Injectable, self-healable and adhesive hydrogels using oxidized Succinoglycan/chitosan for pH-responsive drug delivery

Drug delivery using reduction-responsive hydrogel based on carboxyethyl-succinoglycan with highly improved rheological, antibacterial, and antioxidant properties

The development of exopolysaccharide-based polymers is gaining increasing attention in various industrial biotechnology fields for materials such as thickeners, texture modifiers, anti-freeze agents, antioxidants, and antibacterial agents. High-viscosity carboxyethyl-succinoglycan (CE-SG) was directly synthesized from succinoglycan (SG) isolated from Sinorhizobium meliloti Rm 1021, and its structural, rheological, and physiological properties were investigated. The viscosity of CE-SG gradually increased in proportion to the degree of carboxyethylation substitution. In particular, when the molar ratio of SG and 3-chloropropionic acid was 1:100, the viscosity was significantly improved by 21.18 times at a shear rate of 10 s-1. Increased carboxyethylation of SG also improved the thermal stability of CE-SG. Furthermore, the CE-SG solution showed 90.18 and 91.78 % antibacterial effects against Escherichia coli and Staphylococcus aureus and effective antioxidant activity against DPPH and hydroxyl radicals. In particular, CE-SG hydrogels coordinated with Fe3+ ions, which improved both viscosity and rheological properties, while also exhibiting reduction-responsive drug release through 1,4-dithiothreitol. The results of this study suggest that SG derivatives, such as CE-SG, can be used as functional biomaterials in various fields such as food, cosmetics, and pharmaceutical industries.

Advances in Stimuli-Responsive Chitosan Hydrogels for Drug Delivery Systems

Sustainable and controllable drug transport is one of the most efficient ways of disease treatment. Due to high biocompatibility, good biodegradability, and low costs, chitosan and its derivatives are widely used in biomedical fields. Specifically, chitosan hydrogel enables drugs to pass through biological barriers because of their abundant amino and hydroxyl groups that can interact with human tissues. Moreover, the multi-responsive nature (pH, temperature, ions strength, and magnetic field, etc.) of chitosan hydrogels makes precise drug release a possibility. Here, the synthesis methods, modification strategies, stimuli-responsive mechanisms of chitosan-based hydrogels, and their recent progress in drug delivery are summarized. Chitosan hydrogels that carry and release drugs through subcutaneous (dealing with wound dressing), oral (dealing with gastrointestinal tract), and facial (dealing with ophthalmic, ear, and brain) are reviewed. Finally, challenges toward clinic application and the future prospects of stimuli-responsive chitosan-based hydrogels are indicated.

In Situ-Sprayed Bioinspired Adhesive Conductive Hydrogels for Cavernous Nerve Repair

Cavernous nerve injury (CNI), resulting in erectile dysfunction (ED), poses a significant threat to the quality of life for men. Strategies utilizing conductive hydrogels have demonstrated promising results for the treatment of peripheral nerves with a large diameter (>2 mm). However, integrating convenient minimally invasive operation, antiswelling and immunomodulatory conductive hydrogels for treating small-diameter injured cavernous nerves remains a great challenge. Here, a sprayable adhesive conductive hydrogel (GACM) composed of gelatin, adenine, carbon nanotubes, and mesaconate designed for cavernous nerve repair is developed. Multiple hydrogen bonds provide GACM with excellent adhesive and antiswelling properties, enabling it to establish a conformal electrical bridge with the damaged nerve and aiding in the regeneration process. Additionally, mesaconate-loaded GACM suppresses the release of inflammatory factors by macrophages and promotes the migration and proliferation of Schwann cells. In vivo tests demonstrate that the GACM hydrogel repairs the cavernous nerve and restores erectile function and fertility. Furthermore, the feasibility of sprayable GACM in minimally invasive robotic surgery in beagles is validated. Given the benefits of therapeutic effectiveness and clinical convenience, the research suggests a promising future for sprayable GACM materials as advanced solutions for minimally invasive nerve repair.

Rhizobial oxidized 3-hydroxylbutanoyl glycan-based gelatin hydrogels with enhanced physiochemical properties for pH-responsive drug delivery

Rhizobial exopolysaccharide (EPS) is an acidic polysaccharide involved in nitrogen fixation-related signal transduction in the rhizosphere, serving as a structural support for biofilms, and protecting against various external environmental stresses. Rhizobial EPS as a hydrogel biomaterial was used for a pH-responsive drug delivery system combing with gelatins. Pure gelatin (GA) hydrogels have limited practical applications due to their poor mechanical strength and poor thermal stability. We developed new GA hydrogels using oxidized 3-hydroxylbutanoyl glycan (OHbG) as a polymer cross-linking agent to overcome these limitations. OHbG was synthesized from sodium periodate oxidation of 3-hydroxylbutanoyl glycan directly isolated from Rhizobium leguminosarum bv. viciae VF39. The newly fabricated OHbG/GA hydrogels exhibited 21-fold higher compressive stress and 4.7-fold higher storage modulus (G') than GA at the same strain. This result suggested that OHbG provided mechanical improvement. In addition, these OHbG/GA hydrogels showed effective pH-controlled drug release for 5-fluorouracil, self-healable, and self-antioxidant capacity by uronic acids of OHbG. Cell viability tests using HEK-293 cells in vitro also showed that the OHbG/GA hydrogels were non-toxic. This suggests that the new OHbG/GA hydrogels can be used as a potentially novel biomaterial for drug delivery based on its self-healing ability, antioxidant capacity, and pH-responsive drug delivery.

