Concentration Of Silver Nitrate Solution Research Articles

Efficient Cellulose/Nano‐silver Composite Sheet Derived from Pineapple Leaves for Hydrogen Sulfide Detection

AbstractPineapple leaves, a raw agricultural waste biomass material, were used to synthesize microcrystalline cellulose (MCC) through extraction, bleaching, and hydrolysis. Then, the MCC was mixed with different concentrations of silver nitrate solution to create a regenerated cellulose composite sheet loaded with silver nanoparticles (AgNPs) and used as a hydrogen sulfide (H2S) detector. The physicochemical properties of the cellulose composite sheet loaded with AgNPs before and after H2S exposure were analyzed using various advanced equipment. The H2S adsorption experiments revealed that the composite sheet underwent a visible change from yellow to brown upon exposure to H2S gas. The range for accurate prediction of the H2S concentration was 20–50 ppm. When temperature in the surroundings of the composite sheet was lower and the H2S gas concentration was higher, the color became darker (dark brown). The relative humidity conditions rarely impacted the sensitivity of color change in the cellulose composite sheet. The stability experiment showed that the cellulose composite sheet had exceptional stability at storage temperatures of 4 and 25 °C for 30 days. This composite sheet mixed with AgNPs has the potential to be used as a gas test strip to detect H2S, such as in food packaging.

Eco-friendly Biosynthesis of Silver Nanoparticles from Aloe vera Leaves Based on Various Parameters

In the current study, an ecofriendly and economically very effective method for the biosynthesis of silver nanoparticles (AgNPs) using aqueous extract of Aloe vera leaves has been investigated. The synthesis of AgNPs was checked by the change of color of the solution from yellow to dark blue or black due to a phenomenon known as surface plasmon resonance. The ability of silver nanoparticles to get effected by various process parameters like volume of Aloe vera leaves extract, concentration of silver nitrate solution, and the total incubation time was checked. The analysis and characterization was done using UV-Visible spectroscopy and SEM-EDX. The SEM-EDX analysis confirmed the size, shape and formation of the silver nanoparticles. The best conditions needed for the synthesis of AgNPs using Aloe vera leaves extract was found to be 5mM concentration of silver nitrate solution using 15% volume of Aloe vera leaves extract and incubated for 10minutes under the sunlight.

Microwave-assisted green synthesis of silver nanoparticles using extract of mint leaves

Silver nanoparticles are widely used in areas such as biosensing, hydrogen production, electronics, photovoltaics, antimicrobials, and biomedical engineering applications. Biological synthesis is regarded as a safe and non-toxic process, but its main disadvantage is the slow processing time. The mint leaf extract can act as both a reducing and stabilizing agent for the biological synthesis of silver nanoparticles. In this work, a rapid and green method for the microwave-assisted biological synthesis of silver nanoparticles was investigated using an aqueous leaf extract of mint as a biosource of cost-effective, non-hazardous reducing and stabilizing agents. The optimum conditions for microwave extraction of mint leaves were 220 s at 800 W and a 5 g/L mint-to-water ratio. Meanwhile, the optimal conditions for the biological synthesis of silver nanoparticles were as follows: concentration of silver nitrate solution = 2 mM, microwave reaction time = 100 s at 800 W, and pH = 8. The silver nanoparticles obtained by the microwave heating process showed a surface plasmon band centered at 420 nm with a higher peak height than those prepared by the conventional heating process. Dynamic light scattering analysis has shown the synthesized silver nanoparticles to have an average diameter of 54 nm.

