Thrombogenic and Inflammatory Reactions to Biomaterials in Medical Devices

Evaluation of the interface of metallic-coated biodegradable polymeric stents with prokaryotic and eukaryotic cells

Polymeric coronary stents, like the ABSORB™, are commonly used to treat atherosclerosis due to their bioresorbable and cell-compatible polymer structure. However, they face challenges such as high strut thickness, high elastic recoil, and lack of radiopacity. This study aims to address these limitations by modifying degradable stents produced by additive manufacturing with poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) with degradable metallic coatings, specifically zinc (Zn) and magnesium (Mg), deposited via radiofrequency (rf) magnetron sputtering. The characterisation included the evaluation of the degradation of the coatings, antibacterial, anti-thrombogenicity, radiopacity, and mechanical properties. The results showed that the metallic coatings inhibited bacterial growth, though Mg exhibited a high degradation rate. Thrombogenicity studies showed that Zn-coated stents had anticoagulant properties, while Mg-coated and controls were thrombogenic. Zn coatings significantly improved radiopacity, enhancing contrast by 43 %. Mechanical testing revealed that metallic coatings reduced yield strength and, thus, diminished elastic recoil after stent expansion. Zn-coated stents improved cyclic compression resistance by 270 % for PCL stents, with PLA-based stents showing smaller improvements. The coatings also enhanced crush resistance, particularly for Zn-coated PCL stents. Overall, Zn-coated polymers have emerged as the premier prototype due to their superior biological and mechanical performance, appropriate degradation during the stent life, and ability to provide the appropriate radiopacity to medical devices.

Potential Player of Platelet in the Pathogenesis of Cardiotoxicity: Molecular Insight and Future Perspective

Cancer patients may encounter the onset of cardiovascular disease due to tumor advancement or chemotherapy, commonly known as "cardiotoxicity." In this respect, the conventional chemotherapy treatment protocol involves a mixture of different medications. These medications can be detrimental to cardiac tissue, consequently exposing the patient to the possibility of irreversible cardiac injury. The enhancement of oxidative stress and inflammation is an important mechanism of chemotherapeutic agents for developing cardiotoxicity. Regarding their dual pro- and anti-inflammatory functions, platelets can significantly influence the progression or suppression of cardiotoxicity. Therefore, the expression of platelet activatory markers can serve as valuable prognostic indicators for cardiotoxicity. The primary objective of this study is to examine the significance of platelets in cardiotoxicity and explore potential strategies that could effectively target malignant cells while minimizing their cytotoxic impact, such as cardiotoxicity and thrombosis.

Alternative Anticoagulant Strategy to Improve the Test Sensitivity of ASTM F2888-19 Standard for Platelet and Leukocyte Count Assay

The ASTM F2888-19 standard for platelet and leukocyte count assay is the only standardized test method for assessing platelet and leukocyte interactions with blood-contacting device materials. This study aimed to address two limitations of the ASTM F2888-19 standard: low test sensitivity for leukocyte count and high test sample surface area to blood ratio (12 cm2/mL). Human blood from healthy adult donors was drawn into polypropylene tubes with either 3.2% sodium (Na) citrate or anticoagulant citrate dextrose solution A (ACDA). Immediately before starting the test, the blood was recalcified and heparinized to a concentration of 1, 1.5, or 2 U/mL and incubated with the test materials of varying thrombogenic potential at an exposure ratio of 6 or 12 cm2/mL for 1 h at 37°C ± 2°C in a shaking water bath. Complete blood count was measured using a hematology analyzer. The results show that both, Na-citrated blood (6 or 12 cm2/mL exposure ratio) and ACDA blood (6 cm2/mL ratio), were able to differentiate thrombogenic materials from commonly used biomaterials based on platelet count changes. The magnitudes of difference between the thrombogenic materials and biomaterials depends on heparin concentration. The test sensitivity was highest when ACDA blood, heparinized to 1 U/mL heparin, was used. Moreover, the use of ACDA blood, unlike Na-citrated blood, also allowed the assay to distinguish between the thrombogenic materials from commonly used biomaterials based on leukocyte count changes. In conclusion, the use of ACDA blood significantly increased test sensitivity of the ASTM F2888-19 test method in differentiating materials with varying thrombogenicity based on both platelet and leukocyte counts, while reducing blood exposure ratio to 6 cm2/mL. These findings will be used to revise the ASTM F2888 standard in the future.

Fabrication of nanoparticle-reinforced composite hydrogel for improved durability, antifouling, and thrombosis-resistance in arteriovenous grafts

Arteriovenous grafts are routinely designed to provide a deliberate connection between an artery and vein in patients during hemodialysis. The commonly used grafts present significant drawbacks such as thrombosis, bacterial infection, and biofouling which prevents their functionality. To endow hydrogels with improved anti-thrombosis, stable antifouling, and strong mechanical strength, a surface-modified nanoparticle-reinforced nanohybrid hydrogel is developed. In brief, zwitterionic sulfobetaine methacrylate (SBMA) is coated on bentonite clay (BC) nanoparticles via a simple method. BC-SBMA nanoparticles were then loaded onto sodium alginate /polyvinyl alcohol hydrogel composite. Calcium chloride (Ca2+) crosslinking is employed to form stable network and optimize polyvinyl alcohol/sodium alginate (PS) hydrogel composite. BC-SBMA particles were dispersed into PS hydrogel and crosslinked to form nanohybrid hydrogel (PS@BC-SBMA). The nanohybrid hydrogel was characterized for its morphological, mechanical, physicochemical, antibacterial, biocompatibility, antifouling, ex-vivo anti-thrombogenic, and in-vivo anti-inflammatory properties. The results revealed that the presence ofBC-SBMA particles boosted the mechanical strength and facilitated biocompatibility. The presence of zwitterionic polymers provided excellent antifouling properties toward blood platelets, unnecessary proteins, and bacterial strains. Hence, the cooperative effects of the nanohybrid hydrogel such as biocompatibility, antifouling, and mechanical properties lead to a desirable candidate for blood-contacting implants.

Nanoetched Stainless Steel Architecture Enhances Cell Uptake of Biomacromolecules and Alters Protein Corona Abundancy

Nanotexture on biocompatible surfaces promotes cell adhesion and proliferation. High aspect ratio nanoachitecture serves as an ideal interface between implant materials and host cells that is well-suited for localized therapeutic delivery. Despite this potential, nanotextured surfaces have not been widely applied for biomacromolecule delivery. Here, we employed a low-cost, industrially relevant nanoetching process to modify the surface of biocompatible stainless steel 316 (SS316L), creating nanotextured SS316L (NT-SS316L) as a material for intracellular biomacromolecule delivery. As biomacromolecule cargoes are adsorbed to the steel and ultimately would be used in protein-rich environments, we performed serum protein corona analysis on unmodified SS316L and NT-SS316L using tandem mass spectrometry. We observed an increase in proteins associated with cell adhesion on the surface of NT-SS316L compared to that of SS316L, supporting literature reports of enhanced adhesion on nanotextured materials. For delivery to adherent cells, a "hard corona" of model biomacromolecule cargoes including superfolder green fluorescent protein (sfGFP) charge variants, cytochrome c, and siRNA was adsorbed on NT-SS316L to assess delivery. Nanotextured surfaces enhanced cellular biomacromolecule uptake and delivered cytosolic-functional proteins and nucleic acids through energy-dependent endocytosis. Collectively, these findings indicate that NT-SS316L holds potential as a surface modification for implants to achieve localized drug delivery for a variety of biomedical applications.

Computational Fluid Dynamic Optimization of Micropatterned Surfaces: Towards Biofunctionalization of Artificial Organs

Modifying surface topography to prevent surface-induced thrombosis in cardiovascular implants allows endothelialization, which is the natural thrombo-resistance of blood-contacting surfaces, and is deemed to be the only long-term solution for hemocompatible materials. We adapted a simulation framework to predict platelet deposition on a modified surface and developed an optimization strategy to promote endothelial retention and limit platelet deposition. Under supraphysiological bulk shear stress, a maximum of 79% linear coverage was achieved. This study concludes that the addition of microtrenches promotes endothelial retention and can be improved through the optimal selection of geometric parameters.

