Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.

The extraction of buckwheat protein and its interaction with kappa-carrageenan: Textural, rheological, microstructural, and chemical properties

Current plant-based foods use plant proteins as a key structuring and texturing ingredient. The use of water for extraction can replace conventional protein extraction methods. Water extraction of protein is environmentally friendly and could prevent the loss of protein functionality due to extreme pH changes. This study demonstrates an aqueous extraction method, coupled with ultrasound as pre-treatment, to obtain buckwheat protein (BWPE) and assess its gelling property and composited gel with kappa-carrageenan (k-carr). Textural and rheological analyses showed that the hardness and storage modulus of the composited gel containing 1 % w/w BWPE and 1 % w/w k-carr was 4.2-fold and 100-fold, respectively, higher than k-carr gel at 1 % w/w. Light microscopy showed a mixed bi-continuous gel system, with k-carr reinforcing the protein gel network. Besides volume exclusion effects, chemical bond and FTIR analyses revealed that adding k-carr to BWPE altered the protein's secondary structure and mediated protein denaturation during heating. This results in greater β-sheet content, which creates a more organised gel structure. These results demonstrated that ultrasound-assisted water-extracted BWPE, together with varying concentrations of k-carr, can be used to develop composited gels of tailorable textural and rheological properties to suit different food applications.

Comprehensive investigation into the effects of yeast dietary fiber and temperature on konjac glucomannan/kappa-carrageenan for the development of fat analogs

In this study, yeast dietary fiber (YDF) was incorporated into konjac glucomannan/kappa-carrageenan (KGM/κ-KC) for the development of fat analogs, and the impact of YDF on the gelation properties and behavior of KGM/κ-KC composite gels was assessed. YDF improved the composite gel whiteness value, and affected the mechanical properties of the composite gel, especially enhancing its hardness, and decreasing its chewiness, elasticity, and gel strength, making it more similar to porcine back fat. When the yeast dietary fiber content was 0.033 g/mL and the heating temperature was 80 °C (T80-2), the textural properties of the composite gel were closest to porcine back fat. The frequency sweep results suggested that YDF incorporation led to enhancement of the intermolecular interaction and intermixing and interaction among more easily at higher processing temperatures (80 °C and 90 °C). By scanning electron microscopy, the fatty surface of porcine back fat was flat and covered with a large amount of oil, while KGM/κ-KC/YDF composite gels developed a dense, stacked network structure. YDF caused more fragmented, folded, and uneven structures to emerge. Overall, YDF could influence the gel behavior of KGM/κ-KC composite gels, and change their colors and mechanical properties. This work could serve as a guide for preparing fat analogs with KGM/κ-KC composite gels.

Polyphenol modified CuO nanorods capped by kappa-carrageenan for controlled paclitaxel release in furnishing targeted chemotherapy in breast carcinoma cells

The present work deals with the construction of a nanoscale system that can deliver chemotherapeutic agents to breast cancer cells in a controlled trend. The framework consists of gallic acid functionalized copper oxide nanoparticles (Ga@CuO) loaded with paclitaxel (PTX). To control the release of PTX, Ga@CuO NPs were coated with a red seaweed, Kappa carrageenan (K-carr) layer, and embellished with folic acid (FA) to enhance the targeted chemotherapy approach. Encapsulation efficiency and loading capacity of PTX loaded Ga@CuO@K-carr/FA NPs were estimated to be 84.58 ± 1.85 % and 13.2 ± 0.22 %, respectively. Moreover, the presence of strong cytotoxicity with an IC50 value of 12 ± 2.0 μg/mL and a high percentage of apoptotic cells (40.25 %) within the treated MCF-7 cells provided further evidence of the effective release of PTX from the loaded Ga@CuO@K-carr/FA. Consequently, it was discovered that the altered metabolic activity of cancer cells and the inhibition of cell proliferation are distinct features of apoptotic cell death induced by reactive oxygen species (ROS). Also, it was noted that treatment of MCF-7 cells with Ga@CuO-PTX@K-carr/FA caused a reduction in mitochondrial membrane potential that resulted in cellular apoptosis. Taken together, this study sheds light on the rational design of Ga@CuO-PTX@K-carr/FA, which offers a suitable candidate to transport drugs at an intracellular level for targeted chemotherapy.

