Biogenic Silver Nanoparticles for Targeted Cancer Therapy and Enhancing Photodynamic Therapy.

Different conventional therapeutic procedures are utilized globally to manage cancer cases, yet the mortality rate in patients with cancer remains considerably high. Developments in the field of nanotechnology have included novel therapeutic strategies to deal with cancer. Biogenic (green) metallic silver nanoparticles (AgNPs) obtained using plant-mediated protocols are attractive to researchers exploring cancer treatment. Biogenic AgNPs present advantages, since they are cost-effective, easy to obtain, energy efficient, and less toxic compared to chemically and physically obtained AgNPs. Also, they present excellent anticancer abilities thanks to their unique sizes, shapes, and optical properties. This review provides recent advancements in exploring biogenic AgNPs as a drug or agent for cancer treatment. Thus, great attention was paid to the anticancer efficacy of biogenic AgNPs, their anticancer mechanisms, their efficacy in cancer photodynamic therapy (PDT), their efficacy in targeted cancer therapy, and their toxicity.

Design and development of porous terracotta disc: An eco-friendly novel control agent for mosquito larvae.

In the present work, we synthesized silver nanoparticles supported by rice husk by hydrothermal treatment, as-synthesized silver nanoparticles rice husk (AgNPs-RH) bio-composite mixed with potter clay thoroughly, molded, dried into a disc-shaped before firing and applying as a point of use larvicidal agent. As designed, porous terracotta disc (PTD) infused with AgNPs-RH-biocomposite were characterized by UV spectrophotometer, Fourier-transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction analysis and energy-dispersive X-ray spectroscopy. The amount of silver ions released from the PTD was also found to be within the prescribed limit of 0.1 ppm-level. Later we dropped the PTD and tested its larvicidal activity against the IVth instar larva stage of Aedes, Anopheles and Culex species. We found 100% larvicidal mortality in 24 h of exposure to the designed PTD and the amount of silver released from the porous disc was found to be 0.0343 ppm. Further from the histopathological studies of dead larvae revealed that the silver ions from the PTD have substantially damaged the exoskeleton of larvae.

Revisiting the mechanistic pathways for bacterial mediated synthesis of noble metal nanoparticles.

Synthesis and application of reliable nanoscale materials is a progressive domain and the limelight of modern nanotechnology. Conventional physicochemical approaches for the synthesis of metal nanoparticles have become obsolete owing to costly and hazardous materials. There is a need to explore alternative, cost-effective and eco-friendly strategies for fabrication of nanoparticle (NPs). Green synthesis of noble metal nanoparticles has emerged as a promising approach in the last decade. Elucidation of the molecular mechanism is highly essential in the biological synthesis of noble metal nanoparticles (NPs) for the controlled size, shape, and monodispersity. Moreover, mechanistic insights will help to scale up the facile synthesis protocols and will enable biotransformation of toxic heavy metals hence also providing the detoxification effects. Therefore, the current review article has primarily targeted the mechanisms involved in the green synthesis of metal NPs, which have been reported during the last few years. Detailed mechanistic pathways have highlighted nitrate reductase as a principle reducing agent in the bacterial mediated synthesis and stabilization of NPs. Furthermore, we have highlighted the potential implications of these mechanisms in bioremediation and biomineralization processes, which can play a critical role in biogeochemical cycling and environmental impacts of heavy metals. We anticipate that this review article will help researchers to address the challenges of bioremediation and modern nanotechnology.

A Gold Nanoparticle Bio-Optical Transponder to Dynamically Monitor Intracellular pH.

A pH-sensitive bio-optical transponder (pH-BOT) capable of simultaneously reporting the timing of intracellular DNA cargo release from a gold nanoparticle (AuNP) and the evolving intracellular pH (pH i) during endosomal maturation is demonstrated. The pH-BOT is designed with a triple-dye-labeled duplex DNA appended to a 6.6 nm AuNP, utilizing pH-responsive fluorescein paired with DyLight405 as a surface energy transfer (SET) coupled dye pair to ratiometrically report the pH at and after cargo release. A non-SET-coupled dye, DyLight 700, is used to provide dynamic tracking throughout the experiment. The pH-BOT beacon of the cargo uptake, release, and processing was visualized using live-cell confocal fluorescent microscopy in Chinese hamster ovary cells, and it was observed that while maturation of endosomes carrying pH-BOT is slowed significantly, the pH-BOT is distributed throughout the endolysosomal system while remaining at pH ∼6. This observed decoupling of endosomal maturation from acidification lends support to those models that propose that pH alone is not sufficient to explain endosomal maturation and may enable greater insight into our understanding of the fundamental processes of biology.

Low-Cost and Simple Fabrication of Nanoplasmonic Paper for Coupled Chromatography Separation and Surface Enhanced Raman Detection.

