Physicochemical properties of electrostatically crosslinked carrageenan/chitosan hydrogels and carrageenan/chitosan/Laponite nanocomposite hydrogels

Exploring carrageenan: From seaweed to biomedicine-A comprehensive review

Biomaterials are pivotal in the realms of tissue engineering, regenerative medicine, and drug delivery and serve as fundamental building blocks. Within this dynamic landscape, polymeric biomaterials emerge as the frontrunners, offering unparalleled versatility across physical, chemical, and biological domains. Natural polymers, in particular, captivate attention for their inherent bioactivity. Among these, carrageenan (CRG), extracted from red seaweeds, stands out as a naturally occurring polysaccharide with immense potential in various biomedical applications. CRG boasts a unique array of properties, encompassing antiviral, antibacterial, immunomodulatory, antihyperlipidemic, antioxidant, and antitumor attributes, positioning it as an attractive choice for cutting-edge research in drug delivery, wound healing, and tissue regeneration. This comprehensive review encapsulates the multifaceted properties of CRG, shedding light on the chemical modifications that it undergoes. Additionally, it spotlights pioneering research that harnesses the potential of CRG to craft scaffolds and drug delivery systems, offering high efficacy in the realms of tissue repair and disease intervention. In essence, this review celebrates the remarkable versatility of CRG and its transformative role in advancing biomedical solutions.

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.

Recent advancements in hydrogels as novel tissue engineering scaffolds for dental pulp regeneration

Although conventional root canal treatment offers an effective therapeutic solution, it negatively affects the viability of the affected tooth. In recent years, pulp regeneration technology has emerged as a novel method for treating irreversible pulpitis due to its ability to maintain tooth vitality. The successful implementation of this technique depends on scaffolds and transplantation of exogenous stem cells or recruitment of endogenous stem cells. Accordingly, the three-dimensional structure and viscoelastic characteristics of hydrogel scaffolds, which parallel those of the extracellular matrix, have generated considerable interest. Furthermore, hydrogels support the controlled release of regenerative drugs and to load a wide variety of bioactive molecules. By integrating antibacterial agents into the hydrogel matrix and stimulating an immune response, root canal disinfection can be significantly improved and the rate of pulp regeneration can be accelerated. This review aims to provide an overview of the clinical applications of hydrogels that have been reported in the last 5 years, and offer a comprehensive summary of the different approaches that have been utilized for the optimization of hydrogel scaffolds for pulp regeneration. Advancements and challenges in pulp regeneration using hydrogels treating aged teeth are discussed.

Chitosan-based hydrogels: From preparation to applications, a review

Chitosan, derived from the deacetylation of chitin, is an abundant natural biopolymer on earth. Chitosan and its derivatives have become promising biological materials because of their unique molecular structure and excellent biological activities. The reactive functional groups of chitosan such as the amino and hydroxyl groups play a crucial role in facilitating the synthesis of three-dimensional hydrogel. Chitosan-based hydrogels have been widely used in medical, pharmaceutical, and environmental fields for years. Nowadays, chitosan-based hydrogels have been found in a wide range of applications in the food industry such as food sensors, dye adsorbents and nutrient carriers. In this review, recently developed methods for the preparation of chitosan-based hydrogels were given, and the biological activities of chitosan-based hydrogels were systematically introduced. Additionally, the recent progress in food sensors, packaging, dye adsorbents, and nutrient carriers was discussed. Finally, the challenges and prospects for the future development of chitosan-based hydrogels were discussed.

Carbon dots on LAPONITE® hybrid nanocomposites: solid-state emission and inter-aggregate energy transfer

This study delves into the photoluminescent characteristics of solid-state hybrid carbon dots/LAPONITE® (CDLP). These hybrid materials were synthesized using the hydrothermal method with a precise pH control set at 8.5. The LAPONITE® structure remains intact without structural collapse, and we detected the possible deposition of carbon dots (CDs) aggregates on the clay mineral's edges. The use of different concentrations of citric acid (10-, 6-, 2- and 1-times weight/weight of LAPONITE® mass, maintaining the 1 : 1 molar ratio with ethylenediamine) during synthesis results in different CDs concentrations in CDLP-A (low precursors concentration) and CDLP-D (high concentration) with an amorphous structure and average size around 2.8-3.0 nm. The CDLP displayed visible photoluminescence emission in aqueous and powder, which the last underwent quenching according to lifetimes and quantum yield measurements. Low-temperature measurements revealed an enhancement of the non-radiative pathways induced by aggregation. Energy transfer modelling based on Förster-Dexter suggests an approximate mean distance of 9.5 nm between clusters of CDs.

