Bioresponsive starPEG-heparin hydrogel coatings on vascular stents for enhanced hemocompatibility

Enhancing thromboresistance of neurovascular nickel-titanium devices with responsive heparin hydrogel coatings

BACKGROUND

Neurointerventional devices, particularly laser-cut thin-strut stents made of self-expanding nickel-titanium alloy, are increasingly utilized for endovascular applications in intracranial arteries and dural venous sinuses. Preventing thrombosis and stroke necessitates systemic anticoagulant and antiplatelet therapies with the risk of bleeding complications. Antithrombotic coatings present a promising solution.

METHODS

In this study, we investigated the potential of hydrogels composed of four-armed poly(ethylene glycol) (starPEG) and heparin, with or without coagulation-responsive heparin release, as coatings for neurovascular devices to mitigate blood clot formation. We evaluated the feasibility and efficacy of these coatings on neurovascular devices through in vitro Chandler-Loop assays and implantation experiments in the supra-aortic arteries of rabbits.

RESULTS

Stable and coagulation-responsive starPEG-heparin hydrogel coatings exhibited antithrombotic efficacy in vitro, although with a slightly reduced thromboprotection observed in vivo. Furthermore, the hydrogel coatings demonstrated robustness against shear forces encountered during deployment and elicited only marginal humoral and cellular inflammatory responses compared with the reference standards.

CONCLUSION

Heparin hydrogel coatings offer promising benefits for enhancing the hemocompatibility of neurointerventional devices made of self-expanding nickel-titanium alloy. The variance in performance between in vitro and in vivo settings may be attributed to differences in low- and high-shear blood flow conditions inherent to these models. These models may represent the differences in venous and arterial systems. Further optimization is warranted to tailor the hydrogel coatings for improved efficacy in arterial applications.

PEGNB-Heparin-Liposome composite hydrogels for in situ spraying and ultra-fast adhesion: meeting the challenges of endothelial repair of vascular injury

Carotid atherosclerosis is an essential cause of transient cerebral ischemia, stroke, and other cerebrovascular diseases, and carotid endarterectomy (CEA) is currently the most effective treatment for removing plaque and restoring the vascular lumen. However, the CEA disrupts the integrity and functionality of the endothelium and predisposes it to complications such as restenosis and thrombosis. Hydrogels can closely mimic the natural extracellular matrix, allowing a wide tuning of physical and chemical properties. These properties make hydrogels the most promising candidate materials for the repair of vascular injured intima. In this study, a multifunctional intimal repair hydrogel of poly(ethylene glycol)-norbornene (PEGNB)/ Heparin/ Liposome is proposed with the advantages of ultra-rapid adhesion to the wet tissue of the vascular inner wall, maintenance of adhesion stability under continuous erosion by blood flow. The hydrogel was supplemented with poly(vinyl butyral) (PVB) to reduce its swelling rate, and Rapamycin (RAPA) was encapsulated in this study as the drug into the cationic liposomes. This composite multifunctional (PNHB@Lip(RAPA)) hydrogel has exhibited outstanding anti-coagulation properties, markedly suppressed the proliferation and migration of SMCs, and displayed favourable cytocompatibility and blood compatibility. Concurrently, the capacity of the PNHB@Lip(RAPA) hydrogel to stimulate endovascular regeneration and deter restenosis and thrombus formation was validated through carotid intima damage repair experiments. These findings collectively indicate that the PNHB@Lip(RAPA) hydrogel represents a promising material for intimal injury repair, offering innovative insights into intimal repair methodologies. STATEMENT OF SIGNIFICANCE: Carotid atherosclerosis is a leading cause of transient cerebral ischemia, stroke, and cerebrovascular disorders. Although carotid endarterectomy (CEA) effectively removes plaques, it damages endothelial integrity, increasing the risk of restenosis and thrombosis. To address this, we developed PNHB@Lip(RAPA), a multifunctional intimal repair hydrogel composed of PEGNB, heparin, and rapamycin-encapsulated liposomes. This hydrogel rapidly adheres to wet vascular walls, resists blood flow erosion, and exhibits low swelling. The hydrogel demonstrates superior anticoagulation, inhibits smooth muscle cell proliferation and migration, and shows favourable cytocompatibility. Experimental results confirm its ability to promote endovascular regeneration while preventing restenosis and thrombosis. In summary, PNHB@Lip(RAPA) hydrogel is a promising material for intimal repair, offering innovative solutions to improve CEA postoperative outcomes.

