Advanced Materials Letters

An efficient theragnostic which offers diagnosis and therapy of cancer is developed using a polymer based nanocarrier embedded with fluorescent quantum dots by the ionotropic gelation method. The FTIR spectra provide direct evidence of formation of polymer based nanocarrier comprising chitosan-alginate micro beads (CS-ALG beads). Notably, the SEM images showed highly porous structure of polymeric beads without Ag NPs and CdS QDs. The morphology of CS-ALG beads loaded with Ag NPs and CdS QDs showed smooth surface, glossy, homogenous shape under scanning electron microscopy and it could be due to high loading of fluorescent and silver NPs. The EDX analysis of as synthesised nanoparticle embedded polymeric beads showed X-ray peaks of Cd, S corresponds to CdS NPs. And the X- Ray peaks of C, O corresponds to the polymer beads.  Characterization of nanocarrier for the presence of polymers has been confirmed by studies carried out using thermogravimetric analysis (TGA) showed complete degradation of Chitosan at about 450 °C while calcium alginate exhibits three-step decomposition. Further, the swelling studies of dried CS-ALG beads were carried out at room temperature and about 97% of swelling is being observed at pH 5 in 45 min. and 44% swelling is observed at pH 2. Copyright © VBRI Press.

Silver nanoparticles (Ag NPs) were prepared using Cassia auriculata leaves extract as a reducing agent via green synthesis method. From the PXRD, UV-Visible, FTIR, studies the synthesized NPs were characterized. The morphologies of the prepared NPs were studied by SEM and TEM analysis. The synthesized NPs were tested for antibacterial and anticancer studies. The PXRD data indicated that the synthesized nanoparticles belong to cubic phase structure. Presence of strong silver peaks was confirmed by EDAX studies. The SEM and TEM data revealed that spherical like structure were obtained. Antibacterial (MIC from 75 to 150 μl) activities were noticed for green synthesized Ag NPs. Furthermore, in vitro studies revealed dose-dependent cytotoxic effects of Ag NPs treated PC-3 cell line. This is the first report on the green synthesis of Ag NPs using leaves extract of C. auriculata. Results of present study could contribute to synthesize new and cost-effective drugs from C. auriculata by using green approach. Copyright © VBRI Press.

Silver nanoparticles (AgNPs) embedded double network (DN) nanocomposite hydrogels [of P(AM-co-HEMA) as second network and PVA-Borax as first network] were synthesized by in-situ reduction of silver nitrate using citric acid in presence of the fully swollen high strength DN hydrogels. The AgNPs embedded DN nanocomposites hydrogels (Ag-DNG) were characterized by FTIR, XRD and TEM analyses. Such Ag-DNG hydrogels were studied for their degree of swelling and swelling kinetics. They were also evaluated for their anti-bacterial characteristics using a Gram negative (Escherichia coli) and a Gram positive (Bacillus subtilis) bacteria. The XRD analysis revealed the presence of AgNPs in the DN nanocomposite hydrogels. The AgNPs were observed to be 20-50 nm in diameter as observed by TEM analysis. The degree of swelling of Ag-DNG hydrogels was lower than that of the virgin DN hydrogel which was because of the space of pores of the DN hydrogels occupied by AgNPs. The virgin DN hydrogels did not exhibit any antimicrobial property, whereas Ag-DNG hydrogels exhibited a significant amount of antibacterial activity towards gram positive and gram negative bacteria. Such AgNPs incorporated high strength DN nanocomposite hydrogels may find potential biomedical application.

