Bacterial Cell Membrane Damage Research Articles

Nonphytotoxic and pH-responsive ZnO-ZIF‑8 loaded with honokiol as a “nanoweapon” effectively controls the soil-borne bacterial pathogen Ralstonia solanacearum

The development of intelligently released and environmentally safe nanocarriers not only aligns with the sustainable agricultural strategy but also offers a potential solution for controlling severe soil-borne bacterial diseases. Herein, the core-shell structured nanocarrier loaded with honokiol bactericide (honokiol@ZnO-ZIF-8) was synthesized via a one-pot method for the targeted control of Ralstonia solanacearum, the causative agent of tobacco bacterial wilt disease. Results indicated that honokiol@ZnO-ZIF-8 nanoparticles induced bacterial cell membrane and DNA damage through the production of excessive reactive oxygen species (ROS), thereby reducing bacterial cell viability and ultimately leading to bacterial death. Additionally, the dissociation mechanism of the nanocarriers was elucidated for the first time through thermodynamic computational simulation. The nanocarriers dissociate primarily due to H+ attacking the N atom on imidazole, causing the rupture of the Zn-N bond under acidic conditions and at room temperature. Furthermore, honokiol@ZnO-ZIF-8 exhibited potent inhibitory effects against other prominent Solanaceae pathogenic bacteria (Pseudomonas syringae pv. tabaci), demonstrating its broad-spectrum antibacterial activity. Biosafety assessment results indicated that honokiol@ZnO-ZIF-8 exhibited non-phytotoxicity towards tobacco and tomato plants, with its predominant accumulation in the roots and no translocation to aboveground tissues within a short period. This study provides potential application value for the intelligent release of green pesticides. Environment implicationThe indiscriminate use of agrochemicals poses a significant threat to environmental, ecological security, and sustainable development. Slow-release pesticides offer a green and durable strategy for crop disease control. In this study, we developed a non-phytotoxic and pH-responsive honokiol@ZnO-ZIF-8 nano-bactericide based on the pathogenesis of Ralstonia solanacearum. Thermodynamic simulation revealed the dissociation mechanism of ZIF-8, with different acidity controlling the dissociation rate. This provides a theoretical basis for on-demand pesticide release while reducing residue in the. Our findings provide strong evidence for effective soil-borne bacterial disease control and on-demand pesticide release.

A trinuclear Zn (II) schiff base dicyanamide complex attenuates bacterial biofilm formation by ROS generation and membrane damage and exhibits anticancer activity

A trinuclear Zn (II) complex, [(ZnL{N(CN)2})2Zn], termed complex 1 has been synthesized by the reaction of an aqueous solution of sodium dicyanamide to the methanolic solution of Zn (CH3COO)2, 2H2O and corresponding Schiff base (H2L) which is derived from 1:2 condensation of 1, 4 butane diamine with 3-ethoxy salicylaldehyde. Complex 1 is characterized by elemental analysis, IR, UV and Single X-ray diffraction study. Drug resistance is a growing global public health concern that has prompted researchers to look into advanced alternative treatment modalities. In this context, complex 1 has shown promising antibacterial and antibiofilm efficacy against gram-positive Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus strains. Complex 1 attenuated Staphylococcal biofilm formation by reducing several virulence factors including the formation of extracellular polysaccharide matrix, slime, haemolysin, staphyloxanthin, auto-aggregation, cell surface hydrophobicity, and motility. Notably, complex 1 mechanistically potentiated Reactive Oxygen Species (ROS) generation within the bacterial cells, leading to the damage of bacterial cell membrane followed by DNA leakage and thereby impeding the growth of Staphylococcus aureus. Furthermore, complex 1 significantly exhibited anticancer activity by reducing the growth of prostate adenocarcinoma cells. It obstructed the migration of cancer cells by potentiating apoptosis and arresting the cell cycle at the G2/M phase. In summary, complex 1 could act as a potent candidate for the generation of novel antibacterial, antibiofilm as well as anticancer treatment regimens for the management of drug-resistant biofilm-mediated Staphylococcus aureus infection and lethal prostate malignancy.

