One of the challenges in the field of bioprinting is developing bioinks that are safe and effective. In a paper entitled “Marine Biomaterial-Based Bioinks for Generating 3D Printed Tissue Constructs,” a group of researchers discusses the development of a bioink using alginate and fish gelatin (f-gelatin). They created a marine-based interpenetrating polymer network (IPN) consisting of alginate and f-gelatin methacryloyl (f-GelMA) networks via physical and chemical crosslinking methods, respectively.
“In this study, four different concentrations of alginate (1%, 2%, 3%, and 4%) and three low concentrations of f-GelMA (4%, 5%, and 6%) were investigated and found to form double networked alginate/f-GelMA hydrogels,” the researchers explain. “In the mechanical properties test, the pure alginate hydrogel showed a typical increase in mechanical strength with the increase of concentration and low mechanical strength when its compressive modulus was around 40 kPa, even at 4% alginate, compared with alginate/f-GelMA IPN hydrogel where the modulus of alginate/f-GelMA was approximately 40 kPa at 1% alginate.”
This showed that the mechanical strength of hydrogels was significantly increased by employing an alginate and f-GelMA double network. According to the researchers, the tunable mechanical strength range in alginate/f-GelMA hydrogel would be sufficient to meet the diverse requirements of different tissues.
The researchers also performed swelling tests with pure alginate hydrogel as a control group, and found that the mass swelling ratio decreased with the increase in concentration of alginate.
“For the alginate/f-GelMA hydrogel, the mass swelling ratio for all tested groups was lower than for the pure alginate group,” the researchers continue. “This was due to the increased crosslinking density from the addition of f-GelMA which generated additional polymeric networks via covalent bonding…The swelling properties of hydrogel mainly depend on the hydrogel pore size, polymer concentration, density of cross-linking, and the interaction with solvents.”
The researchers also investigated the degradation characteristics of the hyrdogels. The degradation rate of the alginate/f-GelMA in a saline solution was similar for 2% and 4% alginate, though the 2% degraded faster. The morphology of the hydrogels was tested as well, and the alginate/f-GelMA exhibited a highly porous structure, which can provide enough space for the transport of nutrients and gas exchange for cell survival.
“To assess the cell behavior and examine the feasibility (cell viability, adhesion, and cell proliferation) of alginate/f-GelMA hydrogel, cell adhesion and 3D cell encapsulation assays were performed to examine the ability to bind to alginate/f-GelMA scaffold which is crucial for cell survival,” the researchers state. “…Encapsulated NIH-3T3 cells were cultured for seven days and cell viability was determined using LIVE/DEAD assay kits. As shown in Figure 3C, cells maintained high viability during the culture period (one, three, five, and seven days) and demonstrated that cells can maintain long-term survival rates in alginate/f-GelMA hydrogel.”
The results of the testing showed that alginate/f-GelMA hydrogel has a lot of promise for tissue engineering applications, including 3D bioprinting. To further confirm the morphology and cell viability in the process of 3D printing, a two-layer scaffold was printed and Live/Dead assay was carried out to investigate the cell survival ratio. The scaffold displayed a satisfactory 3D arrangement under microscopy with high cell viability.
This study was the first incidence of using alginate and f-GelMA for 3D bioprinting, and the successful results mean that marine biopolymers could feasibly replace biopolymers from mammalian resources, which can carry diseases or be subject to religious restrictions.
Authors of the paper include Xiaowei Zhang, Gyeong Jin Kim, Min Gyeong Kang, Jung Ki Lee, Jeong Wook Seo, Jeong Tae Do, Kwonho Hong, Jae Min Cha, Su Ryon Chin and Hojae Bae.
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