Shear thinning pectin hydrogels physically cross-linked with chitosan nanogels

Comparative analysis of classic network vs. nanogel junction network in konjac glucomannan/kappa carrageenan hybrid hydrogels

The three-dimensional network architecture of hydrogels significantly influences their mechanical and physical properties; therefore, understanding them is essential for designing optimized hydrogel-based biomaterials. This study presents a comparative analysis of two hybrid hydrogels composed of konjac glucomannan (KGM) and kappa carrageenan (KCAR) with the same stiffness (5.2-5.7 kPa and 1.6-1.7 kPa) thus similar cross-linking density but different network architectures: a classic network formed by extended polysaccharide interactions and a nanogel junction network where nanoscale cross-linked KCAR (KCAR-NGs) links KGM chains. The mechanical behavior, dissolution, and diffusion characteristics were examined, revealing that the classic network demonstrates superior tensile resistance, elongation, and solvent-induced swelling resistance, leading to slower dissolution rates and higher viscosity. Conversely, the nanogel junction network offers higher permeability for small molecules and faster dissolution, suggesting a more open network structure. These findings highlight the nanogel-based hydrogels' advantages for biomedical applications requiring stability, permeability, and rapid dissolution without high temperatures or chelating agents. This study underscores the potential of nanogel junction networks to balance hydrogel stiffness and permeability, advancing the design of hydrogel-based biomaterials.

Fabrication and characterization of responsible approach for targeted intestinal releasing and enhancing the effectivity of kidney tea saponin upon porous starch /xanthan gum /sodium alginate-based hydrogel bead

To enhance the intestinal targeted release of kidney tea saponins, a simple delivery system was designed through the use of porous starch (PS), sodium alginate (ALG) and xanthan gum (XG). Porous starch was prepared by hydrolysis with a combination of α-amylase and amyloglucosidase and it was characterized by scanning electron microscopy, which revealed the formation of porous structures in the starch granules. The results of one-way optimisation illustrated that this unique delivery system achieved 79.00 ± 1.22 % of the optimal encapsulation rate. The carrier structure was subjected to analysis using Fourier transform infrared spectroscopy and X-ray diffraction. The α-glucosidase inhibition assay showed better inhibition of kidney tea saponin compared to the positive control acarbose. In addition, the effectiveness of this delivery design was confirmed via an in vitro simulated digestion method. It was showed that only a 15.57 ± 1.27 % release rate of kidney tea saponin was observed in the upper gastrointestinal tract, whereas release rates of 17.51 ± 1.29 % and 41.07 ± 0.76 % were observed for xanthan gum/sodium alginate/kidney tea saponin and sodium alginate/kidney tea saponin beads, respectively. It was concluded that the utilization of PS and a xanthan gum/sodium alginate coating represents an efficacious methodology for the development of an intestinal targeted delivery system.

Temperature-sensitive injectable chitosan-based hydrogel for endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is an effective treatment for polyps and early gastrointestinal cancers, but requires a high level of operator skill. Injecting submucosal materials (SIM) helps create a fluid cushion between the mucosal and muscular layers, making the procedure easier and reducing associated risks. However, SIMs commonly used in current clinical practice tend to spread quickly and fail to provide long-lasting submucosal fluid cushions (SFC). Thus, there is a critical need for a material that is easy to inject while also maintaining a durable barrier. We prepared succinylated hydroxybutyl chitosan (HBC-SA) by adding succinic anhydride (SA) to hydroxybutyl chitosan (HBC). The hydrogel had excellent temperature-sensitive properties and was able to be injected via an endoscopic injection needle even after gel formation. In vitro and in vivo studies showed that it has satisfactory biocompatibility. Functional experiments showed that the submucosal lifting properties of this hydrogel were significantly better than that of normal saline (NS) and sodium hyaluronate (SH), two commonly used clinical materials. In addition, the hydrogel possessed excellent hemostatic properties. Based on these results, HBC-SA is a promising candidate for submucosal injection during ESD.