A mononuclear N,N,N,O donor schiff base Cu(II) complex inhibits bacterial biofilm formation and promotes apoptosis and cell cycle arrest in prostate cancer cells

In this work, we report a distorted square pyramidal mononuclear copper(II) complex [Cu(L)(NCS)] (1) which was obtained by the reaction of the aqueous solution of ammonium thiocyanate to a methanolic solution of copper nitrate trihydrate and corresponding Schiff-base ligands. Schiff bases, HL (C12H19N3O) act as a tetradentate Schiff base, derived from 1:1 condensation of o-hydroxyacetophenone and diethylenetriamine. The synthesized complex has been successfully characterized based on elemental analysis and Infrared (IR) spectroscopy. The structure of complex 1 was confirmed by single-crystal X-ray diffraction study. In our study, we investigated synthesis, structural characterization, antimicrobial, anti-biofilm, and anti-cancer activity, and plausible mechanism of action of a novel mononuclear copper(II) schiff base complex. Increasing microbial resistance to several commercially available or traditional antimicrobial compounds has become a major global health concern at present time. The mononuclear copper(II) complex exhibited potential antibacterial activity against two strains of the gram-negative pathogen Pseudomonas aeruginosa. The copper compound dependent damage of bacterial cell membrane and inhibition of bacterial biofilm formation were also identified. Moreover, complex 1 inhibited prostate cancer cell growth, and migration by inducing apoptosis and arresting the cell cycle at the G2/M phase. Based on the results, we are suggesting our novel mononuclear copper(II) compound as a potential candidate for the development of new antibacterial and anti-cancer drugs.

A unique C-type lectin, Ladderlectin, from large yellow croaker (Larimichthys crocea) is involved in bacterial cell membrane damage

Ladderlectin is unique C-type lectin because it has been so far found only in teleost fish. In this study, large yellow croaker (Larimichthys crocea) Ladderlecin (LcLL) sequence was identified and characterized. LcLL encodes a polypeptide of 186 amino acids that includes a signal peptide and a C-type lectin-like domains (CTLD) with two sugar-binding motifs of WSD and EPN. Tissues distribution analysis revealed that LcLL is a ubiquitous gene, with the highest expression in head kidney and gill. Subcellular localization showed that LcLL was in cytoplasm and nucleus of HEK 293T cells. Transcripts of LcLL were significantly up regulated after immune challenge with P. plecoglossicida. In contrast to this, a sharp down-regulation occurred after Scuticociliatida infection. Moreover, recombinant LcLL (rLcLL) was prepared and exhibited hemagglutination on L. crocea and N. albiflora erythrocytes in a Ca2+-dependent manner, which can be only inhibited by LPS. rLcLL showed a strong ability of binding to Gram + bacteria (M. lysodeikticus, S. aureus, B. subtilis) and Gram-bacteria (P. plecoglossicida, E. coli, V. Vulnificus, V. harveyi, V. alginolyticus, V. parahaemolyticus. A. hydrophila, and E. tarda), and could agglutinate all tested bacteria except for P. plecoglossicida. Further study showed that rLcLL promoted the gathered bacteria death through damaging cell membrane based on PI staining and SEM observation. However, rLcLL does neither kill bacteria directly nor have complement-activating activities. Altogether, these results demonstrated that LcLL played a vital role in L. crocea innate immune towards bacterial and parasitic challenge.

