Imaging of Targeted Cancer Therapy Using Multifunctional Liposomal Nanoprobes and MRI
Y Kuo1*, C Hung2, S Raghavan1, W D'Souza1,2, (1) University of Maryland, College Park, MD, (2) University of Maryland School of Medicine, Baltimore, MDTH-C-141-2 Thursday 10:30AM - 12:30PM Room: 141
Purpose: To develop a multifunctional liposomal nanoprobe that selectively binds to epidermal growth factor receptor (EGFR) over-expressing tumor cells with an encapsulating a magnetic resonance (MR) imaging contrast agent, gadolinium (Gd) and conjugating an EGFR-specific monoclonal antibody within liposome particles. The function of the probe is to target cancer overexpressing cells so that uptake of anti-EGFR targeted therapeutic agents may be imaged. We tested our nanoprobe using a head and neck cancer cell line and Cetuximab, an anti-EGFR drug.
Methods: Encapsulation of Gd within liposome particles was optimized by combining Dipalmitoylphosphatidylcholine (DPPC), cholesterol, 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine-N-(biotinyl)(sodium salt) (DOPE-Biotin), and Diethylenetriaminepentaacetic acid-bis(stearylamide)-Gd (DTPA-BSA-Gd). Avidin was included in the liposomal membrane to conjugate with biotin-modulated anti-EGFR antibody. The probes were characterized for size, surface potential and structural integrity with dynamic light scattering (DLS) and transmission electronic microscopy (TEM). In-vitro targeting specificity of the probe was evaluated using fluorescence microscopy by comparing the binding capacity of a fluorescence-labeled probe in a human head and neck cancer cell line, 15B (high EGFR overexpression) and a human embryonic kidney cell line, HEK293 (low EGFR control). Finally, the in vitro applicability of MRI contrast Gd within the probe was demonstrated by detecting cell-bound particles with MR imaging.
Results: Using TEM scanning, the probes were near spherical in shape and identical in particle size (~100nm). The surface potential was +5.13mV. The EGFR-specific targeting assay with fluorescence-labeled probes showed significantly high occupancy of the probe on the surface of 15B cells in comparison with HEK293 cells. The T1 relaxation time of this EGFR-specific probe attached to15B cells was measured to be 379.3 ms, shorter than that of control vector without anti-EGFR conjugation (516.2 ms).
Conclusion: We have demonstrated targeting specificity of a nanoprobe in discriminating high and low EGFR-expressing cells. The incorporation of Gd revealed the cell-targeting under MR imaging.