Towards promoting wound healing: A near-infrared light-triggered persistently antibacterial, synergistically hemostatic nanoarchitecture-integrated chitosan hydrogel

The skin, the primary barrier of the body, is inevitably broken. However, the development of materials that facilitate wound healing with sustained antimicrobial, hemostatic, and biocompatible properties remains a formidable challenge. In this article, we prepared a photopolymerizable composite hydrogel consisting of a hydrogel matrix, a hemostatic/antibacterial agent, and a photothermal therapy agent. The photopolymerizable hydrogel matrix was prepared by grafting the photoinitiator and polymerizable active monomer onto the chitosan chain segment, which exhibits excellent biocompatibility. Furthermore, linalool is adsorbed on the surface of halloysite nanotubes (HNTs) to form a hemostatic and antibacterial. Meanwhile, dopamine is employed as a coating material for hollow glass microsphere (HGM), which enables them to function as photothermal therapy agents. Upon exposure to near-infrared radiation, the PHA hydrogel releases linalool molecules from the surface of the HNTs, which diffuse into the hydrogel matrix, resulting in a sustained antimicrobial effect. At the same time, rapid curing of the photopolymerizable hydrogel under UV light forms a physical barrier that synergistically enhances the hemostatic properties of the HNTs. From the above, the results pave the way to develop a potential hemostatic antimicrobial dressing for clinical use in wound healing.

Progress of polysaccharide-based tissue adhesives

Recently, polymer-based tissue adhesives (TAs) have gained the attention of scientists and industries as alternatives to sutures for sealing and closing wounds or incisions because of their ease of use, low cost, minimal tissue damage, and short application time. However, poor mechanical properties and weak adhesion strength limit the application of TAs, although numerous studies have attempted to develop new TAs with enhanced performance. Therefore, next-generation TAs with improved multifunctional properties are required. In this review, we address the requirements of polymeric TAs, adhesive characteristics, adhesion strength assessment methods, adhesion mechanisms, applications, advantages and disadvantages, and commercial products of polysaccharide (PS)-based TAs, including chitosan (CS), alginate (AL), dextran (DE), and hyaluronic acid (HA). Additionally, future perspectives are discussed.

Tissue adhesives based on chitosan for skin wound healing: Where do we stand in this era? A review

Chitosan has been commonly used as an adhesive dressing material due to its excellent biocompatibility, degradability, and renewability. Tissue adhesives are outstanding among wound dressings because they can close the wound, absorb excess tissue exudate from the wound site, provide a moist environment, and act as a carrier for loading various bioactive molecules. They have been widely used in both preclinical and clinical treatment of skin wounds. This review summarizes recent research progresses in the application of chitosan and its derivatives for tissue adhesives. We also introduce their biomedical effects on wound adhesion, contamination isolation, antibacterial, immune regulation, and wound healing, and the strategies to achieve these functions when used as wound dressings. Finally, challenges and future perspectives of chitosan-based tissue adhesives are discussed for wound healing.

Riboflavin mediated UV crosslinking of chitosan-gelatin cryogels for loading of hydrophobic bioactive compounds

Chitosan-gelatin cryogels with good loading capacity of hydrophobic compounds were successfully obtained by UV-induced crosslinking. Using riboflavin as photoinitiator was a suitable alternative to classical carbodiimide crosslinking in obtaining carrier matrices for bioactive hydrophobic compounds. Chitosan had a double role, acting both as a base polymer for the hydrogel network and as co-initiator in riboflavin photo-crosslinking. This co-initiator role of chitosan is due to its electron donor capacity, being well known as a Lewis base type macromolecule. The rheological behaviour of the chitosan-gelatin hydrogel precursor solutions was greatly influenced by riboflavin addition as well as by UV irradiation. As a consequence, the temperature of the sol-gel transition during cooling decreased to 25.5 °C. Compared with classical carbodiimide crosslinking, UV irradiation lead to gels with increased network stability, enhanced elastic behaviour, higher structural strength and almost total stress recovery yield (99 %), the latter indicating self-healing capacity. The cryogels manifested pH responsive swelling, this being highest at close to neutral pH of 7.4. Although hydrophilic in nature, the chitosan-gelatin cryogels crosslinked under the combined effect of riboflavin and UV exposure possess the necessary chemical functionality and morphology that allowed successful embedding of hydrophobic clove essential oil. This was loaded by immersion or fumigation and imparted antioxidant activity to the polymeric matrix.

Hydrogels for Chemical Sensing and Biosensing

The development and synthesis of hydrogels for chemical and biosensing are of great value. Hydrogels can be tailored to its own physical structure, chemical properties, biocompatibility, and sensitivity to external stimuli when being used in a specific environment. Herein, hydrogels and their applications in chemical and biosensing are mainly covered. In particular, it is focused on the manner in which hydrogels serve as sensing materials to a specific analyte. Different types of responsive hydrogels are hence introduced and summarized. Researchers can modify different chemical groups on the skeleton of the hydrogels, which make them as good chemical and biosensing materials. Hydrogels have great application potential for chemical and biosensing in the biomedical field and some emerging fields, such as wearable devices.

