Figure 4 AFM image of beta-CD (a), aldehyde group functionalized beta-CD (b), crosslinked beta-CD nanocage (c) and crosslinked beta-CD nanocage loaded with DOX (d).
The hydrated state of beta-CD reflects its true state in the physiological environment and its subsequent effects on endocytosis pathways. Therefore, DLS was used to evaluate the hydrated size of the beta-CD nanocage. Simultaneously, the change in hydrated size could also reflect the self-assembly process. As shown in Figure 5, the hydrated size of individual beta-CD and aldehyde group-functionalized beta-CD was approximately 20 nm, and the size distribution was relatively stable. Upon assembly with cystamine, the size gradually increased to over 100 nm for the beta-CD nanocage. The size distribution of the beta-CD nanocage exhibited a wider range compared to free beta-CD. One reason for this outcome might be the crosslinking of beta-CD, resulting in a larger spatial structure. Additionally, the crosslinking process may not guarantee the same quantity of beta-CD units every time, leading to imbalanced crosslinked units. After loading with DOX, the beta-CD nanocage still exhibited an appropriate hydrated size of around 200 nm, indicating that the structure of beta-CD remained stable even when loaded with a hydrophobic drug. The size distribution of the DOX-loaded beta-CD nanocage was similar to that of the unloaded beta-CD nanocage. These DLS results suggest that the trends in hydrated size change of beta-CD in different states were similar to the trends in dehydrated size change provided by AFM.