Antibacterial activity of silver nanoparticles synthesized In-situ by solution spraying onto cellulose

Exploring the Potential of Halotolerant Actinomycetes from Rann of Kutch, India: A Study on the Synthesis, Characterization, and Biomedical Applications of Silver Nanoparticles

A tremendous increase in the green synthesis of metallic nanoparticles has been noticed in the last decades, which is due to their unique properties at the nano dimension. The present research work deals with synthesis mediated by the actinomycete Streptomyces tendae of silver nanoparticles (AgNPs), isolated from Little and Greater Rann of Kutch, India. The confirmation of the formation of AgNPs by the actinomycetes was carried out by using a UV-Vis spectrophotometer where an absorbance peak was obtained at 420 nm. The X-ray diffraction pattern demonstrated five characteristic diffraction peaks indexed at the lattice plane (111), (200), (231), (222), and (220). Fourier transform infrared showed typical bands at 531 to 1635, 2111, and 3328 cm-1. Scanning electron microscopy shows that the spherical-shaped AgNPs particles have diameters in the range of 40 to 90 nm. The particle size analysis displayed the mean particle size of AgNPs in aqueous medium, which was about 55 nm (±27 nm), bearing a negative charge on their surfaces. The potential of the S. tendae-mediated synthesized AgNPs was evaluated for their antimicrobial, anti-methicillin-resistant Staphylococcus aureus (MRSA), anti-biofilm, and anti-oxidant activity. The maximum inhibitory effect was observed against Pseudomonas aeruginosa at (8 µg/mL), followed by Escherichia coli and Aspergillus niger at (32 µg/mL), and against Candida albicans (64 µg/mL), whereas Bacillus subtilis (128 µg/mL) and Staphylococcus aureus (256 µg/mL) were much less sensitive to AgNPs. The biosynthesized AgNPs displayed activity against MRSA, and the free radical scavenging activity was observed with an increase in the dosage of AgNPs from 25 to 200 µg/mL. AgNPs in combination with ampicillin displayed inhibition of the development of biofilm in Pseudomonas aeruginosa and Streptococcus pneumoniae at 98% and 83%, respectively. AgNPs were also successfully coated on the surface of cotton to prepare antimicrobial surgical cotton, which demonstrated inhibitory action against Bacillus subtilis (15 mm) and Escherichia coli (12 mm). The present research integrates microbiology, nanotechnology, and biomedical science to formulate environmentally friendly antimicrobial materials using halotolerant actinomycetes, evolving green nanotechnology in the biomedical field. Moreover, this study broadens the understanding of halotolerant actinomycetes and their potential and opens possibilities for formulating new antimicrobial products and therapies.

Traditional Chinese medicine polysaccharide in nano-drug delivery systems: Current progress and future perspectives

Traditional Chinese medicine polysaccharides (TCMPs) have gained increasing attention in the field of nanomedicine due to their diverse biological activities and favorable characteristics as drug carriers, including biocompatibility, biodegradability, safety, and ease of modification. TCMPs-based nano-drug delivery systems (NDDSs) offer several advantages, such as evasion of reticuloendothelial system (RES) phagocytosis, protection against biomolecule degradation, enhanced drug bioavailability, and potent therapeutic effects. Therefore, a comprehensive review of the latest developments in TCMPs-based NDDSs and their applications in disease therapy is of great significance. This review provides an overview of the structural characteristics and biological activities of TCMPs relevant to carrier design, the strategies employed for constructing TCMPs-based NDDSs, and the versatile role of TCMPs in these systems. Additionally, current challenges and future prospects of TCMPs in NDDSs are discussed, aiming to provide valuable insights for future research and clinical translation.

Antidiabetic potential of Gymnemic acid mediated gold nanoparticles (Gym@AuNPs) on Streptozotocin-induced diabetic rats-An implication on in vivo approach

Gymnemic acid is glycosides of triterpene with recognized and valuable applications for several chronic diseases, mainly diabetics. Despite this, it requires a delivery system in order to range its therapeutic target due to its limited solubility and bioavailability. Therefore, the Gymnemic acid mediated gold nanoparticles (Gym@AuNPs) was synthesised by eco-friendly approach. The synthesised Gym@AuNPs was confirmed by the colour change from light yellow to a deep ruby red. UV - visible spectroscopy results showed a strong narrow peak at 530 nm, confirming the controlled synthesis of monodispersed Gym@AuNPs. The reduction potential of standard Gymnemic acid (Gym) on synthesis of Gym@AuNPs was confirmed by using HPLC analysis. The spherical shaped Gym@AuNPs was observed by FESEM and HR-TEM studies with average size of 48.52 ± 5.53 nm. The XRD analysis exhibited a face-centered cubic (FCC) crystalline nature of Gym@AuNPs. The in vivo antidiabetic activity of Gym and Gym@AuNPs were validated using Streptozotocin induced diabetic Albino wistar rats. The Gym@AuNPs and Gym were regulates the glucose and lipid levels in experimental animals. The histopathology outcomes shown that the Gym@AuNPs were restoration of pancreatic islets cells in the animals. This investigation demonstrated that the Gym@AuNPs had the potential anti-diabetic properties.

