Search

Simple Summary Abundance of certain proteins such as epidermal growth factor receptor (EGFR) and their growth factors on cancer cells is in part responsible for their uncontrolled growth. Compounds that selectively bind to such proteins have diagnostic and/or therapeutic implications. EGFR has four binding domains (I-IV). Most anti-EGFR therapeutic antibodies bind to domain III. Compounds that bind to other domains have implications not only for diagnosis but also for monitoring therapy response. We describe the development of a diagnostic agent to be used with positron emission tomography (PET) that binds to domain II of EGFR. We developed 89Zr-8709-scFv-Fc antibody PET agent and evaluated its binding characteristics in cancer cells and mouse models. The presence of a domain III-binding antibody such as nimotuzumab did not inhibit the binding of 89Zr-8709-scFv-Fc, and vice versa. Therefore, 89Zr-8709-scFv-Fc PET/CT can be used for diagnosis and monitoring therapy response in the presence of a domain III-binding agent. Abstract Epidermal growth factor receptor I (EGFR) is overexpressed in many cancers. The extracellular domain of EGFR has four binding epitopes (domains I- IV). All clinically approved anti-EGFR antibodies bind to domain III. Imaging agents that bind to domains other than domain III of EGFR are needed for accurate quantification of EGFR, patient selection for anti-EGFR therapeutics and monitoring of response to therapies. We recently developed a domain II-specific antibody fragment 8709. In this study, we have evaluated the in vitro and in vivo properties of 89Zr-8709-scFv-Fc (105 kDa). We conjugated 8709-scFv-Fc with the deferoxamine (DFO) chelator and radiolabeled the DFO-8970-scFv with 89Zr. We evaluated the binding of 89Zr-DFO-8709-scFv-Fc in EGFR positive and negative cell lines DLD-1, MDA-MB-231 and MDA-MB-435, respectively, and in mouse xenograft models. Simultaneously, we have compared the binding of 89Zr-8709-scFv-Fc with 111In-nimotuzumab, a domain III anti-EGFR antibody. DFO-8709-scFv-Fc displayed similar cell binding specificity as 8709-scFv-Fc. Saturation cell binding assay and immunoreactive fraction showed that radiolabeling did not alter the binding of 8709-scFv-Fc. Biodistribution and microPET showed good uptake of 89Zr-8709-scFv-Fc in xenografts after 120 h post injection (p.i). and was domain-specific to EGFR domain II. 89Zr-8709-scFv-Fc did not compete for binding in vitro and in vivo with a known domain III binder nimotuzumab. The results show that 89Zr-8709-scFv-Fc is specific to domain II of EGFR making it favorable for quantification of EGFR in vivo, hence, patient selection and monitoring of response to treatment with anti-EGFR antibodies.

In any therapeutic modality the usage of drug in high doses often leads to serious side-effects. Herein, we demonstrated a method to enhance the antibacterial efficacy of CuS NPs at lower concentration through interacting with jackfruit seed lectin, jacalin. Fluorescence quenching studies revealed that jacalin form complex with CuS NPs and the association constant was 1.91 × 104 M−1. Upon complex with jacalin, the bacterial minimum inhibitory concentration (MIC) of CuS NPs drastically decreases from 12.5 μM to 0.78 μM. The addition of jacalin specific sugar, galactose to jacalin-CuS NPs complex (JCuS NPs) reverses the MIC from 0.78 μM to 25 μM. Mechanistic study suggests that JCuS NPs kills bacteria in part by reactive oxygen species and membrane damage, but galactose prevents the action of JCuS NPs at 0.78 μM. JCuS NPs successfully reduce (14 fold) A. hydrophila colonization in an infected zerbra fish and rescue them completely from the infection, but galJCuS NPs and CuS NPs were ineffective at 0.78 μM. Collectively, our studies demonstrates that the enhance antibacterial activity of JCuS NPs is likely due to the interaction between the galactose binding site of jacalin and the bacterial strains, as a result NPs are targeted and delivered sufficiently.

Stearyl MethoxyPEGglycol Succinate (SMPS), a designer micellar medium, was reported for organic transformations in an environmentally benign water medium. Phytotoxicity, bacteria toxicity, and aquatic toxicity assays revealed that SMPS was nontoxic. Excellence in organic transformation was reported through the reduction of lipophilic nitroarenes and through the syntheses of aniline tethered indole derivatives with good to excellent yields.