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.

Injectable hydrogels embedded with chitosan nanoparticles coated with hyaluronic acid for sequential release of dual drugs

An effective treatment for some disease, such as the model disease acute retinal necrosis (ARN), requires a combination of different drugs which should be administered at a certain interval. The precise sequential and long-term drug release are the critical questions. In this work, the as-prepared chitosan nanoparticles (CS-NPs) coated with hyaluronic acid (HA) were embedded in the aldehyde β-cyclodextrin (ACD)/aminated hyaluronic acid (NHA) hydrogels to synthesize injectable hydrogels loaded with dual drugs named DEX-CS-NPs/GCV-Gel and HA-DEX-CS-NPs/GCV-Gel. In the first 24 h and 48 h, the releases of DEX from DEX-CS-NPs/GCV-Gel were 128.5 % and 82.8 % faster than those from HA-DEX-CS-NPs/GCV-Gel, respectively. There was no DEX released from HA-DEX-CS-NPs/GCV-Gel at the first 7 h, which has never been reported before, although some hydrogel systems loaded with different drugs release different drugs simultaneously at different rate which have been well studied. This is a good start of a precise sequence release. The composite hydrogels possessed appropriate rheology, gel time, degradation performance, and ideal cytocompatibility. The injectable hydrogel loaded with dual drugs presenting a precise sequential and long-term release has great potential in the treatment of diseases requiring combinations of drugs being released sequentially at different treating stages.

Controlled release of herbicides through glyphosate intercalated layered double hydroxides and enhancement of anti-scouring ability via poly-l-aspartic acid and chitosan modification

Nanocarrier preparations could effectively improve the utilization rate of pesticides, and reduce pesticide loss. In this study, glyphosate (GLY)-loaded MgAl layered double hydroxide (GLY@LDH) was synthesized via an in-situ method. Subsequently, GLY@LDH composite samples were prepared using a layer-by-layer self-assembly approach and modified with poly-L-aspartic acid (PASP) and chitosan (CS). XRD, FT-IR, SEM, and Zeta potential characterization confirmed that GLY was successfully loaded in the interlayer of LDHs and PASP/CS were successfully encapsulated on the surface of the composite sample. The release effect in different ionic solutions and soils was studied and analyzed. The release behavior conforms to the Ritger-Peppas kinetic model, and the release mechanism was ion exchange, which was further explored by means of XRD, SEM, and molecular simulation. The results of the anti-scouring experiment and contact angle measurement indicated that the layered self-assembly material enhanced the washing resistance of the material. The practical application effect of the sample was verified through a pot experiment. This study provides new insights into the simple preparation of pesticide-controlled release formulations that reduce leaching losses.

Hydrogels dressings based on guar gum and chitosan: Inherent action against resistant bacteria and fast wound closure

Hydrogels made with depolymerized guar gum, oxidized with theoretical oxidation degrees of 20, 35 and 50 %, were obtained via Schiff's base reaction with N-succinyl chitosan. The materials obtained were subjected to characterization by FT-IR, rheology, swelling, degradation, and morphology. Additionally, their gelation time categorized all three hydrogels as injectable. The materials' swelling degrees in Phosphate-Buffered Saline (PBS) were in the range of 26-35 g of fluid/g gel and their pore size distribution was heterogeneous, with pores varying from 67 to 93 μm. All hydrogels degraded in PBS solution, but maintained around 40 % of their initial mass after 28 days, which was more than enough time for wound healing. The biomaterials were also flexible, self-repairing, adhesive and cytocompatible and presented intrinsic actions, regardless of the presence of additives or antibiotics, against gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and gram-negative bacteria (Escherichia coli). However, the most pronounced bactericidal effect was against resistant Staphylococcus aureus - MRSA. In vivo assays, performed with 50 % oxidized gum gel, demonstrated that this material exerted anti-inflammatory effects, accelerating the healing process and restoring tissues by approximately 99 % within 14 days. In conclusion, these hydrogels have unique characteristics, making them excellent candidates for wound-healing dressings.

Injectable smart stimuli-responsive hydrogels: pioneering advancements in biomedical applications

Hydrogels have established their significance as prominent biomaterials within the realm of biomedical research. However, injectable hydrogels have garnered greater attention compared with their conventional counterparts due to their excellent minimally invasive nature and adaptive behavior post-injection. With the rapid advancement of emerging chemistry and deepened understanding of biological processes, contemporary injectable hydrogels have been endowed with an "intelligent" capacity to respond to various endogenous/exogenous stimuli (such as temperature, pH, light and magnetic field). This innovation has spearheaded revolutionary transformations across fields such as tissue engineering repair, controlled drug delivery, disease-responsive therapies, and beyond. In this review, we comprehensively expound upon the raw materials (including natural and synthetic materials) and injectable principles of these advanced hydrogels, concurrently providing a detailed discussion of the prevalent strategies for conferring stimulus responsiveness. Finally, we elucidate the latest applications of these injectable "smart" stimuli-responsive hydrogels in the biomedical domain, offering insights into their prospects.

