Peptide nanotube functionalized molecularly imprinted polydopamine based single-use sensor for impedimetric detection of malathion.

In the present study, a peptide nanotube functionalized polydopamine (p-Dop) based molecularly imprinted (MIP) sensor system was constructed, characterized, and studied for the impedimetric sensing of an organophosphorus pesticide, malathion (MLT). Electropolymerization in the presence of a template (MLT) was utilized as a convenient and effective strategy to generate imprinted p-Dop films on peptide nanotubes (PNTs) modified graphite electrodes (PGEs). Upon the removal of template, the adsorption of MLT on the specific cavities formed in the MIP film was tracked using electrochemical impedance spectroscopy (EIS). To attain optimal sensor response, experimental conditions, such as film thickness, analyte/functional monomer ratio, and desorption/adsorption time, were analyzed. The obtained MIP(p-Dop)-PNT-PGE sensor exhibited high sensitivity for electrochemical MLT analysis with a wide dynamic detection range of 13 pg mL-1 - 1.3 µg mL-1 and a LOD of 1.39 pg mL-1. The combination of a bio-inspired p-Dop-based MIP with the EIS technique allowed excellent sensitivity and selectivity toward MLT sensing which also yielded high recoveries in real samples. The success of this research strategy in real samples revealed its potential for various future environmental applications.

Polydopamine nanoparticles-assisted impedimetric sensor towards label-free lung cancer cell detection.

Polydopamine nanoparticles (PDA NPs), among nature-inspired building materials, show special functions for biomedical systems and exploring PDA derived nanostructures for future developments is a fast growing field. Herein, we demonstrated the first evaluation of the PDA NPs for the electrochemical determination of lung cancer cells. In the presented study, PDA NPs were synthesized in a mild and cost-effective fashion by self-polymerization of dopamine in an alkaline environment. The structural and chemical characterizations clearly demonstrated the formation of PDA NPs with controllable size (130 nm), hence applied as a suitable material to functionalize the pencil graphite electrode (PGE) surface to construct a cytosensing nanoprobe. The ability of the developed sensor (PDA NPs/PGE) for label-free electrochemical A-549 lung cancer cells detection was investigated. The designed PDA NPs based cytosensor exhibited good biocompatibility and sensitivity for impedimetric diagnosis of A-549 cells in a wide linear range (1.0 × 102-1.0 × 105 cells mL-1) with low detection limit (25 cells mL-1). Furthermore, the developed bioassay has great potential as liquid biopsy for early cancer detection.

Folic acid conjugated Prussian blue nanoparticles: Synthesis, physicochemical characterization and targeted cancer cell sensing.

In the study, folic acid doped Prussian blue nanoparticles (FA-PB NPs) for theranostic applications were synthesized for the first time. Folic acid was chosen for maintaining nanoparticle stability and also to increase its binding affinity especially for cancer cells. Multifunctional PB NPs were fabricated by one route co-precipitation method to synthesize biocompatible NPs without any further process. Then, FA was doped on the surface of PB NPs. The characterization studies demonstrated that the FA-PB NPs modified sensor surface had large surface area with biocompatible and hydrophilic properties where cancer cells can easily bind. The FA-PB NPs were used for the modification of pencil graphite electrode (PGE) for electrochemical detection of colon cancer cells (DLD-1). Electrochemical impedimetric diagnosis was based on the specific interaction between FA groups on the nanoparticles and FA receptors overexpressed on cancer cells. The voltammetric and impedimetric results showed that the FA-PB NPs based electrode had good sensing performance for the immobilized DLD-1 cells.

Electroactive polyglycine coatings for nanobiosensing applications: Label-free DNA hybridization, DNA-Antitumor agent interaction and antitumor agent determination.

