The purpose of this study is to evaluate the biodistribution properties of random-copolymer-based core-cross-linked
nanogels of various sizes and surface poly(
ethylene glycol) composition. Systematic variations of near-IR labeled
nanogels, comprising varying particle sizes (28-135 nm), PEG corona quantity (0-50 mol %), and PEG length (PEG Mn 1000, 2000, and 5000), were prepared and injected in mice that had been subcutaneously implanted with MDA-MB-231-luc-D3H2LN
human mammary carcinoma. In vivo biodistribution was obtained using fluorescence molecular tomography imaging at 0, 6, 24, 48, and 72 h postinjection. Retention of total body probe and percentages of total injected dose in the
tumor, liver, spleen, lungs, heart, intestines, and kidneys were obtained. Smaller
nanogels (∼30-40 nm) with a high PEG conjugation (∼43-46 mol %) of Mn 2000 on their coronas achieved the highest
tumor specificity with peak maximum 27% ID/g, a statistically significant propensity toward accumulation with 16.5% ID/g increase from 0 to 72 h of imaging, which constitutes a 1.5-fold increase.
Nanogels with greater
tumor localization also had greater retention of total body probe over 72 h.
Nanogels without extensive PEGylation were rapidly excreted, even at similar sizes to PEGylated
nanogels exhibiting whole body retention. Of all tissues, the liver had the highest % ID, however, like other tissues, it displayed a monotonic decrease over time, suggesting
nanogel clearance by hepatic metabolism. Ex vivo quantification of individual tissues from gross necropsy at 72 h postinjection generally correlated with the FMT analysis, providing confidence in tissue signal segmentation in vivo. The parameters determined to most significantly direct a
nanogel to the desired
tumor target can lead to improve effectiveness for
nanogels as therapeutic delivery vehicles.