Multi-mode biodegradable tumour-microenvironment sensitive nanoparticles for targeted breast cancer imaging

Gas-filled ultrasound (US) contrast agents easily collapse in the body, and the gas can easily overflow, which limits the effectiveness of US imaging. To address this issue, an injectable gas-generating multi-mode system was developed that carries the MR negative contrast agent Fe3O4, the fluorescent dye Cy5.5, and the CO2 releasing donor (Na2CO3). The nanoparticles can continuously generate carbon dioxide (CO2) gas in acidic tumour tissue in the body, giving the tumour a strong echo signal under ultrasonic imaging. In addition, the nanoparticles confer excellent effects for MR and fluorescence imaging of the tumour tissue. The results indicate that this pH-responsive NP system provides good effects in MR/US/fluorescent imaging. This study provides a useful reference for multi-mode tumour imaging.