A bioinspired omniphobic surface coating on medical devices prevents thrombosis and biofouling

Transparent and Antifouling Lubrication Coating for Medical Applications Formed by a Self-Assembled Method

Lubrication surfaces reduce the risk of cross-contamination and enhance the long-term stability of medical devices, which holds significance in the realm of antifouling medical materials. However, the complexity of constructing micronano structures to immobilize lubricating fluids and the fluorine content typically found in silane coupling agents restrict their widespread adoption. In this study, we prepared a biomimetic lubricating coating (BLC) through the one-step self-assembly of octadecyltrichlorosilane and oil infusion. The BLC exhibits pronounced repellency to liquids of different surface tensions while maintaining a high transparency. Mechanism exploration indicates that the low surface tension of the coating impedes the binding of fibrinogen to the substrate, thus preventing the adhesion of coagulated blood. To prove this concept, we applied the BLC to pipet tips and endoscope lenses to evaluate the coating's effectiveness. The results indicate that the coating shows significantly less residue, maintains clear visibility, and demonstrates excellent biocompatibility.

Autonomous Anticoagulation on a Biomimetic Al-Based Hierarchical Surface

Studies targeting the blood repellency and autonomous anticoagulation of superhydrophobic (SH) surfaces are potentially valuable for their application in blood contact. The anticoagulation abilities and potential mechanisms of different SH surfaces urgently need to be revealed. In this study, a range of microprotrusion arrays on Al substrates with varying spacings via laser ablation through the utilization of organic adsorption and siloxane coupling reactions were fabricated. Consequently, gridded SH Al-based surfaces were prepared, and their blood-repellency and autonomous anticoagulation properties were evaluated. In vitro experiments demonstrated the effectiveness of these surfaces in preventing nonspecific protein adsorption and platelet adhesion, and the surfaces exhibited no indications of hemolysis or toxicity. Remarkably, the SH surfaces maintained good antiplatelet adhesion and platelet activation inhibition properties after 7 days of incubation in platelet-rich plasma, and the anticoagulation capacity of different SH surfaces was compared with elements analysis on the surfaces. Specifically, the SH Al surface exhibited low protein adsorption when incubated with 10 mg/mL of bovine serum albumin solution. Furthermore, this study illustrated the relationship between the hierarchical micronano structure of the SH surfaces and their autonomous anticoagulant behavior. The integration of a readily available SH surface with autonomous anticoagulant ability represents a promising strategy for the application of metallic materials in medical devices involving blood contact.

Stable Antifouling and Antibacterial Coating Based on Assembly of Copper-Phenolic Networks

Biofilm formation on medical devices has become a worldwide issue arising from its resistance to bactericidal agents and presenting challenges to eradicating biofouling adhesion, especially in biological fluids. Metal-phenolic networks have been demonstrated as a versatile and efficient strategy to prevent biofilm formation by endowing medical devices with prolonged antifouling and antibacterial activities in a one-step surface modification. In this study, we report a simple and environmentally friendly method using coordination chemistry between copper ions (Cu2+) and dopamine-containing copolymer to fabricate metal-phenolic network-based coatings. The phenolic groups also imparted the adhesion of glycopolymer-containing dopamine residues to inorganic and organic substrates, resulting in dual antifouling and bactericidal surfaces. 2-gluconamidoethyl methacrylamide monomer (GAEMA) was first copolymerized with dopamine methacrylamide (DMA) using a free-radical polymerization process. The resulting copolymer (GAEMA-DMA), denoted as GADMA, was then mixed with copper ions in a one-step process to form the GADMA-Cu coating. The GADMA-Cu coating was hydrophilic and significantly reduced the water contact angle (WCA) and adsorption of bovine serum albumin protein even after incubation in a bovine serum albumin solution for 30 h. Moreover, the coating exhibited strong antibacterial activity against Escherichia coli and Staphylococcus aureus and was biocompatible with 99% cell viability toward normal human fibroblast (HDFa) cells. Thus, our coating shows great potential for application in medical devices.

Engineered endothelium-mimicking antithrombotic surfaces via combination of nitric oxide-generation with fibrinolysis strategies

Thrombosis associated with implants can severely impact therapeutic outcomes and lead to increased morbidity and mortality. Thus, developing blood-contacting materials with superior anticoagulant properties is essential to prevent and mitigate device-related thrombosis. Herein, we propose a novel single-molecule multi-functional strategy for creating blood-compatible surfaces. The synthesized azide-modified Cu-DOTA-(Lys)3 molecule, which possesses both NO release and fibrinolysis functions, was immobilized on material surfaces via click chemistry. Due to the specificity, rapidity, and completeness of click chemistry, the firmly grafted Cu-DOTA-(Lys)3 endows the modified material with excellent antithrombotic properties of vascular endothelium and thrombolytic properties of fibrinolytic system. This surface effectively prevented thrombus formation in both in vitro and in vivo experiments, owing to the synergistic effect of anticoagulation and thrombolysis. Moreover, the modified material maintained its functional efficacy after one month of PBS immersion, demonstrating excellent stability. Overall, this single-molecule multifunctional strategy may become a promising surface engineering technique for blood-contacting materials.

Robust, Scalable Microfluidic Manufacturing of RNA-Lipid Nanoparticles Using Immobilized Antifouling Lubricant Coating

Despite the numerous advantages demonstrated by microfluidic mixing for RNA-loaded lipid nanoparticle (RNA-LNP) production over bulk methods, such as precise size control, homogeneous distributions, higher encapsulation efficiencies, and improved reproducibility, their translation from research to commercial manufacturing remains elusive. A persistent challenge hindering the adoption of microfluidics for LNP production is the fouling of device surfaces during prolonged operation, which significantly diminishes performance and reliability. The complexity of LNP constituents, including lipids, cholesterol, RNA, and solvent mixtures, makes it difficult to find a single coating that can prevent fouling. To address this challenge, we propose using an immobilized liquid lubricant layer of perfluorodecalin (PFD) to create an antifouling surface that can repel the multiple LNP constituents. We apply this technology to a staggered herringbone microfluidic (SHM) mixing chip and achieve >3 h of stable operation, a >15× increase relative to gold standard approaches. We also demonstrate the compatibility of this approach with a parallelized microfluidic platform that incorporates 256 SHM mixers, with which we demonstrate scale up, stable production at L/h production rates suitable for commercial scale applications. We verify that the LNPs produced on our chip match both the physiochemical properties and performance for both in vitro and in vivo mRNA delivery as those made on chips without the coating. By suppressing surface fouling with an immobilized liquid lubricant layer, this technology not only enhances RNA-LNP production but also promises to transform the microfluidic manufacturing of diverse materials, ensuring more reliable and robust processes.

One-Pot Fabrication of Highly Flexible Fluorine-Free Lubricant-Infused Poly(vinyl alcohol) Films with Superior Antifouling Properties

In clinical settings, biofluid-contacting devices can suffer from biofouling, leading to thrombus formation and bacterial biofilm buildup, which impair device function and pose health risks. Traditional antifouling methods, including the use of hydrophilic polymers and heparin coatings, often suffer from instability and reduced bioactivity over time. Lubricant-infused surfaces (LIS) have emerged as a promising alternative due to their long-term stability and broad-spectrum repellency. However, current LIS technologies typically involve complex, multistep processes that restrict their application to surface layers, potentially compromising performance under mechanical stress. This study introduces a novel method for bulk modification of poly(vinyl alcohol) (PVA) films, creating flexible lubricant-infused PVA membranes with superior antifouling properties. These films are fabricated by cross-linking the PVA chains using n-propyltrichlorosilane (n-PTCS) and subsequent infusion with silicone oil as a lubricant. The modified PVA films significantly prevent bacterial adhesion and prolong blood and plasma clot formation. Additionally, these films exhibit enhanced mechanical properties, particularly in elasticity and flexibility compared to unmodified PVA films. The developed technique provides a straightforward method for creating flexible, super-repellent biointerfaces with the potential to prevent blood adhesion and bacterial biofilm formation, which are common complications associated with biofluid-contacting devices and medical implants.

