Hyun-Ok Kim

Photoresponse of Si detector based on n-ZnO/p-Si and n-ZnO/n-Si structures

Abstract The ZnO/Si photodiodes have been fabricated depositing n-ZnO films on n- and p-Si by rf sputtering method. All the n-ZnO/p-Si diodes show strong rectifying behavior characterized by the current–voltage ( I – V ) measurement under a dark condition while the n-ZnO/n-Si diodes showed weak rectifying behaviors. Photoelectric effects have been exhibited under an illuminated condition using a red light of 670 nm. High photocurrent or responsivities are obtained under a reverse bias when the crystalline quality of n-ZnO film is good enough to transmit the light into p-Si.

Two-step maturation of immature DCs with proinflammatory cytokine cocktail and poly(I:C) enhances migratory and T cell stimulatory capacity.

Effective induction of cell-mediated immune responses strongly depends on the ability of dendritic cells (DCs) to produce Th1-polarizing cytokines, migrate to lymph nodes and stimulate T cells through antigen-presenting complex and costimulatory molecules. While various protocols for optimizing DC maturation with single or multiple stimuli mimicking infections or inflammatory milieu have been proposed for the generation of DCs with features desired for clinical application, stepwise maturation of DCs by these multiple stimuli has not been systemically assessed. Among the combinations of several immune-modulating factors with known effects on DC maturation, we found that stepwise DC maturation with cytokine cocktail (TNF-alpha+IL-6+IL-1 beta+PGE(2)) followed by poly(I:C) stimulation enhanced the production of IL-12 with strong allostimulatory capacity. While there were no significant differences between DC matured by simultaneous or sequential activation by cytokine cocktail and poly(I:C) in expression of markers and costimulatory molecules of mature DCs, the delivery of inflammatory signal prior to poly(I:C) results in sustained interleukin-12 expression with reduced IL-10 than DC matured by simultaneous stimulation. This sequential stimulation significantly increased migratory capacity in response to CCL21 and CXCL12 compared to DC matured with cytokine cocktail. Furthermore, these DCs retained their responsiveness to CD40L stimulation in secondary IL-12 production and efficiently generated autologous antigen-specific effector T cells as evidenced by ELISPOT assay. Thus, we propose a novel DC maturation protocol in which stimulation of DCs with cytokine cocktail and subsequently with poly(I:C) generates DCs with a high migratory capacity with a preferential Th1 inducing capacity.

Smart blood bag management system in a hospital environment

In order to provide suitable blood transfusion samples to patients, the blood bag should be kept at a uniformly maintained temperature to prevent deterioration during transportation. Therefore, this paper presents a blood monitoring and management system for use in hospitals. This system may continuously report the temperature of the blood bank refrigerator, track the location of a blood bag to increase staff operation efficiency, and can confirm that the assigned blood bag was transported to the intended patient in need of transfusion. We developed and demonstrated the clinical usability of the combined blood temperature management and tracking system using a ubiquitous sensor network and RFID (Radio Frequency Identification) technology.

Hybrid cell sorters for on-chip cell separation by hydrodynamics and magnetophoresis

The classification of cells is important for medical diagnosis and medicine research. A micro-scale analysis system for blood allows immediate diagnosis, regardless of time or location. Rapid handling of biological cells is required for the development of lab-on-a-chip and point-of-care technologies. In previous papers, the reported sample solution flow rates for hydrodynamic cell separation ranged from 0.1 to tens of μl min−1. This paper proposes a hybrid cell sorter that combines hydrodynamics and magnetophoresis. This cell sorter is proposed for improving the classification efficiency of a virtual impactor-based cell sorter and for permitting the hydrodynamic cell separation with high throughput. In addition, its performance has been evaluated in the classification of Jurkat cells and blood cells. In the Jurkat cell experiment, the classification efficiency of Jurkat cells at the major outlet decreased from 70 to 50.8% with the proposed hybrid scheme. The flow rate for cell separation was 1 ml min−1. The classification efficiency of red blood cells (RBCs) increased from 75.2 to 86.8% with the application of a magnetic field. Also, the classification efficiency of white blood cells (WBCs) decreased from 83.8 to 70.9% with an applied magnetic field. Experimental results demonstrated that the classification efficiency of blood cells can be modulated and enhanced by magnetophoresis and that the hybrid cell sorter has potential for lab-on-a-chip applications.