Smart materials strategy for vascular challenges targeting in-stent restenosis: a critical review

In-stent restenosis (ISR) presents a major challenge in vascular disease management, often leading to complications and repeated interventions. This review article explores the potential of existing smart materials strategies in addressing ISR, emphasizing advancements in materials science and biomedical engineering. We focus on innovative solutions such as bioactive coatings and responsive polymers that offer targeted responses to ISR-related internal and external triggers. These smart materials can dynamically adapt to the physiological conditions within blood vessels, responding in real time to various stimuli such as pH, oxidative stress and temperature. Moreover, we discuss preclinical progress and translational challenges associated with these materials as they move toward clinical applications. The review highlights the importance of controlled drug release and the need for materials that can degrade appropriately to minimize adverse effects. This work aims to identify critical research gaps and provide guidance to encourage interdisciplinary efforts to advance the development of smart stent technologies. Ultimately, the goal is to improve patient outcomes in vascular interventions by leveraging the capabilities of intelligent biomaterials to enhance ISR management and ensure better long-term efficacy and safety in-stent applications.

Metal-phenolic network biointerface-mediated cell regulation for bone tissue regeneration

Bone tissue regeneration presents a significant challenge in clinical treatment due to inadequate coordination between implant materials and reparative cells at the biomaterial-bone interfaces. This gap underscores the necessity of enhancing interaction modulation between cells and biomaterials, which is a crucial focus in bone tissue engineering. Metal-polyphenolic networks (MPN) are novel inorganic-organic hybrid complexes that are formed through coordination interactions between phenolic ligands and metal ions. These networks provide a multifunctional platform for biomedical applications, with the potential for tailored design and modifications. Despite advances in understanding MPN and their role in bone tissue regeneration, a comprehensive overview of the related mechanisms is lacking. Here, we address this gap by focusing on MPN biointerface-mediated cellular regulatory mechanisms during bone regeneration. We begin by reviewing the natural healing processes of bone defects, followed by a detailed examination of MPN, including their constituents and distinctive characteristics. We then explore the regulatory influence of MPN biointerfaces on key cellular activities during bone regeneration. Additionally, we illustrate their primary applications in addressing inflammatory bone loss, regenerating critical-size bone defects, and enhancing implant-bone integration. In conclusion, this review elucidates how MPN-based interfaces facilitate effective bone tissue regeneration, advancing our understanding of material interface-mediated cellular control and the broader field of tissue engineering.

Therapeutic functions of medical implants from various material categories with integrated biomacromolecular systems

Medical implants are designed to replace missing parts or improve body functions and must be capable of providing structural support or therapeutic intervention for a medical condition. Advances in materials science have enabled the development of devices made from metals, polymers, bioceramics, and composites, each with its specific advantages and limitations. This review analyzes the incorporation of biopolymers, proteins, and other biomacromolecules into implants, focusing on their role in biological integration and therapeutic functions. It synthesizes advancements in surface modification, discusses biomacromolecules as carriers for controlled drug release, and explores the application of nanoceramics and composites to improve osseointegration and tissue regeneration. Biomacromolecule systems are capable of interacting with device components and therapeutic agents - such as growth factors (GFs), antibiotics, and nanoceramics - allowing control over substance release. Incorporating therapeutic agents into these systems enables localized treatments for tissue regeneration, osseointegration, post-surgery infection control, and disease and pre-existing conditions. The review highlights these materials' therapeutic advantages and customization opportunities, by covering mechanical and biological perspectives. Developing composites and hybrid drug delivery systems align with recent efforts in interdisciplinary personalized medicine and implant innovations. For instance, a trend was observed for integrating inorganic (especially nanoceramics, e.g., hydroxyapatite) and organic phases in composites for better implant interaction with biological tissues and faster recovery. This article supports understanding how integrating these materials can create more personalized, functional, durable, and biocompatible implant devices.