Soy protein isolate/kappa-carrageenan/cellulose nanofibrils composite film incorporated with zenian essential oil-loaded MOFs for food packaging

Edible films applied in food packaging must possess excellent inhibitory and mechanical properties. Protein-based films exhibit a high capacity for film formation and offer good gas barrier properties. However, they have weak mechanical and water barrier characteristics. The objective of this research was to develop active composite films based on reinforced soy protein isolate (SPI)/Kappa-carrageenan (K) with varying concentrations of bacterial cellulose nanofibrils (BCN). Increasing the BCN concentration improved the morphological, structural, mechanical, water vapor barrier, and moisture content properties. In comparison to the pure SPI film (S), the film with a high BCN concentration demonstrated a significant decrease in WS (22.98 ± 0.78 %), MC (21.72 ± 0.68 %), WVP (1.22 ± 0.14 g mm-1 S-1 Pa-1 10-10), and EAB (57.77 ± 5.25 %) properties. It should be emphasized that there was no significant alteration in the physicomechanical properties of the optimal film (SKB0.75) containing Zenian-loaded metal-organic frameworks (ZM). However, it substantially enhanced the thermal stability of this film, which can be attributed to the strong interfacial interactions between polymer chains and ZM. Furthermore, the ZM films inhibited the growth of pathogenic bacteria and increased the DPPH antioxidant activity. Thus, SKB0.75-ZM2 films can be utilized as practical components in food packaging.

Improving water treatment using a novel antibacterial kappa-carrageenan-coated magnetite decorated with silver nanoparticles

In this study, we aimed to fabricate an enhanced antibacterial agent to act against pathogenic bacteria in aqueous environments. To achieve this, silver nanoparticles (AgNPs) were inlaid on a kappa-carrageenan (KC) base and coated on Fe3O4 magnetic cores (Fe3O4@KC@Ag). Superparamagnetic Fe3O4 nanoparticles were designed at the center of the composite nanostructure, allowing magnetic recovery from aqueous media in the presence of a magnet. The synthesized nanoconjugate was characterized in each step using XRD, FT-IR, EDX, FE-SEM, TEM, DLS, VSM, and disk-diffusion antibacterial method. Results show that the nanocomposite system is formed, while the magnetic properties remain practically stable. The agglomeration of the AgNPs was decreased by the trap-like function of KC coating, which resulted in an improved antibacterial activity for the Fe3O4@KC@Ag formulation. These findings suggest that Fe3O4@KC@Ag nanocomposites could be promising agents for combating bacterial infections in aqueous environments.

Optimization of kappa-carrageenan cationization using experimental design for model-drug release and investigation of biological properties

Cationization is a promising chemical modification technique that improves properties by attaching permanent positive charges to the backbone of biopolymers. Carrageenan is a widely available and non-toxic polysaccharide, commonly used in food industry but with low solubility in cold water. We performed a central composite design experiment to check the parameters that most influence the degree of cationic substitution and the film solubility. Hydrophilic quaternary ammonium groups on the carrageenan backbone enhance interaction in drug delivery systems and create active surfaces. Statistical analysis indicated that within the studied range, only the molar ratio between the cationizing reagent and the repeating disaccharide unit of carrageenan had a significant effect. Optimized parameters using 0.086 g of sodium hydroxide and glycidyltrimethylammonium/disaccharide repeating unit of 6.83 achieved 65.47 % degree of substitution and 4.03 % solubility. Characterizations confirmed the effective incorporation of cationic groups into the commercial structure of carrageenan and thermal stability improvement of the derivatives.

Kappa-carrageenan for benign preparation of CdSeNPs enhancing the electrochemical measurement of AC symmetric supercapacitor device based on neutral aqueous electrolyte

This study presents the development of an electrochemical supercapacitor with a cadmium selenide nanoparticles (CdSeNPs) electrode utilizing a straightforward and economical method based on kappa-carrageenan (κ-CGN). The structural, morphological, and optical characteristics of CdSeNPs were assessed. Activated carbon (AC) and green-prepared CdSeNPs were easily mixed to achieve excellent electrochemical properties. The nanoelectrode (AC@CdSe) was tested in an aqueous electrolyte of sodium sulfate (Na₂SO₄) with a concentration of 1 Molar. Specific capacitance (Csp) for the AC electrode and the AC@CdSe electrode at 1 A g^-1 was calculated to be 103 and 480 F g^-1, respectively. Besides, the symmetric supercapacitor AC@CdSe/AC@CdSe device has a high specific energy of 52 Wh kg^-1 and a maximum specific power of 2880 W kg^-1, with a specific capacitance of 115.5 F g^-1. With a coulombic efficiency of between 82 % and 100 %, the device continues to maintain excellent capacitance after 10.000 cycles.

