‘Green’ approach for obtaining stable pectin-capped silver nanoparticles: Physico-chemical characterization and antibacterial activity

New insights into chitosan-Ag nanocomposites synthesis: Physicochemical aspects of formation, structure-bioactivity relationship and mechanism of antioxidant activity

Herein, a novel approach to the controlled formation of chitosan-Ag nanocomposites (NCs) with different structures and tunable chemical/biological properties was proposed. The chitosan-Ag NCs were obtained using hydrothermal synthesis and varying the concentrations of components. The hypothesis of chitosan-Ag NC synthesis using polysaccharide coils as a "microreactor" system was confirmed. A comparative analysis of the physicochemical characteristics of the NCs with single-core-shell and multi-core-shell structures was carried out, and the "structure-property" relationship was revealed. The obtained NCs exhibited excellent antiradical properties, comparable to the activity of phenolic acids: the IC50 values were 0.051, 0.022, and 0.019 mg/mL for CS7, CS5, and caffeic acid, respectively. A mechanism for the antiradical activity of chitosan-Ag NCs was discussed. The redox activity of the NCs was found to be 11.4 and 2.3 mg ABTS per 1 mg of Ag in CS5 and CS7, respectively. The proposed environmentally friendly one-pot, one-step synthesis of silver nanoparticles inside chitosan "microreactors" represents an innovative approach to designing hybrid materials with nanoscale control of desired structure and properties. These findings pave the way for further optimization of biopolymer‑silver nanostructures for various biomedical and industrial applications, including the design of a new type of hybrid catalysts such as nanozymes.

A review on pectin-based nanostructures for drug and gene delivery systems

Pectin, a widely available and cost-effective polysaccharide, has garnered considerable attention in biomedical applications, particularly as a matrix for drug and gene delivery systems. Pectin possesses prominent properties such as biocompatibility, biodegradability, and low toxicity, which are desired features for delivery systems. Various pectin-based nanostructures have been applied to encapsulate therapeutic agents, drugs, and genetic materials with the potential of protecting them until selectively transfer to the objective tissue and sustainably release in controlled conditions. Pectin-based nanostructures have been widely used in oral drug delivery systems because of pectin's stability in the gastric and small intestine biological media. Moreover, pectin-based nanostructures have a high potential usage in liver cancer treatment due to the selective targeting of galactose groups of pectin to liver cancer cells' receptors. Despite applying pectin-coated nanocomposites as non-viral vectors of gene delivery, more clinical trials are required to develop such potential carriers in gene therapy. Pectin has unique biological features such as anticancer, antimicrobial, antioxidant, antidiabetic, and anti-cholesterol properties that synergistically enhance the efficiency of the drug/gene delivery system. This review presents an exhaustive investigation of the recent research on pectin-based nanostructures applied in drug/gene delivery systems and other biomedical applications, its advantages, challenges, and future perspectives.

Physicochemical characterization and antibacterial activities of silver nanoparticles prepared by amidated low-methoxyl pectin

Pectin-based silver nanoparticles (AgNPs) have been used in the field of antibacterials for food due to their excellent antibacterial properties. Herein, in order to achieve higher antibacterial performance, AgNPs were synthesized using high-methoxyl pectin (HMP) and amidated low-methoxyl pectin (ALMP) as precursors. Initially, ALMP-1, -2, and -4 were obtained by pectin amidation with increasing concentrations of NH4OH. Later, HMP and ALMPs were used to prepare AgNPs, and their physicochemical property and antibacterial activities were studied. Transmission electron microscopy (TEM) showed that the mean diameters of HMP-Ag and ALMP-4-Ag were 11.9 ± 3.8 and 13.0 ± 5.4 nm, respectively. EDS analysis revealed that ALMP-4-Ag combined with more Ag element than HMP-Ag. X-ray photoelectron spectroscopy (XPS) indicated that ALMP-4-Ag led to a lower ratio of Ag0 to Ag+ on the surface of AgNPs. Interestingly, ALMP-4-Ag had the strongest antimicrobial effect against Escherichia coli and Staphylococcus aureus, with the lowest inhibitory concentrations (MICs) of up to 33 μg mL-1, which was 16-fold enhanced compared with HMP-Ag (MICs = 533 μg mL-1). Finally, ALMP-4-Ag-treated cells revealed higher levels of protein and sugar leakage as well as increased levels of reactive oxygen species (ROS) and malondialdehyde (MDA) than HMP-Ag.

Green synthesis of pectin-functionalized silver nanocomposites using Carpesium nepalense and evaluation its bactericidal kinetics and hepatoprotective mechanisms

