Biomaterial scientists are those who engineer and develop biomaterials for a wide range of medical applications. A biomaterial is a material used to make a device that replaces an organ or part of the body in a safe, viable, reliable, economic, and ethical manner. The material can be metal, ceramic, polymer, fluid or so. Since there are various options to select upon, it is essential to determine the appropriate material for developing a biomaterial. This depends upon the application. This section deals with the conditions/criteria for choosing an appropriate biomaterial for orthopedic implants.
Orthopedics refers to the surgery related to the musculoskeletal system. Out of all the components in the musculoskeletal system, the joints are given prime importance. The reason is that those structures can wear out soon and these structures work the most. The primary and big joints present in the human body are the hip and the knee. It is essential to consider factors based on these joints for developing a biomaterial.
Both the knee and hip joints are weight-bearing joints. This means that the body weight falls onto these joints. So, the material that we are going to implant must bear heavy stress/load. The material must not deform easily with an increase in stress, it must have a low modulus. It must be resistant to wear and tear; and at the same time, it must be light. Considering all the above factors, titanium would be the perfect choice because of its immense mechanical strength, low modulus, and less density. Stainless steel is also a good choice but it is a bit dense. Cobalt-chromium alloy is also a feasible one.
knee implant
Another problem with metals is corrosion. Corrosion occurs when the metal gets into contact with the fluid. Since these joints have synovial fluid, this is a serious problem to be considered. Stainless steel fails in this case because it undergoes corrosion in fluidic medium and in oxygen depletion. Cobalt-chromium alloy undergoes fretting corrosion and the corroded pieces trigger inflammation and worsen the condition. So, overruling them, titanium is considered as the best choice for orthopedic implants since they are corrosion resistant by forming a layer of TiO2. Regarding the dental implants, titanium screws are used because of its good mechanical properties, light density and osseointegration (ability of metal to integrate with bone without connective tissue).
Biocompatibility is another aspect to be considered. Titanium, Cr-Co and stainless steel has good biocompatibility, but titanium is better. One reason is the osseointegration and another is the TiO2 layer interacts with plasma proteins and enhances growth. So these are the different factors to be considered for orthopedic implants.
Often biomaterial scientists integrate materials or do modifications to improve its performance by characterization methods. One example is in osseointegration for dental implants. HA (hyaluronic acid) is often added to metals in order to improve their osseointegration and reduce the crystallization. Another example is the electropolishing of surfaces of stainless steel to prevent formation of emboli.
The ultimate aim for developing biomaterial is to benefit the human race. There are multiple processes before the release into healthcare. This can be coined as a phrase called ‘bench to bedside’. There are five stages in this journey. This section explains the bench to bedside process with respect to cardiovascular implant.
Biomaterial research
We have to choose the appropriate biomaterial in order to develop an implant. The following are the important parameters to be considered for developing a cardiovascular implant.
- Hemocompatibility
- Durability
- Biocompatibility
- Must not rupture the endothelium
- Mechanical strength
- Corrosion resistance
Proper literature analysis has to be done to find out the ideal biomaterial for cardiovascular implant.
Development of the biomaterial
Then we can proceed to software analysis. Simulation software like COMSOL Multiphysics can aid in the analysis of biomaterials. We can simulate the material in different physical and chemical environment to test the properties of the material. Once it is successful, we can develop an implant out of it. If it didn’t work out successfully, we have to go back to literature research to find a better material.
Preclinical and clinical test
Once we have designed an implant, we can go for preclinical and clinical tests. Generally, animal models are used for this stage of research. The implant is fixed onto these models and are observed for weeks to check to significant improvement. Regarding cardiovascular implants, porcine models (pig) are of the recommended choice. The reason is that the heart of pig is a bit similar to that of human. Recently, doctors have transplanted pig’s heart into human, this is called as xenotransplantation.
Regulatory approval
Once we have obtained significant results in the animal model, we can approach for ethical rights in order to test onto a human. It is essential to test it on a human before release into market. Since testing in human has ethical issues, it is important to clear them out. Once we get significant results in human, then we can claim for regulatory approval. The popular body is FDA (Food and Drug Administration) and CDRS (Center for Devices and Radioactive Study). The following are the requirements needed before releasing the product into the market according to FDA.
- Establishment registration
- Medical Device Listing,
- Premarket Notification 510(k), unless exempt, or Premarket Approval (PMA),
- Investigational Device Exemption (IDE) for clinical studies
- Quality System (QS) regulation
- Labeling requirements
- Medical Device Reporting (MDR)
Product release and usage
Once all these steps are done, your implant is good to go into the market. Reading these steps makes us dizzy, imagine the people behind it. It would be a really difficult job for them. They have to stay in the laboratory for months in order to develop a successful material. They would struggle a lot for getting regulatory approval since it isn’t an easy task. But all those pain fade when they see doctors using their material and treating diseases using them. These people also play an important role in effective treatment but often get unnoticed. This work is a tribute to those legends!!
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