Tough and Functional Hydrogel Coating by Electrostatic Spraying

Hydrogel coatings impart superior surface properties to materials, but their application on large and complicated substrates is hindered by two challenges: limited wetting conditions and intricate curing processes. To overcome the challenges, lyophilized adhesive hydrogel powders (LAHPs) are developed, which consist of poly(acrylic acid-co-3-(trimethoxysilyl)propyl methacrylate) crosslinked with chitosan. These powders are electrostatic sprayed onto substrates to address wetting issues and rehydrated to form bulk hydrogel coatings to circumvent curing challenges. This approach enables the application of hydrogel coatings with a smooth surface and adjustable thickness on various materials, irrespective of category, geometry, or size. The coatings exhibit remarkable mechanical properties (strength of 2.62 MPa, elastic modulus of 6.84 MPa, and stretchability exceeding 3 folds) and robust adhesion (adhesion energy ≈900 J m-2) through a three-step bonding process involving electrostatic attraction, hydrogen bonding, and covalent bonding. Notably, these coatings confer multiple functional attributes to the substrate, including lubricity, hydrophilicity, nucleation inhibition, and pH-responsive actuation. Moreover, incorporating LAHPs with functional agents or rehydrating with functional solutions opens possibilities for diverse functional hydrogel coatings, such as thermal responsiveness and NH3 indication. Leveraging the virtues of simplicity, flexibility, convenience, and broad applicability, this strategy presents an enticing pathway for the widespread applications of hydrogel coatings.

Tremendous advances, multifaceted challenges and feasible future prospects of biodegradable medical polymer materials

In recent years, biodegradable medical polymer materials (BMPMs) have stood out among many biomedical materials due to their unique advantages, such as high mechanical strength, good biocompatibility, strong corrosion resistance and excellent processability. In this review, we first provide a brief introduction of biodegradable medical materials from both natural and synthetic perspectives, and then systematically categorize BMPMs based on their applications in clinical medicine and highlight the great progress they have made in recent years. Additionally, we also point out several overlooked areas in the research of BMPMs, offering guidance for comprehensive future exploration of these materials. Finally, in view of the complex challenges faced by BMPMs today, their future directions are scientifically proposed. This work contributes to the ongoing efforts of BMPMs in the biomedical field and provides a steppingstone for developing more effective BMPM-based products 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.

Synthesis of bimetallic oxides (SrO-CoO) nanoparticles decorated polyacrylamide hydrogels for controlled drug release and wound healing applications

Hydrogels are polymeric structures characterized by their three-dimensional nature, insolubility in aqueous media, and remarkable ability to absorb significant amounts of water. Owing to their exceptional biocompatibility with living tissues, hydrogels find extensive use in various biomedical applications. Guggul gum grafted polyacrylamide hydrogels (SG) were prepared and green synthesized SrO, CoO and SrO-CoO nanoparticles (NPs) were incorporated with hydrogels (SrG, CoG, Sr-CoG) respectively. The fabricated hydrogels were characterized by various analytical techniques such as FTIR, XRD and SEM. XRD results confirmed the presence of Sr and Co metal nanoparticles in the fabricated hydrogels matrix, SrG pattern showed diffraction peaks at 2θ = 30°, 36.59°, 44.11°, 50.22° and 62.20° while CoG peaks appeared at 2θ = 36.59°, 42.32°, 61.18°, 74.05° and 77.08°. SG, SrG, CoG and Sr-CoG hydrogels showed 11%, 32%, 23% and 45% radical scavenging activity respectively as compared to standard BHT (Butylated hydroxyl toluene). In vitro drug release tests results showed that SG, SrG, CoG and Sr-CoG exhibited 21%, 16%, 13% and 10% sustained release of naproxen respectively. The results revealed that SrO and CoO nanoparticles dopped hydrogels possessed good wound healing potential as compared to conventional hydrogels, which provides great potential in clinical treatment for wounds.