Antibacterial effects of peracetic acid disinfection assessed by culturability, enzyme activity and flow cytometry

Aquaculture water disinfection with around 1 mg/L peracetic acid (PAA) was proved in various studies to effectively impair microbial proliferation and reduce pathogen-caused fish mortality. In the present study, we monitored the antibacterial effect of biweekly water disinfection with 1 mg/L PAA at a local flow-through fish farm for 8 weeks. Results from replicate water samples showed inconsistency of antibacterial efficacy assessed with colony forming units (CFU) of total culturable bacteria and a commercial enzyme activity assay. Single PAA disinfection caused up to 90% reduction of CFU in water. In contrast, the microbial hydrolase activity was hardly affected or even enhanced. Both methods have limitations and can't truly represent viable bacteria. We further monitored the temporal response of two Yersinia ruckeri isolates in suspensions to single PAA disinfection via high-throughput flow cytometry. We found out that the bacterial cell membrane damage appeared not instantly but with a lag phase of at least 2 h post disinfection at 4 °C. The abundance of cell membrane damage, considered as cumulative bacterial mortality, kept rising and maximized at 48 h post disinfection. The survived cells were more likely to enter the viable but non-culturable (VBNC) state at higher PAA concentrations. One isolate was more prone to enter the VBNC state than the other. Neither Y. ruckeri isolate showed measurable reaction with the enzyme substrate of the commercial microbial hydrolase activity assay. Our findings refresh knowledge about the dynamics of bacterial cell mortality post PAA disinfection (probably also similar non-thermal disinfection methods). Aquaculture practice should be aware of the delayed disinfection outcomes and pay attention to the dominance of VBNC state.

Antibiotic resistance bacteria and antibiotic resistance genes survived from the extremely acidity posing a risk on intestinal bacteria in an in vitro digestion model by horizontal gene transfer

Antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) are emerging contaminants posing risk to human health. To investigate the pathogenic ARBs and the horizontal gene transfer (HGT) via both extracellular ARGs (eARGs) and intracellular ARGs (iARGs), an in vitro digestion simulation system was established to monitoring the ARB and ARGs passing through the artificial digestive tract. The results showed that ARB was mostly affected by the acidity of the gastric fluid with about 99% ARB (total population of 2.45 × 109–2.54 × 109) killed at pH 2.0 and severe damage of bacterial cell membrane. However, more than 80% ARB (total population of 2.71 × 109–3.90 × 109) survived the challenge when the pH of the gastric fluid was 3.0 and above. Most ARB died from the high acidity, but its ARGs, intI1 and 16 S rRNA could be detected. The eARGs (accounting for 0.03–24.56% of total genes) were less than iARGs obviously. The eARGs showed greater HGT potential than that of iARGs, suggesting that transformation occurred more easily than conjugation. The transferring potential followed: tet (100%) > sul (75%) > bla (58%), related to the high correlation of intI1 with tetA and sul2 (p < 0.01). Moreover, gastric juice of pH 1.0 could decrease the transfer frequency of ARGs by 2–3 order of magnitude compared to the control, but still posing potential risks to human health. Under the treatment of digestive fluid, ARGs showed high gene horizontal transfer potential, suggesting that food-borne ARBs pose a great risk of horizontal transfer of ARGs to intestinal bacteria.

Copper functionalized poly (acrylic acid-co-itaconic acid) nanohydrogel: Its antibacterial properties on oral pathogens and biocompatibility

Although extensive efforts have been made to explore effective antibiotics, the development of antibiotics lags far behind the emergence of drug-resistant bacteria. Antimicrobial materials as an alternative strategy provide effective functions in aiding in relieving the dose of antibiotics. Herein, we report a novel antibacterial agent with high antibacterial effectivity and low toxicity, which is simply composed of a trace amount of Cu2+ ion and nanoscale biocompatible polymer poly (acrylic acid-co-itaconic acid) (PAI-Cu). The polymer shows greatly enhanced antibacterial activity against various Gram-positive and Gram-negative pathogens compared with equal concentrations of copper ion solution, yet shows nearly no toxicity towards human cells. The antibacterial performance and mechanism of copper ionized polymer hydrogel are evaluated in terms of multiple methods, towards various oral bacteria including Streptococcus mutans, Enterococcus faecalis, Lactobacillus acidophilus, Actinomycetes viscosus, Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia. Bacterial cell membrane and wall damage caused by PAI-Cu nanohydrogel should be regarded as an important antibacterial mechanism. Moreover, PAI-Cu nanohydrogel, as the role of catalytic active center, can activate the surrounding oxygen, and generate hydroxyl radical (·OH), which can destroy the proliferation ability of microbial cells. We suggest that PAI-Cu nanohydrogel is a promising antibacterial agent against dental pathogens and beyond.