The green synthesis of silver nanoparticles using Cyamopsis tetragonoloba plant extract and their photocatalytic and antibacterial properties is reported. Three precursor concentrations of 1 mM, 2 mM and 5 mM were used, and at two different ratios of 1:5 and 1:10 plant extract to the precursor. The formation of the nanoparticles was followed by the periodic study of surface plasmon resonance using the UV-visible spectroscopy, which revealed the formation of nanoparticles with regular bands after 45 min. of reaction. Fourier transform infrared spectroscopy was used to study the functional groups present in the plant biomolecules which aided the reduction and stabilization of the nanoparticles. Transmission electron microscopy analysis and X-ray diffraction pattern showed the particle sizes and crystalline structures, while the zeta potential values indicated the stability of the nanoparticles. The 5 mM concentration gave the largest particle sizes of about 12.90 nm and the most stable particles. The photocatalytic properties of the particles studied using Methyl red showed a low efficiency of 17.85% degradation achieved under 2 h. The antibacterial potency of the nanoparticles was screened against some gram-negative and gram-positive bacteria. The results showed that the nanoparticles have good antibacterial activities.

In this paper, ammonia sensor operating at room temperature based on diphenylamine conjugated polymer has been designed and developed. The structure of the polymer was established by UV-Visible, FT-IR and NMR characterization techniques. The polymer was doped with silver nanoparticles by ex-situ method in 0.6 wt%, 1.2wt% and 1.8wt% to form silver nano-composites. The thin films of the polymer and its composites were cast by spin coating on the glass plate. The response of the polymer and its composite with silver nanoparticles has been studied for gas sensor applications. The polymer showed selectivity towards ammonia gas, whereas the polymer composite with silver nanoparticles exhibited selectivity towards ammonia gas and also to ethanol vapors. The response towards ammonia gas was found to increase with the increase in loading of silver nanoparticles. Reproducibility of the polymer and its composite is studied and is found to improve with the loading of silver nanoparticles. 

In the present study, the extracellular phycofabrication (synthesis by algae) of silver nanoparticles was demonstrated using algae i.e. Spirogyra sp. recovered from the fresh water. The reduction of silver ions present in the aqueous solution of silver sulphate (Ag2SO4) was done by the cell filtrate of Spirogyra sp. leading to the synthesis of silver nanoparticles. Phycofabrication of silver nanoparticles was confirmed by using characterization tools like UV-Vis spectrophotometer, FTIR, TEM and NTA. The resulting silver nanoparticles were spherical in shape, in the range of 40-80 nm and capped with proteins. Through the experimental studies, it was found that temperature, pH and salt concentration affects the rate of phycofabrication of silver nanoparticles. Antibacterial study of phycofabricated silver nanoparticles was assessed against human pathogenic bacteria. These silver nanoparticles showed better antibacterial activity against gram positive bacteria i.e. Staphylococcus aureus (ATCC-25923) (13 mm) as compared to Gram negative bacteria i.e. Escherichia coli JM-103 (ATCC-39403) (11 mm). This is the first report of synthesis of silver nanoparticles by Spirogyra sp < /em>. using Ag2SO4 as a salt. Extracellular phycofabrication of silver nanoparticles by Spirogyra sp. was found be easy, simple and eco-friendly method.

In the present study extracellular synthesis of silver nanoparticles (AgNPs) was achieved using cultural supernatant of bacterial isolate Aeromonas dhakensis AS3. Biosynthesis of AgNPs was completed within 120 min by incubating cell free supernatant with silver nitrate solution under illumination. Brown color appearance of solution due to surface plasmon resonance (SPR) and absorption maxima centered at 405 nm was indicated formation of AgNPs. Fourier transform infrared spectroscopy (FTIR) spectrum analysis revealed the presence and association of possible biomolecules with AgNPs during synthesis. Atomic force microscopy (AFM), Field emission scanning electron microscopy (FE-SEM) and High resolution transmission electron microscopy (HR-TEM) showed spherical nanoparticles with an average size of 5 nm. X-ray diffraction (XRD) and Energy Dispersive X-ray (EDX) spectrum confirmed crystallinity and purity of AgNPs. The synthesized AgNPs was found to have significantly independent as well as combined activity against multidrug resistant extended spectrum β-lactamases (ESBLs) producing Acinetobacter junii, E.coli and Klebsiella spp. harboring TEM and/or CTX-M genes. This work demonstrates the possible use of biosynthesized AgNPs to combat ESBLs producing pathogens.

