Fig. 3

Morphology, dimensions, and release kinetics of lanolin/cetyl alcohol-coated capsules. Wax-coated capsules were made using the Michelangelo method, in which the capsule is carved out of a wax layer, exhibited highly reproducible dimensions and weight (n = 6, a, b). The wax-coated capsules were incubated in phosphate buffer at pH 6.8 for 30 min at 37 °C. The non-coated hydroxypropyl methylcellulose capsules released their content almost immediately while the wax-coated capsules remained intact (n = 3, c). After 30 min, the temperature was increased to 43 °C, and after a short delay, the wax-coated capsules released their cargo (n = 3, c). The red arrow indicates the time point when the temperature increase was started. The release kinetics of the uncoated capsules containing freeze-dried gadoterate was further assessed using T1-weighted MRI. One minute after exposing the capsule to water, the capsule was visible as a T1-hypointense signal (n = 3, d). After 20 min, the hypointense capsule was surrounded by a strong T1-hyperintense signal (n = 3, e), stemming from the hydration of lyophilised gadoterate after capsule disintegration. All results are shown as mean ± standard deviation