Gelatine Blends Modified with Polysaccharides: A Potential Alternative to Non-Degradable Plastics.

Non-degradable plastics of petrochemical origin are a contemporary problem of society. Due to the large amount of plastic waste, there are problems with their disposal or storage, where the most common types of plastic waste are disposable tableware, bags, packaging, bottles, and containers, and not all of them can be recycled. Due to growing ecological awareness, interest in the topics of biodegradable materials suitable for disposable items has begun to reduce the consumption of non-degradable plastics. An example of such materials are biodegradable biopolymers and their derivatives, which can be used to create the so-called bioplastics and biopolymer blends. In this article, gelatine blends modified with polysaccharides (e.g., agarose or carrageenan) were created and tested in order to obtain a stable biopolymer coating. Various techniques were used to characterize the resulting bioplastics, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), contact angle measurements, and surface energy characterization. The influence of thermal and microbiological degradation on the properties of the blends was also investigated. From the analysis, it can be observed that the addition of agarose increased the hardness of the mixture by 27% compared to the control sample without the addition of polysaccharides. In addition, there was an increase in the surface energy (24%), softening point (15%), and glass transition temperature (14%) compared to the control sample. The addition of starch to the gelatine matrix increased the softening point by 15% and the glass transition temperature by 6%. After aging, both compounds showed an increase in hardness of 26% and a decrease in tensile strength of 60%. This offers an opportunity as application materials in the form of biopolymer coatings, dietary supplements, skin care products, short-term and single-contact decorative elements, food, medical, floriculture, and decorative industries.

Bactericidal Chitosan Derivatives and Their Superabsorbent Blends with ĸ-Carrageenan.

The aim of this work is research dedicated to the search for new bactericidal systems for use in cosmetic formulations, dermocosmetics, or the production of wound dressings. Over the last two decades, chitosan, due to its special biological activity, has become a highly indispensable biopolymer with very wide application possibilities. Reports in the literature on the antibacterial effects of chitosan are very diverse, but our research has shown that they can be successfully improved through chemical modification. Therefore, in this study, results on the synthesis of new chitosan-based Schiff bases, dCsSB-SFD and dCsSB-PCA, are obtained using two aldehydes: sodium 4-formylbenzene-1,3-disulfonate (SFD) and 2-pyridine carboxaldehyde (PCA), respectively. Chitosan derivatives synthesized in this way demonstrate stronger antimicrobial activity. Carrying out the procedure of grafting chitosan with a caproyl chain allowed obtaining compatible blends of chitosan derivatives with κ-carrageenan, which are stable hydrogels with a high swelling coefficient. Furthermore, the covalently bounded poly(ε-caprolactone) (PCL) chain improved the solubility of obtained polymers in organic solvents. In this respect, the Schiff base-containing polymers obtained in this study, with special hydrogel and antimicrobial properties, are very promising materials for potential use as a controlled-release formulation of both hydrophilic and hydrophobic drugs in cosmetic products for skin health.

Porous Functionally Graded Scaffold prepared by a single-step freeze-drying process. A bioinspired approach for wound care.

Nowadays, chronic wounds are the major cause of morbidity worldwide and the healthcare costs related to wound care are a billion-dollar issue; chronic wounds involve a non-healing process that makes necessary the application of advanced wound dressings to promote skin integrity recovery. Functionally Graded Scaffolds (FGSs) are currently driving interest as promising candidates in mimicking the skin tissue environment and, thus, in enhancing a faster and more effective wound healing process. Aim of the present work was to design and develop a porous FGS based on κ-carrageenan (κCG) for the management of chronic skin wounds; a freeze-drying process was optimized to obtain in a single-step a three-layered FGS characterized by a pore size gradient functional to mimic the structure of native skin tissue. In addition to κCG, arginine and whey protein isolate were used as multifunctional agents for FGS preparation; these substances can not only intervene in some stages of wound healing but are able to establish non-covalent interactions with κCG, which were responsible for the production of layers with different pore size, water content capability and mechanical properties. Cell migration, adhesion and proliferation within the FGS structure were evaluated in vitro on fibroblasts and FGS wound healing potential was also studied in vivo on a murine model.

