Keun-Yong Park

Gene expression of central and peripheral renin-angiotensin system components upon dietary sodium intake in rats.

The effects of dietary sodium intake on the gene expression of the renin-angiotensin system (RAS) were investigated in rat central and peripheral tissues in a single set of experiment. Northern and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques were used to detect mRNA expression in rats fed a low- or a high-sodium diet (5 or 500 mmol Na+/kg diet) for 20 days. Plasma and renal renin levels were elevated in rats maintained on the low-sodium diet. Sodium deprivation enhanced the expression of angiotensinogen, renin, AT1A and AT1B receptor subtypes in the hypothalamus, but suppressed them in the brainstem. Kidney and adrenal levels of those mRNAs were also enhanced in the sodium-restricted rats. Both AT1A and AT1B mRNAs changed in a similar magnitude in each tissue examined upon dietary sodium intake. AT1A was the predominant receptor subtype of AT1 in all the tissues examined in the present study except the adrenal gland. The present study demonstrated that dietary sodium modulated the gene expression of the RAS components in the central and peripheral tissues. It also showed that the RAS components in the brainstem and hypothalamus were differentially expressed upon sodium deprivation. This suggests different roles of the RAS in these tissues in maintaining body fluid homeostasis in response to different sodium intakes.

Development of FET-type albumin sensor for diagnosing nephritis.

An albumin biosensor based on a potentiometric measurement using Biofield-effect-transistor (BioFET) has been designed and fabricated, and its characteristics were investigated. The BioFET was fabricated using semiconductor integrated circuit (IC) technology. The gate surface of the BioFET was chemically modified by newly developed self-assembled monolayer (SAM) synthesized by a thiazole benzo crown ether ethylamine (TBCEA)-thioctic acid to immobilize anti-albumin. SAM formation, antibody immobilization, and antigen-antibody interaction were verified using surface plasmon resonance (SPR). The output voltage changes of the BioFET with respect to various albumin concentrations were obtained. Quasi-reference electrode (QRE) and reference FET (ReFET) has been integrated with the BioFET, and its output characteristic was investigated. The results demonstrate the feasibility of the BioFET as the albumin sensor for diagnosing nephritis.

Fabrication and characteristics of bioFET albumin sensor using new self-assembled monolayer

The BioFET albumin sensor with the gold gate as a gate material was fabricated and its characteristics were investigated. To enable label-free molecular detection, the BioFET gate surface was chemically modified by new immobilized molecular receptors, so called self-assembled monolayer (SAM) synthesized by a thiazole benzo crown ether ethylamine (TBECA)-thioctic acid to bind albumin-antibody. In this paper an albumin antigen-antibody binding generated above the gate surface was used as an albumin sensing mechanism of the BioFET. So the drain current was varied by antigen-antibody interactions on gate surface because the albumins have a negative charge. Experimental results related to the formation of SAM, antibody, and antigen were obtained from quartz crystal microbalance and surface plasmon resonance.

Fabrication and characteristics of MOSFET protein sensor using gold-black gate

Research in the field of biosensor has enormously increased over the recent years. The metal-oxide semiconductor field effect transistor (MOSFET) type protein sensor offers a lot of potential advantages such as small size and weight, the possibility of automatic packaging at wafer level, on-chip integration of biosensor arrays, and the label-free molecular detection. We fabricated MOSFET protein sensor and proposed the gold-black electrode as the gate metal to improve the response. The experimental results showed that the output voltage of MOSFET protein sensor was varied by concentration of albumin proteins and the gold-black gate increased the response up to maximum 13 % because it has the larger surface area than that of planar-gold gate. It means that the expanded gate allows a larger number of ligands on same area, and makes the more albumin proteins adsorbed on gate receptor.

Fabrication and Characteristics of MOSFET Protein Sensor Using Nano SAMs

Protein and gene detection have been growing importance in medical diagnostics. Field effect transistor (FET) - type biosensors have many advantages such as miniaturization, standardization, and mass-production. In this work, we have fabricated metal-oxide-semiconductor (MOS) FET that operates as molecular recognitions based electronic sensor. Measurements were taken with the devices under phosphate buffered saline solution. The drain current () was decreased after forming self-assembled mono-layers (SAMs) used to capture the protein, which resulted from the negative charges of SAMs, and increased after forming protein by 11.5% at

Improved Recovery Time for ISFET Glucose Sensor

An ion sensitive field effect-transistor (ISFET) glucose sensor is a particularly appropriate configuration for application to in situ and in vivo monitoring. Some of the initial problems related to ISFET glucose sensors, i.e., low sensitivity and a slow response time, have already been solved by the oxidation of hydrogen peroxide (H2O2), a residual product generated by the glucose reaction in the enzyme-immobilized membrane. However, for the further application of ISFET glucose sensors, the decrease in reproducibility due to recovery-time delays with repeat-measurements must be solved. Accordingly, this study proposes an electrolysis method to deal with this problem and the experimental results confirm that the recovery-time was reduced to less than two minutes in contrast to the 10 or 20 minutes required with the conventional method.