Fig. 4. Examples of drug delivery systems in development that could substantially improve adherence.

Medication adherence could be improved by systems that enable oral delivery of biologics, autonomously regulate the concentration of a drug in circulation or mimic a multi-dose dosing regimen with a single injection. a–c, Examples of systems in each category include the self-orienting millimetre-scale applicator (SOMA), which injects insulin across the gastric mucosa and leads to near zero-order release for hours (panel a); the glucose-responsive microneedle (GR-MN) insulin patch consisting of an array of polymeric needles that reversibly swell under hyperglycaemic conditions and collapse when blood glucose levels return to normal to modulate insulin release (panel b); and core shell poly(lactic-co-glycolic acid) (PLGA) microparticles synthesized via the stamped assembly of polymer layers microfabrication method capable of releasing active pharmaceutical ingredient cargo in discrete bursts at pre-programmed intervals (panel c). Part a adapted with permission from ref. ^{120, AAAS}. Part b adapted from ref. ¹²¹, Springer Nature Limited. Part c is adapted from ref. ³⁴, CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).