• BMB Reports
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• v.54 no.7
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• pp.356-367
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• 2021

Cell-based therapy is a promising approach in the field of regenerative medicine. As cells are formed into spheroids, their survival, functions, and engraftment in the transplanted site are significantly improved compared to single cell transplantation. To improve the therapeutic effect of cell spheroids even further, various biomaterials (e.g., nano- or microparticles, fibers, and hydrogels) have been developed for spheroid engineering. These biomaterials not only can control the overall spheroid formation (e.g., size, shape, aggregation speed, and degree of compaction), but also can regulate cell-to-cell and cell-to-matrix interactions in spheroids. Therefore, cell spheroids in synergy with biomaterials have recently emerged for cell-based regenerative therapy. Biomaterials-assisted spheroid engineering has been extensively studied for regeneration of bone or/and cartilage defects, critical limb ischemia, and myocardial infarction. Furthermore, it has been expanded to pancreas islets and hair follicle transplantation. This paper comprehensively reviews biomaterials-assisted spheroid engineering for regenerative therapy.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.829-832
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• 2004

실제영상으로 가상환경을 구축해서 사용자가 가상환경을 돌아다님으로써 보다 큰 몰입감과 현실감을 제공하는 영상기반 가상현실 기술은 최근 들어 웹 기반 가상현실시스템을 구축하기 위해서 많이 사용된다. 이 기술은 가상환경 구축에 있어 항해를 쉽게 하기 위한 한 방법으로 넓은 시각 영역(field of view)을 얻을 수 있는 wide-angle 렌즈를 흔히 사용한다. 어안렌즈(fish-eye lens)는 전형적인 넓은 시각 영역을 가진 렌즈로서, 매우 큰 radial distortion 을 가진다. 왜곡을 없앤 영상을 얻기 위해 본 논문에서는 구면기하(spherical geometry) 및 사영기하(projective geometry)를 사용하여 어안영상을 보정하는 non-metric기법을 제안한다. 제안한 이 방법은, 기존의 방법들 보다는 쉽고 빠른 속도로 왜곡을 보정할 수 있으므로 어안영상의 왜곡을 보정하는 하드웨어를 효율적으로 구현할 수 있다. 그리고 spheroid 를 이용해 좀 더 왜곡을 정확히 보정방법과 별도의 서보 모터 없이 pan/title 를 가능케 하는 시점이동에 따른 왜곡 보정 방법을 제시한다.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.137-144
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• 1994

Spherical multicellular aggregates of adult rat hepatocytes (spheroid) which have tissue like structure, were formed and immobilized in the pores of polyurethane foam (PUF) which was used as a culture substratum. These hepatocyte/spheroids, about 100 $\mu\textrm{m}$ in diameter, have maintained higher differentiated functions than those of hepatocyte/monolayer for about 3 weeks in serum-free medium. Then, we designed a prototype module of an artificial liver support system using a PUF/spheroid packed-bed, in which hepatocyte/spheroids were immobilized at high density. The urea synthesis activity of the artificial liver was maintained at least 10 days in 100% rat blood plasma. We start examining the performance of hybrid artificial liver in an ex vivo extracorporeal experiment with an acute hepatic failure rat.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.131-134
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• 2011

We propose a spheroid chip that uses removable cell trapping barriers and that is capable of forming and extracting multicellular spheroids. By using a conventional well plate and flask, it is difficult to form small-sized spheroids, which resemble avascular 3D cell-cell interaction. It was difficult to extract spheroids using conventional microchips and fixed cell trapping barriers. The proposed chip, however, facilitates both formation and extraction of spheroids by using removable cell trapping barriers formed by membrane deflection. The cell trapping barriers, formed at the membrane pressure of 50 kPa, hold the cells in the trapping region at a cell inlet pressure of 145.155 Pa. After incubation for 24 h, the trapped cells form uniform spheroids. We successfully extract the spheroids at a cell inlet pressure of 5 kPa after removing the membrane pressure. The extracted spheroids have a diameter of $197.2{\pm}11.7Bm$ with a viability of $80.3{\pm}7.7%$. Using the proposed chip, uniform spheroids can be formed and these spheroids can be safely extracted for carrying out the post-processing of spheroids.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.3 no.2
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• pp.40-45
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• 1992

