Development of an automated device and mobile application for digoxin detection and quantification from dried blood spots using gold-coated magnetic nanoprobes and the lateral-flow immunoassay.

Digoxin is a commonly prescribed drug for cardiovascular diseases, which is the leading cause of death globally, with those in resource-limited areas disproportionately affected. Unfortunately, digoxin has a narrow therapeutic window of 0.7-1.8 ng/mL and therefore requires therapeutic drug monitoring (TDM) to ensure safe and effective doses are administered. While mobile clinics increase medical accessibility in point-of-care settings, they lack specialized equipment and electricity that TDM requires. To address this lack of TDM technology, we created a fully automated and battery-powered device that executes a newly developed workflow and requires only a push of a single button. Notably, this novel method integrates the simplicity and long-term stability of dried blood spot (DBS) sampling with a custom-made lateral-flow immunoassay (LFA) to measure digoxin concentrations in blood either immediately or for a comprehensive analysis over time. For managing multiple patient samples, we developed a smartphone app that aids clinicians in scanning patient data written on DBS collection cards. Additionally, the app is able to quantify therapeutic levels of digoxin by correlating LFA test line intensity in an image to the DBS's concentration. The automated device used in conjunction with the smartphone app delivers consistent LFA results in a rapid turnaround time of 40 min for digoxin DBS concentrations between 0 and 10 ng/mL. This work integrating an innovative automated system and mobile application advances medical diagnostics as this portable and cost-effective technology enables efficient monitoring of drug levels in patient blood and is especially suitable for mobile clinic settings.