The Analysis of the Urea Biosensors Using Different Sensing Matrices via Wireless Measurement System & Microfluidic Measurement System

Abstract

Two types of urea biosensors were integrated with a wireless measurement system and microfluidic measurement system. The two biosensors used were (i) a magnetic beads (MBs)-urease/graphene oxide (GO)/titanium dioxide (TiO2)-based biosensor and (ii) an MBs-urease/GO/ nickel oxide (NiO)-based biosensor, respectively. The wireless measurement system work exhibited the feasibility for the remote detection of urea, but it will require refinement and modification to improve stability and precision. The microchannel fluidic system showed the measurement reliability. The sensing properties of urea biosensors at different flow rates were investigated. From the measurement results, the decay of average sensitivity may be attributed to the induced vortex-induced vibrations (VIV) at the high flow rate. In the aspect of wireless monitoring, the average sensitivity of the urea biosensor based on MBs-urease/GO/NiO was 4.780 mV/(mg/dl) and with the linearity of 0.938. In the aspect of measurement under dynamic conditions, the average sensitivity of the urea biosensor based on MBs-urease/GO/NiO were 5.582 mV/(mg/dl) and with the linearity of 0.959. Both measurements performed NiO was better than TiO2 according to the comparisons.

A New Calibration Circuit Design to Reduce Drift Effect of RuO2 Urea Biosensors

“…In this chemical equation, urea reacts with urease and is converted to ammonium (NH4 + ), bicarbonate (HCO 3 − ), and hydroxide ions (OH − ) [25]. The sensing properties of the flexible arrayed RuO 2 urea biosensor were measured by the V–T measurement system.…”

“…Next, the RuO 2 film was deposited on the flexible arrayed PET substrate through a sputtering system to form the RuO 2 film window; then, it was encapsulated with an epoxy thermosetting polymer. The urease was immobilized because of the covalent bond, its low diffusivity, and strong binding, which reduced the loss and stability of the urease [25]. Afterward, the aminopropyltriethoxysilane (APTS) solution was dropped on the RuO 2 sensing film at room temperature.…”

“…Although different urea biosensors had been widely studied to achieve better sensing characteristics [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25], the non-ideal effects and drift rates had been barely discussed in previous works. Chou et al [24] presented a flexible arrayed urea sensor based on urease-magnetic beads (MBs) and graphene oxide (GO), but it was only able to measure the drift rate and the drift effect calibration method was not discussed.…”

“…In this study, RuO 2 was used as a sensing film to fabricate a urea biosensor, and a new calibration circuit (NCC) was proposed to reduce the drift effect of an RuO 2 urea biosensor. To verify the functions of the RuO 2 urea biosensor, several sensing characteristics were measured within the normal urea concentration range of the human body (2.5–7.5 mM) [25], using the conventional voltage–time (V–T) measurement system. Based on the results, with the application of the voltage regulation technique, the proposed NCC obtained a significantly lowered drift rate compared to that of the conventional V–T measurement system.…”

Magnetic Particles: Their Applications from Sample Preparations to Biosensing Platforms

“…The main advantages of the instrumentation are that they do not require a reference electrode, are inexpensive, have the ability to minimize the direct electrical response, are fast, and are single-use biological devices [90][91][92]. In this study, urease based magnetic beads were modified with graphene oxide and nickel oxide to have conduction of interfacial electrons and high enzyme binding activity [93]. Upon the target outline in urea samples, the wireless measurement system and the microfluidic measurement system proceeded to separate testing assays.…”