Cellulose nanocrystals reinforced highly stretchable thermal-sensitive hydrogel with ultra-high drug loading

Electroconductive Nanocellulose, a Versatile Hydrogel Platform: From Preparation to Biomedical Engineering Applications

Nanocelluloses have garnered significant attention recently in the attempt to create sustainable, improved functional materials. Nanocellulose possesses wide varieties, including rod-shaped crystalline cellulose nanocrystals and elongated cellulose nanofibers, also known as microfibrillated cellulose. In recent times, nanocellulose has sparked research into a wide range of biomedical applications, which vary from developing 3D printed hydrogel to preparing structures with tunable characteristics. Owing to its multifunctional properties, different categories of nanocellulose, such as cellulose nanocrystals, cellulose nanofibers, and bacterial nanocellulose, as well as their unique properties are discussed here. Here, different methods of nanocellulose-based hydrogel preparation are covered, which include 3D printing and crosslinking methods. Subsequently, advanced nanocellulose-hydrogels addressing conductivity, shape memory, adhesion, and structural color are highlighted. Finally, the application of nanocellulose-based hydrogel in biomedical applications is explored here. In summary, numerous perspectives on novel approaches based on nanocellulose-based research are presented here.

Progress in the Application of Multifunctional Composite Hydrogels in Promoting Tissue Repair

Tissue repair is an extremely complex process, and effectively promoting tissue regeneration remains a significant clinical challenge. Hydrogel materials, which exhibit physical properties closely resembling those of living tissues, including high water content, oxygen permeability, and softness, have the potential to revolutionize the field of tissue repair. However, the presence of various complex conditions, such as infection, ischemia, and hypoxia in tissue defects, means that hydrogels with simple structures and functions are often insufficient to meet the diverse needs of tissue repair. Researchers have focused on integrating multiple drugs, nanomaterials, bioactive substances, and stem cells into hydrogel matrices to develop novel multifunctional composite hydrogels for addressing these challenges, which have superior antibacterial properties, hemostatic abilities, self-healing capacities, and excellent mechanical properties. These composite hydrogels are designed to enhance tissue repair and have become an important direction in the current research. This review provides a comprehensive review of the recent advances in the application of multifunctional composite hydrogels in promoting tissue repair, including drug-loaded hydrogels, nanomaterial composite hydrogels, bioactive substance composite hydrogels, and stem cell composite hydrogels.

Butterfly wing-inspired superhydrophobic photonic cellulose nanocrystal films for vapor sensors and asymmetric actuators

Cellulose nanocrystals (CNCs)-based stimuli responsive photonic materials demonstrate great application potential in mechanical and chemical sensors. However, due to the hydrophilic property of cellulose molecular, a significant challenge is to build a water-resistant photonic CNCs material. Here, inspired by butterfly wings with vivid structural color and superhydrophobic property, we have designed a CNCs based superhydrophobic iridescent film with hierarchical structures. The iridescent colored layer is ascribed to the chiral nematic alignment of CNCs, the superhydrophobic layer is ascribed to the micro-nano structures of polymer microspheres. Specially, superhydrophobic iridescent CNCs film could be used as an efficient colorimetric humidity sensor due to the existence of 'stomates' on superhydrophobic layer, which allowed the humid gas to enter into and out from the humidity responsive chiral nematic layers. Meanwhile, superhydrophobic iridescent films show out-standing self-cleaning and anti-fouling performance. Moreover, when the one side of the CNCs film was covered with superhydrophobic layer, the Janus film displays asymmetric expansion and bending behaviors as well as responsive structural colors in hydrous ethanol. This CNCs based hierarchical photonic materials have promising applications including photonic sensors suitable for extreme environment and smart photonic actuators.

