Silver Nanoparticle Conjugation-Enhanced Antibacterial Efficacy of Clinically Approved Drugs Cephradine and Vildagliptin

Neurospora sp. Mediated Synthesis of Naringenin for the Production of Bioactive Nanomaterials

The application of Neurospora sp., a fungus that commonly thrives on complex agricultural and plant wastes, has proven successful in utilizing citrus peel waste as a source of naringin. A UV-Vis spectrophotometric method proved the biotransformation of naringin, with an absorption maximum (λmax) observed at 310 nm for the biotransformed product, naringenin (NAR). Further verification of the conversion of naringin was provided through thin layer chromatography (TLC). The Neurospora crassa mediated biotransformation of naringin to NAR was utilized for the rapid (within 5 min) synthesis of silver (Ag) and gold (Au) nanoconjugates using sunlight to accelerate the reaction. The synthesized NAR-nano Ag and NAR-nano Au conjugates exhibited monodispersed spherical and spherical as well as polygonal shaped particles, respectively. Both of the nanoconjugates showed average particle sizes of less than 90 nm from TEM analysis. The NAR-Ag and NAR-Au nanoconjugates displayed potential enhancement of the antimicrobial activities, including antibacterial and nematicidal properties over either standalone NAR or Ag or Au NPs. This study reveals the potential of naringinase-producing Neurospora sp. for transforming naringin into NAR. Additionally, the resulting NAR-Ag and NAR-Au nanoconjugates showed promise as sustainable antibiotics and biochemical nematicides.

Therapeutic biliary stents: applications and opportunities

INTRODUCTION

Biliary stents are used to optimize ductal patency and enable bile flow in the management of obstruction or injury related to biliary tract tumors, strictures, stones, or leaks. Although direct therapeutic applications of biliary stents are less well developed, stents can be used to deliver drugs, radioisotopes, and photodynamic therapy.

AREAS COVERED

This report provides an in-depth overview of the clinical indications, and therapeutic utility of biliary stents. Unique considerations for the design of biliary stents are described. The properties and functionalities of materials used for stents such as metal alloys, plastic polymers, or biodegradable materials are described, and opportunities for design of future stents are outlined. Current and potential applications of stents for therapeutic applications for biliary tract diseases are described.

EXPERT OPINION

Therapeutic biliary stents could be used to minimize inflammation, prevent stricture formation, reduce infections, or provide localized anti-cancer therapy for biliary tract cancers. Stents could be transformed into therapeutic platforms using advanced materials, 3D printing, nanotechnology, and artificial intelligence. Whilst clinical study and validation will be required for adoption, future advances in stent design and materials are expected to expand the use of therapeutic biliary stents for the treatment of biliary tract disorders.

The role of silver nanoparticles alone and combined with imipenem on carbapenem-resistant Klebsiella pneumoniae

AIMS

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections poses a significant threat to human health, necessitating urgent development of new antimicrobial agents. Silver nanoparticles (AgNPs), which are among the most widely used engineered nanomaterials, have been extensively studied. However, the impact of AgNPs on CRKP and the potential for drug resistance development remain inadequately explored.

METHODS AND RESULTS

In this study, broth dilution method was used to determine the minimum inhibitory concentration (MIC) was determined using the broth dilution method. Results indicated MIC values of 93.1 ± 193.3 µg ml-1 for AgNPs, 2.3 ± 5.1 µg ml-1 for AgNO3, and 25.1 ± 48.3 µg ml-1 for imipenem (IMI). The combined inhibitory effect of AgNPs and IMI on CRKP was assessed using the checkerboard method. Moreover, after 6-20 generations of continuous culture, the MIC value of AgNPs increased 2-fold. Compared to IMI, resistance of Kl. pneumoniae to AgNPs developed more slowly, with a higher fold increase in MIC observed after 20 generations. Whole-genome sequencing revealed four nonsynonymous single nucleotide polymorphism mutations in CRKP after 20 generations of AgNP treatment.

CONCLUSION

We have demonstrated that AgNPs significantly inhibit CRKP isolates and enhance the antibacterial activity of imipenem against Kl. pneumoniae. Although the development of AgNP resistance is gradual, continued efforts are necessary for monitoring and studying the mechanisms of AgNP resistance.

Biological activity comparison between ciprofloxacin loaded to silica nanoparticles and silver nanoparticles for the inhibition of Brucella melitensis

Background and Aim

Brucella melitensis is responsible for brucellosis, a highly contagious, life-threatening disease that has a high impact in low- and middle-income countries. This study aimed to compare silica nanoparticles (SiO-NPs) loaded with ciprofloxacin with silver nanoparticles (AgNPs) loaded with ciprofloxacin to evaluate the possible replacement of silver by silica to enhance biological activity and reduce cytotoxicity.

Materials and Methods

SiO-NPs and AgNPs loaded with ciprofloxacin were characterized using ultraviolet spectroscopy, scanning electron microscopy, and dynamic light scattering microscopy for size demonstration and loading efficiency. Both nanoparticles were treated with B. melitensis Rev 1 to evaluate their biological activity. Nanoparticle toxicity was also evaluated using cytotoxicity and hemolysis assays.

Results

SiO-NP was found to have a smaller size (80 nm) and higher loading efficiency with polydispersity index and zeta potential of 0.43 and 30.7 mV, respectively, compared to Ag-NP (180 nm and 0.62 and 28.3 mV, respectively). SiO-NP was potent with a minimum inhibitory concentration of 0.043 μg/mL compared to Ag-NP (0.049 μg/mL), with a lower cytotoxicity and hemolysis activity.

Conclusion

SiO-NP, as a drug delivery system for ciprofloxacin, has better antimicrobial activity against B. melitensis with lower cytotoxicity and hemolysis activity. These results can be attributed to the enhanced physical characterization and better loading efficiency when compared to Ag-NP.

