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Abstract Photocatalytic degradation of several harmful organic compounds has been presented as a potential approach to detoxify water in recent decades. Trypan Blue (TB) is an acidic azo dye used to distinguish live cells from dead ones and it's classified as a carcinogenic dye. In this study, silver phosphate (Ag3PO4) nanoparticles and novel Ag3PO4/graphene/SiO2 nanocomposite have been successfully prepared via simple precipitation method. Afterward, their physical properties, chemical composition, and morphology have been characterized using SEM, EDS, TEM, SAED, BET, XRD, FTIR and UV–VIS spectroscopy. The specific surface area of Ag3PO4 and Ag3PO4/G/SiO2 nanocomposite were reported to be 1.53 and 84.97 m2/g, respectively. The band gap energy of Ag3PO4 and Ag3PO4/G/SiO2 nanocomposite was measured to be 2.4 and 2.307 eV, respectively. Photocatalytic degradation of Trypan blue (TB) was studied at different parameters such as pH, catalyst dosage, initial concentration, and contact time. The results showed that, at initial dye concentration of 20 ppm, pH = 2, and using 0.03 g of Ag3PO4/G/SiO2 as a photocatalyst, the degradation percent of TB dye in the aqueous solution was 98.7% within 10 min of light exposure. Several adsorption isotherms such as Langmuir, Freundlich, and Temkin adsorption isotherms have been tested in addition to the photocatalytic degradation kinetics. Both catalysts were found to follow the Langmuir isotherm model and pseudo-second-order kinetic model. Finally, the possible photocatalytic performance mechanism of Ag3PO4/G/SiO2 was proposed.

Reducing fruit and vegetable waste and maintaining quality has become challenging for everyone. Nanotechnology is a new and intriguing technology that is currently being implemented in fruit and vegetable preservation. Silver nanomaterials provide superior antibacterial qualities, biodegradability, and biocompatibility, which expands their potential applications in fruit and vegetable preservation. Silver nanomaterials include silver nanocomposites and Ag-MOF, of which silver nanocomposites are mainly composed of silver nanoparticles. Notably, not all kinds of silver nanoparticles utilized in the preservation of fruits and vegetables are thoroughly described. Therefore, the synthesis, mechanism of action, and advancements in research on silver nanocomposites for fruit and vegetable preservation were discussed in this study. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive investigation on the synthesis and characterization of surfactant-assisted graphene oxide non-covalent functionalized silver nanocomposites (rGS-AgNPs) for achieving remarkable photocatalytic and anti-biofilm properties. The approach involves using an anionic surfactant (sodium lauryl sulfate (SLS)), silver nitrate (AgNO3), and reduced graphene oxide (rGO) as stabilizing/reducing agents, metal precursors, and supporting materials, respectively. Different composites were prepared by varying the concentration of AgNO3, resulting in rGS-AgNPs composites with concentrations of 0.9 × 10−3 mM, 1.8 × 10−3 mM, and 2.7 × 10−3 mM. Characterization techniques including XRD, FTIR, SEM, and TEM/EDS analysis confirmed the formation of face-centered cubic AgNPs and amorphous rGO structures. The composites exhibited a firm binding of the surfactant and AgNPs on the surface of rGO nanosheets, resulting in efficient anti-biofilm and photocatalytic activity. The size of the supported AgNPs on rGO/SL was found to be 8–10 nm. The rGS-AgNPs composites displayed significantly improved anti-biofilm and photocatalytic performance, attributed to the increased surface area of AgNPs. Moreover, the photocatalytic efficiency of the rGS-AgNPs composites reached 96.48 % within 60 min, outperforming pure AgNPs. The synthetic procedure and practical applications will be utilized for biosensors, food packing technology, biomedical and pharmaceutically valuable reactions.

Abstract Traditional Chinese medicines (TCMs)/nanopreparations as viral antagonists exhibited a structure–function correlation, i.e., the differences in surface area/volume ratio caused by the variations in shape and size could result in different biochemical properties and biological activities, suggesting an important impact of morphology and structure on the antiviral activity of TCM-based nanoparticles. However, few studies paid attention to this aspect. Here, the effect of TCM-based nanoparticles with different morphologies on their antiviral activity was explored by synthesizing rhein/silver nanocomposites (Rhe@AgNPs) with spherical (S-Rhe/Ag) and linear (L-Rhe/Ag) morphologies, using rhein (an active TCM ingredient) as a reducing agent and taking its self-assembly advantage. Using porcine reproductive and respiratory syndrome virus (PRRSV) as a model virus, the inhibitory effects of S-Rhe/Ag and L-Rhe/Ag on PRRSV were compared. Results showed that the product morphology could be regulated by varying pH values, and both S- and L-Rhe/Ag exhibited good dispersion and stability, but with a smaller size for L-Rhe/Ag. Antiviral experiments revealed that Rhe@AgNPs could effectively inhibit PRRSV infection, but the antiviral effect was morphology-dependent. Compared with L-Rhe/Ag, S-Rhe/Ag could more effectively inactivate PRRSV in vitro and antagonize its adsorption, invasion, replication, and release stages. Mechanistic studies indicated that Rhe@AgNPs could reduce the production of reactive oxygen species (ROS) induced by PRRSV infection, and S-Rhe/Ag also had stronger ROS inhibitory effect. This work confirmed the inhibitory effect of Rhe@AgNPs with different morphologies on PRRSV and provided useful information for treating PRRSV infection with metal nanoparticles synthesized from TCM ingredients. Graphical abstract

Reducing fruit and vegetable waste and maintaining quality has become challenging for everyone. Nanotechnology is a new and intriguing technology that is currently being implemented in fruit and vegetable preservation. Silver nanomaterials provide superior antibacterial qualities, biodegradability, and biocompatibility, which expands their potential applications in fruit and vegetable preservation. Silver nanomaterials include silver nanocomposites and Ag-MOF, of which silver nanocomposites are mainly composed of silver nanoparticles. Notably, not all kinds of silver nanoparticles utilized in the preservation of fruits and vegetables are thoroughly described. Therefore, the synthesis, mechanism of action, and advancements in research on silver nanocomposites for fruit and vegetable preservation were discussed in this study.

Xiaoyu Huang,1,2 Ming Zhang,1,3 Lin Chang,1,2 Dali Zheng,2 Wei Lin,4 Yan Feng,1,2 Youguang Lu1,2 1Department of Preventive Dentistry, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, Fujian Province, People’s Republic of China; 2Fujian Key Laboratory of Oral Diseases, School of Stomatology, Fujian Medical University, Fuzhou, Fujian Province, People’s Republic of China; 3Department of Conservative and Endodontic Dentistry, School and Hospital of Stomatology, Fujian Medical University, Fuzhou, Fujian Province, People’s Republic of China; 4College of Chemistry, Fuzhou University, Fuzhou, Fujian Province, People’s Republic of ChinaCorrespondence: Youguang Lu, Tel +86-591-83736429, Fax +86-591-83720599, Email fjlyg63@fjmu.edu.cn; Yan Feng, Tel/Fax +86-591-22862632, Email fengyan@fjmu.edu.cnObjective: The study aims to enhance the anti-caries performance of pit and fissure sealants through the synthesis of novel silver nanocomposites, and to evaluate their mechanical properties and biological safety in vitro and in vivo.Methods: The antibacterial properties of synthetic eggshell/Ag were detected by bacterial inhibition zone, minimum bacteriostatic concentration, fluorescence staining and scanning electron microscopy. The synthetic products were then combined with pit and fissure sealants to prepare specimens, and their effects on mechanical properties, antibacterial properties and cytotoxicity were evaluated. Furthermore, an oral mucosal contact model of golden hamsters was established according to the ISO10933 standard to evaluate local stimulation and systemic effects.Results: The novel nanocomposite eggshell/Ag was confirmed to exhibit strong broad-spectrum antibacterial activity, and that the eggshell/Ag-modified pit and fissure sealant had strong antibacterial properties against common dental caries bacterial biofilms, without any significant change in mechanical properties. The gradient dilution extract showed acceptable cytotoxicity, and in the golden hamster oral contact model, there were no visible abnormalities in local mucosal tissues, blood indices, or liver and kidney histopathology.Conclusions: These findings suggest that eggshell/Ag combined with pit and fissure sealants has strong antibacterial activity and excellent biosafety in vitro and in vivo, making it a promising candidate for clinical applications.Keywords: silver nanocomposites, antibacterial, pit and fissure sealants, biosafety

