Application of Heparin/Collagen-REDV Selective Active Interface on ePTFE Films to Enhance Endothelialization and Anticoagulation

Protein-based layer-by-layer films for biomedical applications

The surface engineering of biomaterials is crucial for their successful (bio)integration by the body, i.e. the colonization by the tissue-specific cell, and the prevention of fibrosis and/or bacterial colonization. Performed at room temperature in an aqueous medium, the layer-by-layer (LbL) coating method is based on the alternating deposition of macromolecules. Versatile and simple, this method allows the functionalization of surfaces with proteins, which play a crucial role in several biological mechanisms. Possessing intrinsic properties (cell adhesion, antibacterial, degradable, etc.), protein-based LbL films represent a powerful tool to control bacterial and mammalian cell fate. In this article, after a general introduction to the LbL technique, we will focus on protein-based LbL films addressing different biomedical issues/domains, such as bacterial infection, blood contacting surfaces, mammalian cell adhesion, drug and gene delivery, and bone and neural tissue engineering. We do not consider biosensing applications or electrochemical aspects using specific proteins such as enzymes.

Multifunctional nanoparticle-VEGF modification for tissue-engineered vascular graft to promote sustained anti-thrombosis and rapid endothelialization

Purpose: The absence of a complete endothelial cell layer is a well-recognized reason leading to small-diameter tissue-engineered vascular graft failure. Here we reported a multifunctional system consisting of chitosan (CS), Arg-Glu-Asp-Val (REDV) peptide, heparin, and vascular endothelial growth factor (VEGF) to achieve sustained anti-thrombosis and rapid endothelialization for decellularized and photo-oxidized bovine internal mammary arteries (DP-BIMA). Methods: CS-REDV copolymers were synthesized via a transglutaminase (TGase) catalyzed reaction. CS_-REDV-Hep nanoparticles were formed by electrostatic self-assembly and loaded on the DP-BIMA. The quantification of released heparin and vascular endothelial growth factor was detected. Hemolysis rate, platelets adhesion, endothelial cell (EC) adhesion and proliferation, and MTT assay were performed in vitro. The grafts were then tested in a rabbit abdominal aorta interposition model for 3 months. The patency rates were calculated and the ECs regeneration was investigated by immunofluorescence staining of CD31, CD144, and eNOS antibodies. Results: The nanoparticle-VEGF system (particle size: 61.8 ± 18.3 nm, zeta-potential: +13.2 mV, PDI: .108) showed a sustained and controlled release of heparin and VEGF for as long as 1 month and exhibited good biocompatibility, a lower affinity for platelets, and a higher affinity for ECs in vitro. The nanoparticle-VEGF immobilized BIMA achieved 100% and 83.3% patency in a rabbit abdominal interposition model during 1 and 3 months, respectively, without any thrombogenicity and showed CD31, CD144, eNOS positive cell adhesion as early as 1 day. After 3 months, CD31, CD144, and eNOS positive cells covered almost the whole luminal surface of the grafts. Conclusion: The results demonstrated that the multifunctional nanoparticle-VEGF system can enhance the anti-thrombosis property and promote rapid endothelialization of small-diameter tissue-engineered vascular grafts. Utilizing nanoparticles to combine different kinds of biomolecules is an appropriate technology to improve the long-term patency of small-diameter tissue-engineered vascular grafts.

Heparin/Collagen-REDV Modification of Expanded Polytetrafluoroethylene Improves Regional Anti-thrombosis and Reduces Foreign Body Reactions in Local Tissues