Silver nanoparticles (AgNPs) were synthesized in situ under gamma radiation environment at room temperature using aqueous silk fibroin (SF) solution obtained from Bombyx mori silk. The formation of the Ag NPs was confirmed by its characteristic surface plasmon resonance (SPR) band at around 424 nm in UV-visible spectra. The strength of the photoluminescence (PL) spectra decreases with increasing dosage reveals the optimum dose required for the synthesis of silver nanoparticles. Dynamic light scattering (DLS) measurement indicated the dose dependent size of the Ag NPs formed in the solution. The transmission electron microscopy (TEM) images showed that the formed nanoparticles are roughly spherical in shape. Further the X-ray diffraction (XRD) analysis confirms the nanocrystalline phase of silver with FCC crystal structure. From this study, it was found that the increasing the radiation dose increases the rate of reduction and decreases the particle size. The size of the Ag NPs can be tuned by controlling the radiation dose.

In this work we have successfully prepared spherical and chain type silver nanoparticles of excellent size’s homogeneity, reproducibility and stability using tannic acid. The synthesized nanometallic structures were characterized for their shape, size, thermal stability and crystalline nature. The mechanism for the formation of Ag NPs and shape evolution of the chain structure has been vividly explained. Further, these NPs were found to exhibit significant antibacterial activity against gram negative Escherichia coli bacteria but to different extend indicating the influence of particles morphology on their antibacterial behaviours.

In this paper, we described a simple and single step procedure for the synthesis of horseradish peroxidise enzyme (HRP) capped silver and gold nanoparticles. HRP, a heme-containing enzyme utilises hydrogen peroxide to oxidise a wide variety of organic and inorganic compounds. The biosynthesized nanoparticles were characterized by means of UV-VIS spectroscopy, Dynamic light scattering (DLS), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). FTIR study confirms the presence of peroxidase enzyme on the nanoparticles. Computational studies reveal that exposed amino acids (viz serine, threonine, arginine and glycine) play key role in reduction and as well as stabilization of nanoparticles. The HRP assisted silver and gold nanoparticles retained its biological activity in the nanoparticles. The study indicates that Peroxidase which is found in almost all the plants can be used for the large scale synthesis of nanoparticles. Moreover additional attraction is the retention of the enzymatic activity on the nanoparticles. In a single step reaction enzyme is catalysing and in doing so it gets immobilized on it. The integration of biomolecules to nanoparticles is a tedious method mainly due to the surface of nanoparticles. Functionalization of noble metal nanoparticles with biomolecules (e.g., protein and DNA) is in demand because such systems possess numerous applications in catalysis, delivery, therapy, and imaging, sensing and controlling the structure of biomolecules. Computational study highlighted the amino acids which are interacting with the metal ions, thus synthetic peptides can also be designed to synthesize the metal nanoparticles.

Silver nanoparticles of average sizes ~18-21 nm in diameter were prepared by a green approach via chemical reduction of silver nitrate (AgNO3) using Asiatic Pennywort and Bryophyllum leaf extracts as reducing and capping agents. The bio-reduced silver nanoparticles were characterized by UV-Vis spectroscopic, XRD and TEM techniques. The characteristic surface plasmon band of colloidal solutions of AgNPs synthesized from Asiatic Pennywort and Bryophyllum leaf extracts were found at 445 nm and 405 nm respectively. The results of XRD and SAED pattern showed that the biosynthesized AgNPs have a crystalline structure with cubic phase (fcc). The antimicrobial activities of the as synthesized AgNPs were investigated against gram negative bacteria Pseudomonas Fluorescens and gram positive bacteria Staphylococcus Epidermidis. It was observed that silver nanoparticles obtained from Asiatic Pennywort was more effective on gram positive bacteria Staphylococcus Epidermidis while AgNPs obtained from Bryophyllum was more effective on gram negative bacteria Pseudomonas Fluorescens indicating size dependent activity of AgNPs.

