Monitoring of Bactericidal Effects of Silver Nanoparticles Based on Protein Signatures and VOC Emissions from Escherichia coli and Selected Salivary Bacteria

Silver Lactoferrin as Antimicrobials: Mechanisms of Action and Resistance Assessed by Bacterial Molecular Profiles

A diverse silver-lactoferrin (AgLTF) complex, comprising silver ions (Ag+) and silver nanoparticles, displayed a synergistic antibacterial effect while being almost five times more lethal than LTF alone. Gas chromatography-mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-in linear (LP) and reflectron (RP) positive modes-were used to comprehensively analyze metabolites and proteins profiles of bacteria (Staphylococcus aureus (SA), Pseudomonas aeruginosa (PA) and Enterococcus faecalis (EF)) treated using AgLTF complex versus exclusively Ag+. Although both agents resulted in similar metabolic shifts in bacteria, AgLTF significantly triggered the production of sulfides (related to bacterial stress resistance), ethanol, 2-butanol (indicating exhaustion of cell respiration), decanoic acid, and nonane (suggesting ongoing oxidative stress). Keto acids formation and fermentation pathways were enhanced by AgLTF and suppressed by Ag+. Furthermore, AgLTF appears to interact with proteins fraction of bacteria in a concentration-dependent manner. EF molecular profiles showed less changes between treated and untreated bacteria. On the other hand, SA and PA proteins and metabolic patterns were the most differentiated from untreated bacteria. In conclusion, our study may provide valuable insights regarding the molecular mechanisms involved in AgLTF antimicrobial action.

Retama monosperma chemical profile, green synthesis of silver nanoparticles, and antimicrobial potential: a study supported by network pharmacology and molecular docking

In this study, Retama monosperma extract (RME) was used for the green synthesis of silver nanoparticles (RME-AgNPs). RME's phenolic profile was identified by liquid chromatography coupled to mass spectroscopy (LC-ESI/MS/MS) technique. A tentative identification of 21 phenolic metabolites from the extract was performed. The produced RME-AgNPs showed UV absorbance at 443 nm. FTIR spectroscopy confirmed the presence of RME functional groups. In addition, XRD analysis confirmed the crystallography of RME-AgNPs via exhibiting peaks with 2θ values at 38.34°, 44.29°, and 64.65°. RME-AgNPs were spherical with particle sizes ranging from 9.87 to 21.16 nm, as determined by SEM and HR-TEM techniques. The zeta potential determined the particle's charge value as -15.25 mv. RME-AgNPs exhibited significantly higher antibacterial activity against Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, and Klebsiella pneumoniae) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) compared to RME. Moreover, the SEM images of green-synthesized nanoparticles revealed severe damage and deformation in the bacterial cell wall of the different strains subjected to the current investigation. The bioinformatics study identified 266 targets, among which only 41 targets were associated with bacterial infections. The PI3K-Akt and Relaxin signaling pathways were the top KEGG signaling pathways. Molecular docking was also performed for the 21 identified compounds at the TNF-α active site; kaempferol-3-O-robinoside-7-O-rhamnoside had a higher binding energy (-6.8084). The findings of this study warrant the use of green-synthesized AgNPs from Retama monosperma as potential antibacterial agents.

Volatile composition of the morning breath

We have measured the composition of volatile organic compounds (VOCs) in the morning breath of 30 healthy individuals before and after tooth brushing. The concentrations of VOCs in the breath samples were measured with proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and further identification was performed with a combination of solid phase microextraction (SPME) and offline gas chromatography-mass spectrometry (GC-MS). We hypothesize that compounds, whose concentrations significantly decreased in the breath after tooth brushing are largely of microbial origin. In this study, we found 35 such VOCs. Out of these, 33 have been previously connected to different oral niches, such as salivary and subgingival bacteria. We also compared the concentrations of the 35 VOCs found in increased amounts in the morning breath to their respective odor thresholds to evaluate their ability to cause odor. Compounds that could contribute to the breath odor include many volatile sulfur compounds, such as methanethiol, hydrogen sulfide, dimethyl sulfide, and 2-methyl-1-propanethiol, but also other VOCs, such as acetic acid, butyric acid, valeric acid, acetaldehyde, octanal, phenol, indole, ammonia, isoprene, and methyl methacrylate.

The membrane depolarization and increase intracellular calcium level produced by silver nanoclusters are responsible for bacterial death

This work highlights how our silver ultra nanoclusters (ARGIRIUM-SUNc) hand-made synthesized, are very useful as a bactericide and anti-biofilm agent. The Argirium-SUNc effective antibacterial concentrations are very low (< 1 ppm) as compared to the corresponding values reported in the literature. Different bacterial defense mechanisms are observed dependent on ARGIRIUM-SUNc concentrations. Biochemical investigations (volatilome) have been performed to understand the pathways involved in cell death. By using fluorescence techniques and cell viability measurements we show, for the first time, that membrane depolarization and calcium intracellular level are both primary events in bacteria death. The ARGIRIUM-SUNc determined eradication of different biofilm at a concentration as low as 0.6 ppm. This suggests that the effect of the nanoparticles follows a common mechanism in different bacteria. It is highly probable that the chemical constitution of the crosslinks could be a key target in the disrupting mechanism of our nanoparticles. Since the biofilms and their constituents are essential for bacterial survival in contact with humans, the silver nanoparticles represent a logical target for new antibacterial treatments.

