Synergetic Antibacterial Activity Research Articles

NIR-triggered bacterial cellulose-based wound dressings for multiple synergistic therapy of infected wound

Skin wounds are repaired by a complex series of events and overlapping phases in which bacterial infection and insufficient angiogenesis at the wound site delay the healing process. Thus, functional wound dressings with enhanced antibacterial activity and angiogenic capacity have attracted attention. Herein, bacterial cellulose (BC)-based dressings were successfully fabricated by functionalization with a polydopamine (PDA) coating and copper sulfide nanoparticles (CuS NPs). Under 808 nm laser illumination, the BC/PDA/CuS composite membranes exhibited outstanding adjustable photothermal and photodynamic activities as well as controlled Cu2+ release, endowing the composite membranes with synergetic antibacterial activity. Specially, a bactericidal efficiency of 99.7 % and 88.0 % for Staphylococcus aureus and Escherichia coli was achieved after treatment with BC/PDA/CuS5 sample under NIR irradiation (0.8 W/cm2, 10 min), respectively. Moreover, the BC/PDA/CuS5 composite membrane could enhance the angiogenesis due to the released Cu2+. In vivo experiments revealed that the BC/PDA/CuS5 composite membrane dressing could accelerate the wound closure process of the full-thickness skin defects with S. aureus by synergistically reducing inflammation, enhancing collagen deposition, and promoting vascularization under NIR irradiation. Additionally, the BC/PDA/CuS5 composite membrane exhibited high biocompatibility and biosafety. This work offers a new strategy to prepare multifunctional BC-based dressing for clinical wound healing.

Antiparasitic nitazoxanide potentiates colistin against colistin-resistant Acinetobacter baumannii and Escherichia coli in vitro and in vivo.

Colistin is used as a last resort in many infections caused by multidrug-resistant Gram-negative bacteria; however, colistin-resistant (COL-R) is on the rise. Hence, it is critical to develop new antimicrobial strategies to overcome COL-R. We found that nitazoxanide (NTZ) combined with colistin showed notable synergetic antibacterial activity. These findings suggest that the NTZ/colistin combination may provide an effective alternative route to combat COL-R A. baumannii and COL-R Escherichia coli infections.

Polypyrrole hydrogel with near-infrared light-driven nitric oxide release and photothermal activities for rapid synergistic sterilization and infected wound therapy

Developing low-cost and easy-accessible phototherapy agents with a high sterilization efficiency is urgently needed tackling the increasingly dangerous of bacterial infections. Herein, a broad-spectrum antimicrobial agent (i.e., PP-Mo-NO) with near-infrared laser (NIR) driven nitric oxide (NO) release capacity derived from the assemble of a heat-sensitive NO donor (N, N′-di-sec-butyl-N, N′-dinitroso-1, 4-phenylenediamine, BNN6) with freeze-dried three-dimensional polypyrrole hydrogel crosslinked by the sulfonated dimolybdenum-salen (PP-Mo), was synthesized for the rapid and effective eradicating of Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Upon 808 nm laser irradiation, PP-Mo-NO showed not only superb photothermal efficacy (79.88 %), but also precisely controllable NO release capacity, generating oxidative/nitrosative stress. Within 10 mins of irradiation (1.0 W cm−2), PP-Mo-NO with co-amplified photothermal (PTT)/NO synergetic antibacterial activity presented sterilization rates beyond 99.1% against both the E. coli and S. aureus at a relatively low concentration (100 µg mL−1). Meanwhile, in vivo experiments demonstrated the great application potential of PP-Mo-NO which could effectively kill bacteria at the site of infection, and repair the open infectious wounds, thereby accelerating the tissue reconstruction.

