Hydrogen peroxide sensing and cytotoxicity activity of Acacia lignin stabilized silver nanoparticles

UV-blocking, antibacterial, corrosion resistance, antioxidant, and fruit packaging ability of lignin-rich alkaline black liquor composite film

The novel multifunctional active packaging composite film with antimicrobial, antioxidant, water-vapor and UV-barrier, and corrosion resistance properties was successfully prepared from waste biomass. In this study, waste poplar sawdust was pretreated using green liquor to extract black liquor (BL). BL was then mixed with polyvinyl alcohol (PVA) solution for synthesizing silver nanoparticles (AgNPs). PVA-BL-AgNPs film was fabricated by solution casting method, and the microstructure characterization and macroscopic performance testing of the composite film were conducted. The results revealed that PVA-BL-AgNPs film exhibited inhibitory effects against Staphylococcus aureus (inhibition zone: 33.6 mm), Pseudomonas aeruginosa (inhibition zone: 31.6 mm), and Escherichia coli (inhibition zone: 32.0 mm). It could eliminate over 99 % of 2,2-diazodi (3-ethyl-benzothiazol-6-sulfonic acid) (ABTS) free radicals and provided 100 % UV-blocking, reducing light-induced food damage. It exhibited the improvement of water-vapor barrier properties and corrosion resistance. In vitro cytotoxicity assays demonstrated that no significant impact occurred on cell proliferation, confirming the safety of the film. Packaging experiments showed that PVA-BL-AgNPs film effectively inhibited milk spoilage and prolonged the shelf-life of bread and bananas. Therefore, PVA-BL-AgNPs film might extend the shelf-life of food and offer significant opportunities in addressing the issues of low safety and environmental pollution associated with traditional packaging films.

Sustainable Lignin-Based Nano Hybrid Biomaterials with High-Performance Antifungal Activity

Aspergillus flavus (A. flavus) and Aspergillus niger (A. niger) mainly spread through airborne fungal spores. An effective control to impede the dissemination of the spores of Aspergillus in the air affecting the environment and food was carried out. This study focuses on the sustainable rice husk-extracted lignin, nanolignin, lignin/n-lignin capped silver nanoparticles used for fungal growth inhibition. These biomaterials inhibit the growth of fungi by altering the permeability of cell membranes and influencing intracellular biosynthesis. The antifungal indexes for A. flavus and A. niger on day 5 at a concentration of 2000 μg/100 μL are 50.8 and 43.6%, respectively. The results demonstrate that the hybrid biomaterials effectively prevent the growth or generation of fungal spores. The findings of this research hold significant implications for future investigations focused on mitigating the dissemination of Aspergillus during the cultivation of agricultural products or in the process of assuring agricultural product management, such as peanuts and onions.

Utilization of chestnut shell lignin in alginate films

BACKGROUND

Lignocellulosic structures obtained from agricultural wastes can re-design sustainable packaging materials. The present study investigated the utilization of lignocellulose (LS), alkali lignin (L) and hydroxymethylated (modified) lignin (ML), separated from chestnut shells in alginate (AL) films at 100 and 200 mg g^-1 (10% and 20%, w/w based on AL), as reinforcing agents. Lignin modification and concentration effects on the AL films were characterized by water vapor permeability (WVP), as well as morphological, mechanical, optical, thermal and active properties.

RESULTS

Fourier transform infrared spectroscopy results showed that extracted L and LS had different structures, and the modification of L resulted in a peak shift and a decrease in peak intensities between 1250 and 800 cm^-1 . The antioxidant and antimicrobial activity tests showed that films containing L had higher activity values (P < 0.05). WVP of the films containing ML was the lowest (P < 0.05) and the results revealed that 20% (w/w) concentration had an adverse effect on the WVP of films. The addition of L, LS and ML increased the tensile strength, elastic modulus and thermal properties (P < 0.05) compared to AL control films. With an increasing concentration, films containing L-based structures showed higher opacity and relatively lower L* values (P < 0.05).

CONCLUSION

These results show that the addition of lignin to biopolymers is a promising method for improving the properties of biopolymers and providing functional attributes. LS had no or little effect on the film properties; however, the modification of L had the advantage of enhancing WVP and thermal properties at the same time as showing a decrease in functional properties compared to L. © 2022 Society of Chemical Industry.

