Gallium Liquid Metal Microdroplets for Constructing Active Therapeutic Agents in Photothermal Therapy of Ulcerative Colitis

Gallium-based liquid metals have been extensively studied in the field of biomedical engineering, including applications in tumor and inflammatory disease therapy, as well as targeted drug delivery. Among these, leveraging the photothermal effect of gallium liquid metals enables effective treatment of heat-sensitive cells in tumor regions and enhances the diffusion capability of liquid metal microdroplets. However, research on the active treatment of ulcerative colitis (UC) using photothermal therapy with liquid metals remains unexplored. This study focuses on constructing an active composite colloidal motor based on gallium indium liquid metal alloy, using liquid metal microdroplets as the core. Through layer-by-layer assembly of polyelectrolytes, a liquid metal active droplet loaded with the drug mesalazine (5-aminosalicylic acid), named as LMAD-A was developed. Under asymmetric light fields generated by NIR-II light source irradiation, LMAD-A exhibits autonomous locomotion, achieving an effective diffusion coefficient more than 800 times greater than that of Brownian motion in liquid metal microdroplets of similar size. Furthermore, LMAD-A demonstrates phototactic behavior, moving toward the NIR light source autonomously. Through in vitro and in vivo experiments in mice, it was verified that LMAD-A can aggregate, deform, and fuse in the mouse colon under photothermal effects, leading to enhanced release of the loaded drug. In simulated treatments, LMAD-A significantly alleviated DSS-induced colitis in mice, confirming the targeted therapeutic capability of active liquid metal microdroplets as an active therapeutic agent in UC-affected regions.