Carrageenan/polyvinyl alcohol composite film reinforced with spermidine carbon dots: An active packaging material with dual-mode antibacterial activity.

Exploring biopolymer-based antibacterial packaging materials is promising to tackle the issues caused by petroleum plastic pollution and microbial contamination. Herein, a novel packaging material with two antibacterial modes, continuous and efficient, is constructed by dispersing positively charged spermidine carbon dots (Spd-CDs) in a carrageenan/polyvinyl alcohol (CP) composite biopolymer. The obtained nanocomposite film (CP/CDs film) not only gradually releases the ultra-small Spd-CDs but also rapidly generates reactive oxygen species to inhibit the reproduction of E. coli and S. aureus. Benefiting from the complementary advantages of carrageenan and polyvinyl alcohol, as well as the addition of Spd-CDs, the CP/CDs films exhibit high transparency, good mechanical performance, water vapor barrier ability, low migration, etc. The CP/CDs film as a packaging material is validated to be effective in preventing microbial contamination of pork samples. Our prepared nanocomposite film with sustainability and efficient antibacterial properties is expected as food active packaging.

Hydrothermal processing of Sarcopeltis skottsbergii and study of the potential of its carrageenan for tissue engineering.

The red macroalga Sarcopeltis skottsbergii was subjected to hydrothermal processing to maximize the solubilization and recovery of carrageenan. Once isolated by ethanol precipitation, the carrageenan was further chemically (oligosaccharides composition), and structurally (TGA/DTG, DSC, HPSEC, FTIR-ATR, 1H NMR, SEM, etc.) characterized, as well as employed as source for the synthesis of hydrogels. The rheological properties of the carrageenan showed promising results as biopolymer for food applications due to the high molecular weight (500 kDa) presenting higher cell viability than 70 %. The evaluation of immune activation using ELISA test reflected a lower inflammatory response for concentrations of 0.025 % of carrageenan. Conversely, the cell viability of the synthesized hydrogels did not surpass 50 %. This work represents a considerable step forward to obtain a biopolymer from natural sources and a thorough study of their chemical, structural and biological properties.

Fabrication and evaluation of Dillenia indica-carrageenan blend hybrid superporous hydrogel reinforced with green synthesized MgO nanoparticles as an effective wound dressing material.

An unexplored hybrid superporous hydrogel (MHSPH) of Dillenia indica fruit mucilage (DIFM) and carrageenan blend embedded with green synthesized magnesium oxide nanoparticles (MNPs) is utilized as an effective wound dressing material with appreciable mechanical strength in murine model. The prepared MNPs and the optimized MHSPH were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT- IR) spectroscopy. Size, zeta potential and morphology of MNPs was assessed using Dynamic light scattering technique (DLS) and field-emission scanning electron microscopy (FESEM) respectively. The MHSPH grades were further optimized using swelling study in phosphate buffer solution at pH 1.2, 7.0, and 8. Both MNPs and the optimized grade of MHSPH were evaluated based on hemolysis assay, and protein denaturation assays indicating them to be safe for biological use. Acute toxicity studies of the optimized MHSPH on Zebra fish model, revealed no observable toxic effect on the gill cells. Wound healing in Swiss albino mice with application of optimized grade of MHSPH took only 11 days for healing when compared to control mice where healing took 14 days, thus concluding that MHSPH as an effective dressing material as well as tissue regrowth scaffold.

Process-structure-property relationships of cellulose nanocrystals derived from Juncus effusus stems on Ò¡-carrageenan-based bio-nanocomposite films.