Dynamic silicone hydrogel gauze coatings with dual anti-blood adhesion mechanism for rapid hemostasis and minimal secondary damage

Hemostatic materials that can rapidly control bleeding without causing secondary damage or sharp pain upon removal are receiving increasing demands in acute trauma treatments and first-aid supplies. Here, we report the development of a dynamic silicone hydrogel coating on medical gauze to enable rapid hemostasis and synergistic anti-blood adhesion properties. The silicone hydrogel can spontaneously form oriented cross-linked structures on fibrous medical gauze through a solution-processing method to achieve macroscopic superhydrophobicity with microscopic surface slipperiness, resulting in excellent anti-blood adhesion with the on-wound peeling force at ~0 millinewton. The development of dynamic silicone hydrogel coating on medical gauze enables a unique integration of advanced features including instant bleeding control, excellent anti-blood adhesion, and excellent air permeability. The proposed strategy is also suitable for scalable production, making it promising in the applications of trauma management.

Antithrombotic coating with sheltered positive charges prevents contact activation by controlling factor XII-biointerface binding

Antithrombotic surfaces that prevent coagulation activation without interfering with haemostasis are required for blood-contacting devices. Such materials would restrain device-induced thrombogenesis and decrease the need for anticoagulant use, thereby reducing unwanted bleeding. Here, by optimizing the interactions with coagulation factor XII rather than preventing its surface adsorption, we develop a substrate-independent antithrombotic polymeric coating with sheltered positive charges. The antithrombic properties of the coating were demonstrated in vitro with human blood and in vivo using a carotid artery-jugular vein shunt model in rabbits. The coating exhibits a strong interaction with factor XII, but results in a low reciprocal activation of the contact pathway that triggers clot formation. These findings contradict the prevailing strategy of designing antithrombotic materials through protein-repelling surfaces. Overall, the polymeric coating we describe can benefit most blood-contacting devices and is a useful engineering guideline for designing surfaces with improved antithrombotic properties.

A biomimetic approach towards a universal slippery liquid infused surface coating

One biomimetic approach to surface passivation involves a series of surface coatings based on the slick surfaces of carnivorous pitcher plants (Nepenthes), termed slippery liquid-infused porous surfaces (SLIPS). This study introduces a simplified method to produce SLIPS using a polydopamine (PDA) anchor layer, inspired by mussel adhesion. SLIPS layers were formed on cyclic olefin copolymer, silicon, and stainless steel substrates, by first growing a PDA film on each substrate. This was followed by a hydrophobic liquid anchor layer created by functionalizing the PDA film with a fluorinated thiol. Finally, perfluorodecalin was applied to the surface immediately prior to use. These biomimetic surface functionalization steps were confirmed by several complimentary surface analysis techniques. The wettability of each surface was probed with water contact angle measurements, while the chemical composition of the layer was determined by X-ray photoelectron spectroscopy. Finally, ordering of specific chemical groups within our PDA SLIPS layer was determined via sum frequency generation spectroscopy. The hemocompatibility of our new PDA-based SLIPS coating was then evaluated by tracking FXII activation, fibrin generation time, clot morphology, and platelet adhesion to the surface. This hemocompatibility work suggests that PDA SLIPS coatings slow or prevent clotting, but the observation of both FXII activation and the presence of adherent and activated platelets at the PDA SLIPS samples imply that this formulation of a SLIPS coating is not completely omniphobic.

Aggregation-Disruption-Induced Multi-Scale Mediating Strategy for Anticoagulation in Blood-Contacting Devices

Minimally invasive blood-contacting interventional devices are increasingly used to treat cardiovascular diseases. However, the risk of device-related thrombosis remains a significant concern, particularly the formation of cycling thrombi, which pose life-threatening risks. To better understand the interactions between these devices and blood, the initial stages of coagulation contact activation on extrinsic surfaces are investigated. Direct force measurements reveals that activated contact factors stimulate the intrinsic coagulation pathway and promote surface crosslinking of fibrin. Furthermore, fibrin aggregation is disrupted by surface-grafted inhibitors, as confirmed by ex vivo coagulation tests. An engineered serum protein with zwitterion grafts to resist the deposition of biological species such as fibrin, platelets, and red blood cells is also developed. Simultaneously, a protease inhibitor-based coacervate is incorporated into the coating to inhibit the intrinsic pathway effectively. The loaded coacervate can be released and reloaded through modulation of catechol-amine interactions, facilitating material regeneration. The strategy offers a novel multi-scale mediation strategy that simultaneously inhibits nanoscale coagulation factors and resists microscale thrombus aggregation, providing a long-term solution for anticoagulation in blood-contacting devices.

Advanced Antibacterial Strategies for Combatting Biomaterial-Associated Infections: A Comprehensive Review

Biomaterial-associated infections (BAIs) pose significant challenges in modern medical technologies, being a major postoperative complication and leading cause of implant failure. These infections significantly risk patient health, resulting in prolonged hospitalization, increased morbidity and mortality rates, and elevated treatment expenses. This comprehensive review examines the mechanisms driving bacterial adhesion and biofilm formation on biomaterial surfaces, offering an in-depth analysis of current antimicrobial strategies for preventing BAIs. We explore antimicrobial-eluting biomaterials, contact-killing surfaces, and antifouling coatings, emphasizing the application of antifouling polymer brushes on medical devices. Recent advancements in multifunctional antimicrobial biomaterials, which integrate multiple mechanisms for superior protection against BAIs, are also discussed. By evaluating the advantages and limitations of these strategies, this review aims to guide the design and development of highly efficient and biocompatible antimicrobial biomaterials. We highlight potential design routes that facilitate the transition from laboratory research to clinical applications. Additionally, we provide insights into the potential of synthetic biology as a novel approach to combat antimicrobial resistance. This review aspires to inspire future research and innovation, ultimately improving patient outcomes and advancing medical device technology.

Rapid Construction of Liquid-like Surfaces via Single-Cycle Polymer Brush Grafting for Enhanced Antifouling in Microfluidic Systems

Liquid-like surfaces have demonstrated immense potential in their ability to resist cell adhesion, a critical requirement for numerous applications across various domains. However, the conventional methodologies for preparing liquid-like surfaces often entail a complex multi-step polymer brush modification process, which is not only time-consuming but also presents significant challenges. In this work, we developed a single-cycle polymer brush modification strategy to build liquid-like surfaces by leveraging high-molecular-weight bis(3-aminopropyl)-terminated polydimethylsiloxane, which significantly simplifies the preparation process. The resultant liquid-like surface is endowed with exceptional slipperiness, effectively inhibiting bacterial colonization and diminishing the adherence of platelets. Moreover, it offers promising implications for reducing the dependency on anticoagulants in microfluidic systems constructed from PDMS, all while sustaining its antithrombotic attributes.

