Controlled size green synthesis of bioactive silver nanoparticles assisted by chitosan and its derivatives and their application in biofilm preparation

Starch-based biodegradable films amended with nano-starch and tannic acid-coated nano-starch exhibit enhanced mechanical and functional attributes with antimicrobial activity

Starch-based biofilms are biodegradable, but their application is limited by lower mechanical strength and absence of antimicrobial properties. In this context, the present study attempted to unleash the potential of nanotechnology for synthesizing nano-starch (NS) and tannic acid-coated nano-starch (T-NS) for augmenting the tensile strength and antimicrobial properties of starch-based biofilms. Moreover, this study reports one of the first such attempts to improve the commercial viability of starch extracted from the corms of Amorphophallus paeoniifolius. In this study, NS and T-NS samples were first synthesized by the physical and chemical modification of the native starch (S) molecules. The NS and T-NS samples showed significantly smaller granule size, lower moisture content, and swelling power. Further, amendments with NS and T-NS samples (25 % and 50 %) to the native starch molecules were performed to obtain biofilm samples. The NSB (NS amended) and T-NSB (T-NS amended) biofilms showed comparatively higher tensile strength than SB films (100 % starch-based). The T-NSB showed greater antimicrobial activity against gram-positive and gram-negative bacteria. All the biofilms showed almost complete biodegradation in soil (in 10 days). Therefore, it can be concluded that additives like NS and T-NS can improve starch-based biofilms' mechanical strength and antimicrobial properties with considerable biodegradability.

Bio-formulated chitosan nanoparticles enhance disease resistance against rice blast by physiomorphic, transcriptional, and microbiome modulation of rice (Oryza sativa L.)

Rice blast disease (RBD) caused by Magnaporthe oryzae, threaten food security by cutting agricultural output. Nano agrochemicals are now perceived as sustainable, cost-effective alternatives to traditional pesticides. This study investigated bioformulation of moringa chitosan nanoparticles (M-CsNPs) and their mechanisms for suppressing RBD while minimizing toxic effects on the microenvironment. M-CsNPs, sized 46 nm with semi-spherical morphology, significantly suppressed pathogen growth, integrity, and colonization at 200 mg L-1in vitro. Greenhouse tests with foliar exposure to the same concentration resulted in a substantial 77.7 % reduction in RBD, enhancing antioxidant enzyme activity and plant health. Furthermore, M-CsNPs improved photosynthesis, gas exchange, and the nutritional profile of diseased rice plants. RNA-seq analysis highlighted upregulated defense-related genes in treated rice plants. Metagenomic study showcased reshaping of the rice microbiome, reducing Magnaporthe abundance by 93.5 %. Both healthy and diseased rice plants showed increased microbial diversity, particularly favoring specific beneficial species Thiobacillus, Nitrospira, Nocardioides, and Sphingomicrobium in the rhizosphere and Azonexus, Agarivorans, and Bradyrhizobium in the phyllosphere. This comprehensive study unravels the diverse mechanisms by which M-CsNPs interact with plants and pathogens, curbing M. oryzae damage, promoting plant growth, and modulating the rice microbiome. It underscores the significant potential for effective plant disease management.

Green synthesis of Poria cocos polysaccharides-silver nanoparticles and their applications in food packaging

To reduce pollution caused by traditional plastic packaging and preparation of silver nanoparticles (AgNPs), this work aims to develop biological macromolecular packaging films with green synthesized AgNPs. In this study, a novel P. cocos polysaccharide (PCP) with a unique monosaccharide composition was extracted from Poria cocos (Schw.) Wolf. Then, this polysaccharide containing 24.68 % rhamnose was used as a stabilizer for the green synthesis of PCP-AgNPs for the first time. PCP-AgNPs exhibited excellent antibacterial activity against P. aeruginosa, E. coli, and S. aureus, with the highest antibacterial activity against E. coli (inhibition zone diameter = 11.14 ± 0.79 mm). Subsequently, PCP-AgNPs/chitosan (CS) film was successfully prepared by incorporating PCP-AgNPs into the CS film solution. Several experiments demonstrated that the addition of this nanomaterial promoted the formation of noncovalent interactions between CS and PCP-AgNPs, resulting in a more regular and denser film. Compared to the CS film and control group, the PCP-AgNPs/CS film significantly maintained the quality indexes of strawberries. Therefore, this composite film successfully extended the shelf life of strawberries. Regarding safety, these packaging films were not cytotoxic toward RAW264.7 cells. In conclusion, the environmentally friendly PCP-AgNPs/CS film has the potential to replace some traditional food packaging materials.

Degradable chitosan-based bioplastic packaging: Design, preparation and applications

Food packaging is an essential part of food transportation, storage and preservation. Biodegradable biopolymers are a significant direction for the future development of food packaging materials. As a natural biological polysaccharide, chitosan has been widely concerned by researchers in the field of food packaging due to its excellent film-forming property, good antibacterial property and designability. Thus, the application research of chitosan-based food packaging films, coatings and aerogels has been greatly developed. In this review, recent advances on chitosan-based food packaging materials are summarized. Firstly, the development background of chitosan-based packaging materials was described, and then chitosan itself was introduced. In addition, the design, preparation and applications of films, coatings and aerogels in chitosan-based packaging for food preservation were discussed, and the advantages and disadvantages of each research in the development of chitosan-based packaging materials were analyzed. Finally, the application prospects, challenges and suggestions for solving the problems of chitosan-based packaging are summarized and prospected.

