Just as accurate and ten times less expensive than equipment currently used in hospitals, this nanoscale device has an optical system that can rapidly gauge the optimal dose of methotrexate a patient needs, while minimizing the drug's adverse effects, researchers said.
    
Methotrexate has been used for many years to treat certain cancers, among other diseases, because of its ability to block the enzyme dihydrofolate reductase (DHFR).
    
This enzyme is active in the synthesis of DNA precursors and thus promotes the proliferation of cancer cells.
    
"While effective, methotrexate is also highly toxic and can damage the healthy cells of patients, hence the importance of closely monitoring the drug's concentration in the serum of treated individuals to adjust the dosage," said Jean-Francois Masson from the University of Montreal's Department of Chemistry.
    
Until now, monitoring has been done in hospitals with a device using fluorescent bio assays to measure light polarization produced by a drug sample.
    
"The operation of the current device is based on a cumbersome, expensive platform that requires experienced personnel because of the many samples that need to be manipulated," said Masson, who led the study with Joelle Pelletier, also from Montreal.
    
Six years ago, Pelletier and Masson investigated how to simplify the measurement of methotrexate concentration in patients.
    
Gold nanoparticles on the surface of the receptacle change the colour of the light detected by the instrument. The detected colour reflects the exact concentration of the drug in the blood sample.
    
They developed and manufactured a miniaturised device that works by surface plasmon resonance.
    
Roughly, it measures the concentration of serum (or blood) methotrexate through gold nanoparticles on the surface of a receptacle.
    
In 'competing' with methotrexate to block the enzyme, the gold nanoparticles change the colour of the light detected by the instrument. And the colour of the light detected reflects the exact concentration of the drug in the blood sample.
    
The accuracy of the measurements taken by the new device were compared with those produced by equipment used at the Maisonneuve Rosemont Hospital in Montreal.
    
"Testing was conclusive: not only were the measurements as accurate, but our device took less than 60 seconds to produce results, compared to 30 minutes for current devices," Masson said.

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