Now showing 1 - 4 of 4
  • Publication
    Electrical label-free sensing of cardiac troponin biomarker: FET-based integration with substrate-gate coupling
    Acute myocardial infarction (AMI) is a leading cause of death worldwide despite the existence of therapy’s advances. Therefore, an early diagnosis method by using cardiac biomarkers is essential to enable correct countermeasures. Cardiac Troponin I (cTnI) is one of the cardiac biomarkers for early diagnosis of AMI and considered as ‘gold standard’ for cardiac muscle injury determination. The detection of cTnI through an electrical-based biosensor allows label-free detection by converting biomolecular binding event into a significant electrical signal via a semiconductor transducer. It utilizes conductivity to specify the existence of biomolecules. One of the electrical-based biosensors known as field-effect transistor (FET)-based biosensor has drawn much attention for owning the concept of charge transduction; thus, allows early, high sensitivity, high selectivity, and rapid diagnosis of the specific cardiac biomarker at low concentrations. In this work, the zinc oxide (ZnO)-FET biosensor coupled with substrategate has been designed and fabricated for the detection of cTnI biomarker. ZnO thin film, as n-type biocompatible semiconductor material, and also as transducer was deposited via sol-gel and spin coating techniques between p-type source and drain terminal on SOI substrate, forming a p-n-p junction, a device capable of bio-sensing application. The surface morphology of the thin film was characterized by using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The thin film, which demonstrated hexagonal wurtzite phase as shown by X-ray diffraction (XRD) analysis appropriate for biomolecules interaction. The surface of the ZnO thin film was immobilized with cTnI monoclonal antibody (MAb-cTnI) as biological receptor via covalent binding technique for capturing cTnI biomarker. The process was validated by Fourier transform-infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The device structure was simulated in Silvaco Atlas 2D-simulator, to elucidate its electrical characteristic, by means of hole and electron concentration in the channel and buried oxide/substrate interface, respectively. The device demonstrated a new strategy via electrical characterization with the introduction of substrate-gate coupling that enhanced the formation of hole conduction layer at the channel between drain and source region. Finally, the biosensor shown significant increment in relative changes of drain current level in a linear range of 6.2 to 16.5 % with the increase of positively charge cTnI biomarker concentrations from 1 ng/ml to 10 μg/ml. The device sensitivity of the detection is at 2.51 %·(g/ml)-1 with limit of detection (LOD) down to 3.24 pg/ml.
  • Publication
    FET-biosensor for cardiac troponin biomarker
    Acute myocardial infarction or myocardial infarction (MI) is a major health problem, due to diminished flow of blood to the heart, leads to higher rates of mortality and morbidity. The most specific markers for cardiac injury are cardiac troponin I (cTnI) and cardiac troponin T (cTnT) which have been considered as ‘gold standard’. Due to higher specificity, determination of the level of cardiac troponins became a predominant indicator for MI. Currently, field-effect transistor (FET)-based biosensors have been main interest to be implemented in portable sensors with the ultimate application in point-of-care testing (POCT). In this paper, we review on the FET-based biosensor based on its principle of operation, integration with nanomaterial, surface functionalization as well as immobilization, and the introduction of additional gate (for ambipolar conduction) on the device architecture for the detection of cardiac troponin I (cTnI) biomarker.
  • Publication
    Fabrication and simulation of silicon nanowire pH sensor for Diabetes Mellitus detection
    Diabetes Mellitus (DM) is a disease failed to control the balance of blood sugar level due to lack of insulin thereby it effect human health. In Malaysia, there are around 3.9 millions people aged 18 years old and above have diabetes according to National Health and Morbidity Survey 2019. Silicon Nanowire is a nanostructure which has ultra-high sensitivity and non-radioactive that has potential given good performances when applied on pH sensor and biosensor. Silicon nanowire pH sensor and biosensor is an electronic sensor that investigated to improve the sensitivity and accuracy for detecting DM. This project consists of two parts, which are fabrication of silicon nanowire pH sensor and simulation of silicon nanowire biosensor as preliminary study. In fabrication, silicon nanowire of pH sensor is fabricated by conventional lithography process, reaction ion etching (RIE) and metallization to achieved the width of 100 nm silicon nanowire. The pH6, pH7, pH10 and DI water as analytes to analysis the current-voltage (I-V) characteristics of silicon nanowire pH sensor. In second part, the silicon nanowire biosensor as preliminary study is done simulation by Silvaco ATLAS devices simulator. The silicon nanowire with 30 nm in height and 20 nm in width of biosensor is designed and simulated to analyze the performance in terms of sensitivity. I-V characteristics of silicon nanowire biosensor according to different concentration of negative interface charge is determined. The negative interface charge represent as the Retinol Binding Protein 4 (RBP4) which is used to diagnose DM. The I-V characteristic based on the change in current, resistance and conductance to determine sensitivity. Lastly, the sensitivity of silicon nanowire pH sensor obtained 23.9 pS/pH while the sensitivity of simulated silicon nanowire biosensor obtained 3.91 nS/e.cm2. The results shown the more negative charge of concentration analyte attached on surface silicon nanowire has been accumulated more current flow from drain terminal to source terminal. It leads to the resistance becomes highest and obtained good sensitivity. In summary, the silicon nanowire pH sensor exhibited good performance and high sensitivity in detection pH level. The simulated silicon nanowire biosensor is capable of detecting biomolecular interactions charges to obtained high sensitive and accuracy result.
  • Publication
    Nanoparticle-based biosensors for detection of heavy metal ions
    Heavy metal pollution is one of the most serious environmental problems in the world. Many efforts have been made to develop biosensors for monitoring heavy metals in the environment. Development of nanoparticle-based biosensors is the most effective way to solve this problem. This review presents the latest technology of nanoparticle-based biosensors for environment monitoring to detect heavy metal ions, which are magnetic chitosan biosensor, colorimetric biosensor, and electrochemical biosensor. Magnetic chitosan biosensor acts as a nano-absorbent, which can easily detect and extract poisonous heavy metal ions such as lead ions and copper ions. There are several methods to prepare the chitosan based on the nanoparticle, which are cross-linking, co-precipitation, multi-cyanoguanidine, and covalent binding method. In colorimetric biosensor, gold and silver nanoparticles are commonly used to detect the lead and mercury ions. In addition, this biosensor is very sensitive, fast and selective to detect metal ions based on the color change of the solution mixture. Meanwhile, electrochemical biosensor is widely used to detect heavy metal ions due to a simple and rapid process, easy, convenient and inexpensive. This biosensor is focused on the surface area, which leads to significant improvement in the performance of devices in terms of sensitivity. The wide surface area can affect the performance of the biosensor due to a limited space for operation of electrode. Therefore, reduced graphene oxide is a suitable material for making the electrochemical biosensor due to a wide surface area, good conductivity and high mechanical strength. In conclusion, these three technologies have their own advantages in making a very useful biosensor in the detection of heavy metal ions.