Dosage- and time-dependent antibacterial effect of zinc oxide nanoparticles determined by a highly uniform SERS negating undesired spectral variation

Surface-Enhanced Raman Scattering (SERS) in Combination with PCA and PLS-DA for the Evaluation of Antibacterial Activity of 1-Isopentyl-3-pentyl-1H-imidazole-3-ium Bromide against Bacillus subtilis

In the current study, surface-enhanced Raman scattering (SERS) was performed to evaluate the antibacterial activity of lab-synthesized drug (1-isopentyl-3-pentyl-1H-imidazole-3-ium bromide salt) and commercial drug tinidazole againstBacillus subtilis. The changes in SERS spectral features were studied for unexposed bacillus and exposed one with various dosages of drug synthesized in the lab (1-isopentyl-3-pentyl-1H-imidazole-3-ium bromide salt), and SERS bands were assigned associated with the drug-induced biochemical alterations in bacteria. Multivariate data analysis tools including principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) have been utilized to analyze the antibacterial activity of the imidazole derivative (lab drug). PCA was employed in differentiating all the SERS spectral data sets associated with the various doses of the lab-synthesized drug. There is clear discrimination among the spectral data sets of a bacterial strain treated with different concentrations of the drug, which are analyzed by PLS-DA with 86% area under the curve in receiver operating curve (ROC), 99% sensitivity, 100% accuracy, and 98% specificity. Various dominant spectral features are observed with a gradual increase in the different concentrations of the applied drug including 715, 850, 1002, 1132, 1237, 1396, 1416, and 1453 cm-1, which indicate the possible biochemical changes caused in bacteria during the antibacterial activity of the lab-synthesized drug. Overall, the findings show that imidazole and imidazolium compounds generated from tinidazole with various alkyl lengths in the amide substitution can be effective antibacterial agents with low cytotoxicity in humans, and these results indicate the efficiency of SERS in pharmaceuticals and biomedical applications.

The CuO and AgO co-modified ZnO nanocomposites for promoting wound healing in Staphylococcus aureus infection

Bacterial has become a common pathogen of humans owing to their drug-resistant effects and evasion of the host immune system, with their ability to form biofilm and induce severe infections, a condition which has become a primary public health concern globally. Herein, we report on CuO@AgO/ZnO NPs antibacterial activity enhanced by near-infrared (NIR) light which was effective in the elimination of Staphylococcus aureus and the Pseudomonas aeruginosa. The CuO@AgO/ZnO NPs under NIR significantly eradicated S. aureus and its biofilm and P. aeruginosa in vitro, and subsequently exhibited such phenomenon in vivo, eliminating bacteria and healing wound. This demonstrated the combined intrinsic antibacterial potency of the Cu and Ag components of the CuO@AgO/ZnO NPs was enhanced tremendously to achieve such outcomes in vitro and in vivo. Considering the above advantages and facile preparation methods, the CuO@AgO/ZnO NPs synthesized in this work may prove as an important antibacterial agent in bacterial-related infection therapeutics and for biomedical-related purposes.

A ZIF-8-based multifunctional intelligent drug release system for chronic osteomyelitis

Chronic osteomyelitis (COM) is an inflammatory bone disease caused by bacterial infection. Conventional treatment with antibiotics is prone to resistance and other side effects, and it is ineffective against inflammation caused by infection and bone loss. To treat COM comprehensively, based on the acidic microenvironment of osteomyelitis, we used ZIF-8 and celecoxib to construct a multifunctional intelligent drug release system with pH response effect, named CEL@ZIF-8. Material characterization revealed that celecoxib is successfully loaded into ZIF-8. Ion release and drug release experiments indicated that CEL@ZIF-8 can respond well to the pH and intelligently control the release of ions and drugs. Antibacterial assays manifested that CEL@ZIF-8 is able to inhibit the growth of bacteria significantly. In vitro cell experiments demonstrated that CEL@ZIF-8 can significantly up-regulate the expression of osteogenesis-related cytokines and down-regulate the levels of inflammatory factors. Studies verify that the novel drug release system possesses multiple functions: antibacterial, osteogenesis, anti-inflammatory and intelligent release, suggesting a tremendous clinical promise for the treatment of COM.

