Functional properties of chitosan-based films

Supramolecular interaction-enhanced green active packaging films: Design and performance of Ca2+-crosslinked carboxymethyl chitosan composite films

Given the environmental challenges caused by petroleum-based plastics, this study developed a novel green carboxymethyl chitosan (CMCS)-based active packaging composite film (CP) through a synergistic strategy of precise Ca2+ coordination cross-linking and small-molecule plasticizing. Based on this strategy, the CP-4.5 film (CaCl2: 7 wt%, DL-3-phenyllactic acid (3-PLA): 4.5 wt%) exhibited exceptional mechanical properties, including high flexibility (Young's modulus: 0.747 GPa; elongation at break: 65.2 %) and high toughness (18.4 MJ m-3). The incorporation of CaCl2 not only occupied voids within the CP film but also increased the physical cross-linking strength and density of the polymer network. This structural reorganization impeded the diffusion of O2 and H2O molecules, reducing oxygen permeability by 85.9 % and water vapor permeability by 57.6 %. Additionally, 3-PLA, functioning as a broad-spectrum antibacterial agent, imparted the CP film with superior antibacterial activity. The CP film exhibited recyclability and repairability, and underwent complete biodegradation within 56 days. Overall, the synergistic effect of CaCl2 and 3-PLA endowed the CP film with superior mechanical properties, barrier properties, antimicrobial activity, and environmental sustainability, effectively mitigating the quality deterioration of refrigerated grass carp fillets during storage, demonstrating the promising potential of the CP film for food packaging applications.

Biodegradable Chitosan-Based Stretchable Electronics with Recyclable Silver Nanowires

The combination of biodegradability and biocompatibility makes chitosan a principal bioresourced material in biomedical engineering, wearable technology, and medical diagnostics, particularly for integration in human interfaces for soft electronic applications. However, this requires the introduction of soft electronic circuits with the capability of recycling the functional materials, while biodegrading the substrate. This paper presents the development and characterization of biodegradable soft circuits that are constructed using stretchable and flexible substrates from plasticized chitosan and conductive functional wiring from recyclable silver nanowires (AgNWs). The chitosan substrate demonstrates tunable mechanical properties with a maximum stretchability of ∼116%, in addition to desirable characteristics such as transparency, breathability, and controlled degradation. The plasticizing effect of glycerol reduces the rigidity associated with pure chitosan and imparts flexibility and stretchability to the AgNW-chitosan-glycerol (AgNW-Chi-Gly) composite. The AgNWs embedded in the Chi-Gly matrix are highly conductive, and their functionality in soft electronic devices such as strain sensors and electromyography (EMG) sensors is demonstrated. We show that the soft chitosan-based substrates can be subject to biodegradation at the end of their operational lifespan. The AgNWs can be recycled and reused, enhancing the overall sustainability of such soft electronic devices.

Chitin and chitosan from North Pacific krill (Euphausia Pacifica): Comparative study of conventional and microwave-assisted extraction methods and the potential use in chitosan film production

The characteristics and prospective applications of North Pacific krill chitin and chitosan are currently unexplored, and their conventional isolation method is time- and energy-consuming. In this study, chitin and chitosan were extracted from North Pacific krill using conventional and microwave-assisted methods, followed by comprehensive characterisation and evaluation of chitosan film potential. The extracted chitin was identified as an α-polymorph, and chitosan exhibited a remarkable degree of deacetylation (90 %) in both methods. Microwave-assisted extraction provided comparable chitin and chitosan yields without adversely affecting their properties, and the resulting products also exhibited enhanced crystallinity and thermal stability. Moreover, microwave-assisted-extracted chitosan (MCS) had a significantly lower molecular weight (Mw). Krill chitosan films demonstrated superior performance as food packaging materials compared to films prepared from commercial chitosan, due to their greater extensibility and transparency. Notably, the MCS film exhibited exceptional antioxidant activity and solubility. These findings suggest that North Pacific krill holds promise as a viable source of α-chitin and chitosan, and microwave-assisted extraction is effective in producing low Mw chitosan that has the potential to be used for preparing functional biodegradable film, with a fivefold reduction in treatment time.

A review of chitosan role in milk bioactive-based drug delivery, smart packaging and biosensors: Recent advances and developments

Chitosan, a versatile biopolymer derived from chitin, is increasingly recognized in the milk industry for its multifunctional applications in drug delivery, smart packaging, and biosensor development. This review provides a comprehensive analysis of recent advances in chitosan production techniques. These include chemical, biological, and novel methods such as deep eutectic solvents (DES), microwave-assisted approaches, and laser-assisted processes. Surface modification strategies to enhance its functional properties are also discussed. The review highlights the development of various chitosan-based nanocarriers, including nanoparticles, nanofibers, nanogels, and nanocomposites. It emphasizes their stability when combined with milk bioactive ingredients like lipids, peptides, lactose, and minerals. The gastrointestinal fate and safety of chitosan nanoparticles are critically evaluated, showcasing their potential for safe consumption in dairy-related applications. In drug delivery systems, chitosan exhibits excellent compatibility with milk-derived carbohydrates, proteins, and minerals, enabling the development of innovative drug delivery platforms. Additionally, its incorporation into smart packaging materials enhances the shelf-life and quality of dairy products. Chitosan-based biosensors offer precise contaminant detection in the milk industry by enabling precise detection of contaminants such as Bisphenol A, melamine, bacteria, drugs, antibiotics, toxins, heavy metals, and allergens, thus ensuring food safety and quality. Emerging trends, including the integration of artificial intelligence, advanced gene editing, and multifunctional chitosan, are discussed, offering insights into future personalized delivery systems and merging food and drug technologies. The review concludes by highlighting gaps in current research and offering recommendations for future exploration. These suggestions aim to optimize chitosan's unique properties to address key challenges in the milk industry. This article serves as a valuable resource for researchers, industry professionals, and policymakers aiming to innovate within the dairy sector using chitosan-based technologies.

Preparation of amine-functionalized polyacrylonitrile-TiO2-chitosan multilayer nanofibers as a potential wound dressing: Characterization and investigation of in vitro cell viability, proliferation and antibacterial study

Development of a Multi-layered (ML) nanofibers (NFs) scaffold by combining advanced materials to address the diverse needs of wound healing offers a comprehensive solution. In this study, a ML scaffold composed of amine functionalized polyacrylonitrile (AFP) NFs membrane as base layer, TiO2 NPs (T) as middle layer, and chitosan (CS) NFs membrane as contact layer was fabricated sequentially by electrospinning, surface functionalization and electrospraying to promote the wound healing. The multi-layered NFs scaffold (ML AFPT-CS) demonstrated adequate morphology, porosity, surface roughness and hydrophilicity with a water contact angle of 41.94°. The NFs scaffolds were evaluated for in-vitro cellular activity using NIH3T3-E1cells and antibacterial performance. The in-vitro analysis inferred that ML AFPT-CS scaffold in comparison with other study groups exhibited excellent cell viability proliferation and resulted in a spindle shape morphology with cells extending across the ML AFPT-CS scaffold and spreading over the NFs surface. Similarly, the ML AFPT-CS scaffolds were active against all four types of bacterial pathogens (M. luteus, S. flexeneri, S. aureus and K. pneumonia) with a highest inhibition against M. luteus (1.7 mm). The developed ML AFPT-CS scaffold could be promising candidate for advanced wound dressing in future.

