Physics (Internal)

Antibiofouling ─ how a polymer brush repels proteins and our novel integrated design

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: Grafting a layer of chains on a surface to form a polymer brush has been considered as an effective approach to make it antibiofouling (i.e., less adsorption of proteins). It has been proposed or generally believed that it is the hydration of such a brush with a layer of immobile water molecules that avoids the protein adsorption. If this is the only reason, one should ask a number of questions, including 1) why not using a thin layer of easily prepared hydrogel instead of those grafted chains; and 2) why poly(ethylene glycol) (PEG) is more preferred than other water-soluble polymers. In this lecture, we will look the captioned question from another angle of the entropic elasticity instead of the protein surface interaction (the enthalpy change). Considering that each grafted chain is confined inside a cylindrical “pore” made of its neighboring chains, we can find its optimal length by minimizing its free energy that contains the contributions from the exclude volume interaction and the chain elasticity (both of them have an entropic nature) [1, 2]. After estimating the minimum free energy at the optimal length and comparing it with the kinetic energy (~kBT) of individual protein chains floating in solutions, we are able to predict how both the chain length and the grafting density affect the repelling of proteins and explain why PEG performs better than others. Our predictions are surprisingly and quantitatively comparable with those literature results [3, 4]. In this lecture, we will also illustrate how to develop novel antibiofouling coatings for real marine applications by using an integrated novel design that combines different existing strategies; namely, the self-polishing, the self-structured and the self-generated soft and dynamic surface [5, 6].

References:

1. Fan Jin, Chi Wu, Physical Review Letters, 96, 237801 (2006).
2. Lianwei Li, Chen He, Weidong He, Chi Wu, Macromolecules, 45, 7583 (2012).
3. Tengjiao Hu, Chi Wu, Physical Review Letters, 83, 4105 (1999).
4. Guangming Liu, Yijian Chen, Guangzhao Zhangb, Shihe Yang, Physical Chemistry Chemical Physics, 9, 6073 (2007).
5. Laiyong Xie, Fei Hong, Chuanxin He, Chunfeng Ma, Jianhong Liu, Guangzhao Zhang, Chi Wu, Polymer, 52, 3738-3744 (2011).
6. Fei Hong, Laiyong Xie, Chuanxin He, Jianhong Liu, Guangzhao Zhang, Chi Wu, Journal of Materials Chemistry B, 1, 2048-2055 (2013).