Molecular Biomarkers for In Vitro Thrombogenicity Assessment of Medical Device Materials

To develop standardized in vitro thrombogenicity test methods for evaluating medical device materials, three platelet activation biomarkers, beta-thromboglobulin (β-TG), platelet factor 4 (PF4), soluble p-selectin (CD62P), and a plasma coagulation marker, thrombin-antithrombin complex (TAT), were investigated. Whole blood, drawn from six healthy human volunteers into Anticoagulant Citrate Dextrose Solution A was recalcified and heparinized over a concentration range of 0.5-1.5 U/mL. The blood was incubated with test materials with different thrombogenic potentials for 60 min at 37°C, using a 6 cm2/mL material surface area to blood volume ratio. After incubation, the blood platelet count was measured before centrifuging the blood to prepare platelet-poor plasma (PPP) and platelet-free plasma (PFP) for enzyme-linked immunosorbent assay analysis of the biomarkers. The results show that all four markers effectively differentiated the materials with different thrombogenic potentials at heparin concentrations from 1.0 to 1.5 U/mL. When a donor-specific heparin concentration (determined by activated clotting time) was used, the markers were able to differentiate materials consistently for blood from all the donors. Additionally, using PFP instead of PPP further improved the test method's ability to differentiate the thrombogenic materials from the negative control for β-TG and TAT. Moreover, the platelet activation markers were able to detect reversible platelet activation induced by adenosine diphosphate (ADP). In summary, all three platelet activation markers (β-TG, PF4, and CD62P) can distinguish thrombogenic potentials of different materials and detect ADP-induced reversible platelet activation. Test consistency and sensitivity can be enhanced by using a donor-specific heparin concentration and PFP. The same test conditions are applicable to the measurement of coagulation marker TAT.

Targeting the Contact Pathway of Coagulation for the Prevention and Management of Medical Device-Associated Thrombosis

Hemorrhage remains a major complication of anticoagulants, with bleeding leading to serious and even life-threatening outcomes in rare settings. Currently available anticoagulants target either multiple coagulation factors or specifically coagulation factor (F) Xa or thrombin; however, inhibiting these pathways universally impairs hemostasis. Bleeding complications are especially salient in the medically complex population who benefit from medical devices. Extracorporeal devices-such as extracorporeal membrane oxygenation, hemodialysis, and cardiac bypass-require anticoagulation for optimal use. Nonetheless, bleeding complications are common, and with certain devices, highly morbid. Likewise, pharmacologic prophylaxis to prevent thrombosis is not commonly used with many medical devices like central venous catheters due to high rates of bleeding. The contact pathway members FXI, FXII, and prekallikrein serve as a nexus, connecting biomaterial surface-mediated thrombin generation and inflammation, and may represent safe, druggable targets to improve medical device hemocompatibility and thrombogenicity. Recent in vivo and clinical data suggest that selectively targeting the contact pathway of coagulation through the inhibition of FXI and FXII can reduce the incidence of medical device-associated thrombotic events, and potentially systemic inflammation, without impairing hemostasis. In the following review, we will outline the current in vivo and clinical data encompassing the mechanism of action of drugs targeting the contact pathway. This new class of inhibitors has the potential to herald a new era of effective and low-risk anticoagulation for the management of patients requiring the use of medical devices.

Carbon materials and their metal composites for biomedical applications: A short review

Carbon materials and their hybrid metal composites have garnered significant attention in biomedical applications due to their exceptional biocompatibility. This biocompatibility arises from their inherent chemical stability and low toxicity within biological systems. This review offers a comprehensive overview of carbon nanomaterials and their metal composites, emphasizing their biocompatibility-focused applications, including drug delivery, bioimaging, biosensing, and tissue engineering. The paper outlines advancements in surface modifications, coatings, and functionalization techniques designed to enhance the biocompatibility of carbon materials, ensuring minimal adverse effects in biological systems. A comprehensive investigation into hybrid composites integrating carbon nanomaterials is conducted, categorizing them as fullerenes, carbon quantum dots, carbon nanotubes, carbon nanofibers, graphene, and diamond-like carbon. The concluding section addresses regulatory considerations and challenges associated with integrating carbon materials into medical devices. This review culminates by providing insights into current achievements, challenges, and future directions, underscoring the pivotal role of carbon nanomaterials and their metal composites in advancing biocompatible applications.

Facile engineering of interactive double network hydrogels for heart valve regeneration

Regenerative heart valve prostheses are essential for treating valvular heart disease, which requested interactive materials that can adapt to the tissue remodeling process. Such materials typically involves intricate designs with multiple active components, limiting their translational potential. This study introduces a facile method to engineer interactive materials for heart valve regeneration using 1,1'-thiocarbonyldiimidazole (TCDI) chemistry. TCDI crosslinking forms cleavable thiourea and thiocarbamate linkages which could gradually release H2S during degradation, therefore regulates the immune microenvironment and accelerates tissue remodeling. By employing this approach, a double network hydrogel was formed on decellularized heart valves (DHVs), showcasing robust anti-calcification and anti-thrombosis properties post fatigue testing. Post-implantation, the DHVs could adaptively degrade during recellularization, releasing H2S to further support tissue regeneration. Therefore, the comprehensive endothelial cell coverage and notable extracellular matrix remodeling could be clearly observed. This accessible and integrated strategy effectively overcomes various limitations of bioprosthetic valves, showing promise as an attractive approach for immune modulation of biomaterials.

Endovascular treatment of an aortocaval fistula caused by a late type II endoleak

An aortocaval fistula (ACF) is a rare complication of abdominal aortic aneurysms (AAAs) and constitute <1% of all AAAs, which increases from 2% to 6.7% in ruptured AAAs. Unlike other aortic ruptures, most ACFs are not associated with significant blood loss on admission. The traditional treatment strategy has been open surgery, which is associated with a high mortality rate. Endovascular repair has been performed; however, the results are difficult to interpret due to the low incidence of ACFs and the absence of cases reported with a long follow-up duration. We report the case of a 78-year-old man with previous endovascular aneurysm repair performed in 2015, who presented to our emergency department 6 years later with abdominal pain. A computed tomography angiography scan showed type Ia, Ib, and II endoleaks and an ACF. The endoleaks were selectively treated, and the ACF was covered with a polytetrafluoroethylene endograft inserted in the inferior vena cava. In our single-case experience with a medium-term follow-up of 24 months, our treatment was safe and effective for ACF closure, with no further signs of endoleak or graft thrombosis. We conducted a literature review of reported cases in which a covered stent graft was used for ACF treatment. Although no guidelines are currently available regarding this rare late complication after endovascular aneurysm repair, using a covered stent placed in the inferior vena cava to treat an ACF could be a viable option in selected cases.

Covalent immobilization of human serum albumin on cellulose acetate membrane for scavenging amyloid beta - A stepping extracorporeal strategy for ameliorating Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by interrupted neurocognitive functions and impaired mental development presumably caused by the accumulation of amyloid beta (Aβ) in the form of plaques. Targeting Aβ has been considered a promising approach for treating AD. In the current study, human serum albumin (HSA), a natural Aβ binder, is covalently immobilized onto the surface of a cellulose acetate (CA) membrane to devise an extracorporeal Aβ sequester. The immobilization of HSA at 3.06 ± 0.22 μg/mm2 of the CA membrane was found to be active functionally, as evidenced by the esterase-like activity converting p-nitrophenyl acetate into p-nitrophenol. The green fluorescent protein-Aβ (GFP-Aβ) fusion protein, recombinantly produced as a model ligand, exhibited characteristics of native Aβ. These features include the propensity to form aggregates or fibrils and an affinity for HSA with a dissociation constant (KD) of 0.91 μM. The HSA on the CA membrane showed concentration-dependent sequestration of GFP-Aβ in the 1-10-μM range. Moreover, it had a greater binding capacity than HSA immobilized on a commercial amine-binding plate. Results suggest that the covalent immobilization of HSA on the CA surface can be used as a potential platform for sequestering Aβ to alleviate AD.

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.