A simple emission model applicable for low scattering (scattering << absorption) anisotropic layer is developed and applied to the interpretation of measurements of microwave emission from row crops. The vegetation layer of row crops is modeled as a random slab embedded with small spheroid with major axis aligend paralel to the crop-row direction. The total emission is given in a simple algebraic form based on the zero-order radiative transfer theory. The single scattering albedo for spheroid and its polarimetric phase function are presented. The effects of layer azimuthal dependence on emission are accounted for by using an anisotropic albedo in the zero-order transfer theory. The developed emission theory favorably compares with the brightness temperature measured over soybeans canopy.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.297-299
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• 2015

In this paper we have examined the linear stability of triangular equilibrium points in the photogravitational restricted three body problem when both primaries are triaxial rigid bodies, the bigger one an oblate spheroid and source of radiation. The orbits about the Lagrangian equilibrium points are important for scientific investigation. A number of space missions have been completed and some are being proposed by various space agencies. We analyze the periodic motion in the neighbourhood of the Lagrangian equilibrium points as a function of the value of the mass parameter. Periodic orbits of an infinitesimal mass in the vicinity of the equilibrium points are studied analytically and numerically. The linear stability of triangular equilibrium points in the photogravitational restricted three body problem with Poynting-Robertson drag when both primaries are oblate spheroids has been examined by A. Kumar (2007). We have found the equations of motion and triangular equilibrium points for our problem. With the help of the characteristic equation we have discussed stability conditions. Finally, triangular equilibrium points are stable in the linear sense. It is further seen that the triangular points have long or short periodic elliptical orbits in the same range of ${\mu}$.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.80-91
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• 2018

Here, we engineered spheroids by using ECM mimicking nano-fragments (NFs) with fibroblasts and investigated their effect on proliferation and cell/ECM interactions. NF incorporation resulted in formation of a stable spheroid, which improved proliferation and viability of cells by assisting oxygen transport confirmed by LOX-1 staining. In addition, hypoxic and apoptotic genes were significantly downregulated in spheroids with PD-NFs. Furthermore, ECM and cell junction proteins were highly expressed. Overall, our findings suggest that incorporation of NFs within spheroids for assembly with various cell types can be an alternative approach for 3D cell culture in many applications.

• Proceedings of the Korean Magnestics Society Conference
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• 2016.11a
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• pp.15-16
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• 2016

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.3
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• pp.174-180
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• 2011

This paper shows added mass and inertia can be acquired from the pure heaving motion and pure pitching motion respectively. A Vertical Planar Motion Mechanism (VPMM) test for the spheroid-type Unmanned Underwater Vehicle (UUV) was compared with a theoretical calculation and Computational Fluid Dynamics (CFD) analysis in this paper. The VPMM test has been carried out at a towing tank with specially manufactured equipment. The linear equations of motion on the vertical plane were considered for theoretical calculation, and CFD results were obtained by commercial CFD package. The VPMM test results show good agreement with theoretical calculations and the CFD results, so that the applicability of the VPMM equipment for an underwater vehicle can be verified with a sufficient accuracy.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.2
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• pp.99-105
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• 2000

Cell-Cell interaction and the extracellular matrix (ECM) are belisved to play essential roles during in vitro culturing of primary hepatocytes in the control of differentiation and in the maintenance of tissue spcific functions. The objective of this study was to examine the effects of degree of cell-cell contact (DCC) on liver sperific function of rat promary hepatocytes. Hepatocyte aggregates with various with various degrees of cell-cell contantact, I. e., dispersed cell, longish aggregate, rugged aggregate, and smooth spheroid were obtained at 1, 5-6, 15-20, and 36-48 hrs, respectively in suspension cultures grown in spinner flasks embedded in Caalginate bead and collagen gel in order. The may result from mass transfer limitation and shear damage caused by agitation during aggregation. The rugged aggregate showed a higer viability and albumin secretion rate than the dispersed cells or the other aggregates. This result indicates the possible enhancement of a bioartificial liver's (BAL) performance using primary hepatocytes and the reduction in time to prepare a BAL through optimization of the immobilization time.