Crosslinking konjac-glucomannan with kappa-carrageenan nanogels: A step toward the design of sacrificial materials

The challenge in designing sacrificial materials is to obtain materials that are both mechanically stable and easily dissolvable. This research aimed to meet this challenge by fabricating a new polymer-nanogel hydrogel based solely on hydrogen bonds between two polysaccharides. The study focused on hydrogels formed from soluble konjac-glucomannan and nanogels synthesized from kappa-carrageenan. This novel hydrogel exhibited self-healing and shear-thinning properties due to its weak physical interactions. The hydrogel dissolved simultaneously with its swelling. Changes in temperature or nanogel concentration, or the addition of potassium ions, altered the swelling and dissolution rates. Furthermore, adding KCl to the as-prepared hydrogel increased its compression and tensile moduli and its strength. The new formulation opens numerous possibilities as a potential sacrificial material for different applications since it is mechanically stable yet rapidly dissolves in physiological conditions without applying high temperatures or using chelating agents.

Preparation of octenyl succinylated kappa-carrageenan; reaction optimization, characterization, and application in low-fat vegan mayonnaise

Kappa-carrageenan (KC) esterification reaction with octenyl succinic anhydride was optimized using response surface methodology, leading to the production of a food-based emulsifier. Modified kappa-carrageenan (KC-OSA) with different degrees of substitution (DS) (0.023 and 0.045) was produced, and their functional and structural properties were investigated. The results from FTIR and ¹HNMR verified the successful occurrence of modification. The KC-OSA emulsions with both DS values were utterly stable after 30 days of storage, while KC failed to form emulsions. The viscosity, foaming properties, surface net charge, and gel opacity increased after modification and with an increase in its extent, while emulsion particle size and polydispersity index, gel melting temperature, and gel hardness decreased. Afterward, the KC-OSA (DS = 0.023) potential use was investigated as fat and egg yolk substitute in mayonnaise, which resulted in vegan mayonnaise samples with no phase separation after a month of storage at room temperature. Particle size measurements implied that the particle size of the mayonnaise sample was decreased with an increase in KC-OSA concentration. The results from the sensory evaluation showed that KC-OSA could be successfully implemented in low-fat vegan mayonnaise. The results from this study draw a bright horizon for the use of KC-OSA in the food industry.

Ultra-stable high internal phase emulsions stabilized by protein-anionic polysaccharide Maillard conjugates

This paper reports the production of O/W high internal phase emulsions (HIPEs) using protein-anionic polysaccharide Maillard conjugates. First, Maillard conjugates were prepared from soy protein isolate (SPI) or sodium caseinate (SC) proteins and Alyssum homolocarpum seed gum (AHSG) or kappa-carrageenan (kC) polysaccharides. The conjugation process was confirmed and monitored by UV spectrophotometry, Fourier transform infrared, circular dichroism, fluorescence spectroscopies, and differential scanning calorimetry. Under the optimized reaction conditions, SC-AHSG conjugates exhibited the highest glycation degree and emulsifying properties. Next, HIPEs were made using the optimized conjugates, and their microstructure, droplet size, and physical stability were evaluated. The emulsion stabilized by SC-AHSG conjugate had the lowest mean droplet size (363.07 ± 34.56 nm), orderly-packed oil droplets with monomodal distribution, the highest zeta potential (-27.70 ± 0.70 mV), high storage stability (no creaming or oil-off) and was ultra-stable against environmental stresses. Results of this research are helpful for development of emulsion-based foods with novel functionality.

Alginate/κ-carrageenan oral microcapsules loaded with Agaricus bisporus polysaccharides MH751906 for natural killer cells mediated colon cancer immunotherapy

The current study explores the effect of the extracted novel Mushroom polysaccharides and its formulation onto Alginate (Alg.)/kappa carrageenan microcapsules to exert immunotherapeutic effect upon activating gut resident natural killer cells (NK) against colon cancer. The extracted polysaccharides of Agaricus bisporus MH751906 was microcapsulated in Alg/κ-carrageenan microcapsules as an oral delivery system for colon cancer. The microcapsule is characterized by SEM, FTIR, Raman and TGA; and showed a superior acidic stability, controlled release, and thermal stability at high temperature with higher hydrogel swelling rate in colon-mimicking pH. Upon activation of human NK cells with microcapsules (^ANK cells), a significant increase in CD16⁺CD56⁺ NK cell populations were recorded. These activated NK cells showed 74.09% cytotoxic effects against human colon cancer Caco-2 cells where majority of cancer cell populations arrested at G0/G1 phase leading to apoptosis. The apoptotic molecular mechanism induced by ^ANK cells on Caco-2 treated cells is through down regulations of both BCL2 and TGF surviving genes and up regulation in IkappaB-α gene expression. Therefore, this novel polysaccharides-alginate/κ-carrageenan microcapsules can be used as an oral targeted delivery system for colon cancer immunotherapy.

