Papers by Keyword: Biosensor

Abstract: In this article, we propose a biosensor based on a hybrid photonic crystal, the studied system is a superlattice consisting of a periodic alternation of poly(methyl methacrylate) (PMMA) and silicon dioxide (SiO₂) layers. Our study demonstrates that breaking the periodicity of the superlattice enables the excitation of Bloch surface waves within the photonic bandgap. This feature, along with its experimental convenience, justifies our choice of this structure for designing a biosensor in the Kretschmann configuration. Furthermore, we also analyzed the effect of various parameters, such as the number of layer repetitions, the frequency of the light waves used, and the thickness of the defect layer, on the biosensor's performance, the optimal structure, MgF₂/(PMMA/SiO₂)₃/D, demonstrates excellent sensing performance, achieving an angular sensitivity of 74°/RIU and a high figure of merit (FOM) of 1495/RIU.

Abstract: Point-of-care diagnostic systems face challenges because they are mainly designed for laboratory settings. Biosensor detection plays a crucial role in modern healthcare by enabling real-time monitoring of biomolecules, facilitating rapid diagnosis, and allowing for timely interventions. These sensors are vital for various applications, including glucose monitoring, infectious disease detection, and environmental analysis. The reader-disposable approach is gaining popularity in both research and commercial point-of-care devices. Open-source hardware projects based on microcontrollers are increasingly favored for biosensing applications due to their cost-effectiveness and flexibility. However, biosensors that operate in the nanoampere range still encounter issues with power supply, signal amplification, and result display. This research focuses on designing and developing a portable amperometric device for low-current detection. The system includes a multi-stage circuit featuring a voltage converter, voltage amplifier, microcontroller, display, and power supply. A shunt resistor converts input current to voltage, with an op-amp MAX4238 IC amplifying the voltage at a gain of 100. A NodeMCU microcontroller reads the output voltage and displays it on an LCD. For simulation, LTspice, Proteus 8 Pro, and Arduino software are used. Experimental testing involves using a voltage source and variable resistor to verify accuracy, comparing theoretical, simulation, and experimental results. The system demonstrated a sensitivity down to approximately 45 nA, with output linearity maintained across the tested range. The average error margin between experimental and theoretical values remained within ±2.5%. This advancement improves sensitivity in detecting low currents, enhancing point-of-care biosensing applications.

Abstract: The ethanol-water based extraction of phenolic bioactive components, anthocyanins, from purple cabbage (PC) was carried out. Ultrasound assisted extraction was performed and each cycle was set to 3 minutes. UV-visible absorbance was evaluated at each cycle (total 3 cycles) and the intensity of absorbance at 546~550 nm was interpreted as the extraction efficiency of anthocyanin. The pH sensibility of PC extracts was evaluated at pH 4, 5, 6, 7, and 8 and measured with UV-Visible spectrometry. Each pH condition, the extracts presented different color shades and wavenumbers of maximum absorbance proving their pH sensibility. Antioxidant activity of PC extract was evaluated and the excellent inhibition capacity was observed (~98%). PC extract was then embedded in alginate membrane to use as wound dressing materials. Alginate membrane with PC extract also presented high pH sensibility showing remarkable color changes after exposure to different pH environments.

Abstract: The performance of a commercial GMR with a double-chip configuration has been investigated for detecting nanotag. Fe₃O₄ magnetic nanoparticles (MNPs) as tags were synthesized by co-precipitation method based on green synthesis using Moringa oleifera (MO) extract. Fe₃O₄ showed a soft ferromagnetic material and a magnetic saturation of 55.0 emu/g. MNPs-ethanol solution are dropped onto the surface of each chip of the sensing element. As a comparison, the performance of a single-chip configuration is also investigated. Obtained bias magnetic field used as a magnetic field sensing double-chip sensor is 3.8 Oe smaller than the single-chip sensor, which is 4.3 Oe, confirmed by the shift in the value of the first derivative order. Configuration of double-chip sensor in detecting Fe₃O₄ has a smaller LoD of 2.4 mg/mL compared to the single-chip configuration of 3.8 mg/mL. Therefore, Green-synthesized Fe₃O₄ as biocompatible magnetic tags in combination with commercial GMR sensors using double-chip configuration is promising for magnetic-based biosensor applications in driving more responsive detection and enabling portability by using a smaller energy source.

