Copper-doped bismuth oxychloride nanosheets assembled into sphere-like morphology for improved photocatalytic inactivation of drug-resistant bacteria.

The devastating microbiological contamination as well as emerging drug-resistant bacteria has posed severe threats to the ecosystem and public health, which propels the continuous exploitation of safe yet efficient disinfection products and technology. Here, copper doping engineered bismuth oxychloride (Cu-BiOCl) nanocomposite with a hierarchical spherical structure was successfully prepared. It was found that due to the exposure of abundant active sites for the adsorption of both bacteria cells and molecular oxygen in the structure, the obtained Cu-BiOCl with nanosheets assembled into sphere-like morphology exhibited remarkable photocatalytic antibacterial effects. In particular, compared to the pure BiOCl, composite Cu-BiOCl possessed improved antibacterial effects against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Methicillin-resistant Staphylococcus aureus (MRSA). The combination of physicochemical characterizations and theoretical calculations has revealed that copper doping significantly promoted the light absorbance, inhibited the recombination of electron-hole pairs, and enhanced molecular oxygen adsorption, which resulted in more generation of active species including reactive oxygen species (ROS) and h+ to achieve superior photocatalytic bacterial inactivation. Finally, transcriptome analysis on MRSA pinpointed photocatalytic inactivation induced by Cu-BiOCl may retard largely the development of drug-resistance. Therefore, the built spherical Cu-BiOCl nanocomposite has provided an ecofriendly, economical and robust strategy for the efficient removal of drug-resistant bacteria with promising potentials for environmental and healthcare utilizations.

Curcumin-stabilized silver nanoparticles encapsulated in biocompatible electrospun nanofibrous scaffold for sustained eradication of drug-resistant bacteria.

Due to the misuse of antibiotics, the emerging drug-resistance of pathogenic microbes has aroused considerable concerns for the public health, which demands the continuous search for safe and efficient antimicrobial treatment. In this study, curcumin reduced and stabilized silver nanoparticles (C-Ag NPs) were successfully encapsulated into electrospun nanofiber membranes consisted of polyvinyl alcohol (PVA) cross-linked by citric acids (CA), which exhibited desirable biocompatibility and broad-spectrum antimicrobial activities. The homogeneously distributed and sustained release of C-Ag NPs in the constructed nanofibrous scaffolds yield prominent killing effect against Escherichia coli, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA), which involved the reactive oxygen species (ROS) generation. Outstanding elimination of bacterial biofilms and excellent antifungal activity against Candida albicans was also identified after treated with PVA/CA/C-Ag. Transcriptomic analysis on MRSA treated by PVA/CA/C-Ag revealed the antibacterial process is related to disrupting carbohydrate and energy metabolism, as well as destroying bacterial membranes. Significant down-regulation of the expression of multidrug-resistant efflux pump gene sdrM was observed pointing to the role of PVA/CA/C-Ag to overcome the bacterial resistance. Therefore, the constructed ecofriendly and biocompatible nanofibrous scaffolds provide a robust and versatile nanoplatform of reversal potential to eradicate drug-resistant pathogenic microbe in environmental as well as healthcare applications.

Deciphering the photoactive species-directed antibacterial mechanism of bismuth oxychloride with modulated nanoscale thickness.

As an environmentally benign disinfection strategy, photocatalytic bacterial inactivation using nanoparticles involves photogenerated reactive species that cause cellular oxidative stress. Rationalising the structural performance of photocatalysts for the practical uses such as wastewater treatment has attracted significant attention; however, the contribution of reactive species to their photocatalytic antibacterial activities at the molecular and transcriptomic levels remains unclear. In this study, nontoxic bismuth oxychloride (BiOCl) photocatalysts with different nanoscale thicknesses, including nanosheets (Ns, ∼5.4 nm), nanoplates (Np, ∼1.8 nm), and ultra-nanosheets (Uns, ∼1.1 nm), were synthesised under hydrothermal conditions. Among the three samples, BiOCl Uns exhibited the most effective photocatalytic degradation efficiency with the calculated apparent rate constant of 0.0294 min-1, ∼4 times faster than that of Ns, whereas BiOCl Ns possessed the most pronounced bactericidal effect (5.4 log inactivation). Such findings indicate the distinct role of the photoactive species responsible for photocatalytic bacterial inactivation. Moreover, transcriptome analysis of Escherichia coli after photocatalytic treatment revealed that the underlying photocatalytic antibacterial mechanism at the genetic expression level involves cellular component biosynthesis, energy metabolism, and material transportation. Notably, the differences between BiOCl Ns and BiOCl Uns were significantly enriched in purine metabolism. Therefore, the cost-effective preparation of BiOCl nanosheets with nanoscale thickness-modulated photocatalytic antibacterial activity has remarkable potential for sustainable environmental and biomedical applications.

