High antibacterial activity of chitosan films with covalent organic frameworks immobilized silver nanoparticles

Catharanthus roseus extract-assisted silver nanoparticles chitosan films with high antioxidant and antimicrobial properties for fresh food preservation

Although the potential of chitosan (CS) -based biomass packaging materials for food preservation is encouraging, their use is severely constrained by the poor mechanical, UV, antioxidant, and solubility qualities. This study successfully combined silver nanoparticles made from Catharanthus roseus extracts with chitosan (CS-Ca-Ag) to enrich the functions of CS film. The films' Young's modulus values (45.489 MPa) were considerably raised after adding the extract-biosynthesized silver nanoparticles, in contrast to the chitosan film, and their water vapor permeability (2.386 × 10-12 g·mm-1·Pa-1·h-1) was greatly reduced. Furthermore, the antibacterial, antioxidant, and UV adsorption capabilities of CS-Ca-Ag films were significantly improved. The prepared Cs-Ca-Ag film had high biocompatibility and safety, making it suitable for strawberry coatings and chicken packaging. The CS-Ca-Ag film effectively limited the weight loss of fresh food, reduced nutrient loss, prevented microbial growth, and significantly extended food's shelf life. CS-based reinforced films containing Catharanthus roseus extract and silver nanoparticles showed potential food coating and packaging material applications.

A perspective on recent advances in polysaccharide/covalent organic framework composite materials with applications potential in water remediation

Researching the potential of various composite materials to remove water pollutants is an important issue for scientists, and polysaccharides are considered desirable materials in this field. Despite the unique advantages, combining these natural materials with a secondary component, especially porous compounds, could improve the performance of the desired system. Recently, highly porous constructs, such as covalent organic frameworks (COFs), was introduced for the composition of polysaccharides. Also, this combinations can solve the aggregation concern of COFs in water treatment areas. Therefore, the composition of the polysaccharides and COF materials effectively has demonstrated their ability to remove contaminants. The hydrogels, films, aerogels, and membranes are some formulations for these kind systems. When polysaccharides are combined with other substances like COF and Fe3O4 the resulting system displays new properties that expand its applicability while having the properties of both components. A survey of the published reports shows that up to now some comprehensive research explored the potential of polysaccharide/COF composite materials for water treatment. Considering these, the current mini review paper highlights the conducted studies on evaluated polysaccharide/COF composite materials, with a focus on the chitosan (CS), cellulose, alginate, and κ-carrageenan for water treatment containing various pollutants such as dyes, metals, pharmaceuticals and other chemical compounds.

Eco-friendly catalysts: Chitosan-silver hybrid nanocarriers for efficient oxidative coupling of anilines to azobenzenes

Sustainable, catalytic hybrid nano-carrier (microspheres/films) were synthesized by combining polysaccharides and silver nanoparticles (AgNPs). Chitosan (CS) and microcrystalline cellulose (MCC) acted as stabilizers and reinforcements, respectively, resulting in a bio-composite support with tailored catalytic activity. The hybrid nano-carriers were characterized using various analytical techniques including, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The catalytic performance and stability of the prepared nano-carriers (both microspheres and films) were evaluated in the synthesis of azo compounds. The results demonstrated high catalytic efficiency (up to 90 % conversion) in the production of azobenzene, with good recyclability. This study highlights the potential of chitosan, silver nanoparticles and microcrystalline cellulose as effective components in the development of catalytic nano-carriers for azo compounds synthesis.

Preparation and physicochemical characterization of different biocomposite films blended with bacterial exopolysaccharide EPS MC-5 and bacteriocin for food packaging applications

The study aims to evaluate how bacteriocin and extracellular polymeric substances (EPS) can influence the development of active packaging for food. The components might enhance the performance of packaging materials in terms of their physicochemical properties and their effectiveness in preserving food. Bacteriocin and EPS exert a significant effect in blocking the transmission of UV and visible light radiations. The molecular stability among the different functional groups of the composite films was evaluated using FT-IR analysis. The MG5 film exhibited the lowest percentage of water solubility (11.27 %) and the highest antibacterial activity against L. monocytogenes and E. coli, with a zone of inhibition measured as 21.32 ± 0.76 and 18.81 ± 0.29 mm, respectively. The TGA results indicated a noteworthy level of thermal stability in the composite films. Specifically, the MG5 bacteriocin blended film exhibited an approved metal chelation activity and demonstrated superior antioxidant activity, as evidenced by enhanced DPPH and ABTS+ scavenging activities. The incorporation of bacteriocin enhanced the interactions among the film components, and surface roughness was greatly impacted as revealed by the FE-SEM analysis. MG5 film exhibited excellent biodegradability in the natural soil environment, according to a soil burial study. To sum up, MG5 films can be an effective food packaging material, particularly for fried or high-fat items that are prone to contamination from microorganisms.