Dialdehyde carbohydrates - Advanced functional materials for biomedical applications

Dialdehyde carbohydrates (DCs) have found applications in a wide range of biomedical field due to their great versatility, biocompatibility/biodegradability, biological properties, and controllable chemical/physical characteristics. The presence of dialdehyde groups in carbohydrate structure allows cross-linking of DCs to form versatile architectures serving as interesting matrices for biomedical applications (e.g., drug delivery, tissue engineering, and regenerative medicine). Recently, DCs have noticeably contributed to the development of diverse physical forms of advanced functional biomaterials i.e., bulk architectures (hydrogels, films/coatings, or scaffolds) and nano/-micro formulations. We underline here the current scientific knowledge on DCs, and demonstrate their potential and newly developed biomedical applications. Specifically, an update on the synthesis approach and functional/bioactive attributes is provided, and the selected in vitro/in vivo studies are reviewed comprehensively as examples of the latest progress in the field. Moreover, safety concerns, challenges, and perspectives towards the application of DCs are deliberated.

Multifunctional and theranostic hydrogels for wound healing acceleration: An emphasis on diabetic-related chronic wounds

Hydrogels represent intricate three-dimensional polymeric structures, renowned for their compatibility with living systems and their ability to naturally degrade. These networks stand as promising and viable foundations for a range of biomedical uses. The practical feasibility of employing hydrogels in clinical trials has been well-demonstrated. Among the prevalent biomedical uses of hydrogels, a significant application arises in the context of wound healing. This intricate progression involves distinct phases of inflammation, proliferation, and remodeling, often triggered by trauma, skin injuries, and various diseases. Metabolic conditions like diabetes have the potential to give rise to persistent wounds, leading to delayed healing processes. This current review consolidates a collection of experiments focused on the utilization of hydrogels to expedite the recovery of wounds. Hydrogels have the capacity to improve the inflammatory conditions at the wound site, and they achieve this by diminishing levels of reactive oxygen species (ROS), thereby exhibiting antioxidant effects. Hydrogels have the potential to enhance the growth of fibroblasts and keratinocytes at the wound site. They also possess the capability to inhibit both Gram-positive and Gram-negative bacteria, effectively managing wounds infected by drug-resistant bacteria. Hydrogels can trigger angiogenesis and neovascularization processes, while also promoting the M2 polarization of macrophages, which in turn mitigates inflammation at the wound site. Intelligent and versatile hydrogels, encompassing features such as pH sensitivity, reactivity to reactive oxygen species (ROS), and responsiveness to light and temperature, have proven advantageous in expediting wound healing. Furthermore, hydrogels synthesized using environmentally friendly methods, characterized by high levels of biocompatibility and biodegradability, hold the potential for enhancing the wound healing process. Hydrogels can facilitate the controlled discharge of bioactive substances. More recently, there has been progress in the creation of conductive hydrogels, which, when subjected to electrical stimulation, contribute to the enhancement of wound healing. Diabetes mellitus, a metabolic disorder, leads to a slowdown in the wound healing process, often resulting in the formation of persistent wounds. Hydrogels have the capability to expedite the healing of diabetic wounds, facilitating the transition from the inflammatory phase to the proliferative stage. The current review sheds light on the biological functionalities of hydrogels, encompassing their role in modulating diverse mechanisms and cell types, including inflammation, oxidative stress, macrophages, and bacteriology. Additionally, this review emphasizes the significance of smart hydrogels with responsiveness to external stimuli, as well as conductive hydrogels for promoting wound healing. Lastly, the discussion delves into the advancement of environmentally friendly hydrogels with high biocompatibility, aimed at accelerating the wound healing process.

Water-Induced Phase Separation for Anti-Swelling Hydrogel Adhesives in Underwater Soft Electronics

The development of hydrogel-based underwater electronics has gained significant attention due to their flexibility and portability compared to conventional rigid devices. However, common hydrogels face challenges such as swelling and poor underwater adhesion, limiting their practicality in water environments. Here, a water-induced phase separation strategy to fabricate hydrogels with enhanced anti-swelling properties and underwater adhesion is presented. By leveraging the contrasting affinity of different polymer chains to water, a phase-separated structure with rich hydrophobic and dilute hydrophilic polymer phases is achieved. This dual-phase structure, meticulously characterized from the macroscopic to the nanoscale, confers the hydrogel network with augmented retractive elastic forces and facilitates efficient water drainage at the gel-substrate interface. As a result, the hydrogel exhibits remarkable swelling resistance and long-lasting adhesion to diverse substrates. Additionally, the integration of carboxylic multiwalled carbon nanotubes into the hydrogel system preserves its anti-swelling and adhesion properties while imparting superior conductivity. The conductive phase-separated hydrogel exhibited great potential in diverse underwater applications, including sensing, communication, and energy harvesting. This study elucidates a facile strategy for designing anti-swelling underwater adhesives by leveraging the ambient solvent effect, which is expected to offer some insights for the development of next-generation adhesive soft materials tailored for aqueous environments.