The present study reports the green synthesis of pectin-fabricated silver nanocomposites (Pectin-AgNPs) using Carpesium nepalense leaves extract, evaluating their bactericidal kinetics, in vivo hepatoprotective, and cytotoxic potentials along with possible mechanisms. GC/MS and LC/MS analyses revealed novel phytochemicals in the plant extract. The Pectin-AgNPs were characterized using UV/Vis, AFM, SEM, TEM, DLS, FTIR, and EDX techniques, showing a spherical morphology with a uniform size range of 50-110 nm. Significant antibacterial activity (P < 0.005) was found against four bacterial strains with ZIs of 4.1 ± 0.15 to 27.2 ± 3.84 mm. AFM studies revealed significant bacterial cell membrane damage post-treatment. At 0.05 mg/kg, the nanocomposites showed significant (P < 0.005) hepatoprotective activity in biochemical and histopathology analyses compared to the CCl4 control group. Pectin-AgNPs significantly reduced (P < 0.005) LDH, AST, ALT, ALP, and DB levels. qPCR analysis showed ameliorative effects on PPARs and Nrf2 gene expression, restoring gene alterations caused by CCl4 intoxication. In vivo acute toxicity studies confirmed low toxicity of Pectin-AgNPs in major organs. Pectin-AgNPs exhibited cytotoxic activity against HeLa cell lines at higher doses with an LC50 of 223.7 μg/mL. These findings demonstrate the potential of Pectin-AgNPs as promising antibacterial, hepatoprotective, and cytotoxic agents.

Silver nanoparticles incorporated dental restorative resin and its antibiofilm effect

Dental restoration materials are susceptible to bacterial biofilm formation, which damages the restorations and causes oral health problems. Therefore, to overcome this, silver nanoparticles (AgNPs) are studied widely due to their antimicrobial, anti-inflammatory and healing properties. The purpose of this study was to develop a strategy for incorporating AgNPs onto the surface of bisacrylic resin (Bis) to evaluate its antibiofilm effects using Streptococcus sanguinis and Actinomyces naeslundii. AgNPs with an average size of 25 nm at two different concentrations were dispersed on the Bis surface (Bis-AgNPs) by mechanical deposition. Ag release was quantified until 7 days of incubation. Bacterial growth was assessed using a viability assay kit and observed using confocal microscopy. The biofilm biomass was quantified using arbitrary fluorescence units. Cell viability was evaluated using an MTT assay. The results showed that Bis-AgNPs significantly inhibited biofilm formation along with a significant difference in the viability of human gingival fibroblasts. The quantification confirmed a decrease in Ag release over time, and elemental mapping showed AgNP penetration up to 10 µm from the surface. Therefore, it was concluded that Bis-AgNPs presented enhanced antibiofilm properties, even at a concentration with no adverse effects. Therefore, this nanocomposite may be a promising alternative for biofilm control in temporary restorative materials.

Preparation and characterization of pectin/hydroxyethyl cellulose/clay/TiO2 bionanocomposite films for microbial pathogen removal from contaminated water

Some of conventional wastewater disinfectants can have a harmful influence on the environment as well as human health. The aim of this investigation was synthesis and characterizes ecofriendly pectin/hydroxyethyl cellulose (HEC)/clay and pectin/HEC/clay incorporated with titanium dioxide nanoparticles (TiO2NPs) and use the prepared bionanocomposite as microbial disinfectants for real wastewater. Pectin/HEC/clay and pectin/HEC/clay/TiO2 bionanocomposite were characterized by various methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA). Mechanical properties and water vapor permeability (WVP) were carried out. The results of SEM showed that, the prepared bionanocomposite had a smooth surface. Additionally, TiO2 nanoparticles to the pectin/HEC/clay composites may lead to changes in the FTIR spectrum. The intensity of XRD peaks indicated that, TiO2NPs was small size crystallite. TGA illustrated that pectin has moderate thermal stability, while HEC generally exhibits good thermal stability. The TEM showed that, TiO2 nanoparticles have diameters <25 nm. On the other hand, antimicrobial activities of pectin/HEC/clay against Escherichia coli (E. coli), Staphylococcus aureus and Candida albicans have been enhanced by adding TiO2NPs. The minimum inhibitory concentration (MIC) of pectin/HEC/clay/TiO2 against E. coli was 200 mg/mL. Moreover, complete eradication of E. coli, Salmonella and Candida spp. from real wastewater was observed by using pectin/HEC/clay/TiO2 bionanocomposite. Finally, it can be concluded that, the synthesized bionanocomposite is environmentally friendly and considered an excellent disinfectant matter for removal of the microbial pathogens from wastewater to safely reuse.

Innovative biopolyelectrolytes-based technologies for wastewater treatment

Developing eco-friendly, cost-effective, and efficient methods for treating water pollutants has become paramount in recent years. Biopolyelectrolytes (BPEs), comprising natural polymers like chitosan, alginate, and cellulose, have emerged as versatile tools in this pursuit. This review offers a comprehensive exploration of the diverse roles of BPEs in combating water contamination, spanning coagulation-flocculation, adsorption, and filtration membrane techniques. With ionizable functional groups, BPEs exhibit promise in removing heavy metals, dyes, and various pollutants. Studies showcase the efficacy of chitosan, alginate, and pectin in achieving notable removal rates. BPEs efficiently adsorb heavy metal ions, dyes, and pesticides, leveraging robust adsorption capacity and exceptional mechanical properties. Furthermore, BPEs play a pivotal role in filtration membrane techniques, offering efficient separation systems with high removal rates and low energy consumption. Despite challenges related to production costs and property variability, their environmentally friendly, biodegradable, renewable, and recyclable nature positions BPEs as compelling candidates for sustainable water treatment technologies. This review delves deeper into BPEs' modification and integration with other materials; these natural polymers hold substantial promise in revolutionizing the landscape of water treatment technologies, offering eco-conscious solutions to address the pressing global issue of water pollution.