Nanometals incorporation into active and biodegradable chitosan films

This study investigates the effects of incorporating ZnO, TiO2, and colloidal Ag nanoparticles on the antioxidant, antimicrobial, and physical properties of biodegradable chitosan films. The research focuses on addressing the growing demand for sustainable packaging solutions that offer efficient food preservation while mitigating environmental concerns. In this investigation, the physical properties including thickness, water content, solubility, swelling degree, tensile strength, and elasticity of the chitosan films were examined. Additionally, the samples were analyzed for total polyphenol content, antimicrobial activity, and antioxidant capacity. Notably, the incorporation of ZnO nanoparticles led to the lowest water content and highest strength values among the tested films. Conversely, the addition of colloidal Ag nanoparticles resulted in films with the highest antioxidant capacities (DPPH: 32.202 ± 1.631 %). Remarkably, antimicrobial tests revealed enhanced activity with the inclusion of colloidal silver nanoparticles, yet the most potent antimicrobial properties were observed in films containing ZnO (E.coli: 2.0 ± 0.0 mm; MRSA: 2.0 ± 0.5 mm). The findings of this study hold significant implications for the advancement of edible biodegradable films, offering potential for more efficient food packaging solutions that address environmental sustainability concerns. By elucidating the effects of nanoparticle incorporation on film properties, this research contributes to the ongoing discourse surrounding sustainable packaging solutions in the food industry.

A multifunctional vanillin-infused chitosan-PVA hydrogel reinforced by nanocellulose and CuO-Ag nanoparticles as antibacterial wound dressing

Wound healing is an intricate and ever-evolving phenomenon that involves a series of biological processes and multiple stages. Despite the growing utilization of nanoparticles to enhance wound healing, these approaches often overlook properties like mechanical stability, toxicity, and efficacy. Hence, a multifunctional wound dressing is fabricated using Chitosan-PVA membrane crosslinked with vanillin and reinforced with nano-cellulose and CuO-Ag nanoparticles in this study. FTIR, SEM, and XRD were employed to study the morphology and structural properties of the membrane. Biomedical tests including biodegradability, antimicrobial study, cytotoxicity, and animal models were conducted to evaluate the membrane's performance as a wound healing material. The membrane displayed impressive mechanical strength, measuring as high as 49.985 ± 2.31 MPa, and had a hydrophilic nature, with moisture retention values up to 98.84 % and swelling percentages as high as 191.67 %. It also demonstrated biodegradable properties and high cell viability of up to 92.30 %. Additionally, the fabricated membranes exhibited excellent antimicrobial activity against both gram-positive and gram-negative bacteria, with maximum zone of inhibition measuring 16.8 ± 0.7 mm and 9.2 ± 0.1 mm, respectively. Moreover, the membranes also demonstrated superior wound healing properties. These results suggested great potential of fabricated membranes as an effective wound dressing material.

Metal nanoparticles and carbohydrate polymers team up to improve biomedical outcomes

The convergence of carbohydrate polymers and metal nanoparticles (MNPs) holds great promise for biomedical applications. Researchers aim to exploit the capability of carbohydrate matrices to modulate the physicochemical properties of MNPs, promote their therapeutic efficiency, improve targeted drug delivery, and enhance their biocompatibility. Therefore, understanding various attributes of both carbohydrates and MNPs is the key to harnessing them for biomedical applications. The many distinct types of carbohydrate-MNP systems confer unique capabilities for drug delivery, wound healing, tissue engineering, cancer treatment, and even food packaging. Here, we introduce distinct physicochemical/biological properties of carbohydrates and MNPs, and discuss their potentials and shortcomings (alone and in combination) for biomedical applications. We then offer an overview on carbohydrate-MNP systems and how they can be utilized to improve biomedical outcomes. Last but not least, future perspectives toward the application of such systems are highlighted.

Development of eco-friendly antifungal and antibacterial adhesive derived from modified cassava starch waste/polyvinyl alcohol containing green synthesized nano-silver

Environmentally friendly biopolymer-based wood adhesives are an inevitable trend of wood product development to replace the use of harmful formaldehyde-based adhesives. In this research, a new eco-friendly modified cassava starch waste-based adhesive via carboxymethylation (CMS), and blending with polyvinyl alcohol (PVA), tannic acid (TA) and green synthesized silver nanoparticles (AgNPs) was prepared. The effects of TA content on green synthesis of AgNPs (Ag-TA) and bio-adhesive nanocomposite properties were investigated. The use of 5 wt% TA for AgNPs synthesis (Ag-TA-5) resulted in a uniform particle size distribution. The plywood prepared with Ag-TA-5 provided the highest dry and wet shear strength at 1.95 ± 0.11 MPa and 1.38 ± 0.3 MPa, respectively. The water absorption and thickness swelling of this plywood remarkably decreased up to 10.99% and 6.79%, respectively. More importantly, the presence of Ag-TA in CMS/PVA adhesive successfully inhibited the invasion of mold and bacteria. Based on the cyclic delamination test, the adhesive bond durability of bio-adhesive containing Ag-TA-5 could meet the requirement of the AITC Test T110-2007 and was comparable to commercial adhesives. The added advantage of the prepared bio-adhesive was its synthesis from agro-waste products and possible economically viable production at industrial level.

Novel jointured green synthesis of chitosan‑silver nanocomposite: An approach towards reduction of nitroarenes, anti-proliferative, wound healing and antioxidant applications

Here we present the simple green synthesis of chitosan‑silver nanocomposite (CS-Ag NC) by employing kiwi fruit juice as reducing agent. The structure, morphology, and composition of CS-Ag NC were determined using characterization techniques such as XRD, SEM-EDX, UV-visible, FT-IR, particle size, and zeta potential. The prepared CS-Ag nanocomposite was effectively used as catalyst in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 as reductant, in aqueous medium at room temperature. The toxicity of CS-Ag NC was assessed on Normal (L929) cell line, Lung cancer (A549) cell line and Oral cancer (KB-3-1) cell line and their respective IC50values observed were 83.52 μg/mL, 66.74 μg/mL and 75.11 μg/mL. The CS-Ag NC displayed significant cytotoxic activity and the cell viability percentage for normal, lung and oral cancer cell lines were found to be 42.87 ± 0.0060, 31.28 ± 0.0045 and 35.90 ± 0.0065 respectively. Stronger cell migration was exemplified by CS-Ag NC and the percentage of wound closure (97.92%) was substantially identical to that of the standard drug ascorbic acid (99.27%). Further CS-Ag nanocomposite was subjected for in vitro antioxidant activity.