Biogenic Synthesis of Silver Nanoparticles Using Pantoea stewartii and Priestia aryabhattai and Their Antimicrobial, Larvicidal, Histopathological, and Biotoxicity Potential

In recent years, green nanotechnology has gained considerable importance for the synthesis of nanoparticles due to its economic viability and biosafety. In the current study, silver nanoparticles were synthesized using two bacterial isolates, H2 and H3, which were isolated from soil samples collected from the Western Ghats, Tamil Nadu, and identified at the species level as Pantoeastewartii (H2) and Priestiaaryabhattai (H3) by sequencing their 16s rRNA genes. Intracellularly synthesized silver nanoparticles were characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and particle size analysis. AFM studies show that both of the bacterial synthesized Ag NPs were circular-shaped and disaggregated, with an average size distribution of 4 nm for Pantoeastewartii and 3.6 nm for Priestiaaryabhattai. Furthermore, their larvicidal activity, antimicrobial, histopathological, and biotoxicity effects were determined. The synthesized Ag NPs exhibited potent larvicidal activity against fourth instars of Ae.aegypti, An.stephensi, and Cx.quinquefasciatus exposed to a 50 µg/mL concentration for 24 h based on their LC₅₀ and LC₉₀ values. Histopathological studies of the affected mosquito larvae clearly show damage to the epithelial cells, food bolus, basement membrane, muscles, and midgut parts. The maximum antimicrobial activity of Priestiaaryabhattai-synthesized Ag NPs was observed for Streptomyces varsoviensis MTCC-1537, and that of Pantoea stewartii-synthesized Ag NPs was against Escherichia coli MTCC-43. The toxicity test on non-target organisms such as Artemia nauplii and zebrafish embryos indicates no visible abnormalities or mortality after their exposure for 48h. It is concluded that silver nanoparticles can easily be synthesized using Pantoea stewartii (H2) and Priestia aryabhattai (H3) as capping and reducing agents. Silver nanoparticles showed potent larvicidal activities and could potentially be used in integrated vector control programs because they are safe for other inhabitants of the same aquatic environment as mosquito larvae.

Preparation of SERS active filter paper for filtration and detection of pesticides residue from complex sample

The selectivity is needed mostly in SERS sensing because analytes of interest are commonly present in a complex mixture containing particles and impurities, which hinder the interactions between the laser and analyte being detected. In this manuscript, we describe our efforts developing a simple and instant. method to prepare a filter paper SERS sensor. Colloidal Ag nanoparticles were immobilized on one side of filter paper via an in-situ growth method. The fabrication process of the sensor could be finished in several minutes, and no special facility needed. The filter paper SERS sensor demonstrated a spectra uniformity with a 7.0 % point-by-point signal deviation. And the filter function of the sensor could effectively filter out interferences from samples in 1 min, that allowing the direct detection of thiram in ketchup by SERS with detection limit of 93 ppb. Furthermore, we used a Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method to detect malachite green (MG) in soil with a sensitivity as low as 0.01 ppm without any sample pre-treatment or purification. A SERS filter paper may open a new avenue for rapid testing of food quality during manufacturing as well as fast detection of potential contaminants in a myriad of substrates.

Functionalization of cotton fabrics with titanium oxide doped silver nanoparticles: Antimicrobial and UV protection activities

