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In this present study, the preparation of chitosan functionalized gold‑nickel wire nanomachines (nanomotors) (CS@Au-Ni NMs) for motion-based double-stranded deoxyribonucleic acid (dsDNA) recognition and detection was described. Synthesis of the nanomachines was accomplished by Ni layer formation using direct current (DC) magnetron sputtering over electrochemically deposited Au wires. Subsequently, biopolymer chitosan was dispersed onto this bimetallic layer by drop casting which could provide a novel and functional surface for leading bio-applications. CS@Au-Ni NMs were characterized via scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and zeta potential analysis methods for the elucidation of structural morphology, elemental composition and electrophoretic mobility. On account of presenting the application of these magnetic nanomachines, they were interacted with different concentrations of dsDNA and the changes in their velocities were investigated. The speed CS@Au-Ni NMs were measured as 19 μm/s under 22 mT magnetic field. These magnetically guided nanomachines demonstrated a practical and good sensing ability by recognizing dsDNA between 0.01 mg/L and 10 mg/L. Electrochemical characterization was also performed to identify the surface characteristics. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments presented the interaction of the NMs with dsDNA by indicating the convenient recognition., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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)., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In the present work, preparation of titanium dioxide coated graphene (TiO2/graphene) and the use of this nanocomposite modified electrode for electrochemical biosensing applications were detailed. The nanocomposite was prepared with radio frequency (rf) rotating plasma method which serves homogeneous distribution of TiO2 onto graphene. TiO2/graphene was characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Then, this nanocomposite was dissolved in phosphate buffer solution (pH 7.4) and modified onto disposable pencil graphite electrode (PGE) by dip coating for the investigation of the biosensing properties of the prepared electrode. TiO2/graphene modified PGE was characterized with SEM, EDS and cyclic voltammetry (CV). The sensor properties of the obtained surface were examined for DNA and DNA-drug interaction. The detection limit was calculated as 1.25mgL(-1) (n=3) for double-stranded DNA (dsDNA). RSD% was calculated as 2.4% for three successive determinations at 5mgL(-1) dsDNA concentration. Enhanced results were obtained compared to the ones obtained with graphene and unmodified (bare) electrodes., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The need for sensitive, selective, rapid and low-cost detection systems for DNA and DNA-drug interactions are in crucial demand for diagnostics and real-world applications. This work details the preparation of poly(3,4-ethylenedioxythiophene) (PEDOT) coated chitosan (CHIT) and the use of PEDOT coated CHIT modified disposable pencil graphite electrodes (PGEs) for DNA and DNA-anticancer drug interaction sensing. PEDOT coated CHIT (PEDOT/CHIT) was prepared with rotating plasma polymerization using radio frequency (RF: 13.56 MHz) power generator. Then, modification of PEDOT/CHIT onto PGE was performed. The use of the prepared electrode was carried out using differential pulse voltammetry (DPV). Cyclic voltammetry (CV) and scanning electron microscopy (SEM) were used to characterize the PEDOT/CHIT/PGE. The performance of the electrode was compared with CHIT/PGE and unmodified PGE. The electrode exhibited high sensitivity for the investigation of DNA sensing and DNA-anticancer drug interaction. Such disposable sensing platform hold considerable promise for diverse bioapplications., (Copyright © 2014 Elsevier B.V. All rights reserved.)

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).