Synergetic antibacterial activity of Vernonia auriculifera Hiern and Buddleja polystachya Fresen on selected human pathogenic bacteria

BackgroundMedicinal plants have been used as traditional treatments for various human diseases for many years and they are still widely practiced throughout the world. Due to the long history of the practice, medicinal plants have become an integral part of the Ethiopian culture. This study aimed to evaluate the antibacterial activities of Vernonia auriculifera Hiern and Buddleja polystachya Fresen leaf extracts and their synergistic effect against some selected human pathogenic bacteria. MethodsEthanol, methanol, and n-hexane crude extracts of Vernonia auriculifera, Buddleja polystachya, and a mixture of the two-plant respective of each solvent were evaluated against tested pathogenic bacteria using the agar well diffusion method; the inhibition zones were recorded in millimeters. Gentamycin was used as a positive control, while dimethyl sulfoxide served as a negative control. The minimum inhibitory concentration of the plant extracts against test bacteria was evaluated using two-fold broth dilution methods and then Minimum bactericidal concentration was determined by sub-culturing the test dilutions from minimum inhibitory concentration tubes onto fresh Muller Hinton Agar plates incubated at 37 °C for 24 h. ResultsMaximum antibacterial inhibition zone was observed on methanol extracts of synergism against S. Typhimurium (ATCC 1333) (31.00 ± 1.73 mm) while, a minimum inhibition zone was observed on methanol extract of Buddleja polystachya, against E. coli (ATCC 35218) (5.67 ± 0.57). Minimum inhibitory concentration and minimum bactericidal concentration values of the crude extracts of Vernonia auriculifera, Buddleja polystachya, and their mixture lies between (3.125%–12.5%) and (6.25%–25%) respectively. The data were analyzed using the SPSS software package version 20 for windows. ConclusionThe present study revealed that ethanol and methanol extracts of Vernonia auriculifera and Buddleja polystachya possess significant inhibitory effects against tested pathogens and the antibacterial activity of both plants leaf extracts was greater than the activity of currently used antibiotics (Gentamycin) against some selected organisms.

The Co3O4 nanosheet hybridized with silver nanoparticles affords long-acting synergetic antimicrobial and catalytic degradation activity

Overuse of antibiotics has given rise to drug resistant pathogens, while functional nanomaterials have emerged as a new antimicrobial way to replenish traditional antibiotics. In this work, we reported hybridized Ag/Co 3 O 4 nanosheet composites using a combined synthetic strategy. Using adsorptive sites of 2-dimensional hydroxide, the synthesized α-Co(OH) 2 ultrathin nanosheets used as initial materials captured Ag ions, which were then thermally decomposed into dense Ag nanoparticles assembled on the in-situ formed Co 3 O 4 nanosheets, which were endowed with highly-concentrated Ag nanoparticles, long-acting antimicrobial activity, and more catalytic active centers. The targeted nanocomposite afforded excellent catalytic reduction of toxic para-nitrophenol to aminophenol. Furthermore, hybridized Ag/Co 3 O 4 nanosheets showed the prolonged inhibitory effect (96 h) on microbial growth as typified by Pseudomonas aeruginosa , Escherichia coli , Staphylococcus aureus , and Candida albicans compared with that of silver- and cobalt-based counterparts. Furthermore, the MIC values of Ag/Co 3 O 4 nanosheets against the above-mentioned microbes and Mycobacterium tuberculosis ranging from< 4–32 μg/mL were at least 8- to 32-folds lower than sole Ag or Ag-free Co-200 composites, validating the synergetic antimicrobial effect between silver and cobalt oxide. More importantly, we uncovered that the resulting nanocomposite obtained superior antimicrobial activity by sustained release of Ag and Co ions and superoxide anions against pathogens, which provides the great potential for antimicrobial application on special hospital occasions. • One hybridized Ag/Co 3 O 4 nanosheet composite (Ag-Co) was synthesized via one combined synthetic strategy. • The resultant materials afford high Ag loading. • The functional materials afford excellent catalytic degradation of toxic p-nitrophenol. • The Ag-Co nanocomposite show low MIC values against various microbes. • The synergetic antibacterial activity by released Ag/Co ions and superoxide anions was obtained within 72 h.

