Conjugated Silver Nanoparticles Research Articles

Synthesis, Characterization and In Vitro Antibacterial Evaluation of Pyrenacantha grandiflora Conjugated Silver Nanoparticles.

In the present study, silver nanoparticles (AgNPs) were synthesized using both the chemical and biological methods and conjugated with Pyrenacantha grandiflora extracts. These were then characterized and evaluated for antimicrobial activities against multi-drug resistant pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumonia, and Escherichia coli. Nanoparticles were analyzed with UV-visible spectrophotometer, transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX). Silver nanoparticles, P. grandiflora extracts, and the conjugates were also analyzed with Fourier transform infrared spectroscopy (FTIR). As a result, quasi-sphere-shaped AgNPs with sizes ranging from 5 to 33 nm and spherically shaped AgNPs with sizes ranging from 3 to 25 nm were formed from chemical and biological synthesis, respectively. A well diffusion assay showed that the activity of silver nanoparticles was most improved with acetone extract against all tested bacteria with diameters in the range of 19–24 mm. The lowest MIC value of 0.0063 mg/mL against MRSA was observed when biologically synthesized AgNPs were conjugated with acetone and water extracts. Chemically synthesized silver nanoparticles showed the lowest MIC value of 0.0063 mg/mL against E. coli when conjugated with acetone and methanol extracts. This study indicates that silver nanoparticles conjugated with P. gandiflora tubers extracts exhibit strong antibacterial activities against multi-drug resistant bacterial pathogens. Therefore, biosynthesized conjugates could be utilized as antimicrobial agents for effective disease management due to the synergistic antibacterial activity that was observed.

Detection of antibiofilm formation by sliver nanoparticles created by tetracycline antibiotic

Silver conjugated Tetracycline, was created and characterized by ultraviolet visible spectrophotometry (UV-vis), Fourier transform infrared (FT-IR), X-Ray Diffraction Patterns (XRD). Using antibacterial assays, the effects of tetracycline alone and drugs-conjugated with silver nanoparticles were tested against Gram-ve Pseudomonas aeruginosa isolates by well diffusion assay. The UV-vis spectra of silver-drug Nano conjugates showed a characteristic surface Plasmon resonance band in the range of 400–450 nm. FTIR analysis demonstrated the involvement of Hydroxyl groups in both drugs in the stabilization of silver nanoparticles. (XRD) showed that they cubic structure of silver and, antibacterial assays showed that biosynthesis silver nanoparticle conjugation enhanced antibacterial potential of Tetracycline compared with drug alone.

‘Synergistic-Cidal’ Effect of Amoxicillin Conjugated Silver Nanoparticles Against Escherichia coli

The research article presents the synthesis, characterization, and biological evaluation of amoxicillin functionalized with AgNPs with low toxicity and good antimicrobial property which can be produced with silver nitrate and amoxicillin drug in an environmentally friendly method. The synthesized nanoparticles were subjected to characterization by UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction, field-emission scanning electron microscopy, and atomic force microscopy. The biological evaluation was carried out with the help of agar well diffusion using E. coli, minimum inhibitory concentration, DPPH radical scavenging assay, reducing power activity, total antioxidant activity, and anticancer activity of silver nanoparticles (AgNPs) against Hep-G2 cancer cell lines. The average particle size of the synthesized nanoparticles was 35.50 ± 0.23 nm. The drug release kinetics was carried out to analyze the release of amoxicillin from the AgNPs. The present study clearly establishes the synthesis and the application of amoxicillin functionalized silver nanoparticles to be utilized as an important tool to fight against antibiotic-resistant bacterial strains.

