Biomedical subjects

Sejin Park

Publications and source records attributed to Sejin Park.

7 recordsLinked to original sources

PubMed2006

Electrochemical nanoneedle biosensor based on multiwall carbon nanotube.

We report the fabrication and analytical functions of a biosensor based on a nanoneedle consisting of a multiwall carbon nanotube attached to the end of an etched tungsten tip. The devised electrode is the smallest needle-type biosensor reported to date. The nanoneedles prepared in this work are 30 nm in diameter and 2-3 microm in length. Dopamine and glutamate, which are physiologically important neurotransmitters, were successfully detected using these nanoneedles. Bare nanoneedles detected dopamine in the range from 100 to 1000 microM by differential pulse voltammetry, and enzyme-modified nanoneedles were able to respond to glutamate in the 100-500 microM range by potentiostatic amperometry.

Biosensing Techniques↗

PubMed2005

pH-sensitive solid-state electrode based on electrodeposited nanoporous platinum.

The nanoporous platinum oxide (H1-ePtO) as a hydrogen ion-selective sensing material is reported. Bare nanoporous platinum oxides exhibit near-Nernstian behavior (e.g., -55 mV/pH in PBS), ignorable hysteresis, a short response time, and high precision, which are remarkably better than those of flat platinum oxides. The electrode potential of a nanoporous platinum oxide responds exclusively to hydrogen ion, which implies its usefulness as a solid-state pH sensor. In the present study, the performance of nanoporous platinum oxide was investigated and compared with that of IrOx in terms of selectivity and the influences of ionic strength, temperature, complexing ligands, and surfactants. H1-ePtO functions well as a pH-sensing solid-state material, and it is viewed as a promising alternative to IrOx. Interference by redox couples was successfully suppressed by covering the H1-ePtO surface with a protective layer, e.g., an electropolymerized polyphenol thin film. Since the nanoporous platinum oxide with such a protective layer is particularly suitable for miniaturization and micropatterning, our findings suggest its usefulness in applications such as solid-state pH sensors embedded in chip-based microanalysis systems.

Cations↗

PubMed2004

Ionic strength-controlled virtual area of mesoporous platinum electrode.

Mesoporous electrodes provide an unusual opportunity to observe the dramatic transition of the electrochemical potential distribution in vicinity to mesoporous surfaces as the ionic strength varies. The experimental results were in accordance with what the classical Gouy-Chapman theory predicts on the basis of the correlation between Debye length (kappa-1) and the diameter of mesopores. Using the phenomenon that the electrochemically effective area of mesoporous electrode depends on the ionic strength, the faradaic current density of dioxygen reduction could be controlled by the electrolyte concentration.

Journal Article↗

PubMed2004

Glucose sensor based on glucose oxidase immobilized by zirconium phosphate.

Amperometric glucose sensors were fabricated using glucose oxidase (GOx) entrapped in zirconium hydrogenphosphate (ZrP), and their performance was evaluated. Reportedly, alpha-ZrP is one of the candidates that are expected to improve the stability of enzymes immobilized on solid surfaces. We intercalated GOxs into ZrP (GOx/ZrP), cast the GOx/ZrP suspension in polyvinylalcohol on a platinum electrode, and dried it in a vacuum oven. The morphological layered structure was investigated by scanning electron microscopy. The enzymatic activities, which were determined by open-circuit potentiometric technique, reached the highest when GOxs were immobilized in ZrP at ca. pH 5. In vitro tests showed good linear responses in the 0-25 mM range and the sensitivity of 0.14 nA mM(-1) at 0.4 V vs. Ag/AgCl. The sensors, as made, were stable for more than 3 days within a limited deterioration.

Biosensing Techniques↗

PubMed2003

In vivo calibration of the subcutaneous amperometric glucose sensors using a non-enzyme electrode.

A new two-point calibration method for the subcutaneous amperometric continuous glucose sensor is reported. The proposed method is based on direct measurement of the background current (I(o)) using a non-enzyme electrode. For in vivo test, three electrodes were implanted in rabbits. Two of the three were identical needle-type enzyme electrodes with perfluorinated polymer outer layers (Pt/enzyme layer/Kel-F/PTFE/Kel-F/Nafion) that were placed in subcutaneous tissue and in a vessel (ear artery), respectively. And one non-enzyme electrode with exactly the same membrane composition as those of other two was in the subcutaneous layer to measure the background current. Implantation in the subcutaneous layer generated many crevices on the protecting layers of the electrodes. The signals from enzyme electrodes were effectively corrected by the measured background current from the non-enzyme electrode. In addition, a telemetric monitoring system was developed and evaluated for in vivo continuous glucose monitoring in order to alleviate the problems of motion artifact.

Algorithms↗

PubMed2003

Nonenzymatic glucose detection using mesoporous platinum.

Roughness of nanoscopic dimensions can be used to selectively enhance the faradaic current of a sluggish reaction. Using this principle, we constructed mesoporous structures on the surfaces of pure platinum electrodes responding even more sensitively to glucose than to common interfering species, such as L-ascorbic acid and 4-acetamidophenol. Good sensitivities, as high as 9.6 microA cm(-2) mM(-1), were reproducibly observed in the presence of high concentration of chloride ion. The selectivities, sensitivities, and stabilities determined experimentally have demonstrated the potential of mesoporous platinum as a novel candidate for nonenzymatic glucose sensors.

Biosensing Techniques↗

PubMed2003

In vitro and short-term in vivo characteristics of a Kel-F thin film modified glucose sensor.

A new outer layer composition, consisting of polytetrafluoroethylene (PTFE), Kel-F oil, and Nafion, is suggested to minimize the detrimental effect of dissolved oxygen and to extend the linear response range of a glucose oxidase(GOx)-based sensor using nonconducting polymer. The morphology of Kel-F/PTFE/Kel-F/Nafion polymeric laminate was followed during fabrication by SEM. When Kel-F film was formed on the PTFE outer layer, the linear response was extended to 21 mM, at a sensitivity of 2.8 +/- 0.8 nA/mM mm2. We demonstrate that a sensor without Kel-F/PTFE/Kel-F/Nafion outer layer is relatively oxygen dependent, whereas by comparison a sensor with Kel-F/PTFE/Kel-F/Nafion outer layer is oxygen independent. The current of such a glucose sensor implanted in the subcutaneous tissue stabilized within 60 min, and the lag between blood glucose changes and sensor output was within 1 min. The in vivo characteristics of the glucose sensor described show great promise for one-point in vivo calibration.

Animals↗