Inhibition Effect of Ti3C2Tx MXene on Ice Crystals Combined with Laser-Mediated Heating Facilitates High-Performance Cryopreservation

The phenomena of ice formation and growth are of great importance for climate science, regenerative medicine, cryobiology, and food science. Hence, how to control ice formation and growth remains a challenge in these fields and attracts great interest from widespread researchers. Herein, the ice regulation ability of the two-dimensional MXene Ti3C2Tx in both the cooling and thawing processes is explored. Molecularly speaking, the ice growth inhibition mechanism of Ti3C2Tx MXene is ascribed to the formation of hydrogen bonds between functional groups of -O-, -OH, and -F distributed on the surface of Ti3C2Tx and ice/water molecules, which was elucidated by the molecular dynamics simulation method. In the cooling process, Ti3C2Tx can decrease the supercooling degree and inhibit the sharp edge morphology of ice crystals. Moreover, taking advantage of the outstanding photothermal conversion property of Ti3C2Tx, rapid ice melting can be achieved, thus reducing the phenomena of devitrification and ice recrystallization. Based on the ice restriction performance of Ti3C2Tx mentioned above, Ti3C2Tx is applied for cryopreservation of stem-cell-laden hydrogel constructs. The results show that Ti3C2Tx can reduce cryodamage to stem cells induced by ice injury in both the cooling and thawing processes and finally increase the cell viability from 38.4% to 80.9%. In addition, Ti3C2Tx also shows synergetic antibacterial activity under laser irradiation, thus realizing sterile cryopreservation of stem cells. Overall, this work explores the ice inhibition performance of Ti3C2Tx, elucidates the physical mechanism, and further achieves application of Ti3C2Tx in the field of cell cryopreservation.

Hybrid electrospun scaffolds based on polylactic acid/ PAMAM dendrimer/gemini surfactant for enhancement of synergistic antibacterial ability for biomedical application

Hybrid electrospun scaffolds based on poly (L-lactic acid) (PLLA)/poly (amidoamine) (PAMAM-G2) dendrimer/gemini surfactant were fabricated for the enhancement of synergistic antibacterial activities. The second generation of poly (amidoamine) (PAMAM-G2) and cationic gemini surfactant were utilized to functionalize the optimum electrospun scaffolds. The gelatination process was utilized to improve the wettability of PLLA scaffolds to extend cell attachment and cell proliferation. PLLA nanofibrous scaffolds were characterized by energy dispersion x-ray, scanning electron microscopy images, mechanical properties, water contact angle, Fourier transform infrared spectroscopy, zeta potential and antibacterial assessment. In vitro cell biocompatibility was evaluated by 3-(4, 5- dimethylthiazoyl-2-yl)-2, 5-diphenyltetrazolium bromide assay and morphology of PC-12 cells cultured on hybrid nanofibrous scaffolds and gelatinized ones. The results indicated that the optimum scaffolds could successfully modify the characteristics of PLLA scaffolds leading to much more appropriate physical and chemical properties. In addition, gelatinized nanofibrous scaffolds reveal more wettability enhancing cell attachment and proliferation. Furthermore, using poly (amidoamine) (PAMAM-G2) and gemini surfactant reveals synergetic antibacterial activity due to the competition between both cationic groups of PAMAM and gemini surfactant. Finally, improved cell adhesion and cell viability on modified scaffolds were confirmed. These favorable properties give a chance for these scaffolds to be used in a wide variety of biomedical applications.

Silver nanoparticles anchored magnetic self-assembled carboxymethyl cellulose-ε-polylysine hybrids with synergetic antibacterial activity for wound infection therapy

The severe bacterial infection and chronic wound healing caused by the abuse of antibiotics threaten the public health, which calls the need for the development of novel antibacterial agents and alternative therapeutic strategies. Herein, magnetic carboxymethyl cellulose-ε-polylysine hybrids (FCE) were synthesized via a facile one-pot coprecipitation method and further used as matrix to anchor silver nanoparticles (Ag NPs). The as-resulted Ag/FCE hybrids were employed to inactivate pathogenic bacteria and accelerate bacteria-infected wound healing with the assistance of H2O2. In vitro investigation revealed the combination of hydroxyl radical (·OH) originated from low concentration of H2O2 catalyzed by Ag/FCE and the antimicrobial activity of Ag NPs endowed effective antibacterial performance to the hybrids against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Investigation on antibacterial mechanism indicated antibacterial activity of the synergetic strategy was achieved by destroying bacterial cell integrity, arresting metabolic, producing intracellular ROS, and oxidizing GSH. Additionally, in vivo assay exhibited Ag/FCE possessed satisfactory biocompatibility and effectively accelerated S. aureus-infected wound healing with the presence of low concentration of H2O2. Altogether, the presented results supported the great potential application of the synergistic antibacterial strategy for the therapy of bacterial-infected wound healing.