Transcriptome analysis of Escherichia coli K1 after therapy with hesperidin conjugated with silver nanoparticles

BackgroundsEscherichia coli K1 causes neonatal meningitis. Transcriptome studies are indispensable to comprehend the pathology and biology of these bacteria. Recently, we showed that nanoparticles loaded with Hesperidin are potential novel antibacterial agents against E. coli K1. Here, bacteria were treated with and without Hesperidin conjugated with silver nanoparticles, and silver alone, and 50% minimum inhibitory concentration was determined. Differential gene expression analysis using RNA-seq, was performed using Degust software and a set of genes involved in cell stress response and metabolism were selected for the study.Results50% minimum inhibitory concentration with silver-conjugated Hesperidin was achieved with 0.5 μg/ml of Hesperidin conjugated with silver nanoparticles at 1 h. Differential genetic analysis revealed the expression of 122 genes (≥ 2-log FC, P< 0.01) in both E. coli K1 treated with Hesperidin conjugated silver nanoparticles and E. coli K1 treated with silver alone, compared to untreated E. coli K1. Of note, the expression levels of cation efflux genes (cusA and copA) and translocation of ions, across the membrane genes (rsxB) were found to increase 2.6, 3.1, and 3.3- log FC, respectively. Significant regulation was observed for metabolic genes and several genes involved in the coordination of flagella.ConclusionsThe antibacterial mechanism of nanoparticles maybe due to disruption of the cell membrane, oxidative stress, and metabolism in E. coli K1. Further studies will lead to a better understanding of the genetic mechanisms underlying treatment with nanoparticles and identification of much needed novel antimicrobial drug candidates.

Increasing the accumulation of aptamer AS1411 and verapamil conjugated silver nanoparticles in tumor cells to enhance the radiosensitivity of glioma

Radioresistance significantly decreases the efficacy of radiotherapy, which can ultimately lead to tumor recurrence and metastasis. As a novel type of nano-radiosensitizer, silver nanoparticles (AgNPs) have shown promising radiosensitizing properties in the radiotherapy of glioma, but their ability to efficiently enter and accumulate in tumor cells needs to be improved. In the current study, AS1411 and verapamil (VRP) conjugated bovine serum albumin (BSA) coated AgNPs (AgNPs@BSA-AS-VRP) were synthesized and characterized. Dark-field imaging and inductively coupled plasma mass spectrometry were applied to investigate the accumulation of AgNPs@BSA-AS and AgNPs@BSA-AS-VRP mixed in different ratios in U251 glioma cells. To assess the influences of 19:1 mixed AgNPs@BSA-AS and AgNPs@BSA-AS-VRP on the P-glycoprotein (P-gp) efflux activity, rhodamine 123 accumulation assay was carried out. Colony formation assay and tumor-bearing nude mice model were employed to examine the radiosensitizing potential of 19:1 mixed AgNPs@BSA-AS and AgNPs@BSA-AS-VRP. Thioredoxin Reductase (TrxR) Assay Kit was used to detect the TrxR activity in cells treated with different functionally modified AgNPs. Characterization results revealed that AgNPs@BSA-AS-VRP were successfully constructed. When AgNPs@BSA-AS and AgNPs@BSA-AS-VRP were mixed in a ratio of 19:1, the amount of intracellular nanoparticles increased greatly through AS1411-mediated active targeting and inhibition of P-gp activity. In vitro and in vivo experiments clearly showed that the radiosensitization efficacy of 19:1 mixed AgNPs@BSA-AS and AgNPs@BSA-AS-VRP was much stronger than that of AgNPs@BSA and AgNPs@BSA-AS. It was also found that 19:1 mixed AgNPs@BSA-AS and AgNPs@BSA-AS-VRP significantly inhibited intracellular TrxR activity. These results indicate that 19:1 mixed AgNPs@BSA-AS and AgNPs@BSA-AS-VRP can effectively accumulate in tumor cells and have great potential as high-efficiency nano-radiosensitizers in the radiotherapy of glioma.