The target of our current work was designed to prepare titanium oxide doped silver nanoparticles (Ag/TiO₂ NPs) and their impact on the functionalization of cotton fabrics. Additionally, the effect of Ag/TiO₂ NPs was compared with the individually prepared silver nanoparticles (AgNPs) and titanium oxide nanoparticles (TiO₂ NPs). In this work, AgNPs was prepared in its solid state using Arabic gum as efficient stabilizing and reducing agent. Then, two concentrations of the as-synthesized nanoparticles were used for functionalize the cotton fabrics by pad-dry-cure treatment in the presence of fixing agent to increase the durability of treated cotton fabrics against vigorous washing cycles. The finding implied that the prepared nanoparticles were successfully synthesized in nano-size with spherical shape and homogeneity. The efficacy of the functionalized cotton fabrics with those nanoparticles were evaluated in terms of multifunctional properties including antimicrobial and UV Protection Factor (UPF) and the mechanical features before and after many washing cycles; 10, 15 and 20 times. The resultant also proved that Ag/TiO₂ NPs-treated cotton fabrics exhibited the greater values of both antimicrobial and UPF properties with enhancement in the tensile strength and elongation features. Thus, the combination between these two nanoparticles through doping reaction is suitable for imparting superior antimicrobial properties against the four tested microbial species (S. aureus, E. coli, C. albicans, and A. niger) and good UPF properties.

Effects of NanoAg-ACP Microparticles as Bioactive Fillers on the Mechanical and Remineralization Properties of Dental Resin Cement

PURPOSE

To investigate the potential of adding silver-nanoparticle-containing amorphous calcium phosphate microparticles as bioactive fillers into commercially available non-bioactive dental resin cement.

MATERIALS AND METHODS

Experimental cement was formulated by adding 7.5% silver-nanoparticle-containing amorphous calcium phosphate microparticles to Multilink Automix resin cement (Ivoclar Vivadent). The experimental cement was evaluated for shear bond strength (N=11 per group) and demineralization/remineralization (N=16 per group), with BioCem^® Universal BioActive cement (NuSmile) as the positive control and Multilink Automix cement as the negative control. One-way analysis of variance and post hoc tests were used to assess the significance of differences among or between the groups RESULTS: : The addition of silver-nanoparticle-containing amorphous calcium phosphate microparticles at the level of 7.5% by weight into Multilink Automix did not have a statistically significant effect on the shear bond strength (p>0.05), but statistically significantly increased the depth of remineralization on both dentin and enamel (p=0.01 and p<0.001, respectively.) when compared to Multilink Automix alone. The experimental cement prepared in the present study was comparable to BioCem^® on the depths of remineralization on both dentin and enamel (p=0.59 and p=0.99, respectively).

CONCLUSION

When incorporated into non-bioactive commercial dental resin cements as bioactive fillers at the level of 7.5% by weight, silver-nanoparticle-containing amorphous calcium phosphate microparticles could provide remineralization potential without affecting the shear bond strength. This article is protected by copyright. All rights reserved.

Recent Advancements in Microbial Polysaccharides: Synthesis and Applications

Polysaccharide materials are widely applied in different applications including food, food packaging, drug delivery, tissue engineering, wound dressing, wastewater treatment, and bioremediation sectors. They were used in these domains due to their efficient, cost-effective, non-toxicity, biocompatibility, and biodegradability. As is known, polysaccharides can be synthesized by different simple, facile, and effective methods. Of these polysaccharides are cellulose, Arabic gum, sodium alginate, chitosan, chitin, curdlan, dextran, pectin, xanthan, pullulan, and so on. In this current article review, we focused on discussing the synthesis and potential applications of microbial polysaccharides. The biosynthesis of polysaccharides from microbial sources has been considered. Moreover, the utilization of molecular biology tools to modify the structure of polysaccharides has been covered. Such polysaccharides provide potential characteristics to transfer toxic compounds and decrease their resilience to the soil. Genetically modified microorganisms not only improve yield of polysaccharides, but also allow economically efficient production. With the rapid advancement of science and medicine, biosynthesis of polysaccharides research has become increasingly important. Synthetic biology approaches can play a critical role in developing polysaccharides in simple and facile ways. In addition, potential applications of microbial polysaccharides in different fields with a particular focus on food applications have been assessed.

Phytoproduct, Arabic Gum and Opophytum forsskalii Seeds for Bio-Fabrication of Silver Nanoparticles: Antimicrobial and Cytotoxic Capabilities