Effective antimicrobial activity of ZnO and Yb-doped ZnO nanoparticles against Staphylococcus aureus and Escherichia coli

Nanostructured Zn_1-xYb_xO (0.0 ≤ x ≤ 0.1) powders were prepared by the solution method using polyvinyl alcohol (PVA) and sucrose. The effect of the ytterbium doping content on the structural, morphological, optical and antimicrobial properties was analyzed. X-ray diffraction (XRD) analysis revealed that the hexagonal wurtzite structure was retained, and no secondary phases due to doping were observed. The crystallite size was under 20 nm for all the Zn_1-xYb_xO (0.0 ≤ x ≤ 0.1) powders. The optical band gap was calculated, and the results revealed that this value increased with the ytterbium content, and the E_g values varied from 3.06 to 3.10 eV. The surface chemistry of the powders was analyzed using X-ray photoelectron spectroscopy (XPS), and the results confirmed the oxidation state of ytterbium as 3+ for all the samples. Zn_1-xYb_xO (0.0 ≤ x ≤ 0.1) nanoparticles were tested as antimicrobial agents against Staphylococcus aureus and Escherichia coli, resulting in a potential antimicrobial effect at most of the tested concentrations. These results were used in an artificial neural network (ANN). The results showed that it is possible to generate a model capable of forecasting the absorbance with good precision (error of 1-2%).

Stable Isotope-Labeled Single-Cell Raman Spectroscopy Revealing Function and Activity of Environmental Microbes

Microorganisms play a key role in driving the global element (C, N, H, P, and S) cycling. However, the function and activity of environmental microbes remain largely elusive because the vast majority of them are yet uncultured. Recent achievements in single cell stable isotope-labeled Raman spectroscopy enable direct investigation of function and activity of individual microbes in complex environmental communities. Here, this protocol describes a workflow to investigate environmental microbes in soil and water by combining ¹⁵N, ²D, and ¹³C stable isotope labeling with different single-cell Raman techniques, including normal Raman, resonance Raman (RR), and surface-enhanced Raman spectroscopy (SERS). Their applications in investigating functional bacteria driving the N and C cycles, and metabolically active cells are described.

Functional Single-Cell Approach to Probing Nitrogen-Fixing Bacteria in Soil Communities by Resonance Raman Spectroscopy with 15N2 Labeling

Nitrogen (N) fixation is the conversion of inert nitrogen gas (N₂) to bioavailable N essential for all forms of life. N₂-fixing microorganisms (diazotrophs), which play a key role in global N cycling, remain largely obscure because a large majority are uncultured. Direct probing of active diazotrophs in the environment is still a major challenge. Herein, a novel culture-independent single-cell approach combining resonance Raman (RR) spectroscopy with ¹⁵N₂ stable isotope probing (SIP) was developed to discern N₂-fixing bacteria in a complex soil community. Strong RR signals of cytochrome c (Cyt c, frequently present in diverse N₂-fixing bacteria), along with a marked ¹⁵N₂-induced Cyt c band shift, generated a highly distinguishable biomarker for N₂ fixation. ¹⁵N₂-induced shift was consistent well with ¹⁵N abundance in cell determined by isotope ratio mass spectroscopy. By applying this biomarker and Raman imaging, N₂-fixing bacteria in both artificial and complex soil communities were discerned and imaged at the single-cell level. The linear band shift of Cyt c versus ¹⁵N₂ percentage allowed quantification of N₂ fixation extent of diverse soil bacteria. This single-cell approach will advance the exploration of hitherto uncultured diazotrophs in diverse ecosystems.