Isolation and biological activities of naturally occurring apocarotenoid bixin

The naturally occurring apo-carotenoid bixin is obtained from annatto (Bixa orellana). It is unique among the natural carotenoids through its water solubility and easily extractability from the seed coat of Bixa orellana. Bixin is (2E,4E,6E,8E,10E,12E,14E,16Z, 18E)-20- methoxy-4,8,13,17-tetramethyl-20-oxicosa 2,4,6,8,10,12,14,16,18-nonaenoic acid, an apo-carotenoid which is a terpenoid compound derived from the oxidative cleavage of carotenoids. Several biological activities of bixin has been reported earlier such as selective antimyeloma effects of cis-bixin, antinociceptive and anti-Inflammatory effects, antioxidant action against cis-platine induced chromosome in rats, hypoglycemic effect in alloxan-induced diabetic rats, allodynia, anxious and depressive-like behaviors, targeting NRF2 for improved skin barrier function and photoprotection, antiatherogenic effect in hypercholesterolemic rabbits, triggering apoptosis of cancer cells, immunomodulatory role in dogs, sensitization of human melanoma cells to dacarbazine-induced apoptosis, sensitization of human lung cancer and cervical cancer cell to cisplatin in vitro, anti-SARS-CoV-2 activity, antibacterial activity of cis-bixin conjugated silver nanoparticles, protective effect on carbon tetrachloride-induced hepatotoxicity in rats, bixin/crocetin nanoparticles on quality and shelf life improvement of cheddar cheese etc. In this review, the biological properties of bixin has been discussed. A practical method for the isolation of bixin 1 from the seed coat of Bixa orellana commonly known as “Sinduri” (in Bengali) and its characterization has also been reported.

Impact of metal nanoparticles on the ecology of soil biocenosis (literature review)

This review contains analysis and synthesis of data on the study of metal nanoparticles’ effects on soil, plants, and microbial communities. Absorption of nanoparticles by soil can adversely affect the state of soil biota and plants as its components, posing a serious risk to human health. It is shown soil contamination with metals in nanoform to pronounce negative character, which consists of disrupting the biocenosis, death of its inhabitants, and reducing their reproduction. At the same time, the degree of negative impact was determined by the type of nanometal and composition of soil fauna. It was proposed to study the environmental consequences of nanotechnology by the complex interactions between plants and nano preparation. The review presents a new direction in nanotechnology - the method of extracting metal nanoparticles from plants, due to the ability to accumulate in leaves. The main advantage of the “green” production method over the “chemical” one is the reduction of the toxic properties of nanometals in comparison with the “chemical” analogs. Creation of conjugates of metal nanoparticles and substances of plant origin is promising. Conjugates of silver nanoparticles and phenolic groups contained in leaves are called “plant antibiotics” and do not have side effects on humans. The review presents an adverse dose-dependent effect of the influence of TiO, CuO, and other metal nanoparticles on root growth, seed germination, plant biomass growth, species diversity, the antimicrobial and enzymatic activity of soil microflora. Contrary, some studies emphasize the prospect of using nanocomposites of metals such as copper, iron, zinc, silver on soil and plants due to their bactericidal properties. A joint unification of the efforts of scientists will help to determine the possible consequences of the use of nanomaterials and protect against the potential threat of uncontrolled development of nanotechnology for the natural environment. Search and selection of sources for review were, carried out using open databases, including PubMed, Scopus, Google Scholar, and RSCI, from 2005 to 2019.

Mathematical modelling and optimization studies of photo-mediated green synthesis of 2 hydroxy 4 methoxybenzaldehyde conjugated silver nanoparticles using Decalepis hamiltonii: A note on antioxidant and nano-catalytic activity

The present study focuses on minimized use of chemical and physical methods and to develop environmentally safer method for the sunlight mediated synthesis of silver nanoparticles (SNPs) using aqueous root extract of Decalepis hamiltonii (DHR). Phytochemicals present in DHR extract was screened using qualitative and quantitative methods. Response Surface Methodology (RSM) was used in order to statistically optimize the processing parameters like concentration of root extract, silver nitrate and pH of the solution in order to obtain high yield of SNPs. The characterization techniques revealed hydrodynamic size of SNPs with the diameter of 61 nm, 46.5 nm width and zeta potential of −10.4 mv indicating the presence of functional groups on the SNPs which was also confirmed by Fourier transform infrared spectroscopy (FTIR) studies. Further, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) revealed uniform spherical shape of SNPs. The presence of metallic silver was confirmed by Energy Dispersive X-ray (EDX). Additionally, the study revealed DHR extract and its colloidal SNPs showed a potential antioxidant activity. Further, the SNPs were tested as a Nano-catalyst in dye degradation of brilliant blue (BB), callomil yellow (CY), congo red (CR), methyl orange (MO), and methyl red (MR) and it showed 98 to 100% dye degradation.

