Bacterial cellulose films with ZnO nanoparticles and propolis extracts: Synergistic antimicrobial effect

Enhancing biodegradable smart food packaging: Fungal-synthesized nanoparticles for stabilizing biopolymers

The increasing global concern over environmental plastic waste has propelled the progress of biodegradable supplies for food packaging. Biopolymer-based packaging is undergoing modifications to enhance its mechanical properties, aligning with the requirements of smart food packaging. Polymer nanocomposites, incorporating reinforcements such as fibers, platelets, and nanoparticles, demonstrate significantly improved mechanical, thermal, optical, and physicochemical characteristics. Fungi, in particular, have garnered significant interest for producing metallic nanoparticles, offering advantages such as easy scaling up, streamlined downstream handling, economic feasibility, and a large surface area. This review provides an overview of nano-additives utilized in biopackaging, followed by an exploration of the recent advancements in using microbial-resistant metal nanoparticles for food packaging. The mycofabrication process, involving fungi in the extracellular or intracellular synthesis of metal nanoparticles, is introduced. Fungal functionalized nanostructures represent a promising avenue for application across various stages of food processing, packaging, and safety. The integration of fungal-derived nanostructures into food packaging materials presents a sustainable and effective approach to combatting microbial contamination." By harnessing fungal biomass, this research contributes to the development of economical and environmentally friendly methods for enhancing food packaging functionality. The findings underscore the promising role of fungal-based nanotechnologies in advancing the field of active food packaging, addressing both safety and sustainability concerns. The study concludes with an investigation into potential fungal isolates for nanoparticle biosynthesis, highlighting their relevance and potential in advancing sustainable and efficient packaging solutions.

Bacterial cellulose films for L-asparaginase delivery to melanoma cells

L-asparaginase (L-ASNase) is an enzyme that catalyzes the hydrolysis of L-asparagine to L-aspartic acid and ammonia and is used to treat acute lymphoblastic leukemia. It is also toxic to the cells of some solid tumors, including melanoma cells. Immobilization of this enzyme can improve its activity against melanoma tumor cells. In this work, the properties of bacterial cellulose (BC) and feasibility of BC films as a new carrier for immobilized L-ASNase were investigated. Different values of growth time were used to obtain BC films with different thicknesses and porosities, which determine the water content and the ability to adsorb and release L-ASNase. Fourier transform infrared spectroscopy confirmed the adsorption of the enzyme on the BC films. The total activity of adsorbed L-ASNase and its release were investigated for films grown for 48, 72 or 96 h. BC films grown for 96 h showed the most pronounced release as described by zero-order and Korsmayer-Peppas models. The release was characterized by controlled diffusion where the drug was released at a constant rate. BC films with immobilized L-ASNase could induce cytotoxicity in A875 human melanoma cells. With further development, immobilization of L-ASNase on BC may become a potent strategy for anticancer drug delivery to superficial tumors.

Bacterial cellulose microfilament biochar-architectured chitosan/polyethyleneimine beads for enhanced tetracycline and metronidazole adsorption

This study investigates the potential applications of incorporating 2D bacterial cellulose microfibers (BCM) biochar into chitosan/polyethyleneimine beads as a semi-natural sorbent for the efficient removal of tetracycline (TET) and metronidazole (MET) antibiotics. Batch adsorption experiments and characterization techniques evaluate removal performance and synthesized adsorbent properties. The adsorbent eliminated 99.13 % and 90 % of TET and MET at a 10 mg.L-1 concentration with optimal pH values of 8 and 6, respectively, for 90 min. Under optimum conditions and a 400 mg.L-1 concentration, MET and TET have possessed the maximum adsorption capacities of 691.325 and 960.778 mg.g-1, respectively. According to the isothermal analysis, the adsorption of TET fundamentally follows the Temkin (R2 = 0.997), Redlich-Peterson (R2 = 0.996), and Langmuir (R2 = 0.996) models. In contrast, the MET adsorption can be described by the Langmuir (R2 = 0.997), and Toth (R2 = 0.991) models. The pseudo-second-order (R2 = 0.998, 0.992) and Avrami (R2 = 0.999, 0.999) kinetic models were well-fitted with the kinetic results for MET and TET respectively. Diffusion models recommend that pore, liquid-film, and intraparticle diffusion govern the rate of the adsorption process. The developed semi-natural sorbent demonstrated exceptional adsorption capacity over eleven cycles due to its porous bead structure, making it a potential candidate for wastewater remediation.

Bee pollen as a food and feed supplement and a therapeutic remedy: recent trends in nanotechnology

Pollen grains are the male reproductive part of the flowering plants. It is collected by forager honey bees and mixed with their salivary secretions, enzymes, and nectar, which form fermented pollen or "bee bread" which is stored in cells of wax honeycombs. Bee pollen (BP) is a valuable apitherapeutic product and is considered a nutritional healthy food appreciated by natural medicine from ancient times. Recently, BP has been considered a beneficial food supplement and a value-added product that contains approximately 250 different bioactive components. It contains numerous beneficial elements such as Mg, Ca, Mn, K, and phenolic compounds. BP possesses strong antioxidant, anti-inflammatory, antimicrobial, antiviral, analgesic, immunostimulant, neuroprotective, anti-cancer, and hepatoprotective properties. It is used for different purposes for the welfare of mankind. Additionally, there is a growing interest in honey bee products harvesting and utilizing for many purposes as a natural remedy and nutritive function. In this review, the impacts of BP on different organisms in different ways by highlighting its apitherapeutic efficacy are described.

Bacterial nanocellulose loaded with bromelain and nisin as a promising bioactive material for wound debridement

The bacterial nanocellulose (BnC) membranes were produced extracellularly by a novel aerobic acetic acid bacterium Komagataeibacter melomenusus. The BnC was modified in situ by adding carboxymethyl cellulose (CMC) into the culture media, obtaining a BnC-CMC product with denser fibril arrangement, improved rehydration ratio and elasticity in comparison to BnC. The proteolytic enzyme bromelain (Br) and antimicrobial peptide nisin (N) were immobilized to BnC matrix by ex situ covalent binding and/or adsorption. The optimal Br immobilization conditions towards the maximized specific proteolytic activity were investigated by response surface methodology as factor variables. At optimal conditions, i.e., 8.8 mg/mL CMC and 10 mg/mL Br, hyperactivation of the enzyme was achieved, leading to the specific proteolytic activity of 2.3 U/mg and immobilization efficiency of 39.1 %. The antimicrobial activity was observed against Gram-positive bacteria (S. epidermidis, S. aureus and E. faecalis) for membranes with immobilized N and was superior when in situ modified BnC membranes were used. N immobilized on the BnC or BnC-CMC membranes was cytocompatible and did not cause changes in normal human dermal fibroblast cell morphology. BnC membranes perform as an efficient carrier for Br or N immobilization, holding promise in wound debridement and providing antimicrobial action against Gram-positive bacteria, respectively.

