Synthesis, characterization and potential application of hydrophobically modified carrageenan derivatives as pharmaceutical excipients

Chemically modified seaweed polysaccharides: Improved functional and biological properties and prospective in food applications

Seaweed polysaccharides are natural biomacromolecules with unique physicochemical properties (e.g., good gelling, emulsifying, and film-forming properties) and diverse biological activities (e.g., anticoagulant, antioxidant, immunoregulatory, and antitumor effects). Furthermore, they are nontoxic, biocompatible and biodegradable, and abundant in resources. Therefore, they have been widely utilized in food, cosmetics, and pharmaceutical industries. However, their properties and bioactivities sometimes are not satisfactory for some purposes. Modification of polysaccharides can impart the amphiphilicity and new functions to the biopolymers and change the structure and conformation, thus effectively improving their functional properties and biological activities so as to meet the requirement for targeted applications. This review outlined the modification methods of representative red algae polysaccharides (carrageenan and agar), brown algae polysaccharides (fucoidan, alginate, and laminaran), and green algae polysaccharides (ulvan) that have potential food applications, including etherification, esterification, degradation, sulfation, phosphorylation, selenylation, and so on. The improved functional properties and bioactivities of the modified seaweed polysaccharides and their potential food applications are also summarized.

Fully Physically Crosslinked Conductive Hydrogel with Ultrastretchability, Transparency, and Self-Healing Properties for Strain Sensors

Currently, conductive hydrogels have received great attention as flexible strain sensors. However, the preparation of such sensors with integrated stretchability, transparency, and self-healing properties into one gel through a simple method still remains a huge challenge. Here, a fully physically crosslinked double network hydrogel was developed based on poly(hydroxyethyl acrylamide) (PHEAA) and κ-carrageenan (Car). The driving forces for physical gelation were hydrogen bonds, ion bonding, and electrostatic interactions. The resultant PHEAA-Car hydrogel displayed stretchability (1145%) and optical transparency (92%). Meanwhile, the PHEAA-Car hydrogel exhibited a self-healing property at 25 °C. Additionally, the PHEAA-Car hydrogel-based strain sensor could monitor different joint movements. Based on the above functions, the PHEAA-Car hydrogel can be applied in flexible strain sensors.

Effects of Alkaline Solvent Type and pH on Solid Physical Properties of Carrageenan from Eucheuma cottonii

The effects of alkali type and pH on the physical properties of carrageenan have been extensively studied. However, their effects on certain characteristics of solid-state properties of carrageenan have not been identified. This research aimed to investigate the effect of alkaline solvent type and pH on the solid physical properties of carrageenan isolated from Eucheuma cottonii. Carrageenan was extracted from the algae using NaOH, KOH, and Ca(OH)₂ at pHs of 9, 11, and 13. Based on the results of preliminary characterization, including yield, ash content, pH, sulphate content, viscosity, and gel strength, it was found that all samples followed Food and Agriculture Organization (FAO) specifications. The swelling capacity of carrageenan based on the type of alkali was KOH > NaOH > Ca(OH)₂. The FTIR spectra of all samples were in agreement with that of standard carrageenan. The molecular weight (MW) of carrageenan using KOH as the alkali followed the order pH 13 > pH 9 > pH 11, while using NaOH, the order was pH 9 > pH 13 > pH 11, and while using Ca(OH)₂, the order was pH 13 > pH 9 > pH 11. The results of the solid-state physical characterization of carrageenan with the highest MW in each type of alkali showed that the morphology of carrageenan using Ca(OH)₂ has a cubic shape and is more crystal-like. The order of crystallinity of carrageenan using different types of alkali was Ca(OH)₂ (14.44%) > NaOH (9.80%) > KOH (7.91%), while the order of density was Ca(OH)₂ > KOH > NaOH. The order of solid fraction (SF) of the carrageenan was KOH > Ca(OH)₂ > NaOH, while the tensile strength when using KOH was 1.17, when using NaOH it was 0.08, and while using Ca(OH)₂, it was 0.05. The bonding index (BI) of carrageenan using KOH = 0.04, NaOH = 0.02, and Ca(OH)₂ = 0.02. The brittle fracture index (BFI) of the carrageenan was KOH = 0.67, NaOH = 0.26, and Ca(OH)₂ = 0.04. The order of carrageenan solubility in water was NaOH > KOH > Ca(OH)₂. These data can be used as the basis for the development of carrageenan for excipients in solid dosage forms.

Experimental Analysis and Neural Network Modeling of the Rheological Behavior of Xanthan Gum and Its Derivatives

The main objective of this study was to create a mathematical tool that could be used with experimental data to predict the rheological flow behavior of functionalized xanthan gum according to the types of chemical groups grafted onto its backbone. Different rheological and physicochemical analyses were applied to assess six derivatives synthesized via the etherification of xanthan gum by hydrophobic benzylation with benzyl chloride and carboxymethylation with monochloroacetic acid at three (regent/polymer) ratios R equal to 2.4 and 6. Results from the FTIR study verified that xanthan gum had been modified. The degree of substitution (DS) values varying between 0.2 and 2.9 for carboxymethylxanthan gum derivatives were found to be higher than that of hydrophobically modified benzyl xanthan gum for which the DS ranged from 0.5 to 1. The molecular weights of all the derivatives were found to be less than that of xanthan gum for the two types of derivatives, decreasing further as the degree of substitution (DS) increased. However, the benzyl xanthan gum derivatives presented higher molecular weights varying between 1,373,146 (g/mol) and 1,262,227 (g/mol) than carboxymethylxanthan gum derivatives (1,326,722-1,015,544) (g/mol). A shear-thinning behavior was observed in the derivatives, and the derivatives' viscosity was found to decrease with increasing DS. The second objective of this research was to create an ANN model to predict one of the rheological properties (the apparent viscosity). The significance of the ANN model (R² = 0.99998 and MSE = 5.95 × 10^-3) was validated by comparing experimental results with the predicted ones. The results showed that the model was an efficient tool for predicting rheological flow behavior.

