The environment can have a large deteriorative effect on materials over time, including corrosion and degradation. For biomaterials, the materials have the additional condition for the use of having to be able to survive the unique environment of biological systems. In this lesson, we explore issues around biomaterials including structural requirements, functional requirements, biocompatibility, and ethical concerns.
By the end of this lesson, you should be able to:
Lesson 11 will take us one week to complete. Please refer to Canvas for specific due dates.
To Read | Read the Biomaterials pages in Canvas under Lesson 11, plus the few pages included here. |
---|---|
To Watch | Making Stuff: Smarter |
To Do | Lesson 11 Quiz |
If you have general questions about the course content or structure, please post them to the General Questions and Discussion forum in Canvas. If your question is of a more personal nature, feel free to send a message to all faculty and TAs through Canvas email. We will check daily to respond.
Before beginning a discussion of biomaterials there are several different terms that we should define. One way of classifying biomaterials is to use the following four materials classifications: biological materials, biomaterials, bio-based materials, and biomimetic materials.
Biological materials are materials that are produced by living organisms, such as, blood, bone, proteins, muscle, and other organic material. Biomaterials, on the other hand, are materials which are created specifically to be used for biological applications. These applications can include bone replacement, skin replacement, membranes for dialysis, artificial limbs, etc. Bio-based materials are materials that are derived from living organisms but are repurposed for other applications. One example of a bio-based material would be enzymes mass-produced by microbes to be used in the synthesis of drugs. Biomimetic materials are materials that are physically or chemically similar to materials produced by living organisms.
In the textbook reading for this lesson, materials will be classified as structural or functional and then the natural biological material will be compared and contrasted with the biomaterials designed to replace or interact with it.
Structural biomaterials, as the name implies, have as their primary function physical support and structure. Structural biomaterials are sometimes referred to as inert biomaterials. Functional biomaterials (also known as active biomaterials) have a non-structural application as their primary function. An example of a functional biomaterial would be membranes used during dialysis to filter impurities from blood.
An example of a structural biomaterial would be a titanium steel implant with a ball and socket being used as a hip replacement. Two other terms that might be helpful to define before the reading are immune response and biocompatibility. During the body’s immune response, the body sends white blood cells to attack and destroy foreign material. Biocompatible materials are those biomaterials which typically do not elicit the body’s immune response during the operational lifetime of the biomaterial in the body.
Now that we have covered a few basic terms please continue to the next section and begin the reading for this lesson.
When you read this chapter, use the following questions to guide your reading. Remember to keep the learning objectives listed on the previous page in mind as you learn from this text.
Read the Biomaterials pages in Canvas under Lesson 11, plus the few pages included here.
Ethical issues raised by the use of biological materials are numerous and so complex that an entire field of study known as bioethics has been created.
Will the biomaterial be safe or potentially be harmful to the body in the near term and long term? Will data obtained during testing on animals justify the suffering and sacrifice of living creatures? Will professional and financial interests by researchers result in conflicts of interest which could taint trial data? Should supply and demand, and profit, allow biomaterials companies to charge "what the market will bear"? When evaluating a new biomaterial product what should be the balance between sustaining life versus quality of life issues? What should be the role of regulatory agencies? Should access to biomaterials be determined by medical need or ability to pay? How does society ensure that humans living in the Third World have access to current advances in biomaterial applications? How does society balance scientific advancements in the area of biomaterials with religious doctrines, which are sometimes at odds with those advancements?
Clearly, we could spend another course just on the topic of ethics in biomaterials. Hopefully, the reading in the lesson and on the website has made you aware, if you were not already, of this important subject. In the next section of our website, we will be looking at a biomaterial which is also a smart material.
In the lesson reading this week vascular stents were covered, including the revolutionary nitinol stents. When the body heats up this smart material ‘remembers’ its initial programmed shape. So, in addition to being a biomaterial, nitinol is a smart material as well. What are smart materials? Smart materials are materials that are designed to mimic biological behavior. They are materials that, like biological systems, ‘respond to stimuli.' More smart materials will be presented in the video for this lesson, but right now please watch this short video (1:27) on the amazing nitinol.
Now proceed to the next section to watch the video for this lesson. As you watch this lesson, see if you can answer the following for each of the smart materials presented: what is the stimulus and what is the response?
Now that you have read the text and thought about the questions I posed, take some time to watch this 54-minute video about one type of advanced materials (smart materials) that sense their environment and, in some cases, can even adapt to their environment. As you watch this video see if you can find the following:
Go to Lesson 11 in Canvas and watch NOVA's Making Stuff: Smarter Video. You will be quizzed on the content of this video.
Biomaterials and smart materials are two of the four advanced materials that we discussed in Lesson 1 of this course. Unlike the classical classifications of materials (metals, ceramics, polymers, and composites), advanced materials are defined by their function, i.e., what role that they serve. Biomaterials can be metals, ceramics, polymers, composites, or combinations of these, that are used inside the body. They can serve structural and/or functional purposes within the body. Of course, an important consideration is how bio-compatible the material is, which determines whether the material can be used, where in the body, and the useful lifetime of the material. Smart materials can be metals, ceramics, polymers, composites, or combinations of these, that mimic life. These materials 'respond to stimuli'.
You have reached the end of Lesson 11! Double-check the to-do list on the Overview page to make sure you have completed all of the activities listed there before you begin Lesson 12.