The application of biological materials in synthesizing nanoparticles has become significant issue in nanotechnology. This research was designed to assess biogenic silver nanoparticles (AgNPs) fabricated using two aqueous extracts of Acacia arabica (Arabic Gum) (A-AgNPs) and Opophytum forsskalii (Samh) seed (O-AgNPs), which were used as reducing and capping agents in the NPs development, respectively. The current study is considered as the first report for AgNP preparation using Opophytum forsskalii extract. The dynamic light scattering, transmission electron microscopy, and scanning electron microscopy were employed to analyze the size and morphology of the biogenic AgNPs. Fourier transform infrared (FTIR) spectroscopy and chromatography/mass spectrometry (GC-MS) techniques were used to identify the possible phyto-components of plant extracts. The phyto-fabricated NPs were assessed for their antibacterial activity and also when combined with some antibiotics against Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa and Escherichia coli (Gram-negative) and their anticandidal ability against Candida albicans using an agar well diffusion test. Furthermore, cytotoxicity against LoVo cancer cell lines was studied. The results demonstrated the capability of the investigated plant extracts to change Ag+ ions into spherical AgNPs with average size diameters of 91 nm for the prepared O-AgNPs and 75 nm for A-AgNPs. The phyto-fabricated AgNPs presented substantial antimicrobial capabilities with a zone diameter in the range of 10-29.3 mm. Synergistic effects against all tested strains were observed when the antibiotic and phyto-fabricated AgNPs were combined and assessed. The IC50 of the fabricated O-AgNPs against LoVo cancer cell lines was 28.32 μg/mL. Ten and four chemical components were identified in Acacia arabica (Arabic Gum) and Opophytum forsskalii seed extracts, respectively, by GC-MS that are expected as NPs reducing and capping agents. Current results could lead to options for further research, such as investigating the internal mechanism of AgNPs in bacteria, Candida spp., and LoVo cancer cell lines as well as identifying specific molecules with a substantial impact as metal-reducing agents and biological activities.

Green synthesis of antibacterial and cytotoxic silver nanoparticles by Piper nigrum seed extract and development of antibacterial silver based chitosan nanocomposite

In the present study, we have used seed extract of P. nigrum as an effective reducing agent for the synthesis of silver nanoparticles (Ag NPs) and silver based chitosan nanocomposite (Ag/CS NC). The silver nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR). The appearance of a surface plasmon resonance (SPR) peak located at 430 nm reveals the formation of silver nanoparticles. The TEM analysis indicates that the attained silver nanoparticles were mostly in spherical shapes with sizes ranging between 15 and 38 nm. The high resolution liquid chromatography with mass spectroscopy (HR-LCMS) analysis was performed to screen the phytochemical constituents of P. nigrum seed extract. The silver nanoparticles synthesized by P. nigrum seed extract exhibited effective antibacterial activity against Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli). In addition, the silver nanoparticles showed potent cytotoxicity against hazardous human cancer cell lines MDA-MB-231, PANC-1, SKOV-3, PC-3 and Hela. The observation of bright spots in the TEM dark field images represents the presence of Ag in CS suspension. Besides, the Ag/CS NC coated cotton fabric substantially showed remarkable antibacterial activity against B. subtilis and E. coli.

A sandwich structure composite wound dressing with firmly anchored silver nanoparticles for severe burn wound healing in a porcine model

Wounds may remain open for a few weeks in severe burns, which provide an entry point for pathogens and microorganisms invading. Thus, wound dressings with long-term antimicrobial activity are crucial for severe burn wound healing. Here, a sandwich structure composite wound dressing anchored with silver nanoparticles (AgNPs) was developed for severe burn wound healing. AgNPs were in situ synthesized on the fibers of chitosan nonwoven fabric (CSNWF) as the interlayer of wound dressing for sustained release of silver ion. The firmly anchored AgNPs could prevent its entry into the body, thereby eliminating the toxicity of nanomaterials. The outer layer was a polyurethane membrane, which has a nanoporous structure that could maintain free transmission of water vapor. Chitosan/collagen sponge was selected as the inner layer because of its excellent biocompatibility and biodegradability. The presence of AgNPs in the CSNWF was fully characterized, and the high antibacterial activity of CSNWF/AgNPs was confirmed by against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The superior wound healing effect on deep dermal burns of presented composite wound dressing was demonstrated in a porcine model. Our finding suggested that the prepared AgNPs doped sandwich structure composite wound dressing has great potential application in severe wound care.

One-Pot Reducing Agent-Free Synthesis of Silver Nanoparticles/Nitrocellulose Composite Surface Coating with Antimicrobial and Antibiofilm Activities

Nitrocellulose with silver nanoparticle (AgNP/NC) composite was prepared in situ using Ag(CH₃CO₂) and nitrocellulose without any reducing agent. The composite materials synthesized were spray coated onto glass substrates to obtain thin films. The AgNPs/NC composites were characterized by ultraviolet-visible, Fourier transform infrared, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The antimicrobial activity of AgNPs/NC composite was investigated by tube method and time-kill kinetic studies against three microbial species, including Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923), and Candida albicans (ATCC 10231). The antibiofilm activities were qualitatively determined against all three organisms. Prepared AgNPs/NC films exhibited good antimicrobial activity and significant inhibition of biofilm development against all three microbial species. The effective dispersion of AgNPs/NC in biofilm was responsible for the significant antibiofilm activity of the prepared material. The reported AgNPs/NC composite can be used as coating additive in bacteriocidal paint which can be applied onto surfaces such as in healthcare environments.