Sodium bicarbonate as a local adjunctive agent for limiting platelet activation, aggregation, and adhesion within cardiovascular therapeutic devices

Cardiovascular therapeutic devices (CTDs) remain limited by thrombotic adverse events. Current antithrombotic agents limit thrombosis partially, often adding to bleeding. The Impella® blood pump utilizes heparin in 5% dextrose (D5W) as an internal purge to limit thrombosis. While effective, exogenous heparin often complicates overall anticoagulation management, increasing bleeding tendency. Recent clinical studies suggest sodium bicarbonate (bicarb) may be an effective alternative to heparin for local anti-thrombosis. We examined the effect of sodium bicarbonate on human platelet morphology and function to better understand its translational utility. Human platelets were incubated (60:40) with D5W + 25 mEq/L, 50 mEq/L, or 100 mEq/L sodium bicarbonate versus D5W or D5W + Heparin 50 U/mL as controls. pH of platelet-bicarbonate solutions mixtures was measured. Platelet morphology was examined via transmission electron microscopy; activation assessed via P-selectin expression, phosphatidylserine exposure and thrombin generation; and aggregation with TRAP-6, calcium ionophore, ADP and collagen quantified; adhesion to glass measured via fluorescence microscopy. Sodium bicarbonate did not alter platelet morphology but did significantly inhibit activation, aggregation, and adhesion. Phosphatidylserine exposure and thrombin generation were both reduced in a concentration-dependent manner-between 26.6 ± 8.2% (p = 0.01) and 70.7 ± 5.6% (p < 0.0001); and 14.0 ± 6.2% (p = 0.15) and 41.7 ± 6.8% (p = 0.03), respectively, compared to D5W control. Platelet aggregation via all agonists was also reduced, particularly at higher concentrations of bicarb. Platelet adhesion to glass was similarly reduced, between 0.04 ± 0.03% (p = 0.61) and 0.11 ± 0.04% (p = 0.05). Sodium bicarbonate has direct, local, dose-dependent effects limiting platelet activation and adhesion. Our results highlight the potential utility of sodium bicarbonate as a locally acting agent to limit device thrombosis.

Tracking of Protein Adsorption on Poly(l-lactic acid) Film Surfaces: The Role of Molar Mass

Poly(l-lactic acid) (PLLA) has been extensively utilized as a biomaterial for various biomedical applications. The first and one of the most critical steps upon contact with biological fluids is the adsorption of proteins on the material's surface. Understanding the behavior of protein adsorption is vital for guiding the synthesis and preparation of PLLA for biomedical purposes. In this study, total internal reflection fluorescence microscopy was employed to investigate the adsorption of human serum albumin (HSA) on PLLA films with different molar masses. We found that molar mass affects HSA adsorption in such a way that it affects only the adsorption rate constants, but not the desorption rate constants. Additionally, we observed that HSA adsorption is spatially heterogeneous and exhibits many strong binding sites regardless of the molar mass of the PLLA films. We found that the free volume of PLLA plays a crucial role in determining its water uptake capacity and surface hydration, consequently impacting the adsorption of HSA.

Feasibility of an implantable bioreactor for renal cell therapy using silicon nanopore membranes

The definitive treatment for end-stage renal disease is kidney transplantation, which remains limited by organ availability and post-transplant complications. Alternatively, an implantable bioartificial kidney could address both problems while enhancing the quality and length of patient life. An implantable bioartificial kidney requires a bioreactor containing renal cells to replicate key native cell functions, such as water and solute reabsorption, and metabolic and endocrinologic functions. Here, we report a proof-of-concept implantable bioreactor containing silicon nanopore membranes to offer a level of immunoprotection to human renal epithelial cells. After implantation into pigs without systemic anticoagulation or immunosuppression therapy for 7 days, we show that cells maintain >90% viability and functionality, with normal or elevated transporter gene expression and vitamin D activation. Despite implantation into a xenograft model, we find that cells exhibit minimal damage, and recipient cytokine levels are not suggestive of hyperacute rejection. These initial data confirm the potential feasibility of an implantable bioreactor for renal cell therapy utilizing silicon nanopore membranes.

Challenge of material haemocompatibility for microfluidic blood-contacting applications

Biological applications of microfluidics technology is beginning to expand beyond the original focus of diagnostics, analytics and organ-on-chip devices. There is a growing interest in the development of microfluidic devices for therapeutic treatments, such as extra-corporeal haemodialysis and oxygenation. However, the great potential in this area comes with great challenges. Haemocompatibility of materials has long been a concern for blood-contacting medical devices, and microfluidic devices are no exception. The small channel size, high surface area to volume ratio and dynamic conditions integral to microchannels contribute to the blood-material interactions. This review will begin by describing features of microfluidic technology with a focus on blood-contacting applications. Material haemocompatibility will be discussed in the context of interactions with blood components, from the initial absorption of plasma proteins to the activation of cells and factors, and the contribution of these interactions to the coagulation cascade and thrombogenesis. Reference will be made to the testing requirements for medical devices in contact with blood, set out by International Standards in ISO 10993-4. Finally, we will review the techniques for improving microfluidic channel haemocompatibility through material surface modifications-including bioactive and biopassive coatings-and future directions.

Mitochondria as a therapeutic: a potential new frontier in driving the shift from tissue repair to regeneration

Fibrosis, or scar tissue development, is associated with numerous pathologies and is often considered a worst-case scenario in terms of wound healing or the implantation of a biomaterial. All that remains is a disorganized, densely packed and poorly vascularized bundle of connective tissue, which was once functional tissue. This creates a significant obstacle to the restoration of tissue function or integration with any biomaterial. Therefore, it is of paramount importance in tissue engineering and regenerative medicine to emphasize regeneration, the successful recovery of native tissue function, as opposed to repair, the replacement of the native tissue (often with scar tissue). A technique dubbed 'mitochondrial transplantation' is a burgeoning field of research that shows promise in in vitro, in vivo and various clinical applications in preventing cell death, reducing inflammation, restoring cell metabolism and proper oxidative balance, among other reported benefits. However, there is currently a lack of research regarding the potential for mitochondrial therapies within tissue engineering and regenerative biomaterials. Thus, this review explores these promising findings and outlines the potential for mitochondrial transplantation-based therapies as a new frontier of scientific research with respect to driving regeneration in wound healing and host-biomaterial interactions, the current successes of mitochondrial transplantation that warrant this potential and the critical questions and remaining obstacles that remain in the field.

Stent-Graft Fabrics Incorporating a Specific Corona Ready to Fenestrate

In situ fenestration of endovascular stent-grafts has become a mainstream bailout technique to treat complex emergent aneurysms while maintaining native anatomical visceral and aortic arch blood supplies. Fabric tearing from creating the in situ fenestration using balloon angioplasty may extend beyond the intended diameter over time. Further tearing may result from the physiologic pulsatile motion at the branching site. A resultant endoleak at the fenestrated sites in stent-grafts could ultimately lead to re-pressurization of the aortic sac and, eventually, rupture. In an attempt to address this challenge, plain woven fabrics were designed. They hold a specific corona surrounding a square-shaped cluster with a plain weave fabric structure, a 2/2 twill, or a honeycomb. The corona was designed to stop potential further tearing of the fabric caused by the initial balloon angioplasty and stent or later post-implantation motion. The cluster within the corona was designed with relatively loose fabric structures (plain weave, 2/2 twill weave, and honeycomb) to facilitate the laser fenestration. Two commercial devices, Anaconda (Vascutek, Terumo Aortic) and Zenith TX2 (Cook), were selected as controls for comparison against this new design. All the specimens were characterized by morphology, thickness, and water permeability. The results demonstrated that all specimens with a low thickness and water permeability satisfied the requirements for a stent graft material that would be low profile and resistant to endoleaks. The in situ fenestrations were performed on all fabrics utilizing an Excimer laser followed by balloon angioplasty. The fabrics were further observed by light microscopy and scanning electron microscopy. The dimension of the fenestrated apertures was smaller than the balloon's diameter. The tearing was effectively confined within the corona. The clinical acceptability of this concept deserves additional bench testing and animal experimentation.