While high storage stability of sequence-selective DNA biosensors is crucial towards their routine applications, commonly used electrochemical hybridization biosensors are characterized with limited storage stability. In this article we demonstrate that recently developed ternary thiolated monolayers impart dramatic improvement in the storage stability of DNA electrochemical biosensors. In particular, highly stable multicomponent interfaces are prepared by co-immobilizing the thiolated capture probe (SHCP) with 1,6-hexanedithiol (HDT) on gold substrates, followed by the incorporation of 6-mercapto-1-hexanol (MCH) diluent. The resulting (SHCP/HDT+MCH) DNA hybridization recognition platform offers substantially higher storage stability compared to conventional binary (SHCP+MCH) monolayers. The (SHCP/HDT+MCH) ternary monolayers maintain their initial signal (S)-to-noise (N) ratio (S/N) over a prolonged 3 months period upon storage at 4 °C, compared to the rapid sensitivity loss observed using the common binary interfaces. This attractive stability performance promises the convenient usage of pre-prepared electrodes after prolonged time storage without any treatment. Such dramatic improvements in the storage stability have been achieved through a rational optimization of the concentration ratio of the SHCP and the other components of the ternary SAM. The improved storage stability of SHCP/HDT+MCH interfaces observed at higher concentrations of SHCP is attributed to a hindered displacement of SHCP by MCH in the resulting compact layers. The ability to design highly stable nucleic acid interfaces using common chemicals obviates the need of using specialized expensive reagents., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A new surface based on the natural clay mineral sepiolite and a single-walled carbon nanotubes-modified graphite electrode was developed for the electrochemical detection of DNA, and also for anticancer drug-DNA interactions.

Single-walled carbon nanotubes (SWCNT)-poly(vinylferrocenium) (PVF(+)) modified pencil graphite electrodes (PGEs) were developed in our study for the electrochemical monitoring of a sequence-selective DNA hybridization event. Firstly, SWCNT-PVF(+) modified PGE, PVF(+) modified PGE and unmodified PGE were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was then investigated using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The SWCNT-PVF(+) modified PGEs were optimized for improved DNA sensing ability by measuring the guanine oxidation signal. In order to obtain the full coverage immobilization of the DNA probe following the optimum working conditions, the effect of amino-linked, thiol-linked and, bare oligonucleotides (ODNs), and the concentration of the DNA probe on the response of the modified electrode were examined. After optimization studies, the sequence-selective DNA hybridization was evaluated in the case of hybridization between an amino-linked probe and its complementary (target), a noncomplementary (NC) sequence, calf thymus double stranded DNA (dsDNA), and target/mismatch (MM) mixtures in the ratio of 1:1. SWCNT-PVF(+) modified PGEs presented very effective discrimination of DNA hybridization owing to their superior selectivity and sensitivity., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The transport properties of single-strand DNA probe-modified self-propelling micromachines are exploited for "on-the-fly" hybridization and selective single-step isolation of target nucleic acids from "raw" microliter biological samples (serum, urine, crude E. coli lysate, saliva). The rapid movement of the guided modified microrockets induces fluid convection, which enhances the hybridization efficiency, thus enabling the rapid and selective isolation of nucleic acid targets from untreated samples. The integration of these autonomous microrockets into a lab-on-chip device that provides both nucleic acid isolation and downstream analysis could thus be attractive for diverse applications.

Detection of specific DNA sequences in clinical samples is a key goal of studies on DNA biosensors and gene chips. Herein we present a highly sensitive electrochemical genosensor for direct measurements of specific DNA sequences in undiluted and untreated human serum and urine samples. Such genosensing relies on a new ternary interface involving hexanedithiol (HDT) co-immobilized with the thiolated capture probe (SHCP) on gold surfaces, followed by the incorporation of 6-mercapto-1-hexanol (MCH) as diluent. The performance of ternary monolayers prepared with linear dithiols of different lengths was systematically examined, compared and characterized by cyclic voltammetry and electrochemical impedance spectroscopy, with HDT exhibiting the most favorable analytical performance. The new SHCP/HDT+MCH monolayer led to a 80-fold improvement in the signal-to-noise ratio (S/N) for 1 nM target DNA in undiluted human serum over the common SHCP+MCH binary alkanethiol interface, and allowed the direct quantification of the target DNA down to 7 pM (28 amol) and 17 pM (68 amol) in undiluted/untreated serum and urine, respectively. It also displayed attractive antifouling properties, as indicated from the favorable S/N obtained after a prolonged exposure (24h) to untreated biological matrices. These attractive features of the SHCP/HDT+MCH sensor interface indicate considerable promise for a wide range of clinical applications., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Characterization of redox polymer, poly(vinylferrocenium) perchlorate (PVF+ClO4-) coated as a film on Pt electrodes, and the detection of DNA based on the electrochemical behavior of the polymer were described in this study. PVF+ClO4- modified electrodes were prepared by the electrooxidation of poly(vinylferrocene) (PVF), and DNA immobilized polymer modified electrode was then prepared. The characterization of the polymer modified electrodes were performed by scanning tunneling microscopy (STM), Raman spectroscopy and alternating current (AC) impedance. The effects of DNA concentration, pH, and polymer films in various thicknesses based on the electrode response were also investigated. The electrochemical behavior of DNA modified polymer electrode by using double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) was compared. DNA hybridization was also investigated.