Silk fibroin/polyvinyl alcohol composite film loaded with antibacterial AgNP/polydopamine-modified montmorillonite; characterization and antibacterial properties

In this study, a kind of nanocomposite film was fabricated via combining silk fibroin, polyvinyl alcohol (SF/PVA) and AgNP/polydopamine-modified Montmorillonite (AgNP/PDA-Mt). The structural characteristics and properties of the SF/PVA/AgNP/PDA-Mt nanocomposites films were identified using X-ray diffraction (XRD), Thermal gravimetric analyzer (TGA), Fourier transform infrared spectroscopy (FTIR), EDS-mapping analyses and Scanning electron microscope (SEM). The results indicated enhanced thermal performance of SF/PVA/AgNP/PDA-Mt nanocomposites with increased AgNP/PDA-Mt weight. The nanocomposite film exhibited excellent antibacterial activity against E. coli and S. aureus. The 2 % SF/PVA/AgNP/PDA-Mt film showed the highest zone of inhibition with an average inhibition circle diameter of 26.1 mm against E. coli and 20.61 mm against S. aureus. Cytotoxicity test results indicated that the nanocomposites films were biocompatible with L929 cells with a 100 % survival rate, which can be considered as one of the advantages of new nanocomposites films. These findings suggest that SF/PVA/AgNP/PDA-Mt films have potential clinical applications in wound dressing and antibacterial biomedical applications.

Naringenin biosynthesis and fabrication of naringenin mediated nano silver conjugate for antimicrobial potential

The development of resistance, instability and high doses are some drawbacks of biologically active natural products. Modification of natural compounds to make it broad spectrum is the standard approach in drug design. This paper sets to modify the naringenin by silver nanoparticle conjugation to enhance its already reported pharmacological activities. The naringenin-nano silver conjugate was synthesized by one-step green synthesis, that is, sunlight exposure confirmed by UV spectroscopy. The biosynthesized naringenin-nanosilver conjugate was tested for antiacanthamoebal and antimicrobial potential. The antibacterial potential was increased by 5.8-6.14 fold against Gram positive bacteria, that is, S. aureus and Bacillus subtilis and 4.5-13.6 fold against Gram negative bacteria, that is, Escherichia coli and Pseudomonas aeruginosa. The standard naringenin-nanosilver conjugate significantly reduced the LC50 values against the Acanthamoeba cells, by, 66% and 36%, as compared to substrate naringin and standard naringenin respectively while biotransformed naringinin-nanosilver conjugate reduced LC50 by 50.56%, compared with biotransformed naringenin. Hence modification of natural product as nanoconjugate is the best practice for improvement as an effective drug.

Antibacterial efficacy of synthesized silver nanoparticles of Microbacterium proteolyticum LA2(R) and Streptomyces rochei LA2(O) against biofilm forming meningitis causing microbes

Actinobacteria obtained from the least explored Indian regions were studied for their ability to suppress meningitis-causing bacteria in nanoparticle form. Drug-resistant bacteria and long-term treatment with different medications make meningitis control complicated. Thus, new meningitis drugs are required to combat MDR bacteria. In this study, secondary metabolites isolated from actinomycetes strains, Microbacterium proteolyticum LA2(R) and Streptomyces rochei LA2(O), were employed to synthesize silver nanoparticles (AgNPs) at 37 °C for seven days incubation. UV-Vis spectroscopy, TEM, FTIR, and HPLC studies were used for the confirmation of the synthesis of AgNPs. Furthermore, these NPs demonstrated antibacterial and antibiofilm activities against meningitis-causing bacteria. The average size of LA2(R) and LA2(O) isolated secondary metabolites mediated AgNPs was observed to be 27 ± 1and 29 ± 2 nm by TEM analysis. FTIR study of RAgNPs and OAgNPs revealed that presence of peaks with positions of 1637.17 cm¹ and 1636.10 cm¹ for C=O amide group appearances in the amide I linkage. These NPs were effective against bacterial pathogens such as S. pneumoniae, H. influenzae, and N. meningitidis and confirmed by their MICs, i.e., 109.4, 120.60, and 138.80 μg/ml of RAgNPs and 105.80, 114.40 and 129.06 μg/ml of OAgNPs, respectively. Additionally, the production of biofilms is impeded by these nanoparticles on S. pneumoniae, H. influenzae, and N. meningitidis by 73.14%, 71.89% and 64.81%, respectively. These findings confirm the potential role of synthesized AgNPs against biofilm forming meningitis causing Multidrug resistance (MDR) microbes.

Therapeutic Applications of Biogenic Silver Nanomaterial Synthesized from the Paper Flower of Bougainvillea glabra (Miami, Pink)

In this research, Bougainvillea glabra paper flower extract was used to quickly synthesize biogenic silver nanoparticles (BAgNPs) utilizing green chemistry. Using the flower extract as a biological reducing agent, silver nanoparticles were generated by the conversion of Ag⁺ cations to Ag⁰ ions. Data patterns obtained from physical techniques for characterizing BAgNPs, employing UV-visible, scattering electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), suggested that the nanoparticles have a spherical to oval form with size ranging from 10 to 50 nm. Spectroscopy and microscopic analysis were used to learn more about the antibacterial properties of the biologically produced BAgNPs from Bougainvillea glabra. Further, the potential mechanism of action of nanoparticles was investigated by studying their interactions in vitro with several bacterial strains and mammalian cancer cell systems. Finally, we can conclude that BAgNPs can be functionalized to dramatically inhibit bacterial growth and the growth of cancer cells in culture conditions, suggesting that biologically produced nanomaterials will provide new opportunities for a wide range of biomedical applications in the near future.