Blue Light Enhances Fluoride Anticariogenic Activity against Streptococcus mutans

Previous studies have shown that sub-lethal exposure of blue light caused increased bacterial cell membrane permeability. We hypothesized that combining blue light exposure with other antibacterial agents may increase their efficacy. The aim of the present study was to test the combined effect of blue light and sodium fluoride against dental caries pathogen Streptococcus mutans. Sm biofilms were exposed to blue light (400–500 nm) with or without sodium fluoride. Exposed and non-exposed samples were studied for acid production (lactate assay kit), acid tolerance (ATPase assay kit) and bacterial cell membrane damage (fluorescence microscopy). Results showed that the combined treatment significantly reduced the virulence of Sm concomitant with an increase in bacterial cell membrane permeability. Taken together, these results suggest that adjacent blue light exposure may increase fluoride caries preventive properties.

Which UV wavelength is the most effective for chlorine-resistant bacteria in terms of the impact of activity, cell membrane and DNA?

The widespread use of chlorine disinfectants in drinking water has accelerated the selection of chlorine-resistant bacteria (CRB). The presence of CRB in drinking water (during treatment, distribution, and consumption) has a profound impact on public safety. Ultraviolet (UV) irradiation is an effective control technology for CRB. Nevertheless, the relative efficacies of different UV light wavelengths (traditional mercury lamps, ultraviolet light-emitting diodes (UV-LED 265 nm and 285 nm), and 222 nm krypton-chlorine excilamps) in the control and inactivation of various CRB have not been investigated. In this study, the impacts of different UV light sources on the inactivation rate and microbial cell structure of CRB were evaluated. The results showed that the order of inactivation efficacy was as follows: UV-LED 265 nm > low-pressure ultraviolet (LPUV) ≈ medium-pressure ultraviolet (MPUV) ≈ 222 nm > UV-LED 285 nm. CRB was inactivated via DNA damage and additional ATP decline under UV-LED 265 nm, UV-LED 285 nm and LPUV irradiation, of which UV-LED 265 nm was the most effective based on fluence and inactivation rate constants. The inactivation mechanisms revealed that the 222 nm wavelength was significantly different from other wavelengths; it stimulated the production of a large number of reactive oxygen species (ROS) which resulted in bacterial cell membrane damage, ATP direct decline, and a small number of DNA lesions. Multispectral MPUV induced both of the foregoing mechanisms but mainly damaged DNA. The present study provides empirical evidence for the reasonable application of UV disinfection technology in the treatment of water and wastewater and their conduits and delivery systems.

Pyridine coupled pyrazole analogues as lethal weapon against MRSA: An in-vitro and in-silico approach

The treatment of Methicillin-resistant staphylococcus aureus (MRSA) infections has become challenging due to the growth of multidrug resistance in the bacteria. Here we report the synthesis of pyridine-coupled pyrazoles as an antimicrobial agent against MRSA. A series of pyridine coupled pyrazoles were synthesized and synthesized compounds were characterized using FT-IR, 1H NMR, and Mass spectroscopy. The ADMET results of all the 14 active compounds are interpreted. To identify the potent compound the synthesized compounds screened for minimum inhibitory concentrations against MRSA and compared with standard drug vancomycin. Among the synthesized compounds 6d exhibited good antibacterial activity with MIC value 21 μg/mL, bacterial cell membrane damage study was studied potassium efflux, and cellular content leakage assay. Anticoagulant study for the potent compound also studied and validated by molecular docking and molecular dynamics simulation studies. The docking study of the synthesized compound was carried out and the study depicted that the pyridine ring of all the analogues binds with the various amino acids in the binding pocket of the active site of the Staphylocoagulase and PBP2a protein of MRSA.

