(163d) Detecting Iron in Capillary Blood at the Point of Care with Colorimetric Sensing

Iron deficiency, a leading cause of anemia, is one of the globe’s top nutritional disorders according to the World Health Organization. Hemochromatosis, on the other hand, is associated to excess iron, and is usually diagnosed late in the stages of irreversible organ damage. Blood iron levels are a glimpse into an individual's genetic regulation of nutritionally available iron combined to the natural recycling of heme iron. Since abnormally low or high blood iron levels are common worldwide, standard-of-care metrics for diagnosis of iron-related problems, an ubiquous and more easily available measurement of blood iron could lead to a dramatic change toward proper early prevention of diseases and health maintenance throughout the life span. Here, we introduce a smartphone-based colorimetric detection system for iron quantification in human serum. The system is designed for point-of-care screening and monitoring, as well as low-cost and yet accurate rapid time-to-results assessment. We present a dry sensor strip with an optimized sensor chemistry in which iron ions are stripped from the blood transport proteins, reduced from Fe(III) to Fe(II), and subsequently chelated with ferene, developing a visible color change for smartphone detection of total iron. We compare the common laboratory iron detection assay of human serum to that of our 3-D printed sensors. The prototype smartphone assay was sensitive to iron detection with reasonable measurement variability, giving linear slopes of 0.00047 a.u/μg/dL versus the standard lab approach of 0.00091 a.u/μg/dL and coefficients of variation of 10.5% versus 2.2% respectively, in concentrations between 50 – 300 μg/dL. Further, a detection limit near 15 μg/dL provided by the smartphone system indicated the system’s potential capability for detection of iron deficiencies. Finally, drawn human venous blood sample processed for serum, and measured for total iron were simultaneously sent to a commercial testing facility (LabCorp) and processed by the smartphone system, averaging errors of less than 3% around the true value of 231 μg/dL. This mobile-app based colorimetric assay is comparable to the standard spectrophotometric method, and provides promising features of mobility and low-cost manufacturing.