Figure 2.

Chemical characterization, particle size, and pH-responsive properties of blank and DOX-loaded mPEG-S-PBLG micelles. ¹H NMR spectra of mPEG-NH₂ (A) and mPEG-S-PBLG polymer (B); (C) FT-IR spectra of mPEG-S-PBLG copolymer; (D) CMC measured by plot of the I₃₇₃/I₃₈₃ ratio from pyrene excitation spectra versus the concentration of polymer on a log scale. Representative TEM image of blank micelles (E) and DOX-loaded micelles (F); (G) particle size of blank and DOX/DiD-loaded micelles at pH 7.4 measured by DLS. (H) Particle size of blank micelles measured by DLS after 48-h incubation in PBS with different pH value; (I) in vitro drug release profile from DOX-loaded micelles at different pH value; (J) flow cytometric analysis of U-87 MG cells treated with DOX or DOX-loaded micelles at pH 7.4 and 6.5 for 6 h. Data represent mean ± SD (n = 3). *p < .05 analyzed by Student’s t-test. (K) Representative confocal image of U-87 MG cells after 6-h incubation with free DOX (5 μM) and DOX-loaded micelles (5 μM equivalent DOX) at pH 7.4 or 6.5 at 37 °C. Scale bar: 10 μm.