Repurposing Personal Glucose Monitor for Quantitative Target Measurement in Cell-Free Systems

Cell-Free diagnostic tools are becoming more commonly utilized for micronutrient detection in minimal resource regions. However, these diagnostic tests produce colorimetric readouts requiring the creation of standardized tests for comparison, development of picture software or are vulnerable to human interpretation. To overcome this, we have transformed this colorimetric output into a defined quantitative readout with the help of a personal glucose monitor. Moreover, because of the need for diabetics to monitor their glucose levels daily, personal glucose monitors have been developed to be affordable, ubiquitous, and user-friendly. Our new approach uses the same reaction set up as a typical colorimetric cell free reaction: a transcription factor ZntR activated in the presence of zinc, which in turn activates the production of LacZ. However, instead of having LacZ cleave a substrate to change its color, LacZ now cleaves a stable sugar molecule, lactose, and produces glucose, a molecule that is quantified and easily read using a personal glucose monitor. With this approach, we have shown a dose-dependent readout on the glucose monitor to clinically relevant concentrations of zinc within a water and human serum matrix. Ensuring deploy-ability in low resource regions, we demonstrated the zinc dependence readout remains post lyophilization and rehydration. Taken together, we showed combining cell-free systems with glucose monitor interpretation creates a versatile platform for quantitative measurement of small molecules and can be extremely beneficial to nutritional surveillance programs as well as at home monitoring.