Table of Contents
International Journal of Molecular Imaging
Volume 2015 (2015), Article ID 469047, 10 pages
Research Article

Comparison of Folate Receptor Targeted Optical Contrast Agents for Intraoperative Molecular Imaging

1Division of Thoracic Surgery, Department of Surgery, University of Pennsylvania and Philadelphia VA Medical Center, Philadelphia, PA 19104, USA
2On Target Laboratories, Inc., West Lafayette, IN 47906, USA
3Departments of Biomedical Engineering and Chemistry, Emory University, Atlanta, GA 30322, USA
4Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA

Received 8 June 2015; Accepted 11 August 2015

Academic Editor: Irene J. Virgolini

Copyright © 2015 Elizabeth De Jesus et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background. Intraoperative imaging can identify cancer cells in order to improve resection; thus fluorescent contrast agents have emerged. Our objective was to do a preclinical comparison of two fluorescent dyes, EC17 and OTL38, which both target folate receptor but have different fluorochromes. Materials. HeLa and KB cells lines were used for in vitro and in vivo comparisons of EC17 and OTL38 brightness, sensitivity, pharmacokinetics, and biodistribution. In vivo experiments were then performed in mice. Results. The peak excitation and emission wavelengths of EC17 and OTL38 were 470/520 nm and 774/794 nm, respectively. In vitro, OTL38 required increased incubation time compared to EC17 for maximum fluorescence; however, peak signal-to-background ratio (SBR) was 1.4-fold higher compared to EC17 within 60 minutes (). Additionally, the SBR for detecting smaller quantity of cells was improved with OTL38. In vivo, the mean improvement in SBR of tumors visualized using OTL38 compared to EC17 was 3.3 fold (range 1.48–5.43). Neither dye caused noticeable toxicity in animal studies. Conclusions. In preclinical testing, OTL38 appears to have superior sensitivity and brightness compared to EC17. This coincides with the accepted belief that near infrared (NIR) dyes tend to have less autofluorescence and scattering issues than visible wavelength fluorochromes.