Microgel reinforced zwitterionic hydrogel coating for blood-contacting biomedical devices

Peritoneum-inspired adaptive hydrogel sheath orchestrating long-term lubrication and antibacterial properties for drainage tube intubation

Drainage tube (DT) intubation is frequently accompanied by distressing and even life-threatening complications. Herein, we engineer a peritoneum-inspired adaptive hydrogel sheath orchestrating long-term lubrication and broad-spectrum antibacterial properties onto the commercially-available DT surface for safe medical intervention. A thin conformal hydrogel sheath is formed by constructing the semi-interpenetrating hydrogel network to serve as the hydration layer, mimicking the lubricative peritoneal fluid layer of the peritoneum. The exposed protonated amino group of the semi-interpenetrating hydrogel network imparts the hydrogel sheath with an intrinsic antibacterial capacity, imitating the peritoneal inherent immunoregulatory function that resists bacterial invasion. The resultant hydrogel sheath exhibits the long-term lubricity, prominent broad-spectrum antibacterial property, remarkable robustness in various harsh environments, and excellent antifouling property without comprising biocompatibility. As demonstrated by an in vivo rabbit model of peritoneal drainage, the application of the hydrogel sheath on DT not only alleviates skin tissue trauma and inflammation effectively, but also inhibits bacterial invasion to avoid potential infection. The current work opens a valuable avenue to develop the functional DT to meet clinical needs.

Polycarboxybetaine in advanced drug delivery systems: From structure-function relationship to therapeutic applications

Zwitterionic polycarboxybetaines (PCBs), combining quaternary ammonium cations and carboxylate anions in their repeating units, have emerged as promising materials for drug delivery applications. Their exceptional hydration, biocompatibility, and antifouling properties make them attractive alternatives to polyethylene glycol (PEG), particularly given growing concerns about immunogenicity of PEG. PCBs can be functionalized through various methods, including modification of side-chain moieties, adjustment of spacer length between charged groups, and incorporation of responsive elements. When applied to delivery drug, PCBs have been successfully developed into multiple formats including micelles, hydrogels, liposomes, and nanoparticles. Notably, in protein drug delivery, PCBs demonstrate significant advantages such as enhancing protein stability, extending circulation time, improving penetration through biological barriers, and reducing immunogenicity. Despite these promising features, several challenges remain, including complex synthesis requirements, limited mechanical properties, and pending FDA approval as pharmaceutical excipients. This review provides a comprehensive analysis of PCBs from the structure-function relationship, synthesis methods, and applications in drug delivery systems, while examining current limitations and future prospects.

Moisture-Absorbing and Antimicrobial Semi-Interpenetrating Polymer Network Hydrogels: An Advanced Medical and Healthcare Material

The moisture absorption and antibacterial properties of medical materials are crucial for their clinical efficacy. However, existing hydrogel materials primarily focus on enhancing single properties, leading to issues, such as poor mechanical strength and limited environmental adaptability. Therefore, the development of medical materials with the dual functions of moisture absorption and antibacterial activity is of significant importance. In this study, inspired by biomimetic multilevel porous design, a semi-interpenetrating hydrogel material (CNSL) was successfully developed by incorporating moisture-absorbing component (LiCl) and antibacterial nanoparticles (SDP-NPs) into carboxymethyl cellulose (CMC) and N-isopropylacrylamide (NIPAm) matrix. The multilevel porous structure mimics the hierarchical pore characteristics of biological systems, optimizing the specific surface area and significantly improving the moisture absorption performance in the humidity range of 15-90% (0.613-5.127 g/g). The temperature-sensitive network enables intelligent water adsorption-desorption cycling. SDP-NPs provide long-lasting antibacterial effects through sustained release within the pores and physical barriers, demonstrating bactericidal rates of 99.77 and 99.83% against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively, in vitro. The CNSL hydrogel effectively achieves humidity regulation and broad-spectrum antibacterial performance, offering a unique design for the development of multifunctional medical dressings and other healthcare products. This research holds significant value in enhancing the infection prevention and control efficacy as well as clinical safety of medical materials and devices.

Anti-swelling, antithrombotic and antibacterial zwitterionic hydrogel coatings with a sandwich structure on polymer substrates

Interventional medical catheters and blood-contact biomedical devices are crucial in clinical treatment, but they often face challenges such as thrombosis, infection and inflammation. In this study, a sandwich-structured hydrogel coating was successfully prepared with antithrombotic, antimicrobial and anti-swelling properties. The coating consisted of a polydopamine adhesion base layer, an antimicrobial and anti-swelling middle layer, and an anti-adhesive top layer. The middle layer contains Pluronic F127 diacrylate (FDA) micelles and the poly(methacryloyl sulfobetaine) (pSBMA) hydrogel, wherein glucose oxidase (GOx) encapsulated in FDA micelles is incorporated into the coating for achieving a sustained antimicrobial effect. The top layer consists of zwitterionic polycarboxybetaine (pCBMA), which prevents non-specific protein adhesion and acts as a barrier to reduce the release of GOx and prolong its antimicrobial effect. The coating was applied onto the surface of silicone catheters, which showed excellent durability as well as antithrombotic and antimicrobial properties, providing a new solution to improve the safety and efficacy of clinical treatments.

Fabrication of Microgel-Reinforced Hydrogels via Vat Photopolymerization

We report a facile method for the vat photopolymerization (i.e., digital light processing, DLP) of microgel-reinforced hydrogels that leverages both light and dark polymerization for curing. As an example, norbornene modified hyaluronic acid (NorHA) microgels at varying volume fractions swollen in acrylamide monomer are implemented as resins. When processed with DLP, acrylamide polymerization and cross-linking results in the formation of a secondary, continuous network that percolates through the microgels. At even low volume fractions (e.g., 30% v/v), the addition of microgels results in up to 4-fold increases in the stress at failure and work of fracture and a reduction in hydrogel swelling. The microgel-reinforced hydrogels are 3D printed into intricate shapes (e.g., metamaterial lattices) while maintaining uniform microgel distributions, and microgels with varied cross-link densities, cross-linkers, and fabrication methods are also investigated. This work expands the potential of microgel-reinforced hydrogels across applications where geometric freedom is essential.

A skin-mimicking multifunctional hydrogel via hierarchical, reversible noncovalent interactions

Artificial skin is essential for bionic robotics, facilitating human skin-like functions such as sensation, communication, and protection. However, replicating a skin-matched all-in-one material with excellent mechanical properties, self-healing, adhesion, and multimodal sensing remains a challenge. Herein, we developed a multifunctional hydrogel by establishing a consolidated organic/metal bismuth ion architecture (COMBIA). Benefiting from hierarchical reversible noncovalent interactions, the COMBIA hydrogel exhibits an optimal combination of mechanical and functional properties, particularly its integrated mechanical properties, including unprecedented stretchability, fracture toughness, and resilience. Furthermore, these hydrogels demonstrate superior conductivity, optical transparency, freezing tolerance, adhesion capability, and spontaneous mechanical and electrical self-healing. These unified functions render our hydrogel exceptional properties such as shape adaptability, skin-like perception, and energy harvesting capabilities. To demonstrate its potential applications, an artificial skin using our COMBIA hydrogel was configured for stimulus signal recording, which, as a promising soft electronics platform, could be used for next-generation human-machine interfaces.

Bioaugmented design and functional evaluation of low damage implantable array electrodes

Implantable neural electrodes are key components of brain-computer interfaces (BCI), but the mismatch in mechanical and biological properties between electrode materials and brain tissue can lead to foreign body reactions and glial scarring, and subsequently compromise the long-term stability of electrical signal transmission. In this study, we proposed a new concept for the design and bioaugmentation of implantable electrodes (bio-array electrodes) featuring a heterogeneous gradient structure. Different composite polyaniline-gelatin-alginate based conductive hydrogel formulations were developed for electrode surface coating. In addition, the design, materials, and performance of the developed electrode was optimized through a combination of numerical simulations and physio-chemical characterizations. The long-term biological performance of the bio-array electrodes were investigated in vivo using a C57 mouse model. It was found that compared to metal array electrodes, the surface charge of the bio-array electrodes increased by 1.74 times, and the impedance at 1 kHz decreased by 63.17 %, with a doubling of the average capacitance. Long-term animal experiments showed that the bio-array electrodes could consistently record 2.5 times more signals than those of the metal array electrodes, and the signal-to-noise ratio based on action potentials was 2.1 times higher. The study investigated the mechanisms of suppressing the scarring effect by the bioaugmented design, revealing reduces brain damage as a result of the interface biocompatibility between the bio-array electrodes and brain tissue, and confirmed the long-term in vivo stability of the bio-array electrodes.

