Prof. Vasco Bonifácio (DBE, IBB) and collaborators from NOVA University of Lisbon developed an isoleucine (IsoLEU) sensor using molecularly printed polymers and a photocromic dye. The synthesis of this smart material was performed using a sustainable protocol, without using organic solvents. Sensor's affinity and selectivity were tested using L-leucine (LEU) and IsoLEU mixtures in aqueous solution. The sensor with higher crosslinker degree exhibited the highest affinity and selectivity, with a maximum binding capacity of 127 mg IsoLEU/g polymer. The sensor is activated by UV light, with color change between white and bluish purple, allowing real-time detection, and color reversal by exposure to visible light. This study demonstrates the potential of these materials as low -cost optical sensors for bioprocess monitoring. See more.