Biosynthesize of Silver Nanoparticles by Eschriesca coli isolated from clinical samples in Nassryah city –south of Iraq

Silver nanoparticles was reflected a powerful antimicrobial agents newly exclusively after growing incidence of diseases related with biofilm and multi-drug resistant pathogens which essential required to find a different path to eliminate that‘s challenge. So the aim of present study was to synthesize silver nanoparticles through biological method using bacteria Eschriesca coli . Biological silver nanoparticles were described by several techniques. The UV-visible spectrophotometric indicated absorbance peak at 246 to 356 nm, Fourier Transformer Infrared analysis (FTIR) revealed that carboxylic groups and poly phenolic groups are enclosed on the surface of both silver nanoparticles creating stabilized nanoparticles, and by scanning electron microscope (SEM), which shown that the biosynthesized silver nanoparticles were spherical in size 26.22 to 31.44 nm. Optimization of silver nanoparticle biosynthesis by E. coli was performed for parameters (temperature and pH and concentration of silver nitrate solution) and the results discovered that temperature 60°C , pH 7 and 3 M silver nitrate concentration were the optimum conditions for silver Nano particles biosynthesis by E. coli isolated from clinical samples of Thi -Qar (Nassryah) city-south Iraq.

Green synthesized silver nanoparticles: Optimization, characterization, antimicrobial activity, and cytotoxicity study by hemolysis assay.

Green nanotechnology has emerged as a viable option for the production of nanoparticles. The purpose of the current investigation was to synthesize silver nanoparticles (AgNPs) using Eucalyptus camaldulensis and Terminalia arjuna extracts, as well as their combinations, as green reducing and capping agents. The parameters (concentration of silver nitrate solution and plant extract, time, pH, and temperature) were optimized for maximal yields, regulated size, and stability of silver nanoparticles. The ultraviolet–visible spectrophotometer (UV-Vis) and the surface plasmon resonance band (SPR) were used to validate the synthesis of AgNPs. The size, shape, and stability of nanoparticles were assessed using a zeta analyzer and a scanning electron microscope (SEM). The biomolecules responsible for the reduction of silver ion (Ag+) and the stability of silver nanoparticles generated with the plant extracts were identified using Fourier-transform infrared spectroscopy (FTIR). The agar-well diffusion method was used to test the antimicrobial activity of biosynthesized nanoparticles against Bacillus subtilis, Staphylococcus aureus, Pasteurella multocida, and Escherichia coli. When 1 mM of silver nitrate (AgNO3) was added to plant extracts and incubated for 60 min at 75°C in a neutral medium, maximum nanoparticles were produced. Biosynthesized silver nanoparticles were stable, spherical, and monodispersed according to zeta potential and scanning electron microscopy. Silver nanoparticles synthesized with combination 2 and T. arjuna showed the highest zone of inhibition (16 mm) against B. subtilis while combination 3 showed the largest zone of inhibition against S. aureus (17 ± 0.8). It was concluded that greenly produced silver nanoparticles showed good antibacterial activity while causing negligible cytotoxicity.

Sunlight induced synthesis of silver nanoparticles on cellulose for the preparation of antimicrobial textiles

Antibiotic resistance is a major threat to heath with the use of silver nanoparticles as a possible approach; however, the synthetic routes of such nanomaterials are not environmentally friendly because of the chemicals required. In this work we approach both problems with a single solution that employs sunlight in the visible spectrum to prepare nanosilver on the surface of cotton fabrics soaked in a solution of silver nitrate. Photoactivation leads to the activation of aldehyde groups providing reducing ability to cellulose and enabling the formation of elemental silver without the use of any chemical reducing agents. Concentrations of silver nitrate solution of 30 g/L reached the saturation of the content of elemental silver on fabric at 52.8 mg/dm2. SEM images showed that silver particles were evenly distributed in fabric in the form of spherical particles 100–600 nm in diameter. The materials exhibited antimicrobial properties against E. coli and S. aureus retaining such properties after repeated washings. Moreover, no adverse effects were observed on fibroblast cells exposed to the prepared textiles.