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

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

Diatom Bio-Silica and Cellulose Nanofibril for Bio-Triboelectric Nanogenerators and Self-Powered Breath Monitoring Masks

The application of biodegradable and biocompatible materials to triboelectric nanogenerators (TENGs) for harvesting energy from motions of the human body has been attracting significant research interest. Herein, we report diatom bio-silica as a biomaterial additive to enhance the output performance of cellulose nanofibril (CNF)-based TENGs. Diatom frustules (DFs), which are tribopositive bio-silica having hierarchically porous three-dimensional structures and high surface area, have hydrogen bonds with CNFs, resulting in enhanced electron-donating capability and a more roughened surface of the DF-CNF composite film. Hence, DFs were applied to form a tribopositive composite film with CNFs. The DF-CNF biocomposite film is mechanically strong, electron-rich, low-cost, and frictionally rough. The DF-CNF TENG showed an output voltage of 388 V and time-averaged power of 85.5 mW/m² in the contact-separation mode with an efficient contact area of 4.9 cm², and the generated power was sufficient for instantaneous illumination of 102 light-emitting diodes. In addition, a cytotoxicity study and biocompatibility tests on rabbit skin suggested that the DF-CNF composite was biologically safe. Moreover, a practical application of the DF-CNF TENG was examined with a self-powered smart mask for human breathing monitoring. This study not only suggests high output performance of biomaterial-based TENGs but also presents the diverse advantages of the DFs in human body-related applications such as self-powered health monitoring masks, skin-attachable power generators, and tactile feedback systems.

Microbial Mediated Synthesis of Silver Nanoparticles by Lactobacillus Plantarum TA4 and its Antibacterial and Antioxidant Activity

The present study aimed to investigate the ability of Lactobacillus plantarum TA4 in tolerating Ag+ and its ability to produce silver nanoparticles (AgNPs). The biosynthesized AgNPs were characterized using UV–Visible spectroscopy (UV–Vis), dynamic light scattering (DLS), Fourier-transform infrared (FTIR), and high-resolution transmission electron microscope (HR-TEM). The cell biomass of L. plantarum TA4 demonstrated the ability to tolerate Ag+ at a concentration of 2 mM, followed by the formation of AgNPs. This was confirmed by the visual observation of color changes and a presence of maximum UV–Vis absorption centered at 429 nm. HR-TEM analysis revealed that the AgNPs were spherical with an average size of 14.0 ± 4.7 nm, while the SEM-EDX analysis detected that the particles were primarily located on the cell membrane of L. plantarum TA4. Further, DLS analysis revealed that the polydispersity index (PDI) value of biosynthesized AgNPs was 0.193, implying the monodispersed characteristic of NPs. Meanwhile, the FTIR study confirmed the involvement of functional groups from the cell biomass that involved in the reduction process. Moreover, biosynthesized AgNPs exhibited antibacterial activity against Gram-positive and Gram-negative pathogens in a concentration-dependent manner. Furthermore, the antioxidant property of biosynthesized AgNPs that was evaluated using the DPPH assay showed considerable antioxidant potential. Results from this study provide a sustainable and inexpensive method for the production of AgNPs.

Green synthesis, characterization, antimicrobial and cytotoxic effect of silver nanoparticles using arabinoxylan isolated from Kalmegh

A green synthesis of silver nanoparticles was synthesized by AgNO₃ with arabinoxylan, isolated from green stem of Andrographis paniculata (Kalmegh). The synthesized Ag NPs-arabinoxylan conjugates were characterized by UV-vis spectroscopy, FE-SEM, TEM, XRD, TGA, EDX, and Zeta potential experiments. The Ag NPs formation was established by the surface plasmon resonance band ~410.25 nm. SEM image showed mostly spherical morphology of Ag NPs. The fcc crystalline nature was identified by XRD, SAED and the size were 24.5 and 25 nm from TEM and XRD analysis respectively. The prepared Ag NPs showed dose-dependent antimicrobial activity against Streptococcus pneumonia, Candida albicans and E. coli. The nanoparciles damage 4% hemolysis to human RBCs at 12.5 μg/mL. MTT assay of Ag NPs showed that half of the cell killed at 10 μg/mL and wound healing assay observed effective inhibition cell proliferation.

