Medical Device Link.

Originally Published IVD Technology November/December 2004

INDUSTRY NEWS

In bio–bar code testing, nanoparticle probes bind to genomic or proteomic targets. The probes then release bar code DNA, which reports the presence of the target.

Personalized medicine may soon be practiced in the doctor’s office, according to Chad Mirkin, PhD. The head of Northwestern University’s Institute for Nanotechnology (Evanston, IL), Mirkin has developed an assay that he believes will revolutionize point-of-care (POC) medicine.
The assay is run via a technique called “bio–bar code” testing. This technology uses magnetic microparticles and gold nanoparticles as probes in a signal amplification procedure that relies on bar code DNA to communicate the presence of a target.

Mirkin says bio–bar code technology could move the capabilities for multiplexed molecular testing from the central lab into the hospitals, into the doctors’ offices, onto the battlefield, and ultimately into the home.

Thus far, IVD industry analysts are impressed with the technology.

“This technology is pretty neat stuff and could very well have a place as a diagnostic product,” says Richard Schifreen, PhD, director of technology and market development at Promega Corp. (Madison, WI). According to Schifreen, the flexibility to deliver multiplexed molecular assays in a format that would be compatible for the near-patient testing market was particularly impressive.

Mirkin says the test can rival polymerase chain reaction (PCR) when it comes to sensitivity in detecting nucleic acids. Dan Kolk, PhD, a senior staff scientist at Gen-Probe Inc. (San Diego) is less convinced of this assessment. “While it is a sensitive technology, PCR and transcription-mediated amplification are still more sensitive for detecting nucleic acids,” says Kolk.

Mirkin allows that, “You can’t beat PCR in terms of sensitivity. The best you can try to do is be as good as PCR without the hassles associated with PCR.” One of the advantages offered by the new technique is the freedom from thermocycling. In addition, bio–bar code tests are less prone to contamination, are conducive to multiplexing (and could therefore be used for panels of tests), and are analyte-general.

According to Mirkin, bio– bar code tests also offer PCR-like sensitivity for proteins, certain small molecules, and metal ions. With these capabilities, bio–bar code tests could potentially be used to detect such low-level analytes as markers for Alzheimer’s disease.

“This type of testing is going to change the way we think about what types of markers will be useful markers for a particular disease. We’re not going to be limited to things at picomolar concentration or higher, which is where the ELISA-based assays rest,” he says.

Many questions need to be answered before the technology can truly be deemed viable for use in IVDs.

Studies published thus far have been performed on ideal samples. However, samples that come into the clinical lab often contain confounding substances that can affect how well the assay works.

“Until this assay is run with true clinical samples, the jury is out on how significant an impact this technology will have on the IVD industry,” says Kolk. Although the assay has demonstrated initial promise in terms of sensitivity, evidence of specificity, reproducibility, and consistency of results both between lots and between operators will be necessary before IVD manufacturers are sold.

Mirkin concedes that more work has to be done before the tests are viable for diagnostics. He intends to improve the quantitative abilities of the test. He has also established a company, Nanosphere Inc. (Northbrook, IL), that will commercialize the test for diagnostics and research, and develop the systems on which it will run.

The viability of the instrument will be key to the success of the test on the POC testing market. “Nanosphere has to prove that it can not only get the result [with the bio–bar code assays], but also do it fast enough and that the test would be economical enough for the physician to run in the office, says Schifreen.”

Although much research and development still has to be done, end-users will not have long to wait. Mirkin believes the technology will be available in a matter of years, rather than decades. If all goes well, bio–bar code assays could make their mark on the IVD industry.

Copyright ©2004 IVD Technology