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Imaging Technique Enables Complete Tumor Elimination

Gold nanoparticles allow for the precise detection and eradication of residual microtumors that remain after standard surgery.

By
Janelle Weaver, Contributor
Monday, September 10, 2018

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A significant challenge in cancer surgery is the inability to intraoperatively diagnose and eliminate microscopic residual tumors, which can cause lethal recurrence and metastasis. Surface-enhanced Raman scattering (SERS)-based imaging has the potential to achieve intraoperative microtumor detection with higher specificity and sensitivity, compared to other imaging techniques such as MRI, fluorescence, PET and ultrasound.

Raman imaging relies on the scattering of photons by "Raman reporter" molecules that are excited to higher energy levels. A study published Aug. 28 in the journal ACS Nano explored a Raman imaging strategy using gap-enhanced Raman tags (GERTs) for intraoperative real-time diagnostics and eradication of residual microtumors. GERTs are made of gold core-shell structures with a nanometer-sized interior gap and a porous silica layer coating the surface, with Raman reporters embedded inside the interior gap junction.

The researchers intravenously injected GERTs into mice with prostate tumors before surgery, allowing time for the GERTs to passively accumulate inside tumor tissues due to the enhanced permeability and retention effect -- a phenomenon related to the unique vascular properties of solid tumors. After removing the observable primary bulk tumor based on visual inspection, they used a low-energy laser to elicit the Raman signals of GERTs for localizing residual microtumors. Subsequently, the residual tumors detected by Raman imaging were irradiated using a high-power laser that heated up the GERTs.

This approach enabled the precise detection of microscopic tumor deposits in real time and resulted in complete tumor elimination without any regrowth during the 16-day observation. After 39 days, all mice treated with the GERT method achieved complete tumor-free survival. By contrast, all mice treated with standard surgery alone experienced tumor relapse and metastasis, eventually succumbing to disease. According to the authors, using GERTs for the precise detection and removal of residual microtumors may broaden the biomedical applications of Raman-based imaging.

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