Poster P2 - Fabrication and In Vitro Biocompatible Assessment of Composite-Coated Magnesium Materials

Introduction: Magnesium (Mg) and its alloys have been gaining attention in the field of orthopedic medical devices due to their unique biodegradable nature in aqueous environments. However, Mg degrades too rapidly limiting its broad use as a biomaterial for various orthopedic implants. This research is focused on improving the biodegradability of Mg by applying biocompatible coatings. The Mg alloy, Zk60 (MgZn2), was chosen due its known biocompatibility. The coating was created by a process called Micro-Arc-Oxidation (MAO). Some samples were also infused with graphene oxide (GO) particles and/or dipped in Sol-gel and/or PCL. These types of coatings have been shown to have improved the degradation rate of Mg in other studies and will be compared in this study based on their biocompatibility as orthopedic implants by using MC3T3-E1 osteoblastic cells.

Materials and

Methods: A series of tests were conducted including a cytotoxicity study, a contact angle investigation, and SEM imaging. Regarding the cytotoxicity study, each sample was sterilized in UV light for 45 minutes on each side while being sprayed in 70% ethanol prior to cell culture. The ISO 10993-5 extract method was performed on MC3T3-E1 osteoprogenitor cells. Coupon-leached media was produced by soaking the 5 sample groups in complete αMEM media supplemented with 10% FBS and 1% penicillin-strep-tomycin for 72h according to the weight ratio of 0.2g/mL where the resulting media was diluted to 6x. 10,000 MC3T3 cells were seeded in a 96-well plate in addition to a calibration curve of increasing cell numbers. A PrestoBlue Viability Assay was used to confirm attachment and seeding density and the cells were cultured in the leached media (with controls in complete αMEM media). Cell counts were gathered after a 72h period using fluorescence (530/25 excitation and 590/35 emission). SEM imaging was performed to investigate how the coatings changed the surface properties of the Zk60 alloy. The contact angle investigation was performed using the sessile drop technique combined with the CAM PLUS MICRO contact angle meter to determine the hydrophilicity of the samples.

Results, Conclusions, and Discussions: By investigating the cytotoxicity data, the leached media did not seem to have much effect on the cells’ ability to proliferate and grow, which indicates that the by-products produced by the samples are more on the biocompatible side. The one-way ANOVA indicated that there was no significant difference between samples (p-value=0.205). The follow up Kruskal-Wallis test indicated the same thing with a p-value=0.4156. In addition, sol-gel was the only coating group that averaged a value less than 70% viability making it the most cytotoxic group to the cells. However, this cytotoxicity level is not significantly lower than the 70% level recommended by the ISO10993-5. The contact angle investigation of the uncoated group and the most biocompatible group (PCL) showed that there was a significant difference for both the PCL and the Uncoated Zk60 samples. A Kruskal-Wallis test indicated that there was a significant difference between the two samples for the contact angle investigation with a p-value=0.02016. The PCL sample group showed better hydrophilicity interactions indicated by the lower contact angles with an average of 52° compared to 111.5°. The SEM images have shown that the more complex coatings have smaller pores on their surfaces. This indicates that the more complex coatings (sol-gel and PCL) are more durable than the others (MAO and MAO+GO). The reason for the smaller pores is the addition of the GO to the sol-gel and PCL coatings. These coatings overall seemed to improve the biocompatibility of the Zk60 alloy in terms of the contact angle and without affecting the toxicity of the samples. A more in-depth analysis is required for the rest of the sample types to see how they compare to the PCL coating. In addition, the effect of these coatings on the corrosion properties and adhesion with the Mg alloy substrate is needed. Additionally, this work could benefit from tests like SEM, EDX, and XRD imaging and analysis. These tests would help determine how leaching the samples in cell culture media affects their chemical composition, surface morphology, and internal structure. Understanding these changes may be crucial for future studies.

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