Multiple-Layer Chitosan-Based Patches Medicated With LTX-109 Antimicrobial Peptide for Modulated Local Therapy in the Management of Chronic Wounds

In response to the critical issue of chronic wound management, this research explores the development of a multiple-layer biomaterial loaded with LTX-109 a novel broad-spectrum topical antimicrobial peptide currently investigated for the treatment of bacterial skin infections. The novel patch is conceived to load and preserve the function of LTX-109, release it on site in a progressive manner, and therefore make available a device for simultaneous wounds disinfection and tissues healing. Chitosan, tannic acid and glycerol along with the solvent casting process are selected for the development of a multilayer structure in which each single layer is designed by choosing a specific composition and stability to tune its behavior and function. On the top, a protective layer to protect the wound from external contaminations, in the middle a medicated layer loaded with LTX-109 and at the bottom a multifunctional layer to modulate the release of LTX-109. Extensive characterizations show that the patch meets the essential requirements for creating an effective wound healing environment, such as absorption of exudate, maintenance of good oxygen and moisture permeability, biodegradability, biocompatibility, and sustained release of LTX-109 with fully retained antibacterial activity as demonstrated by MIC values obtained against reference bacteria.

Production of Oncorhynchus mykiss biosensor based on polyvinyl alcohol/chitosan nanocomposite using phycocyanin during refrigerated storage

Smart packaging, also known as intelligent packaging, is responsive to external stimuli, moisture, light, oxygen, heat, pH, and bacterial growth. In this study, polyvinyl alcohol/nanochitosan/phycocyanin nanocomposite (PVA/NCH/PC-NC) for fish fillets of Oncorhynchus mykiss rainbow trout coating was prepared. Five treatments were prepared over a period of 14 days (0, 1, 7 and 14 days) under treatments of T1: fish coated with PVA/NCH-NC without PC; T2, T3, T4 and T5 fish coated with PVA/NCH/PC-NC (0.5, 1, 1.5 and 2% PC respectively). Moreover, the results showed that higher concentrations of PC in PVA/NCH polymer matrix resulted in a net-like morphology on the film's surface. Also, after 21 days of storage, the T4 treatment had the lowest levels of mesophilic, psychrophilic, and Enterobacteriaceae bacteria (8.17 ± 0.02, 7.90 ± 0.04, and 60.67 ± 0.02 log cfu/g, respectively). Additionally, it was seen that PVA/NCH/PC-NC improved the Sensory evaluation of fish fillet samples during 14 days of storage (p < 0.05). Overall, the results showed that the prepared PVA/NCH/PC-NC (2% PC) film function as an intelligent packaging solution in food preservation and freshness monitoring applications of Oncorhynchus mykiss fillet in terms of mechanical, microbial and sensorial evaluation.

Chitosan/sodium alginate/ethyl cellulose-based multilayer film incorporated with l-ascorbic acid for improved barrier and antioxidant properties

A bioactive multilayer film (ML) loaded with l-Ascorbic acid (AA) was developed using chitosan (CH), sodium alginate (SA), and ethyl cellulose (EC). Various properties of the films, including morphological, hydrophobic, barrier, mechanical, optical, and antioxidant characteristics, were evaluated and compared to those of monolayer films made from each biopolymer. The cross-sectional analysis via scanning electron microscopy revealed the successful preparation of the ML film with layering of the different biopolymers. For the ML film the resulting water contact angle was observed with an average of 73.86° and the film showed water resistant properties as compared to the individual CH and SA films. The ML film showed the lowest water vapor transmission rate (WVTR) at 54.99 g·d-1·m-2 as compared to the individual films. Moreover, the ML film had the highest tensile strength at 0.56 MPa as compared to the mono-layer films including CH, SA, and EC with TS values of 0.33, 0.24 and 0.17 MPa, respectively. Furthermore, the AA-loaded ML film exhibited significantly higher DPPH scavenging activity at 66.20 %. These findings suggest that the ML film, due to its superior barrier, mechanical, and antioxidant properties has the potential for the applications in active food packaging.

Development of multifunctional chitosan packaging film by plasticizing novel essential oil-based hydrophobic deep eutectic solvent: Structure, properties, and application

To improve the limited mechanical and water barrier properties of chitosan film while granting extra functionalities simultaneously, present study pioneered the incorporation of chitosan film with newly developed essential oil (EO)-based hydrophobic deep eutectic solvents (HDES, EO:octanoic acid (OA), EO:menthol (ME) and OA:ME:EO). The highest tensile strength (66.22 MPa) and elongation at break (45.99 %) were obtained in OA:ME:EO-40 and OA:ME:EO-80 films, respectively. The OA:EO-based films showed excellent and stable hydrophobicity. HDESs also endowed film with additional functionalities including thermal stability, bio-compatibility, controlled release, antioxidant, and antibacterial capacity. The extension of the storage period of strawberry treated with OA:EO-containing films confirmed their preservation ability. Compared with ME:EO and OA:ME:EO, OA:EO had better compatibility with chitosan matrix and could serve as a promising plasticizer for strengthening functionalities of chitosan film. These results also promote application of HDESs as emerging plasticizers in manufacture of other polymer-based packaging film.

Environmentally Sustainable and Green Polymeric Method for Chitosan (CH) Film Synthesis Using Natural Acids and Impact of Zinc Ferrite Nanoparticles (NPs) on Water Solubility (WS) and Physical Properties

Currently, there is a rush to develop green polymeric films such as biodegradable chitosan (CH) films to control and prevent plastic pollution from degrading the environment. This study reports a novel and sustainable green approach to the development of CH films using lemon juice (LJ) and lemon peel extract (LPE), the latter to dilute the LJ. The LPE was also utilized for the synthesis of ZnFe2O4 nanoparticles (NPs), adding to this work's novelty. The crystalline size of the ZnFe2O4 NPs was computed to be ~16 nm. The introduction of 1% and 2% ZnFe2O4 NPs improved not only the mechanical properties of the films, but also their barrier properties and water solubility (WS). The tensile strength increased from 0.641 MPa to 0.835 MPa when 2% NPs were incorporated, which is almost 1.30 times greater; the NPs also enhanced the surface strength by 2.66 times, which was demonstrated by the puncture strength. The introduction of NPs occupied the vacant spaces and improved the barrier capabilities of the CH film by reducing the water vapor permeability (WVP) value from 8.752 ± 0.015 for bare CH films to 6.299 ± 0.009 for 2% NP-containing CH films. Overall, the introduction of ZnFe2O4 NPs boosted the mechanical and barrier properties of the CH films, and offers a promising method for developing sustainable, eco-friendly, and biodegradable polymeric films for potential packaging and medical applications to contribute to circular economic efforts.

Improving the mechanical properties of chitosan through blending with poly(trimethylene carbonate) copolymer

In this study, a novel flexible material was fabricated by blending chitosan (CS) with a poly(trimethylene carbonate) (PTMC) copolymer. N-methyl-D-glucamine, which acts as a polyol, was grafted onto the PTMC copolymer to produce poly(TMC-co-TMC-glucamine) (PTTG), to enhance the hydrogen bonding interactions. The CS/PTTG blend films were then fabricated using solvent casting. The chemical interactions and thermal properties of the new materials were evaluated using FT-IR and TGA, which revealed a shift in wavenumber and a decrease in T10. Incorporation of PTTG into CS significantly improved tensile strength, reaching up to 16.0 ± 2.6 MPa in the CS75PTTG25 formulation. The flexibility also increased to 55.9 ± 6.6 MPa in the simple blend of CS, PTMC copolymer, and N-methyl-D-glucamine. Additionally, the underlying mechanism is presented and thoroughly explained in this work. Consequently, CS/PTTG blend films, derived from biodegradable polymers with excellent mechanical properties, demonstrate potential for various applications.

