Triggerable Prodrug Nanocoating Enables On-Demand Activation of Microbial and Small-Molecular Therapeutics for Combination Treatment.

The synergy of living microbial and small-molecular therapeutics has been widely explored for treating a variety of diseases, while current combination strategies often suffer from low bioavailability, heterogeneous spatiotemporal distribution, and premature drug release. Here, the use of a triggerable prodrug nanocoating is reported to enable the on-demand activation of microbial and small-molecular therapeutics for combination treatment. As a proof-of-concept study, a reactive oxygen species-responsive aromatic thioacetal linker is employed to prepare cationic chitosan-drug conjugates, which can form a nanocoating on the surface of living bacteria via electrostatic interaction. Following administration, the wrapped bacteria can be prevented from insults by the shielding effect of the nanocoating and be co-delivered with the conjugated drug in a spatiotemporally synchronous manner. Upon reaching the lesion site, the upgraded reactive oxygen species trigger cleavage of the thioacetal linker, resulting in the release of the conjugated drug and a linker-derived therapeutic cinnamaldehyde. Meanwhile, a charge reversal achieved by the generation of negatively charged thiolated chitosan induces the dissociation of the nanocoating, leading to synchronous release of the living bacteria. The adequate activation of the combined therapeutics at the lesion site exhibits superior synergistic treatment efficacy, as demonstrated by an assessment using a mouse model of colitis. This work presents an appealing approach to combine living microbial and small-molecular therapeutics for advanced therapy of diseases.