1 mL of the NR-labelled microcapsule suspension was placed on a microscopy slide, and the capsules were dried at 60 °C, 100 mbar for 30 min in the vacuum oven. The dehydrated NR-labelled capsules were then rinsed from the microscopy slide into 1 mL MilliQ water, left to rehydrate (see above), then 20 µL were centrifuged again and resuspended in 1 mL of a 2 mM fluorescein solution in MilliQ water and incubated for 30 min at room temperature. The measurement proceeded in the same way as the non-dried capsules. The aliquot that was not incubated with fluorescein was dried and rehydrated again, up to 3 cycles.