Design and synthesis of targeted NIR fluorescent nanoparticles for bio-imaging

Abstract

Breast cancer is the second most common cancer, and the chance that a woman will die from breast cancer is 2.6%. One in 8 women develop breast cancer during their lives. Treatment includes various forms of chemotherapy and radiation, and often breast cancer tumor removal, or lumpectomy. Breast tumor removal surgery often consists of a sentinel lymph node (SLN) biopsy and subsequent removal of axillary lymph nodes upon finding metastasis. SLN biopsy is the clinical procedure to determine the presence of metastasis and the removal of axillary lymph nodes based on the histopathological evaluation. The current clinical gold standard for SLN biopsy involves identification of metastatic cells in SLNs by administration of a radiotracer with a blue dye in the peritumor region followed by histopathological examination of frozen tissue sections. While SLN biopsies accurately predict metastasis in axillary lymph nodes, the caveat is the removal of healthy lymph nodes that causes adverse side effects such as lymphedema and reduced ability to fight infections. If we can identify the presence or absence of metastasis during surgery without the wait of histopathological evaluation, the time duration for surgery and anesthesia for patients can be reduced as these factors have implications for patient welfare and health care costs. Therefore, there is a clinical need to identify cancer cells in SLNs during surgery. Real-time fluorescent imaging techniques are being investigated as an alternative approach for blue dye for use in traditional SLN biopsies. FDA approved near-infrared (NIR) dye indocyanine green (ICG) has been used for real-time fluorescent imaging. However, ICG alone cannot distinguish healthy cells from metastatic cells in SLNs during breast cancer tumor surgery. Labeling ICG with an agent to identify cancer cells with high specificity would solve the clinical need. Therefore, it is hypothesized that xvii encapsulation of ICG in nanoparticles and the subsequent surface conjugation of targeting agents to receptors overexpressed on tumors would enable identification of tumor cells with high specificity and selectivity. In this study, a nanoparticle-based system encapsulated with ICG has been developed and targeted with EGFR antibody for selective identification of cancer cells. Design, synthesis, encapsulation, stability, and in vitro studies in cells using the nanoparticles were completed. The phantom gel study, mimicking human tissue, was also performed using nanoparticles to estimate the amount of ICG required for in vivo imaging. The study results suggest that the newly developed targeted NIR delivery system could be used for real-time fluorescent imaging applications.