Biomedical subjects

Hizuru Nakajima

Publications and source records attributed to Hizuru Nakajima.

4 recordsLinked to original sources

PubMed2005

Fabrication of an integrated PDMS microchip incorporating an LED-induced fluorescence device.

A microfluidic device with an integrated fluorescence detection system has been developed in order to miniaturize the entire analytical system. A blue or green light-emitting diode (LED) and an optical fiber were mounted in a polydimethylsiloxane-based microchip. The performance of this device was evaluated by microchip electrophoresis. When a green LED was used as the light source, the calibration curve of Sulforhodamine-101 was linear over the range 1-100 microM. The detection limit was found to be 600 nM (240 amol) for a S/N ratio of 3. When using a blue LED, the calibration curve of Fluorescein was linear over the range 0.2-100 microM. The detection limit was estimated to be 120 nM (50 amol) (S/N=3). The detection sensitivity per unit power was comparable to that of LIF. The RSD values for the migration time, peak height and peak area were 0.74, 7.18 and 9.45%, respectively. The integrated microfluidic device was successfully used to determine amino acid derivatives.

Amino Acids↗

PubMed2005

Chiral separation of NBD-amino acids by ligand-exchange micro-channel electrophoresis.

The chiral separation of amino acid derivatives by ligand-exchange electrophoresis in a microchannel chip was performed for the first time. A Cu(II) complex with L-prolinamide was used as a chiral selector. The migration behaviors of eleven NBD-DL-amino acids were investigated by ligand-exchange capillary electrophoresis (LE-CE). The enantiomer of five NBD-amino acids (Ser, Thr, Val, Phe and His) could be separated by LE-CE using a 20 mM ammonium acetate buffer (pH 9.0) containing 10 mM copper acetate, 20 mM L-prolinamide and 1 mM SDS. NBD-His was eluted in the order D-form and L-form, while the elution order of another enantiomers was L-form and D-form. Under this condition, the enantioseparation of these five NBD-amino acids by ligand-exchange microchip electrophoresis (LE-ME) was investigated using a glass microchip. The enantioseparation of NBD-Ser, -Thr and -His could be successfully accomplished by LE-ME. LE-ME was superior to LE-CE in terms of the short migration time and a good enantiomeric separation.

4-Chloro-7-nitrobenzofurazan↗

PubMed2004

Evaluation of the surface charge properties of porous graphitic carbon stationary phases treated with redox agents.

The effect of treatment of porous graphitic carbon (PGC) stationary phases with hydrogen peroxide and with sodium sulfite on the retention behavior of analyte compounds has been investigated using benzene, aromatic sulfonate ions, and benzyltrialkylammonium ions as model compounds. It is shown that the retention times of the cationic analytes are increased by treating the PGC column with the reducing agent, while decreased by treating it with the oxidizing agent. On the other hand, the retention times of the anionic analytes are decreased by treating the column with the reducing agent, while increased by treating it with the oxidizing agent. The effect of the redox treatment on the retention of benzene is negligibly small. The investigation of the ion-exchange property of the PGC packings have shown that PGC has anion-exchange property and the anion-exchange capacity is decreased by treating PGC with the reducing agent, whereas it is increased by treatment with the oxidizing agent. This means that the modification of the retention selectivity of the PGC stationary phases with redox treatment can be interpreted in terms of the change of the surface charge. The mechanism of chemical modification of the PGC stationary phase with redox treatment is discussed on the basis of the experimental results obtained on the ion-exchange capacity and the redox activity.

Journal Article↗

PubMed2004

Detection method for microchip separations.

The features of analytical systems utilizing microfluidic devices, especially detection methods, are described. Electrochemical detection (EC), laser-induced fluorescence (LIF), mass spectrometry (MS), and chemical luminescence (CL) methods are covered. EC enables detection without labeling and has been used in recent years because of its low cost and sensitivity. LIF is the most generally used detection method in microchip separations. Use of LED as an excitation source for fluorescence measurement was also developed for the purpose of miniaturization of the entire system, including detection and separation. Although MS enables highly sensitive analysis, the interface between MS and micro channels is still under examination. This review with fifty-two references introduces interesting detection methods for microchip separations. Related separation methods using microfluidic devices are also discussed.

Journal Article↗