Abstract
In the paper, poly(ethylene glycol) (PEG) was grafted on the surface of poly(ester-urethane) (SPEU) film with high grafting density for biomedical purposes. The PEG-surface-grafted SPEU (SPEU-PEG) was prepared by a three-step chemical treatment under mild-reaction conditions. Firstly, the SPEU film surface was treated with 1,6-hexanediisocyanate to introduce -NCO groups on the surface with high density (5.28 × 10−7 mol/cm2) by allophanate reaction; subsequently, the -NCO groups attached to SPEU surface were coupled with one of -NH2 groups of tris(2-aminoethyl)amine via condensation reaction to immobilize -NH2 on the surface; finally, PEG with different molecular weight was grafted on the SPEU surface through Michael addition between terminal C = C bond of monoallyloxy PEG and -NH2 group on the film surface. The chemical structure and modified surface were characterized by FT-IR, 1H NMR, X-ray photoelectron spectroscopy (XPS), and water contact angle. The SPEU-PEGs displaying much lower water contact angles (23.9–21.8°) than SPEU (80.5°) indicated that the hydrophilic PEG chains improved the surface hydrophilicity significantly. The SPEU-PEG films possessed outstanding mechanical properties with strain at break of 866–884% and ultimate stress of 35.5–36.4 MPa, which were slightly lower than those of parent film, verifying that the chemical treatments had minimum deterioration on the mechanical properties of the substrate. The bovine serum albumin adsorption and platelet adhesion tests revealed that SPEU-PEGs had improved resistance to protein adsorption (3.02–2.78 μg/cm2) and possessed good resistance to platelet adhesion (781–697 per mm2), indicating good surface hemocompatibility. In addition, due to the high grafting density, the molecular weight of surface-grafted PEG had marginal effect on the surface hydrophilicity and hemocompatibility.
Highlights
Segmented polyurethane (SPU) is widely used in biomedical fields, such as cardiovascular devices, artificial organs, and tissue engineering scaffolds, due to its long-term bio-stability, excellent mechanical properties, and relatively superior biocompatibility [1,2,3,4,5,6]
The bovine serum albumin adsorption and platelet adhesion tests revealed that surface of poly(ester-urethane) (SPEU)-poly(ethylene glycol) (PEG) had improved resistance to protein adsorption (3.02–2.78 μg/cm2 ) and possessed good resistance to platelet adhesion (781–697 per mm2 ), indicating good surface hemocompatibility
The reaction temperature was controlled at room temperature for the purpose of minimum deterioration on the SPEU substrate
Summary
Segmented polyurethane (SPU) is widely used in biomedical fields, such as cardiovascular devices, artificial organs, and tissue engineering scaffolds, due to its long-term bio-stability, excellent mechanical properties, and relatively superior biocompatibility [1,2,3,4,5,6]. When SPU is used as long-term blood-contacting materials, the surface of SPU films will result in significant adsorption of proteins, and induce platelet adhesion by activating the coagulation pathway, eventually leading to the formation of microscopic thrombi [7,8]. A preferred strategy is to immobilize natural or synthetic materials onto the hydrophobic surfaces that shield the surface, introducing a high activation barrier to repel proteins [11,12,13]. Among them, grafting poly(ethylene glycol) (PEG) onto the SPU surface has attracted considerable interest because PEG can effectively prevent protein adsorption and platelet adhesion mostly due to its low interfacial free energy with water, unique solution properties, hydrophilicity, high chain mobility, and steric stabilization effect [14]. Much theoretical work is generated to explain the early discovery that grafted PEG chains resist protein adsorption to a high degree [15,16]
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