial adhesion, and bactericidal activity. We thus conclude that Ag or Zn content alone is insufficient to predict antimicrobial properties, which are further governed by the bioavailability of Ag or Zn at the bristle surface.

Celiac Disease Symptoms in Athletes: Prevalence Indicators of Perceived Quality of Life.

BACKGROUND: Celiac disease (CD) is a common gastrointestinal pathology; however, prevalence and comorbidities are unknown in collegiate athletics. HYPOTHESES: (1) Athletes will have similar odds of CD as general population estimates (approximately 1 in 141) based on self-report and signs and symptoms, (2) athletes scoring higher on the Celiac Symptom Index (CSI) will have lower self-reported quality of life (QoL), (3) athletes scoring higher on the CSI will have higher depression scores, and (4) athletes scoring higher on the CSI will have higher perceived stress scores. STUDY DESIGN: Epidemiological cross-sectional study. LEVEL OF EVIDENCE: Level 4. METHODS: The CSI, WHO Quality of Life-BREF, Beck Depression Inventory, and Perceived Stress Scale were used to assess patients' signs and symptoms of CD and psychosocial measures/QoL in male and female National Collegiate Athletic Association (all divisions) athletes (N = 141). Participants also self-reported a formal diagnosis of CD. Chi-square analyses determined CD prevalence. Odds ratios determined risk for either being diagnosed with CD or reporting more symptoms than the general population. Correlational analyses determined whether symptoms correlated with QoL and psychosocial measures. RESULTS: Athletes were 3.85 times (95% CI, 0.42-34.89) more likely to report a CD diagnosis and were 18.36 times (95% CI, 2.40-140.48) more likely to report a high degree of CD symptoms than the general population. Athletes with more symptoms had worse physical, psychological, social, and environmental QoL indicators and higher depression and perceived stress scores. CONCLUSION: Athletes may be a higher risk population for experiencing CD and report greater signs/symptoms compared with general population estimates. Additionally, athletes with higher CD symptom scores also reported poorer QoL. CLINICAL RELEVANCE: Allied health care professionals should be aware of the diversity of CD symptoms and be prepared to refer athletes when gastrointestinal symptoms persist to ensure proper care and unhampered performance.

Exploring co-occurrence patterns between organic micropollutants and bacterial community structure in a mixed-use watershed.

Complex mixtures of low concentrations of organic micropollutants are commonly found in rivers and streams, but their relationship to the structure of native bacterial communities that underlie critical ecological goods and services in these systems is poorly understood. To address this knowledge gap, we used correlation-based network analysis to explore co-occurrence patterns between measured micropollutant concentrations and the associated surface water and sediment bacterial communities in a restored riparian zone of the Des Plaines River (DPR) in Illinois that is impacted by both wastewater treatment plant (WWTP) effluent and agricultural runoff. Over a two year period, we collected 55 grab samples at 11 sites along the DPR and one of its tributaries (48 surface water samples) and from WWTP effluent (7 samples), and screened for 126 organic micropollutants. In parallel, we used high-throughput 16S rRNA gene amplicon sequencing to characterize the bacterial community in sediment and surface water. Our results revealed quantifiable levels of 102 micropollutants in at least one surface water or WWTP effluent sample, 85 of which were detected in at least one surface water sample. While micropollutants were temporally and spatially variable in terms of both presence and concentration, 21 micropollutants were measured in over 75% of the 48 surface water samples. 16S rRNA gene sequencing documented diverse bacterial communities along the DPR transect, with highly distinct community structures observed in sediment and water. Bacterial community structure in surface water, but not in sediment, was significantly associated with concentrations of micropollutants, based on a Mantel test. Correlation-based network analyses revealed diverse strong and significant co-occurrence and co-exclusion patterns between specific bacterial OTUs and both micropollutant groups (defined based on k-means clustering on chemical substructure) and individual micropollutants. Significantly more associations were documented between micropollutants and bacterial taxa in the water compared to the sediment microbiomes. Taken together, our results document a significant link between complex mixtures of micropollutants commonly found in aquatic systems and associated bacterial community structure. Furthermore, our results suggest that micropollutants may exert a more significant impact on water-associated than on sediment-associated bacterial taxa.

Versatile and High-Throughput Polyelectrolyte Complex Membranes via Phase Inversion.

