Page 206 - IJB-10-3

International Journal of Bioprinting Sr on GO enhances PLLA/PGA scaffold

adding GO. 11,12 In addition to mechanical properties, the antibacterial ability of cellulose by coating PDA, and
bone scaffolds should possess the ability of osteogenic then loading silver ions through the chelation of PDA.
36
induction, which is instrumental for promoting bone Therefore, Sr can be loaded onto GO by encapsulating
2+
regeneration and remodeling. 13-16 However, the LG scaffold PDA on GO and utilizing the chelating properties of PDA.
lacks the osteogenic induction ability, which limits further In this study, GO was encapsulated by PDA (named
application in bone defect repair. 17,18
GP) in order to immobilize Sr (named GPSr), and then
Bioactive substances, such as bone morphogenetic added into the LG scaffold prepared via selective laser
proteins and fibroblast growth factors, have been directly sintering (SLS) to enhance both mechanical properties
added into bone scaffold to enhance the osteogenic and osteogenic induction properties. Fourier transform
induction properties because of their ability to promote infrared spectroscopy (FTIR) and X-ray photoelectron
osteoblast proliferation and differentiation. 19,20 Jarrar spectroscopy (XPS) were conducted to characterize the
et al. have demonstrated that the released osteogenic chemical structure and functional groups of the modified
protein from the chitosan/hydroxyapatite scaffold doped GO. Tensile and compression tests were carried out on
with osteogenic protein and melatonin induced the composite scaffolds with different proportions of modified
differentiation of undifferentiated mesenchymal stem cells GO, and the mechanical enhancement mechanism
to osteogenic cells, enhancing their proliferation capacity of the scaffolds was analyzed. Finally, the bioactivity,
and promoting osteogenic cell maturation. The released cytocompatibility, and osteogenic induction properties of
21
melatonin facilitated the differentiation of osteoblast the scaffolds with and without the addition of modified GO
progenitor cells and inhibited osteoclast differentiation were evaluated by simulated body fluid (SBF) immersion
by increasing the expression of bone protective factors. test and in vitro biological experiments.
Nevertheless, the utilization of these bioactive substances
is subject to certain limitations, including high cost, short 2. Materials and methods
half-life, and potential side effects.
22
2.1. Materials
Certain metallic elements existing in natural bone, PGA (Mw: 150 kDa) was procured from Shenzhen
such as zinc, copper, calcium, magnesium, and strontium Polymtek Biomaterial Co., Ltd. (Shenzhen, China). PLLA
(Sr), can endow straightforward therapeutic signals for (Mw: 260 kDa) was supplied by Jinan Daigang Biomaterial
bone regeneration and play a decisive role in the regulation Co., Ltd. (City, Country). GO (TNGO-3) was obtained
of osteogenic induction properties. 23-25 It has been reported from Chengdu Organic Chemicals Co., Ltd. (Chengdu,
that magnesium could promote osteoblast differentiation, China). DA hydrochloride (Mw: 189.64 Da, purity: >99%),
while high concentrations of magnesium ions could SrCl 6H O (Mw: 266.62 Da), penicillin/streptomycin
2
2
impair osteoblast activity and contribute to bone disease, antibiotics, glutaraldehyde, calcein-AM, propidium
thus limiting its application. Zinc and copper possess iodide, diaminidine phenyl indole (DAPI), and deionized
26
both antibacterial and osteogenic effects but are toxic water were purchased from Aladdin Technology Co., Ltd.
to cells. 27,28 Sr has been found to promote osteogenic (Shanghai, China). Tris-HCl buffer (1 mol/L) and NaOH
cell differentiation and exert stimulatory effect on bone standard solution (1 mol/L) were obtained from Phygene
formation and inhibitory effect on bone resorption. Biotechnology Co., Ltd. (Fuzhou, China). Bone marrow
29
Some of the Sr compounds, such as strontium citrate and stromal cells (BMSCs) were obtained from Xiangya
strontium ranelate, are currently employed in osteoporosis Medical College (Changsha, China). Simulated body
treatment due to their desirable therapeutic efficacy. 30-32 fluid, Dulbecco’s Modified Eagle’s Medium (DMEM), fetal
The incorporation of Sr into bone tissue engineering bovine serum (FBS), and phosphate-buffered saline (PBS)
materials can enhance the osteogenic activity of scaffold. 30,33 were supplied by Mediatech, Inc. (Virginia, USA).
For example, Zhao et al. demonstrated that strontium-
doped three-dimensional (3D) hydroxyapatite whiskers 2.2. Preparation of GPSr powder
exhibited better bone regeneration compared with pure The process for preparing GPSr powder is displayed in
hydroxyapatite. Polydopamine (PDA), a biomimetic Figure 1a. First, 50 mg GO was dispersed in 50 mL diluted
33
polymer formed by the spontaneous oxidation and self- Tris-HCl buffer (10 mmol/L) by ultrasound for 1 h for
polymerization of dopamine (DA) in alkaline conditions, obtaining a homogeneous suspension. DA hydrochloride
can chelate metal ions owing to the phenolic hydroxyl (200 mg) was then mixed into the suspension, and pH was
groups. Using PDA with excellent adhesion ability and controlled at 8.5 followed by magnetic stirring for 24 h. At
excellent biocompatibility as a bridge to immobilize metal this time, DA would undergo self-polymerization reaction
ions on GO has been shown to be an effective and suitable to form PDA, and there was π-π interaction between PDA
approach. 34,35 In another example, Xie et al. improved and GO, which caused PDA to encapsulate GO. 37,38 The

Volume 10 Issue 3 (2024) 198 doi: 10.36922/ijb.1829