Chitosan-Based Antibacterial Films for Biomedical and Food Applications

Antibacterial chitosan films, versatile and eco-friendly materials, have garnered significant attention in both the food industry and medicine due to their unique properties, including biodegradability, biocompatibility, and antimicrobial activity. This review delves into the various types of chitosan films and their distinct applications. The categories of films discussed span from pure chitosan films to those enhanced with additives such as metal nanoparticles, metal oxide nanoparticles, graphene, fullerene and its derivatives, and plant extracts. Each type of film is examined in terms of its synthesis methods and unique properties, establishing a clear understanding of its potential utility. In the food industry, these films have shown promise in extending shelf life and maintaining food quality. In the medical field, they have been utilized for wound dressings, drug delivery systems, and as antibacterial coatings for medical devices. The review further suggests that the incorporation of different additives can significantly enhance the antibacterial properties of chitosan films. While the potential of antibacterial chitosan films is vast, the review underscores the need for future research focused on optimizing synthesis methods, understanding structure-property relationships, and rigorous evaluation of safety, biocompatibility, and long-term stability in real-world applications.

New sustainable antimicrobial chitosan hydrogels based on sulfonamides and its nanocomposites: Fabrication and characterization

Chitosan (Ch), a linear cationic biopolymer, has a broad medical applications. In this paper, new sustainable hydrogels (Ch-3,Ch-5_a,Ch-5_b) based on chitosan/sulfonamide derivatives 2-chloro-N-(4-sulfamoylphenethyl) acetamide (3) and/or 5-[(4-sulfamoylphenethyl) carbamoyl] isobenzofuran-1,3-dione (5) were prepared. Hydrogels (Ch-3, Ch-5_a, Ch-5_b) were loaded (Au,Ag,ZnO) NPs to form its nanocomposites to improve the antimicrobial efficacy of chitosan. The structures of hydrogels and its nanocomposites were characterized using different tools. All hydrogels displayed irregular surface morphology in SEM, however hydrogel (Ch-5_a) revealed the highest crystallinity. The highest thermal stability was shown by hydrogel (Ch-5_b) compared to chitosan. The nanocomposites represented nanoparticle sizes <100 nm. Antimicrobial activity was assayed for hydrogels using disc diffusion method exhibited great inhibition growth of bacteria compared to chitosan against S. aureus, B. subtilis and S. epidermidis as Gram-positive, E. coli, Proteus, and K. pneumonia as Gram-negative and antifungal activity against Aspergillus Niger and Candida. Hydrogel (Ch-5_b) and nanocomposite hydrogel (Ch-3/Ag NPs) showed higher colony forming unit (CFU) and reduction% against S. aureus and E. coli reaching 97.96 % and 89.50 % respectively in comparison with 74.56 % and 40.30 % for chitosan respectively. Overall, fabricated hydrogels and its nanocomposites enhanced the biological activity of chitosan and it can be potential candidate as antimicrobial drugs.

Catheters with Dual-Antimicrobial Properties by Gamma Radiation-Induced Grafting

Dual antimicrobial materials that have a combination of antimicrobial and antifouling properties were developed. They were developed through modification using gamma radiation of poly (vinyl chloride) (PVC) catheters with 4-vinyl pyridine (4VP) and subsequent functionalization with 1,3-propane sultone (PS). These materials were characterized by infrared spectroscopy, thermogravimetric analysis, swelling tests, and contact angle to determine their surface characteristics. In addition, the capacity of the materials to deliver ciprofloxacin, inhibit bacterial growth, decrease bacterial and protein adhesion, and stimulate cell growth were evaluated. These materials have potential applications in the manufacturing of medical devices with antimicrobial properties, which can reinforce prophylactic potential or even help treat infections, through localized delivery systems for antibiotics.

Current Progress and Outlook of Nano-Based Hydrogel Dressings for Wound Healing

Wound dressing is an important tool for wound management. Designing wound dressings by combining various novel materials and drugs to optimize the peri-wound environment and promote wound healing is a novel concept. Hydrogels feature good ductility, high water content, and favorable oxygen transport, which makes them become some of the most promising materials for wound dressings. In addition, nanomaterials exhibit superior biodegradability, biocompatibility, and colloidal stability in wound healing and can play a role in promoting healing through their nanoscale properties or as carriers of other drugs. By combining the advantages of both technologies, several outstanding and efficient wound dressings have been developed. In this paper, we classify nano-based hydrogel dressings into four categories: hydrogel dressings loaded with a nanoantibacterial drug; hydrogel dressings loaded with oxygen-delivering nanomedicines; hydrogel dressings loaded with nanonucleic acid drugs; and hydrogel dressings loaded with other nanodelivered drugs. The design ideas, advantages, and challenges of these nano-based hydrogel wound dressings are reviewed and analyzed. Finally, we envisaged possible future directions for wound dressings in the context of relevant scientific and technological advances, which we hope will inform further research in wound management.

A review: Silver–zinc oxide nanoparticles – organoclay-reinforced chitosan bionanocomposites for food packaging

Research on bionanocomposites has been developed, while its application as food packaging is still being explored. They are usually made from natural polymers such as cellulose acetate, chitosan (CS), and polyvinyl alcohol. Bionanocomposite materials can replace traditional non-biodegradable plastic packaging materials, enabling them to use new, high-performance, lightweight, and environmentally friendly composite materials. However, this natural polymer has a weakness in mechanical properties. Therefore, a composite system is needed that will improve the properties of the biodegradable food packaging. The aim of this mini-review is to demonstrate recent progress in the synthesis, modification, characterization, and application of bionanocomposites reported by previous researchers. The focus is on the preparation and characterization of CS-based bionanocomposites. The mechanical properties of CS-based food packaging can be improved by adding reinforcement from inorganic materials such as organoclay. Meanwhile, the anti-bacterial properties of CS-based food packaging can be improved by adding nanoparticles such as Ag and ZnO.