Self-Assembled Hydrogel Based on (Bio)polyelectrolyte Complex of Chitosan-Gelatin: Effect of Composition on Physicochemical Properties

Taking into account the trends in the field of green chemistry and the desire to use natural materials in biomedical applications, (bio)polyelectrolyte complexes ((bio)PECs) based on a mixture of chitosan and gelatin seem to be relevant systems. Using the approach of self-assembly from the dispersion of the coacervate phase of a (bio)PEC at different ratios of ionized functional groups of chitosan and gelatin (z), hydrogels with increased resistance to mechanical deformations and resorption in liquid media were obtained in this work in comparison to a hydrogel from gelatin. It was found that at z ≥ 1 a four-fold increase in the elastic modulus of the hydrogel occurred in comparison to a hydrogel based on gelatin. It was shown that hydrogels at z ≈ 1 had an increased sorption capacity and water sorption rate, as well as increased resistance to the in vitro model environment of phosphate-buffered saline (PBS) solution containing lysozyme at 37 °C. It was also shown that in PBS and simulated gastric fluid (SGF) solutions, the effect of the polyelectrolyte swelling of the hydrogels was significantly suppressed; however, at z ≥ 1, the (bio)PEC hydrogels had increased stability compared to the samples at z < 1 and based on gelatin.

Physicochemical and biological evaluation of 'click' synthesized vinyl epoxide-chitosan film for active food packaging

Chitosan (Cs) being a natural biopolymer serves as an excellent template to construct active packaging materials for achieving sustainable development. In this study, Cs was chemically modified via epoxide ring opening click reaction using vinyl epoxide to obtain a novel chitosan vinyl epoxide (Cs-VE) derivative with hydroxyl and olefinic functional groups. The Cs-VE transparent film was fabricated through the eco-friendly solution casting technique. A meticulous investigation into the chemical structure and physicochemical properties of the synthesized films was conducted using FT-IR, 1H NMR and XRD analyses. The thermal stability and homogeneity of the film were verified by thermogram and FE-SEM images respectively. Improved mechanical properties (tensile strength of 24.64 MPa and 12.08 % elongation at break) and excellent UV-light blocking ability (9.3 % transmittance at 350 nm and 22.15 % transparency at 600 nm) were observed. Also, important parameters such as water vapor permeability (WVP), swelling degree, water solubility and UV-barrier properties were found to be adequate for food packaging application. Similarly, enhanced antioxidant activity with 27.2 % and 73.6 % radical scavenging against DPPH and ABTS radicals respectively was observed for the synthesized Cs-VE film. The film showed antimicrobial activity against both bacteria and fungi. These results along with food packaging studies on Grewia asiatica fruit established the developed Cs-VE film as a suitable candidate for active food packaging application.

Edible-algae base composite film containing gelatin for food packaging from macroalgae, Gracilaroid (Gracilaria fisheri)

BACKGROUND

Conventional petroleum-based packaging films cause severe environmental problems. In the present study, bio-edible film was introduced as being safe to replace petroleum-based polymers. A food application for edible sachets and a composite edible film (EF) from marine algae, Gracilaria fisheri (GF) extract, were proposed.

RESULTS

Carbohydrates were the most prevalent component in fresh GF fronds. Under neutral conditions comprising 90 °C for 40 min, the structure of the extract was determined by Fourier transform infrared to be a carrageenan-like polysaccharide. Glycerol was the best plasticizer for EF formation because it had the highest tensile strength (TS). The integration of gelatin into the algal composite film with gelatin (CFG) was validated to be significant. The best casting temperatures for 2 h were 70 and 100 °C among the four tested temperatures (25, 60, 70 and 100 °C). Temperatures did not result in any significant (P ≤ 0.05) differences in any character (color values, TS, water vapor permeability, oxygen transmission, thickness and water activity), except elongation at break. Visually, the CFG had a slightly yellow appearance. The best-to-worst order of film stability in the three tested solvents was oil, distilled water (DW) and ethanol. Its stability in ethanol (0-100%), temperature of DW (30-100 °C) and pH (3-7 in DW) demonstrated inverse relationships with the concentration or different conditions, except for pH 8-10 in DW. All treatments were significantly (P ≤ 0.05) different.

CONCLUSION

The novel material made from polysaccharides from algae, G. fisheri, was used to improve EF. The edible sachet application is plausible from the EF. © 2024 Society of Chemical Industry.

Nanocellulose@gallic Acid-Based MOFs: A Novel Material for Ecofriendly Food Packaging

The development of an effective food packaging material is essential for safeguarding against infections and preventing chemical, physical, and biological changes during food storage and transportation. In the present study, we successfully synthesized an innovative food packaging material by combining chitosan (CH), nanocellulose (NC), and a gallic acid-based metal-organic framework (MOF). The CH films were prepared using different concentrations of NC (5 and 10%) and MOFs (1.5, 2.5, and 5%). Various properties of prepared films, including water solubility (WS), moisture content (MC), swelling degree, oxygen permeability, water vapor permeability (WVP), mechanical property, color analysis, and light transmittance, were studied. The chitosan film with a 5% NC and 1.5% MOF (CH-5% NC-1.5% MOF) exhibited the least water solubility, moisture content, and water vapor permeability, indicating the overall stability of the film. Additionally, this film demonstrated low oxygen permeability, as indicated by a peroxide value of 18.911 ± 4.009, ensuring the effective preservation of packaged contents. Notably, this synthesized film exhibited high antioxidant activity, resulting in an extended duration of 52 days. This antioxidant activity was further validated by the preservation of apple slices for 9 days in a CH-5% NC-1.5% MOF film. The findings of the study suggest that the developed films can provide a promising and environmentally friendly solution for active food packaging.

Chitosan Extracted from the Biomass of Tenebrio molitor Larvae as a Sustainable Packaging Film

Waste from non-degradable packaging materials poses a serious environmental risk and has led to interest in developing sustainable bio-based packaging materials. Sustainable packaging materials have been made from diverse naturally derived materials such as bamboo, sugarcane, and corn starch. In this study, we made a sustainable packaging film using chitosan extracted from the biomass of yellow mealworm (Tenebrio molitor) shell waste. The extracted chitosan was used to create films, cross-linked with citric acid (CA) and with the addition of glycerol to impart flexibility, using the solvent casting method. The successful cross-linking was evaluated using Fourier-Transform Infrared (FTIR) analysis. The CA cross-linked mealworm chitosan (CAMC) films exhibited improved water resistance with moisture content reduced from 19.9 to 14.5%. Improved barrier properties were also noted, with a 28.7% and 10.2% decrease in vapor permeability and vapor transmission rate, respectively. Bananas were selected for food preservation, and significant changes were observed over a duration of 10 days. Compared to the control sample, bananas packaged in CAMC pouches exhibited a lesser loss in weight because of excellent barrier properties against water vapor. Moreover, the quality and texture of bananas packaged in CAMC pouch remained intact over the duration of the experiment. This indicates that adding citric acid and glycerol to the chitosan structure holds promise for effective food wrapping and contributes to the enhancement of banana shelf life. Through this study, we concluded that chitosan film derived from mealworm biomass has potential as a valuable resource for sustainable packaging solutions, promoting the adoption of environmentally friendly practices in the food industry.

