Fouling-resistant zwitterionic polymers for complete prevention of postoperative adhesion

An injectable and antifouling hydrogel prevents the development of abdominal adhesions by inhibiting the CCL2/CCR2 interaction

Abdominal adhesion, a serious complication of abdominal surgery, often resists mitigation by current drug administration and physical barriers. To address this issue, we developed an injectable, antifouling hydrogel through the free-radical polymerization of methacrylate chondroitin sulfate (CS-GMA) and 2-methacryloyloxyethyl phosphorylcholine (MPC) monomers, dubbed the CGM hydrogel. We systematically analyzed its physicochemical properties, including rheological strength, biocompatibility, and antifouling capabilities. A rat abdominal cecum adhesion model was constructed to assess the effectiveness of CGM hydrogel in preventing postoperative adhesion and recurrent adhesion. In addition, multi-omics analyses identified the relationship between adhesion development and CCL2/CCR2 interaction. Notably, CGM hydrogel can thwart the recruitment and aggregation of fibroblasts and macrophages by inhibiting the CCL2/CCR2 interaction. Moreover, CGM hydrogel significantly dampens the activity of fibrosis-linked cytokines (TGF-βR1) and recalibrates extracellular matrix deposition-related cytokines (t-PA and PAI-1, Col Ⅰ and MMP-9). Cumulatively, the dual action of CGM hydrogel-as a physical barrier and cytokine regulator-highlights its promising potential in clinical application for abdominal adhesion prevention.

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.

A bifunctional nanocomplex with remineralizing and antibacterial activities to interrupt dental caries

Dental caries result from an imbalance between the demineralization and remineralization of dental hard tissues, primarily caused by biofilm accumulation. According to the theory of interrupting dental caries, effective anticaries materials and techniques should possess both remineralizing and antibacterial properties. However, current anticaries materials fail to mimic the process of amelogenesis to achieve remineralization while inhibiting the adhesion of cariogenic bacteria and the formation of biofilms. In this study, silk fibroin (SF) loaded with benzalkonium chloride (BZC) successfully formed an SF-BZC composite. This composite stabilized amorphous calcium phosphate (ACP), creating an ACP@SF-BZC dual-functional nanocomplex with both remineralizing and antibacterial properties. ACP@SF-BZC demonstrated significant anti-adhesion and biofilm inhibitory effects against Streptococcus mutans and Streptococcus sobrinus. Moreover, compared to fluoride, ACP@SF-BZC significantly enhanced the remineralization of demineralized enamel surfaces, forming a stable remineralized layer with improved mechanical properties, both in vitro and in vivo. In summary, the dual-function ACP@SF-BZC nanocomplex, with its remineralizing and antibacterial effects, offers a promising alternative for preventing and arresting enamel caries.

An injectable and biodegradable zwitterionic gel for extending the longevity and performance of insulin infusion catheters

Continuous subcutaneous insulin infusion (CSII) is an essential insulin replacement therapy in the management of diabetes. However, the longevity of clinical CSII is limited by skin complications, by impaired insulin absorption and by occlusions associated with the subcutaneous insertion of CSII catheters, which require replacement and rotation of the insertion site every few days. Here we show that a biodegradable zwitterionic gel covering the tip end of commercial off-the-shelf CSII catheters fully resolves early skin irritations, extends the longevity of catheters and improves the rate of insulin absorption (also with respect to conventional syringe-based subcutaneous injection) for longer than 6 months in diabetic mice, and by 11 days in diabetic minipigs (from 2 to 13 days, under standard CSII-wearing conditions of insulin pump therapy and in a continuous basal-plus-bolus-infusion setting). The implanted gel displayed anti-inflammatory and anti-foreign-body-reaction properties and promoted the local formation of new blood vessels. The gel is subcutaneously injected before the tip of catheter is inserted into it, and should be generally applicable to CSII catheters and other implantable devices.

A self-fused peptide-loaded hydrogel with injectability and tissue-adhesiveness for preventing postoperative peritoneal adhesions

Peritoneal adhesions commonly occur following abdominal or pelvic surgery and can cause serious complications. Currently, physical barriers are the primary approach used in clinical practice to prevent adhesion, although their effectiveness is frequently inadequate. In this study, we developed an injectable peptide-loaded hydrogel with multiple functions, including self-fusion, tissue-adhesiveness, anti-inflammation, anti-cell adhesion and anti-angiogenesis. To assess the effectiveness of these hydrogels, which are stabilized by dynamic imine bonds and acetal connections, in preventing postoperative abdominal adhesions, we utilized both a rat abdominal adhesion model and a rat model simulating repeated-injury adhesions. In comparison to the commercially available HA hydrogel, as-prepared hydrogels exhibited significant reductions in inflammation, fibrosis, and angiogenesis, leading to an obvious decrease in peritoneal adhesions. Moreover, this peptide-loaded hydrogel demonstrated an ideal degradation time, maintaining an in vivo viability for about 10 days. We believe this peptide-loaded hydrogel presents a promising solution for the challenging clinical issue of postoperative abdominal adhesions.

Neutrophil Extracellular Traps-Inhibiting and Fouling-Resistant Polysulfoxides Potently Prevent Postoperative Adhesion, Tumor Recurrence, and Metastasis

Peritoneal metastasis (PM) is considered one of the most dreaded forms of cancer metastases for both patients and physicians. Aggressive cytoreductive surgery (CRS) is the primary treatment for peritoneal metastasis. Unfortunately, this intensive treatment frequently causes clinical complications, such as postoperative recurrence, metastasis, and adhesion formation. Emerging evidence suggests that neutrophil extracellular traps (NETs) released by inflammatory neutrophils contribute to these complications. Effective NET-targeting strategies thus show considerable potential in counteracting these complications but remain challenging. Here, one type of sulfoxide-containing homopolymer, PMeSEA, with potent fouling-resistant and NET-inhibiting capabilities, is synthesized and screened. Hydrating sulfoxide groups endow PMeSEA with superior nonfouling ability, significantly inhibiting protein/cell adhesion. Besides, the polysulfoxides can be selectively oxidized by ClO- which is required to stabilize the NETs rather than H2O2, and ClO- scavenging effectively inhibits NETs formation without disturbing redox homeostasis in tumor cells and quiescent neutrophils. As a result, PMeSEA potently prevents postoperative adhesions, significantly suppresses peritoneal metastasis, and shows synergetic antitumor activity with chemotherapeutic 5-Fluorouracil. Moreover, coupling CRS with PMeSEA potently inhibits CRS-induced tumor metastatic relapse and postoperative adhesions. Notably, PMeSEA exhibits low in vivo acute and subacute toxicities, implying significant potential for clinical postoperative adjuvant treatment.