Surface-enhanced Raman scattering (SERS) is a powerful analytical tool which enables the detection and identification of analytes adsorbed on nanostructured noble metals. However, SERS analysis of complex mixtures can be challenging due to spectral overlap and interference. In this report, we demonstrate a method to simplify the identification of mixed-analyte samples by coupling SERS detection with chromatographic separation on a nanoplasmonic paper substrate. This "nanopaper" substrate is a silver coated glass microfiber filter paper which possesses large SERS enhancement and can serve as a stationary phase in paper chromatography. Nanopaper is easily synthesized using the silver mirror reaction, making it a highly accessible technology. Nanopaper was successfully used as a combined paper chromatography-SERS (PC-SERS) substrate in the separation and identification of mixed organic dyes. It was further employed to separate and identify lycopene and ß-carotene in commercial food products, demonstrating the versatility and utility of nanopaper in the identification of complex mixtures.

Eco-Friendly Synthesis of Silver Nanoparticles Through Economical Methods and Assessment of Toxicity Through Oxidative Stress Analysis in the Labeo Rohita.

The physicochemical and biological properties of metals change as the particles are reduced to nanoscale. This ability increases the application of nanoparticles in commercial and medical industry. Keeping in view this importance, Silver nanoparticles (Ag-NPs) were synthesized by reduction methods using formaldehyde as reducing agent in the chemical route and lemon extracts in the biological route. The scanning electron microscope (SEM) images of nanoparticles suggested that the particles were either agglomerated or spherical in shape with mean diameter of 16.59 nm in the chemical route and 42.93 nm in the biological route. The particles were between 5 and 80 nm with maximum frequency between 5 and 20 nm in the chemical route and between 5 and 100 nm with maximum frequency between 15 and 50 nm in the biological method. In the second phase of the study, the effect of Ag-NPs on the oxidative stress was studied. For this purpose, Labeo rohita (20 ± 2.5 g in weight and 12 ± 1.4 cm in length) were involved. Six treatments were applied in three replicates having five fishes in each replicate. The first treatment was used as control group, and the other five treatments were exposed to either 10 or 20 or 30 or 45 or 55 mg L-1 of Ag-NPs for 28 days. The treatment of Ag-NPs caused oxidative stress in the liver and gill tissues, which induced alterations in the activities of antioxidant enzymes. The level of catalase (CAT) was decreased in response to Ag-NPs concentration in dose-dependent manner. Ag-NPs treatment stimulated the liver and gill tissues to significantly increase the level of superoxide dismutase (SOD), which might be due to synthesis of SOD and addition in the pre-existing SOD level. The level decreases again due to depletion of SOD level. There was a sharp decline in the activities of glutathione S-transferase (GST) in both gills and liver tissues even at lower concentration, and this decrease in the GST activity was significantly different at each treatment after 28 days of treatment except 20 mg L-1. The malondialdehyde (MDA) levels of gills and liver tissues were increased with the increase in the concentration. The elevated levels of glutathione (GSH) showed that the liver started defensive mechanism against the oxyradicals. This study finds out the cheap eco-friendly and economical method of Ag-NP synthesis. It is further revealed that Ag-NPs caused oxidative stress in the aquatic animals if exposure occurs at high concentrations.

Homogeneous large-scale crystalline nanoparticle-covered substrate with high SERS performance.

This article details the surface-enhanced Raman scattering (SERS) performance of plasmonic substrates fabricated by a physical metal evaporation technique that uses no precursor or intermediate coating. We outline a cost-effective nanofabrication protocol that uses common laboratory equipment to produce homogeneously covered crystalline nanoparticle substrates. Our fabrication yields a homogeneous SERS response over the whole surface. The platform is tested with methylene blue diluted at various concentrations to estimate the sensitivity, homogeneity, and reproducibility of the process. The capacity of the substrates is also confirmed with spectroscopic investigations of human microsomal cytochrome b5.

Biomediated synthesis of silver nanoparticles using Exiguobacterium mexicanum.

Biomediated silver nanoparticle were synthesized using a cell free extract of a soil bacterium, Exiguobacterium mexicanum PR 10.6. The silver nanoparticles were characterised using UV-Vis spectroscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. The nanoparticles ranged from 5 to 40 nm. Extracellular polymeric substance played a critical role in the reduction of silver ion and nanoparticle stabilisation when using the cell free extract. The synthesis using E. mexicanum is an effective eco-friendly, rapid method for silver nanoparticle synthesis within 1 h.

Visual chiral recognition of tryptophan enantiomers using unmodified gold nanoparticles as colorimetric probes.

