Development of a Novel Biosensor Using Cationic Antimicrobial Peptide and Nickel Phthalocyanine Ultrathin Films for Electrochemical Detection of Dopamine

The antimicrobial peptide dermaseptin 01 (DS 01), from the skin secretion of Phyllomedusa hypochondrialis frogs, was immobilized in nanostructured layered films in conjunction with nickel tetrasulfonated phthalocyanines (NiTsPc), widely used in electronic devices, using layer-by-layer technique. The films were used as a biosensor to detect the presence of dopamine (DA), a neurotransmitter associated with diseases such as Alzheimer's and Parkinson's, with detection limits in the order of 10？6？mol？L？1. The use of DS 01 in LbL film generated selectivity in the detection of DA despite the presence of ascorbic acid found in biological fluids. This work is the first to report that the antimicrobial peptide and NiTsPc LbL film exhibits electroanalytical activity to DA oxidation. The selectivity in the detection of DA is a fundamental aspect for the development of electrochemical sensors with potential applications in the biomedical and pharmaceutical industries. 1. Introduction Nanomaterials are causing a great impact on electrochemical biosensors development. Nanotechnology brings new possibilities for biosensors construction and for developing novel electrochemical bioassays [1]. Due to the increased use of organic molecules, the LbL technique has been widely employed in manufacturing ultrathin films with potential application as biosensors [2–6]. The ultrathin films’ technique has many advantages, since it allows the construction of structures that present different chemical properties than those encountered in the originating materials [4–6]. A key feature for LbL films, in particular, is the incorporation of sulfonated groups to metallic phthalocyanines [7–9]. The electrodes modified with PAH/FeTsPc LbL films displayed electroactivity but were not suitable for dopamine detection. The development of voltammetric sensors for the detection of neurotransmitters, as dopamine (DA), in the extracellular fluid of the central nervous system has received much attention in the past few decades due to role in Parkinson disease [10, 11]. The electrochemical methods have advantages over others because they allow the detection of neurotransmitters in living organisms [12]. However, the coexistence of ascorbic acid (AA) with a concentration of 100–1000 times higher than that of DA greatly challenges the electrochemical strategy for DA detection. It was observed that AA could be easily oxidized at a potential close to the DA and the species formed could lead to oxidation of AA, as well as the reaction sites on the electrode surface could be easily blocked by the product