Magnetic Nanofibrous Hydrogels for Dynamic Control of Stem Cell Differentiation

The extracellular matrix in tissue consists of complex heterogeneous soft materials with hierarchical structure and dynamic mechanical properties dictating cell and tissue level function. In many natural matrices, there are nanofibrous structures that serve to guide cell activity and dictate the form and function of tissue. Synthetic hydrogels with integrated nanofibers can mimic the structural properties of native tissue; however, model systems with dynamic mechanical properties remain elusive. Here we demonstrate modular nanofibrous hydrogels that can be reversibly stiffened in response to applied magnetic fields. Iron oxide nanoparticles were incorporated into gelatin nanofibers through electrospinning, followed by chemical stabilization and fragmentation. These magnetoactive nanofibers can be mixed with virtually any hydrogel material and reversibly stiffen the matrix at a low fiber content (≤3%). In contrast to previous work, where a large quantity of magnetic material disallowed cell encapsulation, the low nanofiber content allows matrix stiffening with cells in 3D. Using adipose derived stem cells, we show how nanofibrous matrices are beneficial for both osteogenesis and adipogenesis, where stiffening the hydrogel with applied magnetic fields enhances osteogenesis while discouraging adipogenesis. Skeletal myoblast progenitors were used as a model of tissue morphogenesis with matrix stiffening augmenting myogenesis and multinucleated myotube formation. The ability to reversibly stiffen fibrous hydrogels through magnetic stimulation provides a useful tool for studying nanotopography and dynamic mechanics in cell culture, with a scope for stimuli responsive materials for tissue engineering.

New Polyvinyl Alcohol/Succinoglycan-Based Hydrogels for pH-Responsive Drug Delivery

We fabricated new hydrogels using polyvinyl alcohol (PVA) and succinoglycan (SG) directly isolated and obtained from Sinorhizobium meliloti Rm 1021 via the freeze-thaw method. Both the composition of the hydrogels and the freeze-thaw cycles were optimized to maximize the swelling ratio for the preparation of the PVA/SG hydrogels. During the optimization process, the morphology and conformational change in the hydrogel were analyzed by scanning electron microscopy, rheological measurements, and compressive tests. An optimized hydrogel with a maximum swelling ratio of 17.28 g/g was obtained when the composition of PVA to SG was 50:50 (PVA/SG 50/50) and the total number of freeze-thaw cycles was five. The PVA/SG 50/50 hydrogel had the largest pore with 51.24% porosity and the highest cross-over point (28.17%) between the storage modulus (G') and the loss modulus (G″). The PVA/SG 50/50 hydrogel showed improved thermal stability owing to its interaction with thermally stable SG chains. The improvement in the thermal stability was confirmed by thermogravimetric analysis and differential scanning calorimetry. In addition, the PVA/SG 50/50 hydrogel showed differential drug release according to the corresponding pH under acidic conditions of pH 1.2 and slightly basic conditions of pH 7.4. Furthermore, the cell viability test on the HEK-293 cell line for that hydrogel demonstrated that the PVA/SG 50/50 hydrogel was non-toxic and biocompatible. Therefore, this hydrogel could be a potential scaffold capable of pH-responsive drug delivery for chronic wound dressing applications.

Physicochemical and in vitro biological evaluation of an injectable self-healing quaternized chitosan/oxidized pectin hydrogel for potential use as a wound dressing material

Injectable self-healing hydrogels are attractive materials for use as wound dressings. To prepare such hydrogels, the current study used quaternized chitosan (QCS) to improve the solubility and antibacterial activity and oxidized pectin (OPEC) to introduce aldehyde groups for Schiff's base reaction with the amine groups from QCS. Self-healing hydrogels were made by co-injection of polymer solutions at specific polymer concentrations and reagent ratios that optimized both Schiff's base reactions and ionic interactions. The optimal hydrogel displayed self-healing 30 min after cutting and continuous self-healing during continuous step strain analysis, rapid gelation (< 1 min), a storage modulus of 394 Pa, and hardness of 700 mN, and compressibility of 162 mN s. The adhesiveness of this hydrogel (133 Pa) was within a suitable range for application as a wound dressing. The extraction media from the hydrogel displayed no cytotoxicity to NCTC clone 929 cells and higher cell migration than the control. While the extraction media from the hydrogel was found not to have antibacterial properties, QCS was verified as having MIC50 of 0.04 mg/mL against both E. coli and S. aureus. Therefore, this injectable self-healing QCS/OPEC hydrogel has the potential use as a biocompatible hydrogel material for wound management.

