Innovative fluorescent nanocomposite eutectogels: Design and characterization towards biosensing applications

• Polymer conjugated NPs in deep eutectic solvent retain their fluorescent properties. • Fluorescent nanocomposite eutectogels with different emissions have been obtained. • Fluorescent eutectogels are stable to temperature and storage time. • Enzymes incorporated in fluorescent eutectogels mantain their activity. • Fluorescent eutectozymes can operate as catalytic and biosensing devices. Recent advancements in materials science have led to the creation of innovative gel formulations like eutectogels, which exploit the distinctive characteristics of deep eutectic solvents (DES) to enhance the functionality and versatility of traditional gel systems. By incorporating fluorescent nanoparticles, eutectogels gain luminescent properties, significantly increasing their performance. In this study, we have developed and characterized a novel nanocomposite eutectogel by integrating conjugated polymer-based nanoparticles (CPNs) with varying emission bands, derived from either polyfluorene or poly(phenylenevinylene). Before synthesizing the fluorescent eutectogels, it was confirmed that the nanoparticles maintained the same fluorescent properties in both DES and aqueous solution. The results show that the incorporation of CPNs inside the eutectogels provides fluorescent materials with good properties in terms of integrity, thermal stability, homogeneity and reproducibility allowing their preservation during weeks. The fluorescent nanocomposite eutectogels were tested as sensing platforms by immobilizing enzymes. In particular, the capability of these materials to act as fluorescent biosensors for detecting hydrolase activity was successfully demonstrated, with alkaline phosphatase entrapped in the nanocomposite eutectogel serving as the model enzyme. This finding is one of the first demonstrations of the functioning of an enzyme in an eutectogel.