January 1, 2018 by admin 0 Comments

Proliferation of HDFs on gelatin based three-dimensional scaffolds by 3D bioprinting

Authors
Dong Jin Choi (1,2), Sang Jun Park (1), Bon Kang Gu, Seok Chung (2), Chun-Ho Kim (1,*)
Abstract
Full replacement, restoration, or, regeneration of defective or injured functional living, tissues is important goal in tissue engineering. In order to, achieve these goal, 3D shape of the biomedical scaffold, should be highly porous and with an appropriate pore, size, pore interconnectivity, and exhibit a high surface, area-to-volume ratio1, . In particular, uncontrollable pore, size and porosity may obstruct successful tissue, regeneration. 3D bioprinting technologies is appropriate, method to fabricate these 3D scaffold. Natural, biopolymers, such as gelatin, chitosan and alginate, have, been widely used as 3D bioprinting2-3, . In this study, we, fabricate pore size controlled 3D gelatin scaffolds by, using 3D bioprinting and to evaluate their biological, properties. The pore sizes of 3D scaffolds were controlled, in the range of 600 to 1,200 μm. We successfully, fabricated 3D gelatin scaffold with various pore size by, using 3D bioprinting system with a cryogenic plate. To, evaluate the feasibility of this structure as substrates for, scaffold, human dermal fibroblast (HDFs) were cultured, on the scaffold and the cellular response was compared, with that from various mean pore sizes (600, 800, 1,000,, 1,200 μm) of the scaffold.

December 25, 2017 by admin 0 Comments

Microwave-Assisted Protein Digestion in a Plate Well for Facile Sampling and Rapid Digestion

Authors
Hyeonil Kim †‡, Han Sol Kim †‡, Dabin Lee §‡, Dongwon Shin §, Daeho Shin ∥, Jeongkwon Kim *§, Jungbae Kim *†
Abstract
Protein digestion is one of the most important processes in proteomic analysis. Here, we report microwave-assisted protein digestion in a plate well, which allows for facile sampling as well as rapid protein digestion based on the combination of highly stable enzyme immobilization and 3D printing technologies. Trypsin (TR) was immobilized on polystyrene-based nanofibers via an enzyme coating (EC) approach. The EC with stabilized TR activity was assembled with the 3D-printed structure in the plate well (EC/3D), which provides two separated compartments for the solution sampling and the TR-catalyzed protein digestion, respectively. EC/3D can effectively prevent the interference of sampling by accommodating EC in the separated compartment from the sampling hole in the middle. EC/3D in the plate well maintained its protein digestion performance under shaking over 160 days. Microwave irradiation enabled the digestion of bovine serum albumin within 10 min, generating the MALDI-TOF MS results of 75.0% sequence coverage and 61 identified peptides. EC/3D maintained its protein digestion performance under microwave irradiation after 30 times of recycled uses. EC/3D in the plate well has demonstrated its potential as a robust and facile tool for the development of an automated protein digestion platform. The combination of stable immobilized enzymes and 3D-printed structures can be potentially utilized not only for the protein digestion, but also for many other enzyme applications, including bioconversion and biosensors.

February 1, 2017 by admin 0 Comments

An Ergonomic Shape Design for Automotive Push-Return Switches

Authors
Daewon Choi, Kimin Ban, Jaeho Choe, Eui S. Jung
Abstract
The objective of this study is to understand the effect of angle and curvature of push-return switches, which are external factors in the operation environment inside the cars, on the feel of operation and to propose optimum alternatives. Background: Customers` needs for products are changing from functional and performance aspects to customer-led type where customers can reflect on their needs on the products. The operation inside cars is executed by HMI. The push-return switch is utilized as the most intuitive mode of HMI; therefore, this push-return switch, which is widely used, has to be developed by assessing the preference and satisfaction of the customer. Method: The angle and curvatures, which are external factors that affect the feel of operation, are drawn through surveying the preceding research literatures. The stages to construct alternatives in experiments are as follows: (1) the tactile switch is replaced after dismantling the switch assembly to evaluate the internal characteristics proposed by preceding researches, (2) a drawing is prepared by using a design software, is printed using 3D printer, and then it is attached on the switch assembly, and (3) evaluation for satisfaction of operation is carried out by using a driving simulator. Results: Both the angle and curvature that are external factors of switch significantly affect the feel of operation. However, interaction between the two factors is found insignificant. Therefore, an optimum alternative is proposed considering the experimental outcomes. Conclusion: This study evaluates the satisfaction in operation that affects the feel of operation environment inside the cars. Based on the study results, a guideline for switch design in the center fascia is proposed. Application: This study is expected to be used as basic data for designing automotive switches, as well as switches in the industries similar with the operation environments of cars.

July 5, 2016 by admin 0 Comments

Ti scaffolds with tailored porosities and mechanical properties using porous polymer templates

Authors
Jung-Bin Lee (a), Min-Kyung Ahn (a), Young-Hag Koh (a, b), Hyun Lee (c), Hyoun-Ee Kim (c, d)
Abstract
This study proposes a simple, useful approach to produce three-dimensionally macrochanneled titanium (Ti) scaffolds with tailored porosities and mechanical properties using porous polylactic acid (PLA) templates that can be prepared by conventional solid freeform fabrication (SFF) technique. Specifically, methylcellulose (MC) polymer was used as a binder since it could effectively bind coarse Ti particles and remain chemically stable inert in organic solvents used to dissolve PLA polymer. A Ti slurry-filled PLA was immersed in chloroform to remove the PLA template, followed by sintering at 1300 °C for 3 h in a vacuum. The use of a relatively small amount of a MC binder and removal of the PLA template in solvent enabled the construction of straight Ti frameworks and macrochannels in a 3-D periodic pattern without severe impurity contamination. This tightly controlled porous structure enabled the achievement of high compressive strengths without a catastrophic failure, while the compressive strength increased from ~ 72 MPa to 121 MPa with a decrease in overall porosity from ~ 75 vol% to ~ 67 vol%. In addition, the porous Ti scaffolds showed good biocompatibility, which was assessed by in vitro cell tests in terms of attachment, proliferation, and differentiation of MC3T3-E1 cells.