Nanocomposites for multimodal molecular imaging

Early and accurate diagnosis of tumors requires the combined adoption of different imaging modalities with molecular sensitivity. A successful employment of multimodal molecular imaging is related to the development of smart fully-biodegradable nanoparticle contrast agents (NPCAs), detectable by at least two non-ionizing imaging techniques and suitably sized for tumor targeting. After a short overview of recent findings obtained by our research group in the development and characterization of novel NPCAs, this paper shows for the first time a quantitative assessment of the effectiveness of both a pure silica NPCA and a composite silica/superparamagnetic NPCA as scatterers of low-frequency diagnostic ultrasound (3 MHz) in very low volume concentrations (0.1-0.2%). The pure silica NPCA confirmed the behavior recently reported for higher concentrations at higher frequencies. The composite NPCA followed the same behavior, showing a marked effectiveness peak for a particle diameter of 330 nm, which represents a particularly useful size for tumor targeting purposes. These results open new exciting perspectives for dual-mode molecular imaging of deep tumors, combining ultrasound and magnetic resonance techniques for the accurate, safe and early detection of cancer cells located in internal organs.