Rational design of a fluorescent probe for the detection of LAP and its application in drug-induced liver injury

Rapid-response near-infrared fluorescence probe for colorimetric detection of HClO and its applications in environmental monitoring and biological imaging

As a crucial endogenous reactive oxygen species, hypochlorous acid (HClO) plays an indispensable role in numerous physiological and pathological processes. Additionally, it serves as a biomarker closely associated with inflammation and liver injury. The utilization of near-infrared fluorescence probes has surged in recent years for live biological imaging, owing to their minimal tissue damage and potent tissue penetration capabilities. In this work, a novel near-infrared fluorescence probe MB-HPD was synthesized to sensitively detect HClO. Probe MB-HPD exhibits remarkable selectivity, high sensitivity (14.3 nM), and rapid response towards HClO (20 s). Probe MB-HPD has demonstrated successful application in the imaging of HClO within cells and zebrafish. Remarkably, it has proven to be effective for detecting HClO within environmental samples, as well as imaging HClO in mice models of arthritis and APAP-induced liver injury. These findings indicate the broad applicability of probe MB-HPD, offering a promising avenue for designing highly selective near-infrared fluorescence probes suitable for real-time HClO monitoring.

A novel near-infrared fluorescent probe for real-time monitoring of leucine aminopeptidase activity and metastatic tumor progression

This article discusses the importance of early tumor detection, particularly in liver cancer, and the role of leucine aminopeptidase (LAP) as a potential marker for liver cancer diagnosis and prognosis assessment. The article highlights the limitations of current tumor markers and the need for new markers and multi-marker approaches to improve accuracy. The authors introduce a novel near-infrared fluorescent probe, NTAP, designed for LAP detection. They describe the synthesis of the probe and evaluate its spectral properties, including the LOD was 0.0038 U/mL, and QY was 0.32 %. The kinetic properties of NTAP, such as the relationship between LAP concentration (0-0.08 U/mL), reaction time (3 min), and fluorescence excitation spectra (475 nm) and emission spectra (715 nm) are investigated. The article also discusses the stability and selectivity of the probe and its ability to detect LAP in complex samples. Cellular imaging experiments demonstrate the NATP specificity and selectivity in detecting LAP activity and its inhibition. Animal models of liver and lung metastasis are used to evaluate the probe's imaging capabilities, showing its ability to accurately locate and detect metastatic lesions. The article concludes by emphasizing the potential applications of the NTAP probe in early tumor diagnosis, treatment monitoring, and the study of tumor metastasis mechanisms.

Recent Progress of Activity-Based Fluorescent Probes for Imaging Leucine Aminopeptidase

Leucine aminopeptidase (LAP) is an important protease that can specifically hydrolyze Leucine residues. LAP occurs in microorganisms, plants, animals, and humans and is involved in a variety of physiological processes in the human body. In the physiological system, abnormal levels of LAP are associated with a variety of diseases and pathological processes, such as cancer and drug-induced liver injury; thus, LAP was chosen as the early biochemical marker for many physiological processes, including cancer. Considering the importance of LAP in physiological and pathological processes, it is critical that high-efficiency and dependable technology be developed to monitor LAP levels. Herein, we summarize the organic small molecule fluorescence/chemiluminescence probes used for LAP detection in recent years, which can image LAP in cancer, drug-induced liver injury (DILI), and bacteria. It can also reveal the role of LAP in tumors and differentiate the serum of cirrhotic, drug-induced liver injury and normal models.

Imaging and detection of sulfite in acute liver injury with a novel quinoxaline-based fluorescent probe

Herein, a novel fluorescent probe HZY was developed for monitoring the sulfite (SO₃^2-) dynamics. For the first time, the SO₃^2- triggered implement was applied in the acute liver injury (ALI) model. The levulinate was selected to achieve the specific and relatively steady recognition reaction. With the addition of SO₃^2-, the fluorescence response of HZY exhibited a large Stokes shift of 110 nm under the 380 nm excitation. The merits included high selectivity under various pH conditions. Compared with the reported fluorescent probes for sulfite, HZY indicated above-moderate performances including remarkable and rapid response (40 folds, within 15 min), and high sensitivity (limit of detection = 0.21 μM). Further, HZY could visualize the exogenous and endogenous SO₃^2- level in living cells. Moreover, HZY could gauge the changing levels of SO₃^2- in three types (induced by CCl₄, APAP, and alcohol) of ALI models. Both in vivo imaging and depth-of-penetration fluorescence imaging demonstrated that HZY could characterize the developmental and therapeutic status during the liver injury process by measuring the dynamic of SO₃^2-. The successful implementation of this project would promote the accurate in-situ detection of SO₃^2- in liver injury, which was expected to guide the pre-clinical diagnosis and clinical practice.

Enzyme-activated near-infrared fluorogenic probe with high-efficiency intrahepatic targeting ability for visualization of drug-induced liver injury

Hepatotoxicity is a serious problem faced by thousands of clinical drugs, and drug-induced liver injury (DILI) caused by chronic administration or overdose has become a major biosafety issue. However, the near-infrared (NIR) fluorescent probes currently used for liver injury detection still suffer from poor liver targeting ability and low sensitivity. Enzyme-activated fluorogenic probes with powerful in situ targeting ability are the key to improving the imaging effect of liver injury. Herein, we rationally designed a leucine aminopeptidase (LAP) activated fluorogenic probe hCy-CA-LAP, which greatly improved the hepatocyte-targeting capability by introducing a cholic acid group. The probe hCy-CA-LAP is converted into a high-emission hCy-CA fluorophore in the presence of LAP, showing high selectivity, high sensitivity and low detection limit (0.0067 U mL-1) for LAP, and successfully realizes the sensitive detection of small fluctuations of LAP in living cells. Moreover, the probe can achieve effective in situ accumulation in the liver, thereby achieving precise imaging and evaluation of two different types of drug-induced hepatotoxicity in vivo. Therefore, the probe hCy-CA-LAP may be a potential tool for exploring the roles of LAP and evaluating the degree of DILI.

Corrigendum to "Rational design of a fluorescent probe for the detection of LAP and its application in drug-induced liver injury" [Spectrochim. Acta A Mol. Biomol. Spectrosc. 251 (2021) 119362]

The purpose of this corrigendum to the published work by the author Liu et al. (2021) is to correct the wrong use of Figures during the proof.

A diketopyrrolopyrrole-based ratiometric fluorescent probe for endogenous leucine aminopeptidase detecting and imaging with specific phototoxicity in tumor cells

Leucine aminopeptidase (LAP) is a vital proteolytic enzyme, and its overexpression is often associated with many physiological diseases, such as liver dysfunction and breast cancer. Therefore, the accurate measurement of LAP concentrations in cells is critical for the diagnosis and prevention of related diseases. Herein, a new ratiometric fluorescent probe, DPP-Leu, based on diketopyrrolopyrrole (DPP) was designed and synthesized for LAP detection based on the specific enzymatic cleavage of the N-terminal leucine residue. The fluorescence intensity ratio of DPP-Leu (I₅₄₈/I₆₅₁) showed a remarkable change in the presence of LAP, with a limit of detection of 0.011 U L^-1, and DPP-Leu was successfully applied to detect LAP in fetal bovine serum (FBS) and artificial urine. Cell imaging experiments revealed that DPP-Leu could target mitochondria and distinguish tumor cells with high LAP content from normal cells. Importantly, benefiting from the structural transformation of DPP-Leu to the photosensitizer 4 under LAP catalysis, the probe could kill tumor cells under light irradiation without damaging normal cells.