Traditional Chinese medicines (TCMs)/nanopreparations as viral antagonists exhibited a structure–function correlation, i.e., the differences in surface area/volume ratio caused by the variations in shape and size could result in different biochemical properties and biological activities, suggesting an important impact of morphology and structure on the antiviral activity of TCM-based nanoparticles. However, few studies paid attention to this aspect. Here, the effect of TCM-based nanoparticles with different morphologies on their antiviral activity was explored by synthesizing rhein/silver nanocomposites (Rhe@AgNPs) with spherical (S-Rhe/Ag) and linear (L-Rhe/Ag) morphologies, using rhein (an active TCM ingredient) as a reducing agent and taking its self-assembly advantage. Using porcine reproductive and respiratory syndrome virus (PRRSV) as a model virus, the inhibitory effects of S-Rhe/Ag and L-Rhe/Ag on PRRSV were compared. Results showed that the product morphology could be regulated by varying pH values, and both S- and L-Rhe/Ag exhibited good dispersion and stability, but with a smaller size for L-Rhe/Ag. Antiviral experiments revealed that Rhe@AgNPs could effectively inhibit PRRSV infection, but the antiviral effect was morphology-dependent. Compared with L-Rhe/Ag, S-Rhe/Ag could more effectively inactivate PRRSV in vitro and antagonize its adsorption, invasion, replication, and release stages. Mechanistic studies indicated that Rhe@AgNPs could reduce the production of reactive oxygen species (ROS) induced by PRRSV infection, and S-Rhe/Ag also had stronger ROS inhibitory effect. This work confirmed the inhibitory effect of Rhe@AgNPs with different morphologies on PRRSV and provided useful information for treating PRRSV infection with metal nanoparticles synthesized from TCM ingredients. [ABSTRACT FROM AUTHOR]

Optimizing the electrochemical properties of carbon-based nanocomposites is a fundamental challenge for sensor applications. In this work, the optimization of the electrochemical properties of silver nanocomposites on graphene oxide was studied for the fabrication of a non-enzymatic hydrogen peroxide (H2O2) sensor. To do so, we transform silver nanoparticles (AgNP) into silver nanoplates (AgNC) and anchor them to graphene oxide (GO) via the photochemical reduction method at 540 nm irradiation wavelength for its deposition on the surface of graphite electrodes (GE) and detect low concentrations of H2O2. We performed a physicochemical characterization of the resulting nanocomposite using a combination of UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, to then, analyze the electrochemical properties of GE modified with silver nanocomposites by cyclic voltammetry (CV). Our results reveal an improvement of the sensitivity from 309 µA mM-1 cm-2 to 444 µA mM-1 cm-2 and limits of detection (LOD) and limits of quantification (LOQ) from 0.68 mM and 2.29 mM to 0.28 mM and 0.96 mM using AgNP/GO - GE and AgNC/GO - GE nanocomposites electrodes, respectively. The enhancement of the electrochemical properties reveals a synergistic effect between the planar shape of the AgNC and the oxygen functional groups over the GO surface. In so doing, we have demonstrated the utility of a low-cost photoreduction method to optimize the structural properties of AgNC/GO and, in this way, enhance the electrochemical properties of the modified electrode for H2O2 sensing. These results should greatly interest a wide range of biomedical applications and medical devices. [ABSTRACT FROM AUTHOR]

Newly synthesized mono- and bis-thioureidophosphonate (MTP and BTP) analogues in eco-friendly conditions were employed as reducing/capping cores for 100, 500, and 1000 mg L−1 of silver nitrate. The physicochemical properties of silver nanocomposites (MTP(BTP)/Ag NCs) were fully elucidated using spectroscopic and microscopic tools. The antibacterial activity of the nanocomposites was screened against six multidrug-resistant pathogenic strains, comparable to ampicillin and ciprofloxacin commercial drugs. The antibacterial performance of BTP was more substantial than MTP, notably with the best minimum inhibitory concentration (MIC) of 0.0781 mg/mL towards Bacillus subtilis, Salmonella typhi, and Pseudomonas aeruginosa. Among all, BTP provided the clearest zone of inhibition (ZOI) of 35 ± 1.00 mm against Salmonella typhi. After the dispersion of silver nanoparticles (AgNPs), MTP/Ag NCs offered dose-dependently distinct advantages over the same nanoparticle with BTP; a more noteworthy decline by 4098 × MIC to 0.1525 × 10−3 mg/mL was recorded for MTP/Ag-1000 against Pseudomonas aeruginosa over BTP/Ag-1000. Towards methicillin-resistant Staphylococcus aureus (MRSA), the as-prepared MTP(BTP)/Ag-1000 displayed superior bactericidal ability in 8 h. Because of the anionic surface of MTP(BTP)/Ag-1000, they could effectively resist MRSA (ATCC-43300) attachment, achieving higher antifouling rates of 42.2 and 34.4% at most optimum dose (5 mg/mL), respectively. The tunable surface work function between MTP and AgNPs promoted the antibiofilm activity of MTP/Ag-1000 by 1.7 fold over BTP/Ag-1000. Lastly, the molecular docking studies affirmed the eminent binding affinity of BTP over MTP—besides the improved binding energy of MTP/Ag NC by 37.8%—towards B. subtilis-2FQT protein. Overall, this study indicates the immense potential of TP/Ag NCs as promising nanoscale antibacterial candidates. [ABSTRACT FROM AUTHOR]

The present study reports on the in vivo application of (Bio)silver nanocomposite formulations (LBPC-AgNCs) on wound healing. Additionally, the present study emphasizes the limited uptake of silver by liver and blood tissues as well as the high viability of PBMCs following external LBPC-AgNCs treatment. The wound closure was monitored via stereoscopic microscope, a localization case study in liver and blood tissue was carried out by (Inductively Coupled Plasma–Mass Spectrometers (ICP/MS), and peripheral blood mononuclear cells (PMBC) viability was determined via flow cytometry technique. The silver formulation was applied externally on the site of the wound infection for a period of ten days. At the beginning of the experiment, a moderate decrease in body weight and atypical behavior was observed. However, during the last period of the experiment, no abnormal mouse behaviors were noticed. The wound-healing process took place in a gradual manner, presenting the regeneration effect at around 30% from the fourth day. From the seventh day, the wounds treated with the silver formulation showed 80% of the wound healing potential. The viability of PBMCs was found to be 97%, whereas the concentrations of silver in the liver and blood samples were determined to be 0.022 µg/g and 9.3 µg/g, respectively. Furthermore, the present report becomes a pilot study in transferring from in vitro to in vivo scale (e.g., medical field application) once LBPC-AgNCs have demonstrated a unique wound healing potential as well as a non-toxic effect on the liver and blood. [ABSTRACT FROM AUTHOR]