Green-synthesized silver nanoparticle coating on paper for antibacterial and antiviral applications

The use of active packaging has attracted considerable attention over recent years to prevent and decrease the risk of bacterial and viral infection. Thus, this work aims to develop active packaging using a paper coated with green-synthesized silver nanoparticles (AgNPs). Effects of different silver nitrate (AgNO3) concentrations, viz. 50, 100, 150, and 200 mM (AgNPs-50, AgNPs-100, AgNPs-150, and AgNPs-200, respectively), on green synthesis of AgNPs and coated paper properties were investigated. A bio-reducing agent from mangosteen peel extract (ex-Garcinia mangostana (GM)) and citric acid as a crosslinking agent for a starch/polyvinyl alcohol matrix were also used in the synthetic process. The presence of AgNPs, ex-GM, and citric acid indicated the required synergistic antibacterial activities for gram-positive and gram-negative bacteria. The paper coated with AgNPs-150 showed complete inactivation of virus within 1 min. Water resistance and tensile strength of paper improved when being coated with AgNPs-150. The tensile strength of the coated paper was found to be in the same range as that of a common packaging paper. Result revealed that the obtained paper coated with AgNPs was proven to be effective in antibacterial and antiviral activities; hence, it could be used as an active packaging material for items that require manual handling by a number of people.

New Green Approaches in Nanoparticles Synthesis: An Overview

Nanotechnology is constantly expanding, with nanomaterials being more and more used in common commercial products that define our modern life. Among all types of nanomaterials, nanoparticles (NPs) occupy an important place, considering the great amount that is produced nowadays and the diversity of their applications. Conventional techniques applied to synthesize NPs have some issues that impede them from being appreciated as safe for the environment and health. The alternative to these might be the use of living organisms or biological extracts that can be involved in the green approach synthesis of NPs, a process that is free of harmful chemicals, cost-effective and a low energy consumer. Several factors, including biological reducing agent concentration, initial precursor salt concentration, agitation, reaction time, pH, temperature and light, can influence the characteristics of biologically synthesized NPs. The interdependence between these reaction parameters was not explored, being the main impediment in the implementation of the biological method on an industrial scale. Our aim is to present a brief review that focuses on the current knowledge regarding how the aforementioned factors can control the size and shape of green-synthesized NPs. We also provide an overview of the biomolecules that were found to be suitable for NP synthesis. This work is meant to be a support for researchers who intend to develop new green approaches for the synthesis of NPs.

Modification of Thin Film Composite Membrane by Chitosan-Silver Particles to Improve Desalination and Anti-Biofouling Performance

Reverse osmosis (RO) desalination is a technology that is commonly used to mitigate water scarcity problems; one of its disadvantages is the bio-fouling of the membranes used, which reduces its performance. In order to minimize this problem, this study prepared modified thin film composite (TFC) membranes by the incorporation of chitosan-silver particles (CS-Ag) of different molecular weights, and evaluated them in terms of their anti-biofouling and desalination performances. The CS-Ag were obtained using ionotropic gelation, and were characterized by Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The modified membranes were synthetized by the incorporation of the CS-Ag using the interfacial polymerization method. The membranes (MCS-Ag) were characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle. Bactericidal tests by total cell count were performed using Bacillus halotolerans MCC1, and anti-adhesion properties were confirmed through biofilm cake layer thickness and total organic carbon (%). The desalination performance was defined by permeate flux, hydraulic resistance, salt rejection and salt permeance by using 2000 and 5000 mg L^-1 of NaCl. The MCS-Ag-L presented superior permeate flux and salt rejection (63.3% and 1% higher, respectively), as well as higher bactericidal properties (76% less in total cell count) and anti-adhesion capacity (biofilm thickness layer 60% and total organic carbon 75% less, compared with the unmodified membrane). The highest hydraulic resistance value was for MCS-Ag-M. In conclusion, the molecular weight of CS-Ag significantly influences the desalination and the antimicrobial performances of the membranes; as the molecular weight decreases, the membranes' performances increase. This study shows a possible alternative for increasing membrane useful life in the desalination process.

Antibacterial aerogels with nano‑silver reduced in situ by carboxymethyl cellulose for fresh meat preservation

Bacterial cellulose (BC) was used as a reinforcing agent, citric acid (CA) as a cross-linking agent, and CMC@AgNPs as antibacterial nanomaterials, in which CMC@AgNPs were reduced from AgNO₃ in situ by carboxymethyl cellulose (CMC) as a reducing agent and stabilizer to fight microbial corruption. Its potential application in packaging fresh meat has been investigated. Results showed that the antibacterial CMC@AgNPs/BC/CA aerogels with excellent structural integrity and outstanding water absorption were developed by adding 0.3% BC and 0.25% CA. The CMC@AgNPs/BC/CA aerogel significantly reduced the color change and the total viable bacterial counts (TVC) in fresh meat after 7 days of refrigerated storage. The results indicated that CMC@AgNPs/BC/CA aerogels can effectively extend the shelf life of fresh meat, and can be used for meat packaging as a biologically active absorption pad.

In Situ Green Synthesis of Graphene Oxide-Silver Nanoparticles Composite with Using Gallic Acid

The adoption of plant-derived natural products to synthesize metal nanoparticles and their complexes has the advantages of mild reaction conditions, environmental protection, sustainability and simple operation compared with traditional physical or chemical synthesis methods. Herein, silver nanoparticles (AgNPs) were in situ synthesized on the surface of graphene oxide (GO) by a “one-pot reaction” to prepare graphene oxide-silver nanoparticles composite (GO-AgNPs) based on using AgNO₃ as the precursor of AgNPs and gallic acid (GA) as the reducing agent and stabilizer. The size and morphology of GO-AgNPs were characterized by ultraviolet-visible spectrophotometer (Uv-vis), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), X-ray diffractometer (XRD) and dynamic light scattering (DLS). The effects of pH, temperature, time and material ratio on the synthesis of GO-AgNPs were investigated experimentally. The results showed that ideal GO-AgNPs could be prepared under the conditions of pH = 9, 45°C, 2 h and the 2:1 of molar ratio of AgNO₃ to GA. The AgNPs within GO-AgNPs are highly crystalline spherical particles with moderate density on the surface of GO, and the size of AgNPs is relatively uniform and determined to be about 8.19 ± 4.21 nm. The research results will provide new ideas and references for the green synthesis of metal nanoparticles and their complexes using plant-derived natural products as the reducing agent and stabilizer.

