October 1, 2020 by admin 0 Comments

3D printing of self-healing ferrogel prepared from glycol chitosan, oxidized hyaluronate, and iron oxide nanoparticles

Authors
Eun Seok Ko a,1, Choonggu Kim a,1, Youngtae Choi a, Kuen Yong Lee a,b
Abstract
Hydrogel systems that show self-healing ability after mechanical damage are receiving increasing attention. However, self-healing hydrogels suitable for biomedical applications are limited owing to complex preparation methods. Furthermore, few studies have demonstrated the self-healing property of ferrogels. In this study, we demonstrated that glycol chitosan (GC) and oxidized hyaluronate (OHA) can be used to form a self-healing ferrogel in the presence of superparamagnetic iron oxide nanoparticles (SPIONs) without additional chemical cross-linkers. The overall characteristics of GC/OHA/SPION ferrogel varied based on the GC/OHA ratio, SPION content, and total polymer concentration. Interestingly, GC/OHA/SPION ferrogel was used to fabricate 3D-printed constructs of various shapes via an extrusion printing method. These constructs were responsive to the magnetic field, suggesting their potential application in 4D printing. This approach to developing self-healing ferrogels with biocompatible polysaccharides may prove useful in designing and fabricating drug delivery systems and tissue engineering scaffolds, via 3D printing.

June 9, 2020 by admin 0 Comments

3D Printed Bioresponsive Devices with Selective Permeability Inspired by Eggshell Membrane for Effective Biochemical Conversion

Authors
Yale Jeon, Min Soo Jeon, Jongoh Shin, Sangrak Jin, Jonghun Yi, Seulgi Kang, Sun Chang Kim, Byung-Kwan Cho, Jung-Kul Lee, and Dong Rip Kim*
Abstract
Eggshell membrane has selective permeability that enables gas or liquid molecules to pass through while effectively preventing migration of microbial species. Herein, inspired by the architecture of the eggshell membrane, we employ three-dimensional (3D) printing techniques to realize bioresponsive devices with excellent selective permeability for effective biochemical conversion. The fabricated devices show 3D conductive carbon nanofiber membranes in which precultured microbial cells are controllably deployed. The resulting outcome provides excellent selective permeability between chemical and biological species, which enables acquisition of target responses generated by biological species confined within the device upon input signals. In addition, electrically conductive carbon nanofiber networks provide a platform for real-time monitoring of metabolism of microbial cells in the device. The suggested platform represents an effort to broaden microbial applications by constructing biologically programmed devices for desired responses enabled by designated deployment of engineered cells in a securely confined manner within enclosed membranes using 3D printing methods.

May 12, 2020 by admin 0 Comments

Bactericidal Lubricating Synthetic Materials for Three-Dimensional Additive Assembly with Controlled Mechanical Properties

Authors
Jihoon Ahn, Yale Jeon, Kang Won Lee, Jonghun Yi, Sun Woo Kim, and Dong Rip Kim*
Abstract
3D printable synthetic materials have been developed to realize desired surface and mechanical properties. Lubricating synthetic surfaces have broad technological impacts on many applications including food packaging, microfluidic systems, and biomedical devices. However, combining soft materials with lubricants leads to significant phase separation and swelling phenomena, together with lowered mechanical strength, impeding full utilization of lubricating synthetic surfaces with desired shapes in a highly controllable manner. Here, we report a new platform to create a 3D printable lubricant–polymer composite (3D-LUBRIC) for the seamless fabrication of multidimensional structures with diverse functionalities. The rationally designed lubricant–polymer mixtures including silica aerogel particles not only exhibit suitable rheological properties for direct ink writing without phase separation but also enable the deterministic additive assembly of heterogeneous materials, which have large mismatches of oil permeability, with no distinct shape distortion. While exhibiting excellent lubricating properties for a variety of liquids, 3D-LUBRIC shows tunable mechanical properties with desired functionalities, such as optical transparency, flexibility and stretchability, and anti-icing and antibacterial/bactericidal properties. We employ the proposed platform to fabricate self-cleanable containers and antibacterial/bactericidal medical tubes. Our platform can offer new opportunities for building low-adhesive, multifunctional synthetic materials with customized shapes for diverse applications.

March 26, 2019 by admin 0 Comments

Three-Dimensional Bioprinting of Cell-Laden Constructs Using Polysaccharide-Based Self-Healing Hydrogels