In this study two series (I and II) of Cs Schiff bases based on heterocyclic moieties/silver nanocomposites were prepared via in situ green rapid methodology using ascorbic acid. Cs Schiff bases of series I were synthesized from reaction of chitosan with thiophene-2-carbaldehyde (Cs-T), furane-2-carbaldehyde (Cs-F) and pyridine-3-carbaldehyde (Cs-P), whereas series II from reaction of Cs with 1-phenyl-3-(thiophene-2-yl)-1H-pyrazole-4-carbaldehyde (Cs-TPA), 1-phenyl-3-(furan-2-yl)-1H-pyrazole-4-carbaldehyde (Cs-FPA), 1-phenyl-3-(pyridine-3-yl)-1H-pyrazole-4-carbaldehyde (Cs-PPA). The synthesized materials were characterized using FTIR spectroscopy, XRD, SEM/EDX, TEM and TGA. FTIR revealed the formation of Schiff base reaction, while XRD demonstrated the presence of Ag NPs. SEM–EDX confirmed the dispersion of AgNPs within polymer matrix. TEM revealed that AgNPs had an average size of around 30 nm. The inhibiory activity against three biofilm producing strains, namely: Staphylococcus epidermidis (Gram-positive bacterium), Pseudomonas aeruginosa (Gram-negative bacterium), Cryptococcus neoformans (unicellular fungus) in addition to their activity against these selected microbes in planktonic form using the microdilution method were evaluated. Moreover, a preliminary in vitro assessment for their capacity as anti-schistosomal candidates was carried out. The antimicrobial activity of Cs Schiff bases/AgNPs containing pyrazole moieties against the selected microbes in their planktonic forms was remarkably augmented more than corresponding neat basic ones. Cs-TPA loaded with 0.5% AgNPs (sample Cs-TPA-0.5) had the highest potency against the selected microorganisms with MIC (1.0 and 2.0 and 7.8 µg/ml. The antibiofilm results revealed that Cs-TPA-0.5 at concentrations of 31.3, 15.6 and 62.5 µg/ml inhibited biofilm by 100% for Pseudomonas aeruginosa, Staphylococcus epidermidis, and Cryptococcus neoformans, respectively. The anti-schistosomal activity assessment revealed that S.mansoni worms reached 100% death after 12 h incubation with the medium containing Cs-PPA loaded with 1.0 AgNPs, while 50% of S.mansoni was dead after 12 h incubation with Cs-FPA containing the same amount of AgNPs. Additionally, all Schistosoma worms died after 24 h incubation with Cs-PPA with 0.5 and 1.0% AgNPs and Cs-FPA with 1.0% AgNPs. [ABSTRACT FROM AUTHOR]

Aedes aegypti is responsible for the global spread of several ailments such as chikungunya, dengue, yellow fever, and Zika. The use of synthetic chemicals is the primary intervention in mosquito management. However, their excessive utilization resulting in the spread of toxic ingredients in the environment and posing threats to beneficial organisms has prompted the recommendation for the use of biologically synthesized nanocomposites as a promising approach for vector control. Silver nanocomposites were synthesized using leaf (AL-AgNCs) and stem (AS-AgNCs) extracts of Achyranthes aspera. The early fourth instars of A. aegypti were exposed to lethal doses of these nanocomposites to evaluate their effects on larval development, behavior, morphology, and mid-gut histoarchitecture. The cellular damage and deposition of nanocomposite residues in the mid-gut were studied using light and transmission electron microscopy. The A. aspera silver nanocomposite (AA-AgNC)-exposed larvae exhibited dose-dependent extended duration of development and diminished adult emergence, but did not exhibit modified behavior. Intense damage to the cuticle membrane and slight contraction in the internal membrane of anal papillae were noticed. Morphologically, the mid- gut appeared disorganized, darkly pigmented, and shrunk. Histological investigations of the mid-gut revealed significantly disordered internal architecture with lysed cells, damaged peritrophic membrane and microvilli, disintegrated epithelial layer, and a ruptured and displaced basement membrane. Visualization of the larval mid-gut through TEM showed severe cellular damage and aggregation of black spots, indicating the deposition of silver particles released by AA-AgNCs. The investigations revealed the bio- efficacy of A. aspera-mediated AgNCs against A. aegypti inducing stomach and contact toxicity in the larvae. The utilization of AA-AgNCs is recommended for A. aegypti management as a safe and effective intervention. [ABSTRACT FROM AUTHOR]

Aedes aegypti is responsible for the global spread of several ailments such as chikungunya, dengue, yellow fever, and Zika. The use of synthetic chemicals is the primary intervention in mosquito management. However, their excessive utilization resulting in the spread of toxic ingredients in the environment and posing threats to beneficial organisms has prompted the recommendation for the use of biologically synthesized nanocomposites as a promising approach for vector control. Silver nanocomposites were synthesized using leaf (AL-AgNCs) and stem (AS-AgNCs) extracts of Achyranthes aspera. The early fourth instars of A. aegypti were exposed to lethal doses of these nanocomposites to evaluate their effects on larval development, behavior, morphology, and mid-gut histoarchitecture. The cellular damage and deposition of nanocomposite residues in the mid-gut were studied using light and transmission electron microscopy. The A. aspera silver nanocomposite (AA-AgNC)-exposed larvae exhibited dose-dependent extended duration of development and diminished adult emergence, but did not exhibit modified behavior. Intense damage to the cuticle membrane and slight contraction in the internal membrane of anal papillae were noticed. Morphologically, the mid-gut appeared disorganized, darkly pigmented, and shrunk. Histological investigations of the mid-gut revealed significantly disordered internal architecture with lysed cells, damaged peritrophic membrane and microvilli, disintegrated epithelial layer, and a ruptured and displaced basement membrane. Visualization of the larval mid-gut through TEM showed severe cellular damage and aggregation of black spots, indicating the deposition of silver particles released by AA-AgNCs. The investigations revealed the bio-efficacy of A. aspera-mediated AgNCs against A. aegypti inducing stomach and contact toxicity in the larvae. The utilization of AA-AgNCs is recommended for A. aegypti management as a safe and effective intervention.

