Amorphous magnesium phosphate-graphene oxide nano particles laden 3D-printed chitosan scaffolds with enhanced osteogenic potential and antibacterial properties.

The utilization of 3D printing technology for the fabrication of graft substitutes in bone repair holds immense promise. However, meeting the requirements for printability, bioactivity, mechanical strength, and biological properties of 3D printed structures concurrently poses a significant challenge. In this study, we introduce a novel approach by incorporating amorphous magnesium phosphate-graphene oxide (AMP-GO) into a thermo-crosslinkable chitosan/ß glycerol phosphate (CS/GP) ink. We fabricated thermo-crosslinkable CS inks containing varying concentrations (10 %, 20 %, or 30 % weight) of AMP-GO. The 3D printed scaffolds incorporating 20 % AMP-GO exhibited significantly improved mechanical properties, with compressive strengths of 4.5 ± 0.06 MPa compared to 0.5 ± 0.03 MPa for CS printed scaffolds. Moreover, the CS/AMP-GO inks demonstrated enhanced antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, attributed to the release of magnesium cations and the performance of GO. Additionally, CS/20AMP-GO ink facilitated increased adhesion, viability, proliferation, and osteogenic differentiation of mesenchymal stem cells (MSCs), as evidenced by the upregulation of ALP, COL1, and Runx2 expression, which were elevated 9.8, 6.5, and >22 times, respectively, compared to pure CS scaffolds. Considering its exceptional in vivo osteogenic potential, we anticipate that the CS/20AMP-GO ink holds great potential for 3D printing of bone grafts.

Antibacterial amorphous magnesium phosphate/graphene oxide for accelerating bone regeneration.

Magnesium phosphates (MgP)s have attracted interest as an alternative biomaterial compared to the calcium phosphate (CaP)s compounds in the bone regeneration application in terms of their prominent biodegradability, lack of cytotoxicity, and ability of bone repair stimulation. Among them, amorphous magnesium phosphates (AMP)s indicated a higher rate of resorption, while preserving high osteoblasts viability and proliferation, which is comparable to their CaP peers. However, fast degradation of AMP leads to the initial fast release of Mg2+ ions and adverse effects on its excellent biological features. It seems that the addition of graphene oxide (GO) to magnesium phosphate can moderate its degradation rate. Hence, a novel in situ synthesized AMP powders containing 0.05, 0.25, 0.5, and 1 wt% of graphene oxide (AMP/GO) were developed to achieve a favorable degradation rate, desirable antibacterial properties against both Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) accompanying with proper cell viability and proliferation. The incorporation of 0.5 wt% of graphene oxide into the AMP ceramic led to reduce the release of Mg2+ ions from 571.2 ± 12.9 mg/L to 372.8 ± 14.7 mg/L and P ions from 354.8 ± 11.9 mg/L to 245.3 ± 9.9 mg/L, at day 10 of immersion in PBS. Besides, AMP/0.5 GO bioceramics were capable of eradicating all bacterial colonies of both strains. On the other hand, MG63 cells viability went up from 143.46% ± 7.54 to 184.46% ± 11.54 on the 7th day of culture in the presence of 0.5 wt% of GO compared to pure AMP ceramic. Furthermore, alizarin red staining and alkaline phosphatase (ALP) activity demonstrated the ability of AMP/GO to maintain the osteogenic phenotype of MG63 cells during 7 days culture. Therefore, it can be concluded that well distributed and in situ synthesized AMP/0.5GO powders can be a promising biomaterial for bone tissue regeneration.