Annexin A5-conjugated quantum dots with a paramagnetic lipidic coating for the multimodal detection of apoptotic cells.

Apoptosis, or programmed cell death, plays an important role in the etiology of a variety of diseases, including cancer. Visualization of apoptosis would allow both early detection of therapy efficiency and evaluation of disease progression. To that aim we developed a novel annexin A5-conjugated bimodal nanoparticle. The nanoparticle is composed of a quantum dot that is encapsulated in a paramagnetic micelle to enable its use both for optical imaging and MRI. Multiple recombinant human annexin A5 protein molecules were covalently coupled to the nanoparticle for targeting. In this study the specificity of the annexin A5-conjugated nanoparticles for apoptotic cells was demonstrated both with fluorescence microscopy and MRI, which confirms its potential for the detection of apoptosis with both imaging modalities in vivo.