Antibacterial Effect of Chitosan-Gold Nanoparticles and Computational Modeling of the Interaction between Chitosan and a Lipid Bilayer Model

Designing antibacterial materials through simulation and theory

Antibacterial materials have a wide range of potential applications in bio-antimicrobial, environmental antimicrobial, and food antimicrobial fields due to their intrinsic antimicrobial properties, which can circumvent the development of drug resistance in bacteria. Understanding the intricate mechanisms and intrinsic nature of diverse antibacterial materials is significant for the formulation of guidelines for the design of materials with rapid and efficacious antimicrobial action and a high degree of biomedical material safety. Herein, this review highlights the recent advances in investigating antimicrobial mechanisms of different antibacterial materials with a particular focus on tailored computer simulations and theoretical analysis. From the view of structure and function, we summarize the characteristics and mechanisms of different antibacterial materials, introduce the latest advances of new antibacterial materials, and discuss the design concept and development direction of new materials. In addition, we underscore the significance of employing simulation and theoretical methodologies to elucidate the intrinsic antimicrobial mechanisms, which is crucial for a comprehensive comprehension of the control strategies, safer biomedical applications, and the management of health and environmental concerns associated with antibacterial materials. This review could potentially stimulate further endeavors in fundamental research and facilitate the extensive utilization of computational and theoretical approaches in the design of novel functional nanomaterials.

In Vitro Evaluation of Colistin Conjugated with Chitosan-Capped Gold Nanoparticles as a Possible Formulation Applied in a Metered-Dose Inhaler

Inhaled colistin is used to treat pneumonia and respiratory infections through nebulization or dry powder inhalers. Nevertheless, the development of a metered-dose inhaler (MDI) for colistin, which could enhance patient convenience and treatment efficacy, has not yet been developed. Colistin is known for its ability to induce cellular toxicity. Gold nanoparticles (AuNPs) can potentially mitigate colistin toxicity. Therefore, this study aimed to evaluate the antimicrobial effectiveness of colistin conjugated with chitosan-capped gold nanoparticles (Col-CS-AuNPs) and their potential formulation for use with MDIs to deliver the aerosol directly to the deep lung. Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and elemental analysis were used to characterize the synthesized Col-CS-AuNPs. Drug release profiles fitted with the most suitable release kinetic model were evaluated. An MDI formulation containing 100 µg of colistin per puff was prepared. The aerosol properties used to determine the MDI performance included the fine particle fraction, mass median aerodynamic diameter, and geometric standard deviation, which were evaluated using the Andersen Cascade Impactor. The delivered dose uniformity was also determined. The antimicrobial efficacy of the Col-CS-AuNP formulation in the MDI was assessed. The chitosan-capped gold nanoparticles (CS-AuNPs) and Col-CS-AuNPs had particle sizes of 44.34 ± 1.02 and 174.50 ± 4.46 nm, respectively. CS-AuNPs effectively entrapped 76.4% of colistin. Col-CS-AuNPs exhibited an initial burst release of up to 60% colistin within the first 6 h. The release mechanism was accurately described by the Korsmeyer-Peppas model, with an R2 > 0.95. The aerosol properties of the Col-CS-AuNP formulation in the MDI revealed a high fine particle fraction of 61.08%, mass median aerodynamic diameter of 2.34 µm, and geometric standard deviation of 0.21, with a delivered dose uniformity within 75-125% of the labeled claim. The Col-CS-AuNP MDI formulation completely killed Escherichia coli at 5× and 10× minimum inhibitory concentrations after 6 and 12 h of incubation, respectively. The toxicity of CS-AuNP and Col-CS-AuNP MDI formulations in upper and lower respiratory tract cell lines was lower than that of free colistin. The stability of the Col-CS-AuNP MDI formulation was maintained for at least 3 months. The Col-CS-AuNP MDI formulation effectively eradicated bacteria over a 12-h period, showing promise for advancing lung infection treatments.

Research and Application of Chitosan Nanoparticles in Orthopedic Infections

Orthopedic infection is one of the most intractable orthopedic problems. Bacteria resistant to antibiotics also develop gradually. Chitosan is widely used in the Biomedical field because of its high biocompatibility, biodegradability, and antibacterial activity. Chitosan-based drug delivery systems are frequently utilized to produce controlled medication release. When combined with antibiotics, synergistic antibacterial effects can be achieved. Chitosan-based nanoparticles are one of the most widely used applications in drug delivery systems. The focus of this review is to provide information on new methods being developed for chitosan-based nanoparticles in the field of bone infection treatment, including chitosan nanoparticles for antibacterial purposes, Ch-loaded with antibiotics, Ch-loaded with metal, and used as immune adjuvants. It may Provide ideas for the fundamental research and the prospects of future clinical applications of orthopedic infections.