Enhancing physical characteristics and antibacterial efficacy of chitosan through investigation of microwave-assisted chemically formulated chitosan-coated ZnO and chitosan/ZnO physical composite

This study investigates the creation and analysis of chitosan-zinc oxide (CS-ZnO) nanocomposites, exploring their effectiveness in inhibiting bacteria. Two synthesis approaches, physical and chemical, were utilized. The CS-ZnO nanocomposites demonstrated strong antibacterial properties, especially against Staphylococcus aureus, a Gram-positive bacterium. Chemically synthesized nanocomposites (CZ10 and CZ100) exhibited larger inhibition zones (16.4 mm and 18.7 mm) compared to physically prepared CS-Z5 and CS-Z20 (12.2 mm and 13.8 mm) against Staphylococcus aureus. Moreover, CZ nanocomposites displayed enhanced thermal stability, with decomposition temperatures of 281°C and 290°C, surpassing CS-Z5 and CS-Z20 (260°C and 258°C). The residual mass percentages at 800°C were significantly higher for CZ10 and CZ100 (58% and 61%) than for CS-Z5 and CS-Z20 (36% and 34%). UV-Visible spectroscopy revealed reduced band gaps in the CS-ZnO nanocomposites, indicating improved light absorption. Transmission electron microscopy (TEM) confirmed uniform dispersion of ZnO nanoparticles within the chitosan matrix. In conclusion, this research underscores the impressive antimicrobial potential of CS-ZnO nanocomposites, especially against Gram-positive bacteria, and highlights their enhanced thermal stability. These findings hold promise for diverse applications in industries such as medicine, pharmaceuticals, and materials science, contributing to the development of sustainable materials with robust antimicrobial properties.

Development of collagen-chitosan dressing gel functionalized with propolis-zinc oxide nanoarchitectonics to accelerate wound healing

Using an in situ sol-gel technique, new nanoarchitectonics of propolis loaded zinc oxide nanoarchitectonics (PP/ZnO-NPs) were developed in order to improve the in vivo outcomes of collagen-chitosan gel in wounded rats. The obtained nanoarchitectonics were fully characterized. The XRD results indicate the presence of a Zincite phase for ZnO-NPs and Zincite accompanied by a minor amount of zinc hydroxide for PP/ZnO-NPs samples. While the TEM findings illustrate the transfer of the ZnO-NPs from agglomerated spheres with an average particle size of 230 ± 29 nm to needle-like NPs of 323 ± 173 nm length (PP1/ZnO-NPs) and to a sheet-like NPs of 500 ± 173 nm diameter (PP2/ZnO-NPs). In addition, the incorporation of PP results in an increase in the surface negativity of ZnO-NPs to -31.4 ± 6.4 mV for PP2/ZnO-NPs. The antimicrobial activities of the nanocomposite gel loaded with 10%PP1/ZnO-NPs (G6) revealed the highest inhibition zone against E. coli (26 ± 2.31 mm). Remarkably, the in vivo outcomes showed that the nanocomposite gel (G6) has exceptional collagen deposition, quick wound closure rates, and re-epithelization. The outcomes demonstrate the nanocomposite gel encouraging biological properties for the treatment of damaged and infected wounds.

Antibacterial Food Packaging Nanomaterial Based on Atomic Layer Deposition for Long-Term Food Storage

The aim of the present work is to use the latest achievements of nanotechnology (atomic layer deposition, ALD) in the field of food packaging to prevent biofilm formation by food-associated bacteria. Some potential applications of nanotechnology in the food packaging industry are studied in the manuscript, in the field of antibacterial materials for food packaging. The ALD technique was used to synthesize vanadium (V)-doped TiO2 thin nanofilm on commercially available polypropylene (PP) food container to enhance an antibacterial activity for potential use in food packaging, to reduce spoilage, thereby, prolonging the food shelf- life. To better understand the ability and effectiveness of the antimicrobial packaging material of V-doped TiO2, to prevent the biofilm formation by dairy-associated pathogenic bacteria, the coated and uncoated PP containers with a fresh raw cow's milk were tested. We have illustrated the effectiveness of ALD Al2O3 + TiVOx nanocoating against populations of milk-borne pathogenic bacteria.

Sustained antibacterial activity of orthodontic elastomeric ligature ties coated with a novel kombucha-derived bacterial nanocellulose: An in-vitro study

Incipient carious lesions, the most common complication in orthodontic patients with fixed appliances, call for the development of novel preventive dental materials that do not rely on patient adherence. The present study aimed to assess the ability of elastomeric ligatures coated with bacterial nanocellulose (BNC) to deliver sustained antibacterial activity, during the standard 28-day interval between orthodontic appointments, without compromising their mechanical properties. Kombucha membrane was used to produce cellulose as a secondary product from the fermentation of tea broth with symbiotic bacteria and yeast culture. Characterization of BNC-coated elastomeric ligatures was performed using Fourier Transform Infrared Spectroscopy and Energy Dispersive Spectroscopy analysis. The samples were pre-treated by immersion first in isopropyl alcohol, then in 8 mL nanocellulose solution for 7 days. Tensile strain and strength of the BNC-coated and conventional ligatures were evaluated using a tensile testing machine. Direct contact and agar diffusion tests were performed to assess the antibacterial activity of nanocellulose. In addition, the release profile of BNC was evaluated. Data analysis was performed by one-way analysis of variance (ANOVA) followed by post-hoc Tukey's test and Wilcoxon signed-rank test. P values less than 0.05 was regarded as significant. There was no statistically significant difference in tensile strain and strength between the BNC-coated and conventional ligatures. The coated ligatures provided sustained antibacterial activity during the required 28 days. The use of BNC-coated elastomeric ligatures in patients with fixed orthodontic appliances might be a promising solution to plaque formation and subsequent enamel decalcification.

Starch-based antibacterial food packaging with ZnO nanoparticle

Starch-based biofilms with embedded nanoparticles (NPs) are used to wrap food in biodegradable packaging system that has high antibacterial action against a variety of microorganisms. In this study, ZnO NPs were synthesised using both a green synthesis approach utilising Azadirachta indica (Neem) and a chemical synthesis approach using the sol-gel technique. The structural and morphological properties of all synthesized NPs were characterized through XRD, UV-VIS, UV-DRS, FTIR, and FESEM analysis. Further, these NPs were employed in the development of starch-based biodegradable films. A meticulous comparative analysis was performed to evaluate the functional properties of the nanocomposites, encompassing crucial parameters such as film thickness, moisture content, swelling index, opacity, solubility, water vapor permeability, and tensile strength. In comparison to films embedded with chemically synthesised NPs (F1), nanocomposite with green synthesised NPs (F2) showed 15.27% greater inhibition against Escherichia coli growth and 22.05% stronger inhibition against Staphylococcus aureus bacterial strains. Based on the biodegradability analysis, the nanocomposite film-F2 showed a 53.33% faster degradation rate compared to the film-F1. The developed films were utilized to assess the quality of both wrapped and unwrapped grapes, leading to the generalization of the research for the development of starch-based antibacterial and environmentally friendly food packaging material.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05834-9.

