Figure 4: MPs efficiently deliver chemotherapeutic drug molecules into tumour cells.

(a) H22 cells were treated with 100 μg MTX. After separation by centrifugation, MTX–MPs, the corresponding supernatants or the supernatants from the last MPs washing were co-cultured with H22 cells. After 48 h, the tumour cell killing was observed. Scale bar, 25 μm. (b) MPs were resistant to Triton X-100. MPs from H22 cells were treated with or without 0.5% Triton X-100 for 12 h and then incubated with Hoechst 33342. After 12 h, MPs were isolated for the observation under a fluorescence microscope (left) or counted by a flow cytometer (right). Bars correspond to mean±s.d. Data are representative of three independent experiments. Scale bar, 2 μm. (c,d) H22 cells took up MPs. MPs isolated from CFSE (green)-labelled H22 cells were incubated with PKH 26 (red)-stained H22 cells. After 20 h, cells were observed under two-photon laser scanning fluorescence microscope, (c), or analysed by flow cytometry (d). Data are representative of three reproducible independent experiments. Scale bar, 10 μm. (e) Doxorubicin-packaging MPs were i.p. injected into mice, to which H22 cells were i.p. injected 24 h before. Twenty-four hours after MP injection, peritoneal tumour cells were isolated and stained with FITC–Annexin V for flow cytometric analysis. (f) MPs isolated from MTX-treated or -untreated H22 cells were i.p. injected to mice (n=6). After 5 days injection, peritoneal immune cells were isolated and stained with PE-conjugated Annexin V and FITC-conjugated anti-F4/80, CD19 or CD3 antibody. The cells were analysed by flow cytometry. Bars correspond to mean±s.d. *P<0.05, compared with control. (g) MPs improved the delivery efficiency of chemotherapeutic drug to tumour cells. The details were described in the Result part and Methods. In this figure, 10,000 events were collected for flow cytometric analysis.