A self-adaptive adhesive, mechanically enhanced, and antibacterial non-woven fabric wound dressing functionalized by a semi-interpenetrating network hydrogel for promoting infected wound healing

Bacterial infection poses a primary challenge in wound management. However, the commercial non-woven dressings are incapable of treating infected wounds, limiting their clinical applications. Herein, we developed a novel composite dressing, featuring non-woven fabric (NF) decorated with a Zn2+ enhanced semi-interpenetrating network hydrogel (PNGZn@NF), which was achieved by cross-linking graft copolymers composed of acrylic acid and N-hydroxysuccinimide with Zn2+, followed by a coating-heat curing method to securely bond the hydrogel with the NF. The resultant PNGZn@NF exhibited high strength, self-adaptability, adhesion and antibacterial properties, and biocompatibility. In particular, the bacterial killing ratio was up to 99.99% for E. coli and S. aureus. In the in vivo experiments of Staphylococcus aureus (S. aureus) infection, PNGZn@NF showed enhanced infected wound healing ability by eliminating bacteria and reducing inflammation. Given these positive findings, this versatile wound dressing holds great potential in clinical treatment of infected wounds.

Mechanically Adaptive, Self-Adhesive, Conductive, Cross-Linked Interpenetrating Zwitterionic Hydrogel Sensor for Simultaneous Wound Healing and Monitoring

Hydrogel-based flexible biosensors can monitor biological parameters by responding to changes in the external environment, such as humidity, temperature, pH value, etc., which are converted into electrical signals or other measurable physical quantities. However, balancing biosensors' mechanical, adhesion, and electrical properties is challenging. Here, we design a multifunctional zwitterionic hydrogel-based biosensor with a cross-linked interpenetrating network structure, which consists of covalent and various noncovalent interactions, creating synergistic effects. The unique structure endows the hydrogel with excellent mechanical properties (0.13 ± 0.03 MPa), mechanical stability (10 cycles), and robust bonding strength (32 ± 2 KPa). Remarkably, the synergistic effect gives the hydrogels high conductivity (4.01 ± 0.2 S/m) and sensing ability (GF = 6.28). Noticeably, this synergistic effect improves the comprehensive performance of traditional biosensors and simultaneously endows them with wound-healing monitoring functions. Therefore, multifunctional and high-performance hydrogel-based flexible biosensors display great potential for application in intelligent wound management.

Tough and recyclable polyvinyl alcohol/carboxymethyl chitosan hydrogels with high strength, low modulus and fast self-recovery as flexible strain sensors

Fabrication of soft electronics using hydrogels is in high demand because of their biomimetic structures and favorable flexibility. However, poor mechanical properties of some developed hydrogels limit their use as stretchable sensors that require high strength, low modulus and suitable conductivity simultaneously. In this study, tough and conductive polyvinyl alcohol/carboxymethyl chitosan hydrogels were fabricated using a facile strategy, wherein an acid solution was employed to induce molecular structural transformation, thereby enhancing network interactions and mechanical strength. The resulting hydrogels, which had a high-water content of 83 %, exhibited excellent mechanical properties, with breaking stress of 1.81 MPa, breaking strain of 638 %, toughness of 5.01 MJ/m3, yet the tissue-like low modulus of 35-144 kPa. The hydrogel possessed a suitable conductivity, and fast recoverability after unloading and excellent recyclability after usage. These features made the hydrogels promising candidates for fabricating resistive strain sensors. The resulting sensors demonstrated a broad strain window, outstanding linear response with high sensitivity, and exceptional durability in long-term usage, enabling them to effectively monitor various physical movements as wearable electronics. This research offers a new approach to creating stretchable conductive hydrogels for smart technologies and flexible electronic devices.

Scalable Preparation of Polyzwitterionic Hydrogels Based on Hydration Shielding-Accelerated Redox Self-Catalytic Polymerization (HS-A-RP)

Traditional synthesis methods for polyzwitterionic hydrogels involve harsh conditions, such as thermal or UV irradiation, prolonged durations, and high monomer concentrations. Herein, we address these challenges at the meantime by proposing a novel chemical method, called hydration-shielding accelerated self-catalytic polymerization (HS-A-RP), facilitating the preparation of polyzwitterionic hydrogels. The discovery is that polyvinyl alcohol (PVA) chains can generate hydration shielding around hydrated zwitterionic monomers, promoting their effective aggregation and rapid crosslinking polymerization under the assistance of silver ions (Ag+)-potassium persulfate (S2O8 2-) redox catalyst. The HS-A-RP method performs under mild condition (-5 °C to 37 °C) without extra energy, overcomes the critical monomer polymerization concentration limitation (wt%: 0.3%), and completes within an ultrashort polymerization time (<60 s). The prepared polyzwitterionic hydrogels possesses a denser network and superior mechanical properties compared to those prepared by traditional thermal/UV methods, exhibiting good antiswelling behavior, excellent lubrication performance, and significant antibacterial and anti-fouling properties. These significant advances endow HS-A-RP with attractive application potentials in manufacturing functional hydrogel coatings for biomedical device, in situ encapsulation of thermally sensitive materials, and excellent sand fixation abilities. Moreover, HS-A-RP method is suitable for scalable manufacture and decorative coating of polyzwitterionic hydrogels on diverse substrates in extreme environmental conditions.

Holistic Molecular Design of Ionic Surfaces for Tailored Water Wettability and Technical Applications

This comprehensive review systematically explores the molecular design and functional applications of nano-smooth hydrophilic ionic polymer surfaces. Beginning with advanced fabrication strategies-including plasma treatment, surface grafting, and layer-by-layer assembly-we critically evaluate their efficacy in eliminating surface irregularities and tailoring wettability. Central to this discussion are the types of ionic groups, molecular configurations, and counterion hydration effects, which collectively govern macroscopic hydrophilicity through electrostatic interactions, hydrogen bonding, and molecular reorganization. By bridging molecular-level insights with application-driven design, we highlight breakthroughs in oil-water separation, anti-fogging, anti-icing, and anti-waxing technologies, where precise control over ionic group density, the hydration layer's stability, and the degree of perfection enable exceptional performance. Case studies demonstrate how zwitterionic architectures, pH-responsive coatings, and biomimetic interfaces address real-world challenges in industrial and biomedical settings. In conclusion, we synthesize the molecular mechanisms governing hydrophilic ionic surfaces and identify key research directions to address future material challenges. This review bridges critical gaps in the current understanding of molecular-level determinants of wettability while providing actionable design principles for engineered hydrophilic surfaces.

Thioether-Functionalized Cellulose for the Fabrication of Oxidation-Responsive Biomaterial Coatings and Films

Biomaterial coatings and films can prevent premature failure and enhance the performance of chronically implanted medical devices. However, current hydrophilic polymer coatings and films have significant drawbacks, including swelling and delamination. To address these issues, hydroxyethyl cellulose is modified with thioether groups to generate an oxidation-responsive polymer, HECMTP. HECMTP readily dissolves in green solvents and can be fabricated as coatings or films with tunable thicknesses. HECMTP coatings effectively scavenge hydrogen peroxide, resulting in the conversion of thioether groups to sulfoxide groups on the polymer chain. Oxidation-driven, hydrophobic-to-hydrophilic transitions that are isolated to the surface of HECMTP coatings under physiologically relevant conditions increase wettability, decrease stiffness, and reduce protein adsorption to generate a non-fouling interface with minimal coating delamination or swelling. HECMTP can be used in diverse optical applications and permits oxidation-responsive, controlled drug release. HECMTP films are non-resorbable in vivo and evoke minimal foreign body responses. These results highlight the versatility of HECMTP and support its incorporation into chronically implanted medical devices.