Synergetic effect of petit‐high pressure carbon dioxide combined with cinnamon (Cinnamomum cassia) essential oil against Salmonella typhimurium

SummaryThis work aimed to evaluate the synergistic effect of petit‐high pressure carbon dioxide (p‐HPCD) and cinnamon (Cinnamomum cassia) essential oil (CEO) against Salmonella typhimurium. The results showed synergetic antibacterial activity of p‐HPCD and CEO. After treatment with p‐HPCD and CEO with a final concentration of 0.03125% under 1.3 MPa at 30 °C for 5 h, the population of S. typhimurium was decreased by 6.22 log10 CFU/mL, significantly higher than p‐HPCD or CEO alone. The combined treatment induced severe cellular changes in S. typhimurium, including cell membrane disruption, decreased intracellular protein and ATP, and intracellular reactive oxygen species (ROS) generation. Moreover, p‐HPCD + CEO treatment significantly inhibited the expression of virulence genes including fliC, hilA, invI and ssrA, indicating that p‐HPCD + CEO can reduce the production of virulence factors in S. typhimurium. This study provides a new approach to the application of p‐HPCD and CEO in food processing and preservation.

Functional effectiveness of double essential oils@yam starch/microcrystalline cellulose as active antibacterial packaging

In this work, two combinations of double EOs, i.e., α-terpineol: eugenol (α-T:Eu) and carvacrol:eugenol (CA:Eu), are used to develop the active antibacterial films of double EOs@yam starch/microcrystalline cellulose (EOs@SC). The hydrogen-bonded networks in SC matrix are conducive to thermostability enhancement and the film of SC25 is determined for EO incorporation. The interactions between EOs and SC matrix are also hydrogen bonds and the double EOs@SC are smooth at ratio of ≤2:2 for α-T:Eu or CA:Eu. The ultimate film properties are dependent on the incorporated EOs. The release of EOs is well controlled by two mechanisms of diffusion (predominant) and swelling (secondary). Synergetic antibacterial activity occurs on double EOs@SC. The shelf life of pork can be extended by 1 day at 25 °C by the two typical films of α-T2:Eu2@SC and CA2:Eu2@SC. Moreover, EOs@SC can be well degraded in humus soil. Thereby, the target films will have great potential in active packaging to extend the shelf life of food.

Polyoxometalate-Ionic Liquids (ILs) and Polyvinyl Alcohol/Chitosan/ILs Hydrogels for Inhibiting Bacteria Colonising Wall Paintings

Historical monuments are increasingly being threatened by unexpected microbial colonizers, leading to their subsequent deterioration. Here, two tetraalkylphosphonium polyoxometalate ionic liquids (Q14-IL and Q16-IL) were successfully synthesized, which showed excellent antibacterial activity against four bacteria colonising wall paintings. Notably, Q14-IL exhibited superior antibacterial efficacy compared to longer alkyl Q16-IL. Additionally, polyvinyl alcohol/chitosan (PVA-CS) hydrogels containing two ILs were prepared, and the morphology, thermal stability, swelling ratio and antibacterial activity were systematically evaluated. The results suggest that higher CS content resulted in more uniform micropores and increased the swelling ratio. However, fewer antibacterial ILs were released and diffused over time from the matrix. Hydrogels with 5% CS content exhibited the highest antibacterial activity, which was mainly attributed to the synergetic antibacterial activity of positively charged ammonium (-NH3+) groups of CS and quaternary phosphonium cation of ILs. This study may provide an alternative strategy for fighting against bacterial communities colonising ancient artworks.

A bacteriocin-based antimicrobial formulation to effectively disrupt the cell viability of methicillin-resistant Staphylococcus aureus (MRSA) biofilms

Antibiotic-resistant and biofilm-associated infections brought about by methicillin-resistant Staphylococcus aureus (MRSA) strains is a pressing issue both inside as well as outside nosocomial environments worldwide. Here, we show that a combination of two bacteriocins with distinct structural and functional characteristics, garvicin KS, and micrococcin P1, showed a synergetic antibacterial activity against biofilms produced in vitro by S. aureus, including several MRSA strains. In addition, this bacteriocin-based antimicrobial combination showed the ability to restore the sensitivity of the highly resilient MRSA strain ATCC 33591 to the β-lactam antibiotic penicillin G. By using a combination of bacterial cell metabolic assays, confocal and scanning electron microscopy, we show that the combination between garvicin KS, micrococcin P1, and penicillin G potently inhibit cell viability within S. aureus biofilms by causing severe cell damage. Together these data indicate that bacteriocins can be valuable therapeutic tools in the fight against biofilm-associated MRSA infections.

Enhanced synergetic antibacterial activity by a reduce graphene oxide/Ag nanocomposite through the photothermal effect

Multidrug-resistant (MDR) bacterial strains have led to notable heathy threats to human beings. The demand for the development of effective antibacterial materials is increasing. Silver nanoparticles (AgNPs) and graphene-based nanomaterials are two major types of nanomaterials that are studied to inhibit and/or kill bacteria. In this study, by combining the excellent photothermal effect of graphene and antibacterial activity of AgNPs, we have applied reduced graphene oxide/silver (RGO/Ag) nanocomposite to destroy the MDR bacteria. The antibacterial activity of the RGO/Ag nanocomposite was systematically investigated using a regular bacterium of Escherichia coli (E. coli) and an MDR bacterium of Klebsiella pneumoniae (Kp). Compared with AgNPs, graphene oxide (GO) and RGO, the RGO/Ag nanocomposite showed significant higher antibacterial efficiency for both regular bacteria and MDR bacteria. Under a near-infrared (NIR) irradiation (0.30 W/cm2 for 10 min), the RGO/Ag nanocomposite demonstrated an enhanced synergetic antibacterial activity through the photothermal effect. Nearly 100 % of E. coli and Kp were killed by the treatment of 15 μg/mL and 30 μg/mL of RGO/Ag nanocomposite, respectively. Moreover, a membrane integrity assay and a reactive oxygen species (ROS) assay demonstrated that the RGO/Ag nanocomposite under NIR irradiation induced the cell membrane disruption and generation of ROS, providing possible mechanisms for their high antibacterial activity besides the photothermal effect. Finally, the cytotoxicity of the RGO/Ag nanocomposites toward different mammalian cells was studied, the cell viabilities retained above 60 % at higher concentrations of RGO/Ag, indicating that the RGO/Ag nanocomposites may be a low cytotoxic, efficient antibacterial agent with the irradiation.

Antibacterial effect and mechanism of silver-carried zirconium glycine-N,N-dimethylenephosphonate as a synergistic antibacterial agent

The synergistic effect of hybrid nanoparticles antibacterial agent, which is a heated discussed topic in the related field, can endow antibacterial agent much more antibacterial activity. In this work, silver nanoparticles (Ag NPs), of 16–20 nm in diameter, were immobilized onto the zirconium glycine-N,N-dimethylenephosphonate (ZGDMP) interlayer. As a result, a silver-carried zirconium glycine-N,N-dimethylenephosphonate (Ag-ZGDMP) has been successfully synthesized, which can effectively overcome the problem of Ag NPs' aggregation. The results also showed that Ag-ZGDMP possessed excellent antibacterial ability and long-lasting effects against Gram-positive and Gram-negative bacteria of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), due to the synergetic antibacterial activity between ZGDMP and Ag NPs. Moreover, Ag-ZGDMP exhibited good thermal stability, and did not show obvious cytotoxicity against mammalian cells (A549 cells). It proves that Ag-ZGDMP is an efficient and non-cytotoxic synergetic antibacterial agent.