Stabilized Lignin Nanoparticles for Versatile Hybrid and Functional Nanomaterials

Spherical lignin nanoparticles are emerging biobased nanomaterials, but instability and dissolution in organic solvents and aqueous alkali restrict their applicability. Here, we report the synthesis of hydroxymethylated lignin nanoparticles and their hydrothermal curing to stabilize the particles by internal cross-linking reactions. These colloidally stable particles contain a high biobased content of 97% with a tunable particle size distribution and structural stability in aqueous media (pH 3 to 12) and organic solvents such as acetone, ethanol, dimethylformamide, and tetrahydrofuran. We demonstrate that the free phenolic hydroxyl groups that are preserved in the cured particles function as efficient reducing sites for silver ions, giving rise to hybrid lignin-silver nanoparticles that can be used for quick and facile sensing of hydrogen peroxide. The stabilized lignin particles can also be directly modified using base-catalyzed reactions such as the ring-opening of cationic epoxides that render the particles with pH-dependent agglomeration and redispersion properties. Combining scalable synthesis, solvent stability, and reusability, this new class of lignin nanoparticles shows potential for its use in circular biobased nanomaterials.

Recent advances in biological activities of lignin and emerging biomedical applications: A short review

As an abundant biopolymer, lignin gains interest owing to its renewable nature and polyphenolic structure. It possesses many biological activities such as antioxidant activity, antimicrobial activity, and biocompatibility. Studies are being carried out to relate the biological activities to the polyphenolic structures. These traits present lignin as a natural compound being used in biomedical field. Lignin nanoparticles (LNPs) are being investigated for safe use in drug and gene delivery, and lignin-based hydrogels are being explored as wound dressing materials, in tissue engineering and 3D printing. In addition, lignin and its derivatives have shown the potential to treat diabetic disease. This review summarizes latest research results on the biological activities of lignin and highlights potential applications exampled by selective studies. It helps to transform lignin from a waste material into valuable materials and products.

How far is Lignin from being a biomedical material?

Lignin is a versatile biomass that possesses many different desirable properties such as antioxidant, antibacterial, anti-UV, and good biocompatibility. Natural lignin can be processed through several chemical processes. The processed lignin can be modified into functionalized lignin through chemical modifications to develop and enhance biomaterials. Thus, lignin is one of the prime candidate for various biomaterial applications such as drug and gene delivery, biosensors, bioimaging, 3D printing, tissue engineering, and dietary supplement additive. This review presents the potential of developing and utilizing lignin in the outlook of new and sustainable biomaterials. Thereafter, we also discuss on the challenges and outlook of utilizing lignin as a biomaterial.

Next generation applications of lignin derived commodity products, their life cycle, techno-economics and societal analysis

The pulp and biorefining industries produce their waste as lignin, which is one of the most abundant renewable resources. So far, lignin has been remained severely underutilized and generally burnt in a boiler as a low-value fuel. To demonstrate lignin's potential as a value-added product, we will review market opportunities for lignin related applications by utilizing the thermo-chemical/biological depolymerization strategies (with or without catalysts) and their comparative evaluation. The application of lignin and its derived aromatics in various sectors such as cement industry, bitumen modifier, energy materials, agriculture, nanocomposite, biomedical, H2 source, biosensor and bioimaging have been summarized. This comprehensive review article also highlights the technical, economic, environmental, and socio-economic variable that affect the market value of lignin-derived by-products. The review shows the importance of lignin, and its derived products are a platform for future bioeconomy and sustainability.

Ag immobilized lignin-based PU coating: A promising candidate to promote the mechanical properties, thermal stability, and antibacterial property of paper packaging

A lignin-based PU coating was prepared for paper-based green packaging. Two representative diisocyanate were used to prepare the coatings. Due to the rigid aromatic, the physical properties of the TDI system reached the maximum below the lignin content of 40%. The HDI that contains flexible aliphatic chains alleviated the brittleness of coating, and it showed physical advantages when the lignin content was more than 50%. Owing to the high lignin content, the coating presented enhanced thermal stability. After coated with the lignin-based PU coatings, the dry tensile strength of coated paper was improved by 126%. Amazingly, the wet strength was increased from 0.31 to 12.6 MPa with an improvement nearly 40 times. Based on the coordination of lignin, Ag⁺ was introduced into the PU matrix, which imparted the coating with excellent antibacterial ability. The colony forming units of E. coli and S. aureus were both less than 1. However, no inhibition halo was observed, which indicated that the Ag was firmly anchored on the coating and the antibacterial ability is only available when the bacterial contact the coating surface. The lignin-based PU coating with favorable sustainability and properties shows great potential in paper-based green packaging fields.