Fabrication of conducting polymer networks based on polypyrrole/multi‐walled carbon nanotubes (PPy/MWCNTs) modified graphite electrodes that were achieved with a single‐step electropolymerization and potential use of these electrodes for deoxyribonucleic acid (DNA) recognition and anticancer drug (Paclitaxel, PTX) quantification were presented in the present work. PPy/MWCNTs nanohybrid PGEs were constructed in aqueous solution of pyrrole (Py) and MWCNTs using cyclic voltammetry (CV) and constant potential electrolysis. So‐formed electrodes were characterized with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Surface morphologies of the surfaces were investigated by scanning electron microscopy (SEM) studies. Bio‐application of the PPy/MWCNTs nanohybrid modified PGEs were accomplished by subjecting them to double‐stranded DNA (dsDNA) modification for direct DNA recognition and PTX determination. For the drug determination, interaction of DNA‐based electrodes with PTX was investigated. Detection limit was found as 1.55 x 10−8 M based on the changes in the oxidation of guanine base which made the proposed electrode convenient for clinical trials. [ABSTRACT FROM AUTHOR]

Abstract: The development of rapid, low-cost and reliable diagnostic methods is crucial for the identification and treatment of many diseases. Screen-printed gold electrodes (Au/SPEs), coated with a ternary monolayer interface, involving hexanedithiol (HDT), a specific thiolated capture probe (SHCP), and 6-mercapto-1 hexanol (MCH) (SHCP/HDT/MCH) are shown here to offer direct and sensitive detection of nucleic acid hybridization events in untreated raw biological samples (serum, urine and crude bacterial lysate solutions). The composition of the ternary monolayer was modified and tailored to the surface of the Au/SPE. The resulting SHCP/HDT/MCH monolayer has demonstrated to be extremely useful for enhancing the performance of disposable nucleic acid sensors based on screen-printed electrodes. Compared to common SHCP/MCH binary interfaces, the new ternary self-assembled monolayer (SAM) resulted in a 10-fold improvement in the signal (S)-to-noise (N) ratio (S/N) for 1nM target DNA. The SHCP/HDT/MCH-modified Au/SPEs allowed the direct quantification of the target DNA down to 25pM (0.25fmol) and 100pM (1fmol) in undiluted/untreated serum and urine samples, respectively, and of 16S rRNA Escherichia coli (E. coli) corresponding to 3000CFUμL−1 in raw cell lysate samples. The new SAM-coated screen-printed electrodes also displayed favorable non-fouling properties after a 24h exposure to raw human serum and urine samples, offering great promise as cost-effective nucleic acid sensors for a wide range of decentralized genetic tests. [ABSTRACT FROM AUTHOR]

Poly(vinylferrocenium) (PVF) modified gold (Au) electrode was developed in this study for the electrochemical sensing of deoxyribonucleic acid (DNA) hybridization based on the oxidation signals of polymer and guanine, and also for the electrochemical investigation of interaction of anticancer drug, mitomycin C (MC) and DNA immobilized onto PVF modified Au electrode. PVF modified Au electrode was prepared by electrooxidation of poly(vinylferrocene) PVF at +0.7 V versus Ag/AgCl reference electrode. The polymer modified electrode and DNA immobilized polymer modified electrode were characterized by X-ray photoelectron (XPS), Fourier transform infrared-attenuated total reflentance (FTIR-ATR) and alternating current (AC) impedance spectroscopy. For application studies, differential pulse voltammetry (DPV) technique was used. [ABSTRACT FROM AUTHOR]

