Paper BI+AS-TuA3
Using Binary Solvent Mixtures Produces High Graft Density Poly (Ethylene Glycol) Layers
Tuesday, October 30, 2012, 2:40 pm, Room 23
| Session: |
Characterization of Biointerfaces |
| Presenter: |
P. Kingshott, Swinburne University of Technology, Australia |
| Authors: |
A.R. Arcot, Aalto University, Finland
S. Zhang, Aarhus University, Denmark
R.L. Meyer, Aarhus University, Denmark
R. Ogaki, Aarhus University, Denmark
P. Kingshott, Swinburne University of Technology, Australia
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| Correspondent: |
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The success of PEG based non fouling surfaces depends on several factors such as graft density [1] and nature of head group-substrate interaction. [2] The ‘grafting-to’ technique though simple, often results in low pinning density when compared to ‘grafting-from’ technique. [3] This limitation of ‘grafting-to’ technique can be overcome by grafting under reduced solubility conditions. [4] We demonstrate a simple and versatile way to coat surfaces with PEG at high graft density using binary solvent mixtures, where a poor and a good PEG solvent are mixed with the PEG. The addition of poor solvent decreases the hydrodynamic radius of PEG molecules and hence results in thicker films due to diminished steric repulsion (Supplementary Fig 1a and 1b). The ‘good’ and ‘poor’ solvent pair was chosen based on solubility parameter distance calculated from Hanson solubility parameters. [5]
The PEG thiol films on gold formed from acetone-ethanol mixtures were analyzed using x-ray photoelectron spectroscopy (XPS), ellipsometry and atomic force microscopy. The PEG film gets thicker with more ethanol, which is a poorer solvent for PEG (Supplementary table 1). The high resolution sulfur 2p spectra confirmed the absence of precipitate particles. Grafting under high ionic strength conditions used by Kingshott et al. was used as reference for comparison. [4] The PEG thiol films were exposed to fetal bovine serum (FBS) and it was observed that thicker films could resist protein adsorption better than thin films that were formed from high solubility conditions. This method of using binary solvent mixtures can be extended to any polymer-substrate system by choosing appropriate ‘good-poor’ solvent pair. To demonstrate this point we also studied 5 kDa PEG silane films grafted using acetone-diethyl ether solvent mixture.
References:
1. L. D. Unsworth, H. Sheardown and J. L. Brash, Biomaterials (30), 5927-5933 (2005).
2. P. Kingshott, J. Wei, D. Bagge-Ravn, N. Gadegaard and L. Gram, Langmuir (17), 6912-6921 (2003).
3. N. Luo, J. B. Hutchison, K. S. Anseth and C. N. Bowman, Macromolecules (7), 2487-2493 (2002).
4. P. Kingshott, H. Thissen and H. J. Griesser, Biomaterials (9), 2043-2056 (2002).
5. B. A. Miller-Chou and J. L. Koenig, Progress in Polymer Science (8), 1223-1270 (2003).