New dynamic microreactor system to mimic biofilm formation and test anti-biofilm activity of nanoparticles

Microbial biofilms are composed of surface-adhered microorganisms enclosed in extracellular polymeric substances. The biofilm lifestyle is the intrinsic drug resistance imparted to bacterial cells protected by the matrix. So far, conventional drug susceptibility tests for biofilm are reagent and time-consuming, and most of them are in static conditions. Rapid and easy-to-use methods for biofilm formation and antibiotic activity testing need to be developed to accelerate the discovery of new antibiofilm strategies. Herein, a Lab-On-Chip (LOC) device is presented that provides optimal microenvironmental conditions closely mimicking real-life clinical biofilm status. This new device allows homogeneous attachment and immobilization of Pseudomonas aeruginosa PA01-EGFP cells, and the biofilms grown can be monitored by fluorescence microscopy. P. aeruginosa is an opportunistic pathogen known as a model for drug screening biofilm studies. The influence of flow rates on biofilms growth was analyzed by flow simulations using COMSOL® 5.2. Significant cell adhesion to the substrate and biofilm formation inside the microchannels were observed at higher flow rates > 100 µL/h. After biofilm formation, the effectiveness of silver nanoparticles (SNP), chitosan nanoparticles (CNP), and a complex of chitosan-coated silver nanoparticles (CSNP) to eradicate the biofilm under a continuous flow was explored. The most significant loss of biofilm was seen with CSNP with a 65.5% decrease in average live/dead cell signal in biofilm compared to the negative controls. Our results demonstrate that this system is a user-friendly tool for antibiofilm drug screening that could be simply applied in clinical laboratories.Key Points• A continuous-flow microreactor that mimics real-life clinical biofilm infections was developed.• The antibiofilm activity of three nano drugs was evaluated in dynamic conditions.• The highest biofilm reduction was observed with chitosan-silver nanoparticles.

γ-Irradiated Chitosan Mediates Enhanced Synthesis and Antimicrobial Properties of Chitosan-Silver (Ag) Nanocomposites

Chitosan (CSN) and its derivatives are being exploited for their potential role in agriculture in mitigating environmental stress factors. The present study was aimed to enhance the synthesis of chitosan (CSN)-based silver nanoparticles (Ag NPs) using γ-irradiated chitosan (IR-CSN) and to study the antimicrobial activity of IR-CSN-Ag NPs. The chitosan-silver nanocomposites (CSN-Ag NPs) were prepared by employing the green synthesis method using normal chitosan (high molecular weight (MW), NL-CSN) and oligochitosans (low MW, IR-CSN). The latter was derived by irradiation with γ rays (60Co) at 100 kGy dose to obtain a lower MW (approximately 25 kDa). NL-CSN and IR-CSN (0.0-2.5% w/v) were amalgamated with different concentrations of silver nitrate (0.0-2.5% w/v) and vice versa. The UV-visible spectra displayed a single peak in the range of 419-423 nm, which is the characteristic surface plasmon resonance (SPR) for Ag NPs. The physicochemical properties were assessed using different methods such as transmission electron microscopy (TEM), Fourier transform infrared (FTIR), zetasizer, elemental (CHNS) analysis, etc. The degree of Ag NP synthesis was more in IR-CSN than NL-CSN. The in vitro disc diffusion assay with IR-CSN-Ag NPs exhibited a significantly higher antimicrobial activity against Escherichia coli. Further evaluation of the antifungal activity of IR-CSN and Ag NPs showed a synergistic effect against chickpea wilt (Fusarium oxysporum f. sp. ciceris). The study has provided a novel approach for the improved synthesis of CSN-Ag nanoparticle composites using γ-irradiated chitosan. This study also opens up new options for the development and deployment of γ-irradiated chitosan-silver nanocomposites for the control of phytopathogens in sustainable agriculture.

Green Synthesis of Metal and Metal Oxide Nanoparticles Using Different Plants’ Parts for Antimicrobial Activity and Anticancer Activity: A Review Article

Nanotechnology emerged as a scientific innovation in the 21st century. Metallic nanoparticles (metal or metal oxide nanoparticles) have attained remarkable popularity due to their interesting biological, physical, chemical, magnetic, and optical properties. Metal-based nanoparticles can be prepared by utilizing different biological, physical, and chemical methods. The biological method is preferred as it provides a green, simple, facile, ecofriendly, rapid, and cost-effective route for the green synthesis of nanoparticles. Plants have complex phytochemical constituents such as carbohydrates, amino acids, phenolics, flavonoids, terpenoids, and proteins, which can behave as reducing and stabilizing agents. However, the mechanism of green synthesis by using plants is still highly debatable. In this report, we summarized basic principles or mechanisms of green synthesis especially for metal or metal oxide (i.e., ZnO, Au, Ag, and TiO2, Fe, Fe2O3, Cu, CuO, Co) nanoparticles. Finally, we explored the medical applications of plant-based nanoparticles in terms of antibacterial, antifungal, and anticancer activity.

Chitosan-based nanocomposite films incorporated with NiO nanoparticles: Physicochemical, photocatalytic and antimicrobial properties

The aim of this research was to fabricate active nanocomposite films by incorporation of nickel oxide nanoparticles (NiONPs) (3, 6 and 9% w/w) into the chitosan-based films. The NiONPs were synthesized by solution combustion method and the films were prepared by solvent casting method. The formation of new interactions and increasing of films' crystallinity were confirmed by FT-IR and XRD analyses. Uniform dispersion of NiONPs at lower concentrations and their aggregation at level of 9% was confirmed by FE-SEM observations. Water barrier properties, tensile strength, thermal properties and surface hydrophobicity of films enhanced by addition of 6% NiONPs. Photocatalytic activity of nanocomposites was confirmed by absorption of 72% of methyl orange during 270 min under UV irradiation. The nanocomposite films exhibited good antibacterial activity against gram-positive (S. aureus) and gram-negative (S. typhimurium) bacteria. Therefore, the chitosan-NiONPs nanocomposite films could be used for active food packaging applications and photodecolorization purposes.

