Our system uses a 2007 Nobel Prize winning physical phenomenon called “giant magnetoresistance” (GMR), in which the electrical resistance of a (magnet / normal metal / magnet) thin film multi-layer changes in response to an applied magnetic field.


Figure 1: A) Schematic of specific bonds provided by antibody / antigen pairs. The magnetic nanoparticle remains bound only if other bonds are already in place. B) MNP generates a magnetic stray field onto the GMR sensor. C) Signal derived from modified resistance versus applied magnetic field.

Zepto biosensors actually sense magnetic nanoparticles (MNPs) that are attached to the surface by biospecific bonds (Fig. 1A)  [1]. The MNPs (and bio-molecules as a consequence) are quantified by the observed change in resistance versus applied magnetic field (Fig. 1B-C). This scheme leads to several key features that set the technology apart from other competing technologies. The most important feature is called “matrix insensitivity:” Since biological samples of interest contain negligible amounts of magnetic material, they do not interfere with the magnetic fields which produce the sensor signal. This is in contrast to light-based systems, because many components of biological samples may interfere with light. Matrix insensitivity also implies low limit of detection since the background signal is negligible. Therefore, the GMR biosensor system is well-suited for low concentration detections below the noise threshold of other systems [2].

In addition to matrix insensitivity, the GMR biosensor also provides simple integrated electrical readout which facilitates fast, reliable, low cost and portable systems capable of multiplexed (several simultaneous tests) biological detection. Multiplex detection reduces both false-positive and false-negative results in cases where a particular disease is correlated to several biomolecule concentrations instead of just one.

GMR biosensor systems provide a general platform for many conceivable applications. The biological assay only needs to provide specific binding between biological components of interest. Examples include, but are not limited to, antigen / antibody pairs and complimentary DNA fragments. The specifically bound biological molecules serve as a bridge between the GMR sensor and magnetic nanoparticles (MNPs). This structure utilizes more than 100 years of combined research and development from both the biomolecular and data storage industries. Our goal at Zepto Life is to use this technology to provide a new and more proactive approach to medical diagnostics.



W Wang et al., “Surface Modification for Protein and DNA Immobilization onto GMR Biosensor,” IEEE Transactions on Magnetics, vol. 49, no. 1, 2013.


Y Li et al., “Nanomagnetic Competition Assay for Low-Adundance Protein Biomarker Quantification in Unprocessed Human Sera,” Journal of American Chemical Society, no. 132, pp. 4388-4392, 2010.