Mitochondria-targetable small molecule fluorescent probes for the detection of cancer-associated biomarkers: A review

Dissecting lysosomal viscosity fluctuations in live cells and liver tissues with an ingenious NIR fluorescent probe

Viscosity is a pivotal component in the cell microenvironment, while lysosomal viscosity fluctuation is associated with various human diseases, such as tumors and liver diseases. Herein, a near-infrared fluorescent probe (BIMM) based on merocyanine dyes was designed and synthesized for detecting lysosomal viscosity in live cells and liver tissue. The increase in viscosity restricts the free rotation of single bonds, leading to enhanced fluorescence intensity. BIMM exhibits high sensitivity and good selectivity, and is applicable to a wide pH range. BIMM has near-infrared emission, and the fluorescent intensity shows an excellent linear relationship with viscosity. Furthermore, BIMM possessing excellent lysosomes-targeting ability, and can monitor viscosity changes in live cells stimulated by dexamethasone, lipopolysaccharide (LPS), and nigericin, and differentiate between cancer cells and normal cells. Noticeably, BIMM can accurately analyze viscosity changes in various liver disease models with HepG2 cells, and is successfully utilized to visualize variations in viscosity on APAP-induced liver injury. All the results demonstrated that BIMM is a powerful wash-free tool to monitor the viscosity fluctuations in living systems.

A multi-functional fluorescent probe for visualization of H2S and viscosity/polarity and its application in cancer imaging

As an important endogenous gasotransmitter, hydrogen sulfide (H2S) plays a critical role in various physiological functions and has been regarded as a biomarker of cancer due to its overexpression in cancer cells. In addition, the early stages of cancer are often accompanied by abnormalities in the intracellular microenvironments, and distinguishing between cancer cell/tissues and normal cell/tissues is of great significance to the accuracy of cancer diagnosis. However, deep insights into the simultaneous detection of H2S and viscosity/polarity variations in cancer cells/tissues are rarely reported. In this work, we designed and synthesized a mitochondria-targeting fluorescent probe PDQHS, which exhibits high selectivity for H2S with an emission peak around 632 nm and excellent response (17-fold) to viscosity/polarity beyond 706 nm. Meanwhile, PDQHS shows good biocompatibility and can specifically accumulate into mitochondria. Using PDQHS, the visual distinguishing of cancer cells from normal cells was achieved via dual-channel detection of H2S and viscosity/polarity. More importantly, PDQHS has been successfully applied to visualize endogenous and exogenous H2S in living cells and tumor tissue. Obviously, compared to the detection of a single biomarker, monitoring multiple biomarkers simultaneously through dual-channel response is conducive to amplifying the detection signal, providing a more sensitive and reliable imaging tool in the tumor region, which is beneficial for cancer prediction.

Construction of a Cu2+-Responsive NIR Fluorescent Probe and the Preliminary Evaluation of its Multifunctional Application

Cu2+ was deemed as toxic and the most common heavy metal pollution in the water and food. Meanwhile, endogenous Cu2+ was deeply involved in plenty of physiological and pathological processes of human. Cu2+ imbalance was related to multiple diseases. Here we developed a Cu2+-responsive NIR probe HX, which not only demonstrated obvious color change when subjected to Cu2+, but also showed linear-dependent NIR fluorescence emission to Cu2+ concentration for Cu2+ detection and quantification both in vitro and in vivo. When HX was applied to imaging Cu2+ in the cell or living animals, intracellular Cu2+ fluctuation and Cu2+ accumulation in the liver could be visualized to indicate the copper level in the cell or organs with low background signals. Meanwhile, by applying HX to monitor Cu2+ uptake in the tumor, copper transporter function could be evaluated to screen the patient who are sensitivity to platinum drug.