Mechanistic Study of the Synergistic Antibacterial Activity of Combined Silver Nanoparticles and Common Antibiotics

Changes in the life history traits of Daphnia magna are associated with the gut microbiota composition shaped by diet and antibiotics

The gut microbiota has a crucial role in host physiology and fitness. Host-microbiota relationships can be disrupted by environmental stressors, which further affect host growth and survival. However, the link between host performance and the gut microbiota composition shaped by increasing antibiotic pollution under different food conditions is not clearly understood. In the present study, we used Daphnia magna as a model organism to investigate the interactive effects of diets (Chlorella with or without Microcystis) and antibiotics on its life history traits, gut microbiota alterations, and their relationship. The results showed that poor diet consumption by D. magna at low and high antibiotic concentrations reduced reproduction and survival. Under good diet conditions, the fitness was reduced only at a high antibiotic concentration. Under good diet conditions, high concentration of antibiotics reduced the abundance of Comamonadaceae and increased the abundance of Pseudomonadaceae, whereas under poor diet conditions, both low and high concentrations of antibiotics increased the abundance of Pseudomonadaceae. Performances of life history traits were positively correlated with an increased abundance of Comamonadaceae but were negatively correlated with increased Pseudomonadaceae abundance. The results of this study revealed the interactive effects of diet and antibiotics on D. magna fitness and correlations between bacterial abundance and life history traits, which has important implications for understanding the effects of pollutants on host-microbiota interactions through changes in phenotypes.

Functional Nanomaterials for the Detection and Control of Bacterial Infections

Infections with multidrug-resistant bacteria that are difficult to treat with commonly used antibiotics have spread globally, raising serious public health concerns. Conventional bacterial detection techniques are time-consuming, which may delay treatment for critically ill patients past the optimal time. There is an urgent need for rapid and sensitive diagnosis and effective treatments for multidrug-resistant pathogenic bacterial infections. Advances in nanotechnology have made it possible to design and build nanomaterials with therapeutic and diagnostic capabilities. Functional nanomaterials that can specifically interact with bacteria offer additional options for the diagnosis and treatment of infections due to their unique physical and chemical properties. Here, we summarize the recent advances related to the preparation of nanomaterials and their applications for the detection and treatment of bacterial infection. We pay particular attention to the toxicity of therapeutic nanoparticles based on both in vitro and in vivo assays. In addition, the major challenges that require further research and future perspectives are briefly discussed.

Antagonistic effect of zinc oxide nanoparticle and surfactant on anaerobic digestion: Focusing on the microbial community changes and interactive mechanism

The objective of this study was to evaluate the antagonistic effect of emerging pollutants of zinc oxide nanoparticles (ZnO NPs) and sodium dodecyl sulfate (SDS) on anaerobic digestion and explore their potential mechanism. The results indicated that at a low inhibitory concentration of ZnO NPs (1.0 mM), the practical co-inhibition was decreased by 24% and 18% in co-existence of 50 mg/L SDS and 300 mg/L SDS, respectively. More importantly, the co-existence of 300 mg/L SDS greatly enhanced methanogenesis of organics in seriously inhibited case (2.0 mM of ZnO NPs). The microbial community analysis showed that co-existed SDS enhanced the growth of Methanothrix, Methanosarcina and Methanobacterium. The antagonistic enhancement could be attributed to the net charge reversal, partially agglomeration of ZnO NPs and/or reduction of Zn²⁺ release in the presence of SDS. These findings could provide useful information for evaluating the co-inhibition of SDS and ZnO NPs on biological processes.

Understanding effect of interaction of nanoparticles and antibiotics on bacteria survival under aquatic conditions: Knowns and unknowns

The review provides a comprehensive overview of the available state-of-the-art of nanoparticles (NPs) and antibiotics (ABs) occurrence and their fate in the natural aquatic settings by addressing different research questions and the challenges faced while addressing those questions. Firstly, understand the interaction of NPs and ABs with themselves in addition to other matrix components (presence of natural organic matter, bacteria, biofilms, other anthropogenic pollutants and metals from natural sources). Secondly, summarize the bactericidal activity of NP and AB due to reactive oxygen species (ROS) production. The complete information was gathered from database and analysed as per the conjectured questions under laboratory versus environmental-relevant conditions (1. Fate of NPs and ABs, and 2. Will the presence of NPs and ABs alone and their mixtures influence the ROS concentration and antibacterial activity), and proposed six reactions to describe the fate of NP and AB in natural aquatic settings. However, laboratory-based studies revealed that NP and AB fate largely depend on the ionic strength, organic matter content and pH of the matrix whereas field based information is missing about this. The former was performed at sterile conditions using sophisticated instruments and standard protocol as compared to latter and can't be replicated under natural aquatic settings due to lack of: (i) accurate environmental concentration of NPs and ABs, (ii) knowledge of bacterial type and their concentration, (iii) optimized protocol and tracking systems. The author's recommendation is to verify the proposed reactions experimentally by using the frequently found pairs of NPs and ABs in the natural aquatic settings. Further, ranked them on their decreasing order of toxicity and informed regulatory bodies for further action. Overall research is needed in the suggested directions to reduce uncertainty behind the impacts of NPs and ABs on the aquatic settings and their role in bactericidal activity.

Application of some nanoparticles in the field of veterinary medicine

Nanotechnology is a fast-growing technology that plays an important great impact on various fields of therapeutic applications. It is capable for solving several problems related to animal health and production. There are different nano-systems such as liposomes, metallic nanoparticles, polymeric micelles, polymeric nanospheres, functionalized fullerenes, carbon nanotubes, dendrimers, polymer-coated nanocrystals and nanoshells. In this review, we mentioned different methods for the preparation and characterization of nanoparticles. This review is concerned mainly on nanoparticle systems for antibiotic delivery which suffer from poor bioavailability and many side effects. Nanoparticles are characterized by many features include their minimal size, colossal surface zone to mass extent. The development of antimicrobials in nanoparticle systems is considered an excellent alternative delivery system for antimicrobials for the treatment of microbial diseases by increasing therapeutic effect and overcoming the side effects. In this paper, we reviewed some antimicrobial nanoparticle preparations and we focused on florfenicol and neomycin nanoparticle preparations as well as chitosan and silver nanoparticles preparations to prepare, characterize and compare their different pharmacological effects.