Tunicate cellulose nanocrystals strengthened injectable stretchable hydrogel as multi-responsive enhanced antibacterial wound dressing for promoting diabetic wound healing

The intricate microenvironment of diabetic wounds characterized by hyperglycemia, intense oxidative stress, persistent bacterial infection and complex pH fluctuations hinders the healing process. Herein, an injectable multifunctional hydrogel (QPTx) was developed, which exhibited excellent mechanical performance and triple responsiveness to pH, temperature, and glucose due to dynamic covalent cross-linking involving dynamic Schiff base bonds and phenylboronate esters with phenylboronic-modified quaternized chitosan (QCS-PBA), polydopamine coated tunicate cellulose crystals (PDAn@TCNCs) and polyvinyl alcohol (PVA). Furthermore, the hydrogels can incorporate insulin (INS) drugs to adapt to the complex and variable wound environment in diabetic patients for on-demand drug release that promote diabetic wound healing. Based on various excellent properties of the colloidal materials, the hydrogels were evaluated for self-healing, rheological and mechanical properties, in vitro insulin response to pH/temperature/glucose release, antibacterial, antioxidant, tissue adhesion, coagulation, hemostasis in vivo and in vitro, and biocompatibility and biodegradability. By introducing PDAn@TCNCs particles, the hydrogel has photothermal antibacterial activity, enhanced adhesion and oxidation resistance. We further demonstrated that these hydrogel dressings significantly improved the healing process compared to commercial dressings (Tegaderm™) in full-layer skin defect models. All indicated that the glucose-responsive QPTx hydrogel platform has great potential for treating diabetic wounds.

Recent Progress in Implantable Drug Delivery Systems

In recent years, tremendous effort is devoted to developing platforms, such as implantable drug delivery systems (IDDSs), with temporally and spatially controlled drug release capabilities and improved adherence. IDDSs have multiple advantages: i) the timing and location of drug delivery can be controlled by patients using specific stimuli (light, sound, electricity, magnetism, etc.). Some intelligent "closed-loop" IDDS can even realize self-management without human participation. ii) IDDSs enable continuous and stable delivery of drugs over a long period (months to years) and iii) to administer drugs directly to the lesion, thereby helping reduce dosage and side effects. iv) IDDSs enable personalized drug delivery according to patient needs. The high demand for such systems has prompted scientists to make efforts to develop intelligent IDDS. In this review, several common stimulus-responsive mechanisms including endogenous (e.g., pH, reactive oxygen species, proteins, etc.) and exogenous stimuli (e.g., light, sound, electricity, magnetism, etc.), are given in detail. Besides, several types of IDDS reported in recent years are reviewed, including various stimulus-responsive systems based on the above mechanisms, radio frequency-controlled IDDS, "closed-loop" IDDS, self-powered IDDS, etc. Finally, the advantages and disadvantages of various IDDS, bottleneck problems, and possible solutions are analyzed to provide directions for subsequent research.

Mussel-inspired tissue adhesive composite hydrogel with photothermal and antioxidant properties prepared from pectin for burn wound healing

Biodegradable self-healing hydrogels with antibacterial property attracted growing attentions in biomedication as wound dressings since they can prevent bacterial infection and promote wound healing process. In this research, a biodegradable self-healing hydrogel with ROS scavenging performance and enhanced tissue adhesion was fabricated from dopamine grafted oxidized pectin (OPD) and naphthoate hydrazide terminated PEO (PEO NH). At the same time, Fe3+ ions were incorporated to endow the hydrogel with near-infrared (NIR) triggered photothermal property to obtain antibacterial activity. The composite hydrogel showed good hemostasis performance based on mussel inspired tissue adhesion with biocompatibility well preserved. As expected, the composition of FeCl3 improved conductivity and endowed photothermal property to the hydrogel. The in vivo wound repairing experiment revealed the 808 nm NIR light triggered photothermal behavior of the hydrogel reduced the inflammation response and promoted wound repairing rate. As a result, this composite FeCl3/hydrogel shows great potential to be an excellent wound dressing for the treatment of infection prong wounds with NIR triggers.

Recent advances on thermosensitive hydrogels-mediated precision therapy

Precision therapy has become the preferred choice attributed to the optimal drug concentration in target sites, increased therapeutic efficacy, and reduced adverse effects. Over the past few years, sprayable or injectable thermosensitive hydrogels have exhibited high therapeutic potential. These can be applied as cell-growing scaffolds or drug-releasing reservoirs by simply mixing in a free-flowing sol phase at room temperature. Inspired by their unique properties, thermosensitive hydrogels have been widely applied as drug delivery and treatment platforms for precision medicine. In this review, the state-of-the-art developments in thermosensitive hydrogels for precision therapy are investigated, which covers from the thermo-gelling mechanisms and main components to biomedical applications, including wound healing, anti-tumor activity, osteogenesis, and periodontal, sinonasal and ophthalmic diseases. The most promising applications and trends of thermosensitive hydrogels for precision therapy are also discussed in light of their unique features.