How Magnetic Composites are Effective Anticancer Therapeutics? A Comprehensive Review of the Literature

Chemotherapy is the most prominent route in cancer therapy for prolonging the lifespan of cancer patients. However, its non-target specificity and the resulting off-target cytotoxicities have been reported. Recent in vitro and in vivo studies using magnetic nanocomposites (MNCs) for magnetothermal chemotherapy may potentially improve the therapeutic outcome by increasing the target selectivity. In this review, magnetic hyperthermia therapy and magnetic targeting using drug-loaded MNCs are revisited, focusing on magnetism, the fabrication and structures of magnetic nanoparticles, surface modifications, biocompatible coating, shape, size, and other important physicochemical properties of MNCs, along with the parameters of the hyperthermia therapy and external magnetic field. Due to the limited drug-loading capacity and low biocompatibility, the use of magnetic nanoparticles (MNPs) as drug delivery system has lost traction. In contrast, MNCs show higher biocompatibility, multifunctional physicochemical properties, high drug encapsulation, and multi-stages of controlled release for localized synergistic chemo-thermotherapy. Further, combining various forms of magnetic cores and pH-sensitive coating agents can generate a more robust pH, magneto, and thermo-responsive drug delivery system. Thus, MNCs are ideal candidate as smart and remotely guided drug delivery system due to a) their magneto effects and guide-ability by the external magnetic fields, b) on-demand drug release performance, and c) thermo-chemosensitization under an applied alternating magnetic field where the tumor is selectively incinerated without harming surrounding non-tumor tissues. Given the important effects of synthesis methods, surface modifications, and coating of MNCs on their anticancer properties, we reviewed the most recent studies on magnetic hyperthermia, targeted drug delivery systems in cancer therapy, and magnetothermal chemotherapy to provide insights on the current development of MNC-based anticancer nanocarrier.

A Nonswelling Hydrogel with Regenerable High Wet Tissue Adhesion for Bioelectronics

Reducing the swelling of tissue-adhesive hydrogels is crucial for maintaining stable tissue adhesion and inhibiting tissue inflammation. However, reported strategies for reducing swelling always result in a simultaneous decrease in the tissue adhesive strength of the hydrogel. Furthermore, once the covalent bonds break in the currently reported hydrogels, they cannot be rebuilt, and the hydrogel loses its tissue adhesive ability. In this work, a nonswelling hydrogel (named as "PAACP") possessing regenerable high tissue adhesion is synthesized by copolymerizing and crosslinking poly(vinyl butyral) with acrylic acid, gelatin, and chitosan-grafted N-acetyl-l-cysteine. The tissue adhesive strength of the obtained PAACP reaches 211.4 kPa, which is approximately ten times higher than that of the reported nonswelling hydrogels, and the hydrogel can be reused for multiple cycles. The as-prepared hydrogel shows great potential in soft bioelectronics, as muscle fatigue is successfully monitored via the electrode array and strain sensor integrated on PAACP substrates. The success of these bioelectronics offers potential applicability in the long-term diagnosis of muscle-related health conditions and prosthetic manipulations.

Novel succinoglycan dialdehyde/aminoethylcarbamoyl-β-cyclodextrin hydrogels for pH-responsive delivery of hydrophobic drugs

β-Cyclodextrin cross-linked succinoglycan dialdehyde hydrogels was prepared for hydrophobic drug delivery. Succinoglycan dialdehyde (SGDA) was synthesized from sodium periodate oxidation of succinoglycan isolated from Sinorhizobium meliloti Rm1021. Aminoethylcarbamoyl-β-cyclodextrin (ACD) was crosslinked with SGDA to form a succinoglycan dialdehyde/aminoethylcarbamoyl-β-cyclodextrin (SGDA/ACD) hydrogels. The SGDA/ACD hydrogels exhibited a 65.7 % improvement in storage modulus (G') and a 5.7-fold higher compressive strain than the SGDA/poly(ethylene glycol) diamine (PEG) hydrogels as controls. A hardly soluble drug, baicalein was used for the drug loading and release properties of SGDA/ACD hydrogels. Baicalein was released about 98 % within 48 h at pH 7.4, but not completely released even after 48 h at pH 2.0. In addition, at pH 7.4, only about 56 % of the baicalein loaded on the SGDA/PEG hydrogels was released within 48 h, while about 98 % of the baicalein loaded on the SGDA/ACD hydrogels was released within 48 h. It indicates that ACD significantly improved the solubilization efficacy of the baicalein. In vitro testing of cell viability using HEK-293 cells also showed that the SGDA/ACD hydrogels were suitable for the cells. In conclusion, SGDA/ACD hydrogels significantly enhance the utilization of baicalein and provide potential applications in drug delivery systems for hardly soluble drugs.

pH-sensitive gallol-rich chitosan hydrogel beads for on-off controlled drug delivery

Malignant tumors have emerged as a serious health issue, and the interest in developing pH-sensitive polymers for site-specific drug delivery has increased. The physical and/or chemical properties of pH-sensitive polymers depend on the pH, and thus, drugs can be released by cleaving dynamic covalent and/or noncovalent bonds. In this study, gallic acid (GA) was conjugated to chitosan (CS) to prepare self-crosslinked hydrogel beads containing Schiff base (imine bond) crosslinks. The CS-GA hydrogel beads were formed by the dropwise addition of the CS-GA conjugate solution into a Tris-HCl buffer solution (TBS, pH 8.5). The pH-sensitivity of pristine CS was significantly enhanced following the introduction of GA moiety, and as a result, the CS-GA hydrogel beads swelled more than approximately 5000 % at pH 4.0, indicating an excellent swelling/deswelling ability of the beads at different pH (pH 4.0 and 8.5). The reversible breakage/recovery of the imine crosslinks in the CS-GA hydrogel beads was confirmed through X-ray photoelectron spectroscopic and rheological studies. Finally, Rhodamine B was loaded onto the hydrogel beads as a model drug to investigate the pH-sensitive drug release behavior. At pH 4, the drug was released up to approximately 83 % within 12 h. The findings indicate that the CS-GA hydrogel beads have great potential as a drug delivery system that is sensitive to acidic tumor sites in the body.

