Mustafa Kemal Sezgintürk

A highly sensitive immunosensor based on ITO thin films covered by a new semi-conductive conjugated polymer for the determination of TNFα in human saliva and serum samples

A novel, ultrasensitive impedimetric immunosensor was constructed for the detection of tumor necrosis factor α (TNFα) by using Poly(3-thiophene acetic acid) (P3), a conjugated polymer as an immobilization matrix. The polymer P3 contains a lot of carboxylic acid groups on its surface that provide a larger biorecognition surface. This developed immunosensor was prepared on hydroxy-bearing ITO surface via an ester bond linkage of polymer P3 to immobilize anti-TNF α antibodies. The ITO electrode modification steps and interaction between anti-TNF α antibody and TNF α antigen were monitored by cyclic voltammetry (CV) and by electrochemical impedance spectroscopy (EIS) method. After the analytical parameters optimization, a linear detection response from 0.01pg/mL to 2pg/mL, a limit of detection LOD of 3.7 fg/mL and a limit of quantification (LOQ) of 12.4 fg/mL were achieved, which provided accurate results (relative standard deviation; 4.03%). The characterization of this developed immunosensor was performed by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray (EDX) mapping and atomic force microscopy (AFM). The immunosensor allowed a simple and fast detection of TNF α antigen in human serum and satisfied recoveries (98.69-105.20%) were obtained by using standard addition method.

A disposable immunosensor using ITO based electrode modified by a star-shaped polymer for analysis of tumor suppressor protein p53 in human serum

Label-free immunosensor based on tetra armed star-shaped poly(glycidylmethacrylate) (StarPGMA) modified disposable ITO electrode was developed for detection of p53 protein, an important colorectal cancer biomarker. This disposable biosensor was fabricated by spin-coating technique using star-shaped StarPGMA with epoxy side groups. After formation of a stable film with epoxy ends, anti-p53 antibodies were bound to these groups covalently. Stepwise modification of the electrode was followed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies. The electrochemical performance of the immunosensor was studied by EIS. Furthermore, the antibody and antigen coupling was monitored by single frequency impedance (SFI) technique. The immunosensor showed a low limit of detection (7 fg/mL) and a linear detection range between 0.02 pg/mL and 4 pg/mL. Additionally, atomic force microscopy (AFM) and scanning electron microscopy (SEM) were utilized for monitoring of immunosensor surface at different stages of fabrication. The antibody coupling on the electrode surface was proved by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. Furthermore, the proposed immunosensor had good reproducibility and repeatability.

A novel silanization agent based single used biosensing system: Detection of C-reactive protein as a potential Alzheimer’s disease blood biomarker

HIGHLIGHTSA novel and effective silanization agent 3‐CPTMS was firstly used.CRP biosensor exhibited high analytical performance with a linear range 3.25–208fgmL−1.Constructed biosensor to detect CRP levels of human serum sample experiments showed good agreement with reference method. ABSTRACT This paper illustrates a new and sensitive electrochemical immunosensor for the analysis of C‐reactive protein. Indium Tin Oxide (ITO) disposable sheets were modified by using 3‐cyanopropyltrimethoxysilane (CPTMS) self‐assembled monolayers (SAMs) for the first time for immobilizing the anti‐CRP antibody via covalent interactions without the need for any cross‐linking agent. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), as well as square wave voltammetry (SWV) methods were applied to characterize immobilization steps of anti‐CRP and to determine the CRP concentration. The optimization of the fabricated parameters and the analytical performance of the biosensor were widely evaluated. Charge transfer resistance changes were highly linear and sensitive with CRP concentration of 3.25–208fgmL−1 range and associated with a limit of detection of 0.455fgmL−1. This impedimetric biosensing system have excellent repeatability, reproducibility and reusability. Moreover, the binding characterization of CRP to anti‐CRP was monitored by a single frequency impedance technique. The amount of CRP in human serum samples were analyzed by fabricated biosensor to determine the feasibility of the biosensing system in medical purposes. We suggest that CPTMS, a new silanization agent, is ideal in biosensor applications.

A highly selective electrochemical immunosensor based on conductive carbon black and star PGMA polymer composite material for IL-8 biomarker detection in human serum and saliva

A new approach to enhance the electrochemical performance of biosensor was attempted by using Super P© carbon black/Star polymer composite material. In this study, we developed an electrochemical IL 8 biosensor by modification with a conductive composite including Super P, polyvinylidene fluoride (PVDF) and star polymer (SPGMA) of disposable ITO electrode surface. The Super P carbon black as carbonaceous material had a high conductivity and was used for the enhancement of electron transfer between electrode surface and electrolyte. Anti-IL 8 antibodies were utilized as biorecognition molecules and bound to epoxy groups of star polymer covalently. The chemical characterization of antibody immobilization on this composite was performed by using Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. The characterizations of stepwise modification of this immunosensor were performed by electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Single Frequency Impedance (SFI); and morphological techniques such as Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Several variables that affect the immunosensor performance were optimized. Under optimum conditions, a wide linear range 0.01-3 pg/mL and low detection limit 3.3 fg/mL were obtained. Super P-star polymer composite modified immunosensor was easy, sensitive, cheap and reliable analytical method for IL 8 detection. The applicability of the proposed immunosensor to determine IL 8 in saliva and serum samples were examined. The results of biosensor and Enzyme-linked Immunosorbent Assay (ELISA) kit were in compatible. Consequently, it was concluded that the electrochemical immunosensor offers a potential approach for IL 8 detection in clinical applications.

