Despite significant research regarding
metastasis, there has been limited success in preventing it. However,
gold nanoparticle (AuNP) technology has shown the potential to inhibit
metastasis. Our earlier studies of
gold nanorod-assisted plasmonic
photothermal therapy (AuNRs-PPTT), where
gold nanorods (AuNRs) were irradiated with near-infrared (NIR) light to induce heat, were utilized in slowing
cancer cell migration in vitro. Herein, we have expanded the in vitro studies of the AuNRs-PPTT to xenograft mice to inhibit
metastasis of mammary gland
tumors. The study duration was 32 days from 4T1
cancer cell
injections in four treatment groups: control (PBS), NIR Only, AuNRs, and AuNRs + NIR. Multiple AuNRs-PPTT treatment sessions with intratumoral AuNRs
injections were conducted every 7 days on average on the mice. Photoacoustic spectroscopy has been utilized to study the distribution and aggregation of AuNRs within the
tumors and the drainage of particles to the sentinel right subiliac lymph node. The photoacoustic results revealed that the AuNRs' shapes are still stable regardless of their heterogeneous distributions inside the mammalian
tumor and lymph nodes. Bioluminescence imaging was used to monitor
metastasis using
luciferin labeling techniques and has shown that AuNRs-PPTT inhibited
metastasis completely within the first 21 days. Moreover, proteomics was run to determine the most pivotal inhibitory pathways: NETosis, cell growth, cell proliferation,
inflammation, and extracellular matrix (ECM) degradation. These five mechanisms are interdependent within related networks, which synergistically explains the molecular mechanism of
metastasis inhibition by AuNRs-PPTT. The current in vivo data ensures the viability of PPTT applications in inhibiting
metastasis in humans.