Near-Infrared Dioxetane Luminophores with Direct Chemiluminescence Emission Mode

Abstract

Chemiluminescent luminophores are considered as one of the most sensitive families of probes for detection and imaging applications. Due to their high signal-to-noise ratios, luminophores with near-infrared (NIR) emission are particularly important for in vivo use. In addition, light with such long wavelength has significantly greater capability for penetration through organic tissue. So far, only a few reports have described the use of chemiluminescence systems for in vivo imaging. Such systems are always based on an energy-transfer process from a chemiluminescent precursor to a nearby emissive fluorescent dye. Here, we describe the development of the first chemiluminescent luminophores with a direct mode of NIR light emission that are suitable for use under physiological conditions. Our strategy is based on incorporation of a substituent with an extended π-electron system on the excited species obtained during the chemiexcitation pathway of Schaap's adamantylidene-dioxetane probe. In this manner, we designed and synthesized two new luminophores with direct light emission wavelength in the NIR region. Masking of the luminophores with analyte-responsive groups has resulted in turn-ON probes for detection and imaging of β-galactosidase and hydrogen peroxide. The probes' ability to image their corresponding analyte/enzyme was effectively demonstrated in vitro for β-galactosidase activity and in vivo in a mouse model of inflammation. We anticipate that our strategy for obtaining NIR luminophores will open new doors for further exploration of complex biomolecular systems using non-invasive intravital chemiluminescence imaging techniques.

Advances in bioluminescence imaging: new probes from old recipes

“…[56] Some of these probes comprise embedded dioxetanes that are cleavable—and thus emit light—in response to a variety of triggers. [57*,58] Unlike canonical caged luciferins, these reporters do not require a luciferase to produce light. Such probes further diversify the portfolio of tools for biological imaging.…”

Direct Real‐Time Monitoring of Prodrug Activation by Chemiluminescence

“…BALB/c mice were injected intratumorally with a1 00 mLo f1 00 mm prodrug 1 or control prodrug 2 in 1% DMSO in PBS,pH7.4. [26] These luminophores could be used to compose aplatform for theranostic prodrugs with anear-infrared chemiluminescence readout. Thee mission intensity measured in mice with CT26-LacZ tumors treated with prodrug 1 was about 5-fold higher than that measured in mice with CT26-LacZ tumors treated with control prodrug 2.T he emission intensity measured in mice bearing CT26-wt tumors treated with prodrug 1 was weak but measurable,w hich we attribute to the basal levels of b-gal in these cancer cells.A s far as we know,t his is the first demonstration of in vivo imaging of endogenous enzymatic activity obtained using achemotherapeutic prodrug with achemiluminescent reporting mode.…”

“…[15,16] Monitoring of drug release through analysis of ac hemiluminescence modality offers attractive advantages over fluorescence,m ainly due to the higher signal-to-noise ratio and the fact that an external light source is unnecessary with chemiluminescent agents. [24][25][26][27] Thei nsights obtained from analysis of the chemiexcitation pathway prompted us to develop ad istinct molecular unit that intrinsically integrates ac hemiexcitation turn-on signal with aself immolative release mechanism. [23] Thep robes are composed of phenoxy dioxetane luminophores,m asked by at riggering substrate.R emoval of the substrate by an enzyme or an analyte of choice triggers the direct chemiexcitation mechanism of the dioxetane luminophore.T his meant that, for the first-time,a ni ntense lightemission signal could be obtained under physiological conditions to image endogenous molecular activities in vitro and in vivo.…”

Chemiluminescent Probes for Activity‐Based Sensing of Formaldehyde Released from Folate Degradation in Living Mice

“…[43,46,47] Recent work from one of our labs has identified that introducing electron-withdrawing groups onto the ortho position of the phenol can result in a 1000-fold increase in chemiluminescence quantum efficiency and the ability to tune emission profiles, [43] particularly to the near-IR region to enable better tissue penetration for in vivo imaging. [48] Based on this scaffold, we created a set of chemiluminescent FA probes by caging this phenol with a 2-aza-Cope FA-reactive trigger (Scheme 1). [20] Chemiluminescent Formaldehyde Probes 540 and 700 ( CFAP540 and CFAP700 ) feature visible and near-IR emission profiles designed for in vitro cell and in vivo animal applications, respectively (see Supporting Information for synthetic details).…”