EC-17 (disodium salt) is a folate receptor alpha (FRα) targeting contrast agent with fluorescent properties in the visible light spectrum. The peak excitation and emission wavelengths of EC-17 are 470/520 nm.
EC-17 contains the fluorescein fluorochrome and has a spectral wavelength of 490-530 nm. EC-17 is synthesized by a folate (vitamin B9) and fluorescein isothiocyanate (FITC) conjugated through an ethylenediamine spacer to produce folate-FITC, with a molecular weight of 917 kDa. FITC is a derivative of fluorescein functionalized with an isothiocyanate reactive group. The folate-FITC conjugate forms a negatively charged fluorescent molecule that specifically targets cell-surface FRα and is subsequently internalized into the cytoplasm. The signal-to-background ratio (SBR) of EC-17 for HeLa cells range from 0.97 to 7.32 depending on the molarity and concentration of cancer cells[1].
The mean fluorescence signal from the animals injected with EC-17 to be 42,234 ± 12,234 au[1]. Fluorescence microscopy for folate-FITC shows a strong signal in all malignant tumors with FR-α expression and no signal in FR-α-negative malignant or benign lesions[2].
[1]. Tummers QR, et al. Intraoperative imaging of folate receptor alpha positive ovarian and breast cancer using the tumor specific agent EC17. Oncotarget. 2016 May 31;7(22):32144-55.