Viscosity-triggered near-infrared fluorescence nanoprobe for in vivo non-invasive diagnosis of cancer

A universal and non-invasive approach for cancer diagnosis is desired to lessen the burden of cancer mortality. In this work, we exploited viscosity in the cancer microenvironment as a diagnosis indicator and designed a universal probe, the CBT-Q (4-(2-(5-(9-(4-aminophenyl)-9H-carbazol-3-yl) thiophen-2-yl)vinyl)-1-ethylquinolin-1-ium) nanoprobe, for detecting viscosity variation in the cells, plasma, and solid tumor-mice to obtain a cancer diagnosis. The near infrared (NIR) fluorescence of CBT-Q was specifically triggered due to a change in its structure from a flexible to a rigid one in the presence of a higher viscosity agent, such as a cancer microenvironment or cancer patient plasma. The Stokes shift of CBT-Q nanoprobe (CBT-Q-N) could be up to 178 nm, enabling the diagnosis of cancer with a low biological fluorescent background. Not only could the CBT-Q-N remain in cells for 72 h, but detect the changes in cell viscosity induced by various models. Also, the CBT-Q-N differentiated early and terminal tumor mice via the fluorescent intensity of plasma viscosity. The CBT-Q-N enables non-invasive recognition of tumors in vivo by fluorescence imaging. Hence, this work is beneficial to increase the understanding of tumor-related viscosity, which will facilitate a new universal strategy for present cancer diagnostics.