Self-healing, injectable hydrogel based on dual dynamic covalent cross-linking against postoperative abdominal cavity adhesion

Progress in chitin/chitosan and their derivatives for biomedical applications: Where we stand

Chitin and its deacetylated form, chitosan, have demonstrated remarkable versatility in the realm of biomaterials. Their exceptional biocompatibility, antibacterial properties, pro- and anticoagulant characteristics, robust antioxidant capacity, and anti-inflammatory potential make them highly sought-after in various applications. This review delves into the mechanisms underlying chitin/chitosan's biological activity and provides a comprehensive overview of their derivatives in fields such as tissue engineering, hemostasis, wound healing, drug delivery, and hemoperfusion. However, despite the wealth of studies on chitin/chitosan, there exists a notable trend of homogeneity in research, which could hinder the comprehensive development of these biomaterials. This review, taking a clinician's perspective, identifies current research gaps and medical challenges yet to be addressed, aiming to pave the way for a more sustainable future in chitin/chitosan research and application.

Microenvironment-Responsive Hydrogel Enclosed with Bioactive Nanoparticle for Synergistic Postoperative Adhesion Prevention

Postoperative adhesion (PA) is a severe complication of abdominal surgery caused by the inability of clinical physical barriers to cope with diverse pathological factors in the process of PA formation. Herein, we described a multifunctional hydrogel composed of bioactive nanoparticles (BNs) and dual-responsive hydrogel to serve as a combination of physical and pharmacological therapy for preventing PA. Specifically, BNs with pro-inflammatory cell-targeted aggregation were designed by integrating hyaluronic acid onto the polydopamine (PDA)-coated hollow ZrO2 nanoparticles loaded with antimicrobial peptides and platelet lysates that can eliminate bacterial infection and promote tissue repair. PDA can remove the excessive reactive oxygen species (ROS) and thus suppress the oxidative stress damage and accompanying inflammation in the presence of high ROS. The dynamically cross-linked host hydrogel presents injectable yet microenvironment-responsive properties, which enables complete coverage of the uneven tissue and instantly forms a physical barrier to effectively isolate injured tissues and neighboring organs, and synchronously acts as a niche to deliver the BNs in a controlled way. The hydrogel demonstrates a remarkable antiadhesion effect in a rat cecum-abdominal wall adhesion model. Together, this "all-in-one" composite hydrogel strategy capable of a physical barrier capability and pharmacological effects represents a promising clinical solution to prevent PA.

Injectable and pH-Responsive Metformin-Loaded Hydrogel for Active Inhibition of Posterior Capsular Opacification

Posterior capsular opacification (PCO) is a common complication following cataract surgery, which can lead to a significant vision loss. This study introduces a facile method for developing a metformin-derived hydrogel (HCM6) stabilized by dynamic covalent bonds among natural polymers. This hydrogel demonstrates antifibrotic properties, on-demand drug release, pH responsiveness, injectability, and self-healing capabilities. Our in vitro experiments confirmed that the HCM6 hydrogel exhibits excellent biocompatibility, inhibiting lens epithelial cell migration, and transforming growth factor-2β (TGFβ2)-induced α-smooth muscle actin (α-SMA) expression in lens epithelial cells. In vivo studies conducted in a rat extracapsular lens extraction (ECLE) model revealed that HCM6 significantly suppressed PCO after 21 days of implantation with no observed pathological effects on surrounding tissues or the optic nerve. According to our experimental results, the inhibitory mechanism of PCO may be attributed to metformin's suppressive effect on lens cell migration, epithelial-mesenchymal transition (EMT), and lens fiber formation. In summary, the long-acting, controllable, and on-demand release characteristics of the HCM6 hydrogel not only provide an effective strategy for preventing PCO but also offer new avenues for treating undesirable proliferative conditions in ophthalmology and beyond.