Recent advances in adhesive materials used in the biomedical field: adhesive properties, mechanism, and applications

Adhesive materials are natural or synthetic polymers with the ability to adhere to the surface of luminal mucus or epithelial cells. They are widely used in the biomedical field due to their unique adhesion, biocompatibility, and excellent surface properties. When used in the human body, they can adhere to an accessible target and remain at the focal site for a longer period, improving the therapeutic effect on local disease. An adhesive material with bacteriostatic properties can play an antibacterial role at the focal site and the adhesive properties of the material can prevent the focal site from being infected by bacteria for a period. In addition, some adhesive materials can promote cell growth and tissue repair. In this review, the properties and mechanism of natural adhesive materials, organic adhesive materials, composite adhesive materials, and underwater adhesive materials have been introduced systematically. The applications of these adhesive materials in drug delivery, antibacterials, tissue repair, and other applications are described in detail. Finally, we have discussed the prospects and challenges of using adhesive materials in the field of biomedicine.

Smart stimuli-responsive chitosan hydrogel for drug delivery: A review

Smart stimuli-responsive materials can respond to different signals (pH, temperature, light, electricity, etc.), and they have become a hot research topic for drug delivery. As a polysaccharide polymer with excellent biocompatibility, chitosan can be obtained from diverse natural sources. Chitosan hydrogels with different stimuli-response capabilities are widely applied in the drug delivery field. This review highlights and discusses the research progress on chitosan hydrogels concerning their stimuli-responsive capabilities. The feature of various stimuli-responsive kinds of hydrogels is outlined, and their potential use of drug delivery is summarized. Furthermore, the questions and future development chances of stimuli-responsive chitosan hydrogels are analyzed by comparing the current published literature, and the directions for the intelligent development of chitosan hydrogels are discussed.

Polymeric Gel Systems Cytotoxicity and Drug Release as Key Features for their Effective Application in Various Fields of Addressed Pharmaceuticals Delivery

Modified polymeric gels, including nanogels, which play not only the role of a bioinert matrix, but also perform regulatory, catalytic, and transport functions due to the active fragments introduced into them, can significantly advance the solution to the problem of targeted drug delivery in an organism. This will significantly reduce the toxicity of used pharmaceuticals and expand the range of their therapeutic, diagnostic, and medical application. This review presents a comparative description of gels based on synthetic and natural polymers intended for pharmaceutical-targeted drug delivery in the field of therapy of inflammatory and infectious diseases, dentistry, ophthalmology, oncology, dermatology, rheumatology, neurology, and the treatment of intestinal diseases. An analysis was made of most actual sources published for 2021–2022. The review is focused on the comparative characteristics of polymer gels in terms of their toxicity to cells and the release rate of drugs from nano-sized hydrogel systems, which are crucial initial features for their further possible application in mentioned areas of biomedicine. Different proposed mechanisms of drug release from gels depending on their structure, composition, and application are summarized and presented. The review may be useful for medical professionals, and pharmacologists dealing with the development of novel drug delivery vehicles.

Multifunctional Oxidized Succinoglycan/Poly(N-isopropylacrylamide-co-acrylamide) Hydrogels for Drug Delivery

We prepared the self-healing and temperature/pH-responsive hydrogels using oxidized succinoglycan (OSG) and a poly (N-isopropyl acrylamide-co-acrylamide) [P(NIPAM-AM)] copolymer. OSG was synthesized by periodate oxidation of succinoglycan (SG) isolated directly from soil microorganisms, Sinorhizobium meliloti Rm1021. The OSG/P(NIPAM-AM) hydrogels were obtained by introducing OSG into P(NIPAM-AM) networks. The chemical structure and physical properties of these hydrogels were characterized by ATR-FTIR, XRD, TGA, and FE-SEM. The OSG/P(NIPAM-AM) hydrogels showed improved elasticity, increased thermal stability, new self-healing ability, and 4-fold enhanced tensile strength compared with the P(NIPAM-AM) hydrogels. Furthermore, the 5-FU-loaded OSG/P(NIPAM-AM) hydrogels exhibited effective temperature/pH-responsive drug release. Cytotoxicity experiments showed that the OSG/P(NIPAM-AM) hydrogels were non-toxic, suggesting that OSG/P(NIPAM-AM) hydrogels could have the potential for biomedical applications, such as stimuli-responsive drug delivery systems, wound healing, smart scaffolds, and tissue engineering.