The Activity of Vossia cuspidata Polysaccharides-Derived Monometallic CuO, Ag, Au, and Trimetallic CuO-Ag-Au Nanoparticles Against Cancer, Inflammation, and Wound Healing

The biosynthesis of metal nanoparticles using plant extracts is an eco-friendly and inexpensive solution that has strong potential and applications in science and industry. This study aims to synthesize Cu, Ag, and Au monometallic and trimetallic nanoparticles (NPs) using the extracted polysaccharides (PS) of Vossia cuspidata (Roxb.) Griff. leaves. Besides, the anti-cancer, anti-inflammatory, and wound healing potentials of the synthesized NPs were tested. The synthesized NPs were characterized using standard technological methods. We succeeded in green synthesizing CuO, Ag, Au, monometallic, and CuO-Ag-Au trimetallic NPs. The synthesized NPs had weak cytotoxicity at low concentrations (6.5 µg/ml), but the viability of cancer cells was reduced by increasing the concentration, suggesting that the synthesized NPs have potent anti-cancer properties against the cells. The synthesized NPs had 19.44–45.9 μg/ml cytotoxic activity (IC50) against the MCF-7 cell line, 16.50–51.92 μg/ml against A549, and 115.90–165.9 μg/ml for normal lung cells (WI-38). TMNPs were the most effective cytotoxic agents against all the tested cell lines, followed by AuNPs on MCF-7 and CuONPs on A549. The cotton fabric-treated TMNPs and CuONPs exhibited anti-inflammatory properties greater than fabric-treated AgNPs and AuNPs and showed the highest odema inhibition (84.61% and 79.28%, respectively). In the wound healing assay, CuONPs and TMNPs caused the highest percentages of inhibition (87.82% and 61.98%, respectively) for the wound compared to AgNPs and AuNPs. TMNPs and CuONPs were more efficient in restoring the tissue integrity of wounds than AgNPs and AuNPs. Accordingly, we recommend using TMNPs and CuONPs in the wound healing dressings.

Conjugation of a WOW Peptide with silver nanoparticles to face the increase of antimicrobial resistance during COVID 19 pandemic

Bacterial resistance is a difficult limitation in the treatment of infections. The potential antibacterial activity of WOW peptide conjugation with silver nanoparticles against selected pathogens is investigated in this study. The peptide WOW was created by combining two tryptophan subunits and one ornithine amino acid, and its purity was determined using reverse phase high performance liquid chromatography. Mass spectrometry and electrospray ionization mass spectrometry were used to confirm the WOW peptide. Silver nanoparticles conjugated with WOW were created by adding WOW to a solution of silver nitrate in the presence of the reducing agent sodium borohydride. The yellow-brown color indicated the presence of WOW-AgNPs, which was confirmed by ultraviolet/visible spectrophotometry. The minimum inhibitory and bactericidal concentrations of WOW nanoparticles were determined using the micro dilution method against Staphylococcus aureus, Escherichia coli, Methicillin resistant Staphylococcus aureus (MRSA), and ESBL Escherichia coli. The Erythrocyte Hemolytic Assay was used to assess the toxicity of nanoparticles conjugated with WOW. WOW alone was effective (MICs between 120 and 215 µgml-1) against both standard and resistant strains of bacteria. WOW –AgNPs, on the other hand, were more effective, with MICs ranging from 30 to 100 µgml-1 depending on the bacteria used. WOW -–after 30 minutes of incubation, silver nanoparticles at a concentration of 100 µgml-1 caused only 3% hemolysis in human erythrocytes.in conclusion, WOW –silver nanoparticles were found to have good antibacterial activity against pathogenic strains of gram positive and gram negative bacteria. Furthermore, the conjugate demonstrated low hemolytic activity and cytotoxicity. As a result, WOW conjugation with AgNPs is a promising treatment candidate for bacterial infection with low toxicity.

Silver Nanoparticles Functionalized Nanosilica Grown over Graphene Oxide for Enhancing Antibacterial Effect

The continuous growth of multidrug-resistant bacteria due to the overuse of antibiotics and antibacterial agents poses a threat to human health. Silver nanoparticles, silica-based materials, and graphene-based materials have become potential antibacterial candidates. In this study, we developed an effective method of enhancing the antibacterial property of graphene oxide (GO) by growing nanosilica (NS) of approximately 50 nm on the graphene oxide (GO) surface. The structures and compositions of the materials were characterized through powdered X-ray diffraction (P-XRD), transmission electron microscopy (TEM), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), ultraviolet-visible spectroscopy (UV-VIS), dynamic light scattering (DLS), Raman spectroscopy (RM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmet-Teller (BET) surface area, and pore size determination. The silver nanoparticles (AgNPs) with an average diameter of 26 nm were functionalized on the nanosilica (NS) surface. The composite contained approximately 3% of silver nanoparticles. The silver nanoparticles on nanosilica supported over graphene oxide (GO/NS/AgNPs) exhibited a 7-log reduction of Escherichia coli and a 5.2-log reduction of Bacillus subtilis within one hour of exposure. Both GO/NS and GO/NS/AgNPs exhibited substantial antimicrobial effects against E. coli and B. subtilis.

Silver Nanoparticles Conjugated with Colistin Enhanced the Antimicrobial Activity against Gram-Negative Bacteria

Colistin is a potent peptide antibiotic that is effective against Gram-negative bacteria. However, nephrotoxicity limited its clinical use. Silver nanoparticles (AgNPs) have gained attention as a potential antimicrobial agent and nanodrug carrier. The conjugation of antibiotics and AgNPs has been found to increase the activity and decrease drug toxicity. In this study, colistin was conjugated with AgNPs (Col-AgNPs), which was confirmed by Fourier-transform infrared (FT-IR) and energy-dispersive X-ray (EDX) spectra. The optimized Col-AgNPs had the proper characteristics, including spherical shape, monodispersity, nanosized particle, high surface charge, and good stability. The powder X-ray diffraction (PXRD) pattern supported the crystallinity of Col-AgNPs and AgNPs. The drug loading of Col-AgNPs was 11.55 ± 0.93%. Col-AgNPs had higher activity against Gram-negative bacteria (Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa) than AgNPs and colistin. The mechanism of actions of Col-AgNPs involved membrane disruption and genomic DNA damage. The Col-AgNPs and AgNPs were biocompatible with human red blood cells and renal cells at concentrations up to 16 µg/mL. Interestingly, Col-AgNPs exhibited higher cell survival than AgNPs and colistin at 32 µg/mL. Our results revealed that the Col-AgNPs could enhance the antimicrobial activity and cell biocompatibility more than colistin and AgNPs.

