Zeta potential was evaluated by electrophoretic light scattering (ELS) with PARP inhibitor Zetaplus (Brookhaven Instruments
Corporation, Holtsville, NY, USA). Particle size was evaluated by intensity distribution, and particle size distribution was represented by PDI. The morphology of the PTX-MPEG-PLA NPs was observed on a JEM 2100 transmission electron microscope (JEOL, Tokyo, Japan) operating at 200 kV. One drop of the suspension was diluted with water, subsequently placed on a carbon-coated copper grid, and lastly, dried in the air before observation. PTX-PLA NPs were used for comparison. In vitro drug release behavior Evaluation of in vitro release behavior was conducted to examine how rapidly PTX
was released from the PTX-MPEG NPs. The output obtained by the dynamic dialysis method provided a correlation with in vivo drug release. The lyophilized NPs (equivalent to 5 mg of PTX) were dispersed in 2 mL of PBS (1/15 M, pH 7.4), and the dispersion was added into a dialysis bag. The release selleck inhibitor experiment was initiated by placing the end-sealed dialysis bag in 48 mL of PBS (1/15 M, pH 7.4). The system was kept on a magnetic stirrer under controlled conditions (100 rpm, 37°C). At predetermined time intervals, 2 mL of the release medium was completely withdrawn and subsequently replaced with the same volume of fresh PBS solution. The concentration of PTX in the samples was measured by HPLC. The lyophilized PTX-PLA NPs (equivalent to 5 mg of PTX) were used for comparison. In vitro cellular uptake In vitro cellular uptake was employed to investigate the distribution of PTX-loaded MPEG-PLA NPs in the cell. Following a 24-h culture of HeLa cells in a six-well plate, 100 μL of rhodamine B-labeled PTX-MPEG-PLA NPs (1 mg/mL) was added to the medium and incubated further for 48 h. The HeLa cells were washed five times with PBS and
continuously stained with 50 μL of Hochest 33258 (0.005 mg/mL). The Ribonucleotide reductase cells were observed with CLSM (Leica TCS SP5, Leica Microsystems, Mannheim, Germany). Cells treated with rhodamine B-labeled PTX-PLA NPs were used for comparison. In vitro cell viability assays A549 cells were cultured in standard cell media recommended by the American Type Culture Collection. Cells seeded in 96-well plates were incubated with a series of increasing concentrations of PTX-MPEG-PLA NPs for 48 h. Subsequently, relative cell viability was assessed by the standard MTT assay. Cells treated with free PTX and cells treated with the PTX-PLA NPs were compared. Results and discussion Preparation of the PTX-MPEG-PLA NPs Acetone is water-miscible and a good solvent for MPEG-PLA. PTX and MPEG-PLA were first codissolved in this organic phase and was then extensively dialyzed against the aqueous phase.