REDV/Rapamycin-loaded polymer combinations as a coordinated strategy to enhance endothelial cells selectivity for a stent system

A Study of the Phosphorylcholine Polymer Coating of a Polymethylpentene Hollow Fiber Membrane

A phosphorylcholine polymer (poly(MPC-co-BMA-co-TSMA), PMBT) was prepared by free radical polymerization and coated on the surface of the polymethylpentene hollow fiber membrane (PMP-HFM). ATR-FTIR and SEM analyses showed that the PMBT polymer containing phosphorylcholine groups was uniformly coated on the surface of the PMP-HFM. Thermogravimetric analysis showed that the PMBT had the best stability when the molar percentage of MPC monomer in the polymer was 35%. The swelling test and static contact angle test indicated that the coating had excellent hydrophilic properties. The fluorescence test results showed that the coating could resist dissolution with 90% (v/v%) ethanol solution and 1% (w/v%) SDS solution. The PMBT coating was shown to be able to decrease platelet adherence to the surface of the hollow fiber membrane, and lower the risk of blood clotting; it had good blood compatibility in tests of whole blood contact and platelet adhesion. These results show that the PMBT polymer may be coated on the surface of the PMP-HFM, and is helpful for improving the blood compatibility of membrane oxygenation.

Biodegradable phosphorylcholine copolymer for cardiovascular stent coating

Phosphorylcholine (PC) based polymer coatings with excellent biocompatibility have shown successful commercialization in drug-eluting stents. However, poor degradability represents a challenge in the application of biodegradable stents. Herein, a biodegradable phosphorylcholine copolymer is developed based on one-step radical ring-opening polymerization (RROP). This copolymer was synthesized by copolymerization of a PC unit, degradable ester (2-methylene-1,3-dioxepane, MDO) unit and non-degradable butyl methacrylate (BMA) unit, which showed ratio controllability by changing the monomer ratio during polymerization. We demonstrated that the copolymer with the ratio of 34% MDO, 19% MPC and 47% BMA could form a stable coating by ultrasonic spray, and showed good blood compatibility, anti-adhesion properties, biodegradability, and rapamycin eluting capacity. In vivo study revealed its promising application as a biodegradable stent coating. This work provides a facile path to add biodegradability into PC based polymers for further bio-applications.

Endothelial Cell-Mediated Gene Delivery for In Situ Accelerated Endothelialization of a Vascular Graft

As an urgently needed device for vascular diseases, the small-diameter vascular graft is limited by high thrombogenicity in clinical applications. Rapid endothelialization is a promising approach to construct an antithrombogenic inner surface of the vascular graft. The main bottleneck for rapid endothelialization is the adhesion, migration, and proliferation of endothelial cells (ECs) in situ of the small-diameter vascular graft. Herein, we innovatively fabricated an intelligent gene delivery small-caliber vascular graft based on electrospun poly(lactic acid-co-caprolactone) and gelatin for rapid in situ endothelialization. The graft surface was co-modified with EC adhesive peptide of Arg-Glu-Asp-Val (REDV) and responsive gene delivery system. REDV can selectively adhere ECs onto the graft surface; subsequently, the overexpressed matrix metalloproteinase by ECs can effectively cleave the linker peptide GPQGIWGQ-C; and finally, the gene complexes were intelligently and enzymatically released from the graft surface, and thereby, the gene can efficiently transfect ECs. Importantly, this enzymatically releasing gene surface has been proven to be safe and temporarily stable in blood flow owing to the biotin-avidin interaction to immobilize gene complexes on the inner surface of vascular grafts through the GPQGIWGQ-C peptide linker. It has the advantage of specifically adhering the ECs to the surface and smartly transfecting them with high transfection efficiency. The co-modified surface has been demonstrated to accelerate the luminal endothelialization in vivo, which might be attributed to the synergistic effect of REDV and effective gene transfection. Particularly, the intelligent and responsive gene release surface will open a new avenue to enhance the endothelialization of blood-contacting devices.

Surface Engineering of Cardiovascular Devices for Improved Hemocompatibility and Rapid Endothelialization

Cardiovascular devices have been widely applied in the clinical treatment of cardiovascular diseases. However, poor hemocompatibility and slow endothelialization on their surface still exist. Numerous surface engineering strategies have mainly sought to modify the device surface through physical, chemical, and biological approaches to improve surface hemocompatibility and endothelialization. The alteration of physical characteristics and pattern topographies brings some hopeful outcomes and plays a notable role in this respect. The chemical and biological approaches can provide potential signs of success in the endothelialization of vascular device surfaces. They usually involve therapeutic drugs, specific peptides, adhesive proteins, antibodies, growth factors and nitric oxide (NO) donors. The gene engineering can enhance the proliferation, growth, and migration of vascular cells, thus boosting the endothelialization. In this review, the surface engineering strategies are highlighted and summarized to improve hemocompatibility and rapid endothelialization on the cardiovascular devices. The potential outlook is also briefly discussed to help guide endothelialization strategies and inspire further innovations. It is hoped that this review can assist with the surface engineering of cardiovascular devices and promote future advancements in this emerging research field.

