Soyoung Hong

Sodium Alginate Hydrogel‐Based Bioprinting Using a Novel Multinozzle Bioprinting System

Bioprinting is a technology for constructing bioartificial tissue or organs of complex three-dimensional (3-D) structure with high-precision spatial shape forming ability in larger scale than conventional tissue engineering methods and simultaneous multiple components composition ability. It utilizes computer-controlled 3-D printer mechanism or solid free-form fabrication technologies. In this study, sodium alginate hydrogel that can be utilized for large-dimension tissue fabrication with its fast gelation property was studied regarding material-specific printing technique and printing parameters using a multinozzle bioprinting system developed by the authors. A sodium alginate solution was prepared with a concentration of 1% (wt/vol), and 1% CaCl(2) solution was used as cross-linker for the gelation. The two materials were loaded in each of two nozzles in the multinozzle bioprinting system that has a total of four nozzles of which the injection speed can be independently controlled. A 3-D alginate structure was fabricated through layer-by-layer printing. Each layer was formed through two phases of printing, the first phase with the sodium alginate solution and the second phase with the calcium chloride solution, in identical printing pattern and speed condition. The target patterns were lattice shaped with 2-mm spacing and two different line widths. The nozzle moving speed was 6.67 mm/s, and the injection head speed was 10 µm/s. For the two different line widths, two injection needles with inner diameters of 260 and 410 µm were used. The number of layers accumulated was five in this experiment. By varying the nozzle moving speed and the injection speed, various pattern widths could be achieved. The feasibility of sodium alginate hydrogel free-form formation by alternate printing of alginate solution and sodium chloride solution was confirmed in the developed multinozzle bioprinting system.

Micro Tube Pump for an Implantable Drug Infusion Device

This paper proposes a tube pump composed of small-sized cams and followers for an implantable intrathecal drug infusion device. Each followers is driven by a cam and liquid is discharged by a sequential reciprocal motion of the followers. The advantage of this structure is that it allows the pump to be clean and valveless. To design a small-sized, low power pump some analysis were performed to determine the design parameters of the cam, follower and the tube. To verify the feasibility of the experiment, a prototype was manufactured and its operating characteristics were investigated. Experimental results were in accordance with the expected results obtained from analysis.

Inhibition of Rho-Associated Protein Kinase Increases the Angiogenic Potential of Mesenchymal Stem Cell Aggregates via Paracrine Effects.

The aggregation of multiple cells, such as mesenchymal condensation, is an important biological process in skeletal muscle development, osteogenesis, and adipogenesis. Due to limited in vivo study model systems, a simple and effective in vitro three-dimensional (3D) aggregation system is required to study the mechanisms of multicellular aggregation and its applications. We first generated controlled mesenchymal stem cell (MSC) aggregates using a bioprinting technique to monitor their aggregation and sprouting. We induced the angiogenic potential of the MSCs through chemical inhibition of the Rho/Rho-associated protein kinase (ROCK) pathway, which led to hairy sprouting in the aggregates. The angiogenic potential of this 3D construct was then tested by subcutaneously implanting the Matrigel with 3D MSC aggregates in a rat. Treatment of 3D MSCs with the ROCK inhibitor, Y27632, increased their angiogenic activity in vivo. The gene expressions and histological staining indicated that angiogenesis and neovascularization were mainly regulated by the paracrine factors secreted from human 3D MSC constructs. Our results demonstrate the enhancement of the angiogenic potential of the MSC constructs through the secretion of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) by the inhibition of the Rho/ROCK pathway.

Development of an Implantable Drug Infusion Pump for Pain Control in Cancer Patients

This paper presents a implantable intrathecal drug infusion pump for pain control in cancer patients. This device consists of micropump module, drug reservoir module and control module. The micropump module using cam-follower mechanism composed of small-sized four cams and four followers. Each followers is driven by a cam and liquid is discharged by a sequential reciprocal motion of the followers. The advantage of this structure is that it allows the pump to be clean and valveless. The drug reservoir module composed of drug chamber, gas chamber and diaphragm. The control module composed of battery, wireless communication unit and controller. To design a small-sized, low power pump some analysis were performed to determine the design parameters. To verify the feasibility of the experiment, a prototype was manufactured and its operating characteristics were investigated. Experimental results were in accordance with the expected results obtained from analysis. 1. 서 론***

Development of a vision integration framework for laparoscopic surgical robot.

In order to realize intelligent laparoscopic surgical robot, a vision integrated system constitutes one of the fundamental components. The authors have constructed a vision framework in the current version of NCC (National Cancer Center) laparoscopic surgical robot controlled on a real-time OS (RTLinux-Pro, FSMLabs Inc., U.S.A.). Adding vision framework, we have been applying and testing image processing algorithms- edge detection of object for positioning surgical tool, Watersheds for recognizing object. This paper documents the implementation of the framework and preliminary results of the image segmentation using Watersheds algorithm. Finally the real-time processing capability of our vision system is discussed