Injectable polyamide-amine dendrimer-crosslinked meloxicam-containing poly-γ-glutamic acid hydrogel for prevention of postoperative tissue adhesion through inhibiting inflammatory responses and balancing the fibrinolytic system

Establishing a physical barrier between the peritoneum and the cecum is an effective method to reduce the risk of postoperative abdominal adhesions. Meloxicam (MX), a nonsteroidal anti-inflammatory drug has also been applied to prevent postoperative adhesions. However, its poor water solubility has led to low bioavailability. Herein, we developed an injectable hydrogel as a barrier and drug carrier for simultaneous postoperative adhesion prevention and treatment. A third-generation polyamide-amine dendrimer (G3) was exploited to dynamically combine with MX to increase the solubility and the bioavailability. The formed G3@MX was further used to crosslink with poly-γ-glutamic acid (γ-PGA) to prepare a hydrogel (GP@MX hydrogel) through the amide bonding. In vitro and in vivo experiments evidenced that the hydrogel had good biosafety and biodegradability. More importantly, the prepared hydrogel could control the release of MX, and the released MX is able to inhibit inflammatory responses and balance the fibrinolytic system in the injury tissues in vivo. The tunable rheological and mechanical properties (compressive moduli: from ∼ 57.31 kPa to ∼ 98.68 kPa;) and high anti-oxidant capacity (total free radical scavenging rate of ∼ 94.56 %), in conjunction with their syringeability and biocompatibility, indicate possible opportunities for the development of advanced hydrogels for postoperative tissue adhesions management.

An Environmentally Stable, Biocompatible, and Multilayered Wound Dressing Film with Reversible and Strong Adhesion

Reversible adhesives for wound care improve patient experiences by permitting reuse and minimizing further tissue injury. Existing reversible bandages are vulnerable to water and can undergo unwanted deformation during removal and readdressing procedures. Here, a biocompatible, multilayered, reversible wound dressing film that conforms to skin and is waterproof is designed. The inner layer is capable of instant adhesion to various substrates upon activation of the dynamic boronic ester bonds by water; intermediate hydrogel layer and outer silicone backing layer can enhance the dressing's elasticity and load distribution for adhesion, and the silicone outer layer protects the dressing from exposure to water. The adhesive layer is found to be biocompatible with mouse skin. Skin injuries on the mouse skin heal more rapidly with the film compared to no dressing controls. Evaluations of the film on skin of freshly euthanized minipigs corroborate the findings in the mouse model. The film remains attached to skins without delamination despite subjecting to various degrees of deformation. Exposure to water softens the film to allow removal from the skin without pulling any hair off. The multilayered design considers soft mechanics in each layer and will offer new insights to improve wound dressing performance and patient comfort.

A ROS-responsive and scavenging hydrogel for postoperative abdominal adhesion prevention

Postoperative abdominal adhesion (PAA) widely occurs after abdominal surgery, which often produces severe complications. However, there were still no satisfactory anti-adhesive products including barriers and anti-adhesive agents. Herein, we developed a ROS-responsive and scavenging hydrogel barrier, termed AHBC/PSC, wherein the monomer AHBC was synthesized by phenylboronic acid (PBA)-modified hyaluronic acid (HA-PBA) further grafted with adipic dihydrazide (ADH) and PBA-based chlorogenic acid (CGA) via ROS-sensitive borate ester bond, and the other monomer PSC was constructed by polyvinyl alcohol (PVA) grafted with sulfated betaine (SB) and p-hydroxybenzaldehyde (CHO). Further, the double crosslinked AHBC/PSC hydrogel was successfully fabricated between AHBC and PSC via forming dynamic covalent acylhydrazone bonds and borate ester bonds. Results showed that AHBC/PSC hydrogel had in situ gelation behavior, satisfactory mechanical properties (storage modulus of about 1 kPa and loss factor Tan δ of about 0.5), suitable wet tissue adhesion strength of about 2.3 kPa on rat abdominal wall, and good biocompatibility, achieving an ideal physical barrier. Particularly, CGA could be responsively released from the hydrogel by breakage of borate ester bonds between CGA and PBA based on high reactive oxygen species (ROS) levels of damaged tissue and exhibited great ROS scavenging capability to regulate inflammation and promote the polarization of macrophages from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. Moreover, the grafted SB as a zwitterionic group could reduce protein adsorption and fibroblast adhesion. Finally, the in vivo experiments revealed that AHBC/PSC hydrogel with good safety and in vivo retention behavior of about 2 weeks, effectively prevented PAA by regulating the inflammatory microenvironment and alleviating the fibrosis process. In brief, the versatile AHBC/PSC hydrogel would provide a more convenient and efficient approach for PAA prevention. STATEMENT OF SIGNIFICANCE: Postoperative abdominal adhesion (PAA) widely occurs after surgery and is often accompanied by severe complications. Excessive inflammation and oxidative stress are very crucial for PAA formation. This study provides a ROS-responsive and scavenging hydrogel with suitable mechanical properties, good biocompatibility and biodegradability, and resistance to protein and fibroblast. The antioxidant and anti-inflammatory active ingredient could be responsively released from the hydrogel via triggering by the high ROS levels in the postoperative microenvironment thereby regulating the inflammatory balance. Finally, the hydrogel would effectively regulate the development process of PAA thereby achieving non-adhesion wound healing.