Nonswellable Hydrogel Patch with Tissue-Mimetic Mechanical Characteristics Remodeling In Vivo Microenvironment for Effective Adhesion Prevention

Postoperative adhesion is a common complication after abdominal surgery, but current clinical products have unsatisfactory therapeutic effects. Here, we present a hydrogel patch formed in a single step through dialysis. The exchange of DMSO into water facilitates hydrophobic aggregate in situ formation and the formation of hydrogen bonds within the hydrogel. Thanks to the optimized component ratio and precise structural design. The hydrogel patch has soft-tissue-like mechanical characteristics, including high strength, high toughness, low modulus similar to the abdominal wall, good fatigue resistance, and fast self-recovery properties. The nonswellable hydrogel patch retains over 80% of its original mechanical properties after 7 days of immersion in physiological saline, with a maximum swelling ratio of 5.6%. Moreover, the hydrophobic biomultifunctionality of benzyl isothiocyanate can self-assemble onto the hydrogel patch during the sol-gel transition process, enabling it to remodel the inflammatory microenvironment through synergistic antibacterial, antioxidant, and anti-inflammatory effects. The hydrogel patch prevents postsurgical adhesion in a rat sidewall defect-cecum abrasion model and outperforms the leading commercial Interceed. It holds promising potential for clinical translation, considering that FDA-approved raw materials (PVA and gelatin) form the backbone of this effective hydrogel patch.

Hybrid Bioactive Hydrogel Promotes Liver Regeneration through the Activation of Kupffer Cells and ECM Remodeling After Partial Hepatectomy

Partial hepatectomy is an essential surgical technique used to treat advanced liver diseases such as liver tumors, as well as for performing liver transplants from living donors. However, postoperative complications such as bleeding, abdominal adhesions, wound infections, and inadequate liver regeneration pose significant challenges and increase morbidity and mortality rates. A self-repairing mixed hydrogel (O5H2/Cu2+/SCCK), containing stem cell derived cytokine (SCCK) derived from human umbilical cord mesenchymal stem cells (HUMSCs) treated with the traditional Chinese remedy Tanshinone IIA (TSA), is developed. This SCCK, in conjunction with O5H2, demonstrates remarkable effects on Kupffer cell activation and extracellular matrix (ECM) remodeling. This leads to the secretion of critical growth factors promoting enhanced proliferation of hepatocytes and endothelial cells, thereby facilitating liver regeneration and repair after partial hepatectomy. Furthermore, the hydrogel, featuring macrophage-regulating properties, effectively mitigates inflammation and oxidative stress damage in the incision area, creating an optimal environment for postoperative liver regeneration. The injectability and strong adhesion of the hydrogel enables rapid hemostasis at the incision site, while its physical barrier function prevents postoperative abdominal adhesions. Furthermore, the hydrogel's incorporation of Cu2+ provides comprehensive antibacterial effects, protecting against a wide range of bacteria types and reducing the chances of infections after surgery.

The Unprecedented Biodegradable Polyzwitterion: A Removal-Free Patch for Accelerating Infected Diabetic Wound Healing

Zwitterionic polymers have emerged as an important class of biomaterials to construct wound dressings and antifouling coatings over the past decade due to their excellent hydrophilicity. However, all the reported zwitterionic polymers as wound dressings are nondegradable because of noncleavable carbon─carbon bonding backbones, and must be removed periodically after treatment to avoid hypoxia in the wound, thus leading to potential secondary injury. In this work, a biodegradable polyzwitterion patch is fabricated for the first time by ring-opening polymerization of carboxybetaine dithiolane (CBDS), which is self-crosslinked via inter-amide hydrogen bonds and zwitterionic dipole-dipole interactions on the side chains. The unprecedented polyCBDS (PCBDS) patch demonstrates enough ductility owing to the intermolecular physical interactions to fully cover irregular wounds, also showing excellent biodegradability and antifouling performance resulted from the existence of disulfide bonds and carboxybetaine groups. Besides, the PCBDS degradation-induced released CBDS owns potent antioxidant and antibacterial activities. This PCBDS patch is used as a diabetic wound dressing, inhibiting bacterial adhesion on the external surface, and its degradation products can exactly kill bacteria and scavenge excessive reactive oxygen species (ROS) at the wound site to regulate local microenvironment, including regulation of cytokine express and macrophage polarization, accelerating infected diabetic wound repair, and also avoiding the potential secondary injury.

Injectable and Dynamically Crosslinked Zwitterionic Hydrogels for Anti-Fouling and Tissue Regeneration Applications

A zwitterionic injectable and degradable hydrogel based on hydrazide and aldehyde-functionalized [2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl)ammonium hydroxide (DMAPS) precursor polymers that can address practical in vivo needs is reported. Zwitterion fusion interactions between the zwitterionic precursor polymers create a secondary physically crosslinked network to enable much more rapid gelation than previously reported with other synthetic polymers, facilitating rapid gelation at much lower polymer concentrations or degrees of functionalization than previously accessible in addition to promoting zero swelling and long-term degradation responses and significantly stiffer mechanics than are typically accessed with previously reported low-viscosity precursor gelation systems. The hydrogels maintain the highly anti-fouling properties of conventional zwitterionic hydrogels against proteins, mammalian cells, and bacteria while also promoting anti-fibrotic tissue responses in vivo. Furthermore, the use of the hydrogels for effective delivery and subsequent controlled release of viable cells with tunable profiles both in vitro and in vivo is demonstrated, including the delivery of myoblasts in a mouse skeletal muscle defect model for reducing the time between injury and functional mobility recovery. The combination of the injectability, degradability, and tissue compatibility achieved offers the potential to expand the utility of zwitterionic hydrogels in minimally invasive therapeutic applications.

Zwitterionic Hydrogel Coating with Antisediment Properties for Marine Antifouling Applications

Biofouling is a serious issue affecting the marine industry because the attached micro- and macrocontaminants can increase fuel consumption and damage ship hulls. A hydrophilic hydrogel-based coating is considered a promising antifouling material because it is environmentally friendly and the dense hydration layer can protect the substrate from microbial attachment. However, sediment adsorption can be an issue for hydrogel-based coatings. Their natural soft and porous structures can trap sediment from the marine environment and weaken the antifouling capability. There is still little research on the antisediment properties of hydrogels, and none of them deal with this problem. Here, we report on optimizing zwitterionic hydrogel-based coatings to improve their antisediment properties and achieve comparable performance to commercial biocidal coatings, which are the gold standard in the antifouling coating area. After 1 week of sediment contamination and 2 weeks of diatom coculturing, this optimized zwitterionic hydrogel coating maintained its antifouling properties with a few diatoms on the surface. Its large-scale samples also achieved antifouling performance similar to that of biocidal coatings in the Atlantic Ocean for 1.5 months. More importantly, our research provides a universal strategy to improve the antisediment properties of soft hydrogel-based coatings. For the first time, we report that the introduction of interfacial electrostatic interactions enhanced the antisediment properties of hydrogels.

