MagneSensors'program is aimed at developing a rapid, ultra-sensitive magnetic assay to quantitatively detect nucleic acids without the need for PCR or other amplification. The novel sandwich hybridization assay takes advantage of an exquisitely sensitive magnetic sensor that measures the magnetic field from magnetic nanoparticle labels on nucleic acid probes hybridized to RNA targets. There are many applications in clinical diagnostics, such as the detection of pathogens causing sepsis, where amplified nucleic acid tests have struggled to gain acceptance because of drawbacks including false positives and false negatives due to contamination and other issues. Much effort has been expended on direct detection methods but the challenges in achieving high sensitivity on clinical specimens have proven formidable and limited applications. Magnetic detection offers unique advantages such as high sensitivity, specificity, speed, and simplicity, a combination that is very difficult to achieve in competing platforms. Our latest generation bench top instrument uses a high temperature superconducting quantum interference device (SQUID) that is cooled with a small cryorefrigerator and is capable of measuring 50 assay samples in a minute at very high sensitivity. The user needs not even be aware of the cooling, which has been an often-cited drawback for using SQUIDs, and the instrument is well-suited for clinical diagnostics. The Phase I aim is to demonstrate magnetic detection of ribosomal RNA (rRNA) in Staphylococcus aureus with the following benchmarks: 1) 6 x 104 copies rRNA (100 zmol), equivalent to H 20 CFU/ml S. aureus in 1 ml sample volume, 2) specificity of S. aureus vs. S. epidermidis control, 3) 45 minutes assay preparation and measurement (exclusive of RNA extraction) and 4) no separation of unbound magnetic nanoparticle labels. The assays thus take advantage of the abundance of rRNA (500-2,000 copies) in each bacterium. Another innovative aspect is the use of peptide nucleic acid (PNA) probes. These synthetic nucleic acids offer advantages of better binding, increased specificity, higher stability, reduced hybridization time, and resistance to degradation by enzymes. It is expected that the above aims would be much further improved in Phase II, enabling detection down to a single bacterium as well as specific detection of methicillin resistant Staphylococcus aureus (MRSA) in a total assay time of 30-45 minutes.
The ability to quickly and easily perform quantitative measurement of nucleic acids without amplification would open the door to a host of important applications. Development of an ultra-sensitive platform for rapid, accurate, and cost effective bacterial detection systems would revolutionize the diagnosis, prevention, and treatment of infectious diseases. These include community and hospital acquired infections such as staphylococcus resistant to antibiotics (MRSA), which are on the rise and often lead to sepsis.
