TH-C-141-02: Imaging of Targeted Cancer Therapy Using Multifunctional Liposomal Nanoprobes and MRI

Abstract

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.