Abstract
Non-fouling surfaces that resist non-specific adsorption of proteins, bacteria, and higher organisms are of particular interest in diverse applications ranging from marine coatings to diagnostic devices and biomedical implants. Poly(ethylene glycol) (PEG) is the most frequently used polymer to impart surfaces with such non-fouling properties. Nevertheless, limitations in PEG stability have stimulated research on alternative polymers that are potentially more stable than PEG. Among them, we previously investigated poly(2-methyl-2-oxazoline) (PMOXA), a peptidomimetic polymer, and found that PMOXA shows excellent anti-fouling properties. Here, we compare the stability of films self-assembled from graft copolymers exposing a dense brush layer of PEG and PMOXA side chains, respectively, in physiological and oxidative media. Before media exposure both film types prevented the adsorption of full serum proteins to below the detection limit of optical waveguide in situ measurements. Before and after media exposure for up to 2 weeks, the total film thickness, chemical composition, and total adsorbed mass of the films were quantified using variable angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and optical waveguide lightmode spectroscopy (OWLS), respectively. We found (i) that PMOXA graft copolymer films were significantly more stable than PEG graft copolymer films and kept their protein-repellent properties under all investigated conditions and (ii) that film degradation was due to side chain degradation rather than due to copolymer desorption.
Highlights
Solution electrospun fibers are collected as thin non-woven meshes [20], which has limited their application because the small pore sizes and compromised interconnectivity associated with the random layering of sub-micron diameter fibers acts as a barrier to rather than promotes cell infiltration and subsequent vascularization [21]
3.1 Design of Porous Tubular Structures. Modifying design parameters such as the fiber diameter, number of fibers and the choice of winding angle allows control over the spatial architecture of a tubular scaffold fabricated from direct writing combined with melt electrospinning
One phenomenon we have previously described is an associated tensile drag force imparted on the melt electrospinning jet as it collects onto surfaces moving at relative speeds greater than the jet speed, causing the collected fiber to experience a delay in response (‘‘lag’’) to changes in direction (Fig. 4a)
Summary
Tubular scaffolds fabricated from electrospun fibers are finding increasing use in tissue engineering (TE) applications, including vascular [1,2,3,4,5,6,7,8,9,10,11] (reviewed in detail by Naito et al.), neural [12,13,14] (reviewed in detail by Bell et al.) and more recently growth factor delivery [15,16,17,18,19]. Solution electrospun fibers are collected as thin non-woven meshes [20], which has limited their application because the small pore sizes and compromised interconnectivity associated with the random layering of sub-micron diameter fibers acts as a barrier to rather than promotes cell infiltration and subsequent vascularization [21]. Differences in pressure-dependent mechanical properties between native arteries and artificial grafts induce hydrodynamic flow disturbances and stress concentrations, thereby causing tissue damage as well as impairing cellular function, illustrating the need to match compliance of a designed artificial graft with a small-diameter artery [7]. The presence of a solution electrospun tubular scaffold promotes mineralized matrix synthesis, prevents
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