Page 533 - IJB-9-6

International Journal of Bioprinting High-performance SrCS scaffolds via vat photopolymerization

Keywords: Strontium-doped calcium silicate; 3D print- and very fast degradation ratio pose challenges in ensuring
ing; Vat photopolymerization; Mechanical property; sufficient mechanical reinforcement and a biomimetic
Biodegradability microenvironment for effective bone regeneration.

Barium titanate-based ceramics (BTA) has
demonstrated their good biocompatibility and mechanical
[31]
1. Introduction properties in the application of bone tissue engineering ,
which can enhance mechanical properties as a second
The treatment of large segmental bone defects (>5 phase. For instance, Dubey et al. prepared hydroxyapatite
cm) caused by car accidents, gunshots, and malignant (HA) scaffold doping with 40 wt.% BTA to enhance the
tumor resection is complicated and has many clinical compressive strength by 200% compared to undoped
complications, which easily lead to repair failure [1,2] . samples . Tavangar et al. fabricated HA-BT scaffolds
[32]
Therefore, large segmental bone repair remains a major for orthopedic applications and found that the presence
challenge in clinical treatment. The emerging bone tissue of BTA acted as a second phase to highly increase the
engineering (BTE) provides an ideal treatment strategy bulk density and mechanical properties of composite
for the repair of large segmental bone defects [3,4] . The samples . Therefore, in this study, we proposed an
[33]
biomimetic three-dimensional (3D) scaffolds play a crucial approach to improve the mechanical properties and tune
role in BTE since they can provide the necessary mechanical the degradation rate of SrCS scaffolds by doping BTA
support and biomimetic microenvironment conducive powders with different mass ratios. SrCS-BTA scaffolds
to cell proliferation [5-9] . So far, various manufacturing with biomimetic triply periodic minimal surface (TPMS)
methods have been developed for the fabrication of structures were fabricated by VPP. Finally, the mechanical
biomimetic scaffolds, such as direct foaming, gel-casting, and biological properties of the scaffolds before and after in
and sacrificial template method [10-12] . But these conventional vitro degradation were characterized.
methods are restricted by the geometrical design and
structural complexity of biomimetic structures. Additive 2. Material and methods
manufacturing (known as 3D printing ) has been shown
[13]
through multiple studies to enable the creation of intricate 2.1. Materials
scaffolds that can be customized to individual patients [14-17] . SrCS powders (Xi’an Shuogu Technology Co., LTD.,
These scaffolds possess the capacity to provide mechanical China,) with a particle size of 3.9 μm (D ), a density of
50
3
reinforcement to bone tissues and a microenvironment 2.90 g/cm , and a refractive index of 1.61, were used as raw
that closely resembles that of natural bone [18-20] . Among materials. BTA powders with a particle size of 2.2 μm (D ),
50
3
the various additive manufacturing techniques available, a density of 5.72 g/cm ,and a refractive index of 1.63 were
vat photopolymerization (VPP) is a highly accurate used as the dopant with different mass ratios of 0, 20, 30,
method that is particularly well-suited for printing bone and 40 wt.% (marked as SrCS, SrCS-20BTA, SrCS-30BTA,
implants [21-24] . However, as for large segmental bone and SrCS-40BTA). 1,6-Hexanediol diacrylate (HDDA,
repair, the reconstruction of vascularization capacity for Chengdu Fourth City New Material Co., LTD., China) with
3
3D-printed large-size scaffolds remains a huge challenge. a density of 1.0 g/cm and a refractive index of 1.457 was
used as the photosensitive resin. Polymer 41000 (Lubrizol,
Modulation of cellular behavior through intrinsic Spain) and diphenyl (2,4,6-trimethyl benzoyl) phosphine
properties of biomaterials provides an effective solution for oxide (TPO; BASF, Germany) were used as the dispersant
the complete revascularization of large-size scaffolds. For and photoinitiator, respectively. RAD 2500 (VOK,
instance, the strontium-doped calcium silicate (SrCS) can Germany) and anti-sedimentation thixotropic 8810 (Sago,
significantly upregulate the expression of osteogenic genes Germany) were used as leveling and anti-settling agents,
and angiogenic factors by releasing Si and Sr ions [25-28] . respectively. High-purity alkyl aluminum derivatives
2+
4+
Lin et al. fabricated SrCS scaffolds for osteoporotic bone (Easepi 590, Guangyi Chemical Co., LTD., China) were
repair, and the in vitro experiments revealed that Si and used as the copolymer inhibitor. Simulated body fluid
4+
Sr ions can promote cell viability and expression of alkaline (SBF) (Phygene Life Sciences Company, Fujian, China)
2+
phosphatase (ALP) . Xing et al. designed bioactive was used to perform in vitro immersion tests to analyze the
[29]
alginate hydrogels containing Si and Sr ions to activate biodegradability of materials.
2+
4+
cells in vivo, and revealed a synergistic effect of the ions
on cell proliferation without loss of stemness . In short, 2.2. Fabrication of scaffolds
[30]
SrCS is deemed an ideal biomaterial for reconstructing 4.0 wt.% 41000 (based on powders), 0.5 wt.% TPO (based
vascularization in repairing large segmental bone defects. on photosensitive resin), 0.5 wt.% RAD, 0.5 wt.% 8810
Nonetheless, its suboptimal mechanical characteristics (based on suspension), and 0.1 wt.% copolymer inhibitor
Volume 9 Issue 6 (2023) 525 https://doi.org/10.36922/ijb.1233