Development of a Chitosan-Based Film from Shellfish Waste for the Preservation of Various Cheese Types during Storage

The global concern about the use of disposable plastics has fed the research on sustainable packaging for food products. Among the virtuous materials, chitosan emerges as a valid alternative to conventional polyethylene films because of its abundance in nature. In this work, a novel film for food wrapping was developed by exploiting shellfish waste according to a vision of circular economy. Compared to previous studies, here, novel ingredients, such as polyvinyl alcohol (PVA), fibroin, and essential oils, were used in a synergistic combination to functionally postpone cheese deterioration. The fermentative procedure applied for the obtainment of chitin contributes to filling the existing gap in the literature, since the majority of studies are based on the chemical pathways that dramatically impact the environment. After pretreatment, the shrimp shell waste (SSW) was fermented through two bacterial strains, namely Lactobacillus plantarum and Bacillus subtilis. A deacetylation step in an alkaline environment transformed chitin into chitosan, yielding 78.88 g/kg SWW. Four different film formulations were prepared, all containing chitosan with other ingredients added in order of decreasing complexity from the A to D groups. The novel films were tested with regard to their physico-mechanical and antioxidant properties, including the tensile strength (12.10-23.25 MPa), the elongation at break (27.91-46.12%), the hardness (52-71 Shore A), the film thickness (308-309 μm), and the radical scavenging activity (16.11-76.56%). The performance as a cling film was tested on two groups of cheese samples: the control (CTR), wrapped in conventional polyethylene (PE) film; treated (TRT), wrapped in the chitofilm formulation deemed best for its mechanical properties. The volatiles entrapped into the headspace were investigated by means of the SPME-GC technique. The results varied across soft, Camembert, and semi-hard cheeses, indicating a growing abundance of volatiles during the conservation of cheese. The bacterial growth trends for mesophilic, enterobacteriaceae, and lactic acid bacteria were expressed as the mean colony forming units (CFU)/mL for each type of cheese at different sampling times (day 2, day 8, and day 22): the highest load was quantified as 8.2 × 106 CFU/mL at day 22 in the CTR Camembert cheese. The TRT samples generally exhibited inhibitory activity comparable to or lower than that observed in the CTR samples. The sensory analysis revealed distinctions in cheese taste between the TRT and CTR groups.

Influence of Reduced Graphene Oxide and Carbon Nanotubes on the Structural, Electrical, and Photoluminescent Properties of Chitosan Films

Chitosan is a biopolymer with unique properties that have attracted considerable attention in various scientific fields in recent decades. Although chitosan is known for its poor electrical and mechanical properties, there is interest in producing chitosan-based materials reinforced with carbon-based materials to impart exceptional properties such as high electrical conductivity and high Young's modulus. This study describes the synergistic effect of carbon-based materials, such as reduced graphene oxide and carbon nanotubes, in improving the electrical, optical, and mechanical properties of chitosan-based films. Our findings demonstrate that the incorporation of reduced graphene oxide influences the crystallinity of chitosan, which considerably impacts the mechanical properties of the films. However, the incorporation of a reduced graphene oxide-carbon nanotube complex not only significantly improves the mechanical properties but also significantly improves the optical and electrical properties, as was demonstrated from the photoluminescence studies and resistivity measurements employing the four-probe technique. This is a promising prospect for the synthesis of new materials, such as biopolymer films, with potential applications in optical, electrical, and biomedical bioengineering applications.

Synthesis of novel chitosan/sodium hyaluronate/iridium hydrogel nanocomposite for wound healing application

A novel chitosan/sodium hyaluronate/iridium (CHI/SH/Ir) hydrogel nanocomposite with a unique microstructure containing vertically aligned pores is fabricated via an electrophoresis technique. The formation of orderly vertical pores in CHI/SH/Ir hydrogel nanocomposite is due to the confinement of hydrogen bubbles produced from the water electrolysis during electrophoresis that limits their lateral movement and coalescence. In a wet state, the diameter for the vertical pores is 600-700 μm. With a thickness of 500 μm, the CHI/SH/Ir hydrogel nanocomposite exhibits a porosity of 76.7 % and a water uptake of 350 %. Its tensile strength is almost doubled to 8.7 MPa, as compared to that of counterpart without the addition of iridium. In CHI/SH/Ir hydrogel nanocomposite, the iridium nanoparticles are homogeneously distributed with an average size of 3 nm. The CHI/SH/Ir electrophoresis suspension exhibits a negligible cytotoxicity. In cell migration test using the human keratinocytes HaCaT cells, the CHI/SH/Ir hydrogel nanocomposite reveals a relative migration of 122.15 ± 9.02 % (p < 0.001) as compared to the blank sample. The presence of vertically aligned pores with the use of SH and iridium nanoparticles indicates a promising opportunity in wound healing application.

Effect of Soybean Oil on the Improvement of the Functionality of Edible Membrane-Type Food Packaging Films Based on Caseinate-Carboxymethyl Chitosan Compositions

Edible film biopolymers are gaining attention to tackle problems of plastic waste and food safety to alleviate environmental problems associated with plastic products in food packaging. In this study, caseinate-carboxymethyl chitosan (CA-CMCH) composite films were made with the incorporation of soybean oil (SO) using a casting technique. The influence of different soybean oil concentrations at 0, 0.5, and 1% (w/w) on physical, mechanical, barrier, and surface characteristics of films composed of caseinate-carboxymethyl chitosan (CA-CMCH) was evaluated. The brightest film (L* value of 95.95 ± 0.30) was obtained with the edible film made from the control group of samples with sodium caseinate (NaCA-100; 100% NaCA). The results also indicated that samples with 1% SO in NaCA-75 and CaCA-75 had lower water vapor permeability (WVP), while those with NaCA-50 and CaCA-50 showed higher values of WVP. For mechanical properties, this study found that incorporating soybean oil into the caseinate-carboxymethyl (CA-CMCH) composite films led to an enhancement of both tensile strength and elongation at break. The morphological structures, determined using SEM, of control and composite films showed compact and homogenous surfaces. Overall, the addition of soybean oil contributed to the improvement of the functional properties of the edible films, offering potential solutions to the environmental issues associated with plastic packaging and enhancing the safety and performance of food packaging.

Influence of extracellular polymeric substances on arsenic bioaccumulation and biotransformation in biofilms

It is well recognized that biofilms can biosorb and biotransform heavy metals in aquatic environments. However, the effects of extracellular polymeric substance (EPS) on inorganic arsenic (As) bioaccumulation and biotransformation in biofilms are still unrevealed and need to be investigated. In order to explore the above scientific issues, the As accumulation and speciation in EPS-containing or EPS-free biofilms and growth medium under As(V)/As(III) exposure conditions were measured. After the removal of EPS, the amount of As uptake (Asup) and As adsorption (Asad) in biofilms were significantly reduced, no matter whether exposed to As(V) or As(III). FTIR analysis further suggested that the interaction between these functional groups with As was limited after the removal of EPS. In the EPS-containing biofilms, the Asad was mainly As(V) with low toxicity. However, after the removal of EPS, the Asad was mainly As(III) with high fluidity, and no methylated As was found. Moreover, the removal of EPS inhibited As(III) oxidation and methylation by biofilms, resulting in the decrease of As(V) and methylated As in the growth medium. The findings of this study emphasized the essential impact of EPS on the biosorption and biotransformation of As in biofilms. This study provides a unique understanding of the role of biofilms in As biogeochemical cycle, and water quality purification function in water environments.

Modified polysaccharides for food packaging applications: A review

Development of new food packaging materials is crucial to reduce the use of single-use plastics and to limit their destructive impact on the environment. Polysaccharides provide an alternative solution to this problem. This paper summarizes and discusses recent research results on the potential of modifying polysaccharides as materials for film and coating applications. Modifications of polysaccharides significantly affect their properties, as well as their application usability. Although modifications of biopolymers for packaging applications have been widely studied, polysaccharides have attracted little attention despite being a prospective, environmentally friendly, and economically viable packaging alternative. Therefore, this paper discusses approaches to the development of biodegradable, polysaccharide-based food packaging materials and focuses on modifications of four polysaccharides, such as starch, chitosan, sodium alginate and cellulose. In addition, these modifications are presented not only in terms of the selected polysaccharide, but also in terms of specific properties, i.e. hydrophilic, barrier and mechanical properties, of polysaccharides. Such a presentation of results makes it much easier to select the modification method to improve the unsatisfactory properties of the material. Moreover, very often it happens that the applied modification improves one and worsens another property, which is also presented in this review.