Newly synthesized mono- and bis-thioureidophosphonate (MTP and BTP) analogues in eco-friendly conditions were employed as reducing/capping cores for 100, 500, and 1000 mg L−1 of silver nitrate. The physicochemical properties of silver nanocomposites (MTP(BTP)/Ag NCs) were fully elucidated using spectroscopic and microscopic tools. The antibacterial activity of the nanocomposites was screened against six multidrug-resistant pathogenic strains, comparable to ampicillin and ciprofloxacin commercial drugs. The antibacterial performance of BTP was more substantial than MTP, notably with the best minimum inhibitory concentration (MIC) of 0.0781 mg/mL towards Bacillus subtilis, Salmonella typhi, and Pseudomonas aeruginosa. Among all, BTP provided the clearest zone of inhibition (ZOI) of 35 ± 1.00 mm against Salmonella typhi. After the dispersion of silver nanoparticles (AgNPs), MTP/Ag NCs offered dose-dependently distinct advantages over the same nanoparticle with BTP; a more noteworthy decline by 4098 × MIC to 0.1525 × 10−3 mg/mL was recorded for MTP/Ag-1000 against Pseudomonas aeruginosa over BTP/Ag-1000. Towards methicillin-resistant Staphylococcus aureus (MRSA), the as-prepared MTP(BTP)/Ag-1000 displayed superior bactericidal ability in 8 h. Because of the anionic surface of MTP(BTP)/Ag-1000, they could effectively resist MRSA (ATCC-43300) attachment, achieving higher antifouling rates of 42.2 and 34.4% at most optimum dose (5 mg/mL), respectively. The tunable surface work function between MTP and AgNPs promoted the antibiofilm activity of MTP/Ag-1000 by 1.7 fold over BTP/Ag-1000. Lastly, the molecular docking studies affirmed the eminent binding affinity of BTP over MTP—besides the improved binding energy of MTP/Ag NC by 37.8%—towards B. subtilis-2FQT protein. Overall, this study indicates the immense potential of TP/Ag NCs as promising nanoscale antibacterial candidates.

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. [ABSTRACT FROM AUTHOR]

Chanchal Das,1 Subha Sankar Paul,2 Arighna Saha,1 Tejinder Singh,3 Abhijit Saha,4 Jungkyun Im,3,5 Goutam Biswas1 1Department of Chemistry, Cooch Behar Panchanan Barma University, Cooch Behar, West Bengal 736101, India; 2Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore 637551, Singapore; 3Department of Electronic Materials and Devices Engineering, Soonchunhyang University, Asan 31538, Republic of Korea; 4Chemistry Department, UGC-DAE Consortium for Scientific Research, Kolkata 700106, India; 5Department of Chemical Engineering, Soonchunhyang University, Asan 31538, Republic of KoreaCorrespondence: Jungkyun ImDepartment of Chemical Engineering, Soonchunhyang University, 22 Soonchunhyangro, Asan 31538, Republic of KoreaEmail jkim5279@sch.ac.krGoutam BiswasDepartment of Chemistry, Cooch Behar Panchanan Barma University, Cooch Behar, West Bengal 736101, IndiaEmail goutam@cbpbu.ac.inAbstract: Since the identification of the first human coronavirus in the 1960s, a total of six coronaviruses that are known to affect humans have been identified: 229E, OC43, severe acute respiratory syndrome coronavirus (SARS-CoV), NL63, HKU1, and Middle East respiratory syndrome coronavirus (MERS-CoV). Presently, the human world is affected by a novel version of the coronavirus family known as SARS-CoV-2, which has an extremely high contagion rate. Although the infection fatality rate (IFR) of this rapidly spreading virus is not high (ranging from 0.00% to 1.54% across 51 different locations), the increasing number of infections and deaths has created a worldwide pandemic situation. To provide therapy to severely infected patients, instant therapeutic support is urgently needed and the repurposing of already approved drugs is presently in progress. In this regard, the development of nanoparticles as effective transporters for therapeutic drugs or as alternative medicines is highly encouraged and currently needed. The size range of the viruses is within 60– 140 nm, which is slightly larger than the diameters of nanoparticles, making nanomaterials efficacious tools with antiviral properties. Silver-based nanomaterials (AgNMs) demonstrate antimicrobial and disinfectant effects mostly by generating reactive oxygen species (ROS) and are presently considered as a versatile tool for the treatment of COVID-19 patients. Other metal-based nanoparticles have been primarily reported as delivery agents or surface modifying agents, vaccine adjuvant against coronavirus. The present review summarizes and discusses the possible effectiveness of various surface-modified AgNMs against animal coronaviruses and presents a concept for AgNM-based therapeutic treatment of SARS-CoV-2 in the near future.Keywords: silver nanomaterials, coronavirus, silver nanocomposites, antiviral, SARS-CoV

Objective: To formulate silver nanocomposites from Achyranthes aspera leaf extracts and evaluate its larvicidal activity against Aedes aegypti. Methods: The silver nanocomposites were synthesized from Achyranthes aspera leaf extracts. The process was optimized and traced through UV-visible and photon correlation spectroscopy. The larvicidal potential of silver nanocomposites of Achyranthes aspera leaf extracts was assessed against the early fourth instars of Aedes aegypti and three non-target organisms. Furthermore, the most effective and eco-safe nanocomposite was characterized by different biophysical techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform-infrared spectroscopy (FT-IR). Results: The formulated silver nanocomposites exhibited efficient larvicidal efficacy against Aedes aegypti. Bioassay with silver nanocomposites formulated using different AgNO 3 concentrations (3, 4, and 5 mM) revealed respective LC50 values of 37.570, 6.262 and 1.041 μg/mL; 5.819, 1.412 and 0.489 μg/mL; and 5.519, 1.302 and 0.267 μg/mL after 24, 48 and 72 h. The silver nanocomposites with 4 mM AgNO3 were selected for characterization. SEM and TEM analysis revealed spherical, poly-dispersed structure with varied diameters of 1-25 nm. The XRD analysis established the crystalline and face-centred-cubic structure of silver nanocomposites with the maximum peak at a 2θ value of 37.42°. The EDX pattern showed the presence of Ag, O and C in the nanocomposites in their order of weight%. The FT-IR displayed visibly distinct peaks in different ranges demonstrating the intricacy of silver nanocomposites. In addition, the lethal concentrations of silver nanocomposites of Achyranthes aspera leaf extracts against Aedes aegypti larvae were non-toxic to non-target organisms including Gambusia affinis, Daphnia magna and Moina macrocopa. Conclusions: Silver nanocomposites synthesized with leaf extract of Achyranthes aspera provide a cost-effective and eco-safe alternative to conventional insecticides, and can be utilized as a potent mosquito nano-larvicide.

The present study reports on the in vivo application of (Bio)silver nanocomposite formulations (LBPC-AgNCs) on wound healing. Additionally, the present study emphasizes the limited uptake of silver by liver and blood tissues as well as the high viability of PBMCs following external LBPC-AgNCs treatment. The wound closure was monitored via stereoscopic microscope, a localization case study in liver and blood tissue was carried out by (Inductively Coupled Plasma–Mass Spectrometers (ICP/MS), and peripheral blood mononuclear cells (PMBC) viability was determined via flow cytometry technique. The silver formulation was applied externally on the site of the wound infection for a period of ten days. At the beginning of the experiment, a moderate decrease in body weight and atypical behavior was observed. However, during the last period of the experiment, no abnormal mouse behaviors were noticed. The wound-healing process took place in a gradual manner, presenting the regeneration effect at around 30% from the fourth day. From the seventh day, the wounds treated with the silver formulation showed 80% of the wound healing potential. The viability of PBMCs was found to be 97%, whereas the concentrations of silver in the liver and blood samples were determined to be 0.022 µg/g and 9.3 µg/g, respectively. Furthermore, the present report becomes a pilot study in transferring from in vitro to in vivo scale (e.g., medical field application) once LBPC-AgNCs have demonstrated a unique wound healing potential as well as a non-toxic effect on the liver and blood.