Study the Effect of Conjugate Novel Ultra-Short Antimicrobial Peptide with Silver Nanoparticles against Methicillin Resistant S. aureus and ESBL E. coli

Background: Bacterial resistance is a challenging limitation in infection treatment. This work evaluates the potential antibacterial activity of conjugation of Tryasine peptide with silver nanoparticles against selected pathogens. Materials and Methods: The peptide Tryasine was produced using three subunits of tryptophan and three lysine amino acids, then its purity was determined by reverse-phase high-performance liquid chromatography. The peptide was confirmed using mass spectrometry and electrospray ionization mass spectrometry. Silver nanoparticles conjugate with Tryasine was synthesized by adding Tryasine-silver nitrate solution in the presence of the reducing agent sodium borohydride. The presence of Tryasine-silver nanoparticles was indicated by the yellow-brown color and was further confirmed through ultraviolet-visible spectrophotometry. The minimum inhibitory and minimum bactericidal concentrations for Tryasine nanoparticles were determined against Staphylococcus aureus, Escherichia coli, methicillin resistant Staphylococcus aureus, and ESBL Escherichia coli using the microdilution method. Toxicity for nanoparticles conjugated with Tryasine was determined using erythrocyte hemolytic assay. Results: Tryasine alone was effective (MIC around 100 and 200 μM) against standard and resistant strains of bacteria used. However, Tryasine-silver nanoparticles were more effective with MICs ranging from 30 to 100 μM depending on the bacterial strain used. Tryasine-silver nanoparticles at concentration of 100 μM only caused 1% hemolysis on human erythrocytes after 30 min of incubation. Conclusions: The findings indicate that Tryasine-silver nanoparticles had good antibacterial activity against pathogenic strains of Gram-positive and Gram-negative bacteria. Additionally, the conjugate showed low hemolytic activity and cytotoxicity. Therefore, conjugation of Tryasine with silver nanoparticles is a promising treatment candidate for bacterial infection with low toxicity.

Silver nanoparticle-conjugated antibiotics inhibit in vitro growth of Brucella melitensis

Background and Aim:

Brucellosis is a contagious livestock disease with a significant economic impact. This study aimed to compare the efficacy of antibiotics used alone or in combination with silver nanoparticles (AgNPs) against Brucella melitensis Rev 1 invitro.

Materials and Methods:

AgNps conjugated with ciprofloxacin was synthesized and thoroughly characterized by ultraviolet visible spectrophotometry (UV-vis). The antimicrobial effect of ciprofloxacin alone and ciprofloxacin conjugated with AgNPs against B. melitensis Rev 1 was determined by minimum inhibitory concentration (MIC) and the erythrocyte hemolytic assay determined the capability of conjugation to cause hemolysis in human erythrocyte.

Results:

The UV-vis spectra of both silver-drug nanoconjugates showed a characteristic surface plasmon resonance band at 420 nm. The MIC assays showed that AgNPs conjugation to antibiotics enhanced the antibacterial potential of the selected antibiotics against B. melitensis Rev 1 relative to non-conjugated antibiotics. The results show that low concentrations of AgNPs can kill B. melitensis Rev 1. The MICs of ciprofloxacin and ciprofloxacin–AgNPs were 0.75 and 0.05 μM, respectively.

Conclusion:

The conjugation of ciprofloxacin with AgNPs enhanced the antibacterial effects against B. melitensis Rev 1. In addition, this conjugation appears to inhibit the capability of this bacterium to adapt to the presence of antibiotics, thereby inhibiting bacterial resistance. Further studies are required to examine its potential as an in vivo treatment.

Antiamoebic Properties of Laboratory and Clinically Used Drugs against Naegleria fowleri and Balamuthia mandrillaris

Naegleria fowleri and Balamuthia mandrillaris are pathogenic free-living amoebae that infect the central nervous system with over 95% mortality rates. Although several compounds have shown promise in vitro but associated side effects and/or prolonged approval processes for clinical applications have led to limited success. To overcome this, drug repurposing of marketed compounds with known mechanism of action is considered a viable approach that has potential to expedite discovery and application of anti-amoebic compounds. In fact, many of the drugs currently employed in the treatment of N. fowleri and B. mandrillaris, such as amphotericin B, fluconazole, rifampin and miltefosine, are repurposed drugs. Here, we evaluated a range of clinical and laboratory compounds including metformin, quinclorac, indaziflam, inositol, nateglinide, 2,6-DNBT, trans-cinnamic acid, terbuthylazine, acarbose, glimepiride, vildagliptin, cellulase, thaxtomin A, repaglinide and dimethyl peptidase (IV) inhibitor against N. fowleri and B. mandrillaris. Anti-amoebic assays revealed that indaziflam, nateglinide, 2,6-DNBT, terbuthylazine, acarbose and glimepiride exhibited potent amoebicidal properties against both N. fowleri and B. mandrillaris. Notably, all compounds tested showed minimal human (HaCaT) cell cytotoxicity as determined by lactate dehydrogenase release. Prospective research using animal models is warranted to determine the potential of these repurposed compounds, as well as the need for investigating the intranasal route of delivery to treat these devastating infections.

Collagen Hydrogels Loaded with Silver Nanoparticles and Cannabis Sativa Oil

Wounds represent a major healthcare problem especially in hospital-associated infections where multi-drug resistant strains are often involved. Nowadays, biomaterials with therapeutic molecules play an active role in wound healing and infection prevention. In this work, the development of collagen hydrogels loaded with silver nanoparticles and Cannabis sativa oil extract is described. The presence of the silver nanoparticles gives interesting feature to the biomaterial such as improved mechanical properties or resistance to collagenase degradation but most important is the long-lasting antimicrobial effect. Cannabis sativa oil, which is known for its anti-inflammatory and analgesic effects, possesses antioxidant activity and successfully improved the biocompatibility and also enhances the antimicrobial activity of the nanocomposite. Altogether, these results suggest that this novel nanocomposite biomaterial is a promising alternative to common treatments of wound infections and wound healing.

