Preparation of Vascular Endothelial Cadherin Loaded-Amphoteric Copolymer Decorated Coronary Stents for Anticoagulation and Endothelialization

Recent advances of multifunctional zwitterionic polymers for biomedical application

Zwitterionic polymers possess equal total positive and negative charges in the repeating units, making them electrically neutral overall. This unique property results in superhydrophilicity, which makes the zwitterionic polymers highly effective in resisting protein adsorption, thus endowing the drug carriers with long blood circulation time, inhibiting thrombus formation on biomedical devices in contact with blood, and ensuring the good sensitivity of sensors in biomedical application. Moreover, zwitterionic polymers have tumor-targeting ability and pH-responsiveness, rendering them ideal candidates for antitumor drug delivery. Additionally, the high ionic conductivity of zwitterionic polymers makes them an important raw material for ionic skin. Zwitterionic polymers exhibit remarkable resistance to bacterial adsorption and growth, proving their suitability in a wide range of biomedical applications such as ophthalmic applications, and wound dressings. In this paper, we provide an in-depth analysis of the different structures and characteristics of zwitterionic polymers and highlight their unique qualities and suitability for biomedical applications. Furthermore, we discuss the limitations and challenges that must be overcome to realize the full potential of zwitterionic polymers and present an optimistic perspective for zwitterionic polymers in the biomedical fields. STATEMENT OF SIGNIFICANCE: Zwitterionic polymers have a series of excellent properties such as super hydrophilicity, anti-protein adsorption, antibacterial ability and good ionic conductivity. However, biomedical applications of multifunctional zwitterionic polymers are still a major field to be explored. This review focuses on the design and application of zwitterionic polymers-based nanosystems for targeted and responsive delivery of antitumor drugs and cancer diagnostic agents. Moreover, the use of zwitterionic polymers in various biomedical applications such as biomedical devices in contact with blood, biosensors, ionic skin, ophthalmic applications and wound dressings is comprehensively described. We discuss current results and future challenges for a better understanding of multifunctional zwitterionic polymers for biomedical applications.

Zwitterionic Biomaterials

The term "zwitterionic polymers" refers to polymers that bear a pair of oppositely charged groups in their repeating units. When these oppositely charged groups are equally distributed at the molecular level, the molecules exhibit an overall neutral charge with a strong hydration effect via ionic solvation. The strong hydration effect constitutes the foundation of a series of exceptional properties of zwitterionic materials, including resistance to protein adsorption, lubrication at interfaces, promotion of protein stabilities, antifreezing in solutions, etc. As a result, zwitterionic materials have drawn great attention in biomedical and engineering applications in recent years. In this review, we give a comprehensive and panoramic overview of zwitterionic materials, covering the fundamentals of hydration and nonfouling behaviors, different types of zwitterionic surfaces and polymers, and their biomedical applications.

Biofunctionalization of cardiovascular stents to induce endothelialization: Implications for in- stent thrombosis in diabetes

Stent thrombosis remains one of the main causes that lead to vascular stent failure in patients undergoing percutaneous coronary intervention (PCI). Type 2 diabetes mellitus is accompanied by endothelial dysfunction and platelet hyperactivity and is associated with suboptimal outcomes following PCI, and an increase in the incidence of late stent thrombosis. Evidence suggests that late stent thrombosis is caused by the delayed and impaired endothelialization of the lumen of the stent. The endothelium has a key role in modulating inflammation and thrombosis and maintaining homeostasis, thus restoring a functional endothelial cell layer is an important target for the prevention of stent thrombosis. Modifications using specific molecules to induce endothelial cell adhesion, proliferation and function can improve stents endothelialization and prevent thrombosis. Blood endothelial progenitor cells (EPCs) represent a potential cell source for the in situ-endothelialization of vascular conduits and stents. We aim in this review to summarize the main biofunctionalization strategies to induce the in-situ endothelialization of coronary artery stents using circulating endothelial stem cells.