Pectin-Chitosan Hydrogel Beads for Delivery of Functional Food Ingredients

A common challenge in hydrogel-based delivery systems is the premature release of low molecular weight encapsulates through diffusion or swelling and reduced cell viability caused by the low pH in gastric conditions. A second biopolymer, such as chitosan, can be incorporated to overcome this. Chitosan is usually associated with colonic drug delivery systems. We intended to formulate chitosan-coated pectin beads for use in delaying premature release of the encapsulate under gastric conditions but allowing release through disintegration under intestinal conditions. The latter is of utmost importance in delivering most functional food ingredients. Therefore, this study investigated the impact of formulation and process conditions on the size, sphericity, and dissolution behavior of chitosan-coated hydrogel beads prepared by interfacial coacervation. The size and sphericity of the beads depend on the formulation and range from approximately 3 to 5 mm and 0.82 to 0.95, respectively. Process conditions during electro-dripping may be modulated to tailor bead size. Depending on the voltage, bead size ranged from 1.5 to 4 mm. Confocal laser scanning microscopy and scanning electron microscopy confirmed chitosan shell formation around the pectin bead. Chitosan-coated beads maintained their size and shape in simulated gastric fluid but experienced structural damage in simulated intestinal fluid. Therefore, they represent a novel delivery system for functional food ingredients.

Tailor-Made Polysaccharides for Biomedical Applications

Polysaccharides (PSAs) are carbohydrate-based macromolecules widely used in the biomedical field, either in their pure form or in blends/nanocomposites with other materials. The relationship between structure, properties, and functions has inspired scientists to design multifunctional PSAs for various biomedical applications by incorporating unique molecular structures and targeted bulk properties. Multiple strategies, such as conjugation, grafting, cross-linking, and functionalization, have been explored to control their mechanical properties, electrical conductivity, hydrophilicity, degradability, rheological features, and stimuli-responsiveness. For instance, custom-made PSAs are known for their worldwide biomedical applications in tissue engineering, drug/gene delivery, and regenerative medicine. Furthermore, the remarkable advancements in supramolecular engineering and chemistry have paved the way for mission-oriented biomaterial synthesis and the fabrication of customized biomaterials. These materials can synergistically combine the benefits of biology and chemistry to tackle important biomedical questions. Herein, we categorize and summarize PSAs based on their synthesis methods, and explore the main strategies used to customize their chemical structures. We then highlight various properties of PSAs using practical examples. Lastly, we thoroughly describe the biomedical applications of tailor-made PSAs, along with their current existing challenges and potential future directions.

One-step of ionic liquid-assisted stabilization and dispersion: Exfoliated graphene and its applications in stimuli-responsive conductive hydrogels based on chitosan

Conductive hydrogels, as novel flexible biosensors, have demonstrated significant potential in areas such as soft robotics, electronic devices, and wearable technology. Graphene is a promising conductive material, but its dispersibility in aqueous solutions exists difficulties. Here, we discover that untreated graphene, after exfoliation by different ionic liquids, can disperse well in aqueous solutions. We investigate the impact of four ionic liquids with varying alkyl chain lengths ([Bmim]Cl, [Omim]Cl, [Dmim]Cl, [Hmim]Cl) on the dispersibility of grapheme, and a dual physically cross-linked network hydrogel structure is designed using acrylamide (AM), acrylic acid (AA), methyl methacrylate octadecyl ester (SMA), ionic liquid@graphene (ILs@GN), and chitosan (CS). Notably, SMA, CS, AA and AM act as dynamic cross-linking points through hydrophobic interactions and hydrogen bonding, playing a crucial role in energy dissipation. The resulting hydrogel exhibits outstanding stretchability (2250 %), remarkable toughness (1.53 MJ/m3) in tensile deformation performance, high compressive strength (1.13 MPa), rapid electrical responsiveness (response time ∼ 50 ms), high electrical conductivity (12.11 mS/cm), and excellent strain sensing capability (GF = 12.31, strain = 1000 %). These advantages make our composite hydrogel demonstrate high stability in extensive deformations, offering repeatability in pressure and strain and making it a promising candidate for multifunctional sensors and flexible electrodes.

