In vivo magnetic nanoparticle cytometer for stem cells in small animals

Parkinson's Disease (PD) is a degenerative disorder that causes the malfunction and death of neurons in the substantia nigra and afflicts hundreds of thousands of Americans. There is no known cure for PD. However, stem cell transplant therapy holds promise for reversing the effects of PD. Preclinically, the mouse model of stem cell therapy for PD is used to assess stem cell viability and analyze neuron regeneration in the substantia nigra. However, tracking stem cell viability in these experiments remains difficult at best because conventional imaging methods may inaccurately quantify stem cell number in vivo due to penetration depth or other effects. Here, we propose a new magnetic nanoparticle cytometer for small animals to quantify cells implanted in vivo labeled with superparamagnetic iron oxide (SPIO) nanoparticles. This cytometer, which uses MPI principles, is well-suited for determining stem cell viability as it provides linear signals for accurate quantification of cell number in vivo without suffering from depth or tissue attenuation or relying on ionizing radiation or radioactive materials with short half-lives.