By Nick Gilbert
Topics CoveredIntroductionBiomedical Material RequirementsMaterial Properties of Platinum useful for BiomedicinePlatinum in Biomedical Applications Benefits of Platinum for Biomedical ApplicationsReferences
Biomedical devices can be extremely advanced, technologically challenging and complex products. Using the latest manufacturing techniques and often exotic materials, biomedical devices particularly those used in humans, present some of the biggest engineering challenges for the material science and medical research communities today. By their very nature, Biomedical devices being implanted in the human body must perform exactly as they were designed, without fail from the time they are surgically implanted, until the day they are no longer in use (Patient death or implant upgrades).
The development of biomedical devices can be extremely costly requiring heavy investment across the entire supply chain focusing particularly on the design, protoyping, materials selection, manufacturing and testing of these devices.
Biomedical Material Requirements
Biomedical devices come in many shapes and sizes and can vary from the extremely complex (pace makers) to the relatively simple (pins / artificial joints). One of the principle requirements of the materials used in the design and manufacture of Biomedical devices is that they must not react with or harm the bodily tissues exposed to them. Therefore, a driving factor in the materials selection for the design and fabrication of Biomedical devices is the ability of the material to withstand the corrosive nature of the bodies naturally occurring fluids. An added complication is the fact that the chemical make-up and concentration of fluids does not stay consistent over time; a factor of both internal and external situations. For example, the pH levels within the human body can change dramatically with changes in environment or bodily exertion. This in turn can cause large changes in the corrosive nature of the fluids circulating within the body through increased chloride ionic content - known to be very corrosive to surgically implanted foreign bodies.
If corrosion were to occur, there is a possibility that metal ions could be released into the system, with potentially toxic consequences for the patient. Accidentally released metal ions can form dangerous compounds with other elements within the body having potentially harmful effects, both short and longer term. As a result of this, all biomedical devices and implants must be designed to be able to withstand large changes in the chemical environment in which they are placed, without loss of stability.
Material Properties of Platinum useful for Biomedicine
Since the early 1970's the medical research community has exploited the material properties of Platinum in the design and manufacture of a range of medical implants. Platinum is a particularly useful material for use in biomedical devices and implants as it's high corrosion resistance (it is inert unlike base metals) is not susceptible to the perturbation in chemical environments within the body.
Some other useful material properties for the specific purpose of biomedical devices include:
Table 1: Material Properties of Platinum useful for Biomedical applications
|Oxidation resistance 1200 °C / 1600 °C
||Electrochemical oxidation potential
||DC corrosion resistance
|0.1 - 0.3 g m-2 h-1 / 1.2 g m-2 h-1
||5-7 mg amp-1 year-1
||30 x Ti 6.7 x Ni
||9.937 x 106 S m-1|
Platinum in Biomedical Applications
An inherent corrosive resistance, high biocompatibility and radiopaque properties make Platinum perfect for a range of biomedical applications. Platinum's biocompatability makes it ideal for both short and long-term medical implants while, its mechanical properties and ductility make it perfect for fabricating into small, complex and strong shapes that can withstand high stress without deformation or cracking (mitigating against a potentially toxic release of material). Some base metals like copper or nickel (commonly used in biomedical applications) can corrode and react with body tissue causing allergic reactions and have adverse affects on the patient.
For over 40 years, Platinum and Platinum alloys have been used widely in surgical operations to help cure a range of patient ailments, from the very minor to the high risk and complex operations. Procedures such as angioplasty, balloon angioplasty and stenting use Platinum mainly for its inert qualities, hard wearing material properties, fine machinability and visibility under X-Ray. Further qualities of Platinum like its high electrical conductivity make it the perfect electrode material for pacemakers, electrophysical catheters, internal defibrillator's, heart pumps, hearing aids etc. Many less-invasive medical practices use platinum as a good electrical conductor for the electrical diode parts of devices designed to help diagnose and treat illnesses.
For all the non-medical people out there - Angioplasty: What is it? is a great introductory video to set the scene and offer and insight into how Platinum is helping to save peoples lives.
Video AngioPlasty: What is it? Created by North Shore University Hospital (NSUH)
Run Time - 3:15mins
More recently Platinum has been extensively used within many developments in neuroscience and in particular neuromodulation, where devices are implanted into a patients brain to help regulate, prompt or mediate activity within the brain. Platinum has also been used in the manufacture of implanted hearing aids (cochlear implants) to help restore a person's hearing in a more discreet way.
Benefits of Platinum for Biomedical Applications
- Highly Corrosion resistant
- High biocompatibility
- Good mechanical resistance
- Electrical conductivity
- Radiopaque (visible for x-ray images)
Examples of Platinum Being Used in Biomedical Devices and Procedures
Stents are a great example of where the unique material properties of Platinum are put to the test in biomedical procedures and devices. The following animations are examples of how stents are surgically inserted into a patient and how they work in situ.
Video: Coronary Stent Animation - Animation produced by Johnson and Johnson Health
A short animation depicting the placement of a coronary stent. Inserted via a guide wire within an artery.
Run time - 0:40Mins
Video: Drug-eluting Coronary Stent - Animation produced by Johnson and Johnson Health
A clever addition of a polymer coating allows doctors to prescribe medicine, in situ from the stent itself. - Is there no end to what materials can do!?
Run Time - 0.09Mins
This article was composed from a number of sources including the following references.