Plant-Derived Nanocellulose with Antibacterial Activity for Wound Healing Dressing

The medical sector is one of the biggest consumers of single-use materials, and while the insurance of sterile media is non-negotiable, the environmental aspect is a chronic problem. Nanocellulose (NC) is one of the safest and most promising materials that can be used in medical applications due to its valuable properties like biocompatibility and biodegradability, along with its good mechanical properties and high water uptake capacity. However, NC has no bactericidal activity, which is a critical need for the effective prevention of infections in chronic diabetic wound dressing applications. Therefore, in this work, a natural product, propolis extract (PE), was used as an antibacterial agent, in different amounts, together with NC to obtain sponge-like structures (NC/PE). The scanning electron microscope (SEM) images showed well-impregnated cellulose fibers and a more compact structure with the addition of PE. According to the thermogravimetric analysis (TGA), the samples containing PE underwent thermal degradation before the unmodified NC due to the presence of volatile compounds in the extract. However, the peak degradation temperature in the first derivative thermogravimetric curves was higher for all the sponges containing PE when compared to the unmodified NC. The antibacterial efficacy of the samples was tested against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, as well as on two clinically resistant isolates. The samples completely inhibited the development of Staphylococcus aureus, and Pseudomonas aeruginosa was partially inhibited, while Escherichia coli was resistant to the PE action. Considering the physical and biological properties along with the environmental and economic benefits, the development of an NC/PE wound dressing seems promising.

Cellulose-Based Metallogels-Part 3: Multifunctional Materials

The incorporation of the metal phase into cellulose hydrogels, resulting in the formation of metallogels, greatly expands their application potential by introducing new functionalities and improving their performance in various fields. The unique antiviral, antibacterial, antifungal, and anticancer properties of metal and metal oxide nanoparticles (Ag, Au, Cu, CuxOy, ZnO, Al2O3, TiO2, etc.), coupled with the biocompatibility of cellulose, allow the development of composite hydrogels with multifunctional therapeutic potential. These materials can serve as efficient carriers for controlled drug delivery, targeting specific cells or pathogens, as well as for the design of artificial tissues or wound and burn dressings. Cellulose-based metallogels can be used in the food packaging industry to provide biodegradable and biocidal materials to extend the shelf life of the goods. Metal and bimetallic nanoparticles (Au, Cu, Ni, AuAg, and AuPt) can catalyze chemical reactions, enabling composite cellulose hydrogels to be used as efficient catalysts in organic synthesis. In addition, metal-loaded hydrogels (with ZnO, TiO2, Ag, and Fe3O4 nanoparticles) can exhibit enhanced adsorption capacities for pollutants, such as dyes, heavy metal ions, and pharmaceuticals, making them valuable materials for water purification and environmental remediation. Magnetic properties imparted to metallogels by iron oxides (Fe2O3 and Fe3O4) simplify the wastewater treatment process, making it more cost-effective and environmentally friendly. The conductivity of metallogels due to Ag, TiO2, ZnO, and Al2O3 is useful for the design of various sensors. The integration of metal nanoparticles also allows the development of responsive materials, where changes in metal properties can be exploited for stimuli-responsive applications, such as controlled release systems. Overall, the introduction of metal phases augments the functionality of cellulose hydrogels, expanding their versatility for diverse applications across a broad spectrum of industries not envisaged during the initial research stages.

Recent Advances in Sustainable Antimicrobial Food Packaging: Insights into Release Mechanisms, Design Strategies, and Applications in the Food Industry

In response to the issues of foodborne microbial contamination and carbon neutrality goals, sustainable antimicrobial food packaging (SAFP) composed of renewable or biodegradable biopolymer matrices with ecofriendly antimicrobial agents has emerged. SAFP offers longer effectiveness, wider coverage, more controllability, and better environmental performance. Analyzing SAFP information, including the release profile of each antimicrobial agent for each food, the interaction of each biomass matrix with each food, the material size, form, and preparation methods, and its service quality in real foods, is crucial. While encouraging reports exist, a comprehensive review summarizing these developments is lacking. Therefore, this review critically examines recent release-antimicrobial mechanisms, kinetics models, preparation methods, and key regulatory parameters for SAFPs based on slow- or controlled-release theory. Furthermore, it discusses fundamental physicochemical characteristics, effective concentrations, advantages, release approaches, and antimicrobial and preservative effects of various materials in food simulants or actual food. Lastly, inadequacies and future trends are explored, providing practical references to regulate the movement of active substances in different media, reduce the reliance on petrochemical-based materials, and advance food packaging and preservation technologies.

Advances in propolis and propolis functionalized coatings and films for fruits and vegetables preservation

Propolis, as a natural active substance, is rich in polyphenols, with low toxicity, antioxidant, antifungal and antibacterial properties, which can be applied to the post-harvest preservation of fruits and vegetables. Propolis extracts and propolis functionalized coatings and films have exhibited good freshness in various types of fruits and vegetables as well as fresh-cut vegetables. They are mainly used to prevent water loss after harvesting, to inhibit the infestation of bacteria and fungi after harvesting and to enhance the firmness and apparent quality of fruits and vegetables. Moreover, propolis and propolis functionalized composites have a small or even insignificant effect on the physicochemical parameters of fruits and vegetables. Furthermore, how to cover the special smell of propolis itself so that it does not affect the flavor of fruits and vegetables, and the application of propolis extract in wrapping paper and packaging bag of fruits and vegetables, are worthwhile to further investigate.

Metal-Based Nanoparticles in Food Packaging and Coating Technologies: A Review

Food security has continued to be a topic of interest in our world due to the increasing demand for food. Many technologies have been adopted to enhance food supply and narrow the demand gap. Thus, the attempt to use nanotechnology to improve food security and increase supply has emerged due to the severe shortcomings of conventional technologies, which have made them insufficient to cater to the continuous demand for food products. Hence, nanoparticles have been identified to play a major role in areas involving food production, protection, and shelf-life extensions. Specifically, metal-based nanoparticles have been singled out to play an important role in manufacturing materials with outstanding properties, which can help increase the shelf-life of different food materials. The physicochemical and biological properties of metal-based nanoparticles, such as the large surface area and antimicrobial properties, have made them suitable and adequately useful, not just as a regular packaging material but as a functional material upon incorporation into biopolymer matrices. These, amongst many other reasons, have led to their wide synthesis and applications, even though their methods of preparation and risk evaluation remain a topic of concern. This review, therefore, briefly explores the available synthetic methods, physicochemical properties, roles, and biological properties of metal-based nanoparticles for food packaging. Furthermore, the associated limitations, alongside quality and safety considerations, of these materials were summarily explored. Although this area of research continues to garner attention, this review showed that metal-based nanoparticles possess great potential to be a leading material for food packaging if the problem of migration and toxicity can be effectively modulated.