Folic Acid-Decorated Nanocrystals as Highly Loaded Trojan Horses to Target Cancer Cells

The nanocrystal (NC) technology has become one of the most commonly used strategies for the formulation of poorly soluble actives. Given their large specific surface, NCs are mainly used to enhance the oral absorption of poorly soluble actives. Differently from conventional nanoparticles, which require the use of carrier materials and have limited drug loadings, NCs' drug loading approaches 100% since they are formed of the pure drug and surrounded by a thin layer of a stabilizer. In this work, we report the covalent decoration of curcumin NCs with folic acid (FA) using EDC/NHS chemistry and explore the novel systems as highly loaded "Trojan horses" to target cancer cells. The decorated NCs demonstrated a remarkable improvement in curcumin uptake, exhibiting enhanced growth inhibition in cancer cells (HeLa and MCF7) while sparing healthy cells (J774A.1). Cellular uptake studies revealed significantly heightened entry of FA-decorated NCs into cancer cells compared to unmodified NCs while also showing reduced uptake by macrophages, indicating a potential for prolonged circulation in vivo. These findings underline the potential of NC highly loaded nanovectors for drug delivery and, in particular, for cancer therapies, effectively targeting folate receptor-overexpressing cells while evading interception by macrophages, thus preserving their viability and offering a promising avenue for precise and effective treatments.

Exfoliated MXene-AuNPs hybrid in sensing and multiple catalytic hydrogenation reactions

The increasing use of nanomaterials in consumer products is expected to lead to environmental contamination sometime soon. As water pollution is a pressing issue that threatens human survival and impedes the promotion of human health, the search for adsorbents for removing newly identified contaminants from water has become a topic of intensive research. The challenges in the recyclability of contaminated water continue to campaign the development of highly reusable catalysts. Although exfoliated 2D MXene sheets have demonstrated the capability towards water purification, a significant challenge for removing some toxic organic molecules remains a challenge due to a need for metal-based catalytic properties owing to their rapid response. In the present study, we demonstrate the formation of hybrid structure AuNPs@MXene (Mo2CTx) during the sensitive detection of Au nanoparticle through MXene sheets without any surface modification, and subsequently its applications as an efficient catalyst for the degradation of 4-nitrophenol (4-NP), methyl orange (MO), and methylene blue (MB). The hybrid structure (AuNPs@MXene) reveals remarkable reusability for up to eight consecutive cycles, with minimal reduction in catalytic efficiency and comparable apparent reaction rate constant (Kapp) values for 4-NP, MB, and MO, compared to other catalysts reported in the literature.

Research Progress of Polysaccharide-Gold Nanocomplexes in Drug Delivery

Clinical drug administration aims to deliver drugs efficiently and safely to target tissues, organs, and cells, with the objective of enabling their therapeutic effects. Currently, the main approach to enhance a drug's effectiveness is ensuring its efficient delivery to the intended site. Due to the fact that there are still various drawbacks of traditional drug delivery methods, such as high toxicity and side effects, insufficient drug specificity, poor targeting, and poor pharmacokinetic performance, nanocarriers have emerged as a promising alternative. Nanocarriers possess significant advantages in drug delivery due to their size tunability and surface modifiability. Moreover, nano-drug delivery systems have demonstrated strong potential in terms of prolonging drug circulation time, improving bioavailability, increasing drug retention at the tumor site, decreasing drug resistance, as well as reducing the undesirable side effects of anticancer drugs. Numerous studies have focused on utilizing polysaccharides as nanodelivery carriers, developing delivery systems based on polysaccharides, or exploiting polysaccharides as tumor-targeting ligands to enhance the precision of nanoparticle delivery. These types of investigations have become commonplace in the academic literature. This review aims to elucidate the preparation methods and principles of polysaccharide gold nanocarriers. It also provides an overview of the factors that affect the loading of polysaccharide gold nanocarriers with different kinds of drugs. Additionally, it outlines the strategies employed by polysaccharide gold nanocarriers to improve the delivery efficiency of various drugs. The objective is to provide a reference for further development of research on polysaccharide gold nanodelivery systems.

