Lysososmal dissolution of LM Fe(III) poly oxo-hydroxide.

<p><b>A</b>, Solubility in simulated lysosomal conditions at pH 5.0 with 10 mM citric acid and 0.15 M NaCl. Soluble Fe was measured by ICP-OES following 5 min ultrafiltration (3000 Da MWCO) for the LM Fe(III) poly oxo-hydroxide (black) and for un-modified Fe(III) poly oxo-hydroxide (solid blue). Nanoparticulate Fe was obtained from the Fe in the supernatant following centrifugation excluding the soluble (ultrafilterable) Fe, and is shown for LM Fe(III) poly oxo-hydroxide (red) and for un-modified Fe(III) poly oxo-hydroxide (dotted blue). Values are plotted as mean ± s.d. of 3 independent experiments (each experiment with 3 replicates). <b>B</b>, Effect of inhibition of lysosomal acidification using monensin on Fe utilization by differentiated Caco-2 cells. Data are shown as a percentage of the control (without monensin) at 24 h: i.e. 1 h exposure to 200 µM nanoparticulate LM Fe(III) poly oxo-hydroxide (open circles) or Fe(III) maltol (closed squares) ± 5-30 µM monensin followed by 23 h in non-supplemented MEM. Results are means ± s.d. of 3 independent experiments (each experiment with 3 replicate wells). **, <i>p</i><0.005; ***, <i>p</i><0.001 in relation to the soluble Fe control (Fe(III)maltol). <b>C</b>, Change in TEER in the Caco-2 cell monolayer following 1 h exposure to 10 μM monensin (closed squares), 30 μM monensin (open diamonds) or non-supplemented BSS control (closed inverted triangles) and with 23 h further incubation in fresh MEM (24 h in total). Values are expressed as a percentage of the initial measurement at the start of the exposure time (corresponding to 0 h) and are shown as mean ± s.d. of 2 independent experiments (each experiment with 3 replicate wells). Experimental points are connected with a solid line to aid visualization and not because a linear relationship is assumed between time and TEER measurement. ***, <i>p</i>=0.0003; ****, <i>p</i><0.0001 in relation to the non-supplemented BSS control.