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. At the top left, an ester bonded NG is shown, followed by an arrow labeled ’Cell lysate’ pointing to smaller particles representing degradation. To the right, a pathway leads to a cell where NGs are internalized. Below, three structures are depicted: NG1 at C6 amide, NG2 at C6 amide/ester and NG3 at C6 ester. Each structure is enclosed in a circle with different linkages and components. NG1 at C6 amide shows blue amide-linkages and red modified beta-cyclodextrin. NG2 at C6 amide/ester includes both blue amide-linkages and orange ester-linkages. NG3 at C6 ester primarily shows orange ester-linkages. An arrow labeled ’Intracellular degradation’ points from these structures to the right, indicating further breakdown. The diagram includes a legend on the right, identifying symbols: a blue circle for amide-linkage, an orange circle for ester-linkage, a green structure for Coumarin 6 and a red structure for modified beta-cyclodextrin.A diagram showing ester bonded NG degradation and intracellular degradation of NG1, NG2 and NG3. Keywords: cyclodextrin-based nanogels, hydrolytic stability, host–guest interactions, intracellular distribution
Zhang et al. (Wed,) studied this question.