An antibacterial nanoclay- and chitosan-based quad composite with controlled drug release for infected skin wound healing

Microbial infections of surgical sites and other wounds represent a major impediment for patients. Multifunctional low-cost dressings promoting tissue reparation while preventing infections are of great interest to medical professionals. Here, clay-based laponite nanodiscs (LAP) were loaded with the antibacterial drug kanamycin (KANA) before being embedded into a poly(lactic-co-glycolic acid) (PLGA) membrane and coated with the biopolymer chitosan (CS). Results indicated that these biocompatible materials combined the excellent capacity of LAP for controlled drug release with the mechanical robustness of PLGA and the antibacterial properties of CS as well as its hydrophilicity to form a composite highly suitable as an infection-preventing wound dressing. In vitro, PLGA/LAP/KANA/CS released drugs in a sustainable manner over 30 d, completely inhibited the growth of infectious bacteria, prompted the adhesion fibroblasts, and accelerated their proliferation 1.3 times. In vivo, the composite enabled the fast healing of infected full-thickness skin wounds with a 96.19 % contraction after 14 d. During the healing process, PLGA/LAP/KANA/CS stimulated re-epithelization, reduced inflammation, and promoted both angiogenesis and the formation of dense collagen fibers with an excellent final collagen volume ratio of 89.27 %. Thus, multifunctional PLGA/LAP/KANA/CS made of low-cost components demonstrated its potential for the treatment of infected skin wounds.

Bilayer wound dressing composed of asymmetric polycaprolactone membrane and chitosan-carrageenan hydrogel incorporating storax balsam

A comprehensive approach is needed to develop multifunctional wound dressing that is simple yet efficient. In this work, Liquidambar orientalis Mill. storax loaded hydroxyethyl chitosan (HECS)-carrageenan (kC) based hydrogel (HECS-kC) and polydopamine coated asymmetric polycaprolactone membrane (PCL-DOP) were used to develop a multifunctional and modular bilayer wound dressing. Asymmetric PCL-DOP membrane was prepared by non-solvent induced phase separation (NIPS) followed by polydopamine coating and demonstrated an excellent barrier against bacteria while allowing permeability for 5.45 ppm dissolved‑oxygen and 2130 g/m2 water vapor transmission in 24 h in addition to 805 kPa tensile strength. Storax loaded HECS-kC hydrogel, on the other hand, demonstrated a pH-responsive degradation and swelling to provide necessary conditions to facilitate wound healing. The hydrogels showed stretchability above 140 %, mild adhesive strength on sheep skin and PCL-DOP membrane, while the storax incorporation enhanced antibacterial and antioxidant activity. Furthermore, rat full-thickness skin defect model showed that the developed bilayer wound dressing could significantly facilitate wound healing compared to Tegaderm™ and control groups. This study shows that the bilayered wound dressing has the potential to be used as a simple and effective wound care system.

Recent advances in biopolymer-based hydrogels and their potential biomedical applications

Hydrogels are three-dimensional networks of polymer chains containing large amounts of water in their structure. Hydrogels have received significant attention in biomedical applications owing to their attractive physicochemical properties, including flexibility, softness, biodegradability, and biocompatibility. Different natural and synthetic polymers have been intensely explored in developing hydrogels for the desired applications. Biopolymers-based hydrogels have advantages over synthetic polymers regarding improved cellular activity and weak immune response. These properties can be further improved by grafting with other polymers or adding nanomaterials, and they structurally mimic the living tissue environments, which opens their broad applicability. The hydrogels can be physically or chemically cross-linked depending on the structure. The use of different biopolymers-based hydrogels in biomedical applications has been reviewed and discussed earlier. However, no report is still available to comprehensively introduce the synthesis, advantages, disadvantages, and biomedical applications of biopolymers-based hydrogels from the material point of view. Herein, we systematically overview different synthesis methods of hydrogels and provide a holistic approach to biopolymers-based hydrogels for biomedical applications, especially in bone regeneration, wound healing, drug delivery, bioimaging, and therapy. The current challenges and prospects of biopolymers-based hydrogels are highlighted rationally, giving an insight into the progress of these hydrogels and their practical applications.