Photoelectric, stoichiometric and structural properties of n-ZnO film on p-Si

Abstract n-ZnO/p-Si heterojunction photodiodes have been fabricated by sputter deposition of n-ZnO films on p-Si substrates. Substrate temperatures of 300, 400, 500 and 600°C were used for the n-ZnO film deposition using various Ar/O2 ratios from 1:1 to 6:1. All the diodes, except for one obtained at a high substrate temperature of 600°C, show strong rectifying behavior as characterized by current–voltage (I–V) measurement in a dark room. Photoelectric effects from the diodes have been observed under illumination using monochromatic red light with a wavelength of 670 nm. High levels of photocurrent or responsivity were obtained under reverse bias conditions when the stoichiometry of n-ZnO films was improved by optimizing the process conditions, such as the substrate temperature and Ar/O2 ratio. The n-ZnO/p-Si structure prepared at 300°C was found to be unsuitable because photoelectric effects were not apparent from this structure. A heterojunction diode with n-ZnO deposited at 600°C was also found to be unsuitable because the dark leakage current was too high, even though the diode showed photoelectric effects.

Genetic Comparison of Stemness of Human Umbilical Cord and Dental Pulp

This study focuses on gene expression patterns and functions in human umbilical cord (UC) and dental pulp (DP) containing mesenchymal stem cells (MSCs). DP tissues were collected from 25 permanent premolars. UC tissue samples were obtained from three newborns. Comparative gene profiles were obtained using cDNA microarray analysis and the expression of tooth development-associated and MSC-related genes was assessed by the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Genes related to cell proliferation, angiogenesis, and immune responses were expressed at higher levels in UC, whereas genes related to growth factor and receptor activity and signal transduction were more highly expressed in DP. Although UC and DP tissues exhibited similar expression of surface markers for MSCs, UC showed higher expression of CD29, CD34, CD44, CD73, CD105, CD146, and CD166. qRT-PCR analysis showed that CD146, CD166, and MYC were expressed 18.3, 8.24, and 1.63 times more highly in UC, whereas the expression of CD34 was 2.15 times higher in DP. Immunohistochemical staining revealed significant differences in the expression of genes (DSPP, DMP1, and CALB1) related to odontogenesis and angiogenesis in DP. DP and UC tissue showed similar gene expression, with the usual MSC markers, while they clearly diverged in their differentiation capacity.

Hydrodynamics and magnetophoresis based hybrid blood cell sorter

The classification of cells is important for medical diagnosis and medicine research. A micro-scale analysis system for blood allows immediate diagnosis, regardless of time or location. Rapid handling of target cells is required for accurate analysis because WBCs are easily altered during cell separation. In previous papers, the reported sample solution flow rates for cell sorting were on the order of tens of micro-liters per minute. This paper proposes a hybrid cell sorter (HCS) that combines hydrodynamics and magnetophoresis. The HCS is proposed for improving the classification efficiency of a virtual impactor-based cell sorter. Also, its performance has been evaluated in the classification of blood cells. The overall classification efficiency of red blood cells (RBCs) increased from 68.26% to 88.63% when using the proposed hybrid scheme. Experimental results show that the classification efficiency of blood cells could be modulated and enhanced by magnetophoresis.

Design of blood temperature management system using RFID and ubiquitous sensor network

We focus on the solutions to prevent fatal risk to patients life caused by transfusing blood which is wrong type or has exceeded norm temperature. Also, this study gives priority to the verification of medical safety of using blood, of which management is applied advanced sensor tag technology adopted RFID(Radio Frequency Identification) temperature sensor and USN(Ubiquitous Sensor Network) for temperature management of blood. Therefore, this study can contribute to protect of health of patients who take blood transfusion through construction of basis of new process of blood management.