Figure 8 The fluorescence imaging analysis for treating SKOV3
cells with coumarin 6-loaded beta-CD nanocage in acidic environment for
3 h and 6 h (a), reduction environment for 3 h and 6 h (b) and normal
physiological environment for 3 h and 6 h (c) respectively.
3.5 Flow cytometry analysis of coumarin 6-loaded beta-CD nanocage
The beta-CD nanocage, containing dual-dynamic covalent bonds based on
imine and disulfide, played a critical role in controlling drug release.
Maintaining the superior performance of beta-CD with specific release
properties remains a driving force for further exploration. Therefore,
further evidence from flow cytometry analysis was employed. Similar to
cell fluorescence imaging, tumor cells were treated with upregulated
acidity, upregulated GSH, or left untreated before flow cytometry
analysis. As shown in Figure 9, the relative fluorescence intensity
increased from untreated tumor cells to GSH-treated tumor cells and
further to acid-treated tumor cells at 3 h. Over time, the fluorescence
intensity of each group continued to increase, with the variation
becoming more significant. The maximum fluorescence enhancement in
acid-treated tumor cells was more than 2-fold compared to untreated
tumor cells. This comparative analysis of fluorescence intensity
confirmed that the imine and disulfide bonds in the beta-CD nanocage
played a key role in drug release. Furthermore, the acidic and reductive
tumor microenvironment acted as a driver for a controlled drug release
pathway.