Janus Nanofibrous Patch with In Situ Grown Superlubricated Skin for Soft Tissue Repair with Inhibited Postoperative Adhesion

The patch with a superlubricated surface shows great potential for the prevention of postoperative adhesion during soft tissue repair. However, the existing patches suffer from the destruction of topography during superlubrication coating and lack of pro-healing capability. Herein, we demonstrate a facile and versatile strategy to develop a Janus nanofibrous patch (J-NFP) with antiadhesion and reactive oxygen species (ROS) scavenging functions. Specifically, sequential electrospinning is performed with initiators and CeO2 nanoparticles (CeNPs) embedded on the different sides, followed by subsurface-initiated atom transfer radical polymerization for grafting zwitterionic polymer brushes, introducing superlubricated skin on the surface of single nanofibers. The poly(sulfobetaine methacrylate) brush-grafted patch retains fibrous topography and shows a coefficient of friction of around 0.12, which is reduced by 77% compared with the pristine fibrous patch. Additionally, a significant reduction in protein, platelet, bacteria, and cell adhesion is observed. More importantly, the CeNPs-embedded patch enables ROS scavenging as well as inhibits pro-inflammatory cytokine secretion and promotes anti-inflammatory cytokine levels. Furthermore, the J-NFP can inhibit tissue adhesion and promote repair of both rat skin wounds and intrauterine injuries. The present strategy for developing the Janus patch exhibits enormous prospects for facilitating soft tissue repair.

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.

Poly(Glutamic Acid-Lysine) Hydrogels with Alternating Sequence Resist the Foreign Body Response in Rodents and Non-Human Primates

The foreign body response (FBR) to implanted biomaterials and biomedical devices can severely impede their functionality and even lead to failure. The discovery of effective anti-FBR materials remains a formidable challenge. Inspire by the enrichment of glutamic acid (E) and lysine (K) residues on human protein surfaces, a class of zwitterionic polypeptide (ZIP) hydrogels with alternating E and K sequences to mitigate the FBR is prepared. When subcutaneously implanted, the ZIP hydrogels caused minimal inflammation after 2 weeks and no obvious collagen capsulation after 6 months in mice. Importantly, these hydrogels effectively resisted the FBR in non-human primate models for at least 2 months. In addition, the enzymatic degradability of the gel can be controlled by adjusting the crosslinking degree or the optical isomerism of amino acid monomers. The long-term FBR resistance and controlled degradability of ZIP hydrogels open up new possibilities for a broad range of biomedical applications.

Injectable Asymmetric Adhesive-Antifouling Bifunctional Hydrogel for Peritoneal Adhesion Prevention

Peritoneal adhesion is a common problem after abdominal surgery and can lead to various medical problems. In response to the lack of in situ retention and pro-wound healing properties of existing anti-adhesion barriers, this work reports an injectable adhesive-antifouling bifunctional hydrogel (AAB-hydrogel). This AAB-hydrogel can be constructed by "two-step" injection. The tissue adhesive hydrogel based on gallic acid-modified chitosan and aldehyde-modified dextran is prepared as the bottom hydrogel (B-hydrogel) by Schiff base reaction. The aldehyde-modified zwitterionic dextran/carboxymethyl chitosan-based hydrogel is formed on the B-hydrogel surface as the antifouling top hydrogel (T-hydrogel). The AAB-hydrogel exhibits good bilayer binding and asymmetric properties, including tissue adhesive, antifouling, and antimicrobial properties. To evaluate the anti-adhesion effect in vivo, the prepared hydrogels are injected onto the wound surface of a mouse abdominal wall abrasion-cecum defect model. Results suggest that the AAB-hydrogel has antioxidant capacity and can reduce the postoperative inflammatory response by modulating the macrophage phenotype. Moreover, the AAB-hydrogel could effectively inhibit the formation of postoperative adhesions by reducing protein deposition, and resisting fibroblast adhesions and bacteria attacking. Therefore, AAB-hydrogel is a promising candidate for the prevention of postoperative peritoneal adhesions.

Human umbilical cord-derived mesenchymal stem cells and auto-crosslinked hyaluronic acid gel complex for treatment of intrauterine adhesion

OBJECTIVE

The purpose of this study was to explore the therapeutic characteristics of mesenchymal stem cells generated from human umbilical cord (hUC-MSCs) when utilized in conjunction with auto-crosslinked hyaluronic acid gel (HA-gel) for the management of intrauterine adhesion (IUA). The goal was to see how this novel therapy could enhance healing and improve outcomes for IUA patients.

METHODS

In this study, models of intrauterine adhesion (IUA) were established in Sprague-Dawley (SD) rats, which were then organized and divided into hUC-MSCs groups. The groups involved: hUC-MSCs/HA-gel group, control group, and HA-gel group. Following treatment, the researchers examined the uterine cavities and performed detailed analyses of the endometrial tissues to determine the effectiveness of the interventions.

RESULTS

The results indicated that in comparison with to the control group, both HA-gel, hUC-MSCs, and hUC-MSCs/HA-gel groups showed partial repair of IUA. However, in a more notable fashion transplantation of hUC-MSCs/HA-gel complex demonstrated significant dual repair effects. Significant outcomes were observed in the group treated with hUC-MSCs and HA-gel, they showed thicker endometrial layers, less fibrotic tissue, and a higher number of endometrial glands. This treatment strategy also resulted in a significant improvement in fertility restoration, indicating a profound therapeutic effect.

CONCLUSIONS

The findings of this study suggest that both HA-gel, hUC-MSCs, and hUC-MSCs/HA-gel complexes have the potential for partial repair of IUA and fertility restoration caused by endometrium mechanical injury. Nonetheless, the transplantation of the hUC-MSCs/HA-gel complex displayed exceptional dual healing effects, combining effective anti-adhesive properties with endometrial regeneration stimuli.

What else should hemostatic materials do beyond hemostasis: A review

Massive blood loss due to injury is the leading cause of prehospital deaths in disasters and emergencies. Hemostatic materials are used to realize rapid hemostasis and protect patients from death. Researchers have designed and developed a variety of hemostatic materials. However, in addition to their hemostatic effect, hemostatic materials must be endowed with additional functions to meet the practical application requirements in different scenarios. Here, strategies for modifications of hemostatic materials for use in different application scenarios are listed: effective positioning at the site of deep and narrow wounds to stop bleeding, resistance to high blood pressure and wound movement to maintain wound formation, rapid and easy removal from the wound without affecting further treatment after hemostasis is completed, and continued function when retained in the wound as a dressing (such as antibacterial, antiadhesion, tissue repair, etc.). The problems encountered in the practical use of hemostatic materials and the strategies and progress of researchers will be further discussed in this review. We hope to provide valuable references for the design of more comprehensive and practical hemostatic materials.