Effect of apple polyphenols on physicochemical properties of pea starch/pulp cellulose nanofiber composite biodegradable films

A pea starch (PS) and pulp cellulose nanofibers (CNF-P) hybrid matrix biodegradable film was prepared using apple polyphenol (AP) as the active substance. SEM and thermogravimetric analyses showed that apple polyphenols could be uniformly distributed and form hydrogen bonds with the matrix, and the increase in crystallinity improved the thermal stability of the films (the final residue of the films increased from 22.66 % to 31.82 %). The TS and EAB of the films reached their maximum values of 11.14 ± 1.73 MPa and 71.55 ± 8.8 %, respectively, at an AP content of 1.5 %. It should be noted that the antioxidant properties of the films were significantly positively correlated with the AP content, and the DPPH radical scavenging rate of the films reached 73.77 % at an AP content of 4.5 %, which was about 49 times higher than that of the control film. The same trend was observed in the UV-vis spectra. In addition, the total color difference and water solubility of the membranes increased from 4.29 ± 0.29 to 31.86 ± 1.90 and from 20.01 ± 0.97 % to 21.70 ± 1.99 %, respectively, and the biodegradability also showed an upward trend. These findings provide a theoretical basis and data support for the development of multifunctional biodegradable food packaging materials.

UV- shielding and antioxidant properties of chitosan film impregnated with Acacia catechu modified with calcium carbonate for food packaging

Acacia catechu contains polyphenolic compounds such as catechin and tannins, which exhibit antioxidant and antimicrobial properties that have the potential to be used in food packaging applications. In this study, chitosan-based (CH) antioxidant films were developed with the incorporation of calcium carbonate (CC) and Acacia catechu (CT). The films were fabricated by the solvent-casting method, and the effects of the different concentrations of Acacia catechu were analyzed. The physicomechanical, antioxidant, and UV shielding properties of the films were determined. The addition of Acacia catechu and calcium carbonate has significantly increased the tensile from 2.30 MPa to 4.95 MPa, respectively, for neat CH and CH/CC/CT-4 film. At the same time, there is a reduction in the elongation at break from 26.75 % in neat CH film to 12.11 % in CH/CC/CT-4 film. The CH/CC/CT-4 film has shown the highest ferric-reducing antioxidant power (FRAP) of 0.440 mg Trolox/g dried weight of the film and 2,2 diphenyl picrylhydrazyl (DPPH) radical scavenging activity of 93.05 %. The UV transmittance of CH/CC/CT-4 film was 0.46 %, the lowest compared to the rest of the fabricated films. These active properties depict that CH/CC/CT-4 film has the potential to be utilized for the packaging of light and oxygen-sensitive food products.

Optimization of an edible film formulation by incorporating carrageenan and red wine lees into fish gelatin film matrix

The study aimed to use response surface methodology (RSM) to create and understand a novel edible film made from fish gelatin (FG). This film includes wine lees (WL) and carrageenan (CAR). The concentrations of WL (0, 1, 2, and 3 %) and CAR (0, 1, and 3 %) were considered independent variables. The process variable combinations for the optimal response functions were 1.926 % WL and 3 % CAR, forming soft and rigid films with low tensile strength (TS) and high elongation at break (EAB%). Based on the evaluation of each response, FG film had the highest TS value, FG/CAR(3 %) film had the maximum EAB, and FG/WL (3 %)/CAR (3 %) film had the lowest vapor permeability (WVP) and the highest opacity (OP). The incorporation of WL considerably improved the functional properties of these films, enabling strong antioxidant activity and high phenolic content. Characterization of the films with analytical techniques: Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis demonstrated a considerable interaction between WL and FG, indicating a high level of compatibility between the two substances. Our data suggest that the formulation of edible films can be adjusted to fit the specific requirements of the design.

Chitin and Its Derivative Chitosan: Distribution in Nature, Applications, and Technology Research (A Review)

The present review highlights the chitin/chitosan as biopolymers that are promising for biomedical research development. Our goal was to assess the potential for practical use of these biopolymers and to summarize information on traditional and innovative technologies for their production and purification. The widespread occurrence of chitin and chitosan in nature as well as the unique chemical and biological properties of chitosan are reasons of growing interest in the use of the latter in several pharmaceutical fields. The main stages of chitin extraction and its further modification into chitosan are deproteinization, demineralization, deacetylation, and the main methods of chitosan purification are filtration, dialysis and reprecipitation. The profitability of the production of chitin/chitosan from crustaceans and edible mushrooms is approximately at the same level. The cost of mushroom products can be reduced by using agricultural or forestry waste as nutrient substrates. This makes the use of fungi as sources of chitin/chitosan in forested regions a rather promising issue.

Green interconnected network structure of chitosan-microcrystalline cellulose-lignin biopolymer film for active packaging applications

As an excellent alternative to petroleum-based food packaging materials, a novel green hybrid composite film with an excellent interconnected network structure was successfully fabricated by integrating chitosan (chi), microcrystalline cellulose (MCC), and lignin nanoparticles (LNP), including the desired amount of plasticizer glycerol (gly). Overall, 36 combinations were developed and investigated for superior biocomposite film formation. Among the various concentration ratios, the 40:35:25 chi-MCC-gly film provided well-organized film formation, good physicochemical properties, mechanical stability, efficient water contact angle, reduced water solubility, and lower water vapor permeability (11.43 ± 0.55 × 10-11 g.m-1.s-1.Pa-1). The performance of the chi-MCC-gly film further enhanced by the homogeneous incorporation of ∼100 nm LNP. With 1 % LNP addition, the tensile strength of the film increased (28.09 MPa, 47.10 % increase) and the water vapor permeability reached a minimum of 11.43 × 10-11 g.m-1.s-1.Pa-1, which proved the impact of LNP in composite films. Moreover, the films showed excellent resistance to thermal shrinkage even at 100 °C and exhibited nearly 100 % UV blocking efficiency at higher LNP concentrations. Interestingly, the green composite films extended the shelf life of freshly cut cherry tomatoes to seven days without spoilage. Overall, the facile synthesis of strong, insoluble, UV-blocking, and thermally stable green composite films realized for food packaging applications.

Effects of carboxymethyl cellulose fiber formations with chitosan incorporation via coating and mixing processes

To date, the utilization of carboxymethyl cellulose (CMC) fibers are only restricted to weak mechanical application such as wound dressing. Physically, CMC has a weak mechanical strength due to the high hydrophilicity trait. However, this flaw was saved by the extensive number of reactive functional groups, allowing this macromolecule to form linkages with chitosan to ensure its versatility. This work successfully fabricated CMC-chitosan fiber via dissolution, crosslinking, dry-jet wet-spinning extrusion, and coagulation processes. Chitosan was constituted with CMC fiber in two approaches, coating, and inclusion at various concentrations. Morphologically, chitosan incorporation has triggered agglomerations and roughness toward CMC fibers (CMCF). Chemically, the interaction between CMC and chitosan was proved through FTIR analysis at peaks 1245 cm-1 (ECH covalent crosslinking), while 3340 cm-1 and 1586 cm-1 were due to ionic and hydrogen bonding. The result from analysis showed that at higher chitosan concentrations, the chitosan-included CMC fiber (CMCF-I) and chitosan-coated CMC fiber (CMFC) were mechanically enhanced (up to 86.77 and 82.72 MPa), thermally more stable (33 % residual mass), and less hydrophilic compared to the plain CMCF. The properties of CMC-chitosan fibers have opened up vast possible applications, especially as a reinforcement in a watery medium such as a hydrogel.