Pectin hydrogels for controlled drug release: Recent developments and future prospects

Pectin hydrogels have emerged as a highly promising medium for the controlled release of pharmaceuticals in the dynamic field of drug delivery. The present review sheds light on the broad range of applications and potential of pectin-based hydrogels in pharmaceutical formulations. Pectin, as a biopolymer, is a versatile candidate for various drug delivery systems because of its wide range of properties and characteristics. The information provided on formulation strategies and crosslinking techniques provides researchers with tools to improve drug entrapment and controlled release. Furthermore, this review provides a more in-depth understanding of the complex factors influencing drug release from pectin hydrogels, such as the impact of environmental conditions and drug-specific characteristics. Pectin hydrogels demonstrate adaptability across diverse domains, ranging from applications in oral and transdermal drug delivery to contributions in wound healing, tissue engineering, and ongoing clinical trials. While standardization and regulatory compliance remain significant challenges, the future of pectin hydrogels appears to be bright, opening up new possibilities for advanced drug delivery systems.

Aldehyde group pendant-grafted pectin-based injectable hydrogel

Periodate oxidation has been the widely accepted route for obtaining aldehyde group-functionalized polysaccharides but significantly influenced the various physicochemical properties due to the ring opening of the backbone of polysaccharides. The present study, for the first time, presents a novel method for the preparation of aldehyde group-functionalized polysaccharides that could retain the ring structure and the consequent rigidity of the backbone. Pectin was collected as the representative of polysaccharides and modified with cyclopropyl formaldehyde to obtain pectin aldehyde (AP), which was further crosslinked by DL-lysine (LYS) via the Schiff base reaction to prepare injectable hydrogel. The feasibility of the functionalization was proved by FT-IR and 1H NMR techniques. The obtained hydrogel showed acceptable mechanical properties, self-healing ability, syringeability, and sustained-release performance. Also, as-prepared injectable hydrogel presented great biocompatibility with a cell proliferation rate of 96 %, and the drug-loaded hydrogel exhibited clear inhibition of cancer cell proliferation. Overall, the present study showed a new method for the preparation of aldehyde group-functionalized polysaccharides, and the drug-loaded hydrogel has potential in drug release applications.

Hydrogel-mediated extracellular vesicles for enhanced wound healing: the latest progress, and their prospects for 3D bioprinting

Extracellular vesicles have shown promising tissue recovery-promoting effects, making them increasingly sought-after for their therapeutic potential in wound treatment. However, traditional extracellular vesicle applications suffer from limitations such as rapid degradation and short maintenance during wound administration. To address these challenges, a growing body of research highlights the role of hydrogels as effective carriers for sustained extracellular vesicle release, thereby facilitating wound healing. The combination of extracellular vesicles with hydrogels and the development of 3D bioprinting create composite hydrogel systems boasting excellent mechanical properties and biological activity, presenting a novel approach to wound healing and skin dressing. This comprehensive review explores the remarkable mechanical properties of hydrogels, specifically suited for loading extracellular vesicles. We delve into the diverse sources of extracellular vesicles and hydrogels, analyzing their integration within composite hydrogel formulations for wound treatment. Different composite methods as well as 3D bioprinting, adapted to varying conditions and construction strategies, are examined for their roles in promoting wound healing. The results highlight the potential of extracellular vesicle-laden hydrogels as advanced therapeutic tools in the field of wound treatment, offering both mechanical support and bioactive functions. By providing an in-depth examination of the various roles that these composite hydrogels can play in wound healing, this review sheds light on the promising directions for further research and development. Finally, we address the challenges associated with the application of composite hydrogels, along with emerging trends of 3D bioprinting in this domain. The discussion covers issues such as scalability, regulatory considerations, and the translation of this technology into practical clinical settings. In conclusion, this review underlines the significant contributions of hydrogel-mediated extracellular vesicle therapy to the field of 3D bioprinting and wound healing and tissue regeneration. It serves as a valuable resource for researchers and practitioners alike, fostering a deeper understanding of the potential benefits, applications, and challenges involved in utilizing composite hydrogels for wound treatment.