Investigation of anti-adhesion ability of 8-arm PEGNHS-modified porcine pericardium

In post-adhesion surgery, there is a clinical need for anti-adhesion membranes specifically designed for the liver, given the limited efficacy of current commercial products. To address this demand, we present a membrane suitable for liver surgery applications, fabricated through the modification of decellularized porcine pericardium with 20 KDa hexaglycerol octa (succinimidyloxyglutaryl) polyoxyethylene (8-arm PEGNHS). We also developed an optimized modification procedure to produce a high-performance anti-adhesion barrier. The modified membrane significantly inhibited fibroblast cell adherence while maintaining minimal levels of inflammation. By optimizing the modification ratio, we successfully controlled post-adhesion formation. Notably, the 8-arm PEG-modified pericardium with a molar ratio of 5 exhibited the ability to effectively prevent post-adhesion formation on the liver compared to both the control and Seprafilm®, with a low adhesion score of 0.5 out of 3.0. Histological analysis further confirmed its potential for easy separation. Furthermore, the membrane demonstrated regenerative capabilities, as evidenced by the proliferation of mesothelial cells on its surface, endowing anti-adhesion properties between the abdominal wall and liver. These findings highlight the membrane's potential as a reliable barrier for repeated liver resection procedures that require the removal of the membrane multiple times.

Chitosan-crosslinked polyvinyl alcohol anti-swelling hydrogel designed to prevent abdominal wall adhesion

Abdominal adhesion is a frequent clinical issue with a high incidence rate and consequences following intra-abdominal surgery. Although many anti-adhesion materials have been used in surgical procedures, additional research is still needed to determine which ones have the most robust wet tissue adhesion, the best anti-postoperative adhesion, and the best anti-inflammatory properties. We have developed an excellent tissue adhesion and anti-swelling polyvinyl alcohol-chitosan hydrogel (AS hydrogel). According to in vitro cell testing, AS hydrogel significantly decreased inflammation around cells and exhibited good biocompatibility. Further, we assessed how well AS hydrogel prevented intraperitoneal adhesion using a rabbit model with cecum and abdominal wall injuries. According to the data, AS hydrogel has excellent anti-inflammatory and biodegradability properties compared to the control group. It can also prevent intestinal and abdominal wall injuries from occurring during surgery. Based on these results, hydrogel appears to be a perfect new material to prevent postoperative abdominal wall adhesion.

A Janus adhesive hydrogel sheet for preventing postoperative tissue adhesion of intestinal injuries

Although adhesive hydrogels represent an alternative to surgical sutures for non-invasive tissue wound sealing, those with indiscriminate adhesion fail to hold wounds while inhibiting postoperative tissue adhesion, thus limiting their application in intestinal repair. In this study, an asymmetric adhesive hydrogel sheet composed mainly of polyacrylic acid (PAA) and gelatin (GA) that can be wet-adhered to the surface of intestinal tissue was developed. One side of the GA-PAA hydrogel sheet was complexed with polyvinyl alcohol (PVA), which shielded the excess adhesion based on a physical barrier. Both sides of the PVA/GA-PAA hydrogel showed distinct adhesive and antiadhesive properties. Intriguingly, the anti-adhesive side showed significant anti-adhesion toward specific proteins. The results of animal experiments showed that the PVA/GA-PAA hydrogel could firmly adhere to the intestine to stop leakage and prevent post-operative tissue adhesion two weeks after surgery. The hematoxylin and eosin (H&E) staining results showed that the damaged intestinal serosa was repaired without tissue adhesion. It is believed that the controllable adhesion of the adhesive hydrogel offers better prospects for intestinal repair.

Unravelling Surface Modification Strategies for Preventing Medical Device-Induced Thrombosis

The use of biomaterials in implanted medical devices remains hampered by platelet adhesion and blood coagulation. Thrombus formation is a prevalent cause of failure of these blood-contacting devices. Although systemic anticoagulant can be used to support materials and devices with poor blood compatibility, its negative effects such as an increased chance of bleeding, make materials with superior hemocompatibility extremely attractive, especially for long-term applications. This review examines blood-surface interactions, the pathogenesis of clotting on blood-contacting medical devices, popular surface modification techniques, mechanisms of action of anticoagulant coatings, and discusses future directions in biomaterial research for preventing thrombosis. In addition, this paper comprehensively reviews several novel methods that either entirely prevent interaction between material surfaces and blood components or regulate the reaction of the coagulation cascade, thrombocytes, and leukocytes.

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.

Injectable Zwitterionic Physical Hydrogel with Enhanced Chemodynamic Therapy and Tumor Microenvironment Remodeling Properties for Synergistic Anticancer Therapy

Surgical resection is the first-line therapy for breast cancer. However, residual tumor cells and the highly immunosuppressive tumor microenvironment (TME) continue to have a serious impact on tumor recurrence and metastasis postresection. Implantation of an in situ hydrogel system postresection has shown to be an effective treatment with great clinical potential. Herein, an injectable zwitterionic hydrogel system was developed for local drug delivery with enhanced immune activation and prevention of tumor recurrence. Driven by electrostatic interactions, poly(sulfobetaine methacrylate) (PSBMA) self-assembles into a hydrogel in saline, achieving low protein adsorption and tunable biodegradability. The chemotherapy drug doxorubicin (DOX) was loaded into copper peroxide nanoparticles (CuO2/DOX), which were coated with macrophage membranes to form tumor-targeting nanoparticles (M/CuO2/DOX). Next, M/CuO2/DOX and the stimulator of interferon genes (STING) agonist 2',3'-cGAMP were coloaded into PSBMA hydrogel (Gel@M/CuO2/DOX/STING). The hydrophilic STING agonist was first released by diffusion from hydrogel to activate the STING pathway and upregulate interferon (IFN) signaling related genes, remodeling the immunosuppressive TME. Then, M/CuO2/DOX targeted the residual tumor cells, combining with DOX-induced DNA damage, immunogenic tumor cell death, and copper death. Hence, this work combines chemodynamic therapy with STING pathway activation in TME, encouraging residual tumor cell death, promoting the maturation of dendritic cells, enhancing tumor-specific CD8+ T cell infiltration, and preventing postoperative recurrence and metastasis.

A Zwitterionic Hydrogel with Anti-Oxidative and Anti-Inflammatory Properties for the Prevention of Peritoneal Adhesion by Inhibiting Mesothelial-Mesenchymal Transition

Postoperative peritoneal adhesion is a serious clinical complication. Various hydrogel barriers have been developed to prevent peritoneal adhesion. However, it remains a challenge to design a hydrogel with desirable physicochemical properties and bioactivities. In this study, a zwitterionic polysaccharide-based multifunctional hydrogel is developed using epigallocatechin-3-gallate (EGCG) to prevent postoperative abdominal adhesion. This hydrogel is simple to use and has desirable properties, such as excellent injectability, self-healing, and non-swelling properties. The hydrogel also has ultralow fouling capabilities, such as superior bactericidal performance, cell and protein adhesion, and low immunogenicity resistance. Moreover, the hydrogel exhibits good antioxidant activity, which is attributed to the integration of EGCG. Furthermore, the detailed mechanism from in vivo and in vitro experimental studies illustrates that hydrogel compositions can synergistically prevent adhesion formation through multiple pathways, including anti-inflammatory and antioxidant capabilities and inhibition effects on the mesothelial-mesenchymal transition (MMT) process induced by transforming growth factor (TGF-β). In summary, this zwitterionic multifunctional hydrogel has great potential to prevent postoperative adhesion formation in the clinical setting.