The Role of Intermediate Water in Enhancing Blood and Cellular Compatibility of Chitosan-Based Biomaterials

Tissue engineering and regenerative medicine require biomaterials that balance blood compatibility with cell adhesion, proliferation, and differentiation. Chitosan and its derivatives, owing to their biocompatibility, biodegradability, and functional versatility, have been extensively explored for biomedical applications, including vascular grafts and tissue engineering scaffolds. This study investigates the effect of chemical modifications on the water state of chitosan derivatives─specifically, free water (FW), intermediate water (IW), and nonfreezing water (NFW)─and their implications for protein interactions, platelet adhesion, and mesenchymal stem cell (MSC) behavior. By incorporating hydrophilic and hydrophobic groups, the hydration of chitosan derivatives was precisely controlled, which significantly influenced blood compatibility and cell adhesion. Hexanoyl glycol chitosan (HGC) demonstrated reduced platelet adhesion, low fibrinogen denaturation, and favorable MSC adhesion, making it a promising candidate for applications requiring both enhanced blood compatibility and regenerative potential. These findings underscore the importance of hydration water modulation in designing advanced biomaterials for blood-contacting and regenerative medicine applications.

Microenvironment-Responsive Biomimetic Bioprosthetic Valve with Antithrombosis and Immunoregulation Performance

The prevalence of heart valve disease (HVD) has escalated worldwide, because of population aging. Currently, artificial heart valve replacement is considered the most effective treatment for HVD. The complexity and risk of heart valve replacement have been markedly reduced with the development of minimally invasive interventional techniques, which has resulted in the more widespread implantation of bioprosthetic heart valves (BHVs); however, they still present with defects including thrombosis, poor cytocompatibility, immune responses, and calcification, which reduces their service life. We developed a microenvironment-responsive zwitterionic glycocalyx-mimetic hydrogel-engineered BHV (Hes@HS-PP) with a profile of on-demand drug release. Inspired by the structure and function of the glycocalyx on the inner wall of blood vessels, a zwitterionic glycocalyx-mimetic hydrogel coating was covalently constructed on the BHV by photoinduced polymerization. This coating significantly resisted the fouling of blood components and thrombosis and improved the endothelialization potential and biocompatibility of BHVs by shielding the interactions between blood and the xenogeneic collagenous BHV matrix. Following the introduction of dynamic borate ester bonds into the hydrogel, the anti-inflammatory drug hesperidin (Hes) was loaded onto the BHVs. Excess reactive oxygen species were scavenged, and Hes was released into the inflammatory region on demand to achieve immune regulation and ameliorate inflammatory reactions on BHVs. Moreover, Hes@HS-PP exhibited a markedly lower degree of calcification in a rat subcutaneous implantation model. In summary, the construction of microenvironment-responsive zwitterionic glycocalyx-mimetic hydrogels on BHVs significantly enhanced their antithrombotic, anti-inflammatory, endothelialization, and anticalcification properties and mitigated the risk of structural valvular degradation, offering new perspectives for the functional modification of BHVs.

Enzyme-Mimetic Zwitterionic Microgel Coatings for Antifouling and Enhanced Antithrombosis

Blood-contacting devices serve as a mainstay in clinical treatment, yet thrombosis remains a major cause of device failure and poses risks to patient health. In this study, we developed a diselenide cross-linker, N,N'-bis(methacryloyl)selenocystamine (BMASC), incorporated into poly(sulfobetaine methacrylate) (PSBMA) microgels (defined as BSM) to create an enzyme-mimetic zwitterionic microgel coating (BSMC). The superhydrophilicity of PSBMA provides outstanding antifouling performance, while the diselenide bonds mimic the catalytic action of glutathione peroxidase (GPx) in generating nitric oxide (NO). The microgels are covalently anchored to substrates pretreated with polydopamine (PDA) and polyethylenimine (PEI) through an epoxy-amine ring-opening reaction. During the drying process, the interpenetrating PSBMA chains of the microgels diffuse, forming a dense and smooth hydrogel coating. The BSMC exhibits exceptional resistance to nonspecific adhesion of proteins, cells, and bacteria, with the synergistic effects of antifouling properties and NO effectively inhibiting platelet adhesion. Furthermore, rabbit blood circulation experiments demonstrate the superior antithrombotic efficacy of the BSMC. This coating holds promise as an effective solution to address the thrombus formation challenges of blood-contacting devices.

Ultrasound-Controllable Release of Carbon Monoxide in Multifunctional Polymer Coating for Synergetic Treatment of Catheter-Related Infections

Medical catheters are susceptible to biological contamination and pathogen invasion, leading to infection and inflammatory complications. The development of antimicrobial coatings for medical devices has emerged as a promising strategy. However, limited biological functionality and the incompatibility between bactericidal properties and biosafety remain great challenges. Herein, a multifunctional polymer coating (CPB-Ac) is created, incorporating an ultrasonic-responsive carbon monoxide release unit (CORM-Ac) and antifouling unit to treat catheter-related complications. As-synthesized CPB-Ac polymer can be stably anchored to various medical devices with arbitrary shapes and compositions via facile UV treatment. Both in vivo and vitro experiments demonstrated that this multi-functional coating exhibits anti-fouling, anti-inflammatory, and broad-spectrum antibacterial activities as well as good biosafety. During the initial implantation phase, the antifouling units of CPB-Ac coating effectively inhibit the attachment of biological contaminants, significantly reducing the risk of thrombosis and bacterial infection. Once bacterial infection occurs, ultrasonic irradiation can activate CPB-Ac coating to release CO with a much higher amount of 55.3 µm than non-ultrasound controls, therefore rapidly eliminating bacteria and alleviating inflammatory response. It is believed that the work may provide an effective method for the development of next-generation intelligent medical coatings against catheter-related complications.

Zwitterionic Hydrogels: From Synthetic Design to Biomedical Applications

Zwitterionic hydrogels have emerged as a highly promising class of biomaterials, attracting considerable attention due to their unique properties and diverse biomedical applications. Zwitterionic moieties, with their balanced positive and negative charges, endow hydrogels with exceptional hydration, resistance to nonspecific protein adsorption, and low immunogenicity due to their distinctive molecular structure. These properties facilitate various biomedical applications, such as medical device coatings, tissue engineering, drug delivery, and biosensing. This review explores the structure-property relationships in zwitterionic hydrogels, highlighting recent advances in their design principles, synthesis methods, structural characteristics, and biomedical applications. To meet the evolving and growing demand for the biomedical field, this review examines current challenges and explores future research directions for optimizing the multifunctional properties of zwitterionic hydrogels. As promising candidates for advanced biomaterials, zwitterionic hydrogels are poised to address critical challenges in biomedical applications, paving the way for improved therapeutic outcomes and broader applicability in healthcare.

Stability Study of Anticoagulant Hydrogel Coatings Toward Long-Term Cardiovascular Devices

Implantable cardiovascular devices have revolutionized the treatment of cardiovascular diseases, yet their long-term functionality without causing thrombosis is a persistent challenge. Although the surface modification of anticoagulant coating has greatly improved the biocompatibility of the devices, its long-term stability in complex physiological environments still remains questionable. Herein, the stability of three anticoagulant hydrogel coatings, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(sodium 2-acryloyl-2-methylpropanesulfonate) (PAMPS), and poly(4-styrenesulfonate sodium) (PSS), is studied. The fabrication of these coatings onto device surfaces is validated by using X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. In vitro anticoagulation assays confirm the coatings' significant anticoagulant effects. Among all three coatings, the PSS coating demonstrated superior chemical and mechanical stability in the comprehensive tests, showing great potential for improving the long-term anticoagulant performance of implantable cardiovascular devices.