Therapeutic Agent-Loaded Fibrous Scaffolds for Biomedical Applications

Tissue engineering is a sophisticated field that involves the integration of various disciplines, such as clinical medicine, material science, and life science, to repair or regenerate damaged tissues and organs. To achieve the successful regeneration of damaged or diseased tissues, it is necessary to fabricate biomimetic scaffolds that provide structural support to the surrounding cells and tissues. Fibrous scaffolds loaded with therapeutic agents have shown considerable potential in tissue engineering. In this comprehensive review, we examine various methods for fabricating bioactive molecule-loaded fibrous scaffolds, including preparation methods for fibrous scaffolds and drug-loading techniques. Additionally, we delved into the recent biomedical applications of these scaffolds, such as tissue regeneration, inhibition of tumor recurrence, and immunomodulation. The aim of this review is to discuss the latest research trends in fibrous scaffold manufacturing methods, materials, drug-loading methods with parameter information, and therapeutic applications with the goal of contributing to the development of new technologies or improvements to existing ones.

Strategies for surface coatings of implantable cardiac medical devices

Cardiac medical devices (CMDs) are required when the patient's cardiac capacity or activity is compromised. To guarantee its correct functionality, the building materials in the development of CMDs must focus on several fundamental properties such as strength, stiffness, rigidity, corrosion resistance, etc. The challenge is more significant because CMDs are generally built with at least one metallic and one polymeric part. However, not only the properties of the materials need to be taken into consideration. The biocompatibility of the materials represents one of the major causes of the success of CMDs in the short and long term. Otherwise, the material will lead to several problems of hemocompatibility (e.g., protein adsorption, platelet aggregation, thrombus formation, bacterial infection, and finally, the rejection of the CMDs). To enhance the hemocompatibility of selected materials, surface modification represents a suitable solution. The surface modification involves the attachment of chemical compounds or bioactive compounds to the surface of the material. These coatings interact with the blood and avoid hemocompatibility and infection issues. This work reviews two main topics: 1) the materials employed in developing CMDs and their key characteristics, and 2) the surface modifications reported in the literature, clinical trials, and those that have reached the market. With the aim of providing to the research community, considerations regarding the choice of materials for CMDs, together with the advantages and disadvantages of the surface modifications and the limitations of the studies performed.

4-Methylumbelliferone-Functionalized Polyphosphazene and Its Assembly into Biocompatible Fluorinated Nanocoatings with Selective Antiproliferative Activity

Advanced multifunctional biomaterials are increasingly relying on clinically dictated patterns of selectivity against various biological targets. Integration of these frequently conflicting features into a single material surface may be best achieved by combining various complementary methodologies. Herein, a drug with a broad spectrum of activity, i.e., 4-methylumbelliferone (4-MU), is synthetically multimerized into water-soluble anionic macromolecules with the polyphosphazene backbone. The polymer structure, composition, and solution behavior are studied by ¹H and ³¹P NMR spectroscopy, size-exclusion chromatography, dynamic light scattering, and UV and fluorescence spectrophotometry. To take advantage of the clinically proven hemocompatibility of fluorophosphazene surfaces, the drug-bearing macromolecule was then nanoassembled onto the surface of selected substrates in an aqueous solution with fluorinated polyphosphazene of the opposite charge using the layer-by-layer (LbL) technique. Nanostructured 4-MU-functionalized fluoro-coatings exhibited a strong antiproliferative effect on vascular smooth muscle cells (VSMCs) and fibroblasts with no cytotoxicity against endothelial cells. This selectivity pattern potentially provides the opportunity for highly desirable fast tissue healing while preventing the overgrowth of VSMCs and fibrosis. Taken together with the established in vitro hemocompatibility and anticoagulant activity, 4-MU-functionalized fluoro-coatings demonstrate potential for applications as restenosis-resistant coronary stents and artificial joints.

Expanded Polytetrafluoroethylene Membranes for Vascular Stent Coating: Manufacturing, Biomedical and Surgical Applications, Innovations and Case Reports

Coated stents are defined as innovative stents surrounded by a thin polymer membrane based on polytetrafluoroethylene (PTFE)useful in the treatment of numerous vascular pathologies. Endovascular methodology involves the use of such devices to restore blood flow in small-, medium- and large-calibre arteries, both centrally and peripherally. These membranes cross the stent struts and act as a physical barrier to block the growth of intimal tissue in the lumen, preventing so-called intimal hyperplasia and late stent thrombosis. PTFE for vascular applications is known as expanded polytetrafluoroethylene (e-PTFE) and it can be rolled up to form a thin multilayer membrane expandable by 4 to 5 times its original diameter. This membrane plays an important role in initiating the restenotic process because wrapped graft stent could be used as the treatment option for trauma devices during emergency situations and to treat a number of pathological vascular disease. In this review, we will investigate the multidisciplinary techniques used for the production of e-PTFE membranes, the advantages and disadvantages of their use, the innovations and the results in biomedical and surgery field when used to cover graft stents.

Polymeric Heart Valves Will Displace Mechanical and Tissue Heart Valves: A New Era for the Medical Devices

The development of a novel artificial heart valve with outstanding durability and safety has remained a challenge since the first mechanical heart valve entered the market 65 years ago. Recent progress in high-molecular compounds opened new horizons in overcoming major drawbacks of mechanical and tissue heart valves (dysfunction and failure, tissue degradation, calcification, high immunogenic potential, and high risk of thrombosis), providing new insights into the development of an ideal artificial heart valve. Polymeric heart valves can best mimic the tissue-level mechanical behavior of the native valves. This review summarizes the evolution of polymeric heart valves and the state-of-the-art approaches to their development, fabrication, and manufacturing. The review discusses the biocompatibility and durability testing of previously investigated polymeric materials and presents the most recent developments, including the first human clinical trials of LifePolymer. New promising functional polymers, nanocomposite biomaterials, and valve designs are discussed in terms of their potential application in the development of an ideal polymeric heart valve. The superiority and inferiority of nanocomposite and hybrid materials to non-modified polymers are reported. The review proposes several concepts potentially suitable to address the above-mentioned challenges arising in the R&D of polymeric heart valves from the properties, structure, and surface of polymeric materials. Additive manufacturing, nanotechnology, anisotropy control, machine learning, and advanced modeling tools have given the green light to set new directions for polymeric heart valves.

Hemp-Based Sustainable Slippery Surfaces: Icephobic and Antithrombotic Properties

With the passage of the 2018 Farm Bill that removed hemp from the Controlled Substances Act altogether, production of hemp is experiencing a renaissance. Building on this revival and re-emergence of hemp, we designed and fabricated hemp-based sustainable and robust slippery surfaces by coating hemp paper with beeswax and subsequently infusing it with hemp oil. A wide variety of aqueous liquids and beverages easily slide on our hemp-based sustainable slippery surfaces, without leaving a trace. We also fabricated hemp-based sustainable slippery surfaces using different textured metals. Our hemp-based sustainable slippery metal surfaces display good icephobic and antithrombotic properties. With these attributes, we envision that our hemp-based sustainable slippery surfaces will pave the path to more safe, non-toxic, and biodegradable or recyclable slippery surfaces for applications in food packaging, anti-icing or de-icing coatings, and antithrombotic medical devices.

Construction of Hierarchical Micro/Nanostructured ZnO/Cu-ZnMOFs@SA Superhydrophobic Composite Coatings with Excellent Multifunctionality of Anticorrosion, Blood-Repelling, and Antimicrobial Properties

Naked medical devices are often damaged by blood, bacteria, and other extreme environmental conditions (heat, humidity, acid, alkali, salts, and others), causing device failure and increasing difficulty for the operator. They can also cause inflammation and coagulation resulting in severe complications and even death. In this work, the superhydrophobic ZnO/copper-zinc metal-organic frameworks@stearic acid (ZnO/Cu-ZnMOFs@SA) composite coatings with hierarchical micro/nanostructures were fabricated on Zn substrates via a one-step hydrothermal method. The effects of hierarchical micro/nanostructures on surface wettability, physicochemical stability, and biological properties have been studied in this manuscript. The structure not only provided the coatings with robust waterproofing, abrasive resistance, durability, and thermal and light irradiation stability but also successfully recovered their superhydrophobicity by remodifying the surface with SA, showing excellent repeatability. In addition, the coating demonstrates excellent corrosion resistance and self-cleaning ability and rejects various solid and liquid contaminants. The superhydrophobic ZnO/Cu-ZnMOFs@SA composite coatings also exhibited excellent antibacterial and thrombosis resistance. The findings indicated that the superhydrophobic composite coatings have a strong potential for application in medical instruments for exhibiting multifunctional properties in various extreme environments.