Tetracycline affects the toxicity of P25 n-TiO2 towards marine microalgae Chlorella sp

Pollutants such as n-TiO₂ and tetracycline enter the marine environment through various sources starting from their production until disposal. Hence, it is vital to determine the interactive effect of one pollutant with the other when they coexist in the environment. In the present study, the effect of antibiotic - tetracycline (TC) on the toxicity of P25 n-TiO₂ was studied with marine microalgae, Chlorella sp. The impact of TC (1 mg L^-1) on five different concentrations of n-TiO₂ (0.25, 0.5, 1, 2 and 4 mg L^-1) under both visible and UV-A illuminations was evaluated. Effective diameter of n-TiO₂ in ASW at 0^th h increased from 690.69 ± 19.55 nm (0.25 mg L^-1) to 1183.04 ± 37.10 nm (0.25 mg L^-1 + 1 mg L^-1) and 971.51 ± 14.61 nm (4 mg L^-1) to 1324.12 ± 11.59 nm (4 mg L^-1 + 1 mg L^-1) in presence of TC. A significant increase in the toxicity of 4 mg L^-1 n-TiO₂ upon the addition of TC (68.16 ± 0.37% under visible and 80.21 ± 0.3% under UV-A condition) was observed. No significant difference in toxicity was observed between visible and UV-A illuminations. Further the toxicity data was corroborated through the measurement of oxidative stress and antioxidant enzyme activities. Independent action model showed antagonistic effect for lower concentrations of n-TiO₂ and additive effect for higher concentrations of n-TiO₂ when present in mixture with TC under both illuminations. For the higher mixture concentration of 4 mg L^-1 n-TiO₂ and 1 mg L^-1 TC, the percentage TC removal was about 55.29% and 30% and the corresponding TOC removal was found to be 54.29% and 31.04% under visible and UV-A illuminations respectively. The site of ROS generation in Chlorella sp. was identified with electron transfer chain inhibitors. Both mitochondria and chloroplast acted as the site for the ROS generation in Chlorella sp. The SEM images of the algal cells upon exposure to n-TiO₂ and mixture revealed the aggregation of cells and distortion of cell membrane.

Enhancement of antibiotics antimicrobial activity due to the silver nanoparticles impact on the cell membrane

The ability of microorganisms to generate resistance outcompetes with the generation of new and efficient antibiotics; therefore, it is critical to develop novel antibiotic agents and treatments to control bacterial infections. An alternative to this worldwide problem is the use of nanomaterials with antimicrobial properties. Silver nanoparticles (AgNPs) have been extensively studied due to their antimicrobial effect in different organisms. In this work, the synergistic antimicrobial effect of AgNPs and conventional antibiotics was assessed in Gram-positive and Gram-negative bacteria. AgNPs minimal inhibitory concentration was 10–12 μg mL^-1 in all bacterial strains tested, regardless of their different susceptibility against antibiotics. Interestingly, a synergistic antimicrobial effect was observed when combining AgNPs and kanamycin according to the fractional inhibitory concentration index, FICI: <0.5), an additive effect by combining AgNPs and chloramphenicol (FICI: 0.5 to 1), whereas no effect was found with AgNPs and β-lactam antibiotics combinations. Flow cytometry and TEM analysis showed that sublethal concentrations of AgNPs (6–7 μg mL^-1) altered the bacterial membrane potential and caused ultrastructural damage, increasing the cell membrane permeability. No chemical interactions between AgNPs and antibiotics were detected. We propose an experimental supported mechanism of action by which combinatorial effect of antimicrobials drives synergy depending on their specific target, facilitated by membrane alterations generated by AgNPs. Our results provide a deeper understanding about the synergistic mechanism of AgNPs and antibiotics, aiming to combat antimicrobial infections efficiently, especially those by multi-drug resistant microorganisms, in order to mitigate the current crisis due to antibiotic resistance.

Integrated nanotechnology of synergism-sterilization and removing-residues for neomycin through nano-Cu2O

The abuse of antibiotics has led to widespread antimicrobial resistance (AMR) and environmental pollution. In order to solve these problems, a lot of studies have been carried out mainly focusing on the modification and recombination of organic reagents, but bacteria are still easy to adapt to it, so they cannot be thoroughly solved. Here, we present an integrated pollution-free synergistic antibacterial nanotechnology using inorganic nano-Cu₂O, which could not only enhance the efficacy of aminoglycoside antibiotics, but also eliminate their environmental pollution by photocatalytic degradation. It was found that Cu₂O showed significantly synergistic antibacterial effect (1+1>2) when combined with aminoglycoside antibiotics against Escherichia coli. The inhibition zone area increased by 59.0% when Cu₂O combined with neomycin. This reduces dosage and the risk of AMR, and does not pollute the environment after degradation. Next, to explore the synergistic mechanisms, we have studied the interaction of antibiotics with nanoparticles, as well as the interaction of antibacterial agents with bacteria. At last, we believe that the destruction of cell walls by Cu₂O facilitates the entry of antibiotics into cells is the reason for their synergy.

Black phosphorus nanomaterials as multi-potent and emerging platforms against bacterial infections

Black phosphorus (BP) has attracted research interest due to its excellent physiochemical properties in various biomedical applications. However, challenges remain of establishing BP as a practical nanomaterial platform against bacterial infections caused by hard-to-treat pathogens. This review highlights the novel approaches for functional properties and advantages of BP over currently available two-dimensional nanomaterials for antibacterial activity. The latest research findings regarding BP for antibacterial activity, potential as alternative antibacterial approach to current antibiotics, and its promise for the future platform are also considered. We believe that our discussions and perspectives on current topics will provide researchers with an up-to-date and handy reference to apply BP as a beneficial nanostructured biomaterial to the human health against various bacterial infections.

Effective Antibacterial Glass Fiber Membrane Prepared by Plasma-Enhanced Chemical Grafting

This paper reports a novel glass fiber membrane with an effective antibacterial performance by chemical grafting of quaternary ammonium salt (QAS) which is enhanced by a plasma bombardment technique. Plasma bombardment as a pretreatment of the membrane can increase the QAS anchored on the membrane from 0.8 to 1.3 wt %. The chemical grafting technique can increase the membrane zeta potential from negative values to positive values in aqueous solutions at various pHs. Furthermore, the plasma-enhanced chemical-grafting membrane has more positive zeta potentials (49.0 mV at pH = 7) than the chemical-grafting membrane without the plasma bombardment technique (38.9 mV at pH = 7). In the antibacterial performance evaluation, the Escherichia coli survival rate decreased from 127.0% of the pristine membrane to 4.1 and 11.3% of the plasma-enhanced chemical-grafting membrane and the chemical-grafting membrane, respectively. In addition, the plasma-enhanced chemical-grafting membrane shows durable antibacterial activity against E. coli with copious water rinsing as much as 3 L·cm-2.