Intensified inactivation efficacy of pulsed ohmic heating for pathogens in soybean milk due to sodium lactate

Pulsed ohmic heating (POH) is a promising alternative to conventional heat processing for microbial safety. It has been reported that the efficacy of POH depends on the concentration of electrolytes. This research investigated the effect of sodium lactate as an electrolyte on the efficacy of POH with respect to the heating rate and inactivation of pathogens in PBS and soybean milk. When PBS and soybean milk with 0–3% sodium lactate were subjected to POH, as the sodium lactate content increased, the electrical conductivity increased, thereby accelerating the heating rate of POH. For instance, the heating rate of POH was 0.3 and 1.3°C/s for 0 and 3% of sodium lactate in soybean milk. Reductions in pathogens increased as the sodium lactate content increased. When 3% of sodium lactate was added to PBS or soybean milk, the bacterial reduction was more than 1 log unit compared to 0%. We hypothesized that sodium lactate intensified the damage to bacterial membrane by accelerating the heating rate of POH and amplifying the electric current; thus, the extent of bacterial cell membrane damage was determined using propidium iodide (PI) and transmission electron microscopy (TEM). The PI uptake values of pathogens significantly (P < 0.05) increased as the sodium lactate content increased, indicating that the membrane damage increased in proportion to the sodium lactate content. Furthermore, the analysis of TEM images of Escherichia coli O157:H7 and Listeria monocytogenes showed fatal morphological cell rupture at 3% sodium lactate. After soybean milk with 0–3% sodium lactate was treated with POH, no electrode corrosion was observed, and pH and color of samples were not changed. Thus, this research corroborated that sodium lactate intensifies the efficacy of POH without electrode corrosion and quality degradation of soybean milk.

Inhibitory activities of propolis, nisin, melittin and essential oil compounds on Paenibacillus alvei and Bacillus subtilis.

BackgroundNatural products represent important sources of antimicrobial compounds. Propolis and compounds from essential oils comprise good examples of such substances because of their inhibitory effects on bacterial spores, including bee pathogens.MethodsEthanol extracts of propolis (EEP) from Apis mellifera were prepared using different methods: double ultrasonication, double maceration and maceration associated with ultrasonication. Together with the antimicrobial peptides nisin and melittin, and compounds present in the essential oils of clove (Syzygium aromaticum) and cinnamon (Cinnamomum zeylanicum), assays were carried out on one Bacillus subtilis isolate and Paenibacillus alvei (ATCC 6344) against vegetative and sporulated forms, using the resazurin microtiter assay. Synergism with all the antimicrobials in association with tetracycline was verified by the time-kill curve method. Potassium and phosphate efflux, release of proteins and nucleic acids were investigated.ResultsEEPs showed the same MIC, 156.25 µg/mL against B. subtilis and 78.12 µg/mL against P. alvei. The peptides showed better activities against B. subtilis (MIC of 12 µg/mL for melittin and 37.50 µg/mL for nisin). Antimicrobials showed similar inhibitory effects, but cinnamaldehyde (39.06 µg/mL) showed the best action against P. alvei. Melittin and nisin showed the greatest capacity to reduce spores, regarding B. subtilis there was a 100% reduction at 6.25 and 0.78 µg/mL, respectively. Concerning P. alvei, the reduction was 93 and 98% at concentrations of 80 µg/mL of melittin and 15 µg/mL of nisin. EEPs showed the highest effects on the protein release against B. subtilis and P. alvei. Nucleic acid release, phosphate and potassium efflux assays indicated bacterial cell membrane damage. Synergism between antimicrobials and tetracycline was demonstrated against both bacteria.ConclusionAll antimicrobials tested showed antibacterial activities against vegetative and sporulated forms of P. alvei and B. subtilis, especially nisin and melittin. Synergism with tetracycline and damage on bacterial cell membrane also occurred.

Quercetin Rejuvenates Sensitization of Colistin-Resistant Escherichia coli and Klebsiella Pneumoniae Clinical Isolates to Colistin.

