The Magnetic-PCR project propose a brand-new and ultrasensitive methodology for detection and classification of breast cancer subtypes based on detection of specific genes expression. For this, the project develops a new “magnetic relaxation switch” (MRSw) biosensor based on superparamagnetic nanoparticles to improve the sensitivity of the Polymerase Chain Reaction (PCR) for detecting nucleic acids. Relaxometry and Magnetic Resonance Imaging (MRI) will be used to sensing DNA or RNA biomolecules. The ultimate goal is to achive direct application of a MRSw sensor for detection and classification of breast cancer malignancy by magnetic resonance (MR).