Injectable Nanocomposite Hydrogels Improve Intraperitoneal Co-delivery of Chemotherapeutics and Immune Checkpoint Inhibitors for Enhanced Peritoneal Metastasis Therapy

Intraperitoneal co-delivery of chemotherapeutic drugs (CDs) and immune checkpoint inhibitors (ICIs) brings hope to improve treatment outcomes in patients with peritoneal metastasis from ovarian cancer (OC). However, current intraperitoneal drug delivery systems face issues such as rapid drug clearance from lymphatic drainage, heterogeneous drug distribution, and uncontrolled release of therapeutic agents into the peritoneal cavity. Herein, we developed an injectable nanohydrogel by combining carboxymethyl chitosan (CMCS) with bioadhesive nanoparticles (BNPs) based on polylactic acid-hyperbranched polyglycerol. This system enables the codelivery of CD and ICI into the intraperitoneal space to extend drug retention. The nanohydrogel is formed by cross-linking of aldehyde groups on BNPs with amine groups on CMCS via reversible Schiff base bonds, with CD and ICI loaded separately into BNPs and CMCS network. BNP/CMCS nanohydrogel maintained the activity of the biomolecules and released drugs in a sustained manner over a 7 day period. The adhesive property, through the formation of Schiff bases with peritoneal tissues, confers BNPs with an extended residence time in the peritoneal cavity after being released from the nanohydrogel. In a mouse model, BNP/CMCS nanohydrogel loaded with paclitaxel (PTX) and anti-PD-1 antibodies (αPD-1) significantly suppressed peritoneal metastasis of OC compared to all other tested groups. In addition, no systemic toxicity of nanohydrogel-loaded PTX and αPD-1 was observed during the treatment, which supports potential translational applications of this delivery system.

Rapid in situ formation of κ-carrageenan-carboxymethyl chitosan-kaolin clay hydrogel films enriched with arbutin for enhanced preservation of cherry tomatoes

Food waste resulting from perishable fruits and vegetables, coupled with the utilization of non-renewable petroleum-based packaging materials, presents pressing challenges demanding resolution. This study addresses these critical issues through the innovative development of a biodegradable functional plastic wrap. Specifically, the proposed solution involves the creation of a κ-carrageenan/carboxymethyl chitosan/arbutin/kaolin clay composite film. This film, capable of rapid in-situ formation on the surfaces of perishable fruits, adeptly conforms to their distinct shapes. The incorporation of kaolin clay in the composite film plays a pivotal role in mitigating water vapor and oxygen permeability, concurrently bolstering water resistance. Accordingly, tensile strength of the composite film experiences a remarkable enhancement, escalating from 20.60 MPa to 34.71 MPa with the incorporation of kaolin clay. The composite film proves its efficacy by preserving cherry tomatoes for an extended period of 9 days at 28 °C through the deliberate delay of fruit ripening, respiration, dehydration and microbial invasion. Crucially, the economic viability of the raw materials utilized in the film, coupled with the expeditious and straightforward preparation method, underscores the practicality of this innovative approach. This study thus introduces an easy and sustainable method for preserving perishable fruits, offering a cost-effective and efficient alternative to petroleum-based packaging materials.