Development of a surface-modified paper-based colorimetric sensor using synthesized Ag NPs-alginate composite

There has been an increase in the discovery and usage of sensors for the detection of chemical compounds in the field of analytical chemistry since the last several years. This has led to progressive research in nanotechnology for developing efficient nanomaterials for bio-chemical sensing applications. Thereby, a deft synthesis of silver nanoparticles (Ag NPs) under microwave irradiation was achieved using sodium alginate as a reducing and capping agent in a fast and cost-effective approach. As per the X-ray diffraction analysis, the average particle size of Ag NPs was found to be 10 nm. X-ray photoelectron spectroscpopy analysis showed characteristic peaks at binding energies of 368.10 and 374.11 eV indicating the formation of Ag NPs. The synthesized Ag NPs-alginate composite was further used to develop a paper-based sensor for the detection of H₂O₂. Detection of H₂O₂ is based on the discolouration of the Ag NPs-alginate composite modified paper sensor as a function of H₂O₂ concentration. The analysis of the decoloured paper strips was done by a smartphone camera and an RGB Colour Reader application (app) to measure colour intensity. The sensing characteristics were found in the range of 0.1-10 mM. The colour analysis revealed piecewise linear relationship of intensity of RGB to H₂O₂ concentration in the range of 0.1-1.5 and 2-10 mM with R² values of 0.97 and 0.9778, respectively. Owing to the high sensitivity, selectivity, and cost-effectiveness, the developed paper sensor can be a potential tool for real-time analysis of H₂O₂.

A review on plant-mediated synthesis of silver nanoparticles, their characterization and applications

For decades, silver has been used as a non-toxic inorganic antimicrobial agent. Silver has a lot of potential in a variety of biological/chemical applications, particularly in the form of nanoparticles (NPs). Eco-friendly synthesis approach for NPs are becoming more common in nanobiotechnology, and the demand for biological synthesis methods is growing, with the goal of eliminating hazardous and polluting agents. Cultures of bacteria, fungi, and algae, plant extracts, and other biomaterials are commonly used for NP synthesis in the ‘green synthesis’ process. Plant-based green synthesis is a simple, fast, dependable, cost-effective, environmentally sustainable, and one-step method that has a significant advantage over microbial synthesis due to the lengthy process of microbial isolation and pure culture maintenance. In this report, we focussed on phytosynthesis of silver nanoparticles (AgNPs) and their characterization using various techniques such as spectroscopy (UV–vis, FTIR), microscopy (TEM, SEM), X-Ray diffraction (XRD), and other particle analysis. The potential applications of AgNPs in a variety of biological and chemical fields are discussed.

Fabricating Antibacterial and Antioxidant Electrospun Hydrophilic Polyacrylonitrile Nanofibers Loaded with AgNPs by Lignin-Induced In-Situ Method

Concerning the environmental hazards owing to the chemical-based synthesis of silver nanoparticles (AgNPs), this study aimed to investigate the possibility of synthesizing AgNPs on the surface of polyacrylonitrile (PAN) nanofibers utilizing biomacromolecule lignin. SEM observations revealed that the average diameters of the produced nanofibers were slightly increased from ~512 nm to ~673 nm due to several factors like-swellings that happened during the salt treatment process, surface-bound lignin, and the presence of AgNPs. The presence of AgNPs was validated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. The amount of synthesized AgNPs on PAN nanofibers was found to be dependent on both precursor silver salt and reductant lignin concentration. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectra confirm the presence of lignin on PAN nanofibers. Although the X-ray diffraction pattern did not show any AgNPs band, the reduced intensity of the stabilized PAN characteristics bands at 2θ = 17.28° and 29.38° demonstrated some misalignment of PAN polymeric chains. The water contact angle (WCA) of hydrophobic PAN nanofibers was reduced from 112.6 ± 4.16° to 21.4 ± 5.03° for the maximum AgNPs coated specimen. The prepared membranes exhibited low thermal stability and good swelling capacity up to 20.1 ± 0.92 g/g and 18.05 ± 0.68 g/g in distilled water and 0.9 wt% NaCl solution, respectively. Coated lignin imparts antioxidant activity up to 78.37 ± 0.12% at 12 h of incubation. The resultant nanofibrous membranes showed a proportional increase in antibacterial efficacy with the rise in AgNPs loading against both Gram-positive S. aureus and Gram-negative E. coli bacterial strains by disc diffusion test (AATCC 147-1998). Halos for maximum AgNPs loading was calculated to 18.89 ± 0.15 mm for S. aureus and 21.38 ± 0.17 mm for E. coli. An initial burst release of silver elements within 24 h was observed in the inductively coupled plasma-atomic emission spectrometry (ICP-AES) test, and the release amounts were proportionally expansive with the increase in Ag contents. Our results demonstrated that such types of composite nanofibers have a strong potential to be used in biomedicine.

