Fig. 4. (a) UV-Vis absorption spectra of PMSNs, DOX, and PMSNs@DOX; (b) zeta potentials of the PMSNs and PMSNs@DOX; (c) UV-Vis absorption spectra of FA, PMSNs@DOX, and PMSNs@DOX@FA; (d) in vitro drug release kinetic profiles of PMSNs@DOX in pH 4.0 and pH 6.9 PBS buffer solutions, respectively.