Cytotoxic effects of fresh aloe vera gel mediated silver nano composite

Aim: To evaluate the cytotoxic effect if fresh aloevera gel mediated silver nano composites Materials And Methods: A 10 gram portion of thoroughly washed fresh cut aloe vera was used in this study. 10 gram of the pulp of the leaf was extracted and was used for the experiments. 10 gram of silver nitrate powder was dissolved in 40 ml of distilled water. To this 40 ml of distilled water the fresh aloe vera extract was added. The solution was placed in the shaker and an observation was made for every two hours for analysing the synthesis of nanoparticles under UV visual spectroscopy . This was followed by the placement of the solution onto the magnetic stirrer for the formation of the nanoparticle .The mixture is then centrifuged at 8000 rpm for 10 minutes and then the nano particles were collected .The resulting solution was further characterised by the TEM measurements. The cytotoxicity was tested by seeding brine shrimps into a 6 well plate. Various concentration of silver nitrate solution was added on the mixture.

Formulation of Clitoria ternatea Leaves-mediated Silver Nanoparticles to Control Aedes aegypti Larvae

Introduction: Global rise in the Aedes-borne diseases and harmful effects of synthetic insecticides has diverted research to explore secondary metabolites in plants as mosquito control agent in the form of nanoparticles. Current study investigated Clitoria ternatea-mediated nanoparticles against Aedes aegypti. Methods: The aqueous and hexane leaf extracts of C. ternatea were assayed against Ae. aegypti early fourth instars. The extract-mediated silver nanocomposites (AgNCs) were synthesized after optimizing the volume and concentration of silver nitrate solution. The synthesis was tracked by the colour change of reaction mixture from pale yellow to dark brown followed by monitoring with UV-Visible spectroscopy and Dynamic Light Scattering. Results: The biosynthesis of 3 mM, 4 mM and 5 mM AgNCs was traced at 438, 401 and 407 nm, respectively. The average particle size distribution ranged from 34.62 to 60.64 nm and polydispersity index was 0.6-0.7. The 24 h larval exposure with aqueous and hexane leaf extracts demonstrated respective LC50 values of 53.057 and 42.179 mg/L, which decreased significantly on larvicidal assay with NCs. The 5mM AgNCs showed the maximum efficiency with LC50 of 10.317 mg/L after 24 h. Scanning and transmission electron microscopy images demonstrated a spherical, poly-dispersed structure with diameter in the 1-27 nm range. The assays against non-targets; Moina and Cyclops ascertained the eco-safety of NCs. Conclusion: The study demonstrated the C. ternatea leaf extract as possible effective mosquito nano-larvicide, alternate to traditional insecticides. Field studies, which could not be held due to the current pandemic, would further ascertain the possible use of these NCs against Aedes larvae.

Biosynthesis of silver nanoparticles using the Falcaria Vulgaris (Alisma Plantago-Aquatica L.) extract and optimum synthesis

There are many reports about the use of medicinal plants in traditional medicine, as well as the application of metal nanoparticles in various biomedical fields. The purpose of the present study is bio synthesize of silver nanoparticles, using the aqueous extract of Alisma Plantago-Aquatica L plant and to achieve optimal conditions for the synthesis of these nanoparticles. For this reason, the effect of different parameters such as pH, extract volume, concentration of silver nitrate solution, temperature and reaction time were studied and their optimal amount was determined. Then, the nanoparticles synthesized in optimum conditions, were evaluated (UV-Vis), X-ray diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscope (TEM) and Fourier-Transform Infrared spectroscopy (FTIR). Strong and width peak of the visible UV spectrophotometer, at 438 nm wavelength, showed the formation of silver nanoparticles. The X-ray diffraction pattern confirmed the formation of crystalline silver nanoparticles at a size of about 25 nm. The results of FESEM showed nanoparticle shape in a spherical and monodisperse, with a particle size range of 20 to 58 nm. The TEM analysis also yielded a nanoparticle size of about 20 nm. The results of the Fourier transform infrared spectroscopy (FTIR), indicate the involvement of hydroxyl, amine and carboxyl groups in the plant extract in the synthesis of silver nanoparticles. The results of this study showed that theAlisma Plantago-Aquatica L. plant extract can be introduced as an appropriate, affordable and safe alternate in terms of green chemistry, instead of toxic and high-risk chemicals.

