Synthesis and Characterization of PEDOT Derivative with Carboxyl Group and Its Chemo/Bio Sensing Application as Nanocomposite, Immobilized Biological and Enhanced Optical Materials

Innovative molecularly imprinted electrochemical sensor for the nanomolar detection of Tenofovir as an anti-HIV drug

Tenofovir (TNF) is an antiviral medicine that is utilized to treat the human immunodeficiency virus (HIV). However, its level must be controlled in the human body and environment at the risk of causing kidney and liver problems. Therefore, determining TNF concentration in real samples with more advanced, inexpensive, and accurate sensing systems is essential. In this work, a novel electrochemical nanosensor for TNF determination based on molecularly imprinted polymer (MIP) on the screen-printed electrode modified with functionalized multi-walled carbon nanotubes, graphite carbon nitride, and platinum nanoparticles (MIP-Pt@g-C₃N₄/F-MWCNT/SPE) was constructed through the electro-polymerization approach. The molecularly imprinted polymers were prepared on the electrode surface with TNF as the template molecule and 2-aminophenol (2-AP) as the functional monomer. Moreover, factors that affect sensor response were optimized. Pt@g-C₃N₄/F-MWCNT nanocomposite had an excellent synergistic effect on MIP, allowing rapid and specific identification of the test substance. The results demonstrated that the electro-polymerization of 2-AP supplies large amounts of functional groups for the binding of the template molecules, which remarkably enhances the sensitivity and specific surface area of the MIP sensor. This surface enlargement increased the analyte accessibility to imprinted molecular cavities. Under optimum conditions, the oxidation peak current had a linear relationship with TNF concentration ranging from 0.005 to 0.69 μM with a low detection limit of 0.0030 μM (S/N = 3). The results demonstrated that the designed MIP sensor possesses acceptable sensitivity, repeatability, and reproducibility toward TNF determination. Moreover, the developed sensor was applied to biological and water samples to determine TNF, and satisfactory recovery results of 95.6-104.8% were obtained (RSD less than 10.0%). We confirm that combining as-synthesized nanocomposite Pt@g-C₃N₄/F-MWCNT with MIP improves the limitations of MIP-based nanosensors. The proposed electrode is also compatible with portable potentiostats, allowing on-site measurements and showing tremendous promise as a point-of-care (POC) diagnostic platform.

Effect of surface properties on the electrochemical response of cynarin by electro-synthesized functionalized-polybithiophene/MWCNT/GNP

Cynarin is one of the biologically active functional components present a wide range of pharmacological applications. Herein, we reported the fabrication and surface properties investigation of a new highly sensitive electrochemical sensor for the detection of cynarin. The electrochemical sensors were fabricated in several steps; the first being the synthesis of bi-thiophene derivatives-based monomers 3,3'-bithiophen (M1); 2-methoxy-5-carbaldehyde-[3,3'-bithiophene] (M2) and 2-((2-methoxy-[3,3'-bithiophen]-5-yl)methylene)malononitrile) (M3) followed by electrochemical polymerization on a glassy carbon electrode after which multi-walled carbon nanotube (MWCNT) and gold nanoparticles (GNP's) were electrodeposited layer-by-layer on the polymer coating to obtain multilayer electrochemical sensors. The morphological properties of the formed polymers were evaluated using SEM analysis and the apparent contact angles to preview the changes in surface properties after the functionalization of monomers and therefore their effects on the detection of cynarin. Analytical parameters such as the accumulation time and pH of the PBS solution which influence the sensitivity of the electrochemical sensors were optimized. Under the optimal conditions the GCE/P3/MWCNT/GNP's showed a wide range of analyte concentrations (1 to 100 μM and 0.01 to 1 μM) and detection limit of 0.0095 using pulse differential voltammetry. In addition, the electrochemical sensors showed good reproducibility, stability and selectivity and they were used successfully for the determination of cynarin in real solutions.

Construction of multifunctional electrochemical sensor based on electroactivity-adjustable poly (ionic liquids)/reduced graphene oxide

In this article, a novel electroactivity-adjustable poly (ionic liquids)/reduced graphene oxide (PIL-GP) was developed and utilized for the fabrication of multifunctional, high stable electrochemical sensors. The structure, morphology and surface charge properties of PIL-GP have been systematically studied. And the selective detection performance of dopamine (DA) on PIL-GP modified glassy carbon electrode (GCE) were further explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). More importantly, by virtue of the anion exchange property of PIL, electroactive Fe(CN)₆^3-/PIL-GP/GCE and Polyoxometalates (PWA)/PIL-GP/GCE were easily fabricated and their electrochemical detection performance of ascorbic acid (AA) and bromate were investigated respectively. The results showed that PIL-GP/GCE based electrochemical sensors provided higher sensitivity, lower detection limits and outstanding anti-interference ability in certain detection system. It was indicated that this general approach to construct electroactivity-adjustable sensors with various electroactive anions possessed a broad application prospect.