Silver nanoparticles (Ag NPs) has resulted their incorporation into consumer products due to their extensive application in health, electronic, and household products. In particular, the oral toxicity of Ag NPs is of particular concern to ensure public health. For the present study, a genotoxic and cytotoxic approach was employed to elucidate the activity of 5 nm size and spherical shaped Ag NPs in liver cells of Swiss albino mice by using alkaline comet assay. Statistically significant DNA damage raise the concern about the safety associated with the applications of the Ag NPs. The result showed that Ag NPs induced a significant concentration dependent increase in the frequency of tailed nuclei (DNA damage), tail moment, %DNA in the tail, and tail length in the liver cells. Additionally significant histopathological alterations were also observed. The results of present study suggest that exposure to silver nanoparticles has the potential to cause genetic damage.

Stable aqueous dispersions with high concentration of silver nanoparticles were synthesized by a facile and green synthetic route by treating silver ions with aqueous Citrus limon extract, used as a reducing and capping agent. The formation and growth of silver nanoparticles, prepared by this simple and convenient method, was monitored using UV-visible absorption spectroscopy. The effects of Ag concentration, Citrus limon extract concentration, in-situ and ex-situ pH variations upon NaOH addition on the structural, optical and plasmonic properties of the synthesized Ag nanoparticles were investigated. X-ray diffraction studies revealed the formation of Ag nanoparticles, whose morphology was studied using atomic force microscopy. UV-visible absorption studies revealed surface plasmon resonance (SPR) peak around 465 nm, confirming the presence of Ag nanoparticles. The SPR peak blue shifted along with significant enhancement in intensity with increase in Ag concentration and pH, due to the growth and increased aggregation of Ag nanoparticles. We have shown that addition of NaOH is a key to rapid biosynthesis of stable aqueous dispersions of high concentration of silver nanoparticles. This green synthetic route provides faster synthesis of silver nanoparticles with improved colloidal stability, which can be used in foods, cosmetics and biomedical applications.

Silver nanoparticles (AgNPs) have been synthesized via the green pomosynthetic procedure, using Passiflora tripartita var. mollissima fruit pigments as both the reducing and stabilizing agents. UV–Vis Spectroscopy, Dynamic Light Scattering, Transmission Electron Microscopy with Selected Area Electron Diffraction and Powder X-Ray Diffraction are used to completely characterize the AgNPs. The prepared AgNPs are found to be mostly spherical shapes with an average diameter of 49.7 ± 24.6 nm at room temperature. XRD analysis revealed the face-centered cubic geometry of AgNPs whereas Infrared spectrum and cyclic voltammetry measurements hypothesize the possible biomolecules (flavonoid C & O-glycosides) responsible for stabilization of the AgNPs. Synthesized AgNPs shows significant antioxidant efficacy (67%, 0.15 mM) against 1, 1-diphenyl-2- picrylhydrazyl. The AgNPs (0.01 – 20 μΜ) did not affect cell proliferation of the human cancer cell lines A -549 and HeLa, from lung and cervix, respectively. The use of environmentally benign, cost-effective and renewable materials like P. tripartita extract offers numerous benefits of eco-friendliness and compatibility for potential future pharmaceutical and biomedical applications.

A simple and eco-friendly biosynthesis of silver nanoparticles (AgNPs) is reported here using apple fruit extract as reducing and capping media under microwave irradiation. AgNPs were characterized by UV–visible spectroscopy, XRD, FT-IR and TEM. The kinetics of reduction of aqueous silver ions during reaction with the apple fruit extract were monitored with the help of UV-visible spectroscopy. The XRD pattern of AgNPs was found agreeing with the fcc structure of Ag metal. Further, where TEM analysis exhibited formation of spherical shaped nanoparticles in the range of 10–45nm; FTIR analysis was carried out to identify the functional groups which were responsible for reduction/capping of AgNPs and conclude that the characterized AgNPs carry the potential for adoption in various medical and industrial applications.

