Targeted tumor detection: guidelines for developing biotinylated diagnostics

A new-type HOCl-activatable fluorescent probe and its applications in water environment and biosystems

The outbreak and spread of Corona Virus Disease 2019 (COVID-19) has led to a significant increase in the consumption of sodium hypochlorite (NaOCl) disinfectants. NaOCl hydrolyzes to produce hypochlorous acid (HOCl) to kill viruses, which is a relatively efficient chlorine-based disinfectant commonly used in public disinfection. While people enjoy the convenience of NaOCl disinfection, excessive and indiscriminate use of it will affect the water environment and threaten human health. Importantly, HOCl is an indispensable reactive oxygen species (ROS) in human body. Whether its concentration is normal or not is closely related to human health. Excessive production of HOCl in the body contributes to some inflammatory diseases and even cancer. Also, we noticed that the concentration of ROS in cancer cells is about 10 times higher than that in normal cells. Herein, we developed a HOCl-activatable biotinylated dual-function fluorescent probe BTH. For this probe, we introduced biotin on the naphthalimide fluorophore, which increased the water solubility and enabled the probe to aggregate in cancer cells by targeting specific receptor overexpressed on the surface of cancer cell membrane. After reacting to HOCl, the p-aminophenylether moiety of this probe was oxidatively removed and the fluorescence of the probe was recovered. As expected, in the PBS solution with pH of 7.4, BTH could give full play to the performance of detecting HOCl, and it has made achievements in detecting the concentration of HOCl in actual water samples. Besides that, BTH had effectively distinguished between cancer cells and normal cells through a dual-function discrimination strategy, which used biotin to enrich the probe in cancer cells and reacted with overexpressed HOCl in cancer cells. Importantly, this dual-function discrimination strategy could obtain the precision detection of cancer cells, thereby offering assistance for improving the accuracy of early cancer diagnosis.

Log P analyzation-based discovery of GSH activated biotin-tagged fluorescence probe for selective colorectal cancer imaging

Targeted activatable fluorescent probes could provide an effective approach for colorectal cancer imaging. In this study, F1 was found as an effective targeted activatable fluorescent probe based on log P analysis. In vitro experiments demonstrated that the initial fluorescence of the developed probe F1 was initially well quenched, and the fluorescence increased after the probe interacted with glutathione. Cell imaging results showed that the probe had good cell permeability and selectivity. Remarkably, F1 displayed enhanced tumor tissue fluorescence in MC-38 tumor-bearing mice. Notably, it showed selectivity in imaging clinical specimens of human colorectal cancer tissues. Accordingly, this study shows that log P analysis can facilitate the developing efficient of biotin-tagged activatable probes, and the identified F1 has a good potential in clinical colorectal cancer diagnosis.

AminoBODIPY Conjugates for Targeted Drug Delivery Systems and Real-Time Monitoring of Drug Release

In this work, we report two concepts of drug delivery based on small-molecule drug conjugates with the ability of specific targeting and drug release monitoring via ratiometric fluorescence. The functionality of these concepts has been verified by two model systems consisting of three parts: (i) fluorescent aminoBODIPY for real-time detection of conjugate cleavage, (ii) a c(RGDfK) peptide specific for α_vβ₃ integrin receptors targeting angiogenesis in most solid tumors or redBODIPY for conjugate cleavage monitoring via FRET, and (iii) pegylated-2-phenyl-3-hydroxy-4(1H)-quinolinone (3HQ) as a model drug. The model drug release is based on a self-immolative disulfide linker sensitive to environments containing thiols, especially glutathione, which is overexpressed in cancer cells. The results show effective thiol-mediated cleavage of the fluorescent reporter and the subsequent liberation of the drug in a tube. The conjugate with c(RGDfK) was confirmed to penetrate the cells via interaction with integrin receptors. Drug release from this conjugate is possible to monitor inside the cells. Further, the synthetic approach to the conjugates and the method of fluorescence monitoring of the drug release have also been described.

Fluorescent Probe for Monitoring Hydrogen Peroxide in COX-2-Positive Cancer Cells

Hydrogen peroxide (H₂O₂), an important marker for oxidative stress, plays a vital role in cellular biological functions. Overproduction of H₂O₂ causes oxidative damage to cellular functions and promotes cancer and other neurodegenerative diseases. Also, cyclooxygenase-2 (COX-2) enzyme is known to be expressed in several cancer types and exerts multifaceted roles in carcinogenesis and resistance to cancer treatment. Hence, it is important to monitor the H₂O₂ concentration changes in the COX-2-expressing cancer cells. Herein, we have developed a molecular fluorescent ratiometric H₂O₂-responsive probe (NPDIN) composed of indomethacin (COX-2 inhibitor) conjugated with 1,8-napthalimide boronate ester as fluorescent reporter through a chemical linker. The probe was capable of imaging the endogenous H₂O₂ in COX-2 overexpressing cancer cell lines (A549, LoVo, HT29, and Caco-2). Further studies revealed the critical role of the indomethacin moiety in the cellular uptake behavior of NPDIN in COX-2-overexpressing cancer cells. Collectively, our results demonstrated NPDIN as a COX-2-positive cancer-targeting sensitive ratiometric fluorescent probe (I₅₅₄/I₃₉₈) for H₂O₂ imaging and showed its promising biological applications in the future.

A gadolinium-complex-based theranostic prodrug for in vivo tumour-targeted magnetic resonance imaging and therapy

A molecular theranostic prodrug for treatment of tumour and real-time monitoring via MRI in vivo was reported.

Synthesis of Two-Photon Active Tricomponent Fluorescent Probe for Distinguishment of Biotin Receptor Positive and Negative Cells and Imaging 3D-Spheroid

A fluorescence microscopy-based distinguishment between biotin receptor (BiR) positive and negative cell lines via receptor-mediated endocytosis has been demonstrated. A water-soluble, three-component, two-photon (2P) active solvatofluorochromic probe has been designed and synthesized. The applicability of the probe for 2P microscopy and 3D-spheroid was also assessed.

Development of a theranostic prodrug for colon cancer therapy by combining ligand-targeted delivery and enzyme-stimulated activation

The high incidence of colorectal cancer worldwide is currently a major health concern. Although conventional chemotherapy and surgery are effective to some extent, there is always a risk of relapse due to associated side effects, including post-surgical complications and non-discrimination between cancer and normal cells. In this study, we developed a small molecule-based theranostic system, Gal-Dox, which is preferentially taken up by colon cancer cells through receptor-mediated endocytosis. After cancer-specific activation, the active drug Dox (doxorubicin) is released with a fluorescence turn-on response, allowing both drug localization and site of action to be monitored. The therapeutic potency of Gal-Dox was also evaluated, both in vivo and ex vivo, thus illustrating the potential of Gal-Dox as a colorectal cancer theranostic with great specificity.