Green synthesis of silver nanoparticles using pollen extract: Characterization, assessment of their electrochemical and antioxidant activities

In the present study, a simple, cheaply and environmental friendly method was evaluated for the synthesis of silver nanoparticle via Cupressus sempervirens L. (CSPE) pollen extract as reducing and stabilizing agent. Various parameters such as volume of CSPE, temperature and reaction time on AgNPs formation were investigated spectrophotometrically to optimize reaction conditions. The electrochemical behavior of the biosynthesized AgNPs were investigated by cyclic voltammetry and square wave voltammetry techniques. An electrosensor based on AgNPs modified glassy carbon electrode were constructed and tested on electro reduction of hydrogen peroxide in phosphate buffer medium. The prepared electrosensor could detect the H₂O₂ in the range of 5.0 μM - 2.5 mM with a detection limit of 0.23 μM. In addition, the antioxidant activity of biosynthesized AgNPs were evaluated against DPPH free radical. Results obtained from the antioxidant study suggested that CSPE mediated AgNPs exhibit a good antioxidant effect.

Cytotoxic, Antimitotic, DNA Binding, Photocatalytic, H2O2 Sensing, and Antioxidant Properties of Biofabricated Silver Nanoparticles Using Leaf Extract of Bryophyllum pinnatum (Lam.) Oken

Bryophyllum pinnatum is a perennial herb traditionally used in ethnomedicine. In the present report, silver nanoparticles (AgNPs) were synthesized using B. pinnatum leaf extract. BP-AgNPs were confirmed following UV-Vis spectroscopy with SPR peak at 412 nm and further characterized by FTIR, XRD, SEM-EDX, and TEM. Microscopic images confirmed the spherical shape and ~15 nm average size of nanostructures. BP-AgNPs were evaluated for photocatalytic degradation of hazardous dyes (methylene blue and Rhodamine-B) and showed their complete reduction within 100 and 110 min., respectively. BP-AgNPs have emerged as a unique SPR-based novel sensor for the detection of H2O2, which may deliver exciting prospects in clinical and industrial areas. DPPH and ABTS free radical scavenging activity were studied with respective IC50 values of 89 and 259 μg/mL. A strong intercalating interaction of CT-DNA with BP-AgNPs was investigated. Observed chromosomal abnormalities confirm the antimitotic potential of BP-AgNPs in the meristematic root tip. The cytotoxicity of BP-AgNPs against B16F10 (melanoma cell line) and A431 (squamous cell carcinoma cell line), was assessed with respective IC50 values of 59.5 and 96.61 μg/ml after 24 h of treatment. The presented green synthetic approach provides a novel and new door for environmental, industrial, and biomedical applications.

Eco-friendly synthesis of lignin mediated silver nanoparticles as a selective sensor and their catalytic removal of aromatic toxic nitro compounds

The development of an eco-friendly and reliable process for the production of nanomaterials is essential to overcome the toxicity and exorbitant cost of conventional methods. As such, a facile and green synthesis method is introduced for the preparation of lignin mediated silver nanoparticles (L-Ag NPs). This is produced by reducing Ag precursors using lignin biopolymers which are formulated by pulsed laser irradiation and an ultrasonication process. Lignin operates as both a reducing and stabilizing agent. The various analytical techniques of ultraviolet-visible spectroscopy, transmission electron microscope and X-ray diffractometer studies were employed to verify the formation of non-aggregated spherical L-Ag NPs with an average size as small as 7-8 nm. The selective sensing capability of the synthesized L-Ag NPs was examined for the detection of hydrogen peroxide and mercury ions in an aqueous environment. Furthermore, the superior catalytic performance of L-Ag NPs was demonstrated by the rapid conversion of toxic 4-nitrophenol and nitrobenzene as targeted pollutants to the corresponding amino compounds. A plausible catalytic reduction mechanism for the removal of toxic nitro-organic pollutants over L-Ag NPs is proposed. This research coincides with existing studies and affirms that L-Ag NPs are an effective sensor that be applied as a catalytic material within environmental remediation and also alternative biomedical applications.