Improved Hemocompatibility on Superhemophobic Micro-Nano-Structured Titanium Surfaces

Blood-contacting titanium-based implants such as endovascular stents and heart valve casings are prone to blood clotting due to improper interactions at the surface level. In complement, the current clinical demand for cardiovascular implants is at a new apex. Hence, there is a crucial necessity to fabricate an implant with optimal mechanical properties and improved blood compatibility, while simultaneously interacting differentially with cells and other microbial agents. The present study intends to develop a superhydrophobic implant surface with the novel micro-nano topography, developed using a facile thermochemical process. The surface topography, apparent contact angle, and crystal structure are characterized on different surfaces. The hemo/blood compatibility on different surfaces is assessed by evaluating hemolysis, fibrinogen adsorption, cell adhesion and identification, thrombin generation, complement activation, and whole blood clotting kinetics. The results indicate that the super-hemo/hydrophobic micro-nano titanium surface improved hemocompatibility by significantly reducing fibrinogen adsorption, platelet adhesion, and leukocyte adhesion. Thus, the developed surface has high potential to be used as an implant. Further studies are directed towards analyzing the mechanisms causing the improved hemocompatibility of micro/nano surface features under dynamic in vitro and in vivo conditions.

Surface Texturing and Combinatorial Approaches to Improve Biocompatibility of Implanted Biomaterials

Biomaterial associated microbial infection and blood thrombosis are two of the barriers that inhibit the successful use of implantable medical devices in modern healthcare. Modification of surface topography is a promising approach to combat microbial infection and thrombosis without altering bulk material properties necessary for device function and without contributing to bacterial antibiotic resistance. Similarly, the use of other antimicrobial techniques such as grafting poly(ethylene glycol) (PEG) and nitric oxide (NO) release also improve the biocompatibility of biomaterials. In this review, we discuss the development of surface texturing techniques utilizing ordered submicron-size pillars for controlling bacterial adhesion and biofilm formation, and we present combinatorial approaches utilizing surface texturing in combination with poly(ethylene glycol) (PEG) grafting and NO release to improve the biocompatibility of biomaterials. The manuscript also discusses efforts towards understanding the molecular mechanisms of bacterial adhesion responses to the surface texturing and NO releasing biomaterials, focusing on experimental aspects of the approach.

Assessment of the Anti-Thrombogenic Activity of Polyurethane Starch Composites

The increasing morbidity and mortality of patients due to post-surgery complications of coronary artery bypass grafts (CABPG) are related to blood–material interactions. Thus, the characterization of the thrombogenicity of the biomaterial for cardiovascular devices is of particular interest. This research evaluated the anti-thrombogenic activity of polyurethanes–starch composites. We previously synthesized polyurethane matrices that were obtained from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE), and isophorone diisocyanate (IPDI). In addition, potato starch (AL-N) and zwitterionic starch (AL-Z) were added as fillers. The anti-thrombogenic property was characterized by the clot formation time, platelet adhesion, protein absorption, TAT complex levels, and hemolysis. Additionally, we evaluated the cell viability of the endothelial and smooth muscle cells. Statically significant differences among the polyurethane matrices (P1, P2, and P3) were found for protein absorption and the blood clotting time without fillers. The polyurethanes composites with AL-Z presented an improvement in the anti-thrombogenic property. On the other hand, the composites with AL-Z reduced the viability of the endothelial cells and did not significantly affect the AoSCM (except for P1, which increased). These results classify these biomaterials as inert; therefore, they can be used for cardiovascular applications.

Hybrid heart valves with VEGF-loaded zwitterionic hydrogel coating for improved anti-calcification and re-endothelialization

With the aging of the population in worldwide, valvular heart disease has become one of the most prominent life-threatening diseases in human health, and heart valve replacement surgery is one of the therapeutic methods for valvular heart disease. Currently, commercial bioprosthetic heart valves (BHVs) for clinical application are prepared with xenograft heart valves or pericardium crosslinked by glutaraldehyde. Due to the residual cell toxicity from glutaraldehyde, heterologous antigens, and immune response, there are still some drawbacks related to the limited lifespan of bioprosthetic heart valves, such as thrombosis, calcification, degeneration, and defectiveness of re-endothelialization. Therefore, the problems of calcification, defectiveness of re-endothelialization, and poor biocompatibility from the use of bioprosthetic heart valve need to be solved. In this study, hydrogel hybrid heart valves with improved anti-calcification and re-endothelialization were prepared by taking decellularized porcine heart valves as scaffolds following grafting with double bonds. Then, the anti-biofouling zwitterionic monomers 2-methacryloyloxyethyl phosphorylcholine (MPC) and vascular endothelial growth factor (VEGF) were utilized to obtain a hydrogel-coated hybrid heart valve (PEGDA-MPC-DHVs@VEGF). The results showed that fewer platelets and thrombi were observed on the surface of the PEGDA-MPC-DHVs@VEGF. Additionally, the PEGDA-MPC-DHVs@VEGF exhibited excellent collagen stability, biocompatibility and re-endothelialization potential. Moreover, less calcification deposition and a lower immune response were observed in the PEGDA-MPC-DHVs@VEGF compared to the glutaraldehyde-crosslinked DHVs (Glu-DHVs) after subcutaneous implantation in rats for 30 days. These studies demonstrated that the strategy of zwitterionic hydrogels loaded with VEGF may be an effective approach to improving the biocompatibility, anti-calcification and re-endothelialization of bioprosthetic heart valves.

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A new and promising strategy of overcoming defects of bioprosthetic heart valves.

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The zwitterionic hydrogel with VEGF is utilized to improve anti-calcification and re-endothelialization properties of heart valves.

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The hybrid heart valves with a VEGF-loaded zwitterionic hydrogel coating exhibits excellent biocompatibility.

A fibrin enhanced thrombosis model for medical devices operating at low shear regimes or large surface areas

Over the past decade, much of the development of computational models of device-related thrombosis has focused on platelet activity. While those models have been successful in predicting thrombus formation in medical devices operating at high shear rates (> 5000 s⁻¹), they cannot be directly applied to low-shear devices, such as blood oxygenators and catheters, where emerging information suggest that fibrin formation is the predominant mechanism of clotting and platelet activity plays a secondary role. In the current work, we augment an existing platelet-based model of thrombosis with a partial model of the coagulation cascade that includes contact activation of factor XII and fibrin production. To calibrate the model, we simulate a backward-facing-step flow channel that has been extensively characterized in-vitro. Next, we perform blood perfusion experiments through a microfluidic chamber mimicking a hollow fiber membrane oxygenator and validate the model against these observations. The simulation results closely match the time evolution of the thrombus height and length in the backward-facing-step experiment. Application of the model to the microfluidic hollow fiber bundle chamber capture both gross features such as the increasing clotting trend towards the outlet of the chamber, as well as finer local features such as the structure of fibrin around individual hollow fibers. Our results are in line with recent findings that suggest fibrin production, through contact activation of factor XII, drives the thrombus formation in medical devices operating at low shear rates with large surface area to volume ratios.

Patients treated with blood-contacting medical devices suffer from clotting complications. Over the past decades, a great effort has been made to develop computational tools to predict and prevent clot formation in these devices. However, most models have focused on platelet activity and neglected other important parts of the problem such as the coagulation cascade reactions that lead to fibrin formation. In the current work, we incorporate this missing element into a well-established and validated model for platelet activity. We then use this novel approach to predict thrombus formation in two experimental configurations. Our results confirm that to accurately predict the clotting process in devices where surface area to volume ratios are large and flow velocity and shear stresses remain low, coagulation reactions and subsequent fibrin formation must be considered. This new model could have great implications for the design and optimization of medical devices such as blood oxygenators. In the long term, the model could evolve into a functional tool to inform anticoagulation therapies for these patients.