This study investigates the potential of Juncus plant fibers as a renewable source for producing cellulose nanocrystals (CNs) to reinforce polymers. Cellulose microfibers (CMFs) were extracted with a 0.43 ± 0.2 µm diameter and 69 % crystallinity through alkaline and bleaching treatments, then subjected to sulfuric acid hydrolysis, yielding four CN types (CN10, CN15, CN20 and CN30) with distinct physico-chemical properties and aspect ratios (47, 55, 57, and 60). The study assessed the influence of cellulose nanocrystals (CNs), incorporated at different weight percentages (3 %, 5 %, and 8 %), on thermal, transparency, and mechanical properties in k-carrageenan (CA) biocomposite films. The results indicate significant enhancements in these characteristics, highlighting good compatibility between CNs and CA matrix. Particularly noteworthy is the observed substantial improvement in tensile strength at an 8 wt% loading, with values of 23.43 ± 0.83 MPa for neat CA, 33.53 ± 0.83 MPa for CA-CN10, 36.67 ± 0.71 MPa for CA-CN15, 37.65 ± 0.56 MPa for CA-CN20, and 39.89 ± 0.77 MPa for CA-CN30 composites. Furthermore, the research explores the connection between the duration of hydrolysis and the properties of cellulose nanocrystals (CNs), unveiling their influence on the characteristics of nanocomposite films. Prolonged hydrolysis enhances CN crystallinity (CrI), aspect ratio, and surface charge content, consequently enhancing mechanical features like strength and flexibility in these films. These findings demonstrate the potential of Juncus plant fibers as a natural and eco-friendly resource for producing CNs that effectively reinforce polymers, making them an attractive option for diverse applications in the field.

Marine polysaccharides: Biological activities and applications in drug delivery systems.

The ocean is the common home of a large number of marine organisms, including plants, animals, and microorganisms. Researchers can extract thousands of important bioactive components from the oceans and use them extensively to treat and prevent diseases. In contrast, marine polysaccharide macromolecules such as alginate, carrageenan, Laminarin, fucoidan, chitosan, and hyaluronic acid have excellent physicochemical properties, good biocompatibility, and high bioactivity, which ensures their wide applications and strong therapeutic potentials in drug delivery. Drug delivery systems (DDS) based on marine polysaccharides and modified marine polysaccharide molecules have emerged as an innovative technology for controlling drug distribution on temporal, spatial, and dosage scales. They can detect and respond to external stimuli such as pH, temperature, and electric fields. These properties have led to their wide application in the design of novel drug delivery systems such as hydrogels, polymeric micelles, liposomes, microneedles, microspheres, etc. In addition, marine polysaccharide-based DDS not only have smart response properties but also can combine with the unique biological properties of the marine polysaccharide base to exert synergistic therapeutic effects. The biological activities of marine polysaccharides and the design of marine polysaccharide-based DDS are reviewed. Marine polysaccharide-based responsive DDS are expected to provide new strategies and solutions for disease treatment.

Synergistic adsorption of methylene blue with carrageenan/hydrochar-derived activated carbon hydrogel composites: Insights and optimization strategies.

The study explores the use of hydrochar-derived activated carbon (AC) to improve the adsorption capacity and mechanical properties of carrageenan (CAR) hydrogel beads. Four distinct samples, with carrageenan to activated carbon ratios of 1:0 (CAR), 2:1 (CAC2), 4:1 (CAC4), and 10:1 (CAC10), were prepared. These polymeric beads underwent comprehensive evaluation for their methylene blue (MB) adsorption capacity, gel content (GC), and swelling ratio (SR). Increasing activated carbon content up to 50 % of carrageenan mass significantly enhanced GC and SR by 20.57 % and 429.24 %, respectively. Various analytical techniques were employed to characterize the composites, including FTIR, XRD, Raman Spectroscopy, BET, SEM, and EDS-Mapping. Batch adsorption tests investigated the effects of pH, contact time, dye concentration, and temperature on MB adsorption. Maximum adsorption capacities for CAR, CAC10, CAC4, and CAC2 were 475.48, 558.54, 635.93, and 552.35 mg/g, respectively, under optimal conditions. Kinetic models (Elovich and pseudo-second-order) and isotherm models (Temkin for CAR and Freundlich for CAC10, CAC4, and CAC2) fitted well with the experimental data. Thermodynamic analysis showed spontaneous, exothermic MB adsorption. Primary mechanisms include electrostatic attraction, hydrogen bonding, n-π, and π-π stacking. The study highlights enhanced adsorption capacity of carrageenan hydrogel via carrageenan/activated carbon composites, providing cost-effective wastewater treatment.