Lignin-mediated in-situ synthesis of CuO nanoparticles on cellulose nanofibers: A potential wound dressing material

Herein we present our research on the synthesis of CuO nanoparticles on the surface of electrospun cellulose (CE) nanofibers using alkali lignin as a reducing agent. Fascinatingly, CA nanofibers were deacetalized during alkali lignin treatment, which was verified by FTIR-ATR spectra. The morphology of the produced nanofibers was observed with SEM and TEM. The presence of CuO nanoparticles was verified by EDX, XRD, and XPS. The Cu/CE nanofibers showed low thermal stability. MVTR values of 2100-1900 g/m²/day are adequate for the transport of air and moisture from the wound surface. The Cu/CE showed faster release (80%) of copper ions to aqueous environment within 24 h and seemed to advance towards plateau for the next five days. The Cu/CE nanofibrous mats exhibited excellent antibacterial efficacy against both gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) bacteria. NIH3T3 fibroblast cells have excellent migrating and proliferating ability on our prepared nanofibrous mats. The presence of bound alkali lignin on the surface of nanofibers added a benefit of antioxidant activity. These findings revealed that such type of nanofibrous mats could be used as a potential wound dressing material.

Facile synthesis of easily separated and reusable silver nanoparticles/aminated alkaline lignin composite and its catalytic ability

Green synthesis of silver nanoparticles (AgNPs) has received increasing attention. In this study, AgNPs were prepared through in-situ reduction by aminated alkaline lignin (AAL). Compared with alkaline lignin (AL), AAL exhibited stronger reduction capacity (increased by 36%) due to the introduced amine groups and better water solubility. Moreover, the coordination effect of amine groups on AAL improved the binding force between lignin and AgNPs. The content of AgNPs in AgNPs/AAL composite were 2.4 times higher than that in AgNPs/AL, such content could be further increased through increasing the reduction pH or prolonging the heating time. The results of XPS, XRD and TEM showed that the AgNPs were spherical and monodisperse with an average particle size about 17 nm. Additionally, the size of AgNPs was affected by the amination degree of lignin. AgNPs/AAL exhibited good catalytic performance for the reduction of 4-nitrophenol to 4-aminophenol, and this compound could be easily recovered and reused for at least eight cycles.

Lignin from oil palm empty fruit bunches: Characterization, biological activities and application in green synthesis of silver nanoparticles

Lignin was extracted from oil palm empty fruit bunches under four different conditions. The lignin samples were characterized and employed in the green synthesis of silver nanoparticles. Two-dimensional HSQC NMR analysis showed that lignins extracted under more aggressive conditions (3.5% acid, 60 min) exhibited less signals and thus, presented a more degraded chemical structure. Additionally, those lignins obtained under harsh conditions (3.5% acid, 60 min) exhibited higher antioxidant capacity than those obtained under mild conditions (1.5% acid, 20 min). Formation of lignin-mediated silver nanoparticles was confirmed by color change during their synthesis. The surface plasmon resonance peaks (423-427 nm) in UV-visible spectra also confirmed the synthesis of AgNPs. AgNPs showed spherical shape, polycrystalline nature and average size between 18 and 20 nm. AgNPs, in suspension, presented a negative Zeta potential profile. Lignin was assumed to contribute in the antioxidant capacity exhibited by AgNPs. All AgNPs presented no significant differences on the disk diffusion antimicrobial susceptibility test against E. coli. The minimum inhibitory concentration of HAL3-L AgNPs (62.5 μg·mL^-1) was better than other physicochemically produced AgNPs (100 μg·mL^-1).

Very Strong, Super-Tough, Antibacterial, and Biodegradable Polymeric Materials with Excellent UV-Blocking Performance