Green Synthesis of Chitosan-Capped Gold Nanoparticles Using Salvia officinalis Extract: Biochemical Characterization and Antimicrobial and Cytotoxic Activities

Increasing antimicrobial resistance to the action of existing antibiotics has prompted researchers to identify new natural molecules with antimicrobial potential. In this study, a green system was developed for biosynthesizing gold nanoparticles (BAuNPs) using sage (Salvia officinalis L.) leaf extract bioconjugated with non-toxic, eco-friendly, and biodegradable chitosan, forming chitosan/gold bioconjugates (Chi/BAuNPs). Characterization of the BAuNPs and Chi/BAuNPs conjugates takes place using transmission electron microscopy (TEM), X-ray spectra, Fourier transform infrared (FT-IR) spectroscopy, and zeta potential (Z-potential). The chemical composition of S. officinalis extract was evaluated via gas chromatography/mass spectrometry (GC/MS). This study evaluated the antioxidant and antimicrobial activities of human pathogenic multidrug-resistant (MDR) and multisensitive (MS) bacterial isolates using the agar diffusion method. Chi/BAuNPs showed inhibition of the MDR strains more effectively than BAuNPs alone as compared with a positive standard antibiotic. The cytotoxicity assay revealed that the human breast adenocarcinoma cancer cells (MCF7) were more sensitive toward the toxicity of 5-Fu + BAuNPs and 5-Fu + Chi/BAuNPs composites compared to non-malignant human fibroblast cells (HFs). The study shows that BAuNPs and Chi/BAuNPs, combined with 5-FU NPs, can effectively treat cancer at concentrations where the free chemical drug (5-Fu) is ineffective, with a noted reduction in the required dosage for noticeable antitumor action.

Advances in preparation, biomedical, and pharmaceutical applications of chitosan-based gold, silver, and magnetic nanoparticles: A review

During the last decades, the ever-increasing incidence of various diseases, like cancer, has led to a high rate of death worldwide. On the other hand, conventional modalities (such as chemotherapy and radiotherapy) have not indicated enough efficiency in the diagnosis and treatment of diseases. Thus, potential novel approaches should be taken into consideration to pave the way for the suppression of diseases. Among novel approaches, biomaterials, like chitosan nanoparticles (CS NPs, N-acetyl-glucosamine and D-glucosamine), have been approved by the FDA for some efficient pharmaceutical applications. These NPs owing to their physicochemical properties, modification with different molecules, biocompatibility, serum stability, less immune response, suitable pharmacokinetics and pharmacodynamics, etc. have received deep attention among researchers and clinicians. More importantly, the impact of CS polysaccharide in the synthesis, preparation, and delivery of metallic NPs (like gold, silver, and magnetic NPs), and combination of CS with these metallic NPs can further facilitate the diagnosis and treatment of diseases. Metallic NPs possess some features, like converting NIR photon energy into thermal energy and anti-microorganism capability, and can be a potential candidate for the diagnosis and treatment of diseases in combination with CS NPs. These combined NPs would be efficient pharmaceuticals in the future.

Chitosan and Its Derivatives: Preparation and Antibacterial Properties

This comprehensive review illuminates the various methods of chitosan extraction, its antibacterial properties, and its multifarious applications in diverse sectors. We delve into chemical, physical, biological, hybrid, and green extraction techniques, each of which presents unique advantages and disadvantages. The choice of method is dictated by multiple variables, including the desired properties of chitosan, resource availability, cost, and environmental footprint. We explore the intricate relationship between chitosan's antibacterial activity and its properties, such as cationic density, molecular weight, water solubility, and pH. Furthermore, we spotlight the burgeoning applications of chitosan-based materials like films, nanoparticles, nonwoven materials, and hydrogels across the food, biomedical, and agricultural sectors. The review concludes by highlighting the promising future of chitosan, underpinned by technological advancements and growing sustainability consciousness. However, the critical challenges of optimizing chitosan's production for sustainability and efficiency remain to be tackled.