Recycling protein selective adsorption on fluorine-modified surface through fluorine-fluorine interaction

Low surface energy materials with micro-nano structures have been widely developed to prevent non-specific adhesion of biomolecules. Herein we put forward a new approach based on the antifouling and self-assembly properties of fluorine components, to construct a non-specific protein resistance surface with selective protein adsorption property. Briefly, the antifouling surface (SN-F) was obtained by a simple one-step modification on silicon nanowire arrays (SiNWAs) with fluorine coupling agent 1 H,1 H,2 H,2 H-perfluorodecyltrimethoxysilane (FAS). And protein was fluorinated by conjugation with an amphiphilic fluoro-copolymer, produced from 2-methacrylamido glucopyranose (MAG) and trifluoroethyl methacrylate (TFEMA) via RAFT polymerization. The properties of the materials were characterized by ¹H nuclear magnetic resonance (¹H NMR), infrared spectroscopy (FTIR), water contact angle, and X-ray photoelectron spectroscopy (XPS) etc., and protein adsorption was investigated by protein content measurement, fluorescence detection, and electrophoresis. It was observed that the adsorption for native proteins on SN-F was at an extremely low level, while the adsorption for the fluoro-copolymer conjugated protein (PFG-BSA) was significantly increased. When the percentage of TFEMA in the fluoro-copolymer was as high as 52.0%, the fluorinated protein adsorbed on SN-F was more than 35 times of native proteins on the surface. Moreover, the platform could resist IgG adhesion in serum after the adsorption of fluorinated protein, and it could be recycled three times after 75% ethanol treatment. In conclusion, SN-F showed non-specific protein resistance through low surface energy and specific protein adsorption by fluorine-fluorine self-assembly. The fluorinated nanostructured platform has a great potential in controlling protein adsorption and release.

Doxorubicin-Loaded Walnut-Shaped Polydopamine Nanomotor for Photothermal-Chemotherapy of Cancer

The combination of photothermal therapy and chemical drug therapy shows good prospects in cancer treatment, but there are also some limitations such as low permeability of therapeutic agents and uneven photothermal therapy. Here, we synthesized a walnut-shaped polydopamine (PDA) nanomotor driven by near infrared (NIR) light. The nanomotor was modified by methoxy polyethylene glycol amine (mPEG-NH₂) for improving water solubility. PDA-PEG loaded adriamycin through π-π accumulation and hydrogen bonding. The experimental results showed that the PDA nanomotors had good biocompatibility and photothermal effect. Further, the NIR light irradiation and tumor cell microenvironment are conducive to drug release. In addition, under the irradiation of an NIR laser, the asymmetry of walnut-shaped nanoparticles makes the particles obtain the ability of autonomous movement, which can improve the permeability of particles in 3D tumor balls, which can provide support for drug penetration and heat dispersion. This strategy offers potential innovative materials for photothermal/chemotherapy synergistic therapy of tumors.

A Uniform and Robust Bioinspired Zwitterion Coating for Use in Blood-Contacting Catheters with Improved Anti-Inflammatory and Antithrombotic Properties

Inflammation and thrombosis are two major complications of blood-contacting catheters that are used as extracorporeal circuits for hemodialysis and life-support systems. In clinical applications, complications can lead to increased mortality and morbidity rates. In this work, a biomimetic erythrocyte membrane zwitterion coating based on poly(2-methacryloyloxyethyl phosphorylcholine-co-dopamine methacrylate) (pMPCDA) copolymers is uniformly and robustly modified onto a polyvinyl chloride (PVC) catheter via mussel-inspired surface chemistry. The zwitterionic pMPCDA coating exhibits excellent antifouling activity and resists bacterial adhesion, fibrinogen adsorption, and platelet adhesion/activation. The material also demonstrates great hemocompatibility, cytocompatibility, and anticoagulation properties in vitro. Additionally, this biocompatible pMPCDA coating reduces in vivo foreign-body reactions by mitigating inflammatory response and collagen capsule formation, due to its outstanding ability to resist nonspecific protein adsorption. More importantly, when compared with a bare PVC catheter, the pMPCDA coating exhibits outstanding antithrombotic properties when tested in an ex vivo rabbit perfusion model. Thus, it is envisioned that this biomimetic erythrocyte membrane surface strategy will provide a promising way to mitigate inflammation and thrombosis caused by the use of blood-contacting catheters.

