Evaluation of novel Fmoc-tripeptide based hydrogels as immobilization supports for electrochemical biosensors

The immobilization procedure is one of the key factors affecting the electron transfer based biosensors performance. It must assure both the enzyme retention activity and an efficient communication between the redox center of the enzyme and the electrode surface. In this regard, hydrogels are attractive materials due to their three-dimensional hydrophilic networks and their high-water concentration, promoting the biomolecule long-term stability and providing a suitable scaffold for trapping. To this aim, we have synthesized a gelling tripeptide Fluorenylmethyloxycarbonyl-triphenylalanine (FmocPhe3) produced starting from Fmoc-phenylalanine and diphenylalanine by the catalytic activity of Lipase in water and characterized its performance as a new immobilization support for biosensors. For this purpose, we have evaluated the main bioelectrochemical properties of Trametes versicolor Laccase (TvL) immobilized within the hydrogel and a hydrogel-nanocomposite structure in the presence of gold nanoparticles (AuNPs). Either the Fmoc and the benzyl rings inside the tripeptide structure contributed to the hydrogel network formation by π-π stacking interactions, which promoted the physical entrapment of Laccase as well as the interaction with the carbon-based electrode surface. Furthermore, the π-electrons flow throughout the tripeptide based hydrogel allowed a good electron transfer between the immobilized enzyme and the electrode. The obtained results showed a significative increase in the hydrogel nanocomposite-based graphite biosensor performance with respect to those obtained with the hydrogel-based graphite biosensor. The experimental results, in terms of analytical performance and costs, assessed the possible use of FmocPhe3 based hydrogels in the development of electrochemical biosensors. © 2017 Elsevier B.V.