Rapid Buildup Arrays with Orthogonal Biochemistry Gradients via Light-Induced Thiol-Ene "Click" Chemistry for High-Throughput Screening of Peptide Combinations

The concept of high-throughput screening sheds new light on fabrication and analysis of materials. Herein, a combinatorial surface-modified platform with biochemical gradients was developed through thiol-ene "click" chemistry by adjusting the intensity of ultraviolet (UV) irradiation. Contact angle, X-ray photoelectron spectroscopy, and ellipsometry measurement results demonstrated that the sulfhydryl molecules including polyethylene glycol and RGD (arginine-glycine-aspartic acid) and REDV (arginine-glutamic acid-aspartic acid-valine) peptides can be directly attached onto alkene-modified substrates, in which the graft density can be well controlled by the intensity of UV irradiation. The multistep attachment of different molecules onto substrates is archived via the multistep UV-initiated thiol-ene "click" reaction. The high-throughput arrays with the gradient density of single ligand and the orthogonal gradient density of two ligands were rapidly fabricated via the one-step UV gradient irradiation and the two-step orthogonal UV gradient-initiated thiol-ene "click" reaction. Endothelial cells (ECs) and smooth muscle cells (SMCs) were cocultured on the array with the orthogonal gradient density of RGD and REDV to screen the peptide combination with high EC selectivity, which is essential for in situ endothelialization during stent implant. From 64, 8 × 8, combinations investigated, a special combinatorial surface representing the really high competitiveness of ECs over SMCs was screened. This platform puts forward a facile, high-throughput method to study the combinatorial variation of biochemical signals to cell behavior.

Combinatorial functionalization with bisurea-peptides and antifouling bisurea additives of a supramolecular elastomeric biomaterial

The bioactive additive toolbox to functionalize supramolecular elastomeric materials expands rapidly. Here we have set an explorative step toward screening of complex combinatorial functionalization with antifouling and three peptide-containing additives in a bisurea-based supramolecular system. Thorough investigation of surface properties of thin films with contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy, was correlated to cell-adhesion of endothelial and smooth muscle cells to apprehend their respective predictive values for functional biomaterial development. Peptides were presented at the surface alone, and in combinatorial functionalization with the oligo(ethylene glycol)-based non-cell adhesive additive. The bisurea-RGD additive was cell-adhesive in all conditions, whereas the endothelial cell-specific bisurea-REDV showed limited bioactive properties in all chemical nano-environments. Also, aspecific functionality was observed for a bisurea-SDF1α peptide. These results emphasize that special care should be taken in changing the chemical nano-environment with peptide functionalization. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1725-1735.

Co-immobilization of ACH11 antithrombotic peptide and CAG cell-adhesive peptide onto vascular grafts for improved hemocompatibility and endothelialization

Surface modification by conjugating biomolecules has been widely proved to enhance biocompatibility of small-caliber artificial vascular grafts. In this study, we aimed at developing a multifunctional vascular graft that provides not only good hemocompatibility but also in situ rapid endothelialization. Herein, a vascular graft (inner diameter ∼2 mm) was fabricated by electrospinning with poly(lactic acid-co-caprolactone) and gelatin, and then biofunctionalized with antithrombotic peptide with sequence LTFPRIVFVLG (ACH₁₁) and cell adhesion peptide with sequence CAG through adhesive poly(dopamine) coating. We developed this graft with the synergistic properties of low thrombogenicity and rapid endothelialization. The successful grafting of both CAG and ACH₁₁ peptides was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface micromorphology of the modified surfaces was observed by field emission scanning electron microscopy. Our results demonstrated that the multifunctional surface suppressed the denaturation of absorbed fibrinogen, hindered coagulation factor Xa activation, and inhibited platelet adhesion and aggregation. Importantly, this modified surface could selectively enhance endothelial cells adhesion, proliferation and release of nitric oxide. Upon in vivo implantation of 6 weeks, the multifunctional vascular graft showed improved patency and superior vascular endothelialization. Overall, the results effectively demonstrated that the co-immobilization of ACH₁₁ and CAG provided a promising method for the improvement of hemocompatibility and endothelialization of vascular grafts. STATEMENT OF SIGNIFICANCE: Electrospun small-caliber vascular grafts are increasingly used to treat cardiovascular diseases. Despite their success related to their good biodegradation and mechanical strength, they have some drawbacks, such as low hemocompatibility and endothelialization. The single-function ligands are insufficient to modify surface with both good hemocompatibility and rapid endothelialization simultaneously. Therefore, we functionalized electrospun vascular graft by novel antithrombotic peptide and cell-adhesive peptide to construct superior anticoagulation and ECs-selective adhesion surface in present study. The multifunctional vascular grafts benefit for high long-term patency and rapid endothelialization.

