Page 410 - IJB-9-5

International Journal of Bioprinting 3D-printed Mg scaffolds promote bone defect repair

1. Introduction alloy implants, traditional manufacturing methods (such as
melt foaming, powder metallurgy, investment casting, etc.)
Considering population aging, osteoporosis has become cannot achieve precise control of the internal pore structure
a global public health problem that cannot be ignored. of porous Mg alloys, and it is impossible to prepare a fully
Osteoporosis is characterized by decreased bone mass, interconnected complex porous structure . In recent
[10]
increased bone fragility, and decreased bone strength years, the development of three-dimensional (3D) printing
caused by bone microstructure destruction. Osteoporotic technologies has made it possible to prepare Mg alloy
bones are prone to fracture. According to statistics, more bone-repair scaffolds with personalized interconnected
than 8.9 million osteoporotic fracture cases occur every porous structures and geometric shapes [11,12] . Previously,
year worldwide, with an average of one case of osteoporotic Mg alloy scaffolds have been successfully fabricated with
fracture every 3 s . About 50% women and 20% men will a controllable appearance, good mechanical properties,
[1]
[2]
have at least one osteoporotic fracture after the age of 50 . and an interconnected porous structure through selective
As the fracture site is extremely loose and the fracture is laser melting (SLM) technology; however, their very rapid
mostly comminuted, bone defects often form after fracture degradation rate is not favorable for applications in clinical
reduction. Neglecting treatment of bone defects may lead settings .
[13]
to delayed union, malunion, or nonunion of the fracture,
which can seriously affect the quality of life of patients Polysilazane is a polymer with Si-N as the main chain
and even endanger their lives. Therefore, it is important to and can be converted into SiCN, SiCNO, or SiO ceramics
2
promote the repair of bone defects caused by osteoporotic with excellent corrosion resistance under high-temperature
fractures. conditions. Owing to the polarity of Si-N in its structure,
Autogenous bone graft, which is the traditional “gold the generated ceramics exhibited strong adhesion and
standard” for filling bone defects, is not recommended for could not easily fall off. Therefore, polysilazane is a
use in elderly patients considering several issues such as good corrosion-resistant coating material and has broad
increased number of surgical sites, donor site infection, application prospects in the construction of functional
pain, and limited number of bone harvested . Medical corrosion-resistant coatings, which is often used for metal
[3]
metal materials such as stainless steel (316SS), titanium anti-corrosion, carbon material anti-oxidation, organic
(Ti) and its alloys, and cobalt-chromium (Co-Cr) alloys material wear resistance, and other industrial fields, but it
[14]
may cause many problems after implantation into the is rarely applied in the medical field . Anti-osteoporosis
human body, such as stress shielding, toxic ion release, drugs include anti-bone resorption and bone formation-
secondary surgery, and imaging artifacts . Additionally, promoting drugs. Bisphosphonates, a class of anti-bone
[4]
the repair of osteoporotic bone defects differs from that resorption drugs, inhibit bone resorption by directly
of common bone defects. The repair of defective parts inhibiting the activation and proliferation of osteoclasts
is slow or impossible because of the imbalance between and are the most commonly used drugs in the treatment
bone absorption and bone formation. This is mainly of osteoporosis [15,16] . As a third-generation bisphosphate
because osteoclast-mediated bone resorption is more preparation, zoledronic acid (ZA) has a high affinity for
pronounced than osteoblast-mediated bone formation in the surface of bone mineralization, especially for the active
patients with osteoporosis, resulting in a reduced repair area of bone turnover, which mainly acts on osteoclasts,
capacity . Therefore, one of the major difficulties in promotes osteoclast apoptosis, and inhibits bone
[5]
[17]
promoting the repair of osteoporotic bone defects is to resorption with a positive effect . Local administration
restore the balance between local osteogenesis and bone of bisphosphonates can expedite drug action and augment
[18]
destruction. drug bioavailability .
As a new biodegradable metal material, magnesium Here, we prepared biodegradable controllable
(Mg) and its alloys have attracted much attention in 3D-printed Mg alloy scaffolds with a ZA-loaded
the field of biomedical materials due to their excellent ceramic corrosion control coating using 3D printing
mechanical properties and good biocompatibility and and surface modification technology. The degradation,
biodegradability [6,7] . Most importantly, Mg implants can biocompatibility, and bioactivity of the 3D-printed Mg
promote bone formation, increase mineral attachment and alloy scaffolds were evaluated in vitro and in vivo. We
bone mass around the implants in the bone, and promote expect to reduce the corrosion rate of Mg alloys by loading
the repair of bone defects . In addition, ideal bone implants a ZA ceramic coating, which has the function of both Mg
[8]
should have interconnected porous structures similar to in promoting osteogenesis and ZA in inhibiting bone
those of natural bone to facilitate the growth of new bone resorption, and introduce a method for promoting the
tissues and blood vessels . For manufacturing porous Mg healing of osteoporotic bone defects.
[9]

Volume 9 Issue 5 (2023) 402 https://doi.org/10.18063/ijb.769