Escherichia coli-Based In Situ Triggerable Probe as an Amplifier for Sensitive Diagnosis and Penetrated Therapy of Cancer.

Escherichia coli ( E. coli ) was used for cancer therapy due to the tumor-targeting, catalytic, and surface-reducing properties. Effective diagnosis combined with treatment of cancer based on E. coli , however, was rarely demonstrated. In this study, E. coli was used to surface reduce HAuCl ₄ and as a carrier to modify riboflavin (Rf) and luminol (E-Au@Rf@Lum). After targeted delivery to tumor, the E-Au@Rf@Lum probe could actively emit 425 nm blue-violet chemiluminescence (CL) to achieve cell imaging for cancer diagnosis. Furthermore, this light could in situ trigger the photosensitizer (Rf) through CL resonance energy transfer, which produces reactive oxygen species (ROS) for accurate photodynamic therapy. In return, the excessive ROS enhanced the blue-violet light which was further absorbed by Rf, and ROS production was cyclically amplified. Abundant ROS broke down the dense extracellular matrix network and penetrated deep into tumors. Besides, E. coli with excellent catalytic property could decompose H ₂ O ₂ to O ₂ to relieve tumor hypoxia for a long time and enhance the photosensitized process of Rf. By self-illumination, effective penetration, and tumor hypoxia relief, this work opens a self-amplified therapy modality to tumor.