Egyptian propolis extract for functionalization of cellulose nanofiber/poly(vinyl alcohol) porous hydrogel along with characterization and biological applications

Bee propolis is one of the most common natural extracts and has gained significant interest in biomedicine due to its high content of phenolic acids and flavonoids, which are responsible for the antioxidant activity of natural products. The present study report that the propolis extract (PE) was produced by ethanol in the surrounding environment. The obtained PE was added at different concentrations to cellulose nanofiber (CNF)/poly(vinyl alcohol) (PVA), and subjected to freezing thawing and freeze drying methods to develop porous bioactive matrices. Scanning electron microscope (SEM) observations displayed that the prepared samples had an interconnected porous structure with pore sizes in the range of 10-100 μm. The high performance liquid chromatography (HPLC) results of PE showed around 18 polyphenol compounds, with the highest amounts of hesperetin (183.7 µg/mL), chlorogenic acid (96.9 µg/mL) and caffeic acid (90.2 µg/mL). The antibacterial activity results indicated that both PE and PE-functionalized hydrogels exhibited a potential antimicrobial effects against Escherichia coli, Salmonella typhimurium, Streptococcus mutans, and Candida albicans. The in vitro test cell culture experiments indicated that the cells on the PE-functionalized hydrogels had the greatest viability, adhesion, and spreading of cells. Altogether, these data highlight the interesting effect of propolis bio-functionalization to enhance the biological features of CNF/PVA hydrogel as a functional matrix for biomedical applications.

Hybrid Silver-Containing Materials Based on Various Forms of Bacterial Cellulose: Synthesis, Structure, and Biological Activity

Sustained interest in the use of renewable resources for the production of medical materials has stimulated research on bacterial cellulose (BC) and nanocomposites based on it. New Ag-containing nanocomposites were obtained by modifying various forms of BC with Ag nanoparticles prepared by metal-vapor synthesis (MVS). Bacterial cellulose was obtained in the form of films (BCF) and spherical BC beads (SBCB) by the Gluconacetobacter hansenii GH-1/2008 strain under static and dynamic conditions. The Ag nanoparticles synthesized in 2-propanol were incorporated into the polymer matrix using metal-containing organosol. MVS is based on the interaction of extremely reactive atomic metals formed by evaporation in vacuum at a pressure of 10^-2 Pa with organic substances during their co-condensation on the cooled walls of a reaction vessel. The composition, structure, and electronic state of the metal in the materials were characterized by transmission and scanning electron microscopy (TEM, SEM), powder X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and X-ray photoelectron spectroscopy (XPS). Since antimicrobial activity is largely determined by the surface composition, much attention was paid to studying its properties by XPS, a surface-sensitive method, at a sampling depth about 10 nm. C 1s and O 1s spectra were analyzed self-consistently. XPS C 1s spectra of the original and Ag-containing celluloses showed an increase in the intensity of the C-C/C-H groups in the latter, which are associated with carbon shell surrounding metal in Ag nanoparticles (Ag NPs). The size effect observed in Ag 3d spectra evidenced on a large proportion of silver nanoparticles with a size of less than 3 nm in the near-surface region. Ag NPs in the BC films and spherical beads were mainly in the zerovalent state. BC-based nanocomposites with Ag nanoparticles exhibited antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli bacteria and Candida albicans and Aspergillus niger fungi. It was found that AgNPs/SBCB nanocomposites are more active than Ag NPs/BCF samples, especially against Candida albicans and Aspergillus niger fungi. These results increase the possibility of their medical application.

Biodegradable Polymers and Polymer Composites with Antibacterial Properties

Antibiotic resistance is one of the greatest threats to global health and food security today. It becomes increasingly difficult to treat infectious disorders because antibiotics, even the newest ones, are becoming less and less effective. One of the ways taken in the Global Plan of Action announced at the World Health Assembly in May 2015 is to ensure the prevention and treatment of infectious diseases. In order to do so, attempts are made to develop new antimicrobial therapeutics, including biomaterials with antibacterial activity, such as polycationic polymers, polypeptides, and polymeric systems, to provide non-antibiotic therapeutic agents, such as selected biologically active nanoparticles and chemical compounds. Another key issue is preventing food from contamination by developing antibacterial packaging materials, particularly based on degradable polymers and biocomposites. This review, in a cross-sectional way, describes the most significant research activities conducted in recent years in the field of the development of polymeric materials and polymer composites with antibacterial properties. We particularly focus on natural polymers, i.e., polysaccharides and polypeptides, which present a mechanism for combating many highly pathogenic microorganisms. We also attempt to use this knowledge to obtain synthetic polymers with similar antibacterial activity.

Untargeted metabolomics description of propolis's in vitro antibacterial mechanisms against Clostridium perfringens

Propolis is a natural resinous substance that is collected by honeybees (Apis mellifera) with promising antibacterial effects. Here, we examined the antibacterial activity of Chinese propolis against Clostridium perfringens, a bacterial pathogen that threatens food safety and causes intestinal erosion. The inhibitory effects of the ethanolic extract of Chinese propolis (CPE) on human-associated C. perfringens strains were determined by using the circle of inhibition, the minimum inhibitory concentrations, and bactericidal concentrations. CPE also induced morphological elongation, bacterial cell wall damage, and intracellular material leakage in C. perfringens. Untargeted HPLC-qTOF-MS-based metabolomics analysis of the bacterial metabolic compounds revealed that propolis triggered glycerophospholipid metabolism, one carbon pool by folate, and d-glutamine and d-glutamate metabolism alterations in C. perfringens. Finally, caffeic acid phenethyl ester was identified as the key active ingredient in CPE. This study suggested the usage of propolis as an alternative to antibiotics in controlling C. perfringens.

Antimicrobial Nano-Zinc Oxide Biocomposites for Wound Healing Applications: A Review

Chronic wounds are a major concern for global health, affecting millions of individuals worldwide. As their occurrence is correlated with age and age-related comorbidities, their incidence in the population is set to increase in the forthcoming years. This burden is further worsened by the rise of antimicrobial resistance (AMR), which causes wound infections that are increasingly hard to treat with current antibiotics. Antimicrobial bionanocomposites are an emerging class of materials that combine the biocompatibility and tissue-mimicking properties of biomacromolecules with the antimicrobial activity of metal or metal oxide nanoparticles. Among these nanostructured agents, zinc oxide (ZnO) is one of the most promising for its microbicidal effects and its anti-inflammatory properties, and as a source of essential zinc ions. This review analyses the most recent developments in the field of nano-ZnO–bionanocomposite (nZnO-BNC) materials—mainly in the form of films, but also hydrogel or electrospun bandages—from the different preparation techniques to their properties and antibacterial and wound-healing performances. The effect of nanostructured ZnO on the mechanical, water and gas barrier, swelling, optical, thermal, water affinity, and drug-release properties are examined and linked to the preparation methods. Antimicrobial assays over a wide range of bacterial strains are extensively surveyed, and wound-healing studies are finally considered to provide a comprehensive assessment framework. While early results are promising, a systematic and standardised testing procedure for the comparison of antibacterial properties is still lacking, partly because of a not-yet fully understood antimicrobial mechanism. This work, therefore, allowed, on one hand, the determination of the best strategies for the design, engineering, and application of n-ZnO-BNC, and, on the other hand, the identification of the current challenges and opportunities for future research.

