Near-Infrared Photoactivatable Nitric Oxide Donors with Integrated Photoacoustic Monitoring

Abstract

Photoacoustic (PA) tomography is a noninvasive technology that utilizes near-infrared (NIR) excitation and ultrasonic detection to image biological tissue at centimeter depths. While several activatable small-molecule PA sensors have been developed for various analytes, the use of PA molecules for deep-tissue analyte delivery and monitoring remains an underexplored area of research. Herein, we describe the synthesis, characterization, and in vivo validation of photoNOD-1 and photoNOD-2, the first organic, NIR-photocontrolled nitric oxide (NO) donors that incorporate a PA readout of analyte release. These molecules consist of an aza-BODIPY dye appended with an aryl N-nitrosamine NO-donating moiety. The photoNODs exhibit chemostability to various biological stimuli, including redox-active metals and CYP450 enzymes, and demonstrate negligible cytotoxicity in the absence of irradiation. Upon single-photon NIR irradiation, photoNOD-1 and photoNOD-2 release NO as well as rNOD-1 or rNOD-2, PA-active products that enable ratiometric monitoring of NO release. Our in vitro studies show that, upon irradiation, photoNOD-1 and photoNOD-2 exhibit 46.6-fold and 21.5-fold ratiometric turn-ons, respectively. Moreover, unlike existing NIR NO donors, the photoNODs do not require encapsulation or multiphoton activation for use in live animals. In this study, we use PA tomography to monitor the local, irradiation-dependent release of NO from photoNOD-1 and photoNOD-2 in mice after subcutaneous treatment. In addition, we use a murine model for breast cancer to show that photoNOD-1 can selectively affect tumor growth rates in the presence of NIR light stimulation following systemic administration.

Photoacoustic Imaging: Contrast Agents and Their Biomedical Applications

“…Compared to the saline control experiment, the PA was enhanced by 1.9‐fold at 680 nm, and the PA 680nm /PA 770nm ratiometric turn‐on response relative increased by 1.3 times, respectively (Figure G). Recently, Chan and co‐workers designed NIR photoactivatable NO donors that employed a direct PA readout to endow noninvasive sensing of analyte release …”

A Photoacoustic Probe for the Imaging of Tumor Apoptosis by Caspase‐Mediated Macrocyclization and Self‐Assembly

“…[8] PA imaging can produce 3D images with improved spatial resolution (up to tens of micrometers) and penetration depth (up to afew centimeters) in vivo,showing promise for detecting essential physiological and pathological processes. [10][11][12] Activatable PA probes that can selectively switch PA signal "on" from an "off" state upon interaction with essential biomolecules and environments (e.g., ions, [13] reactive oxygen species, [14] nitric oxide, [15] hypoxia, [16] and enzymes [17] )h ave also been reported. [10][11][12] Activatable PA probes that can selectively switch PA signal "on" from an "off" state upon interaction with essential biomolecules and environments (e.g., ions, [13] reactive oxygen species, [14] nitric oxide, [15] hypoxia, [16] and enzymes [17] )h ave also been reported.…”

“…[9] Several PA imaging probes capable of accumulating in disease sites through passive delivery or active targeting have been developed, providing increased PA contrast to assess disease states in living animals. [10][11][12] Activatable PA probes that can selectively switch PA signal "on" from an "off" state upon interaction with essential biomolecules and environments (e.g., ions, [13] reactive oxygen species, [14] nitric oxide, [15] hypoxia, [16] and enzymes [17] )h ave also been reported. These probes have advantages of low background and high sensitivity in vivo, facilitating the real-time detection of molecular targets with high imaging depth and spatial resolution.…”

Stable J‐Aggregation of an aza‐BODIPY‐Lipid in a Liposome for Optical Cancer Imaging

“…[9] Recent developments of aza-BODIPY synthetic derivatives have allowed tailored design for specific moieties to promote their use as photoacoustic probes, [10] targeting conjugates, [11] optical sensors, [12] and off/ on switch systems. [9] Recent developments of aza-BODIPY synthetic derivatives have allowed tailored design for specific moieties to promote their use as photoacoustic probes, [10] targeting conjugates, [11] optical sensors, [12] and off/ on switch systems.…”

“…Aza-boron dipyrromethenes (aza-BODIPYs) are ar apidly emerging class of near-infrared (NIR) fluorophores with NIR emission, high fluorescence quantum yields,a nd excellent photostability,which are attractive properties for cancer imaging applications. [9] Recent developments of aza-BODIPY synthetic derivatives have allowed tailored design for specific moieties to promote their use as photoacoustic probes, [10] targeting conjugates, [11] optical sensors, [12] and off/ on switch systems. [13] While the in vitro applications for small molecule aza-BODIPYs grow,h ydrophobicity remains am ajor challenge hindering their in vivo applications.…”