Correlation of Structure and Dynamics Behavior in Polyzwitterions: From Concentrated Solution to Gel-Like State

The dynamic behaviors of polyzwitterions, poly(4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate) (PSBP), are investigated using dynamic light scattering, small angle X-ray scattering, and rheology.  The findings reveal two relaxation modes, including a fast and a slow mode, which  are observed in both solution state and gel-like state, with varying polyzwitterion concentration (CP ) and NaCl concentration (CNaCl ). As CP and CNaCl increasing, a slower slow mode and a faster fast mode are observed. The fast mode corresponds to the diffusion of chains, while the slow mode arises from chain aggregations. In solutions, the slow mode is dominated by the diffusion of chain aggregations. However, in the gel-like state, the "cage network" traps aggregations more densely, leading to their dynamic behavior being dominated by enhanced topological entanglements and ionic interactions. This difference highlights the unique nature of the slow relaxation mode between concentrated solution and gel-like state, arising from changes in the average distance between chain aggregations resulting from increased CP and CNaCl concentrations.

An Injectable and Antifouling Supramolecular Polymer Hydrogel with Microenvironment-Regulatory Function to Prevent Peritendinous Adhesion and Promote Tendon Repair

The imbalance of extrinsic and intrinsic healing of tendon is thought to be the main cause of peritendinous adhesions. In this work, an injectable supramolecular poly(N-(2-hydroxypropyl) acrylamide) (PHPAm) hydrogel is prepared merely via side chain hydrogen-bonding crosslinks. This PHPAm exhibits good antifouling and self-healing properties. The supramolecular hydrogel simultaneously loaded with Prussian blue (PB) nanoparticles and platelet lysate (PL) is explored as a functional physical barrier, which can significantly resist the adhesion of fibrin and fibroblasts, attenuate the local inflammatory response, and enhance the tenocytes activity, thus balancing extrinsic and intrinsic healing. The PHPAm hydrogel is shown to prevent peritendinous adhesions considerably by inhibiting NF-κB inflammatory pathway and TGF-β1/Smad3-mediated fibrosis pathway, thereby significantly improving tendon repair by releasing bioactive factors to regulate the tenocytes behavior. This work provides a new strategy for developing physical barriers to prevent peritendinous adhesions and promote tissue repair effectively.

Antiadhesive Copolymers at Solid/Liquid Interfaces: Complementary Characterization of Polymer Adsorption and Protein Fouling by Sum Frequency Generation Vibrational Spectroscopy and Quartz-Crystal Microbalance Measurements with Dissipation Monitoring

Amphiphilic copolymers comprising hydrophilic segments of poly(ethylene glycol) and hydrophobic domains that are able to adhere to solid/liquid interfaces have proven to be versatile ingredients in formulated products for various types of applications. Recently, we have reported the successful synthesis of a copolymer designed for modifying the surface properties of polyesters as mimics for synthetic textiles. Using sum frequency generation (SFG) spectroscopy, it was shown that the newly developed copolymer adsorbs effectively on the targeted substrates even in the presence of surfactants as supplied by common detergents. In the present work, these studies were extended to evaluate the ability of the formed copolymer adlayers to passivate polyester surfaces against undesired deposition of bio(macro)molecules, as represented by fibrinogen as model protein foulants. In addition, SFG spectroscopy was used to elucidate the structure of fibrinogen at the interface between polyester and water. To complement the obtained data with an independent technique, analogous experiments were performed using quartz-crystal microbalance with dissipation monitoring for the detection of the relevant interfacial processes. Both methods give consistent results and deliver a holistic picture of brush copolymer adsorption on polyester surfaces and subsequent antiadhesive effects against proteins under different conditions representing the targeted application in home care products.

Prevention strategies of postoperative adhesion in soft tissues by applying biomaterials: Based on the mechanisms of occurrence and development of adhesions

Postoperative adhesion (POA) widely occurs in soft tissues and usually leads to chronic pain, dysfunction of adjacent organs and some acute complications, seriously reducing patients' quality of life and even being life-threatening. Except for adhesiolysis, there are few effective methods to release existing adhesion. However, it requires a second operation and inpatient care and usually triggers recurrent adhesion in a great incidence. Hence, preventing POA formation has been regarded as the most effective clinical strategy. Biomaterials have attracted great attention in preventing POA because they can act as both barriers and drug carriers. Nevertheless, even though much reported research has been demonstrated their efficacy on POA inhibition to a certain extent, thoroughly preventing POA formation is still challenging. Meanwhile, most biomaterials for POA prevention were designed based on limited experiences, not a solid theoretical basis, showing blindness. Hence, we aimed to provide guidance for designing anti-adhesion materials applied in different soft tissues based on the mechanisms of POA occurrence and development. We first classified the postoperative adhesions into four categories according to the different components of diverse adhesion tissues, and named them as "membranous adhesion", "vascular adhesion", "adhesive adhesion" and "scarred adhesion", respectively. Then, the process of the occurrence and development of POA were analyzed, and the main influencing factors in different stages were clarified. Further, we proposed seven strategies for POA prevention by using biomaterials according to these influencing factors. Meanwhile, the relevant practices were summarized according to the corresponding strategies and the future perspectives were analyzed.

Salt sensitive purely zwitterionic physical hydrogel for prevention of postoperative tissue adhesion

Abdominal adhesions are a class of serious complications following abdominal surgery, resulting in a complicated and severe syndrome and sometimes leading to a Gordian knot. Traditional therapies employ hydrogels synthesized using complicated chemical formulations-often with click chemistry or thermal responsive hydrogel. The complicated synthesis process and severe conditions limit the extent of the hydrogels' applications. In this work, poly 3-[2-(methacryloyloxy)ethyl](dimethyl)-ammonio]-1-propanesulfonate (PSBMA) polymer was synthesized to self-assemble into physical hydrogels due to the inter- and intramolecular ion interactions. The strong static interaction bonding density has a substantial impact on the gelation and physicochemical properties, which is beneficial to clinical applications and offers a novel way to obtain the desired hydrogel for a specific biomedical application. Intriguingly, this PSBMA polymer can be customized into a transient network with outstanding antifouling capability depending on the ion concentration. As ion concentration increases, the PSBMA hydrogel dissociated completely, endowing it as a candidate for adhesion prevention. In the cecum-sidewall model, the PSBMA hydrogel demonstrated superior anti-adhesion properties than commercial HA hydrogel. Furthermore, we have demonstrated that this PSBMA hydrogel could inhibit the inflammatory response and encourage anti-fibrosis resulting in adhesion prevention. Most surprisingly, the recovered skins of cecum and sidewall are as smooth as the control skin without any scar and damage. In conclusion, a practical hydrogel was synthesized using a facile method based on purely zwitterionic materials, and this ion-sensitive, antifouling adjustable supramolecular hydrogel with great clinic transform potential is a promising barrier for preventing postoperative tissue adhesion. STATEMENT OF SIGNIFICANCE: The development of hydrogels with satisfactory coverage, long retention time, facile synthetic method, and good biocompatibility is vital for preventing peritoneal adhesions. Herein, we developed a salt sensitive purely zwitterionic physical hydrogel poly 3-[2-(methacryloyloxy)ethyl](dimethyl)-ammonio]-1-propanesulfonate (PSBMA) hydrogel to effectively prevent postoperative and recurrent abdominal adhesions. The hydrogel was simple to synthesize and easy to use. In the cecum-sidewall model, PSBMA hydrogel could instantaneously adhere and fix on irregular surfaces and stay in the wound for more than 10 days. The PSBMA hydrogel could inhibit the inflammatory response, encourage anti-fibrosis, and restore smoothness to damaged surfaces resulting in adhesion prevention. Overall, the PSBMA hydrogel is a promising candidate for the next generation of anti-adhesion materials to meet clinical needs.