Colistin is being considered as “the last ditch” treatment in many infections caused by Gram-negative stains. However, colistin is becoming increasingly invalid in treating patients who are infected with colistin-resistant Escherichia coli (E. coli) and Klebsiella Pneumoniae (K. pneumoniae). To cope with the continuous emergence of colistin resistance, the development of new drugs and therapies is highly imminent. Herein, in this work, we surprisingly found that the combination of quercetin with colistin could efficiently and synergistically eradicate the colistin-resistant E. coli and K. pneumoniae, as confirmed by the synergy checkboard and time-kill assay. Mechanismly, the treatment of quercetin combined with colistin could significantly downregulate the expression of mcr-1 and mgrB that are responsible for colistin-resistance, synergistically enhancing the bacterial cell membrane damage efficacy of colistin. The colistin/quercetin combination was notably efficient in eradicating the colistin-resistant E. coli and K. pneumoniae both in vitro and in vivo. Therefore, our results may provide an efficient alternative pathway against colistin-resistant E. coli and K. pneumoniae infections.

Antibacterial mechanism of Brevinin-2GHk, an antimicrobial peptide from Fejervarya limnocharis skin

To investigate the secondary structure, physicochemical properties and antibacterial activity of Brevinin- 2GHk (BR2GK), an antimicrobial peptide from frog skin, and explore its antibacterial mechanism. BR2GK was synthesized, purified with high performance liquid chromatography (HPLC) and identified using mass spectrometry. Circular dichroism was used to determine the secondary structure and physicochemical properties of BR2GK. Two-fold dilution method was used to determine the antibacterial activity of BR2GK, and its antibacterial mechanism was explored using laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). The hemolytic activity of BR2GK was analyzed in red blood cells. Isothermal titration calorimetry (ITC) and surface plasmon resonance imaging (SPRi) were employed to detect the binding of BR2GK to lipopolysaccharide (LPS), and the antioxidant activity of BR2GK was evaluated using biochemical kits. The synthesized BR2GK, with a purity exceeding 95% after purification, had the basic characteristics of cationic antimicrobial peptides. BR2GK consisted mainly of α-helical structure in SDS solution and exhibited a broad-spectrum antibacterial activity. Antibacterial activity assay showed that BR2GK had inhibitory and killing activity against a variety of strains with a minimum inhibitory concentration (MIC) of 2.76 μmol/L against Staphylococcus aureus. Observation with LSCM and SEM showed that BR2GK at an active concentration caused bacterial cell membrane damage, cell swelling, contraction, deformation, and massive exudation of intracellular contents without causing hemolysis. ITC showed that the binding affinity KD of BR2GK to LPS was 18.2±0.8 μmol/L. The antioxidant test showed that BR2GK was capable of effectively scavenging NO, ABTS and DPPH. BR2GK, as a broad-spectrum antibacterial peptide with also a strong antioxidant capacity, does not cause hemolysis and is capable of binding to LPS. BR2GK has an important value for future design and synthesis of antimicrobial peptides with stronger antibacterial activity and lower cytotoxicity.

Synergistic interaction of tap water-based neutral electrolyzed water combined with UVA irradiation to enhance microbial inactivation on stainless steel

As an emerging electrolyzed water (EW) technology, tap water-based neutral electrolyzed water (TNEW) is an attractive alternative to other types of conventional EW for sterilization of food contact surfaces. In this study, we sought to identify strategies for improving TNEW inactivation efficiencies of major foodborne pathogenic bacteria. We investigated the synergistic antimicrobial effect of TNEW and ultraviolet-A light (UVA) combination treatment against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on stainless steel. The data confirmed that simultaneous TNEW and UVA treatment for 60 min reduced E. coli O157:H7, S. Typhimurium, and L. monocytogenes population by 2.15, 1.55, and 2.65 log CFU/cm2, respectively. The synergistic cell count reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes in the combination treatment group were 1.17, 0.59, and 1.62 log units, respectively. Additionally, the mechanisms of the synergistic bactericidal effects of TNEW and UVA were identified through several approaches. Mechanistic investigations suggested that the synergistic effect was associated with intracellular reactive oxygen species generation, bacterial cell membrane damage, and inactivation of dehydrogenase. These findings demonstrate that treatment with TNEW and UVA light can enhance the microbiological safety of food contact surfaces during food processing.

