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International Journal of Bioprinting A regulated GelMA-MSCs scaffold by three-dimensional bioprinting

can be directed to move in the desired direction during the The sample was washed, and the medium was aspirated to
process of repairing defects in vivo, so as to achieve better complete GelMA hydrogel preparation.
repair effects. Studies have shown that adding icariin to
scaffolds can regulate the generation of new osteoblasts 2.1.3. Scanning electron microscopy
in vivo through BMP-2/Smad5/Runx2 signaling pathway Scanning electron microscope (SEM; Gemini 2, Sigma,
to promote fracture repair , as well as glioma epithelial- USA) was used to observe the surface morphology of
[25]
mesenchymal transition through hypoxia-induced ferritin GelMA hydrogel. The bottom of a 2 mL Eppendorf tube
light chain (FTL) and chemotherapy resistance . Some was cut with a tube cutter, and then, the tube was turned
[26]
of the above studies have shown that regulatory factors over. GelMA hydrogel was added and irradiated with
can find corresponding repair targets in vivo, regulate a 405 nm light source for 10 – 30 s. Three samples were
stem cell behavior in a targeted manner, and precisely gelatinized and put into −80°C for 2 h. After GelMA was
achieve multifunctional differentiation, migration, and frozen, it was quickly moved into a vacuum freeze-dryer
proliferation of stem cells. with the pump turned on for 18 h. After freeze-drying, the
We have developed a 3D bioextrusion printing strategy sample was wiped gently with a sharp blade and lightly
to fabricate a cartilage repair scaffold that mimics cartilage incised to a depth of about 1 mm. Then, the sample was
surface and superficial subchondral tissue to provide a opened by hand, sputtered with 10 nm gold film, and
suitable microenvironment for repair. In our strategy, a put into the SEM for capturing images. Air was extracted
GelMA-MSCs scaffold was fabricated by a 3D extrusion from the electron microscope to create vacuum before the
bioprinter. The scaffold showed high biocompatibility process.
and suitable physicochemical properties and, further,
promoted the migration, proliferation, and chondrogenic 2.1.4. Characterization of the GelMA scaffolds
differentiation of MSCs by upregulating microRNA-410. 2.1.4.1. Mechanical properties
The resulting scaffold can provide a favorable The mechanical properties (Young’s modulus) of GelMA
microenvironment and biochemical cues for cell-cell and hydrogels were tested at 37°C. Based on the linear portion
cell-matrix interactions, thereby promoting regeneration of the stress-strain curve, the velocity compresses the
and functional recovery of cartilage-damaged collagen hydrogel with Young’s modulus (n = 3).
fibers.
2.1.4.2. Porosity
2. Materials and methods
According to the SEM photos of GelMA scaffolds, the
2.1. Preparation of GelMA scaffolds average diameter of each pore was measured by ImageJ
2.1.1. Preparation of photoinitiators software, and the pore size and porosity of each scaffold
were calculated (n = 3).
20 mL of phosphate-buffered saline (PBS; Gibco, USA) was
added to a lightproof bottle containing the initiator LAP 2.1.4.3. Swelling rate
(EFL, China) and, then, heated and dissolved in a water By dissolving GelMA hydrogels with different
bath set at 40 – 50°C for 15 min in the dark. The bottle was concentrations in deionized water, the equilibrium
shaken several times during this period until the content swelling behavior of GelMA hydrogels was observed. The
turned white after the powder was fully dissolved; a 0.25% prepared GelMA solution was placed at room temperature
initiator standard solution was prepared. and irradiated with 405 nm UV light for solidification.

2.1.2. Synthesis of gelatin-photoinitiators 5 mL of PBS was added to cover the solution, which is
then incubated for 24 h, weighed, and denoted as Ms. The
200 mg of GelMA (EFL-GM-60, China) and 2 mL of sample was put into a freezer set at −80℃ and frozen for
initiator standard solution were added into a lightproof 2 h, before being transferred to a vacuum freeze-dryer with
centrifuge tube. The sample was shaken to fully infiltrate the pump turned on for 18 h. After the freeze-drying was
GelMA and dissolved by heating in a water bath at 40–50°C completed, it was weighed and denoted as Md. The formula
in the dark. The tube was shaken several times for 30 min, of swelling ratio is: Q = (Ms-Md)/Md (n = 3).
and the GelMA solution was immediately sterilized with
a 0.22 μm sterile syringe filter to prevent low-temperature 2.2. MSCs culture
gelation. The GelMA solution was transferred into the 2.2.1. Isolation and culture of MSCs
well plate and irradiated with a 405 nm light source for
10–30 s to make it gel. The medium was added to the well New Zealand rabbits weighing about 0.5 kg (regardless
to cover the gel and placed in a 37°C incubator for 5 min. of gender) were selected as the source of primary MSCs.

Volume 9 Issue 2 (2023) 178 https://doi.org/10.18063/ijb.v9i2.662