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    Temperature-Activated PEG Surface Segregation Controls the Protein Repellency of Polymers

    Year: 2019

    Journal: Langmuir, Volume 35, 1-Jul, page 9769–9776

    Authors: Murthy, N. Sanjeeva; Wang, Wenjie; Sommerfeld, Sven D.; Vaknin, David; Kohn, Joachim

    Organizations: RESBIO; National Resource for Polymeric Biomaterials - National Institutes of Health (NIH)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [EB001046]; New Jersey Center for Biomaterials; U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and EngineeringUnited States Department of Energy (DOE); U.S. Department of EnergyUnited States Department of Energy (DOE) [DE-AC02-07CH11358]; U.S. DOEUnited States Department of Energy (DOE) [DE-AC02-06CH11357]

    Poly(ethylene glycol) (PEG) is widely used to modulate the hydration states of biomaterials and is often applied to produce nonfouling surfaces. Here, we present Xray scattering data, which show that it is the surface segregation of PEG, not just its presence in the bulk, that makes this happen by influencing the hydrophilicity of PEG-containing substrates. We demonstrate a temperature-dependent trigger that transforms a PEG-containing substrate from a protein-adsorbing to a protein-repelling state. On films of poly(desaminotyrosyl-tyrosine-co-PEG carbonate) with high (20 wt %) PEG content, in which very little protein adsorption is expected, quartz crystal microbalance data showed significant adsorption of fibrinogen and bovine serum albumin at 8 degrees C. The surface became protein-repellent at 37.5 degrees C. When the same polymer was iodinated, the polymer was protein-adsorbent, even when 37 wt % PEG was incorporated into the polymer backbone. This demonstrates that high PEG content by itself is not sufficient to repel proteins. By inhibiting phase separation either with iodine or by lowering the temperature, we show that PEG must phase-separate and bloom to the surface to create an antifouling surface. These results suggest an opportunity to design materials with high PEG content that can be switched from a protein-attractant to a protein-repellent state by inducing phase separation through brief exposure to temperatures above their glass transition temperature.
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