Enhancing antimicrobial activity and reducing cytotoxicity of silver nanoparticles through gelatin nanoparticles

Aim: To develop a novel stabilizing agent for silver nanoparticles (AgNPs) with the aim of enhancing its antibacterial efficacy against wound associated pathogens while mitigating their cytotoxic effect on human cells. Materials & methods: In this study, monodispersed gelatin nanoparticles were synthesized to stabilize AgNPs. The stability, antibacterial activity and biocompatibility of the gelatin-stabilized AgNPs (Gel-AgNPs) were compared with citrate-stabilized AgNPs (citrate-AgNPs) or silver ions. Results & conclusion: Gelatin-stabilized AgNPs showed significantly better antibacterial activities compared with citrate-stabilized AgNPs against both Gram-positive and Gram-negative bacteria. These Gel-AgNPs showed significantly lower cytotoxicity to human dermal fibroblasts compared with Ag+. These findings provided the first evidence substantiating a novel functionality of gelatin nanoparticles in both stabilizing and enhancing the activity of AgNPs.

Alginate coated biogenic silver nanoparticles for the treatment of Pseudomonas infections in rainbow trout

Pseudomonas species are among the main pathogens causing rainbow trout infections. The present study provides a simple, green, sustainable, and rapid technique to synthesize of biogenic alginate-capped silver nanoparticles (Alg-Ag NPs) suitable for the treatment of Pseudomonas infections. It has been shown that the mechanism (aggregative or autocatalytic) of Alg-Ag NPs formation depended on Alg concentration and the heating approach used. The rate constants and activation energy were calculated. Alg-Ag NPs were characterized by UV-Vis, FTIR, XRD, TEM, AFM, XPS, and DLS. The optimal conditions for the fabrication of spherically-shaped (17-19 nm) and negatively-charged (zeta-potential <-50 mV) Alg-Ag NPs, which are stable during 9 months, included hot-plate assisted synthesis at 100 °C in diluted (1 mg/mL) Alg solutions. In vitro studies showed that Alg-Ag NPs exhibited prominent antimicrobial activity against collection Pseudomonas strains (inhibition zones ranged from 9.0 ± 1.0 to 19.0 ± 1.0 mm), with no significant loss of antibacterial efficacy after 9 months of storage. AFM analysis confirmed that the antibacterial effect of Alg-Ag NPs dealt with the direct nanomechanical disrupting of bacterial cells. The ability of Alg-Ag NPs to inhibit the growth of virulent P.aeruginosa, P.fluorescens and P. putida strains isolated from infected rainbow trout was evaluated. All tested strains were susceptible to Alg(10)-Ag NPs, while Alg(1)-Ag NPs demonstrated a limited strain-specific antibacterial effect. The obtained data displayed the prospects for the application of biogenic Alg-Ag NPs to create novel delivery systems for combating Pseudomonas infections in rainbow trout.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

Effect of Size, Shape and Surface Functionalization on the Antibacterial Activity of Silver Nanoparticles

Silver nanoparticles (AgNPs) are the most investigated antibacterial agents against multidrug resistant (MDR) pathogens. They can lead to cellular death by means of different mechanisms, damaging several cell compartments, from the external membrane, to enzymes, DNA and proteins; this simultaneous attack amplifies the toxic effect on bacteria with respect to traditional antibiotics. The effectiveness of AgNPs against MDR bacteria is strongly correlated with their chemical and morphological properties, which influence the pathways involved in cellular damage. In this review, AgNPs' size, shape and modification by functional groups or other materials are reported, both to investigate the different synthetic pathways correlated with nanoparticles' modifications and to evaluate the related effect on their antibacterial activity. Indeed, understanding the synthetic conditions for obtaining performing antibacterial AgNPs could help to tailor new and improved silver-based agents to combat multidrug resistance.

Phyto-Assisted Synthesis of Nanoselenium-Surface Modification and Stabilization by Polyphenols and Pectins Derived from Agricultural Wastes

Raw and purified mandarin peel-derived pectins were characterized and combined with olive pomace extract (OPE) in the green synthesis of selenium nanoparticles (SeNPs). SeNPs were characterized in terms of size distribution and zeta potential, and their stability was monitored during 30 days of storage. HepG2 and Caco-2 cell models were used for the assessment of biocompatibility, while antioxidant activity was investigated by the combination of chemical and cellular-based assays. SeNP average diameters ranged from 171.3 nm up to 216.9 nm; smaller SeNPs were obtained by the utilization of purified pectins, and functionalization with OPE slightly increased the average. At concentrations of 15 mg/L SeNPs were found to be biocompatible, and their toxicity was significantly lower in comparison to inorganic selenium forms. Functionalization of SeNPs with OPE increased their antioxidant activity in chemical models. The effect was not clear in cell-based models, even though all investigated SeNPs improved cell viability and protected intracellular reduced GSH under induced oxidative stress conditions in both investigated cell lines. Exposure of cell lines to SeNPs did not prevent ROS formation after exposure to prooxidant, probably due to low transepithelial permeability. Future studies should focus on further improving the bioavailability/permeability of SeNPs and enhancing the utilization of easily available secondary raw materials in the process of phyto-mediated SeNP synthesis.

