Handheld device for cancer adapted to detect biothreats

A point-of-care device used by Massachusetts General Hospital investigators used to diagnose cancer was recently adapted to rapidly diagnose biothreats like E. coli and other pathogens like tuberculosis.

The portable devices combine nuclear magnetic resonance and microfluidic technology to both diagnose infections and determine the presence of antibiotic-resistant strains of bacteria. MGH researchers published their findings in Nature Nanotechnology and Nature Communications.

"Rapidly identifying the pathogen responsible for an infection and testing for the presence of resistance are critical not only for diagnosis but also for deciding which antibiotics to give a patient," Ralph Weissleder, the co-senior author of both papers, said. "These described methods allow us to do this in two to three hours, a vast improvement over standard culturing practice, which can take as much as two weeks to provide a diagnosis."

The system detects DNA from a particular strain of bacteria in small sputum samples. Scientists extract DNA from the sample and amplify any strains of the target sequence using a standard procedure. The device uses polymer beads with complementary nucleic acid sequences labeled with magnetic nanoparticles with sequences that bind to parts of the target DNA. The miniature NMR coil detects any of the target bacteria DNA in the sample.

In the Nanotechnology study, the researchers developed a universal nucleic acid probe to detect 13 target pathogens, including E. coli, Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus.

Weissleder said the devices would be ideal for use in developing countries because they are small and easy to use.

"The magnetic interactions that pathogen detection is based on are very reliable, regardless of the quality of the sample, meaning that extensive purification - which would be difficult in resource-limited setting - is not necessary," Weissleder said. "The ability to diagnose TB in a matter of hours could allow testing and treatment decisions within the same clinic visit, which can be crucial to controlling the spread of TB in developing countries."