Molecular Interaction Mechanisms Between Lubricant-Infused Slippery Surfaces and Mussel-Inspired Polydopamine Adhesive and DOPA Moiety

Lubricant-infused slippery surfaces have recently emerged as promising antifouling coatings, showing potential against proteins, cells, and marine mussels. However, a comprehensive understanding of the molecular binding behaviors and interaction strength of foulants to these surfaces is lacking. In this work, mussel-inspired chemistry based on catechol-containing chemicals including 3,4-dihydroxyphenylalanine (DOPA) and polydopamine (PDA) is employed to investigate the antifouling performance and repellence mechanisms of fluorinated-based slippery surface, and the correlated interaction mechanisms are probed using atomic force microscopy (AFM). Intermolecular force measurements and deposition experiments between PDA and the surface reveal the ability of lubricant film to inhibit the contact of PDA particles with the substrate. Moreover, the binding mechanisms and bond dissociation energy between a single DOPA moiety and the lubricant-infused slippery surface are quantitatively investigated employing single-molecule force spectroscopy based on AFM (SM-AFM), which reveal that the infused lubricant layer can remarkably influence the dissociation forces and weaken the binding strength between DOPA and underneath per-fluorinated monolayer surface. This work provides new nanomechanical insights into the fundamental antifouling mechanisms of the lubricant-infused slippery surfaces against mussel-derived adhesive chemicals, with important implications for the design of lubricant-infused materials and other novel antifouling platforms for various bioengineering and engineering applications.

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.

Study of the Structure of Hyperbranched Polyglycerol Coatings and Their Antibiofouling and Antithrombotic Applications

While blood-contacting materials are widely deployed in medicine in vascular stents, catheters, and cannulas, devices fail in situ because of thrombosis and restenosis. Furthermore, microbial attachment and biofilm formation is not an uncommon problem for medical devices. Even incremental improvements in hemocompatible materials can provide significant benefits for patients in terms of safety and patency as well as substantial cost savings. Herein, a novel but simple strategy is described for coating a range of medical materials, that can be applied to objects of complex geometry, involving plasma-grafting of an ultrathin hyperbranched polyglycerol coating (HPG). Plasma activation creates highly reactive surface oxygen moieties that readily react with glycidol. Irrespective of the substrate, coatings are uniform and pinhole free, comprising O─C─O repeats, with HPG chains packing in a fashion that holds reversibly binding proteins at the coating surface. In vitro assays with planar test samples show that HPG prevents platelet adhesion and activation, as well as reducing (>3 log) bacterial attachment and preventing biofilm formation. Ex vivo and preclinical studies show that HPG-coated nitinol stents do not elicit thrombosis or restenosis, nor complement or neutrophil activation. Subcutaneous implantation of HPG coated disks under the skin of mice shows no evidence of toxicity nor inflammation.

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.

On-demand bactericidal and self-adaptive antifouling hydrogels for self-healing and lubricant coatings of catheters

Catheter-related infections are one of the most common nosocomial infections with increasing morbidity and mortality, and robust antibacterial or antifouling catheter coatings remain great challenges for long-term implantation. Herein, multifunctional hydrogel coatings were developed to provide persistent and self-adaptive antifouling and antibacterial effects with self-healing and lubricant capabilities. Polyvinyl alcohol (PVA) with β-cyclodextrin (β-CD) grafts (PVA-Cd) and 4-arm polyethylene glycol (PEG) with adamantane and quaternary ammonium compound (QAC) terminals (QA-PEG-Ad) were crosslinked through host-guest recognitions between adamantane and β-CD moieties to acquire PVEQ coatings. In response to bacterial infections, QACs exhibit reversible transformation between zwitterions (pH 7.4) and cationic lactones (pH 5.5) to generate on-demand bactericidal effect. Highly hydrophilic PEG/PVA backbones and zwitterionic QACs build a lubricate surface and decrease the friction coefficient 10 times compared with that of bare catheters. The antifouling hydrated layer significantly inhibits blood protein adsorption and platelet activation and reveals negligible hemolysis and cytotoxicity. The dynamic host-guest crosslinking achieves full self-healing of cracks in PVEQ hydrogels, and the mechanical profiles were recovered to over 90 % after rejuvenating the broken hydrogels, exhibiting a long-term stability after mechanical stretching, twisting, knotting and compression. After subcutaneous implantation and local bacterial infection, the retrieved PVEQ-coated catheters display no tissue adhesion and 3 log folds lower bacterial number than that of bare catheters. PVEQ coatings effectively prevent the repeated bacterial infections and there are few inflammatory reactions in the surrounding tissue, while substantial lymphoid infiltration and inflammatory cell aggregation occur in muscle tissues around the bare catheter. Thus, this study demonstrates a catheter coating strategy by on-demand bactericidal, self-adaptive antifouling, self-healing and lubricant hydrogels to address medical devices-related infections. STATEMENT OF SIGNIFICANCE: It is estimated over two billion peripheral intravenous catheters are annually used in hospitals around the world, and catheter-associated infection has become a great clinical challenge with rapidly rising morbidity and mortality. Surface coating is considered a promising approach, but substantial challenges remain in the development of coatings that simultaneously satisfy both anti-fouling and antibacterial attributes. Even more, few attempts have been made to design mechanically robust coatings and reversible antibacterial or antifouling capabilities, which are critical for long-term medical implants. To address these challenges, we propose a concise strategy to develop hydrogel coatings from commercially available poly(ethylene glycol) and polyvinyl alcohol. In addition to self-healing and lubricant capabilities, the reversible conversion between zwitterionic and cationic lactones of quaternary ammonium compounds enables on-demand bactericidal and self-adaptive antifouling effects.

"Reactive" Chemical Strategy to Attain Substrate Independent "Liquid-Like" Omniphobic Solid Anti-Biofouling Coatings

Covalent and defect-free surface-grafted solid lubricating chains that can impart 'liquid-like' slippery behavior have proven advantageous over lubricant infused and textured anti-wetting surfaces. Herein, the co-hydrolysis and co-condensation of a mixture of organosilanes followed by the epoxy-amine ring opening reaction at the interface results in a highly robust, transparent and 'liquid-like' solid slippery omniphobic coating (LL-OSC). The presence of the epoxy-terminated organosilane a) acts as a molecular spacer in between the low-surface energy, rigid fluorine terminated silane and b) provides 'reactive' epoxy groups for covalent binding to a pre-functionalized amine surface for potential applicability in droplet transport and manipulation, diagnostics etc. LL-OSC exhibits resistance to both solid and liquid abrasions such as sandpaper abrasions, prolonged UV irradiation, DI water and high temperature (30 days), submersion in chemically contaminated aqueous solutions. This is the first report of a hemocompatible solid slippery coating for inhibiting platelet adhesion, thus, paving way for blood-contacting medical device applications. Our LL-OSC exhibits remarkable cytocompatibility, repellence to plasma protein, cells and prevents biofilm formation. Additionally, the substrate independent LL-OSC can be applied onto metals and polymers. We envision that the reported durable, solid slippery coating will find widespread applicability in hospital settings, electronic devices etc.