Chitosan-based nanocomposite films incorporated with AgNPs/porphyrinic MOFs for killing pathogenic bacteria

In this work, a nanocomposite film, designated as CS/PA, was fabricated by integrating chitosan (CS), porphyrinic porous coordination network (PCN), and silver nanoparticles (AgNPs). PCN modified AgNPs was denoted as PCN-AgNPs (PA). The synthesis of PA was verified through transmission electron microscope, Zeta potential, hydrated particle size, element mapping. Furthermore, varying concentrations of PA (0.3 %, 0.4 %, 0.5 %, and 0.6 % w/w) were integrated into the CS matrix to preparate the CS/PA nanocomposite film. The experimental data demonstrated a significant enhancement (p < 0.05) in the tensile strength and elongation at break of the nanocomposite films, while water vapor permeability and water solubility significantly decreased (p < 0.05) as the PA content increased. Additionally, the CS/PA film showed good antibacterial properties against both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. Notably, the CS/PA film effectively retarded the spoilage of fresh fish slices. The silver migration from the CS/PA film, measured at 33.02 μg/L, was found to be within the permissible limits set by the USEPA. Consequently, the CS/PA nanocomposite film holds immense promise for applications in food packaging industry.

Postbiotic-biosynthesized silver nanoparticles anchored on covalent organic frameworks integrated into carboxymethyl chitosan-based film for enhancing antibacterial packaging

Food packaging plays a vital role in guaranteeing the quality and safety of fresh products during the storage and distribution. Carboxymethyl chitosan (CMCS) is identified as a promising polymer for food packaging film owing to its film-forming ability, non-toxicity, and biodegradability. Nevertheless, the practical applications of pure CMCS film usually suffer from some limits owing to its poor antibacterial effect and mechanical strength. In this study, postbiotic-biosynthesized silver nanoparticles (AgNPs) anchored on covalent organic frameworks (COF) (namely COF-AgNP) were integrated into the CMCS film to enhance antibacterial packaging performance for preservation of fruits. Utilizing postbiotic as a reducing agent, COF-AgNPs composite nanomaterials were prepared by anchoring AgNPs on COF via in-situ reduction of Ag+. Furthermore, antibacterial packaging film was prepared using CMCS and COF-AgNPs (CMCS@COF-AgNPs) via a solution-casting method. Furthermore, characterization results proved that mechanical strength of CMCS@COF-AgNP films exhibited a gradual enhancement with the increased COFs-AgNPs content. Moreover, CMCS@COF-AgNP films exhibited an enhanced antibacterial activity and excellent biocompatibility. Importantly, CMCS@COF-AgNP coating can effectively preserve citrus quality and prolong its storage time. Therefore, CMCS@COF-AgNP films could be used as a promising and economically viable solution to diminish postharvest losses and prolong the shelf life of fresh products.

