Figure 2.

Characterization of in vitro RTL release. (A) Demonstration of the pH dependent release trigger as measured by carboxyfluorescein release from RTLs upon acidification with 70 µL of 0.1 M HCl to a final pH of 5.7–5.9. (B) Carboxyfluorescein release from RTLs formulated with varying concentrations of chloral hydrate (CH; 50 mM or 500 mM) and phosphate buffer (1 mM or 10 mM) over 3 h of incubation alone or after 20 Gy irradiaton. Data representative of a single experiment. (C) Cell viability after exposure to supernatant after incubation of SN-38 loaded RTLs at 37 °C in neutral or acidic pH. Liposomes were incubated in different pH buffers and then supernatant added to the LLC tumor cells. (D) Clonogenic survival after incubating cells with SN-38 loaded liposomes or SN-38 alone for 4 h before exposure to 2.5 or 5 Gy of radiation. The drug/liposomes were rinsed off after radiation and replaced with fresh culture medium to allow for surviving cells to form colonies. Average of 3 independent experiments with the bars showing the SD of the mean. Two-way ANOVA with repeated measures for comparison of drug treatments plus radiation vs. radiation alone (**** p < 0.0001).