Purification of antibacterial proteins from Coffee senna (Senna occidentalis) seeds

Senna occidentalis (L.) Link formally known as Cassia occidentalis is a popular herb in folk medicine for the treatment of a wide range of microbial infections. Crude, ammonium sulphate precipitated and dialyzed proteins of S. occidentalis seeds were evaluated for their antibacterial potential by agar well diffusion and broth dilution techniques, against ten bacterial isolates made up of five Gram positive bacteria; Staphylococcus aureus, Streptococcus pyogenes, Enterococcus Sp, Listeria monocytogene and Bacillus subtilis and five Gram negative bacteria; Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Salmonella typhi and Shigella dysentria. The proteins were isolated by gel filtration on sephadex G-75 column and tested for antibacterial activity. The crude, dialyzed and precipitated proteins were active against all Gram positive bacterial isolates tested but were inactive against all Gram negative bacterial isolates used. The Minimum Inhibitory Concentration (MIC) of the crude, precipitated and dialyzed proteins against the most significantly (p < 0.05) sensitive bacterial B. subtilis were 0.67, 0.73 and 3.34 mg/ml respectively while the Minimum Bactericidal Concentration (MBC) were 2.67, 1.46 and 6.67 mg/ml respectively. Isolation however, resulted in total loss of antibacterial activities. SDS/PAGE analysis showed that the seed contains different proteins with molecular weights ranging from 14,400 to 66,200 kDa. The results of this study suggest that S. occidentalis seed contains proteins that have narrow spectrum, synergetic antibacterial activity against important food spoilage bacterial and can therefore be exploited for the development of novel antibacterial agent(s) for food preservation.

Light‐Activated Rapid Disinfection by Accelerated Charge Transfer in Red Phosphorus/ZnO Heterointerface

AbstractA red phosphorus (RP)/ZnO heterojunction thin film is developed to harvest solar or light emitting diode (LED) light for rapid, effective, ecofriendly, lower‐cost, and safe disinfection, which is convenient for universal and large‐scale deposition. The most stable geometrical structure of the RP/ZnO heterojunction, i.e., an RP (001) plane and a ZnO (002) plane, exhibits charge redistribution largely at the interface region. Therefore, the effective interfacial charge transfer and the improved separation efficiency of photogenerated electron–hole pairs can strongly boost reactive oxygen species (ROS)‐generation reactions to enhance photocatalytic bacterial inactivation. The excellent light‐activated point‐of use disinfection can be achieved even through LED light of phone. Additionally, the RP/ZnO heterojunction also possesses excellent solar light‐to‐heat conversion efficiency, leading to further lethality to bacteria through hyperthermia. Antibacterial efficacy of 99.96 ± 0.03% against Staphylococcus aureus at 5 min and 99.97 ± 0.02% against Escherichia coli at 4 min can be attributed to the synergetic antibacterial activity of solar photocatalysis and photothermal effect (more than 50 °C in 2 min). This platform provides a surface strategy for designing synergetic photocatalytic and photothermal materials to fully harvest solar energy for not only water disinfection but also antibacterial surfaces in medical facilities, touch screen devices, or seawater desalination.

Synergetic effect of vancomycin loaded silver nanoparticles for enhanced antibacterial activity.

In recent years, there is significant growth in the bacterial resistance to various classic antibiotics. This has opened and enhanced the field of metal nanoparticles and antibiotic-metal nanoparticle complex. This research was designed to load a glycopeptide antibiotic named vancomycin on citrate-capped silver nanoparticles to enhance its antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Colloidal solution of silver nanoparticles (AgNPs) was prepared by chemical reduction method using silver nitrate (AgNO3) as a precursor in the presence of ionic surfactant trisodium-citrate which acts as a both capping and reducing agent. Synthesized nanoparticles were functionalized with vancomycin to form nano-drug complex (Van@AgNPs). Various analytical techniques such as UV-vis absorption spectra, FTIR, DLS, TEM and XRD were carried out to study the loading and interaction of drug with silver nanoparticles. The observed shift in SPR peak of UV-vis and various reflections of XRD spectra is attributed towards the loading of vancomycin on silver nanoparticle surface. FTIR studies shows the hydrogen bonding between vancomycin and silver nanoparticles through NH (amine) group of vancomycin and oxygen of anionic citrate. The increase in average particle size and particle size distribution of vancomycin-loaded nanoparticles in comparison to bare NPs also hints the drug loading. Agar well diffusion method was used to study the synergetic antibacterial activity of vancomycin-loaded silver nanoparticles against both test strains. The well diffusion test showed the notable enhancement in antibacterial activity against both class of bacteria. This enhancement has been observed to be synergetic rather than the additive.