A Self-Healing, Magnetic and Injectable Biopolymer Hydrogel Generated by Dual Cross-Linking for Drug Delivery and Bone Repair

Injectable hydrogels based on various functional biocompatible materials have made rapid progress in the field of bone repair. In this study, a self-healing and injectable polysaccharide-based hydrogel was prepared for bone tissue engineering. The hydrogel was made of carboxymethyl chitosan (CMCS) and calcium pre-cross-linked oxidized gellan gum (OGG) cross-linked by the Schiff-base reaction. Meanwhile, magnetic hydroxyapatite/gelatin microspheres (MHGMs) were prepared by the emulsion cross-linking method. The antibacterial drugs, tetracycline hydrochloride (TH) and silver sulfadiazine (AgSD), were embedded into the MHGMs. To improve the mechanical and biological properties of the hydrogels, composite hydrogels were prepared by compounding hydroxyapatite (HAp) and drug-embedded MHGMs. The physical, chemical, mechanical and rheological properties of the composite hydrogels were characterized, as well as in vitro antibacterial tests and biocompatibility assays, respectively. Our results showed that the composite hydrogel with 6% (w/v) HAp and 10 mg/mL MHGMs exhibited good magnetic responsiveness, self-healing and injectability. Compared with the pure hydrogel, the composite hydrogel showed a 38.8% reduction in gelation time (196 to 120 s), a 65.6% decrease in swelling rate (39.4 to 13.6), a 51.9% increase in mass residual after degradation (79.5 to 120.8%), and a 143.7% increase in maximum compressive stress (53.6 to 130.6 KPa). In addition, this composite hydrogel showed good drug retardation properties and antibacterial effects against both S. aureus and E. coli. CCK-8 assay showed that composite hydrogel maintained high cell viability (> 87%) and rapid cell proliferation after 3 days, indicating that this smart hydrogel is expected to be an alternative scaffold for drug delivery and bone regeneration. STATEMENT OF SIGNIFICANCE: Biopolymer hydrogels have been considered as the promising materials for the treatment of tissue engineering and drug delivery. Injectable hydrogels with and self-healing properties and responsiveness to external stimuli have been extensively investigated as cell scaffolds and bone defects, due to their diversity and prolonged lifetime. Magnetism has also been involved in biomedical applications and played significant roles in targeted drug delivery and anti-cancer therapy. We speculate that development of dual cross-linked hydrogels basing biopolymers with multi-functionalities, such as injectable, self-healing, magnetic and anti-bacterial properties, would greatly broaden the application for bone tissue regeneration and drug delivery.

Injectable light-assisted thermo-responsive methylcellulose-sodium humate hydrogel proposed for photothermal ablation and localized delivery of cisplatin

This study aimed to develop injectable light-assisted thermo-responsive methylcellulose hydrogels filled with sodium humate, which were proposed for photothermal ablation and localized cisplatin delivery. Sodium humate converts light energy from laser beams into thermal energy, which causes methylcellulose to gel, thereby controlling the release of chemotherapy agents. Meanwhile, light emission causes to the photothermal ablation of tumor cells. For determining the optimal production conditions, different concentrations of sodium humate and light emission times were investigated. Results show that hydrogel uniformity is highly dependent on variables. An increase in sodium humate concentration and emission time resulted in a slight reduction in swelling ratio and an increase in durability. According to the simulation conditions, the cisplatin release profile was consistent with a non-Fickian mechanism with a predominant erosion contribution. In conjugation with increasing light emission time and sodium humate content, the storage modulus and viscosity increased, demonstrating hydrogel’s sol-gel transition and long-lasting durability. The intrinsic fluorescence spectroscopy study revealed that the hydrogel-model protein complex empowered hydrogel bio-performance. Laser emission and cisplatin release synergistically reduced the number of viable osteosarcoma cell lines, suggesting the possibility of tumor ablation. This study describes the potential of simultaneous photothermal therapy and chemotherapy in osteosarcoma treatment, laying the groundwork for future preclinical and clinical trials.

Cerium oxide decorated 5-fluorouracil loaded chitosan nanoparticles for treatment of hepatocellular carcinoma

Reactive oxygen species (ROS) play a crucial role in the mammalian system in both normal and pathological conditions. Hence, this work prepared and characterized the ROS responsive cerium oxide nanoparticles (CeO₂ NPs) decorated 5-fluorouracil (5FU) loaded chitosan (CS) nanoparticles (CS-5FU NPs) for enhanced anticancer activity in hepatocellular carcinoma (HepG2 cells). CeO₂ NPs decorated CS-5FU NPs were found to be spherical in shape and black dense aggregated particles sized 200 nm. The functional properties and cubic crystalline structure of CeO₂ NPs were studied by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis, respectively. Further, CS-5FU-CeO₂ NPs attenuated the 2,2'-Azobis (2-methylpropionamidine) dihydrochloride (AAPH) induced ROS formation in mouse embryonic fibroblasts (NIH3T3 cells) while enhancing apoptotic cell death in HepG2 cells by controlled delivery of 5FU. Furthermore, CS-5FU-CeO₂ NPs have not exhibited toxicity to red blood cells (RBCs) and chick chorioallantoic membrane (CAM). Hence, this work concluded that CeO₂ NPs decorated CS-5FU NPs synergistically enhanced anticancer activity in HepG2 cells through the regulation of ROS.

CSH/SBE-β-CD nanoparticles: controlled synthesis and application for loading and pH-responsive drug release

CSH and SBE-β-CD were assembled via electrostatic interaction and hydrogen bonding for the loading and pH-responsive release of BSA.