Bioinspired materials have attracted great attention due to their great functionality, bioactivity and biocompability. In particular, electroactive polyamino acid surfaces endow preparation of robust coatings for various applications. In this research article, preparation of carbon nanotubes doped polyglycine coated electrodes and their applications in the biomedical field such as DNA hybridization, DNA-antitumor agent interaction and antitumor agent determination were described. This biosensing platform was created using a simple, reproducible and fast in situ and one-pot electropolymerization procedure onto graphite surfaces by cyclic voltammetry. The coated electrodes were characterized with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). After the characterization studies, bioapplications of the proposed electrode were demonstrated. The new electrode led to significant improvement for the investigation of the electrochemical behavior of double-stranded DNA (dsDNA). 6-fold and 5-fold improvements were obtained for oxidation of the electroactive DNA bases, guanine (G) and adenine (A), respectively over the bare electrode. For these steps, each electrode was characterized with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Then, DNA hybridization studies were performed in the light of these results. The proposed electrode allowed the quantification of specific target DNA down to 11.2 fM in serum samples (n = 3). In addition, it constituted a sensitive biosensing platform for electrochemical monitoring of the interaction between dsDNA and a commonly used antitumor agent, Mitomycin C. Mitomycin C determination was also carried out using the inhibition effect occurred at the guanine oxidation signal. The detection limit of this antitumor agent was found as 1.78 mg L-1 in untreated serum samples (n = 3).

Development of clay-protein based composite nanoparticles modified single-used sensor platform for electrochemical cytosensing application.

A novel sensor platform modified with clay-protein based composite nanoparticles (Mt-HSA NCs) was developed to be used in electrochemical cytosensing application for the first time. The nanocomposite synthesized with desolvation method was structurally clarified by various characterization methods. Then, the working electrode was constructed by modifying the surface of the disposable pencil graphite (PGE) with physical adsorption to perform a simple sensor system. The characterization studies proved that the Mt-HSA NCs modified surface had a biocompatible, hydrophilic and large surface area where cancer cells can easily attach to the surface. As a diagnostic method, electrochemical impedance spectroscopy (EIS), which has become very popular in recent years, was carried out. The linearity range was found as from 1.5 × 102 to 7.5 × 106 breast cancer (MCF-7) cells and the limit of detection was calculated as 148 cells mL-1. From these results, a simple, effortless, cost effective and rapid electrochemical impedimetric sensor system for the diagnosis of breast cancer was developed by examining the interaction of Mt-HSA NCs/PGE surface with MCF-7 cells.

Development of Titania Nanotube-based Electrochemical Immunosensor and Determination of Prostate Specific Antigen.

Early diagnosis of cancer is the most important factor that increases the success of treatment. Therefore, the development of new diagnostic tools is a necessity. In this study, a new electrode surface was developed via modification of a disposable titanium electrode with anodic oxidation and coating of gold nanoparticle and chitosan. Titanium electrodes were anodized by several anodization parameters to obtain a nanoporous surface and characterized by scanning electron microscopy. Electrodes anodized in optimum conditions were modified with gold nanoparticles and chitosan for enhancing conductivity and functionalizing the surface of electrode, respectively. To detect prostate specific antigen (PSA), anti-PSA was bound onto the functional electrode surface. Modified electrodes were characterized with scanning electron microscopy and cyclic voltammetry and used for chronoamperometric detection of PSA. Limit of detection (LOD) of the designed electrode was found to be 7.8 ng mL-1 for PSA in a linear range of 0 - 100 ng mL-1.

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 immunoassay for detection of prostate specific antigen based on peptide nanotube-gold nanoparticle-polyaniline immobilized pencil graphite electrode.

In this work, we developed a disposable amperometric sandwich-type immunoassay to detect prostate specific antigen (PSA). A self-assembled peptide nanotube (PNT), gold nanoparticle (AuNP) and polyaniline (PANI) composite (PANI/AuNP-PNT) were used to modify a pencil graphite electrode (PGE). Anti-PSA (Ab1) was immobilized on the modified electrode (PANI/AuNP-PNT/PGE) to capture PSA. Horseradish peroxidase (HRP) labeled anti-PSA (HRP-Ab2) was used as a tracer antibody. The modified electrodes were characterized with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). PSA concentration in phosphate buffer (pH=7.4) was determined with electro-catalytic reduction of H2O2 on the modified working electrode by using the chronoamperometric method. Limit of detection was found out to be 0.68ng/mL in a linear range of 1-100ng/mL with a high regression (R2=0.990). To show the practicality of the modified biosensor in real matrixes, it was successfully applied for the detection of PSA in blood serum samples. The proposed method was also compared with enzyme-linked immunosorbent assay (ELISA) and compatible results were obtained. The developed immunoassay exhibited good reproducibility together with high stability and provides an efficient approach to detect PSA cost-effectively compared to traditional methods.

Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode.

A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability.