0 and pH 7.4. pDNA release was determined by measuring UV absorption at 260 nm at specific time points. The data showed that 40.5% of the loaded pDNA was released rapidly from PEI-modified TPGS-b-(PCL-ran-PGA) nanoparticles within 48 h at pH 7.4, followed by sustained release until day 8 (Figure 5). This fact may be due to the dependency of the TPGS-b-(PCL-ran-PGA)

degradation on the external conditions. It was reported that at low pH values, cleavage of the ester linkage of the polyester backbone VRT752271 such as PLGA was catalyzed to accelerate the polymer degradation. However, at pH 7.4, the release kinetics of pDNA was similar with that at pH 5.0. PEI, which is a hydrophilic molecule located at the surface of the TPGS-b-(PCL-ran-PGA) YH25448 concentration matrix, may hasten degradation of the nanoparticles by increasing hydration and PX-478 thereby promoting hydrolysis [30]. Figure 5 In vitro release profile of TRAIL- and endostatin-loaded TPGS- b -(PCL- ran -PGA)/PEI nanoparticles at pH 7.4 and 5.0. Cellular uptake of TPGS-b-(PCL-ran-PGA)/PEI nanoparticles To determine cellular uptake of nanoparticles, HeLa cells were incubated with TPGS-b-(PCL-ran-PGA)/PEI nanoparticles. Figure 6 shows the fluorescence imaging of

HeLa cells after incubation with pIRES2-EGFP-loaded and pDsRED-loaded TPGS-b-(PCL-ran-PGA)/PEI nanoparticles. As can be seen in Figure 6, HeLa cells showed strong green (Figure 6B) and red (Figure 6C) fluorescence, indicating that pIRES2-EGFP-loaded and pDsRED-loaded TPGS-b-(PCL-ran-PGA)/PEI nanoparticles could be efficiently internalized into the cells. Figure 6 Fluorescence and confocal laser scanning microscopy images of HeLa cells after incubation. (A to C) The fluorescence microscopy images of HeLa cells after incubation with pIRES2-EGFP-loaded and pDsRED-loaded TPGS-b-(PCL-ran-PGA)/PEI nanoparticles. (D to F) Confocal laser scanning microscopy images of HeLa cells after incubation with pIRES2-EGFP-loaded TPGS-b-(PCL-ran-PGA)/PEI nanoparticles at 37.0°C. The cells were until stained by DAPI (blue), and the pIRES2-EGFP-loaded

TPGS-b-(PCL-ran-PGA)/PEI nanoparticles are in green. The cellular uptake was visualized by overlaying images obtained using DAPI filter and FITC filter: (D) from DAPI channel, (E) from FITC channel, (F) from combined DAPI channel and FITC channel. CLSM images showed that the fluorescence of the pIRES2-EGFP-loaded TPGS-b-(PCL-ran-PGA)/PEI nanoparticles (green) was located around the entire cell including the nucleus area (blue, stained by DAPI) (Figure 6D,E,F), which further confirmed that the nanoparticles could efficiently deliver plasmids into HeLa cells. Cell viability of gene nanoparticles Cytotoxicity of all gene nanoparticles (groups FNP, GNP, and HNP), blank TPGS-b-(PCL-ran-PGA) nanoparticles (group DNP), and blank TPGS-b-(PCL-ran-PGA)/PEI nanoparticles (group ENP) was compared to that of PBS by the MTT assay.