Multimodal Biomedical Implant with Plasmonic and Simulated Body Temperature Responses

This work presents a novel nanoparticle-based thermosensor implant able to reveal the precise temperature variations along the polymer filaments, as it contracts and expands due to changes in the macroscale local temperature. The multimodal device is able to trace the position and the temperature of a polypropylene mesh, employed in abdominal hernia repair, by combining plasmon resonance and Raman spectroscopy with hydrogel responsive system. The novelty relies on the attachment of the biocompatible nanoparticles, based on gold stabilized by a chitosan-shell, already charged with the Raman reporter (RaR) molecules, to the robust prosthesis, without the need of chemical linkers. The SERS enhanced effect observed is potentiated by the presence of a quite thick layer of the copolymer (poly(N-isopropylacrylamide)-co-poly(acrylamide)) hydrogel. At temperatures above the LCST of PNIPAAm-co-PAAm, the water molecules are expulsed and the hydrogel layer contracts, leaving the RaR molecules more accessible to the Raman source. In vitro studies with fibroblast cells reveal that the functionalized surgical mesh is biocompatible and no toxic substances are leached in the medium. The mesh sensor opens new frontiers to semi-invasive diagnosis and infection prevention in hernia repair by using SERS spectroscopy. It also offers new possibilities to the functionalization of other healthcare products.

Chitosan and chito-oligosaccharide: a versatile biopolymer with endless grafting possibilities for multifarious applications

Chito-oligosaccharides (COS), derived from chitosan (CH), are attracting increasing attention as drug delivery carriers due to their biocompatibility, biodegradability, and mucoadhesive properties. Grafting, the process of chemically modifying CH/COS by adding side chains, has been used to improve their drug delivery performance by enhancing their stability, targeted delivery, and controlled release. In this review, we aim to provide an in-depth study on the recent advances in the grafting of CH/COS for multifarious applications. Moreover, the various strategies and techniques used for grafting, including chemical modification, enzymatic modification, and physical modification, are elaborated. The properties of grafted CH/COS, such as stability, solubility, and biocompatibility, were reported. Additionally, the review detailed the various applications of grafted CH/COS in drug delivery, including the delivery of small drug molecule, proteins, and RNA interference therapeutics. Furthermore, the effectiveness of grafted CH/COS in improving the pharmacokinetics and pharmacodynamics of drugs was included. Finally, the challenges and limitations associated with the use of grafted CH/COS for drug delivery and outline directions for future research are addressed. The insights provided in this review will be valuable for researchers and drug development professionals interested in the application of grafted CH/COS for multifarious applications.

Chitosan capped-gold nanoparticles as skin penetration enhancer for small molecules: A study in porcine skin

Skin is considered one of the most convenient sites for drug administration. The present study evaluated the effect of gold nanoparticles stabilized by chitosan (CS-AuNPs) and citrate ions (Ci-AuNPs) on skin permeation of sodium fluorescein (NaFI) and rhodamine b base (RhB) as small model hydrophilic and lipophilic permeants, respectively. CS-AuNPs and Ci-AuNPs were characterized by transmitted electron microscopy (TEM) and dynamic light scattering (DLS). Skin permeation was investigated using porcine skin with diffusion cells and confocal laser scanning microscopy (CLSM). The CS-AuNPs and Ci-AuNPs were spherical-shaped nanosized particles (38.4±0.7 and 32.2±0.7 nm, respectively). The zeta potential of CS-AuNPs was positive (+30.7±1.2 mV) whereas that of Ci-AuNPs was negative (-60.2±0.4 mV). The skin permeation study revealed that CS-AuNPs could enhance the permeation of NaFI with enhancement ratio (ER) of 38.2±7.5, and the effect was superior to that of Ci-AuNPs. CLSM visualization suggested that skin permeation was enhanced by improving the delivery through the transepidermal pathway. However, the permeability of RhB, a lipophilic molecule, was not significantly affected by CS-AuNPs and Ci-AuNPs. Moreover, CS-AuNPs had no cytotoxic toward human skin fibroblast cells. Therefore, CS-AuNPs are a promising skin permeation enhancer of small polar compounds.

Synthesis of Cellulose Nanoparticles from Ionic Liquid Solutions for Biomedical Applications

A method for the synthesis of cellulose nanoparticles using the ionic liquid 1-ethyl-3-methylimidazolium acetate has been optimised. The use of a highly biocompatible biopolymer such as cellulose, together with the use of an ionic liquid, makes this method a promising way to obtain nanoparticles with good capability for drug carrying. The operating conditions of the synthesis have been optimised based on the average hydrodynamic diameter, the polydispersity index, determined by Dynamic Light Scattering (DLS) and the Z-potential, obtained by phase analysis light scattering (PALS), to obtain cellulose nanoparticles suitable for use in biomedicine. The obtained cellulose nanoparticles have been characterised by Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR), field emission scanning electron microscopy (FESEM) and thermogravimetric analysis (TGA/DTA). Finally, cell viability studies have been performed with a cancer cell line (HeLa) and with a healthy cell line (EA.hy926). These have shown that the cellulose nanoparticles obtained are not cytotoxic in the concentration range of the studied nanoparticles. The results obtained in this work constitute a starting point for future studies on the use of cellulose nanoparticles, synthesised from ionic liquids, for biomedical applications such as targeted drug release or controlled drug release.

