Host-Guest Complexes of Cyclodextrins and Nanodiamonds as a Strong Non-Covalent Binding Motif for Self-Assembled Nanomaterials

We report the inclusion of carboxy- and amine-substituted molecular nanodiamonds (NDs) adamantane, diamantane, and triamantane by beta-cyclodextrin and gamma-cyclodextrin (beta-CD and gamma-CD), which have particularly well-suited hydrophobicity and symmetry for an optimal fit of the host and guest molecules. We studied the host-guest interactions in detail and generally observed 1:1 association of the NDs with the larger gamma-CD cavity, but observed 1:2 association for the largest ND in the series (triamantane) with beta-CD. We found higher binding affinities for carboxy-substituted NDs than for amine-substituted NDs. Additionally, cyclodextrin vesicles (CDVs) were decorated with D-mannose by using adamantane, diamantane, and triamantane as non-covalent anchors, and the resulting vesicles were compared with the lectin concanavalinA in agglutination experiments. Agglutination was directly correlated to the host-guest association: adamantane showed lower agglutination than di- or triamantane with beta-CDV and almost no agglutination with gamma-CDV, whereas high agglutination was observed for di- and triamantane with gamma-CDV.