Abstract: This work aims to optimize Plasma-Enhanced Chemical Vapour Deposition (PECVD) amorphous hydrogenated silicon carbide (a-SiC:H) as a conformal passivation layer for invasive microelectrode array (MEA) neural interface applications. By carefully tuning the PECVD deposition parameters, the composition, structure, electrical, and mechanical properties of the films can be optimized for high resistivity, low stress, and great resistance to chemical attack. This optimization will eventually allow a-SiC:H to be used as an ideal insulation, passivation and protection layer for thin and biocompatible all-SiC neural interfaces.

Abstract: In this paper, a suitable process technology is employed to fabricate a new open gate silicon carbide-based junction field-effect transistor (OG-4H-SiC-JFET) intended to be used for all types of biochemical sensing applications. The main focus is dedicated to the fabrication steps and specifically the plasma etching of the SiC as it is the key step to pattern the device components. All necessary I-V characteristics (I_DS-V_DS and I_DS-V_GS) have been derived and show acceptable electrical performance. Furthermore, the electrical characteristics of the OG-4H-SiC JFET were simulated using 3D Silvaco ATLAS and are in line with the experimental electrical characteristics. The efficacity and simplicity of the process described in this paper is the first step for future development of biochemical sensors based on SiC-FETs.

Abstract: In this work, a diagnostic application was performed by utilizing magnetic nanoparticles for the bio-sensing. A novel Fe₃O₄ nanostructure was synthesized in this paper using a simple hydrothermal method, the Fe₃O₄ nanoparticles are successfully controlled to provide a more dynamic site for catalytic reaction. FTIR-analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) was used to examine the morphology of the synthesized nanoparticles. The findings showed that a unique Fe₃O₄ nanostructure was obtained nanoparticles confined in nanosphere. The relative catalytic kinetics of Fe₃O₄ nanostructure has followed Michaelis–Menten behaviours, according to an analysis of peroxidase-like activity. An effective approach for colorimetric sensing of glucose was formulated on the bases of efficient peroxidase-mimicking activity of Fe₃O₄ nanoparticles. The synthesized Fe₃O₄ nanoparticles are very hopeful for the application of bio-sensors.

Abstract: A novel leaky waveguide grating (LWG) biosensor is reported where a continuous waveguide film of chitosan was photo patterned, resulting in a periodic modulation of the concentration of recognition elements (streptavidin in this case). This resulted in a periodic variation in the refractive index of the waveguide film, forming a phase grating at resonance angles of the LWG. Thus, a diffraction pattern was observed at resonance angles, but not at other angles. The position of resonance angles and hence diffraction pattern was a function of the refractive index of chitosan waveguide strips, forming the basis of biosensing and quantitative measurements.

Abstract: A SiCNWFET device serving as a biosensor was designed and simulated using Silvaco ATLAS device simulation software. The performance of the designed device in charges sensing was investigated. The device shows the ability to recognize different interface charge values ranging from-1.10E11 to-5.10E12 cm^-2 applied on the surface of the silicon carbide nanowire channel to simulate target charge biomolecules that bound to the biosensor. A significant change in the output current is observed due to the presence of different values of fixed interface charge densities. An optimum, according to the TCAD simulation, the 4H-SiC epitaxial structure has been grown. The designed device was fully fabricated on this structure and it exhibited acceptable electrical characteristics.

Abstract: This report studies the charge-based sensing modality of FET-embedded nanopore biosensors through FEM simulation. PNP equation is solved to analyze the mirror charge introduced by charged biomolecule while threading through the nanopore-FET sensor. Negative and positive charged molecules are analyzed respectively. Obvious local potential change induced by the presenting of charged molecules nearby is observed. In addition, the transport-induced descreening effect is observed under intensive bias, which might explain the capability of charge sensing even under high concentrations such as 1 M for FET-nanopore biosensors.