Nanoparticles lower lysosomal pH.

<p>A. While NP1 did not alter baseline levels of lysosomal pH (pHL), NP2 and NP3 acidified the lysosomes significantly. Lysosomal pH was measured 1 hr. after addition of nanoparticles. Here and throughout the figure, nanoparticles were given at 1 mg/ml. n = 8. * <i>p</i><0.05 vs. control, ANOVA on ranks, Dunn’s posthoc test. B. Chloroquine (CHQ; 10 µM) raised the lysosomal pH. NP2 and NP3 significantly lowered lysosomal pH, while NP1 had little effect. Chloroquine and nanoparticles were applied concurrently 1 hr. before pH measurements. *<i>p</i><0.001 vs. control, **<i>p</i><0.001 vs. CHQ, ANOVA with Tukey post hoc test. n = 8. C. NP2 and NP3 induced sustained acidification of lysosomal pH in cells treated with 10 µM chloroquine. The acidification decreased with time but was still detected. Chloroquine and nanoparticles were added on day 1 and remained in the bath without a solution change. The effect of the nanoparticles was defined as their relative effectiveness at bringing lysosomal pH towards baseline; the absolute numbers did vary somewhat but this normalization accounted for such differences. % Reacidification = 100*((CHQ-(CHQ+NP))/(CHQ-Control)). Data from 31 plates.