EC-17 (disodium salt), a folate receptor alpha (FRα) targeting contrast agent, exhibits fluorescent properties within the visible light spectrum, characterized by peak excitation and emission wavelengths of 470/520 nm, respectively.

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. 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.

Fluorescence microscopy for folate-FITC shows a strong signal in all malignant tumors with FR-α.The mean fluorescence signal from the animals injected with EC-17 to be 42,234 ± 12,234?au. expression and no signal in FR-α–negative malignant or benign lesions[2].