Nanodimer cyclodextrin ligands with high affinity to steroids

Molecular-imprinting by cross-linking of ligands of beta-cyclodextrin (CD) complex with steroids has been developed for the synthesis of tailor-made CD dimer. Steroids of androstane (9 alpha-hydroxy-androst-4-en-3,17-dione, androst-4-en-3,17-dione, androsta-1,4-dien-3,17-dione (ADD)) and pregnane (hydrocortisone, 6-methyl-hydrocortisone, 20-hydroxymethylpregna-1,4-diene-3-one (HMPD)) series were used as template molecules. For imprinting procedure, crystalline beta-CD complexes of exact stoichiometry (b-CD: steroid template = 2: 1) were synthesized following by toluene 2,4-diisocyanate (TDI) cross-linking. The attempts to produce CD dimer for steroid without hydrophobic side chain failed, while tailor-made CD dimer has been obtained using HMPD as a template. The dimer was characterized by H-1 NMR and mass-spectrometry. The complex stability constant (K-S) towards HMPD template exceeded 10(7) M-1. The K-S of CD dimer with ADD exceeded the corresponded value of TDI-modified CD monomer by more than an order of magnitude. The dimer was applied for quantitative extraction of ADD from aqueous solution using dialysis membranes impermeable for CD. The value of K-S for ADD estimated from balanced concentrations of dialysis data corresponded to that calculated by nonlinear spectrometric method.