New emerging materials with potential antibacterial activities

The increasing prevalence of multidrug-resistant pathogens is a critical public health issue, necessitating the development of alternative antibacterial agents. Examples of these pathogens are methicillin-resistant Staphylococcus aureus (MRSA) and the emergence of "pan-resistant" Gram-negative strains, such as Pseudomonas aeruginosa and Acinetobacter baumannii, which occurred more recently. This review examines various emerging materials with significant antibacterial activities. Among these are nanomaterials such as quantum dots, carbon quantum dots, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and layered double hydroxides, all of which demonstrate excellent antibacterial properties. Interestingly, including antibacterial agents within the structure of these materials can help avoid bacterial resistance and improve the long-term efficacy of the materials. Additionally, the antibacterial potential of liquid solvents, including ionic liquids and both deep eutectic solvents and natural deep eutectic solvents, is explored. The review discusses the synthesis methods, advantages, and antibacterial efficacy of these new materials. By providing a comprehensive overview of these innovative materials, this review aims to contribute to the ongoing search for effective solutions to combat antibiotic resistance. Key studies demonstrating antibacterial effects against pathogens like Escherichia coli, Staphylococcus aureus, and multidrug-resistant strains are summarized. MOFs have exhibited antibacterial properties through controlled ion release and surface interactions. COFs have enhanced the efficacy of encapsulated antibiotics and displayed intrinsic antibacterial activity. Other nanomaterials, such as quantum dots, have generated reactive oxygen species, leading to microbial inactivation. This review aims to provide insights into these new classes of antibacterial materials and highlight them for addressing the global crisis of antibiotic resistance. KEY POINTS: • Nanomaterials show strong antibacterial effects against drug-resistant bacteria • Emerging solvents like ionic liquids offer novel solutions for bacterial resistance • MOFs and COFs enhance antibiotic efficacy, showing promise in combating resistance.

Standardization of silver nanoparticle synthesis: Photocatalytic application (immobilized with chitosan complex) with textile dyes and antibacterial activity against Staphylococcus aureus using banana pseudo stem

The purpose of the study is to standardize the silver nanoparticle (BP-AgNPs) synthesis and its antibacterial activity and photocatalytic application with the selected dyes using the banana pseudo stem extract. "One-factor analysis (OFTA)" was carried out for the standardization of silver nanoparticle synthesis and nanoparticle-chitosan complex immobilization. The parameters were identified with plant quantity (20 g), silver nitrate concentration (1 mM), the ratio of plant extract and silver nitrate solution (2:8), pH (12), temperature (37 °C), dispersed light conditions, shaking conditions (120 rpm), and time (6 h) were analysed. The photocatalytic decolorization efficiency of the standardized BP-AgNPs (immobilized with chitosan complex) has shown 96.92% for methylene blue (10 ppm) at 3 h and 97.55% for safranin (100 ppm) at 15 h. The antibacterial activity for the synthesised BP-AgNPs was determined. MIC value of the BP-AgNPs was determined to be 15.62 μg. mL-1 for S. aureus. The synthesised BP-AgNPs treated with 0.5×, 1× and 2× MIC concentration (x = 15.62 μg. mL-1) showed decreased viable counts of S. aureus (99.6% at 2× concentration having viable count of 22.6 × 102 CFU. mL-1) at 24 h incubation when compared with the control culture. The structural characteristics of the BP-AgNPs were identified as spherical with SEM and the size was identified as 12.19 ± 1.62 nm with TEM and as 37.23 ± 17.89 nm with XRD. The parameters such as FTIR, Zeta potential, EDS further supports the nanoparticle synthesis with banana pseudostem extract. The current result suggested that, the silver nanoparticles (BP-AgNPs) synthesised using the extract of the banana pseudo stem could be used as an alternative source for dye decolorization and antibacterial activities.

Chitosan-based film incorporated with silver-loaded organo-bentonite or organo-bentonite: Synthesis and characterization for potential food packaging material

Biopolymer-clay composite films were synthesized and characterized for food packaging material. The synthesis was conducted in two stages. Cetrimonium bromide-modified bentonite (CTAB-bentonite) was first exchanged with Ag ions to obtain Ag-CTAB-bentonite. Biopolymer-clay composite films were then performed by a solution-casting method between chitosan (biopolymer) and Ag-CTAB-bentonite or between chitosan and CTAB-bentonite. Different weights of CTAB-bentonite (3% and 5% wt.) and Ag-CTAB-bentonite (3% and 5% wt.) were used during the second stage. The resultant films were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscope coupled with energy dispersive X-ray spectroscopy, atomic force microscopes, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, optical measurement, and others (moisture content, swelling behavior, water solubility, antibacterial, shredded carrot preservation, and biodegradability). Results indicated that the properties (thermal stability, thermomechanical ability, UV-visible light barrier, shredded carrot preservation) of the chitosan-based film incorporated with the synthesized composites were enhanced compared to those of the CS film. The CS/(CTAB-bentonite)-3% and CS/(Ag-CTAB-bentonite)-3% films exhibited antibacterial properties against Escherichia coli, Salmonella enterica subp. enterica, Staphylococcus aureus, and Listeria monocytogenes. The chitosan-based film reinforced with the two prepared composites can be potential for food preservation and packaging.