A method was developed for the preparation of polymer silver nanocomposites using copolymer of N, N-diallyl-N'-acetylliydrazine with N-vinylpyrrolidone as reducing agent for silver ions and stabilizer of the obtained nanoparticles in an aqueous-alcoholic and aqueous medium. The obtained polymer nanocomposites consist of isolated silver nanoparticles having predominantly spherical shapes and diameters of 5 to 30 nm. The dependence of particle size on the medium and the concentration of silver ions was observed. The structural features of the nanocomposites were investigated using UV, IR, NMR spectroscopy, SEM microscopy, and powder X-ray diffraction. [ABSTRACT FROM AUTHOR]

Chronic wounds are a silent epidemic threatening the lives of many people worldwide. They are associated with social, health care and economic burdens and can lead to death if left untreated. The treatment of chronic wounds is very challenging as it may not be fully effective and may be associated with various adverse effects. New wound healing agents that are potentially more effective are being discovered continuously to combat these chronic wounds. These agents include silver nanoformulations which can contain nanoparticles or nanocomposites. To be effective, the discovered agents need to have good wound healing properties which will enhance their effectiveness in the different stages of wound healing. This review will focus on the process of wound healing and describe the properties of silver nanoformulations that contribute to wound healing.

New silver nanocomposites based on polysulfones of 2,2-diallyl-1,1,3,3-tetraethylguanidiniumchloride [poly(AGC–SO2)], tris(diethylamino)diallylaminophosphonium tetrafluoroborate [poly(DAAP–BF4–SO2)] and chloride [poly(DAAP–Cl–SO2)] have been developed. UV-spectroscopy, SEM and XRD techniques were used to characterize the formation of silver nanoparticles in copolymers. Antibacterial action of new silver nanocomposites on S. epidermidis 33 and Escherichia coli (planktonic cells and biofilms) was studied. The silver nanocomposites strongly inhibited biofilms formation of S. epidermidis 33 and Escherichia coli. The silver nanocomposites based on phosphonium polysulfones have a significant cytotoxic activity against RD and MS line cells. [ABSTRACT FROM AUTHOR]

This study investigated natural polymer-based stimuli-responsive hydrogels (TGIAVE) and their silver nanocomposites (TGIAVE-Ag). The hydrogels were composed of tragacanth gum, N-isopropyl acrylamide, and 2-(vinlyoxy) ethanol and were prepared via simple redox polymerization using N , N′-methylene-bis-acrylamide as a crosslinker and potassium persulfate as an initiator. The TGIAVE-Ag were synthesized via a green method involving an aqueous extract of Terminalia bellirica seeds. Structural, thermal, crystallinity, morphology, and size characteristics of the TGIAVE and TGIAVE-Ag were investigated by FTIR, UV–Vis, XRD, DSC, SEM, EDS, DLS, and TEM. To understand the physicochemical interaction and diffusion characteristics of TGIAVEs, network parameters such as zero-order, first-order, Hixson-Crowell, Higuchi, and Korsmeyer-Peppas values were calculated by assessing swelling data. TGIAVE hydrogels at pH 1.2 and 7.4 and temperatures of 25 and 37 °C may be used for time-dependent controlled release of 5-fluorouracil, an anticancer drug, TGIAVE-Ag may be applied for the inactivation of multidrug resistant (MDR) bacteria. • Tragacanth gum polymer based dual responsive hydrogels were fabricated. • AgNPs were formed in the hydrogel networks via Terminlia bellirica seed extract. • Evaluation of significant network parameters of hydrogels. • Hydrogels utilized for controlled drug delivery and antibacterial properties. [ABSTRACT FROM AUTHOR]

Global antimicrobial crisis and advent of drug resistant fungal strains has substantially distressed disease management for clinicians. Biodegradable silver nanoparticles (AgNps) emerge as an excellent alternative remedial option. In the current study, the anti-biofilm activity of microwave irradiated kappa-carrageenan (CRG) capped AgNps against Candida albicans , and Candida glabrata was investigated in terms of their effect on reactive oxygen species (ROS) generation, cellular morphology, biochemical composition, and the activity of enzymes of extracellular matrix. Minimum inhibitory concentration and fungicidal concentration value of CRG-AgNps against both Candida spp. ranged between 400 and 500 μg/mL. The 80% of Candida biofilm was inhibited and eradicated by CRG-AgNps at a concentration of ~300 μg/mL. Microscopic studies indicate that CRG-AgNps caused morphological damage through membrane disruption and pore formation. Further, CRG-AgNps generated ROS in a concentration-dependent manner and modulated the composition of Candida biofilm ECM by increasing the carbohydrate and eDNA content. CRG-AgNps also significantly inactivated the hydrolytic enzymes, thus hindering the biofilm forming ability. In conclusion, all these results suggest that the CRG-AgNps are potential antifungal agents against Candida biofilms, and they inhibit/eradicate the fungal biofilms through multiple signalling mechanisms. Unlabelled Image • CRG-AgNp have successfully eradicated preformed fungal biofilm. • CRG-AgNp generates ROS and inactivates hydrolytic enzymes. • CRG-AgNp inhibited biosynthesis of ECM components. [ABSTRACT FROM AUTHOR]

Chitosan (commercial and shrimp)–silver active agent nanocomposites (Ag–CC–NCs and Ag–SC–NCs) for inclusion in biopolymer films were synthetized in this study and characterized (mechanical, optical, transport, and structural properties and the in vitro antifungal activity). The hydrocolloid was integrated into linseed mucilage (LMF) commercial chitosan (CCF) and shrimp chitosan (SCF) films. The films were transparent, smooth, and continuous. The incorporation of Ag–CC–NCs or Ag–SC–NCs did not modify the film strength but did modify film elasticity. Based on the morphological characterization, the nanocomposites had a spherical shape (100 to 250 nm diameter). The LMF + Ag–SC–NCs film showed the highest water solubility (85.7%). The water vapor permeability increased with the addition of Ag–NCs–chitosan reaching the CCF-based films higher permeabilities (5.491–3.953 g/Pa.s.m × 1010), which indicates that they could be used in foods with high moisture content. The differences between treatments are indicative of the various applications that films can have in foods of different natures. [ABSTRACT FROM AUTHOR]

Silver nanocomposites based on copolymers of N, N-diallyl-N′-acylhydrazines (DAH) with acrylic acid, methacrylic acid, and acrylamide have been developed. They exhibit cytotoxic activity against melanoma MS and rhabdomyosarcoma RD. [ABSTRACT FROM AUTHOR]

In this work, a novel nanocomposite containing silver nanoparticles (AgNPs) embedded poly(1-naphthylamine) nanospheres (Ag/PNA) was prepared by in situ chemical reduction of silver nitrate. The structure, composition, and morphology of the prepared Ag/PNA nanocomposites were established by Fourier transform infrared spectrometry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the PNA and Ag/PNA-modified carbon paste electrodes were analyzed using cyclic voltammetry (cyclic voltammogram) and electrochemical impedance spectroscopy. It is observed that the electrochemical and charge transfer characteristics of PNA have significantly enhanced upon the incorporation of AgNPs. The prepared Ag/PNA nanocomposite has shown impressive electrocatalytic and electrochemical sensing performance toward H2O2. Remarkably, the present Ag/PNA-based enzymeless voltammetric H2O2 sensor showed a wide detection range in the concentration range of 1–3000 μM with a lower detection limit of 0.972 μM. The study revealed that Ag/PNA-modified carbon paste electrodes are an ideal platform for the fabrication of low-cost non-enzymatic H2O2 sensor with high sensitivity, good reproducibility, better selectivity, and stability. [ABSTRACT FROM AUTHOR]