Authors
Sang Woo Kim, Do Yoon Kim, Hyun Ho Roh, Hyun Seung Kim, Jae Won Lee, Kuen Yong Lee*
Abstract
Development of biomaterial-based bioinks is critical for replacement and/or regeneration of tissues and organs by three-dimensional (3D) printing techniques. However, the number of 3D-printable biomaterials in practical use remains limited despite the rapid development of 3D printing techniques. Controlling the flow properties of bioinks and mechanical properties of the resultant printed objects is key considerations in the design of biomaterial-based bioinks for practical applications. In this study, a printable hydrogel comprising biocompatible polysaccharides that has potential for cartilage regeneration via tissue engineering approaches was designed. Self-healing hydrogels were prepared from partially oxidized hyaluronate (OHA) and glycol chitosan (GC) in the presence of adipic acid dihydrazide (ADH). The self-healing ability of OHA/GC/ADH hydrogels was attributed to the combination of two dynamic bonds in the gels, including imine bonds obtained via a Schiff base reaction between OHA and GC, as well as acylhydrazone bonds formed by the reaction between OHA and ADH. The OHA/GC/ADH hydrogels did not require any postgelation or additional cross-linking processes for use in the fabrication of 3D constructs using an extrusion-based 3D printer. The concentrations and molecular weights of the constituent polymers were found to be critical parameters affecting the flow and mechanical properties of the self-healing hydrogels, which showed great potential as bioinks for fabricating cell-laden structures using a 3D printer. The expression of chondrogenic marker genes such as SOX-9 and collagen type II of ATDC5 cells encapsulated in the OHA/GC/ADH hydrogel was not significantly affected by the printing process. This self-healing hydrogel system may have the potential in tissue engineering applications, including cartilage regeneration.

January 1, 2019 by admin 0 Comments

Hydrogels with an embossed surface: An all-in-one platform for mass production and culture of human adipose-derived stem cell spheroids

Authors
Se-jeong Kim (a, b), Jaesung Park (a, b), Hayeon Byun (a, b), Young-Woo Park (a, b), Luke G. Major (c), Dong Yun Lee (a, b, d), Yu Suk Choi (c), Heungsoo Shin (a, b, d)
Abstract
Stem cell spheroids have been studied extensively in organoid culture and therapeutic transplantation. Herein, hydrogels with an embossed surface (HES) were developed as an all-in-one platform that can enable the rapid formation and culture of a large quantity of size-controllable stem cell spheroids. The embossed structure on the hydrogel was adjustable according to the grit designation of the sandpaper. Human adipose-derived stem cells (hADSCs) were rapidly assembled into spheroids on the hydrogel, with their size distribution precisely controlled from 95 ± 6 μm to 181 ± 15 μm depending on surface roughness. The hADSC spheroids prepared from the HES demonstrated expression of stemness markers and differentiation capacity. In addition, HES-based spheroids showed significantly greater VEGF secretion than spheroids grown on a commercially available low-attachment culture plate. Exploiting those advantages, the HES-based spheroids were used for 3D bioprinting, and the spheroids within the 3D-printed construct showed improved retention and VEGF secretion compared to the same 3D structure containing single cell suspension. Collectively, HES would offer a useful platform for mass fabrication and culture of stem cell spheroids with controlled sizes for a variety of biomedical applications.

November 1, 2018 by admin 0 Comments

Design of a shape memory composite(SMC) using 4D printing technology

Authors
Minkyu Kang, Youngjun Pyo, Joon young Jang, Yunchan Park, Yeon-Ho Son, MyungChan Choi, Joo wan Ha, Young-Wook Chang, Caroline Sunyong Lee
Abstract
A fused deposition modeling (FDM) tool was used to fabricate a shape memory composite (SMC) that combined a shape memory alloy (SMA) with a shape memory polymer (SMP). The SMA caused a shape memory effect due to a phase change between martensite and austenite phases, in turn due to a temperature change. Also, the SMP had a shape memory effect caused by changes in the proportions of hard and soft segments near the glass transition temperature (Tg). Usually, common SMAs and SMPs are not reversible, so these materials do not go back to their original shapes once they are deformed. In this study, we fabricated 4D printing actuator via reversible SMC actuations using 3D printing technology. Nylon 12 was used as the 3D printing material in filament form. Moreover, the volume fraction of SMA to SMP was varied to find the optimum ratio for good operation cycles. A volume fraction of SMA:SMP of 1:5 showed the largest length change, of 8 mm, and the most rapid response time, of 4 s in overall dimension of 140mm×10mm×1mm (length×width×thickness).Thus, the SMC showed promising results for the application of stents and valve controllers that could be manufactured by 3D printing technology.

December 4, 2017 by admin 0 Comments

Toward Functional 3D Architectured Platform: Advanced Approach to Anchor Functional Metal Oxide onto 3D Printed Scaffold

Authors
Junghyun Choi, Patrick Joo Hyun Kim, Jihoon Seo, Jiseok Kwon, Sangkyu Lee, Taeseup Song
Abstract
The authors first report the three‐dimensional (3D) structured CeO2–PLA scaffold using a 3D printing methodology. The scaffold is prepared by decorating functional metal‐oxide nanoparticles onto the 3D‐printed polylactic acid (PLA) platform via an electrostatic interaction and is applied to the applications for photochemical degradation. As‐designed CeO2–PLA scaffold shows high photocatalytic degradation performance toward methyl orange under a light irradation. Furthermore, the CeO2–PLA scaffold shows reasonable degradation performance even after it is washed and reevaluated; this result demonstrates the benefit of 3D‐printed CeO2–PLA scaffold that it can be recycled several times without losing the catalysts.