Herein, we report a simple and rapid method for the visual detection of sulfide ion in an aqueous environment with high sensitivity and specificity by using ciprofloxacin capped silver nanoparticles (Cip-AgNPs). The sensor system can be used to detect as low as 16 nM of S2− in aqueous environment by only naked-eye and 0.112 nM of S2− by absorption spectrophotometer. The visual detection limit of 16 nM is much lower than the maximum allowable level of S2− (15 μM) in the drinking water defined by the world health organisation. The proposed sensor detects S2− at a wide range of pH and also demonstrated to sense S2− in tap water and river water, with good recovery. For portable use, we synthesized highly stable Cip-AgNPs on cotton and demonstrated good sensitivity against S2− ion. As prepared Cip-AgNPs embedded cotton detects S2− in an aqueous solution and S2− in a gaseous state, indicating that our sensor meets the requirement for on-site detection of S2− in the environment by only-naked eye.

Surface functionalizations of quantum dots (QDs) are expected to improve their optoelectronic properties and advance their targeting nature, which is highly warranted for application in molecular imaging and biomedical diagnostics. Therefore, an understanding the interaction between surface functionalization agents and QDs is a prerequisite for their application. Herein, we investigated the interaction between cadmium sulfide (CdS) QDs and dietary T-antigen binding lectin (jacalin) isolated from Indian jack fruit seeds. Fluorescence spectroscopy study showed that CdS QDs effectively quenched the intrinsic fluorescence of jacalin. Analysis of fluorescence quenching at a different temperature indicated that the mechanism of interaction is static and a non-radiation energy transfer occurred within the molecules. The obtained binding constant, K a value in the order of 10 4 M −1 at the tested temperature range suggested that the binding affinity between jacalin and CdS QDs is in the same range as those obtained for the interaction of lectin with carbohydrate. Thermodynamic analysis of the binding data, Δ H 0 =−44.24±1.21 kJ mol −1 , Δ S 0 =−60.92±4.10 J mol − 1 K −1 and Δ G 0 =−26.21±0.1 kJ mol −1 suggested that the binding reaction is enthalpy-driven spontaneous process. Hemagglutination activity of jacalin is well preserved even after binding to CdS QDs, indicating that the jacalin-CdS QDs complex can recognize T-antigens of the malignant tissues. To support the claim, we demonstrated selective fluorescence labeling of chronic myeloid leukemia cells, K562 with jacalin-CdS QDs complex.

Copper(ii) ion mediated C-H oxidation of dipyrromethanes (DPMs) to the corresponding dipyrrins followed by complexation invoked the selective sensing of copper(ii) ions in aqueous solutions. On the addition of copper, the colour of the DPM solution instantaneously changes from yellow to pink with the detection limit of 0.104 μM measured by absorption spectroscopy, whereas visible colour changes could be observed by the naked eye for concentrations as low as 3 μM.

In this study, a facile method to synthesize non-toxic copper sulfide nanoparticles was reported, and the antibacterial activity of the nanoparticles in infected zebrafish was evaluated. Transmission electron microscopy showed that the CuS NPs are spherical in shape with a size range from 10 to 25 nm. FTIR spectra revealed that the CuS NPs were stabilized by N-lauryltyramine. CuS NPs exhibit very good antibacterial activity against Gram-negative and Gram-positive bacteria, and the minimum inhibitory concentration was determined as 12.5 μM. In vitro mechanistic studies revealed that CuS NPs kill the bacteria by damaging their cell membranes and producing reactive oxygen species. Therapeutic activity of CuS NPs was tested in bacteria-infected zebrafish. The route of administration of CuS NPs was via an injection and medicated bath. Both routes of drug administration were suitable to cure the fish from bacterial infection. Bacterial colony count assay revealed that the CuS NPs depleted the infectious bacteria from the fish body within 24 h. Strikingly, CuS NPs in concentration eight times than the MIC did not show toxicity in the liver and brain of zebrafish. Moreover, the NPs exhibited good hemocompatibility with human red blood cells. Our study demonstrated for the first time that CuS NPs are a safe antibacterial agent, and medicated bath with zebrafish is a hassle-free model for testing the antibacterial activity of nanoparticles.

