A HPQ-based far-red fluorescent probe for monitoring viscosity in mice model of acute inflammation

Viscosity is an essential microenvironmental parameter, which is related to various diseases such as acute inflammation. So it is necessary to develop a probe to monitor viscosity changes during the inflammatory progression in vivo. Herein, a HPQ (2-(2'-hydroxyphenyl)-4(3H)-quinazolinone)-based fluorescent probe named HPQ-BI-V is prepared for detecting viscosity in biological systems. The introduction of benzindole groups extends the π conjugation of HPQ, resulting in far-red emission wavelength at 610 nm. When the viscosity raises from 3.11 cP to 567.1 cP, the fluorescence signal increases 711 times, indicating the high sensitivity of the probe. Furthermore, this probe displays excellent selectivity for viscosity in comparison with other interfering analytes. Furthermore, the probe has excellent photostability and outstanding response capability in the physiological pH range. Given these advantages, HPQ-BI-V can be applied for detecting viscosity changes in HepG2 cells and zebrafish. In particular, the probe can successfully visualize viscosity changes in acute inflammatory mice induced by LPS and the assessment of anti-inflammatory drug.