Research for (In Vivo)

            Researchers at CBBE Department discovered key mechanism of in vivo degradation through carefully-planned in vitro study. The research published online in Acta Biomaterialia, shows that critical and indispensable first step in the successful development of medical implants is to gain a thorough and fundamental understanding of corrosion behavior in vivo. Further controlling degradation behavior through surface treatment improved hemocompatibility and biocompatibility for cardiovascular devices.

            Dr. Y. Yun (a faculty member at CBBE) said, “Various physiological factors related the corrosion of biodegradable metal medical device should be taken into consideration to obtain similar results at in vivo when in vitro test is conducted. Because complex environment in the human body such as various physiological salts, flow and diffusion kinetics, proteins absorption and active tissue formation affect the biodegradation process and formation of corrosion products for biodegradable metal implants. In vivo experiments can unfortunately lead to major ethical concerns, costs and limited experimental capacity. Thus, we keenly feel that a new design of elaborate and complicated test-bed should be developed on the basis of massive data acquired from previous tests to reduce the gap of corrosion behavior between in vitro and in vivo test”,

            “An ideal surface treatment method for biodegradable metals to achieve a desirable period of implantation should be designed through the following optimizations: (i) suitable biodegradation behavior of the coating; (ii) well-matched chemical interaction between coating and biodegradable metal substrate during the degradation; (iii) good biocompatibility, such as hemocompatibility, cytocompatibility, and histocompatibility”,

            “The knowledge gained is allowing the team to establish protocols for the corrosion testing standard for biodegradable metal evaluation. Iterative application of these protocols is informing the judicious selection of new alloys that lead a more clinically relevant, better biodegradable metal system and also better design of medical devices. While there remains much yet to be learned, in vivo and in vitro behavior knowledge convergence is providing a pathway to improved biodegradable magnesium medical devices.”

            This research was supported by Engineering Research Center for Revolutionizing Metallic Biomaterials (REC-RMB) from National Science Foundation (NSF-0812348) and International Collaboration with China. 

Figure 1

Figure 1. Optical, Scanning Electron Microscopy (SEM) and Micro X-ray Computed tomography (Micro-CT) images of corroded AZ31B magnesium alloy after immersion test in each solution with various ions for 10 days. “Reprinted from Acta biomaterialia, 9(10), Jang, Y.; Collins, B.; Sankar, J.; Yun, Y, Effect of biological relevant ions on the corrosion products formed on alloy AZ31B: Improved understanding of magnesium corrosion, 8761-8770, Copyright (2013), with permission from Elsevier.”

Link: http://www.sciencedirect.com/science/article/pii/S174270611300144X

Figure 2

Figure 2. Reconstructions of X-ray nano-CT 3-D with representative 2-D slices of the uncoated, PCL-coated  and PTMC-coated Magnesium alloys after 1 year implantation, respectively. Yellow arrowsindicate corrosion products. “Reprinted from Acta biomaterialia, 9(10), Wang J, He Y, Maitz MF, Collins B, Xiong K, Guo L, Yun Y, Wan G, Huang N. A surface-eroding poly(1,3-trimethylene carbonate) coating for fully biodegradable magnesium-based stent applications: Toward better biofunction, biodegradation and biocompatibility, 8678-89 , Copyright (2013), with permission from Elsevier.”

Link: http://www.sciencedirect.com/science/article/pii/S1742706113001116