A Wet-Adhesion and Swelling-Resistant Hydrogel for Fast Hemostasis, Accelerated Tissue Injury Healing and Bioelectronics

Hydrogel bioadhesives with adequate wet adhesion and swelling resistance are urgently needed in clinic. However, the presence of blood or body fluid usually weakens the interfacial bonding strength, and even leads to adhesion failure. Herein, profiting from the unique coupling structure of carboxylic and phenyl groups in one component (N-acryloyl phenylalanine) for interfacial drainage and matrix toughening as well as various electrostatic interactions mediated by zwitterions, a novel hydrogel adhesive (PAAS) is developed with superior tissue adhesion properties and matrix swelling resistance in challenging wet conditions (adhesion strength of 85 kPa, interfacial toughness of 450 J m-2, burst pressure of 514 mmHg, and swelling ratio of <4%). The PAAS hydrogel can not only realize fast hemostasis of liver, heart, artery rupture, and sealing of pulmonary air-leakage but also accelerate the recovery of stomach and liver defects in rat, rabbit, and pig models. Moreover, PAAS hydrogel can precisely and durably monitor various physiological activities (pulse, electrocardiogram, and electromyogram) even under humid environments (immersion in water for 3 days), and can be employed for the evaluation of in vivo sealing efficiency for artery rupture. The work provides a promising hydrogel adhesive for clinical hemostasis, tissue injury repair, and bioelectronics.

Integrating Hydrogels and Biomedical Plastics via In Situ Physical Entanglements and Covalent Bonding

Both rigid plastics and soft hydrogels find ample applications in engineering and medicine but bear their own disadvantages that limit their broader applications. Bonding these mechanically dissimilar materials may resolve these limitations, preserve their advantages, and offer new opportunities as biointerfaces. Here, a robust adhesion strategy is proposed to integrate highly entangled tough hydrogels and diverse plastics with high interfacial adhesion energy and strength. Systemic investigations on the effects of hydrogel monomer content and crosslink fraction revealed the significant contributions of both polymer physical entanglements and interfacial covalent bonding. This hybrid engineering strategy also enables the plastic-hydrogel composite to attenuate foreign body response caused by pristine rigid plastics in vivo in mice. This versatile materials engineering approach may be broadly applicable to other polymer-based devices commonly used in regenerative medicine and surgical robotics.

Atomistic Insights into the Ionic Response and Mechanism of Antifouling Zwitterionic Polymer Brushes

Zwitterionic polymer brushes are not a practical choice since their ionic response mechanisms are unclear, despite their great potential for surface antifouling modification. Therefore, atomic force microscopy and molecular dynamics simulations investigated the ionic response of the surface electrical properties, hydration properties, and protein adhesion of three types of zwitterionic brushes. The surface of PMPC (poly(2-methacryloyloxyethyl phosphorylcholine)) and PSBMA (poly(sulfobetaine methacrylate)) zwitterionic polymer brushes in salt solution exhibits a significant accumulation of cations, which results in a positive shift in the surface potential. In contrast, the surface of PSBMA polymer brushes demonstrates no notable change in potential. Furthermore, divalent Ca2+ enhances protein adhesion to polymer brushes by Ca2+ bridges. Conversely, monovalent Na+ diminishes the number of salt bridges between PSBMA and PCBMA (poly(carboxybetaine methacrylate)) zwitterionic polymer brushes and proteins via a competitive adsorption mechanism, thereby reducing protein adhesion. A summary of polymer brush material selection and design concepts in a salt solution environment is provided based on the salt response law of protein adhesion resistance of various zwitterionic materials. This work closes a research gap on the response mechanism of zwitterionic polymer brushes' antifouling performance in a salt solution environment, significantly advancing the practical use of these brushes.

Polyzwitterions: controlled synthesis, soft materials and applications

Polyzwitterions refer to polymers containing both positive and negative charged groups in one side chain, which have shown unique physicochemical properties and significant potential in diverse applications due to their amphiphilic and net-neutral charged properties. This review aims to highlight the recent advances in the design and synthesis of polyzwitterions including direct polymerization of zwitterionic monomers and deionization of polymers. Furthermore, the formation of polyzwitterion based soft materials such as nanoparticles by self-assembly, hydrogels, coatings and polyzwitterion brushes, as well as the influence of the microstructure on their properties and applications are discussed. The potential applications of polyzwitterions in drug delivery, antifouling, lubrication, energy storage and antibacterial are also summarized. Finally, the prospects of polyzwitterions are proposed.

AB-Type Zwitterionic Hydrogel Paint

Zwitterionic hydrogels exhibit excellent nonfouling and hemocompatibility. However, the practical application of these materials as antifouling coatings for biomedical devices is hindered by several key challenges, including the harsh preparation conditions and the weak coating stability. Here, we present a two-component zwitterionic hydrogel paint for the in situ preparation of robust zwitterionic hydrogel coatings on various substrate surfaces without UV assistance. It is performed by the curing and adhesion of a zwitterionic hydrogel simultaneously through the ring opening reaction of epoxy and amino inspired by the successful commercial two-component epoxy structural glue. The obtained AB-type PSBMA coating can withstand water flow velocities of up to 15 m/s and still maintain its structural integrity and functional stability. It is noteworthy that the coating preparation process does not require the use of any organic solvent, which greatly simplifies the postprocessing steps for its application in medical devices. Moreover, the coating not only resists bacterial and cell adhesion but also exhibits favorable hemocompatibility. This approach offers a novel concept for the design of zwitterionic hydrogel coatings for biomedical devices.

Influence of Electrostatic Interactions on the Self-Assembly of Charged Peptides

Peptides can be designed to self-assemble into predefined supramolecular nanostructures, which are then employed as biomaterials in a range of applications, including tissue engineering, drug delivery, and vaccination. However, current self-assembling peptide (SAP) hydrogels exhibit inadequate self-healing capacities and necessitate the use of sophisticated printing apparatus, rendering them unsuitable for 3D printing under physiological conditions. Here, we report a precisely designed charged peptide, Z5, with the object of investigating the impact of electrostatic interactions on the self-assembly and the rheological properties of the resulting hydrogels. This peptide displays salt-triggered self-assembly resulting in the formation of a nanofiber network with a high β-sheet content. The peptide self-assembly and the hydrogel properties can be modified according to the ionic environment. It is noteworthy that the Z5 hydrogel in normal saline (NS) shows exceptional self-healing properties, demonstrating the ability to recover its initial strength in seconds after the removal of shear force, thus rendering it an acceptable material for printing. In contrast, the strong salt shielding effect and the ionic cross-linking of Z5 hydrogels in PBS result in the bundling of peptide nanofibers, which impedes the recovery of the initial strength post-destruction. Furthermore, incorporating materials with varied charging properties into Z5 hydrogels can alter the electrostatic interactions among peptide nanofibers, further modulating the rheological properties and the printability of SAP hydrogels.

Hydrogels in wearable neural interfaces

The integration of wearable neural interfaces (WNIs) with the human nervous system has marked a significant progression, enabling progress in medical treatments and technology integration. Hydrogels, distinguished by their high-water content, low interfacial impedance, conductivity, adhesion, and mechanical compliance, effectively address the rigidity and biocompatibility issues common in traditional materials. This review highlights their important parameters-biocompatibility, interfacial impedance, conductivity, and adhesiveness-that are integral to their function in WNIs. The applications of hydrogels in wearable neural recording and neurostimulation are discussed in detail. Finally, the opportunities and challenges faced by hydrogels for WNIs are summarized and prospected. This review aims to offer a thorough examination of hydrogel technology's present landscape and to encourage continued exploration and innovation. As developments progress, hydrogels are poised to revolutionize wearable neural interfaces, offering significant enhancements in healthcare and technological applications.

Graphical Abstract

Engineering anti-thrombogenic and anti-infective catheters through a stepwise metal-catechol-(amine) surface engineering strategy

Thrombosis and infection are pivotal clinical complications associated with interventional blood-contacting devices, leading to significant morbidity and mortality. To address these issues, we present a stepwise metal-catechol-(amine) (MCA) surface engineering strategy that efficiently integrates therapeutic nitric oxide (NO) gas and antibacterial peptide (ABP) onto catheters, ensuring balanced anti-thrombotic and anti-infective properties. First, copper ions were controllably incorporated with norepinephrine and hexanediamine through a one-step molecular/ion co-assembly process, creating a NO-generating and amine-rich MCA surface coating. Subsequently, azide-polyethylene glycol 4-N-hydroxysuccinimidyl and dibenzylcyclooctyne modified ABP were sequentially immobilized on the surface via amide coupling and bioorthogonal click chemistry, ensuring the dense grafting of ABP while maintaining the catalytic efficacy for NO. This efficient integration of ABP and NO-generating ability on the catheter surface provides potent antibacterial properties and ability to resist adhesion and activation of platelets, thus synergistically preventing infection and thrombosis. We anticipate that this synergistic modification strategy will offer an effective solution for advancing surface engineering and enhancing the clinical performance of biomedical devices.