Nanoparticles are being widely used as antibacterial agents with metal nanoparticles emerging as the most efficient antibacterial agents. There have been many studies which have reported the mechanism of antibacterial activity of nanoparticles on bacteria. In this review we aim to emphasize on all the possible mechanisms which are involved in the antibacterial activity of nanoparticles and also to understand their mode of action and role as bacterial enzyme inhibitor by comparing their antibacterial mechanism to that of antibiotics with enzyme inhibition as a major mechanism. With the emergence of widespread antibiotic resistance, nanoparticles offer a better alternative to our conventional arsenal of antibiotics. Once the biological safety of these nanoparticles is addressed, these nanoparticles can be of great medical importance in our fight against bacterial infections.

Herein, we report a facile method to synthesis copper nanoparticles (CuNPs) using fatty acid amide, N -lauryltyramine (NLTA) and hydrazine as capping and reducing agent, respectively. As prepared CuNPs aqueous solution appears brown in color and shows intense surface plasmon resonance (SPR) band at 580 nm. In presence of amino acid, cysteine (Cys), the brown CuNPs solution turned to olive green with concomitant change in SPR maximum, while other amino acids show negligible change in the color and UV–vis spectra of CuNPs. The spectrophotometry detection limit of the proposed sensor is 0.10 μM, whereas naked eye limit of detection was estimated to 20 μM. FTIR studies revealed that Cys forms layer on the surface of the CuNPs, which was further supported by electrochemical studies. The proposed method has been successfully validated by detecting Cys in blood plasma and tap water samples.

Herein, we report a laboratory convenient method for the preparation of blue color emitting fluorescent carbon dots (C-dots) in 60 min by boiling the alkaline solution of pectin. The C-dots derived from pectin detects selectively silver ion by forming silver nanoparticles (AgNPs) without any irradiation or heating or additional reducing agents. As prepared AgNPs appears yellow in color and showed the characteristic surface plasmon resonance maximum at 410 nm. Transmission electron microscopy (TEM) revealed crystalline, spherical AgNPs with size range from 10–15 nm. Cyclic voltammetry study revealed that the lower reduction potential of C-dots than that of silver ion favors the reduction of Ag+ to Ag°. Electrochemical impedance spectroscopy showed the charge transfer value for the redox reaction of C-dots as 200 Ωcm2. In the presence of Ag+, C-dots fluorescence emission was turned from blue to cyan to green to colorless, accompanying the quenching and red shift in emission maximum at 450 nm. Interference study clearly showed that the C-dots have high preference for Ag+ ion than the other interfering metal ions. The proposed sensor system selectively senses Ag+ ion in water at micromolar concentration and also offers an easy procedure to prepare AgNPs in the presence of other interfering metal ions.

6-azauridine (AzU), a pyrimidine nucleoside antimetabolite, was known to inhibit the growth of microorganism and transplantable tumors. The binding affinity of AzU to blood serum proteins might influence the effectiveness of the drug. Herein, we investigated the interaction of AzU with bovine serum albumin (BSA) under near physiological conditions. Fluorescence spectroscopy analysis revealed that AzU strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and a non-radiation energy transfer occurred within the molecules. Thermodynamic parameter determined from the temperature dependent binding constant suggests that the interaction of AzU with BSA is governed by enthalpic forces with a negative entropic contribution. Displacement studies and protein/drug docking studies suggest that AzU binds non-competitively to both sub-domain IIA and sub-domain IIIA of BSA. The obtained results reveal that AzU can bind to BSA with considerable affinity even in the presence of coexisting drug and can be used along with other drugs.

Herein, we present a simple and green method for the synthesis of gold nanoparticles (AuNPs) using the phytoproteins of spinach leaves. Under ambient sunlight irradiation, the isolated phytoprotein complex from spinach leaves reduces the gold chloride aqueous solution and stabilizes the formed AuNPs. As prepared nanoparticles were characterized by UV-visible spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, zeta potential, transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDS). The surface plasmon resonance (SPR) maximum for AuNPs was observed at 520 nm. The zeta potential value estimated for the AuNPs is -27.0 mV, indicating that the NPs are well separated. Transmission electron micrographs revealed that the particles are spherical in nature with the size range from 10 to 15 nm. AuNPs act as a catalyst in the degradation of an azo dye, methyl orange in an aqueous environment. The reduction rate was determined to be pseudo-first order. Electrocatalytic efficiency of the synthesized AuNPs via this green approach was studied by chronoamperometry using ascorbic acid and hydrogen peroxide as a model compound for oxidation and reduction, respectively. Electrocatalytic studies indicate that the gold nanoparticles can be used to detect ascorbic acid and hydrogen peroxide in micromolar concentrations with response time less than 3s.