High-flux filtration membranes constructed through scalable and sustainable methods are desirable for energy-efficient separations. Often, these criteria are difficult to be reconciled with one another. Polymeric membranes can provide high flux but frequently involve organic solvents in processing steps. Solubility of many polymeric membranes in organic media also restricts their implementation in solvent filtration. In the present work, we report a simple and high-throughput aqueous processing approach for polyelectrolyte complex (PEC) membranes with controllable porosity and stability in various aqueous and organic environments. PECs are materials composed of oppositely charged polymer chains that can form solids in aqueous environments, yet which can be dissolved in very specific salt solutions capable of breaking the interpolymer ion pairs. By exploiting the salt-induced dissolution and subsequent reformation of the complex, nano- to microporous films are rapidly synthesized which resemble membranes obtained through conventional solvent-phase inversion techniques. PECs remain stable in organic solvents because of the low dielectric constant of the environment, which enhances electrostatic interactions, making them suitable for a wide range of water and solvent filtration applications. Here, we elucidate how the polymer-phase behavior can be manipulated to exercise morphological control, test membrane performance for water and solvent filtration, and quantify the mechanical stability of PECs in relevant conditions.

TiO2-based transparent coatings create self-cleaning surfaces.

Implementation of self-cleaning surfaces is gaining attention as a tool to combat the healthcare associated infections (HAIs). In this study, we prepared TiO2-based transparent coatings as one such potential self-cleaning surface for touchscreen application and evaluated their antimicrobial efficacy under dark and illuminated conditions. To maintain high transparency and TiO2 coverage, clean borosilicate glass slides were dip-coated multiple times in a suspension of TiO2-based materials at a low concentration. The as-prepared samples were tested for their roughness and hydrophilicity via atomic force microscopy (AFM) and contact angle analysis, respectively. To screen the antimicrobial performance of the TiO2 coated samples, the number and viability of attached bacteria on the film surfaces were recorded after submerging them in a bacterial suspension for 45 min under dark or ultraviolet (UV) illuminated conditions. The antimicrobial performance of the commercially available regular and Ag-coated antimicrobial Corning® Gorilla® Glass were also evaluated under the same conditions and compared with those of the TiO2 coated samples. Among the test samples, n-Ag/TiO2 (<100 nm) coated samples achieved greater than 80% bactericidal efficacy with the lowest bacterial attachment after the UV exposure. TiO2-based transparent coatings show promise as an effective tool against bacterial attachment and displays greater bactericidal activity in comparison to commercial antibacterial glass.

Synergistic Bacterial Stress Results from Exposure to Nano-Ag and Nano-TiO2 Mixtures under Light in Environmental Media.

Due to their widespread use and subsequent release, engineered nanomaterials (ENMs) will create complex mixtures and emergent systems in the natural environment where their chemical interactions may cause toxic stress to microorganisms. We previously showed that under dark conditions n-TiO2 attenuated bacterial stress caused by low concentrations of n-Ag (<20 µg L-1) due to Ag+ adsorption, yet, since both n-Ag and n-TiO2 are photoactive, their photochemistries may play a key role in their interactions. In this work, we study the chemical interactions of n-Ag and n-TiO2 mixtures in a natural aqueous medium under simulated solar irradiation to investigate photoinduced stress. Using ATP levels and cell membrane integrity as probes, we observe that n-Ag and n-TiO2 together exert synergistic toxic stress in Escherichia coli. We find increased production of hydrogen peroxide by the n-Ag/n-TiO2 mixture, revealing that the enhanced photocatalytic activity and production of ROS likely contribute to the stress response observed. Based on STEM-EDS evidence, we propose that a new composite Ag/TiO2 nanomaterial forms under these conditions and explains the synergistic effects of the ENM mixture. Overall, this work reveals that environmental transformations of ENM mixtures under irradiation can enhance biological stress beyond that of individual components.

Photo-Initiated Reduction of CO2 by H2 on Silica Surface.

The reduction of CO2 is a promising route to produce valuable chemicals or fuels and create C-neutral resource cycles. Many different approaches to CO2 reduction have been investigated, but the ability of vacuum UV (VUV) irradiation to cleave C-O bonds has remained largely unexplored for use in processes that convert CO2 into useful products. Compared with other photo-driven CO2 conversion processes, VUV-initiated CO2 reduction can achieve much greater conversion under common photochemical reaction conditions when H2 and non-reducible oxides are present. Infrared spectroscopy provides evidence for a chain reaction initiated by VUV-induced CO2 splitting, which is enhanced in the presence of H2 and silica. When the reaction is carried out in the presence of silica or alumina surfaces, CO yields are increased and CH4 is formed as the only other detected product. CH4 production is not promoted by traditional photocatalysts such as TiO2 under these conditions. Assuming improvements in lamp and reactor efficiencies with scale up, or coupling with other available CO/CO2 hydrogenation techniques, these results reveal a potential, simple strategy by which CO2 could be valorized.