Sterilized Polyhexanide-Releasing Chitosan Membranes with Potential for Use in Antimicrobial Wound Dressings

Wound infection is a common complication of chronic wounds. It can impair healing, which may not occur without external help. Antimicrobial dressings (AMDs) are a type of external help to infected chronic wounds. In this study, highly porous membranes made of only chitosan and containing the antiseptic polyhexanide (poly(hexamethylene biguanide); PHMB) were prepared by cryogelation, aiming to be used in AMDs. These membranes exhibited a water swelling capacity of 748%, a water drop penetration time of 11 s in a dry membrane and a water vapor transmission rate of 34,400 g H2O/m2/24 h when in contact with water. The best drug loading method involved simultaneous loading by soaking in a PHMB solution and sterilization by autoclaving, resulting in sterilized, drug-loaded membranes. When these membranes and a commercial PHMB-releasing AMD were assayed under the same conditions, albeit far from the in vivo conditions, their drug release kinetics were comparable, releasing PHMB for ca. 6 and 4 h, respectively. These membranes exhibited high antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, which are bacterial species commonly found in infected wounds and blood clotting activity. The obtained results suggest that these membranes may have potential for use in the development of AMDs.

Packaging films based on biopolymers from seafood processing wastes: Preparation, properties, and their applications for shelf-life extension of seafoods-A comprehensive review

Biopolymers derived from seafood processing byproducts are used to prepare active and biodegradable films as the packaging of food products. These films possess bioactivities to enhance the shelf life of packed foods by proactively releasing antimicrobial/antioxidative agents into the foods and providing sufficient barrier properties. Seafood processing byproducts are an eminent source of valuable compounds, including biopolymers and bioactive compounds. These biopolymers, including collagen, gelatin, chitosan, and muscle proteins, could be used to prepare robust and sustainable food packaging with some antimicrobial agents or antioxidants, for example, plant extracts rich in polyphenols or essential oils. These active packaging are not only biodegradable but also prevent the deterioration of packed foods caused by spoilage microorganisms as well as chemical deterioration. Seafood discards have a promising benefit for the development of environmentally friendly food packaging systems via the appropriate preparation methods or techniques. Therefore, the green packaging from seafood leftover can be better exploited and replace the synthetic counterpart.

Effect of Nano-Silica and Sorbitol on the Properties of Chitosan-Based Composite Films

Chitosan and its derivatives are widely used in food packaging, pharmaceutical, biotechnology, medical, textile, paper, agriculture, and environmental industries. However, the flexibility of chitosan films is extremely poor, which limits its relevant applications to a large extent. In this paper, chitosan/sorbitol/nano-silica (CS/sorbitol/SiO2) composite films were prepared by the casting film method using chitosan, sorbitol, Tween-80 and nano-SiO2 as raw materials. The structure of the films was characterized by infrared spectroscopy, electron scanning microscopy, and X-ray diffraction analysis. The effects of sorbitol and nano-silica dosage on the mechanical properties, thermal properties and water vapor barrier properties of the composite film were investigated. The results show that with the gradual increase in sorbitol (≤75 wt %), the elongation at the break of chitosan/sorbitol films significantly increased. When the addition of sorbitol was 75 wt %, the elongation at break of the chitosan/sorbitol composite film was 13 times higher than that of the chitosan film. Moreover, nano-SiO2 can further improve the mechanical properties and thermal stability of the chitosan/sorbitol composite films. When the amount of nano-silica was 4.5 wt %, the composite film became more flexible, with a maximum elongation of 90.8% (which is 14 times that of chitosan film), and its toughness increased to 10.52 MJm-3 (which is 6 times that of chitosan film). This study balances the tensile strength and elongation at break of the composite films by adding a plasticizer and nano-filler, providing a reference for the preparation of chitosan composites or their blending with other polymers, and has practical guiding significance for the industrial production of biomass plastics.

Colorimetric pH indicators based on well-defined amylose and amylopectin matrices enriched with anthocyanins from red cabbage

This study aimed to prepare a novel colorimetric indicator film from virtually pure (99 %) amylose (AM) and anthocyanins extracted from red cabbage (RCA). The AM used was a unique engineered bulk material extracted from transgenic barley grains. Films produced by solution casting were compared to normal barely starch (NB) and pure barley amylopectin (AP), with amylose contents of 30 % and 0 %, respectively. The pH-indicator films were produced by incorporation of RCA into the different starch support matrices with different amylose contents. Barrier, thermal, and mechanical properties, photo degradation stability, and release behavior data revealed that RCA interact differently through the glucan matrices. Microstructural observations showed that RCA were evenly dispersed in the glucan matrix, and AM+RCA indicator films showed high UV-barrier and mechanical performance over normal starch. FTIR revealed that RCA was properly affected by the AM matrix. Moreover, the AM+RCA films showed sensitive color changes in the pH range (2-11) and a predominant Fickian diffusion release mechanism for RCA. This study provides for the first time data regarding AM films with RCA and their promising potential for application as support matrices in responsive food and other industrial biodegradable packaging materials.

Eco-sustainable coatings based on chitosan, pectin, and lemon essential oil nanoemulsion and their effect on strawberry preservation

Films and coatings manufactured with bio-based renewable materials, such as biopolymers and essential oils, could be a sustainable and eco-friendly alternative for protecting and preserving agricultural products. In this work, we developed films and coatings from pectin and chitosan to protect strawberries (Fragaria x ananassa Duch.) from spoilage and microbial contamination. We developed three coatings containing equal amounts of glycerol and Sicilian lemon essential oil (LEO) nanoemulsion. We identified seventeen chemicals from LEO by GC-MS chromatogram, including d-limonene, α-Pinene, β-Pinene, and γ-Terpinene. The pectin and chitosan coatings were further characterized using different physicochemical, mechanical, and biological methods. The films demonstrated satisfactory results in strength and elongation at the perforation as fruit packaging. In addition, the coatings did not influence the weight and firmness of the strawberry pulps. We observed that 100 % essential oil was released in 1440 min resulting from the erosion process. Also, the oil preserved the chemical stability of the films. Antioxidant activity (AA), measured by Electron Paramagnetic Resonance (EPR), showed that the coatings loaded with 2 % LEO nanoemulsion (PC + oil) showed that almost 50 % of AA from LEO nanoemulsion was preserved. The chitosan and the pectin-chitosan coatings (PC + oil) inhibited filamentous fungi and yeast contaminations in strawberries for at least 14 days, showing a relationship between the AA and antimicrobial results.

Chitosan: a green adhesive for surface functionalization and fabrication of thermoplastic biomedical microdevices

Chitosan (CS) is a natural polymer that exhibits many biological properties and is used as a biomaterial for antibacterial coatings, tissue engineering, cell research, drug delivery, and negatively charged molecule capture. In our previous study, we used a CS-polydopamine mixture to realize UV-assisted bonding between poly(methyl methacrylate) (PMMA) substrates to fabricate microdevices for self-assembled stem cell spheroid cultures. Herein, we attained reliable adhesive bonding between PMMAs using CS at room temperature assisted by oxygen plasma. The bond strength of adhesion was as high as 2.1 MPa, which could be stable for over two months according to the leak test. The adhesive bonding and surface functionalization of the microchannels were simultaneously completed such that the microdevices could be directly used for mesenchymal stem cell culture for spheroid generation and DNA purification for point-of-care testing (POCT) devices. Surface characterization was performed by contact angle measurements, Fourier-transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The POCT device allows sequential on-chip DNA purification, amplification, and colorimetric detection of pathogenic bacteria. This method provides a convenient and reliable strategy for the fabrication of PMMA microdevices that can be directly implemented in biological studies and POCT applications without involving prior surface modification steps.