Design of cationic surfactant reinforced carrageenan waterproof composite films and applied as water induced electricity generator

Carrageenan (CR) is a renewable polysaccharide material for packaging application due to its good film-forming property, but its use can be limited by the water solubility. In this research, CR hydrogels were modified by quaternary ammonium surfactants with different length of hydrocarbon tails (n, 8≦n≦16) by adsorption method and waterproof films were obtained after drying. The composition and charge interaction of composite films was confirmed by FTIR. Both thermogravimetric analysis and energy dispersive spectrometer indicated that the surfactant ions replaced K+ to form complexes with CR. The X-ray diffraction revealed the decreased amorphous nature of composite films compared to neat CR film. Water-related physical properties, such as water content, weight percentage change after contact with water, water vapor transmission, and water contact angle were intimately related to n. When 8≦n≦14, the waterproof properties were enhanced with the increase of n. Meanwhile, the waterproof property of composite film was ascertained by the no leakage result in the boiling water packaging experiment. When n = 16, sandwich structure was found in the sectional micromorphology images, and water bag structure formed after immersed into water. By comparing the mechanical properties of the composite films in different condition, we found that quaternary ammonium surfactants improved significantly the tensile strength in water and increased elongation at break in dry state. The composite films can be used as water induced voltage generator for their polyelectrolyte nature. Benefiting from the high stability of the composite films in water, their water-induced voltage generation process had good recyclability. Due to the antimicrobial activity of the quaternary ammonium salts and the waterproof property, composite films were more stable and degraded more slowly than neat CR film in nature environment.

Advances in chitosan-based hydrogels for pharmaceutical and biomedical applications: A comprehensive review

The treatment of diseases, such as cancer, is one of the most significant issues correlated with human beings health. Hydrogels (HGs) prepared from biocompatible and biodegradable materials, especially biopolymers, have been effectively employed for the sort of pharmaceutical and biomedical applications, including drug delivery systems, biosensors, and tissue engineering. Chitosan (CS), one of the most abundant bio-polysaccharide derived from chitin, is an efficient biomaterial in the prognosis, diagnosis, and treatment of diseases. CS-based HGs possess some potential advantages, like high values of bioactive encapsulation, efficient drug delivery to a target site, sustained drug release, good biocompatibility and biodegradability, high serum stability, non-immunogenicity, etc., which made them practical and useful for pharmaceutical and biomedical applications. In this review, we summarize recent achievements and advances associated with CS-based HGs for drug delivery, regenerative medicine, disease detection and therapy.

Photo-crosslinking modified sodium alginate hydrogel for targeting delivery potential by NO response

In recent years, the incidence of inflammatory bowel disease has gradually increased. Traditional drugs can reduce inflammation, but cannot be targeting released and often require the coordination with delivery systems. However, a good targeting performance delivery system is still scarce currently. Inflammation can trigger oxidative stress, producing large amounts of oxides such as nitric oxide (NO). Based on this, the present experiment innovatively designed a hydrogel delivery system with NO response that could be inflammation targeting. The hydrogel is composed of sodium alginate modified with glycerol methacrylate, crosslinked with NO response agent by photo-crosslinking method, which have low swelling (37 %) and good mechanical properties with a stable structure even at 55 °C. The results of in vitro digestion also indicated that the hydrogel had a certain tolerance to gastrointestinal digestion. And in the NO environment, it was interestingly found that the structure and mechanical properties of the hydrogels changed significantly. Moreover, hydrogels have good biocompatibility, which ensures their safe use in vivo. In conclusion, this NO-responsive-based delivery system is feasible and provides a new approach for drugs and active factors targeting delivery in the future.