Effect of the type of reducing agents of silver ions in interpolyelectrolyte-metal complexes on the structure, morphology and properties of silver-containing nanocomposites

The objective of this work is to study the peculiarities of structural organization, morphology, thermomechanical, electrical and antimicrobial properties of nanocomposites based on pectin-polyethyleneimine interpolyelectrolyte complexes and silver nanoparticles in dependence on the type of reducing agent being applied for chemical reduction of silver ions in the interpolyelectrolyte-metal complexes. The average size of Ag nanoparticles is shown to be increased with decreasing of the activity of reducing agent (E₀) and equals to 3.8 nm, 4.3 nm, and 15.8 nm, respectively, when engaging sodium borohydride (-1.24 V), hydrazine (-1.15 V) and ascorbic acid (-0.35 V). Moreover, it was found that the crystallite size of Ag nanoparticles also had the smallest value for nanocomposites obtained involving NaBH₄ as reducing agent. Ag-containing nanocomposites prepared by reduction of silver ions in interpolyelectrolyte-metal complexes while applying a range of reducing agents are characterized by different electrical properties and polymer matrix' glass transition temperature. The influence of silver nanoparticles' size incorporated in the polymer matrix on the antimicrobial activity of nanocomposites has been established. The inhibition zone diameter of Staphylococcus aureus and Escherichia coli was higher for nanocomposites obtained using sodium borohydride and hydrazine compared to nanocomposites where ascorbic acid was used as the reducing agent.

Resistance of Gram-Negative Bacteria to Current Antibacterial Agents and Approaches to Resolve It

Antimicrobial resistance represents an enormous global health crisis and one of the most serious threats humans face today. Some bacterial strains have acquired resistance to nearly all antibiotics. Therefore, new antibacterial agents are crucially needed to overcome resistant bacteria. In 2017, the World Health Organization (WHO) has published a list of antibiotic-resistant priority pathogens, pathogens which present a great threat to humans and to which new antibiotics are urgently needed the list is categorized according to the urgency of need for new antibiotics as critical, high, and medium priority, in order to guide and promote research and development of new antibiotics. The majority of the WHO list is Gram-negative bacterial pathogens. Due to their distinctive structure, Gram-negative bacteria are more resistant than Gram-positive bacteria, and cause significant morbidity and mortality worldwide. Several strategies have been reported to fight and control resistant Gram-negative bacteria, like the development of antimicrobial auxiliary agents, structural modification of existing antibiotics, and research into and the study of chemical structures with new mechanisms of action and novel targets that resistant bacteria are sensitive to. Research efforts have been made to meet the urgent need for new treatments; some have succeeded to yield activity against resistant Gram-negative bacteria by deactivating the mechanism of resistance, like the action of the β-lactamase Inhibitor antibiotic adjuvants. Another promising trend was by referring to nature to develop naturally derived agents with antibacterial activity on novel targets, agents such as bacteriophages, DCAP(2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2(hydroxymethyl)propane1,3-diol, Odilorhabdins (ODLs), peptidic benzimidazoles, quorum sensing (QS) inhibitors, and metal-based antibacterial agents.

Antibacterial application of natural and carboxymethylated cashew gum-based silver nanoparticles produced by microwave-assisted synthesis

This study presents a green synthesis route to silver nanoparticles (AgNPs) stabilized with cashew gum (CG) or carboxymethylated cashew gum (CCG) using microwave-assisted synthesis and evaluates their antibacterial activity. The antimicrobial activity was measured by determining the minimum inhibitory concentration (MIC) with Staphylococcus aureus and Escherichia coli. In both cases of the presence of CG and CCG, it was found that higher pH lead to more efficient conversion of silver nitrate to AgNPs with well dispersed, spherical and stable particles as well as low crystallinity. CCG-capped AgNPs were slightly smaller (137.0 and 96.3 nm) than those coated with non-modified gum (144.7 and 100.9 nm). The samples presented promising antibacterial activity, especially on Gram-negative bacteria, resulting in significant membrane damage on treated bacteria in comparison to the untreated control, observed by atomic force microscopy. Thus, a quick and efficient synthesis route was applied to produce CGAgNPs and CCGAgNPs with antimicrobial potential.

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.

