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Chitosan is a prominent biopolymer in research for of its physicochemical properties and uses. Each year, the number of publications based on chitosan and its derivatives increases. Because of its comprehensive biological properties, including antibacterial, antioxidant, and tissue regeneration activities, chitosan and its derivatives can be used to prevent and treat soft tissue diseases. Furthermore, chitosan can be employed as a nanocarrier for therapeutic drug delivery. In this review, we will first discuss chitosan and chitosan-based hydrogel polymers. The structure, functionality, and physicochemical characteristics of chitosan-based hydrogels are addressed. Second, a variety of characterization approaches were used to analyze and validate the physicochemical characteristics of chitosan-based hydrogel materials. Finally, we discuss the antibacterial, antibiofilm, and antifungal uses of supramolecular chitosan-based hydrogels. This review study can be used as a base for future research into the production of various types of chitosan-based hydrogels in the antibacterial and antifungal fields.

In recent years, the antimicrobial activity of chitosan-based hydrogels has been at the forefront of research in wound healing and the prevention of medical device contamination. Anti-infective therapy is a serious challenge given the increasing prevalence of bacterial resistance to antibiotics as well as their ability to form biofilms. Unfortunately, hydrogel resistance and biocompatibility do not always meet the demands of biomedical applications. As a result, the development of double-network hydrogels could be a solution to these issues. This review discusses the most recent techniques for creating double-network chitosan-based hydrogels with improved structural and functional properties. The applications of these hydrogels are also discussed in terms of tissue recovery after injuries, wound infection prevention, and biofouling of medical devices and surfaces for pharmaceutical and medical applications.

Systematic administration of small molecular drugs often suffered from the low efficacy and systemic toxicity in cancer therapy. In addition, application of single mode drug usually leads to unsatisfactory therapeutic outcomes. Currently, developing multimodal-drug combination strategy that acts on different pathways without increasing side effects remains great challenge. Here, we developed a hydrogel system that co-delivered glycolysis inhibitor apigenin and chemo-drug gemcitabine to realize combination strategy for combating cancer with minimal systemic toxicity. We demonstrated that this system can not only eliminate tumor cells in situ, but also induce abscopal effect on various tumor models. These results showed that our study provided a safe and effective strategy for clinical cancer treatment. [Display omitted] •Hydrogel loaded with the glycosidase inhibitor apigenin and chemotherapeutic drug gemcitabine enhances the drug's half-life, intensifies the inhibition of the glycolytic pathway, and severs the tumor's energy source.•Hydrogel for in-situ tumor treatment extends the drug's efficacy period, reduces systemic circulation loss and overall toxicity, regulates the tumor microenvironment, and maximizes therapeutic effects.•Demonstrated through metastatic and re-injection models, this sustained-release system not only eliminates tumors in situ but also induces extracorporeal effects.

Extracellular vesicles are membrane-packed entities that are involved in various physiological and pathological processes. Recently, the role of exosomes and microvesicles in regenerative medicine has been elucidated. Indeed, therapeutic potential of stem cells may be partly due to exosomes or microvesicles. However, injection of these vesicles may lead to their rapid clearance from the injection site. To address this challenge, different delivery systems for these vesicles’ sustained delivery have been developed. In this regard, chitosan based hydrogels have been successfully utilized as delivery platforms for exosomes and microvesicles. In the current review, the prospects, challenges, and applications of chitosan-based hydrogels as a delivery vehicle for exosomes and microvesicles will be discussed.

Chitosan is widely used in the production of various hydrogels due to its non-biological toxicity, good biocompatibility, and strong biodegradability. However, chitosan-based hydrogels have not been widely used in tissue engineering due to their poor mechanical strength, poor stability and high biotoxicity of cross-linking agents. As a green technology, low temperature plasma is rich in active groups that can be involved in various chemical reactions, such as replacing the components on the chitosan chain, contributing to the cross-linking of chitosan. In this study, a plasma-assisted preparation method of chitosan-based hydrogels was developed and the properties, including mechanics, water absorption, and degradation (or stability), were characterized and analyzed. It is proved that plasma treatment plays a significant role in improving the mechanical strength and stability of hydrogels.

Currently, as research on hydrogel beads intensifies, the application scope of chitosan-based hydrogel beads is increasingly expanding. Owing to their unique three-dimensional network structure, chitosan-based hydrogel beads are frequently utilized for encapsulating bioactive substances and adsorbing impurities. The primary material used in the preparation of chitosan-based hydrogel beads is chitosan, which is uniquely a natural polysaccharide possessing a positive charge. Derived from a diverse array of sources, chitosan is non-toxic, exhibits excellent biocompatibility, and possesses certain antibacterial properties. Because of these remarkable attributes, it has found widespread application in tissue engineering, the formulation of drug carriers, and the adsorption of heavy metals and dyes in wastewater. The preparation method for chitosan-based hydrogel beads largely mirrors that of other hydrogel beads. According to existing research, numerous methods exist for crafting hydrogel beads with diverse properties. This paper reviews the preparation methods of chitosan-based hydrogel beads, encompassing both physical and chemical crosslinking techniques. The physical crosslinking method leverages electrostatic interactions between materials to form hydrogel beads, whereas the chemical crosslinking method involves the use of chemical crosslinking agents to facilitate the formation of hydrogel beads through material-based chemical reactions. Given that chitosan carries a positive charge and other polysaccharide materials possess a negative charge, the combination of these materials can yield hydrogel beads with a dense structure, effectively encapsulating bioactive substances. This dense internal structure offers superior protection for the encapsulated bioactive substances. Chitosan-based hydrogel beads typically feature large pore sizes, providing numerous adsorption sites, which makes them well suited for wastewater treatment. Additionally, this paper examines the recent applications of chitosan-based hydrogel beads in food preservation, medicine, and environmental protection. Starting with the materials and methods for preparing chitosan-based hydrogel beads, this paper delves into their applications in food preservation, biomedicine, and environmental protection, offering insights for future developments and applications of chitosan-based hydrogel beads and fostering further innovation and advancement in this field.