Bifunctional polymer brush-grafted coronary stent for anticoagulation and endothelialization

At present, cardiovascular stent intervention faces clinical complications such as delayed endothelialization, late thrombosis and restenosis after implantation. In this work, a kind of bifunctional polymer brush-grafted coronary stent with anticoagulant and endothelial functions was developed. First, a block copolymer brush with zwitterionic structure consisting of sulfoethyl methacrylate (SBMA) and glycidyl methacrylate (GMA) was surface-induced grafted onto the surface of bare metal coronary stent by atom transfer radical polymerization. The diethylenetriamine NONOate (DETA NONOate), acted as nitric oxide (NO) donor to promote endothelialization, was then attached to polyglycidyl methacrylate (PGMA) brush by a reactive epoxy group to produce NO. The process of chemical modification and the release behavior of NO were characterized in detail. Moreover, the results of anticoagulant test, cytotoxicity test, endothelial cells (ECs) proliferation test and animal experiment of this bifunctional polymer brush-grafted coronary stent we proposed indicate that the zwitterion modified and NO supplied bifunctional coatings has good anticoagulant property, no cytotoxicity and significant endothelialization effect. This work opens the door to combine biological activity of NO and anticoagulant effect of zwitterions, which has great potential to address post-operative side effects associated with restenosis and late stent thrombosis.

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.

Platelet-derived porous nanomotor for thrombus therapy

The treatment difficulties of venous thrombosis include short half-life, low utilization, and poor penetration of drugs at thrombus site. Here, we develop one kind of mesoporous/macroporous silica/platinum nanomotors with platelet membrane (PM) modification (MMNM/PM) for sequentially targeting delivery of thrombolytic and anticoagulant drugs for thrombus treatment. Regulated by the special proteins on PM, the nanomotors target the thrombus site and then PM can be ruptured under near-infrared (NIR) irradiation to achieve desirable sequential drug release, including rapid release of thrombolytic urokinase (3 hours) and slow release of anticoagulant heparin (>20 days). Meantime, the motion ability of nanomotors under NIR irradiation can effectively promote them to penetrate deeply in thrombus site to enhance retention ratio. The in vitro and in vivo evaluation results confirm that the synergistic effect of targeting ability from PM and motion ability from nanomotors can notably enhance the thrombolysis effect in both static/dynamic thrombus and rat model.

Coronary Stents Decorated by Heparin/NONOate Nanoparticles for Anticoagulant and Endothelialized Effects

In the treatment of coronary artery disease (CAD), the use of stent implantation often leads to clinical complications such as restenosis, delayed endothelial healing, and thrombosis. Here, we develop a double drug sustained-release coating for the stent surface by grafting heparin/NONOate nanoparticles (Hep/NONOates). The Hep/NONOates and surface modification of the stent were characterized by X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, static water contact angle, and scanning electron microscopy (SEM), and the release behaviors of the anticoagulant, heparin (Hep) and the bioactive molecule, nitric oxide (NO) were studied. Furthermore, the blood compatibility and cytotoxicity of the modified stent were evaluated by whole blood adhesion and platelet adhesion tests, hemolysis assay, morphological changes of red blood cells, plasma recalcification time assay, in vitro coagulation time tests, and MTT assay. Finally, the results of a rabbit carotid artery stent implantation experiment showed that the double drug sustained-release coating for the stent can accelerate regeneration of endothelial cells and keep good anticoagulant activity. This study can provide new design ideas based on nanotechnology for improving the safety and effectiveness of drug-eluting stents.

