An alarming side effect of many medications is liver damage, which if unchecked, can cause death. Monitoring liver damage is a challenge in developing regions without access to clinical tools and skilled personnel. Now researchers have created a cheap device that quickly and easily measures a patient’s liver health without a hospital’s laboratory tools (Anal. Chem., DOI: 10.1021/ac203434x).
Researchers have been developing clinical diagnostics on paper devices for at least five years but none of the devices have been tested outside laboratory settings. Now chemist George Whitesides, with colleagues at Harvard University and Diagnostics For All, a nonprofit organization he helped to found, have designed a device that is close to ready for manufacturing for field tests.
The investigators’ postage-stamp-sized device consists of a filter membrane on top of a piece of paper. The paper carries a wax pattern that defines three microfluidic chambers. The chambers contain color-changing reagents that indicate the levels of three proteins used to monitor liver health: serum protein, alkaline phosphatase, and aspartate aminotransferase. In cases of liver damage, levels of the two enzymes rise while the serum protein level drops. “These tests that we put on the paper are exactly the ones used in a hospital,” says Whitesides. As a result, he and his team can compare their paper device’s results with those of conventional liver analysis.
The device is simple to use: A person presses a pricked fingertip against a hole in the top of the device. The filter membrane catches the red blood cells--so that they don’t interfere with the color-changing reagents--and lets the remainder of the blood seep onto the patterned paper. Nonexperts can take note of any color changes; if calibration curves are available, clinicians can quantitatively note changes in the protein levels as a patient follows a drug regimen. Plastic sheets enclose the device to let users handle it without coming into contact with blood. Finally, the user burns the blood-soaked device to eliminate any biologically hazardous waste.
Whitesides says that his group tested the device on samples obtained from a volunteer and from a blood bank. The researchers spiked some of the samples with clinically relevant quantities of the enzymes and serum protein. The investigators found that correct answers for enzyme levels appeared within 30 minutes of the device’s receiving a blood drop. Diagnostics For All is now testing the devices using actual patients’ blood. The organization’s global health operations manager, Patrick Beattie, estimates the device will cost 10 cents or less to manufacture.
Polymer chemist Robert Pelton at McMaster University, who is also the scientific director of the Sentinel Bioactive Paper Network, a Canadian multi-organization partnership, says he can envision the device working in the field as is, without further research or development. He adds that, unlike proof-of-principle work done on other paper devices, Whitesides’ device already appears to be “a really strong prototype.”