Development of low-cost bacterial cellulose-pomegranate peel extract-based antibacterial composite for potential biomedical applications

This study was aimed to develop low-cost bacterial cellulose (BC)-based antibacterial composite with pomegranate (Punica granatum L.) peel extract (PGPE) for potential biomedical applications. BC was cost-effectively produced by utilizing food wastes, and PGPE was ex situ impregnated into its hydrogel. Field-emission scanning electron microscopic (FE-SEM) observation showed a nanofibrous and microporous morphology of pristine BC and confirmed the development of BC-PGPE composite. Fourier transform infrared (FTIR) spectroscopy indicated the chemical interaction of PGPE with BC nanofibers. BC-PGPE composite held 97 % water of its dry weight and retained it for more than 48 h. The BC-PGPE composite exhibited better reswelling capabilities than pristine BC after three consecutive re-wetting cycles. The antibacterial activity of the BC-PGPE composite was determined via minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), disc diffusion, and plate count methods. The PGPE extract showed good antimicrobial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), both in the form of extract and composite with BC, with relatively better activity against the former. The BC-PGPE composite produced a 17 mm zone of inhibition against S. aureus, while no inhibition zone was formed against E. coli. Furthermore, BC-PGPE composite caused a 100 % and 50 % reduction in the growth of S. aureus and E. coli, respectively. The findings of this study indicate that BC-PGPE composite could be a promising antibacterial wound dressing material.

Valorization of Peels of Eight Peach Varieties: GC-MS Profile, Free and Bound Phenolics and Corresponding Biological Activities

Sustainability, becoming essential for food processing and technology, sets goals for the characterization of resources considered as food waste. In this work, information about the GC-MS metabolites of peach peels was provided as a tool that can shed more light on the studied biological activities. In addition, distribution patterns and contribution of the chemical profile and free and bound phenolic compounds as antioxidant, antimicrobial, and enzymatic clusters in peach peels of different varieties of Bulgarian origin were studied. The two applied techniques (alkaline and acid hydrolysis) for releasing the bound phenolics reveal that alkaline hydrolysis is a better extraction approach. Still, the results indicate the prevalence of the free phenolics in the studied peach peel varieties. Total phenolics of peach wastes were positively correlated with their antioxidant activity. The antioxidant activity results certainly defined the need of an individual interpretation for each variety, but the free phenolics fractions could be outlined with the strongest potential. The limited ability of the peels' extracts to inhibit α-amylase and acetylcholinesterase, and the moderate antimicrobial activity, on the other hand, indicate that the potential of peach peels is still sufficient to seek ways to valorize this waste. Indeed, this new information about peach peels can be used to characterize peach fruits from different countries and/or different food processes, as well as to promote the use of this fruit waste in food preparation.

Active Packaging Material Based on Immobilized Diatomaceous Earth/Zinc Oxide/High-Density Polyethylene Composite for Sea Food and Products

One of the key factors of supporting the rapidly expanding seafood product industry in terms of quality control is the utilization of active packaging materials. Microorganisms are primarily responsible for the perishability and rapid disintegration of seafood. The incorporation of an inorganic compound, such as silica-based diatomaceous earth (DE), and a metal oxide, such as zinc oxide (ZnO), is proposed to develop active packaging materials with excellent antibacterial activity, minimized fishy odor, and brittleness at subzero temperatures. The mechanical, morphological, and physicochemical properties of these materials were investigated. The results show that the addition of DE/ZnO improved the antibacterial activity of high-density polyethylene (HDPE) samples by up to approximately 95% against both gram-positive and -negative bacteria. Additionally, it enhanced the Izod strength and stability at subzero temperatures of the samples. The odor evaporation test revealed that trimethylamine can be minimized in proportion to increasing DE/ZnO composite concentration. As a result, the development of active packaging materials from DE/ZnO composites is an emerging polymeric packaging technology for seafood products, wherein packaging and seafood quality are linked.

Structural, Optical, and Electrical Characterization of Biological and Bioactive Propolis Films

Natural substances are potential compounds for green electronic devices. So, scientists have to explore and optimize their properties to insert them as active layers in electronic heterostructures. In this study, microstructural, optical, and electrical properties of thin layers of the propolis are investigated. Propolis is a biological organic bioactive material produced by honeybees. A stable, bioactive, green, and low-cost thin layer of this biocompatible material was deposited on different substrates using a propolis alcohol solution. The morphological studies show that the propolis thin film is dense and well covers the substrate surfaces. Transmittance spectra show that propolis film cuts off blue and ultraviolet (UV) radiation, which are responsible for food oxidation, nutrient losses, flavor degradation, and discoloration. Therefore, to prevent food deterioration, a propolis film can be used in food packaging. For red and near-infrared radiation (∼600-2700 nm), a propolis film is transparent. Between near-infrared and mid-infrared radiation (∼2700-3200 nm), a propolis film reveals significant photosensitivity and so can be used as a photosensor. The propolis film reveals an energy gap of 2.88 eV at room temperature, which enables potential optoelectronic applications in the UV and blue ranges. The electrical study shows that the propolis layer has semiconductor behavior and can be a potential active layer in biocompatible temperature sensors. In addition to its medical, pharmaceutical, and food industry applications, in light of this study, propolis presents amazing optical and electrical properties and is a promising candidate for food packaging, optoelectronics, transparent electronics, and bioelectronics.

Effect of Bacterial Cellulose Plasma Treatment on the Biological Activity of Ag Nanoparticles Deposited Using Magnetron Deposition

New functional medical materials with antibacterial activity based on biocompatible bacterial cellulose (BC) and Ag nanoparticles (Ag NPs) were obtained. Bacterial cellulose films were prepared by stationary liquid-phase cultivation of the Gluconacetobacter hansenii strain GH-1/2008 in Hestrin-Schramm medium with glucose as a carbon source. To functionalize the surface and immobilize Ag NPs deposited by magnetron sputtering, BC films were treated with low-pressure oxygen-nitrogen plasma. The composition and structure of the nanomaterials were studied using transmission (TEM) and scanning (SEM) electron microscopy and X-ray photoelectron spectroscopy (XPS). Using electron microscopy, it was shown that on the surface of the fibrils that make up the network of bacterial cellulose, Ag particles are stabilized in the form of aggregates 5-35 nm in size. The XPS C 1s spectra show that after the deposition of Ag NPs, the relative intensities of the C-OH and O-C-O bonds are significantly reduced. This may indicate the destruction of BC oxypyran rings and the oxidation of alcohol groups. In the Ag 3d_5/2 spectrum, two states at 368.4 and 369.7 eV with relative intensities of 0.86 and 0.14 are distinguished, which are assigned to Ag⁰ state and Ag acetate, respectively. Nanocomposites based on plasma-treated BC and Ag nanoparticles deposited by magnetron sputtering (BCP-Ag) exhibited antimicrobial activity against Aspergillus niger, S. aureus and Bacillus subtilis.