In this work, inspired by the dynamic sacrificial hydrogen bonds in biological materials, a very strong, super-tough, antibacterial, and cost-effective biodegradable poly(vinyl alcohol) (PVA) nanocomposite material was developed by incorporating the nanoscale antibacterial agent TA@LS-Ag. TA@LS-Ag was prepared from the green biomass tannic acid (TA) and sodium lignosulfonate (LS), and was facilely incorporated into the PVA matrix with a homogeneously interspersed nanoparticle size of about 20 nm. The PVA nanocomposite film with 2 wt % addition of TA@LS-Ag achieved the highest specific toughness of 262 J g^-1 among the PVA-based films to date, which is far higher than that of natural spider silk (150-190 J g^-1 ), as well as a very high tensile strength of 131.6 MPa. The excellent tensile strength and superior toughness were attributed to synergy of the nanophase separation structure and the intense hydrogen-bonding interactions between the nanoparticles and PVA matrix. The PVA/TA@LS-Ag nanocomposite films exhibited good antibacterial properties, despite the extremely low silver content (0.032-0.32 wt ‰). TA@LS-Ag also endowed the PVA films with excellent antioxidant and UV-shielding performance. As the biomass-derived LS and TA and the PVA matrix are all biodegradable, this work offers a facile strategy for preparing high-performance antibacterial and biodegradable polymeric materials.

Lignin-Inorganic Interfaces: Chemistry and Applications from Adsorbents to Catalysts and Energy Storage Materials

Lignin is one the most fascinating natural polymers due to its complex aromatic-aliphatic structure. Phenolic hydroxyl and carboxyl groups along with other functional groups provide technical lignins with reactivity and amphiphilic character. Many different lignins have been used as functional agents to facilitate the synthesis and stabilization of inorganic materials. Herein, the use of lignin in the synthesis and chemistry of inorganic materials in selected applications with relevance to sustainable energy and environmental fields is reviewed. In essence, the combination of lignin and inorganic materials creates an interface between soft and hard materials. In many cases it is either this interface or the external lignin surface that provides functionality to the hybrid and composite materials. This Minireview closes with an overview on future directions for this research field that bridges inorganic and lignin materials for a more sustainable future.

Adsorption Characteristics of Ag Nanoparticles on Cellulose Nanofibrils with Different Chemical Compositions

The adsorption characteristics of silver nanoparticles (AgNPs) on cellulose nanofibrils (CNFs) were investigated herein with different chemical compositions. Pure cellulose nanofibers (PCNFs), lignocellulose nanofibers (LCNFs) with different lignin contents (LCNF-20% and LCNF-31%), and holocellulose nanofibers (HCNFs) with hemicellulose were used in this study. Furthermore, CNFs and silver nitrate were mixed and reacted at different temperatures, and NaBH4 was used as the reducing agent. First, the effect of temperature on the adsorption of AgNPs on PCNF was studied. At an optimal temperature (45 °C), the effect of the chemical composition of CNF was studied. The overall properties were analyzed using UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The AgNPs were found to be spherical under all conditions with average diameter of 5.3 nm (PCNF), 5.6 nm (HCNF), 6.3 nm (LCNF-20%) and 6.6 nm (LCNF-31%). The amount of AgNPs adsorbed on the CNF was observed to vary, based on the chemical composition of the CNF. The adsorption amount of AgNPs was observed to increase in the order of LCNF-20% > PCNF > LCNF-31% > HCNF. The results indicated that phenolic hydroxyl groups present in LCNF significantly affected the adsorption of AgNPs.

Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica

Using aqueous cyanobacterial extracts in the synthesis of silver nanoparticle is looked as green, ecofriendly, low priced biotechnology that gives advancement over both chemical and physical methods. In the current study, an aqueous extract of Oscillatoria limnetica fresh biomass was used for the green synthesis of Ag-NPs, since O. limnetica extract plays a dual part in both reducing and stabilizing Oscillatoria-silver nanoparticles (O-AgNPs). The UV-Visible absorption spectrum, Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were achieved for confirming and characterizing the biosynthesized O-AgNPs. TEM images detected the quasi-spherical Ag-NPs shape with diverse size ranged within 3.30-17.97 nm. FT-IR analysis demonstrated the presence of free amino groups in addition to sulfur containing amino acid derivatives acting as stabilizing agents as well as the presence of either sulfur or phosphorus functional groups which possibly attaches silver. In this study, synthesized Ag-NPs exhibited strong antibacterial activity against multidrug-resistant bacteria (Escherichia coli and Bacillus cereus) as well as cytotoxic effects against both human breast (MCF-7) cell line giving IC50 (6.147 µg/ml) and human colon cancer (HCT-116) cell line giving IC50 (5.369 µg/ml). Hemolytic activity of Ag-NPs was investigated and confirmed as being non- toxic to human RBCs in low concentrations.