Recent advances in nano-scaffolds for tissue engineering applications: Toward natural therapeutics

Among the promising methods for repairing or replacing tissue defects in the human body and the hottest research topics in medical science today are regenerative medicine and tissue engineering. On the other hand, nanotechnology has been expanded into different areas of regenerative medicine and tissue engineering due to its essential benefits in improving performance in various fields. Nanotechnology, a helpful strategy in tissue engineering, offers new solutions to unsolved problems. Especially considering the excellent physicochemical properties of nanoscale structures, their application in regenerative medicine has been gradually developed, and a lot of research has been conducted in this field. In this regard, various nanoscale structures, including nanofibers, nanosheets, nanofilms, nano-clays, hollow spheres, and different nanoparticles, have been developed to advance nanotechnology strategies with tissue repair goals. Here, we comprehensively review the application of the mentioned nanostructures in constructing nanocomposite scaffolds for regenerative medicine and tissue engineering. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Diagnostic Tools > Biosensing.

Acylhydrazone-derived whole pectin-based hydrogel as an injectable drug delivery system

Injectable hydrogel-based drug delivery systems have attracted more and more attention due to their sustained-release performance, biocompatibility, and 3D network. The present study showed whole pectin-based hydrogel as an injectable drug delivery system, which was developed from oxidized pectin (OP) and diacylhydrazine adipate-functionalized pectin (Pec-ADH) via acylhydrazone linkage. The as-prepared hydrogels were characterized by 1H NMR, FT-IR, and SEM techniques. The equilibrium swelling ratio of obtained hydrogel (i.e., sample gel 5) was up to 4306.65 % in the distilled water, which was higher than that in PBS with different pH values. Increasing the pH of the swelling media, the swelling ratio of all hydrogels decreased significantly. The results that involved the swelling properties indicated the salt- and pH-responsiveness of the as-prepared hydrogels. The drug release study presented that 5-FU can be persistently released for more than 12 h without sudden release. Moreover, the whole pectin-based hydrogel presented high cytocompatibility toward L929 cell lines, and the drug delivery system showed a high inhibitory effect on MCF-7 cell lines. All these results manifested that the acylhydrazone-derived whole pectin-based hydrogel was an excellent candidate for injectable drug delivery systems.

MOF-based stimuli-responsive controlled release nanopesticide: mini review

By releasing an adequate amount of active ingredients when triggered by environmental and biological factors, the nanopesticides that respond to stimuli can enhance the efficacy of pesticides and contribute to the betterment of both the environment and food safety. The versatile nature and highly porous structure of metal-organic frameworks (MOFs) have recently garnered significant interest as drug carriers for various applications. In recent years, there has been significant progress in the development of metal-organic frameworks as nanocarriers for pesticide applications. This review focuses on the advancements, challenges, and potential future enhancements in the design of metal-organic frameworks as nanocarriers in the field of pesticides. We explore the various stimuli-responsive metal-organic frameworks carriers, particularly focusing on zeolitic imidazolate framework-8 (ZIF-8), which have been successfully activated by external stimuli such as pH-responsive or multiple stimuli-responsive mechanisms. In conclusion, this paper presents the existing issues and future prospects of metal-organic frameworks-based nanopesticides with stimuli-responsive controlled release.

Combined Effect of Citric Acid and Polyphenol-Rich Grape Seed Extract towards Bioactive Smart Food Packaging Systems

Alginate films (2% w·v^-1) were prepared with varying concentrations (5-20% w/w) of citric acid and aqueous grape seed extract (GSE) filtrate (11.66 ± 1.32 g GAE/L) using the solvent-evaporation method. Crosslinking alginate via ester bonds (FTIR analysis) with citric acid up to 10% (w/w) led to a 33% increase in tensile strength, a 34% reduction in water vapor transmission rate (WVTR), and had no impact on elongation at break. Crosslinking alginate with citric acid in the presence of GSE increased the tensile strength by 17%, decreased WVTR by 21%, and significantly improved DPPH scavenging activity. Moreover, after incubation for 24 h at 37 °C, the film-forming solutions exhibited increased antimicrobial activity, resulting in 0.5- and 2.5-log reductions for Escherichia coli and Staphylococcus aureus, respectively, compared to the values obtained without the addition of GSE. The stronger inhibitory effect observed against Gram-positive bacteria can be attributed to the unique composition and structure of their cell walls, which creates a barrier that restricts the penetration of polyphenols into the cells. The pH adjustment of the GSE film-forming solution from 2.0 to 10.0 shifted the UV/VIS absorption spectra, resulting in a colour change from yellow to red. The findings of this study have showcased the potential of combining GSE and citric acid to enhance the functionality and bioactivity of alginate films for applications in smart food packaging.

Chitosan and Pectin Hydrogels for Tissue Engineering and In Vitro Modeling

Hydrogels are fascinating biomaterials that can act as a support for cells, i.e., a scaffold, in which they can organize themselves spatially in a similar way to what occurs in vivo. Hydrogel use is therefore essential for the development of 3D systems and allows to recreate the cellular microenvironment in physiological and pathological conditions. This makes them ideal candidates for biological tissue analogues for application in the field of both tissue engineering and 3D in vitro models, as they have the ability to closely mimic the extracellular matrix (ECM) of a specific organ or tissue. Polysaccharide-based hydrogels, because of their remarkable biocompatibility related to their polymeric constituents, have the ability to interact beneficially with the cellular components. Although the growing interest in the use of polysaccharide-based hydrogels in the biomedical field is evidenced by a conspicuous number of reviews on the topic, none of them have focused on the combined use of two important polysaccharides, chitosan and pectin. Therefore, the present review will discuss the biomedical applications of polysaccharide-based hydrogels containing the two aforementioned natural polymers, chitosan and pectin, in the fields of tissue engineering and 3D in vitro modeling.

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.

Green and Superior Adsorbents Derived from Natural Plant Gums for Removal of Contaminants: A Review

The ubiquitous presence of contaminants in water poses a major threat to the safety of ecosystems and human health, and so more materials or technologies are urgently needed to eliminate pollutants. Polymer materials have shown significant advantages over most other adsorption materials in the decontamination of wastewater by virtue of their relatively high adsorption capacity and fast adsorption rate. In recent years, "green development" has become the focus of global attention, and the environmental friendliness of materials themselves has been concerned. Therefore, natural polymers-derived materials are favored in the purification of wastewater due to their unique advantages of being renewable, low cost and environmentally friendly. Among them, natural plant gums show great potential in the synthesis of environmentally friendly polymer adsorption materials due to their rich sources, diverse structures and properties, as well as their renewable, non-toxic and biocompatible advantages. Natural plant gums can be easily modified by facile derivatization or a graft polymerization reaction to enhance the inherent properties or introduce new functions, thus obtaining new adsorption materials for the efficient purification of wastewater. This paper summarized the research progress on the fabrication of various gums-based adsorbents and their application in the decontamination of different types of pollutants. The general synthesis mechanism of gums-based adsorbents, and the adsorption mechanism of the adsorbent for different types of pollutants were also discussed. This paper was aimed at providing a reference for the design and development of more cost-effective and environmentally friendly water purification materials.

Pectin functionalized metal-organic frameworks as dual-stimuli-responsive carriers to improve the pesticide targeting and reduce environmental risks

Encapsulation of active ingredients into intelligent response controlled release carriers has been recognized as a promising approach to enhance the utilization efficiency and reduce the environmental risks of pesticides. In this work, an intelligent redox and pectinase dual stimuli-responsive pesticide delivery system was constructed by bonding pectin with metal-organic frameworks (FeMOF nanoparticles) which were loaded with pyraclostrobin (PYR@FeMOF-pectin nanoparticles). The successful fabrication of PYR@FeMOF-pectin nanoparticles was proved by a series of physicochemical characterizations. The results indicated that the loading capacity of PYR@FeMOF-pectin nanoparticles for pyraclostrobin was approximately 20.6%. The pectin covered on the surface of PYR@FeMOF nanoparticles could protect pyraclostrobin from photolysis and improve their spreadability on rice blades effectively. Different biological stimuli associated with Magnaporthe oryzae could trigger the release of pyraclostrobin from the pesticide-loaded core-shell nanoparticles, resulting in the death of pathogens. The bioactivity survey determined that PYR@FeMOF-pectin nanoparticles had a superior fungicidal activity and a longer duration against Magnaporthe oryzae than pyraclostrobin suspension concentrate. In addition, the FeMOF-pectin nanocarriers showed no obvious phytotoxicity and could enhance the shoot length and root length of rice plants. More importantly, PYR@FeMOF-pectin nanoparticles had an 8-fold reduction in acute toxicity to zebrafish than that of pyraclostrobin suspension concentrate. Therefore, the dual-responsive FeMOF-pectin nanocarriers have great potential for realizing site-specific pesticide delivery and promoting plant growth.

Self-healing pectin/cellulose hydrogel loaded with limonin as TMEM16A inhibitor for lung adenocarcinoma treatment

Lung cancer as one of the highest incident malignant tumors did not receive satisfactory chemotherapy due to lack of specific drug targets and targeted drugs. This study screened a new effective lung tumor inhibitor limonin from herbal medicine, which inhibited proliferation and promoted apoptosis of lung adenocarcinoma cells by targeting specific high expressed TMEM16A ion channel. Moreover, a novel biodegradable self-healing hydrogel was prepared from acylhydrazide functionalized carboxymethyl cellulose (CMC-AH) and oxidized pectin (pec-CHO) to reduce the side effects of the limonin to the body. The hydrogels showed fast gelation, good biocompatibility and sustained limonin release property. The limonin-loaded hydrogel significantly inhibited the growth of lung adenocarcinoma in xenografts mice because the limonin inhibited the proliferation, migration and promoted apoptosis of LA795 cells, and eliminated the acute toxicity through sustained release from the hydrogel. Combined the antitumor performance of the limonin and sustained release of pec-CHO/CMC-AH hydrogel, this limonin/hydrogel system achieved satisfactory antitumor effect and eliminated side effects in vivo. Therefore, this system has great potential application for enhanced lung adenocarcinoma therapy.

Injectable hyaluronan/MnO2 nanocomposite hydrogel constructed by metal-hydrazide coordinated crosslink mineralization for relieving tumor hypoxia and combined phototherapy

Hydrogel-based drug delivery holds great promise in topical tumor treatment. However, the simple construction of multifunctional therapeutic hydrogels under physiological conditions is still a huge challenge. Herein, for the first time, a multifunctional hyaluronan/MnO₂ nanocomposite (HHM) hydrogel with injectable and self-healing capabilities was constructed under physiological conditions through innovative in situ mineralization-triggered Mn-hydrazide coordination crosslinking. The hydrogel formed from Mn²⁺ and hydrazided hyaluronan under optimized conditions exhibited a high elastic modulus >1 kPa, injectability, self-healing function, stimuli-responsiveness and catalase-like activity. In vitro and in vivo biological experiments demonstrated that our HHM hydrogel could not only efficiently relieve hypoxia by in situ catalytic decomposition of endogenous H₂O₂ into O₂ but also achieve synergistic photodynamic/photothermal therapy of 4T1 breast cancer in a mouse tumor model. This study presented a novel mineralization-driven metal-hydrazide coordination crosslinking approach and developed a multifunctional therapeutic platform for O₂-enhanced efficient topical dual-phototherapy of breast cancer.

The role of surface functional groups of pectin and pectin-based materials on the adsorption of heavy metal ions and dyes

Natural macromolecules have been used to adsorb pollutants including heavy metal ions and organic dyes due to low-cost, accessible, biodegradable, and eco-friendly advantages. Pectin, an important natural polymer, possesses abundant carboxyl and hydroxyl functional groups that can interact with the metal and organic cations via electrostatic interaction; as well as be modified by other chemicals for preparing hybrid and composite materials. The resultant materials have been employed to remove pollutants from aqueous solution; the importance of chemical composition was unlocked. Here, we reviewed contaminant removal by pectin, and pectin-based hybrid and composite materials, and highlighted the role of functional groups on pollutant removal. The removal of heavy metal ions was mainly due to surface coordination, while that of organic cations to electrostatic interactions of the functional groups. Moreover, the influence of initial contaminant concentration was critically discussed. The comprehensive review can provide valuable information on pectin and its application in contaminant removal.

A thermo-sensitive chitosan/pectin hydrogel for long-term tumor spheroid culture

Hydrogels represent a key element in the development of in vitro tumor models, by mimicking the typical 3D tumor architecture in a physicochemical manner and allowing the study of tumor mechanisms. Here we developed a thermo-sensitive, natural polymer-based hydrogel, where chitosan and pectin were mixed and, after a weak base-induced chitosan gelation, a stable semi-Interpenetrating Polymer Network formed. This resulted thermo-responsive at 37 °C, injectable at room temperature, stable up to 6 weeks in vitro, permeable to small/medium-sized molecules (3 to 70 kDa) and suitable for cell-encapsulation. Tunable mechanical and permeability properties were obtained by varying the polymer content. Optimized formulations successfully supported the formation and growth of human colorectal cancer spheroids up to 44 days of culture. The spheroid dimension and density were influenced by the semi-IPN stiffness and permeability. These encouraging results would allow the implementation of faithful tumor models for the study and development of personalized oncological treatments.

