Time filter

Source Type

Kim J.H.,Medical Device Development Center | Ozkan M.,University of California at Riverside
Proceedings of SPIE - The International Society for Optical Engineering

We fabricated 1.4 nm nanogold and molecular dark quencher assembled quantum dot for estimating their performances in a target specific conformal changing molecular event. For the assembling, we immobilized each acceptor linked molecular beacons using interaction between biotin at molecular beacon and streptavidins on quantum dot. Through optical analysis of the purified hybrids of the acceptors and quantum dots, we could estimate numbers of the assembled acceptors per quantum dot and their efficiency of energy transfer depending on conformal changes of molecular beacons. We obtained maximum 95 % and 78% of energy transfer efficiency with 17 metallic nanocrystals and 41 black hole quencher 2, the molecular dark quencher per single quantum dote, respectively. Molecular beacons form linear helix from a hair-pin structure by hybridizing with complementary DNA. In the presence of target DNA, energy transfer efficiency of the organic quencher was 22 % while only 2 % decreased efficiency was obtained with the nanogold, indicating higher fluorescence recovery with the ordinary organic quencher. Considering the relatively low assembled number and the large size, a steric hindrance might be attributed to the low fluorescence recovery. Since the energy transfer efficiency obtained with the nanogold at a fixed distance is high enough, it would be still effective to apply nanogold a system, where nanogold is removed permanently from quantum dots. © 2014 SPIE. Source

Choi J.-R.,Medical Device Development Center | Lee S.,Pusan National University | Kim K.,Pusan National University
Biomedical Engineering Letters

Developments of super-resolution imaging techniques have considerable interests to detect and image tiny molecular events under a diffraction limit. Stimulated emission and depletion (STED) microscopy, photo-activated light microscopy (PALM) and structured illumination microscopy (SIM) are representative successful novel imaging techniques. Recently, surface plasmons (SP) based super resolution imaging techniques which can achieve super resolution with no deviation from conventional microscopic schematics have been actively investigated. In this paper, we explain the principle of SP phenomena which can apply for bioimaging, and introduce localized SP based super resolution imaging techniques to increase lateral and axial resolution below the diffraction limits. Three different novel techniques based on field localization are introduced to increase lateral resolution. Also, additional three imaging techniques based on extraordinary transmission and Förster resonance energy transfer are introduced to increase axial resolution. Consequently, we explore a future direction of SP based imaging researches for 3D spatiotemporal super resolution microscopy. © 2014, Korean Society of Medical and Biological Engineering and Springer. Source

Shin J.-H.,Medical Device Development Center
Journal of Mechanical Science and Technology

Time-varying pressure produced in a cylinder chamber of an axial hydraulic pump is closely associated with various crucial issues such as system noise emission, swash-plate control, lubrication in sliding parts and etc. In this paper a computational study was performed to investigate the dynamic behavior of the cylinder pressure considering a general system of a piston pump, a hydraulic line, and an end resistance. Combined lumped and distributed parameter model was used, and led to successful fitting with existing experimental data obtained from a pump/line/resistance system which included a pressure relief valve in series. Using the developed tool, the effects of several dimension and operation parameters were investigated assuming that the end resistance was a simple orifice valve. The calculation results, depicted in both time domain and frequency domain, showed that the harmonics of the dynamic pressure and their amplitudes varied with line size capriciously. It was also shown that the harmonic of maximum pulsation amplitude changed in a periodic way as rotating frequency increased. Lastly, the pulsation amplitudes increased with the increase of discharge pressure proportionally with no change of the harmonics. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

Song Y.S.,Yonsei University | Won Y.J.,Medical Device Development Center | Kim D.Y.,Yonsei University
Current Applied Physics

To study the mechanisms of and conditions for adipogenesis, an accurate in situ observation tool is necessary to monitor the quantity of intracellular neutral lipids in differentiating preadipocytes. Although conventional fluorescence intensity imaging is a powerful tool for observing the formation and growth of an individual lipid droplet, it suffers from photobleaching and ambiguous autofluorescence or background signals from cells. In this paper, we present a fluorescence lifetime imaging microscopy (FLIM) technique that has the potential to quantify the ratio of neutral to polar lipids in a cell. Measurement of time-lapse FLIM images of differentiating 3T3-L1 cells that contained the Nile Red (NR) probe showed that the average lifetime of NR decreased from 4 ns in preadipocytes to 3 ns in fully differentiated adipocytes after 10 days of differentiation. This large change in the lifetime of NR can be used to monitor the early stages of adipogenesis, even when the lipid droplet is too small to be identified with a conventional microscope. © 2015 Elsevier B.V. Source

Kim S.,Hanyang University | Kim S.I.,Hanyang University | Kim S.I.,Medical Device Development Center
Investigative Ophthalmology and Visual Science

PURPOSE. To report confocal red-free imaging as a novel, noninvasive imaging modality for the detection of the foveal avascular zone (FAZ) and to compare its effectiveness to that of fluorescein angiography (FA) in diabetic retinopathy (DR) and retinal vein occlusion (RVO). METHODS. This was a retrospective, observational, cross-sectional study. The authors enrolled 50 eyes with DR and 20 eyes with RVO. All subjects underwent confocal red-free imaging and FA using a scanning laser ophthalmoscope. For all subjects, the FAZ was identified on both confocal red-free and corresponding FA images and was delineated by two independent readers. The authors evaluated the concordance between the two imaging methods by comparing the sizes of the delineated areas and determining the overlapping ratio after image processing. RESULTS. The image analysis showed a high correlation (r > 0.9) in the mean size of the FAZ between the red-free and corresponding FA images with DR or RVO. Reliable agreement between the two methods was confirmed by the comparison of size (P = 0.925 on independent t-test) and overlapping correspondence (overlapping ratio, 0.77) of the delineated area. CONCLUSIONS. The findings suggest that confocal red-free imaging is a simple, reliable, safe, and noninvasive method for effectively imaging the FAZ. This procedure has the potential to be used for the noninvasive detection and quantification of FAZ in screening, initial evaluation, and follow-up observation of progressive ischemic retinopathies such as DR and RVO. © 2012 The Association for Research in Vision and Ophthalmology, Inc. Source

Discover hidden collaborations