Neoteric Biofilms Applied to Enhance the Safety Characteristics of Ras Cheese during Ripening

The milk's natural flora, or the starter, can preserve cheesemaking and allow for microbial competition. This investigation aimed to improve cheese safety and assess its characteristics using probiotic cell pellets (LCP) or cell-free extracts (CFS). Cheese samples were collected from different areas to investigate the current contamination situation. Six CFSs of probiotics were assessed as antifungal against toxigenic fungi using liquid and solid media and their aflatoxin reduction impact. The most effective CFS was chosen for cheese coating in nanoemulsion. Coated cheese with CFS, LCP, and LCP-CFS was assessed against control for changes in chemical composition, ripening indications, rheological properties, and microbiology. Results showed significant contamination levels in the collected samples, and toxic fungi were present. Lactobacillus rhamnosus CFS has aflatoxins reducibility in liquid media. During cheese ripening, uncoated cheese showed higher fat, protein, salt content, soluble nitrogen, total volatile fatty acids, tyrosine, and tryptophan contents than coated samples, except for LCP-coating treatment. Cheese rheology indicated that coating treatments had the lowest hardness, cohesiveness, gumminess, chewiness, and springiness compared to uncoated cheese. Uncoated cheese had the highest yeast and mold counts compared to the treated ones. The LCP-CFS-coated cheese showed no Aspergillus cells for up to 40 days. Uncoated Ras cheese recorded slightly lower flavor, body, texture, and appearance scores than coated cheeses. In conclusion, coating cheese with L. rhamnosus nanoemulsion has antifungal and antiaflatoxigenic properties, even for LCP, CFS, and CFS-LCP, which could extend cheese shelf life.

Effect of Time on the Properties of Bio-Nanocomposite Films Based on Chitosan with Bio-Based Plasticizer Reinforced with Nanofiber Cellulose

The deterioration of the performance of polysaccharide-based films over time, particularly their hydrophilicity and mechanical properties, is one of the main problems limiting their applications in the packaging industry. In the present study, we proposed to improve the performance of chitosan-based films through the use of: (1) nanocellulose as an additive to reduce their hydrophilic nature; (2) bio-based plasticizer to improve their mechanical properties; and (3) chestnut extract as an antimicrobial agent. To evaluate their stability over time, the properties of as-formed films (mechanical, hydrophilic, barrier and antibacterial) were studied immediately after preparation and after 7, 14 and 30 days. In addition, the morphological properties of the films were characterized by scanning electron microscopy, their structure by FTIR, their transparency by UV-Vis and their thermal properties by TGA. The films showed a hydrophobic character (contact angle above 100°), barrier properties to oxygen and carbon dioxide and strong antibacterial activity against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. Moreover, the use of nanofillers did not deteriorate the elongation at breaks or the thermal properties of the films, but their addition reduced the transparency. In addition, the results showed that the greatest change in film properties occurred within the first 7 days after sample preparation, after which the properties were found to stabilize.

Characteristics of Chitosan Films with the Bioactive Substances-Caffeine and Propolis

Chitosan is a natural and biodegradable polymer with promising potential for biomedical applications. This study concerns the production of chitosan-based materials for future use in the medical industry. Bioactive substances-caffeine and ethanolic propolis extract (EEP)-were incorporated into a chitosan matrix to increase the bioactivity of the obtained films and improve their mechanical properties. Acetic and citric acids were used as solvents in the production of the chitosan-based films. The obtained materials were characterized in terms of their antibacterial and antifungal activities, as well as their mechanical properties, including tensile strength and elongation at break. Moreover, the chemical structures and surface morphologies of the films were assessed. The results showed that the solution consisting of chitosan, citric acid, caffeine, and EEP exhibited an excellent antiradical effect. The activity of this solution (99.13%) was comparable to that of the standard antioxidant Trolox (92.82%). In addition, the film obtained from this solution showed good antibacterial activity, mainly against Escherichia coli and Enterococcus faecalis. The results also revealed that the films produced with citric acid exhibited higher activity levels against pathogenic bacteria than the films obtained with acetic acid. The antimicrobial effect of the chitosan-based films could be further enhanced by adding bioactive additives such as caffeine and propolis extract. The mechanical tests showed that the solvents and additives used affected the mechanical properties of the films obtained. The film produced from chitosan and acetic acid was characterized by the highest tensile strength value (46.95 MPa) while the chitosan-based film with citric acid showed the lowest value (2.28 MPa). The addition of caffeine and propolis to the film based on chitosan with acetic acid decreased its tensile strength while in the case of the chitosan-based film with citric acid, an increase in strength was observed. The obtained results suggested that chitosan films with natural bioactive substances can be a promising alternative to the traditional materials used in the medical industry, for example, as including biodegradable wound dressings or probiotic encapsulation materials.

Films of Poly(Hydroxybutyrate) (PHB) and Copper with Antibacterial Activity

Poly(3-hydroxybutyrate), PHB, is a hydrophobic biopolymer with good mechanical and barrier properties. However, neat PHB is a semicrystalline polymer with a relative high degree of crystallinity and poor film properties. In this work, this biopolymer was plasticized with glycerol tributyrate and functionalized with copper (II) sulfate, allowing us to obtain biodegradable antimicrobial flexible films. Films with the minimum inhibitory concentration (MIC) of copper (II) sulfate presented a higher roughness than neat PHB films. The presence of plasticizer significantly improved the copper sulfate diffusion process, which was evidenced by a greater inhibition halo for plasticized materials compared to unplasticized ones, at the same salt concentration. Plasticized PHB with 2.5% copper (II) sulfate inhibited both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomona aeruginosa) bacteria, as determined by the bacterial inhibition halo. In addition, neat PHB films and PHB containing copper (II) sulfate did not show in vitro cytotoxicity in the L-929 cell line. Thus, plasticized PHB functionalized with copper (II) sulfate can be used as biodegradable antimicrobial flexible films for different applications.

Characterization of heat-treated chitosan cast films and their antimicrobial activity on the growth of natural flora of pasteurized milk

This research aimed to evaluate the physicochemical and biocidal properties of chitosan films obtained through the solvent casting method using two different molecular weights, and thermally treated for an extended time (3 weeks) at 70 °C under vacuum condition (RH 0 %). The effect of storage time (for 30 and 180 days) under ambient conditions (23 °C and RH 40 %) on the properties of heat-treated cast films and their biocidal effectiveness was also assessed. FTIR-ATR, TGA and XRD of resulting films were analyzed to explore the dependency of antibacterial performance on the alteration in molecular and chemical structure. The results demonstrated that the solubility of treated films at 70 °C was proportionally reduced, resulting from the reduction of protonated amines and an increase in crystallinity. Likewise, increasing storage time led to a significant lowering in the solubilization of cast films. It was found that the solubilized fraction of chitosan cast films is the active fraction with the biocide behavior that can act against bacteria. In addition, the effectiveness of migrated chitosan was examined against the natural flora of pasteurized milk, such as Paenibacillus and Pseudomonas fluorescens. The results showed that cast films obtained from chitosan with lower molecular weight caused a reduction in the total count of viable cells without a significant effect on the properties of milk.

Antimicrobial activity of nanocellulose composite hydrogel isolated from an agricultural waste

Infectious diseases and antimicrobial resistance have become one of the extreme health threats of this century. Overuse of antibiotics leads to pollution. To overcome this threat, the current strategy is to develop a substitute for these antibiotics that are extracted from natural sources. In this study, nanocellulose (NC) was isolated from an agricultural waste (wheat straw) and then oxidized with the help of sodium periodate to obtain dialdehyde nanocellulose (DA-NC). Then, chitosan (Ch) and DA-NC are both crosslinked with each other in different weight ratios, to obtain NC/Ch composite hydrogels. The resulted hydrogel is also characterized to confirm its structure, morphology and composition. The hydrogel was also tested for antimicrobial activities against bacteria, algae as well as fungal species to check its applicability for biomedical applications. The six microbes used for the ananlysis are Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis, Candida albicans, Aspergillus niger and Fusarium solani. The antimicrobial assessment of the hydrogel is evaluated via inhibition zone and optical density analysis. The resulted nanocellulose/chitosan (NC/Ch) hydrogel shows the uniform distribution of nanocellulose in the composite and the synergistic effect of their properties. Hydrogel serves excellent antimicrobial results which makes it a promising candidate for various biomedical applications.