Carrageenan-xanthan nanocomposite film with improved bioadhesion and permeation profile in human skin: A cutaneous-friendly platform for ketoprofen local delivery.

Ketoprofen (KET), commonly used for inflammation in clinical settings, leads to systemic adverse effects with prolonged use, mitigated by topical administration. Nanotechnology-based cutaneous forms, like films, may enhance KET efficacy. Therefore, this study aimed to prepare and characterize films containing KET nanoemulsions (F-NK) regarding mechanical properties, chemical composition and interactions, occlusive potential, bioadhesion, drug permeation in human skin, and safety. The films were prepared using a κ-carrageenan and xanthan gum blend (2 % w/w, ratio 3: 1) plasticized with glycerol through the solvent casting method. Non-nanoemulsioned KET films (F-K) were prepared for comparative purposes. F-NK was flexible and hydrophilic, exhibited higher drug content and better uniformity (94.40 ± 3.61 %), maintained the NK droplet size (157 ± 12 nm), and was thinner and lighter than the F-K. This film also showed increased tensile strength and Young's modulus values, enhanced bioadhesion and occlusive potential, and resulted in more of the drug in the human skin layers. Data also suggested that nano-based formulations are homogeneous and more stable than F-KET. Hemolysis and chorioallantoic membrane tests suggested the formulations' safety. Thus, the nano-based film is suitable for cutaneous KET delivery, which may improve the drug's efficacy in managing inflammatory conditions.

Biocatalytic Conversion of Carrageenans for the Production of 3,6-Anhydro-D-galactose.

Marine biomass stands out as a sustainable resource for generating value-added chemicals. In particular, anhydrosugars derived from carrageenans exhibit a variety of biological functions, rendering them highly promising for utilization and cascading in food, cosmetic, and biotechnological applications. However, the limitation of available sulfatases to break down the complex sulfation patterns of carrageenans poses a significant limitation for the sustainable production of valuable bioproducts from red algae. In this study, we screened several carrageenolytic polysaccharide utilization loci for novel sulfatase activities to assist the efficient conversion of a variety of sulfated galactans into the target product 3,6-anhydro-D-galactose. Inspired by the carrageenolytic pathways in marine heterotrophic bacteria, we systematically combined these novel sulfatases with other carrageenolytic enzymes, facilitating the development of the first enzymatic one-pot biotransformation of ι- and κ-carrageenan to 3,6-anhdyro-D-galactose. We further showed the applicability of this enzymatic bioconversion to a broad series of hybrid carrageenans, rendering this process a promising and sustainable approach for the production of value-added biomolecules from red-algal feedstocks.

To gel or not to gel - Tuning the sulfation pattern of carrageenans to expand their field of application.

Carrageenans represent a major cell wall component of red macro algae and, as established gelling and thickening agents, they contribute significantly to a broad variety of commercial applications in the food and cosmetic industry. As a highly sulfated class of linear polysaccharides, their functional properties are strongly related to the sulfation pattern of their carrabiose repeating units. Therefore, the biocatalytic fine-tuning of these polymers by generating tailored sulfation architectures harnessing the hydrolytic activity of sulfatases could be a powerful tool to produce novel polymer structures with tuned properties to expand applications of carrageenans beyond their current use. To contribute to this vision, we sought to identify novel carrageenan sulfatases by studying several putative carrageenolytic clusters in marine heterotrophic bacteria. This approach revealed two novel formylglycine-dependent sulfatases from Cellulophaga algicola DSM 14237 and Cellulophaga baltica DSM 24729 with promiscuous hydrolytic activity towards the sulfated galactose in the industrially established ι- and κ-carrageenan, converting them into α- and ß-carrageenan, respectively, and enabling the production of a variety of novel pure and hybrid carrageenans. The rheological analysis of these enzymatically generated structures revealed significantly altered physicochemical properties that may open the gate to a variety of novel carrageenan-based applications.

