Smartphone Compass May Assist In Managing Diabetes

NISt scientist Gary Zabow says that this technology could be used to rapidly and cheaply measure a host of other biomedical properties for monitoring or diagnosing human disease, and it also holds the potential for detecting environmental toxins by using the magnetometer in conjunction with magnetic materials designed to change their shape in response to biological or environmental cues. 

For this study, cell phones with a tiny well containing the solution to be tested and a strip of hydrogel were clamped to the researchers. Tiny magnetic particles were embedded within the “smart” hydrogel which were engineered to reach to the presence of glucose or pH levels by either expanding or contracting, changing pH levels can be associated with a variety of biological disorders. 

As the hydrogel reacted they moved the magnetic particles closer or further from the cellphone magnetometer which detected the corresponding changes on the strength of the magnetic field. Using this strategy the researchers measured glucose concentrations as small as a few millionths of a mole. Although this high level of sensitivity is not required for at-home glucose testing using a drop of blood, this level of accuracy may enable future routine testing for glucose in saliva which contain smaller concentrations of the sugar, rather than using blood. 

Engineered “smart” hydrogels such as this are inexpensive and relatively easy to fabricate, according to the researchers, and they can be tailored to react to a wide range of different compounds. This study stacked two layers of different hydrogels which both responded in different manners and rates in response to glucose or pH, the bilayers amplified the motion of the hydrogels making it easier for the magnetometer to track changes in the magnetic field strength.

Additionally, this technique does not require the use of any electronics or power source other than that included in the cell phone, nor did it require any special processing of the samples, and it offers a inexpensive way to conduct testing, even in locations with relatively few resources which could prove to be beneficial for example quickly testing pH of ground water of various liquid samples on site with higher accuracy than a litmus test strip could provide. 

Next steps will include efforts to even further the accuracy of this technique so that it may allow detection of DNA strands, specific proteins, and histamines involved in immune responses at concentrations as low as a few tens of nanomoles (billionths of a mole) which could have substantial benefits. In order to make this a commercial success, they will also need to develop a method to mass produce the hydrogel test strips and ensure that they have a long shelf life. 

"An at-home test using a cellphone magnetometer sensitive to nanomolar concentrations would allow measurements to be done with much less hassle," said fellow NIST researcher Mark Ferris. More generally, enhanced sensitivity would be essential when only a small amount of a substance is available for testing in extremely dilute quantities, Zabow added.