Bio-Inspired Proline Sensors for the Diagnosis and Surveillance of Stress in Living Systems

From decorative houseplants to the crops that feed the world, plants are subjected to various environmental stresses over their lifetimes. Factors like changes in climate, pollution, and disease threaten plant health, requiring time-sensitive interventions to prevent widespread crop losses. We present a bioinspired colorimetric sensing strategy for measuring proline, a biomarker of stress in plants, by leveraging the condensation reaction between sinapaldehyde and proline to form a natural red pigment called nesocodin. We prepared paper-based sensors embedded with sinapaldehyde that supported nesocodin synthesis when we introduced the proline analyte. Signals range from pale yellow, indicative of unreacted sinapaldehyde, to deep red, indicative of proline-dependent formation of nesocodin. These sensors can quantitatively differentiate between 0 and 15 mM proline, which sufficiently measured relative increases in proline concentrations of plants exposed to controlled stresses. This approach highlights the opportunity to design field-deployable, user-friendly tools for agricultural monitoring, improved farming efficiency, and strengthened food security.