Wound microenvironment self-adaptive all-in-one hydrogel for rapid healing of the diabetic wound

The natural healing of diabetic wounds is collectively impeded by multiple factors, including hyperglycemia, angiogenesis disorders, acute oxidative stress, and prolonged inflammation. Although considerable effort has been devoted to solving these problems, the treatment of diabetic wounds remains a major clinical obstacle. In light of this, we developed an innovative wound microenvironment self-adaptive hydrogel to promote the healing of diabetic wounds. The hydrogel was constructed by the crosslinking of 3-aminobenzeneboronic acid (PBA)-modified gelatin (Gel) and polyvinyl alcohol (PVA) by borate ester bonds, which showed high responsiveness to glucose. Meanwhile, the liposomes that encapsulated metformin, L-arginine, and L(+)-ascorbic acid were incorporated into the hydrogel framework. The hydrogel@lipo composite demonstrated shape adaptability, glucose responsiveness, and all-in-one capability, thereby effectively improving the intricate microenvironment of diabetic wounds. In vitro and in vivo experiments demonstrated the ability of hydrogel@lipo to mitigate oxidative stress, enhance angiogenesis, and attenuate inflammatory responses. Consequently, the hydrogel@lipo could accelerate diabetic wound healing (within two weeks). The cumulative findings strongly suggest the potential of hydrogel@lipo as a highly promising therapeutic dressing for advancing diabetic wound recovery.

Designing Composite Stimuli-Responsive Hydrogels for Wound Healing Applications: The State-of-the-Art and Recent Discoveries

Effective wound treatment has become one of the most important challenges for healthcare as it continues to be one of the leading causes of death worldwide. Therefore, wound care technologies significantly evolved in order to provide a holistic approach based on various designs of functional wound dressings. Among them, hydrogels have been widely used for wound treatment due to their biocompatibility and similarity to the extracellular matrix. The hydrogel formula offers the control of an optimal wound moisture level due to its ability to absorb excess fluid from the wound or release moisture as needed. Additionally, hydrogels can be successfully integrated with a plethora of biologically active components (e.g., nanoparticles, pharmaceuticals, natural extracts, peptides), thus enhancing the performance of resulting composite hydrogels in wound healing applications. In this review, the-state-of-the-art discoveries related to stimuli-responsive hydrogel-based dressings have been summarized, taking into account their antimicrobial, anti-inflammatory, antioxidant, and hemostatic properties, as well as other effects (e.g., re-epithelialization, vascularization, and restoration of the tissue) resulting from their use.

Gel/hydrogel-based in situ biomaterial platforms for cancer postoperative treatment and recovery

Tumor surgical resection is the major strategy for cancer treatment. Meanwhile, perioperative treatment especially the postoperative adjuvant anticancer strategies play essential roles in satisfying therapeutic results and rapid recovery. Postoperative tumor recurrence, metastasis, bleeding, inter-tissue adhesion, infection, and delayed wound healing are vital risks that could lead to poor prognosis or even treatment failure. Therefore, methods targeting these postoperative complications are in desperate need. In situ biomaterial-based drug delivery platforms are promising candidates for postoperative treatment and recovery, resulting from their excellent properties including good biocompatibility, adaptive shape, limited systemic effect, designable function, and easy drug loading. In this review, we focus on introducing the gel/hydrogel-based in situ biomaterial platforms involving their properties, advantages, and synthesis procedures. Based on the loaded contents in the gel/hydrogel such as anticancer drugs, immunologic agents, cell components, and multifunctional nanoparticles, we further discuss the applications of the in situ platforms for postoperative tumor recurrence and metastasis inhibition. Finally, other functions aiming at fast postoperative recovery were introduced, including hemostasis, antibacterial infection, adhesion prevention, tissue repair, and wound healing. In conclusion, gel/hydrogel is a developing and promising platform for postoperative treatment, exhibiting gratifying therapeutic effects and inconspicuous toxicity to normal tissues, which deserves further research and exploration.