Green synthesis of silk sericin-embedded silver nanoparticles and their antibacterial application against multidrug-resistant pathogens

BackgroundThe green synthesis strategy of metallic nanoparticles (NPs) has become popular due to being environmentally friendly. Stable silver nanoparticles (AgNPs) have been synthesized by natural products such as starch, soy protein, various extract of leaves, barks, and roots functioning both as reducing and stabilizing agents. Likewise, silk sericin (SS) is a globular protein discarded in the silk factory might be used for NP synthesis. In this research, we focus on the green synthesis and stabilization of AgNPs by SS as well as assessment of their antibacterial activities against some drug-resistant pathogen. ResultsSS was extracted from Bombyx mori silkworm cocoons in an aqueous medium. 17 w/w% of dry sericin powder with respect to the cocoon’s weight was obtained by freeze-drying. Furthermore, AgNPs conjugated to sericin, i.e., SS-capped silver nanoparticles (SS-AgNPs) were synthesized by easy, cost-effective, and environment-friendly methods. The synthesized SS-AgNPs were characterized by UV-visible spectroscopy, Fourier-transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction measurement. It has been found from the absorbance of UV-visible spectroscopy that a higher percent of SS-AgNPs was obtained at a higher concentration of silver nitrate solution. FTIR-ATR spectra showed that the carboxylate groups obtained from silk sericin act as a reducing agent for the synthesis of silver nanoparticles, while NH2+ and COO− act as a stabilizer of AgNPs. The X-ray diffractogram of SS-AgNPs was quite different from AgNO3 and sericin due to a change in the crystal structure. The diameter of AgNPs was around 20–70 nm observed using TEM. The synthesized SS-AgNPs exhibited strong antibacterial activity against multidrug-resistant pathogens, Escherichia coli and Pseudomonas aeruginosa. Minimal inhibitory/bactericidal concentrations against E. coli and P. aeruginosa were 20μg/mL. ConclusionsThis study encourages the use of Bombyx mori for the ecofriendly synthesis of SS-AgNPs to control multidrug-resistant microorganisms.

Investigating the Possibility of Green Synthesis of Silver Nanoparticles Using Vaccinium arctostaphlyos Extract and Evaluating Its Antibacterial Properties.

Objective Vaccinium genus plants have medicinal value, of which Vaccinium arctostaphylos (Caucasian whortleberry or Qare-Qat in the local language) is the only available species in Iran. Public tendency to use herbal remedies and natural products such as synthesized nanoparticles is increasing due to the proof of the destructive side effects of chemical drugs. Nanosilver products have been effective against more than 650 microbe types. This study was aimed at assessing the possibility of green synthesis of silver nanoparticles using Vaccinium arctostaphylos aqueous extract and at evaluating its antibacterial properties, as well. Materials and Methods In order to synthesize silver nanoparticles, different volumes of Vaccinium arctostaphylos aqueous extract (3, 5, 10, 15, and 30 ml) were assessed with different silver nitrate solution concentrations (0.5, 1, 3, 5, and 10 mM) and different reaction time durations (1, 3, 5, 10, and 20 minutes) at room temperature using a rotary shaker with a speed of 150 rpm. Ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were carried out. The antibacterial activity of the aqueous extract and the synthesized nanoparticles was evaluated, as well. Results Silver nanoparticle formation process was confirmed with XRD analysis, transmission electron microscopy (TEM), and FTIR spectroscopy. The UV-Vis spectroscopy of silver colloidal nanoparticles showed a surface plasmon resonance peak at 443 nm under optimal conditions (3 ml aqueous extract volume, 1 mM silver nitrate solution concentration, and 3 min reaction time under sunlight exposure). The reduction of silver ions to silver nanoparticles in solution was confirmed, as well. Based on X-ray diffraction analysis, the size of silver nanoparticles was in the range of 7-16 nm. TEM images showed an even distribution of silver nanoparticles, with a spherical shape. FTIR spectroscopy demonstrated the presence of different functional groups of oxygenated compounds such as carboxyl, hydroxyl, and nitrogenous groups. The antibacterial properties of the synthesized nanoparticles were confirmed. Conclusion The synthesized nanoparticles showed more antibacterial properties against gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than gram-negative ones (Escherichia coli and Salmonella enteritidis).