Antibacterial Nanomaterials: Mechanisms, Impacts on Antimicrobial Resistance and Design Principles

Antimicrobial resistance (AMR) is one of the biggest threats to the environment and health. AMR rapidly invalidates conventional antibiotics, and antimicrobial nanomaterials have been increasingly explored as alternatives. Interestingly, several antimicrobial nanomaterials show AMR-independent antimicrobial effects without detectable new resistance and have therefore been suggested to prevent AMR evolution. In contrast, some are found to trigger the evolution of AMR. Given these seemingly conflicting findings, a timely discussion of the two faces of antimicrobial nanomaterials is urgently needed. This review systematically compares the killing mechanisms and structure-activity relationships of antibiotics and antimicrobial nanomaterials. We then focus on nano-microbe interactions to elucidate the impacts of molecular initiating events on AMR evolution. Finally, we provide an outlook on future antimicrobial nanomaterials and propose design principles for the prevention of AMR evolution.

Green synthesis of multifunctional MgO@AgO/Ag2O nanocomposite for photocatalytic degradation of methylene blue and toluidine blue

Introduction: In this paper, MgO@AgO/Ag₂O nanoparticles were greenly synthesized, the current idea is to replace the harmful chemical technique with an ecofriendly synthesis of metal oxide nanoparticles (NPs) utilizing biogenic sources. Methods: The current investigation was conducted to create silver oxide NPs decorated by MgO NPs (namely, MgO@AgO/Ag₂O nanocom-posite) using the leaves extract of Purslane (Portulaca Oleracea) as the reducing and capping agent. The nanopowder was investigated by means of X-ray diffraction, scanning electron mi-croscope, BET surface area, Fourier transform infrared, and UV-vis spectrophotom-eter studies. XRD studies reveal the monophasic nature of these highly crystalline silver nano-particles. SEM studies the shape and morphology of the synthesis AgO/Ag₂O and MgO@AgO/Ag₂O NPs. The presence of magnesium and oxygen was further confirmed by EDS profile. Results and discussion: The surface area was found to be 9.1787 m²/g and 7.7166 m²/g, respectively. FTIR analysis showed the presence of specific functional groups. UV-vis spectrophotometer studies show the absorption band at 450 nm due to surface plasmon resonance. The results have also indicated the high performance of the greenly synthesized AgO/Ag₂O NPs and MgO@AgO/Ag₂O NPs for photocatalytic activity dye degradation (methylene blue and toluidine blue).

Self-induced transformation of raw cotton to a nanostructured primary cell wall for a renewable antimicrobial surface

Herein, raw cotton is shown to undergo self-induced transformation into a nanostructured primary cell wall. This process generates a metal nanoparticle-mediated antimicrobial surface that is regenerable through multiple washings. Raw cotton, without being scoured and bleached, contains noncellulosic constituents including pectin, sugars, and hemicellulose in its primary cell wall. These noncellulosic components provide definitive active binding sites for the in situ synthesis of silver nanoparticles (Ag NPs). Facile heating in an aqueous solution of AgNO3 activated raw cotton to produce Ag NPs (ca. 28 nm in diameter and 2261 mg kg-1 in concentration). Compared with scoured and bleached cotton, raw cotton requires lower concentrations of AgNO3-ten times lower for Klebsiella pneumonia and two times lower for Staphylococcus aureus-to achieve 99.9% reductions of both Gram-positive and Gram-negative bacteria. The Ag NPs embedded in the primary cell wall, which was confirmed via transmission electron microscopy images of the fiber cross-sections, are immobilized, exhibiting resistance to leaching as judged by continuous laundering. A remarkable percentage (74%) of the total Ag NPs remained in the raw cotton after 50 laundering cycles.

Effect of the physicochemical changes in the antimicrobial durability of green synthesized silver nanoparticles during their long-term storage

It is generally recognized that the stability of nanoparticles (NPs) has a great impact on their potential biological applications. Despite this, very few studies have investigated the change in toxicity of NPs over time but none has studied the periodic physicochemical changes contributing to it. To address this, we analyzed the effects of long-term storage on the physicochemical changes of green synthesized silver nanoparticles (AgNPs) that directly influences their antimicrobial durability. Light-induced slow synthesis of AgNPs was carried out using Saraca asoca aqueous leaf extract. The synthesis was optimized with respect to parameters known to play a major role in the long-term stability of AgNPs: pH, temperature, light exposure time, AgNO₃ concentration, extract proportion in the reaction mixture and storage conditions. Freshly synthesized AgNPs were characterized and then stored under optimized conditions. UV-vis spectrophotometry, AAS, conventional TEM and HR-TEM along with EDX spectroscopy were used at regular intervals to test the physicochemical properties that influence their long-term stability. Broth dilution assay was used to test antimicrobial activity of AgNPs against Escherichia coli and Staphylococcus aureus. Under dark storage conditions at room temperature, the AgNPs exhibited excellent stability with very good dispersity, throughout the study period of 18 months, despite the particles undergoing physicochemical changes in largescale. AgNPs exhibited sufficient antimicrobial activity against both strains tested. Due to the stronger stabilizing effect of the extract, we observed the lowest inhibition of E. coli and S. aureus by the freshly synthesized and 15 day old AgNPs; however, the inhibition rate escalated after a month and the highest rate of inhibition was observed with the particles between 2 months to 6 months of storage. After 6 months, we observed the particles losing their antimicrobial potential gradually, that lasted throughout the rest of our study period. This observation was in accord with the physicochemical changes that AgNPs were undergoing with time. By deepening our understanding of the changes in the physicochemical properties of green synthesized AgNPs over time, this study contributes to the development of more effective, durable, and potent AgNPs.