Silver Nanoparticle Surface Enabled Self-Assembly of Organic Dye Molecules

Fluorescence titration of methylene blue, rhodamine B and rhodamine 6G (R6G) by silver nanoparticle (AgNP) all resulted in an initial steep quenching curve followed with a sharp turn and a much flatter quenching curve. At the turn, there are about 200,000 dye molecules per a single AgNP, signifying self-assembly of approximately 36-layers of dye molecules on the surface of the AgNP to form a micelle-like structure. These fluorescence-quenching curves fit to a mathematical model with an exponential term due to molecular self-assembly on AgNP surface, or we termed it "self-assembly shielding effect", and a Stern-Volmer term (nanoparticle surface enhanced quenching). Such a "super-quenching" by AgNP can only be attributed to "pre-concentration" of the dye molecules on the nanoparticle surface that yields the formation of micelle-like self-assembly, resulting in great fluorescence quenching. Overall, the fluorescence quenching titration reveals three different types of interactions of dye molecules on AgNP surface: 1) self-assembly (methylene blue, rhodamine B and R6G), 2) absorption/tight interaction (tryptamine and fluorescein), and 3) loose interaction (eosin Y). We attribute the formation of micelle-like self-assembly of these three dye molecules on AgNP to their positive charge, possession of nitrogen atoms, and with relatively large and flat aromatic moieties.

Bifunctional nano-Ag3PO4 with capabilities of enhancing ceftazidime for sterilization and removing residues

Since the efficacy of antibiotics towards bacteria is decreasing over time, the rising of antibiotic emission has become an increasingly grave issue. In this study, we proposed an integrated antibacterial nanotechnology without pollution residues, which synergistically enhances the antibacterial activity of ceftazidime by using the inorganic nano-Ag3PO4, and subsequently removes drug residues by photocatalysis. Ag3PO4 were synthesized using a simple ion-exchange method without any reducing agent or protectant. The combined antibacterial activity of Ag3PO4 and 22 kinds of antibiotics against Escherichia coli was first studied. The results showed that Ag3PO4 and ceftazidime exhibited the best synergistic effect. Next, the synergy mechanism was proposed, the non-chemical bond forces between Ag3PO4 and ceftazidime was determined by zeta potential analyzer, X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). The interaction between antimicrobials and bacteria was further demonstrated by surface plasma resonance spectroscopy (SPR), scanning electron microscopy (SEM) and propidium iodide (PI) staining. In addition, the production of reactive oxygen species (ROS), the induction of oxidative stress and dissolution of silver ions in Ag3PO4 were studied and found out that only under light, could the ROS be generated. In conclusion, the synergistic effect of Ag3PO4 and ceftazidime is responsible for the joint destruction of cell wall.

Synergistic antibacterial mechanism of Bi2Te3 nanoparticles combined with the ineffective β-lactam antibiotic cefotaxime against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infections have become a serious threat to public health because traditional antibiotics are less efficient. Here, we developed a simple and efficient combination of Bi₂Te₃ nanoparticles (NPs) with β-lactam antibiotics cefotaxime (CTX), which presented significant synergistic antibacterial activity against MRSA. The minimal inhibitory concentration of CTX decreased from 256 to 32 μg/mL in the presence of 8 μg/mL Bi₂Te₃ NPs. The results of cell membrane potential and cellular K⁺ content measurements demonstrated that the destruction of membrane functions is a factor in the synergistic mechanism. Furthermore, the induction of cellular reactive oxygen species generation, inhibition of β-lactamases induced by CTX and direct damage to the cell structure constituted other factors of the synergistic mechanism. These observations suggest that reviving the efficacy of ineffective β-lactam antibiotic CTX by Bi₂Te₃ NPs may be a potentially effective therapeutic strategy to overcome refractory MRSA infections.

Synthesis of silver nanoparticles using plant derived 4-N-methyl benzoic acid and evaluation of antimicrobial, antioxidant and antitumor activity

The present study is to investigate the antitumor, antioxidant and antibacterial potential of silver nanoparticles (Ag NPs) synthesized from a phenolic derivative 4-N-methyl benzoic acid, isolated from a medicinal plant (Memecylon umbellatum Burm F). The Bio-inspired nanoparticles (NPs) were analyzed by using UV-vis spectroscopy, FTIR, HRTEM, Zeta potential and XRD techniques. The UV-vis spectroscopy study at the band of 430 nm confirmed the nanoparticles formation. HRTEM report showed that the AgNPs synthesized were in the size range 7-23 nm. The harvested nanoparticles were subjected to anti-bacterial assay and a dose dependent inhibitory action was observed against the tested human pathogens. Among the tested bacteria, Acinetobacter baumannii was found to be highly sensitive to AgNPs (diameter of zone of inhibition was 31 mm). Further, the silver nanoparticles exhibited a good anti-tumor activity against the breast cancer cell line (MCF 7) with an IC₅₀ value of 42.19 µg/mL. As the present study confirmed a good antibacterial, antioxidant and antitumor activity in the nanoparticles synthesized using 4-N-methyl benzoic acid derived from a medicinal plant, the product can be further tested to formulate a good lead compound for biomedical applications.

Synergistic antibacterial effects of curcumin modified silver nanoparticles through ROS-mediated pathways

Due to their remarkable antibacterial properties, silver nanoparticles (Ag NPs) and curcumin (CCM) have been widely used in the antimicrobial field. In our study, we have fabricated the uniform and stable silver/curcumin composite nanoparticles by a facile ultrasound treatment process and the synergistic antibacterial activity were evaluated. The curcumin not only played a role of reducing agent but also acted as a capping agent. The antibacterial effects of silver/curcumin (cAgNPs) were studied by measuring the growth curve and surface plate assay based on the E. coli and B. subtilis, which showed concentration dependent bacteriostatic and bactericidal effects of cAgNPs. The presence of CCM enhance the binding of Ag to bacterial membrane and Ag⁺ release in comparison to that without CCM, so that creating a temporary and local high Ag⁺ concentration near the surface of the bacterium, meanwhile, generation of more reactive oxygen species, lead to membrane damage, bacterial lipases and induce leakage of intracellular contents followed by bacterial death that lead to growth inhibition of the bacteria. The antibacterial effects were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the effect which were further found to decrease by introducing antioxidant N-acetyl-l-cysteine (NAC) act as a reactive oxygen species (ROS) scavenging agent. These initial data suggest that cAgNPs have a highly antibacterial efficient and might have potential to be developed as an effective antimicrobial nanomaterial.