Bioinspired Slippery Surfaces for Liquid Manipulation from Tiny Droplet to Bulk Fluid

Slippery surfaces, which originate in nature with special wettability, have attracted considerable attention in both fundamental research and practical applications in a variety of fields due to their unique characteristics of superlow liquid friction and adhesion. Although research on bioinspired slippery surfaces is still in its infancy, it is a rapidly growing and enormously promising field. Herein, a systematic review of recent progress in bioinspired slippery surfaces, beginning with a brief introduction of several typical creatures with slippery property in nature, is presented. Subsequently,this review gives a detailed discussion on the basic concepts of the wetting, friction, and drag from micro- and macro-aspects and focuses on the underlying slippery mechanism. Next, the state-of-the-art developments in three categories of slippery surfaces of air-trapped, liquid-infused, and liquid-like slippery surfaces, including materials, design principles, and preparation methods, are summarized and the emerging applications are highlighted. Finally, the current challenges and future prospects of various slippery surfaces are addressed.

Liquid-Like Surfaces with Enhanced De-Wettability and Durability: From Structural Designs to Potential Applications

Liquid-like surfaces (LLSs) with dynamic repellency toward various pollutants (e.g., bacteria, oil, and ice), have shown enormous potential in the fields of biology, environment, and energy. However, most of the reported LLSs cannot meet the demands for practical applications, particularly in terms of de-wettability and durability. To solve these problems, considerable progress has been made in enhancing the de-wettability and durability of LLSs in complex environments. Therefore, this review mainly focuses on the recent progress in LLSs, encompassing designed structures and repellent capabilities, as well as their diverse applications, offering greater insights for the targeted design of desired LLSs. First, a detailed overview of the development of LLSs from the perspective of their molecular structural evolution is provided. Then highlight recent approaches for enhancing the dynamic de-wettability and durability of LLSs by optimizing their structural designs, including linear, looped, crosslinked, and hybrid structures. Later, the diverse applications and unique advantages of recently developed LLSs, including repellency (e.g., liquid anti-adhesion/transportation/condensation, anti-icing/scaling/waxing, and biofouling repellency) are summarized. Finally, Perspectives on potential innovative advancements and the promotion of technology selection to advance this exciting field are offered.

Multi-component liquid-infused systems: a new approach to functional coatings

Antifouling liquid-infused surfaces have generated interest in multiple fields due to their diverse applications in industry and medicine. In nearly all reports to date, the liquid component consists of only one chemical species. However, unlike traditional solid surfaces, the unique nature of liquid surfaces holds the potential for synergistic and even adaptive functionality simply by including additional elements in the liquid coating. In this work, we explore the concept of multi-component liquid-infused systems, in which the coating liquid consists of a primary liquid and a secondary component or components that provide additional functionality. For ease of understanding, we categorize recently reported multi-component liquid-infused surfaces according to the size of the secondary components: molecular scale, in which the secondary components are molecules; nanoscale, in which they are nanoparticles or their equivalent; and microscale, in which the additional components are micrometer size or above. We present examples at each scale, showing how introducing a secondary element into the liquid can result in synergistic effects, such as maintaining a pristine surface while actively modifying the surrounding environment, which are difficult to achieve in other surface treatments. The review highlights the diversity of fabrication methods and provides perspectives on future research directions. Introducing secondary components into the liquid matrix of liquid-infused surfaces is a promising strategy with significant potential to create a new class of multifunctional materials. Keywords: Active surfaces; Antimicrobial; Antifouling; Interfaces; Sensing surfaces.

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.

Wetting on silicone surfaces

Silicone is frequently used as a model system to investigate and tune wetting on soft materials. Silicone is biocompatible and shows excellent thermal, chemical, and UV stability. Moreover, the mechanical properties of the surface can be easily varied by several orders of magnitude in a controlled manner. Polydimethylsiloxane (PDMS) is a popular choice for coating applications such as lubrication, self-cleaning, and drag reduction, facilitated by low surface energy. Aiming to understand the underlying interactions and forces, motivated numerous and detailed investigations of the static and dynamic wetting behavior of drops on PDMS-based surfaces. Here, we recognize the three most prevalent PDMS surface variants, namely liquid-infused (SLIPS/LIS), elastomeric, and liquid-like (SOCAL) surfaces. To understand, optimize, and tune the wetting properties of these PDMS surfaces, we review and compare their similarities and differences by discussing (i) the chemical and molecular structure, and (ii) the static and dynamic wetting behavior. We also provide (iii) an overview of methods and techniques to characterize PDMS-based surfaces and their wetting behavior. The static and dynamic wetting ridge is given particular attention, as it dominates energy dissipation, adhesion, and friction of sliding drops and influences the durability of the surfaces. We also discuss special features such as cloaking and wetting-induced phase separation. Key challenges and opportunities of these three surface variants are outlined.

Thermally Drawn-Based Microtubule Soft Continuum Robot for Cardiovascular Intervention

Cardiovascular disease is becoming the leading cause of human mortality. In order to address this, flexible continuum robots have emerged as a promising solution for miniaturizing and automating vascular interventional equipment for diagnosing and treating cardiovascular diseases. However, existing continuum robots used for vascular intervention face challenges such as large cross-sectional sizes, inadequate driving force, and lack of navigation control, preventing them from accessing cerebral blood vessels or capillaries for medical procedures. Additionally, the complex manufacturing process and high cost of soft continuum robots hinder their widespread clinical application. In this study, we propose a thermally drawn-based microtubule soft continuum robot that overcomes these limitations. The proposed robot has cross-sectional dimensions several orders of magnitude smaller than the smallest commercially available conduits, and it can be manufactured without any length restrictions. By utilizing a driving strategy based on liquid kinetic energy advancement and external magnetic field for steering, the robot can easily navigate within blood vessels and accurately reach the site of the lesion. This innovation holds the potential to achieve controlled navigation of the robot throughout the entire blood vessel, enabling in situ diagnosis and treatment of cardiovascular diseases.

Recent Developments in Slippery Liquid-Infused Porous Surface Coatings for Biomedical Applications

Slippery liquid-infused porous surface (SLIPS), inspired by the Nepenthes pitcher plant, exhibits excellent performances as it has a smooth surface and extremely low contact angle hysteresis. Biomimetic SLIPS attracts considerable attention from the researchers for different applications in self-cleaning, anti-icing, anticorrosion, antibacteria, antithrombotic, and other fields. Hence, SLIPS has shown promise for applications across both the biomedical and industrial fields. However, the manufacturing of SLIPS with strong bonding ability to different substrates and powerful liquid locking performance remains highly challenging. In this review, a comprehensive overview of research on SLIPS for medical applications is conducted, and the design parameters and common fabrication methods of such surfaces are summarized. The discussion extends to the mechanisms of interaction between microbes, cells, proteins, and the liquid layer, highlighting the typical antifouling applications of SLIPS. Furthermore, it identifies the potential of utilizing the controllable factors provided by SLIPS to develop innovative materials and devices aimed at enhancing human health.

Protein adsorption on blood-contacting surfaces: A thermodynamic perspective to guide the design of antithrombogenic polymer coatings

Blood-contacting medical devices often succumb to thrombosis, limiting their durability and safety in clinical applications. Thrombosis is fundamentally initiated by the nonspecific adsorption of proteins to the material surface, which is strongly governed by thermodynamic factors established by the nature of the interaction between the material surface, surrounding water molecules, and the protein itself. Along these lines, different surface materials (such as polymeric, metallic, ceramic, or composite) induce different entropic and enthalpic changes at the surface-protein interface, with material wettability significantly impacting this behavior. Consequently, protein adsorption on medical devices can be modulated by altering their wettability and surface energy. A plethora of polymeric coating modifications have been utilized for this purpose; hydrophobic modifications may promote or inhibit protein adsorption determined by van der Waals forces, while hydrophilic materials achieve this by mainly relying on hydrogen bonding, or unbalanced/balanced electrostatic interactions. This review offers a cohesive understanding of the thermodynamics governing these phenomena, to specifically aid in the design and selection of hemocompatible polymeric coatings for biomedical applications. STATEMENT OF SIGNIFICANCE: Blood-contacting medical devices often succumb to thrombosis, limiting their durability and safety in clinical applications. A plethora of polymeric coating modifications have been utilized for addressing this issue. This review offers a cohesive understanding of the thermodynamics governing these phenomena, to specifically aid in the design and selection of hemocompatible polymeric coatings for biomedical applications.

