Figure 3 FTIR analysis 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 size of the beta-CD nanocage plays a crucial role in determining the
endocytosis pathways for internalizing these nanoparticles into tumor
cells. Therefore, the size and evolution process of the beta-CD nanocage
were investigated using AFM. First, the size of pristine beta-CD was
examined. As shown in Figure 4, the size of individual beta-CD molecules
appeared small, with a diameter of approximately 10 nm. However, the
larger size observed in the AFM image might be attributed to
agglomeration of the molecules. Following the oxidation process, the
size of beta-CD showed slight variation, but the agglomeration
phenomenon persisted. After crosslinking with cystamine, the resulting
nanocage-like structure of beta-CD exhibited a larger size compared to
the individual beta-CD, with sizes ranging between 100 nm and 200 nm. It
is noted that there was an oversizing of the beta-CD nanocage due to the
induced agglomeration between beta-CD molecules. More importantly, after
drug loading, DOX-loaded beta-CD exhibited an appropriate size (100-200
nm) for endocytosis. The size of DOX-loaded beta-CD was similar to that
of unloaded beta-CD nanocage. This suggests that the physical size of
the prepared nanocage could essentially meet the requirements for
endocytosis2829[,
].