Broad-Spectrum Antibacterial Activity of Synthesized Carbon Nanodots from d-Glucose.

Carbon nanodots, a class of carbon nano-allotropes, have been synthesized through different routes and methods from a wide range of precursors. The selected precursor, synthetic method, and conditions can strongly alter the physicochemical properties of the resulting material and their intended applications. Herein, carbon nanodots (CNDs) have been synthesized from d-glucose by combining pyrolysis and chemical oxidation methods. The effect of the pyrolysis temperature, equivalents of oxidizing agent, and refluxing time were studied on the product and quantum yield. In the optimum conditions (pyrolysis temperature of 300 °C, 4.41 equiv of H2O2, 90 min of reflux) CNDs were obtained with 40% and 3.6% of product and quantum yields, respectively. The obtained CNDs are negatively charged (ζ-potential = -32 mV), excellently dispersed in water, with average diameter of 2.2 nm. Furthermore, ammonium hydroxide (NH4OH) was introduced as dehydrating and/or passivation agent during CNDs synthesis resulting in significant improvement of both product and quantum yields of about 1.5 and 3.76-fold, respectively. The synthesized CNDs showed a broad spectrum of antibacterial activities toward different Gram-positive and Gram-negative bacteria strains. Both synthesized CNDs caused highly colony forming unit reduction (CFU), ranging from 98% to 99.99% for most of the tested bacterial strains. However, CNDs synthesized in the absence of NH4OH, due to a negatively charged surface enriched in oxygenated groups, performed better in zone inhibition and minimum inhibitory concentration. The elevated antibacterial activity of high-oxygen-containing carbon nanodots is directly correlated to their ROS formation ability.

Covalent Functionalization of Graphene Sheets with Different Moieties and Their Effects on Biological Activities.

The ongoing spread of multi-drug-resistant bacteria over the past few decades necessitates collateral efforts to develop new classes of antibacterial agents with different mechanisms of action. The utilization of graphene nanosheets has recently gained attention with this respect. Herein, we have synthesized and tested the antibacterial activity of an array of graphene materials covalently functionalized with hydroxyl-, amine-, or carboxyl-containing groups. Fourier transform infrared spectroscopy and transmission electron microscopy confirmed successful functionalization of the few-layer graphene (FLG). The percentage of weight loss was measured by thermogravimetric analysis, which was found to be 22%, 23%, and 37% for FLG-TEG-OH, FLG-NH2, and FLG-DEG-COOH, respectively. In comparison with pristine graphene sheets, the functionalized few-layer graphene (f-FLG) materials gained an adequate dispersibility in water as confirmed by ζ potential analysis. Moreover, there was a significant improvement in the antibacterial activity against Staphylococcus aureus and Escherichia coli, where all f-FLG compounds were able to suppress bacterial growth, with a complete suppression achieved by FLG-DEG-COOH. The minimum inhibitory concentration (MIC) was 250 µg mL-1 for both FLG-TEG-OH and FLG-NH2, while it was 125 µg mL-1 for FLG-DEG-COOH. The glutathione oxidation test demonstrated an oxidative stress activity by all f-FLG compounds. However, FLG-DEG-COOH demonstrated the highest reduction in glutathione activity. FLG-DEG-COOH and FLG-TEG-OH showed adequate biocompatibility and hemocompatibility. The chemical functionalization of graphene might be a step toward the foundation of an effective class of antimicrobial agents.

Pharmacological and phytochemical screening of Palestinian traditional medicinal plants Erodium laciniatum and Lactuca orientalis.

BACKGROUND: Various epidemiological studies showed that herbal remedies containing polyphenols may protect against various diseases such as cancers, vascular diseases and inflammatory pathologies. Currently, such groups of bioactive compounds have become a subject of many antimicrobials and antioxidant investigations. Accordingly, the current study aimed to conduct biological and phytochemical screening for two Palestinian traditional medicinal plants, Erodium laciniatum and Lactuca orientalis. METHODS: Current plants phytoconstituents and their antioxidant activities were evaluated by using standard phytochemical methods; meanwhile, antimicrobial activities were estimated by using several types of American Type Culture Collection and multidrug resistant clinical isolates by using agar diffusion well-variant, agar diffusion disc-variant and broth microdilution methods. RESULTS: Phytochemical screenings showed that L. orientalis and E. laciniatum contain mixtures of secondary and primary metabolites Moreover, total flavonoid, tannins and phenols content in E. laciniatum extract were higher than the L. orientalis extracts with almost the same antioxidant potentials. Additionally, both plants organic and aqueous extracts showed various potentials of antimicrobial activity Conclusions: Overall, the studied species have a mixture of phytochemicals, flavonoids, phenols and tannins also have antioxidant and antimicrobial activities which approved their folk uses in treatments of infectious and Alzheimer diseases and simultaneously can be used as therapeutic agents in the pharmaceutical industries.

Single-walled carbon nanotubes-ciprofloxacin nanoantibiotic: strategy to improve ciprofloxacin antibacterial activity.

As infectious diseases continue to be one of the greatest health challenges worldwide, the demand toward alternative agents is continuously increasing. Recent advancement in nanotechnology has expanded our ability to design and construct nanomaterials to treat bacterial infections. Carbon nanotubes are one among these nanomaterials. Herein, we describe the covalent functionalization of the single-walled carbon nanotubes (SWCNTs) with multiple molecules of ciprofloxacin. The prepared nanoantibiotics were characterized using different techniques, including transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The characterization of the nanoantibiotics confirmed the successful covalent functionalization of the SWCNTs with 55% of functionalization as has been observed by thermogravimetric analysis. The release profile revealed that 90% of the loaded ciprofloxacin was released within 2.5 h at pH 7.4 showing a first-order release profile with R2>0.99. Interestingly, the results of the antibacterial activity indicated that the functionalized SWCNTs have significant increase in the antibacterial activity against the three strains of bacteria - by 16-fold for Staphylococcus aureus and Pseudomonas aeruginosa and by 8-fold for Escherichia coli - in comparison to the ciprofloxacin free drug. Moreover, the synthesized nanoantibiotic showed high hemocompatibility and cytocompatibility over a wide concentration range.

Macrolide and lincosamide resistance in staphylococcal clinical isolates in Nablus, Palestine.

BACKGROUND/AIM: Macrolide and lincosamide antibiotics are used for the treatment of staphylococcal infections, especially for penicillin-allergic patients. In the present study, we evaluate the prevalence of resistance to macrolide and lincosamide antibiotics among staphylococci isolates. MATERIALS AND METHODS: A total of 200 staphylococcal clinical isolates were collected from January 2012 to April 2013. Minimal inhibitory concentrations of erythromycin and clindamycin were determined by agar dilution method. An erythromycin-clindamycin induction test was performed for isolates that were only resistant to erythromycin. Representative erythromycin-resistant isolates were examined for erythromycin resistance genes using PCR. RESULTS: Among staphylococci isolates, resistance frequencies of erythromycin and clindamycin were 65.5% and 20.5%, respectively. Erythromycin resistance was found to be mediated by putative efflux (50.4%) and target site modification (49.6%). Inducible target site modification resistance was detected in 19.1% of erythromycin-resistant isolates. Among the examined 36 staphylococci isolates, msr(A), erm(C), erm(A), and mef(A/E) genes were detected in 55.6%, 30.6%, 25%, and 0%, respectively. CONCLUSION: Results of the current study indicate the presence of high rates of macrolide resistance and inducible phenotypes among staphylococcal isolates. It is also essential to keep in mind variations of resistance rates among various age groups and specimen types.