Development of pH-responsive nanocomposites with remarkably synergistic antibiofilm activities based on ultrasmall silver nanoparticles in combination with aminoglycoside antibiotics

Bacterial biofilms are responsible for many chronic infections because antibacterial agents exhibit poor penetration into the dense matrix barrier and cannot easily reach the internal bacteria. Herein, we reported pH-responsive nanocomposites (PDA@Kana-AgNPs) that could penetrate and disperse biofilms, which were synthesized by the combination of ultrasmall silver nanoparticles (AgNPs) and kanamycin, and then coating with polydopamine. Confocal fluorescence imaging indicated that PDA@Kana-AgNPs could respond to the acidic microenvironment of biofilms, leading to biofilm-triggered on- demand drug release in situ. The zone of inhibition test and Resazurin assay showed that the combination of kanamycin and AgNPs had greater antimicrobial activity against test strains (Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Escherichia coli BL21) than when applied separately. The crystal violet staining test demonstrated that biofilms were effectively dispersed by the proposed nanocomposites. Biocompatibility was also evaluated, which showed that PDA@Kana-AgNPs were non-toxic to mammalian cells. Therefore, the proposed pH-responsive nanocomposites held great potential for efficient antibiotics delivery and showed synergistic antibacterial and antibiofilm activities. This strategy could also be used to encapsulate a variety of antibiotics in combination with other drugs or materials, thereby showing therapeutic potential in preventing biofilm-related infections and realizing fluorescence imaging in situ.

Interpenetrating polysaccharide-based hydrogel: A dynamically responsive versatile medium for precisely controlled synthesis of nanometals

Herein, we reported an interpenetrating polysaccharide-based hydrogel in which carboxymethyl chitosan (CMC) chains were physically dispersed throughout the thermoplastic elastomer gel network has been developed as a versatile platform for precisely controlled synthesis of nanometals. Results indicated the interpenetrated CMC chains could serve as multifunctional fillers for metal ions adsorption and stabilization while the thermally reconfigurable agarose (Agar) gel medium provides three-dimensional semi-solid framework for entrapping and recollecting of the fabricated nanometals. Specifically, the CMC chains were found to strongly coordinate with silver ions as a dynamically responsive metal-biopolymer complex within the bulk gel network as confirmed by the enhanced mechanical properties and regulated shape memory performances. Moreover, by varying CMC concentrations and coupling with a layer-stacking approach, multiple biochemical gradients could be facilely generated for in-situ synthesis of silver nanoparticles, achieving a narrow size of ~7 nm, confined sphere-shape and high concentrations. The monodispersed nanometals are confirmed to be highly active (e.g., considerable catalytic performance), and which could be easily recycled from the bulk gel system via a heating treatment. Thus, this work would provide a generic methodology for the multifunctional metallogel assembly and great possibility for controllable and largescale synthesis of noble nanometals toward biomedical applications.

Effect of glucose substitution by low-molecular weight chitosan-derivatives on functional, structural and antioxidant properties of maillard reaction-crosslinked chitosan-based films

In this study, the effects of different temperatures, incubation times and types of reducing sugars, including glucose and different low molecular weight (Mw) chito-oligosaccharides (COS) with varying acetylation degree (AD), on the extent of Maillard reaction (MR) on chitosan-based films were studied. Interestingly, an improvement of structural and functional properties of all MR-crosslinked films was noted, which is more pronounced by heating at higher temperature and exposure time. These findings were proved through Fourier-transform infrared and X-ray diffraction analyses. In addition, color change and Ultraviolet spectra demonstrate that glucose addition provides the high extent of MR, followed by COS1 (Mw < 4.4 kDa; AD, 18.20%) and COS2 (Mw < 4.4 kDa; AD, 10.63%). These results were confirmed by enhanced water resistance and thermal properties. Moreover, MR-chitosan/COS films showed the highest mechanical properties, whereas, glucose-loaded films were brittle, as demonstrated by scanning electron microscopy micrographs. Furthermore, MR-chitosan/COS1 films exhibited the better antioxidant behavior followed by chitosan/glucose and chitosan/COS2 films, mainly at higher heating-conditions. Thereby, MR-crosslinked chitosan/COS based films were attractive to be applied as functional and active coating-materials in various fields.

New chitosan derivatives inspired on heterocyclic anhydride of potential bioactive for medical applications

In the present work new chitosan derivatives inspired heterocyclic anhydride were prepared to improve the biological activities of chitosan via imidization reaction of chitosan (CS) and N-(1,3-dioxoisoindolin-2-yl)-1,3-dioxo-1,3-dihydroiso-benzofuran-5-carboxamide (5) to yield amic acid CS-6 at room temperature and imide CS-8 thermally. However, the reaction between (CS) and anhydride (5) in presence of sodium tripolyphosphate (TPP) or Poly (ethylene glycol) diglycidyl ether (PEGDG) at room temperature yielded CS-6 NPs and CS-7 respectively. The structure of new chitosan derivatives was characterized using morphological and spectroscopic analyses. From evaluation of the biological activities, the greatest enzymatic inhibitory for trypsin and α-chymotrypsin revealed by CS-7 at 88.33 ± 2.27 and 79.63 ± 3.16% respectively. Furthermore, the highest inhibition zones, (MIC) and (MBC) against S. aureus and B. subtilis recorded by CS-6 NPs at 21 ± 0.75, 22 ± 0.98 mm, 19.5, 19.5, 38 and 38 ppm respectively. Additionally, CS-8 displayed the best cell growth inhibition against vero cell line at 93.17 ± 0.29%.

Antibacterial and wound healing-promoting effect of sponge-like chitosan-loaded silver nanoparticles biosynthesized by iturin

Silver nanoparticles (AgNPs) are widely used in wound dressing, but are limited in the application due to its high toxicity at effective concentrations. iturin-AgNPs was previously found to have much higher antibacterial activity at lower AgNPs content than the commercial AgNPs. To verify its potential application in the promotion of wound healing, a chitosan (CS) composite sponge dressing-loaded iturin-AgNPs was developed and evaluated for their antibacterial activity in vitro and used for wound healing in vivo. As results, the synthesized CS dressing had high porosity and water absorption. As expected, the antibacterial activity of CS dressing was significantly promoted by the incorporation of iturin-AgNPs. The CS dressing-loaded iturin-AgNPs showed more effective inhibition of bacterial infection and promotion of wound healing processing and quality than the commercial wound dressing loaded AgNPs in vivo. The mechanisms for the promotion of wound healing by the CS dressing-loaded iturin-AgNPs were found as the enhancement of re-epithelialization and collagen formation, as well as the increased antibacerial activity. No toxicity was found to all organs of mice. The study developed an efficient way to enhance the antibacterial activity of CS dressing loaded AgNPs at low toxicity, which has great potential in wound care application.