Silver Nanoparticles Formation by Jatropha integerrima and LC/MS-QTOF-Based Metabolite Profiling

The broad application of metal nanoparticles in different fields encourages scientists to find alternatives to conventional synthesis methods to reduce negative environmental impacts. Herein, we described a safe method for preparing silver nanoparticles (J-AgNPs) using Jatropha integerrima leaves extract as a reducing agent and further characterize its physiochemical and pharmacological properties to identify its therapeutic potential as a cytotoxic and antimicrobial agent. The biogenic synthesized J-AgNPs were physiochemically characterized by ultraviolet-visible spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy. HPLC-DAD, followed by LC/MS and the Fourier-transform infrared spectroscopy (FTIR), was applied to detect the biomolecules of J. integerrima involved in the fabrication of NPs. Furthermore, J-AgNPs and the ampicillin-nanocomposite conjugate were investigated for their potential antibacterial effects against four clinical isolates. Finally, cytotoxic effects were also investigated against cancer and normal cell lines, and their mechanism was assessed using TEM analysis and confocal laser scanning microscopy (LSM). Ag ions were reduced to spherical J-AgNPs, with a zeta potential of −34.7 mV as well as an average size of 91.2 and 22.8 nm as detected by DLS and TEM, respectively. HPLC GC/MC analysis identified five biomolecules, and FTIR suggested the presence of proteins besides polyphenolic molecules; together, these molecules could be responsible for the reduction and capping processes during NP formation. Additionally, J-AgNPs displayed a strong antibacterial effect, although the ampicillin conjugated form had a very weak antibacterial effect. Furthermore, the NPs caused a reduction in cell viability of all the treated cells by initiating ultrastructural changes and apoptosis, as identified by TEM and LSM analysis. Therefore, J-AgNPs can be formed using the leaf extract from the J. integerrima plant. Furthermore, J-AgNPs may serve as a candidate for further biochemical and pharmacological testing to identify its therapeutic value.

Biological Potential of Silver Nanoparticles Mediated by Leucophyllum frutescens and Russelia equisetiformis Extracts

Awareness about environmental concerns is increasing, specially the pollution resulting from nanoparticles (NPs) production, which has led to great interest in the usage of biogenic agents for their fabrication. The current investigation used eco-friendly organic phytomolecules from Leucophyllum frutescens and Russelia equisetiformis leaves extract for the first time in the fabrication of silver NPs from silver ions and further an assessment of their biological activities was performed. The leaves extract from both plant sources were used as capping and reducing agents and added to AgNO₃. The mixtures were observed for colour changes, and after a stable dark brown colour was obtained, the NPs were separated and further investigated using dynamic light scattering, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The Fourier transform infrared spectroscopy technique was employed to determine the active organic ingredients in the plant extracts. The prepared NPs were tested against three cell lines (two cancer ones and one normal control) and the effects observed using TEM and confocal laser scanning microscopy (LSM). Antibacterial activity against two Gram positive and two Gram negative species was examined and the synergistic effect of the ampicillin-NPs conjugate was studied. Findings showed successful conversion of Ag ions into L-AgNPs and R-AgNPs achieved using L.frutescens and R. equisetiformis extracts, respectively. A mean size of 112.9 nm for L-AgNPs and 151.7 nm for R-AgNPs and negative zeta potentials were noted. TEM analysis showed spherical NPs and EDS indicated Ag at 3 keV. Reduction in cancer cell viability with low half-maximal inhibitory concentrations was noted for both tested NPs. Structural changes and apoptotic features in the treated cancer cell lines were noted by TEM and cell death was confirmed by LSM. Furthermore, higher antibacterial activity was noticed against Gram positive compared with Gram negative bacteria as well as high synergistic effect was noted for the Amp-NPs conjugate, specially against Gram positive bacteria. The current investigation has thus developed an eco-friendly NPs synthesis route by applying plant extracts to efficiently produce NPs endowed with potential cytotoxic and antibacterial capacity, which therefore could be recommended as new approaches to overcome human diseases with minimal environmental impact.

Moxifloxacin and Sulfamethoxazole-Based Nanocarriers Exhibit Potent Antibacterial Activities

Antibiotic resistance is a major concern given the rapid emergence of multiple-drug-resistant bacteria compared to the discovery of novel antibacterials. An alternative strategy is enhancing the existing available drugs. Nanomedicine has emerged as an exciting area of research, showing promise in the enhanced development of existing antimicrobials. Herein, we synthesized nanocarriers and loaded these with available clinically approved drugs, namely Moxifloxacin and Sulfamethoxazole. Bactericidal activity against Gram-negative (Serratia marcescens, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Salmonella enterica) and Gram-positive (methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, and Bacillus cereus) bacteria was investigated. To characterize the nanocarriers and their drug-loaded forms, Fourier-transform infrared spectroscopy, dynamic light scattering, and atomic force microscopy were utilized. Antibacterial assays and hemolysis assays were carried out. Moreover, lactate dehydrogenase assays were performed to determine cytotoxicity against human cells. The results depicted the successful formation of drug-nanocarrier complexes. The potent antibacterial activities of the drug-loaded nanocarriers were observed and were significantly enhanced in comparison to the drugs alone. Hemolysis and cytotoxicity assays revealed minimal or negligible cytotoxic effects against human red blood cells and human cells. Overall, metronidazole-based nanocarriers loaded with Moxifloxacin and Sulfamethoxazole showed enhanced bactericidal effects against multiple-drug-resistant bacteria compared with drugs alone, without affecting human cells. Our findings show that drug-loaded nanocarriers hold promise as potent chemotherapeutic drugs against multiple-drug-resistant bacteria.