Semi-synthesis of hybrid ulvan-kappa-carrabiose polysaccharides and evaluation of their cytotoxic and anticoagulant effects

In this study we described the synthesis of a hybrid polysaccharide harboring moieties of ulvan and kappa-carrabiose. Alkylamines (1,3-diaminopropane and 1,6-diaminohexane) were selectively inserted into β-D-GlcAp and α-L-IdoAp units in the ulvan structure via an amide bond formation producing ulvan-amide derivatives F-DAP (N% = 1.77; M_w = 208 kg mol^-1) and F-DAH (N% = 1.77; M_w = 202 kg mol^-1), which were reacted with kappa-carrabiose via reductive amination to produce hybrid ulvan-kappa-carrabiose polysaccharides F-DAP-Kb (N% = 1.56; M_w = 206 kg mol^-1) and F-DAH-Kb (N% = 1.16; M_w = 200 kg mol^-1). All the ulvan derivatives were characterized by ¹H and ¹³C NMR spectroscopy and did not show cytotoxicity against human dermal fibroblasts (HDFa) at the concentrations of 25, 100, and 500 μg mL^-1, neither anticoagulant properties at the range of 10-150 μg mL^-1. Therefore, the ulvan-amide derivatives and the hybrid ulvan-kappa-carrabiose polysaccharides showed good biocompatibility in vitro, presenting as worthy candidates for tailoring scaffolds for biomedical applications.

Effect of konjac glucomannan/carrageenan-based edible emulsion coatings with camellia oil on quality and shelf-life of chicken meat

The quality and safety of chicken meat are prone to deteriorate due to bacteria reproduction and oxidation reaction. In this study, the antimicrobial and antioxidant effects of KGM-KC coatings incorporated camellia oil were evaluated to extend the shelf-life of chicken meat. The result showed that the KGM/KC-CO coating significantly (P < 0.05) decreased weight loss, pH, thiobarbituric acid reactive substance (TBARS), total volatile nitrogen (TVN) and microbial counts when compared to uncoated samples. The obtained results revealed that KGM/KC-based coating incorporated with CO significantly extended the shelf-life of chicken meat by restraining the oxidation of lipid and protein, and retarding the microbial growth. The sensory evaluation showed that the addition of CO did not affect the odor of chicken meat, maintained the overall acceptability of coated samples. The shelf-life of chicken meat was extended up to 10 days using KGM/KC-based coating containing 3.5% CO at refrigeration (4 °C) compared to control samples. These results indicated CO could be used as an active agent to be dispersed in KGM/KC matrix by emulsification method, and the prepared emulsion coating had positive effects on extending the shelf-life of chicken meat.

Semi-synthesis of N-alkyl-kappa-carrageenan derivatives and evaluation of their antibacterial activity

In this article, we describe the semi-synthesis of N-alkyl-kappa-carrageenan derivatives and their antibacterial activity against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 8739), and Pseudomonas aeruginosa (ATCC 9027). Kappa-carrageenan was submitted to partial acid hydrolysis promoting the selective cleavage of α-glycosidic bonds involving 3,6-anhydro-α-D-Galp units, giving rise to reducing low-molecular weight polysaccharide fragments, which were reacted with alkylamines of varying chain lengths by reductive amination. The carrageenan derivatives were characterized by HPSEC-MALLS-RID and 1D and 2D ¹H and ¹³C NMR spectroscopy. The antibacterial activity of N-alkyl-kappa-carrageenan derivatives was compared with N-alkyl-(1-deoxylactitol-1-yl)-amines using a microdilution test, which indicated that inhibitory activity was dependent on the degree of substitution by hydrophobic groups at the polysaccharide structure. Comparing the effect of different N-alkyl chains, those with longer chains showed higher activity.

