Evaluation of new cholinium-amino acids based room temperature ionic liquids (RTILs) as immobilization matrix for electrochemical biosensor development: Proof-of-concept with Trametes Versicolor laccase

In this work, we present new cholinium-amino acids room temperature ionic liquids (ChAARTILs) that can be used as an efficient immobilization matrix for electrochemical biosensor development. The ideal immobilization strategy should be able to ensure the highest enzyme loading and a tight enzymatic immobilization, preserving its native structure and biological activity. In this regard, ChAARTILs present different side chains on the amino acids giving rise to van der Waals, π-π stacking and hydrogen bonding interactions. All these interactions can affect the nanomaterial organization onto the electrode surface. To this aim, we have evaluated the main electrochemical parameters, namely electroactive area (AEA) and the heterogeneous electron transfer rate constant (k0), showing how both cations and anions of room temperature ionic liquids (RTILs) can independently affect multi-walled carbon nanotubes (MWCNTs) organization. In particular, [Ch][Phe] showed the best performance in terms of AEA (3.432 cm2) and k0 (4.71·10−3 cm s−1) with a homogeneous distribution of MWCNTs bundles onto the electrodes and a faster electron transfer rate. Finally, the modified electrode (MWCNTs-[Ch][Phe]) has been tested with a model enzyme, namely Trametes versicolor laccase (Tvl), in order to evaluate the possibility to use ChAARTILs as immobilization matrix, preventing enzymatic denaturation phenomena which would affect the biosensor performance in terms of sensitivity, linear range, and stability.