Copolymers of 2-dimethyl- and 2-diethylaminoethyl methacrylate with 2-deoxy-2-methacryalamido-D-glucose and N-vinyl-N-methylacetamide with 20 – 80 mol% of 2-dialkylaminoethyl methacrylate units and molecular mass (40 – 80)·103 Da were synthesized. Silver nanocomposites based on these copolymers were obtained. The synthesized Ag-containing nanocomposites were found to exhibit antibacterial and antiviral activity. [ABSTRACT FROM AUTHOR]

In the current research, we present a single-step, one-pot, room temperature green synthesis approach for the development of functional poly(tannic acid)-based silver nanocomposites. Silver nanocomposites were synthesized using only tannic acid (plant polyphenol) as a reducing and capping agent. At room temperature and under mildly alkaline conditions, tannic acid reduces the silver salt into nanoparticles. Tannic acid undergoes oxidation and self-polymerization before the encapsulating of the synthesized silver nanoparticle and forms silver nanocomposites with a thick capping layer of poly(tannic acid). No organic solvents, special instruments, or toxic chemicals were used during the synthesis process. The results for the silver nanocomposites prepared under optimum conditions confirmed the successful synthesis of nearly spherical and fine nanocomposites (10.61 ± 1.55 nm) with a thick capping layer of poly(tannic acid) (~3 nm). With these nanocomposites, iron could be detected without any special instrument or technique. It was also demonstrated that, in the presence of Fe3+ ions (visual detection limit ~20 μM), nanocomposites aggregated using the coordination chemistry and exhibited visible color change. Ultraviolet-visible (UV–vis) and scanning electron microscopy (SEM) analysis also confirmed the formation of aggregate after the addition of the analyte in the detection system (colored nanocomposites). The unique analytic performance, simplicity, and ease of synthesis of the developed functional nanocomposites make them suitable for large-scale applications, especially in the fields of medical, sensing, and environmental monitoring. For the medical application, it is shown that synthesized nanocomposites can strongly inhibit the growth of Escherichia coli and Staphylococcus aureus. Furthermore, the particles also exhibit very good antifungal and antiviral activity.

To fabricate new smart materials that can deliver both the pharmaceutically active molecules and metal nanoparticles, we have formulated chitosan-based semi-IPN hydrogels and their silver nanocomposites (Ag NCs) along with amoxicillin (AMX). Semi-IPN hydrogels and their Ag NCs were synthesized from chitosan, dimethylamino ethyl methacrylate and 2-hydroxyethyl methacrylate via simple-free radical polymerization method and reducing with NaBH4. The resultant formulations were evaluated for in vitro release of AMX, anti-bacterial studies and DNA cleavage studies. The hydrogels with AMX-derived silver nanoparticles (Ag NPs) show better ability to cleave DNA and anti-microbial activity than individual AMX and Ag NPs. [ABSTRACT FROM AUTHOR]

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Highlights • Ag-chitosan nanocomposites were used in edible coatings for fresh-cut melon. • Properties and composition of chitosan, origin-depending, influence its functionality. • Coated samples with Ag-chitosan (extracted) nanocomposites (T5) showed better quality. • Coated T5 samples showed lower respiration rates and higher vitamin C after 13 d at 5 °C. • T5 coating of fresh-cut melon may potentially extend its shelf life further than 13 d at 5 °C. Abstract The effect of incorporating Ag-chitosan nanocomposites into chitosan coatings on the quality of fresh-cut melon over 13 d at 5 °C has been studied. The respiration rate of fresh-cut melon was reduced after coating treatments. Particularly, the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) showed lower RR increments during storage compared to that of the rest of coatings. Coated samples reached a steady-state atmosphere within packages of 12.6–16.2 kPa of CO 2 /2.3–3.7 kPa of O 2 after 9–10 d. Softening was prevented in advanced storage periods by the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites). The colour, soluble solids content, sucrose, glucose and fructose, pH, TA, and citric and malic acids were not greatly affected by the coating treatments. Furthermore, the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) showed the highest total vitamin C content after 13 d at 5 °C compared to the rest of the coating treatments. The coated samples were better sensory-scored than were the uncoated samples. Particularly, the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) showed lower translucency, which is the most important visual alteration in fresh-cut melon. Only the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) induced a microbicidal reduction (0.6 log units) from days 10 to 13. We conclude that the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) has the potential to be applied in the fresh-cut industry to extend the shelf-life of these products. [ABSTRACT FROM AUTHOR]

The application of silver nanoparticles as an antibacterial agent is becoming more common. Unfortunately, their effect on microorganisms is still not fully understood. Therefore, this paper attempts to investigate the influence of silver ions, biologically synthesized silver nanoparticles and nanoparticles functionalized with antibiotics on molecular bacteria profiles. The initial stage of research was aimed at the mechanism determination involved in antibiotics sorption onto nanoparticles’ surface. For this purpose, the kinetics study was performed. Next, the functionalized formulations were characterized by Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS) and a zeta potential study. The results reveal that functionalization is a complex process, but does not significantly affect the stability of biocolloids. Furthermore, the antimicrobial assays, in most cases, have shown no increases in antibacterial activity after nanoparticle functionalization, which suggests that the functionalization process does not always generate the improved antimicrobial effect. Finally, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technique was employed to characterize the changes in the molecular profile of bacteria treated with various antibacterial agents. The recorded spectra proved many differences in bacterial lipids and proteins profiles compared to untreated cells. In addition, the statistical analysis of recorded spectra revealed the strain-dependent nature of stress factors on the molecular profile of microorganisms.

Two xerogels made of 4-pyridyl cholesterol (PC) and silver-nanocomposites (SNCs) thereof have been studied for their efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of aqueous sodium borohydride. Since in-situ silver doping will be effective in ethanol and acetone solvents with a PC gelator, two silver-loaded PC xerogels were prepared and successive SNCs were achieved by using an environmentally benign trisodium citrate dehydrate reducing agent. The formed PC xerogels and their SNCs were comprehensively investigated using different physico-chemical techniques, such as field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), powdered X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis). The FE-SEM results confirm that the shape of xerogel-covered silver nanoparticles (SNPs) are roughly spherical, with an average size in the range of 30−80 nm. Thermal degradation studies were analyzed via the sensitive graphical Broido’s method using a TGA technique. Both SNC-PC (SNC-PC-X1 and SNC-PC-X2) xerogels showed remarkable catalytic performances, with recyclable conversion efficiency of around 82% after the fourth consecutive run. The apparent rate constant (kapp) of SNC-PC-X1 and SNC-PC-X2 were found to be 6.120 × 10-3 sec-1 and 3.758 × 10-3 sec-1, respectively, at an ambient temperature.