Synthesis and characterization of silver nanoparticles loaded poly(vinyl alcohol)-lignin electrospun nanofibers and their antimicrobial activity

In the present study, poly(vinyl alcohol) (PVA) - Acacia lignin (PL) nanofiber mats loaded with silver nanoparticles were prepared and characterized. In-situ synthesis of silver nanoparticles was accomplished using alkali lignin extracted from Acacia wood as a reducing agent. Ultrafine nanofiber mats of PL incorporated with silver nanoparticles were fabricated using the electrospinning technique. The fiber morphology of the resultant nanofiber was characterized using scanning electron microscopy. The average diameter of the nanofiber was in the range of 100 to 300 nm. The existence of silver nanoparticles was confirmed by X-ray diffraction analysis. The influence of silver nanoparticles on the polymer structure was investigated by mechanical and thermal properties analysis. The antimicrobial activity of the PL nanofibers containing silver nanoparticles was tested against Bacillus circulans (MTCC 7906) and Escherichia coli (MTCC 739) and showed significant results against both microorganisms. The results revealed that PL nanofiber containing silver nanoparticles may have potential applications as membrane filtration, antimicrobial fabrics and wound dressing material.

Cytotoxicity of Plant-Mediated Synthesis of Metallic Nanoparticles: A Systematic Review

In the field of medicine, nanomaterials, especially those derived using the green method, offer promise as anti-cancer agents and drug carriers. However, the biosafety of metallic nanoparticles used as anti-cancer agents remains a concern. The goal of this systematic review was to compare the cytotoxicity of different plant-mediated syntheses of metallic nanoparticles based on their potency, therapeutic index, and cancer cell type susceptibility in the hopes of identifying the most promising anti-cancer agents. A literature search of electronic databases including Science Direct, PubMed, Springer Link, Google Scholar, and ResearchGate, was conducted to obtain research articles. Keywords such as biosynthesis, plant synthesis, plant-mediated, metallic nanoparticle, cytotoxicity, and anticancer were used in the literature search. All types of research materials that met the inclusion criteria were included in the study regardless of whether the results were positive, negative, or null. The therapeutic index was used as a safety measure for the studied compound of interest. Data from 76 selected articles were extracted and synthesised. Seventy-two studies reported that the cytotoxicity of plant-mediated synthesis of metallic nanoparticles was time and/or dose-dependent. Biosynthesised silver nanoparticles demonstrated higher cytotoxicity potency compared to gold nanoparticles synthesised by the same plants (Plumbago zeylanica, Commelina nudiflora, and Cassia auriculata) irrespective of the cancer cell type tested. This review also identified a correlation between the nanoparticle size and morphology with the potency of cytotoxicity. Cytotoxicity was found to be inversely proportional to nanoparticle size. The plant-mediated syntheses of metallic nanoparticles were predominantly spherical or quasi-spherical, with the median lethal dose of 1⁻20 µg/mL. Nanoparticles with other shapes (triangular, hexagonal, and rods) were less potent. Metallic nanoparticles synthesised by Abutilon inducum, Butea monosperma, Gossypium hirsutum, Indoneesiella echioides, and Melia azedarach were acceptably safe as anti-cancer agents, as they had a therapeutic index of >2.0 when tested on both cancer cells and normal human cells. Most plant-mediated syntheses of metallic nanoparticles were found to be cytotoxic, although some were non-cytotoxic. The results from this study suggest a focus on a selected list of potential anti-cancer agents for further investigations of their pharmacodynamic/toxicodynamic and pharmacokinetic/toxicokinetic actions with the goal of reducing the Global Burden of Diseases and the second leading cause of mortality.

In vivo antimicrobial activity of silver nanoparticles produced via a green chemistry synthesis using Acacia rigidula as a reducing and capping agent

Introduction

One of the main issues in the medical field and clinical practice is the development of novel and effective treatments against infections caused by antibiotic-resistant bacteria. One avenue that has been approached to develop effective antimicrobials is the use of silver nanoparticles (Ag-NPs), since they have been found to exhibit an efficient and wide spectrum of antimicrobial properties. Among the main drawbacks of using Ag-NPs are their potential cytotoxicity against eukaryotic cells and the latent environmental toxicity of their synthesis methods. Therefore, diverse green synthesis methods, which involve the use of environmentally friendly plant extracts as reductive and capping agents, have become attractive to synthesize Ag-NPs that exhibit antimicrobial effects against resistant bacteria at concentrations below toxicity thresholds for eukaryotic cells.

Purpose

In this study, we report a green one-pot synthesis method that uses Acacia rigidula extract as a reducing and capping agent, to produce Ag-NPs with applications as therapeutic agents to treat infections in vivo.