Abstract: Poly(vinylferrocenium) (PVF+) modified electrode was developed in this study for the electrochemical sensing of DNA based on the oxidation signals of polymer, adenine and guanine. Experimental parameters, such as; polymeric film thickness, DNA immobilization time and DNA concentration were examined in order to obtain more sensitive and selective electrochemical signals. After optimization studies, DNA hybridization was investigated. [Copyright &y& Elsevier]

Scanning electron microscopy and EDS layered images of the PEDOT NE and the use of this electrode for DNA electrochemistry and DNA-anticancer drug interaction. [Display omitted] • Functional dsDNA/PEDOT biointerfaces on PGE were constructed effectively. • Advanced electrochemical characteristics were obtained with dsDNA/PEDOT/NEs. • Improved label-free dsDNA electrochemistry was achieved. • The interaction between DNA and anticancer drugs were identified successfully. • Sensitive and facile detection of anticancer drugs were accomplished. In the present study, preparation of poly(3,4-ethylenedioxythiophene) coated pencil graphite electrode with the addition of multi-walled carbon nanotubes (MWCNTs) (PEDOT nanoelectrode, NE); incorporation of double-stranded deoxyribonucleic acid (dsDNA) onto NE (dsDNA/PEDOT NE); and the bio-application of dsDNA/PEDOT NE were described. PEDOT NEs were first used to immobilize dsDNA onto the electrode surfaces in a high efficiency to detect dsDNA with advanced oxidation signals. Afterwards, these functional biointerfaces were used for the investigation of DNA interaction with Mitomycin C (MC) and Paclitaxel (PTX) based on guanine and adenine oxidation signals. dsDNA/PEDOT NE was presented a linearity in the concentration of 1 mg L−1 to 50 mg L−1 for MC with a detection limit of 0.26 mg L−1. The linear range was between 0.5 mg L−1 and 60 mg L−1 for PTX with a detection limit of 0.14 mg L−1 (n = 3). In addition, dsDNA/PEDOT NE was presented good stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rapid and effective synthesis of platinum nanoparticles on the carbon black:reduced graphene oxide hybrids were achieved. • Facile and efficient electrode modification was performed with the hybrids. • Characterization of the surfaces proved homogeneous and robust distribution of the structures. • Sensitive fsDNA detection was accomplished with a low detection limit. • DNA damage and protection monitoring were carried out successfully. Carbon black-based hybrid materials have attracted great attention in the design of electrochemical sensors due to their consistent electroanalytical properties. With this in mind, for the first time, we present the preparation of platinum nanoparticles loaded carbon black:reduced graphene oxide (PtNPs/CB:rGO) hybrid platforms for label-free electrochemical DNA and DNA damage sensing. Synthesis of different hybrids was performed via microwave-assisted reduction method for the impregnation of platinum nanoparticles efficiently. These materials were characterized with X-ray diffraction analysis (XRD), Raman spectroscopy, transmission emission spectroscopy (TEM) and subsequently they were used for pencil graphite electrode modification in order to improve the characteristics of the surface. Modified electrodes were firstly applied for fish sperm DNA (fsDNA) analysis. The effect of different ratios (wt.:wt. %) of CB and rGO was investigated and it was shown that the hybrid material with 50:50 ratio had better sensitivity with a low detection limit of 0.14 mg L−1 and a good linearity to fsDNA between 1 and 200 mg L−1 (n = 3) based on guanine (G) oxidation by using differential pulse voltammetry (DPV). In order to expand this comparison, PtNPs/CB and PtNPs/rGO modified electrodes were also incorporated. Furthermore, the electroanalytical response of the hybrid material modified electrode was investigated based on the oxidation of thymine (T). Later on, oxidative DNA damage detection in the presence of Cu(II)/H 2 O 2 reagents and protection studies in the presence of ascorbic acid were performed successfully by using electrochemical impedance spectroscopy (EIS). The study pointed out the remarkable reproducibility and sensitivity of the CB-based modification for nanoparticle decoration. [ABSTRACT FROM AUTHOR]