Preparation of kapa carrageenan-based acidic heterogeneous catalyst for conversion of sugars to high-value added materials

A novel composite based on kappa-Carrageenan (κC) was prepared using N,N-methylene bisacrylamide (MBA) as the crosslinking agent. 5-Hydroxymethylfurfural (5-HMF) was produced by catalytic dehydration of fructose and glucose with MBA grafted κC (κC-g-MBA) as the solid acid catalyst due to sulfonic acid groups in biopolymer skeletons. Various reaction parameters such as optimization of the quantity of the catalyst, temperature, reaction time, and solvent were performed. It was established that for fructose dehydration, the best reaction conditions were the 160 °C as the optimized reaction temperature and 1 h reaction time, respectively. Under these conditions, the HMF yield and fructose conversion were 94.2% and 95.5%, respectively. Furthermore, 160 °C and 2 h were the best reaction temperature and reaction time for glucose dehydration, respectively. Under similar conditions, the HMF yield and glucose conversion are 47% and 93%, respectively. The catalyst was readily prepared from inexpensive materials with considerable reusability and reactivity.

Influence of two functional dextrins on the gel properties of kappa-carrageenan

The physicochemical properties of κ-carrageenan (KC) can be improved by incorporation with small-molecule cosolvents. The texture and rheological properties, micromorphology, and crystallinity of KC incorporating indigestible dextrin (IDD) and beta-limit dextrin (BLD) were investigated. The rheological properties and sol-gel transition temperatures of the gels were slightly improved and the hardness of KC gels was significantly increased after the two dextrins were mixed in. Fourier transform infrared spectroscopy results indicated hydrogen-bonding interactions were strengthened in the presence of the dextrins. Confocal laser scanning microscope images revealed that a more homogenous structure was formed of the KC gel after the addition of dextrins. Moreover, X-ray diffraction patterns indicated the crystallinity of KC gel decreased upon dextrin addition. At the same dextrin content, IDD exerted a greater influence than BLD. IDD contents exceeding 3% (w/w) led to undesirable effects, whereas up to 5% (w/w) of BLD could be added. The two dextrins affected the rearrangement of the KC random coils in the sol state, and facilitated aggregation of the KC chains during cooling to form gel network structures after gelation. Therefore, the appropriate addition of these two dextrins can improve the texture and stability of KC gels and expand their application in functional foods.

Biodegradable κ-carrageenan/nanoclay nanocomposite films containing Rosmarinus officinalis L. extract for improved strength and antibacterial performance

In this study, biodegradable κ-carrageenan films containing 3% nanoclay and different amounts of rosemary extract (1, 2 and 3% v/v) were fabricated and their physical, thermal, and mechanical properties, as well as antimicrobial activity were examined. The film thickness did not change significantly by the addition of rosemary extract. UV light transmission value in the control film was 20.46%, while the value for the film with 3% v/v rosmary extract reduced to 0.13%. Elongation at break (EB%) and tensile strength (TS) of the carrageenan film without the extract were 19.07% and 15.96MPa, respectively, while after adding 3% v/v of rosemary extract, the EB and TS were increased to 27.17% and 30.77MPa, respectively. Incorporation of rosemary extract greatly reduced water vapor permeability (WVP) (5.27×10^-10g/m·s·Pa in control film vs 2.14×10^-10g/m·s·Pa in the film containing 3% v/v rosemary extract). More importantly, the carrageenan film with 3% extract displayed >99% inhibition against B. cereus, E. coli, P. aeruginosa, and S. aureus compared with the control film. The present study showed that rosemary extract is an excellent additive to enhance the mechanical strength and antibacterial activity of carrageenan films and can be used for active packing in food packing industry.

Nanoengineered injectable hydrogels for wound healing application

We report injectable nanoengineered hemostats for enhanced wound healing and tissue regeneration. The nanoengineered system consists of the natural polysaccharide, κ-carrageenan (κCA), loaded with synthetic two-dimensional (2D) nanosilicates. Nanoengineered hydrogels showed shear-thinning characteristics and can be injected for minimally invasive approaches. The injectable gels can be physically crosslinked in presence of monovalent ions to form mechanically strong hydrogels. By controlling the ratio between κCA and nanosilicates, compressive stiffness of crosslinked hydrogels can be modulated between 20 and 200 kPa. Despite high mechanical stiffness, nanocomposite hydrogels are highly porous with an interconnected network. The addition of nanosilicates to κCA increases protein adsorption on nanocomposite hydrogels that results in enhance cell adhesion and spreading, increase platelets binding and reduce blood clotting time. Moreover, due to presence of nanosilicates, a range of therapeutic biomacromolecules can be deliver in a sustain manner. The addition of nanosilicates significantly suppresses the release of entrap vascular endothelial growth factor (VEGF) and facilitate in vitro tissue regeneration and wound healing. Thus, this multifunctional nanocomposite hydrogel can be used as an injectable hemostat and an efficient vehicle for therapeutic delivery to facilitate tissue regeneration.

