Publication details

Authors: Zhao, Daoli; Brown, Andrew; Wang, Tingting; Yoshizawa, Sayuri; Sfeir, Charles; Heineman, William R. 
Title: In vivo quantification of hydrogen gas concentration in bone marrow surrounding magnesium fracture fixation hardware using an electrochemical hydrogen gas sensor 
Type: Journal Article 
Publisher: Acta Biomaterialia  
Year: 2018 
Volume: 73 
Start Page: 559-566 
End Page:  
DOI: 10.1016/j.actbio.2018.04.032 
Abstract: Magnesium (Mg) medical devices are currently being marketed for orthopedic applications and have a complex degradation process which includes the evolution of hydrogen gas (H2). The effect of H2 exposure on relevant cell types has not been studied; and the concentration surrounding degrading Mg devices has not been quantified to enable such mechanistic studies. A simple and effective method to measure the concentration of H2 in varying microenvironments surrounding Mg implants is the first step to understanding the biological impact of H2 on these cells. Here, the in vivo measurement of H2 surrounding fracture fixation devices implanted in vivo is demonstrated. An electrochemical H2 microsensor detected increased levels of H2 at three anatomical sites with a response time of about 30/s. The sensor showed the H2 concentration in the bone marrow at 1/week post-implantation (1460//320/M) to be much higher than measured in the subcutaneous tissue (550//210/M) and at the skin surface (120//50/M). Additionally, the H2 concentrations measured in the bone marrow exceeded the concentration in a H2 saturated water solution (<800/M). These results suggest that H2 emanating from Mg implants in bone during degradation pass through the bone marrow and become at least partially trapped because of slow permeation through the bone. This study is the first to identify H2 concentrations in the bone marrow environment and will enable in vitro experiments to be executed at clinically relevant H2 concentrations to explore possible biological effects of H2 exposure. Statement of Significance An electrochemical H2 sensor was used to monitor the degradation of a Mg fracture fixation system in a lapine ulna fracture model. Interestingly, the H2 concentration in the bone marrow is 82% higher than H2 saturated water solution. This suggests H2 generated in situ is trapped in the bone marrow and bone is less permeable than the surrounding tissues. The detectable H2 at the rabbit skin also demonstrates a H2 sensors ability to monitor the degradation process under thin layers of tissue. H2 sensing shows promise as a tool for monitoring the degradation of Mg alloy in vivo and creating in vitro test beds to more mechanistically evaluate the effects of varying H2 concentrations on cell types relevant to osteogenesis.  
Keywords: Magnesium 
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