Preparation and Characterization of Salt-Mediated Injectable Thermosensitive Chitosan/Pectin Hydrogels for Cell Embedding and Culturing

In recent years, growing attention has been directed to the development of 3D in vitro tissue models for the study of the physiopathological mechanisms behind organ functioning and diseases. Hydrogels, acting as 3D supporting architectures, allow cells to organize spatially more closely to what they physiologically experience in vivo. In this scenario, natural polymer hybrid hydrogels display marked biocompatibility and versatility, representing valid biomaterials for 3D in vitro studies. Here, thermosensitive injectable hydrogels constituted by chitosan and pectin were designed. We exploited the feature of chitosan to thermally undergo sol-gel transition upon the addition of salts, forming a compound that incorporates pectin into a semi-interpenetrating polymer network (semi-IPN). Three salt solutions were tested, namely, beta-glycerophosphate (βGP), phosphate buffer (PB) and sodium hydrogen carbonate (SHC). The hydrogel formulations (i) were injectable at room temperature, (ii) gelled at 37 °C and (iii) presented a physiological pH, suitable for cell encapsulation. Hydrogels were stable in culture conditions, were able to retain a high water amount and displayed an open and highly interconnected porosity and suitable mechanical properties, with Young's modulus values in the range of soft biological tissues. The developed chitosan/pectin system can be successfully used as a 3D in vitro platform for studying tissue physiopathology.

Structurally Dynamic Hydrogels for Biomedical Applications: Pursuing a Fine Balance between Macroscopic Stability and Microscopic Dynamics

Owing to their unique chemical and physical properties, hydrogels are attracting increasing attention in both basic and translational biomedical studies. Although the classical hydrogels with static networks have been widely reported for decades, a growing number of recent studies have shown that structurally dynamic hydrogels can better mimic the dynamics and functions of natural extracellular matrix (ECM) in soft tissues. These synthetic materials with defined compositions can recapitulate key chemical and biophysical properties of living tissues, providing an important means to understanding the mechanisms by which cells sense and remodel their surrounding microenvironments. This review begins with the overall expectation and design principles of dynamic hydrogels. We then highlight recent progress in the fabrication strategies of dynamic hydrogels including both degradation-dependent and degradation-independent approaches, followed by their unique properties and use in biomedical applications such as regenerative medicine, drug delivery, and 3D culture. Finally, challenges and emerging trends in the development and application of dynamic hydrogels are discussed.

Pectin in biomedical and drug delivery applications: A review

Natural macromolecules have attracted increasing attention due to their biocompatibility, low toxicity, and biodegradability. Pectin is one of the few polysaccharides with biomedical activity, consequently a candidate in biomedical and drug delivery Applications. Rhamnogalacturonan-II, a smaller component in pectin, plays a major role in biomedical activities. The ubiquitous presence of hydroxyl and carboxyl groups in pectin contribute to their hydrophilicity and, hence, to the favorable biocompatibility, low toxicity, and biodegradability. However, pure pectin-based materials present undesirable swelling and corrosion properties. The hydrophilic groups, via coordination, electrophilic addition, esterification, transesterification reactions, can contribute to pectin's physicochemical properties. Here the properties, extraction, and modification of pectin, which are fundamental to biomedical and drug delivery applications, are reviewed. Moreover, the synthesis, properties, and performance of pectin-based hybrid materials, composite materials, and emulsions are elaborated. The comprehensive review presented here can provide valuable information on pectin and its biomedical and drug delivery applications.