Colorimetric sensing of cephradine through polypropylene glycol functionalized gold nanoparticles

The development of metal nanoparticle-based facile colorimetric assays for drugs and insecticides is an emerging area of current scientific research. In the present work, polypropylene glycol was used for stabilization of gold nanoparticles (AuNPs) in a simple one-pot two-phase process and subsequently employed it for the specific detection of cephradine (CPH). The characterization of the prepared PPG-AuNPs was conducted through various analytical techniques such as UV-visible spectrophotometry, Fourier transform infrared spectroscopy, atomic force microscopy (AFM), zeta potential and zetasizer techniques. As the major target of the study, the stabilized PPG-AuNPs were employed for colorimetric detection of CPH and other drugs. Typical wine-red colour of PPG-AuNPs disappeared immediately and surface plasmon resonance band quenched by addition of CPH in the presence of several other interferents (drugs and salts) and in real samples. PPG-AuNPs permitted efficient, selective, reliable and rapid determination in a concentration range of 0.01-120 mM with a detection limit (LoD) of 11.0 mM. The developed sensor has the potential to be used for fast scanning of pharmaceutical formulations for quantification of CPH at production facilities.

Gut Bacteria of Rattus rattus (Rat) Produce Broad-Spectrum Antibacterial Lipopeptides

Among several animals, Rattus rattus (rat) lives in polluted environments and feeds on organic waste/small invertebrates, suggesting the presence of inherent mechanisms to thwart infections. In this study, we isolated gut bacteria of rats for their antibacterial activities. Using antibacterial assays, the findings showed that the conditioned media from selected bacteria exhibited bactericidal activities against Gram-negative (Escherichia coli K1, Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia marcescens, and Salmonella enterica) and Gram-positive (Bacillus cereus, methicillin-resistant Staphylococcus aureus, and Streptococcus pyogenes) pathogenic bacteria. The conditioned media retained their antibacterial properties upon heat treatment at boiling temperature for 10 min. Using MTT assays, the conditioned media showed minimal cytotoxic effects against human keratinocyte cells. Active conditioned media were subjected to tandem mass spectrometry, and the results showed that conditioned media from Bacillus subtilis produced a large repertoire of surfactin and iturin A (lipopeptides) molecules. To our knowledge, this is the first report of isolation of lipopeptides from bacteria isolated from the rat gut. In short, these findings are important and provide a platform to develop effective antibacterial drugs.

Nanobiosystems for Antimicrobial Drug-Resistant Infections

The worldwide increased bacterial resistance toward antimicrobial therapeutics has led investigators to search for new therapeutic options. Some of the options currently exploited to treat drug-resistant infections include drug-associated nanosystems. Additionally, the use of bacteriophages alone or in combination with drugs has been recently revisited; some studies utilizing nanosystems for bacteriophage delivery have been already reported. In this review article, we focus on nine pathogens that are the leading antimicrobial drug-resistant organisms, causing difficult-to-treat infections. For each organism, the bacteriophages and nanosystems developed or used in the last 20 years as potential treatments of pathogen-related infections are discussed. Summarizing conclusions and future perspectives related with the potential of such nano-antimicrobials for the treatment of persistent infections are finally highlighted.

Antimicrobial properties of multifunctional polypyrrole-cobalt oxide-silver nanocomposite against pathogenic bacteria and parasite

BACKGROUND

Conducting polymer based nanocomposites are known to be effective against pathogens. Herein, we report the antimicrobial properties of multifunctional polypyrrole-cobalt oxide-silver nanocomposite (PPy-Co₃O₄-AgNPs) for the first time. Antibacterial activities were tested against multi-drug-resistant Gram-negative Escherichia coli (E. coli) and Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) bacteria, while antiamoebic effects were assessed against opportunistic protist Acanthamoeba castellanii (A. castellanii).

RESULTS

The ternary nanocomposite containing conducting polymer polypyrrole, cobalt oxide, and silver nanoparticles showed potent antimicrobial effects against these pathogens. The antibacterial assay showed that PPy-Co₃O₄-AgNPs exhibited significant bactericidal activity against neuropathogenic E. coli K1 at only 8 μg/mL as compared to individual components of the nanocomposite, whereas a 70 % inhibition of A. castellanii viability was observed at 50 μg/mL. Moreover, PPy-Co₃O₄-AgNPs were found to have minimal cytotoxicity against human keratinocytes HaCaT cells in vitro even at higher concentration (50 μg/mL), and also reduced the microbes-mediated cytopathogenicity against host cells.

CONCLUSION

These results demonstrate that PPy-Co₃O₄-AgNPs hold promise in the development of novel antimicrobial nanomaterials for biomedical applications.

KEY POINTS

•Synthesis of polypyrrole-cobalt oxide-silver (PPy-Co₃O₄-AgNPs) nanocomposite. •Antimicrobial activity of nanocomposite. •PPy-Co₃O₄-AgNPs hold promise for biomedical applications.

Potential of silver nanoparticles synthesized using low active mosquitocidal Lysinibacillus sphaericus as novel antimicrobial agents

Silver nanoparticles (AgNPs) were synthesized using extracellular filtrates of some Lysinibacillus sphaericus (Ls) strains under simple conditions. Ls synthesized AgNPs showed the optical absorption peaks at 388-412 nm as detected by UV-visible spectrophotometer. Transmission electron micrographs of bacterial synthesized AgNPs revealed that they were polycrystalline with spherical, hexagonal, cuboidal, rod and irregular shapes. The average diameter of the tested AgNPs were ranged from 14-21 nm and they were negatively charged as detected by DLS (-18.2 to -28.9). FTIR spectra showed the presence of nitrogenous biomolecules capping the synthesized AgNPs. The filtrates of tested Ls strains showed nitrate reductase activity (1.45-2.56 µmol/ml/min). Tested AgNPs showed bactericidal activity against Gram positive and Gram negative bacteria, fungicidal activity against yeast and filamentous fungi, and virucidal activity against rotavirus. In addition, it showed synergistic antimicrobial effect to cephradine and nizoarm against all tested microorganisms. Cytotoxicity test revealed the safety of the tested nanoparticles at tested concentrations.Finally, Ls strains represent microbial sources for ecofriendly, simple and economic biosynthesis of antimicrobial AgNPs. Also, this research may contribute to the medicinal chemistry and pharmaceutical industry for the development of new products used for the public health.

