Enhanced biosensing by green, switchable photochromic molecularly imprinted polymers

Photochromic Molecularly Imprinted Polymers (PC–MIPs) synthesized using supercritical carbon dioxide (scCO 2 ) represent a key approach to produce green stimuli–responsive polymers. In this work, methacryloyloxyethyl)–3’,3’–dimethyl–6–nitrospiro(2H–1benzopyran–2,2’–indoline (SPMA) was incorporated as the functional photochromic monomer (M), L–isoleucine (IsoLEU) as the template (T) molecule, and ethylene glycol dimethacrylate (EGDMA) as the crosslinker (C). Two different PC–MIP systems were explored by changing the crosslinker degree, T:M:C (1:12:50 and 1:12:100). Moreover, enantiomeric separation was evaluated by static binding tests using L–leucine (LEU) and IsoLEU from aqueous solutions. The PC–MIP with high crosslinker degree (PC–MIP1) exhibited the highest affinity and selectivity in template solutions, with a maximum binding capacity of 127 mg IsoLEU/g polymer and an imprinting factor of 1.6. The experiments performed under UV–light (365 nm), both PC–MIPs (PC–MIP1 and PC–MIP2), ranged from white to bluish purple, with reversible color changes upon exposure to visible light. Additionally, both PC–MIPs demonstrated delayed optical responses upon incorporation of the target molecule into the polymeric matrix, enabling real–time detection. This study underscores the potential of PC–MIPs as green and cost–effective optical sensors for bioprocess monitoring, offering high sensitivity and selectivity for IsoLEU detection in aqueous media. • PC–MIPs were developed for the first time using scCO 2 technology. • PC–MIPs display affinity and selectivity for L–isoleucine ( Q = 127 mg IsoLEU/g). • UV–light leads to color change from white to purple, and reversible at VIS light. • Delayed optical response when IsoLEU is incorporated within the polymeric matrix. • PC–MIPs are green, cheap and tailor–made alternative optical sensors.