Construction of multifunctional porcine acellular dermal matrix hydrogel blended with vancomycin for hemorrhage control, antibacterial action, and tissue repair in infected trauma wounds

Prevention of bacterial infection and reduction of hemorrhage, the primary challenges posed by trauma before hospitalization, are essential steps in prolonging the patient's life until they have been transported to a trauma center. Extracellular matrix (ECM) hydrogel is a promising biocompatible material for accelerating wound closure. However, due to the lack of antibacterial properties, this hydrogel is difficult to be applied to acute contaminated wounds. This study formulates an injectable dermal extracellular matrix hydrogel (porcine acellular dermal matrix (ADM)) as a scaffold for skin defect repair. The hydrogel combines vancomycin, an antimicrobial agent for inducing hemostasis, expediting antimicrobial activity, and promoting tissue repair. The hydrogel possesses a porous structure beneficial for the adsorption of vancomycin. The antimicrobial agent can be timely released from the hydrogel within an hour, which is less than the time taken by bacteria to infest an injury, with a cumulative release rate of approximately 80%, and thus enables a relatively fast bactericidal effect. The cytotoxicity investigation demonstrates the biocompatibility of the ADM hydrogel. Dynamic coagulation experiments reveal accelerated blood coagulation by the hydrogel. In vivo antibacterial and hemostatic experiments on a rat model indicate the healing of infected tissue and effective control of hemorrhaging by the hydrogel. Therefore, the vancomycin-loaded ADM hydrogel will be a viable biomaterial for controlling hemorrhage and preventing bacterial infections in trauma patients.

Metabolic Profiling of VOCs Emitted by Bacteria Isolated from Pressure Ulcers and Treated with Different Concentrations of Bio-AgNPs

Considering the advent of antibiotic resistance, the study of bacterial metabolic behavior stimulated by novel antimicrobial agents becomes a relevant tool to elucidate involved adaptive pathways. Profiling of volatile metabolites was performed to monitor alterations of bacterial metabolism induced by biosynthesized silver nanoparticles (bio-AgNPs). Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae and Proteus mirabilis were isolated from pressure ulcers, and their cultures were prepared in the presence/absence of bio-AgNPs at 12.5, 25 and 50 µg mL-1. Headspace solid phase microextraction associated to gas chromatography-mass spectrometry was the employed analytical platform. At the lower concentration level, the agent promoted positive modulation of products of fermentation routes and bioactive volatiles, indicating an attempt of bacteria to adapt to an ongoing suppression of cellular respiration. Augmented response of aldehydes and other possible products of lipid oxidative cleavage was noticed for increasing levels of bio-AgNPs. The greatest concentration of agent caused a reduction of 44 to 80% in the variety of compounds found in the control samples. Pathway analysis indicated overall inhibition of amino acids and fatty acids routes. The present assessment may provide a deeper understanding of molecular mechanisms of bio-AgNPs and how the metabolic response of bacteria is untangled.

Green Synthesis of Silver Nanoparticles Using Astragalus tribuloides Delile. Root Extract: Characterization, Antioxidant, Antibacterial, and Anti-Inflammatory Activities

Today, the green synthesis of metal nanoparticles is a promising strategy in material science and nanotechnology. In this research, silver nanoparticles (AgNPs) were synthesized through the high-efficient, cost-effective green and facile process, using the Astragalus tribuloides Delile. root extract as a bioreduction and capping agent at room temperature. UV-Vis spectroscopy was applied for the investigation of the reaction proceedings. To characterize the greenly synthesized AgNPs, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), and transmission electron microscopy (TEM) analyses were utilized. In addition, the total phenolics and flavonoids contents, antioxidant, antibacterial, and anti-inflammatory activities of the greenly synthesized AgNPs and the A. tribuloides root extract were evaluated. The results indicated that the AgNPs had spherical morphology and crystalline structure with the average size of 34.2 ± 8.0 nm. The total phenolics and flavonoids contents of the greenly synthesized AgNPs were lower than those for the A. tribuloides root extract. The resultant AgNPs exhibited the appropriate antioxidant activity (64%) as compared to that for the A. tribuloides root extract (47%). The antibacterial test approved the higher bactericidal activity of the resulting AgNPs on the Gram-positive and Gram-negative bacteria in comparison to the A. tribuloides root extract. Considering the anti-inflammatory activity, the greenly synthesized AgNPs showed a stranger effect than the A. tribuloides root extract (82% versus 69% at 500 μg/mL). Generally, the AgNPs that were fabricated by using the A. tribuloides root extract had appropriate antioxidant, antibacterial, and anti-inflammatory activities and, therefore, can be considered as a promising candidate for various biomedical applications.