Versatile Injectable Carboxymethyl Chitosan Hydrogel for Immediate Hemostasis, Robust Tissue Adhesion Barrier, and Antibacterial Applications

Iatrogenic ulcers resulting from endoscopic submucosal dissection surgery remain a significant clinical concern due to the risk of uncontrolled bleeding. Herein, we have developed an injectable shear-thinning hydrogel cross-linked through electrostatic interactions and hydrogen bonding. The hydrogel underwent comprehensive characterization, focusing on rheological behavior, injectability, microstructure, film-forming capability, adhesion, swelling behavior, degradation kinetics, antibacterial efficacy, hemostatic performance, and biocompatibility. The incorporation of poly(vinyl alcohol) notably enhanced the internal structural stability and injection pressure, while the Laponite content influenced self-healing ability, modulus, and viscosity. Additionally, the hydrogel exhibited pH sensitivity, appropriate degradation, and swelling rates and displayed favorable film-forming and adhesion properties. Notably, it demonstrated excellent resistance against Escherichia coli and Staphylococcus aureus, highlighting its potential to create an optimal wound environment. In vivo studies further confirmed the hydrogel's exceptional hemostatic performance, positioning it as an optimal material for endoscopic submucosal dissection (ESD) surgery. Moreover, cell experiments and hemolysis tests revealed high biocompatibility, supporting their potential to facilitate the healing of iatrogenic ulcers post-ESD surgery. In conclusion, our hydrogels hold great promise as endoscopic treatment materials for ESD-induced ulcers given their outstanding properties.

A Comprehensive Review of Polysaccharide-Based Hydrogels as Promising Biomaterials

Polysaccharides have emerged as a promising material for hydrogel preparation due to their biocompatibility, biodegradability, and low cost. This review focuses on polysaccharide-based hydrogels' synthesis, characterization, and applications. The various synthetic methods used to prepare polysaccharide-based hydrogels are discussed. The characterization techniques are also highlighted to evaluate the physical and chemical properties of polysaccharide-based hydrogels. Finally, the applications of SAPs in various fields are discussed, along with their potential benefits and limitations. Due to environmental concerns, this review shows a growing interest in developing bio-sourced hydrogels made from natural materials such as polysaccharides. SAPs have many beneficial properties, including good mechanical and morphological properties, thermal stability, biocompatibility, biodegradability, non-toxicity, abundance, economic viability, and good swelling ability. However, some challenges remain to be overcome, such as limiting the formulation complexity of some SAPs and establishing a general protocol for calculating their water absorption and retention capacity. Furthermore, the development of SAPs requires a multidisciplinary approach and research should focus on improving their synthesis, modification, and characterization as well as exploring their potential applications. Biocompatibility, biodegradation, and the regulatory approval pathway of SAPs should be carefully evaluated to ensure their safety and efficacy.

Legume protein/polysaccharide food hydrogels: Preparation methods, improvement strategies and applications

For the development of innovative foods and nutritional fortification, research into food gel is essential. As two types of rich natural gel material, both legume proteins and polysaccharides have high nutritional value and excellent application potential, attracting wide attention worldwide. Research has focused on combining legume proteins with polysaccharides to form hybrid hydrogels as their combinations show improved texture and water retention compared to single legume protein or single polysaccharide gels, and these properties can be tailored for specific applications. This article reviews hydrogels of common legume proteins and discusses heat induction, pH induction, salt ion induction, and enzyme-induced assembly of legume protein/polysaccharide mixtures. The applications of these hydrogels in fat replacement, satiety enhancement, and delivery of bioactive ingredients are discussed. Challenges for future work are also highlighted.

pH-sensitive biocompatible chitosan/sepiolite-based cross-linked citric acid magnetic nanocarrier for efficient sunitinib release

In this study, the magnetite nanoparticles were immobilized on the sepiolite needles via co-precipitation of iron ions. Then, the resulted magnetic sepiolite (mSep) nanoparticles were coated with chitosan biopolymer (Chito) in the presence of citric acid (CA) to prepare mSep@Chito core-shell drug nanocarriers (NCs). TEM images showed magnetic Fe₃O₄ nanoparticles with small sizes (less than 25 nm) on the sepiolite needles. Sunitinib anticancer drug loading efficiencies were ⁓45 and 83.7 % for the NCs with low and high content of Chito, respectively. The in-vitro drug release results exhibited that the mSep@Chito NCs have a sustained release behavior with high pH-dependent properties. Cytotoxic results (MTT assay) showed that the sunitinib-loaded mSep@Chito2 NC had a significant cytotoxic effect on the MCF-7 cell lines. Also, the in-vitro compatibility of erythrocytes, physiological stability, biodegradability, and antibacterial and antioxidant activities of NCs was evaluated. The results showed that the synthesized NCs had excellent hemocompatibility, good antioxidant properties, and were sufficiently stable and biocompatible. Based on the antibacterial data, the minimal inhibitory concentration (MIC) values for mSep@Chito1, mSep@Chito2, and mSep@Chito3 were obtained as 125, 62.5, and 31.2 μg/mL towards S. aureus, respectively. All in all, the prepared NCs could be potentially used as a pH-triggered system for biomedical applications.