Enhancing the anti-ageing, antimicrobial activity and mechanical properties of surface-coated paper by Ag@TiO2-modified nanopigments

In this work, the effect of using Ag-doped TiO2 nanopigments on optical, mechanical and antimicrobial properties of coated paper was explored. Furthermore, the long-term antimicrobial activity of the coated paper was examined for up to 25 years. Titanium dioxide (TiO2) nanoparticles have been synthesized and doped with different percentages of Ag nanoparticles (Ag NPs) using a simple wet chemical approach. The Ag@TiO2 modified nanopigments were in the form of nanorods with an average size of about 20 nm as observed from TEM images. Increasing Ag content from 0.01 to 1.0% showed an increase in the mechanical properties of coated paper in terms of tensile, stretching, tensile energy absorption and burst while preserving the optical properties. Moreover, the antimicrobial inhibition activity increased with increasing the Ag content. The 1% Ag@TiO2 showed a long-lasting antimicrobial effect against Staphylococcus aureus (S. aureus) Gram-positive bacteria even after 25 years of ageing (93.4% inhibition). Investigation of reactive oxygen species (ROS) generation and reaction mechanism of antimicrobial activity over Ag/TiO2 under visible light is proposed. These results suggest that Ag/TiO2 NPs can be potentially used as a disinfection coating for paper and improving its mechanical properties.

Designing novel MgFe2O4 coupled V2O5 nanorod for synergetic photodegradation of tetracycline with enhanced visible-light energy harvesting: Photoluminescence, kinetics, intrinsic mechanism and bactericidal effect

The present study focused on the enhancement of degradation of an important pharmaceutical pollutant, tetracycline with the help of nano photocatalyst under visible light irradiation. The study found that the synergetic effect of novel MgFe₂O₄-V₂O₅ enhanced the photocatalytic degradation of tetracycline. Here, the photocatalyst was synthesized by sonochemical technique. Scanning electron microscopy image indicates the coupling of MgFe₂O₄ nanocapsules on the surface of the V₂O₅ nanorod. The bandgap of MgFe₂O₄ (1.8 eV) and V₂O₅ (2.5 eV) was shifted to 2.32 eV in MgFe₂O₄-V₂O₅ to promote visible-light harvesting and it was depicted by the UV-visible DRS. XPS was used to identify the presence of chemical states with the existence of Mg 1s, Fe 2p, V 2p, and O 1s. The electrochemical impedance spectroscopy and photoluminescence spectra indicate the better separation of charge carriers owing to the formation of type II heterojunction formation. The tetracycline (25 mg/L) was degraded with MgFe₂O₄-V₂O₅ (150 mg/L) that exhibited 3.3 and 5 folds enhanced rates than its counterparts (MgFe₂O₄ and V₂O₅) owing to synergism. The possible intermediate formation and degradation pathway was determined based on GC/MS analysis. TOC analysis of end products indicated maximum mineralization of tetracycline. The MgFe₂O₄-V₂O₅ showed excellent recycling ability and reusability. The key photo-degradation of tetracycline was occurred by the generation of hydroxyl radicals. The MgFe₂O₄-V₂O₅ exhibited high antibacterial activity that ensures the dual functionality of the prepared nanocomposites (NCs). Therefore, the present study displays MgFe₂O₄ decorated V₂O₅ nanorod as an ideal candidate for environmental remediation.

Investigating Chaperone like Activity of Green Silver Nanoparticles: Possible Implications in Drug Development

Protein aggregation and amyloidogenesis have been associated with several neurodegenerative disorders like Alzheimer's, Parkinson's etc. Unfortunately, there are still no proper drugs and no effective treatment available. Due to the unique properties of noble metallic nanoparticles, they have been used in diverse fields of biomedicine like drug designing, drug delivery, tumour targeting, bio-sensing, tissue engineering etc. Small-sized silver nanoparticles have been reported to have anti-biotic, anti-cancer and anti-viral activities apart from their cytotoxic effects. The current study was carried out in a carefully designed in-vitro to observe the anti-amyloidogenic and inhibitory effects of biologically synthesized green silver nanoparticles (B-AgNPs) on human serum albumin (HSA) aggregation taken as a model protein. We have used different biophysical assays like thioflavin T (ThT), 8-Anilino-1-naphthalene-sulphonic acid (ANS), Far-UV CD etc. to analyze protein aggregation and aggregation inhibition in vitro. It has been observed that the synthesized fluorescent B-AgNPs showed inhibitory effects on protein aggregation in a concentration-dependent manner reaching a plateau, after which the effect of aggregation inhibition was significantly declined. We also observed meaningful chaperone-like aggregation-inhibition activities of as-synthesized florescent B-AgNPs in astrocytes.

Green synthesis of metallic nanoparticles using pectin as a reducing agent: a systematic review of the biological activities

CONTEXT

Pectin is a plant heteropolysaccharide that is biocompatible and biodegradable, enabling it to be an excellent reducing agent (green synthesis) for metallic nanoparticles (MNPs). Nevertheless, in the biological industry, pectin has been left behind in synthesising MNPs, for no known reason.

