Since its discovery in 2004, graphene has enticed engineers and researchers from various fields to explore its possibilities

Nephrogenic diabetes insipidus (NDI), which can be congenital or acquired, results from the failure of the kidney to respond to the anti-diuretic hormone (ADH). This will lead to excessive water loss from the body in the form of urine. The kidney, therefore, has a crucial role in maintaining water balance and it is vital to restore this function in an artificial kidney. Herein, an ultrasensitive and highly selective aptameric graphene-based field-effect transistor (GFET) sensor for ADH detection was developed by directly immobilizing ADH-specific aptamer on a surface-modified suspended graphene channel. This direct immobilization of aptamer on the graphene surface is an attempt to mimic the functionality of collecting tube V 2 receptors in the ADH biosensor. This aptamer was then used as a probe to capture ADH peptide at the sensing area which leads to changes in the concentration of charge carriers in the graphene channel. The biosensor shows a significant increment in the relative change of current ratio from 5.76 to 22.60 with the increase of ADH concentration ranging from 10 ag/mL to 1 pg/mL. The ADH biosensor thus exhibits a sensitivity of 50.00 µA· ( g / mL ) − 1 with a limit of detection as low as 3.55 ag/mL. In specificity analysis, the ADH biosensor demonstrated a higher current value which is 338.64 µA for ADH-spiked in phosphate-buffered saline (PBS) and 557.89 µA for ADH-spiked in human serum in comparison with other biomolecules tested. This experimental evidence shows that the ADH biosensor is ultrasensitive and highly selective towards ADH in PBS buffer and ADH-spiked in human serum.

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<p>The exclusive monoatomic framework of graphene makes it as an alluring material to be implemented in electronic devices. Thus, using graphene as charge carrying conducting channel material in Field Effect Transistors (FET) expedites the opportunities for production of ultrasensitive biosensors for future device applications. However, performance of GFET is influenced by various parameters, particularly by the length of conducting channel. Therefore, in this study we have investigated channel length scaling in performance of graphene field effect transistor (GFET) via simulation technique using Lumerical DEVICE software. The performance was analyzed based on electrical characterization of GFET with long and short conducting channels. It proves that conducting channel lengths have vast effect on ambipolar curve where short channel induces asymmetry in transfer characteristics curve where the n-branch is suppressed. Whereas for output characteristics, the performance of GFET heavily degraded as the channel length is reduced in short channels of GFET. Therefore, channel length scaling is a vital parameter in determining the performance of GFET in various fields, particularly in biosensing applications for ultrasensitive detection.</p>

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The race towards the development of user-friendly, portable, fast-detection, and low-cost devices for healthcare systems has become the focus of effective screening efforts since the pandemic attack in December 2019, which is known as the coronavirus disease 2019 (COVID-19) pandemic. Currently existing techniques such as RT-PCR, antigen–antibody-based detection, and CT scans are prompt solutions for diagnosing infected patients. However, the limitations of currently available indicators have enticed researchers to search for adjunct or additional solutions for COVID-19 diagnosis. Meanwhile, identifying biomarkers or indicators is necessary for understanding the severity of the disease and aids in developing efficient drugs and vaccines. Therefore, clinical studies on infected patients revealed that infection-mediated clinical biomarkers, especially pro-inflammatory cytokines and acute phase proteins, are highly associated with COVID-19. These biomarkers are undermined or overlooked in the context of diagnosis and prognosis evaluation of infected patients. Hence, this review discusses the potential implementation of these biomarkers for COVID-19 electrical biosensing platforms. The secretion range for each biomarker is reviewed based on clinical studies. Currently available electrical biosensors comprising electrochemical and electronic biosensors associated with these biomarkers are discussed, and insights into the use of infection-mediated clinical biomarkers as prognostic and adjunct diagnostic indicators in developing an electrical-based COVID-19 biosensor are provided.

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In this paper, three-dimensional (3D) porous carbon interdigitated electrode arrays (IDEAs) are developed utilizing standard photolithography of electrospun mats of SU-8 photoresist nanofibers. Porous IDEAs have the potential to produce higher aspect ratio than non-porous electrode due to the reduced stress at the interface between the substrate and the carbon structure [1]. In a first step, a layer of polymeric nanofibers is deposited on a silicon substrate by optimizing the conditions for far-field electrospinning of SU-8 photoresist. Subsequently, the SU-8 mat is patterned using conventional photolithography to generate the polymer precursor for the carbon electrode structure. Finally, the polymer precursor is pyrolysed at 900°C in an inert atmosphere to produce a porous carbon IDEA [2]. The porous carbon IDEAs were optimized as a function of the nanofibers diameter, thickness of the electrospun SU-8 mat and width/gap ratio of the IDEAs. To characterize the porous carbon IDEAs, electrochemistry studies (cyclic voltammetry and electrical impedance spectroscopy) were conducted and the results were compared with traditional flat carbon IDEAs (the latter was fabricated by spin coating a non-porous SU-8 film on a silicon substrate).  The redox amplification factor of both porous and flat carbon IDEAs was studied to gain an understanding of the effect of electrode porosity on the redox amplification. This factor was optimized for width and gap of the IDEAs and the nanofibers diameter.   Acknowledgments This research is supported by Flagship grant project number FL001A-14AET, Transdisiplinary Research Grant Scheme (TRGS TR002A-2014B) from University of Malaya and Ministry of Science Technology and Innovation (MOSTI) Science Fund (SF-020-2014).   References 1.         Sharma, C.S., A. Sharma, and M. Madou, Multiscale carbon structures fabricated by direct micropatterning of electrospun mats of SU-8 photoresist nanofibers. Langmuir, 2010. 26(4): p. 2218-2222. 2.         Kamath, R.R. and M.J. Madou, Three-Dimensional Carbon Interdigitated Electrode Arrays for Redox-Amplification. Analytical chemistry, 2014. 86(6): p. 2963-2971.