(229c) Bubble-Based Microrobots for Epithelial Pinning and Sustained Drug Delivery

Remotely powered active colloids have been recognized as next-generation medical microrobots for drug and gene delivery. However, most microrobots swim with linear trajectories and lack the capacity to robustly adhere to soft tissues. This limits their ability to navigate complex biological environments and sustainably release drugs at target sites. In this work, bubble-based microrobots with complex geometries are shown to efficiently swim with non-linear trajectories in a mouse bladder, robustly pin to the epithelium, and slowly release therapeutic drugs for sustained effects. The asymmetric fins on the exterior bodies of the microrobots induce a rapid rotational component to their swimming motions of up to ~150 body lengths per second. Due to their fast speeds and sharp fins, the microrobots can mechanically pin themselves to the bladder epithelium and endure shear stresses commensurate with urination. Dexamethasone, a small molecule drug used for inflammatory bladder diseases, is encapsulated within the polymeric bodies of the microrobots. The sustained release of dexamethasone is shown to temper inflammation in a manner that surpasses the performance of free drug controls by comparing the molecular expression of key inflammatory markers on murine macrophages. This system provides a potential strategy to use microrobots to efficiently navigate large volumes, pin at soft tissue boundaries, and release drugs over several days for a range of diseases.