A review of recent advancement in covalent organic framework (COFs) synthesis and characterization with a focus on their applications in antibacterial activity

The primary objective of this review is to present a comprehensive examination of the synthesis, characterization, and antibacterial applications of covalent organic frameworks (COFs). COFs represent a distinct category of porous materials characterized by a blend of advantageous features, including customizable pore dimensions, substantial surface area, and adaptable chemical properties. These attributes position COFs as promising contenders for various applications, notably in the realm of antibacterial activity. COFs exhibit considerable potential in the domain of antibacterial applications, owing to their amenability to functionalization with antibacterial agents. The scientific community is actively exploring COFs that have been imbued with metal ions, such as copper or silver, given their observed robust antibacterial properties. These investigations strongly suggest that COFs could be harnessed effectively as potent antibacterial agents across a diverse array of applications. Finally, COFs hold immense promise as a novel class of materials for antibacterial applications, shedding light on the synthesis, characterization, and functionalization of COFs tailored for specific purposes. The potential of COFs as effective antibacterial agents beckons further exploration and underscores their potential to revolutionize antibacterial strategies in various domains.

Citrate silver nanoparticles impregnated cellulose as a photocatalytic filter in the degradation of organic dye in the aqueous media

Photocatalysis is a clean and efficient process pursued under light irradiation with a suitable photocatalyst to degrade a contaminant. We report citrate functionalization of silver nanoparticles (SNPs) for effective immobilization on cellulosic fabric. The porous cellulosic matrix could be explored as microfiltration membranes for the photocatalytic degradation of organic dyes in the aqueous media. Where valid, the citrate functionalized SNPs and the treated cellulose fabrics were considered for optical, structural, surface chemical, thermal, textile, flowability, photocatalytic, and antibacterial attributes. The SNPs expressed the bandgap energy of 2.56 and 2.43 eV and Urbach energy of 3.38 and 5.21 eV before and after functionalization with the citrate moieties, respectively. The liquid chromatographic and FTIR analyses indicated that the crystal violet (CV) organic dye has been successfully photodegraded to environmentally safer and nontoxic species on passing the contaminated water through the SNPs-treated cellulosic filter. The spectroscopic data also supported the said outcomes. The results demonstrated that the citrate-SNPs-treated cellulose could be efficiently employed as antibacterial photocatalytic membranes for degrading organic dyes in the aqueous media for multiple cycles.

Novel Highly Efficient Antibacterial Chitosan-Based Films

In this study, we elaborated new chitosan-based films reinforced by iron(III)-containing chitosan nanoparticles Fe(III)-CS-NPs at different concentrations. We found that the optimum concentration of Fe(III)-CS-NPs for the improvement of antibacterial and mechanical properties of the films was 10% (σ_b = ca. 8.8 N/mm², ε_b = ca. 41%, inhibition zone for S. aureus = ca. 16.8 mm and for E. coli = ca. 11.2 mm). Also, using the click-chemistry approach (thiol-ene reaction), we have synthesized a novel water-soluble cationic derivative of chitin. The addition of this derivative of chitin to the chitosan polymer matrix of the elaborated film significantly improved its mechanical (σ_b = ca. 11.6 N/mm², ε_b = ca. 75%) and antimicrobial (inhibition zone for S. aureus = ca. 19.6 mm and for E. coli = ca. 14.2 mm) properties. The key mechanism of the antibacterial action of the obtained films is the disruption of the membranes of bacterial cells. The elaborated antibacterial films are of interest for potential biomedical and food applications.

Improving the functionality of biodegradable food packaging materials via porous nanomaterials

Non-biodegradability and disposal problems are the major challenges associated with synthetic plastic packaging. This review article discusses a new generation of biodegradable active and smart packaging based on porous nanomaterials (PNMs), which maintains the quality and freshness of food products while meeting biodegradability requirements. PNMs have recently gained significant attention in the field of food packaging due to their large surface area, peculiar structures, functional flexibility, and thermal stability. We present for the first time the recently published literature on the incorporation of various PNMs into renewable materials to develop advanced, environmentally friendly, and high-quality packaging technology. Various emerging packaging technologies are discussed in this review, along with their advantages and disadvantages. Moreover, it provides general information about PNMs, their characterization, and fabrication methods. It also briefly describes the effects of different PNMs on the functionality of biopolymeric films. Furthermore, we examined how smart packaging loaded with PNMs can improve food shelf life and reduce food waste. The results indicate that PNMs play a critical role in improving the antimicrobial, thermal, physicochemical, and mechanical properties of natural packaging materials. These tailor-made materials can simultaneously extend the shelf life of food while reducing plastic usage and food waste.