Prosthetic implants of expanded polytetrafluoroethylene (ePTFE) in the cardiovascular system have a high failure rate over the long term because of thrombosis and intimal hyperplasia. Although multiple surface modification methods have been applied to improve the anti-thrombotic and in situ endothelialization abilities of ePTFE, none have delivered outstanding results in vivo. Our previous study combined heparin/collagen multilayers and REDV peptides to modify ePTFE, and the in-vitro results showed that modification ePTFE with heparin/collagen-REDV can promote the cytocompatibility and antiplatelet property. This study illustrated the physical change, selective endothelial cells capture ability, and in vivo performance in further. The physical test demonstrated that this modification improved the hydrophilicity, flexibility and strength of ePTFE. A competition experiment of co-cultured endothelial cells and vascular smooth muscle cells verified that the heparin/collagen-REDV modification had high specificity for endothelial cell capture. A rabbit animal model was constructed to evaluate the in vivo performance of modified ePTFE implanted in the right ventricular outflow tract. The results showed that heparin/collagen-REDV modification was safe, promoted endothelialization, and successfully achieved regional anti-thrombosis without influencing body-wide coagulation function. The pathologic manifestations and mRNA expression pattern in tissues in contact with modified ePTFE indicated that this modification method may reduce M2-type macrophage infiltration and the expression of genes related to immune and inflammatory responses. The heparin/collagen-REDV modification may lower the incidence of complications related to ePTFE implantation and has good prospects for clinical use.

Collagen-Based Osteogenic Nanocoating of Microrough Titanium Surfaces

The aim of the present study was to develop a collagen/heparin-based multilayer coating on titanium surfaces for retarded release of recombinant human bone morphogenic protein 2 (rhBMP2) to enhance the osteogenic activity of implant surfaces. Polyelectrolyte multilayer (PEM) coatings were constructed on sandblasted/acid-etched surfaces of titanium discs using heparin and collagen. PEM films of ten double layers were produced and overlayed with 200 µL of a rhBMP2 solution containing 15 µg rhBMP2. Subsequently, cross-linking of heparin molecules was performed using EDC/NHS chemistry to immobilize the incorporated rhBMP2. Release characteristics for 3 weeks, induction of Alkaline Phosphatase (ALP) in C2C12 cells and proliferation of human mesenchymal stem cells (hMSCs) were evaluated to analyze the osteogenic capacity of the surface. The coating incorporated 10.5 µg rhBMP2 on average per disc and did not change the surface morphology. The release profile showed a delivery of 14.5% of the incorporated growth factor during the first 24 h with a decline towards the end of the observation period with a total release of 31.3%. Cross-linking reduced the release with an almost complete suppression at 100% cross-linking. Alkaline Phosphatase was significantly increased on day 1 and day 21, indicating that the growth factor bound in the coating remains active and available after 3 weeks. Proliferation of hMSCs was significantly enhanced by the non-cross-linked PEM coating. Nanocoating using collagen/heparin-based PEMs can incorporate clinically relevant amounts of rhBMP2 on titanium surfaces with a retarded release and a sustained enhancement of osteogenic activity without changing the surface morphology.

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.

Mid-term Outcomes for Polytetrafluoroethylene Valved Conduits

BACKGROUND

Various conduits for right ventricular outflow tract reconstruction (RVOTR) have been reported but most of them are not available in China. We developed a simple handsewn valved conduit using expanded polytetrafluoroethylene (ePTFE). This study evaluated the mid-term outcomes for this conduit.

METHODS

This retrospective study included a total of 72 patients who underwent RVOTR with ePTFE valved conduits between January 2014 and June 2020. During follow-up, echocardiograms were performed for all patients and magnetic resonance imaging for patients with repaired Fallot.

RESULTS

Patients had a median age of 69 (interquartile range, 28-127) months and a median follow-up period of 33 (interquartile range, 9-51) months . There was no early death , but two late deaths (2.78%) occurred. The median conduit size was 18 mm (interquartile range, 18-20) and Z score was +1.3 (interquartile range, +0.6-+2). Peak velocity across the ePTFE valve was 2.38 m/s (95% confidence interval, 2.11 - 2.63 m/s). Pulmonary valve regurgitation was none or trivial in 27 (38.5%) patients, mild in 42 (60.0%) patients and moderate in one (1.4%) patient. Conduit dysfunction occurred in five patients: four developed moderate conduit stenosis and one moderate regurgitation. The right ventricular end diastolic volume index in repaired Fallot was significantly decreased after surgery(171 ml/m² vs 130 ml/m², P<0.001).No reintervention or conduit replacement was needed.