Cellulose Nanocrystal (CNC) Gels: A Review

The aim of this article is to review the research conducted in the field of aqueous and polymer composites cellulose nanocrystal (CNC) gels. The experimental techniques employed to characterize the rheological behavior of these materials will be summarized, and the main advantages of using CNC gels will also be addressed in this review. In addition, research devoted to the use of numerical simulation methodologies to describe the production of CNC-based materials, e.g., in 3D printing, is also discussed. Finally, this paper also discusses the application of CNC gels along with additives such as cross-linking agents, which can represent an enormous opportunity to develop improved materials for manufacturing processes.

Insight into the Latest Medical Applications of Nanocellulose

Nanocelluloses (NCs) are appealing nanomaterials that have experienced rapid development in recent years, with great potential in the biomedical field. This trend aligns with the increasing demand for sustainable materials, which will contribute both to an improvement in wellbeing and an extension of human life, and with the demand to keep up with advances in medical technology. In recent years, due to the diversity of their physical and biological properties and the possibility of tuning them according to the desired goal, these nanomaterials represent a point of maximum interest in the medical field. Applications such as tissue engineering, drug delivery, wound dressing, medical implants or those in cardiovascular health are some of the applications in which NCs have been successfully used. This review presents insight into the latest medical applications of NCs, in the forms of cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs) and bacterial nanocellulose (BNC), with an emphasis on the domains that have recently experienced remarkable growth, namely wound dressing, tissue engineering and drug delivery. In order to highlight only the most recent achievements, the presented information is focused on studies from the last 3 years. Approaches to the preparation of NCs are discussed either by top-down (chemical or mechanical degradation) or by bottom-up (biosynthesis) techniques, along with their morphological characterization and unique properties, such as mechanical and biological properties. Finally, the main challenges, limitations and future research directions of NCs are identified in a sustained effort to identify their effective use in biomedical fields.

Stimulus-Responsive Drug Delivery Nanoplatforms for Osteoarthritis Therapy

Osteoarthritis (OA) is one of the most prevalent age-related degenerative diseases. With an increasingly aging global population, greater numbers of OA patients are providing clear economic and societal burdens. Surgical and pharmacological treatments are the most common and conventional therapeutic strategies for OA, but often fall considerably short of desired or optimal outcomes. With the development of stimulus-responsive nanoplatforms has come the potential for improved therapeutic strategies for OA. Enhanced control, longer retention time, higher loading rates, and increased sensitivity are among the potential benefits. This review summarizes the advanced application of stimulus-responsive drug delivery nanoplatforms for OA, categorized by either those that depend on endogenous stimulus (reactive oxygen species, pH, enzyme, and temperature), or those that depend on exogenous stimulus (near-infrared ray, ultrasound, magnetic fields). The opportunities, restrictions, and limitations related to these various drug delivery systems, or their combinations, are discussed in areas such as multi-functionality, image guidance, and multi-stimulus response. The remaining constraints and potential solutions that are represented by the clinical application of stimulus-responsive drug delivery nanoplatforms are finally summarized.

Preparation, thermal response mechanisms and biomedical applications of thermosensitive hydrogels for drug delivery

INTRODUCTION

Drug treatment is one of the main ways of coping with disease today. For the disadvantages of drug management, thermosensitive hydrogel is used as a countermeasure, which can realize the simple sustained release of drugs and the controlled release of drugs in complex physiological environments.

AREAS COVERED

This paper talks about thermosensitive hydrogels that can be used as drug carriers. The common preparation materials, material forms, thermal response mechanisms, characteristics of thermosensitive hydrogels for drug release and main disease treatment applications are reviewed.