Effect of Silver Nanoparticles on Blue Light Phototoxicity against Fusobacterium nucleatum

A previous study showed that sub-lethal exposure of blue light caused cell membrane damage in Fusobacterium nucleatum (Fn). The aim of the present study was to test the combined effect of blue light and silver nanoparticles against Fn. Bacterial suspensions were exposed to blue light (400–500 nm) with or without silver nanoparticles (10 nm). Exposed and non-exposed samples were studied for malodor production (Odor judge scores), VSC levels (Halimeter), reactive oxygen species (ROS) production (fluorimeter), and bacterial cell membrane damage (fluorescence microscopy). The results showed that combining blue light exposure and silver nanoparticles significantly reduced malodor and VSC production by Fn concomitant with increased ROS levels and bacterial cell membrane damage. These results suggest that silver nanoparticles may increase blue light phototoxicity against Fn.

Novel biosynthesis, characterization and bio-catalytic potential of green algae (Spirogyra hyalina) mediated silver nanomaterials

In recent years green nanotechnology gained significant importance to synthesize nanoparticles due to their cost effectiveness and biosafety. In the current study, silver nanoparticles were synthesized by using extract of Spirogyra hyalina as a capping and reducing agent. The synthesized nanoparticles were characterized by UV–Visible spectroscopy, Fourier transform infrared spectroscopy, Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractive analysis. Silver nanoparticles give a characteristic Surface Plasmon Resonance peak of 451 nm at 2.21 a.u (arbitrary unit). SEM micrograph revealed the spherical morphology and average grain size of 52.7 nm. Furthermore, antibacterial, antifungal, insecticidal, antioxidant and membrane damage activities were determined. The maximum antibacterial and antifungal activity was observed for Pseudomonas aeruginosa (18 ± 1.2 mm) and Fusarium solani (14.3 ± 0.6 mm), respectively. In membrane damage assay, Pseudomonas aeruginosa absorbed A260 wavelength and gave maximum peak values of 0.286, 0.434 and 0.629 at 25, 35 and 45 µg/mL of silver nanoparticles. The membrane damage assay confirmed that nanoparticles are involved in bacterial cell membrane damage. At 500 ppm silver nanoparticles showed 30% mortality against Tribolium castaneum (a common grain pest). The silver nanoparticles also showed potent antioxidant activity and successfully scavenged the DPPH free radicals upto 53.43 ± 0.17, 43.26 ± 0.97, 31.39 ± 0.33, 24.62 ± 0.85, and 14.13 ± 0.12% at a concentration of 400, 200, 100, 50, and 25 µg/mL of nanoparticles, respectively. It is concluded that silver nanoparticles can easily be synthesized by using green algae Spirogyra hyalina as a capping and reducing agent. Silver nanoparticles showed potent biomedical activities and thus can be used for therapeutic applications invitro and invivo.

Infection microenvironment-activated nanoparticles for NIR-II photoacoustic imaging-guided photothermal/chemodynamic synergistic anti-infective therapy

Subcutaneous abscesses caused by drug-resistant bacteria pose huge challenges to human health. The design of infection microenvironment-activated biomaterials has an advantage for the diagnosis and treatment of infective diseases due to its high specificity and efficiency. Herein, a novel theranostic platform based on Cu2O nanoparticles (NPs) is successfully constructed via a simple, fast and low-cost approach. The Cu2O NPs exhibit high sensitivity to overexpressed H2S and H2O2 in the bacterial infection microenvironment. After in situ injection, the Cu2O NPs will rapidly react with the endogenous H2S to generate Cu9S8 NPs, which exhibits high absorbance in the second near-infrared (NIR-II) biowindow. The Cu9S8 NPs serving as NIR-II photoacoustic contrast agents can exactly distinguish between inflammatory and normal tissues. With the guidance of NIR-II photoacoustic imaging (PAI), H2S-activated photothermal antibacterial therapy (PTAT) can realize excellent antibacterial performance under 1060 nm laser irradiation. Meanwhile, the Cu2O NPs can effectively catalyze H2O2 at the site of inflammation to produce hydroxyl radicals with strong antibacterial property via Fenton-like reaction, resulting in the damage of bacterial cell membrane. Furthermore, the application of Cu2O NPs can enhance epidermic migration and facilitate the re-epithelialization of the infected skin. In vivo experiment shows that 97.9% methicillin-resistant Staphylococcus aureus are eliminated by the synergistic PTAT and chemodynamic antibacterial therapy.