Repeated consumption of a chemotherapeutic drug in high doses often leads to drug resistance. The objective of this study was to develop a facile method to enhance the anticancer activity of the phytomolecules, acetylshikonin (AS) and beta,beta-dimethylacrylshikonin (BDS). Herein, we demonstrated that jacalin-capped silver nanoparticles (JAgNPs) loaded with AS/BDS induce maximum cytotoxicity effects on human chronic myeloid leukemia (CML), K562 at low concentration (100 nM), whereas for a similar effect about 500 nM of pure AS/BDS was required. Fluorescence microscopy data revealed the internalization of JAgNPs-AS/BDS complex into K562 cells. The intracellular localization of the drug caused the production of excess reactive oxygen species (ROS), elevation in the secretion of tumor necrosis factor (TNF-α), suppression in the production of interleukin-10 (IL-10), losses of mitochondrial membrane potential, DNA damage and apoptosis. The effective role of ROS and TNF-α in JAgNPs-AS/BDS mediated cell death was proven by pretreatment of cells with N-acetyl cysteine, a ROS scavenger, and pentoxifylline, a potent TNF-α blocker. The mode of K562 cell death was confirmed by annexin-FITC/PI staining followed by flow-cytometric analysis. Further, we disclosed the contribution of different caspase activation pathways in TNF-α mediated cell death. Taken together, our study elucidated that the judicious use of AgNPs might improve the therapeutic efficacy of AS/BDS against CML at lower doses.

Platinum nanoparticles (PtNPs) with potent antibacterial activity were synthesized using pectin and sodium borohydride as capping and reducing agents, respectively. For the first time, the in vivo antibacterial activity of PtNPs was demonstrated using adult zebrafish as the animal model. As a proof of concept, zebrafish infected with a model pathogen, Escherichia coli and a fish-specific pathogen, Aeromonas hydrophila, were subjected to treatment with PtNPs. A bacteria colony count assay revealed that the PtNPs exhibit dose-dependent inhibition of bacterial proliferation and rescued zebrafish completely from bacteria infection. The mechanism of antibacterial action includes the loss of membrane integrity and generation of reactive oxygen species. Toxicology studies reveal that the antibacterial concentration of PtNPs used in this study is non-toxic to zebrafish. Being non-toxic to zebrafish, these PtNPs might open up new avenues in antimicrobial therapy for future biomedical applications.

The surface plasmon resonance properties of copper nanoparticles (CuNPs) are rarely explored for colorimetric sensor applications. Herein, we demonstrated the CuNPs prepared with a stabilizing agent, N-lauryltyramine (NLTA) selectively induce a colorimetric response toward mercury(II) ions from wine red to gray color at micromolar concentrations. The reported sensor system can detect Hg2+ in complex water bodies, which was proven through sensing Hg2+ in sewage water and also in the presence of interfering ions. The mechanism of sensing Hg2+ was through a galvanic displacement reaction. The as prepared CuNPs exhibited antibacterial activity by releasing copper ions from CuNPs, and we were interested in exploring the ability of NLTA capped CuNPs to prevent biofilm formation. Strikingly, the anti-biofilm activity of the CuNPs was not mediated by copper ion release and the minimum biofilm inhibitory concentration (MBIC) was observed to be much lower than the minimum inhibitory concentration (MIC), which implies that NLTA–CuNPs display a true anti-biofilm effect. At 0.5×MIC, CuNPs also displayed a remarkable 128 fold reversal in EtBr MIC and a drastic 256 fold reversal in ciprofloxacin MIC, implying an efflux pump inhibitory effect in E. coli. When tested against multidrug resistant (MDR) K. pneumoniae and A. baumanii, NLTA–CuNP displayed a remarkable 16 fold reversal in ciprofloxacin MIC validating its EPI effect against MDR Gram-negative bacteria. Mechanistic studies revealed that CuNPs alter the outer membrane permeability to retain an efflux inhibitory effect while displaying a true anti-biofilm effect.

