Rational design of a fluorescent microneedle tattoo for minimally invasive monitoring of lymphatic function

The monitoring of lymphatic drainage is of great importance, particularly in the context of the early detection and diagnosis of several diseases. Existing methods of imaging and monitoring lymphatic drainage can be costly and require trained personnel, posing problems for at-home or point-of-care monitoring. Recently, an alternative approach has been proposed, consisting of using microneedles to deliver a near-infrared (NIR) fluorescent tattoo to the skin, which can be monitored with traditional laboratory-based fluorescence detectors. In this work, we present further development of this approach, using a specifically designed NIR-fluorescent probe and rational optimization of microneedle properties and the spatial location of the NIR dye within the microneedles. Moreover, we demonstrate that this method is compatible with a custom-made portable fluorescence measurement device and able to discriminate between drainage and lack of drainage in vivo in rats.