Formulation and Evaluation of Xanthan Gum Microspheres for the Sustained Release of Metformin Hydrochloride

This work aimed to formulate xanthan gum microspheres for the encapsulation of metformin hydrochloride, according to the process of ionotropic gelation. The obtained microparticles, based on various fractions of xanthan gum (0.5-1.25), were subjected to different physico-chemical tests and a drug release study. Microspheres with an average size varying between 110.96 μm and 208.27 μm were obtained. Encapsulation efficiency reached 93.11% at a 1.25% biopolymer concentration. The swelling study showed a swelling rate reaching 29.8% in the gastric medium (pH 1.2) and 360% in the intestinal medium (pH 6.8). The drug release studies showed complete metformin hydrochloride release from the beads, especially those prepared from xanthan gum at the concentration of 1.25%, in intestinal medium at 90.00% after 6 h. However, limited and insignificant drug release was observed within the gastric medium (32.50%). The dissolution profiles showed sustained release kinetics.

Chemical modification of κ-carrageenan with poly(2-hydroxypropylmethacrylamide) through microwave induced graft copolymerization: Characterization and swelling features

In the last decade, interest in the development of new graft copolymers based on natural polysaccharides has grown remarkably due to their potential applications in the wastewater treatment, biomedical, nanomedicine, and pharmaceutical fields. Herein, a novel graft copolymer of κ-carrageenan with poly(2-hydroxypropylmethacrylamide) (κ-Crg-g-PHPMA) was synthesized using a 'microwave induced' technique. The synthesized novel graft copolymer has been well characterized in terms of FTIR, ¹³C NMR, molecular weight determination, TG, DSC, XRD, SEM, and elemental analyses, taking κ-carrageenan as a reference. The graft copolymers' swelling characteristics were investigated at pH 1.2 and 7.4. The results of swelling studies displayed that the incorporation of PHPMA groups on κ-Crg provides increasing hydrophilicity. The effect of PHPMA percentage in the graft copolymers and pH of the medium on the swelling percentage was studied and the findings exhibited that swelling ability increased with the increment in PHPMA percentage and pH of the medium. The best swelling percentage was attained at pH = 7.4 and a grafting percentage of 81 % reaching 1007 % at the end of 240 min. Moreover, cytotoxicity of the synthesized κ-Crg-g-PHPMA copolymer was assessed on the L929 fibroblast cell line and obtained to be non-toxic.

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.

Biomaterials from the sea: Future building blocks for biomedical applications

Marine resources have tremendous potential for developing high-value biomaterials. The last decade has seen an increasing number of biomaterials that originate from marine organisms. This field is rapidly evolving. Marine biomaterials experience several periods of discovery and development ranging from coralline bone graft to polysaccharide-based biomaterials. The latter are represented by chitin and chitosan, marine-derived collagen, and composites of different organisms of marine origin. The diversity of marine natural products, their properties and applications are discussed thoroughly in the present review. These materials are easily available and possess excellent biocompatibility, biodegradability and potent bioactive characteristics. Important applications of marine biomaterials include medical applications, antimicrobial agents, drug delivery agents, anticoagulants, rehabilitation of diseases such as cardiovascular diseases, bone diseases and diabetes, as well as comestible, cosmetic and industrial applications.

One-pot synthesis of magnetic self-assembled carrageenan-ε-polylysine composites: A reusable and effective antibacterial agent against Alicyclobacillus acidoterrestris

Epsilon-polylysine (EPL) is a cationic polymer with broad antibacterial activity. Base on this property, anionic carrageenan (CG) was self-assembled with EPL and introduced into the one-pot coprecipitation process to fabricate the magnetic Fe₃O₄-CG-EPL composites. To demonstrate the successful synthesis of composites, characterization techniques including XRD, FT-IR, TEM, XPS and VSM were employed. The prepared composites exhibited effective antibacterial activity against Alicyclobacillus acidoterrestris with the minimum inhibitory concentration of 10.0 mg mL^-1. Investigations into deciphering the antibacterial mechanism demonstrated that the presence of Fe₃O₄-CG-EPL caused irreversible damage to the cell membrane and serious leakage of intracellular protein, resulting in the inactivation of bacteria. The aim of this work is to develop a new effective control method for A. acidoterrestris in food field.

Hydrophilic carrageenan functionalized magnetic carbon-based framework linked by silane coupling agent for the enrichment of N-glycopeptides from human saliva

In this work, a magnetic graphene material coated with mesoporous silica was selected as the substrate, 3-glycidoxypropyltrimethoxysilane and polyethyleneimine were sequentially bonded through chemical reactions, and then carrageenan was successfully introduced by electrostatic interaction; finally, hydrophilic nanocomposite material was prepared. Due to the large number of hydrophilic groups, and polyethyleneimine was connected by means of chemical bonds, this material exhibits good hydrophilicity and stability for glycopeptide enrichment. In the actual enrichment process, nanomaterial exhibits high selectivity (1:500), high sensitivity (2 fmol), and good repeatability (five cycles). In addition, the synthesized material also shows a good enrichment effect in the face of actual complex biological samples, which captured 40 N-glycopeptides from human saliva, indicating the application potential for enrichment of N-glycopeptides.