Biosynthesis of Silver Nanoparticles Using Banana <i>Raja</i> (<i>Musa paradisiaca var. raja</i>) Peel Extract: Effect of Different Concentrations of the AgNO<sub>3</sub> Solution

This study focuses on the biosynthesis of silver nanoparticles using Banana Raja (Musa Paradisiaca Var. Raja) peel extract. The aim is to determine the effect of concentration differences of silver nitrate (AgNO3) as the precursor on the production of silver nanoparticles. In this study, banana peel extract (BPE) was reacted with AgNO3 solution at several concentrations of silver nitrate solution i.e. 0.125; 0.1; 0.075 and 0.05 M at temperature of 50 °C. The ratio of banana peel extract and AgNO3 solution used was 5:500 (v/v). The stirring was done by using a magnetic stirrer. The reaction took place when the color of the mixture (extract and AgNO3) changed until the color of the mixture became constant. The results of the colloidal silver nanoparticles were characterized using UV-Vis Spectrometer, while the functional groups of the banana extract was analyzed using a Fourier Transform Infra-Red (FT-IR) apparatus. Whereas, the morphology of the silver nanoparticles was studied using a Scanning Electron Microscopy (SEM). The UV-Vis Spectrometer result show that the concentration of AgNO3 which gave the highest absorbance value was at 0.1 M. The SEM micrographs could not clearly show the difference in the morphology of silver nanoparticles samples at different concentrations of AgNO3 solution.

One-Pot Preparation for Agar/Gros Michel/Silver Nanoparticles Biocomposite Films and Antibacterial Activities

Agar and banana (Gros Michel) powder composite film with silver nanoparticles were prepared using a solution casting method. Then, the ratio of agar and banana powder also the concentrations of silver nitrate solution have affected the properties of biocomposite film. These physical properties were characterized by UV-Vis spectrophotometer and colorimeter. The results indicated that biocomposite film with the mass ratio of agar to banana = 3:1 (A3B1_Ag50) was brown and had the maximum absorption of UV-Vis light at 432 nm. This biocomposite film exhibited strong antibacterial activity against both Escherichia coli and Staphylococcus aureus. Because of their microbial activity and physical properties, these biocomposite films have the potential to be used extending the shelf life of food packaging.

Optimizing Synthesis of Citrus limetta Peel Silver Nanocomposites Possessing Larvicidal Potential against Dengue Vector, Aedes aegypti L.

Aedes aegypti L. is the major vector accountable for the spread of several diseases of medical importance. The control strategies primarily relying on chemical insecticides have caused negative impact on our environment and human health. Thus, current study employed Citrus limetta peel extracts (CLPE) against larvae of Ae. aegypti. Silver nanocomposites (AgNCs) from CLPE were synthesised and the process of synthesis was optimized by varying temperature; volume and concentration of silver nitrate solution; and the volume of catalyst. A conspicuous change in colour of the reaction mixture was noticed from pale yellow to dark brown. This indicated the synthesis of AgNCs which was traced by UV-Visible spectroscopy. The optimum synthesis of CLPE-AgNCs was obtained with the mixture of 4 mL AgNO3 (3mM) and 3 mL CLPE. The larvicidal assay with these nanoparticles against Ae. aegypti resulted in LC50 and LC90 values of 26.82 μg/mL and 99.32 μg/mL after 24 h of exposure; which respectively decreased to 19.51 μg/mL and 71.99 μg/mL after 48 h of exposure. The results elucidate 1.3-fold higher larvicidal efficacy of nanoparticles with increased duration of larval exposure. We suggest that synthesis of AgNCs by utilizing peel extract of C. limetta is a cost-effective and eco-safe alternative to conventional insecticides; and can be utilized as the potent mosquito larvicide.

Histopathological study of the maternal exposure to the biologically produced silver nanoparticles on different organs of the offspring.