EXPERT OPINION

When thermosensitive hydrogels are used as drug loading and delivery platforms, desired drug release patterns and release profiles can be tailored by selecting raw materials, thermal response mechanisms, and material forms. The properties of hydrogels prepared from synthetic polymers will be more stable than natural polymers. Integrating multiple thermosensitive mechanisms or different kinds of thermosensitive mechanisms on the same hydrogel is expected to realize the spatiotemporal differential delivery of multiple drugs under temperature stimulation. The industrial transformation of thermosensitive hydrogels as drug delivery platforms needs to meet some important conditions.

Photothermal Hydrogels for Promoting Infected Wound Healing

Photothermal therapies (PTT), with spatiotemporally controllable antibacterial capabilities without inducing resistance, have shown encouraging prospects in the field of infected wound treatments. As an important platform for PTT, photothermal hydrogels exhibit attractive advantages in the field of infected wound treatment due to their excellent biochemical properties and have been intensively explored in recent years. This review summarizes the progress of the photothermal hydrogels for promoting infected wound healing. Three major elements of photothermal hydrogels, i.e., photothermal materials, hydrogel matrix, and construction methods, are introduced. Furthermore, different strategies of photothermal hydrogels in the treatment of infected wounds are summarized. Finally, the challenges and prospects in the clinical treatment of photothermal hydrogels are discussed.

Nanocellulose-based drug carriers: Functional design, controllable synthesis, and therapeutic applications

With rising living standards and environmental awareness, materials-oriented chemical engineering has increasingly transitioned from traditional rough models to more resource-saving and eco-friendly models, providing an avenue for bio-based materials in the drug carrier field. Because of its excellent physical and chemical properties, including high specific surface area, abundant accessible hydroxyl groups, biocompatibility, and degradability, nanocellulose (NC) is an emerging bio-based material that has been widely exploited as biomedical materials. The modification techniques of NC, as well as advancements in the design and applications of drug carriers, were primarily discussed in this study. First, the NC modification methods are described; second, the applications of NC and its derivatives as drug carriers are summarized, focusing on NC-based carrier models, types of loaded therapeutic agents, and controlled release stimulators; and finally, the current challenges of NC in the drug carrier field and the directions of future research are also discussed.

Cellulose Nanocrystals-Incorporated Thermosensitive Hydrogel for Controlled Release, 3D Printing, and Breast Cancer Treatment Applications

In situ-gel-forming thermoresponsive copolymers have been widely exploited in controlled delivery applications because their critical gel temperature is similar to human body temperature. However, there are limitations to controlling the delivery of biologics from a hydrogel network because of the poor networking and reinforcement between the copolymer networks. This study developed an in situ-forming robust injectable and 3D printable hydrogel network based on cellulose nanocrystals (CNCs) incorporated amphiphilic copolymers, poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide (PCLA). In addition, the physicochemical and mechanical properties of injectable hydrogels were controlled by physically incorporating CNCs with amphiphilic PCLA copolymers. CNCs played an unprecedented role in physically reinforcing the PCLA copolymers' micelle network via intermicellar bridges. Apart from that, the free-flowing closely packed rod-like CNCs incorporated PCLA micelle networks at low temperature transformed to a stable viscoelastic hydrogel network at physiological temperature. CNC incorporated PCLA copolymer sols effectively coordinated with hydrophobic doxorubicin and water-soluble lysozyme by a combination of hydrophobic and hydrogen bonding interaction and controlled the release of biologics. As shown by the 3D printing results, the biocompatible PCLA hydrogels continuously extruded during printing had good injectability and maintained high shape fidelity after printing without any secondary cross-linking steps. The interlayer bonding between the printed layers was high and formed stable 3D structures up to 10 layers. Subcutaneous injection of free-flowing CNC incorporated PCLA copolymer sols to BALB/c mice formed a hydrogel instantly and showed controlled biodegradation of the hydrogel depot without induction of toxicity at the implantation sites or surrounding tissues. At the same time, the in vivo antitumor effect on the MDA-MB-231 tumor xenograft model demonstrated that DOX-loaded hydrogel formulation significantly inhibited the tumor growth. In summary, the CNC incorporated biodegradable hydrogels developed in this study exhibit a prolonged release with special release kinetics for hydrophobic and hydrophilic biologics.