Bone fractures are common in the geriatric population and pose a great economic burden worldwide. While traditional methods for repairing bone defects have primarily been autografts, there are several drawbacks limiting its use. Bone graft substitutes have been used as alternative strategies to improve bone healing. However, there remain several impediments to achieving the desired healing outcomes. Injectable hydrogels have become attractive scaffold materials for bone regeneration, given their high performance in filling irregularly sized bone defects and their ability to encapsulate cells and bioactive molecules and mimic the native ECM of bone. We investigated the use of an injectable chitosan-based hydrogel scaffold to promote the differentiation of preosteoblasts in vitro. The hydrogels were characterized by evaluating cell homogeneity, cell viability, rheological and mechanical properties, and differentiation ability of preosteoblasts in hydrogel scaffolds. Cell-laden hydrogel scaffolds exhibited shear thinning behavior and the ability to maintain shape fidelity after injection. The CNC-CS hydrogels exhibited higher mechanical strength and significantly upregulated the osteogenic activity and differentiation of preosteoblasts, as shown by ALP activity assays and histological analysis of hydrogel scaffolds. These results suggest that this injectable hydrogel is suitable for cell survival, can promote osteogenic differentiation of preosteoblasts, and structurally support new bone growth.

Biocompatible electroactive hydrogels with bidirectional pH-responsive bending are important for the creation of biomedical actuators. This study developed chitosan/carboxymethylcellulose (CS/CMC) semi-interpenetrating networks (SIPNs) with different volume ratios, which were crosslinked with glutaraldehyde. The swelling and bending behaviors of SPINs were systematically characterized as a function of the pH of the solution and the magnitude of the applied electric field. The hydrogels exhibited pH-dependent bidirectional actuation, with the maximum swelling of 4.67–6.00 at pH ≈ 3.9 and minimum swelling of 1.58–2.53 at pH ≈ 5.7. The SPINs with CS/CMC = 1:1 composition achieved the highest bending angle of 77° at pH ≈ 5.7, while cathodic bending up to an angle of −13.7° was observed in basic conditions. The electromechanical response was significantly enhanced by decreasing the electrode distance and increasing the applied voltage. The observed correlation between the composition, swelling behavior, and bending performance was explained in terms of the electrostatic interactions between NH3+ and COO− groups present in the CS/CMC mixtures. These findings provided novel insight into the ongoing efforts for the development of non-toxic electroactive hydrogels with tailored electromechanical bending behavior necessary for use as artificial muscles and biomedical actuators.

Hydrogels are cross‐linked polymeric networks that can retain a moisture environment and mimic human soft tissues. Chitosan, a linear polysaccharide with pH‐responsive self‐assembling properties, is an attractive candidate for hydrogel construction owing to the existence of intrinsic intermolecular and intramolecular hydrogen bonds and versatile reactive amino groups. Recently, a variety of chitosan‐based hydrogels have been developed via diverse approaches, which could be generally categorized as multilayered hydrogels, hydrogels based on alkali/urea solvent system, injectable hydrogels, self‐healing hydrogels, shape memory hydrogels, and superabsorbent hydrogels. Following a brief introduction of the chitosan hydrogels, this chapter introduces recent advances in chitosan‐based hydrogels with emphasis on their preparation, characterization, properties, and possible applications. In addition, current challenges and future perspectives in this field are also discussed to suggest a new developing direction.

With the rapid progress of industrialization, the incidence of peripheral nerve injuries caused by trauma has been continuously increasing. These injuries result in a significant number of disabilities and irreversible functional impairments, not only severely impacting the health and quality of life of patients but also placing a heavy economic burden on families and society. Effectively promoting peripheral nerve regeneration has thus become a key focus and challenge in current research. In recent years, hybrid biohydrogels with adhesive properties have gained widespread attention due to their excellent biocompatibility, mechanical stability, conductivity, and biodegradability. These materials can provide an optimal microenvironment to promote neuron adhesion and axonal extension while offering outstanding mechanical strength to meet the fixation requirements in clinical surgeries. This paper systematically reviews the application of adhesive hybrid biohydrogels in peripheral nerve injury repair, highlighting the latest research progress in promoting nerve regeneration and improving functional recovery, and discusses the challenges and future prospects for their clinical application.