Facile and green synthesis of silver nanoparticles using oxidized pectin

Preparation of functional and reactive nanosilver nanogels using oxidized carboxymethyl cellulose

The designing of functional and reactive nanosilver has been carried out by in-situ reduction of silver nitrate using oxidized carboxymethyl cellulose (OCMC). The reduction process is also accompanied by the stabilization of nanoparticles using the OCMC polymer chain, leading to the formation of a structure where nanosilver is entrapped within OCMC gel. The silver nanogels characterized using transmission electron microscopy (TEM) are found to be ∼22 nm. By virtue of the presence of dialdehyde functionality around the silver nanogels, they have the ability to react with a polymer having a complementary functional group. The nanogels have exhibited prominent antimicrobial activity against both gram-negative and gram-positive bacteria. It has been observed that a 0.3 mM concentration of silver nanogel is active in inhibiting bacterial growth. The antibacterial activity of the synthesized Ag nanogels was dose-dependent, with 99.9 % of E. coli and S. aureus destroyed within 5 h at a concentration of 0.4 mM Ag nanogels. The nanogels disrupted the bacterial cell wall and generated reactive oxygen species inside the cell, which resulted in cell death. This investigation provides a very interesting application as a coating for biomedical implants and devices.

Bioactive Khadi Cotton Fabric by Functional Designing and Immobilization of Nanosilver Nanogels

The antimicrobial finishing is the most suitable alternative for designing medical textiles for biomedical applications. The present investigation aims at the preparation of skin-contacting khadi cotton fabric that would prevent microbial infection and offer excellent skin compatibility. A simple approach has been followed for the preparation of bioactive nanogels for antimicrobial finishing of the khadi cotton fabric. Bioactive nanogels were synthesized by using aloe vera (AV) as a reducing agent for silver ions in the presence of polyvinyl alcohol (PVA). PVA stabilizes the growth of silver nanoparticles, which is influenced by the variation in the reaction time and the temperature. Nanogels were characterized by transmission electron microscopy and scanning electron microscopy analyses. The nanogels exhibited strong antimicrobial behavior against both Staphylococcus aureus and Escherichia coli, as confirmed by the colony count method. Almost 100% antibacterial behavior was observed for the nanosilver content of 10 mM. The nanogel-finished khadi fabric showed bactericidal properties against both S. aureus and E. coli. The nanogel-finished fabric exhibited high hydrophilicity allowing complete water droplet penetration within 10 s as compared to 136 s in virgin fabric. Moreover, the skin irritation study of the fabric on male Swiss albino mice did not show any appearance of dermal toxicity. These results demonstrated that the bioactive finished khadi fabric is appropriate as skin contacting material in human health care.

AgNPs Ornamented Modified Bacterial Cellulose Based Self-Healable L-B-L Assembly via a Schiff Base Reaction: A Potential Wound Healing Patch

A layer-by-layer (L-B-L) bacterial cellulose (BC)-based transdermal patch has been prepared via a Schiff base reaction. The L-B-L assembly consisting of covalently cross-linked ethylene diamine-modified carboxymethylated BC isolated from the Glucanoacetobacter xylinus (MTCC7795) bacterial strain and aldehyde-modified pectin formed via a Schiff base reaction. The presence of the imine bond assists the self-healing process after being scratched in the presence of a pH 7.4 buffer solution monitored via optical microscopy, atomic force microscopy, and tensile strength analyses. The formation of the L-B-L assembly was confirmed using field-emission scanning electron microscopy (FESEM) analysis. Simultaneously, water swelling and deswelling studies were carried out to test its water retention efficiency. The presence of silver nanoparticles (AgNPs) has been confirmed by ultraviolet-visible spectroscopy and FESEM analyses. The antimicrobial activity of the AgNPs-incorporated transdermal patch has been examined over Staphylococcus aureus and Escherichia coli using the zone of inhibition method. Additionally, the cell viability assay was performed using the fluorescent dyes 4',6-diamidino-2-phenylindole and propidium iodide. The AgNPs in the L-B-L assembly showed antimicrobial property against both types of bacteria. The cytotoxicity and wound healing property of the patch system have been studied over NIH 3T3 fibroblast and A549 epithelial cell lines. The L-B-L film also influenced the wound healing process of these two cell lines.

Studies of simultaneous electrochemical sensing of Hg2+ and Cd2+ ions and catalytic reduction properties of 4-nitrophenol by CuO, Au, and CuO@Au composite nanoparticles synthesised using a graft copolymer as a bio-template

Simultaneous electrochemical detection of Hg2+ and Cd2+ ions and catalytic reduction of 4NP to 4AP using a novel synthesized graft copolymer/CuO@Au NPs composite.