Chitosan-Coated Polymeric Silver and Gold Nanoparticles: Biosynthesis, Characterization and Potential Antibacterial Applications: A Review

Biosynthesized metal nanoparticles, especially silver and gold nanoparticles, and their conjugates with biopolymers have immense potential in various fields of science due to their enormous applications, including biomedical applications. Polymeric nanoparticles are particles of small sizes from 1 nm to 1000 nm. Among different polymeric nanoparticles, chitosan-coated silver and gold nanoparticles have gained significant interest from researchers due to their various biomedical applications, such as anti-cancer, antibacterial, antiviral, antifungal, anti-inflammatory technologies, as well as targeted drug delivery, etc. Multidrug-resistant pathogenic bacteria have become a serious threat to public health day by day. Novel, effective, and safe antibacterial agents are required to control these multidrug-resistant pathogenic microorganisms. Chitosan-coated silver and gold nanoparticles could be effective and safe agents for controlling these pathogens. It is proven that both chitosan and silver or gold nanoparticles have strong antibacterial activity. By the conjugation of biopolymer chitosan with silver or gold nanoparticles, the stability and antibacterial efficacy against multidrug-resistant pathogenic bacteria will be increased significantly, as well as their toxicity in humans being decreased. In recent years, chitosan-coated silver and gold nanoparticles have been increasingly investigated due to their potential applications in nanomedicine. This review discusses the biologically facile, rapid, and ecofriendly synthesis of chitosan-coated silver and gold nanoparticles; their characterization; and potential antibacterial applications against multidrug-resistant pathogenic bacteria.

AuNP/Chitosan Nanocomposites Synthesized through Plasma Induced Liquid Chemistry and Their Applications in Photothermal Induced Bacteria Eradication

In this work, a facile direct current atmospheric pressure micro-plasma (APM) technology was deployed for the synthesis of functional gold nanoparticle/chitosan (AuNP/CS) nanocomposites for the first time. Different experimental parameters, such as metal salt precursor concentration and chitosan viscosity, have been investigated to understand their effects on the resulting nanocomposite structures and properties. The nanocomposites were fully characterized using a wide range of material characterization techniques such as UV–vis, transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. Potential reaction pathways have been proposed for the nanocomposite synthesis process. Finally, potential of the synthesized nanocomposites towards photothermal conversion and bacteria eradiation applications has been demonstrated. The results show that APM is a facile, rapid and versatile technique for the synthesis of AuNP/CS functional nanocomposites. Through this work, a more in-depth understanding of the multi-phase system (consisting of gas, plasma, liquid and solid) has been established and such understanding could shine a light on the future design and fabrication of new functional nanocomposites deploying the APM technique.

Emerging Effects of Resveratrol on Wound Healing: A Comprehensive Review

Resveratrol (RSV) is a natural extract that has been extensively studied for its significant anti-inflammatory and antioxidant effects, which are closely associated with a variety of injurious diseases and even cosmetic medicine. In this review, we have researched and summarized the role of resveratrol and its different forms of action in wound healing, exploring its role and mechanisms in promoting wound healing through different modes of action such as hydrogels, fibrous scaffolds and parallel ratio medical devices with their anti-inflammatory, antioxidant, antibacterial and anti-ageing properties and functions in various cells that may play a role in wound healing. This will provide a direction for further understanding of the mechanism of action of resveratrol in wound healing for future research.

Progress and prospects of nanomaterials against resistant bacteria

Drug-resistant bacterial infections are increasingly heightening, which lead to more severe illness, higher cost of treatment and increased risk of death. Nanomaterials-based therapy, an "outrider", serving as a kind of innovative antimicrobial therapeutics, showing promise in replacing antimicrobial agents and enhancing the activity of antibiotics, generally bases on the various inorganic and/or organic materials. When the size of those materials is below to a certain nano-level and the content of nanomaterials is above a certain amount, they are lethal to the resistant bacteria, which bypass the traditional bacterial resistance mechanisms. This review highlights the effect of nanomaterials in combating extracellular/intracellular bacteria and eradicating biofilms. Based on the studies searched on the Web of Science through relevant keywords, this review article starts with analyzing the current situation, resistance mechanisms, and treatment difficulties of bacteria resistance. Then, the efficacy of nanomaterials against resistant bacteria and their mechanisms (e.g., physical impairment, biofilm lysis, regulating bacterial metabolism, protein and DNA replication as well as enhancing the antibiotics concentration in infected cells) are collected. Lastly, the factors affecting the antibacterial efficacy are argued from the side of nanomatrials and bacterium, which followed by the emerging challenges and recent perspectives of achieving higher targeting released nanomaterials as antibacterial therapeutics.