Addressing Antimicrobial Resistance Through Nanoantibiotics

In recent years, the irrational use of antibiotics has escalated the evolution of multidrug-resistant (MDR) bacterial strains. The infectious diseases caused by these MDR bacterial strains remain a major threat to human health and have emerged as the leading cause of morbidity and mortality. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. The antimicrobial resistance (AMR) poses a severe global threat of growing concern to human health and economic burden. Bacteria have developed the ability to resist antimicrobials by altering target site/enzyme, inactivation of the enzyme, decreasing cell permeability, increasing efflux due to over-expression of efflux pumps, target protection, target overproduction, and many other ways. The shortage of new antimicrobials and rapid rise in antibiotic resistance demands pressing need to develop alternate antibacterial agents.

The Efficacy of Imipenem Conjugated with Synthesized Silver Nanoparticles Against Acinetobacter baumannii Clinical Isolates, Iran

Carbapenem-resistant Acinetobacter baumannii (CRAB) remains as a serious cause of infectious diseases and septic mortality in hospitalized patients worldwide. This study was conducted to evaluate the antimicrobial effect of imipenem conjugated silver nanoparticles (AgNPs) on resistant isolated A. baumannii from nosocomial infections.The antimicrobial susceptibility test of 100 A. baumannii clinical isolates against different antibiotics was performed. PCR was used to confirm bacterial resistance and to identify different genes encoding Ambler class β-lactamases. The chemically synthesized AgNPs were characterized using UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR). The stability, drug release kinetic, and cytotoxicity (MTT assay) of AgNPs were also investigated. The imipenem were conjugated with AgNPs, and conjugants were characterized as discussed above. Minimum inhibitory concentration (MIC) of the AgNPs and conjugants were tested against A. baumannii isolates and compared with imipenem alone.The results revealed that among all isolated A. baumannii, 76% showed resistant to imipenem (MIC ≥ 64 μg/mL to ≥ 256 μg/mL). The bla_OXA-23, bla_PER, bla_OXA-40, and bla_IMP genes were the most prevalent genes. UV-vis spectroscopy, XRD, TEM, and FTIR analysis confirmed synthesis of AgNPs (average size of 10-40 nm) and conjugation with imipenem. The release of imipenem from AgNPs can be defined as Fickian diffusion model. The MIC values of AgNPs conjugated with imipenem against resistant A. baumannii were decreased in a dose dependent manner and were based on existence of resistant genes. The AgNPs also showed low cytotoxic effects.The results suggest that imipenem-AgNPs has a strong potency as a powerful antibacterial agent against multi-resistant A. baumannii.

Probing the Mode of Antibacterial Action of Silver Nanoparticles Synthesized by Laser Ablation in Water: What Fluorescence and AFM Data Tell Us

We aim to elucidate the mode of antibacterial action of the laser-synthesized silver colloid against Escherichia coli. Membrane integrity was studied by flow cytometry, while the strain viability of the treated culture was determined by plating. The spectrofluorometry was used to obtain the time development of the reactive oxygen species (ROS) inside the nanoparticle-treated bacterial cells. An integrated atomic force and bright-field/fluorescence microscopy system enabled the study of the cell morphology, Young modulus, viability, and integrity before and during the treatment. Upon lethal treatment, not all bacterial cells were shown to be permeabilized and have mostly kept their morphology with an indication of cell lysis. Young modulus of untreated cells was shown to be distinctly bimodal, with randomly distributed softer parts, while treated cells exhibited exponential softening of the stiffer parts in time. Silver nanoparticles and bacteria have shown a masking effect on the raw fluorescence signal through absorbance and scattering. The contribution of cellular ROS in the total fluorescence signal was resolved and it was proven that the ROS level inside the lethally treated cells is not significant. It was found that the laser-synthesized silver nanoparticles mode of antibacterial action includes reduction of the cell's Young modulus in time and subsequently the cell leakage.

Gut bacteria of animals living in polluted environments exhibit broad-spectrum antibacterial activities

Infectious diseases, in particular bacterial infections, are the leading cause of morbidity and mortality posing a global threat to human health. The emergence of antibiotic resistance has exacerbated the problem further. Hence, there is a need to search for novel sources of antibacterials. Herein, we explored gut bacteria of a variety of animals living in polluted environments for their antibacterial properties against multi-drug resistant pathogenic bacteria. A variety of species were procured including invertebrate species, Blaptica dubia (cockroach), Gromphadorhina portentosa (cockroach), Scylla serrata (crab), Grammostola rosea (tarantula), Scolopendra subspinipes (centipede) and vertebrate species including Varanus salvator (water monitor lizard), Malayopython reticulatus (python), Cuora amboinensis (tortoise), Oreochromis mossambicus (tilapia fish), Rattus rattus (rat), Gallus gallus domesticus (chicken) and Lithobates catesbeianus (frog). Gut bacteria of these animals were isolated and identified using microbiological, biochemical, analytical profiling index (API) and through molecluar identification using 16S rRNA sequencing. Bacterial conditioned media (CM) were prepared and tested against selected Gram-positive and Gram-negative pathogenic bacteria as well as human cells (HaCaT). The results revealed that CM exhibited significant broad-spectrum antibacterial activities. Upon heat inactivation, CM retained their antibacterial properties suggesting that this effect may be due to secondary metabolites or small peptides. CM showed minimal cytotoxicity against human cells. These findings suggest that gut bacteria of animals living in polluted environments produce broad-spectrum antibacterial molecule(s). The molecular identity of the active molecule(s) together with their mode of action is the subject of future studies which could lead to the rational development of novel antibacterial(s).

Bacteria Exposed to Silver Nanoparticles Synthesized by Laser Ablation in Water: Modelling E. coli Growth and Inactivation

This study is aimed to better understand the bactericidal mode of action of silver nanoparticles. Here we present the production and characterization of laser-synthesized silver nanoparticles along with growth curves of bacteria treated at sub-minimal and minimal inhibitory concentrations, obtained by optical density measurements. The main effect of the treatment is the increase of the bacterial apparent lag time, which is very well described by the novel growth model as well as the entire growth curves for different concentrations. The main assumption of the model is that the treated bacteria uptake the nanoparticles and inactivate, which results in the decrease of both the nanoparticles and the bacteria concentrations. The lag assumes infinitive value for the minimal inhibitory concentration treatment. This apparent lag phase is not postponed bacterial growth. It is a dynamic state in which the bacterial growth and death rates are close in value. Our results strongly suggest that the predominant mode of antibacterial action of silver nanoparticles is the penetration inside the membrane.

