Fluorescence imaging of the lymph node uptake of proteins in mice after subcutaneous injection: molecular weight dependence.

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 (149 kDa), bovine serum albumin (BSA, 66 kDa), ovalbumin (44.3 kDa) or VEGF-C156S (23 kDa), 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 6.81 h for bevacizumab, 2.85 h for BSA, 1.57 h for ovalbumin and 0.31 h 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 {bullet operator} 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.