Host–Guest Chemistry of Dendrimer–Cyclodextrin Conjugates: Selective Encapsulations of Guests within Dendrimer or Cyclodextrin Cavities Revealed by NOE NMR Techniques

In this study, G5 PAMAM dendrimer and α-, β-, γ-cyclodextrin (CD) conjugates were synthesized. Host–guest behaviors of the conjugates toward five guest molecules including sodium methotrexate (MTX), amantadine hydrochloride (ADH), sulfamethoxazole (SMZ), sodium deoxycholate (SDC), and sodium dodecyl sulfate (SDS) were analyzed by NOE NMR techniques. Among the five guest molecules, ADH only binds with β-CD in G5−β-CD, SDC shows higher priority to localize within the cavity of γ-CD in G5−γ-CD, while MTX exhibits selective encapsulation within the cavities of G5 dendrimer in G5−α-CD. SDS has high binding affinity with α-CD in G5−α-CD but forms a precipitate in the complex solution. SMZ shows simultaneous encapsulation within CDs (α-, β-, and γ-CD) or G5 in the presence of the three conjugates. The host behavior of G5–CD conjugates depends on CD cavity size, guest size, and hydrophobicity. The results obtained in this study are helpful in the optimization of dendrimer–CD conjugate-based drug delivery systems