The Use of Nanomedicine for Targeted Therapy against Bacterial Infections

The emergence of drug resistance combined with limited success in the discovery of newer and effective antimicrobial chemotherapeutics poses a significant challenge to human and animal health. Nanoparticles may be an approach for effective drug development and delivery against infections caused by multi-drug resistant bacteria. Here we discuss nanoparticles therapeutics and nano-drug delivery against bacterial infections. The therapeutic efficacy of numerous kinds of nanoparticles including nanoantibiotics conjugates, small molecules capped nanoparticles, polymers stabilized nanoparticles, and biomolecules functionalized nanoparticles has been discussed. Moreover, nanoparticles-based drug delivery systems against bacterial infections have been described. Furthermore, the fundamental limitation of biocompatibility and biosafety of nanoparticles is also conferred. Finally, we propose potential future strategies of nanomaterials as antibacterials.

Gut bacteria of Cuora amboinensis (turtle) produce broad-spectrum antibacterial molecules

Antimicrobial resistance is a major threat to human health, hence there is an urgent need to discover antibacterial molecule(s). Previously, we hypothesized that microbial gut flora of animals are a potential source of antibacterial molecules. Among various animals, Cuora amboinensis (turtle) represents an important reptile species living in diverse ecological environments and feed on organic waste and terrestrial organisms and have been used in folk medicine. The purpose of this study was to mine turtle’s gut bacteria for potential antibacterial molecule(s). Several bacteria were isolated from the turtle gut and their conditioned media were prepared. Conditioned media showed potent antibacterial activity against several Gram-positive (Bacillus cereus, Streptococcus pyogenes and methicillin-resistant Staphylococcus aureus) and Gram-negative (neuropathogenic Escherichia coli K1, Serratia marcescens, Pseudomonas aeruginosa, Salmonella enterica and Klebsiella pneumoniae) pathogenic bacteria. Conditioned media-mediated bactericidal activity was heat-resistant when treated at 95°C for 10 min. By measuring Lactate dehydrogenase release, the results showed that conditioned media had no effect on human cell viability. Tandem Mass Spectrometric analysis revealed the presence of various secondary metabolites, i.e., a series of known as well as novel N-acyl-homoserine lactones, several homologues of 4-hydroxy-2-alkylquinolines, and rhamnolipids, which are the signature metabolites of Pseudomonas species. These findings are significant and provide the basis for rational development of therapeutic interventions against bacterial infections.

Surface Modification by Media Organics Reduces the Bacterio-toxicity of Cupric Oxide Nanoparticle against Escherichia coli

Prevalence of antibiotic-resistant bacteria demands alternatives to antibiotics. Copper-based nanoparticles with a high antibacterial property may be a solution to the problem. It is, therefore, important to understand the mode of antibacterial action of the nanoparticles (NPs). Despite reports on induction of reactive oxygen species (ROS) in bacteria by copper and copper-oxide nanoparticles and involvement of such ROS in cell killing, it is still unclear (a) if surface modification of the nanoparticles by media organics has any role on their antibacterial potency and (b) whether the bactericidal effects of these NPs are 'particle-specific' or 'ion-specific' in nature. We address these issues for cupric oxide nanoparticle (CuO-NP) in this study. Instead of nutrient medium, when E. coli bacterial cells were suspended in saline (0.9% NaCl), CuO-NP had a more anti-bacterial effect, with MBC (minimum bactericidal concentration) value of 6 µg/mL, than in nutrient medium with MBC value of 160 µg/mL. Moreover, the lysine-modified CuO-NP in saline had MBC at 130 µg/mL. Thus, unmodified CuO-NP was more efficient killer than modified one. Our finding further revealed that in saline;CuO-NP had 'particle-specific' antibacterial effect through generation of ROS and consequent oxidative damage by lipid peroxidation, protein oxidation and DNA degradation in cells.

Antibacterial Effects of Quinazolin-4(3H)-One Functionalized-Conjugated Silver Nanoparticles

Infections due to multi-drug resistant bacteria are on the rise and there is an urgent need to develop new antibacterials. In this regard, a series of six functionally diverse new quinazolinone compounds were synthesized by a facile one-pot reaction of benzoic acid derivatives, trimethoxymethane and aniline derivatives. Three compounds of 3-aryl-8-methylquinazolin-4(3H)-one, and 3-aryl-6,7-dimethoxyquinazolin4(3H)-one were prepared and tested against multi-drug resistant bacteria. Furthermore, we determined whether conjugation with silver nanoparticles improved the antibacterial efficacy of these quinazolinone derivatives. The newly synthesized compounds were characterized by ultraviolet visible spectrophotometry (UV-vis), Zetasizer analysis, Fourier transform infrared spectroscopic methods (FT-IR), and scanning electron microscopy (SEM). Using bactericidal evaluation, effects were determined against selected Gram-negative and Gram-positive bacteria. Furthermore, cytotoxicity of nanoconjugates on human cells were determined. The UV-vis spectrum of silver nanoparticles conjugated quinazolinone displayed surface plasmon resonance band in the range of 400–470 nm, and the size of nanoparticles was detected to be in the range of 100–250 nm by dynamic light scattering (DLS). FT-IR study confirmed the stabilization of silver nanoparticles by the presence of diverse functional arayl on each compound. SEM further revealed the construction of spherical nanoparticles. Among the quinazolinone derivative tested, two compounds (QNZ 4, QNZ 6) conjugated with silver nanoparticles showed enhanced antibacterial activity against Escherichia coli K1, Streptococcus pyogenes, Klebsiella pneumoniae, B. cereus and P. aeruginosa as compared to the compounds.