Figure 6 The release curves of DOX-loaded beta-CD nanocage in
acidic environment (pH 4.5 PBS) (a), reduction environment (5 mM GSH)
(b) and normal physiological environment (pH 7.4 PBS) (c).
3.3 The cytocompatibility of drug-free beta-CD nanocage and cell-killing
effect of DOX-loaded beta-CD nanocage
After confirming the structure, characterizing the size, and testing the
drug release performance, the cytocompatibility of drug-free beta-CD
nanocage and the cell-killing effect of DOX-loaded beta-CD nanocage were
further evaluated in vitro using a CCK-8 method. As shown in Figure 7,
drug-free samples demonstrated good biocompatibility with over 80% cell
viability at a concentration of 800 ng/ml. This result suggests that the
composition of the beta-CD nanocage is almost non-toxic. Efficient
delivery of DOX to tumor cells and killing tumor cells are crucial for
using this proposed beta-CD nanocage. Therefore, SKOV 3 cells were
incubated in acidic, GSH, and normal environments to verify the
cell-killing effect of DOX-loaded beta-CD nanocage. In the acidic
culture environment, DOX-loaded beta-CD nanocage exhibited an
outstanding cell-killing effect with an IC50 of 600 ng/ml DOX-loaded
beta-CD nanocage, equivalent to a DOX concentration of 225 ng/mL. In the
GSH culture environment, DOX-loaded beta-CD nanocage also showed a
superior cell-killing effect (IC50 of 700 ng/ml DOX-loaded beta-CD
nanocage) but lower than in the acidic culture environment. In the
normal culture environment, DOX-loaded beta-CD nanocage demonstrated a
lower cell-killing effect. The proposed beta-CD nanocage with
acid/reduction-responsive properties stands out from the normal
physiological environment. When free DOX was directly treated with Skov
3 cells, the cell-killing rate was the highest, as shown in Figure 7(f),
with the tumor cells exhibiting the lowest cell viability. These cell
killing tests suggest that the beta-CD nanocage can self-regulate drug
release, especially in the tumor microenvironment, effectively avoiding
nonspecific release. Additionally, the beta-CD nanocage improved the
drug release behavior in the tumor microenvironment to minimize toxicity
to normal cells and maximize the anti-tumor effect.