Determination of C-reactive protein by PAMAM decorated ITO based disposable biosensing system: A new immunosensor design from an old molecule

This paper demonstrates a new and sensitive electrochemical immunosensor for the analysis of C-reactive protein, an important marker of inflammation. Indium Tin Oxide (ITO) disposable sheets were modified by using 11-cyanoundecyltrimethoxysilane (CUTMS) and PAMAM dendrimers (G:1 amino surfaces) for the first time to immobilize the anti-CRP antibody via covalent interactions. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), as well as square wave voltammetry (SWV) methods, were applied to characterize the immobilization stages of anti-CRP and to determine the CRP concentrations. Charge transfer resistance changes were highly linear and sensitive to CRP concentration in the range 21-6148 fg mL-1 and were associated with a limit of detection of 0.34 fg mL-1. The system had acceptable repeatability (6.45%, n = 18) and good storage stability (4.5% loss after 6 weeks). Moreover, the binding characterization of CRP to anti-CRP was monitored by a single frequency impedance technique. The amount of CRP in human serum samples was analyzed with a fabricated biosensor to determine the feasibility of the biosensing system for medical purposes. We suggest that 11-CUTMS, a new silanization agent, is ideal for biosensor applications.

An impedimetric immunosensor for highly sensitive detection of IL-8 in human serum and saliva samples: A new surface modification method by 6-phosphonohexanoic acid for biosensing applications

In this study, we fabricated a sensitive and label-free impedimetric immunosensor based on 6-phosphonohexanoic acid (PHA) modified ITO electrode for detection of interleukin-8 (IL-8) in human serum and saliva. PHA was first employed to cancer biomarker sensing platform. Anti-IL-8 antibody was used as a biorecognition element and the detection principle of this immunosensor was based on monitoring specific interaction between anti-IL-8 antibody and IL-8 antigen. The morphological characterization of each electrode modification step was analyzed by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) while electrochemical characterization was performed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and single frequency impedance (SFI) techniques. Moreover, the antibody immobilization on the electrode surface was proved Fourier-transform infrared spectroscopy (FTIR) and Raman Spectroscopy. This proposed impedimetric immunosensor exhibited good performances with a wide linear in the range from 0.02 pg/mL to 3 pg/mL as well as a relative low detection limit of 6 fg/mL. The impedimetric immunosensor had a good specificity, stability and reproducibility. This study proved that PHA was a suitable interface material to fabricate an electrochemical biosensor.

A disposable and ultrasensitive ITO based biosensor modified by 6-phosphonohexanoic acid for electrochemical sensing of IL-1β in human serum and saliva

In this study, we constructed a new and sensitive ITO based electrochemical immunosensor for detection of interleukin 1β (IL-1β), a cancer biomarker found in serum and saliva. 6-phosphonohexanoic acid (PHA) was used as a biomolecule immobilization matrix for the first time. Anti-IL-1β antibody was utilized as a biorecognition molecule that immobilized onto carboxyl groups of 6-phosphohexanoic acid (PHA) via amide bond. Selective interaction between anti- IL-1β antibodies and IL-1β antigens was investigated by Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Single Frequency Impedance (SFI) methods. The surface characterization of the immunosensor was performed by fourier transform infrared spectroscopy (FTIR), raman spectroscopy, scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) in order to illustrate individual steps of biosensor construction. Under the optimized experimental conditions, the change in impedance was proportional to IL-1β concentrations in the range of 0.025-3 pg/mL (R2 = 0.99) with detection limit of 7.5 fg/mL. The reproducibility, repeatability, stability, and specificity of the developed immunosensor were analyzed. In addition, the developed immunosensor was successfully utilized for the determination of IL-1β in serum and saliva samples by using the standard addition method with recoveries of 96.7-105.4%. This immunosensor was applicable for the requirements of routine analysis with respect to performance, functionality and cost.

A label-free electrochemical biosensor for direct detection of RACK 1 by using disposable, low-cost and reproducible ITO based electrode

In this study we designed an ultrasensitive electrochemical immunosensor for RACK 1 detection using 11-cyanoundecyltrimethoxysilane (11-CUTMS) as a immobilization matrix to immobilize biorecognition element. The used silane agent (11-CUTMS) provides a favorable platform for efficient loading of anti-RACK 1 antibody. The effective loading of the biorecognition element on the 11-CUTMS matrix was monitored by scanning electron microscopy (SEM), atomic force microscopy (AFM) images and fourier transform infrared spectroscopy (FTIR) spectra. The electrochemical characterization of the immunosensor was performed by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Moreover, biorecognition interaction between anti-RACK1 antibodies and RACK1 antigens was monitored by using single frequency technique (SFI). The operating conditions, calibration curves obtained during optimization of experiments and reproducibility of the proposed impedimetric RACK1 biosensor are also investigated and discussed. The electrochemical immunosensor illustrated a sensitive response to RACK 1 antigen with detection limit of 10.8 fg/mL and in the linear range of 0.036-2.278 pg/mL (R2 = 0.999). Owing to high specificity, good reproducibility, long stability and reusability, the fabricated immunosensor will provide a sensitive, selective approach to RACK 1 detection. Furthermore, the practical applicability in human serum samples were investigated with a satisfactory result.