NIR-Responsive injectable hydrogel cross-linked by homobifunctional PEG for photo-hyperthermia of melanoma, antibacterial wound healing, and preventing post-operative adhesion

Current therapeutic approaches for skin cancer face significant challenges, including wound infection, delayed skin regeneration, and tumor recurrence. To overcome these challenges, an injectable adhesive near-infrared (NIR)-responsive hydrogel with time-dependent enhancement in viscosity is developed for combined melanoma therapy and antibacterial wound healing acceleration. The multifunctional hydrogel is prepared through the chemical crosslinking between poly(methyl vinyl ether-alt-maleic acid) and gelatin, followed by the incorporation of CuO nanosheets and allantoin. The synergistic inherent antibacterial potential of CuO nanosheets, the regenerative and smoothing effect of allantoin, the extracellular matrix-mimicking effect of gelatin, and the desirable swelling behavior of the hydrogel results in fast wound recovery after photothermal ablation of the tumor. Additionally, the hydrogel can serve as an alternative to sutures owing to its tissue adhesiveness ability, which can further render it the merits for accelerated repair of abdominal lesions while acting as a biocompatible barrier to prevent peritoneal adhesion.

Hemoadhican-Based Bioabsorbable Hydrogel for Preventing Postoperative Adhesions

Postoperative peritoneal adhesions are a prevalent clinical issue following abdominal and pelvic surgery, frequently resulting in heightened personal and societal health burdens. Traditional biomedical barriers offer limited benefits because of practical challenges for doctors and their incompatibility with laparoscopic surgery. Hydrogel materials, represented by hyaluronic acid gels, are receiving increasing attention. However, existing antiadhesive gels still have limited effectiveness or carry the risk of complications in clinical applications. Herein, we developed a novel hydrogel using polysaccharide hemoadhican (HD) as the base material and polyethylene glycol diglycidyl ether (PEGDE) as the cross-linking agent. The HD hydrogels exhibit appropriate mechanical properties, injectability, and excellent cytocompatibility. We demonstrate resistance to protein adsorption and L929 fibroblast cell adhesion to the HD hydrogel. The biodegradability and efficacy against peritoneal adhesion are further evaluated in C57BL/6 mice. Our results suggest a potential strategy for anti-postoperative tissue adhesion barrier biomaterials.

A Review of Advanced Abdominal Wall Hernia Patch Materials

Tension-free abdominal wall hernia patch materials (AWHPMs) play an important role in the repair of abdominal wall defects (AWDs), which have a recurrence rate of <1%. Nevertheless, there are still significant challenges in the development of tailored, biomimetic, and extracellular matrix (ECM)-like AWHPMs that satisfy the clinical demands of abdominal wall repair (AWR) while effectively handling post-operative complications associated with abdominal hernias, such as intra-abdominal visceral adhesion and abnormal healing. This extensive review presents a comprehensive guide to the high-end fabrication and the precise selection of these advanced AWHPMs. The review begins by briefly introducing the structures, sources, and properties of AWHPMs, and critically evaluates the advantages and disadvantages of different types of AWHPMs for AWR applications. The review subsequently summarizes and elaborates upon state-of-the-art AWHPM fabrication methods and their key characteristics (e.g., mechanical, physicochemical, and biological properties in vitro/vivo). This review uses compelling examples to demonstrate that advanced AWHPMs with multiple functionalities (e.g., anti-deformation, anti-inflammation, anti-adhesion, pro-healing properties, etc.) can meet the fundamental clinical demands required to successfully repair AWDs. In particular, there have been several developments in the enhancement of biomimetic AWHPMs with multiple properties, and additional breakthroughs are expected in the near future.

One-Step Synthesis of Hydrogel Adhesive with Acid-Responsive Tannin Release for Diabetic Oral Mucosa Defects Healing

The complex preparation, weak wet tissue adhesion, and limited biological activity of traditional oral wound dressings usually impede their efficient treatment and healing for diabetic oral mucosal defects. To overcome these problems, a novel hydrogel adhesive (named CFT hydrogel) is rapidly constructed using a one-step method based on dual-dynamic covalent cross-linking. Compared with the commercial oral patches, the CFT hydrogel shows superior in vivo (rat tongue) wet tissue adhesion performance. Additionally, the CFT hydrogel exhibits unique acid-responsive properties, thereby facilitating the release of bioactive molecule tannic acid in the acidic diabetic wound microenvironment. And a series of in vitro experiments substantiate the favorable biocompatibility and bioactivity properties (including antibacterial, antioxidative, anti-inflammatory, and angiogenetic effects) exhibited by CFT hydrogel. Moreover, in vivo experiments conducted on a diabetic rat model with oral mucosal defects demonstrate that the CFT hydrogel exhibits significant efficacy in protecting against mucosal wounds, alleviating inflammatory reactions, thereby facilitating the wound-healing process. Taken together, this study provides a promising and comprehensive therapeutic option with great potential for the clinical management of oral mucosa defects in diabetic patients.