Evaluation of the gut microbiome alterations in healthy rats after dietary exposure to different synthetic ZnO nanoparticles.

AIMS: Although synthetic ZnO nanoparticles (Nano-ZnO) as an alternative of ZnO compounds have been extensively used such as in livestock production, the increased consuming of Nano-ZnO has raised considerable concerns in environmental pollution and public health. Because of the low digestion of Nano-ZnO, the systematic studies on their interactions with gut microbiota remain to be clarified. MATERIALS AND METHODS: Nano-ZnOs were prepared by co-precipitation (ZnO-cp) and high temperature thermal decomposition (ZnO-td) as well as the commercial type (ZnO-s). Transmission electron microscopy (TEM) was used to monitor the morphology of Nano-ZnO. CCK-8 assay was used for cytotoxicity evaluation. Total antioxidant capacity assay, total superoxide dismutase assay, and lipid peroxidation assay were used to evaluate oxidative states of rats. 16S rRNA was used to study the impact of Nano-ZnO on the rat gut microbiome. KEY FINDINGS: Both ZnO-cp and ZnO-td exhibited low cytotoxicity while ZnO-s and ZnO-td exhibited prominent antibacterial activities. After a 28-day oral feeding with 1000 mg/kg Zn at dietary dosage, ZnO-s showed slight effect on causing oxidative stress in comparison with that of ZnO-cp and ZnO-td. Results of 16S rRNA sequencing analysis indicated that ZnO-td as a promising short-term nano-supplement can increase probiotics abundances like strains belonged to the genus Lactobacillus and provide the antipathogenic effect. SIGNIFICANCE: The results of the gut microbiome alteration by synthetic Nano-ZnO not only provide solution to exposure monitoring of environmental hazard, but rationalize their large-scale manufacture as alternative additive in the food chain.

One-pot synthesis of α-Linolenic acid nanoemulsion-templated drug-loaded silica mesocomposites as efficient bactericide against drug-resistant Mycobacterium tuberculosis.

Nowadays, pathogenic infection has posed a severe threat to the public health and environmental sanitation, urging a continuous search of efficacious and safe bactericidal agents of various formulated forms. Here, a facile one-pot hydrothermal preparation of mesoporous silica nanoparticles using ultrasonication-assisted nanoemulsion of α-Linolenic acid (α-LA) as template was developed. The formed silica mesocomposite at water/fatty-acid surface provides an easy yet green synthesis route, which can be generalized for the further encapsulation of hydrophobic drugs such as antimycobacterial Rifampicin (RIF). The obtained α-LA nanoemulsion-templated silica nanoparticles (LNS NPs), with a weight content of ∼17% α-LA in the composite, showed apparent antibacterial effect against Staphylococcus aureus (S. aureus). By comparison, the removal of α-LA from the silica nanoparticles (LNS-1 NPs) resulted in the composite of enlarged pore size with negligible bactericidal activities. Notably, the Isoniazide (INH) and Rifampicin (RIF)-encapsulated LNS NPs exhibited outstanding antimycobacterial activity against both drug-sensitive and drug-resistant Mycobacterium tuberculosis (M. tuberculosis). The obtained highly biocompatible, biosafe and low-energy consumptive α-LA-contained mesostructured silica-based bactericide holds promising therapeutic potentials to tackle the emerging drug-resistant infectious microbes.

Electrospun chitosan oligosaccharide/polycaprolactone nanofibers loaded with wound-healing compounds of Rutin and Quercetin as antibacterial dressings.

