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Achieving Ultralow Fouling under Ambient Conditions via SI-ARGET ATRP of Carboxybetaine Daewha Hong, Hsiang-Chieh Hung, Kan Wu, Xiaojie Lin, Fang Sun, Peng Zhang, Sijun Liu, Keith E. Cook, and Shaoyi Jiang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b01530 • Publication Date (Web): 02 Mar 2017 Downloaded from http://pubs.acs.org on March 7, 2017
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ACS Applied Materials & Interfaces
Achieving Ultralow Fouling under Ambient Conditions via SI-ARGET ATRP of Carboxybetaine Daewha Hong,† Hsiang-Chieh Hung,† Kan Wu,† Xiaojie Lin,† Fang Sun,† Peng Zhang,† Sijun Liu,‡ Keith E. Cook§ and Shaoyi Jiang*,†,‡
†Department of Chemical Engineering, University of Washington, Seattle, WA 98195, USA. ‡Department of Bioengineering, University of Washington, Seattle, WA 98195, USA. §Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15219, USA. KEYWORDS Zwitterionic materials, carboxybetaine, ultralow fouling, activator regenerated by electron transfer (ARGET), atomic transfer radical polymerization (ATRP)
ABSTRACT
We achieved ultralow fouling on target surfaces by controlled polymerization of carboxybetaine under ambient conditions. The polymerization process for grafting polymer films onto the
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surfaces was carried out in air and did not require any deoxygenation step or specialized equipment. This method allows one to conveniently introduce nonfouling polymer network onto large substrates.
The nonspecific binding of proteins is a common problem encountered in many applications, including drug delivery systems, biosensors, and implanted biomedical devices.1 For these applications, protein adsorption is the first event occurring on surfaces when these systems are in contact with biological media. Even a small amount of protein adsorption onto surfaces hinders their performances.2 For example, nonspecific protein adsorption from complex media onto a sensing platform significantly reduces detection sensitivity and specificity.3 In addition, even very low amounts of adsorbed fibrinogen (5- 10 ng/cm2) can induce full-scale blood platelet adhesion, indicating the necessity to minimize protein fouling for implanted devices.4 Therefore, surface chemistry that can achieve ultralow fouling (< 5 ng/cm2) against complex media is highly desirable. Nonfouling materials, such as polyethylene glycol (PEG), and zwitterionic materials, such as phosphorylcholine, sulfobetaine (SB), and carboxybetaine (CB), have been introduced to surfaces of interest via “graft-to” or “graft-from” approaches.5 The “graft-to” approach can be described as direct immobilization of nonfouling materials via surface anchoring groups, such as hydrophobic chains,6 catechol,7 silane8 or thiol9, depending on target surfaces. Although their coating conditions are simple and capable of coating a variety of surfaces when combined with mussel-inspired chemistry,10 it is generally difficult to achieve polymer films of high surface packing densities and thus ultralow fouling surfaces. In contrast, the “graft-from” approach,
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ACS Applied Materials & Interfaces
represented by surface-initiated atomic transfer radical polymerization (SI-ATRP) can readily achieve dense polymer brushes with well-controlled film thicknesses and thus ultralow fouling surfaces.11-13 However, the polymerization conditions for SI-ATRP require a large amount of copper catalyst,14 which is not cost-effective and has potential toxicity concerns for biomedical applications.15 The polymerization process also involves a deoxygenation step in a sealed reactor under oxygen-free conditions to avoid uncontrolled radical termination.16 Thus, the conventional SI-ATRP method makes it harder for real-world applications, particularly for large sample sizes. To date, ultralow fouling surfaces have mainly been demonstrated on fixed surfaces, such as gold, silicon, or glass, of small sample sizes under air-free conditions within a reactor, restricting their practical use in terms of cost and applicability. Recently, air-tolerant, activator regenerated by electron transfer (ARGET) ATRP was developed to overcome these limitations. ARGET ATRP uses a small amount of a Cu(II) species (typically a concentration of parts per million) and an excess reducing agent, such as tin(II) 2ethylhexanoate, phenols, glucose, hydrazine, or ascorbic acid.17 The essential feature of ARGET ATRP is to reduce the usage of Cu-related agents, which repeatedly generates the active Cu(I) species from the inactive Cu(II) species in air. Several monomers, such as butyl acrylate, poly(2hydroxyethyl methacrylate) (PHEMA), poly(N-isopropylacrylamide) (PNIPAAm), and poly(SB) were applied to various surfaces via ARGET ATRP.17-21 However, to the best of our knowledge, no study results have reported to achieve ultralow fouling through the “graft-from” approach in air, which would offer a practical tool for combating unwanted fouling. In this study, we report the surface-initiated ARGET ATRP (SI-ARGET ATRP) of CB, achieving ultralow fouling. Among various nonfouling materials, CB was selected since its dense
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polymer brushes on surfaces were demonstrated to achieve ultralow fouling (