Bio-inspired hemocompatible surface modifications for biomedical applications

When blood first encounters the artificial surface of a medical device, a complex series of biochemical reactions is triggered, potentially resulting in clinical complications such as embolism/occlusion, inflammation, or device failure. Preventing thrombus formation on the surface of blood-contacting devices is crucial for maintaining device functionality and patient safety. As the number of patients reliant on blood-contacting devices continues to grow, minimizing the risk associated with these devices is vital towards lowering healthcare-associated morbidity and mortality. The current standard clinical practice primarily requires the systemic administration of anticoagulants such as heparin, which can result in serious complications such as post-operative bleeding and heparin-induced thrombocytopenia (HIT). Due to these complications, the administration of antithrombotic agents remains one of the leading causes of clinical drug-related deaths. To reduce the side effects spurred by systemic anticoagulation, researchers have been inspired by the hemocompatibility exhibited by natural phenomena, and thus have begun developing medical-grade surfaces which aim to exhibit total hemocompatibility via biomimicry. This review paper aims to address different bio-inspired surface modifications that increase hemocompatibility, discuss the limitations of each method, and explore the future direction for hemocompatible surface research.

Molecular Characterization and Biocompatibility of Exopolysaccharide Produced by Moderately Halophilic Bacterium Virgibacillus dokdonensis from the Saltern of Kumta Coast

The use of natural polysaccharides as biomaterials is gaining importance in tissue engineering due to their inherent biocompatibility. In this direction, the present study aims to explore the structure and biocompatibility of the EPS produced by Virgibacillus dokdonensis VITP14. This marine bacterium produces 17.3 g/L of EPS at 96 h of fermentation. The EPS was purified using ion exchange and gel permeation chromatographic methods. The porous web-like structure and elemental composition (C, O, Na, Mg, P, S) of the EPS were inferred from SEM and EDX analysis. AFM analysis revealed spike-like lumps with a surface roughness of 84.85 nm. The zeta potential value of −10 mV indicates the anionic nature of the EPS. Initial molecular characterization showed that the EPS is a heteropolysaccharide composed of glucose (25.8%), ribose (18.6%), fructose (31.5%), and xylose (24%), which are the monosaccharide units in the HPLC analysis. The FTIR spectrum indicates the presence of functional groups/bonds typical of EPSs (O-H, C-H, C-O-H, C-O, S=O, and P=O). The polymer has an average molecular weight of 555 kDa. Further, NMR analysis revealed the monomer composition, the existence of two α- and six β-glycosidic linkages, and the branched repeating unit as → 1)[α-D-Xylp-(1 → 2)-α-D-Glcp-(1 → 6)-β-D-Glcp-(1 → 5)]-β-D-Frup-(2 → 2)[β-D-Xylp-(1 → 4)]-β-D-Xylp-(1 → 6)-β-D-Fruf-(2 → 4)-β-D-Ribp-(1 →. The EPS is thermally stable till 251.4 °C. X-ray diffraction analysis confirmed the semicrystalline (54.2%) nature of the EPS. Further, the EPS exhibits significant water solubility (76.5%), water-holding capacity (266.8%), emulsifying index (66.8%), hemocompatibility (erythrocyte protection > 87%), and cytocompatibility (cell viability > 80% on RAW264.7 and keratinocyte HaCaT cells) at higher concentrations and prolongs coagulation time in APTT and PT tests. Our research unveils the significant biocompatibility of VITP14 EPS for synthesizing a variety of biomaterials.

Development of Antithrombogenic ECM-Based Nanocomposite Heart Valve Leaflets

Thrombogenicity, which is commonly encountered in artificial heart valves after replacement surgeries, causes valvular failure. Even life-long anticoagulant drug use may not be sufficient to prevent thrombogenicity. In this study, it was aimed to develop a heart valve construct with antithrombogenic properties and suitable mechanical strength by combining multiwalled carbon nanotubes within a decellularized bovine pericardium. In this context, the decellularization process was performed by using the combination of freeze–thawing and sodium dodecyl sulfate (SDS). Evaluation of decellularization efficiency was determined by histology (Hematoxylin and Eosin, DAPI and Masson’s Trichrome) and biochemical (DNA, sGAG and collagen) analyses. After the decellularization process of the bovine pericardium, composite pericardial tissues were prepared by incorporating −COOH-modified multiwalled carbon nanotubes (MWCNTs). Characterization of MWCNT incorporation was performed by ATR-FTIR, TGA, and mechanical analysis, while SEM and AFM were used for morphological evaluations. Thrombogenicity assessments were studied by platelet adhesion test, Calcein-AM staining, kinetic blood clotting, hemolysis, and cytotoxicity analyses. As a result of this study, the composite pericardial material revealed improved mechanical and thermal stability and hemocompatibility in comparison to decellularized pericardium, without toxicity. Approximately 100% success is achieved in preventing platelet adhesion. In addition, kinetic blood-coagulation analysis demonstrated a low rate and slow coagulation kinetics, while the hemolysis index was below the permissible limit for biomaterials.

Development and Blood Compatibility of a Stable and Bioactive Metal-Organic Framework Composite Coating for Blood-Circulation Tubing

Medical devices that require substantial contact between blood and a foreign surface would be dramatically safer if constructed from materials that prevent clot formation and coagulation disturbance at the blood-biomaterial interface. Nitric oxide (NO), an endogenous inhibitor of platelet activation in the vascular endothelium, could provide anticoagulation at the blood-surface interface when applied to biomaterials. We investigated an application of a copper-based metal-organic framework, H₃[(Cu₄Cl)₃(BTTri)₈-(H₂O)₁₂]·72H₂O where H₃BTTri = 1,3,5-tris(1H-1,2,3-triazole-5-yl)benzene] (CuBTTri), which has been shown to be an effective catalyst to generate NO from S-nitrosothiols that are endogenously present in blood. A method was developed to apply a CuBTTri composite coating to Tygon medical tubing used for extracorporeal lung support devices. The stability and activity of the coating were evaluated during 72 h dynamic saline flow testing (1.5-2.5 L/min, n = 3) with scanning electron microscopy imaging and inductively coupled mass-spectroscopy analysis. Compatibility of the coating with whole blood was assessed with a panel of hemocompatibility tests during 6 h circulation of swine donor blood in an ex vivo circulation loop constructed with CuBTTri tubing or unmodified Tygon (1.5 L/min blood flow rate, n = 8/group). Thrombus deposition and catalytic activity of the CuBTTri tubing were assessed following blood exposure. The coating remained stable during 72 h saline flow experiments at clinically relevant flow rates. No adverse effects were observed relative to controls during blood compatibility testing, to include no significant changes in platelet count (p = 0.42), platelet activation indicated by P-selectin expression (p = 0.57), coagulation panel values, or methemoglobin fraction (p = 0.18) over the 6 h circulation period. CuBTTri within the coating generated NO following blood exposure in the presence of biologically relevant concentrations of an NO donor. CuBTTri composite coating was stable and blood compatible in this pilot study and requires further investigation of efficacy using in vivo models conducted with clinically relevant blood flow rates and study duration.

Biting Innovations of Mosquito-Based Biomaterials and Medical Devices

Mosquitoes are commonly viewed as pests and deadly predators by humans. Despite this perception, investigations of their survival-based behaviors, select anatomical features, and biological composition have led to the creation of several beneficial technologies for medical applications. In this review, we briefly explore these mosquito-based innovations by discussing how unique characteristics and behaviors of mosquitoes drive the development of select biomaterials and medical devices. Mosquito-inspired microneedles have been fabricated from a variety of materials, including biocompatible metals and polymers, to mimic of the mouthparts that some mosquitoes use to bite a host with minimal injury during blood collection. The salivary components that these mosquitoes use to reduce the clotting of blood extracted during the biting process provide a rich source of anticoagulants that could potentially be integrated into blood-contacting biomaterials or administered in therapeutics to reduce the risk of thrombosis. Mosquito movement, vision, and olfaction are other behaviors that also have the potential for inspiring the development of medically relevant technologies. For instance, viscoelastic proteins that facilitate mosquito movement are being investigated for use in tissue engineering and drug delivery applications. Even the non-wetting nanostructure of a mosquito eye has inspired the creation of a robust superhydrophobic surface coating that shows promise for biomaterial and drug delivery applications. Additionally, biosensors incorporating mosquito olfactory receptors have been built to detect disease-specific volatile organic compounds. Advanced technologies derived from mosquitoes, and insects in general, form a research area that is ripe for exploration and can uncover potential in further dissecting mosquito features for the continued development of novel medical innovations.