Injectable hydrogels as promising in situ therapeutic platform for cartilage tissue engineering

Injectable hydrogels are gaining prominence as a biocompatible, minimally invasive, and adaptable platform for cartilage tissue engineering. Commencing with their synthesis, this review accentuates the tailored matrix formulations and cross-linking techniques essential for fostering three-dimensional cell culture and melding with complex tissue structures. Subsequently, it spotlights the hydrogels' enhanced properties, highlighting their augmented functionalities and broadened scope in cartilage tissue repair applications. Furthermore, future perspectives are advocated, urging continuous innovation and exploration to surmount existing challenges and harness the full clinical potential of hydrogels in regenerative medicine. Such advancements are crucial for validating the long-term efficacy and safety of hydrogels, positioning them as a promising direction in regenerative medicine to address cartilage-related ailments.

Inducing in situ M2 macrophage polarization to promote the repair of bone defects via scaffold-mediated sustained delivery of luteolin

Immunoregulation mediated bone tissue engineering (BTE) has demonstrated huge potential in promoting repair of critical-size bone defects (CSBDs). The trade-off between stable immunoregulation function and extended immunoregulation period has posed a great challenge to this strategy. Here, we reported a 3D porous biodegradable Poly(HEMA-co-3APBA)/LUT scaffold, in which reversible boronic acid ester bond was formed between the 3APBA moiety and the catechol moiety of luteolin (LUT). The boronic acid ester bond not only protected the bioactivity of LUT but also extended the release period of LUT. The rationale behind the phenomenon of sustained LUT release was explained using a classical transition state theory. In vitro/in vivo assays proved the immunoregulation function of the scaffold in inducing M2 polarization of both M0 and M1 Mφ. The crosstalk between the scaffold treated Raw 264.7 and BMSCs were also investigated through the in vitro co-culture assay. The results demonstrated that the scaffold could induce immunoregulation mediated osteogenic differentiation of BMSCs. In addition, CSBDs model of SD rats was also applied, and the corresponding data proved that the scaffold could accelerate new bone formation, therefore promoting repair of CSBDs. The as-prepared scaffold might be a promising candidate for repair of CSBDs in the future.

Injectable Multifunctional Composite Hydrogel as a Combination Therapy for Preventing Postsurgical Adhesion

Postsurgical adhesion (PA) is a common and serious postoperative complication that affects millions of patients worldwide. However, current commercial barrier materials are insufficient to inhibit diverse pathological factors during PA formation, and thus, highly bioactive materials are needed. Here, this work designs an injectable multifunctional composite hydrogel that can serve as a combination therapy for preventing PA. In brief, this work reveals that multiple pathological events, such as chronic inflammatory and fibrotic processes, contribute to adhesion formation in vivo, and such processes can not be attenuated by barrier material (e.g., hydrogel) alone treatments. To solve this limitation, this work designs a composite hydrogel made of the cationic self-assembling peptide KLD2R and TGF-β receptor inhibitor (TGF-βRi)-loaded mesenchymal stem cell-derived nanovesicles (MSC-NVs). The resulting composite hydrogel displays multiple functions, including physical separation of the injured tissue areas, antibacterial effects, and local delivery and sustained release of anti-inflammatory MSC-NVs and antifibrotic TGF-βRi. As a result, this composite hydrogel effectively inhibited local inflammation, fibrosis and adhesion formation in vivo. Moreover, the hydrogel also exhibits good biocompatibility and biodegradability in vivo. Together, the results highlight that this "all-in-one" composite hydrogel strategy may provide insights into designing advanced therapies for many types of tissue injury.

Multifunctional Oxidized Dextran-Metformin as a Tissue-Adhesive Hydrogel to Prevent Postoperative Peritoneal Adhesions in Patients with Metabolic Syndrome

Patients with metabolic syndrome (MetS) undergoing surgery are at high risk of developing peritoneal adhesions and other severe postoperative complications. However, the single shielding function and absence of physiological activity render conventional methods less useful in preventing adhesions in patients with MetS. To address this challenge, a convenient method is introduced for developing a novel tissue-adhesive hydrogel called oxidized dextran-metformin (ODE-ME) via Schiff base linkages. This injectable ODE-ME hydrogel exhibits excellent tissue-adhesive properties and various physiological functions, particularly enhanced antibacterial effects. Furthermore, in vivo experiments demonstrate that the hydrogel can effectively alleviate hyperglycemia, reduce excessive inflammation, and improve fibrinolytic activity in MetS mice, thereby preventing adhesions and promoting incisional healing. The hydrogel concurrently isolates injured tissues and lowers the blood glucose levels immediately after surgery in mice. Therefore, the ODE-ME hydrogel functions as a multifunctional barrier material and has potential for preventing postoperative peritoneal adhesions in patients with MetS in clinical settings.