Safe and sustainable food packaging: Argemone albiflora mediated green synthesized silver-carrageenan nanocomposite films.

Silver-Carrageenan (Ag/Carr) nanocomposite film for food packing application by the green method using Argemone albiflora leaf extract has been developed in this study. Different plant parts of Argemone albiflora (blue stem prickly poppy) are used all over the world for the treatment of microbial infections, jaundice, skin diseases etc. GC-MS analysis was used to examine the phytochemical found in the Argemone albiflora leaf extract which reduces the metal ions to nanoscale. The biopolymer employed in the synthesis of nanocomposite film was carrageenan, a natural carbohydrate (polysaccharide) extracted from edible red seaweeds. We developed a food packing that is biodegradable, eco-friendly, economical and free from harmful chemicals. These films possess better UV barrier and mechanical and antimicrobial properties with 1 mM AgNO3 solution. The presence of silver nanoparticles in the carrageenan matrix was evident from FESEM. The mechanical properties were analysed by a Universal testing machine (UTM) and different properties like water vapour permeability (WVP), moisture content (MC) and total soluble matter (TSM) important for food packing applications were also analysed. The antimicrobial properties of the synthesized film samples were studied against E. coli and S. aureus pathogenic bacteria. These films were employed for the storage of cottage cheese (dairy product) and strawberries (fruit). This packing increased the shelf life of the packed food effectively. Ag/Carr films are biodegradable within four weeks.

Polyvinyl alcohol/kappa-carrageenan-based package film with simultaneous incorporation of ferric ion and polyphenols from Capsicum annuum leaves for fruit shelf-life extension.

Bio-based food packaging materials have elicited growing interests due to their great degradability, high safety and active biofunctions. In this work, by simultaneously introducing the polyphenolic extracts from Capsicum annuum leaves and ferric ion (Fe3+) into the Polyvinyl alcohol/kappa-carrageenan (PVA/κ-carrageenan)-based film-forming matrix, an active package film was developed, with the purpose to improve the food shelf life. The experimental results indicated that the existence of Fe3+ can not only improve the mechanical properties owing to the multiple dynamic coordinated interactions, but also endow the composite films with excellent fire-retardancy. Moreover, the composite films could display excellent UV resistant performance, water vapor/oxygen gas barrier properties and antioxidant activities with the corporation of polyphenols. In particular, the highest DPPH and ABTS radical scavenging capacities for composite film (PC-PLP7 sample) were evaluated to be 82.5 % and 91.1 %, respectively. Higher polyphenol concentration is favorable to the bio-functions of the materials. Benefitting from these features, this novel kind of films with a dense and steady micro-structure could be further applicated in fruit preservations, where the ripening bananas were ensured with the high storage quality. This integration as a prospective food packaging material provides an economic and eco-friendly approach to excavate the high added-values of biomass.

Preparation, antibacterial activity, and structure-activity relationship of low molecular weight κ-carrageenan.