Green synthesis of novel stable biogenic gold nanoparticles for breast cancer therapeutics via the induction of extrinsic and intrinsic pathways

Biosynthesis of gold nanoparticles (AuNPs) using algal polysaccharides is a simple, low-cost, and an eco-friendly approach. In the current study, different concentrations of Arthospira platensis exopolysaccharides (EPS) were used to synthetize AuNPs via the reduction of gold ions. The biologically synthesized AuNPs (AuNPs1, AuNPs2, AuNPs3) were prepared in 3 different forms through the utilization of three different ratios of EPS-reducing agents. AuNPs analysis confirmed the spherical shape of the EPS-coated AuNPs. Furthermore, AuNPs prepared by EPS and l-ascorbic acid (AuNPs3) showed more stability than the AuNPs colloidal solution that was prepared using only l-ascorbic acid. Analysis of the antimicrobial effects of AuNPs showed that E. coli was the most sensitive bacterial species for AuNPs3 and AuNPs1 with inhibition percentages of 88.92 and 83.13%, respectively. Also, safety assay results revealed that AuNPs3 was the safest biogenic AuNPs for the tested noncancerous cell line. The anticancer assays of the biogenic AuNPs1, AuNPs2, and AuNPs3 against MCF-7 cell line indicated that this cell line was the most sensitive cell line to all treatments and it showed inhibition percentages of 66.2%, 57.3%, and 70.2% to the three tested AuNPs, respectively. The AuNPs also showed abilities to arrest MCF-7 cells in the S phase (77.34%) and increased the cellular population in the sub G0 phase. Gene expression analysis showed that AuNPs3 down regulated Bcl2, Ikapα, and Survivn genes in MCF-7 treated-cells. Also, transmission electron microscopy (TEM) analysis of MCf-7 cells revealed that AuNPs 3 and AuNPs2 were localized in cell vacuoles, cytoplasm, and perinuclear region.

Roles of chitosan in synthesis, antibacterial and anti-biofilm properties of bionano silver and gold

Antibiotic-resistance and bacterial bioburden on wound surfaces are the significant challenges to wound healing. Silver and gold nanoparticles (are termed as AgNPs and AuNPs) have been investigated as alternative antimicrobial agents to combat antibiotic-resistant bacterial infections owing to their antibacterial and anti-biofilm activities. Chitosan (CS) has largely been used in nanoparticle synthesis as a stabilizing or capping agent. In this study, AgNPs and AuNPs were synthesized using different concentrations of aqueous extract of tiger milk mushroom (Lignosus rhinocerotis) (WETMM) and CS as reducing and stabilizing agent, respectively. Particle size and morphology of both were determined by dynamic light scattering (DLS) method and transmission electron microscopic analysis (TEM). FTIR analysis was conducted to determine the interactions between nanoparticle precursors. The observed peaks at 450 nm and 534-565 nm using a spectrophotometer were corresponded to the surface Plasmon resonance of AgNPs and AuNPs respectively, indicating the formation of respective nanoparticles. FTIR analysis confirmed the role of WETMM as a reducing agent and CS as a stabilizer of AgNPs and AuNPs. Faster formation of nanoparticles was observed besides an increase in particle size when higher CS concentrations were used. TEM micrographs revealed the spherical shape of most nanoparticles with particle sizes in the range of 4 to 58 nm and 18 to 28 nm for AgNPs and AuNPs, respectively. Both nanoparticles exhibited antimicrobial activity against Gram-positive and -negative bacteria, with AgNPs showing a superior antibacterial efficacy than AuNPs. Both microbroth dilution and agar well diffusion assays indicated that CS was an important component to facilitate antibacterial activity for AuNPs. Contrarily, CS stabilization did not enhance the antibacterial efficacy of AgNPs. CS-stabilized AgNPs and AuNPs achieved biofilm inhibition of 53.21% and 79.39% for Pseudomonas aeruginosa and 48.71% and 48.16% for Staphylococcus aureus, respectively. Similarly, CS stabilization enhanced the anti-biofilm activity of AuNPs but no such effect was seen for AgNPs. In conclusion, CS-stabilized AgNPs and AuNPs possess both antimicrobial and anti-biofilm activities. However, CS acted differently when combined with AgNPs and AuNPs, needing further investigation and optimization to improve the antimicrobial activity of both nanoparticles.