CONCLUSIONS

The handsewn ePTFE valved conduit we developed has appreciable hemodynamic outcomes during the mid-term follow-up period. Long-term follow-up studies are needed to corroborate our findings.

What Does the Future Hold?: Ideal Device, Newer Devices, and More

Please verify if "pigtail guided" should be "pigtail catheter-guided": Recent design changes for left atrial appendage (LAA) closure devices have led to significant improvement by facilitating the procedural workflow (no need for pigtail guided LAA intubation), moving the workspace from distal LAA to the landing zone (closed distal end design), and improving device stability (different anchor design). The availability of different device types (plug vs disc-lobe design) offers an option to tailor a device type to a patient's anatomy; thereby, sealing results have improved substantially. The issue of device-related thrombus has not been resolved and deserves future research, with the goal of eliminating postprocedural antithrombotic medication without increasing risk for stroke.

Pathological Change and Whole Transcriptome Alternation Caused by ePTFE Implantation in Myocardium

Expanded polytetrafluoroethylene (ePTFE) is commonly used in cardiovascular surgery, but usually causes postoperation complications. Although great efforts have been done to relieve these complications or to understand their mechanism, there are no applicable strategies available and no understanding mechanisms, especially in the myocardium. Here, ePTFE membranes are implanted into the right ventricular outflow tract of rabbits, and the implant-related myocardium is dissected and analyzed by histology and transcriptome sequencing. ePTFE implantation causes myocardium inflammation and fibrosis. There are 1867 differently expressed mRNAs (DEmRNAs, 1107 upregulated and 760 downregulated) and 246 differently expressed lncRNAs (DElncRNAs, 110 upregulated and 136 downregulated) identified. Bioinformatic analysis indicates that the upregulated DEmRNAs and DElncRNAs are mainly involved in inflammatory, immune responses, and extracellular matrix remodeling, while the downregulated DEmRNAs and DElncRNAs are predominantly functioned in the metabolism and cardiac remodeling. Analysis of coexpression and regulatory relationship of DEmRNAs and DElncRNAs reveals that most DElncRNAs are trans-regulated on the relevant DEmRNAs. In conclusion, ePTFE implantation causes severe myocardial tissue damages and alters the transcriptome profiles of the myocardium. Such novel data may provide a landscape of mechanisms underlying the adverse reactions caused by ePTFE implantation and uncover new therapeutic targets for inhibiting the ePTFE-related complications.

Polysiloxane Nanofilaments Infused with Silicone Oil Prevent Bacterial Adhesion and Suppress Thrombosis on Intranasal Splints

Like all biofluid-contacting medical devices, intranasal splints are highly prone to bacterial adhesion and clot formation. Despite their widespread use and the numerous complications associated with infected splints, limited success has been achieved in advancing their safety and surface biocompatibility, and, to date, no surface-coating strategy has been proposed to simultaneously enhance the antithrombogenicity and bacterial repellency of intranasal splints. Herein, we report an efficient, highly stable lubricant-infused coating for intranasal splints to render their surfaces antithrombogenic and repellent toward bacterial cells. Lubricant-infused intranasal splints were prepared by creating superhydrophobic polysiloxane nanofilament (PSnF) coatings using surface-initiated polymerization of n-propyltrichlorosilane (n-PTCS) and further infiltrating them with a silicone oil lubricant. Compared with commercially available intranasal splints, lubricant-infused, PSnF-coated splints significantly attenuated plasma and blood clot formation and prevented bacterial adhesion and biofilm formation for up to 7 days, the typical duration for which intranasal splints are kept. We further demonstrated that the performance of our engineered biointerface is independent of the underlying substrate and could be used to enhance the hemocompatibility and repellency properties of other medical implants such as medical-grade catheters.

Single and multi-functional coating strategies for enhancing the biocompatibility and tissue integration of blood-contacting medical implants

Device-associated clot formation and poor tissue integration are ongoing problems with permanent and temporary implantable medical devices. These complications lead to increased rates of mortality and morbidity and impose a burden on healthcare systems. In this review, we outline the current approaches for developing single and multi-functional surface coating techniques that aim to circumvent the limitations associated with existing blood-contacting medical devices. We focus on surface coatings that possess dual hemocompatibility and biofunctionality features and discuss their advantages and shortcomings to providing a biocompatible and biodynamic interface between the medical implant and blood. Lastly, we outline the newly developed surface modification techniques that use lubricant-infused coatings and discuss their unique potential and limitations in mitigating medical device-associated complications.