Hydrocephalus: An update on latest progress in pathophysiological and therapeutic research

Hydrocephalus is a severe and life-threatening disease associated with the imbalance of CSF dynamics and affects millions globally at any age, including infants. One cause of pathology that is wide-ranging is genetic mutations to post-traumatic injury. The most effective current pharmacological treatments provide only symptomatic relief and do not address the underlying pathology. At the same time, surgical procedures such as VP shunts performed in lower-income countries are often poorly tolerated due to insufficient diagnostic resources and suboptimal outcomes partially attributable to inferior materials. These problems are compounded by an overall lack of funding that keeps high-quality medical devices out of reach for all but the most developed countries and even among those states. There is a massive variance in treatment effectiveness. This review indicates the necessity for innovative and low-cost, accessible treatment strategies to close these gaps, focusing on current advances in novel therapies, including Pharmacological, gene therapy, and nano-based technologies, which are currently at different stages of clinical trial phases. This review provides an overview of pathophysiology, current treatments, and promising new therapeutic strategies for hydrocephalus.

Self-Polymerized Tough and High-Entanglement Zwitterionic Functional Hydrogels

Zwitterionic hydrogels exhibit great potential in biomedical applications due to their antifouling properties and biocompatibility. However, the single-network structure of pure zwitterionic hydrogels leads to a low toughness and strength, limiting their application in biomedical fields. In this work, a high entanglement sulfobetaine methacrylate-dopamine hydrogel (SBMA-DA-PE) with low cross-linker content and high monomer concentration is prepared by using a dopamine oxidative radical polymerization method. Compared to a regular zwitterionic hydrogel, the SBMA-DA-PE hydrogel exhibits a 5-fold increase in tensile fracture stress and a 10-fold increase in compressive fracture stress. The SBMA-DA-PE hydrogel possesses excellent mechanical properties (the maximum compressive stress ≥4.85 MPa, the maximum compressive strain ≥90%). Besides, the non-covalent interactions between catechol or ortho-quinones within the SBMA-DA-PE hydrogel, combined with strong intermolecular electrostatic interactions, endow the SBMA-DA-PE hydrogel with great self-healing capabilities and fatigue resistance. The SBMA-DA-PE hydrogel demonstrates low swellability and possesses good antifouling properties. Furthermore, the good printability and conductivity of the tough SBMA-DA-PE hydrogel endows it with new possibilities for developing biological 3D scaffolds and electronic devices. Overall, this work provides new insights into the preparation of zwitterionic hydrogels with high mechanical strength and multi-functionality for biomedical applications.

Preparation of Nonfouling Zwitterionic Coatings by Plasma-Enhanced Chemical Vapor Deposition under Ambient Pressure

Nonspecific protein adsorption significantly impacts the performance of biomedical devices in both hemocompatibility and tissue compatibility. Polyzwitterionic coatings are a promising solution. However, conventional zwitterionic coatings always have to rely on sophisticated wet chemistry methods, leading to low controllability and high cost. In this work, zwitterionic coatings were prepared by nitrogen plasma-enhanced chemical vapor deposition (PECVD) of precursors for 90 s under ambient pressure followed by hydrolysis. The results showed that the PECVD-coated thermoplastic polyurethane (TPU), Tecoflex, effectively resists nonspecific protein adsorption, platelet adhesion, and bacterial adhesion without changing the mechanic properties of TPU. This approach simplified the zwitterionic coating process with highly controllability, showing a promising potential for the surface modification of biomedical devices.

Super-Tough, Non-Swelling Zwitterionic Hydrogel Sensor Based on the Hofmeister Effect for Potential Motion Monitoring of Marine Animals

Hydrogel-based electronic devices in aquatic environments have sparked widespread research interest. Nevertheless, the challenge of developing hydrogel electronics underwater has not been profoundly surmounted because of the fragility and swelling of hydrogels in aquatic environments. In this work, a zwitterionic double network hydrogel comprised of polyvinyl alcohol (PVA), poly(sulfobetaine methacrylate) (PSBMA), and sulfuric acid (H2SO4) demonstrates super-tough and non-swelling performance. The Hofmeister effect of H2SO4 and PSBMA induces the PVA chains to form numerous nanocrystalline domains, which serve as the primary physical crosslinking points and provide effective energy dissipation. H2SO4 induces a strong salting-out effect to facilitate PVA crystallization and the formation of a dense and stable network structure that inhibits swelling. The resulting hydrogel exhibits an ultra-high toughness of 4.61 MJ m-3, non-swelling, and long-term stability for up to a month in pure water and seawater. Based on this, a hydrogel-based seawater strain sensor has been developed to monitor the underwater movements of marine animal models. Reliable and stable sensing performance ensures real-time collection of underwater motion signals, despite the impacts of water flow and the interference of ions. This study provides a facile approach to designing super-tough and non-swelling hydrogels and further expands the application of underwater electronic devices.

Gum Arabic microgel-based biomimetic waterborne anticorrosive coatings with reinforced water and abrasive resistances

The inadequate water resistance and mechanical properties of waterborne anticorrosive coatings is a serious problem that leads to coating failure. When the bark of acacia trees sustains damage, the liquid Gum Arabic (GA) that oozes from the trunk coagulates at the site of injury to safeguard it, which is called "gummosis" self-protection. Inspired by this, biomimetic GA microgel-based waterborne anticorrosive coatings are designed. Microgel exhibits a crosslinked polymer network structure with a combination of advantageous characteristics derived from both solids and liquids. By encapsulating the liquid corrosion inhibitors (MeBT) within the solid microgel matrix, the coating system is endowed with self-protective capabilities. The as-prepared GAMG-MeBT microgels are introduced into waterborne epoxy (WE) matrix and sprayed onto the surface of Q235 steel. Corrosion studies reveal the 3.0-wt% GAMG-MeBT/WE coating exhibits an impedance modulus value in the low-frequency region (Z0.01Hz) of 1.37 × 109 Ω cm2 after immersing in 3.5-wt% NaCl solution for 60 days, which is nearly two orders of magnitude higher than that of the pure WE coatings. Moreover, the coatings display improved water resistance, enhanced abrasive resistance, and active corrosion protection. This work provides a new approach to solving the failure of WE anticorrosive coatings.

Precise Lubrication and Protection of Cartilage Damage by Targeting Hydrogel Microsphere

Osteoarthritis (OA) is a degenerative bone and joint disease characterized by decreased cartilage lubrication, leading to continuous wear and ultimately irreversible damage. This situation is particularly challenging for early-stage OA, as current bio-lubricants lack precise targeting for small inflammatory lesions. In this work, an antibody-mediated targeting hydrogel microspheres (HMS) is developed to precisely lubricate the local injury site of cartilage and prevent the progression of early OA. Anti-Collagen type I (Anti-Col1) is an antibody that targets cartilage injury sites in early OA stages. It is anchored on a HMS matrix made of Gelatin methacrylate (GelMA) and poly (sulfobetaine methacrylate) (PSBMA) to create targeted HMS (T-G/S HMS). The T-G/S HMS's high hydrophilicity, along with the dynamic interaction between its surficial Anti-Col1 and the Col1 on cartilage injury site, ensures its precise and effective lubrication of early OA lesions. Consequently, injecting T-G/S HMS into rats with early OA significantly slows disease progression and reduces symptoms. In conclusion, the developed injectable targeted lubricating HMS and the precisely targeted lubrication strategy represent a promising, convenient technique for treating OA, particularly for slowing the early-stage OA progression.

