Chiral carbon dots, prepared from the unnatural d-enantiomer of cysteine, inhibit the growth of Escherichia coli ATCC 25922 and MG1655 at a lower concentration than l-carbon dots, prepared from the l-enantiomer.
Chronic
wounds present a high risk of infection due to delayed
and incomplete healing, leading to increased health risks and financial
burden to health-care systems. Numerous approaches to promote wound
healing have been extensively explored, especially the development
of effective wound dressing materials embedded with therapeutic drug
molecules. Despite advances made in this area, a remaining challenge
to be addressed is the controlled, on-demand release of therapeutic
molecules using noncytotoxic stimulus, for example, near-infrared
(NIR) excitation. Here, we report a platform that allows for the development
of electrospun poly(vinyl alcohol) (PVA) fibrous hybrids embedded
with upconverting nanoparticles (UCNPs) and UV-cleavable levofloxacin
conjugates for wound dressings. Upon irradiation with NIR light, the
excited UCNPs emit UV light around 365 nm, which can cleave the o-nitrobenzyl (ONB) linkage of the levofloxacin conjugates
in the PVA fiber, leading to controlled drug release. The release
was observed to be triggered only under NIR and UV irradiation, with
no effect in the dark. Furthermore, the antibacterial effect against Escherichia coli and Staphylococcus
aureus was successfully demonstrated, highlighting
the versatility of the electrospun upconverting fiber platform. The
development of antibacterial fibrous meshes with on-demand release
of encapsulated drugs is imperative for precise treatment of wound
infections.
One of the key chemicals that give soil its earthy aroma, geosmin is a frequent water contaminant produced by a range of unrelated microbes. Many animals, including humans, are able to detect geosmin at minute concentrations, but the benefit that this compound provides to its producing organisms is poorly understood.
Known as the smell of earth after rain, geosmin is an odorous terpene detectable by humans at picomolar concentrations. Geosmin production is heavily conserved in actinobacteria, myxobacteria, cyanobacteria, and some fungi, but its biological activity is poorly understood. We theorized that geosmin was an aposematic signal used to indicate the unpalatability of toxin-producing microbes, discouraging predation by eukaryotes. Consistent with this hypothesis we found that geosmin and the related terpene 2-methylisoborneol reduced predation of Streptomyces coelicolor and Myxococcus xanthus by the bacteriophagous Caenorhabditis elegans. Predation was restored by the removal of both terpene biosynthetic pathways or deletion of the C. elegans ASE sensory neuron, and resulted in the death of the nematodes. Geosmin itself was non-toxic. This is the first warning chemical to be identified in bacteria or fungi, and suggests molecular signalling affects microbial predator-prey interactions in a manner similar to the well-studied visual markers of poisonous animal prey.
A new synthetic route utilizing biomass-derived furans as a starting material for the production of bis(5-arylfuran-2yl)methane scaffolds was developed. Decarboxylative crosscoupling of 5-hydroxymethylfuroic acid (HMFA) was studied in detail with overall good yields. Acid-catalyzed self-condensation was optimized to produce the target structures in excellent yields. Overall, this report introduces a new expedient synthesis to obtain bis(furyl) methane scaffolds that avoids the use of protecting groups and highlights the utilization of renewable carbon sources as starting materials.
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