This research for the first time presents the possibility of crossing the biologically produced SNPs through the placenta to different organs of rat offspring. SNPs were produced using Fusarium oxysporum. After adding 1mmol final concentration of silver nitrate solution to the culture supernatant and 5min heating, SNPs were produced, and their production was proved using visible spectrum, transmission electron microscope (TEM), and X-ray diffraction (XRD) analyses. SNPs were washed, and their concentration determined using inductively coupled plasma (ICP) instrument. SNPs were used for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and after determination of their half maximal inhibitory concentration (IC50) dose, their toxic and nontoxic doses were determined and used for in vivo studies. A total of 24 female rats, after detection of their vaginal plugs, were divided into 3 groups each having 8 members. A control group was treated with normal saline. The other two groups were treated by toxic and nontoxic doses of SNPs, respectively. After delivery and breastfeeding, the pups were scarified, and their organs were collected and analyzed using histological examinations. Results showed that SNPs had a maximum absorbance peak around 450nm, with polygonal and round shapes. XRD results confirmed the presence of SNPs. The concentration of the SNPs after washing was 19ppm/mL based on the ICP results. MTT assay results showed that SNPs had a dose-dependent toxic effect. Histopathological examination results showed that SNPs could pass through the placenta; both their nontoxic and toxic doses induced somehow mild alternations in the liver, kidney, testis, and ovary and had no effects on the brains of the rat offspring. In conclusions, the use of the biologically produced SNPs should be limited during pregnancy and breastfeeding.

Optimization of silver nanoparticle biosynthesis process using cell-free filtrate of Aspergillus niger

Nanotechnology and nanoparticle (NPs) research has attracted a lot of interest in recent decades, and there is growing attention to find more effective ways for their synthesis. The use of biological organism as bionanofactories provides a clean and promising alternative process for the fabrication of silver nanoparticles. This study confirmed the production of silver nanoparticles (SNPs) by a cost effective, safe and environment-friendly technique using silver nitrate and cell free filtrate of the fungus Aspergillus niger as the reducing agent. The optimization of different parameters, including the culture media, pH, reaction temperature, concentration of silver nitrate solution and reduction time, were carried out to achieve better control of size, shape, stability, and to increase the yield of SNPs production. The UV-visible spectrophotometric analysis of the biosynthesized silver nanoparticles by Aspergillus niger cell-free filtrate showed characteristic surface plasmon absorption peak at 420 nm. The presence of proteins as viable reducing agents for the formation and stability of SNPs was recorded using Fourier transform infrared spectroscopic analysis (FTIR) .Further scanning electron microscopy (SEM) micrograph showed the formation of spherical, well-dispersed nanoparticles with size ranging between 15 and 50 nm in diameter. The element composition of the mixture sample was obtained from the Energy Dispersive Analysis of X-ray (EDX). It concluded that the optimum condition for biosynthesis of SNPs were the use of Potato dextrose broth medium at pH 9, 30°C for 120 h with 1mM silver nitrate.

Ethylene glycol mediated facile and controlled growth of ultralong hexagonal silver molybdate microrods

A controlled growth of nano/micro rods with defined morphologies are of great interest due to its special and unique properties. Here we report ethylene glycol mediated facile and controlled synthesis of ultra-long (∼100 μm) perfect hexagon shaped microrods of silver molybdate by a cost effective method of hydrothermal. The exact conditions are optimized by varying the effective parameters. The synthesis involves the mixing of different concentration of silver nitrate solution (0.025, 0.075, 0.125 M) with ammonium molybdate in the presence of 10 ml of ethylene glycol and then post hydrothermal treatment at 150 °C for 12 hrs. Only 0.075 M conc. of silver nitrate results perfect hexagons whereas the lower and higher concentrations result the formation of distorted edge shaped and longer microrods of Ag6Mo10O33. The magnetic measurement shows the perfect diamagnetic behavior of these mircorods.