The current application of nanotechnology in food and agriculture

The rapid development of nanotechnology has been facilitating the transformations of traditional food and agriculture sectors, particularly the invention of smart and active packaging, nanosensors, nanopesticides and nanofertilizers. Numerous novel nanomaterials have been developed for improving food quality and safety, crop growth, and monitoring environmental conditions. In this review the most recent trends in nanotechnology are discussed and the most challenging tasks and promising opportunities in the food and agriculture sectors from selected recent studies are addressed. The toxicological fundamentals and risk assessment of nanomaterials in these new food and agriculture products are also discussed. We highlighted the potential application of bio-synthesized and bio-inspired nanomaterial for sustainable development. However, fundamental questions with regard to high performance, low toxic nanomaterials need to be addressed to fuel active development and application of nanotechnology. Regulation and legislation are also paramount to regulating the manufacturing, processing, application, as well as disposal of nanomaterials. Efforts are still needed to strengthen public awareness and acceptance of the novel nano-enabled food and agriculture products. We conclude that nanotechnology offers a plethora of opportunities, by providing a novel and sustainable alternative in the food and agriculture sectors.

Phytotoxic effect of silver nanoparticles on seed germination and growth of terrestrial plants

Silver nanoparticles (AgNP) exhibit size and concentration dependent toxicity to terrestrial plants, especially crops. AgNP exposure could decrease seed germination, inhibit seedling growth, affect mass and length of roots and shoots. The phytotoxic pathway has been partly understood. Silver (as element, ion or AgNP) accumulates in roots/leaves and triggers the defense mechanism at cellular and tissue levels, which alters metabolism, antioxidant activities and related proteomic expression. Botanical changes (either increase or decrease) in response to AgNP exposure include reactive oxygen species generation, superoxide dismutase activities, H₂O₂ level, total chlorophyll, proline, carotenoid, ascorbate and glutathione contents, etc. Such processes lead to abnormal morphological changes, suppression of photosynthesis and/or transpiration, and other symptoms. Although neutral or beneficial effects are also reported depending on plant species, adverse effects dominate in majority of the studies. More in depth research is needed to confidently draw any conclusions and to guide legislation and regulations.

Silver nanomaterials in the natural environment: An overview of their biosynthesis and kinetic behavior

Silver nanomaterials (Ag NMs) are fabricated by many biological components in our environment. Recently, research on their biosynthesis and reactions has become a focus of attention. Due to the complexity of biological systems and samples, specific processes and mechanisms involving Ag NMs are difficult to identify and elucidate on the molecular and chemical-bond level. The microorganisms and composite components of plant extracts are of great interest in many biological syntheses. Although potential biomolecules have been shown to play essential roles in biological systems in Ag NM biosynthesis, the detailed mechanism of the electron transfer process and crucial molecules that control this reaction have only recently come into focus. The reactive behavior of the Ag NMs is of great significance for understanding their overall behavior and toxicity. Additionally, only limited knowledge is available about their kinetics. All reactions involve chemical bond formation, electron transfer, or electrostatic interactions. An overview is presented of the biosynthesis of Ag NMs based on molecular supports including a nitrate reductase/NADH oxidase-involved electron transfer reaction and their mechanisms in Ag⁺ reduction: quinol-mediated mechanism and superoxide-dependent mechanism, and molecular supports in plant extracts, is presented. The environmental reaction kinetics and mechanisms of the interactions of Ag NMs with substances are introduced based on the formation and classification of chemical bonds. The particle-particle reaction kinetics of Ag NMs in the environment are discussed to directly explain their stability and aggregation behavior. The toxicity of Ag NMs is also presented. In addition, future prospects are summarized. This review is the first to provide an insight into the mediating molecules and chemical bonds involved in the biosynthesis, kinetics, and mechanisms of action of Ag NMs.

Antibacterial and immunogenic behavior of silver coatings on additively manufactured porous titanium

Implant-associated infections (IAI) are often recurrent, expensive to treat, and associated with high rates of morbidity, if not mortality. We biofunctionalized the surface of additively manufactured volume-porous titanium implants using electrophoretic deposition (EPD) as a way to eliminate the peri-operative bacterial load and prevent IAI. Chitosan-based (Ch) coatings were incorporated with different concentrations of silver (Ag) nanoparticles or vancomycin. A full-scale in vitro and in vivo study was then performed to evaluate the antibacterial, immunogenic, and osteogenic activity of the developed implants. In vitro, Ch + vancomycin or Ch + Ag coatings completely eliminated, or reduced the number of planktonic and adherent Staphylococcus aureus by up to 4 orders of magnitude, respectively. In an in vivo tibia intramedullary implant model, Ch + Ag coatings caused no adverse immune or bone response under aseptic conditions. Following Staphylococcus aureus inoculation, Ch + vancomycin coatings reduced the implant infection rate as compared to chitosan-only coatings. Ch + Ag implants did not demonstrate antibacterial effects in vivo and even aggravated infection-mediated bone remodeling including increased osteoclast formation and inflammation-induced new bone formation. As an explanation for the poor antibacterial activity of Ch + Ag implants, it was found that antibacterial Ag concentrations were cytotoxic for neutrophils, and that non-toxic Ag concentrations diminished their phagocytic activity. This study shows the potential of EPD coating to biofunctionalize porous titanium implants with different antibacterial agents. Using this method, Ag-based coatings seem inferior to antibiotic coatings, as their adverse effects on the normal immune response could cancel the direct antibacterial effects of Ag nanoparticles. STATEMENT OF SIGNIFICANCE: Implant-associated infections (IAI) are a clinical, societal, and economical burden. Surface biofunctionalization approaches can render complex metal implants with strong local antibacterial action. The antibacterial effects of inorganic materials such as silver nanoparticles (Ag NPs) are often highlighted under very confined conditions in vitro. As a novelty, this study also reports the antibacterial, immunogenic, and osteogenic activity of Ag NP-coated additively-manufactured titanium in vivo. Importantly, it was found that the developed coatings could impair the normal function of neutrophils, the most important phagocytic cells protecting us from IAI. Not surprisingly, the Ag NP-based coatings were outperformed by an antibiotic-based coating. This emphasizes the importance of also targeting implant immune-modulatory functions in future coating strategies against IAI.

