Metin Ak

Peptide-modified conducting polymer as a biofunctional surface: monitoring of cell adhesion and proliferation

Here, we report the electropolymerization of 3-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline monomer on indium tin oxide (ITO) glass and its use as a coating material for cell culture applications. Functional amino groups on the conducting polymer provide post-modification of the surface with the arginylglycylaspartic acid (RGD) peptide via EDC chemistry. Scanning electron microscopy, atomic force microscopy, and contact angle and surface conductivity measurements were carried out for the surface characterization. The peptide-conjugated surface was tested for adhesion and proliferation of several cell lines such as monkey kidney epithelial (Vero), human neuroblastoma (SH-SY5Y), and human immortalized skin keratinocyte (HaCaT). These cells were cultured on RGD-modified, polymer-coated ITO glass as well as conventional polystyrene surfaces for comparison. The data indicate that the RGD-modified surfaces exhibited better cell adhesion and proliferation among all surfaces compared. Cell imaging studies up to 72 h in length were performed on these surfaces using different microscopy techniques. Therefore, the novel biofunctional substrate is a promising candidate for further studies such as monitoring the effects of drugs and chemicals on cellular viability and morphology as well as cell-culture-on-a-chip applications.

A novel organic–inorganic hybrid conducting copolymer for mediated biosensor applications

A novel ferrocenyldithiophosphonate (TPFc) functionalized monomer and its conductive copolymer were synthesized, characterized and its potential use for biosensor applications was investigated. The structure of copolymer (P(TPFc-co-TPA)) which has free amino and ferrocene (Fc) groups was characterized by various techniques such as NMR and cyclic voltammetry. Afterwards, covalent immobilization of glucose oxidase (GOx) was carried out with glutaraldehyde using the amino groups on both the conducting copolymer and GOx. Fc on the backbone played a role as redox mediator during the electrochemical measurements. Therefore, the proposed copolymer P(TPFc-co-TPA) served as a functional platform for stable biomolecule immobilization and for obtaining the oxygen free mediated electrochemical responses. The current signals were recorded using glucose as substrate, at +0.45 V vs. Ag/AgCl in Na-acetate buffer (pH 4.5; 50 mM). Additionally, Kappm (20.23 mM), Imax (3.03 μA) and sensitivity (0.10 μA mM−1 cm−2) values were determined. Finally, the biosensor was successfully applied to glucose analysis in various beverages and the results were compared with data obtained from the spectrophotometric glucose detection kit as a reference method.

Ferrocene-Functionalized 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1- yl)aniline: A Novel Design in Conducting Polymer-Based Electrochemical Biosensors

Herein, we report a novel ferrocenyldithiophosphonate functional conducting polymer and its use as an immobilization matrix in amperometric biosensor applications. Initially, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)amidoferrocenyldithiophosphonate was synthesized and copolymerized with 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine at graphite electrodes. The amino groups on the polymer were utilized for covalent attachment of the enzyme glucose oxidase. Besides, ferrocene on the backbone was used as a redox mediator during the electrochemical measurements. Prior to the analytical characterization, optimization studies were carried out. The changes in current signals at +0.45 V were proportional to glucose concentration from 0.5 to 5.0 mM. Finally, the resulting biosensor was applied for glucose analysis in real samples and the data were compared with the spectrophotometric Trinder method.

A novel functional conducting polymer as an immobilization platform

Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. To obtain immobilization platforms for both pyranose oxidase (PyOx) and Gluconobacter oxydans, the graphite electrode surface was modified with the polymer of 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) which has free amino groups on the surface for further bioconjugation reactions with the biomolecules. Initially, the electrode surface was covered with HKCN via electropolymerization. Then, either PyOx or G. oxydans cell was stabilized using glutaraldehyde as a cross-linker. After optimization of biosensors, analytical characterization and surface imaging studies were investigated. The change of current depends on glucose concentration between 0.05-1.0mM and 0.25-2.5mM with HKCN/PyOx and HKCN/G. oxydans biosensors in batch systems. Also, the calibration graphs were obtained for glucose in FIA mode, and in this case, linear ranges were found to be 0.01-1.0mM and 0.1-7.5mM for HKCN/PyOx and HKCN/G. oxydans, respectively.

Fabricating multicolored electrochromic devices using conducting copolymers

A centrosymmetric polymer precursor, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)butan-1-amine (TPBA), was synthesized via a Knorr‐Paal reaction and its copolymer with EDOT was electrochemically synthesized and characterized. While P(TPBA) has only two colors in its oxidized and neutral states, its copolymer with EDOT has eight different colors. Electrochromic devices based on P(TPBA)/PEDOT and P(TPBA-co-EDOT)/PEDOT were constructed and characterized. The oxidized state of the device shows blue color whereas it shows purple for the reduced state. At moderate potentials the device has good transparency with green and gray colors. The maximum contrast and switching time of the multielectrochromic copolymer device were measured as 25% and 0.8 s at 575 nm. Copolymerization not only increases the polymer’s color scheme, but also improves its properties, such as redox stability and switching time. S Online supplementary data available from stacks.iop.org/SMS/22/115022/mmedia (Some figures may appear in colour only in the online journal)

Comparative investigation of spectroelectrochemical and biosensor application of two isomeric thienylpyrrole derivatives

In the present work, we performed a comparative investigation of spectroelectrochemical and biosensor application of isomeric thienylpyrrole derivatives. For this purpose two thienylpyrrole derivatives were synthesized characterized and electrochemically polymerized. Characterizations of the resulting polymers were performed by cyclic voltammetry (CV), UV-vis spectroscopy. Moreover, the spectroelectrochemical, electrochromic properties and biosensing applications of the polymer films were investigated. The resulting polymer films have distinct electrochromic properties and show five different colors. The 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline (SNS-NH2) and 3-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline P(SNS-mNH2) films show maximum optical contrast (ΔT%) of 41.5%, 25.4% at 431 nm, 422 nm with a response time of 1.5 s. For biosensing studies, P(SNS-NH2) and P(SNS-mNH2) were polymerized on graphite electrodes electrochemically and used as immobilization matrices. After electrochemical deposition, glucose oxidase (GOx) was immobilized on the modified electrodes as the model enzyme. Effects of the position of the amine group on spectroelectrochemical properties and biosensing capability of the polymers were investigated.