Degradable carrier-free spray hydrogel based on self-assembly of natural small molecule for prevention of postoperative adhesion

Postoperative peritoneal adhesion (PPA) is frequent and extremely dangerous complication after surgery. Different tactics have been developed to reduce it. However, creating a postoperative adhesion method that is multifunctional, biodegradable, biocompatible, low-toxic but highly effective, and therapeutically applicable is still a challenge. Herein, we have prepared a degradable spray glycyrrhetinic acid hydrogel (GAG) based on natural glycyrrhetinic acid (GA) by straightforward heating and cooling without the use of any additional chemical cross-linking agents to prevent postoperative adhesion. The resultant hydrogel was demonstrated to possess various superior anti-inflammatory activity, and multiple functions, such as excellent degradability and biocompatibility. Specifically, spraying characteristic and excellent antibacterial activities essentially eliminated secondary infections during the administration of drugs in surgical wounds. In the rat models, the carrier-free spray GAG could not only slow-release GA to inhibit inflammatory response, but also serve as physical anti-adhesion barrier to reduce collagen deposition and fibrosis. The sprayed GAG would shed a new light on the prevention of postoperative adhesion and broaden the application of the hydrogels based on natural products in biomedical fields.

A hydrogel system for drug loading toward the synergistic application of reductive/heat-sensitive drugs

The preparation of hydrogels as drug carriers via radical-mediated polymerization has significant prospects, but the strong oxidizing ability of radicals and the high temperatures generated by the vigorous reactions limits the loading for reducing/heat-sensitive drugs. Herein, an applicable hydrogel synthesized by radical-mediated polymerization is reported for the loading and synergistic application of specific drugs. First, the desired sol is obtained by polymerizing functional monomers using a radical initiator, and then tannic-acid-assisted specific drug mediates sol-branched phenylboric acid group to form the required functional hydrogel (New-gel). Compared with the conventional single-step radical-mediated drug-loading hydrogel, the New-gel not only has better chemical/physical properties but also efficiently loads and releases drugs and maintains drug activity. Particularly, the New-gel has excellent loading capacity for oxygen, and exhibits significant practical therapeutic effects for diabetic wound repair. Furthermore, owing to its high light transmittance, the New-gel synergistically promotes the antibacterial effect of photosensitive drugs. This gelation strategy for loading drugs has further promising biomedical applications.

Cascade enzymatic preparation of carboxymethyl chitosan-based multifunctional hydrogels for promoting cutaneous wound healing

Designing wound dressings with inherent multifunctional therapeutic effects is desirable for clinical applications. Herein, a series of multifunctional carboxymethyl chitosan (CMCS)-based hydrogels were fabricated by the facile urate oxidase (UOX)-horseradish peroxidase (HRP) cascade enzymatic crosslinking system. For the first time, the cascade enzymatic crosslinking system was not only used for preparing hydrogel wound dressings but also for accelerating wound healing due to the activity retention of the self-compartmental enzymes. A CMCS derivative (HCMCS-mF) synthesized by successively grafting 4-hydroxybenzaldehyde (H) and 5-methylfurfural (mF) on CMCS and a quaternary ammonium crosslinker (QMal) with terminal grafting maleimide (Mal) groups were combined with enzymatic system for the facile preparation of hydrogels. The mild Diels-Alder (DA) crosslinking reaction between mF and Mal groups constructed the first network of hydrogels. The cascade UOX-HRP system mediated the oxidative crosslinking of phenols thus forming the second gel network. Self-entrapped UOX maintained its enzymatic activity and could continuously catalyze the oxidation of uric acid, generating therapeutic allantoin. These porous, degradable, mechanically stable hydrogels with excellent antioxidant performance and enhanced antibacterial capacity could effectively accelerate skin wound repair by simultaneously reducing oxidative stress, relieving inflammation, promoting collagen deposition and upregulating the expression level of CD31.