A sandwiched patch toward leakage-free and anti-postoperative tissue adhesion sealing of intestinal injuries

Ideal repair of intestinal injury requires a combination of leakage-free sealing and postoperative antiadhesion. However, neither conventional hand-sewn closures nor existing bioglues/patches can achieve such a combination. To this end, we develop a sandwiched patch composed of an inner adhesive and an outer antiadhesive layer that are topologically linked together through a reinforced interlayer. The inner adhesive layer tightly and instantly adheres to the wound sites via -NHS chemistry; the outer antiadhesive layer can inhibit cell and protein fouling based on the zwitterion structure; and the interlayer enhances the bulk resilience of the patch under excessive deformation. This complementary trilayer patch (TLP) possesses a unique combination of instant wet adhesion, high mechanical strength, and biological inertness. Both rat and pig models demonstrate that the sandwiched TLP can effectively seal intestinal injuries and inhibit undesired postoperative tissue adhesion. The study provides valuable insight into the design of multifunctional bioadhesives to enhance the treatment efficacy of intestinal injuries.

Progress in diagnosis and treatment of surgery-related adhesive small intestinal obstruction

Adhesive small bowel obstruction is a relatively common surgical acute abdomen, which is caused by various factors that result in the contents of the small bowel failing to pass smoothly. The clinical symptoms include abdominal pain, distension, nausea and vomiting, and defecation disorder. The chance of adhesive small bowel obstruction to develop in patients with a history of abdominal surgery is around 2.4%. This paper discusses the most recent developments in the conservative and surgical management of adhesive small bowel obstruction based on clinical manifestation, laboratory analysis, and imaging examination.

Liquid-Liquid Phase-Separated Hydrogel with Tunable Sol-Gel Transition Behavior as a Hotmelt-Adhesive Postoperative Barrier

Postoperative barriers have been widely used to prevent adhesions. However, there are currently few barriers that satisfy clinical requirements, such as tissue adhesion, operability, and biocompatibility. Inspired by the adhesion system of living organisms, we report a liquid-liquid phase-separated hydrogel as a single-syringe hotmelt-type postoperative barrier. Mixing polyethylene glycol with gelatin formed liquid-liquid phase-separated hydrogels through segregative liquid-liquid phase separation. Incorporation of a liquid-liquid phase-separated system into gelatin can enhance the sol-gel transition temperature to give a hotmelt-adhesive property to hydrogels. Hotmelt-adhesive hydrogels became a sol phase and cohered into tissue gaps when warmed and solidified at body temperature to adhere to soft tissues. The hydrogels exhibited tissue adhesion to large intestine tissues and showed improved mechanical strength, gelation time, and shear-thinning properties. In rat cecum-abdominal adhesion models, it was confirmed that the resulting hydrogels prevented abdominal adhesion and did not prevent tissue regeneration. Hotmelt-adhesive hydrogels with high tissue adhesive properties, operability, and biocompatibility have enormous potential as barriers to prevent postoperative complications.

Microgel reinforced zwitterionic hydrogel coating for blood-contacting biomedical devices

Zwitterionic hydrogels exhibit eminent nonfouling and hemocompatibility. Several key challenges hinder their application as coating materials for blood-contacting biomedical devices, including weak mechanical strength and low adhesion to the substrate. Here, we report a poly(carboxybetaine) microgel reinforced poly(sulfobetaine) (pCBM/pSB) pure zwitterionic hydrogel with excellent mechanical robustness and anti-swelling properties. The pCBM/pSB hydrogel coating was bonded to the PVC substrate via the entanglement network between the pSB and PVC chain. Moreover, the pCBM/pSB hydrogel coating can maintain favorable stability even after 21 d PBS shearing, 0.5 h strong water flushing, 1000 underwater bends, and 100 sandpaper abrasions. Notably, the pCBM/pSB hydrogel coated PVC tubing can not only mitigate the foreign body response but also prevent thrombus formation ex vivo in rats and rabbits blood circulation without anticoagulants. This work provides new insights to guide the design of pure zwitterionic hydrogel coatings for biomedical devices.

Bioinspired zwitterionic microgel-based coating: Controllable microstructure, high stability, and anticoagulant properties

Zwitterionic polymers have shown promising results in non-fouling and preventing thrombosis. However, the lack of controlled surface coverage hinders their application for biomedical devices. Inspired by the natural biological surfaces, a facile zwitterionic microgel-based coating strategy is developed by the co-deposition of poly (sulfobetaine methacrylate-co-2-aminoethyl methacrylate) microgel (SAM), polydopamine (PDA), and sulfobetaine-modified polyethyleneimine (PES). The SAMs were used to construct controllable morphology by using the PDA combined with PES (PDAS) as the intermediate layer, which can be easily modulated via adjusting the crosslinking degree and contents of SAMs. The obtained SAM/PDAS coatings exhibit high anti-protein adhesive properties and can effectively inhibit the adhesion of cells, bacteria, and platelet through the synergy of high deposition density and controllable morphology. In addition, the stability of SAM/PDAS coating is improved owing to the anchoring effects of PDAS to substrate and SAMs. Importantly, the ex vivo blood circulation test in rabbits suggests that the SAM/PDAS coating can effectively decrease thrombosis without anticoagulants. This study provides a versatile coating method to address the integration of zwitterionic microgel-based coatings with high deposition density and controllable morphology onto various substrates for wide biomedical device applications. STATEMENT OF SIGNIFICANCE: Thrombosis is a major cause of medical device implantation failure, which results in significant morbidity and mortality. In this study, inspired by natural biological surfaces (fish skin and vascular endothelial layer) and the anchoring ability of mussels, we report a convenient and efficient method to firmly anchor zwitterionic microgels using an oxidative co-deposition strategy. The prepared coating has excellent antifouling and antithrombotic properties through the synergistic effect of physical morphology and chemical composition. This biomimetic surface engineering strategy is expected to provide new insights into the clinical problems of blood-contacting devices related to thrombosis.

