Attachment of cyclodextrin acids to PEGA resin and study of binding with fluorescence microscopy

Three different cyclodextrin acids, 6^A,6^D-di-O-(prop-2-carboxy-1,3-dienyl)-α-cyclodextrin (1), 6-deoxy-β-cyclodextrin-6-carboxylic acid (2), 6-deoxy-β-cyclodextrin-6-ethylenecarboxylic acid (3), were prepared and attached to amino PEGA resin as amides using coupling conditions with COMU and NEM. Host-guest binding to the resins was studied by fluorescence microscopy using 8-anilinoaphtalene-1-sulfonic acid (ANS) as guest, and was found to follow the equation I_F = I_Fmax*[ANS]/([ANS] + K_d) where F, F_max and K_d are the fluorescence, maximum fluorescence and K_d the dissociation constant for the ANS-cyclodextrin complex, respectively. K_d was 4.4, 2.4 and 4.9 × 10^-4 M for the three resins. Competitive inhibition of ANS binding was performed with 1-adamantanylamine and octyl β-d-glucoside with the latter being selective for the α-cyclodextrin as expected.