Gulcin Bolat

Peptide nanoparticles (PNPs) modified disposable platform for sensitive electrochemical cytosensing of DLD-1 cancer cells

A novel diphenylalaninamid (FFA) based peptide nanoparticles (PNPs) modified pencil graphite electrodes (PGEs) for construction of electrochemical cytosensor was demonstrated for the first time in this study. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed the spherical nanostructure of the synthesized FFA based PNPs while attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectra provided information about the structure and conformation of proteins in their structure. Self-assembly of PNPs on PGE surface and adhesion of DLD-1 cancer cells on this surface was also characterized by electrochemical measurements. PNP/PGEs acted as a sensitive platform for simple and rapid quantification of low concentration of DLD-1 cancer cells in early diagnosis using the electrochemical impedance method (EIS). The offered cytosensor demonstrated outstanding performance for the detection of DLD-1 cells by the EIS method. The impedance of electronic transduction was associated with the amount of the immobilized cells ranging from 2 × 102 to 2.0 × 105 cellsmL-1 with a limit of detection of 100 cellsmL-1. The efficient performance of the cytosensor was attributed to the well-defined nanostructure and biocompability of PNPs on the substrate.

Electrochemical behavior and voltammetric detection of fenitrothion based on a pencil graphite electrode modified with reduced graphene oxide (RGO)/poly(E)-1-(4-((4-(phenylamino)phenyl)diazenyl)phenyl)ethanone (DPA) composite film

A combination of a novel synthesized azo dye (E)-1-(4-((4-(phenylamino)phenyl)diazenyl) phenyl)ethanone and reduced graphene oxide was used to electrochemically modify the surface of a pencil graphite electrode. The surfaces of the modified electrodes were characterized using electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) and spectroscopic techniques (scanning electron microscopy and attenuated total reflectance). This azo dye/reduced graphene oxide modified electrode was applied first time for the electrochemical detection of an organophosphorus pesticide, fenitrothion. The modified pencil graphite electrode displayed excellent performance for the detection of fenitrothion. Cyclic voltammetry was used to study the dependence of the scan rate on the peak current and peak potential and to determine the kinetic parameters for fenitrothion. Square wave voltammetry was used to determine the effect of pH on the peak potential and for the sensitive and selective detection of fenitrothion using the modified electrode. Satisfactory results were obtained with the proposed sensor for the analysis of FT in tomato samples.

Fabrication of a Polyaniline Ultramicroelectrode via a Self Assembled Monolayer Modified Gold Electrode

Herein, we report a simple and inexpensive way for the fabrication of an ultramicroelectrode and present its characterization by electrochemical techniques. The fabrication of polyaniline UME involves only two steps: modification of a gold (Au) electrode by self assembled monolayers (SAM) and then electrodeposition of polyaniline film on this thiol-coated Au electrode by using cyclic voltammetry and constant potential electrolysis methods. Two types of self-assembled monolayers (4-mercapto-1-butanol, MB, and 11-mercaptoundecanoic acid, MUA) were used, respectively, to see the effect of chain length on microelectrode formation. Microelectrode fabrication and utility of the surface was investigated by cyclic voltammetric measurements in a redox probe. The thus prepared polyaniline microelectrode was then used for DNA immobilization. Discrimination between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) was obtained with enhanced electrochemical signals compared to a polyaniline-coated Au electrode. Different modifications on the electrode surfaces were examined using scanning electron microscopy (SEM).

Non-Enzymatic Electrochemical Sensing of Malathion Pesticide in Tomato and Apple Samples Based on Gold Nanoparticles-Chitosan-Ionic Liquid Hybrid Nanocomposite

Malathion (MLT) is an organophosphorous type pesticide and having seriously high toxicity and electrochemical platforms for rapid, simple, inexpensive and sensitive determination of pesticides is still a special concern. This paper describes a simple preparation of a composite film consisting of ionic liquid (IL), chitosan (CS) and electrochemically synthesized gold nanoparticles (AuNPs) on single use pencil graphite electrodes (PGEs). The microscopic and electrochemical characterization of AuNP-CS-IL/PGE was studied using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. This fabricated surface was then explored for the first time as a sensing matrix for the non-enzymatic electrochemical sensing of malathion by cyclic voltammetry and square wave voltammetry measurements. The proposed AuNP-CS-IL/PGE showed excellent characteristics and possessed remarkable affinity for malathion. The voltammetric current response exhibited two linear dynamic ranges, 0.89–5.94 nM and 5.94–44.6 nM reflecting two binding sites, with a detection limit of 0.68 nM. The method was applied in real sample analysis of apple and tomato. The results demonstrate the feasibility of AuNP-CS-IL-modified electrodes for simple, fast, ultrasensitive and inexpensive detection of MLT.

Preparation of gold nanoparticles/single-walled carbon nanotubes/polyaniline composite-coated electrode developed for DNA detection

This work details the preparation of gold nanoparticles/single-walled carbon nanotubes/polyaniline composite-modified disposable pencil graphite electrode (AuNPs/SWCNTs/PANI/PGEs), and its application for electrochemical DNA sensing. Disposable pencil graphite electrode was modified with single-walled carbon nanotubes/polyaniline composite via one-step electropolymerization of aniline solution containing well-dispersed single-walled carbon nanotubes. AuNPs were then immobilized onto the SWCNTs/PANI/PGE. Electrochemical results exhibited improved sensitivity for DNA detection with AuNPs/SWCNTs/PANI/PGE compared to the SWCNTs/PANI/PGE, PANI/PGE or unmodified PGE due to the strong interaction between AuNPs, SWCNTs, and PANI based on the effective degree of electron delocalization. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the prepared electrode. Thiol-linked ssDNA was immobilized onto the AuNPs/SWCNTs/PANI/PGE for DNA detection. Experimental parameters such as the concentration of AuNPs and ssDNA were investigated to optimize the experimental conditions.