Enhanced cell-wall damage mediated, antibacterial activity of core-shell ZnO@Ag heterojunction nanorods against Staphylococcus aureus and Pseudomonas aeruginosa.

Hybrid ZnO@Ag core-shell nanorods have been synthesized by a synthetic strategy based on seed mediated growth. Formation of core-shell nanostructures was confirmed by UV- diffused reflectance spectroscopy (UV-DRS), X-ray diffraction studies, field emission scanning electron microscopy and high resolution transmission electron microscopy. UV-DRS analysis of hybrid core-shell nanorods suggests the possibility of interfacial electron transfer between surface anchored Ag nanoclusters and ZnO nanorods. Successful decoration of Ag nanoclusters with an average diameter of ~7±0.5nm was observed forming the heterojunctions on the surface of the ZnO nanorods. An enhanced antibacterial property was observed for the ZnO@Ag core-shell nanorods against both Staphylococcus aureus and Pseudomonas aeruginosa lbacteria. The synergetic antibacterial activity of ZnO@Ag nanorods was found to be more prominent against Gram-positive bacteria than Gram-negative bacteria. The plausible reason for this enhanced antibacterial activity of the core-shell nanorods can be attributed to the physical damage caused by the interaction of the material with outer cell wall layer due to the production of reactive oxygen species by interfacial electron transfer between ZnO nanorods and plasmonic Ag nanoclusters. Overall, the ZnO@Ag core-shell nanorods were found to be promising materials that could be developed further as an effective antibacterial agent against wide range of microorganisms to control spreading and persistence of bacterial infections.

Synergetic antibacterial activity of reduced graphene oxide and boron doped diamond anode in three dimensional electrochemical oxidation system

A 100% increment of antibacterial ability has been achieved due to significant synergic effects of boron-doped diamond (BDD) anode and reduced graphene oxide (rGO) coupled in a three dimensional electrochemical oxidation system. The rGO, greatly enhanced by BDD driven electric field, demonstrated strong antibacterial ability and even sustained its excellent performance during a reasonable period after complete power cut in the BDD-rGO system. Cell damage experiments and TEM observation confirmed much stronger membrane stress in the BDD-rGO system, due to the faster bacterial migration and charge transfer by the expanded electro field and current-carrying efficiency by quantum tunnel. Reciprocally the hydroxyl-radical production was eminently promoted with expanded area of electrodes and delayed recombination of the electron–hole pairs in presence of the rGO in the system. This implied a huge potential for practical disinfection with integration of the promising rGO and the advanced electrochemical oxidation systems.

Chitosan/silver nanocomposites: Synergistic antibacterial action of silver nanoparticles and silver ions

In the present work chitosan–silver (CS/Ag) nanocomposites, either in the form of nanoparticles (AgNP) or as ionic dendritic structures (Ag+), are synthesized by a simple and environmentally friendly in situ chemical reduction process. The antibacterial activity of the resulting nanocomposites in the form of films is studied against two bacteria, Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The relationship between electrical, structural and antibacterial properties of CS/AgNP and CS/Ag+ nanocomposites are studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, and UV–Vis, impedance, infrared and X-ray photoelectron spectroscopies. The results demonstrate that in contrast to CS/Ag+ ion films, the CS/AgNP composites films (average particle size less than 10nm) showed a significantly higher antibacterial potency. The collective action of AgNP and Ag+ ions facilitate the enhancement and synergetic antibacterial activity below certain critical concentration. The bactericide activity of both CS/AgNP and CS/Ag+ ion composite films increases by increasing the concentration of Ag. The composites containing 1wt.% of silver nanoparticles and about of 2wt.% of silver ions exhibit a maximum antibacterial activity, which is close to their electrical percolation threshold. The concentration of AgNP and Ag+ ions above the threshold level greatly diminish the antibacterial potential.