Chung-Yuan Chen

Carbon nanotube composites for glucose biosensor incorporated with reverse iontophoresis function for noninvasive glucose monitoring.

This study aims to develop an amperometric glucose biosensor, based on carbon nanotubes material for reverse iontophoresis, fabricated by immobilizing a mixture of glucose oxidase (GOD) and multiwalled carbon nanotubes (MWCNT) epoxy-composite, on a planar screen-printed carbon electrode. MWCNT was employed to ensure proper incorporation into the epoxy mixture and faster electron transfer between the GOD and the transducer. Results showed this biosensor possesses a low detection potential (+500 mV), good sensitivity (4 μA/mM) and an excellent linear response range (r2 = 0.999; 0–4 mM) of glucose detection at +500 mV (versus Ag/AgCl). The response time of the biosensor was about 25 s. In addition, the biosensor could be used in conjunction with reverse iontophoresis technique. In an actual evaluation model, an excellent linear relationship (r2 = 0.986) was found between the glucose concentration of the actual model and the biosensor’s current response. Thus, a glucose biosensor based on carbon nanotube composites and incorporated with reverse iontophoresis function was developed.

The use of bioimpedance in the detection/screening of tongue cancer

Oral cancers are the 11th most common malignancy reported worldwide, accounting for 3% of all newly diagnosed cancer cases, and one with high mortality ratios among all malignancies. The objectives of this study were therefore to study the electrical properties of cancerous tongue tissue and normal tongue tissue, as well as to investigate a new approach for low-cost, noninvasive, and real-time screening of oral cancer. Twelve tongue cancer patients and twelve healthy subjects participated in this study. A disposable probe with four silver electrodes was used to measure the electrical properties of patients and healthy subjects tongue tissues at six different frequencies, which were 20Hz, 50kHz, 1.3MHz, 2.5MHz, 3.7MHz and 5MHz. The amplitude of the applied voltage was limited to 200mV. Four measurement parameters of impedance, phase angle, real part of impedance, and imaginary part of impedance of tongue were assessed to see if significant difference in values obtained in patients and healthy subjects tongue tissues existed. Intraclass correlation coefficient showed that all measurements had good reliability and validity (ICC>0.95 for all measurements). Significant differences were found at 20Hz (p<0.05-0.001 for the four measurement parameters) and 50kHz (p<0.001 for the four measurement parameters) between patients and healthy subjects tongue tissues. In conclusion, bioimpedance at a particular frequency is a potentially promising technique for tongue cancer screening.

A preliminary study of the use of bioimpedance in the screening of squamous tongue cancer

Oral cancers are the 11th most common malignancy reported worldwide, accounting for 3% of all newly diagnosed cancer cases, and one with high mortality ratios among all malignancies. The objective of this study was to study the electrical properties of cancerous tongue tissue (CTT) and normal tongue tissue (NTT). Five tongue cancer patients participated in this study. A disposable probe incorporating four silver electrodes was used to measure the electrical properties of CTT and the surrounding NTT of patients. Measurements were performed at six frequencies: 20 Hz; 50 kHz; 1.3 MHz; 2.5 MHz; 3.7 MHz; and 5 MHz, with the amplitude of the applied voltage limited to 200mV. Four measurement parameters of impedance (Z), phase angle (θ), real part of impedance (R), and imaginary part of impedance (X) of tongue tissue were assessed to see if there was any significant difference in the values obtained in CTT and surrounding NTT. The intraclass correlation coefficient showed that all measurements were reliable. A significant difference (P < 0.05 for the four measurement parameters) was found at 50kHz between CTT and surrounding NTT. It was also found that Z and R of CTT were generally smaller than that of surrounding NTT. In conclusion, bioimpedance at a particular frequency is a potentially promising technique for tongue cancer screening.