Modification of ZnO nanoparticles with silanes enables their application as anticancer agents

Introduction Nanoparticles (NPs) are a wide class of materials that include particulate substances sized less than 100 nm. Inorganic ZnO NPs have found applications in several industrial fields such as the optical, electronic, pharmaceutical and cosmetics [1]. However, in many specific fields the applications are limited, since the particles tend to aggregate/agglomerate due to the hydrophilic nature of the surface. For potential clinical applications, surface modification of ZnO plays a crucial role in the biocompatibility of ZnO NPs [2]. Using organosilane modifying agents, improved hydrophobicity of the resulting ZnO NPs, induced by the non-polar terminal groups, can be achieved, and thus, very small and highly dispersed particles can be obtained. ZnO silanes were found to have antibacterial activity against several pathogens [3]. The NP size highly influenced the antibacterial activity, which increase with decreasing size. The ZnO NPs may induce bacterial cell membrane damage, resulting in bacterial cell death. Motivated by these findings and others reporting anticancer activity for pristine ZnO NPs [4], the aim of this study was to investigate the anticancer activity and mechanism of cell death of silane-modified ZnO nanoparticles against A2780 ovarian cancer cells and evaluate if for the cancer cells a correlation between size and activity was also observed. Materials and Mmethods The silane modified ZnO NPs were prepared by the addition of (3-glycidyloxypropyl) trimethoxysilane (GPTMS) as a surface modifier at 0% (G0) and 10% (G3) molar ratio of Si/Zn. The obtained NPs were characterised by high resolution transmission electron microscopy (HRTEM), X-ray diffraction and UV-Vis spectrometry. The cytotoxic activity in ovarian cancer cells were assessed by the MTT colorimetric assay. The morphological cellular alterations were visualised by electron microscopy (TEM). Results The silane modified ZnO NPs exhibited significant cytotoxic activity against A2780 ovarian cancer cells. The NP size, ca. 13 nm for G0 and ca. 3 nm for G3, highly influenced the cytotoxic activity, which increased with decreasing particle size, IC50: ∼100 µg/mL(G0) and ∼30 µg/mL(G3). The ZnO silanes affected the cellular integrity by the induction of organelle damage evidenced by TEM. Discussion and conclusions Although preliminary, results indicate that ZnO silanes are interesting platforms to explore as anticancer agents. Studies on the ultrastructural level (TEM/SEM) are needed to understand their cytotoxic mechanism and to give clues on their potential targets.

Synergistic effect of citric acid and xenon light for inactivating foodborne pathogens on spinach leaves

The aim of this study was to evaluate the synergistic antimicrobial effect of xenon light (XL) and citric acid (CA) combination against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on spinach leaves and determine the effect of XL-CA combination on quality of spinach leaves. The XL-CA combined treatment for 8 min synergistically decreased the cell counts of E. coli O157:H7 and S. Typhimurium by 5.25 and 5.05 log CFU/cm2, respectively, and additively decreased the L. monocytogenes cells by 5.02 log unit on spinach. The mechanisms underlying synergistic lethal effect of the XL-CA combination were investigated. Qualitative and quantitative analyses revealed that the bacterial cell membrane damage was strongly associated with the synergistic antimicrobial effect of the XL-CA combination. Additionally, treatment with XL-CA combination for 8 min did not affect the quality attributes (color, total phenol contents, and texture) of spinach leaves. These results suggest that the XL-CA combination treatment can be effectively used to control major pathogens on fresh produce.