*3.2. Morphological Observation*

TEM showed that RSANs (Figure 3) were mostly spherical and uniformly distributed. RSANs presented a complete core-shell structure, which demonstrated that the RBCM successfully wrapped SANs. The particle size measured by TEM was about 50–100 nm, and it was smaller than the results obtained by Zetasizer. The di fference might be due to the elimination of the water film outside the nanoparticles after the samples were dried.

**Figure 3.** The TEM images of RSANs.

### *3.3. In Vitro Release Study*

Analyzed by ICP-AES, the average EE and DL were 14.31% and 4.98%, respectively (Table S1). As shown in Figure 4, the release of 3 groups was fast for 4 h. For the ATO group, the highest burst release of 98.61% was observed within 2 h, and all ATO was released in 4 h. After 4 h, the release of the SANs was slightly slow down with a cumulative release rate of 91% in 12 h, and the drug was completely released at 36 h. The release of RSANs was further slowed down to 67% at 12 h. The drug was then gradually released until the cumulative release rate of 95% was achieved at 84 h. Resultantly, RSANs showed more significant sustained release than SANs. The result revealed that forming a physical barrier around the nanoparticles by RBCM can significantly control the drug release.

**Figure 4.** In vitro release curve of ATO, SANs and RSANs at 37 ◦C for 84 h. Data are shown as ± SD of the mean (*n* = 3).
