Manganese(III)-chelated porphyrin microbubbles for enhanced ultrasound/MR bimodal tumor imaging through ultrasound-mediated micro-to-nano conversion

Manganese(III)-chelated porphyrin microbubbles (MnP-MBs) were fabricated by self-assembly from a Mn-chelated porphyrin lipid followed by encapsulating perfluoropropane—an inert gas. The obtained MnP-MBs exhibited enhanced ultrasound imaging ability after intravenous injection. Under the guidance of ultrasound imaging, MnP-MBs could be converted into nanoparticles in situ with local tumor ultrasound disruption, achieving rapid tumor MRI contrast enhancement within 30 min at a very low Mn injection dose of 0.09 mg (1.65 μmol) per kg.