Dramatic advancements in nanomagnetic sensor technology, driven by the needs of the magnetic data storage industry, have now brought us disk drives with magnetic read heads addressing features of less than 100nm across, at a wholesale cost of about 50¢ per Gigabyte. An extension of this magnetic recording technology can be used as the basis of extremely powerful biosensors at low cost, while opening the broad and promising field of bio-nanomagnetics. The goal of this work is to develop a nanomagnetic biosensor system capable of sensing individual biomolecule-conjugated nanoparticles less than 50 nm in diameter. Even at extremely high sensor array densities, the sensitivity of the device to low-abundance mRNAs or proteins (which includes most key regulatory elements) or pathogens will be unprecedentedly high, likely at the single-molecule level. The ability to detect and base measurements on only one or a few probe and target molecules will improve data quality by suppressing avidity effects arising from multiple interactions, and can also reveal genuine target heterogeneity not detectable by mass-averaged measurements.
Bionanomagnetic detector arrays will open a new area of nanomagnetic biosensing, and advance the study and application of molecular recognition at the few- or single-molecule level. It will allow testing of nanomagnetic interactions at extremely small scales, and in unusually well-controlled geometries, and will elucidate “design rules” for an entirely new class of devices. This research will significantly enhance the knowledge base directly related to a new kind of generally-applicable biosensor with properties so superior (single-molecule sensitivity, massive arrayability, continuous data, low cost) as to transform genomics, proteomics, and molecular diagnostics. Immediate applications include DNA probe arrays for SNP scoring, biodetection, and expression analysis, and antibody/aptamer arrays for high-resolution, high-throughput proteomics. A robust, low-cost sensor/detection platform capable of extremely sensitive detection in a large-array format would likely find very broad applications throughout biological research and biochemical technology.
Figure: (a) A sensor with a known magnetoresistance loop is functionalized with capture antibodies. (b) A magnetic nanoparticle functionalized with target antibody binds to the sensor via an antigen and the fringe field of the particle shifts the sensor’s switching field. (c)-(d) SEM micrographs of a sensor without (c) and with (d) a magnetic nanoparticle. (e) Magnetoresistance loops for the sensor in (c)-(d) without and with a magnetic nanoparticle.