Uncertainty quantification of a thrombosis model considering the clotting assay PFA-100®

Mathematical models of thrombosis are currently used to study clinical scenarios of pathological thrombus formation. As these models become more complex to predict thrombus formation dynamics high computational cost must be alleviated and inherent uncertainties must be assessed. Evaluating model uncertainties allows to increase the confidence in model predictions and identify avenues of improvement for both thrombosis modeling and anti-platelet therapies. In this work, an uncertainty quantification analysis of a multi-constituent thrombosis model is performed considering a common assay for platelet function (PFA-100®). The analysis is facilitated thanks to time-evolving polynomial chaos expansions used as a parametric surrogate for the full thrombosis model considering two quantities of interest; namely, thrombus volume and occlusion percentage. The surrogate is thoroughly validated and provides a straightforward access to a global sensitivity analysis via computation of Sobol' coefficients. Six out of 15 parameters linked to thrombus consitution, vWF activity, and platelet adhesion dynamics were found to be most influential in the simulation variability considering only individual effects; while parameter interactions are highlighted when considering the total Sobol' indices. The influential parameters are related to thrombus constitution, vWF activity, and platelet to platelet adhesion dynamics. The surrogate model allowed to predict realistic PFA-100® closure times of 300,000 virtual cases that followed the trends observed in clinical data. The current methodology could be used including common anti-platelet therapies to identify scenarios that preserve the hematological balance.

Development and In Vitro Whole Blood Hemocompatibility Screening of Endothelium-Mimetic Multifunctional Coatings

Multifunctional antithrombotic surface modifications for blood-contacting medical devices have emerged as a solution for foreign surface-mediated coagulation disturbance. Herein, we have developed and evaluated an endothelium-inspired strategy to reduce the thrombogenicity of medical plastics by imparting nitric oxide (NO) elution and heparin immobilization on the material surface. This dual-action approach (NO+Hep) was applied to polyethylene terephthalate (PET) blood incubation vials and compared to isolated modifications. Vials were characterized to evaluate NO surface flux as well as heparin density and activity. Hemocompatibility was assessed in vitro using whole blood from human donors. Compared to unmodified surfaces, blood incubated in the NO+Hep vials exhibited reduced platelet aggregation (15% decrease AUC, p = 0.040) and prolonged plasma clotting times (aPTT = 147% increase, p < 0.0001, prothrombin time = 5% increase, p = 0.0002). Prolongation of thromboelastography reaction time and elevated antifactor Xa levels in blood from NO+Hep versus PET vials suggests some heparin leaching from the vial surface, confirmed by post-blood incubation heparin density assessment. Results suggest NO+Hep surface modification is a promising approach for blood-contacting plastics; however, careful tuning of NO flux and heparin stabilization are essential and require assessment using human blood as performed here.

The Mechanisms of Restenosis and Relevance to Next Generation Stent Design

Stents are lifesaving mechanical devices that re-establish essential blood flow to the coronary circulation after significant vessel occlusion due to coronary vessel disease or thrombolytic blockade. Improvements in stent surface engineering over the last 20 years have seen significant reductions in complications arising due to restenosis and thrombosis. However, under certain conditions such as diabetes mellitus (DM), the incidence of stent-mediated complications remains 2–4-fold higher than seen in non-diabetic patients. The stents with the largest market share are designed to target the mechanisms behind neointimal hyperplasia (NIH) through anti-proliferative drugs that prevent the formation of a neointima by halting the cell cycle of vascular smooth muscle cells (VSMCs). Thrombosis is treated through dual anti-platelet therapy (DAPT), which is the continual use of aspirin and a P2Y₁₂ inhibitor for 6–12 months. While the most common stents currently in use are reasonably effective at treating these complications, there is still significant room for improvement. Recently, inflammation and redox stress have been identified as major contributing factors that increase the risk of stent-related complications following percutaneous coronary intervention (PCI). The aim of this review is to examine the mechanisms behind inflammation and redox stress through the lens of PCI and its complications and to establish whether tailored targeting of these key mechanistic pathways offers improved outcomes for patients, particularly those where stent placement remains vulnerable to complications. In summary, our review highlights the most recent and promising research being undertaken in understanding the mechanisms of redox biology and inflammation in the context of stent design. We emphasize the benefits of a targeted mechanistic approach to decrease all-cause mortality, even in patients with diabetes.

Failure Analysis of TEVG’s II: Late Failure and Entering the Regeneration Pathway

Tissue-engineered vascular grafts (TEVGs) are a promising alternative to treat vascular disease under complex hemodynamic conditions. However, despite efforts from the tissue engineering and regenerative medicine fields, the interactions between the material and the biological and hemodynamic environment are still to be understood, and optimization of the rational design of vascular grafts is an open challenge. This is of special importance as TEVGs not only have to overcome the surgical requirements upon implantation, they also need to withhold the inflammatory response and sustain remodeling of the tissue. This work aims to analyze and evaluate the bio-molecular interactions and hemodynamic phenomena between blood components, cells and materials that have been reported to be related to the failure of the TEVGs during the regeneration process once the initial stages of preimplantation have been resolved, in order to tailor and refine the needed criteria for the optimal design of TEVGs.

Cationic Fluoropolyphosphazenes: Synthesis and Assembly with Heparin as a Pathway to Hemocompatible Nanocoatings

The development of state-of-the-art blood-contacting devices can be advanced through integrating hemocompatibility, durability, and anticoagulant functionalities within engineered nanoscale coatings. To enable all-aqueous assembly of nanocoatings combining omniphobic fluorinated features with the potent anticoagulant activity of hydrophilic heparin, two fluoropolymers containing cationic functionalities were synthesized─poly[(trifluoroethoxy)(dimethylaminopropyloxy)phosphazene], PFAP-O, and poly[(trifluoroethoxy)(dimethylaminopropylamino)phosphazene], PFAP-A. Despite a relatively high content of fluorinated pendant groups─approximately 50% (mol) in each─both polymers displayed solubility in aqueous solutions and were able to spontaneously form stable supramolecular complexes with heparin, as determined by dynamic light scattering and asymmetric flow field-flow fractionation methods. Heparin-containing coatings were then assembled by layer-by-layer deposition in aqueous solutions. Nanoassembled coatings were evaluated for potential thrombogenicity in three important categories of in vitro tests─coagulation by thrombin generation, platelet retention, and hemolysis. In all assays, heparin-containing fluoro-coatings consistently displayed superior performance compared to untreated titanium surfaces or fluoro-coatings assembled using poly(acrylic acid) in the absence of heparin. Short-term stability studies revealed the noneluting nature of these noncovalently assembled coatings.

Control of Blood Coagulation by Hemocompatible Material Surfaces-A Review

Hemocompatibility of biomaterials in contact with the blood of patients is a prerequisite for the short- and long-term applications of medical devices such as cardiovascular stents, artificial heart valves, ventricular assist devices, catheters, blood linings and extracorporeal devices such as artificial kidneys (hemodialysis), extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass. Although lower blood compatibility of materials and devices can be handled with systemic anticoagulation, its side effects, such as an increased bleeding risk, make materials that have a better hemocompatibility highly desirable, particularly in long-term applications. This review provides a short overview on the basic mechanisms of blood coagulation including plasmatic coagulation and blood platelets, as well as the activation of the complement system. Furthermore, a survey on concepts for tailoring the blood response of biomaterials to improve the hemocompatibility of medical devices is given which covers different approaches that either inhibit interaction of material surfaces with blood components completely or control the response of the coagulation system, blood platelets and leukocytes.

Mathematical and Computational Modeling of Device-Induced Thrombosis

Given the extensive and routine use of cardiovascular devices, a major limiting factor to their success is the thrombotic rate that occurs. This both poses direct risk to the patient and requires counterbalancing with anticoagulation and other treatment strategies, contributing additional risks. Developing a better understanding of the mechanisms of device-induced thrombosis to aid in device design and medical management of patients is critical to advance the ubiquitous use and durability. Thus, mathematical and computational modelling of device-induced thrombosis has received significant attention recently, but challenges remain. Additional areas that need to be explored include microscopic/macroscopic approaches, reconciling physical and numerical timescales, immune/inflammatory responses, experimental validation, and incorporating pathologies and blood conditions. Addressing these areas will provide engineers and clinicians the tools to provide safe and effective cardiovascular devices.

