# In vivo detection of HER2-positive breast cancer and sentinel lymph node metastasis using activatable ICG-conjugated Trastuzumab

## TL;DR

This study introduces a new non-invasive method using a fluorescent probe to detect HER2-positive breast cancer and its spread to lymph nodes.

## Contribution

The novel use of an activatable ICG-conjugated Trastuzumab probe for in vivo detection of HER2-positive breast cancer and metastasis.

## Key findings

- The Trastuzumab–ICG conjugate specifically bound to and emitted fluorescence in HER2-positive cells.
- In vivo models confirmed the conjugate's specificity for HER2-positive tumors and lymph node metastases.
- The probe shows potential for high-contrast tumor visualization and personalized treatment guidance.

## Abstract

Breast cancer continues to pose a significant health threat to women globally, with sentinel lymph node (SLN) metastasis playing a crucial role in treatment planning and prognosis. Conventional diagnostic techniques are invasive, lack dynamic capability, and have limited specificity. Moreover, detecting intraductal spread or microinvasion remains a challenge. Here, we utilized an activatable (quenched) fluorescence probe by conjugating indocyanine green (ICG) with the anti-HER2 antibody Trastuzumab for non-invasive detection of HER2-positive breast cancer and its sentinel lymph node metastasis. Specifically, we conjugated ICG-sulfo-EG4-OSu to Trastuzumab and purified it to obtain Trastuzumab–ICG. In vitro live-cell imaging and flow cytometry demonstrated that the conjugate bound specifically to HCC-1419-Luc (HER2-positive) cells and emitted fluorescence, whereas no fluorescence was observed in BT-20-Luc (HER2-negative) cells. Orthotopic tumor models and lymph node metastasis models further confirmed its in vivo specificity. These results indicate the potential of Trastuzumab–ICG for high-specificity detection of HER2-positive breast cancer and its lymph node metastases, offering a promising tool for high-contrast tumor visualization and personalized treatment guidance.