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Organic semiconductors, including graphitic carbon nitride (g-C3N4, CN), represent an important class of materials for the development of novel antimicrobial or biomedical technologies. Of principal interest is the ability of these materials to catalyze the reduction of elemental oxygen to generate reactive oxygen species (ROS), including hydrogen peroxide (H2O2). Here, we describe the fabrication of photoactive van der Waals heterojunctions incorporating 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) and CN. The composite heterojunction systems were characterized by a combination of physical (TEM, SEM, pXRD), spectroscopic (FT-IR, XPS, DRUV, photoluminescence, TCSPC) and kinetic experiments. Electronic interactions between the two components of the heterojunction increase the rate of photochemical production of H2O2 from elemental oxygen by 410%, relative to samples of pure CN. Mechanistic analysis reveals that interaction of NTCDA with the surface of CN modifies the mechanism of H2O2 formation in the heterojunction photocatalysts. The photochemical production of H2O2 by irradiation of the most active heterojunction composition is sufficient to reduce the viability of E. coli O157:H7, S. aureus and Ps. aeruginosa PAO1 by 99%. Importantly, H2O2 production by the NTCDA/CN heterojunctions suppresses Ps. aeruginosa biofilm formation, even at light exposure doses that had a lesser impact on overall planktonic cell growth.

In this manuscript, we describe the fabrication of photoactive biocidal or sporicidal films from urea-derived graphitic carbon nitride (u-g-C3N4). Co-deposited films of u-g-C3N4 and Escherichia coli O157:H7 (IC50 = 14.1 ± 0.2 mJ) or Staphylococcus aureus (methicillin resistant IC50 = 33.5 ± 0.2 mJ, methicillin sensitive IC50 = 42.7 ± 0.5 mJ) demonstrated significantly enhanced bactericidal behavior upon administration of visible radiation (400 nm ≤ λ ≤ 426 nm). In all cases, complete eradication of the microbial sample was realized upon administration of 100 mJ of visible radiation, while no antimicrobial activity was observed for non-irradiated samples. In contrast, Bacillus anthracis endospores were more resistant to u-g-C3N4 mediated killing with only a ca. 25% reduction in spore viability when treated with a 200 mJ dose of visible radiation. Characterization of u-g-C3N4 reveals that the improved activity results from enhancements of both the surface area and reduction potential of the material’s conduction band edge, coupled with fast injection of charge carriers into localized states and a decline in radiative recombination events. The results of this study demonstrate that g-C3N4-based materials offer a viable scaffold for the development of new, visible light driven technologies for controlling potentially pathogenic microorganisms.

Photoactive films derived from nanostructured samples of metal-free, intermediate band gap semiconductor graphitic carbon nitride (ns-g-C3N4) have been synthesized and characterized for their particle properties and antimicrobial activity. Physical characterization reveals that these materials are composed of discrete nanoparticles whose dimensions range from 200 nm to 700 nm. Investigation of the photochemical reactivity of ns-g-C3N4 using coumarin-3-carboxylic acid (3-CCA) indicates that this material produces reactive oxygen species (ROS) under visible radiation. When irradiated with 0.31 J visible light, ns-g-C3N4-based materials reduced the viability of both Gram-negative Escherichia coli O157:H7 and Gram-positive Staphylococcus aureus by approximately 50%. Nearly complete inactivation of both strains of microorganisms was achieved upon administration of a 0.62 J dose of visible radiation. Importantly, no biocidal activity was observed for non-irradiated samples, indicating that the g-C3N4-derived films are not inherently toxic in the absence of visible light. The results of this study suggest that materials and, by extention, films and coatings derived from g-C3N4 may present a novel route for controlling pathogenic microorganisms on surfaces in the environment, and could be useful in reducing incidents of hospital-acquired infections.

Background Borrelia burgdorferi causes Lyme disease, the most common tick-borne illness in the United States. The Center for Disease Control and Prevention estimates that the occurrence of Lyme disease in the U.S. has now reached approximately 300,000 cases annually. Early stage Borrelia burgdorferi infections are generally treatable with oral antibiotics, but late stage disease is more difficult to treat and more likely to lead to post-treatment Lyme disease syndrome. Methods Here we examine three unique 5′-methylthioadenosine/S-adenosylhomocysteine (MTA/SAH) nucleosidases (MTNs or MTANs, EC 3.2.2.9) responsible for salvage of adenine and methionine in B. burgdorferi and explore their potential as antibiotic targets to treat Lyme disease. Recombinant Borrelia MTNs were expressed and purified from E. coli. The enzymes were extensively characterized for activity, specificity, and inhibition using a UV spectrophotometric assay. In vitro antibiotic activities of MTN inhibitors were assessed using a bioluminescent BacTiter-Glo™ assay. Results The three Borrelia MTNs showed unique activities against the native substrates MTA, SAH, and 5′-deoxyadenosine. Analysis of substrate analogs revealed that specific activity rapidly dropped as the length of the 5′-alkylthio substitution increased. Non-hydrolysable nucleoside transition state analogs demonstrated sub-nanomolar enzyme inhibition constants. Lastly, two late stage transition state analogs exerted in vitro IC50 values of 0.3–0.4 μg/mL against cultured B. burgdorferi cells. Conclusion B. burgdorferi is unusual in that it expresses three distinct MTNs (cytoplasmic, membrane bound, and secreted) that are effectively inactivated by nucleoside analogs. General significance The Borrelia MTNs appear to be promising targets for developing new antibiotics to treat Lyme disease.

The Faculty of Accident and Emergency Medicine was inaugurated on 2 November 1993. The new council decided that it would like a logo or badge to signify its identity and to adorn such items as headed notepaper and the president's badge of office. As registrar I was instructed to approach the College of Arms for letters-patent granting the faculty its own coat of arms. Because of the multidisciplinary nature of accident and emergency medicine, the faculty is an intercollegiate one based on six royal colleges. The faculty has flourished, it has a steadily increasing membership, and the faculty board's examination committee holds regular examinations for fellowship of the faculty twice a year. The first step was to approach the College of Arms in London and the duty herald, who in our case was William Hunt, Portcullis Pursuivant of Arms. He led me through the detailed process of acquiring our armorial bearings. We submitted the articles of constitution of the faculty to Portcullis, who submitted them to the Kings of Arms. The faculty was then given permission to petition the Earl Marshal for armorial bearings. Portcullis had made it clear that the smaller the committee designing the coat of arms the better. He favoured a committee of one. In the event we formed a small subcommittee of three. Figure 1 shows the principal elements of an achievement of arms, in this case those of the Worshipful …

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