Bioinspired chitosan based functionalization of biomedical implant surfaces for enhanced hemocompatibility, antioxidation and anticoagulation potential: an in silico and in vitro study

Endowing implanted biomaterials with better hemocompatibility, anticoagulation, antioxidant and antiplatelet adhesion is necessary because of their potential to trigger activation of multiple reactive mechanisms including coagulation cascade and potentially causing serious adverse clinical events like late thrombosis. Active ingredients from natural sources including Foeniculum vulgare, Angelica sinensis, and Cinnamomum verum have the ability to inhibit the coagulation cascade and thrombus formation around biomedical implants. These properties are of interest for the development of a novel drug for biomedical implants to potentially solve the current blood clotting and coagulation problems which lead to stent thrombosis. The objective of this study was to incorporate different anticoagulants from natural sources into a degradable matrix of chitosan with varying concentrations ranging from 5% to 15% and a composite containing all three drugs. The presence of anticoagulant constituents was identified using GC-MS. Subsequently, all the compositions were characterized principally by using Fourier transform infrared spectroscopy and scanning electron microscopy while the drug release profile was determined using UV-spectrometry for a 30 days immersion period. The results indicated an initial burst release which was subsequently followed by the sustained release pattern. Compared to heparin loaded chitosan, DPPH and hemolysis tests revealed better blood compatibility of natural drug loaded films. Moreover, the anticoagulation activity of natural drugs was equivalent to the heparin loaded film; however, through docking, the mechanism of inhibition of the coagulation cascade of the novel drug was found to be through blocking the extrinsic pathway. The study suggested that the proposed drug composite expresses an optimum composition which may be a practicable and appropriate candidate for biomedical implant coatings.

Co-immobilization of natural marine polysaccharides and bioactive peptides on ZE21B magnesium alloy to enhance hemocompatibility and cytocompatibility

Degradable magnesium alloy stents are considered to be ideal candidates to replace the traditional non-degradable stents for the treatment of cardiovascular diseases. However, bare magnesium alloy stents usually degrade too fast and show poor hemocompatibility and cytocompatibility, which seriously affects their clinical use. In this study, surface modification based on the MgF2 layer, polydopamine (PDA) coating, fucoidan and CAG peptides was performed on the Mg-Zn-Y-Nd (ZE21B) magnesium alloy with the purpose of improving its corrosion resistance, hemocompatibility and cytocompatibility for vascular stent application. After modification, the ZE21B alloy showed better corrosion resistance. Moreover, the lower hemolysis rate, platelet adhesion and activation, and fibrinogen adsorption and denaturation proved the improved hemocompatibility of modified ZE21B alloy in in vitro blood experiments. Furthermore, the co-immobilization of fucoidan and CAG peptides significantly promoted the adhesion, proliferation, migration and NO release of endothelial cells (ECs) on the modified ZE21B alloy, and meanwhile the modification with fucoidan and CAG peptides inhibited the adhesion and proliferation of smooth muscle cells (SMCs) and suppressed the expression of proinflammatory factors in the macrophages (MAs). The surface modification obviously enhanced the corrosion resistance, hemocompatibility and cytocompatibility of ZE21B alloy, and provided an effective strategy for the development of degradable vascular stents.

Mass-Spectrometric Identification of Proteins and Pathways Responsible for Fouling on Poly(ethylene glycol) Methacrylate Polymer Brushes

Prevention of fouling from proteins in blood plasma attracts significant efforts, and great progress is made in identifying surface coatings that display antifouling properties. In particular, poly(ethylene glycol) (PEG) is widely used and dense PEG-like cylindrical brushes of poly[oligo(ethylene glycol) methacrylate] (poly(OEGMA)) can drastically reduce blood plasma fouling. Herein, a comprehensive study of the variation of blood plasma fouling on this surface, including the analysis of the composition of protein deposits on poly(OEGMA) coatings after contact with blood plasma from many different donors, is reported. Correlation between the plasma fouling behavior and protein deposit composition points to the activation of the complement system as the main culprit of dramatically increased and accelerated deposition of blood plasma proteins on this type of antifouling coating, specifically through the classical pathway. These findings are consistent with observations on PEGylated drug carriers and highlight the importance of understanding the potential interactions between antifouling coatings and their environment.