Sensing Applications of Triazole Conjugated Silver Nanoparticles

This study involves synthesis and physicochemical evaluation of triazole conjugated silver nanoparticles (TBS-AgNPs). The triazole derivative (TBS) was synthesized via click reaction followed by its conjugation with silver nanoparticles through the chemical reduction method. The TBS-AgNPs were characterized by various spectroscopic techniques, for instance, UV-Visible, atomic force microscopy (AFM), Fourier transform infrared (FTIR),and dynamic light scattering (DLS). TBS-AgNPs showed maximum absorption at 400 nm with an average particle size of 60-80 nm. Sensitivity and selectivity of TBS-AgNPs towards metal ions were evaluated using UV-Visible spectroscopy and the addition of Pd2+ produced a significant decrease in absorption intensity of TBS-AgNPs. Whereas, all other tested metal ions such as Sn2+, Ni2+, Ca2+, Bi3+, NH4+, K+, Mg2+, Na+, Co2+, Mn2+, and Ba2+ did not alter the optical properties of TBS-AgNPs for Pd2+. TBS-AgNPs nanoparticles are highly selective for Pd2+ as no interference was observed in competitive experiments. Job's plot indicated a 1:1 binding ratio between Pd2+ and TBS-AgNPs. Furthermore, TBS-AgNPs were effectively used for the detection of Pd2+ ion in laboratory tap water.

Potency of Mancozeb Conjugated Silver Nanoparticles Synthesized from Goat, Cow and Buffalo Urine Against Colletotrichum gloeosporioides Causing Anthracnose Disease

Potency of Mancozeb Conjugated Silver Nanoparticles Synthesized from Goat, Cow and Buffalo Urine Against Colletotrichum gloeosporioides Causing Anthracnose Disease

Synthetic nanoparticle-conjugated bisindoles and hydrazinyl arylthiazole as novel antiamoebic agents against brain-eating amoebae

Balamuthia mandrillaris and Naegleria fowleri are free-living amoebae that can cause life-threatening infections involving the central nervous system. The high mortality rates of these infections demonstrate an urgent need for novel treatment options against the amoebae. Considering that indole and thiazole compounds possess wide range of antiparasitic properties, novel bisindole and thiazole derivatives were synthesized and evaluated against the amoebae. The antiamoebic properties of four synthetic compounds i.e., two new bisindoles (2-Bromo-4-(di (1H-indol-3-yl)methyl)phenol (denoted as A1) and 2-Bromo-4-(di (1H-indol-3-yl)methyl)-6-methoxyphenol (A2)) and two known thiazole (4-(3-Nitrophenyl)-2-(2-(pyridin-3-ylmethylene)hydrazinyl)thiazole (A3) and 4-(Biphenyl-4-yl)-2-(2-(1-(pyridin-4-yl)ethylidene)hydrazinyl)thiazole (A4)) were evaluated against B. mandrillaris and N. fowleri. The ability of silver nanoparticle (AgNPs) conjugation to enrich antiamoebic activities of the compounds was also investigated. The synthetic heterocyclic compounds demonstrated up to 53% and 69% antiamoebic activities against B. mandrillaris and N. fowleri respectively, while resulting in up to 57% and 68% amoebistatic activities, respectively. Antiamoebic activities of the compounds were enhanced by up to 71% and 51% against B. mandrillaris and N. fowleri respectively, after conjugation with AgNPs. These compounds exhibited potential antiamoebic effects against B. mandrillaris and N. fowleri and conjugation of synthetic heterocyclic compounds with AgNPs enhanced their activity against the amoebae.

C-Phycocyanin primed silver nano conjugates: Studies on red blood cell stress resilience mechanism

Green synthesis of metal-encased nutraceutical nano-hybrids has been a target for research over the last few years. In the present investigation, we have reported temperature dependent facile synthesis of silver nanoparticles using FDA approved c phycocyanin (cPC). The cPC conjugated silver nanoparticles (AgcPCNPs) were characterized by TEM, Zeta Potential, UV–vis, XPS, FTIR, and CD Spectroscopy. The temperature optimization studies suggested the synthesis of stable AgcPCNPs at 40 °C while at higher temperature system shows aggregated appearance. Molecular docking studies predicted the exclusive interaction of C, D, I, and J chains of cPC with the surface of AgNPs. Moreover, AgcPCNPs significantly (p < 0.1 %) counteract the toxic nature of AgNPs on red blood cell by measuring parameters like total RBC count, % hemolysis, % hematocrit, coagulation time, pH, electrolyte concentrations and degree of blood cell lipid peroxidation by the anti-oxidation mechanism. Skin fibroblast in vitro cell migration result suggeststhat AgcPCNPs enhanced the degree of cell movement towards the wound area. Data obtained collectively demonstrate that AgcPCNPs can be a better agent in the dermal wound healing with reduced toxicity with the bi-phasic advantage of cPC as a wound healer and Ag nano-metal as an anti-bacterial agent.