Potential application of postbiotics metabolites from bioprotective culture to fabricate bacterial nanocellulose based antimicrobial packaging material

Postbiotics (P) of FreshQ, a food protective culture, was prepared and used to develop an antimicrobial membrane by bacterial nanocellulose (BNC). Postbiotics were prepared in de Man, Rogosa and Sharpe medium and freeze-dried. The chemical composition was investigated by GC-MS and the antibacterial activity of postbiotics on different bacterial and fungal strains was investigated. Finally, postbiotics were included in wet and lyophilized BNC by ex-situ method, and their antibacterial activity and FTIR specifications were studied. The GC-MS analysis of postbiotics revealed the presence of fatty acids, alkanes, aldehydes, hydrocarbones fatty acid esters, propionic acid, and certain antibacterial and antifungal compounds such as 2,4-Di-tert-butyl phenol and dotriacontane. Postbiotics revealed antibacterial activity on all investigated strains in a concentration-dependent manner and as the concentation decreased, there was a significant reduction in antimicrobial effects. The zone of inhibition for all bacterial pathogens exceeded 20 mm, then they were classified as "extremely sensitive microorganisms" to the postbiotics at 50 % concentration, while fungal strains revealed a lower zone of inhibition (<17 mm). The order of antimicrobial susceptibility was as follows: Listeria monocytogenes > Staphylococcus aureus > Escherichia coli > Salmonella Typhimurium > Aspergillus flavus > Penicillium citrinum. We also recognized that P-BNC in wet form has significant antimicrobial activity than lyophilized form due to the high adsorption capacity and open 3D structure of BNC in wet form. The fabricated material can serve as an antimicrobial membrane for food applications.

Biomedical engineering aspects of nanocellulose: a review

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Active Potential of Bacterial Cellulose-Based Wound Dressing: Analysis of Its Potential for Dermal Lesion Treatment

The use of innate products for the fast and efficient promotion of healing process has been one of the biomedical sector's main bets for lesion treatment modernization process. The aim of this study was to develop and characterize bacterial cellulose-based (BC) wound dressings incorporated with green and red propolis extract (2 to 4%) and the active compounds p-coumaric acid and biochanin A (8 to 16 mg). The characterization of the nine developed samples (one control and eight active wound dressings) evidenced that the mechanics, physics, morphological, and barrier properties depended not only on the type of active principle incorporated onto the cellulosic matrix, but also on its concentration. Of note were the results found for transparency (28.59-110.62T₆₀₀ mm^-1), thickness (0.023-0.046 mm), swelling index (48.93-405.55%), water vapor permeability rate (7.86-38.11 g m² day^-1), elongation (99.13-262.39%), and antioxidant capacity (21.23-86.76 μg mL^-1). The wound dressing based on BC and red propolis was the only one that presented antimicrobial activity. The permeation and retention test revealed that the wound dressing containing propolis extract presented the most corneal stratum when compared with viable skin. Overall, the developed wound dressing showed potential to be used for treatment against different types of dermal lesions, according to its determined proprieties.

A Critical Review of the Antimicrobial and Antibiofilm Activities of Green-Synthesized Plant-Based Metallic Nanoparticles

Metallic nanoparticles (MNPs) produced by green synthesis using plant extracts have attracted huge interest in the scientific community due to their excellent antibacterial, antifungal and antibiofilm activities. To evaluate these pharmacological properties, several methods or protocols have been successfully developed and implemented. Although these protocols were mostly inspired by the guidelines from national and international regulatory bodies, they suffer from a glaring absence of standardization of the experimental conditions. This situation leads to a lack of reproducibility and comparability of data from different study settings. To minimize these problems, guidelines for the antimicrobial and antibiofilm evaluation of MNPs should be developed by specialists in the field. Being aware of the immensity of the workload and the efforts required to achieve this, we set out to undertake a meticulous literature review of different experimental protocols and laboratory conditions used for the antimicrobial and antibiofilm evaluation of MNPs that could be used as a basis for future guidelines. This review also brings together all the discrepancies resulting from the different experimental designs and emphasizes their impact on the biological activities as well as their interpretation. Finally, the paper proposes a general overview that requires extensive experimental investigations to set the stage for the future development of effective antimicrobial MNPs using green synthesis.

From propolis to nanopropolis: An exemplary journey and a paradigm shift of a resinous substance produced by bees

Propolis, a natural resinous mixture produced by honey bees is poised with diverse biological activities. Owing to the presence of flavonoids, phenolic acids, terpenes, and sesquiterpenes, propolis has garnered versatile applications in pharmaceutical industry. The biopharmaceutical issues associated with propolis often beset its use as being too hydrophobic in nature; it is not absorbed in the body well. To combat the problem, various nanotechnological approaches for the development of novel drug delivery systems are generally applied to improve its bioavailability. This paradigm shift and transition of conventional propolis to nanopropolis are evident from the literature wherein a multitude of studies are available on nanopropolis with improved bioavailability profile. These approaches include preparation of gold nanoparticles, silver nanoparticles, magnetic nanoparticles, liposomes, liquid crystalline formulations, solid lipid nanoparticles, mesoporous silica nanoparticles, etc. Nanopropolis has further been explored to assess the potential benefits of propolis for the development of futuristic useful products such as sunscreens, creams, mouthwashes, toothpastes, and nutritional supplements with improved solubility, bioavailability, and penetration profiles. However, more high-quality clinical studies assessing the effects of propolis either alone or in combination with synthetic drugs as well as natural products are warranted and its safety needs to be firmly established.

Ixiolirion tataricum anthocyanins-loaded biocellulose label: Characterization and application for food freshness monitoring

A new intelligent pH-sensitive colorimetric label was fabricated by immobilizing Ixiolirion tataricum anthocyanins (ITA) into biocellulose (bacterial nanocellulose; BNC) film and was then studied to determine how it can be used as a label for monitoring freshness/spoilage of shrimp during storage at 4 °C. The formation of new interactions between ITA and BNC film and disruption of crystalline structure of BNC after anthocyanins immobilization were approved by FT-IR and XRD analyses, respectively. According to FE-SEM observations, the porosity of the BNC network decreased after ITA incorporation. The fabricated BNC-ITA label showed a distinct color change from violet to green over the pH range of 4-12. The pH, total volatile basic nitrogen (TVB-N), total psychrophiles count (TPC), and the quantity of biogenic amines (histamine, cadaverine, putrescine, and tyramine) in the shrimp samples and their correlation with color changes on the label were measured over a 4-day storage period. Consistent with changes in levels of TVB-N, TPC, pH, and biogenic amines, a visually distinguishable color change occurred on the BNC-ITA label as blue (fresh), dark green (medium fresh), and kelly green (spoiled). This research showed that ITA as a novel pH-sensitive dye is a promising candidate for developing pH labels for seafood intelligent packaging.

Shape-controlled synthesis of zinc nanostructures mediating macromolecules for biomedical applications

Zinc nanostructures (ZnONSs) have attracted much attention due to their morphological, physicochemical, and electrical properties, which were entailed for various biomedical applications such as cancer and diabetes treatment, anti-inflammatory activity, drug delivery. ZnONS play an important role in inducing cellular apoptosis, triggering excess reactive oxygen species (ROS) production, and releasing zinc ions due to their inherent nature and specific shape. Therefore, several new synthetic organometallic method has been developed to prepare ZnO crystalline nanostructures with controlled size and shape. Zinc oxide nanostructures' crystal size and shape can be controlled by simply changing the physical synthesis condition such as microwave irradiation time, reaction temperature, and TEA concentration at reflux. Physicochemical properties which are determined by the shape and size of ZnO nanostructures, directly affect their biological applications. These nanostructures can decompose the cell membrane and accumulate in the cytoplasm, which leads to apoptosis or cell death. In this study, we reviewed the various synthesis methods which affect the nano shapes of zinc particles, and physicochemical properties of zinc nanostructures that determined the shape of zinc nanomaterials. Also, we mentioned some macromolecules that controlled their physicochemical properties in a green and biological approaches. In addition, we present the recent progress of ZnONSs in the biomedical fields, which will help centralize biomedical fields and assist their future research development.

