Thermodynamic Behaviour and Sensing Properties of two Carnosine-based Derivatives

L-Carnosine is a naturally occurring dipeptide, covalently bonded to β-alanine and Lhistidine moieties. It was found that it plays several physiological roles, including intracellular buffering, calcium regulation and metal ions chelation. Albeit it is widely studied for its antioxidant properties, the mechanistic pathways, in which the dipeptide is involved, are not fully understood [1]. For these purposes, a comprehensive speciation study was crucial to elucidate the complexing and sequestering ability of carnosine towards Ca2+, Mg2+, Cu2+, Mn2+, Zn2+, Hg2+, Pb2+ and Cd2+ in different ionic strength (0.1 ≤ I/ mol L-1 ≤ 1) and temperature (288.15 ≤ T/ K ≤ 310.15) conditions. On the other hand, an electrochemical study was also performed, with the aim of investigating the sensing properties of the dipeptide towards bivalent metal cations. However, because of they are not marked, a more electroactive derivative, ferrocenylcarnosine (FcCAR) (Figure 1), was synthetized. This carnosine product was electrochemically investigated in 0.1 mol L-1 KCl aqueous solution. Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) were performed on glassy carbon electrodes (GCEs). Electrochemical response was assessed by CV using 1 mmol L-1 [Fe(CN)6]3- as a redox probe in 0.1 mol L-1 KCl. Among the investigated metal cations, FcCAR shows a promising behavior in the detection of the potentially toxic Hg2+ cation. Figure 1. FcCAR To improve the electrochemical performances of the FcCAR probe, GCEs were modified, by drop casting [2], with an appropriate homogeneous dispersion of MultiWalled Carbon NanoTubes modified with amino CycloDextrins (MWCNT-CDs). Nanostructured materials, in fact, are useful as outstanding ion-to-electrode transducers in solid-contact ion-selective electrodes [3].