Study of Hydration Repulsion of Zwitterionic Polymer Brushes Resistant to Protein Adhesion through Molecular Simulations

The fabrication of antifouling zwitterionic polymer brushes represents a leading approach to mitigate nonspecific adhesion on the surfaces of medical devices. This investigation seeks to elucidate the correlation between the material composition and structural attributes of these polymer brushes in preventing protein adhesion. To achieve this goal, we modeled three different zwitterionic brushes, namely, carboxybetaine methacrylate (CBMA), sulfobetaine methacrylate (SBMA), and (2-(methacryloyloxy)ethyl)-phosphorylcholine (MPC). The simulations revealed that elevating the grafting density enhances the structural stability, hydration strength, and resistance to protein adhesion exhibited by the polymer brushes. PCBMA manifests a more robust hydration layer, while PMPC demonstrates the slightest interaction with proteins. In a comprehensive evaluation, PSBMA polymer brushes emerged as the best choice with superior stability, enhanced protein repulsion, and minimally induced protein deformation, resulting in effective resistance to nonspecific adhesion. The high-density SBMA polymer brushes significantly reduce the level of protein adhesion in AFM testing. In addition, we have pioneered the quantitative characterization of hydration repulsion in polymer brushes by analyzing the hydration repulsion characteristics at different materials and graft densities. In summary, our study provides a nuanced understanding of the material and structural determinants influencing the capacity of zwitterionic polymer brushes to thwart protein adhesion. Additionally, it presents a quantitative elucidation of hydration repulsion, contributing to the advancement and application of antifouling polymer brushes.

Achieving Extreme Pressure Resistance to Liquids on a Super-Omniphobic Surface with Armored Reentrants

Static repellency and pressure resistance to liquids are essential for high-performance super-omniphobic surfaces. However, these two merits appear mutually exclusive in conventional designs because of their conflicting structural demands: Static liquid repellency necessitates minimal solid-liquid contact, which in turn inevitably undercuts the surface's ability to resist liquid invasion exerted by the elevated pressure. Here, inspired by the Springtail, these two merits can be simultaneously realized by structuring surfaces at two size scales, with a micrometric reentrant structure providing static liquid repellency and a nanometric reentrant structure providing pressure resistance, which dexterously avoids the dilemma of their structural conflicts. The nanometric reentrants are densely packed on the micrometric ones, serving as "armor" that prevents liquids invasion by generating multilevel energy barriers, thus naming the surface as the armored reentrants (AR) surface. The AR surface could repel liquids with very low surface tensions, such as silicone oil (21 mN m-1), and simultaneously resist great pressure from the liquids, exemplified by enduring the impact of low-surface-tension liquids under a high weber number (>400), the highest-pressure resistance ever reported. With its scalable fabrication and enhanced performance, our design could extend the application scope of liquid-repellent surfaces toward ultimate industrial settings.

High-density zwitterionic polymer brushes exhibit robust lubrication properties and high antithrombotic efficacy in blood-contacting medical devices

High-performance catheters are essential for interventional surgeries, requiring reliable anti-adhesive and lubricated surfaces. This article develops a strategy for constructing high-density sulfobetaine zwitterionic polymer brushes on the surface of catheters, utilizing dopamine and sodium alginate as the primary intermediate layers, where dopamine provides mussel-protein-like adhesion to anchor the polymer brushes to the catheter surface. Hydroxyl-rich sodium alginate increases the number of grafting sites and improves the grafting mass by more than 4 times. The developed high-density zwitterionic polymer brushes achieve long-lasting and effective lubricity (μ<0.0078) and are implanted in rabbits for four hours without bio-adhesion and thrombosis in the absence of anticoagulants such as heparin. Experiments and molecular dynamics simulations demonstrate that graft mass plays a decisive role in the lubricity and anti-adhesion of polymer brushes, and it is proposed to predict the anti-adhesion of polymer brushes by their lubricity to avoid costly and time-consuming bioassays during the development of amphoteric polymer brushes. A quantitative influence of hydration in the anti-adhesion properties of amphiphilic polymer brushes is also revealed. Thus, this study provides a new approach to safe, long-lasting lubrication and anticoagulant surface modification for medical devices in contact with blood. STATEMENT OF SIGNIFICANCE: High friction and bioadhesion on medical device surfaces can pose a significant risk to patients. In response, we have developed a safer, simpler, and more application-specific surface modification strategy that addresses both the lubrication and anti-bioadhesion needs of medical device surfaces. We used dopamine and sodium alginate as intermediate layers to drastically increase the grafting density of the zwitterionic brushes and enabled the modified surfaces to have an extremely low coefficient of friction (μ = 0.0078) and to remain non-bioadhesive for 4 hours in vivo. Furthermore, we used molecular dynamics simulations to gain insight into the mechanisms behind the superior anti-adhesion properties of the high-density polymer brushes. Our work contributes to the development and application of surface-modified coatings.

Evolution of Hybrid Hydrogels: Next-Generation Biomaterials for Drug Delivery and Tissue Engineering

Hydrogels, being hydrophilic polymer networks capable of absorbing and retaining aqueous fluids, hold significant promise in biomedical applications owing to their high water content, permeability, and structural similarity to the extracellular matrix. Recent chemical advancements have bolstered their versatility, facilitating the integration of the molecules guiding cellular activities and enabling their controlled activation under time constraints. However, conventional synthetic hydrogels suffer from inherent weaknesses such as heterogeneity and network imperfections, which adversely affect their mechanical properties, diffusion rates, and biological activity. In response to these challenges, hybrid hydrogels have emerged, aiming to enhance their strength, drug release efficiency, and therapeutic effectiveness. These hybrid hydrogels, featuring improved formulations, are tailored for controlled drug release and tissue regeneration across both soft and hard tissues. The scientific community has increasingly recognized the versatile characteristics of hybrid hydrogels, particularly in the biomedical sector. This comprehensive review delves into recent advancements in hybrid hydrogel systems, covering the diverse types, modification strategies, and the integration of nano/microstructures. The discussion includes innovative fabrication techniques such as click reactions, 3D printing, and photopatterning alongside the elucidation of the release mechanisms of bioactive molecules. By addressing challenges, the review underscores diverse biomedical applications and envisages a promising future for hybrid hydrogels across various domains in the biomedical field.

