Impedimetric sensor for toxigenic Penicillium sclerotigenum detection in yam based on magnetite-poly(allylamine hydrochloride) composite.

We describe a new DNA biosensor for the detection of toxigenic Penicillium sclerotigenum in pure culture or infected yams. The P. sclerotigenum detection takes place on a self-assembled monolayer of a (magnetite)/(poly(allylamine hydrochloride)) (Fe3O4-PAH) composite that serves as an anchoring layer for the DNA hybridization interaction. Electrical impedance spectroscopy (EIS) was used to evaluate and quantify the hybridization degree. The Fe3O4-PAH composite is a good platform for the immobilization of biomolecules, due to the presence of many possible binding sites for nucleotides and to its large surface-to-volume ratio and good biocompatibility. The biosensor was capable of not only qualitatively detecting the presence of the fungus genome at low concentrations, but also shown a good quantitative impedimetric response its electrical resistance was monitored along the time of exposure. A Fe3O4-PAH-probe biosensor would require only small volumes and low concentrations of the analyte when used, for instance, in detecting P. sclerotigenum contamination of food, besides presenting many comparative advantages, such as selectivity, specificity and reproducibility, relative to alternative techniques.

An impedimetric biosensor for detection of dengue serotype at picomolar concentration based on gold nanoparticles-polyaniline hybrid composites.

In this work, we describe the preparation and characterization of a novel gold nanoparticles-polyaniline hybrid composite (AuNpPANI) with SH-terminal groups that, due to its ability of immobilizing dengue serotype-specific primers 1, 2 and 3 (ST1, ST2 and ST3), can be used for the development of biosensors. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were performed. CV and EIS results demonstrated that the AuNpPANI can immobilize ST1, ST2 and ST3, forming AuNpPANI-ST complexes. Well-defined cyclic voltammograms characteristic of a diffusion-limited redox process were observed both for the bare gold electrode and after these electrodes have been modified by the adsorption of AuNpPANI or AuNpPANI-ST. The AuNpPANI-ST(1-3) systems were able to recognize the dengue serotype of different patients at picomolar concentrations. Even when small volumes and low concentrations of the analyte were used, the CV and EIS results showed unequivocal evidence of an existing interaction between dengue serotype-specific primers and their complementary genomic DNA targets.