Enhanced antifouling and anti-swarming properties poly (sulfobetaine methacrylate-co-2-hydroxy-3-phenoxypropyl acrylate) hydrogel coatings for urinary catheters

Catheter-associated urinary tract infection (CAUTI) remains an unsolved challenge to date, particularly with the emergence and rapid spread of antimicrobial-resistant bacterial pathogens. Despite extensive research, a catheter coating that can offer intrinsic resistance to host protein deposition, bacterial biofilm formation, and swarming is still urgently required. Zwitterionic hydrogel coatings due to their superior lubricity and antifouling properties represent a promising candidate, but their weak mechanical stability in water and poor resistance to bacterial swarming migration limit their application in urinary catheters for infection control. In this research, we describe the fabrication of a multifunctional catheter coating by copolymerizing zwitterionic sulfobetaine methacrylate (SBMA) polymers and a swarming inhibitor material, 2-hydroxy-3-phenoxypropyl acrylate (HPA). The introduction of polyHPA (PHPA) effectively impeded the uncontrolled swelling behavior of the zwitterionic PSBMA hydrogel, resulting in enhanced mechanical stability. Moreover, the copolymer coating retains the antifouling and anti-swarming properties of the homopolymers when challenged with fibrinogen, Escherichia coli, and Proteus mirabilis. The HPA content significantly correlated with its anti-adhesion activity against fibrinogen and biofilm, and the coating with an SBMA: HPA monomer feed molar ratio of 4:1 showed the best antifouling activity, reducing fibrinogen deposition by about 40 % and biofilm coverage by around fourfold compared to the uncoated polydimethylsiloxane (PDMS) surface. Furthermore, the copolymer coating also exhibited no cytotoxicity, suggesting it as a promising catheter coating for preventing CAUTI.

Covalent bonding coating of quantum-sized TiO2 with polydopamine on catheter surface for synergistically enhanced antimicrobial and anticoagulant performances

The catheters coating can be effective in reducing bloodstream infection and thrombosis, which are the major complications in blood contact catheters. However, the surface functional coating is difficult to be implemented due to the high surface stretching force from the minor-caliber. In this work, we propose a covalent bonding coating of polydopamine/titanium dioxide quantum dots (PDA/TiO2 QDs) on polyurethane (PU) catheters, which can fulfill a dual-function of antibacterial and antithrombosis. The PDA/TiO2 QDs layer was prepared by dip-coating, where the intermediate transition layer of PDA was reacted with the internal hydroxyls of PU surface by pre-oxidation and bonds with the external TiO2 QDs coating. The surface microstructures are analyzed by SEM, TEM and XPS methods, and the antimicrobial and anticoagulant performances are investigated by bacterial plate count and platelet adhesion tests. The oxidizing and hydrophilic effect of the top layer of TiO2 QDs were enhanced by the QD-sized particles. The antibacterial activities of the PDA/TiO2 QDs coating on PU catheters against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), especially to S. aureus, are evidenced by bacterial plate count test, reaching good bactericidal rates of 49.9 % against E. coli and 83.7 % against S. aureus, respectively. Platelet adhesion test and whole blood dynamic circulation modeling demonstrate that the PDA/TiO2 QDs coating effectively inhibits platelet adhesion due to an excellent hydrophilicity of TiO2 QDs surface, and thereafter reduce thrombus formation.

An endothelium membrane mimetic antithrombotic coating enables safer and longer extracorporeal membrane oxygenation application

Thrombosis and plasma leakage are two of the most frequent dysfunctions of polypropylene (PP) hollow fiber membrane (PPM) used in extracorporeal membrane oxygenation (ECMO) therapy. In this study, a superhydrophilic endothelial membrane mimetic coating (SEMMC) was constructed on polydopamine-polyethyleneimine pre-coated surfaces of the PPM oxygenator and its ECMO circuit to explore safer and more sustainable ECMO strategy. The SEMMC is fabricated by multi-point anchoring of a phosphorylcholine and carboxyl side chained copolymer (PMPCC) and grafting of heparin (Hep) to form PMPCC-Hep interface, which endows the membrane superior hemocompatibility and anticoagulation performances. Furthermore, the modified PPM reduces protein adsorption amount to less than 30 ng/cm2. More significantly, the PMPCC-Hep coated ECMO system extends the anti-leakage and non-clotting oxygenation period to more than 15 h in anticoagulant-free animal extracorporeal circulation, much better than the bare and conventional Hep coated ECMO systems with severe clots and plasma leakage in 4 h and 8 h, respectively. This SEMMC strategy of grafting bioactive heparin onto bioinert zwitterionic copolymer interface has great potential in developing safer and longer anticoagulant-free ECMO systems. STATEMENT OF SIGNIFICANCE: A superhydrophilic endothelial membrane mimetic coating was constructed on surfaces of polypropylene hollow fiber membrane (PPM) oxygenator and its ECMO circuit by multi-point anchoring of a phosphorylcholine and carboxyl side chain copolymer (PMPCC) and grafting of heparin (Hep). The strong antifouling nature of the PMPCC-Hep coating resists the adsorption of plasma bio-molecules, resulting in enhanced hemocompatibility and anti-leakage ability. The grafted heparin on the zwitterionic PMPCC interface exhibits superior anticoagulation property. More significantly, the PMPCC-Hep coating achieves an extracorporeal circulation in a pig model for at least 15 h without any systemic anticoagulant. This endothelial membrane mimetic anticoagulation strategy shows great potential for the development of safer and longer anticoagulant-free ECMO systems.

Heparinized self-healing polymer coating with inflammation modulation for blood-contacting biomedical devices

The current techniques for antithrombotic coating on blood-contacting biomedical materials and devices are usually complex and lack practical feasibility with weak coating stability and low heparin immobilization. Here, a heparinized self-healing polymer coating with inflammation modulation is introduced through thermal-initiated radical copolymerization of methacrylate esterified heparin (MA-heparin) with methyl methacrylate (MMA) and n-butyl acrylate (nBA), followed by the anchoring of reactive oxygen species (ROS)-responsive polyoxalate containing vanillyl alcohol (PVAX) onto the coating through esterification. The aspirin, which is readily dissolved in the solution of MMA and nBA, is encapsulated within the coating after copolymerization. The copolymerization of MA-heparin with MMA and nBA significantly increases the heparin content of the coating, effectively inhibiting thrombosis and rendering the coating self-healing to help maintain long-term stability. ROS-responsive PVAX and aspirin released in a temperature-dependent manner resist acute and chronic inflammation, respectively. The heparinized self-healing and inflammation-modulated polymer coating exhibits the ability to confer long-term stability and hemocompatibility to blood-contacting biomedical materials and devices. STATEMENT OF SIGNIFICANCE: Surface engineering for blood-contacting biomedical devices paves a successful way to reduce thrombotic and inflammatory complications. However, lack of effectiveness, long-term stability and practical feasibility hinders the development and clinical application of existing strategies. Here we design a heparinized self-healing and inflammation-modulated polymer coating, which possesses high heparin level and self-healing capability to maintain long-term stability. The polymer coating is practically feasible to varied substrates and demonstrated to manipulate inflammation and prevent thrombosis both in vitro and in vivo. Our work provides a new method to develop coatings for blood-contacting biomedical materials and devices with long-term stability and hemocompatibility.

Mucus Mimic Hydrogel Coating for Lubricous, Antibiofouling, and Anti-Inflammatory Urinary Catheters

Silicone is a common elastomer used in indwelling urinary catheters, and catheters are widely used in various medical applications due to their exceptional biocompatibility, hypoallergenic properties, and flexibility. However, silicones exhibit hydrophobic characteristics, lack inherent biolubrication, and are susceptible to nonspecific biosubstance adsorption, resulting in complications including but not limited to tissue trauma, postoperative pain, and urinary tract infections (UTIs). The development of effective surface designs for biomedical catheters to mitigate invasive damage and UITs has been a longstanding challenge. Herein, we present a novel approach to prepare a mucus mimic hydrogel coating. A thin layer of hydrogel containing xylitol is fabricated via photopolymerization. The surface modification technique and the interface-initiated hydrogel polymerization method ensure robust interfacial coherence. The resultant coating exhibits a low friction coefficient (CoF ≈ 0.1) for urinary catheter applications. Benefiting from the hydration layer and the antifouling of the xylitol unit, the xylitol hydrogel-coated surfaces (pAAAMXA) demonstrate outstanding antibiofouling properties against proteins (98.9% reduction relative to pristine polydimethylsiloxane (PDMS)). Furthermore, the pAAAMXA shows general adhesion resistance against bacteria primarily responsible for UITs (Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Methicillin-resistant strains of Staphylococcus aureus (MRSA), and Staphylococcus epidermidis (S. epidermidis)) without compromising biotoxicity (cell viability 98%). In vivo, catheters coated with the mucus mimic hydrogel displayed excellent biocompatibility, resistance to adhesion of bio substance, and anti-inflammatory characteristics. This work describes a promising alternative to conventional silicone catheters, offering potential for clinical interventional procedures with minimized complications.