Sunlight induced strategy for the rapid green synthesis of silver nanoparticles (AgNPs) is reported for the first time using aqueous leaf extract of Achyranthes aspera. On exposing a mixture of silver nitrate solution and aqueous leaf extract of A. aspera to sunlight, stable silver nanoparticles were obtained within few seconds. The water soluble biomolecules from the A. aspera served as both reducing and capping agents in the synthesis of silver nanoparticles. The nanoparticles were characterized using UV–Vis., Fourier transform infrared (FTIR), transmission electron microscopy (TEM), and EDAX techniques. The pseudo first order rate constant kobs, for the formation of AgNPs was found to be 3.49 x 10 -2 min -1 . The particles were stable for 3 months. The nanoparticles were mono-dispersed, spherical in shape with the average size of 12.82 nm. FT-IR analysis revealed that the -OH groups, possibly, from saponin were responsible for the reduction of silver ions to silver nanoparticles (AgNPs). Thus prepared AgNPs have desirable cytotoxicity towards bacterial strains and fungus and the effect was compared with standard drugs, Amikacin and fluconazole respectively. This green and mild technique can be used for the large scale extracellular synthesis of silver nanoparticles and the AgNPs thus prepared may be used for biological applications.

A one-pot synthesis method has been developed for preparation of silver nanoparticles in aqueous poly (vinyl pyrrolidone) (PVP) solution by synchrotron X-ray radiation. The hydrated electrons (eaq - ) and hydrogen atom radical (H·), products of radiolysis of water molecules by synchrotron X-rays brings about the reduction of the metal ions, resulting in homogeneous nucleation and nanoparticle formation. The nanoparticles were characterized by UV-visible spectroscopy and TEM analysis. A comparative study has been done to know the effectiveness of this synthesis method with that of gamma and EB- irradiation methods. In gamma radiation method the nanoparticle size obtained was ~8nm, whereas in synchrotron X-ray irradiation 10-15nm particles were obtained. Smaller size particles with narrow size distribution were obtained by g-radiolysis and EB-irradiation than those obtained by X-ray radiolysis. The effects of different experimental parameters, such as concentration of Ag + , PVP concentration on nanoparticle formation were studied.

This paper reports a rapid and eco-friendly green method for synthesis of silver nanoparticles from silver nitrate solution using loquat leaf extract. Effect the amount of leaf extract, reaction time, silver nitrate concentration and temperature were investigated. Biosynthesized silver nanoparticles (AgNPs) were characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS) and Fourier transform infrared spectroscopy (FT-IR). UV-vis spectroscopy showed that the surface plasmon resonance (SPR) at 425 nm. The structural peaks in XRD pattern and average crystalline size around 18 nm clearly illustrates that AgNPs synthesized by our green method were nanocrystalline in nature with face centered cubic geometry. The antibacterial activity of biosynthesized silver nanoparticles showed effective inhibitory activity against water borne pathogens, Shegella and Listeria bacteria.

Silver nanoparticles have been widely used in consumer products due to their excellent antimicrobial properties. Release of nanosilver into natural waters may induce negative environmental impacts on local microorganism communities. This work evaluated the influence of anions such as sulfate, phosphate, chloride and sulfide on the toxicity of silver nanoparticles. Results revealed that sulfide anion could significantly reduce their toxicity in comparison with other anions, which provides an in-depth investigation on the toxicity control of released silver nanoparticles.

Conducting polyaniline/silver nanoparticles (PANI-Ag) nanocomposite was synthesized by in-situ polymerization of aniline in the presence of silver nitrate as precursor. Nanocomposite was characterized by UV-VIS, PL, XRD, FTIR, SEM and TGA to study the effect of silver nanoparticles embedded into PANI on the morphology, structure, crystalline and thermal stability of the conducting polyaniline. The optical studies show that the absorption edge of PANI-Ag nanocomposite exhibits the significant blue shift. The photoluminescence studies show that the emission peak shifted towards the blue when compared to that of bulk PANI-Ag. The broadening sharp peaks in the XRD pattern indicate that the synthesized PANI-Ag nanocomposite is nanocrystalline. FTIR reveals the presence of silver metal ions uniformly embedded into PANI. SEM reveals the rod structure surface morphology of PANI-Ag nanocomposite. Thermogravimetric analysis suggests the presence of silver and also an oligomeric component in the nanocomposite. The combination of PANI as a semiconducting polymer with silver as a noble metal may produce hybrid material that behaves as semiconductor at low temperature and as metal at high temperature.