Extended base H + -ion sensitive bipolar junction transistor with SnO 2 /ITO glass sensing membrane

In this study, an extended base bipolar junction transistor (EBBJT) as an H+ ion sensitive device have been investigated. The SnO2/ITO glass, fabricated by sputtering SnO2 on the conductive ITO glass, is used as a pH-sensitive membrane for electrode, which is connected with a commercial bipolar junction transistor (BJT) device. The experimental data show that this structure has a linear pH response, about 57–60 mV/pH in the ion concentration range between pH 2 and 10, and hysteresis effect is about 4.2 mV. The thermal stability of EBBJT has been validated by the experimental results on pH values ranging from 2 to 10 in a temperature range of 25°C to 55 °C. In addition, it is easier to fabricate and package the sensitive membrane structure and the measurement is simple for the application of disposable biosensor without complex temperature compensation.

Extended Gate H+-Ion Sensitive Field Effect Transistor with Signal Interface

H + -ion concentration into digital form. This chip, fabricated in a 0.18-um CMOS 1P6M process, operated at a 1.8V supply voltage and normal sampling rate of 6.25MHz. The circuit (without pad) occupied an area of 0.66mm × 0.43mm. The experimental data showed that this structure has a linear pH response about 97 digital counts/pH in the ion concentration range between pH2 and pH12, and the gain errors within the H + -ion concentrations are less than 3%. The minimum detectable pH value can reach as small as ±0.25pH.

Portable urea biosensor based on the extended base bipolar junction transistor

In this study, an extended base bipolar junction transistor (EBBJT) was proposed to fabricate disposable urea biosensor. The detection of the urea is based on the variation of pH value. The gels, fabricated by the poly vinyl alcohol with pendent styrylpyridinium groups, were used to immobilize the urease. The SnO2/ITO glass, fabricated by sputtering SnO2 on the conductive ITO glass, was used as a pH-sensitive membrane for electrode, which is connected with a commercial bipolar junction transistor device. This readout circuit, fabricated in a 0.35-um CMOS 2P4M process, operated at 3.3V supply voltage. The circuit occupied an area of 1.0 mm × 0.9 mm. The dynamic range of the urea biosensor is from 1.4 to 64 mg/dl at the 10 mM phosphate buffer solution and the sensitivity of this range is about 65.8 mV/pUrea.

Urea biosensor based on an extended-base bipolar junction transistor.

In this study, a urea biosensor was prepared by the immobilization of urease onto the sensitive membrane of an extended-base bipolar junction transistor. The pH variation was used to detect the concentration of urea. The SnO2/ITO glass, fabricated by sputtering SnO2 on the conductive ITO glass, was used as a pH-sensitive membrane, which was connected with a commercial bipolar junction transistor device. The gels, fabricated by the poly vinyl alcohol with pendent styrylpyridinium groups, were used to immobilize the urease. This readout circuit, fabricated in a 0.35-um CMOS 2P4M process, operated at 3.3V supply voltage. This circuit occupied an area of 1.0 mm × 0.9 mm. The dynamic range of the urea biosensor was from 1.4 to 64 mg/dl at the 10 mM phosphate buffer solution and the sensitivity of this range was about 65.8 mV/pUrea. The effect of urea biosensors with different pH values was considered, and the characteristics of urea biosensors based on EBBJT were described.

CMOS

A CMOS delta-sigma (ΣΔ) pH-to-digital converter has been developed for continuous monitoring of H⁺-ion concentrations. The SnO₂/ITO glass, fabricated sputtering SnO₂ on the conductive ITO glass, was used as a pH-sensitive membrane of extended gate field effect transistor (EGFET) operational amplifier. The ΣΔ pH-to-digital converter, constructed by using EGFET-OP to realize switched-capacitor (SC) ΣΔ converter, converted the H⁺-ion concentration into digital form. This chip, fabricated in a 0.18-μm CMOS 1P6M process, operated at a 1.8 V supply voltage and normal sampling rate of 6.25 MHz. The gain error of the converter in the H⁺-ion concentration range between pH2 and pH12 is less than 2%, and the measurement error over the H⁺-ion concentration range of pH2 to pH12 can reach as small as ±0.02 pH.