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Interleukin-6 (IL-6) as a pro-inflammatory cytokine demonstrate a critical role in the inflammatory response. Especially, the high levels of IL-6 measured in plasma have been associated with pathological inflammation. In this report, new molecularly imprinting biosensor on graphene quantum dots (GQDs)/functionalized multi-walled carbon nanotubes (f-MWCNTs) composite were prepared for IL-6 protein detection. The structures of GQDs, f-MWCNTs and GQDs/f-MWCNTs composite were highlighted by scanning electron microscope (SEM), transmission electron microscopy (TEM), raman spectroscopy, UV-vis spectroscopy, fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and X-ray diffraction (XRD) method. Surface morphology characterization shows the nanoporous cavities as an effective biosensing area. IL-6 protein imprinted electrode was prepared on GQDs/f-MWCNTs composite in the presence of 100.0 mM pyrrole containing 25.0 mM IL-6 protein. 0.01-2.0 pg ml-1 and 0.0030 pg ml-1 were found as linearity range and the detection limit (LOD) for analytical application in plasma samples. Finally, the validated biosensor was examined in terms of stability, repeatability and reproducibility. © 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

A major application of microfluidic paper-based analytical devices (mu PADs) includes the field of point-of-care (POC) diagnostics. It is important for POC diagnostics to possess properties such as ease-of-use and low cost. However, mu PADs need multiple instruments and fabrication steps. In this study, two different chemicals (Hexamethyldisilazane and Tetra-ethylorthosilicate) were used, and three different methods (heating, plasma treatment, and microwave irradiation) were compared to develop mu PADs. Additionally, an inkjet-printing technique was used for generating a hydrophilic channel and printing certain chemical agents on different regions of a modified filter paper. A rapid and effective fabrication method to develop mu PADs within 10 min Was introduced using an inkjet-printing technique in conjunction with a microwave irradiation method. Environmental scanning electron microscope (ESEM) and x-ray photoelectron spectroscopy (XPS) were used for morphology characterization and determining the surface chemical compositions of the modified filter paper, respectively. Contact angle measurements were used to fulfill the hydrophobicity of the treated filter paper. The highest contact angle value (141 degrees +/- 1) was obtained using the microwave irradiation method over a period of 7 min, when the filter paper was modified by TEOS. Furthermore, by using this method, the XPS results of TEOS-modified filter paper revealed Si2p (23%) and Si-O bounds (81.55%) indicating the presence of Si-O-Si bridges and Si(OEt) groups, respectively. The ESEM results revealed changes in the porous structures of the papers and decreases in the pore sizes. Washburn assay measurements tested the efficiency of the generated hydrophilic channels in which similar water penetration rates were observed in the TEOS-modified filter paper and unmodified (plain) filter paper. The validation of the developed mu PADs was performed by utilizing the rapid urease test as a model test system. The detection limit of the developed mu PADs was measured as 1 unit ml(-1) urease enzyme in detection zones within a period of 3 min. The study findings suggested that a combination of microwave irradiation with inkjet-printing technique could improve the fabrication method of mu PADs, enabling faster production of mu PADs that are easy to use and cost-effective with long shelf lives. (C) 2016 Elsevier B.V. All rights reserved.