Highly Bright Near‐Infrared Chemiluminescent Probes for Cancer Imaging and Laparotomy

Abstract

Near-infrared (NIR) chemiluminescence imaging holds potential for sensitive imaging of cancer due to its low background; however, few NIR chemiluminophores are available, which share the drawback of low chemiluminescence quantum yields (Φ CL ). Herein, we report the synthesis of NIR chemiluminophores for cancer imaging and laparotomy. Molecular engineering of the electron-withdrawing group at the para-position of the phenol-dioxetane leads to a highly bright NIR chemiluminophore (DPT), showing the Φ CL (4.6 × 10 À 2 Einstein mol À 1 ) that is 3 to 5-fold higher than existing NIR chemiluminophores. By caging the phenol group of DPT with a cathepsin B (CatB) responsive moiety, an activatable chemiluminescence probe (DPT CB ) is developed for real-time turn-on detection of deeply buried tumor tissues in living mice. Due to its high brightness, DPT CB permits accurate chemiluminescence-guided laparotomy.

Leveraging Long-Distance Singlet-Oxygen Transfer for Bienzyme-Locked Afterglow Imaging of Intratumoral Granule Enzymes

“…The afterglow moiety (N 3 DPT) was synthesized according to previous literature with an additional azide group as the click handle . The (ε) of N 3 DPT in PBS (10 mM, pH = 7.4, 10% DMSO) was 1.29 × 10 4 L mol –1 cm –1 . , The hydroxyl group from N 3 DPT was then caged with CaB-cleavable z-Val-Cit (CitV) and PABA, producing C B N 3 DPT that can be specifically activated by CaB from tumor cells. After the two enzyme-responsive moieties were successfully synthesized and characterized, BAAP was then constructed by covalently linking G B HCySI and C B N 3 DPT together with a PEG chain having an average molecular weight of 600 Da via the copper­(I)-catalyzed alkyne–azide cycloaddition (CuAAc), respectively.…”

“…37−39 To achieve the intratumoral selectivity, another enzyme, cathepsin B (CaB), a tumor biomarker that plays a significant role in tumor survival and progression, is selected. 27,40,41 As depicted in Figure 1a (middle row), BAAP comprises a biomarker 1(GrB)-activatable 1 O 2 donor and a biomarker 2 (CaB)-activatable 1 O 2 acceptor, covalently linked together by polyethylene glycol (PEG). Initially, BAAP is nonfluorescent and incapable of generating afterglow signals due to the suppression of SOT.…”

“…As this approach hinges on the transfer of 1 O 2 that has a larger diffusion distance (60 nm in cell; 125 nm in water) − to result in afterglow signal readout, it does not require real-time light excitation, significant spectral overlap, and close donor–acceptor distance as FRET does (Figure a). Because the high infiltration of cytotoxic T lymphocytes (CTLs) is associated with a positive prognosis for cancer therapy, granzyme B (GrB), a serine protease overexpressed by CTLs for elimination of tumor, is chosen as the immunoactivation biomarker. − To achieve the intratumoral selectivity, another enzyme, cathepsin B (CaB), a tumor biomarker that plays a significant role in tumor survival and progression, is selected. ,, …”

Chemiexcitation Acceleration of 1,2-Dioxetanes via a Spiro-Fused Inductive Electron-Withdrawing Motifs

“…4 Noticeably, this development ended almost 30 years of dormancy in the field and enabled the use of chemiluminescent probes, for the first time, as a sole component in water with no required additives. Numerous research groups worldwide, [5][6][7][8][9][10][11] including ours, used the ortho-substituted phenoxy-adamantyl-1,2-dioxetane luminophore to develop new turn-on chemiluminescent probes for the detection and imaging of a variety of enzymes and analytes in living systems. Despite the encouraging progress in the field, further advancements could be attained by gaining a deeper understanding of the chemiexcitation mechanism of dioxetanes.…”