Fluorescence Imaging of the Lymph Node Uptake of Proteins in Mice after Subcutaneous Injection: Molecular Weight Dependence

Abstract

To use noninvasive fluorescence imaging to investigate the influence of molecular weight (MW) of proteins on the rate of loss from a subcutaneous (SC) injection site and subsequent uptake by the draining lymph nodes in mice. Bevacizumab (149kDa), bovine serum albumin (BSA, 66kDa), ovalbumin (44.3kDa) or VEGF-C156S (23kDa), labeled with the near infrared dye IRDye 680, were injected SC into the front footpad of SKH-1 mice. Whole body non-invasive fluorescence imaging was performed to quantitate the fluorescence signal at the injection site and in axillary lymph nodes. The half-life values, describing the times for 50% loss of proteins from the injection site, were 6.81h for bevacizumab, 2.85h for BSA, 1.57h for ovalbumin and 0.31h for VEGF-C156S. The corresponding axillary lymph node exposure, represented as the area of the % dose versus time curve, was 6.27, 5.13, 4.06 and 1.54% dose ∙ h, respectively. Our results indicate that the rate of loss of proteins from a SC injection site is inversely related to MW of proteins, while lymph node exposure is proportionally related to the MW of proteins in a mouse model.