Slippery Porous-Liquid-Infused Porous Surface (SPIPS) with On-Demand Responsive Switching between "Defensive" and "Offensive" Antifouling Modes

Slippery liquid-infused porous surfaces (SLIPS) have received widespread attention in the antifouling field. However, the reduction in antifouling performance caused by lubricant loss limits their application in marine antifouling. Herein, inspired by the skin of a poison dart frog which contains venom glands and mucus, a porous liquid (PL) based on ZIF-8 is prepared as a lubricant and injected into a silicone polyurethane (SPU) matrix to construct a new type of SLIPS for marine antifouling applications: the slippery porous-liquid-infused porous surface (SPIPS). The SPIPS consists of a responsive antifoulant-releasing switch between "defensive" and "offensive" antifouling modes to intelligently enhance the antifouling effect after lubricant loss. The SPIPS can adjust antifouling performance to meet the antifouling requirements under different light conditions. The wastage of antifoulants is reduced, thereby effectively maintaining the durability and service life of SLIPS materials. The SPIPS exhibits efficient lubricant self-replenishment, self-cleaning, anti-protein, anti-bacterial, anti-algal, and self-healing (97.48%) properties. Furthermore, it shows satisfactory 360-day antifouling performance in actual marine fields during boom seasons, demonstrating the longest antifouling lifespan in the field tests of reported SLIPS coatings. Hence, the SPIPS can effectively promote the development of SLIPS for neritic antifouling.

Tannic Acid-Based Coatings Containing Zwitterionic Copolymers for Improved Antifouling and Antibacterial Properties

The prevention of biofilm formation on medical devices has become highly challenging in recent years due to its resistance to bactericidal agents and antibiotics, ultimately resulting in chronic infections to medical devices. Therefore, developing inexpensive, biocompatible, and covalently bonded coatings to combat biofilm formation is in high demand. Herein, we report a coating fabricated from tannic acid (TA) as an adhesive and a reducing agent to graft the zwitterionic polymer covalently in a one-step method. Subsequently, silver nanoparticles (AgNPs) are generated in situ to develop a coating with antifouling and antibacterial properties. To enhance the antifouling property and biocompatibility of the coating, the bioinspired zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) was copolymerized with 2-aminoethyl methacrylamide hydrochloride (AEMA) using conventional free-radical polymerization. AEMA moieties containing amino groups were used to facilitate the conjugation of the copolymer with quinone groups on TA through the Michael addition reaction. Three copolymers with different ratios of monomers were synthesized to understand their impacts on fouling resistance: PMPC100, p(MPC80-st-AEMA20), and p(MPC90-st-AEMA10). To impart antibacterial properties to the surface, AgNPs were formed in situ, utilizing the unreacted quinone groups on TA, which can reduce the silver ions. The successful coating of TA and copolymer onto the surfaces was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and its excellent wettability was verified by the water contact angle (CA). Furthermore, the functionalized coatings showed antibacterial properties against E. coli and S. aureus and remarkably decreased the adhesion of the BSA protein. The surfaces can also prevent the adhesion of bacteria cells, as confirmed by the inhibition zone test. In addition, they showed negligible cytotoxicity to normal human lung fibroblast cells (MRC-5). The as-prepared coatings are potentially valuable for biomedical applications.

Visualization and Experimental Characterization of Wrapping Layer Using Planar Laser-Induced Fluorescence

Droplets on nanotextured oil-impregnated surfaces have high mobility due to record-low contact angle hysteresis (∼1-3°), attributed to the absence of solid-liquid contact. Past studies have utilized the ultralow droplet adhesion on these surfaces to improve condensation, reduce hydrodynamic drag, and inhibit biofouling. Despite their promising utility, oil-impregnated surfaces are not fully embraced by industry because of the concern for lubricant depletion, the source of which has not been adequately studied. Here, we use planar laser-induced fluorescence (PLIF) to not only visualize the oil layer encapsulating the droplet (aka wrapping layer) but also measure its thickness since the wrapping layer contributes to lubricant depletion. Our PLIF visualization and experiments show that (a) due to the imbalance of interfacial forces at the three-phase contact line, silicone oil forms a wrapping layer on the outer surface of water droplets, (b) the thickness of the wrapping layer is nonuniform both in space and time, and (c) the time-average thickness of the wrapping layer is ∼50 ± 10 nm, a result that compares favorably with our scaling analysis (∼50 nm), which balances the curvature-induced capillary force with the intermolecular van der Waals forces. Our experiments show that, unlike silicone oil, mineral oil does not form a wrapping layer, an observation that can be exploited to mitigate oil depletion of nanotextured oil-impregnated surfaces. Besides advancing our mechanistic understanding of the wrapping oil layer dynamics, the insights gained from this work can be used to quantify the lubricant depletion rate by pendant droplets in dropwise condensation and water harvesting.

Zwitterionic polymers-armored amyloid-like protein surface combats thrombosis and biofouling

Proteins, cells and bacteria adhering to the surface of medical devices can lead to thrombosis and infection, resulting in significant clinical mortality. Here, we report a zwitterionic polymers-armored amyloid-like protein surface engineering strategy we called as "armored-tank" strategy for dual functionalization of medical devices. The "armored-tank" strategy is realized by decoration of partially conformational transformed LZM (PCTL) assembly through oxidant-mediated process, followed by armoring with super-hydrophilic poly-2-methacryloyloxyethyl phosphorylcholine (pMPC). The outer armor of the "armored-tank" shows potent and durable zone defense against fibrinogen, platelet and bacteria adhesion, leading to long-term antithrombogenic properties over 14 days in vivo without anticoagulation. Additionally, the "fired" PCTL from "armored-tank" actively and effectively kills both Gram-positive and Gram-negative bacterial over 30 days as a supplement to the lacking bactericidal functions of passive outer armor. Overall, this "armored-tank" surface engineering strategy serves as a promising solution for preventing biofouling and thrombotic occlusion of medical devices.

Reduced Sliding Friction of Lubricant-Impregnated Catheters

During urethral catheterization, sliding friction can cause discomfort and even hemorrhaging. In this report, we use a lubricant-impregnated polydimethylsiloxane coating to reduce the sliding friction of a catheter. Using a pig urethra attached to a microforce testing system, we found that a lubricant-impregnated catheter reduces the sliding friction during insertion by more than a factor of two. This suggests that slippery, lubricant-impregnated surfaces have the potential to enhance patient comfort and safety during catheterization.

In vitro hemocompatibility screening of a slippery liquid impregnated surface coating for extracorporeal organ support applications

INTRODUCTION

Clot formation, infection, and biofouling are unfortunate but frequent complications associated with the use of blood-contacting medical devices. The challenge of blood-foreign surface interactions is exacerbated during medical device applications involving substantial blood contact area and extended duration of use, such as extracorporeal life support (ECLS). We investigated a novel surface modification, a liquid-impregnated surface (LIS), designed to minimize protein adsorption and thrombus development on medical plastics.

METHODS

The hemocompatibility and efficacy of LIS was investigated first in a low-shear model with LIS applied to the lumen of blood incubation vials and exposed to human whole blood. Additionally, LIS was evaluated in a 6 h ex vivo circulation model with swine blood using full-scale ECLS circuit tubing and centrifugal pumps with clinically relevant flow rate (1.5 L/min) and shear conditions for extracorporeal carbon dioxide removal.

RESULTS

Under low-shear, LIS preserved fibrinogen concentration in blood relative to control polymers (+40 ± 6 mg/dL vs polyvinyl chloride, p < .0001), suggesting protein adsorption was minimized. A fibrinogen adhesion assay demonstrated a dramatic reduction in protein adsorption under low shear (87% decrease vs polyvinyl chloride, p = .01). Thrombus deposition and platelet adhesion visualized by scanning electron microscopy were drastically reduced. During the 6 h ex vivo circulation, platelets in blood exposed to LIS tubing did not become significantly activated or procoagulant, as occurred with control tubing; and again, thrombus deposition was visually reduced.

CONCLUSIONS

A LIS coating demonstrated potential to reduce thrombus formation on medical devices. Further testing is needed specialized to clinical setting and duration of use for specific medical target applications.

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.

