Cyclodextrin-Based Nanogels with Chemistry-Tunable Intracellular Stability and Distribution.

Introduction: Cyclodextrin-based nanogels (CD-nGels) uniquely enable encapsulation of hydrophobic pharmaceuticals within hydrophilic networks through host-guest interactions, thereby improving drug solubility, stability, and therapeutic efficacy. Methods: Here, we report the surfactant-free synthesis of Nile Blue-labeled fluorescent CD-nGels with tunable hydrolytic properties by integrating amide or ester linkages in both β-cyclodextrin (βCD) moieties and crosslinking sites. Three formulations were prepared with progressively increasing hydrolytic sensitivity: NG1 (fully amide-linked), NG2 (ester-functionalized βCD with amide crosslinking), and NG3 (ester linkages in both βCD and crosslinker domains). Results: The resulting CD-nGels were monodisperse with hydrodynamic diameters ranging from 247 to 431 nm. Hydrolysis study in mildly acidic conditions (pH 5.1) and in intracellular-mimicking MCF-7 lysate demonstrated that the structural stability is predominantly dictated by chemical compositions. Coumarin-6 (C6), a hydrophobic fluorescent model drug, was efficiently encapsulated via host-guest interactions to visualize the intracellular redistribution after cellular uptake. The confocal microscopy revealed that the three CD-nGel formulations exhibited progressively enhanced intracellular degradability, leading to distinct intracellular fluorescence distributions: while the fully amide-linked NG1 maintained a compact intracellular fluorescence pattern, the ester-containing NG2 and NG3 exhibited progressively diffuse cytoplasmic signals consistent with reduced structural stability. Discussion: Overall, this modular platform enables chemical tuning of intracellular stability and distribution of CD-nGels, providing a design basis for the future development of CD-based nGels for controlled intracellular drug delivery applications.