Layer by Layer Films Containing Peptides of the Cry1Ab16 Toxin from Bacillus thuringiensis for Nanodevices Development

Abstract

Among thin film production techniques, layer-by-layer (LbL) self-assembly stands out because of its versatility, which has enabled applications in the fields of biomaterials, biosensors, drug/gene delivery, tissue engineering, implantable materials, diagnostics, electronics, energy, and optics [1]. Peptides are potential candidates to meet the needs of the modern world in relation to diagnosis, disease monitoring, quality control in industry, and more recently,detection of genetically modified organisms (GMOs) and food safety through the development of biosensors [2]. Cry1Ab16 is a toxin of crystalline insecticidal proteins that has beenwidely used in GMOs to gain resistance to pests. For the first time, in this study, peptides derived from the immunogenic Cry1Ab16 toxin were immobilized asLbL films. Given the concern about food and environmental safety, a peptide with immunogenic potential, PcL342-354C, was selected for characterization of its electrochemical, optical, and morphological properties. The results obtained by cyclic voltammetry (CV) showed that the peptide have an irreversible oxidation process in electrolyte of 0.1 mol L-1 potassium phosphate buffer(PBS) at pH 7.2. It was also observed that the electrochemical response of the peptide is governed mainly by charge transfer. In an attempt to maximize the electrochemical signal of peptide, it was intercalated with natural (agar,alginate and chitosan) or synthetic polymers (polyethylenimine (PEI) andPoly(sodium 4-styrenesulfonate) (PSS)). The presence of synthetic polymers on the film increased the electrochemical signal of PcL342-354C up to 100 times.Images by Atomic Force Microscopy showed that the immobilized PcL342-354Cformed self-assembled nanofibers with diameters ranging from 100 to 200 nm on the polymeric film (Fig. 1). By UV-Visible spectroscopy (UV-Vis) it was observed that the ITO/PEI/PSS/PcL342-354C film grows linearly up to the fifthlayer, there after tending to saturation. X-ray diffraction confirmed the presence on the films of crystalline ITO and amorphous polypeptide phases. In general, the ITO/PEI/PSS/PcL342-354C film characterization proved that this system is an excellent candidate for applications in electrochemical sensors and other biotechnological applications for GMOs and environmental indicators.