Hydrogel Combined with Phototherapy in Wound Healing

Wound healing is a complex biological process that involves tissue regeneration. Traditional wound dressings are dry, cannot provide a moist environment for wound healing, and do not have high antibacterial properties. Hydrogels, which are capable of retaining large amounts of water, can create a moist healing environment. Currently, phototherapies have exhibited a high potential for the treatment of bacterial infections. Therefore, combining hydrogels with phototherapy can adequately overcome the shortcomings of traditional wound treatment methods and show great potential for wound healing owing to their high efficiency, low irritation, and good antibacterial performance. In this review, the application of hydrogels combined with phototherapy in wound healing is summarized. First, the basic principles of photodynamic therapy and photothermal therapy are briefly introduced. In addition, the progress of the application of hydrogel combined with phototherapy in wound healing is systematically investigated. Finally, the challenges and prospects of combining hydrogel with phototherapy in wound healing are discussed.

Poly(N-isopropylacrylamide)-Based Hydrogels for Biomedical Applications: A Review of the State-of-the-Art

A prominent research topic in contemporary advanced functional materials science is the production of smart materials based on polymers that may independently adjust their physical and/or chemical characteristics when subjected to external stimuli. Smart hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) demonstrate distinct thermoresponsive features close to a lower critical solution temperature (LCST) that enhance their capability in various biomedical applications such as drug delivery, tissue engineering, and wound dressings. Nevertheless, they have intrinsic shortcomings such as poor mechanical properties, limited loading capacity of actives, and poor biodegradability. Formulation of PNIPAM with diverse functional constituents to develop hydrogel composites is an efficient scheme to overcome these defects, which can significantly help for practicable application. This review reports on the latest developments in functional PNIPAM-based smart hydrogels for various biomedical applications. The first section describes the properties of PNIPAM-based hydrogels, followed by potential applications in diverse fields. Ultimately, this review summarizes the challenges and opportunities in this emerging area of research and development concerning this fascinating polymer-based system deep-rooted in chemistry and material science.

Aggressive strategies for regenerating intervertebral discs: stimulus-responsive composite hydrogels from single to multiscale delivery systems

As our research on the physiopathology of intervertebral disc degeneration (IVD degeneration, IVDD) has advanced and tissue engineering has rapidly evolved, cell-, biomolecule- and nucleic acid-based hydrogel grafting strategies have been widely investigated for their ability to overcome the harsh microenvironment of IVDD. However, such single delivery systems suffer from excessive external dimensions, difficult performance control, the need for surgical implantation, and difficulty in eliminating degradation products. Stimulus-responsive composite hydrogels have good biocompatibility and controllable mechanical properties and can undergo solution-gel phase transition under certain conditions. Their combination with ready-to-use particles to form a multiscale delivery system may be a breakthrough for regenerative IVD strategies. In this paper, we focus on summarizing the progress of research on the stimulus response mechanisms of regenerative IVD-related biomaterials and their design as macro-, micro- and nanoparticles. Finally, we discuss multi-scale delivery systems as bioinks for bio-3D printing technology for customizing personalized artificial IVDs, which promises to take IVD regenerative strategies to new heights.

A rapid-triggered approach towards antibacterial hydrogel wound dressing with synergic photothermal and sterilization profiles

Developing non-antibiotic-dependent antibacterial hydrogels for repairing infected skin defect remains largely unexplored. Herein, a synergic photothermal and synergic antibacterial hydrogel was designed via one-pot approach to cope with full-thickness skin wound infection. In this work, the mixture of silver‑sodium lignin sulfonate nanoparticles (Ag-SLS NPs) and polypyrrole-polydopamine nanoparticles (PPy-PDA NPs) for the first time as synergic photothermal agent was introduced into poly (ethylene glycol) diacrylate (PEGDA) to form Ag-SLS/PPy-PDA@PEGDA hydrogel. Thanks to the near-infrared light into heat conversion capacity of both Ag and PPy-PDA NPs, the formed hydrogel shows ultrahigh photothermal activity, and outstanding antibacterial activity to both Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria in vitro. Additionally, in vivo assay indicates that the hydrogel has outstanding long-term antibacterial effect due to the photothermal sterilization along with Ag ions release. Overall, the dual-synergic photothermal and antibacterial effects of the Ag-SLS/PPy-PDA@PEGDA hydrogel could highly accelerate infection wound healing, and thus has great potential to be used for tissue engineering.