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

Expanded polytetrafluoroethylene (ePTFE) prosthetic valves have been widely used in clinical applications in Asian countries. However, these valves still have limits with regard to thrombosis, neointimal hyperplasia, restenosis, and valvar vegetation. The achievement of in situ endothelialization on implant materials is a promising way to overcome those limits. Here, heparin/collagen multilayers were fabricated on ePTFE films via a layer-by-layer (LBL) self-assembly technique, and then, the endothelial cell (EC) adhesive peptide sequence Arg-Glu-Asp-Val (REDV) was immobilized on the multilayers. After modification with the heparin/collagen multilayers with or without REDV peptide, less platelet activation and aggregation were observed, the blood coagulation time was increased, and the hemolysis rate was decreased compared to that on pristine ePTFE films. The REDV-functionalized ePTFE films positively impacted early EC adhesion, later cell proliferation and cell activity. The EC barrier was confirmed to be successfully achieved on the functionalized ePTFE film surface in vitro. The successful assembly of the REDV-functionalized heparin/collagen multilayer on ePTFE films improved the blood compatibility, anticoagulant properties, and cell compatibility of the films in vitro, and thus, represents a candidate approach for applications requiring quick in situ endothelialization in vivo.

Oligohistidine and targeting peptide functionalized TAT-NLS for enhancing cellular uptake and promoting angiogenesis in vivo

BACKGROUND

Gene therapy has been developed and used in medical treatment for many years, especially for the enhancement of endothelialization and angiogenesis. But slow endosomal escape rate is still one of the major barriers to successful gene delivery. In order to evaluate whether introducing oligohistidine (H_n) sequence into gene carriers can promote endosomal escape and gene transfection or not, we designed and synthesized Arg-Glu-Asp-Val (REDV) peptide functionalized TAT-NLS-H_n (TAT: typical cell-penetrating peptide, NLS: nuclear localization signals, H_n: oligohistidine sequence, n: 4, 8 and 12) peptides with different H_n sequence lengths. pEGFP-ZNF580 (pZNF580) was condensed by these peptides to form gene complexes, which were used to transfect human umbilical vein endothelial cells (HUVECs).

RESULTS

MTT assay showed that the gene complexes exhibited low cytotoxicity for HUVECs. The results of cellular uptake and co-localization ratio demonstrated that the gene complexes prepared from TAT-NLS-H_n with long H_n sequence (n = 12) benefited for high internalization efficiency of pZNF580. In addition, the results of western blot analysis and PCR assay of REDV-TAT-NLS-H₁₂/pZNF580 complexes showed significantly enhanced gene expression at protein and mRNA level. Wound healing assay and transwell migration assay also confirmed the improved proliferation and migration ability of the transfected HUVECs by these complexes. Furthermore, the in vitro and in vivo angiogenesis assay illustrated that these complexes could promote the tube formation ability of HUVECs.

CONCLUSION

The above results indicated that the delivery efficiency of pZNF580 and its expression could be enhanced by introducing H_n sequence into gene carriers. The H_n sequence in REDV-TAT-NLS-H_n is beneficial for high gene transfection. These REDV and H_n functionalized TAT-NLS peptides are promising gene carriers in gene therapy.

Peptide-Functionalized Polyurethane Coatings Prepared via Grafting-To Strategy to Selectively Promote Endothelialization

Endothelialization, formation of endothelial cells (ECs) layer on cardiovascular implant surface, is considered an ideal approach to prevent restenosis (renarrowing of blood vessel mainly due to the accumulation of proliferated vascular smooth muscle cells, SMCs) and thrombosis. In this study, the possibility of using polyurethane (PU) as a coating platform for functionalization with peptide to enhance endothelialization on implants is explored. PUs are synthesized through metal-free organocatalytic polymerization followed by chemical conjugation with an EC-specific REDV peptide through thiol-ene reaction. Meanwhile, the free isocyanate groups of PU allow for covalent grafting of REDV-functionalized PU (PU/REDV) to silanize implant materials (nitinol and PET). PU/REDV coating with peptide grafting density of ≈2 nmol cm^-2 selectively accommodates primary human umbilical vein ECs (HUVECs) and retards spreading of primary human umbilical artery SMCs (HUASMCs). In addition, a layer of HUVECs is formed within 3 d on PU/REDV-coated surfaces, while proliferation of HUASMCs is inhibited. The selectivity is further confirmed by coculture of HUVECs and HUASMCs. Moreover, the PU/REDV-coated surfaces are less thrombogenic as evidenced by reduced number and activity of adhered platelets. Therefore, PU/REDV can be potentially used as a coating of cardiovascular implants to prevent restenosis and thrombosis by promoting endothelialization.

Multi-targeting peptides for gene carriers with high transfection efficiency

Non-viral gene carriers for gene therapy have been developed for many years.

Fluorescent genipin cross-linked REDV-conjugated polymeric microbubbles for human vascular endothelial cell (HVEC) targeting

Fluorescent polymeric microbubbles conjugated with REDV peptides were fabricated to achieve HVECs active targeting. The degradation, cytotoxicity and targeting features endowed them potential candidates in early molecular diagnosis for cardiovascular diseases.