Chitosan: A Sustainable Material for Multifarious Applications

Due to the versatility of its features and capabilities, chitosan generated from marine crustacean waste is gaining importance and appeal in a wide variety of applications. It was initially used in pharmaceutical and medical applications due to its antibacterial, biocompatible, and biodegradable properties. However, as the demand for innovative materials with environmentally benign properties has increased, the application range of chitosan has expanded, and it is now used in a variety of everyday applications. The most exciting aspect of the chitosan is its bactericidal properties against pathogens, which are prevalent in contaminated water and cause a variety of human ailments. Apart from antimicrobial and water filtration applications, chitosan is used in dentistry, in water filtration membranes to remove metal ions and some heavy metals from industrial effluents, in microbial fuel cell membranes, and in agriculture to maintain moisture in fruits and leaves. It is also used in skin care products and cosmetics as a moisturizer, in conjunction with fertilizer to boost plant immunity, and as a bi-adhesive for bonding woods and metals. As it has the capacity to increase the life span of food items and raw meat, it is an unavoidable component in food packing and preservation. The numerous applications of chitosan are reviewed in this brief study, as well as the approaches used to incorporate chitosan alongside traditional materials and its effect on the outputs.

Synthesis of Chitosan-Based Gold Nanoparticles: Antimicrobial and Wound-Healing Activities

The global spread of multidrug-resistant bacteria has become a significant hazard to public health, and more effective antibacterial agents are required. Therefore, this study describes the preparation, characterization, and evaluation of gold nanoparticles modified with chitosan (Chi/AuNPs) as a reducing and stabilizing agent with efficient antimicrobial effects. In recent years, the development of an efficient and ecofriendly method for synthesizing metal nanoparticles has attracted a lot of interest in the field of nanotechnology. Colloidal gold nanoparticles (AuNPs) were prepared by the chemical reduction of gold ions in the presence of chitosan (Chi), giving Chi/AuNPs. The characterization of Chi/AuNPs was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and X-ray diffraction (XRD). Chi/AuNPs appeared spherical and monodispersed, with a diameter ranging between 20 to 120 nm. The synergistic effects of AuNPs and Chi led to the disruption of bacterial membranes. The maximum inhibitory impact was seen against P. aeruginosa at 500 µg/mL, with a zone of inhibition diameter of 26 ± 1.8 mm, whereas the least inhibitory effect was reported for S. aureus, with a zone of inhibition diameter of 16 ± 2.1 mm at the highest dose tested. Moreover, Chi/AuNPs exhibited antifungal activity toward Candida albicans when the MIC was 62.5 µg/mL. Cell viability and proliferation of the developed nanocomposite were evaluated using a sulphorhodamine B (SRB) assay with a half inhibitory concentration (IC50) of 111.1 µg/mL. Moreover, the in vitro wound-healing model revealed that the Chi/AuNP dressing provides a relatively rapid and efficacious wound-healing ability, making the obtained nanocomposite a promising candidate for the development of improved bandage materials.

Ceftriaxone Mediated Synthesized Gold Nanoparticles: A Nano-Therapeutic Tool to Target Bacterial Resistance

Ceftriaxone has been a part of therapeutic regime for combating some of the most aggressive bacterial infections in the last few decades. However, increasing bacterial resistance towards ceftriaxone and other third generation cephalosporin antibiotics has raised serious clinical concerns especially due to their misuse in the COVID-19 era. Advancement in nanotechnology has converted nano-therapeutic vision into a plausible reality with better targeting and reduced drug consumption. Thus, in the present study, gold nanoparticles (GNPs) were synthesized by using ceftriaxone antibiotic that acts as a reducing as well as capping agent. Ceftriaxone-loaded GNPs (CGNPs) were initially characterized by UV-visible spectroscopy, DLS, Zeta potential, Electron microscopy and FT-IR. However, a TEM micrograph showed a uniform size of 21 ± 1 nm for the synthesized CGNPs. Further, both (CGNPs) and pure ceftriaxone were examined for their efficacy against Escherichia coli, Staphylococcus aureus, Salmonella abony and Klebsiella pneumoniae. CGNPs showed MIC50 as 1.39, 1.6, 1.1 and 0.9 µg/mL against E. coli, S. aureus, S. abony and K. pneumoniae, respectively. Interestingly, CGNPs showed two times better efficacy when compared with pure ceftriaxone against the tested bacterial strains. Restoring the potential of unresponsive or less efficient ceftriaxone via gold nanoformulations is the most alluring concept of the whole study. Moreover, applicability of the findings from bench to bedside needs further validation.