Research on the osteogenic properties of 3D-printed porous titanium alloy scaffolds loaded with Gelma/PAAM-ZOL composite hydrogels

Although titanium alloy is the most widely used endoplant material in orthopedics, the material is bioinert and good bone integration is difficult to achieve. Zoledronic acid (ZOL) has been shown to locally inhibit osteoclast formation and prevent osteoporosis, but excessive concentrations of ZOL exert an inhibitory effect on osteoblasts; therefore, stable and controlled local release of ZOL may reshape bone balance and promote bone regeneration. To promote the adhesion of osteoblasts to many polar groups, researchers have applied gelatine methacryloyl (Gelma) combined with polyacrylamide hydrogel (PAAM), which significantly increased the hydrogen bonding force between the samples and improved the stability of the coating and drug release. A series of experiments demonstrated that the Gelma/PAAM-ZOL bioactive coating on the surface of the titanium alloy was successfully prepared. The coating can induce osteoclast apoptosis, promote osteoblast proliferation and differentiation, achieve dual regulation of bone regeneration, successfully disrupt the balance of bone remodelling and promote bone tissue regeneration. Additionally, the coating improves the metal biological inertness on the surface of titanium alloys and improves the bone integration of the scaffold, offering a new strategy for bone tissue engineering to promote bone technology.

Multifunctional Conductive Hydrogel Interface for Bioelectronic Recording and Stimulation

The past few decades have witnessed the rapid advancement and broad applications of flexible bioelectronics, in wearable and implantable electronics, brain-computer interfaces, neural science and technology, clinical diagnosis, treatment, etc. It is noteworthy that soft and elastic conductive hydrogels, owing to their multiple similarities with biological tissues in terms of mechanics, electronics, water-rich, and biological functions, have successfully bridged the gap between rigid electronics and soft biology. Multifunctional hydrogel bioelectronics, emerging as a new generation of promising material candidates, have authentically established highly compatible and reliable, high-quality bioelectronic interfaces, particularly in bioelectronic recording and stimulation. This review summarizes the material basis and design principles involved in constructing hydrogel bioelectronic interfaces, and systematically discusses the fundamental mechanism and unique advantages in bioelectrical interfacing with the biological surface. Furthermore, an overview of the state-of-the-art manufacturing strategies for hydrogel bioelectronic interfaces with enhanced biocompatibility and integration with the biological system is presented. This review finally exemplifies the unprecedented advancement and impetus toward bioelectronic recording and stimulation, especially in implantable and integrated hydrogel bioelectronic systems, and concludes with a perspective expectation for hydrogel bioelectronics in clinical and biomedical applications.

Spatiotemporal coordination of antigen presentation and co-stimulatory signal for enhanced anti-tumor vaccination

Controlled-release systems enhance anti-tumor effects by leveraging local antigen persistence for antigen-presenting cells (APCs) recruitment and T cell engagement. However, constant antigen presentation alone tends to induce dysfunction in tumor-specific CD8+ T cells, neglecting the synergistic effects of co-stimulatory signal. To address this, we developed a soft particle-stabilized emulsion (SPE) to deliver lipopeptides with controlled release profiles by adjusting their hydrophobic chain lengths: C6-SPE (fast release), C10-SPE (medium release), and C16-SPE (slow release). Following administration, C6-SPE release antigen rapidly, inducing early antigen presentation, whereas C16-SPE's slow-release delays antigen presentation. Both scenarios missed the critical window for coordinating with the expression of CD86, leading to either T cell apoptosis or suboptimal activation. In contrast, C10-SPE achieved a spatiotemporally synergetic effect of the MHC-I-peptide complex and co-stimulatory signal (CD86), leading to effective dendritic cell (DC) activation, enhanced T cell activation, and tumor regression in EG7-OVA bearing mice. Additionally, co-delivery of cytosine-phosphate-guanine (CpG) with SPE provided a sustained expression of the CD86 window for DC activation, improving the immune response and producing robust anti-tumor effects with C6-SPE comparable to C10-SPE. These findings highlight that synchronizing the spatiotemporal dynamics of antigen presentation and APC activation may confer an optimal strategy for enhanced vaccinations.

Bioinspired Zwitterionic Block Polymer-Armored Nitric Oxide-Generating Coating Combats Thrombosis and Biofouling

Thrombosis and infection are 2 major complications associated with central venous catheters (CVCs), resulting in substantial mortality and morbidity. The concurrent long-term administration of antibiotics and anticoagulants to address these complications have been demonstrated to cause severe side effects such as antibiotic resistance and bleeding. To mitigate these complications with minimal or no drug utilization, we developed a bioinspired zwitterionic block polymer-armored nitric oxide (NO)-generating functional coating for surface modification of CVCs. This armor was fabricated by precoating with a Cu-dopamine (DA)/selenocysteamine (SeCA) (Cu-DA/SeCA) network film capable of catalytically generating NO on the CVCs surface, followed by grafting of a zwitterionic p(DMA-b-MPC-b-DMA) polymer brush. The synergistic effects of active attack by NO and copper ions provided by Cu-DA/SeCA network and passive defense by zwitterionic polymer brush imparted the CVCs surface with durable antimicrobial properties and marked inhibition of platelets and fibrinogen. The in vivo studies confirmed that the surface-armored CVCs could effectively reduce inflammation and inhibit thrombosis, indicating a promising potential for clinical applications.

Mechanical-Enhanced and Durable Zwitterionic Hydrogel Coating for Inhibiting Coagulation and Reducing Bacterial Infection

Blood-contact medical devices are indispensable for clinical interventions, yet their susceptibility to thrombosis and bacterial infections poses substantial risks to treatment efficacy and patient well-being. This study introduces a polysulfobetaine/alginate-CuII (SAC) zwitterionic hydrogel coating on polyurethane (PU) surfaces. This approach retains the superhydrophilic and antifouling nature of pSBMA while conferring the antibacterial effects of copper ions. Meanwhile, the copper alginate network intertwines with the polysulfobetaine (pSBMA) network, enhancing its mechanical properties and overcoming inherent weaknesses, thereby improving coating durability. Compared to the substrate, the SAC hydrogel coating significantly reduces thrombus adhesion mass by approximately 81.5% during extracorporeal blood circulation and effectively prevents bacterial biofilm formation even in a high-concentration bacterial milieu over 30 days. Moreover, the results from an isolated blood circulation model in New Zealand white rabbits affirm the impressive anticoagulant efficacy of the SAC hydrogel coating. The findings suggest that this hydrogel coating and its application method hold promise as a solution for blood-contact material surface modification to address thrombosis and bacterial biofilm formation simultaneously.

Chemically Programmed Hydrogels for Spatiotemporal Modulation of the Cardiac Pathological Microenvironment

After myocardial infarction (MI), sustained ischemic events induce pathological microenvironments characterized by ischemia-hypoxia, oxidative stress, inflammatory responses, matrix remodeling, and fibrous scarring. Conventional clinical therapies lack spatially targeted and temporally responsive modulation of the infarct microenvironment, leading to limited myocardial repair. Engineered hydrogels have a chemically programmed toolbox for minimally invasive localization of the pathological microenvironment and personalized responsive modulation over different pathological periods. Chemically programmed strategies for crosslinking interactions, interfacial binding, and topological microstructures in hydrogels enable minimally invasive implantation and in situ integration tailored to the myocardium. This enhances substance exchange and signal interactions within the infarcted microenvironment. Programmed responsive polymer networks, intelligent micro/nanoplatforms, and biological therapeutic cues contribute to the formation of microenvironment-modulated hydrogels with precise targeting, spatiotemporal control, and on-demand feedback. Therefore, this review summarizes the features of the MI microenvironment and chemically programmed schemes for hydrogels to conform, integrate, and modulate the cardiac pathological microenvironment. Chemically programmed strategies for oxygen-generating, antioxidant, anti-inflammatory, provascular, and electrointegrated hydrogels to stimulate iterative and translational cardiac tissue engineering are discussed.