High-resolution 3D printing of xanthan gum/nanocellulose bio-inks

The current study provides a comprehensive rheology study and a survey on direct ink writing of xanthan gum/cellulose nanocrystal (XG/CNC) bio-inks for developing 3D geometries that mimic soft tissue engineering scaffolds' physical and mechanical properties. The presence of CNC was found to be a critical prerequisite for the printability of XG bio-inks; accordingly, the hybrid XG/CNC bio-inks revealed the excellent viscoelastic properties that enabled precise control of hydrogel shaping and printing of lattice structures composed of up to eleven layers with high fidelity and fair resolution without any deformation after printing. The lyophilized 3D scaffolds presented a porous structure with open and interconnected pores and a porosity higher than 70%, vital features for tissue engineering scaffolds. Moreover, they showed a relatively high swelling of approximately 11 g/g, facilitating oxygen and nutrient exchange. Furthermore, the elastic and compressive moduli of the scaffolds that enhanced significantly upon increasing CNC content were in the range of a few kPa, similar to soft tissues. Finally, no significant cell cytotoxicity was observed against human liver cancer cells (HepG2), highlighting the potential of these developed 3D printed scaffolds for soft tissue engineering applications.

Tea polyphenol/glycerol-treated double-network hydrogel with enhanced mechanical stability and anti-drying, antioxidant and antibacterial properties for accelerating wound healing

Frequent dressing changes can result in secondary wound damage. Therefore, it is of great significance to construct a wound dressing that can be used for a long time without changing. Here, a double-network hydrogel was synthesized through hydrogen bonding interactions of tea polyphenol (TP)/glycerol with photo-crosslinked N-acryloyl glycinamide (NAGA), gelatin methacrylate (GelMA), and nanoclay hydrogel. The glycerol/water solvent slowed the diffusion of TP into the NAGA/GelMA/Laponite (NGL)hydrogel, thereby avoiding excessive crosslinking, and forming a uniform network. The hydrogel exhibited excellent water retention (84% within 28 days). Additionally, due to the hygroscopicity of glycerol, the hydrogel's mechanical strength (0.73-1.14 MPa) and tensile strain (207%-353%) increased further after 14 days in an open environment. Additionally, the hydrogel exhibited superior anti-ultraviolet and antioxidant properties, which effectively alleviated the wound site's oxidative stress and accelerated wound healing. Moreover, antibacterial activity was observed against both E. coli and S. aureus in the hydrogel wound dressing. Thus, by promoting wound closure, angiogenesis and collagen deposition, the double-network NGLG20/TG hydrogel dressing can successfully accelerate wound healing. The multifunctional double-network hydrogel, therefore, shows immense potential as an ideal candidate for wound dressings because it is long-lasting and prevents secondary damage caused by frequent dressing changes.

Enhanced postoperative cancer therapy by iron-based hydrogels

Surgical resection is a widely used method for the treatment of solid tumor cancers. However, the inhibition of tumor recurrence and metastasis are the main challenges of postoperative tumor therapy. Traditional intravenous or oral administration have poor chemotherapeutics bioavailability and undesirable systemic toxicity. Polymeric hydrogels with a three-dimensional network structure enable on-site delivery and controlled release of therapeutic drugs with reduced systemic toxicity and have been widely developed for postoperative adjuvant tumor therapy. Among them, because of the simple synthesis, good biocompatibility, biodegradability, injectability, and multifunctionality, iron-based hydrogels have received extensive attention. This review has summarized the general synthesis methods and construction principles of iron-based hydrogels, highlighted the latest progress of iron-based hydrogels in postoperative tumor therapy, including chemotherapy, photothermal therapy, photodynamic therapy, chemo-dynamic therapy, and magnetothermal-chemical combined therapy, etc. In addition, the challenges towards clinical application of iron-based hydrogels have also been discussed. This review is expected to show researchers broad perspectives of novel postoperative tumor therapy strategy and provide new ideas in the design and application of novel iron-based hydrogels to advance this sub field in cancer nanomedicine.