Researchers from Harvard Medical School and Harvard-MIT Health Sciences and Technology just published a paper in Lab on a Chip that describes a new technique to read ELISA results with a cell phone camera. This new ELISA readout method will bring diagnostic ability closer to the bedside. It can be employed in resource-limited settings and clinical data can be easily transferred to other physicians and specialists.
The investigators tested their readout system on an ovarian cancer biomarker HE4. A few drops of urine were loaded on a small microchip which contained polyclonal immobilized capturing antibodies. The HE4 peptide was detected using a sandwich ELISA with a horseradish peroxidase (HRP) labeled secondary antibody. Tetramethylbenzidine (TMB) is added to the chip as a reagent, and it turns blue when it is catalyzed with the paroxidase. The blue color can be measured and correlated with the HE4 concentration in the sample.
A Sony Ericson i790 cell phone with a 3.2 megapixel camera (5 years old!?) was used to image the blue color development of the ELISA. To measure the color intensities of red, green and blue pixels, a customized MATLAB algorithm was developed and integrated in a mobile app. The app can take pictures for processing, select regions for analysis, calculate a standard curve and, of course, report the HE4 concentration in the patient sample.
To validate, the samples were also tested in a microplate on a conventional sprectrophotometer. With a specificity set to 90%, a sensitivity of 89.5% was achieved. These results seem comparable to conventional microplate ELISA. The cell phone-based test, which can be performed at bedside, has the potential to become a widely used method for screening several biomarkers.