P. S. AK, Olaiya NG, Abdullah CK, Alfatah T, Gopakumar DA, Pasquini D. Improved Hydrophobicity of Macroalgae Biopolymer Film Incorporated with Kenaf Derived CNF Using Silane Coupling Agent

Hydrophilic behaviour of carrageenan macroalgae biopolymer, due to hydroxyl groups, has limited its applications, especially for packaging. In this study, macroalgae were reinforced with cellulose nanofibrils (CNFs) isolated from kenaf bast fibres. The macroalgae CNF film was after that treated with silane for hydrophobicity enhancement. The wettability and functional properties of unmodified macroalgae CNF films were compared with silane-modified macroalgae CNF films. Characterisation of the unmodified and modified biopolymers films was investigated. The atomic force microscope (AFM), SEM morphology, tensile properties, water contact angle, and thermal behaviour of the biofilms showed that the incorporation of Kenaf bast CNF remarkably increased the strength, moisture resistance, and thermal stability of the macroalgae biopolymer films. Moreover, the films’ modification using a silane coupling agent further enhanced the strength and thermal stability of the films apart from improved water-resistance of the biopolymer films compared to unmodified films. The morphology and AFM showed good interfacial interaction of the components of the biopolymer films. The modified biopolymer films exhibited significantly improved hydrophobic properties compared to the unmodified films due to the enhanced dispersion resulting from the silane treatment. The improved biopolymer films can potentially be utilised as packaging materials.

Chitosan derivatives-based films as pH-sensitive drug delivery systems with enhanced antioxidant and antibacterial properties

The purpose of this study was to develop and characterize chitosan (Ch)-based films incorporated with varying molecular weight (Mw) and acetylation degree (AD) chitosan-depolymerization-products (CDP), to be applied as drug delivery materials. As compared to Ch-film, optical and antioxidant potentials of Ch/CDP-based films were improved, particularly using low Mw and AD-CDP. Whereas, films water resistance, mechanical and antibacterial properties increased as CDP-Mw increased and AD decreased. For the thermal and swelling behaviors, better values were obtained using higher Mw and AD-CDP. Further, to assess their in vitro ciprofloxacin (CFX)-release behavior, loaded-CFX Ch/CDP-based films, crosslinked using glutaraldehyde, were prepared. Expect of elongation at break, crosslinked CFX-loaded films showed increased optical, water resistance, tensile strength and thermal properties, as compared to unloaded films. The CFX-release profiles indicated that a slower and sustained release was observed, particularly when using lower Mw and AD-CDP, and mainly for the crosslinked films during 48 h. These films can release CFX for up to 54% in 6 and 24 h, at pH 1.2 and 7.4, respectively. Through this study, novel biodegradable, swellable and pH-sensitive crosslinked Ch/CDP-based films may be considered as suitable and promising drug delivery systems.

Chitosan and Derivatives: Bioactivities and Application in Foods

Chitosan is a biodegradable, biocompatible, and nontoxic aminopolysaccharide. This review summarizes and discusses the structural modifications, including substitution, grafting copolymerization, cross-linking, and hydrolysis, utilized to improve the physicochemical properties and enhance the bioactivity and functionality of chitosan and related materials. This manuscript also reviews the current progress and potential of chitosan and its derivatives in body-weight management and antihyperlipidemic, antihyperglycemic, antihypertensive, antimicrobial antioxidant, anti-inflammatory, and immunostimulatory activities as well as their ability to interact with gut microbiota. In addition, the potential of chitosan and its derivatives as functional ingredients in food systems, such as film and coating materials, and delivery systems is discussed. This manuscript aims to provide up-to-date information to stimulate future discussion and research to promote the value-added utilization of chitosan in improving the safety, quality, nutritional value and health benefits, and sustainability of our food system while reducing the environmental hazards.

Electrochemical synthesis of chitosan/silver nanoparticles multilayer hydrogel coating with pH-dependent controlled release capability and antibacterial property

By coupling in situ electrochemical synthesis of silver nanoparticles (AgNPs) with the pre-deposited chitosan multilayer hydrogel, a novel type of nanocomposite coating was successfully fabricated on the stainless-steel needle electrode. Experimental results demonstrated the chitosan film can serve as a versatile medium for metal salt adsorption and stabilization, and finally electrochemical reduction of loaded silver ions to nanoparticles. The AgNPs were fabricated with a spherical shape and an average size of ∼15 nm endowing considerable antibacterial property to the hydrogel. Furthermore, the unique layered architecture consisted of porous segments and compact boundaries is almost retained, resulting in a pH-dependent and staged release pattern of silver nanoparticles based on acid triggered dissolution of the multi-membrane layer by layer. Thus, considering the mild synthesizing approach, multi-functionalities and relatively low cytotoxicity, this antibacterial hydrogel would show great potential either to be used as a newly coating material for interfacial improvement of implants or as a free-standing film after being peeled off for wound dressing.

Transformation of Biowaste for Medical Applications: Incorporation of Biologically Derived Silver Nanoparticles as Antimicrobial Coating

Nanobiotechnology has undoubtedly influenced major breakthroughs in medical sciences. Application of nanosized materials has made it possible for researchers to investigate a broad spectrum of treatments for diseases with minimally invasive procedures. Silver nanoparticles (AgNPs) have been a subject of investigation for numerous applications in agriculture, water treatment, biosensors, textiles, and the food industry as well as in the medical field, mainly due to their antimicrobial properties and nanoparticle nature. In general, AgNPs are known for their superior physical, chemical, and biological properties. The properties of AgNPs differ based on their methods of synthesis and to date, the biological method has been preferred because it is rapid, nontoxic, and can produce well-defined size and morphology under optimized conditions. Nevertheless, the common issue concerning biological or biobased production is its sustainability. Researchers have employed various strategies in addressing this shortcoming, such as recently testing agricultural biowastes such as fruit peels for the synthesis of AgNPs. The use of biowastes is definitely cost-effective and eco-friendly; moreover, it has been reported that the reduction process is simple and rapid with reasonably high yield. This review aims to address the developments in using fruit- and vegetable-based biowastes for biologically producing AgNPs to be applied as antimicrobial coatings in biomedical applications.