Fabrication of self-healing pectin/chitosan hybrid hydrogel via Diels-Alder reactions for drug delivery with high swelling property, pH-responsiveness, and cytocompatibility

Self-healing hydrogels with pH-responsiveness could protect loaded drugs from being destroyed till it arrives to the target. The pectin-based hydrogel is a candidate due to the health benefit, anti-inflammation, antineoplastic activity, nontoxicity, and biospecific degradation, et al. However, the abundant existence of water-soluble branched heteropolysaccharide chains influenced its performance resulting in limitation of the potential. In the present study, we prepared a series of self-healing pectin/chitosan hydrogels via the Diels-Alder reaction. Moreover, pectin/chitosan composite hydrogel was prepared as a contrast. By comparison, it can be seen that the Diels-Alder reaction greatly improved the cross-linking density of hydrogels. The self-healing experiments showed excellent self-healing performance. In different swelling mediums, significant transformation in the swelling ratio was shown, indicating well-swelling property, pH- and thermo-responsiveness. The drug loading and release studies presented high loading efficiency and sustained release performance. The cytotoxicity assay that showed a high cell proliferation ratio manifested great cytocompatibility.

Encapsulation of essential oils using cinnamic acid grafted chitosan nanogel: Preparation, characterization and antifungal activity

Chemical modifications in the chitosan structure may result in obtaining a new material with improved chemical properties, such as an ability to encapsulate lipophilic compounds. This study aimed to synthesize cinnamic acid grafted chitosan nanogel to encapsulate the essential oils of Syzygium aromaticum and Cinnamomum ssp., in order to develop a material to be applied in the control of dermatophytosis caused by the fungus Microsporum canis. The cinnamic acid graft in chitosan was verified by the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Solid State Nuclear Magnetic Resonance of the ¹³C Nucleus (¹³C SSNMR) and Thermal analysis coupled to mass spectrometry (TG-MS) techniques. The nanogel obtained showed affinity for the essential oils of S. aromaticum and Cinnamomum, with encapsulation efficiencies equal to 74% and 89%, respectively. When in an aqueous medium the nanogel with the encapsulated essential oils was able to form stable nanoparticles with average sizes of 176.0 ± 54.3 nm and 263.0 ± 81.4 nm. The cinnamic acid grafted chitosan nanogel showed antifungal activity in vitro against M. canis, inhibiting up to 53.96% of its mycelial growth. Complete inhibition of mycelial growth was achieved by the nanogel with encapsulated essential oils. The results found in this work demonstrated the development of a material with potential application in the control of dermatophytosis caused by the fungus M. canis.

Celery cellulose hydrogel as carriers for controlled release of short-chain fatty acid by ultrasound

The feasibility of using celery cellulose hydrogels as carriers was explored for controlled release of short-chain fatty acids (SCFAs) triggered by ultrasound. The hydrogels were prepared with the phase inversion method and further characterized using FT-IR, SEM and XRD techniques. At the optimal cellulose concentration (8.33 and 6.25 mg/mL), the hydrogels (F₄ and F₅) exhibited the swelling ratio of 185%, and Young's modulus of the F₄ and F₅ was lower than that of others. The hydrogels were loaded with SCFAs owing to its hydrophilicity and swelling properties, and the maximum loading capacity of SCFAs achieved nearly 80%. Interestingly, the loaded SCFAs within hydrogel carrier could be readily released if an ultrasound trigger is exerted. Our results indicate that the ultrasound-triggered strategy for the SCFAs delivery system could provide a promising basis to achieve on-demand, reproducible, repeated, and tunable dosing of bioactive molecules.

Dynamic plant-derived polysaccharide-based hydrogels

Plant-derived polysaccharides are widely used to fabricate hydrogels because of their ease of gelation and functionalization, plus exceptional biological properties. As an example, nanocellulose is a suitable candidate to fabricate hydrogels for tissue engineering applications due to its enhanced mechanical and biological properties. However, hydrogels are prone to permanent failure whilst under load without the ability to reform their networks once damaged. Recently, considerable efforts are being made to fabricate dynamic hydrogels via installation of reversible crosslinks within their networks. In this paper, we review the developments in the design of dynamic hydrogels from plant-derived polysaccharides, and discuss their applications in tissue engineering, sensors, bioelectronics devices, etc. The main goal of the paper is to elucidate how the network design of hydrogels can influence their dynamic properties: self-healing and self-recovery. Complementary to this, current challenges and prospects of dynamic plant-derived hydrogels are discussed.