STATEMENT OF SIGNIFICANCE

Hemorrhage is a leading cause of death in battlefield wounds, anastomosis hemorrhage and percutaneous intervention. Thus, there is a need for the development of novel bioactive materials to reduce the likelihood of hemorrhagic shock stemming from internal wounds. Here, we introduce an injectable hemostat from kappa-carrageenan and two-dimensional (2D) nanosilicates. Nanosilicates mechanically reinforce the hydrogels, provide enhanced physiological stability and accelerate the clotting time by two-fold. The sustained release of entrapped therapeutics due to presence of nanosilicates promotes enhanced wound healing. The multifunctional nanocomposite hydrogels could be used as an injectable hemostat for penetrating injury and percutaneous intervention during surgery.

Supramolecular structure of methyl cellulose and lambda- and kappa-carrageenan in water: SAXS study using the string-of-beads model

A detailed data analysis utilizing the string-of-beads model was performed on experimental small-angle X-ray scattering (SAXS) curves in a targeted structural study of three, very important, industrial polysaccharides. The results demonstrate the quality of performance for this model on three polymers with quite different thermal structural behavior. Furthermore, they show the advantages of the model used by way of excellent fits in the ranges where the classic approach to the small-angle scattering data interpretation fails and an additional 3D visualization of the model's molecular conformations and anticipated polysaccharide supramolecular structure. The importance of this study is twofold: firstly, the methodology used and, secondly, the structural details of important biopolymers that are widely applicable in practice.

In vitro and in vivo ocular safety and eye surface permanence determination by direct and Magnetic Resonance Imaging of ion-sensitive hydrogels based on gellan gum and kappa-carrageenan

Gellan gum, kappa-carrageenan and alginates are natural polysaccharides able to interact with different cations that can be used to elaborate ion-activated in situ gelling systems for different uses. The interaction between fluid solutions of these polysaccharides and cations presents into the tear made these biopolymers very interesting to elaborate ophthalmic drug delivery systems. The main purpose of this study is to evaluate the ability of mixtures of these polymers to obtain ion-activated ophthalmic in situ gelling systems with optimal properties for ocular use. To achieve this purpose different proportion of the biopolymers were analyzed using a mixture experimental design evaluating their transparency, mechanical properties and bioadhesion in the absence and presence of simulated tear fluid. Tear induces a rapid sol-to-gel phase transition in the mixtures forming a consistent hydrogel. The solution composed by 80% of gellan gum and 20% kappa-carrageenan showed the best mechanical and mucoadhesive properties. This mixture was evaluated for rheological behavior, microstructure, cytotoxicity, acute corneal irritancy, ex-vivo and in vivo ocular toxicity and in vivo corneal contact time using Magnetic Resonance Images (MRI) techniques. Result indicates that the system is safe at ophthalmic level and produces an extensive ocular permanence higher than 6h.

Synthesis and application of polypyrrole/carrageenan nano-bio composite as a cathode catalyst in microbial fuel cells

A novel nano-bio composite polypyrrole (PPy)/kappa-carrageenan(KC) was fabricated and characterized for application as a cathode catalyst in a microbial fuel cell (MFC). High resolution SEM and TEM verified the bud-like shape and uniform distribution of the PPy in the KC matrix. X-ray diffraction (XRD) has approved the amorphous structure of the PPy/KC as well. The PPy/KC nano-bio composites were then studied as an electrode material, due to their oxygen reduction reaction (ORR) ability as the cathode catalyst in the MFC and the results were compared with platinum (Pt) as the most common cathode catalyst. The produced power density of the PPy/KC was 72.1 mW/m(2) while it was 46.8 mW/m(2) and 28.8 mW/m(2) for KC and PPy individually. The efficiency of the PPy/KC electrode system is slightly lower than a Pt electrode (79.9 mW/m(2)) but due to the high cost of Pt electrodes, the PPy/KC electrode system has potential to be an alternative electrode system for MFCs.