Photocontrolled miR-148b nanoparticles cause apoptosis, inflammation and regression of Ras induced epidermal squamous cell carcinomas in mice

Despite evidence that microRNAs (miRNAs) are essential in modulating tumorigenesis, a major challenge in cancer treatment is to achieve tumor-specific selectivity and efficient yet safe delivery of miRNAs in vivo. In this study, we have developed a light-inducible silver nanoparticle nucleic acid delivery system that demonstrates precise spatiotemporal control, high cellular uptake, low cytotoxicity, escape from endosomes and release of functional miRNA into the cytosol. Using this approach, we delivered exogenous miR-148b to induce apoptosis in Ras-expressing keratinocytes and murine squamous cell carcinoma cells while avoiding cytotoxicity in untransformed keratinocytes. When administered to transgenic mice with HRasG12V-driven skin tumors, a single dose of silver nanoparticle conjugates followed by 415 nm LED irradiation at the tumor site caused a rapid and sustained reduction in tumor volume by 92.8%, recruited T cells to the tumor site, and acted as a potent immunomodulator by polarizing the cytokine balance toward Th1 both locally and systemically. In summary, our results demonstrate that spatiotemporal controlled miR-148b mimic delivery can promote tumor regression efficiently and safely.

Antiamoebic activity of plant-based natural products and their conjugated silver nanoparticles against Acanthamoeba castellanii (ATCC 50492)

Acanthamoeba spp. are the causative agent of Acanthamoeba keratitis and granulomatous amoebic encephalitis (GAE). The current options to treat Acanthamoeba infections have limited success. Silver nanoparticles show antimicrobial effects and enhance the efficacy of their payload at the specific biological targets. Natural folk plants have been widely used for treating diseases as the phytochemicals from several plants have been shown to exhibit amoebicidal effects. Herein, we used natural products of plant or commercial sources including quercetin (QT), kolavenic acid (PGEA) isolated from plant extracts of Polyalthia longifolia var pendula and crude plant methanolic extract of Caesalpinia pulcherrima (CPFLM) as antiacanthamoebic agents. Furthermore, these plant-based materials were conjugated with silver nanoparticles (AgNPs) to determine the effects of the natural compounds and their nanoconjugates against a clinical isolate of A. castellanii from a keratitis patient (ATCC 50492) belonging to the T4 genotype. The compounds were conjugated with AgNPs and characterized by using ultraviolet visible spectrophotometry and atomic force microscopy. Quercetin coated silver nanoparticles (QT-AgNPs) showed characteristic surface plasmon resonance band at 443 nm and the average size distribution was found to be around 45 nm. The natural compounds alone and their nanoconjugates were tested for the viability of amoebae, encystation and excystation activity against A. castellanii. The natural compounds showed significant growth inhibition of A. castellanii while QT-AgNPs specifically exhibited enhanced antiamoebic effects as well as interrupted the encystation and excystation activity of the amoebae. Interestingly, these compounds and nanoconjugates did not exhibit in vitro cytotoxic effects against human cells. Plant-based compounds and extracts could be an interesting strategy in development of alternative therapeutics against Acanthamoeba infections.