Influence of Chitosan and Grape Seed Extract on Thermal and Mechanical Properties of PLA Blends

Blends based on polylactic acid (PLA), chitosan, and grape seed extract (GE) were prepared by extrusion and injection molding. The effect of chitosan (5% and 15% on PLA basis) and natural extract (1% on PLA basis) incorporated into the PLA host matrix was explored regarding the thermal and mechanical properties. GE showed antioxidant activity, as determined by the DPPH assay method. Chitosan and GE affect the degree of crystallinity up to 30% as the polysaccharide acts as a nucleating agent, while the extract reduces the mobility of PLA chains. The decomposition temperature was mainly affected by adding chitosan, with a reduction of up to 25 °C. The color of the blends was specially modified after the incorporation of both components, obtaining high values of b* and L* after the addition of chitosan, while GE switched to high values of a*. The elongation at break (EB) exhibited that the polysaccharide is mainly responsible for its reduction of around 50%. Slight differences were accessed in tensile strength and Young's modulus, which were not statistically significant. Blends showed increased irregularities in their surface appearance, as observed by SEM analysis, corresponding to the partial miscibility of both polymers.

Development of pullulan-based nanocomposite films reinforced with starch nanocrystals for the preservation of fresh beef

BACKGROUND

Incorporation of polysaccharide-based nanofillers is an effective strategy to fabricate bio-nanocomposite films with preferable mechanical, barrier, and surface hydrophobicity properties compared to pure biopolymer films. The objective of this research is to investigate the influence of starch nanocrystals obtained from native (NSNC) and waxy rice starch (WSNC) on the physical-chemical properties of pullulan-based nanocomposite films and their preservation performance on fresh beef.

RESULTS

Continuous SNCs network structure was observed for pullulan-10% SNCs nanocomposite films, whereas the percolation network of SNCs was destroyed and became no longer continuous with increasing SNCs concentration up to 20% in pullulan films. Among the tested films, pullulan-10% SNCs films showed the highest TS values, lowest WVP and OTR values, due to the formation of percolating SNCs network in pullulan matrix. It is noteworthy that the WVP and OTR values of pullulan-10% WSNC films were significantly lower than that of pullulan-10% NSNC films, probably due to higher hydrophobicity and crystallinity of WSNC compared with NSNC. Beef pieces coated with pullulan-SNCs films had higher L^* and a^* values, lower TVB-N, TBARS, and TVC values during 7 days' storage at 4 °C compared with samples coated with pullulan films.

CONCLUSION

Pullulan-SNCs nanocomposite films, especially pullulan-WSNC films, could be potentially used as a coating material for fresh beef due to their desirable oxygen and water barrier properties. © 2022 Society of Chemical Industry.

Impact of formulation design and lyophilisation on the physicochemical characteristics of finasteride nanosystems

The fundamental purpose of this study was to develop a stable lyophilised finasteride nanosystem (FNS-NS) for topical delivery. The FNS-NS was fabricated using an ultrasonication technique. The impact of two different cryoprotectants on the physicochemical characteristics of FNS-NS before and after lyophilisation was thoroughly investigated. The lyophilised FNS-NS had spherical shape with particle size lied between 188.6 nm ± 4.4 and 298.7 nm ± 4.7, low PDI values (0.26 ± 0.02 to 0.32 ± 0.02) and zeta potential ranging from -38.3 to +53.3 mV. The confocal laser microscopy depicted a comparatively higher cellular internalisation achieved for undecorated FNS-NS with respect to its chitosan-decorated counterpart. The lyophilised FNS-NS was stable for 90 days at proper storage conditions. The FNS-NS with 15% trehalose had appropriate physicochemical attributes that could be a promising carrier for topical delivery to treat androgenic alopecia.

Recovery and Purification of Cutin from Tomato By-Products for Application in Hydrophobic Films

Tomato pomace is a low-cost, renewable resource that has been studied for the extraction of the biopolyester cutin, which is mainly composed of long-chain hydroxy fatty acids. These are excellent building blocks to produce new hydrophobic biopolymers. In this work, the monomers of cutin were extracted and isolated from tomato pomace and utilized to produce cutin-based films. Several strategies for the depolymerization and isolation of monomeric cutin were explored. Strategies differed in the state of the raw material at the beginning of the extraction process, the existence of a tomato peel dewaxing step, the type of solvent used, the type of alkaline hydrolysis, and the isolation method of cutin monomers. These strategies enabled the production of extracts enriched in fatty acids (16-hydroxyhexadecanoic, hexadecanedioic, stearic, and linoleic, among others). Cutin and chitosan-based films were successfully cast from cutin extracts and commercial chitosan. Films were characterized regarding their thickness (0.103 ± 0.004 mm and 0.106 ± 0.005 mm), color, surface morphology, water contact angle (93.37 ± 0.31° and 95.15 ± 0.53°), and water vapor permeability ((3.84 ± 0.39) × 10^-11 mol·m/m²·s·Pa and (4.91 ± 1.33) × 10^-11 mol·m/m²·s·Pa). Cutin and chitosan-based films showed great potential to be used in food packaging and provide an application for tomato processing waste.

Chitosan with Natural Additives as a Potential Food Packaging

Recently, the development of materials based on natural polymers have been observed. This is the result of increasing environmental degradation, as well as increased awareness and consumer expectations. Many industries, especially the packaging industry, face challenges resulting from legal regulations. Chitin is the most common biopolymer right after cellulose and is used to produce chitosan. Due to the properties of chitosan, such as non-toxicity, biocompatibility, as well as antimicrobial properties, chitosan-based materials are used in many industries. Many studies have been conducted to determine the suitability of chitosan materials as food packaging, and their advantages and limitations have been identified. Thanks to the possibility of modifying the chitosan matrix by using natural additives, it is possible to strengthen the antioxidant and antimicrobial activity of chitosan films, which means that, in the near future, chitosan-based materials will be a more environmentally friendly alternative to the plastic packaging used so far. The article presents literature data on the most commonly used natural additives, such as essential oils, plant extracts, or polysaccharides, and their effects on antimicrobial, antioxidant, mechanical, barrier, and optical properties. The application of chitosan as a natural biopolymer in food packaging extends the shelf-life of various food products while simultaneously reducing the use of synthetic plastics, which in turn will have a positive impact on the natural environment. However, further research on chitosan and its combinations with various materials is still needed to extent the application of chitosan in food packaging and bring its application to industrial levels.

Development and characterization of active packaging films based on chitosan, plasticizer, and quercetin for repassed oil storage

Novel chitosan (Ch) films containing choline chloride and citric acid mixture as plasticizer (deep eutectic solvent, DES) and different amounts of quercetin (QUE) as antioxidant additive were prepared. Physicochemical and mechanical characteristics of the developed Ch/DES/QUE films were studied using FTIR, SEM, and AFM techniques. FTIR spectra revealed the possible interactions between all the components. The surface of the films was dense and rough. The addition of quercetin caused an increase in the tensile strength (TS) and Young's modulus, but significantly decreased the elongation at break. The films containing quercetin showed improved antioxidant activity in relation to Ch/DES film. Finally, the oxidation phenomena of rapeseed oils with and without chitosan films were evaluated as amounts of primary and secondary oxidation products and total oxidation index. The addition of Ch/DES films with quercetin to oil samples successfully retarded secondary lipid oxidation processes and improved its antioxidant activity under the accelerated storage condition.