Nowadays, nanotechnology has grown to be an important research field in all areas including medicinal chemistry. The size, orientation and physical properties of nanoparticles have reportedly shown to change the performance of any material. For several years, scientists have constantly explored different synthetic methods to synthesize nanoparticles. On the contrary, the green method of synthesis of nanoparticles is easy, efficient, and eco-friendly in comparison to chemical-mediated or microbe-mediated synthesis. The chemical synthesis involves toxic solvents, high pressure, energy and high temperature conversion and microbe involved synthesis is not feasible industrially due to its lab maintenance. Since, green synthesis is the best option to opt for the synthesis of nanoparticles, therefore the nanoparticles were synthesized by using aqueous extract of Moringa oleifera and metal ions (such as silver). Silver was of particular interest due to its distinctive physical and chemical properties. M. oleifera leaf extract was selected as it is of high medicinal value and it does not require any sample preparation and hence is cost-effective. The fixed ratio of plant extract and silver ions were mixed and kept at room temperature for reduction. The color change from yellow to reddish brown confirmed the formation of nanoparticles. Further, the synthesized nanoparticles were characterized by UV, EPMA, XRD and FTIR data. The antimicrobial activity of synthesized nanoparticle has also been examined in gram positive and gram negative bacteria and encouraging results are in hand.

This report presents a rapid, reproducible and a green biogenic approach for the biosynthesis of gold and silver nanoparticles using leaf extract of Dalbergia sissoo. The biomolecules present in the plant induced the reduction of Au 3+ and Ag + ions from HAuCl4 and AgNO3 respectively, which resulted in the formation of Dalbergia conjugated nanoparticles. The growth of nanoparticles was monitored by UV-vis spectrophotometer that demonstrated a peak at 545 and 425 nm corresponding to Plasmon absorbance of gold and silver nanoparticles respectively. The leaf extract was found to direct different shape and sized gold nanoparticles. Gold nanoparticles were 50-80 nm in size and their shape varied from spherical to few triangular and hexagonal polyshaped. While silver nanoparticle synthesized were spherical, in the range of 5-55 nm in size. X-ray diffraction studies corroborated that the biosynthesized nanoparticles were crystalline gold and silver. Fourier transform infra-red spectroscopy analysis revealed that biomolecules were involved in the synthesis and capping of silver nanoparticles and gold nanoparticles.

Biological synthesis of silver nanoparticles using Murraya koenigii leaf extract was investigated and the effect of broth concentration in reduction mechanism and particle size is reported. The rapid reduction of silver (Ag + ) ions was monitored using UV-visible spectrophotometry and showed formation of silver nanoparticles within 15 minutes. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis showed that the synthesized silver nanoparticle are varied from 10-25 nm and have the spherical shape. Further, the XRD analysis confirms the nanocrystalline phase of silver with FCC crystal structure. From this study, it was found that the increasing broth concentration increases the rate of reduction and decreases the particle size.

This work reports a novel biological method for the synthesis of rod shaped silver nanoparticles by exploiting sundried Stevia rebaudiana leaves at ambient conditions. On treatment of aqueous solutions of silver with leaf powder, not only the rod shaped silver nanoparticles ranging from 80-200 nm diameter and 400-800 nm height, but also cubes ranging from 55 to 80 nm in size, could be rapidly fabricated. The rate of reduction is much faster than those observed in earlier studies, highlighting the possibility that biological methodologies will achieve rates of synthesis comparable to those of chemical methods. The approach also appears to be a cost-efficient alternative to conventional methods, so it would be suitable for developing a biological process for large scale production. Instead of the boiled leaf broth used in previous studies, sundried leaf biomass could be preserved as an excellent bio-reductant, conveniently available any time for biosynthesis of the nanoparticles.