Burn injury has posed devastating burdens on the public health due to its inevitable damage to the skin structure resulting in the increased risk of infection. Therefore, it is highly demanding to develop efficacious antibacterial wound-healing dressing. Despite the favourable wound-healing activities, the curative efficacy of phytochemical compounds of quercetin (Qe) and its derivatives is limited by their poor water solubility. Here, we have fabricated a novel electrospun nanofiber membrane (ENM) consisting of polycaprolactone (PCL), chitosan oligosaccharides (COS), and Qe/Rutin (Ru) as the potential bioactive dressing for wound healing. The incorporation of chitosan oligosaccharides (COSs) in the PCL scaffold at the optimized molar ratio not only contributed to the improved hydrophilicity and water absorption performance of the ENM but effectively increased the specific surface area of the formed nanofibers. In particular, the antioxidant and antibacterial activities of the Qe/rutin-loaded nanofiber membranes were tested, which revealed that the PCL-COS-Qe membrane exhibited superior performance among all nanofiber membranes. Therefore, the developed PCL-COS-Qe/Ru nanofiber membranes hold enormous potential as healthcare products, such as wound dressings for burn injuries.

Toxicity-attenuated mesoporous silica Schiff-base bonded anticancer drug complexes for chemotherapy of drug resistant cancer.

Multidrug resistance (MDR), evoked by improper chemotherapeutic practices, poses a serious threat to public health, which leads to increased medical burdens and weakened curative effects. Taking advantage of the enhanced pharmaceutical effect of Schiff base compounds, an aldehyde-modified mesoporous silica SBA-15 (CHO-SBA-15)-bonded anticancer drug combined with doxorubicin hydrochloride (DOX) was synthesized via a Schiff base reaction. Due to the acid-sensitive imine bonds formed between CHO-SBA-15 and DOX, the as-prepared nanocomposites exhibited pH-responsive drug releasing behaviours, resulting in a more enhanced cytotoxic effect on DOX-resistant tumour cells than that of free drugs. Notably, the in vivo studies indicated that mice treated with CHO-SBA-15/DOX composites evidently showed more attenuated systemic toxicity than the free drug molecules. The siliceous mesopore Schiff base-bonded anticancer drug nanocomposite, with minimal chemical modifications, provides a simplified yet efficient therapeutic nanoplatform to deal with drug-resistant cancer.

Visible-Light-Responsive Nanofibrous α-Fe2O3 Integrated FeOx Cluster-Templated Siliceous Microsheets for Rapid Catalytic Phenol Removal and Enhanced Antibacterial Activity.

Visible-light-driven environmental contaminants control using 2D photocatalytic nanomaterials with an unconfined reaction-diffusion path is advantageous for public health. Here, cost-effective siliceous composite microsheets (FeSiO-MS) combined with two distinct refined α-Fe2O3 nanospecies as photofunctional catalysts were constructed via a one-pot synthesis approach. Through precise control of Fe2+ precursor addition, specially configured α-Fe2O3 nanofibers combined with FeOx cluster-functionalized siliceous microsheets of ∼15 nm gradually evolved from the iron oxide-bearing molecular sieve, endowing a superior light-response characteristic of the formed nanocomposite. The catalytic experiment along with the ESR study demonstrated that the produced FeSiO-MS showed reinforced photo-Fenton reactivity, which was effective for rapid phenol degradation under visible light radiation. Moreover, the phenol removal process was found to be regulated by the specially configured types and concentrations of iron oxides. Notably, the obtained composites exhibited a considerable visible-light-induced bactericidal effect against E. coli. The constructed FeSiO-MS nanocomposites as integrated and eco-friendly photocatalysts exhibit enormous potentials for environmental and hygienic application.

A green electrolysis of silver-decorated MoS2 nanocomposite with an enhanced antibacterial effect and low cytotoxicity.