Microenvironment-Responsive Magnetic Nanocomposites Based on Silver Nanoparticles/Gentamicin for Enhanced Biofilm Disruption by Magnetic Field

Biofilms contribute to persistent bacterial infections as well as formidable resistances to conventional antibiotics. However, it is still a major challenge to establish an advanced antibacterial nanoplatform that can efficiently eradicate biofilms while overcoming bacterial resistances. Taking advantage of the stimuli-responsive technique and the magnetic guidance strategy, here we present a highly efficient nanoplatform for planktonic inactivation and biofilm disruption. The multilayer films consisting of antibiotic gentamicin (Gen), tannic acid, and silver nanoparticles (AgNPs) were fabricated and coated on magnetic nanoparticles via electrostatic interactions. To achieve controlled drug release and improved biocompatibility, biodegradable hyaluronic acid was capped on the outer surface as a responsive shell. In vitro release profiles suggested that the nanocomposites showed both enzyme and pH-responsive release properties. The nanoplatform could be employed as a powerful nanocarrier for small molecular Gen and AgNPs delivery and on-demand release in response to bacterial infection microenvironment. The nanocomposites also showed satisfying antibacterial capacities against planktonic Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Intriguingly, with magnetic field navigation (NdFeB, 2000 gauss), the nanocomposites could be guided to handily penetrate into S. aureus biofilm and performed dual-responsive release, showing significantly enhanced biofilm disruption. Moreover, excess reactive oxygen species production resulting from the nanocomposites contributed to the decomposition of biofilm matrix and ultimate biofilm eradication. As a consequence, the ingenious antibacterial nanoplatform could be promising for combating biofilm infections while overcoming bacterial resistances with extra environmental factors such as magnetic field.

Silver nanoparticles as antimicrobial therapeutics: current perspectives and future challenges

Utility of silver metal in antimicrobial therapy is an accepted practice since ages that faded with time because of the identification of a few silver resistant strains in the contemporary era. A successive development of antibiotics soon followed. However, due to an indiscriminate and unregulated use coupled with poor legal control measures and a dearth of expertise in handling the critical episodes, the antibiotics era has already seen a steep decline in the past decades due to the evolution of multi-drug resistant 'superbugs' which pose a sizeable challenge to manage with. Due to limited options in the pipeline and no clear strategy in the forefront, the aspirations for novel, MDR focused drug discovery to target the 'superbugs' arose which once again led to the rise of AgNPs in antimicrobial research. In this review, we have focused on the green routes for the synthesis of AgNPs, the mode of microbial inhibition by AgNPs, synergistic effect of AgNPs with antibiotics and future challenges for the development of nano-silver-based therapeutics.

PREPARATION AND PROPERTIES OF KANAMYCIN-CONTAINING HYDROGELS BASED ON PECTIN-Ag NANOCOMPOSITE

The hydrogels based on nanocomposite pectin-Ag exhibiting the antibacterial activity (MIСAg = 0.02–0.81 mM) were obtained by ionotropic gelation. It was shown that the synthesized hydrogels had a high capacity for kanamycin (up to 70 wt. %). The obtained hydrogels provided a prolonged release of kanamycin in 0.9 % NaCl and enhanced its antibacterial activity (MIC decreased 10–20 times) due to the synergistic effect.

Environmental mixtures of nanomaterials and chemicals: The Trojan-horse phenomenon and its relevance for ecotoxicity

The usage of engineered nanomaterials (NM) offers many novel products and applications with advanced features, but at the same time raises concerns with regard to potential adverse biological effects. Upon release and emission, NM may interact with chemicals in the environment, potentially leading to a co-exposure of organisms and the occurrence of mixture effects. A prominent idea is that NM may act as carriers of chemicals, facilitating and enhancing the entry of substances into cells or organisms, subsequently leading to an increased toxicity. In the literature, the term 'Trojan-horse effect' describes this hypothesis. The relevance of this mechanism for organisms is, however, unclear as yet. Here, a review has been performed to provide a more systematic picture on existing evidence. It includes 151 experimental studies investigating the exposure of various NM and chemical mixtures in ecotoxicological in vitro and in vivo model systems. The papers retrieved comprised studies investigating (i) uptake, (ii) toxicity and (iii) investigations considering both, changes in substance uptake and toxicity upon joint exposure of a chemical with an NM. A closer inspection of the studies demonstrated that the existing evidence for interference of NM-chemical mixture exposure with uptake and toxicity points into different directions compared to the original Trojan-horse hypothesis. We could discriminate at least 7 different categories to capture the evidence ranging from no changes in uptake and toxicity to an increase in uptake and toxicity upon mixture exposure. Concluding recommendations for the consideration of relevant processes are given, including a proposal for a nomenclature to describe NM-chemical mixture interactions in consistent terms.

Silver Nanoparticles Combined With Naphthoquinones as an Effective Synergistic Strategy Against Staphylococcus aureus

Staphylococcus aureus is a human pathogen responsible for many antibiotic-resistant infections, for instance burn wound infections, which pose a threat to human life. Exploring possible synergy between various antimicrobial agents, like nanoparticles and plant natural products, may provide new weapons to combat antibiotic resistant pathogens. The objective of this study was to examine the potential of silver nanoparticles (AgNPs) to enhance the antimicrobial activity of selected naphthoquinones (NQs): plumbagin (PL), ramentaceone (RAM), droserone (DR), and 3-chloroplumbagin (3ChPL). We also attempted to elucidate the mechanism by which the AgNPs enhance the antimicrobial activity of NQs. We analyzed the interaction of AgNPs with bacterial membrane and its effect on membrane stability (TEM analysis, staining with SYTO9 and propidium iodide), as well as aggregation of NQs on the surface of nanoparticles (UV-Vis spectroscopy and DLS analysis). Our results demonstrated clearly a synergistic activity of AgNPs and three out of four tested NQs (FBC indexes ≤ 0.375). This resulted in an increase in their combined bactericidal effect toward the S. aureus reference strain and the clinical isolates, which varied in resistance profiles. The synergistic effect (FBC index = 0.375) resulting from combining 3ChPL with silver nitrate used as a control, emphasized the role of the ionic form of silver released from nanoparticles in their bactericidal activity in combination with NQs. The role of membrane damage and AgNPs-NQ interactions in the observed synergy of silver nanoparticles and NQs was also confirmed. Moreover, the described approach, based on the synergistic interaction between the above mentioned agents enables a reduction of their effective doses, thus significantly reducing cytotoxic effect of NQs toward eukaryotic HaCaT cells. Therefore, the present study on the use of a combination of agents (AgNPs-NQs) suggests its potential use as a possible strategy to combat antibiotic-resistant S. aureus.

