Target Nanodiamonds as Phenotype Specific Photoacoustic Contrast Agents for Breast Cancer

AIM: The aim is to develop irradiated nanodiamonds (INDs) as a molecularly-targeted contrast agent for high resolution and phenotype-specific detection of breast cancer with photoacoustic (PA) imaging. MATERIALS & METHODS: The surface of acid treated radiation-damaged nanodiamonds was grafted with polyethylene glycol (PEG) to improve its stability and circulation time in blood, followed by conjugation to an anti-Human epidermal growth factor receptor-2 (HER2) peptide (KCCYSL) with a final nanoparticle size of ca. 92 nm. Immunocompetent mice bearing orthotopic HER2 positive or negative tumors were administered INDs and PA imaged using an 820-nm near infrared laser. RESULTS: PA images demonstrated that INDs accumulate in tumors and completely delineated the entire tumor within 10 hours. HER2 targeting significantly enhanced imaging of HER2-positive tumors. Pathological examination demonstrated INDs are non-toxic. CONCLUSIONS: PA technology is adaptable to low-cost bedside medicine, and with new contrast agents described herein, PA can achieve high resolution (sub-mm) and phenotype specific monitoring of cancer growth