title: In vivo monitoring the biodegradation of magnesium alloys with an electrochemical H2 sensor.
abstract: Monitoring the biodegradation process of magnesium and its alloys in vivo is challenging. Currently, this process is monitored by micro-CT and X-ray imaging in vivo, which require large and costly instrumentation. Here we report a simple and effective methodology to monitor the biodegradation process in vivo by sensing H2 transdermally above a magnesium sample implanted subcutaneously in a mouse. An electrochemical H2 microsensor was used to measure the biodegradation product H2 at the surface of the skin for two magnesium alloys (ZK40 and AZ31) and one high purity magnesium single crystal (Mg8H). The sensor was able to easily detect low levels of H2 (30-400μM) permeating through the skin with a response time of about 30s. H2 levels were correlated with the biodegradation rate as determined from weight loss measurements of the implants. This new method is noninvasive, fast and requires no major equipment.
  
  
  
  Biomedical devices such as plates and screws used for broken bone repair are being developed out of biodegradable magnesium alloys that gradually dissolve when no longer needed. This avoids subsequent removal by surgery, which may be necessary if complications arise. A rapid, non-invasive means for monitoring the biodegradation process in vivo is needed for animal testing and point of care (POC) evaluation of patients. Here we report a novel, simple, fast, and noninvasive method to monitor the biodegradation of magnesium in vivo by measuring the biodegradation product H2 with an electrochemical H2 sensor. Since H2 rapidly permeates through biological tissue, measurements are made by simply pressing the sensor tip against the skin above the implant; the response is within 30s.
authors.affiliation: Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Daoli
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Tingting
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Kuhlmann
authors.affiliation: Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA.
authors.forename: Zhongyun
authors.initials: Z
authors.lastname: Dong
authors.affiliation: Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA.
authors.forename: Shuna
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Madhura
authors.initials: M
authors.lastname: Joshi
authors.affiliation: Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Pravahan
authors.initials: P
authors.lastname: Salunke
authors.affiliation: Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA.
authors.forename: Vesselin N
authors.initials: VN
authors.lastname: Shanov
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
authors.forename: Daeho
authors.initials: D
authors.lastname: Hong
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA; Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA; Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA.
authors.forename: Prashant N
authors.initials: PN
authors.lastname: Kumta
authors.affiliation: Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA. Electronic address: William.Heineman@uc.edu.
authors.forename: William R
authors.initials: WR
authors.lastname: Heineman
mesh_terms: D020341:Absorbable Implants; D000497:Alloys / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006859:Hydrogen / Q000032:analysis* / Q000378:metabolism; D008274:Magnesium / Q000737:chemistry / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D012867:Skin / Q000378:metabolism*
chemical_list: D000497:Alloys; D006859:Hydrogen; D008274:Magnesium
keywords: Biodegradation; Electrochemical sensor; Gas cavity; Hydrogen; Hydrogen sensor; Magnesium alloys