64CuS‐labeled nanoparticles: a new sentinel‐lymph‐node‐mapping agent for PET–CT and photoacoustic tomography

Determining sentinel lymph node (SLN) status is critical to cancer staging and treatment decisions. Currently, in clinical practice, 99mTc‐radiocolloid‐mediated planar scintigraphy and single‐photon emission computed tomography (SPECT) are used to guide the biopsy and resection of SLNs. Recently, an emerging technique that combines positron emission tomography (PET) and photoacoustic tomography (PAT; PET–PAT) may offer accurate information in detecting SLNs. Herein, we report a kind of 64CuS‐labeled nanoparticle (64CuS‐NP) for the detection of SLNs with PET–PAT. We subcutaneously injected 64CuS‐NPs into the rats’ forepaw pads. After 24 h, the rats’ first draining axillary lymph nodes (i.e. the SLNs) could be clearly visualized with micro‐PET (μPET)–CT. Rats were sacrificed after μPET–CT imaging, their axillary lymph nodes were surgically identified, and then PAT was employed to discover 64CuS‐NP‐avid SLNs, which were embedded inside tissues. Biodistribution, autoradiography, and copper staining analyses confirmed the SLNs’ high uptake of 64CuS‐NPs. Our study indicates that 64CuS‐NPs are a promising dual‐function agent for both PET–CT and PAT and could be used with multi‐modal imaging strategies such as PET–PAT to identify SLNs in a clinical setting.