Synthesis of bioactive silver nanoparticles using alginate, fucoidan and laminaran from brown algae as a reducing and stabilizing agent

In this report, polysaccharides - alginate, fucoidan, laminaran - were isolated from marine algae Saccharina cichorioides and Fucus evanescens and their activity as a reducing and stabilizing agents in the biogenic synthesis of silver nanoparticles was evaluated. The cytotoxic and antibacterial properties of obtained nanoparticles were also assessed. It was found that all tested polysaccharides could be used as a reducing agent; however, their catalytic activities varied significantly in the following range alginate < fucoidan < laminaran. Nanoparticles demonstrated cytotoxicity against rat C6 glioma cells. It was considerably higher for alginate- and laminaran-obtained nanosilver samples compared to fucoidan. Additionally, silver nanoparticles possessed considerable antibacterial properties more pronounced in fucoidan-obtained samples. Our data demonstrate that different algal polysaccharides can be used for the synthesis of silver nanoparticles with varying bioactivities.

Noble Metal Nanoparticles in Pectin Matrix. Preparation, Film Formation, Property Analysis, and Application in Electrocatalysis

Stable polymeric materials with embedded nano-objects, retaining their specific properties, are indispensable for the development of nanotechnology. Here, a method to obtain Pt, Pd, Au, and Ag nanoparticles (ca. 10 nm, independent of the metal) by the reduction of their ions in pectin, in the absence of additional reducing agents, is described. Specific interactions between the pectin functional groups and nanoparticles were detected, and they depend on the metal. Bundles and protruding nanoparticles are present on the surface of nanoparticles/pectin films. These films, deposited on the electrode surface, exhibit electrochemical response, characteristic for a given metal. Their electrocatalytic activity toward the oxidation of a few exemplary organic molecules was demonstrated. In particular, a synergetic effect of simultaneously prepared Au and Pt nanoparticles in pectin films on glucose electro-oxidation was found.

Nano-biotechnology: a new approach to treat and prevent malaria

Malaria, the exterminator of ~1.5 to 2.7 million human lives yearly, is a notorious disease known throughout the world. The eradication of this disease is difficult and a challenge to scientists. Vector elimination and effective chemotherapy for the patients are key tactics to be used in the fight against malaria. However, drug resistance and environmental and social concerns are the main hurdles in this fight against malaria. Overcoming these limitations is the major challenge for the 21st-century malarial researchers. Adapting the principles of nano-biotechnology to both vector control and patient therapy is the only solution to the problem. Several compounds such as lipids, proteins, nucleic acid and metallic nanoparticles (NPs) have been successfully used for the control of this lethal malaria disease. Other useful natural reagents such as microbes and their products, carbohydrates, vitamins, plant extracts and biodegradable polymers, are also used to control this disease. Among these particles, the plant-based particles such as leaf, root, stem, latex, and seed give the best antagonistic response against malaria. In the present review, we describe certain efforts related to the control, prevention and treatment of malaria. We hope that this review will open new doors for malarial research.

Bioengineering of Functional Nanosilver Nanogels for Smart Healthcare Systems

Functional designing of nanogels has become an attractive domain of biomedical engineering to develop bioactive materials with innovative features for the human healthcare system. Nanosilver has attracted enormous attention due to its wide antimicrobial spectrum and ability to kill almost all types of bacteria in its vicinity. However, the most crucial challenge for bioscientists is the lack of binding ability of nanosilver with the material surfaces that allow nanosilver to leach out to the surrounding tissue and exert toxicity while the biomaterial is in contact with the living system. Designing nanosilver within a nanogel confinement offers enormous possibilities to develop functional bioactive nanoparticles that may be bonded to any biomaterial surface via the nanogel functionality. This approach requires the proper combination of material science with nanotechnology and biotechnology to innovate interesting domain of functional nanogels with unique features. This work aims at providing a critical review on the current progress, approaches, and vision in designing nanosilver-entrapped nanogel particles with diverse functionality, and their bioactivity against microorganisms for human healthcare devices.

Biomedical Potential of Ultrafine Ag Nanoparticles Coated on Poly (Gamma-Glutamic Acid) Hydrogel with Special Reference to Wound Healing

In wound care management, the prevention of wound infection and the retention of an appropriate level of moisture are two major challenges. Therefore, designing an excellent antibacterial hydrogel with a suitable water-adsorbing capacity is very important to improve the development of wound dressings. In this paper, a novel silver nanoparticles/poly (gamma-glutamic acid) (γ-PGA) composite dressing was prepared for biomedical applications. The promoted wound-healing ability of the hydrogels were systematically evaluated with the aim of attaining a novel and effective wound dressing. A diffusion study showed that hydrogels can continuously release antibacterial factors (Ag). Hydrogels contain a high percentage of water, providing an ideal moist environment for tissue regeneration, while also preventing contraction of the wound. Moreover, an in vivo, wound-healing model evaluation of artificial wounds in mice indicated that silver/γ-PGA hydrogels could significantly promote wound healing. Histological examination revealed that hydrogels can successfully help to reconstruct intact epidermis and collagen deposition during 14 days of impaired wound healing. Overall, this research could shed new light on the design of antibacterial silver/γ-PGA hydrogels with potential applications in wound dressing.