Reducing Bacterial Infections and Biofilm Formation Using Nanoparticles and Nanostructured Antibacterial Surfaces

With the rapid spreading of resistance among common bacterial pathogens, bacterial infections, especially antibiotic-resistant bacterial infections, have drawn much attention worldwide. In light of this, nanoparticles, including metal and metal oxide nanoparticles, liposomes, polymersomes, and solid lipid nanoparticles, have been increasingly exploited as both efficient antimicrobials themselves or as delivery platforms to enhance the effectiveness of existing antibiotics. In addition to the emergence of widespread antibiotic resistance, of equal concern are implantable device-associated infections, which result from bacterial adhesion and subsequent biofilm formation at the site of implantation. The ineffectiveness of conventional antibiotics against these biofilms often leads to revision surgery, which is both debilitating to the patient and expensive. Toward this end, micro- and nanotopographies, especially those that resemble natural surfaces, and nonfouling chemistries represent a promising combination for long-term antibacterial activity. Collectively, the use of nanoparticles and nanostructured surfaces to combat bacterial growth and infections is a promising solution to the growing problem of antibiotic resistance and biofilm-related device infections.

In Vitro Synergism of Silver Nanoparticles with Antibiotics as an Alternative Treatment in Multiresistant Uropathogens

The increase in the prevalence of bacterial resistance to antibiotics has become one of the main health problems worldwide, thus threatening the era of antibiotics most frequently used in the treatment of infections. The need to develop new therapeutic strategies against multidrug resistant microorganisms, such as the combination of selected antimicrobials, can be considered as a suitable alternative. The in vitro activities of two groups of conventional antimicrobial agents alone and in combination with silver nanoparticles (AgNPs) were investigated against a set of ten multidrug resistant clinical isolate and two references strains by MIC assays and checkerboard testing, as well as their cytotoxicity, which was evaluated on human fibroblasts by MTT assay at the same concentration of the antimicrobial agents alone and in combination. Interesting results were achieved when the AgNPs and their combinations were characterized by Dynamic Light Scattering (DLS), Zeta Potential, Transmission Electron Microscopy (TEM), UV⁻visible spectroscopy and Fourier Transforms Infrared (FTIR) spectroscopy. The in vitro activities of ampicillin, in combination with AgNPs, against the 12 microorganisms showed one Synergy, seven Partial Synergy and four Additive effects, while the results with amikacin and AgNPs showed three Synergy, eight Partial Synergy and one Additive effects. The cytotoxic effect at these concentrations presented a statistically significant decrease of their cytotoxicity (p < 0.05). These results indicate that infections caused by multidrug resistant microorganisms could be treated using a synergistic combination of antimicrobial drugs and AgNPs. Further studies are necessary to evaluate the specific mechanisms of action, which could help predict undesirable off-target interactions, suggest ways of regulating a drug&rsquo;s activity, and identify novel therapeutic agents in this health problem.

Bactericidal Properties of Plants-Derived Metal and Metal Oxide Nanoparticles (NPs)

Nanoparticles (NPs) are nano-sized particles (generally 1–100 nm) that can be synthesized through various methods. The wide range of physicochemical characteristics of NPs permit them to have diverse biological functions. These particles are versatile and can be adopted into various applications, particularly in biomedical field. In the past five years, NPs’ roles in biomedical applications have drawn considerable attentions, and novel NPs with improved functions and reduced toxicity are continuously increasing. Extensive studies have been carried out in evaluating antibacterial potentials of NPs. The promising antibacterial effects exhibited by NPs highlight the potential of developing them into future generation of antimicrobial agents. There are various methods to synthesize NPs, and each of the method has significant implication on the biological action of NPs. Among all synthetic methods, green technology is the least toxic biological route, which is particularly suitable for biomedical applications. This mini-review provides current update on the antibacterial effects of NPs synthesized by green technology using plants. Underlying challenges in developing NPs into future antibacterials in clinics are also discussed at the present review.

Antibacterial and Cytotoxic Potential of Biosynthesized Silver Nanoparticles by Some Plant Extracts

The provision of nanoparticles using biogenic material as a part of green chemistry is an attractive nanotechnology. The current research aimed to test the antimicrobial and cytotoxic efficacy of silver nanoparticles synthesized by extracts of Phoenix dactylifera, Ferula asafetida, and Acacia nilotica as reductant and stabilizing agents in silver nanoparticle formation. Synthesized nanoparticles were evaluated for their antimicrobial activity against Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa and Escherichia coli (Gram-negative) using an agar well diffusion assay. Furthermore, cytotoxic ability was investigated against LoVo cells. The potential phyto-constituents of plant extracts were identified by Fourier-transform infrared spectroscopy (FT-IR) techniques. Field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), and zeta potential analyzed the size and morphology of the biogenic nanoparticles. The current study revealed the ability of the tested plant extract to convert silver ions to silver nanoparticles with an average size that ranged between 67.8 ± 0.3 and 155.7 ± 1.5 nm in diameter. Biogenic AgNPs showed significant antibacterial ability (10 to 32 mm diameter) and anticancer ability against a LoVo cell with IC50 ranged between 35.15–56.73 μg/mL. The innovation of the present study is that the green synthesis of NPs, which is simple and cost effective, provides stable nano-materials and can be an alternative for the large-scale synthesis of silver nanoparticles.

Bio-fabrication of silver nanoparticles using the leaf extract of an ancient herbal medicine, dandelion (Taraxacum officinale), evaluation of their antioxidant, anticancer potential, and antimicrobial activity against phytopathogens

In recent years, the use of nanoparticle-based antimicrobials has been increased due to many advantages over conventional agrochemicals. This study investigates the utilization of common medicinal plant dandelion, Taraxacum officinale, for the synthesis of silver nanoparticles (TOL-AgNPs). AgNPs were evaluated for antimicrobial activity against two important phytopathogens, Xanthomonas axonopodis and Pseudomonas syringae. The morphology, size, and structure of TOL-AgNPs were characterized using UV-visible spectroscopy and X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FT-IR) showed the presence of phytochemicals involved during synthesis of NPs. High-resolution transmission electron microscopy (HR-TEM) analysis shed light on the size of monodispersed spherical AgNPs ranging between 5 and 30 nm, with an average particle size of about 15 nm. The TOL-AgNPs (at 20 μg/mL concentration) showed significant antibacterial activity with significant growth inhibition of phytopathogens X. axonopodis (22.0 ± 0.84 mm) and P. syringae (19.5 ± 0.66 mm). The synthesized AgNPs had higher antibacterial activity in comparison with commercial AgNPs. Synergistic assays with standard antibiotics revealed that nanoformulations with tetracycline showed better broad-spectrum efficiency to control phytopathogens. They also possessed significant antioxidant potential in terms of ABTS (IC₅₀ = 45.6 μg/mL), DPPH (IC₅₀ = 56.1 μg/mL), and NO (IC₅₀ = 55.2 μg/mL) free radical scavenging activity. The TOL-AgNPs showed high cytotoxic effect against human liver cancer cells (HepG2). Overall, dandelion-mediated AgNPs synthesis can represent a novel approach to develop effective antimicrobial and anticancer drugs with a cheap and eco-friendly nature.