Predicting the In Vivo Performance of Cardiovascular Biomaterials: Current Approaches In Vitro Evaluation of Blood-Biomaterial Interactions

The therapeutic efficacy of a cardiovascular device after implantation is highly dependent on the host-initiated complement and coagulation cascade. Both can eventually trigger thrombosis and inflammation. Therefore, understanding these initial responses of the body is of great importance for newly developed biomaterials. Subtle modulation of the associated biological processes could optimize clinical outcomes. However, our failure to produce truly blood compatible materials may reflect our inability to properly understand the mechanisms of thrombosis and inflammation associated with biomaterials. In vitro models mimicking these processes provide valuable insights into the mechanisms of biomaterial-induced complement activation and coagulation. Here, we review (i) the influence of biomaterials on complement and coagulation cascades, (ii) the significance of complement-coagulation interactions for the clinical success of cardiovascular implants, (iii) the modulation of complement activation by surface modifications, and (iv) in vitro testing strategies.

A Recombinant Fusion Construct between Human Serum Albumin and NTPDase CD39 Allows Anti-Inflammatory and Anti-Thrombotic Coating of Medical Devices

Medical devices directly exposed to blood are commonly used to treat cardiovascular diseases. However, these devices are associated with inflammatory reactions leading to delayed healing, rejection of foreign material or device-associated thrombus formation. We developed a novel recombinant fusion protein as a new biocompatible coating strategy for medical devices with direct blood contact. We genetically fused human serum albumin (HSA) with ectonucleoside triphosphate diphosphohydrolase-1 (CD39), a promising anti-thrombotic and anti-inflammatory drug candidate. The HSA-CD39 fusion protein is highly functional in degrading ATP and ADP, major pro-inflammatory reagents and platelet agonists. Their enzymatic properties result in the generation of AMP, which is further degraded by CD73 to adenosine, an anti-inflammatory and anti-platelet reagent. HSA-CD39 is functional after lyophilisation, coating and storage of coated materials for up to 8 weeks. HSA-CD39 coating shows promising and stable functionality even after sterilisation and does not hinder endothelialisation of primary human endothelial cells. It shows a high level of haemocompatibility and diminished blood cell adhesion when coated on nitinol stents or polyvinylchloride tubes. In conclusion, we developed a new recombinant fusion protein combining HSA and CD39, and demonstrated that it has potential to reduce thrombotic and inflammatory complications often associated with medical devices directly exposed to blood.

Invited Review: Optimal Management of Upper Extremity DVT: Is Venous Thoracic Outlet Syndrome Underrecognized?

BACKGROUND

UEDVT accounts for approximately 10% of all cases of deep vein thrombosis. In the most widely referenced general review of deep vein thrombosis (DVT the American Academy of Chest Physicians essentially recommend that upper extremity DVT (UEDVT) essentially be treated identically to that of lower extremity DVT, with anticoagulation being the default therapy. Unfortunately, the medical literature does not well differentiate between DVT in the arm and the leg, and does not emphasize the effects of the costoclavicular junction (CCJ) and the lack of effect of gravity, to the point where UEDVT due to extrinsic bony compression at the CCJ is classified as "primary."

METHODS

Comprehensive literature review, beginning with both Medline and Google Scholar searches in addition to collected references, then following relevant citations within the initial manuscripts studied. Both surgical and medical journals were explored RESULTS: It is proposed that effort thrombosis be classified as a secondary cause of UEDVT, limiting the definition of primary to that which is truly idiopathic. Other causes of secondary UEDVT include catheter- and pacemaker-related thrombosis (the most common cause, but often asymptomatic), thrombosis related to malignancy and hypercoagulable conditions, and the rare case of thrombosis due to compression of the vein by a focal malignancy or other space-occupying lesion. In true primary UEDVT and in those secondary cases where no mechanical cause is present or can be corrected, anticoagulation remains the treatment of choice, usually for three months or the duration of a needed catheter. However, evidence suggests that many cases of effort thrombosis are likely missed by a too-narrow adherence to this protocol.

CONCLUSIONS

Because proper treatment of effort thrombosis drops the long-term symptomatic status rate from 50% to almost zero and these are healthy patients with a long lifespan ahead, it is proposed that a more aggressive attitude toward thrombolysis be followed in any patient who has a reasonable degree of suspicion for venous thoracic outlet syndrome.

Effect of Recombinant Human Perlecan Domain V Tethering Method on Protein Orientation and Blood Contacting Activity on Polyvinyl Chloride

Surface modification of biomaterials is a promising approach to control biofunctionality while retaining the bulk biomaterial properties. Perlecan is the major proteoglycan in the vascular basement membrane that supports low levels of platelet adhesion but not activation. Thus, perlecan is a promising bioactive for blood-contacting applications. This study furthers the mechanistic understanding of platelet interactions with perlecan by establishing that platelets utilize domains III and V of the core protein for adhesion. Polyvinyl chloride (PVC) is functionalized with recombinant human perlecan domain V (rDV) to explore the effect of the tethering method on proteoglycan orientation and bioactivity. Tethering of rDV to PVC is achieved via either physisorption or covalent attachment via plasma immersion ion implantation (PIII) treatment. Both methods of rDV tethering reduce platelet adhesion and activation compared to the pristine PVC, however, the mechanisms are unique for each tethering method. Physisorption of rDV on PVC orientates the molecule to hinder access to the integrin-binding region, which inhibits platelet adhesion. In contrast, PIII treatment orientates rDV to allow access to the integrin-binding region, which is rendered antiadhesive to platelets via the glycosaminoglycan (GAG) chain. These effects demonstrate the potential of rDV biofunctionalization to modulate platelet interactions for blood contacting applications.

An uncommon case of bioprosthetic mitral valve thrombosis with subsequent prosthesis dehiscence

Bioprosthetic valve thrombosis (BVT) is uncommon. An 82-year-old gentleman presented following a cardioembolic stroke due to a mitral valve infective endocarditis. The patient underwent bioprosthetic mitral valve replacement. Following discharge, he re-presented with weakness due to a new left-sided stroke and right-sided occipital intracerebral haemorrhage. Both transthoracic and transoesophageal echocardiography revealed BVT on the anterior portion of the prosthesis. Following a multidisciplinary team discussion, it was felt that thrombolytics and anticoagulation would be detrimental. The patient continued to worsen and eventually succumbed to congestive cardiac failure. BVT is uncommon, and patients often present with signs and symptoms of heart failure, shock or embolism. There are no guidelines available on managing BVT in patients with concurrent intracerebral haemorrhage, highlighting the importance of multidisciplinary efforts and patient inclusivity in decision making.

Ambient temperature sulfonated carbon fiber reinforced PEEK with hydroxyapatite and reduced graphene oxide hydroxyapatite composite coating

30% carbon fiber reinforced polyetheretherketone (CFR-PEEK) has in recent times, become significant in the orthopedic industry because its elastic modulus can be engineered to match that of the human bone. But it is bioinert and does not integrate well with the immediate bone tissue environment. In this study, a combined surface modification technique involving ambient temperature sulfonation and surface coating of (hydroxyapatite (HA), 5%reduced graphene oxide hydroxyapatite(5%RGO/HA) and 10%reduced graphene oxide hydroxyapatite(10%RGO/HA) composites) on 30%CFR-PEEK was achieved with an appropriate temperature treatment at 345°C in nitrogen. The coatings adhered unto the surface of S30%CFR-PEEK with an improved hydrophilicity and bioactivity. With the sample S30%CFR-PEEK+HA, having the highest enhanced hydrophilicity from 112.5 ± 2.5° to 20 ± 2° and bioactivity. An improvement in hydrophilicity and bioactivity depicts a change in surface chemistry which will have a positive impact in the interaction of the materials surface with immediate bone environment for a successful application in the orthopedic industry.