κ-Carrageenan (KC) is a polysaccharide widely used in food industry. It has been widely studied for its excellent physicochemical and beneficial properties. However, the high molecular weight and high viscosity of KC make it difficult to be absorbed and to exert its' biological activities, thus limit its extensive industrial application. In order to solve this problem, five low molecular weight κ-carrageenans (DCPs) were prepared by the degradation of KC using hydrogen peroxide (H2O2) and ascorbic acid (AH2). The chemical compositions and structure characteristics of the DCPs were then determined. The results showed that H2O2 and AH2 could effectively degrade KC to DCPs, and DCPs remained the basic skeletal structure of KC. DCPs showed good antibacterial activities against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis. The Minimum Inhibitory Concentration (MIC) of DCPs with the highest antibacterial effects were 5.25, 4.5, 5.25, and 4.5 mg/mL, respectively. This is due to the underlying mechanism of DCPs that bind to the bacterial membrane proteins and change the membrane permeability, thus exerting antibacterial activity. In addition, Spearman's rank correlation and Ridge regression analysis revealed that the molecular weight and the contents of 3,6-anhydro-D-galactose, aldehyde group, carboxyl, and sulfate were the main structural characteristics affecting the antibacterial activity. Our findings reveal that the H2O2-AH2 degradation treatment could significantly improve the antibacterial activity of KC and provide insights into the quantitative structure-activity relationships of the antibacterial activity of DCPs.

Coconut husk-lignin derived carbon dots incorporated carrageenan based functional film for intelligent food packaging.

Carbon dots (CDs) derived from sustainable natural feed-stocks like lignin have gained wide acceptance by virtue of their renewability and promising potential in intelligent sensing applications. The precursor lignin is isolated from agro-biomass waste, coconut husk through sodium hydroxide based extraction process. CDs are synthesised from amine functionalized lignin through solvothermal process and integrated into carrageenan biopolymer matrix (1, 2 and 3 wt%). The composite film with 2 wt% CDs (CARR2CD) showed optimum fluorescent emission intensity, excellent pH dependent fluorescent color change in the food pH range, reasonable tensile strength (46.50 ± 1.32 MPa) and 27 % increase in elongation at break. CDs imparted UV-light blocking properties (70 % UV-light) and enhanced hydrophobicity of the carrageenan matrix. CARR2CD film showed 84 % visible light transparency, 79 % reduction in oxygen transmittance rate (OTR), 81 % reduction in CO2 gas permeability and excellent antioxidant and antibacterial properties (against E. coli and S. aureus). As a practical application, the developed responsive packaging material is used to track pH change associated with milk spoilage via noticeable color change in fluorescent emission of the composite film. Thus, the developed responsive composite film paves a way for use as green and sustainable transparent intelligent food packaging material.

Electrospun fiber mats based on chitosan-carrageenan containing Malva sylvestris anthocyanins: Physic-mechanical, thermal, and barrier properties along with application as intelligent food packaging materials.

This study aimed to encapsulate Malva sylvestris extract (MSE) into chitosan-carrageenan (CH-KC) fibers using the electrospinning technique and monitor the freshness of silver carp fillets during the refrigerated storage conditions for 8 days. The CH-KC + MSE 4 % fiber mats were red at pH values lower than 3, purple at pH 4-6, dark blue at pH 7, green at pH 8-10, and brown at pH 11-12. The tensile strength, elongation at break, water vapor permeability, oxygen transmission rate, moisture content, and water solubility of fabricated fiber mats were 7.71-11.02 MPa, 13.12 %-30.00 %, 7.35-20.01 × 10-4 g mm/m2 h Pa, 3.81-8.23 cm3/m2 h, 15.74 %-27.34 %, and 3.90 %-7.56 %, respectively. Regarding the potential application of a fabricated indicator for freshness monitoring of silver carp fillets, total viable count, psychrotrophic bacterial count, pH, and total volatile basic nitrogen reached 8.91 log CFU/g, 8.03 log CFU/g, 8.10, and 40.18 mg N/100 g at the end of the study, respectively. Meanwhile, the CH-KC + MSE 4 % fiber mat color changed from white to green. These findings suggest that CH-KC + MSE 4 % fiber mats can be further utilized in the food industry to control the freshness of refrigerated silver carp fillets.