Characterization of Photoluminescent Polylactone-Based Nanoparticles for Their Applications in Cardiovascular Diseases

Cardiovascular diseases (CVD) affect a large number of the population across the globe and are the leading cause of death worldwide. Nanotechnology-based drug delivery has currently offered novel therapeutic options to treat these diseases, yet combination of both diagnostic and therapeutic abilities is further needed to understand factors and/or mechanisms that affect the treatment in order to design better therapies to challenge CVD. Biodegradable photoluminescent polylactones (BPLPLs) enable to bridge this gap as these materials exhibit a stable, long-term intrinsic fluorescence as well as offers excellent cytocompatibility and biodegradability properties. Herein, we formulated three different BPLPL based nanoparticles (NPs), including BPLP-co-poly (L-lactic acid) (BPLPL-PLLA), BPLP-co-poly (lactic-co-glycolic acid) copolymers with lactic acid and glycolic acid ratios of 75:25 (BPLPL-PLGA75:25) and 50:50 (BPLPL-PLGA50:50), and extensively evaluated their suitability as theranostic nanocarriers for CVD applications. All BPLPL based NPs were <160 nm in size and had photoluminescence characteristics and tunable release kinetics of encapsulated protein model depending on polylactones copolymerized with BPLP materials. Compared to BPLPL-PLLA NPs, BPLPL-PLGA NPs demonstrated excellent stability in various formulations including deionized water, serum, saline, and simulated body fluid over 2 days. In vitro cell studies with human umbilical vein derived endothelial cells showed dose-dependent accumulation of BPLPL-based NPs, and BPLPL-PLGA NPs presented superior compatibility with endothelial cells in terms of viability with minimal effects on cellular functions such as nitric oxide production. Furthermore, all BPLPL NPs displayed hemocompatibility with no effect on whole blood kinetic profiles, were non-hemolytic, and consisted of comparable platelet responses such as platelet adhesion and activation to those of PLGA, an FDA approved material. Overall, our results demonstrated that BPLPL-PLGA based NPs have better physical and biological properties than BPLPL-PLLA; hence they have potential to be utilized as functional nanocarriers for therapy and diagnosis of CVD.

Novel heparin-loaded mesoporous tubular micromotors formed via template-assisted electrochemical deposition

Based on the concept of the active drug delivery of micro- and nanomotors and the longer cycle time in the blood for drug-loaded tubular particles, it is important to develop novel tubular micromotors that could increase drug loading and achieve more effective treatments in the biomedical field. Here, a novel kind of mesoporous tubular micromotor used to load heparin (Hep) and formed via template-assisted electrochemical deposition is presented. Firstly, the mesoporous tubular micromotors were composed of poly(3,4-ethylenedioxythiophene) (PEDOT), mesoporous silica (MS) and manganese dioxide (MnO₂), and were simply fabricated via template-assisted electrochemical growth. Then, the drug Hep was loaded into PEDOT/MS/MnO₂via a simple soaking process. Finally, the release process, cytotoxicity, and blood compatibility tests and motion study for these mesoporous tubular micromotors of PEDOT/MS/MnO₂-Hep were performed. Results indicated that the micromotors we prepared showed good controlled release of Hep, anticoagulant effects, non-cytotoxicity and autonomous motion ability. The new drug carrier and motion mode will give rise to more potential applications of Hep in the biomedical field.

Multiple Drug Delivery from Mesoporous Coating Realizing Combination Therapy for Bare Metal Stents

The simultaneous loading of multifunctional drugs has been regarded as one of the major challenges in the drug delivery system. Herein, a mesoporous silica coating was constructed on a bare metal stent surface by an evaporation-induced self-assembly method, in which both hydrophilic and hydrophobic drugs (heparin and rapamycin) were encapsulated by a one-pot method for the first time, and the release behaviors of these drugs were studied. The releasing mechanisms of these drugs were investigated in detail. Rapid release of heparin can achieve anticoagulation and endothelialization, whereas slow release of rapamycin can realize antiproliferative therapy for long term. In vitro hemocompatibility and promotion for proliferation of vein endothelial cells and the inhibition of smooth muscle cells were conducted. In vivo stent implantation results verify that the mesoporous silica coating with both heparin and rapamycin can successfully accelerate the endothelialization process and realize the antiproliferative therapy for as long as 3 months. These results indicate that this multifunctional mesoporous coating containing both hydrophilic and hydrophobic drugs might be a promising stent coating in the future.