Combined systems of different antibiotics with nano-CuO against Escherichia coli and the mechanisms involved

Aim: The combined efficacy of CuO nanoparticles (NPs) with 22 kinds of antibiotics against Escherichia coli was systematic studied, and CuO with cephalexin synergistic system was screened out. Methods: Antimicrobial susceptibility test included disk diffusion test, checkerboard method and time-kill assay. The interactions of CuO NPs and antibiotics were analyzed by x-ray photoelectron spectroscopy, Fourier transform infrared spectra and Zeta. The interactions between bacteria and antibacterial agents were studied by surface plasmon resonance sensor for the first time. Results & Conclusion: Synergistic effect (1+1>2) was observed when CuO NPs combined with cephalexin against E. coli. The concentrated cephalexin molecules interacted more strongly with the E. coli cells to make cell wall become loose. Then, CuO NPs were more easily to damage and penetrate cells. Besides, the presence of antibiotics did not enhance Cu2+ release, Cu2+ uptake and reactive oxygen species generation. But the presence of cephalexin greatly enhanced cell permeability in comparison to others.

Application of Nanoparticle Technologies in the Combat against Anti-Microbial Resistance

Anti-microbial resistance is a growing problem that has impacted the world and brought about the beginning of the end for the old generation of antibiotics. Increasingly, more antibiotics are being prescribed unnecessarily and this reckless practice has resulted in increased resistance towards these drugs, rendering them useless against infection. Nanotechnology presents a potential answer to anti-microbial resistance, which could stimulate innovation and create a new generation of antibiotic treatments for future medicines. Preserving existing antibiotic activity through novel formulation into or onto nanotechnologies can increase clinical longevity of action against infection. Additionally, the unique physiochemical properties of nanoparticles can provide new anti-bacterial modes of action which can also be explored. Simply concentrating on antibiotic prescribing habits will not resolve the issue but rather mitigate it. Thus, new scientific approaches through the development of novel antibiotics and formulations is required in order to employ a new generation of therapies to combat anti-microbial resistance.

Nanoparticles considered as mixtures for toxicological research

Nanoparticles are used widely in our lives, but the understanding of their impacts on human and environmental health is still limited, at least due in part to the fact that nanoparticles are mixtures. This review describes that "nanotoxicity" is actually a test of the overall effect of a nanoparticle mixture: starting materials for nanoparticle preparation, surface coating agents, surface reaction-generated species, and transformed byproducts of the nanoparticle in biological and environmental media, as well as variations of the intrinsic nanoparticle structures.

Impact of tetracycline on the toxic effects of titanium dioxide (TiO2) nanoparticles towards the freshwater algal species, Scenedesmus obliquus

Titanium dioxide nanoparticles (TiO₂ NPs) are the most risk assessed nanoparticles in the aquatic environment due to their increased usage in the various sectors from electronics to consumer products. The natural aquatic system also comprises of numerous toxicants like antibiotics, whose impact on the toxicity of nanoparticles are less assessed. Hence, it is essential to determine the effect of other toxicants on the TiO₂ NP toxicity. In the current study, the impact of antibiotic (tetracycline, TC) on the toxic effect of TiO₂ NPs was studied on a freshwater alga, Scenedesmus obliquus. The median effective concentrations (EC₅₀) of TiO₂ NPs and TC were noted to be 136.88±2.30μM and 0.63±0.02μM, respectively. Based on the EC₅₀ obtained, three different concentrations of TC, such as 0.34, 0.68, and 1.36μM have been selected to evaluate their effect on the toxicity of 18.75, 37.5, and 75μM of TiO₂ NPs. Existence of TC provoked the growth inhibition of TiO₂ NPs at their lower concentrations. In contrast, a reduction in the growth inhibition was noted as the concentrations of TC and TiO₂ NPs were increased. Abbott modeling confirmed the additive and antagonistic effects noted. The stability profile of TiO₂ NPs elucidated the aggregation of NPs with an increase in time. Even though a similar trend has been followed for TiO₂ NPs+TC, a significant difference in the aggregation has not been observed in most cases when compared with TiO₂ NPs alone. The presence of TC lowered the Ti uptake by the algal cells, which portrayed the dominance of TC in the toxic effect of TiO₂ NPs to be either additive or antagonistic. The SEM images of the algal cells upon exposure to TiO₂ NPs, TC, and their mixture elucidated the aggregation of algal cells, cellular deformations like compromised cell membrane, and vacuole formation, etc. In addition, the release of algal exudates was also noticed as a protective layer over the cells to counteract the stress. EPS secretion in response to TiO₂ NPs along with TC is found to be in corroboration with the toxicity patterns observed.

Metal-Based Nanoparticles for the Treatment of Infectious Diseases

Infectious diseases can be transmitted and they cause a significant burden on public health globally. They are the greatest world killers and it is estimated that they are responsible for the demise of over 17 million people annually. The impact of these diseases is greater in the developing countries. People with compromised immune systems and children are the most affected. Infectious diseases may be caused by bacteria, viruses, and protozoa. The treatment of infectious diseases is hampered by simultaneous resistance to multiple drugs, indicating that there is a serious and pressing need to develop new therapeutics that can overcome drug resistance. This review will focus on the recent reports of metal-based nanoparticles that are potential therapeutics for the treatment of infectious diseases and their biological efficacy (in vitro and in vivo).