Characterization of sodium alginate-carrageenan films prepared by adding peanut shell flavonoids as an antioxidant: Application in chilled pork preservation.

This study prepared and characterized sodium alginate and carrageenan (SAC) composite films incorporated with peanut shell flavonoids (PSFs). PSFs compound identification research was implemented. The physicochemical features of PSFs-SAC composite films and their ability to preserve chilled pork in a 4 °C refrigerator were determined. PSFs consist of luteolin, eriodictyol, 5,7-dihydroxychromone, and 8 other components. They significantly improved the mechanical properties, barrier properties, thermal stability, and antioxidant properties of SAC composite films (P < 0.05). PSFs were also responsible for increasing the density of the film structure between the sodium alginate and carrageenan molecules. During storage, compared with the control group, the prepared PSFs-SAC composite films did not allow the total viable count (TVC), pH and total volatile base nitrogen (TVB-N) of the chilled pork to increase rapidly. Further, they were able to inhibit lipid oxidation more effectively (P < 0.05). For these reasons, the use of the PSFs-SAC composite films prolonged shelf life of chilled pork from 6 days to the 12 days. Therefore, PSFs-SAC composite films are expected to be used as bioactive substances in food preservation.

Carrageenan films as promising mucoadhesive ocular drug delivery systems.

Polymer mucoadhesive films being developed for use in ophthalmology represent a new tool for drug delivery and are considered an alternative to traditional dosage forms. Due to their mucoadhesive properties, carrageenans (CRGs) are widely used in various forms for drug delivery. In this study, films based on CRGs of various structural types (κ/ß, κ, x, and λ) for use in ophthalmology were studied. The films were loaded with the active substance echinochrome (ECH), a sea urchin pigment used in ophthalmology. Spectral data showed that ECH remained stable after its incorporation into the CRG films and did not oxidize for at least six months. Hydrophilic CRG films with a thickness of 10-12 µm were characterized in terms of their swelling and mucoadhesive properties. The rheological properties of solutions formed after film dissolution in artificial tears were also assessed. κ- and κ/ß-CRG films with ECH exhibited pseudoplastic behavior after rehydrating films with an artificial tear solution. The CRG-loaded films had different swelling characteristics depending on the structure of the CRG used. The films based on highly sulfated CRGs dissolved in artificial tears, while the films of low-sulfated κ/ß-CRG exhibited limited swelling. All studied ECH-loaded films exhibited mucoadhesive properties, which were evaluated by a texture analyzer using mucous tissue of the small intestine of the pig as a model. There was a slight prolongation of ECH release from CRG films in artificial tears. The effect of CRG/ECH on the epithelial cell lines of the outer shell of the human eye was investigated. At low concentrations, ECH in the composition of the CRG/ECH complex had no cytotoxic effect on corneal epithelial and conjunctival human cells. The use of ECH-containing films can prevent the drug from being immediately washed away by tears and help to retain it by increasing viscosity and having mucoadhesive properties.

Gelation of crocodile myofibrillar protein - κ-carrageenan mixtures in two low-NaCl solution.

Crocodile meat is a novel reptile meat source, but its processing method is rare. This study investigated the effect of κ-carrageenan addition and partial substitution of NaCl on the gel properties of crocodile myofibrillar protein (CMP). Result showed that CMP formed gel when temperature above 60 ℃. The water-holding capacity, gel strength, denaturation degree, sulfhydryl content covalent bond and hydrophobic bond of gel in KCl solution were significantly higher than those in CaCl2 solution (P < 0.05). K+ induced CMP to form a tight network structure with uniform small pores though covalent and hydrophobic bonds, but the gel properties were reduced by κ-carrageenan. In CaCl2 solution, κ-carrageenan improved the gel structure by filling the protein network through hydrogen bonding. Therefore, it can be concluded that KCl is better than CaCl2 in the manufacturing of low-sodium crocodile foods. Moreover, κ-carrageenan was only beneficial to gel quality in CaCl2 solution.