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Overview
In the field of biomedical engineering, applications of electrochemistry deal primarily with the behavior of implant devices in terms of corrosion. Today, medical implant devices in the body cover a range of materials and applications: orthopedic screws,plates, rods and prosthetics; cosmetic surgery utilizing liquid and solid polymers; internal electric devices for the monitoring of pulse rates, blood pressure and bladder function; and biliary and cardiac stents for the prevention of restenosis, to name a few.
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Complete hip replacement implant device |
It should be of no surprise that there are more than a few corrosion problems associated with implanted metal components in the human body (1). Therefore, the corrosion resistance of a metallic implant device is a very important aspect of its biocompatibility (2). Before any device can be implanted into your body, it must first be approved by the FDA, which requires extensive testing for any medical device. |
| One aspect of this testing is determination of the corrosion behavior of the device under physiological conditions. A standardized test method to assess the corrosion susceptibility of small, metallic implant devices can be found in ASTM F2129-04, “Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptibility of Small Implant Devices” (3). |
Biliary stent device
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| Biosensors are generally based on the interaction between a “target molecule” (i.e. the molecule of interest) and a “probe molecule” which is immobilized onto a substrate. The selection of the “probe molecule” is specific for the target molecule of interest, and the interaction between the two can be quantitatively monitored using techniques such as amperometry, coulometry or potentiometry. For example, one of the most common methods for making dissolved oxygen measurements using amperometry is the Clark oxygen sensor (5). The first biosensor was a glucose enzyme electrode (6) which was the basis for the growing market of glucose biosensors and is the most successful commercial biosensor developed to date (7). |
Blood Glucose Sensor
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Instrumentation for Biomedical Applications
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The potentiostats/galvanostats offered by Princeton Applied Research that meet or exceed the specifications as outlined in standard methods ASTM F2129-04 and ASTM G5-94 (for DC measurements) are: Models 273A, 263A, 2263, 2273, VersaStat3 and the VersaSTAT MC. While all of these potentiostats/galvanostats have outstanding performance specifications, the model best suited for the material of interest that is being studied will be determined by the current range requirements. For example, if very low current measurements (< 1 nA) are required, the model 2273 potentiostat/galvanostat is recommended. |
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Software
For implant biocompatibility studies, the most common methods involve DC corrosion techniques such as cyclic potentiodynamic polarization for the determination of the breakdown or critical pitting potential (Eb), the corrosion or open  circuit potential (Ecorr), the repassivation or protection potential (Ep), corrosion current (Icorr) and corrosion rates based on Tafel analysis are all contained within the PowerCORR ® corrosion measurement software package.
Biosensor development and analysis relies on techniques that are contained within the PowerCV cyclic voltammetry, PowerSTEP chronoamperometry/chronopotentiometry and PowerPULSE electroanalytical software packages.
Accessories
The K0047 Corrosion Cell (as used in ASTM G5-94) is the standard test cell for making corrosion measurements on a variety of sample geometries, allowing for the insertion of the test specimen holder, counter electrodes, Luggin capillary with a salt bridge connection to the reference electrode, inlet and outlet for inert gas purge and a thermometer.
The Model K0264 Micro-Cell Kit is a complete electrochemical cell allowing for the measurement and analysis of various microelectrodes using voltammetric and amperometric techniques, or the Model K0026 Coulometry cell kit for coulometric techniques for sensor applications.
References
1. M.G. Fontana (1986). In: Corrosion Engineering: Other Environments, Third Edition, McGraw-Hill, Inc. New York, NY pp 398-399.
2. J. Black (1992). In: Biological Performance of materials: Fundamentals of Biocompatibility, Second Edition, Marcel Decker Inc. New York, NY pp –38-60.
3. ASTM F2129-01 (2003). Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements to Determine the Corrosion Susceptibility of Small Implant Devices. In: Annual Book of ASTM Standards: Medical Devices; Emergency Medical Services, Vol 13.01 Philadelphia, PA: American Society for Testing and Materials.
4. ASTM G5 (1995). Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements. In: Annual Book of ASTM Standards: Metals, test Methods and Analytical Procedures, Vol 3.02 Philadelphia, PA: American Society for Testing and Materials.
5. M.L. Hitchman (1978). In: Measurement of Dissolved Oxygen, John Wiley & Sons New York NY.
6. L.C. Clark and C. Lyons (1962). Ann. NY Acad. Sci. 102, 29-45.
7. D. G. Griffiths and G. Hall (1993). Trends in Biotech. 111, 122-130.
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