To tackle the devastating microbial infections for the public health, a continuous search for effective and safe nanobiocides based on their prominent nanoscale effects has been extensively explored during past decades. In this study, a green electrolysis method was employed to synthesize silver-doped molybdenum sulfide (Ag@MoS2) composite materials. The obtained nanocomposites exhibited a sheet-like structure with a large specific surface area, which contributed to the efficient loading and refined distribution of silver nanoparticles. G- E. coli and G + S. aureus were used as model bacteria for the antibacterial test, which revealed enhanced antibacterial activity of produced nanocomposites with an identified destructive effect on preformed biofilms. It was found that within 72 hour incubation, 20 µg mL-1 Ag@MoS2 was sufficient to inhibit the growth of E. coli and S. aureus without visible colony formation, pointing to a desirable long-term antibacterial activity. Further a mechanistic antibiosis study of Ag@MoS2 indicated the involvement of a generation of reactive oxygen species. Notably, owing to the well-distributed silver nanoparticles on the nontoxic MoS2 nanosheet, the cytotoxicity evaluation results revealed that produced nanocomposites exhibited negligible toxicity to mammalian cells, and thereby held promising potential for biomedical applications.

Encapsulating insoluble antifungal drugs into oleic acid-modified silica mesocomposites with enhanced fungicidal activity.

Recently, with increasing medical practices, including organ transplantation and tumor chemotherapy, fungal infections, particularly the occurrence of drug-resistant fungal strains, remain a severe problem for the public health, which cause worse complications in the immunocompromised patients. The search for efficacious yet safe antifungal agents is in high demand in precision medicine. However, fungicides are often poorly water soluble for oral absorption, which is difficult for pharmaceutical efficacy evaluation. In this study, lipophilic oleic acid (OA)-grafted mesoporous silica (SBA-15) was facilely modified by cetyltrimethylammonium bromide (CTAB), which acts as an efficient antifungal drug matrix of itraconazole (ITZ). Characterized by physicochemical methods, the rod-like SBA-15-OA-CTAB/ITZ composite with retained mesostructural regularity shows that the loading amount of ITZ in the mesopore is ∼18%, contributing to the enhanced antifungal activity against Aspergillus fumigatus (A. fumigatus) and Candida albicans (C. albicans). The antimicrobial mechanism study suggests that the reactive oxygen species (ROS) were formed when fungal cells were incubated with the formulated ITZ, while there was no ROS formation in the presence of pure ITZ, which may result from the quaternary ammonium moieties of CTAB in the nanocomposites. Due to the potential toxicity of CTAB on mammalian cells, the as-synthesized mesoporous SBA-15-OA-CTAB/ITZ provides an alternative molecular design for the formulation improvement of a lipophilic antifungal drug applicable for external uses such as topical therapy.

[The Study of Infrared Spectra of Acetophenone Molecule].

By implying the density functional theory method, the geometry of acetophenone molecular is fully optimized at the B3LYP/6-311++G(d, p) level and the frequency is also calculated at the same level. The infrared spectrum and complete vibrational modes of acetophenone molecular are attained. Meanwhile, the infrared spectrum is obtained by experimental measurements. Through the comparison and analysis, it is found that the theoretical calculation results meet well with those of experiments. Finally, the vibrational modes of acetophenone molecule are assigned, and the strong vibration peaks in the experiment results belong to infrared characteristic peaks of acetophenone molecule.

[Theory study of the structures and IR of (C5H5N)n(H2O), (n = 1-2, m = 1-4) clusters].

Using density functional theory, the possible geometrical structures of (C5H5N)n (H2O)m (n = 1-2, m = 1- 4) clusters were optimized at the B3LYP/6-311++G(d, p) level and the stable structures were attained. For the dimer formed between C5H5N and H2O, the calculation result shows that there is only one stable structure and the configuration of cluster formed through pi hydrogen bond (O-H...pi) interaction was not found. In order to study the stability of the clusters, the total energies and binding energies of the clusters were calculated at the same level of theory, and the result shows that the four-membered ring structures of water molecules in (C5H5N)n (H2O)4 (n = 1-2) clusters are more stable than structures of the triatomic ring of water molecules. The lowest energy structure of the C5H5N (H2O)4 cluster is more stable than the others and is probably a magic number structure by the analysis to the energy gap between HOMO and LUMO. At the end, the IR spectra of (C5H5N)n (H2O)m (n = 1-2, m = 1-4) clusters were analysed and the stronger peaks appearing in infrared spectra were assigned.

Structural, electronic, and photophysical properties of thieno-expanded tricyclic purine analogs: a theoretical study.