Materials and methods

The Ag-NPs were characterized using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive spectroscopy, ultraviolet–visible, and Fourier transform infrared.

Results

We show that Ag-NPs are spherical with a narrow size distribution. The Ag-NPs show antimicrobial activities in vitro against Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and a clinical multidrug-resistant strain of P. aeruginosa) and Gram-positive (Bacillus subtilis) bacteria. Moreover, antimicrobial effects of the Ag-NPs, against a resistant P. aeruginosa clinical strain, were tested in a murine skin infection model. The results demonstrate that the Ag-NPs reported in this work are capable of eradicating pathogenic resistant bacteria in an infection in vivo. In addition, skin, liver, and kidney damage profiles were monitored in the murine infection model, and the results demonstrate that Ag-NPs can be used safely as therapeutic agents in animal models.

Conclusion

Together, these results suggest the potential use of Ag-NPs, synthesized by green chemistry methods, as therapeutic agents against infections caused by resistant and nonresistant strains.

Adsorption of AgNO3 onto bamboo hemicelluloses in aqueous medium

An insight into the adsorption behavior between hemicellulose biomass and metal ions is important to utilize hemicelluloses as adsorbent. In this study, bamboo hemicelluloses were used as adsorbent for AgNO₃ in aqueous medium. The adsorption amount of AgNO₃ onto hemicelluloses was determined through an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The morphology and the elemental composition of the recovered hemicelluloses were characterized using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) techniques, respectively. The filtrate after removing undissolved hemicelluloses was analyzed by ultraviolet-visible spectroscopy (UV-vis). Results demonstrated that the obtained highest adsorption amount of AgNO₃ onto hemicelluloses was 42.82 mg/g under the conditions discussed. Some Ag⁺ was in situ reduced by hemicelluloses to form silver nanoparticles. Ag⁺ and the formed silver nanoparticles possibly destroyed the hydrogen-bonding network of hemicelluloses, resulting in the stretch of molecules and formed rod-like agglomerates with irregular length. Even an agglomerate with the length of 420 nm was found. The side chains and the newly formed carboxyl groups through oxidation of hemicelluloses by silver ions removed away from the hemicelluloses during adsorption. A part of Ag⁺ and silver nanoparticles were adsorbed on the unresolved hemicelluloses, and the other part was dispersed in the aqueous solution.

Biocompatibility and photo-induced antibacterial activity of lignin-stabilized noble metal nanoparticles

One-pot thermal and photochemical syntheses of lignin-doped silver and gold nanoparticles were developed and their antimicrobial properties were studied against Escherichia coli and Staphylococcus aureus. The nature of the lignin as well as the metal are directly involved in the antimicrobial activity observed in these nanocomposites. Whereas one of the nanocomposites is innocuous under dark conditions and shows photoinduced activity only against Staphylococcus aureus, the rest of the lignin-coated silver nanoparticles studied show antimicrobial activity under dark and light conditions for both bacteria strains. Additionally, only photoinduced activity is observed for lignin-coated gold nanoparticles. Importantly, the particles are non-cytotoxic towards human cells at the bactericidal concentrations. Preliminary assays show these silver nanoparticles as potential antimicrobial agents towards S. aureus biofilm eradication.

Natural derived compounds, lignins, can be used as reducing and stabilizing agents to synthesize noble metal nanoparticles with antimicrobial properties.

Sasa borealis leaf extract-mediated green synthesis of silver–silver chloride nanoparticles and their antibacterial and anticancer activities

Ecofriendly procedure for silver–silver chloride nanoparticle synthesis with different reaction parameters tested.

Orthopedic application of spikenard herbal rhizome decorated microstructured polymer biocomposites and their in vitro cytotoxicity

The present study explores the synthesis of highly potential polymer biocomposite from Nardostachys jatamansi rhizome extract. The polymer biocomposites were synthesized from methyl methacrylate by free radical polymerization. ATR-IR enunciate the functional groups attributed at 956 cm-1 (aromatic), a peak appeared at 1685 cm-1 (-C[bond, double bond]O), 1186 cm-1 (-O-CH3), 1149 cm-1 (-C-O-C) framework and 1279 cm-1 (-C-O), which are good agreement for the formation composites. The quantitative evaluations of antimicrobial studies were analyzed by serial dilution method and also improved activity in orthopedic infection pathogens. Cytocompatibility was analyzed by keratinocyte cell lines and it may be used for various biomedical applications.