Design Strategy of Fluorescent Probes for Live Drug-Induced Acute Liver Injury Imaging

Drug-induced acute liver injury (DIALI) is increasingly recognized as a significant cause of acute liver injury (ALI), which is characterized by a rapid loss of hepatocyte function in patients without pre-existing liver diseases. Evaluation of corresponding biomarkers, including alanine transaminase and aspartate amino transferase, is available as a diagnostic tool for hepatotoxicity. However, these blood tests have certain limitations: (1) they are generally not available for early estimation; (2) it is difficult to visualize and identify hepatotoxicity unambiguously in real-time; and (3) the biomarkers are not unique and are usually influenced by a variety of diseases, leading to potential false results. It is of grave importance and burgeoning demand to develop an early diagnostic approach for such diseases, but the ideal toolkit remains an unresolved challenge. As an alternative, molecular optical probes (fluorescence, chemiluminescence, bioluminescence, etc.) display a lot of advantages, such as high sensitivity, noninvasive fast analysis, and real-time in situ detection. They have emerged as potent and promising tools for the biomedical study of DIALI in living system. Until now, a number of optical probes for DIALI have been reported with some great potential for clinical trials. However, most of the probes still suffer from false signals because of the limitations in clinical application, including poor selectivity, low sensitivity, and biocompatibility. One key challenge that probes face in the ALI environment is the excessive exposure to reactive oxygen/nitrogen species and diffusivity, which may lead to false-positive or negative signals. Our group has employed multiple rational approaches to engineer high-performance optical probes for DIALI. With such development, we have successfully achieved the accurate detection of DIALI with minimal false signals both ex vivo and in vivo. While marching firmly toward understanding the biogenesis and progression of DIALI, we ultimately aim at the early stage dinical diagnosis of the disease, as well as mechanism understanding for clinical trials. In this Account, we summarize and present our three new approaches for the development of high-fidelity optical probes: (1) a combined screening and rational design strategy, (2) a double-locked probe design strategy, and (3) in situ imaging based on the release of a precipitating fluorochrome strategy. Using these strategies, we have formulated probes for a range of biological species that are biomarkers of DIALI, including reactive nitrogen species (ONOO-), reactive sulfur species (H2S and H2Sn), and enzymes (LAP, MAO, and ALP). We have highlighted the rationale for our design and screening strategy and methods to achieve high-fidelity optical probes. Some recent examples of optical probes developed by our laboratory and collaborations are mainly illustrated herein. We anticipate the strategies summarized here to inspire future molecular optical probe design, to contribute to studies of the detailed molecular mechanisms underlying liver diseases, and to improve the efficiency of the diagnosis and treatment of these diseases in clinical settings.