Nonfouling Tunable βCD Dextran Polymer Films for Protein Applications

Polymeric beta-cyclodextrin (beta CD) films tunable with respect to thickness and beta CD content were prepared in order to develop a suitable platform, allowing for inclusion of nonpolar guest molecules in the beta CD cavity, while suppressing nonspecific protein adsorption. The beta CD films were synthesized from linear beta CD dextran polymers, and grafted onto silicon oxide surfaces by click chemistry. Topographic and morphological characteristics are controllable by reaction conditions and polymer type, with average film heights from 2.5 to 12.5 nm. Reversible introduction of electrostatic charges in the beta CD dextran by complex formation with 1-adamantanecarboxylic acid prior to surface grafting resulted in a thinner and denser film, presumably by decompaction of the polymers. Total internal reflection fluorescence spectroscopy (TIRF) was employed to evaluate the accessibility of beta CD cavities to the fluorescent probe 2-anilinonaphthalene-6-sulfonic acid. Only a minor fraction of the beta CD cavities was accessible in the thicker and less dense films; however, accessibility was largely improved with increased ionic strength using NaCl up to 1 M. Antifouling properties of the beta CD dextran polymer films were assessed by TIRF real-time monitoring, using bovine serum albumin as a model protein, and showed a 5- to 10-fold reduction in nonspecific adsorption as compared to a bare quartz surface with the degree of reduction reflecting film thickness and interfacial polymer density.