Degradable Temperature-Sensitive Hydrogel Loaded with Heparin Effectively Prevents Post-Operative Tissue Adhesions

Tissue adhesions could occur following surgeries, and severe tissue adhesions can lead to serious complications. Medical hydrogels could be applied at surgical sites as a physical barrier to prevent tissue adhesion. For practical reasons, spreadable, degradable, and self-healable gels are highly demanded. To meet these requirements, we applied carboxymethyl chitosan (CMCS) to poloxamer-based hydrogels to generate low Poloxamer₃₃₈ (P₃₃₈) content gels displaying low viscosity at refrigerator temperature and improved mechanical strength at body temperature. Heparin, an effective adhesion inhibitor, was also added to construct P₃₃₈/CMCS-heparin composite hydrogel (PCHgel). PCHgel presents as a flowable liquid below 20 °C and could rapidly transform into gel when spread on the surface of damaged tissue due to temperature change. The introduction of CMCS enabled hydrogels to form a stable self-healable barrier at injured positions and slowly release heparin during the wound healing period before being degraded after ∼14 days. Ultimately, PCHgel significantly reduced tissue adhesion in model rats and displayed higher efficiency than P₃₃₈/CMCS gel without heparin. Its adhesion suppression mechanism was verified, and it also displayed good biosafety. Therefore, PCHgel showed good clinical transformation potential with high efficacy, good safety, and ease of use.

Advances in Functional Hydrogel Wound Dressings: A Review

One of the most advanced, promising, and commercially viable research issues in the world of hydrogel dressing is gaining functionality to achieve improved therapeutic impact or even intelligent wound repair. In addition to the merits of ordinary hydrogel dressings, functional hydrogel dressings can adjust their chemical/physical properties to satisfy different wound types, carry out the corresponding reactions to actively create a healing environment conducive to wound repair, and can also control drug release to provide a long-lasting benefit. Although a lot of in-depth research has been conducted over the last few decades, very few studies have been properly summarized. In order to give researchers a basic blueprint for designing functional hydrogel dressings and to motivate them to develop ever-more intelligent wound dressings, we summarized the development of functional hydrogel dressings in recent years, as well as the current situation and future trends, in light of their preparation mechanisms and functional effects.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Room-Temperature Self-Healing Conductive Elastomers for Modular Assembly as a Microfluidic Electrochemical Biosensing Platform for the Detection of Colorectal Cancer Exosomes

Modular components for rapid assembly of microfluidics must put extra effort into solving leakage and alignment problems between individual modules. Here, we demonstrate a conductive elastomer with self-healing properties and propose a modular microfluidic component configuration system that utilizes self-healing without needing external interfaces as an alternative to the traditional chip form. Specifically, dual dynamic covalent bond crosslinks (imine and borate ester bonds) established between Polyurethane (PU) and 2-Formylbenzeneboronic acid (2-FPBA) are the key to a hard room-temperature self-healing elastomeric substrate PP (PU/2-FPBA). An MG (MXene/GO) conductive network with stable layer spacing (Al-O bonds) obtained from MXene and graphene oxide (GO) by in situ reduction of metals confers photothermal conductivity to PP. One-step liquid molding obtained a standardized modular component library of puzzle shapes from PP and MGPP (MG/PP). The exosomes were used to validate the performance of the constructed microfluidic electrochemical biosensing platform. The device has a wide detection range (50-10⁵ particles/μL) and a low limit of detection (LOD) (42 particles/μL) (S/N = 3), providing a disposable, reusable, cost-effective, and rapid analysis platform for quantitative detection of colorectal cancer exosomes. In addition, to our knowledge, this is the first exploration of self-healing conductive elastomers for a modular microfluidic electrochemical biosensing platform.