A green route to phytofabricated synthesis of Gymnema sylvestre conjugated silver nanoparticles (GS-AgNPs) and its antimicrobial activity

The plant-derived chemicals present in the leaf extract of Gymnema sylvestre (LEGS) commonly known as "Gurmer" has been utilized for the synthesis of Gymnema sylvestre conjugated silver nanoparticles (GS-AgNPs) at room temperature without any auxiliary reducing and capping agents. Spherical shaped GS-AgNPs of 26.6 nm average diameters were observed. A selective dose dependent antimicrobial activity of the freshly synthesized GS-AgNPs on both gram-positive Staphylococus aureus and gramnegative Proteus vulgaris strain showed the same minimum inhibitory concentration (MIC) value at 50 µg/mL, as revealed by in-vitro MIC assay. Zone inhibition study carried out by Disk agar diffusion (DAD) test showed that the GS-AgNPs is sensitive on both the bacteria cell having a comparatively better antimicrobial activity towards Gram-negative over Gram-positive bacteria. The synthesized GS-AgNPs showed very low toxic effect in normal human cells. Dichlorodihydrofluorescein diacetate (DCDHFDA) and ethidium bromide-acridine orange (EB-AO) staining studies revealed that the GS-AgNPs mainly produces Reactive Oxygen Species (ROS) by altering its electron transport chain (ETC) system and it leads to cell death or necrosis through apoptosis of bacterial cells.

Green synthesis and formulation a modern chemotherapeutic drug of Spinacia oleracea L. leaf aqueous extract conjugated silver nanoparticles; Chemical characterization and analysis of their cytotoxicity, antioxidant, and anti‐acute myeloid leukemia properties in comparison to doxorubicin in a leukemic mouse model

There is an increasing commercial demand for nanoparticles due to their wide applicability in various areas such as electronics, catalysis, chemistry, energy, and medicine. Recently, researchers have tried to synthesize the chemotherapeutic drugs from metallic nanoparticles especially gold and silver nanoparticles. In the current study, silver nanoparticles using Spinacia oleracea L. leaf aqueous extract (AgNPs) are reported for the first time to exert a dietary remedial property compared to doxorubicin in an animal model of acute myeloid leukemia. The synthesized AgNPs were characterized using different techniques including UV‐Vis., EDS, TEM, FT‐IR, and FE‐SEM. UV‐Vis. indicates an absorption band at 462 nm that is related to the surface plasmon resonance of AgNPs. In EDS, metallic silver nanocrystals indicated an optical absorption peak at roughly 4keV. TEM and FE‐SEM images exhibited a uniform spherical morphology and diameters of 20–40 nm for the nanoparticles. FT‐IR findings suggested antioxidant compounds in the nanoparticles were the sources of reducing power, reducing silver ions to AgNPs. In vivo design, induction of acute myeloid leukemia was done by 7,12‐Dimethylbenz[a]anthracene in 75 mice. Then, the animals were randomly divided into six subgroups, including control, untreated, AgNO3, S. oleracea, AgNPs, and doxorubicin. Similar to doxorubicin, AgNPs significantly (p ≤ 0.01) reduced the pro‐inflammatory cytokines, and the total WBC, blast, neutrophil, monocyte, eosinophil, and basophil counts and increased the weight of the body, the anti‐inflammatory cytokines and the lymphocyte, platelet, and RBC parameters as compared to the untreated mice. DPPH free radical scavenging test was done to evaluate the antioxidant potentials of AgNO3, S. oleracea, AgNPs, and doxorubicin. DPPH test revealed similar antioxidant potentials for doxorubicin and AgNPs. For the analyzing of cytotoxicity effects of AgNO3, S. oleracea, AgNPs, and doxorubicin, MTT assay was used on HUVEC, Human HL‐60/vcr, 32D‐FLT3‐ITD, and Murine C1498 cell lines. AgNPs similar to doxorubicin had low cell viability dose‐dependently against Human HL‐60/vcr, 32D‐FLT3‐ITD, and Murine C1498 cell lines without any cytotoxicity on HUVEC cell line. These results reveal that the inclusion of S. oleracea leaf aqueous extract improves the remedial effects of AgNPs, which led to a significant enhancement in the antioxidant, cytotoxicity, and anti‐acute myeloid leukemia potentials of the nanoparticles. It seems that AgNPs can be applied as a chemotherapeutic supplement or drug for the treatment of acute myeloid leukemia in the clinical trial.

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 blaOXA-23, blaPER, blaOXA-40, and blaIMP 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.

