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Mechanism for corrosion protection of β-TCP reinforced ZK60 via laser rapid solidification

A B

Figure 5. The (A) compressive strength and (B) hardness of the ZK60/xβ-TCP composites. (n = 3, *p < 0.05, **p < 0.01).

A B

Figure 6. (A) The pH variation of SBF after immersion of ZK60/xβ-TCP composites and (B) calculated corrosion rate based on weight loss.

3.4 In Vitro Cell Response 0.05) were observed between ZK60/8β-TCP and ZK60.
Besides, all the ZK60/xβ-TCP composites exhibited
Fluorescent images of the live/dead assay were presented higher O.D. values than ZK60, indicating better cell
in Figure 8. Live cells were indicated by the fluorescent viability. Clearly, ZK60/8β-TCP showed higher cell
green, while dead cells were indicated by the fluorescent viability than ZK60, ZK60/4β-TCP and ZK60/12β-TCP.
red. It could be observed that cells cultured in the
extracts of ZK60/8β-TCP presented a typical fusiform 4. 4. Discussion
shape after 1 day culture (Figure 8C), suggesting their
normal cell growth. As a comparison, cells cultured in 4.1 The Effect of Laser Rapid Solidification on
ZK60 and ZK60/12β-TCP clearly showed a contraction Microstructure
of round shape (Figure 8A and Figure 8D), indicating Laser melting technology is able to process various
its unhealthy growth. Meanwhile, a few of dead biomaterials, including bioceramics and biometals.
cells were observed for ZK60 and ZK60/12β-TCP. It Nevertheless, bioceramics, such as hydroxyapatite,
should be noted that both ZK60/4β-TCP and ZK60/8β- TCP and 45s bioglass, exhibit a too low mechanical
TCP presented more live cells compared with ZK60 strength for bone implant. Furthermore, bioceramic
specimens, indicating an improved cytocompatibility of usually has a high viscosity and low fluidity, which
incorporating β-TCP into ZK60. impaired the density of laser processed part [21] . While
CCK-8 assay was used to determine the cell viability Mg alloys exhibit suitable mechanical strength but poor
as a function of culture time, with results shown in corrosion resistance. Thus, substantial efforts have been
Figure 9. Obviously, the cell activity gradually increased devoted to fabricating bioceramic reinforced Mg alloys
with the culture time increasing for all groups. At days as candidates for bone implants. For instance, some
1, 3 and 5, significant differences in O.D. values (p < researchers had fabricated β-TCP reinforced Mg-based

6 International Journal of Bioprinting (2018)–Volume 4, Issue 1