Novel copolymers of C-3 esters of betulin derivatives (3-hydroxy-1-cyano-2,3-seco-2-nor-19β,28-epoxyoleane 3-O-vinylbenzoate (I), 3-hydroxy-1-cyano-2,3-seco-2-nor-19β,28-epoxyoleane 3-O-vinylacetate (II), methyl 3-hydroxy-1-cyano-2,3-seco-2-norlup-20(29)-en-28-oate 3-O-vinylbenzoate (III)) with N-vinylpyrrolidone and acrylonitrile have been prepared by free radical copolymerization. Kinetic regularities of the process were investigated. New water-soluble silver nanocomposites based on (III) copolymer with N-vinylpyrrolidone [poly((III)-VP)] have been developed. The average silver particle size ranged from 40 to 52 nm, with the corresponding UV-vis absorption peak position at 400 nm. The nanocomposite obtained has a significant cytotoxic activity toward melanoma cell line and may be considered for the development of new materials for medical applications. [ABSTRACT FROM AUTHOR]

Chitosan–silver nanocomposites (CS-HDA-AgNCs) was prepared using chitosan, biogenic silver nanocomposites, and crosslinker, hexamethylene 1,6-di(amino carboxysulfonate) (HDA). The film is flexible and transparent. Its physical, mechanical, thermal, hydrophilicity, and swelling properties were improved by HDA (2.5%). The antimicrobial activity of CS-HDA-AgNCs were not displayed any remarkable zone of inhibition but showed toxic effect in the presence of normal 3T3 fibroblasts and cancer HeLa cells. It decreases to ca. 5–7% for both cell lines. In conclusion, it can be mentioned that the CS-HDA-AgNCs, a kind of new functional biomaterial, could be useful for health-care applications. [ABSTRACT FROM AUTHOR]

A mucoadhesive drug delivery system can improve the effectiveness of a drug, allowing targeting and localization at a specific site. According to this assumption, γ-irradiation as eco-friendly technique was employed to synthesize (acrylic acid/polyethylene glycol) copolymer hydrogel of different compositions. Silver nanoparticles were prepared within (acrylic acid/polyethylene glycol) hydrogel network by means of in situ reduction of silver nitrate using sodium borohydride as a reducing agent. Swelling characteristics in distilled water and simulated saliva solution were studied as a function of copolymer composition and preparation irradiation dose. (Acrylic acid/polyethylene glycol) hydrogels and their developed Agº nanocomposites have been characterized using scanning electron microscope, thermogravimetric analysis, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Mucoadhesive strength as well as self-disinfection efficiency expressed as antibacterial activity against different bacterial strains was evaluated. Propranolol HCl as model drug was used to evaluate the potential efficiency of the obtained (acrylic acid/polyethylene glycol)-Agº nanocomposites as mucoadhesive drug carrier. The obtained results showed that the (acrylic acid/polyethylene glycol)-Agº nanocomposites show a promising self-disinfection property, and the propranolol HCl–loaded composites were able to deliver the loaded drug in a sustainable manner that lasts for about 600 min. [ABSTRACT FROM AUTHOR]

Iron is a transition metal of tremendous eco-physiological significance. This work aimed at constructing a simple plasmonic Ag-nanocomposite (LBG/PRAg-NC) based on locust bean gum and Phyllanthus reticulatus anthocyanin in a sustainable manner for the optical detection of ferrous ions (Fe2+) in aqueous solution. LBG/PRAg-NC was prepared via a green chemistry route and thoroughly characterized for its physico-chemical and plasmonic attributes. Successful synthesis of LBG/PRAg-NC under room temperature with Phyllanthus reticulatus anthocyanin as reductant and locust bean gum as stabilizer was accomplished within 15 min. LBG/PRAg-NC exhibited small size (∼8.04 nm), spherically shaped nanosilver, with good colloidal dispersion, stability and prominent SPR absorption peak at 420 nm. XPS analysis revealed the existence of both Ag0 and Ag + species embedded in the biopolymer support. Furthermore, LBG/PRAg-NC was highly selective for Fe2+ as opposed to other interferents including Fe3+. The presence of Fe2+ engendered a redox oxidation of the analyte by the Ag+ species, prompting a rapid, concentration dependent increase in color and SPR absorption band intensity of LBG/PRAg-NC colloidal solution. In aqueous solution, the probe displayed a good linear range for Fe2+ (0.1–100 μM), and a low detection limit (LOD of 0.38 μM). The obtained detection limit is much lower than the guideline limit of Fe2+ content in drinking water, ∼5 μM. Additionally, the probe was successfully applied in determination of Fe2+ in aqueous solutions of apple juice, iron supplement tablet, and tap water, with commendable analytical performances. Therefore, our research findings demonstrate a facile, efficacious, cost-effective, and eco-friendly approach for the sustainable synthesis of plasmonic Ag-nanocomposites based solely on locust bean gum and Phyllanthus reticulatus anthocyanin. Importantly, these results validate the capacity of plasmonic Ag-nanocomposite constructed via green chemistry route as a simple, rapid, and selective probe for effective monitoring of trace amounts of Fe2+ in aqueous environment. [Display omitted] • Plasmonic nanocomposite, LBG/PRAg-NC, based on locust bean gum was successfully fabricated via a green chemistry approach. • LBG/PRAg-NC exhibited Ag+ and silver nanospheres with good colloidal dispersion, stability, and prominent SPR absorption band. • Addition of Fe2+ to LBG/PRAg-NC engenders a redox oxidation of the cation with attendant potentiation of the plasmonic peak. • An eco-friendly, rapid, selective and sensitive technique for detection of Fe2+ using LBG/PRAg-NC SPR absorption band as a probe is presented. • Practical utility of the probe was demonstrated in apple juice, iron supplement tablet and water with satisfactory outcomes. [ABSTRACT FROM AUTHOR]

The ionic crosslinked 2-acrylamido-2-methylpropane sulfonic acid-co-acrylic acid hydrogel, AMPS/AA and its Ag and Fe3O4 composites were synthesized using an in situ technique. The surface charge, particle sizes, morphology, and thermal stability of the prepared AMPS/AA-Ag and AMPS/AA-Fe3O4 composites were evaluated using different analytical techniques and their adsorption characteristics were evaluated to remove the methylene blue cationic dye, MB, from their aqueous solutions at optimum conditions. Also, the same monomers were used to synthesize AMPS/AA microgel and its Ag and Fe3O4 nanocomposites, which were synthesized using the same technique. The AMPS/AA-Fe3O4 nanocomposite was selected as conventional iron-supported catalyst due to the presence of both Fe(II) and Fe(III) species besides its magnetic properties that allow their easy, fast, and inexpensive separation from the aqueous solution. It was then evaluated as a heterogeneous catalyst for complete MB degradation from aqueous solution by heterogeneous Fenton oxidation. It achieved a high rate of degradation, degrading 100 mg L−1 of MB during a short time of 35 min as compared with the reported literature.

Potential dual responsive hydrogel networks (PPAD) are fabricated from pectin, poly((2-dimethylamino)ethyl methacrylate)) and phosphate crosslinker bis[2-methacryloyloxy] ethyl phosphate (BMEP) by a simple free radical polymerization. These hydrogel networks are successfully utilized for encapsulation of an anti-cancer drug, 5-fluorouracil (5-FU) and also employed as versatile platforms for production of silver nanoparticles. Fabricated hydrogel networks and silver nanocomposites were characterized by FTIR, SEM, EDX, TEM, DLS, DSC, TGA and XRD. Different polymer network parameters such as M C ¯ , χ , ξ and υ e and diffusion constant ( D ) were evaluated to assess the drug release profile. The 5FU loaded PPAD hydrogels were used to perform in vitro release studies in both gastric and intestinal conditions of GIT (pH 1.2 & pH 7.4) at two different temperatures (25 and 37 °C). On the other hand various kinetic models (zero, first, Higuchi & Koresmeyer-Peppas) have also been employed to fit drug release profile. In addition, the antibacterial activity of PPAD silver nanocomposites were tested against four bacterial species Escherichia coli (−ve), Klebsiella pneumoniae (−ve), Bacillus cereus (+ve) and Staphylococcus aereus (+ve) using zone of inhibition test. [ABSTRACT FROM AUTHOR]