Star-shaped poly(ethylene oxide)‑block‑poly(caprolactone) conjugated silver nanoparticles: A colorimetric probe for cephalexin in environmental, biological and pharmaceutical samples

Polymer-metal nanocomposites have recently been employed for various analytical and biomedical applications. In this study, a highly stable silver nanoparticles (AgNPs) conjugated with four arm poly(ethylene oxide‑block‑caprolactone), P(EO-b-CL), were synthesized using two-phase one-pot protocol. The characterization of P(EO-b-CL)-AgNPs was accomplished through UV–visible and Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM)and zetasizer. Complete reduction of AgNO3 is indicated by highest intensity of SPR band obtained by using a volume ratio of 1:50 for solutions of P(EO-b-CL) and AgNO3. P(EO-b-CL)-AgNPs were further exploited as spectrophotometric sensor for antibacterial drug, Cephalexin (Cp). P(EO-b-CL)-AgNPs permitted selective, efficient, rapid and quantitative detection of Cp in concentration range of 1–100 μM with detection limit as low as 1.8 μM. The developed sensor is found to be effective and efficient in presence of other interfering drugs. P(EO-b-CL)-AgNPs revealed great potential for in situ quantitative detection of Cp in environmental and biological samples. Furthermore, the proposed sensor has potential to be employed as quality control of commercial pharmaceutical samples containing cephalexin. The proposed colorimetric sensor in this study allows rapid and quantitative detection of cephalexin for on-spot alarm system away from highly sophisticated laboratory setup.

Rifampicin conjugated silver nanoparticles: a new arena for development of antibiofilm potential against methicillin resistant Staphylococcus aureus and Klebsiella pneumoniae.

Background: Infections caused by drug resistant bacteria are a major health concern worldwide and have prompted scientists to carry out efforts to overcome this challenge. Researchers and pharmaceutical companies are trying to develop new kinds of antimicrobial agents by using different physical and chemical methods to overcome these problems.Materials and methods: In the present study, rifampicin conjugated silver (Rif-Ag) nanoparticles have successfully been synthesized using a chemical method. Characterization of the nanoparticles was performed using a UV-Vis spectrophotometer, FTIR, SEM, TEM, and AFM.Results: The AFM, SEM, and TEM results showed that the average particle size of Rif-Ag nanoparticles was about 15–18±4 nm. The FTIR spectra revealed the conjugation of –NH2 and –OH functional moiety with silver nanoparticles surface. Considering the penetrating power of rifampicin, the free drug is compared with synthesized nanoparticle for antimicrobial, biofilm inhibition, and eradication potential. Synthesized nanoparticles were found to be significantly active as compared to drug alone.Conclusion: This study has shown greater biofilm inhibitory and eradicating potential against methicillin resistant Staphylococcus aureus and Klebsiella pneumoniae, as evident by crystal violet, MTT staining, and microscopic analysis. So, it will be further modified, and studies for the mechanism of action are needed.

Antidiabetic Drugs and Their Nanoconjugates Repurposed as Novel Antimicrobial Agents against Acanthamoeba castellanii.

Acanthamoeba castellanii belonging to the T4 genotype may cause a fatal brain infection known as granulomatous amoebic encephalitis, and the vision-threatening eye infection Acanthamoeba keratitis. The aim of this study was to evaluate the antiamoebic effects of three clinically available antidiabetic drugs, Glimepiride, Vildagliptin and Repaglinide, against A. castellanii belonging to the T4 genotype. Furthermore, we attempted to conjugate these drugs with silver nanoparticles (AgNPs) to enhance their antiamoebic effects. Amoebicidal, encystation, excystation, and host cell cytotoxicity assays were performed to unravel any antiacanthamoebic effects. Vildagliptin conjugated silver nanoparticles (Vgt-AgNPs) characterized by spectroscopic techniques and atomic force microscopy were synthesized. All three drugs showed antiamoebic effects against A. castellanii and significantly blocked the encystation. These drugs also showed significant cysticidal effects and reduced host cell cytotoxicity caused by A. castellanii. Moreover, Vildagliptin-coated silver nanoparticles were successfully synthesized and are shown to enhance its antiacanthamoebic potency at significantly reduced concentration. The repurposed application of the tested antidiabetic drugs and their nanoparticles against free-living amoeba such as Acanthamoeba castellanii described here is a novel outcome that holds tremendous potential for future applications against devastating infection.