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.

Preparation of covalent organic framework-based nanofibrous films with temperature-responsive release of thymol for active food packaging

Thymol (THY) is commonly used in active food packaging, however because of its high volatility, poor water solubility, and strong aromatic odor, the application of THY is facing challenges. Herein, covalent organic frameworks (COFs) were synthesized in room temperature by asymmetric monomer exchange method for THY encapsulation, and solution blow spinning was used to fabricate the THY@COF/polycaprolactone (PCL) nanofibrous films. The synthesized COFs had a large specific surface area, porous structure, and loading capacity of 30.35% for THY, and THY@COFs possessed good thermal stability. Characterization analysis showed that THY@COFs were successfully incorporated into the PCL films and increased the barrier property of the films. Besides, the films showed good biocompatibility and antibacterial activity. Moreover, THY@COF/PCL films exhibited temperature-responsive THY release profiles, which is important for practical preservation applications, especially for preserving food in warm environments. Overall, THY@COF/PCL films possess promising potential in active food packaging.

Effect of Kaolin clay and Ficus carica mediated silver nanoparticles on chitosan food packaging film for fresh apple slice preservation

In this work, a novel antioxidant, antibacterial, and biodegradable food packaging film was elaborated, by incorporating natural kaolin clay (KC) and Ficus carica mediated silver nanoparticles (AgNPs) into Chitosan (Cht). A comparison of the physico-chemical and functional characteristics of the Cht/KC/AgNPs film was performed with those of Cht, Cht/KC, and Cht/AgNPs. SEM analysis showed a rough surface in the composite films containing KC particles because of their large diameter (50-120 μm) compared to AgNPs (20-80 nm). The FTIR analysis suggested that the interactions between Cht and AgNPs were stronger than those between Cht and KC. The tensile strength of Cht film increased from 16 MPa to ∼24 MPa in Cht/KC/AgNPs film. The introduction of KC and/or AgNPs considerably improved the light and moisture barrier capacity of the Cht film. The UV light transmittance decreased by 50 % for Cht film when incorporated by KC and AgNPs. Moreover, Cht/AgNPs was better in terms of antioxidant, antibacterial, and mechanical compared to Cht/KC, which was superior in biodegradability and water vapor barrier capacity. In particular, the Cht/KC/AgNPs film presented good barrier, antioxidants, antibacterial, mechanical, and biodegradable properties, owing to the synergistic effect between KC and AgNPs. For the packaging properties, all the films were tested for their ability to keep the freshness of apple slices as wrapping material. The films exhibited good results, and the Cht/KC/AgNPs showed promising performance regarding the moisture loss, browning index, total phenolic compound, and antioxidant activity of the apple slices. Moreover, the Cht/KC/AgNPs film exhibited a migration of silver meeting the standards set by EFSA and ECHA, which makes this film safe for food packaging.

κ-Carrageenan/triazin-based covalent organic framework bionanocomposite: Preparation, characterization, and its application in fast removing of BB41 dye from aqueous solution

A novel and high efficient adsorbent was prepared based on an environmentally friendly substrate, κ-carrageenan, and a triazine-based covalent organic framework as a co-adsorbent component. Combining these two precursors leads to an effective nanocomposite for removing Basic blue 41 dye from aqueous media. After confirm the structural of prepared composite by various analysis, the adsorption properties were investigated. The optimum conditions were obtained in: pH: 7, temperature: 25 °C and contact time: 210 min; and adsorbent dosage of 10 mg. According to the isotherms study, the basic blue 41 dye adsorption was matched to the Longmuir model with single-layer mechanism. The kinetic of adsorption was studied and fitted with pseudo-second order model with R² = 0.971. From the results the maximum adsorption capacity of 833 mg/g was obtained in 15 min and the reusability tests showed 24% decrease in yield after three cycles.