Deprotonation-Induced Conductivity Shift of Polyethylenedioxythiophenes in Aqueous Solutions: The Effects of Side-Chain Length and Polymer Composition

Deprotonation-induced conductivity shift of poly(3,4-ethylenedixoythiophene)s (PEDOTs) in aqueous solutions is a promising platform for chemical or biological sensor due to its large signal output and minimum effect from material morphology. Carboxylic acid group functionalized poly(Cn-EDOT-COOH)s are synthesized and electrodeposited on microelectrodes. The microelectrodes are utilized to study the effect of carboxylic acid side-chain length on the conductivity curve profiles in aqueous buffer with different pH. The conductivity shifts due to the buffer pH are effected by the length of the carboxylic acid side-chains. The shifts can be explained by the carboxylic acid dissociation property (pKa) at the solid-liquid interface, self-doping effect, and effective conjugation length. Conductivity profiles of poly(EDOT-OH-co-C₂-EDOT-COOH) copolymers are also studied. The shifts show linear relationship with the feed monomer composition used in electrochemical polymerization.

Optimization and Application of Electrochemical Transducer for Detection of Specific Oligonucleotide Sequence for Mycobacterium tuberculosis

In this study, the electropolymerization of 4-hydroxyphenylacetic acid (4-HPA) over graphite electrodes (GE) was optimized, aiming its application as a functionalized electrochemical platform for oligonucleotides immobilization. It was investigated for the number of potential cycles and the scan rate influence on the monomer electropolymerization by using cyclic voltammetry technique. It was observed that the polymeric film showed a redox response in the region of +0.53/+0.38 V and the increase in the number of cycles produces more electroactive platforms because of the better electrode coverage. On the other hand, the decrease of scan rate produces more electroactive platforms because of the occurrence of more organized coupling. Scanning electron microscopy (SEM) images showed that the number of potential cycles influences the coverage and morphology of the electrodeposited polymeric film. However, the images also showed that at different scan rates a more organized material was produced. The influence of these optimized polymerization parameters was evaluated both in the immobilization of specific oligonucleotides and in the detection of hybridization with complementary target. Poly(4-HPA)/GE platform has shown efficient and sensitive for oligonucleotides immobilization, as well as for a hybridization event with the complementary oligonucleotide in all investigated cases. The electrode was modified with 100 cycles at 75 mV/s presented the best responses in function of the amplitude at the monitored peak current values for the Methylene Blue and Ethidium Bromide intercalators. The construction of the genosensor to detect a specific oligonucleotide sequence for the Mycobacterium tuberculosis bacillus confirmed the results regarding the poly(4-HPA)/GE platform efficiency since it showed excellent sensitivity. The limit of detection and the limit of quantification was found to be 0.56 (±0.05) μM and 8.6 (±0.7) μM, respectively operating with very low solution volumes (15 µL of probe and 10 µL target). The biosensor development was possible with optimization of the probe adsorption parameters and target hybridization, which led to an improvement in the decrease of the Methylene Blue (MB) reduction signal from 14% to 34%. In addition, interference studies showed that the genosensor has satisfactory selectivity since the hybridization with a non-specific probe resulted in a signal decrease (46% lower) when compared to the specific target.

Synthesis of a functionalized multi-walled carbon nanotube decorated ruskin michelle-like ZnO nanocomposite and its application in the development of a highly sensitive hydroquinone sensor

Electrochemical determination of hydroquinone based on a f-MWCNT decorated ruskin michelle-like ZnO nanocomposite.

A facile graphene oxide based sensor for electrochemical detection of prostate anti-cancer (anti-testosterone) drug flutamide in biological samples

An electrochemical sensor based on graphene oxide modified glassy carbon electrode for the determination of anti-cancer drug flutamide.

Synthesis and characterization of chiral PEDOT enantiomers bearing chiral moieties in side chains: chiral recognition and its mechanism using electrochemical sensing technology

This manuscript reports a couple of novel polymers of side-chain functionalized PEDOT. The new polymers can be employed to successfully recognize 3,4-dihydroxyphenylalanine enantiomers and we also discuss the mechanism of chiral recognition.

A graphene oxide/conducting polymer nanocomposite for electrochemical dopamine detection: origin of improved sensitivity and specificity

This work describes the performance of a graphene oxide/poly(3,4-ethylenedioxythiophene) nanocomposite material as a sensitive and selective electrochemical dopamine sensor.