Antibacterial, Antioxidation, UV-Blocking, and Biodegradable Soy Protein Isolate Food Packaging Film with Mangosteen Peel Extract and ZnO Nanoparticles

The objective of this study was to prepare a functional biodegradable soy protein isolate (SPI) food packaging film by introducing a natural antimicrobial agent, mangosteen peel extract (MPE, 10 wt% based on SPI), and different concentrations of functional modifiers, ZnO NPs, into the natural polymer SPI by solution casting method. The physical, antioxidant, antibacterial properties and chemical structures were also investigated. The composite film with 5% ZnO NPs had the maximum tensile strength of 8.84 MPa and the lowest water vapor transmission rate of 9.23 g mm/m² h Pa. The composite film also exhibited excellent UV-blocking, antioxidant, and antibacterial properties against Escherichia coli and Staphylococcus aureus. The TGA results showed that the introduction of MPE and ZnO NPs improved the thermal stability of SPI films. The microstructure of the films was analyzed by SEM to determine the smooth surface of the composite films. ATR-FTIR and XPS analyses demonstrated the strong hydrogen bonding of SPI, MPE, and ZnO NPs in the films. The presence of ZnO NPs in the composite films was also proved by EDX and XRD. These results suggest that SPI/MPE/ZnO composite film is promising for food-active packaging to extend the shelf life of food products.

Mechanical properties of cellulose nanofibril papers and their bionanocomposites: A review

Cellulose nanofibril (CNF) paper has various applications due to its unique advantages. Herein, we present the intrinsic mechanical properties of CNF papers, along with the preparation and properties of nanoparticle-reinforced CNF composite papers. The literature on CNF papers reveals a strong correlation between the intrafibrillar network structure and the resulting mechanical properties. This correlation is found to hold for all primary factors affecting mechanical properties, indicating that the performance of CNF materials depends directly on and can be tailored by controlling the intrafibrillar network of the system. The parameters that influence the mechanical properties of CNF papers were critically reviewed. Moreover, the effect on the mechanical properties by adding nanofillers to CNF papers to produce multifunctional composite products was discussed. We concluded this article with future perspectives and possible developments in CNFs and their bionanocomposite papers.

Hybrid "Kill and Release" Antibacterial Cellulose Papers Obtained via Surface-Initiated Atom Transfer Radical Polymerization

Infectious diseases triggered by bacteria cause a severe risk to human health. To counter this issue, surfaces coated with antibacterial materials have been widely used in daily life to kill these bacteria. The substrates enabled with a hybrid kill and release strategy can be employed not only to kill the bacteria but also to wash them using external stimuli (temperature, pH, etc.). Utilizing this concept, we develop thermoresponsive antibacterial-cellulose papers to exhibit hybrid kill and release properties. Thermoresponsive copolymers [p(NIPAAm-co-AEMA)] are grafted on cellulose papers using a surface-initiated atom transfer radical polymerization approach for bacterial debris release. Later for antibacterial properties, silver nanoparticles (AgNPs) are immobilized on thermoresponsive copolymer-grafted cellulose papers using electrostatic interactions. We confirm the thermoresponsive copolymer grafting and AgNP coating by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Thermoresponsiveness and reusability of the modified cellulose papers are confirmed through water contact angle measurements. The interaction potency between AgNPs and modified cellulose is validated by inductively coupled plasma atomic emission spectroscopy analysis. Gram-negative bacteria Escherichia coli (E. coli DH5-α) is used to demonstrate antibacterial hybrid kill and release performance. Agar-diffusion testing demonstrates the antibacterial nature of the modified cellulose papers. The fluorescence micrograph reveals that modified cellulose papers can effectively release almost all the dead bacterial debris from their surfaces after thermal stimulus wash. The modified cellulose paper surfaces are expected to have wide applications in the field of exploring more antibacterial and smart surfaces.

Polyphenolics profile effects upon the antioxidant and antimicrobial activity of propolis extracts

Propolis, a complex bee product, is a source of numerous bioactive principles, beneficial for human health, therefore it is intensively studied. In the present work, extracts of propolis from Bihor Romanian County were studied to identify the relationship between the polyphenolic derivatives profile and their antioxidant and antimicrobial activity. Extracts were obtained using water and 25%, 50%, and 70% ethanolic solutions (w/w), at 2:1, 4:1, and 6:1 liquid: solid ratios (w/w). 21 polyphenolic derivatives were quantified by UHPLC-MS, proving that the extracts composition strongly depends on the solvent. The sum of quantified polyphenolics extracted varied between 1.5 and 91.2 mg/g propolis. The antioxidant capacity was evaluated using the free radicals 2,2’-azino-bis (3-ethylbenzothiazoline-6 sulfonic acid) diammonium salt (ABTS) and 1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging methods. Antimicrobial efficiency was tested against Gram-positive (B. subtilis), Gram-negative bacteria (E. coli), and fungi (C. albicans) by disc-diffusion method. All extracts, even the aqueous ones, demonstrated antibacterial and antifungal activity. Chemometric methods (partial least squares) and a saturation-type model were used to evaluate the contribution of various bioactive principles in building the antioxidant capacity of extracts. Both experimental and modelling results show that 50% ethanolic extracts provide a rich polyphenolics profile and ensure a good antioxidant capacity.

Alginate/Gelatin Sponges Composited with ZnO Sponge Effective Extensibility and Compressibility as a Wound Dressing for the Care of Fracture Surgery

We designed and synthesized highly porous alginate and gelatin hydrogels with zinc oxide nanoparticles (AGZNPs) as dressings using sol–gel methods. The presence of functional groups and the surface characteristics of the as-synthesised dressings were analyzed via Fourier transforminfrared (FT-IR) spectroscopy, while their morphology was studied via scanning electron microscopy (SEM). Additionally, the mechanical, inflammatory, and antibacterial properties and biocompatibility of the AGZNPs were evaluated to determine the efficiency of these bandages for wound healing applications. The AGZNPs demonstrated enhanced inflammatory and antibacterial properties. The biocompatibility of the nanocomposites was investigated in noncancerous NIH3T3 human fibroblasts. Furthermore, in-vivo examinations showed that the composition of the synthesized AGZNPs enhanced wound healing and promoted rapid cell construction and growth. Therefore, the AGZNP strategy promotes the future application of these nanoformulation hydrogels for wound bandaging in fracture surgeries.

Fabrication of Paper Sheets Coatings Based on Chitosan/Bacterial Nanocellulose/ZnO with Enhanced Antibacterial and Mechanical Properties

Here, we designed paper sheets coated with chitosan, bacterial cellulose (nanofibers), and ZnO with boosted antibacterial and mechanical activity. We investigated the compositions, with ZnO exhibiting two different sizes/shapes: (1) rods and (2) irregular sphere-like particles. The proposed processing of bacterial cellulose resulted in the formation of nanofibers. Antimicrobial behavior was tested using E. coli ATCC® 25922™ following the ASTM E2149-13a standard. The mechanical properties of the paper sheets were measured by comparing tearing resistance, tensile strength, and bursting strength according to the ISO 5270 standard. The results showed an increased antibacterial response (assigned to the combination of chitosan and ZnO, independent of its shape and size) and boosted mechanical properties. Therefore, the proposed composition is an interesting multifunctional mixture for coatings in food packaging applications.