Nanosilver: new ageless and versatile biomedical therapeutic scaffold

Silver nanotechnology has received tremendous attention in recent years, owing to its wide range of applications in various fields and its intrinsic therapeutic properties. In this review, an attempt is made to critically evaluate the chemical, physical, and biological synthesis of silver nanoparticles (AgNPs) as well as their efficacy in the field of theranostics including microbiology and parasitology. Moreover, an outlook is also provided regarding the performance of AgNPs against different biological systems such as bacteria, fungi, viruses, and parasites (leishmanial and malarial parasites) in curing certain fatal human diseases, with a special focus on cancer. The mechanism of action of AgNPs in different biological systems still remains enigmatic. Here, due to limited available literature, we only focused on AgNPs mechanism in biological systems including human (wound healing and apoptosis), bacteria, and viruses which may open new windows for future research to ensure the versatile application of AgNPs in cosmetics, electronics, and medical fields.

Templated green synthesis of plasmonic silver nanoparticles in onion epidermal cells suitable for surface-enhanced Raman and hyper-Raman scattering

We report fast and simple green synthesis of plasmonic silver nanoparticles in the epidermal cells of onions after incubation with AgNO3 solution. The biological environment supports the generation of silver nanostructures in two ways. The plant tissue delivers reducing chemicals for the initial formation of small silver clusters and their following conversion to plasmonic particles. Additionally, the natural morphological structures of the onion layers, in particular the extracellular matrix provides a biological template for the growth of plasmonic nanostructures. This is indicated by red glowing images of extracellular spaces in dark field microscopy of onion layers a few hours after AgNO3 exposure due to the formation of silver nanoparticles. Silver nanostructures generated in the extracellular space of onion layers and within the epidermal cell walls can serve as enhancing plasmonic structures for one- and two-photon-excited spectroscopy such as surface enhanced Raman scattering (SERS) and surface enhanced hyper-Raman scattering (SEHRS). Our studies demonstrate a templated green preparation of enhancing plasmonic nanoparticles and suggest a new route to deliver silver nanoparticles as basic building blocks of plasmonic nanosensors to plants by the uptake of solutions of metal salts.

Drug loaded composite oxidized pectin and gelatin networks for accelerated wound healing

Biocomposite interactive wound dressings have been designed and fabricated using oxidized pectin (OP), gelatin and nonwoven cotton fabric. Due to their inherent virtues of antimicrobial activity and cytocompatibility, these composite structures are capable of redirecting the healing cascade and influencing cell attachment and proliferation. A novel in situ reduction process has been followed to synthesize oxidized pectin-gelatin-nanosilver (OP-Gel-NS) flower like nanohydrocolloids. This encapsulation technology controls the diffusion and permeation of nanosilver into the surrounding biological tissues. Ciprofloxacin hydrochloride has also been incorporated into the OP-Gel matrix to produce OP-Gel-Cipro dressings. While OP-Gel-NS dressings exhibited 100% antimicrobial activity at extremely low loadings of 3.75μg/cm(2), OP-Gel-Cipro dressings were highly antimicrobial at 1% drug loading. While NIH3T3 mouse fibroblasts proliferated remarkably well when cultured with OP-Gel and OP-Gel-Cipro dressings, OP-Gel-NS hindered cell growth and Bactigras(®) induced complete lysis. Full thickness excisional wounds were created on C57BL/6J mice and the wound healing potential of the OP-Gel-NS dressings led to accelerated healing within 12days, while OP-Gel-Cipro dressings healed wounds at a rate similar to that of Bactigras(®). Histological examination revealed that OP-Gel-NS and OP-Gel-Cipro treatment led to organized collagen deposition, neovascularization and nuclei migration, unlike Bactigras(®). Therefore, the OP-Gel-NS and OP-Gel-Cipro biocomposite dressings exhibiting good hydrophilicity, sustained antimicrobial nature, promote cell growth and proliferation, and lead to rapid healing, can be considered viable candidates for effective management.

Development of novel wound care systems based on nanosilver nanohydrogels of polymethacrylic acid with Aloe vera and curcumin

This study is aimed at the development of a composite material for wound dressing containing nanosilver nanohydrogels (nSnH) along with Aloe vera and curcumin that promote antimicrobial nature, wound healing and infection control. Nanosliver nanohydrogels were synthesized by nanoemulsion polymerization of methacrylic acid (MAA) followed by subsequent crosslinking and silver reduction under irradiation. Both the polymerization and irradiation time had significant influence on the nanoparticle shape, size and its formation. Polyvinyl alcohol/polyethylene oxide/carboxymethyl cellulose matrix was used as gel system to blend with nSnH, A. vera, curcumin and coat it on the hydrolysed PET fabric to develop antimicrobial dressings. The cumulative release of silver from the dressing was found to be ~42% of the total loading after 48h. The antimicrobial activity of the dressings was studied against both Staphylococcus aureus and Escherichia coli. In vivo wound healing studies were carried out over a period of 16d on full-thickness skin wounds created on Swiss albino mice. Fast healing was observed in Gel/nSnH/Aloe treated wounds with minimum scarring, as compared to other groups. The histological studies showed A. vera based dressings to be the most optimum one. These results suggest that nSnH along with A. vera based dressing material could be promising candidates for wound dressings.