Bentonite-in hypromellose-poloxamer sol-gel for corneal application of trimetazidine: Study of rheology and ocular anti inflammatory potential

Bentonite is reported to be used for extending ocular drug delivery safely in a controlled manner. Bentonite combined hydroxypropyl methylcellulose (HPMC)-poloxamer based sol-to-gel formulation has been developed for the prophylactic ocular anti-inflammatory effect of trimetazidine after corneal application. HPMC-poloxamer sol formulation was prepared incorporating trimetazidine to bentonite at 1: 2*10^-5 to 1:5*10^-6 ratios using cold method, and investigations were carried out in carrageenan-induced rabbit eye model. Pseudoplastic shear thinning behavior without any yield value and high viscosity at low shear rate were the positive attribute of the tolerability of the sol formulation after ocular instillation. Presence of bentonite nanoplatelets revealed more sustained in vitro release (~79-97 %) and corneal permeation (~79-83 %) over a period of 6 h in comparison to its absence. Prominent acute inflammation has been produced in the carrageenan-induced untreated eye, whereas the absence of ocular inflammation has been noticed in the previously sol-treated eye even after carrageenan injection. HPMC-poloxamer-based formulation exhibited stronger binding affinity (5.13 kcal/mol) in the presence of bentonite rather than its absence (3.99 kcal/mol), resulting in a stable and sustained effect. HPMC-poloxamer in-situ gel of trimetazidine containing bentonite could be utilized for sustained ocular delivery and the control of ophthalmic inflammation prophylactically.

Structural Strategies for Supramolecular Hydrogels and Their Applications

Supramolecular structures are of great interest due to their applicability in various scientific and industrial fields. The sensible definition of supramolecular molecules is being set by investigators who, because of the different sensitivities of their methods and observational timescales, may have different views on as to what constitutes these supramolecular structures. Furthermore, diverse polymers have been found to offer unique avenues for multifunctional systems with properties in industrial medicine applications. Aspects of this review provide different conceptual strategies to address the molecular design, properties, and potential applications of self-assembly materials and the use of metal coordination as a feasible and useful strategy for constructing complex supramolecular structures. This review also addresses systems that are based on hydrogel chemistry and the enormous opportunities to design specific structures for applications that demand enormous specificity. According to the current research status on supramolecular hydrogels, the central ideas in the present review are classic topics that, however, are and will be of great importance, especially the hydrogels that have substantial potential applications in drug delivery systems, ophthalmic products, adhesive hydrogels, and electrically conductive hydrogels. The potential interest shown in the technology involving supramolecular hydrogels is clear from what we can retrieve from the Web of Science.

Recent advances in exploiting carrageenans as a versatile functional material for promising biomedical applications

Carrageenans are a group of biopolymers widely found in red seaweeds. Commercial carrageenans have been traditionally used as emulsifiers, stabilizers, and thickening and gelling agents in food products. Carrageenans are regarded as bioactive polysaccharides with disease-modifying and microbiota-modulating activities. Novel biomedical applications of carrageenans as biocompatible functional materials for fabricating hydrogels and nanostructures, including carbon dots, nanoparticles, and nanofibers, have been increasingly exploited. In this review, we describe the unique structural characteristics of carrageenans and their functional relevance. We summarize salient physicochemical features, including thixotropic and shear-thinning properties, of carrageenans. Recent results from clinical trials in which carrageenans were applied as both antiviral and antitumor agents and functional materials are discussed. We also highlight the most recent advances in the development of carrageenan-based targeted drug delivery systems with various pharmaceutical formulations. Promising applications of carrageenans as a bioink material for 3D printing in tissue engineering and regenerative medicine are systematically evaluated. We envisage some key hurdles and challenges in the commercialization of carrageenans as a versatile material for clinical practice. This comprehensive review of the intimate relationships among the structural features, unique rheological properties, and biofunctionality of carrageenans will provide novel insights into their biomedicine application potential.