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.

January 1, 2019 by admin 0 Comments

3D Bioprinting of human adipose stem cells (hADSCs) encapsulated hyaluronic acid (HA) based biomimetic double crosslinked hydrogel bioink for cartilage tissue engineering (CTE)

Authors
Parikshit Banerjee
Abstract
Articular cartilage covers the edges of the bones and provides wear resistant load bearing capacity which ultimately supports the flexible joint movement. Therefore, once these articular cartilages get damaged, they limit the free joint movements in patients and cause severe complication. Also, articular cartilage is avascular in nature, which also restricts its ability to repair itself after any damage. To address these issues associated with articular cartilage damage, cartilage tissue engineering (CTE) has been introduced. CTE helps in repairing or regenerating damaged cartilages by using a combined strategy which involves cell, growth factors, and biomaterial scaffolds. Hydrogel with the ability to absorb a large amount of water viewed as an ideal material for cartilage mimetic scaffold owing to the similarity between the hydrogel and native cartilage. Combining stem cell or chondrocytes with hydrogel scaffold is regarded as a promising approach for CTE. This strategy is capable of supporting highly dense cell population, cell attachment, homogeneous cell distribution, and also offer an ideal microenvironment for cell growth and differentiation. Unfortunately, developing hydrogel scaffold with required structural integrity is a major issue that limits the application of hydrogel in CTE. Therefore, to address the problems associated with existing CTE, this thesis aimed to utilize 3D bioprinting to print cartilage constructs by combining adipose-derived stem cells (ADSCs) and hyaluronic acid (HA) based hydrogels. First, to develop a new cartilage extracellular matrix (ECM) mimetic hydrogel system, we synthesized biotinylated-hyaluronic acid (HA-Biotin) and confirmed the successful grafting of biotin with HA trough Fourier Transform Infrared Spectroscopy (FTIR) analysis. Next, HA-Bio hydrogel was prepared and Streptavidin was mixed with this hydrogel to form partially crosslinked HA-based hydrogel through non-covalent bonding between biotin and streptavidin. Addition of streptavidin also supports higher cell attachment due to the presence of cell adhesion sites in streptavidin. After that, partially crosslinked HA-Bio-Streptavidin (HBS) hydrogel was mixed with sodium alginate and subsequently printed using Rokit INVIVO bioprinter. After printing, 3D scaffolds were submerged into CaCl2 solution achieve ionic crosslinking through ion transfer between sodium alginate and CaCl2. Different parameters such as fiber formation, self-supporting ability, printing resolution, and crosslinker concentration were optimized to get desired 3D printed constructs. In vitro cell proliferation and live/dead staining assay were also performed on 3D cell-laden scaffolds. The result showed that partially crosslinking the biotinylated-HA based hydrogel with streptavidin has a significant effect on printability. Morphological analysis of optimal 3D printed scaffold showed clearly visible pores with desired shape and geometry. Favorable cell proliferation and growth was also observed in 3D HBSA based hydrogel scaffolds. These result further confirmed that double crosslinking HA-based hydrogel could be a good choice for 3D bioprinting based tissue engineering.