Glycocalyx-inspired dynamic antifouling surfaces for temporary intravascular devices

Protein and cell adhesion on temporary intravascular devices can lead to thrombosis and tissue embedment, significantly increasing complications and device retrieval difficulties. Here, we propose an endothelial glycocalyx-inspired dynamic antifouling surface strategy for indwelling catheters and retrievable vascular filters to prevent thrombosis and suppress intimal embedment. This strategy is realized on the surfaces of substrates by the intensely dense grafting of hydrolyzable endothelial polysaccharide hyaluronic acid (HA), assisted by an amine-rich phenol-polyamine universal platform. The resultant super-hydrophilic surface exhibits potent antifouling property against proteins and cells. Additionally, the HA hydrolysis induces continuous degradation of the coating, enabling removal of inevitable biofouling on the surface. Moreover, the dense grafting of HA also ensures the medium-term effectiveness of this dynamic antifouling surface. The coated catheters maintain a superior anti-thrombosis capacity in ex vivo blood circulation after 30 days immersion. In the abdominal veins of rats, the coated implants show inhibitory effects on intimal embedment up to 2 months. Overall, we envision that this glycocalyx-inspired dynamic antifouling surface strategy could be a promising surface engineering technology for temporary intravascular devices.

Surface modification of polyvinyl chloride with sodium alginate/carboxymethyl chitosan and heparin for realizing the anticoagulation

Thrombosis of extracorporeal circuits causes significant morbidity and mortality worldwide. In this study, plasma treatment technology and chemical grafting method were used to construct heparinized surfaces on the PVC substrate, which could not only reduce thrombosis but also decrease the side effects of the direct injection of anticoagulants. The PVC substrate was modified by plasma treatment technology firstly to obtain the active surface with the hydroxyl groups used for grafting. Then, heparin was grafted onto the modified PVC surface using different grafting strategies to prepare different heparinized surfaces. The experimental results indicated that the sodium alginate (SA) and carboxymethyl chitosan (CCS) used as interlayers could significantly increase the graft density of heparin to improve the anticoagulant effects and hemocompatibility of heparinized surfaces. In addition, the modification of heparin can further improve the anticoagulant effects. The CCS/low-molecular-weight heparin (LWMH) surface has the best anticoagulant properties, which can prolong the activated partial thromboplastin time (APTT) values of human plasma for about 35 s, reduce the hemolysis rates to <0.3 %, and perform well in the in-vitro blood circulation test. The heparinized surfaces prepared in this work have great application potential in anticoagulant treatment for medical devices.

Enhanced Anticoagulation of Hierarchy Liquid Infused Surfaces in Blood Flow

Liquid infused surfaces (LIS) hold remarkable potential in anticoagulation. However, liquid loss of LIS in the bloodstream remains a challenge toward its clinical application. Here, micronano hierarchy structures are obtained on the titanium alloy substrate by regulating the microspheres' distribution. When the gap between the microspheres is smaller than the diameter of the red blood cell (RBC), the LIS is more stable under the blood wash and presents a better anticoagulation performance. The proper interval is found to prevent the RBCs from entering the gap and remove the liquid on the surface. The retained thickness of the liquid film is measured by the atomic force microscopy (AFM) technique. The LIS is applied on the front guide vane of an artificial heart pump and exhibits significant improvement on anticoagulation in the blood circulation in vitro for 25 h. The techniques and findings can be used to optimize the anticoagulation performance of LIS-related biomedical implant devices.

Visualizing a Nanoscale Lubricant Layer under Blood Flow

Tethered-liquid perfluorocarbons (TLPs) are a class of liquid-infused surfaces with the ability to reduce blood clot formation (thrombosis) on blood-contacting medical devices. TLP comprises a tethered perfluorocarbon (TP) infused with a liquid perfluorocarbon (LP); this LP must be retained to maintain the antithrombotic properties of the layer. However, the stability of the LP layer remains in question, particularly for medical devices under blood flow. In this study, the lubricant thickness is spatially mapped and quantified in situ through confocal dual-wavelength reflection interference contrast microscopy. TLP coatings prepared on glass substrates are exposed to the flow of 37% glycerol/water mixtures (v/v) or whole blood at a shear strain rate of around 2900 s-1 to mimic physiological conditions (similar to flow conditions found in coronary arteries). Excess lubricant (>2 μm film thickness) is removed upon commencement of flow. For untreated glass, the lubricant is completely depleted after 1 min of shear flow. However, on optimized TLP surfaces, nanoscale films of lubricants (thickness between 100 nm and 2 μm) are retained over many tens of minutes of flow. The nanoscale films conform to the underlying structure of the TP layer and are sufficient to prevent the adhesion of red blood cells and platelets.

A Mucin-Based Bio-Ink for 3D Printing of Objects with Anti-Biofouling Properties

With its potential to revolutionize the field of personalized medicine by producing customized medical devices and constructs for tissue engineering at low costs, 3D printing has emerged as a highly promising technology. Recent advancements have sparked increasing interest in the printing of biopolymeric hydrogels. However, owing to the limited printability of those soft materials, the lack of variability in available bio-inks remains a major challenge. In this study, a novel bio-ink is developed based on functionalized mucin-a glycoprotein that exhibits a multitude of biomedically interesting properties such as immunomodulating activity and strong anti-biofouling behavior. To achieve sufficient printability of the mucin-based ink, its rheological properties are tuned by incorporating Laponite XLG as a stabilizing agent. It is shown that cured objects generated from this novel bio-ink exhibit mechanical properties partially similar to that of soft tissue, show strong anti-biofouling properties, good biocompatibility, tunable cell adhesion, and immunomodulating behavior. The presented findings suggest that this 3D printable bio-ink has a great potential for a wide range of biomedical applications, including tissue engineering, wound healing, and soft robotics.

Antifouling Surfaces Based on Polyzwitterion Loop Brushes

Antifouling surfaces have attracted increasing interest in recent years due to their potential application in various fields. In this work, we report a loop polyzwitterionic coating that exhibits excellent resistance to protein adsorption. Triblock and diblock copolymers of 2-[(2-hydroxyethyl)disulfanyl]ethyl methacrylate) (HSEMA) and 2-(dimethylamino)ethyl methacrylate) (DMAEMA) were synthesized by atom-transferred radical polymerization, followed by betainization of the DMAEMA block with 1,3-propane sultone and reduction of the disulfide bond in HSEMA to yield a triblock copolymer comprising a zwitterionic poly(sulfobetaine methacrylate) (PSBMA) midblock and poly(2-sulfanylethyl methacrylate) (PSEMA) terminal blocks as well as its diblock analogue that was of the same composition as the former and half the chain length. Both copolymers adsorbed to the gold substrate via the thiol groups in the terminal PSEMA block(s), creating loop and linear PSBMA brush coatings of comparable thickness, as revealed by X-ray photoelectron spectroscopy and ellipsometry. Adsorption of bovine serum albumin and fibrinogen as model proteins from solution to these surfaces was investigated by a quartz crystal microbalance with dissipation and confocal laser scanning microscopy (CLSM), and platelet and bacterial adhesions were assessed by scanning electron microscopy and CLSM. The results demonstrate that both linear and loop polyzwitterion brushes are excellent in resisting the adsorption of the foulants, and the loop brushes are superior to the linear analogues.