A facile method to produce silver nanoparticle-loaded regenerated cellulose membranes via the reduction of silver nitrate in a homogeneous system

Regenerated cellulose (RC) membranes loaded with silver nanoparticles (AgNPs) were prepared in this study. Cellulose acted as a reducing agent, silver nitrate acted as an oxidizing agent, and N-methylmorpholine-N-oxide (NMMO) acted as a direct cellulose solvent. The AgNP-loaded RC membranes were obtained via the redox reaction between cellulose and silver nitrate. The results of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis suggest that AgNPs were reduced on the RC membranes during the dissolution and regeneration of cellulose. Atomic force microscopy (AFM) showed that the RC membranes exhibited high surface roughness, with a value of 7.19 nm. The Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results demonstrated that the crystal lattice type of RC membranes changed from cellulose I to cellulose II, without any derivatization. The detection results of atomic absorption spectrometry (AAS) indicated that the silver content of the RC membranes increased with increasing silver nitrate solution concentration. Antibacterial experiments showed that the AgNP-loaded RC membranes exhibited good antibacterial properties with respect to both Escherichia coli and Staphylococcus aureus.

Biomimetic fabrication of antibacterial calcium phosphates mediated by polydopamine

In this work we developed new antibacterial composite materials using polydopamine (PDA) to trigger the deposition of silver nanoparticles (AgNPs) onto calcium phosphates, namely octacalcium phosphate (OCP) and α-tricalcium phosphate (αTCP). Functionalization of OCP and αTCP with a self-polymerized polydopamine layer was obtained by soaking the calcium phosphates in dopamine solution. The PDA surface of functionalized calcium phosphates (OCPd and αTCPd) promoted the deposition of AgNPs by reducing silver ions when soaked in a silver nitrate solution. The amount of deposited AgNPs can be modulated by varying the concentration of silver nitrate solution and the type of substrate. The results of in vitro tests carried out with osteoblast-like MG63 cells indicate that the combination of AgNPs with OCP provides more biocompatible materials than those obtained using αTCP as substrate. In particular, the study of osteoblast activity and differentiation was focused on the samples OCPdAg5 (silver content=8.2wt%) and αTCPdAg5 (silver content=4.7wt%), which did not show any cytotoxicity, and compared with those obtained on pure OCP and αTCP. The results demonstrate that the AgNPs loaded materials support osteoblast viability and differentiation, whereas they significantly inhibit the growth of relevant antibiotic-resistant pathogenic bacteria.

Synthesis, characterization and antibacterial properties of novel nano-silver loaded acid activated montmorillonite

This paper reports synthesis, characterization and antibacterial properties of a novel silver-exchanged montmorillonite (Ag-Mt) synthesized from acid activated sodium montmorillonite (Na-Mt). The silver-loaded nanostructures (Ag-Mt) were synthesized in a two-step approach in which Na-Mt was first converted into acid activated Na-Mt and further treated with two concentrations of silver nitrate solution to obtain two types of acid activated Ag-Mt for comparison, Ag-Mt without the acid activation step and isotropic silver nanoparticles were synthesized as control samples. EDX confirmed successful loading of elemental silver in all types of Ag-Mt and WXRD analysis showed undisturbed crystal structure with increased interlayer space compared to Na-Mt. TEM micrographs revealed formation of spherical silver nanocrystals on the supporting silicate layers although no external reducing agent was employed due to high reduction potential of silver ions. The results were further confirmed in UV spectroscopy where strong absorption bands related to the surface plasmon resonance (SPR) was observed. The bactericidal efficacy of the clay minerals were evaluated against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus using disk diffusion method which showed excellent inhibitory properties and large inhibition zones of all synthesized Ag-Mt. The minimum inhibitory concentration (MIC) of the clay minerals was also quantified and compared with synthesized isotropic silver nanoparticles. Acid activated Ag-Mt showed antimicrobial activity marginally lower than silver nanoparticles alone, although the silver content was ~10 times lower than Ag-NP. This antibacterial agent is thus very effective and more attractive in terms of cost and environment friendly nature.