Chromium is recognized as a serious environmental pollutant because of high toxicity and carcinogenic properties. In this paper, we have developed cadmium sulfide quantum dots (CdS QDs) based fluorescence sensor for sensitive and selective detection of chromium ions. CdS QDs were synthesized by wet chemical method using pectin biopolymer as capping agent and taurine as an antioxidant. The fluorescence emission intensity of CdS QDs at 450 nm was selectively quenched by chromium ions, whereas other cations and anions showed negligible changes. The fluorescence intensity of CdS QDs is linearly proportional to the chromium concentration from 0.016 to 0.260 μM with a detection limit of 16 × 10 −9 M. The proposed sensor recognizes chromium ion at a wide range of pH from 4 to 10. In addition, CdS QDs were also used to detect chromium ions in biological fluid, sewage water, pond water and tap water samples, with low interference.

Several ruthenium complexes are regarded as anticancer agents and considered as an alternative to the widely used platinum complexes. Owing to the preferential interaction of jacalin with tumor-associated T-antigen, we report the interaction of jacalin with four ruthenium complex namely, tris(1,10-phenanthroline)ruthenium(II)chloride, bis(1,10-phenanthroline)(N-[1,10]phenanthrolin-5-yl-pyrenylmethanimine)ruthenium(II)chloride, bis(1,10-phenanthroline)(dipyrido[3,2-a:2′,3′-c]-phenazine)ruthenium(II)chloride, bis(1,10-phenanthroline)(11-(9-acridinyl)dipyrido[3,2-a:2′,3′-c]phenazine)ruthenium(II) chloride. Fluorescence spectroscopic analysis revealed that the ruthenium complexes strongly quenched the intrinsic fluorescence of jacalin through a static quenching procedure, and a non-radiative energy transfer occurred within the molecules. Association constants obtained for the interaction of different ruthenium complexes with jacalin are in the order of 105 M−1, which is in the same range as those obtained for the interaction of lectin with carbohydrate and hydrophobic ligand. Each subunit of the tetrameric jacalin binds one ruthenium complex, and the stoichiometry is found to be unaffected by the presence of the specific sugar, galactose. In addition, agglutination activity of jacalin is largely unaffected by the presence of the ruthenium complexes, indicating that the binding sites for the carbohydrate and the ruthenium complexes are different. These results suggest that the development of lectin–ruthenium complex conjugate would be feasible to target malignant cells in chemo-therapeutics.

Nanotoxicology is an important field that has started to unravel the adverse effects of nanoparticles. The major emphasis is on developing strategies to reduce the toxicity of nanomaterials. Chemical transformations of metal nanoparticles have been suggested to be an important method of mitigating nanoparticle toxicity. In the present study, we investigated the toxicity of copper and copper sulfide nanoparticles in a zebrafish model using a series of biomarkers of toxicity. The exposure of zebrafish to copper nanoparticles enhanced the oxidative stress of the liver, altered the detoxification enzymes and affected the brain acetylcholinesterase activity. However, the exposure of zebrafish to sulfidated copper nanoparticles rescued these parameters. Histopathological analyses of the liver and metallothionein levels also support the significance of sulfidation as a potential mechanism for controlling copper nanoparticle toxicity. More importantly, micronucleus formation was significantly reduced in the liver of fish exposed to sulfidated copper nanoparticles when compared to non-sulfidated nanoparticles. The presented biochemical data provides strong evidence for a reduction in the toxicity of copper nanoparticles when it undergoes chemical transformation as copper sulfide.

We explored whether copper nanoparticles (CuNPs) can function as an efflux pump inhibitor and as an anti-biofilm agent. Our results showed that at 0.5× (0.065 mM) Minimum Inhibitory Concentration (MIC), CuNPs exhibited remarkable efflux inhibitory effect in wild type strains of both Staphylococcus aureus and Pseudomonas aeruginosa and less but significant efflux inhibitory effect against MRSA and drug resistant mutant strains of Staphylococcus aureus. At 1× MIC (0.13 mM) concentration, they significantly inhibited monoculture biofilms formed by Staphylococcus aureus and Pseudomonas aeruginosa. Membrane permeability, membrane integrity and confocal imaging provided insight into the mechanism of the antibacterial effect of CuNPs. Efflux inhibition and antibacterial effect of CuNPs was partly mediated by particle effect and partly by ion effect. A novel efflux pump inhibitory role for CuNPs is reported in our study. Proof of concept experiments revealed that CuNPs could reverse the MIC of the mutant Staphylococci aureus strain for ciprofloxacin by 4 fold (from 64 μg ml−1 to 16 μg ml−1), hence our study reveals that CuNPs could be potentially employed as bacterial adjuvants to curtail Multi Drug Resistant (MDR) bacteria.

