Surface Characterization and Protein Interactions of Segmented Polyisobutylene-Based Thermoplastic Polyurethanes

Abstract

The surface properties and biocompatibility of a class of thermoplastic polyurethanes (TPUs) with applications in blood-contacting medical devices have been studied. Thin films of commercial TPUs and novel polyisobutylene (PIB)-poly(tetramethylene oxide) (PTMO) TPUs were characterized by contact angle measurements, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM) imaging. PIB-PTMO TPU surfaces have significantly higher C/N ratios and lower amounts of oxygen than the theoretical bulk composition, which is attributed to surface enrichment of PIB. Greater differences in the C/N ratios were observed with the softer compositions due to their higher relative amounts of PIB. The contact angles were higher on PIB-PTMO TPUs than on commercial polyether TPUs, indicating lower surface energy. AFM imaging showed phase separation and increasing domain sizes with increasing hard segment content. The biocompatibility was investigated by quantifying the adsorption of fouling and passivating proteins, fibrinogen (Fg) and human serum albumin (HSA) respectively, onto thin TPU films spin coated onto the electrode of a quartz crystal microbalance with dissipation monitoring (QCM-D). Competitive adsorption experiments were performed with a mixture of Fg and albumin in physiological ratio followed by binding of GPIIb-IIIa, the platelet receptor ligand that selectively binds to Fg. The QCM-D results indicate similar adsorbed amounts of both Fg and HSA on PIB-PTMO TPUs and commercial TPUs. The strength of the protein interactions with the various TPU surfaces measured with AFM (colloidal probe) was similar among the various TPUs. These results suggest excellent biocompatibility of these novel PIB-PTMO TPUs, similar to that of polyether TPUs.

Improved thromboresistance and analytical performance of intravascular amperometric glucose sensors using optimized nitric oxide release coatings

“…E2As Elast-Eon, a polymer composed of a mixed soft segment of poly(dimethylsiloxane) and poly(hexamethylene oxide) with a methylene diphenyl isocyanate (MDI) hard segment, was used as the outermost coatings in the fabrication of the glucose sensors because it has been reported to exhibit excellent intrinsic biocompatibility and biostability, with low levels of blood protein adhesion [13,14]. Since inherent hemocompatibility of the top coat should enhance the overall thromboresistant properties from the NO release devices, E2As was selected as a replacement for PurSil Thermoplastic Silicone Polyether used in our previous in vivo glucose sensor designs [5].…”

Characterization of an S-nitroso-N-acetylpenicillamine–based nitric oxide releasing polymer from a translational perspective

“…[36, 47] Therefore, altering the surface chemistry of E2As can have large implication on the effectiveness of the material to resist clot formation. Contact angle was measured for pure E2As (111.7 °± 3.3) and 10 wt% SNAP-E2As films (110.7° ± 0.4) ( p = 0.20).…”

“…[34] Among different polymers studied, Elast-eon E2As polymer (a copolymer of mixed soft segments of polydimethylsiloxane and poly(hexamethylene oxide)), possesses excellent intrinsic biocompatibility properties, exhibiting low levels of blood protein adhesion. [35, 36] In a previous study, diazeniumdiolates (NONOate) added to the E2As coating was able to retain 97 ± 10% of platelet counts in vivo in a 4 hour extracorporeal circuit (ECC) in a rabbit model. [10] These promising in vivo results have prompted the study of SNAP as the NO donor in E2As, where E2As-SNAP ECC loops preserved 100 ± 7% of the platelet count in a 4 hour ECC study in rabbits, while showing great stability of the NO donor after 2 months of storage.…”

Cell and Protein Fouling Properties of Polymeric Mixtures Containing Supramolecular Poly(ethylene glycol) Additives

“…1,14 QCM-D offers label-free frequency and real-time monitoring of the hydrated mass adsorption using the change in resonance frequency and dissipation energy of a piezoelectric quartz crystal with a resolution of 1 ng/cm 2 . 15 Recently, protein adsorption has been investigated on spin-coated layers of different thermoplastic polyurethanes 16 and on varying antifouling coatings containing chondroitin sulfate, PEG, carboxymethylated dextran, or zwitterions. 17−20 …”