Assessment of antimicrobial activity of chitosan/silver nanoparticles hydrogel and cryogel microspheres

This research investigates the synthesis and characterization of hydrogel and cryogel microspheres that are doped with green synthesised silver nanoparticles (CS-AgNPs). Also, the study assesses the antibacterial activity of hydrogel and cryogel microspheres by comparing them with commercial antibiotics. The porous structure of CS and the adequate dispersion of AgNPs were confirmed by SEM and EDX techniques, respectively. The disk diffusion method and the optical density measurement (OD600) confirm the outstanding antimicrobial activity of CS-AgNPs hydrogel and cryogel microspheres in comparison to antibiotics for both Gram-positive and Gram-negative bacteria. The CS-AgNPs microspheres demonstrate promising antimicrobial and biocompatible agents for medical field applications.

Photocatalytic Organic Contaminant Degradation of Green Synthesized ZrO2 NPs and Their Antibacterial Activities

The green synthesis of metal oxide nanoparticles is an efficient, simple, and chemical-free method of producing nanoparticles. The present work reports the synthesis of Murraya koenigii-mediated ZrO2 nanoparticles (ZrO2 NPs) and their applications as a photocatalyst and antibacterial agent. Capping and stabilization of metal oxide nanoparticles were achieved by using Murraya koenigii leaf extract. The optical, structural, and morphological valance of the ZrO2 NPs were characterized using UV-DRS, FTIR, XRD, and FESEM with EDX, TEM, and XPS. An XRD analysis determined that ZrO2 NPs have a monoclinic structure and a crystallite size of 24 nm. TEM and FESEM morphological images confirm the spherical nature of ZrO2 NPs, and their distributions on surfaces show lower agglomerations. ZrO2 NPs showed high optical absorbance in the UV region and a wide bandgap indicating surface oxygen vacancies and charge carriers. The presence of Zr and O elements and their O=Zr=O bonds was categorized using EDX and FTIR spectroscopy. The plant molecules’ interface, bonding, binding energy, and their existence on the surface of ZrO2 NPs were established from XPS analysis. The photocatalytic degradation of methylene blue using ZrO2 NPs was examined under visible light irradiation. The 94% degradation of toxic MB dye was achieved within 20 min. The antibacterial inhibition of ZrO2 NPs was tested against S. aureus and E. coli pathogens. Applications of bio-synthesized ZrO2 NPs including organic substance removal, pathogenic inhibitor development, catalysis, optical, and biomedical development were explored.

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.

Metalated covalent organic frameworks: from synthetic strategies to diverse applications

Covalent organic frameworks (COFs) are a class of organic crystalline porous materials discovered in the early 21st century that have become an attractive class of emerging materials due to their high crystallinity, intrinsic porosity, structural regularity, diverse functionality, design flexibility, and outstanding stability. However, many chemical and physical properties strongly depend on the presence of metal ions in materials for advanced applications, but metal-free COFs do not have these properties and are therefore excluded from such applications. Metalated COFs formed by combining COFs with metal ions, while retaining the advantages of COFs, have additional intriguing properties and applications, and have attracted considerable attention over the past decade. This review presents all aspects of metalated COFs, from synthetic strategies to various applications, in the hope of promoting the continued development of this young field.

A Facile In Situ Synthesis of Resorcinol-Mediated Silver Nanoparticles and the Fabrication of Agar-Based Functional Nanocomposite Films

The in situ synthesis of silver nanoparticles (AgNPs) was performed using resorcinol and agar to produce agar-based antioxidant and antimicrobial films. AgNPs were regularly dispersed on the film matrix, and their presence improved the thermal stability of films. Additionally, the addition of AgNPs slightly increased the agar-based film’s tensile strength (~10%), hydrophobicity (~40%), and water vapor barrier properties (~20%) at 1.5 wt% of AgNP concentration. The resorcinol also imparted UV-barrier and antioxidant activity to the agar-based film. In particular, the agar-based film containing a higher quantity of AgNPs (>1.0 wt%) was highly effective against the foodborne pathogenic bacteria L. monocytogenes and E. coli. Therefore, agar-based composite films with improved physicochemical and functional properties may be promising for active packaging.