Bacterial resistance is a major clinical problem, which is compounded by both a lack of new antibiotics and emergence of multi- and extremely-drug resistant microbes. In this context, non-toxic nanoparticles could play an important role in conferring protection against bacterial infections and in this study we have made an attempt to show the usefulness of jacalin capped platinum nanoparticles in protecting zebrafish against multiple infections with Aeromonas hydrophila. Our results also indicate that use of nanoparticles promotes adaptive immune response against the pathogen, so much so that zebrafish is able to survive repetitive infection even after twenty one days of being treated with jacalin-capped platinum nanoparticles. This is significant given that platinum salt is not antibacterial and jacalin is non-immunogenic. Our study for the first time reveals a novel mechanism of action of nanoparticles, which could form an alternate antibacterial strategy with minimal bacterial resistance.

With a vision of finding greener materials to synthesize nanoparticles, we report the production and isolation of levan, a polysaccharide with repeating units of fructose, from Acetobacter xylinum NCIM2526. The isolated levan were characterized using potassium ferricyanide reducing power assay, Fourier transform infra-red (FTIR) spectroscopy and (1)H nuclear magnetic resonance spectroscopy ((1)H NMR). To exploit levan in nanotechnology, we present a simple and greener method to synthesize silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using biopolymer, levan as both reducing and stabilizing agents. The morphology and stability of the AgNPs and AuNPs were examined by transmission electron microscopy (TEM) and UV-vis absorption (UV-vis) spectroscopy. The possible capping mechanism of the nanoparticles was postulated using FTIR studies. As synthesized biogenic nanoparticles showed excellent catalytic activity as evidenced from sodium borohydride mediated reduction of 4-nitro phenol and methylene blue.

A facile method was reported for preparing silver nanoparticles (AgNPs) based on naturally occurring N -acylethanolamine (NAE) as a capping agent and sodium borohydride as a reducing agent. NAEs have been found in the infracted areas of canine myocardium and ischemic brain tissues. AgNPs prepared by N -steroylethanolamine (NSEA) are very stable and can be reliably and reproducibly synthesized. These particles have a capability to selective colorimetric sensing of the potentially hazardous Hg 2+ ion in water at micromolar concentration. The proposed method was successfully employed for the determination of Hg 2+ ion in blood plasma and also in various water bodies, such as tap water, pond water and sewage water. Further, degradation of hazardous organic pollutant, methylene blue dye, was explored using NSEA–AgNPs as catalyst. Besides selective sensing of Hg 2+ and degrading hazardous dye, NSEA–AgNPs also shows excellent catalytic activity in the reduction of nitro aromatics. In addition, NSEA–AgNPs shows bactericidal effect in Gram-positive and Gram negative test bacteria, for which the values of minimum inhibitory concentration were determined and reported. In summary, the NSEA–AgNPs reported in this work was a promising candidate for versatile application, such as a sensor, antimicrobial and catalyst.

A simple method was developed for the synthesis of copper nanoparticles (CuNPs) with relatively high concentration by using casein, hydrazine, and ascorbic acid as stabilizing, reducing and antioxidant agents, respectively. The obtained nanoparticles were characterized by UV-Vis spectroscopy, transmission electron microscopy, FTIR and X-ray diffraction. The synthesized CuNPs exhibited good antibacterial activity against Gram positive and Gram negative bacterial strains. Notably, they exhibited excellent antibacterial activity against the multi drug resistant Staphylococcus aureus ATCC 43300 strain. Additionally, the optical properties of CuNPs for the first time to our knowledge have been utilized for the selective colorimetric sensing of tryptophan amino acid and Hg2+ metal cations in aqueous solution at ppm and ppb level, respectively.

In this work, we report a completely green chemistry approach to synthesize silver nanoparticles (AgNPs) using the compound β-sitosterol-D-glucopyranoside (BS) isolated from the Indian sacred grass Desmostachya bipinnata, using natural sunlight as the initiator. BS synthesizes the AgNPs, in a free radical exchange process involving reactive oxygen species. The possible mechanism of the influence of BS on the reduction and stabilization of AgNPs is also discussed. The optical properties and morphology of the AgNPs were characterized by absorption spectroscopy and transmission electron microscopy. These bio-inspired AgNPs exhibited good catalytic activity during the catalytic degradation of environmentally hazardous organic dyes like methylene blue, methyl red, Congo red and acridine orange, in aqueous media.