In Vivo Photoacoustic Detection of Lymph Node Metastasis using Glycol-Chitosan-Coated Gold Nanoparticles

Metastasis rather than primary tumor determines prognosis and mortality in the majority of cancer patients. Detection of metastatic lesions is critical for diagnosis and staging, which helps establish the best course of treatment. We developed a method for identifying sentinel lymph node (SLN) metastasis, using combined ultrasound and photoacoustic (US/PA) imaging augmented with glycolchitosan- coated gold nanoparticles (GC-AuNPs). Upon peritumoral injection, GC-AuNPs are uptaken by immune cells and transported to the SLN, where they accumulate. We show that presence of metastasis affects distribution of GC-AuNP-loaded cells in the SLN, which can be monitored via US/PA imaging. A significant reduction in nanoparticle accumulation was seen in metastatic breast cancer mouse models compared to healthy controls. The results of our studies suggest that US/PA imaging of GC-AuNPs can identify sentinel lymph node metastasis with statistical significance. Our approach is cost-effective and does not require complex molecular targets. The developed US/PA imaging tool is expected to aid physicians in detection of micrometastasis thus potentially avoiding unnecessary SLN biopsy.