The purpose of this communication is to develop a nanocomposite of poly(meta -aminophenol)/silver for chemiresistive sensing of free ammonia selectively in aqueous medium. Uniformly distributed silver nanoparticles was formed within the poly(meta -aminophenol) matrix by thermal reduction of silver mono-positive complexes with the functional groups of polymer. The silver loading within the poly(meta -aminophenol) matrix was optimized with respect to size and dispersion of the nanoparticles. The surface morphology and the interfacial interaction between the components of the prepared nanocomposite were characterized by various standard characterization techniques. The highest average DC-conductivity of the nanocomposite with ∼5 % silver loading with an average diameter of 50 nm ranging from 10 to 80 nm was achieved as 1.3 × 10−4 S cm−1 without using any other dopant. This poly(meta -aminophenol)/silver nanocomposite was found to have chemiresistive type sensing response towards ammonia in aqueous medium. The poly(meta -aminophenol)/silver nanocomposite film was responded significantly towards free ammonia in water with response time of 15–20 s, recovery time of 2.5–3 min and limit of detection or quantification of 5 mM. The selectivity of the ammonia sensing by the nanocomposite was also confirmed over ammonium sulfate, ammonium chloride, sodium nitrate and urea in aqueous medium. [Display omitted] • Easy preparation of uniformly distributed silver nanoparticles in PmAP matrix. • 1.3 × 10−4 S cm−1 average DC-conductivity of nanocomposite with ∼5 % silver. • Successful sensing of free aqueous ammonia with detection limit of 5 mM. • The response time of 15–20 s and the recovery time of 2.5–3 min. • Selective sensing of free aqueous ammonia over ammonium ion and urea. [ABSTRACT FROM AUTHOR]

[Display omitted] • The silver nanocomposite is in situ synthesized on paper substrate. • Detection of Fe3+ is based on the aggregation of silver nanocomposite. • The sensitivity for Fe3+ detection can be tuned by the pre-concentration steps. • On site detection of Fe3+ can be realized with the aid of a smartphone. In this study, a green and novel method for in situ synthesis of silver nanocomposites on paper substrate was developed and used for the pre-concentration and determination of Fe3+. Silver nanocomposites were in situ synthesized using tannic acid as reducing and capping agent under a mildly alkaline condition. The mechanism for the Fe3+ detection is based on its coordination with the tannic acid present on the surface of the silver nanocomposites and the formation of aggregates. The colorimetric response between Fe3+ and tannic acid modified silver nanocomposites deposited on the surface of the paper substrate was collected by a smartphone followed by processing with Adobe Photoshop CS 5.1 software. Under the optimal conditions, the color response showed a good linear relationship with Fe3+ concentration in the range of 25.0–500.0 μM. The limit of detection for Fe3+ was calculated to be 10.0 μM. Finally, the developed smartphone assisted paper-based chemical sensor was used to detect Fe3+ in two lake water samples, and the recoveries are in the range of 83.5 %−106.7 %. The sensitivity for Fe3+ detection can be tuned through the pre-concentration steps based on the porous nature of the filter paper. The platform highlights the advantage of simplicity, ease of synthesis, fast response time, and low reagent/analyte volume requirement, which is suitable for point-of-use application in iron ions contamination, especially in the remote or resource-limited regions. [ABSTRACT FROM AUTHOR]

Full polysaccharide crosslinked-chitosan membranes were prepared by crosslinking of chitosan with chitosan dialdehyde followed by reduction with sodium borohydride. Partially oxidized chitosan, generated from periodate oxidation of chitosan, was used as a crosslinker. The modulus values and elongation at break were increased with increasing the crosslinker weight ratio. The rheological measurements showed that depolymerization of chitosan can take place rapidly in the presence of the oxidizing agent. The weight reduction of crosslinked-chitosan membrane after 12 h, at pH = 4 and pH = 2 was found to be 85.0% and 90.0%, respectively. The structure of the crosslinked-chitosan and the silver nanocomposite were confirmed by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) reveals the presence of well-separated Ag nanoparticles with diameters in the range of 4-10 nm. The silver ion loading increases with increasing the silver ion concentration, and decreasing the crosslink density. The MBC/MIC ratio of 2.0, 2.0, and 1.0 was achieved for E. coli, S. aureus, and P. aeruginosa, respectively. [ABSTRACT FROM AUTHOR]

The reaction of 2-ethynylpyridine (2EP) with stoichiometric equivalent of an alkyl halide RX (R is ethyl, nonyl, or hexadecyl and X is Br or I) gives a poly( N-alkyl-2-ethynylpyridinium halide) type ionic polymer that belongs to the family of π-conjugated polyelectrolytes (CPEs). Reaction conditions significantly influence configuration of the polymer main chains: polymerization in acetonitrile solution gives polymers with high content of cis units while bulk polymerization provides irregular cis/trans polymers. Increased regularity of the high-cis polymers is documented by the NMR and IR as well as SERS (surface enhanced Raman scattering) spectra measured on Ag-nanoparticles/CPE systems. Both polymerization processes give polymers in which 2EP monomeric units are ionized only from ca one half, which exhibit good stability in air and good solubility in polar solvents such as MeOH, DMF, and DMSO and those with N-ethylpyridinium groups even in water. [ABSTRACT FROM AUTHOR]

Polyurethane-extracellular matrix bionanocomposites containing in situ generated silver nanoparticles and biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, were obtained by solvent casting method in order to achieve improved antibacterial biomaterials for medical devices. Using thermal analyses the stabilizing effect of polymeric components on the incorporated silver nanoparticles (metallic silver and/or silver in oxidized state) was evidenced. The non-isothermal kinetic parameters of the thermal degradation of studied bionanocomposites are evaluated in terms of integral methods. The variation of kinetic parameters in function of conversion was determined. By means of FTIR spectroscopy analysis the hydrolytic stability in PBS solutions (pH 4.6 and 7.4) of the studied silver bionanocomposites was investigated. It was found that the hydrolytic degradation occurred at the ester and urethane bonds in the poly(ester urethanes). The incorporated extracellular matrix components increased the hydrophilicity and favoured the hydrolysis. During hydrolysis increased hydrogen bonding and crystallinity principally for AgNPs stabilized polyurethane matrices which indicate a “chemicrystallization” effect. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse (SCB) was grafted with acrylamide (AAm) and glycidyl methacrylate (GMA) by chemical oxidation method. The effect of monomer/initiator molar ratio, reaction time, reaction temperature and material to liquor ratio on the degree of grafting was investigated. The optimum conditions for grafting were: monomer/initiator molar ratio 1 for AAm and 2 for GMA, reaction time 4 h, reaction temperature 80 °C and materials to liquor ratio 1:20. Silver nanoparticles (AgNPs) were prepared and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ungrafted SCB, SCB-g-AAm and SCB-g-GMA were impregnated into silver (Ag) nanoparticles colloidal solution. The ungrafted SCB, grafted SCB and their nanocomposites with Ag nanoparticles were characterized by FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The grafted SCB/Ag nanoparticles exhibit better antimicrobial activity against Escherichia coli as the model Gram-negative bacteria, Staphylococcus aureus as the model Gram-positive bacteria and Aspergillus flavus and Candida albicans (yeasts) than ungrafted SCB/AgNPs. [ABSTRACT FROM AUTHOR]