Adhesive and Self-Healing Polyurethanes with Tunable Multifunctionality

Many polyurethanes (PUs) are blood-contacting materials due to their good mechanical properties, fatigue resistance, cytocompatibility, biosafety, and relatively good hemocompatibility. Further functionalization of the PUs using chemical synthetic methods is especially attractive for expanding their applications. Herein, a series of catechol functionalized PU (CPU-PTMEG) elastomers containing variable molecular weight of polytetramethylene ether glycol (PTMEG) soft segment are reported by stepwise polymerization and further introduction of catechol. Tailoring the molecular weight of PTMEG fragment enables a regulable catechol content, mobility of the chain segment, hydrogen bond and microphase separation of the C-PU-PTMEG elastomers, thus offering tunability of mechanical strength (such as breaking strength from 1.3 MPa to 5.7 MPa), adhesion, self-healing efficiency (from 14.9% to 96.7% within 2 hours), anticoagulant, antioxidation, anti-inflammatory properties and cellular growth behavior. As cardiovascular stent coatings, the C-PU-PTMEGs demonstrate enough flexibility to withstand deformation during the balloon dilation procedure. Of special importance is that the C-PU-PTMEG-coated surfaces show the ability to rapidly scavenge free radicals to maintain normal growth of endothelial cells, inhibit smooth muscle cell proliferation, mediate inflammatory response, and reduce thrombus formation. With the universality of surface adhesion and tunable multifunctionality, these novel C-PU-PTMEG elastomers should find potential usage in artificial heart valves and surface engineering of stents

Improved corrosion resistance and biocompatibility of biomedical magnesium alloy with polypeptide TK14 functionalised hydrophobic coating

Abstract Magnesium (Mg) and its alloys can be used as biomedical materials because of their excellent mechanical properties and biocompatibility. However, the rapid degradation rate of Mg‐based materials limits their application in biodegradable intravascular stents. To overcome this issue, we constructed a hydrophobic coating on magnesium. After pre‐treatments with alkali and a silane coupling agent of pure magnesium, 4,4’‐diphenylmethane‐diisocyanate (MDI) and amino‐terminated polydimethylsiloxane (H2N–PDMS–NH2) were stepwise deposited on the surface, forming an amino‐containing hydrophobic coating (–(M/P)3) to enhance the corrosion resistance. Furthermore, polypeptide TK14 was immobilised on the hydrophobic coating to promote vascular endothelial cell adhesion and proliferation. The electrochemical results revealed that the self‐corrosion current density (icorr) of –(M/P)3 decreased by approximately 4.5 orders of magnitude compared with that of pure Mg. After TK14 immobilisation, the number of endothelial cells adhering to the surface of –(M/P)3–T increased significantly. Although the corrosion resistance of –(M/P)3–T was slightly reduced, the subcutaneous implantation inflammatory response of the surrounding tissues was lower, showing suitable biocompatibility. Therefore, the polypeptide TK14 functionalised hydrophobic coating may be a promising candidate material for the interface of magnesium‐based cardiovascular implants

A microfluidic system simulating physiological fluid environment for studying the degradation behaviors of magnesium-based materials

Magnesium (Mg)-based materials have excellent potential for application in biodegradable vascular stents. Before application, all these materials need to be screened and optimized, especially the screening of corrosion resistance, which is one of the key indicators for stent material screening. Based on the characteristics of the structure of the stent, we focus on the study of the corrosion and degradation behavior of the micron-scale stent struts in the simulated in vivo environment. The struts are simplified into Mg-based wires, and a microfluidic system is established to provide near physiological conditions. A flow-induced shear stress (FISS) of approximately 0.68 Pa close to the wall shear stress of the human coronary artery is applied to the sample surface relying on the microfluidic system. The degradation behaviors of Mg-based wire samples close to the size of struts are studied simultaneously parallel under FISS conditions using this microfluidic system. The immersion test and in vivo experiments demonstrated the feasibility of this microfluidic system for studies of the degradation behavior of Mg-based materials under simulated physiological conditions. In addition, it was also investigated that the effect of degradation products produced under dynamic conditions on vascular cell behavior. The results show that the degradation rate is significantly accelerated under the effect of FISS in the in vitro study, the degradation rate is obviously higher than that in vivo, and AZ31 has the fastest degradation rate compared with pure magnesium and Mg–Zn–Y–Nd alloys. Taken together, this microfluidic system can be used to evaluate and screen the corrosion resistance of Mg-based materials, providing a basis for the design and optimization of Mg-based cardiovascular stent materials