Recent advances in the design and immobilization of heparin for biomedical application: A review

Heparin, a member of the glycosaminoglycan family, is renowned as the most negatively charged biomolecule discovered within the realm of human biology. This polysaccharide serves a vital role as a regulator for various proteins, cells, and tissues within the human body, positioning itself as a pivotal macromolecule of significance. The domain of biology has witnessed substantial interest in the intricate design of heparin and its derivatives, particularly focusing on heparin-based polymers and hydrogels. This intrigue spans a wide spectrum of applications, encompassing diverse areas such as protein adsorption, anticoagulant properties, controlled drug release, development of implants, stent innovation, enhancement of blood compatibility, acceleration of wound healing, and pioneering strides in tissue engineering. This comprehensive overview delves into a multitude of developed heparin conjugates, employing various methods, and explores their functions in both the biomedicine and electronics fields. The efficacy of materials derived from heparin is also thoroughly investigated, encompassing considerations such as thrombogenicity, drug release kinetics, affinity for growth factors (GFs), biocompatibility, and electrochemical analyses. We firmly believe that by redirecting focus towards research and advancements in heparin-related polymers/hydrogels, this study will ignite further research and accelerate potential breakthroughs in this promising and evolving field of discovery.

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.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

An underwater stable and durable gelatin composite hydrogel coating for biomedical applications

Developing underwater stable and durable hydrogel coatings with drag-reducing, drug release, and antibacterial properties is essential for lots of biomedical applications. However, most hydrogel coatings cannot meet the requirement of underwater stability and versatility, which severely limits their widespread use. In this work, an underwater stable, durable and substrate-independent gelatin composite hydrogel (GMP) coating is developed through covalent crosslinks, where a silane coupling agent with an unsaturated double bond is grafted onto a substrate of co-deposited polydopamine and polyethylenimine. GMP coating can be easily coated onto various medical device surfaces, such as artificial joints, catheters, tracheal tubes and titanium alloys, showing excellent structural stability and mechanical tunability under extreme conditions of ultrasonic treatment for 1 h (400 W of ultrasonic power) or underwater shearing for 14 days (400 rpm). Besides, friction experiment reveals that GMP coating exhibits good lubrication properties (coefficient of friction < 0.003). The drug-loading and bacterial inhibition ring tests show that the GMP coating has a tunable drug release ability with the final releasing ratios of 70-95% by changing the content of poly (ethylene glycol) diacrylate. This work offers a scalable approach of fabricating bio-functional and stable hydrogel coatings, which can be potentially used in biomedical applications.

Fucoidan- and Ciprofloxacin-Doped Plasma-Activated Polymer Coatings on Biodegradable Zinc: Hemocompatibility and Drug Release

Blood-contacting medical devices such as biodegradable metallic bone implant materials are expected to show excellent hemocompatibility both in vitro and in vivo. Different approaches are being studied and used to modify biomaterial surfaces for enhanced biocompatibility and hemocompatibility. However, the composition of degradable biomaterial must address several drawbacks at once. Iron-reinforced zinc material was used as a metallic substrate with improved mechanical properties when compared with those of pure zinc. Poly(lactic) acid (PLA) or polyethylenimine (PEI) was selected as a polymeric matrix for further doping with antibiotic ciprofloxacin (CPR) and marine-sourced polysaccharide fucoidan (FU), which are known for their antibacterial and potential anticoagulant properties, respectively. Radiofrequency air plasma was employed to induce metallic/polymer-coated surface activation before further modification with FU/CPR. Sample surface morphology and composition were studied and evaluated (contact angle measurements, AFM, SEM, and FT-IR) along with the hemolysis ratio and platelet adhesion test. Successful doping of the polymer layer by FU/CRP was confirmed. While PEI induced severe hemolysis over 12%, the PLA-coated samples exhibited even lower hemolysis (∼2%) than uncoated samples while the uncoated samples showed the lowest platelet adhesion. Moreover, gradual antibiotic release from PLA determined by the electrochemical methods using screen-printed carbon electrodes was observed after 24, 48, and 72 h, making the PLA-coated zinc-based material an attractive candidate for biodegradable material design.