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

Clinically, increasing the peritoneal barrier is an effective adjunct to reducing postoperative peritoneal adhesion. This study presents a facile template for preparing a supramolecular hybrid hydrogel through dynamic covalent cross-linking between carboxymethyl chitosan (CMCS), 2-formylphenylboronic acid (2-FPBA), and quercetin (Que). The as-prepared complex CMCS/2-FPBA/Que (CFQ) hydrogel exhibited favorable antibacterial, anti-inflammatory, and antioxidant effects. A L929 cytotoxicity evaluation confirmed the favorable cytocompatibility of the CFQ hydrogel. The postoperative anti-adhesion ability of the CFQ hydrogel was further evaluated in rats with lateral wall defects and cecal abrasions. Compared with control groups, the tissue adhesion rate was significantly reduced by increasing the Que concentration in all the hydrogel-treated groups. Additionally, the sustained-release time of the C3F0.8Q0.08 hydrogel can exceed 14 days, which is highly desirable for clinical wound treatment. STATEMENT OF SIGNIFICANCE: Postoperative adhesions are a very common postoperative complication that seriously affects the quality of life of patients. The currently commonly used methods for preventing adhesion mainly use degradable barrier materials for physical separation. In this study, we prepared a dual dynamic covalently cross-linked CFQ hydrogel, which is not only degradable and injectable, but also has multiple properties such as antibacterial, antioxidant and anti-inflammatory, which can effectively prevent postoperative adhesion and promote wound healing.

Hotmelt tissue adhesive with supramolecularly-controlled sol-gel transition for preventing postoperative abdominal adhesion

Postoperative adhesion is a serious and frequent complication, but there is currently no reliable anti-adhesive barrier available due to low tissue adhesiveness, undesirable chemical reactions, and poor operability. To overcome these problems, we report a single-syringe hotmelt tissue adhesive that dissolves upon warming over 40 °C and coheres at 37 °C as a postoperative barrier. Tendon-derived gelatin was conjugated with the ureidopyrimidinone unit to supramolecularly control the sol-gel transition behavior. This functionalization improved bulk mechanical strength, tissue-adhesive properties, and stability under physiological conditions through the augmentation of intermolecular hydrogen bonding by ureidopyrimidinone unit. This biocompatible adhesive prevented postoperative adhesion between cecum and abdominal wall in adhesion models of rats. This hotmelt tissue adhesive has enormous potential to prevent postoperative complications and may contribute to minimally invasive surgery. STATEMENT OF SIGNIFICANCE: There is a strong need to develop medical tissue adhesives with high biocompatibility, tissue adhesiveness, and operatability to prevent postoperative complications. In this report, single syringe, hotmelt-type tissue adhesive was developed by controlling sol-gel transition behavior of gelatin through supramolecular approach. The functionalization of gelatin with quadruple hydrogen bonding improved key features necessary for anti-adhesive barrier including bulk mechanical strength, tissue adhesive property, stability under physiological conditions, and anti-adhesive property. The hotmelt tissue adhesive can be used for a sealant, hemostatic reagent, and wound dressing to prevent postoperative complications including delayed bleeding, perforation, and inflammation and contribute to minimally invasive surgery.

Bio-inspired Antibacterial Hydrogel Adhesives with High Adhesion Strength

Traditional adhesives such as cyanoacrylate glue are mostly solvent based. They are facing the problem of insufficient adhesion to some substrates, and also the drawback of volatilization and release of small organic molecules in the process of usage. Therefore, a novel adhesive with non-irritating, high adhesive strength and antibacterial properties is highly required. In this study, a full physically crosslinked zwitterionic poly(betaine sulfonate methacrylate) (PSBMA) hydrogel is proposed. The physical crosslinking interactions endow the hydrogel with good self-healing property. Besides, the pure physical crosslinking hydrogel can form PSBMA powder adhesive after lyophilization and return to the hydrogel state after hydration. The mechanical properties of PSBMA adhesive can be modulated via adjusting the solid content and initiator dosage. Following the cure process similar to that of snail mucus or insect exoskeleton does in nature, adhesion of the PSBMA adhesive is improved at least 100 times than its wet state. In addition, the PSBMA adhesive is easy to be removed due to the dissociation of cross-linked structure in salt water environment. Moreover, PSBMA adhesive with antifouling properties can effectively prevent adhesion of proteins and bacteria, which shows potential applications in assembly of medical devices. This article is protected by copyright. All rights reserved.

COCu: A Robust Self-Regenerative Hydrogel with Applicability as Both Hydrated Gel Dressing and Dry Suture for Seamless Tissue Fixation and Repair

Self-regenerative hydrogels have recently been developed, and represent a special type of self-healing hydrogels with the ability to restore a dehydrated hydrogel with physical damage. In this study, a self-regenerative hydrogel (COCu) based on two chitosan polymers assembled by slow-released Cu²⁺ is developed. The COCu hydrogel displays an excellent regeneration ability after being dehydrated and fractured. By simple hydration at room temperature, the fragments of the dehydrated gel fuse into one seamless whole, thereby preserving the mechanical properties and functionalities of the original hydrogel. The regeneration process can be conducted repeatedly after different methods of dehydration (natural volatilization, heat drying, lyophilization) and various modes of deconstruction (flakes, powder, lumpy sponge, etc.). Furthermore, the COCu hydrogel provides ultra-stretchability, and it can be stretched into thin (0.01-0.1 mm) filaments, which, when dried (dtCOCu), can be used as suture lines. Moreover, when used as a dry suture, it regenerates into the hydrogel in the presence of the tissue fluid, forming an excellent sealant to immobilize tissues and seamlessly seal wounds. The fast self-regeneration allows for its facile application as both a hydrated gel dressing and dry suture, and offers customized strategies for fixing and repair of different wounds in soft tissues.

Arrowhead Composite Microneedle Patches with Anisotropic Surface Adhesion for Preventing Intrauterine Adhesions

Biomedical patches are considered as a promising strategy to help tissue repair and regeneration, prevent tissue adhesion, and reduce neighboring friction. Here, novel arrowhead composite microneedle patches (MNPs) are presented with anisotropic surface adhesion and growth factor encapsulation using a heterogeneous template replication approach for endometrium repair and intrauterine adhesions (IUAs) prevention. The arrowhead structures bring about interlocking between the microneedle (MN) tips and tissues, allowing these MNPs to steadily adhere to the tissues. Besides, benefitting from the cytoadhesive needle-tip material and the antiadhesive base material, these MNPs possess anisotropic surface adhesion and can facilitate cell adhesion on one surface to repair damaged tissues while restrain tissue contact on the other to prevent adverse adhesion. In the meanwhile, the encapsulated growth factor can be delivered through the MNs to the deep tissue, further accelerating tissue repair. Additionally, as the bases are soft and their patterns are highly tunable, the MNPs can change their shapes flexibly to adjust to the irregular morphology of uteri. It is demonstrated that these MNPs show good performances in treating injured endometrium and preventing IUAs of a rat model, indicating their great potential in versatile postoperative adhesion prevention and other clinical applications.