In situ synthesis of poly (γ- glutamic acid)/alginate/AgNP composite microspheres with antibacterial and hemostatic properties

In the present work, a poly(γ-glutamic acid)/alginate/silver nanoparticle (PGA/Alg/AgNP) composite microsphere with excellent antibacterial and hemostatic properties was prepared by the in situ UV reduction and emulsion internal gelation method, and its potential application for antibacterial hemostatic dressing was explored. Well dispersed AgNPs were in situ synthesized by a UV reduction method with alginate as stabilizer and reductant. The AgNPs showed excellent antibacterial activities against both gram-negative and gram-positive bacteria. Additionally, the AgNPs prepared by the in-situ UV reduction exhibited better biocompatibility and antibacterial effects than those prepared by the conventional chemical reduction method. PGA/Alg/AgNP composite microspheres were then prepared with the AgNPs by an emulsion internal gelation method. Such microspheres were found to be a porous and hollow network with pH-sensitive swelling properties and excellent hemostatic performance, indicating its application potentials as an advanced antibacterial hemostatic material.

Multifunctional nanocellulose/metal and metal oxide nanoparticle hybrid nanomaterials

Nanocellulose materials are derived from cellulose, the most abundant biopolymer on the earth. Nanocellulose have been extensively used in the field of food packaging materials, wastewater treatment, drug delivery, tissue engineering, hydrogels, aerogels, sensors, pharmaceuticals, and electronic sectors due to their unique chemical structure and excellent mechanical properties. On the other hand, metal and metal oxide nanoparticles (NP) such as Ag NP, ZnO NP, CuO NP, and Fe₃O₄ NP have a variety of functional properties such as UV-barrier, antimicrobial, and magnetic properties. Recently, nanocelluloses materials have been used as a green template for producing metal or metal oxide nanoparticles. As a result, multifunctional nanocellulose/metal or metal oxide hybrid nanomaterials with high antibacterial properties, ultraviolet barrier properties, and mechanical properties were prepared. This review emphasized recent information on the synthesis, properties, and potential applications of multifunctional nanocellulose-based hybrid nanomaterials with metal or metal oxides such as Ag NP, ZnO NP, CuO NP, and Fe₃O₄ NP. The nanocellulose-based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics.

Assessment of silver nanoparticles decorated starch and commercial zinc nanoparticles with respect to their genotoxicity on onion

High throughput production of silver nanoparticles (AgNPs) having controlled size appropriate for industrial purposes were achieved via using facile and ecofriendly chemical reduction method. Native rice starch was used as reductant for silver ions (Ag⁺) to silver atoms (Ag⁰), as well as stabilizing for the obtainable AgNPs. Two different concentrations; 2000 ppm and 4000 ppm were successfully prepared and coded as AgNPs-2000 and AgNPs-4000 respectively. The attained AgNPs were characterized via ultra-visible (UV-vis) spectra, Transmission Electron Microscope (TEM), Energy dispersive X-ray (EDX), Particle size analyzer, polydispersity index (PDI) and zeta potential (ζ-potential). The average particle size of AgNPs (2000 ppm) was 8 nm with PDI = 0.01 which affirm the monodispersity and homogeneity of the produced AgNPs. Meanwhile, the size majority for the as prepared AgNPs (4000 ppm) was 24 nm with PDI = 0.021. Based on the aforementioned data, AgNPs prepared with a high concentration (4000 ppm) compared with the commercialized ZnNPs were used for the genotoxicity study on onion. Root-tips was used for cytogenetic studies using onion (Allium cepa L.) which are excellent materials for cytological and genotoxicity studies. Genotoxicity results explored that, by using AgNPs ≥40 ppm, the abnormalities disturbed chromosomes were observed and detected, that reflects the genotoxicity effect of these nanoparticles at this dose. In addition, the commercial available ZnNPs with the recommended dose (2 g/L) displayed also severe genotoxicity on A. cepa L. root meristem cells.

Applications of cellulose and chitin/chitosan derivatives and composites as antibacterial materials: current state and perspectives

The bacterial infections have always a serious problem to public health. Scientists are developing new antibacterial materials to overcome this problem. Polysaccharides are promising biopolymers due to their diverse biological functions, low toxicity, and high biodegradability. Chitin and chitosan have antibacterial properties due to their cationic nature, while cellulose/bacterial cellulose does not possess any antibacterial activity. Moreover, the insolubility of chitin in common solvents, the poor solubility of chitosan in water, and the low mechanical properties of chitosan have restricted their biomedical applications. In order to solve these problems, chemical modifications such as quaternization, carboxymethylation, cationization, or surface modification of these polymers with different antimicrobial agents, including metal and metal oxide nanoparticles, are carried out to obtain new materials with improved physiochemical and biological properties. This mini review describes the recent progress in such derivatives and composites with potential antibacterial applications.