Polyquaternium enhances the colloidal stability of chitosan-capped platinum nanoparticles and their antibacterial activity

Here, for the first time, we have developed a novel green synthesis method where chitosan acts as a reducing agent and as a colloidal stabilizer, together with polyquaternium for the synthesis of platinum nanoparticles (PtNPs). It was observed that only chitosan-stabilized PtNPs (Ch@PtNPs) were stable up to pH 5, with a diameter of around 89 nm. The diameter of the Ch@PtNPs increased with the increase in pH, indicating the instability of Ch@PtNPs at neutral and alkaline mediums. However, when polyquaternium (PQ) (a cationic polymer) was added as a stabilizer along with chitosan, the diameter of chitosan/polyquaternium stabilized PtNPs (Ch/PQ@PtNPs), i.e. 87 nm, remained almost constant up to pH 9. Similarly, the pH-dependent decrease in the surface charge of Ch@PtNPs was also attenuated with the addition of polyquaternium. This indicates high colloidal stability of Ch/PQ@PtNPs in acidic, neutral, as well as alkaline mediums. It was observed that Ch/PQ@PtNPs exhibited high antibacterial activity againstStaphylococcus aureus, as compared to uncapped PtNPs and Ch@PtNPs. Thus, the addition of PQ increases the antibacterial properties of Ch/PQ@PtNPs againstStaphylococcus aureusby enhancing the stability of PtNPs at neutral pH.

Embelin-loaded chitosan gold nanoparticles interact synergistically with ciprofloxacin by inhibiting efflux pumps in multidrug-resistant Pseudomonas aeruginosa and Escherichia coli

A global upsurge in emergence and spread of antibiotic resistance (ABR) in bacterial populations is a serious threat for human health. Unfortunately, ABR is no longer confined to nosocomial environments and is frequently reported from community microbes as well. The ABR is resulting in shrinking potent antibiotics pool and thus necessitating novel and alternative therapies and therapeutics. Current investigation was aimed to assess the synergistic potential of a synthesized, phytomolecule-loaded, polysaccharide-stabilized metallic nanoparticles (NPs) against Pseudomonas aeruginosa (PA) and Escherichia coli (EC) isolated from river waters. ABR profiling of these strains characterized them as multidrug resistant (MDR). Synthesized embelin (Emb, isolated from Embelia tsjeriam-cottam)-loaded, chitosan-gold (Emb-Chi-Au) NPs were assessed for their potential synergistic activity with ciprofloxacin (CIP) via checker-board assay and time-kill curve analysis. The NPs reduced the minimal inhibitory concentration (MIC) of CIP by 16- and 4-fold against MDR PA (PA-r) and EC (EC-r) strains, respectively. Fractional inhibitory concentration (FIC) indices with ≤0.5 values confirmed the synergy between the Emb-Chi-Au NPs and CIP, which was further confirmed at ½ MICs in both PA-r and EC-r via time-kill curve analysis. In order to decipher the mode of action, efflux pump inhibitory effects of Emb-Chi-Au NPs were evaluated in terms of the increase in the EtBr mediated fluorescence in control versus NP-treated MDR strains. Molecular docking based in silico simulations were used to predict the interactions between Emb and the active sites of the efflux pump related proteins in PA-r (MexA, MexB and OprM) and EC-r (AcrA, AcrB and TolC), which revealed the probable bond formation between Emb and respective amino acid residues.

Roles of Chitosan in Green Synthesis of Metal Nanoparticles for Biomedical Applications

Chitosan (CS) is a well-known stabilizer for metal nanoparticles in biomedical engineering. However, very few studies have explored other important roles of CS including reducing, shape-directing, and size-controlling. This review aims to provide the latest and most comprehensive overview of the roles of CS in the green synthesis of metal nanoparticles for biomedical applications. To the best of our knowledge, this is the first review that highlights these potentialities of CS. At first, a brief overview of the properties and the bioactivity of CS is presented. Next, the benefits of CS for enhancing the physicochemical behaviors of metal nanoparticles are discussed in detail. The representative biomedical applications of CS-metal nanoparticles are also given. Lastly, the review outlines the perceptual vision for the future development of CS-metal nanoparticles in the biomedicine field.