Biomimetic nanoporous oxygenation membranes with high hemocompatibility and fast gas transport property

Membrane technology holds great potential for separation applications and also finds critical needs in biomedical fields, such as blood oxygenation. However, the bottlenecks in gas permeation, plasma leakage, and especially hemocompatibility hamper the development of membrane oxygenation. It remains extremely challenging to design efficient membranes and elucidate underlying principles. In this study, we report biomimetic decoration of asymmetric nanoporous membranes by ultrathin FeIII-tannic acid metal-ligand networks to realize fast gas exchange with on plasma leakage and substantially enhance hemocompatibility. Because the intrinsic nanopores facilitate gas permeability and the FeIII-catechol layers enable superior hydrophilicity and electronegativity to original surfaces, the modified membranes exhibit high transport properties for gases and great resistances to protein adsorption, platelet activation, coagulation, thrombosis, and hemolysis. Molecular docking and density functional theory simulations indicate that more preferential adsorption of metal-ligand networks with water molecules than proteins is critical to anticoagulation. Moreover, benefiting from the better antiaging property gave by biomimetic decoration, the membranes after four-month aging present gas permeances similar to or even larger than those of pristine ones, despite the initial permeation decline. Importantly, for blood oxygenation, the designed membranes after aging show fast O2 and CO2 exchange processes with rates up to 28-17 and 97-47 mL m-2 min-1, respectively, accompanied with no detectable thrombus and plasma leakage. We envisage that the biomimetic decoration of nanoporous membranes provide a feasible route to achieve great biocompatibility and transport capability for various applications.

UV-Triggered Hydrogel Coating of the Double Network Polyelectrolytes for Enhanced Endothelialization

The left atrial appendage (LAA) occluder is an important medical device for closing the LAA and preventing stroke. The device-related thrombus (DRT) prevents the implantation of the occluder in exerting the desired therapeutic effect, which is primarily caused by the delayed endothelialization of the occluder. Functional coatings are an effective strategy for accelerating the endothelialization of occluders. However, the occluder surface area is particularly large and structurally complex, and the device is subjected to a large shear friction in the sheath during implantation, which poses a significant challenge to the coating. Herein, a hydrogel coating by the in situ UV-triggered polymerization of double-network polyelectrolytes is reported. The findings reveal that the double network and electrostatic interactions between the networks resulted in excellent mechanical properties of the hydrogel coating. The sulfonate and Arg-Gly-Asp (RGD) groups in the coating promoted hemocompatibility and endothelial growth of the occluder, respectively. The coating significantly accelerated the endothelialization of the LAA occluder in a canine model is further demonstrated. This study has potential clinical benefits in reducing both the incidence of DRT and the postoperative anticoagulant course for LAA closure.

Recent advances of multifunctional zwitterionic polymers for biomedical application

Zwitterionic polymers possess equal total positive and negative charges in the repeating units, making them electrically neutral overall. This unique property results in superhydrophilicity, which makes the zwitterionic polymers highly effective in resisting protein adsorption, thus endowing the drug carriers with long blood circulation time, inhibiting thrombus formation on biomedical devices in contact with blood, and ensuring the good sensitivity of sensors in biomedical application. Moreover, zwitterionic polymers have tumor-targeting ability and pH-responsiveness, rendering them ideal candidates for antitumor drug delivery. Additionally, the high ionic conductivity of zwitterionic polymers makes them an important raw material for ionic skin. Zwitterionic polymers exhibit remarkable resistance to bacterial adsorption and growth, proving their suitability in a wide range of biomedical applications such as ophthalmic applications, and wound dressings. In this paper, we provide an in-depth analysis of the different structures and characteristics of zwitterionic polymers and highlight their unique qualities and suitability for biomedical applications. Furthermore, we discuss the limitations and challenges that must be overcome to realize the full potential of zwitterionic polymers and present an optimistic perspective for zwitterionic polymers in the biomedical fields. STATEMENT OF SIGNIFICANCE: Zwitterionic polymers have a series of excellent properties such as super hydrophilicity, anti-protein adsorption, antibacterial ability and good ionic conductivity. However, biomedical applications of multifunctional zwitterionic polymers are still a major field to be explored. This review focuses on the design and application of zwitterionic polymers-based nanosystems for targeted and responsive delivery of antitumor drugs and cancer diagnostic agents. Moreover, the use of zwitterionic polymers in various biomedical applications such as biomedical devices in contact with blood, biosensors, ionic skin, ophthalmic applications and wound dressings is comprehensively described. We discuss current results and future challenges for a better understanding of multifunctional zwitterionic polymers for biomedical 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.

Comparison study of surface-initiated hydrogel coatings with distinct side-chains for improving biocompatibility of polymeric heart valves

Polymeric heart valves (PHVs) present a promising alternative for treating valvular heart diseases with satisfactory hydrodynamics and durability against structural degeneration. However, the cascaded coagulation, inflammatory responses, and calcification in the dynamic blood environment pose significant challenges to the surface design of current PHVs. In this study, we employed a surface-initiated polymerization method to modify polystyrene-block-isobutylene-block-styrene (SIBS) by creating three hydrogel coatings: poly(2-methacryloyloxy ethyl phosphorylcholine) (pMPC), poly(2-acrylamido-2-methylpropanesulfonic acid) (pAMPS), and poly(2-hydroxyethyl methacrylate) (pHEMA). These hydrogel coatings dramatically promoted SIBS's hydrophilicity and blood compatibility at the initial state. Notably, the pMPC and pAMPS coatings maintained a considerable platelet resistance performance after 12 h of sonication and 10 000 cycles of stretching and bending. However, the sonication process induced visible damage to the pHEMA coating and attenuated the anti-coagulation property. Furthermore, the in vivo subcutaneous implantation studies demonstrated that the amphiphilic pMPC coating showed superior anti-inflammatory and anti-calcification properties. Considering the remarkable stability and optimal biocompatibility, the amphiphilic pMPC coating constructed by surface-initiated polymerization holds promising potential for modifying PHVs.

Generalized Multifunctional Coating Strategies Based on Polyphenol-Amine-Inspired Chemistry and Layer-by-Layer Deposition for Blood Contact Catheters

Blood-contacting catheters play a pivotal role in contemporary medical treatments, particularly in the management of cardiovascular diseases. However, these catheters exhibit inappropriate wettability and lack antimicrobial characteristics, which often lead to catheter-related infections and thrombosis. Therefore, there is an urgent need for blood contact catheters with antimicrobial and anticoagulant properties. In this study, we employed tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) to create a stable hydrophilic coating under mild conditions. Heparin (Hep) and poly(lysine) (PL) were then modified on the TA-APTES coating surface using the layer-by-layer (LBL) technique to create a superhydrophilic TA/APTES/(LBL)4 coating on silicone rubber (SR) catheters. Leveraging the superhydrophilic nature of this coating, it can be effectively applied to blood-contacting catheters to impart antibacterial, antiprotein adsorption, and anticoagulant properties. Due to Hep's anticoagulant attributes, the activated partial thromboplastin time and thrombin time tests conducted on SR/TA-APTES/(LBL)4 catheters revealed remarkable extensions of 276 and 103%, respectively, when compared to uncoated commercial SR catheters. Furthermore, the synergistic interaction between PL and TA serves to enhance the resistance of SR/TA-APTES/(LBL)4 catheters against bacterial adherence, reducing it by up to 99.9% compared to uncoated commercial SR catheters. Remarkably, the SR/TA-APTES/(LBL)4 catheter exhibits good biocompatibility with human umbilical vein endothelial cells in culture, positioning it as a promising solution to address the current challenges associated with blood-contact catheters.