Development of NIR-II Photoacoustic Probes Tailored for Deep-Tissue Sensing of Nitric Oxide

• Published in: Journal of the American Chemical Society Vol. 143; no. 18; pp. 7196 - 7202
• Main Authors: Lucero, Melissa Y, East, Amanda K, Reinhardt, Christopher J, Sedgwick, Adam C, Su, Shengzhang, Lee, Michael C, Chan, Jefferson
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.05.2021
• Subjects: A549 Cells; Animals; Drug Development; Fluorescent Dyes - chemical synthesis; Fluorescent Dyes - chemistry; Humans; Infrared Rays; Mice; Molecular Structure; Neoplasms, Experimental - diagnostic imaging; Nitric Oxide - analysis; Optical Imaging; Photoacoustic Techniques
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.1c03004

Photoacoustic (PA) imaging has emerged as a reliable in vivo technique for diverse biomedical applications ranging from disease screening to analyte sensing. Most contemporary PA imaging agents employ NIR-I light (650–900 nm) to generate an ultrasound signal; however, there is significant interference from endogenous biomolecules such as hemoglobin that are PA active in this window. Transitioning to longer excitation wavelengths (i.e., NIR-II) reduces the background and facilitates the detection of low abundance targets (e.g., nitric oxide, NO). In this study, we employed a two-phase tuning approach to develop APNO-1080, a NIR-II NO-responsive probe for deep-tissue PA imaging. First, we performed Hammett and Brønsted analyses to identify a highly reactive and selective aniline-based trigger that reacts with NO via N-nitrosation chemistry. Next, we screened a panel of NIR-II platforms to identify chemical structures that have a low propensity to aggregate since this can diminish the PA signal. In a head-to-head comparison with a NIR-I analogue, APNO-1080 was 17.7-fold more sensitive in an in vitro tissue phantom assay. To evaluate the deep-tissue imaging capabilities of APNO-1080 in vivo, we performed PA imaging in an orthotopic breast cancer model and a heterotopic lung cancer model. Relative to control mice not bearing tumors, the normalized turn-on response was 1.3 ± 0.12 and 1.65 ± 0.07, respectively.