Pre-mounted dry TAVI valve with improved endothelialization potential using REDV-loaded PEGMA hydrogel hybrid pericardium

Schematic diagram for the preparation of hydrogel hybrid dry valve.

Surface modification of polyvinyl alcohol (PVA)/polyacrylamide (PAAm) hydrogels with polydopamine and REDV for improved applicability

Developing a small-diameter vascular graft with a satisfactory performance in terms of mechanical and biological properties remains a challenging issue because of comprehensive requirements from clinical applications. Polyvinyl alcohol (PVA)/polyacrylamide (PAAm) hydrogels exhibit many desirable characteristics for small-diameter vascular grafts because of their tunable mechanical properties, especially high compliance. However, poor cells adhesion hinders their application for endothelialization in situ. Therefore, in the present work, polydopamine (PDA) and tetrapeptide Arg-Glu-Asp-Val (REDV) were used to functionalize the hydrogels surface and improve cells adhesion. A series of characterizations were systematically conducted to examine the applicability of coated hydrogels to small-diameter vascular grafts. Results showed that bare and coated hydrogels have appropriate structural stability, and no significant differences in tensile properties could be found after being coated with PDA or PDA-REDV. The hydrophilicity of the hydrogels decreased with the coatings of PDA and especially PDA-REDV to improve protein adsorption, porcine iliac artery endothelial cells (PIECs) adhesion, viability, proliferation, and spreading on the hydrogels. Lower hemolysis percentages and higher blood clotting index values were attained for the hydrogels, suggesting their satisfactory hemocompatibility. Overall, the present work provided insights into the development of a novel hydrogel-based small-diameter vascular graft. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:117-127, 2020.

Artificial Organs 2018: A Year in Review

In this Editor's Review, articles published in 2018 are organized by category and summarized. We provide a brief reflection of the research and progress in artificial organs intended to advance and better human life while providing insight for continued application of these technologies and methods. Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. Peer-reviewed special issues this year included contributions from the 13th International Conference on Pediatric Mechanical Circulatory Support Systems and Pediatric Cardiopulmonary Perfusion edited by Dr. Akif Undar, and the 25th Congress of the International Society for Mechanical Circulatory Support edited by Dr. Marvin Slepian. Additionally, many editorials highlighted the worldwide survival differences in hemodialysis and perspectives on mechanical circulatory support and stem cell therapies for cardiac support. We take this time also to express our gratitude to our authors for offering their work to this journal. We offer our very special thanks to our reviewers who give so generously of time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.

Facile preparation of a controlled-release tubular scaffold for blood vessel implantation

Salvianic acid-loaded mesoporous silica nanoparticles into gelatin/polyurethane bilayered small-diameter tubular scaffold were prepared by thermally induced phase separation (TIPS) and electrospinning. Mesoporous silica nanoparticles (MSNs) were selected as carriers to load salvianic acid (SAL). The SAL-loaded MSNs (SAL@MSNs) with an optimized SAL loading efficiency of 10% was initially dispersed in gelatin solution and under a vacuum freeze-drying process as an inner layer of vascular scaffolds. Then, poly(ester-urethane)urea (C-PEEUU) nanofibers were electrospun outside the SAL@MSNs/Gelatin vascular scaffold to strengthen the spongy matrix. The loaded SAL within the MSNs/Gelatin/C-PEEUU bilayered small-diameter tubular scaffold showed a sustained release profile and good mechanical properties. In addition, the drug-loaded composite scaffold showed no unfavorable effects on the adhesion and proliferation of endothelial cells. Moreover, no intimal hyperplasia and acute thrombosis was observed in the short-term implantation in rabbit's carotid artery. We believe the SAL@MSNs/Gelatin/C-PEEUU bilayered vascular scaffolds have promise for vascular tissue engineering applications.