OBJECTIVE

To systematically review the biological activities of pectin synthesised MNPs (Pe-MNPs).

METHODS

The databases Springer Link, Scopus, ScienceDirect, Google Scholar, PubMed, Mendeley, and ResearchGate were systematically searched from the date of their inception until 10^th February 2020. Pectin, green synthesis, metallic nanoparticles, reducing agent and biological activities were among the key terms searched. The data extraction was focussed on the biological activities of Pe-MNPs and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations for systematic reviews.

RESULTS

A total of 15 studies outlined 7 biological activities of Pe-MNPs in the only three metals that have been explored, namely silver (Ag), gold (Au) and cerium oxide (CeO₂). The activities reported from the in vitro and in vivo studies were antimicrobial (9 studies), anticancer (2 studies), drug carrier (3 studies), non-toxic (4 studies), antioxidant (2 studies), wound healing (1 study) and anti-inflammation (1 study).

CONCLUSIONS

This systematic review demonstrates the current state of the art of Pe-MNPs biological activities, suggesting that Ag and Au have potent antibacterial and anticancer/chemotherapeutic drug carrier activity, respectively. Further in vitro, in vivo, and clinical research is crucial for a better understanding of the pharmacological potential of pectin synthesised MNPs.

Bioinspired Nanomodification Strategies: Moving from Chemical-Based Agrosystems to Sustainable Agriculture

Agrochemicals have supported the development of the agricultural economy and national population over the past century. However, excessive applications of agrochemicals pose threats to the environment and human health. In the last decades, nanoparticles (NPs) have been a hot topic in many fields, especially in agriculture, because of their physicochemical properties. Nevertheless, the prevalent methods for fabricating NPs are uneconomical and involve toxic reagents, hindering their extensive applications in the agricultural sector. In contrast, inspired by biological exemplifications from microbes and plants, their extract and biomass can act as a reducing and capping agent to form NPs without any toxic reagents. NPs synthesized through these bioinspired routes are cost-effective, ecofriendly, and high performing. With the development of nanotechnology, biosynthetic NPs (bioNPs) have been proven to be a substitute strategy for agrochemicals and traditional NPs in heavy-metal remediation of soil, promotion of plant growth, and management of plant disease with less toxicity and higher performance. Therefore, bioinspired synthesis of NPs will be an inevitable trend for sustainable development in agricultural fields. This critical review will demonstrate the bioinspired synthesis of NPs and discuss the influence of bioNPs on agricultural soil, crop growth, and crop diseases compared to chemical NPs or agrochemicals.

Synthesis of Capsaicin Loaded Silver Nanoparticles Using Green Approach and Its Anti-Bacterial Activity Against Human Pathogens

Nanotechnology is drawing attention nowadays due to its ability to regulate metals into nanosize, ultimately changing metal's physical, chemical, and optical properties. Silver nanoparticles are known for their potential impact as antimicrobial agents due to their inherent property penetrating the cell wall. The present study aimed to develop and statistically optimise using a novel combination of capsaicin loaded silver nanoparticles (AgCNPs) as an effective anti-bacterial agent to treat psoriasis using a green approach. Ascorbic acid was used as a reducing agent to fabricate silver nanoparticles. The formulation parameters optimisation was conducted using Box-Behnken Design (3×3 factorial design). The loading of capsaicin was confirmed by attenuated total reflectance-fourier transform infrared spectroscopy. Energy-dispersive X-ray spectroscopy-scanning electron microscopy (EDX-SEM) confirmed the existence of silver; net-like structure revealed in SEM and high-resolution transmission electron microscopy further confirmed the nano size of the formulation. Differential scanning calorimetry and X-ray diffraction demonstrated the capsaicin transformed into amorphous after encapsulated. An in-vitro microbial study showed that the 0.10 M formulation of AgCNPs exerted potent anti-bacterial activity, which can be considered an alternative anti-bacterial agent. It also displayed that the zone of inhibition was significantly high in gram-negative bacteria (E. coli) than gram-positive bacteria (S. aureus). Green synthesised AgCNPs showed highly significant anti-bacterial activity, which indicates that this formulation can be very promising for treating psoriasis.

Physicochemical aspects of design of ultrathin films based on chitosan, pectin, and their silver nanocomposites with antiadhesive and bactericidal potential

Implant-related infection is one of the serious problems in regenerative medicine. Promising approach to overcome the problems caused by bacterial growth on the medical implants is their modification by bioactive coatings. A versatile technique for designing multilayer films with tailored characteristics at the nanometer scale is layer-by-layer assembly. In this study, multilayer films based on biopolymers (pectin and chitosan) and their nanocomposites with silver nanoparticles have been prepared and evaluated. The buildup of multilayers was monitored using the quartz crystal microbalance with dissipation technique. The morphology of the obtained films was investigated by atomic force microscopy. We have demonstrated that pectin-Ag-containing films were characterized by the linear growth and smooth defect-free surface. When pectin-Ag was substituted for the pectin in the multilayer systems, the properties of the formed coatings were significantly changed: the film rigidity and surface roughness increased, as well as the film growth acquired the parabolic character. All prepared multilayer films have shown antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The significant decrease in the number of the adhered E. coli on the multilayer surface has been determined; moreover, many of the cells were misshapen with cytoplasm leaking. The prepared multilayer films showed a mild activity against S. aureus predominantly due to the antiadhesive effect. Our results indicate that antibacterial activity of biopolymer multilayers is determined by the film composition and physicochemical characteristics and can be associated with their antiadhesive and bactericidal behaviors.