Injectable hydrogel based on dodecyl-modified N-carboxyethyl chitosan/oxidized konjac glucomannan effectively prevents bleeding and postoperative adhesions after partial hepatectomy

Hemostasis and prevention of postoperative adhesions after hepatectomy are still challenges. In this work, we chose chitosan, a competitive candidate hemostatic material, as the backbone, and konjac glucomannan as the functional moieties, to form an injectable hydrogel. The hydrogel was prepared by the Schiff base reaction of dodecyl-modified N-carboxyethyl chitosan (DCEC) and oxidized konjac glucomannan (OKGM), which could effectively prevent bleeding and postoperative adhesions. The resultant hydrogel possessed self-healing and tissue adhesive capability, and combined the unique bioactivities of two polysaccharides: DCEC endowed the hydrogel with excellent antibacterial and hemostatic ability by the electrostatic and hydrophobic interactions between the cell membrane and amine/dodecyl groups, and OKGM imparted hydrogel anti-inflammatory action by activating macrophages. Moreover, the notable hemostatic efficacy of the hydrogel was confirmed in a rat hepatectomy model. The hydrogel could prevent postoperative adhesions and down-regulate the inflammatory factor TNF-α and the pro-fibrotic factor TGF-β₁ in situ, which might be caused by the combination of the barrier function of hydrogel and instinct bioactivities of DCEC and OKGM. Thus, this multifunctional injectable hydrogel is potentially valuable for preventing bleeding and postoperative adhesions after hepatectomy.

Polyzwitterion Manipulates Remineralization and Antibiofilm Functions against Dental Demineralization

Biomineralization technology has become a trend for the arrest and prevention of dental caries. In particular, the bioactivity and ability to release large amounts of Ca²⁺ and PO₄^3- ions make amorphous calcium phosphate (ACP) for hard tissue remineralization are highly desired. However, the instability of ACP limits its clinical application. Under continuous bacterial challenge in the oral cavity, the currently developed ACP-based remineralization system lacks the ability to inhibit bacterial adhesion and biofilm formation. Here, a dual-functional nanocomposite with antibiofilm and remineralization properties was designed by combining zwitterionic poly(carboxybetaine acrylamide) (PCBAA) and ACP. The resulting nanocomposite was stable in solution for at least 3 days without any aggregation. The PCBAA/ACP nanocomposite exerted a significant inhibitory effect on the adhesion and biofilm formation of Streptococcus mutans and exhibited bactericidal activities under acidic conditions resulting from bacteria. Moreover, compared with fluoride, this nanocomposite demonstrated superior effects in promoting the remineralization of demineralized enamel and the occlusion of exposed dentinal tubules in vivo and in vitro. The present work provides a theoretical and experimental basis for the use of the PCBAA/ACP nanocomposite as a potential dual-functional agent for arresting and preventing caries.

Facile preparation of thermosensitive and antibiofouling physically crosslinked hydrogel/powder for wound healing

To improve the therapeutic effect of hydrogel for damaged tissue, a series of hydroxybutyl chitosan (HBC) and poly (sulfobetaine methacrylate) (PSBMA) composite hydrogels (HBC-PSB) with thermosensitivity, self-healing, antibiofouling, and synergistic...

Organic carboxylate salt-enabled alternative synthetic routes for bio-functional cyclic carbonates and aliphatic polycarbonates

A cyclic carbonate with an ammonium carboxylate residue was found to serve as a nucleophile for esterification with alkyl bromides via the SN2 mechanism.

Application of Bioactive Hydrogels for Functional Treatment of Intrauterine Adhesion

Intrauterine adhesion (IUA) is a common endometrial disease and one of the main causes of infertility in women of childbearing age. Current treatment strategies, such as hysteroscopic adhesion resection, hysteroscopic transcervical resection of adhesion (TCRA), the use of local hormone drugs, and anti-adhesion scaffold implantation, do not provide a satisfactory pregnancy outcome for moderate-severe IUA, which presents a great challenge in reproductive medicine. With the development of material engineering, various bioactive and functional hydrogels have been developed using natural and synthetic biomaterials. These hydrogels are not only used as barely physical barriers but are also designed as vectors of hormone drugs, growth factors, and stem cells. These characteristics give bioactive hydrogels potentially important roles in the prevention and treatment of IUA. However, there is still no systematic review or consensus on the current advances and future research direction in this field. Herein, we review recent advances in bioactive hydrogels as physical anti-adhesion barriers, in situ drug delivery systems, and 3D cell delivery and culture systems for seeded cells in IUA treatment. In addition, current limitations and future perspectives are presented for further research guidance, which may provide a comprehensive understanding of the application of bioactive hydrogels in intrauterine adhesion treatment.

Injectable Self-Healing Hydrogel via Biological Environment-Adaptive Supramolecular Assembly for Gastric Perforation Healing

Developing effective internal wound dressing materials is important for postoperative tissue regeneration while remains a challenge due to the poor biological environment-adaptability of conventional materials. Here, we report an example of injectable self-healing hydrogel based on gastric environment-adaptive supramolecular assembly, and have explored its application for gastric perforation healing. By leveraging the gastric environment-modulated supramolecular interactions, the self-assembled hydrogel network is orchestrated with sensitive thermo-responsibility, injectability, printability and rapid self-healing capability. The hydrogel dressing can effectively inhibit the attachment of microorganisms and demonstrates outstanding antibiofouling property. In vivo rat model further demonstrates the as-prepared hydrogel dressing simplifies the surgical procedures, reduces postoperative complications as well as enhances the healing process of gastric perforation compared with the conventional treatment. This work provides useful insights into the development of biological environment-adaptive functional materials for various biomedical applications.

An Ultrasoft Self-Fused Supramolecular Polymer Hydrogel for Completely Preventing Postoperative Tissue Adhesion

The intermolecular H-bonding density heavily influences the gelation and rheological behavior of hydrogen-bonded supramolecular polymer hydrogels, thus offering a delicate pathway to tailor their physicochemical properties for meeting a specific biomedical application. Herein, one methylene spacer between two amides in the side chain of N-acryloyl glycinamide (NAGA) is introduced to generate a variant monomer, N-acryloyl alaninamide (NAAA). Polymerization of NAAA in aqueous solution affords an unprecedented ultrasoft and highly swollen supramolecular polymer hydrogel due to weakened H-bonds caused by an extra methylene spacer, which is verified by variable-temperature Fourier transform infrared (FTIR) spectroscopy and simulation calculation. Intriguingly, poly(N-acryloyl alaninamide) (PNAAA) hydrogel can be tuned to form a transient network with a self-fused and excellent antifouling capability that results from the weakened dual amide H-bonding interactions and enhanced water-amide H-bonding interactions. This self-fused PNAAA hydrogel can completely inhibit postoperative abdominal adhesion and recurrent adhesion after adhesiolysis in vivo. This transient hydrogel network allows for its disintegration and excretion from the body. The molecular mechanism studies reveal the signal pathway of PNAAA hydrogel in inhibiting inflammatory response and regulating fibrinolytic system balance. This self-fused, antifouling ultrasoft supramolecular hydrogel is promising as a barrier biomaterial for completely preventing postoperative tissue adhesion.