Bismuth Phosphinates in Bi-Nanocellulose Composites and their Efficacy towards Multi-Drug Resistant Bacteria

A series of poorly soluble phenyl bis-phosphinato bismuth(III) complexes [BiPh(OP(=O)R¹ R² )₂ ] (R¹ =R² =Ph; R¹ =R² =p-OMePh; R¹ =R² =m-NO₂ Ph; R¹ =Ph, R² =H; R¹ =R² =Me) have been synthesised and characterised, and shown to have effective antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The bismuth complexes were incorporated into microfibrillated (nano-) cellulose generating a bismuth-cellulose composite as paper sheets. Antibacterial evaluation indicates that the Bi-cellulose materials have analogous or greater activity against Gram positive bacteria when compared with commercial silver based additives: silver sulfadiazine loaded at 0.43 wt % into nanocellulose produces a 10 mm zone of inhibition on the surface of agar plates containing S. aureus whereas [BiPh(OP(=O)Ph₂ )₂ ] loaded at 0.34 wt % produces an 18 mm zone of inhibition. These phenyl bis-phosphinato bismuth(III) complexes show potential to be applied in materials in healthcare facilities, to inhibit the growth of bacteria capable of causing serious disease.

Wound Dressings Based on Chitosan-Dialdehyde Cellulose Nanocrystals-Silver Nanoparticles: Mechanical Strength, Antibacterial Activity and Cytotoxicity

The present work envisages a simple approach to synthesize a new wound dressing based on chitosan-dialdehyde cellulose nanocrystal-silver nanoparticles (CS-DCNC-AgNPs). Silver nanoparticles (AgNPs) were generated in-situ by periodate oxidation of cellulose nanocrystals to generate aldehyde functions, which were used to reduce Ag⁺ into Ag⁰ in mild alkaline conditions. Subsequently, the dialdehyde cellulose nanocrystal-silver nanoparticles (DCNC-AgNPs) were added to chitosan (CS) to form the wound dressings by solution casting method. The aim was to enhance the antibacterial effect of CS by incorporation of AgNPs and to improve the mechanical strength and hydrophobicity of CS by incorporation of DCNC that cross-linked by hydrogen bonds. The antibacterial activities were evaluated against five gram-negative bacteria, one gram-positive bacteria, and three fungi. The in vitro cytotoxicity assay was performed using the NIH3T3 cell lines by Sulforhodamine B assay. Research outputs signified that CS-DCNC-AgNPs possessed good mechanical strength and hydrophobicity, high antibacterial activity and less cytotoxicity. Our results propose that CS-DCNC-AgNPs can be a promising, safe antibacterial to be incorporated in wound dressings.

Solvent-free and one-pot synthesis of silver and zinc oxide nanoparticles: Activity toward cell membrane component and insulin signaling pathway in experimental diabetes

OBJECTIVE

To investigate and compare between the effect of both silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) on insulin signaling pathway and insulin sensitivity in experimental diabetes. Preparation of AgNPs and ZnONPs in their solid state were carried out using pullulan (Natural polymer) as both reducing and stabilizing agent. The synthesis of these nanoparticles in a large scale were carried out without using any solvents. The experimental male albino rats received diluted solutions of AgNPs and ZNONPs. After the experimental period, blood was withdrawn; erythrocyte membrane lipids were extracted and fatty acids were determined by HPLC. Oxidant, antioxidant profile and phosphatidylinositol 3-kinase (PI₃K) were estimated.

RESULTS

It was observed that the as synthesized AgNPs and ZnONPs have nearly spherical shape with small size due to the stabilization effect of pullulan as proved by UV-vis spectroscopy (UV-vis), Transmission electron microscy (TEM) and Field emission scanning electron microscopy (FESEM), Zeta potential, Dynamic light scattering (DLS) and X-ray diffraction (XRD) techniques. The average hydrodynamic size of the formed AgNPs was 15 nm which is considered as very small size when compared with that of ZnONPs (above 50 nm). Fasting blood sugar was significantly increased in diabetic group along with elevation of MDA and DNA damage indicating the oxidative properties of streptozotocin. Whereas, the treatment with nanoparticles significantly attenuated these elevations.

CONCLUSION

AgNPs and ZnONPs represent promising materials in attenuating diabetic complications and insulin resistance in experimental diabetes; no Impressive differences were observed between the effect of ZnONPs and AgNPs in this current research.