# Ru(terpy)-Based Conducting Polymer in Electrochemical Biosensing of Epinephrine
## 4 Conclusions  
In this study, the behavior of a Ru(II)-based conducting polymer in the development of two amperometric biosensors for epinephrine was investigated. A Ru(II) complex coordinated by two different terrpyridine (terpy) ligands was used as polymerizable specie. The first termy was functionalized by a terthiophene unit and was able to polymerize on a proper electrode surface, whereas the second termy ligand bore a \(-\)COOH functionalization in the _para_ position in each nitrogen ring. The anchoring of the enzyme was achieved by cross-linking with glutaraldehyde. A CP film was obtained either on a gold or on a glassy carbon electrode, and tyrosinase was immobilized on the modified electrode. The comparison, in terms of the limit of detection, the limit of quantification, the linear range, \begin{table}
\begin{tabular}{c c c c} \hline
**EP in Samples** & **EP Found** & & \\
**(umol dm\({}^{-3}\))** & **(umol dm\({}^{-3}\))** & **RSD\%** & **Recovery \%** \\ \hline
25.0 & 26.1 & 2.84 & 104.4 \\
100.0 & 89.4 & 1.59 & 89.4 \\ \hline \end{tabular}
\end{table} 
Table 4: Recovery tests results for GC/RuTt/Tyr. Figure 7: Effect of AA, UA, Trp, and L-cys in a 10 μmol dm\({}^{-3}\) EP solution at EP:interferent ratios = 1:1 (a), 1:5 (b), 1:10 (c) in 0.1 mol dm\({}^{-3}\) phosphate buffer at the GC/pRuTt/Tyr biosensor. and sensitivity, between the Au- and the GC-based biosensors showed more satisfactory analytical performances for the Au-based one. Furthermore, the Au/pRuTt/Tyr biosensor showed a good affinity towards epinephrine. On the other hand, the GC/pRuTt/Tyr biosensor seemed to be less affected by the presence of some typical interfering substances than Au/pRuTt/Tyr, even at a EP/interfering ratio lower than 1. Because of the features reported herein, the [Ru(terpy)2]2+ unit can be considered a potential tool as a central component in the development of amperometric biosensors for pharmaceutical formulations, acting as an efficient transducer as well as an immobilizing agent for enzymatic receptors. The following are available online at [[https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)]([https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)) 7/11/5/2065/s1, Figure S1: CV characterization in CH3 CN/0.1 mol dm\({}^{-3}\) TEAPF6 solvent system of a pRuTt film grown by scanning the potential in the range 0 \(\div\) 1.3 V on a gold disk electrode. The two anodic peaks at 0.98 V and 1.2 V are ascribable to the polaron and bipolaron form, respectively, according to ref. [14], Figure S2: CV responses in absence (blue line) and presence (red line) of EP (500 nM) at Au/pRuTt electrode (on the left), and at Au/pRuTt/Tyr sensor (on the right), Figure S3: DPV responses of EP between 1 and 100 umol dm\({}^{-3}\) in 0.1 M phosphate buffer (pH 7.0) at Au/pRuT sensor; Figure S4: DPV curves of solutions containing EP:AA 1:10 (top left), EP:UA 1:10 (top right), EP:Trp 1:10 (bottom left) in 0.1 mol dm\({}^{-3}\) phosphate buffer at Au/pRuTt/Tyr biosensor. Concentration of interfering analytes as in Figure 5.  
Conceptualization, F.M. and M.I.P. ; methodology, M.I.P. and A.Z. ; validation, M.I.P. and A.Z. ; formal analysis, F.M. ; investigation, F.M. ; writing--original draft preparation, M.I.P. ; writing--review and editing, F.M., G.S., N.S., A.Z. ; supervision, M.I.P. and A.Z. ; funding acquisition, M.I.P., G.S., N.S., A.Z. All authors have read and agreed to the published version of the manuscript. This research was funded by Universita degli Studi di Sassari (\"Fondo di Ateneo per la ricerca 2019\"). Not applicable. The data presented in this study are available in [[https://www.mdpi.com/2076-3417/11/5/2065/s1](https://www.mdpi.com/2076-3417/11/5/2065/s1)]([https://www.mdpi.com/2076-3417/11/5/2065/s1](https://www.mdpi.com/2076-3417/11/5/2065/s1)). Authors gratefully acknowledge Universita degli Studi di Sassari for financial support (\"Fondo di Ateneo per la ricerca 2019\"). The authors declare no conflict of interest.