Synthesis of Ag@chitosan/copolymer with dual-active centers for high antibacterial activity

The prevention and treatment of microorganism contamination on substrate surfaces have recently generated significant concern of scientists. In this paper, a novel diblock copolymer containing antibacterial quaternary ammonium groups as pendant groups, poly(3-(methacryloylamino) propyltrimethyl ammonium chloride)-b-poly(styrene) (PMS), was synthesized by interfacial polymerization. Also, PMS anisotropic particles (APs) could be successfully obtained based on different assembly behaviors by adjusting the ratios of monomers and the toluene/styrene (Tol/St). Moreover, silver loaded chitosan (Ag@CS) and PMS APs were combined to prepare natural/synthetic polymer antibacterial materials with dual-active centers (Ag@CS/PMS-4 APs), aiming to expand the application of carbohydrate polymers and improve the antibacterial activity of composite materials. Remarkably, the resulting series of PMS particles, especially worm-like PMS-4 APs, and Ag@CS/PMS-4 APs composite film ((Ag@CS/PMS-4 APs)-F) exhibited excellent antibacterial properties, which can be employed as interface materials to prevent the transmission of infectious diseases caused by microorganism contamination.

Food and Beverage Ingredients Induce the Formation of Silver Nanoparticles in Products Stored within Nanotechnology-Enabled Packaging

Nanotechnology-based packaging may improve food quality and safety, but packages manufactured with polymer nanocomposites (PNCs) could be a source of human dietary exposure to engineered nanomaterials (ENMs). Previous studies showed that PNCs release ENMs to foods predominantly in a dissolved state, but most of this work used food simulants like dilute acetic acid and water, leaving questions about how substances in real foods may influence exposure. Here, we demonstrate that food and beverage ingredients with reducing properties, like sweeteners, may alter exposure by inducing nanoparticle formation in foods contacting silver nanotechnology-enabled packaging. We incorporated 12.8 ± 1.4 nm silver nanoparticles (AgNPs) into polyethylene and stored media containing reducing ingredients in packages manufactured from this material under accelerated room-temperature and refrigerated conditions. Analysis of the leachates revealed that reducing ingredients increased the total silver transferred to foods contacting PNC packaging (by as much as 7-fold) and also induced the (re)formation of AgNPs from this dissolved silver during storage. AgNP formation was also observed when Ag⁺ was introduced to solutions of natural and artificial sweeteners (glucose, sucrose, aspartame), commercial beverages (soft drinks, juices, milk), and liquid foods (yogurt, starch slurry), and the amount and morphology of reformed AgNPs depended on the ingredient formulation, silver concentration, storage conditions, and light exposure. These results imply that food and beverage ingredients may influence dietary exposure to nanoparticles when PNCs are used in packaging applications, and the practice of using food simulants may in certain cases underpredict the amount of ENMs likely to be found in foods stored in these materials.

Green synthesis of silver nanoparticles using soluble soybean polysaccharide and their application in antibacterial coatings

In the present work, a facile and green synthesis approach for the production of monodispersed, small-sized (2.9 ± 0.7 nm) and stable silver nanoparticles (AgNPs) using soluble soybean polysaccharide (SSPS) was reported. SSPS was used as the reducing and stabilizing agent. The obtained SSPS-stabilized AgNPs (SA) were characterized by UV-vis absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The antimicrobial activity of the SA colloidal dispersion (SACD) was evaluated based on the growth kinetics of bacteria E. coli and S. aureus. Afterwards, the colloidal dispersion was applied as a coating material to Kraft paper. The SACD-coated Kraft paper exhibited excellent antimicrobial activity against above bacteria strains and P. aeruginosa. The effects of SACD coating on surface wettability, barrier property and microstructure of the Kraft paper were also studied. The results suggested that the SSPS-stabilized AgNPs have great potential in antibacterial applications.

Leveraging the water electrolysis reaction in bipolar electrophoresis to form robust and defectless chitosan films

Electrophoresis of chitosan and its composites are widely used to form a coating on selective substrates, but the parasitic water electrolysis causes structural defects that weaken the resulting film. In this work, we demonstrate a bipolar electrophoresis technique that leverages the water electrolysis to produce a chitosan film with less porosity and surface cavities. The process involves a negative bias to deposit the protonated chitosan molecules from the solution, followed by a positive bias to remove the entrapped hydrogen bubbles via the re-protonation of chitosan deposit. Since water electrolysis occurs for both positive and negative bias, the bipolar profile is designed to engender pH changeup near the electrode for "surface conditioning" of chitosan film. The bipolar electrophoresis route demonstrates better coulomb efficiency than that of conventional potentiostatic electrophoresis, resulting in a free-standing chitosan film with sufficient mechanical strength and large area.

In situ generation of silver nanoparticles and nanocomposite films based on electrodeposition of carboxylated chitosan

Herein, for the first time the electrodeposition of carboxylated chitosan is studied and utilized for the synthesis of silver nanoparticles (AgNPs) and generation of AgNPs/carboxylated chitosan nanocomposite films. Particularly, AgNPs are in situ synthesized on electrodes or substrates during the electrodeposition. Carboxylated chitosan not only acts as the green reducing agent and stabilizing agent for preparing AgNPs, but also serves as the main component in the electrodeposited nanocomposite film. The experimental results indicate that a smooth and homogeneous film is formed on the silver plate after electrodeposition, and the electrodeposited film can be detached from the silver plate as an independent film. The TEM observation and spectroscopic analysis results confirm the existence of AgNPs (the average size of 10 nm) in the nanocomposite film. The nanocomposite films with various shapes can be fabricated by the spatial selectivity of electrodeposition. In addition, the nanocomposite film containing AgNPs shows favorable antibacterial properties.