Polymer Nanocomposites of Selenium Biofabricated Using Fungi

Nanoparticle-reinforced polymer-based materials effectively combine the functional properties of polymers and unique characteristic features of NPs. Biopolymers have attained great attention, with perspective multifunctional and high-performance nanocomposites exhibiting a low environmental impact with unique properties, being abundantly available, renewable, and eco-friendly. Nanocomposites of biopolymers are termed green biocomposites. Different biocomposites are reported with numerous inorganic nanofillers, which include selenium. Selenium is a micronutrient that can potentially be used in the prevention and treatment of diseases and has been extensively studied for its biological activity. SeNPs have attracted increasing attention due to their high bioavailability, low toxicity, and novel therapeutic properties. One of the best routes to take advantage of SeNPs' properties is by mixing these NPs with polymers to obtain nanocomposites with functionalities associated with the NPs together with the main characteristics of the polymer matrix. These nanocomposite materials have markedly improved properties achieved at low SeNP concentrations. Composites based on polysaccharides, including fungal beta-glucans, are bioactive, biocompatible, biodegradable, and have exhibited an innovative potential. Mushrooms meet certain obvious requirements for the green entity applied to the SeNP manufacturing. Fungal-matrixed selenium nanoparticles are a new promising biocomposite material. This review aims to give a summary of what is known by now about the mycosynthesized selenium polymeric nanocomposites with the impact on fungal-assisted manufactured ones, the mechanisms of the involved processes at the chemical reaction level, and problems and challenges posed in this area.

New pectin derivatives with antimicrobial and emulsification properties via complexation with metal-terpyridines

Pectin is widely used in food and pharmaceutical industries. However, due to its polysaccharide nature it lacks antimicrobial activity. In the current work, new pectin derivatives with interesting optical and antimicrobial properties were prepared via supramolecular chemistry utilizing Fe- or Cu-terpyridine (Tpy-Fe and Tpy-Cu) motifs. To proof derivatization of pectin, ultraviolet-visible spectroscopy (UV-Vis) and Fourier Transform infrared (FTIR) were used. In addition, the prepared pectin derivatives retained the known emulsification activity of the non-modified sugar beet pectin as seen from the particle size analysis of oil-in-water emulsions. The prepared derivatives showed antibacterial activity toward selected Gram-positive and Gram-negative bacteria. In addition, cytotoxicity test showed that the Tpy-Fe-pectin derivative was non-toxic to cells of human hepatocarcinoma, breast adenocarcinoma MCF7, and colorectal carcinoma cells at concentrations up to 100 μg/ml, while Tpy-Cu-pectin had moderate toxicity toward the aforementioned cells at the same concentration levels. The prepared derivatives could have potential applications in emulsions with antibacterial activity.

Photo induced mechanistic activity of GO/Zn(Cu)O nanocomposite against infectious pathogens: Potential application in wound healing

Treating infection causing microorganisms is one of the major challenges in wound healing. These may gain resistance due to the overuse of conventional antibiotics. A promising technique is antimicrobial photodynamic therapy (aPDT) used to selectively cause damage to infectious pathogenic cells via generation of reactive oxygen species (ROS). We report on biocompatable nanomaterials that can serve as potential photosensitizers for aPDT. GO/Zn(Cu)O nanocomposite was synthesized by co-precipitation method. Graphene Oxide (GO) is known for its high surface to volume ratio, excellent surface functionality and enhanced antimicrobial property. ZnO nanoparticle induces the generation of reactive oxygen species (ROS) under light irradiation and it leads to recombination of electron-hole pair. Nanocomposites of GO and Cu doped ZnO increases visible light absorption and enhances the photocatalytic property. It generates more ROS and increases the bacterial inhibition. GO/Zn(Cu)O nanocomposite was tested against Staphylococcus aureus (S. aureus), Enterococcus faecium (E. faecium), Escherichia coli (E. coli), Salmonella typhi (S. typhi), Shigella flexneri (S. flexneri) and Pseudomonas aeruginosa (P. aeruginosa) by well diffusion method, growth curve, colony count, biofilm formation under both dark and visible light condition. Reactive Oxygen Species assay (ROS), Lactate dehydrogenase leakage (LDH) assay, Protein estimation assay and membrane integrity study proves the mechanism of inhibition of bacteria. Inhibition kinetics shows the sensitivity between bacteria and GO/Zn(Cu)O nanocomposite.

