Head and Neck Oncology

Original research study

Translational Innovations & Methodology

Foster RC, Krell AM, Chung TK, Warram JM, Zinn KR, Rosenthal EL. Temperature-dependent fluorescence of IRDye800CW in imaging of head and neck cancers. Head Neck Oncol 2014 Aug 18;6(4):38.

Abstract

Introduction: Proteins conjugated to the near infrared (NIR) moieties for detection of head and neck cancers are being translated to the clinic. However, little is known about the fluorescent properties of IRDye800CW after conjugation to antibodies. We investigated factors that may alter the real-time observed fluorescence of antibody conjugated dye and the rate of fluorescent signal loss.

Methods: Signal loss was examined using three FDA approved monoclonal antibodies conjugated to IRDye800CW (LI-COR) over a period of 15 days. Temperature effects on fluorescence were examined for conjugated dye in both solution and a mouse tumor model. Samples were cooled to -20°C then warmed to predetermined temperatures up to 60°C with imaging performed using the PEARL Impulse (LI-COR) and LUNA (Novadaq) systems.

Results:  Short term fluorescent signal loss (< 1 hour) was linear, while long term loss (15 days) was exponential with significant increases in rate observed with light exposure and increased temperatures.  Cooling of tumor tissue at -20°C was shown to significantly increase tumor fluorescence on both imaging modalities when compared to room temperature (p=0.008, p=0.019). Concurrently the ratio of tumor to background fluorescent signal (TBR) increased with decreasing temperature with statistically significant increases seen at -20°C and 4°C (p=0.0015, p=0.03).

Conclusions: TBR is increased with decreasing sample temperature, suggesting that the clinical exam of fluorescently labeled tissues may be improved at cooler temperatures. Our results indicate that both the rate of signal loss and the change in fluorescence with temperature observed for IRDye800CW are independent of the conjugating antibody.

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