Multifunctional Microgel-Based Cream Hydrogels for Postoperative Abdominal Adhesion Prevention

Postoperative abdominal adhesions are a common problem after surgery and can produce serious complications. Current antiadhesive strategies focus mostly on physical barriers and are unsatisfactory and inefficient. In this study, we designed and synthesized advanced injectable cream-like hydrogels with multiple functionalities, including rapid gelation, self-healing, antioxidation, anti-inflammation, and anti-cell adhesion. The multifunctional hydrogels were facilely formed by the conjugation reaction of epigallocatechin-3-gallate (EGCG) and hyaluronic acid (HA)-based microgels and poly(vinyl alcohol) (PVA) based on the dynamic boronic ester bond. The physicochemical properties of the hydrogels including antioxidative and anti-inflammatory activities were systematically characterized. A mouse cecum-abdominal wall adhesion model was implemented to investigate the efficacy of our microgel-based hydrogels in preventing postoperative abdominal adhesions. The hydrogels, with a high molecular weight HA, significantly decreased the inflammation, oxidative stress, and fibrosis and reduced the abdominal adhesion formation, compared to the commercial Seprafilm group or Injury-only group. Label-free quantitative proteomics analysis demonstrated that S100A8 and S100A9 expressions were associated with adhesion formation; the microgel-containing hydrogels inhibited these expressions. The microgel-containing hydrogels with multifunctionality decreased the formation of postoperative intra-abdominal adhesions in a murine model, demonstrating promise for clinical applications.

The Controlled Release and Prevention of Abdominal Adhesion of Tannic Acid and Mitomycin C-Loaded Thermosensitive Gel

Postoperative abdominal adhesion is one of the most common complications after abdominal surgery. A single drug or physical barrier treatment does not achieve the ideal anti-adhesion effect. We developed a thermosensitive hydrogel (PPH hydrogel) consisting of poloxamer 407 (P407), poloxamer (P188), and hydroxypropyl methylcellulose (HPMC) co-blended. An injectable thermosensitive TA/MMC-PPH hydrogel was obtained by loading tannic acid (TA) with an anti-inflammatory effect and mitomycin C (MMC), which inhibits fibroblast migration or proliferation. The optimal prescriptions of PPH hydrogels with a suitable gelling time (63 s) at 37 °C was 20% (w/v) P407, 18% (w/v) P188, and 0.5% (w/v) HPMC. The scanning electron microscopy (SEM) revealed that the PPH hydrogel had a three-dimensional mesh structure, which was favorable for drug encapsulation. The PPH hydrogel had a suitable gelation temperature of 33 °C, a high gel strength, and complicated viscosity at 37 °C, according to the rheological analysis. In vitro release studies have shown that the PPH hydrogel could delay the release of TA and MMC and conform to the first-order release rate. Anti-adhesion tests performed on rats in vivo revealed that TA/MMC-PPH hydrogel significantly reduced the risk of postoperative adhesion. In conclusion, the TA/MMC-PPH hydrogel prepared in this study showed an excellent performance in both controlled drug release and anti-adhesive effects. It can be used as a protocol to prevent or reduce postoperative abdominal adhesion.

Gallium-modified gelatin nanoparticles loaded with quercetin promote skin wound healing via the regulation of bacterial proliferation and macrophage polarization

Background: Wound healing is a complicated process involving multiple cell components and can help the re-establishment of the skin's barrier function. Previous studies have pointed out that bacterial infection and sustained inflammatory reactions are the main causes of the delay of wound closure and scar formation during wound healing. The effect of current approaches for scar-free wound repair still faces many challenges, and alternative therapeutic methods are urgently needed to be established. Methods: The basic characteristics of the new-designed nanoparticles were clarified through the characterization of the material. The biocompatibility of the nanoparticles, as well as its effect on fibroblast function, anti-bacterial capacity, inflammation suppressive role, and the underlying mechanism were further verified by a panel of biochemical assays in vitro. Ultimately, pre-clinical rat model was employed to testify its role in wound healing and scar formation in vivo. Results: Firstly, gallium-modified gelatin nanoparticles loaded with quercetin was successfully established, displaying good biocompatibility and facilitative effect on fibroblast function. In addition, the nanoparticles showed prominent anti-bacterial and inflammation-suppressive effects. What's more important, the nanoparticles could also induce the polarization of macrophages from M1 to M2 phenotype to exert its inflammatory inhibitory role through TGF-β/Smad signaling pathway. Ultimately, in vivo experiment showed that the nanoparticles could effectively promote wound repair and inhibit scar formation during the process of wound healing. Conclusion: Taken together, the new nanoparticles have good anti-bacterial and anti-scar formation effects and great potential in the field of skin wound repair, which provides a promising therapeutic strategy for wound treatment.