Allicin-Loaded Intelligent Hydrogel Coating Improving Vascular Implant Performance

Coronary atherosclerosis is closely related to inflammation and oxidative stress. Owing to poor biocompatibility, lack of personalized treatment, and late toxic side effects, traditional drug-eluting stent intervention, releasing antiproliferative drugs, can delay endothelial repair and cause late thrombosis. The inflammation caused by atherosclerosis results in an acidic microenvironment and oxidative stress, which can be considered as triggers for precise and intelligent treatment. Here, we used catechol hyaluronic acid (C-HA) and cystamine (Cys) to prepare C-HA-Cys hydrogel coatings by amide reaction. The H2S-releasing donor allicin was loaded in the hydrogel to form an intelligent biomimetic coating. The disulfide bond of Cys made the cross-linked network redox-responsive to the inflammation and oxidative stress in the microenvironment by releasing the drug and H2S intelligently to combat the side effects of stent implantation. This study evaluated the hemocompatibility, anti-inflammatory capacity, vascular wall cytocompatibility, and in vivo histocompatibility of this intelligent hydrogel coating. Furthermore, the effect of H2S released from the coating on atherosclerosis-related signaling pathways such as CD31 and cystathionine γ-lyase (CSE), CD36, and ACAT-1 was investigated. Our results indicate that the C-HA-Cys-Allicin hydrogel coating could be manufactured on the surface of vascular interventional devices to achieve a precise response to the microenvironment of the lesion to release drug, which can attain the purpose of prevention of in-stent restenosis and ensure the effectiveness and safety of the application of interventional devices.

Silane coupling agent in biomedical materials

Medical devices are becoming more and more significant in our daily life. For implantable medical devices, good biocompatibility is required for further use in vivo. Thus, surface modification of medical devices is really important, which gives a wide application scene for a silane coupling agent. The silane coupling agent is able to form a durable bond between organic and inorganic materials. The dehydration process provides linking sites to achieve condensation of two hydroxyl groups. The forming covalent bond brings excellent mechanical properties among different surfaces. Indeed, the silane coupling agent is a popular component in surface modification. Metals, proteins, and hydrogels are using silane coupling agent to link parts commonly. The mild reaction environment also brings advantages for the spread of the silane coupling agent. In this review, we summarize two main methods of using the silane coupling agent. One is acting as a crosslinker mixed in the whole system, and the other is to provide a bridge between different surfaces. Moreover, we introduce their applications in biomedical devices.

Antibacterial-Based Hydrogel Coatings and Their Application in the Biomedical Field-A Review

Hydrogels exhibit excellent moldability, biodegradability, biocompatibility, and extracellular matrix-like properties, which make them widely used in biomedical fields. Because of their unique three-dimensional crosslinked hydrophilic networks, hydrogels can encapsulate various materials, such as small molecules, polymers, and particles; this has become a hot research topic in the antibacterial field. The surface modification of biomaterials by using antibacterial hydrogels as coatings contributes to the biomaterial activity and offers wide prospects for development. A variety of surface chemical strategies have been developed to bind hydrogels to the substrate surface stably. We first introduce the preparation method for antibacterial coatings in this review, which includes surface-initiated graft crosslinking polymerization, anchoring the hydrogel coating to the substrate surface, and the LbL self-assembly technique to coat crosslinked hydrogels. Then, we summarize the applications of hydrogel coating in the biomedical antibacterial field. Hydrogel itself has certain antibacterial properties, but the antibacterial effect is not sufficient. In recent research, in order to optimize its antibacterial performance, the following three antibacterial strategies are mainly adopted: bacterial repellent and inhibition, contact surface killing of bacteria, and release of antibacterial agents. We systematically introduce the antibacterial mechanism of each strategy. The review aims to provide reference for the further development and application of hydrogel coatings.

Bio-Performance of Hydrothermally and Plasma-Treated Titanium: The New Generation of Vascular Stents

The research presented herein follows an urgent global need for the development of novel surface engineering techniques that would allow the fabrication of next-generation cardiovascular stents, which would drastically reduce cardiovascular diseases (CVD). The combination of hydrothermal treatment (HT) and treatment with highly reactive oxygen plasma (P) allowed for the formation of an oxygen-rich nanostructured surface. The morphology, surface roughness, chemical composition and wettability of the newly prepared oxide layer on the Ti substrate were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) analysis. The alteration of surface characteristics influenced the material’s bio-performance; platelet aggregation and activation was reduced on surfaces treated by hydrothermal treatment, as well as after plasma treatment. Moreover, it was shown that surfaces treated by both treatment procedures (HT and P) promoted the adhesion and proliferation of vascular endothelial cells, while at the same time inhibiting the adhesion and proliferation of vascular smooth muscle cells. The combination of both techniques presents a novel approach for the fabrication of vascular implants, with superior characteristics.