Nanoparticles have been extensively used for inflammation imaging and photodynamic therapy of cancer. However, the major translational barriers to most nanoparticle-based imaging and therapy applications are the limited depth of tissue penetration, inevitable requirement of external irradiation, and poor biocompatibility of the nanoparticles. To overcome these critical limitations, we synthesized a sensitive, specific, biodegradable luminescent nanoparticle that is self-assembled from an amphiphilic polymeric conjugate with a luminescent donor (luminol) and a fluorescent acceptor [chlorin e6 (Ce6)] for in vivo luminescence imaging and photodynamic therapy in deep tissues. Mechanistically, reactive oxygen species (ROS) and myeloperoxidase generated in inflammatory sites or the tumor microenvironment trigger bioluminescence resonance energy transfer and the production of singlet oxygen (¹O₂) from the nanoparticle, enabling in vivo imaging and cancer therapy, respectively. This self-illuminating nanoparticle shows an excellent in vivo imaging capability with suitable tissue penetration and resolution in diverse animal models of inflammation. It is also proven to be a selective, potent, and safe antitumor nanomedicine that specifically kills cancer cells via in situ ¹O₂ produced in the tumor microenvironment, which contains a high level of ROS.

The incidence and prevalence of inflammatory bowel disease (IBD) increases steadily worldwide. There is an urgent need for effective and safe IBD therapies. Accelerated resolution of inflammation is a new strategy for the management of inflammatory diseases. For effective and safe IBD treatment, herein a smart nanotherapy (i.e. oxidation‐responsive nanoparticles containing a proresolving annexin A1‐mimetic peptide Ac2‐26, defined as AON) is developed, which can release packaged Ac2‐26, in response to highly expressed reactive oxygen species (ROS) at diseased sites. AON effectively protects Ac2‐26 from degradation in the enzyme‐rich environment of the gastrointestinal tract. By delivering this nanotherapy to the inflamed colons of mice with IBD, site‐specific release and accumulation of Ac2‐26 in response to high levels of ROS at the inflammatory sites are achieved. Mechanistically, the Ac2‐26‐containing, oxidation‐labile nanotherapy AON effectively decreases the expression of proinflammatory mediators, attenuates trafficking and infiltration of inflammatory cells, promotes efferocytosis of apoptotic neutrophils, and increases phenotypic switching of macrophages. Therapeutically, AON reduces symptoms of inflammation, accelerates intestinal mucosal wound healing, reshapes the gut microbiota composition, and increases short‐chain fatty acid production. Additionally, oral delivery of this nanomedicine shows excellent safety profile in a mouse model, conferring the confidence for further development of a targeted precision therapy for IBD and other inflammatory diseases.