Selective Uptake and Imaging of Aptamer- and Antibody-Conjugated Hollow Nanospheres Targeted to Epidermal Growth Factor Receptors Overexpressed in Head and Neck Cancer

The purpose of this study was to compare the binding affinity and selective targeting of aptamer- and antibody-coated hollow gold nanospheres (HAuNS) targeted to epidermal growth factor receptors (EGFR). EGFR-targeting aptamers were conjugated to HAuNS (apt-HAuNS) by attaching a thiol-terminated single-stranded DNA to the HAuNS and then adding the complementary RNA targeted to EGFR. Apt-HAuNS was characterized in terms of size, surface charge, absorption, and number of aptamers per particle. The in vivo pharmacokinetics, in vivo biodistribution, and micro-SPECT/CT imaging of In-111-labeled apt-HAuNS and anti-EGFR antibody (C225)-conjugated HAuNS were evaluated in nude mice bearing highly malignant human OSC-19 oral tumors. In-111-labeled PEG-HAuNS was used as a control (n = 5/group). Apt-HAuNS did not have an altered absorbance profile or size (lambda(max) = 800 nm; diameter = 55 nm) compared to C225-HAuNS or PEG-HAuNS. The surface charge became more negative upon conjugation of the aptamer (-51.4 vs -19.0 for PEG-HAuNS and -25.0 for C225-HAuNS). The number of aptamers/particle was similar to 250. In vitro cell binding and in vivo biodistribution showed selective binding of the apt-HAuNS to EGFR. mu SPECT/CT imaging confirmed that there was more tumor uptake of apt-HAuNS than C225-HAuNS. Aptamer is a promising ligand for image-guided delivery of nanoparticles for treatment of tumor cells overexpressing EGFR.