Rational design of MMP-independent fluorescent probe for in vivo visualization of mitochondrial viscosity in fatty liver and cancer models

Abstract

Unraveling the intrinsic correlation between disease and mitochondrial viscosity presents a significant challenge. Traditional mitochondrial viscosity probes, which depend on mitochondrial membrane potential (MMP), within the context of disease-related physiology and pathology, the decline of MMP in response to varying biological conditions can diminish the electrostatic forces binding probes to mitochondria. As a result, these probes are susceptible to diffusing away from the mitochondrial matrix, leading to unreliable detection outcomes and spatiotemporal data. To date, the visualization of abnormal mitochondrial viscosity in clinical samples from cancer patients has not been achieved. To overcome this pressing challenge, we have meticulously synthesized a potent mitochondrial immobilization and viscosity-sensitive fluorescent probe bearing a lengthy alkyl chain (M-KZ-C8). This probe comprises a carbazole moiety serving as an electron donor (D) and an indole group functioning as an electron acceptor (A), thus adopting a classical d-A molecular structure. Utilizing the twisted intramolecular charge transfer, M-KZ-C8 exhibits exceptional sensitivity to viscosity fluctuations. Moreover, we have observed that M-KZ-C8 possesses an impressive capability for precisely monitoring mitochondrial viscosity changes within living cells, unaffected by alterations in MMP. Leveraging M-KZ-C8, we have successfully imaged heightened mitochondrial viscosity in fatty liver and cancerous tissues. Remarkably, the probe has achieved the visualization of mitochondrial viscosity not only at tissue and organ levels but also in surgical specimens from clinical cancer patients for the first time, heralding its vast potential for clinical diagnosis of human cancers. These attributes render M-KZ-C8 an efficacious diagnostic tool for the precise detection, unwavering fidelity, and prolonged imaging of diseases associated with mitochondrial viscosity.