Electrochromic Properties of ‘Trimeric' Thiophene‐pyrrole‐thiophene Derivative Grown from Electrodeposited 6‐(2,5‐di(thiophen‐2‐yl)‐1H‐pyrrol‐1‐yl)hexan‐1‐amine and its Copolymer

A centrosymmetric polymer precursor, namely 6‐(2,5‐di(thiophen‐2‐yl)‐1H‐pyrrol‐1‐yl)hexan‐1‐amine (TPHA), was synthesized via a Knorr–Paal reaction using 1,4‐di(2‐thienyl)‐1,4‐butanedione and hexane‐1,6‐diamine. The resultant monomer was characterized by Nuclear Magnetic Resonance (1H‐NMR). Electroactivity of TPHA was investigated via cyclic voltammetry. The electronic structure and the nature of electrochromism in P(TPHA) and its copolymer with EDOT, (P(TPHA‐co‐EDOT)), were examined via spectroelectrochemistry studies. P(TPHA) switches between claret red neutral state and blue oxidized state. Optical response times for coloring and bleaching processes of the P(TPHA) and P(TPHA‐co‐EDOT) were found as 2.1 s and 1.6 s, respectively. The copolymer of TPHA was used to construct dual type polymer electrochromic devices (ECDs) against poly(3,4‐ethylenedioxythiophene) (PEDOT). Spectroelectrochemistry and electrochromic switching out of the devices were investigated.

Preparation of an EDOT-based polymer: optoelectronic properties and electrochromic device application

Here we present the synthesis, characterization and electropolymerization of a new EDOT-based monomer; 5,10-dihydrobenzo[f]thieno[3,4-b][1,4]dioxocine (DTD). Electrochemical polymerization of DTD was performed potentiostatically by using dichloromethane (DCM) as solvent and tetrabutylammonium hexafluorophosphate (TBPF6) as supporting electrolyte. Homopolymer [P(DTD)] films and copolymer [P(DTD-co-TPA)] films of DTD prepared by using 4-(2,5-di(thiophen-2-yl)-1H-pyrrole-1-yl)butane-1-amine (TPA) were characterized via CV and UV-vis spectroscopy. Spectroelectrochemical analysis of P(DTD) revealed electronic transitions at 585 nm (π–π* transition) with an electronic band gap of 1.69 eV. Electrochromic studies revealed that P(DTD) has competitive properties to EDOT. Furthermore, a dual-type complementary colored polymer electrochromic device based on P(DTD) and P(TPA) was constructed in sandwich configuration. Spectroelectrochemical studies revealed that the oxidized state of the device shows a blue color whereas it is yellow in the reduced state. The maximum contrast (Δ%T) and switching time of the device were measured as 25.5% and 0.5 s for 385 nm and 21% and 1.0 s for 550 nm.

Smart window application of a new hydrazide type SNS derivative

In this article the smart window application of a new type of thienylpyrrole derivative is presented. For this purpose, the new type of 2,5-di(2-thienyl)pyrrole derivative, which is named N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)-4-(vinyloxy)benzamide (TPVB), has been prepared by the reaction of 1,4-di(2-thienyl)-1,4-butanedione and 4-(vinyloxy)benzohydrazide. Using hydrazine instead of amine in the synthesis process has significantly improved the related polymers optical properties. Spectroelectrochemical investigations revealed that P(TPVB) is more durable with better long-term stability and has the lowest band gap compared with the other SNS derivatives. A chronoamperometry experiment showed that the P(TPVB) polymer film has excellent redox stability, moderate switching time and high optical contrast. So it is possible to use this polymer with superior optical properties in smart window applications. A smart window based on P(TPVB) and poly(3,4-ethylenedioxythiophene) (P(EDOT)) was set up in a sandwich configuration. Optoelectrochemical investigations displayed that the reduced state of the device displays an orange color whereas it is blue for the oxidized state. The switching time and optical contrast (ΔT%) of the device at 625 nm are 1.0 s and 43%, respectively.

The effect of the monomer feed ratio and applied potential on copolymerization: investigation of the copolymer formation of ferrocene-functionalized metallopolymer and EDOT

Abstract In this study, we reported synthesis of ferrocene functioned conducting metallopolymer to enhance the understanding of properties of polymers. One of the crucial ways in the electrochromic polymer materials research was tuning color by means of copolymerization and change of polymer backbones and side groups. For this purpose, we synthesized copolymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)amido ferrocenyl dithiophosphonate with EDOT via potentiodynamic electrolysis. Spectral and electrochemical characterizations of the copolymer were investigated. In addition, the spectral properties of the copolymers prepared by different applied potentials and different monomer feed ratio were studied. For the first time, copolymer composition and the monomer reactivity ratios were approximately calculated by using the spectral data.