A simple protocol to distinguish enantiomers is extremely intriguing and useful. In this study, we propose a low-cost, facile, sensitive method for visual chiral recognition of enantimers. It is based on the inherent chirality of gold nanoparticles (AuNPs), and the unmodified AuNPs are used as chiral selector for D- and L-Tryptophan (Trp). In the presence of D-Trp, an appreciable red-to-blue color change of AuNPs solution can be observed, whereas no color change is found in the presence of L-Trp. The method can be used to detect D-Trp in the range of 0.2-10 µM, and the limit of detection is 0.1 µM. The chiral assay described in this work is easily readout with the naked eye or using a UV-vis spectrometer. Furthermore, the AuNPs can selectively adsorb D-Trp, and simple centrifugation can allow the precipitation of D-Trp with AuNPs and leave a net excess of the other enantiomer in solution, thus resulting in enantioseparation. In this method, AuNPs do not need any labeling or modifying with chiral molecules. The method is more attractive because of its high sensitivity, low cost, ready availability and simple manipulation.

Aquacel(®) Ag dressing versus Acticoat™ dressing in partial thickness burns: a prospective, randomized, controlled study in 100 patients. Part 1: burn wound healing.

INTRODUCTION: Studies comparing contemporary silver dressings in burns are scarce. METHODS: In a prospective, randomized, controlled study, counting 50 patients/research group, we compared two frequently used silver dressings, Acticoat™ and Aquacel(®) Ag, in the management of partial thickness burns with a predicted healing time between 7 and 21 days as assessed by laser Doppler imaging between 48 and 72h after burn. Variables investigated were related to baseline research group characteristics, wound healing, bacteriology, economics, nurse, and patient experience. RESULTS: Both research groups were comparably composed taking into account gender, age and burn characteristics. Similar results were obtained as to healing time and bacterial control with both silver dressings. A statistically significant difference in favor of the Aquacel(®) Ag dressing was found for average ease of use (p<0.001), average ease of application (p=0.001), patient pain (p<0.001), patient comfort with the dressing (p=0.017), silver staining (p<0.001), and cost effectiveness (p<0.001). CONCLUSION: Both silver dressings resulted in comparable healing times and bacterial control but the Aquacel(®) Ag dressing significantly increased comfort for patients as well as nurses and was significantly more cost-effective than the Acticoat™ dressing for the given indication.

Intact cell/intact spore mass spectrometry (IC/ISMS) on polymer-based, nano-coated disposable targets.

Identification and differentiation of microorganisms has and still is a long arduous task, involving culturing of the organism in question on different growth media. This procedure, which is still commonly applied, is an established method, but takes a lot of time, up to several days or even longer. It has thus been a great achievement when other analytical tools like matrix-assisted laser desorption/ionization (MALDI) mass spectrometry were introduced for faster analysis based on the surface protein pattern. Differentiation and identification of human pathogens as well as plant/animal pathogens is of increasing importance in medical care (e.g. infection, sepsis, and antibiotics resistance), biotechnology, food sciences and detection of biological warfare agents. A distinction between microorganisms on the species and strain level was made by comparing peptide/protein profiles to patterns already stored in databases. These profiles and patterns were obtained from the surface of vegetative forms of microorganisms or even their spores by MALDI MS. Thus, an unknown sample can be compared against a database of known pathogens or microorganisms of interest. To benefit from newly available, metal-based disposable microscope-slide format MALDI targets that promise a clean and even surface at a fraction of the cost from full metal targets or MTP (microtiter plate) format targets, IC/ISMS analysis was performed on these and the data evaluated. Various types of bacteria as well as fungal spores were identified unambiguously on this disposable new type of metal nano-coated targets. The method even allowed differentiation between strains of the same species. The results were compared with those gained from using full metal standard targets and found to be equal or even better in several aspects, making the use of disposable MALDI targets a viable option for use in IC/ISMS, especially e.g. for large sample throughput and highly pathogenic species.

Convenient detection of E. coli in Ringer's solution.

An easy and inexpensive detection method for DNA hybridization assays combining magnetic beads and enzymatically generated silver nanoparticles is introduced. The main advantage of this approach is the possibility to distinguish between positive and negative test results with the naked eye. In the case of complementary DNA sequences the sample will turn black within a few minutes, allowing readout without any hardware. In order to illustrate the applicability of the assay genomic DNA isolated from E. coli contaminated Ringer's solution was used for testing the sensitivity as well as specificity.

Design of an anti-aggregated SERS sensing platform for metal ion detection based on bovine serum albumin-mediated metal nanoparticles.

Based on bovine serum albumin (BSA)-modified Au NPs, a simple and cost-effective approach was proposed to fabricate an anti-aggregated Au NP sensing platform for the detection of metal ions. It exhibits excellent stability even under highly ionic conditions due to its electrostatic stabilization, as well as the steric stabilization.

A comparative study of economical separation and aggregation properties of biologically capped and thiol functionalized gold nanoparticles: selecting the eco-friendly trojan horses for biological applications.