Modified forms of DNA are under intense research because of their potential applications in nanotechnology and medical science. In the present work, comprehensive theoretical investigations into the structural, electronic, and optical properties of four newly designed thieno-expanded base analogs, namely ttA, ttG, ttX, and ttHX, have been performed. The results are compared against the findings obtained for the natural ones. Geometrically, ttA and ttG have nonplanar ground-state geometries caused by the pyramidalization of the amino groups, while ttX and ttHX have planar geometries. Electronically, the ionization potentials and HOMO-LUMO gaps are smaller than natural ones, while the electron affinities are larger than natural ones. The nature of the low-lying excited states is discussed, and it was found that the lowest transitions are of ππ* nature and were mainly dominated by the configuration HOMO → LUMO. The calculated excitation maxima are 283, 302, 294, and 290 nm for ttA, ttG, ttX, and ttHX, respectively, and they are greatly red-shifted compared with natural bases. In the gas phase, the fluorescence from them would be expected to occur around 291, 331, 317, and 323 nm, respectively. The effects of micro-hydration, bulk water solution, and base pairing with their complementary natural bases on the low-lying electronic transitions of these modified bases were also examined.

Fluorescence lifetimes of the Ã1Πu state of C3.

The fluorescence lifetimes of 115 vibrational levels of the Ã1Π(u) state of C3 have been measured under supersonic molecular beam conditions. Of these, ninety-one are Π(u) vibronic levels, for which the lifetimes lie in the range 190-700 ns. The lifetimes of those Π(u) levels where only the bending vibration is excited lie in the range 190-235 ns. There is very little variation with bending quantum number, and the lifetimes of the two orbital components of the 1Π(u) state are essentially the same. When ν1 and ν3 are excited, the lifetimes become longer and/or reach a maximum for levels with v1 + v3 ~ 4. Excitation of the bending vibration in addition to the stretching vibrations shortens the lifetime slightly. Several of the levels show double-exponential decays. Another 23 levels, of Σ(u)+ vibronic symmetry, mostly have lifetimes that are longer than 300 ns. Interaction with nearby "dark" electronic states, such as B1Σ(u)-, B'1Δ(u), C1Π(g), and b3Π(g), is proposed to account for the observed lifetime lengthening. A particularly clear instance of such an interaction is the long lifetime (914 ns) of a perturbing Σ(u)+ level at 30,181 cm(-1), which is confirmed as belonging to the perturbing B'1Δ(u) state. A single level of Δ(u) symmetry at 29,170 cm(-1), which perturbs one of the Π(u) levels, is shown to belong to the à state.

Excited state properties of naphtho-homologated xxDNA bases and effect of methanol solution, deoxyribose, and base pairing.

Design and synthesis of fluorescent nucleobase analogues for studying structures and dynamics of nucleic acids have attracted much attention in recent years. In the present work, a comprehensive theoretical study of electronic transitions of naphtho-homologated base analogues, namely, xxC, xxT, xxA, and xxG, was performed. The nature of the low-lying excited states was discussed, and the results were compared with those of x-bases. Geometrical characteristics of the lowest excited singlet ππ* states were explored using the CIS method. The calculated excitation maxima are 423, 397, 383, and 357 nm for xxA, xxG, xxC, and xxT, respectively, and they are greatly red-shifted compared with x-bases and natural bases, allowing them to be selectively excited in the presence of the natural bases. In the gas phase, the fluorescence from them would be expected to occur around 497, 461, 457, and 417 nm, respectively. The effects of methanol solution, deoxyribose, and base paring with their complementary natural bases on the relevant absorption and emission spectra of these modified bases were also examined.

[The study of infrared spectra of 2-pyridinemethanol by density functional theory].

Using density functional theory (DFT), geometry optimizations and frequencies calculation of 2-pyridinemethanol were performed at B3LYP/6-311G(d, p) level, the stable structure and complete vibrational modes of 2-pyridinemethanol were attained. The calculated geometric parameters are in good agreement with the reported experimental measurement of pyridine and the reported data of pertinent literature. When comparing the calculated IR data with those reported by experiments, it was found that the calculated results are in good agreement with the experimental results. Finally, the vibrational modes of 2-pyridinemethanol molecule were assigned.