Green Synthesis of Silver Nanoparticles Using Extract of Cilembu Sweet Potatoes (Ipomoea batatas L var. Rancing) as Potential Filler for 3D Printed Electroactive and Anti-Infection Scaffolds

Electroactive biomaterials are fascinating for tissue engineering applications because of their ability to deliver electrical stimulation directly to cells, tissue, and organs. One particularly attractive conductive filler for electroactive biomaterials is silver nanoparticles (AgNPs) because of their high conductivity, antibacterial activity, and ability to promote bone healing. However, production of AgNPs involves a toxic reducing agent which would inhibit biological scaffold performance. This work explores facile and green synthesis of AgNPs using extract of Cilembu sweet potato and studies the effect of baking and precursor concentrations (1, 10 and 100 mM) on AgNPs’ properties. Transmission electron microscope (TEM) results revealed that the smallest particle size of AgNPs (9.95 ± 3.69 nm) with nodular morphology was obtained by utilization of baked extract and ten mM AgNO₃. Polycaprolactone (PCL)/AgNPs scaffolds exhibited several enhancements compared to PCL scaffolds. Compressive strength was six times greater (3.88 ± 0.42 MPa), more hydrophilic (contact angle of 76.8 ± 1.7°), conductive (2.3 ± 0.5 × 10⁻³ S/cm) and exhibited anti-bacterial properties against Staphylococcus aureus ATCC3658 (99.5% reduction of surviving bacteria). Despite the promising results, further investigation on biological assessment is required to obtain comprehensive study of this scaffold. This green synthesis approach together with the use of 3D printing opens a new route to manufacture AgNPs-based electroactive with improved anti-bacterial properties without utilization of any toxic organic solvents.

Recent advances in functionalized nanomaterials for the diagnosis and treatment of bacterial infections

The growing problem of resistant infections due to antibiotic misuse is a worldwide concern that poses a grave threat to healthcare systems. Thus, it is necessary to discover new strategies to combat infectious diseases. In this review, we provide a selective overview of recent advances in the use of nanocomposites as alternatives to antibiotics in antimicrobial treatments. Metals and metal oxide nanoparticles (NPs) have been associated with inorganic and organic supports to improve their antibacterial activity and stability as well as other properties. For successful antibiotic treatment, it is critical to achieve a high drug concentration at the infection site. In recent years, the development of stimuli-responsive systems has allowed the vectorization of antibiotics to the site of infection. These nanomaterials can be triggered by various mechanisms (such as changes in pH, light, magnetic fields, and the presence of bacterial enzymes); additionally, they can improve antibacterial efficacy and reduce side effects and microbial resistance. To this end, various types of modified polymers, lipids, and inorganic components (such as metals, silica, and graphene) have been developed. Applications of these nanocomposites in diverse fields ranging from food packaging, environment, and biomedical antimicrobial treatments to diagnosis and theranosis are discussed.

An Updated Review on Silver Nanoparticles in Biomedicine

Silver nanoparticles (AgNPs) represent one of the most explored categories of nanomaterials for new and improved biomaterials and biotechnologies, with impressive use in the pharmaceutical and cosmetic industry, anti-infective therapy and wound care, food and the textile industry. Their extensive and versatile applicability relies on the genuine and easy-tunable properties of nanosilver, including remarkable physicochemical behavior, exceptional antimicrobial efficiency, anti-inflammatory action and antitumor activity. Besides commercially available and clinically safe AgNPs-based products, a substantial number of recent studies assessed the applicability of nanosilver as therapeutic agents in augmented and alternative strategies for cancer therapy, sensing and diagnosis platforms, restorative and regenerative biomaterials. Given the beneficial interactions of AgNPs with living structures and their nontoxic effects on healthy human cells, they represent an accurate candidate for various biomedical products. In the present review, the most important and recent applications of AgNPs in biomedical products and biomedicine are considered.

Anti-cancer activity of biosynthesized silver nanoparticles using Avicennia marina against A549 lung cancer cells through ROS/mitochondrial damages

The biosynthesized Ag NPs was synthesized by using marine mangrove plant extract Avicennia marina. The synthesized Ag NPs was confirmed by various physiochemical characterization including UV-spectrometer and XRD analysis. In addition, the shape and of the synthesized Ag NPs was morphologically identified by SEM initially and TEM finally. After confirmation, the anti-cancer property of synthesized Ag NPs was confirmed at 50 µg/mL concentration against A549 lung cancer cells by MTT assay. Further, the ability to stimulate the ROS generation and mitochondrial membrane at the IC50 concentration of Ag NPs was confirmed by fluorescence microscopy using DCFH-DA and rhodamine 123 dyes respectively. Finally, the result was concluded that the synthesized Ag NPs has improved anti-cancer activity against A549 cells at lowest concentration.

Novel Ecogenic Plasmonic Biohybrids as Multifunctional Bioactive Coatings

The objective of the present study is the valorization of natural resources and the recycling of vegetal wastes by converting them into novel plasmonic bio-active hybrids. Thus, a “green” approach was used to design pectin-coated bio-nanosilver. Silver nanoparticles were generated from two common garden herbs (Mentha piperita and Amaranthus retroflexus), and pectin was extracted from lemon peels. The samples were characterized by the following methods: Ultraviolet–visible (UV-Vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), dynamic light scattering (DLS), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM)–Energy-dispersive X-ray Spectroscopy (EDX), and zeta potential measurements. Microscopic investigations revealed the spherical shape and the nano-scale size of the prepared biohybrids. Their bioperformances were checked in terms of antioxidant and antibacterial activity. The developed plasmonic materials exhibited a strong ability to scavenge short-life (96.1% ÷ 98.7%) and long-life (39.1% ÷ 91%) free radicals. Microbiological analyses demonstrated an impressive antibacterial effectiveness of pectin-based hybrids against Escherichia coli. The results are promising, and the obtained biomaterials could be used in many bio-applications, especially as antioxidant and antimicrobial biocoatings.