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Klockow JL, Hettie KS, LaGory EL, Moon EJ, Giaccia AJ, Graves EE, Chin FT. An Activatable NIR Fluorescent Rosol for Selectively Imaging Nitroreductase Activity. SENSORS AND ACTUATORS. B, CHEMICAL 2020; 306:127446. [PMID: 32265579 PMCID: PMC7138224 DOI: 10.1016/j.snb.2019.127446] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Hypoxia (pO2 ≤ ~1.5%) is an important characteristic of tumor microenvironments that directly correlates with resistance against first-line therapies and tumor proliferation/infiltration. The ability to accurately identify hypoxic tumor cells/tissue could afford tailored therapeutic regimens for personalized treatment, development of more-effective therapies, and discerning the mechanisms underlying disease progression. Fluorogenic constructs identifying aforesaid cells/tissue operate by targeting the bioreductive activity of primarily nitroreductases (NTRs), but collectively present photophysical and/or physicochemical shortcomings that could limit effectiveness. To overcome these limitations, we present the rational design, development, and evaluation of the first activatable ultracompact xanthene core-based molecular probe (NO 2 -Rosol) for selectively imaging NTR activity that affords an "OFF-ON" near-infrared (NIR) fluorescence response (> 700 nm) alongside a remarkable Stokes shift (> 150 nm) via NTR activity-facilitated modulation to its energetics whose resultant interplay discontinues an intramolecular d-PET fluorescence-quenching mechanism transpiring between directly-linked electronically-uncoupled π-systems comprising its components. DFT calculations guided selection of a suitable fluorogenic scaffold and nitroaromatic moiety candidate that when adjoined could (i) afford such photophysical response upon bioreduction by upregulated NTR activity in hypoxic tumor cells/tissue and (ii) employ a retention mechanism strategy that capitalizes on an inherent physical property of the NIR fluorogenic scaffold for achieving signal amplification. NO 2 -Rosol demonstrated 705 nm NIR fluorescence emission and 157 nm Stokes shift, selectivity for NTR over relevant bioanalytes, and a 28-/12-fold fluorescence enhancement in solution and between cells cultured under different oxic conditions, respectively. In establishing feasibility for NO 2 -Rosol to provide favorable contrast levels in solutio/vitro, we anticipate NO 2 -Rosol doing so in preclinical studies.
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Affiliation(s)
| | - Kenneth S. Hettie
- Department of Radiology, Stanford University, Stanford, CA, 94305, USA
- Corresponding author: Kenneth S. Hettie, Ph.D., 3165 Porter Drive, Palo Alto, CA 94304, , Frederick T. Chin, Ph.D., 3165 Porter Drive, Room 2129, Palo Alto, CA 94304,
| | - Edward L. LaGory
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305, USA
| | - Eui Jung Moon
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305, USA
| | - Amato J. Giaccia
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305, USA
| | - Edward E. Graves
- Department of Radiology, Stanford University, Stanford, CA, 94305, USA
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305, USA
| | - Frederick T. Chin
- Department of Radiology, Stanford University, Stanford, CA, 94305, USA
- Corresponding author: Kenneth S. Hettie, Ph.D., 3165 Porter Drive, Palo Alto, CA 94304, , Frederick T. Chin, Ph.D., 3165 Porter Drive, Room 2129, Palo Alto, CA 94304,
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