We are presenting facile bio-fabrication of extremely stable gold nanoparticles (GNPs) using medicinal plant Azadirachta indica (commonly called Neem) and its comparison with most commonly used glutathione (GSH) protected GNPs in terms of stability under physiological conditions, seperation using density gradient centrifugation and aggregation properties in the solution. There was dual peak at 536 and 662 nm indicating the presence of non-spherical GNPs including triangles, rods and hexagons in case of A. indica mediated GNPs unlike citrate stabilized GNPs which exhibited single sharp peak. Spherical GNPs were separated from the consortium of uniquely shaped nanoparticles bio-fabricated using A. indica leaf extract using sucrose density gradient centrifugation (SDGC).To comprehend the anti-agglomeration potentials of A. indica leaf mediated GNPs and GSH-GNPs under physiological conditions, flocculation parameters (FP) were calculated and found to be least for A. indica leaf mediated GNPs, indicating their exceptional stability.

A facile and cost-effective TEM grid approach to design gold nano-structured substrates for high throughput plasmonic sensitive detection of biomolecules.

A commercial TEM grid was used as a mask for the creation of extremely well-organized gold micro-/nano-structures on a glass substrate via a high temperature annealing process at 500 °C. The structured substrate was (bio)functionalized and used for the high throughput LSPR immunosensing of different concentrations of a model protein named bovine serum albumin.

Estimating production data for five engineered nanomaterials as a basis for exposure assessment.

The magnitude of engineered nanomaterials (ENMs) being produced and potentially released to the environment is a crucial and thus far unknown input to exposure assessment. This work estimates upper and lower bound annual United States production quantities for 5 classes of ENMs. A variety of sources were culled to identify companies producing source ENM products and determine production volumes. Using refining assumptions to attribute production levels from companies with more reliable estimates to companies with little to no data, ranges of U.S. production quantities were projected for each of the 5 ENMs. The quality of data is also analyzed; the percentage of companies for which data were available (via Web sites, patents, or direct communication) or unavailable (and thus extrapolated from other companies' data) is presented.

Appreciating the role of thermodynamics in LCA improvement analysis via an application to titanium dioxide nanoparticles.

Although many regard it as the most important step of life cycle assessment, improvement analysis is given relatively little attention in the literature. Most available improvement approaches are highly subjective, and traditional LCA methods often do not account for resources other than fossil fuels. In this work exergy is evaluated as a thermodynamically rigorous way of identifying process improvement opportunities. As a case study, a novel process for producing titanium dioxide nanoparticles is considered. A traditional impact assessment, a first law energy analysis, and an exergy analysis are done at both the process and life cycle scales. The results indicate that exergy analysis provides insights not available via other methods, especially for identifying unit operations with the greatest potential for improvement. Exergetic resource accounting at the life cycle scale shows that other materials are at least as significant as fossil fuels for the production of TiO2 nanoparticles in this process.

In vivo observation of gold nanoparticles in the central nervous system of Blaberus discoidalis.

BACKGROUND: Nanoparticles (NPs) are widely studied for biomedical applications. Understanding interactions between NPs and biomolecules or cells has yet to be achieved. Here we present a novel in vivo method to study interactions between NPs and the nervous system of the discoid or false dead-head roach, Blaberus discoidalis. The aims of this study were to present a new and effective method to observe NPs in vivo that opens the door to new methods of study to observe the interactions between NPs and biological systems and to present an inexpensive and easy-to-handle biological system. RESULTS: Negatively charged gold nanoparticles (nAuNPs) of 50 nm in diameter were injected into the central nervous system (CNS) of the insect. By using such a cost effective method, we were able to characterize nAuNPs and to analyze their interactions with a biological system. It showed that the charged particles affected the insect's locomotion. The nAuNPs affected the insect's behavior but had no major impacts on the life expectancy of the cockroach after two months of observation. This was apparently due to the encapsulation of nAuNPs inside the insect's brain. Based on cockroach's daily activity, we believed that the encapsulation occurred in the first 17 days. CONCLUSIONS: The method proposed here is an inexpensive and reliable way of observing the response of biological systems to nanoparticles in-vivo. It opens new windows to further understand how nanoparticles affect neural communication by monitoring insect activity and locomotion.

Sunlight-driving formation and characterization of size-controlled gold nanoparticles.

Exposing a sodium citrate-HAuCl4 aqueous solution to sunlight results in the formation of size-controlled, citrate-capped gold nanoparticles. The gold nanoparticles were characterized by UV-visible, transmission electron microscopy (TEM), scanning electron microcopy (SEM), and X-ray diffraction (XRD) spectroscopic methods. It provides a general methodology for the economic, convenient, mild preparation of citrate-capped noble metal nanoparticles.