Bioinspired and Biomimetic AgNPs/Gentamicin-Embedded Silk Fibroin Coatings for Robust Antibacterial and Osteogenetic Applications

With the progressively increasing demand for orthopedic Ti implants, the balance between two primary complications restricting implant applications is needed to be solved: the lack of bone tissue integration and biomedical device-associated infections (BAI), where emergence of multiresistance bacteria make it worse. Notably, a combination of silver nanoparticles (AgNPs) and a kind of antibiotic can synergistically inhibit bacterial growth, where a low concentration of AgNPs has been confirmed to promote the proliferation and osteogenesis of osteoblasts. In this work, we built AgNPs/gentamicin (Gen)-embedded silk fibroin (SF)-based biomimetic coatings on orthopedic titanium by a facile dipping-drying circular process and with the assistance of polydopamine (PD). Ag⁺ was reduced to AgNPs by SF under ultraviolet (UV) irradiation, and then they were detected by transmission electron microscope (TEM) images and UV-visible (UV-vis) analyses. Intriguingly, the addition of Gen highly improved the reduction efficiency of Ag⁺. The antibacterial efficiency of SF-based coatings was examined by challenging them with pathogenic Staphylococcus aureus (S. aureus) bacteria which produced biofilms, and consequently, we found that low concentration loading, durable release of Ag⁺ (28 days), and 10-fold improvement of antibacterial efficiency were achieved for our novel AgNPs- and Gen-embeded silk fibroin coatings. In bacteria and a cells cocultured system, AgNPs/Gen-embedded coatings strongly inhibited adhesion and proliferation of S. aureus, simultaneously improving cell adhesion and growth. To investigate cytocompatibility and osteogenic potential, different coatings were cultured with MC3T3 cells; AgNPs/Gen-embedded coatings showed generally acceptable biocompatibility (cell adhesion, proliferation, and viability) and accelerated osteoblast maturation (alkaline phosphatase production, matrix secretion, and calcification). Expectantly, this novel biofunctional coating will have promising applications in orthopedic and dental titanium implants thanks to its excellently antibacterial, biocompatible, and osteogenic activities.

Silver-Decorated Polymeric Micelles Combined with Curcumin for Enhanced Antibacterial Activity

Because of the mounting prevalence of complicated infections induced by multidrug-resistant bacteria, it is imperative to develop innovative and efficient antibacterial agents. In this work, we design a novel polymeric micelle for simultaneous decorating of silver nanoparticles and encapsulating of curcumin as a combination strategy to improve the antibacterial efficiency. In the constructed combination system, silver nanoparticles were decorated in the micellar shell because of the in situ reduction of silver ions, which were absorbed by the poly(aspartic acid) (PAsp) chains in the shell. Meanwhile, natural curcumin was encapsulated into the poly(ε-caprolactone) (PCL) core of the micelle through hydrophobic interaction. This strategy could prevent aggregation of silver nanoparticles and improve the water solubility of curcumin at the same time, which showed enhanced antibacterial activity toward Gram-negative P.aeruginosa and Gram-positive S.aureus compared with sliver-decorated micelle and curcumin-loaded micelle alone, due to the cooperative antibacterial effects of the silver nanoparticles and curcumin. Furthermore, the achieved combinational micelles had good biocompatibility and low hemolytic activity. Thus, our study provides a new pathway in the rational design of combination strategy for efficiently preventing the ubiquitous bacterial infections.

Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents

Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 μg mL-1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe3O4@SiO2@Ag microflowers exhibit promising applications in the antibacterial fields.

Antibacterial Activity and Synergistic Antibacterial Potential of Biosynthesized Silver Nanoparticles against Foodborne Pathogenic Bacteria along with its Anticandidal and Antioxidant Effects

Silver nanoparticles plays a vital role in the development of new antimicrobial substances against a number of pathogenic microorganisms. These nanoparticles due to their smaller size could be very effective as they can improve the antibacterial activity through lysis of bacterial cell wall. Green synthesis of metal nanoparticles using various plants and plant products has recently been successfully accomplished. However, few studies have investigated the use of industrial waste materials in nanoparticle synthesis. In the present investigation, synthesis of silver nanoparticles (AgNPs) was attempted using the aqueous extract of corn leaf waste of Zea mays, which is a waste material from the corn industry. The synthesized AgNPs were evaluated for their antibacterial activity against foodborne pathogenic bacteria (Bacillus cereus ATCC 13061, Listeria monocytogenes ATCC 19115, Staphylococcus aureus ATCC 49444, Escherichia coli ATCC 43890, and Salmonella Typhimurium ATCC 43174) along with the study of its synergistic antibacterial activity. The anticandidal activity of AgNPs were evaluated against Candida species (C. albicans KACC 30003 and KACC 30062, C. glabrata KBNO6P00368, C. geochares KACC 30061, and C. saitoana KACC 41238), together with the antioxidant potential. The biosynthesized AgNPs were characterized by UV-Vis spectrophotometry with surface plasmon resonance at 450 nm followed by the analysis using scanning electron microscope, X-ray diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis. The AgNPs displayed moderate antibacterial activity (9.26-11.57 mm inhibition zone) against all five foodborne pathogenic bacteria. When AgNPs were mixed with standard antibacterial or anticandidal agent, they displayed strong synergistic antibacterial (10.62-12.80 mm inhibition zones) and anticandidal activity (11.43-14.33 mm inhibition zones). In addition, the AgNPs exhibited strong antioxidant potential. The overall results highlighted the potential use of maize industrial waste materials in the synthesis of AgNPs and their utilization in various applications particularly as antibacterial substance in food packaging, food preservation to protect against various dreadful foodborne pathogenic bacteria together with its biomedical, pharmaceutical based activities.

Synergistic antibacterial effect of Bi2S3 nanospheres combined with ineffective antibiotic gentamicin against methicillin-resistant Staphylococcus aureus

In this paper, Bi₂S₃ nanospheres with size of 212nm were prepared by a simple hydrothermal process. The selectively enhanced antibacterial effects of Bi₂S₃ nanospheres with three classes of ineffective antibiotics, β-lactam (cefuroxime, CXM; cefotaxime, CTX and piperacillin, PIP), quinolone (ciprofloxacin, CIP) and aminoglycoside (gentamicin, GEN) against clinical isolated methicillin-resistant Staphylococcus aureus (MRSA) were investigated for the first time. GEN shows significantly synergistic growth inhibition against MRSA when combined with Bi₂S₃ nanospheres, while CXM, CTX, PIP and CIP do not. Raman spectroscopy and Z potential studies reveal that Bi₂S₃ could interact with GEN and the combination showed small electronegativity, which probably induced the increase of GEN content in cytoplasm of bacteria. Furthermore, the combination of Bi₂S₃ nanospheres and GEN can destroy the bacterial membrane function and induce more bactericidal reactive oxygen generation than that of Bi₂S₃ or GEN alone. The cytotoxicity test indicates that the combination of Bi₂S₃ and GEN presented low toxicity to human normal hepatocyte L02. This work shows that Bi₂S₃ nanospheres can be used to enhance the action of ineffective antibiotic GEN against MRSA, thus strengthening the antibiotic capacity for fighting MRSA infections.