Water-Triggered Segment Orientation of Long-Lasting Anti-Biofouling Polyurethane Coatings on Biomedical Catheters via Solvent Exchange Strategy

The formation of biofilm and thrombus on medical catheters poses a significant life-threatening concern. Hydrophilic anti-biofouling coatings upon catheter surfaces with complex shapes and narrow lumens are demonstrated to have the potential in reducing complications. However, their effectiveness is constrained by poor mechanical stability and weak substrate adhesion. Herein, a novel zwitterionic polyurethane (SUPU) with strong mechanical stability and long-term anti-biofouling is developed by controlling the ratio of sulfobetaine-diol and ureido-pyrimidinone. Once immersed in water, as-synthesized zwitterionic coating (SUPU3 SE) would undergo a water-driven segment reorientation to obtain much higher durability than its direct drying one, even under various extreme treatments, including acidic solution, abrasion, ultrasonication, flushing, and shearing, in PBS at 37 °C for 14 days. Moreover, SUPU3 SE coating could achieve a 97.1% of exceptional reducing protein fouling, complete prevention of cell adhesion, and long-lasting anti-biofilm performance even after 30 days. Finally, the good anti-thrombogenic formations of SUPU3 SE coating with bacterial treatment are validated in blood circulation through an ex vivo rabbit arteriovenous shunt model. This work provides a facile approach to fabricating stable hydrophilic coating through a simple solvent exchange to reduce thrombosis and infection of biomedical catheters.

Ice-Inspired Polymeric Slippery Surface with Excellent Smoothness, Stability, and Antifouling Properties

Ice is omnipresent in our daily life and possesses intrinsic slipperiness as a result of the formation of a quasi-liquid layer. Thus, the functional surfaces inspired by ice show great prospects in widespread fields from surface lubrication to antifouling coatings. Herein, we report an ice-inspired polymeric slippery surface (II-PSS) constructed by a self-lubricating liquid layer and a densely surface-grafted polymer brush. The polymer brush layer could act as a homogeneous matrix to capture lubricant molecules via strong and dynamic dipole-dipole interactions to form a stable quasi-liquid layer that resembles the ice surface. The II-PSS can be easily fabricated on various solid substrates (e.g., silicon, glass, aluminum oxide, plastics, etc.) with excellent smoothness (roughness of ∼0.4 nm), optical transmittance (∼94.5%), as well as repellence toward diverse liquids with different surface tensions (22.3-72.8 mN m-1), pH values (1-14), salinity, and organic pollutants. Further investigation shows that the II-PSS exhibits extremely low attachment for proteins and marine organisms (e.g., algae and mussels) for over one month. These results demonstrate a robust and promising strategy for high-performance antifouling coatings.

Self-anticoagulant sponge for whole blood auto-transfusion and its mechanism of coagulation factor inactivation

Clinical use of intraoperative auto-transfusion requires the removal of platelets and plasma proteins due to pump-based suction and water-soluble anticoagulant administration, which causes dilutional coagulopathy. Herein, we develop a carboxylated and sulfonated heparin-mimetic polymer-modified sponge with spontaneous blood adsorption and instantaneous anticoagulation. We find that intrinsic coagulation factors, especially XI, are inactivated by adsorption to the sponge surface, while inactivation of thrombin in the sponge-treated plasma effectively inhibits the common coagulation pathway. We show whole blood auto-transfusion in trauma-induced hemorrhage, benefiting from the multiple inhibitory effects of the sponge on coagulation enzymes and calcium depletion. We demonstrate that the transfusion of collected blood favors faster recovery of hemostasis compared to traditional heparinized blood in a rabbit model. Our work not only develops a safe and convenient approach for whole blood auto-transfusion, but also provides the mechanism of action of self-anticoagulant heparin-mimetic polymer-modified surfaces.

Progress on Improved Fouling Resistance-Nanofibrous Membrane for Membrane Distillation: A Mini-Review

Nanofibrous membranes for membrane distillation (MD) have demonstrated promising results in treating various water and wastewater streams. Significant progress has been made in recent decades because of the development of sophisticated membrane materials, such as superhydrophobic, omniphobic and Janus membranes. However, fouling and wetting remain crucial issues for long-term operation. This mini-review summarizes ideas as well as their limitations in understanding the fouling in membrane distillation, comprising organic, inorganic and biofouling. This review also provides progress in developing antifouling nanofibrous membranes for membrane distillation and ongoing modifications on nanofiber membranes for improved membrane distillation performance. Lastly, challenges and future ways to develop antifouling nanofiber membranes for MD application have been systematically elaborated. The present mini-review will interest scientists and engineers searching for the progress in MD development and its solutions to the MD fouling issues.

Functionalization of in vivo tissue-engineered living biotubes enhance patency and endothelization without the requirement of systemic anticoagulant administration

Vascular regeneration and patency maintenance, without anticoagulant administration, represent key developmental trends to enhance small-diameter vascular grafts (SDVG) performance. In vivo engineered autologous biotubes have emerged as SDVG candidates with pro-regenerative properties. However, mechanical failure coupled with thrombus formation hinder translational prospects of biotubes as SDVGs. Previously fabricated poly(ε-caprolactone) skeleton-reinforced biotubes (PBs) circumvented mechanical issues and achieved vascular regeneration, but orally administered anticoagulants were required. Here, highly efficient and biocompatible functional modifications were introduced to living cells on PB lumens. The 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-methoxy (DMPE)-PEG-conjugated anti-coagulant bivalirudin (DPB) and DMPE-PEG-conjugated endothelial progenitor cell (EPC)-binding TPS-peptide (DPT) modifications possessed functionality conducive to promoting vascular graft patency. Co-modification of DPB and DPT swiftly attained luminal saturation without influencing cell viability. DPB repellent of non-specific proteins, DPB inhibition of thrombus formation, and DPB protection against functional masking of DPT's EPC-capture by blood components, which promoted patency and rapid endothelialization in rat and canine artery implantation models without anticoagulant administration. This strategy offers a safe, facile, and fast technical approach to convey additional functionalization to living cells within tissue-engineered constructs.

Strongly adhesive zwitterionic composite hydrogel paints for surgical sutures and blood-contacting devices

Hydrogels show eminent advantages in biomedical and pharmaceutical fields. However, their application as coating materials for biomedical devices is limited by several key challenges, such as lack of universality, weak mechanical strength, and low adhesion to the substrate. Here we report versatile and tough adhesion composite hydrogel paints (CHPs), which consist of zwitterionic copolymers and microgels, both with reactive groups. The CHPs exhibit tunable rheology and thickness, hydrophilicity, biofouling resistance, durability, and convenient fabrication on metal, polymer, and inorganic surfaces with arbitrary shapes. As a proof-of-concept, the CHP-surgical sutures demonstrate exceptional lubrication, drug delivery, anti-infection, and anti-fibrous capsule properties. Moreover, the CHP-PVC tubing effectively prevents thrombus formation in vitro and ex vivo rabbit blood circulation without anticoagulants. This work provides valuable insights for enhancing and developing integrated hydrogel technologies for biomedical devices. STATEMENT OF SIGNIFICANCE: The combination of hydrogel and biomedical devices can enable numerous existing applications in medicine. In this study, inspired by the principle of microgel reinforcement in industrial paints, we propose a simple and versatile zwitterionic composite hydrogel paints (CHPs) strategy, which can be easily applied to diverse substrates with arbitrary shapes by covalent grafting between complementary groups by brush, dip, or spray. The CHPs integrated universality, tough adhesion, mechanical durability, and anti-biofouling properties because of their unique chemical composition and coating structure design. This strategy provides a simple and versatile route for surface modification of biomedical devices.