A key component of regenerative medicine are materials that can be used to support and replace degraded or missing body parts or tissue. These man-made materials, which are intended for functional use in living biological tissue, are called biomaterials. Over the years, the understanding of what material properties that are important for optimal performance has increased. Prof. Kasemo, who has long experience in this area, shares some perspectives on the past and future development of this field.
In 1979, when sitting in his office, Prof Bengt Kasemo, got a phone call from a person he didn’t know. The caller, who was working at the nearby hospital, introduced himself as P.I. Brånemark. “I have invented what I think is the world’s best dental implant”, he said. Then he continued, “It’s made of titanium, but we don’t know how it works. I was told that you know something about titanium. Can you help us?” This was the beginning of a long-term relation and collaboration between Prof Kasemo and P. I. Brånemark, the father of modern dental implantology. Over the years, the collaboration resulted in a very creative and intense interdisciplinary dialogue, and eventually real research, about the situation and processes at the biomaterial-tissue interface.
In retrospect, Brånemark was indeed right. His invention, the fixture which is screwed into the jawbone and then provided with a dental mimic, called prosthetic crown, proved to be a successful approach and it resulted in a world leading company in dental implants.
The question that was asked at the time, and that had to be answered, was “how do these dental implants integrate with bone”. This question and its many subquestions, constituted the core of the Brånemark-Kasemo teams’ collaboration. In fact, this specific question “what happens at the surface?” relates to all situations where a biomaterial is interfacing with living biological tissue, as this is linked to the success or failure of the implant’s integration with biological tissue.
But let’s take a few steps back and look at what materials that we are talking about. Prof. Kasemo describes what a biomaterial is – “briefly you can say it’s a material intended for functional use in living matter, e.g. in tissue. Its essentially the same as a biocompatible material, but there are some subtle differences. ‘Biocompatible’ means that the material is functionally working with the host tissue without causing unacceptable, adverse effects”, Prof Kasemo continues.
The area of biomaterials has been around for decades, both in research and clinical therapy. Over the years, the focus has varied in terms of what materials that have been addressed and used and what material properties that have been considered important and why. Before the work with Brånemark, off-the shelf materials were frequently being used, Prof. Kasemo explains. These were materials intended for other than clinical uses but supposed to function in vivo. One example is stainless steel, which was used in orthopedics. Stainless steel was available on the market and could easily be used to make implant devices. It was known to be strong and stainless. At the time, there was very much focus on mechanical properties. Eventually, however, surface chemistry started to be recognized as (also) very important, and eventually also surface microtopography was considered important. Then, along the time axis, release from the implant surface, either unintentional or intentional, came up as an important factor that could affect implant performance. And even later on, viscoelastic properties came up as important for mechanical matching to the host. Bone was not so much of a problem in this respect, but matching to soft tissue, such as blood vessels and tendons, created a challenge, Prof. Kasemo explains. As the field of nanotechnology emerged, the focus moved from microtopography to nano-topography. And eventually, it was realized that a good biocompatible material and device had to combine many of the above and even some additional properties. Depending on the specific type of implant and function, some of these properties were more or less important. This has led to the situation today where biomaterials are made by sophisticated tailoring of the implant surface in order to interface the biological host in an optimal way, Prof Kasemo says.
Looking back at the biomaterials development that now has been going on for decades, it is interesting to speculate about its future. Prof Kasemo estimates that the biomaterials science will, in general, be guided by and adopt the development in general materials science and biology. For example, when graphene was discovered as a material, it immediately initiated a lot of studies about the biointerfacial properties of graphene, he says. In general, all new material science findings and breakthroughs will have an impact on and generate biomaterials activities, Prof Kasemo continues. The adoption of materials science development into biomaterials R&D will also be combined with molecular development in biology and nanotechnology, where nanomedicine is one example. As a second example, there is very rapid development of analytical and diagnostic methods in biomedicine, and these methods are likely to have a large impact also for studies and understanding of implant – biomaterial interfaces.
We will also see hybrids in the future, where implants, before implantation, are provided with growing cell cultures or tissue made by tissue engineering, so that the success rate can be increased, and the healing-in time can be reduced. And these types of hybrids will become very important in the future, Prof. Kasemo predicts. There is already work going on in that direction.
Listen to the webinar, where Prof. Kasemo talks about key aspects of the field of biomaterials. In the presentation, he talks about the development of the area and gives examples of different biomaterials and how they are used in regenerative medicine. He also talks about the importance of the biointerface and analytical and preparative techniques.
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