ACS Nano http://doi.org/2bn (2015)

Sci. Transl. Med. 7, 273re1 (2015)

The camera, data processing and communication components in smartphones are increasingly being adapted for health applications. Friendly user interfaces, portability and decreasing prices mean that they can be a useful part of point-of-care devices for resource-limited places. Two independent research teams have now developed attachments for smartphones that allow expensive laboratory diagnostic tests to be done in minutes and at affordable cost.

Warren Chan and colleagues at the University of Toronto combined batteries, laser diodes, lenses, filters and an assay chip in a plastic chassis, which could be mounted on the front a smartphone camera. The assay consists of wells loaded with different quantum dot barcodes — polystyrene microbeads infused with quantum dots and functionalized with a capture DNA sequence that binds target analytes. Detection occurs through a typical sandwich assay using a secondary fluorescently labelled probe. Using a custom-made algorithm, the optical emission of the barcodes and probe captured by the camera can be interpreted as a positive or negative presence of an analyte. The device could detect more than one type of infectious disease biomarker in a single test in less than an hour.

Samuel Sia and colleagues — at Columbia University and Rwanda Biomedical Centre — developed a similar, but more streamlined, smartphone attachment for diagnosing syphilis in Rwanda. The attachment contained gold nanoparticles, silver ions and other components similar to a laboratory-based enzyme-linked immunosorbent assay (ELISA). It was designed to be manually activated to reduce battery consumption and to accept blood specimens from a fingerprick. When deployed to health centres in Rwanda, the device produced diagnostic results in 15 minutes with sensitivities close to 100% and specificity between 79 to 100%, rivalling laboratory screening tests for syphilis.