In less than a minute, a miniature device can measure a patient's blood for methotrexate, a commonly used but potentially toxic cancer drug. 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.
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.
Until now, monitoring has been done in hospitals with a device using fluorescent bioassays 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.
Six years ago, the researchers 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. In the course of their research, they developed and manufactured a miniaturized 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.
In addition to producing results in real time, the device is small and portable and requires little manipulation of samples.