White-rot fungus mediated green synthesis of zinc oxide nanoparticles and their impregnation on cellulose to develop environmental friendly antimicrobial fibers

An economic, eco-friendly and efficient synthesis route for Zinc oxide (ZnO) nanoparticles (NPs) using fungus Phanerochaete chrysosporium has been explored along with the single-step impregnation of these nanoparticles on cellulose fibers. The transmission electron microscopy confirmed 50 nm as an average size of ZnO NPs and showed the presence of hexagonal phases. ZnO NPs-cellulose composite was fabricated by amending sugarcane bagasse-extracted cellulose in the reaction mixture during the nanoparticle synthesis. The composite was characterized using Fourier transform infrared, X-ray diffraction patterns, Scanning electron microscopy, and Energy dispersive spectroscopy, thermogravimetric analysis, and also evaluated for its antimicrobial potential. The analyses revealed that well-dispersed hexagonal wurtzite ZnO NPs were present on the surface of the cellulose fibers. ZnO NPs-cellulose demonstrated antibacterial activity against Staphylococcus aureus and Escherichia coli, and antifungal activity against Aspergillus niger , Geotrichum candidum, and Phanerochaete chrysosporium. Thus, the study demonstrated an environmental friendly synthesis of ZnO NPs-cellulose composite using an economic and efficient method, which can be used for developing antimicrobial cellulosic fabric for numerous applications.

Antimicrobial-coated films as food packaging: A review

Antimicrobial food packaging involves packaging the foods with antimicrobials to protect them from harmful microorganisms. In general, antimicrobials can be integrated with packaging materials via direct incorporation of antimicrobial agents into polymers or application of antimicrobial coating onto polymer surfaces. The former option is generally achieved through thermal film-making technology such as compression molding or film extrusion, which is primarily suitable for heat-stable antimicrobials. As a nonthermal technology, surface coating is more promising compared to molding or extrusion for manufacturing food packaging containing heat-sensitive antimicrobials. In addition, it also has advantages over direct incorporation to preserve the packaging materials' bulk properties (e.g., mechanical and physical properties) and minimize the amount of antimicrobials to reach sufficient efficacy. Herein, antimicrobial food packaging films achieved through surface coating is explored and discussed. The two components (i.e., film substrate and antimicrobials) consisting of the antimicrobial-coated films are reviewed as plastic/biopolymer films; and synthetic/naturally occurring antimicrobials. Furthermore, special emphasis is given to different coating technologies to deposit antimicrobials onto film substrate. Laboratory coating techniques (e.g., knife coating, bar coating, and spray coating) commonly applied in academic research are introduced briefly, and scalable coating methods (i.e., electrospinning/spraying, gravure roll coating, flexography coating) that have the potential to bring laboratory-developed antimicrobial-coated films to an industrial level are explained in detail. The migration profile, advantages/drawbacks of antimicrobial-coated films for food applications, and quantitative analyses of the reviewed antimicrobial-coated films from different aspects are also covered in this review. A conclusion is made with a discussion of the challenges that remain in bringing the production of antimicrobial-coated films to an industrial level.

Facile in situ fabrication of ZnO-embedded cellulose nanocomposite films with antibacterial properties and enhanced mechanical strength via hydrogen bonding interactions

Nano-ZnO were in situ prepared and permanently embedded in regenerated cellulose (RC) films by chemical precipitation to endow antibacterial of films and simultaneously strengthen tensile strength. ZnCl₂ was selected as a promoter of 1-allyl-3-methylimidazolium chloride for cellulose dissolution and as a precursor for nano-ZnO synthesis. Zn²⁺-absorbed cellulose solution was reacted with NaOH under ultrasonic to obtain nano-ZnO embedded RC films. The results indicated that RC films treated with the longest sonication time, highest regeneration solution basicity, and highest cellulose concentration were demonstrated to be the most effective against S. aureus, which agreed well with the dense and homogeneous distribution of high content of nano-ZnO on the film surface. The nanocomposite films achieved particularly high mechanical strength of 202.0 MPa with improved thermal stability. Strong H-bonding formed between nano-ZnO and cellulose, which contributed to high tensile strength and thermal stability of films. This work affords a simple approach to prepare cellulose nanocomposite with outstanding performance for potential application in packaging.

Wound Healing Composite Materials of Bacterial Cellulose and Zinc Oxide Nanoparticles with Immobilized Betulin Diphosphate

A design of new nanocomposites of bacterial cellulose (BC) and betulin diphosphate (BDP) pre-impregnated into the surface of zinc oxide nanoparticles (ZnO NPs) for the production of wound dressings is proposed. The sizes of crystalline BC and ZnO NPs (5-25%) corresponded to 5-6 nm and 10-18 nm, respectively (powder X-ray diffractometry (PXRD), Fourier-infrared (FTIR), ultraviolet (UV), atomic absorption (AAS) and photoluminescence (PL) spectroscopies). The biological activity of the wound dressings "BC-ZnO NPs-BDP" was investigated in rats using a burn wound model. Morpho-histological studies have shown that more intensive healing was observed during treatment with hydrophilic nanocomposites than the oleophilic standard (ZnO NPs-BDP oleogel; p < 0.001). Treatment by both hydrophilic and lipophilic agents led to increases in antioxidant enzyme activity (superoxide dismutase (SOD), catalase) in erythrocytes and decreases in the malondialdehyde (MDA) concentration by 7, 10 and 21 days (p < 0.001). The microcirculation index was restored on the 3rd day after burn under treatment with BC-ZnO NPs-BDP wound dressings. The results of effective wound healing with BC-ZnO NPs-BDP nanocomposites can be explained by the synergistic effect of all nanocomposite components, which regulate oxygenation and microcirculation, reducing hypoxia and oxidative stress in a burn wound.

Antimicrobial Activity of Zinc Oxide Nano/Microparticles and Their Combinations against Pathogenic Microorganisms for Biomedical Applications: From Physicochemical Characteristics to Pharmacological Aspects

Zinc oxide (ZnO) nano/microparticles (NPs/MPs) have been studied as antibiotics to enhance antimicrobial activity against pathogenic bacteria and viruses with or without antibiotic resistance. They have unique physicochemical characteristics that can affect biological and toxicological responses in microorganisms. Metal ion release, particle adsorption, and reactive oxygen species generation are the main mechanisms underlying their antimicrobial action. In this review, we describe the physicochemical characteristics of ZnO NPs/MPs related to biological and toxicological effects and discuss the recent findings of the antimicrobial activity of ZnO NPs/MPs and their combinations with other materials against pathogenic microorganisms. Current biomedical applications of ZnO NPs/MPs and combinations with other materials are also presented. This review will provide the better understanding of ZnO NPs/MPs as antibiotic alternatives and aid in further development of antibiotic agents for industrial and clinical applications.