But biobased biomedical materials are not new. Linen and cotton have been used for bandages for centuries, for instance, largely because of their absorbent properties. This article is not so much about the common biomedical materials as about the ‘new generation’, with the focus on biopolymers which can replace their fossil counterparts. ‘The bulk of biomedical materials – materials which are used in the human body in the healing process – are of fossil origin,’ says Menno Knetsch, associate professor Biobased Materials at Maastricht University. ‘Metal alloys and silicones are also used. Some examples are surgical mesh made from PP, catheters made from PU, metal stents and metal alloys for hip prostheses.’
Patient welfare first, sustainability not important
Instances of biopolymers and/or biocomposites are few and far between, according to Knetsch. ‘PLA has become well established now, for example for orthopaedic implants (including screws) or soluble sutures. Because the degradability of PLA can be controlled, it is an excellent material to use for temporary solutions, such as drug delivery within the body. In the case of the first two applications mentioned, it prevents the need for a second operation to remove the materials.’ The latter illustrates the most important driving force behind the development of biomedical materials. The medical profession does not care which materials are used – it is concerned with the implications for the patient. ‘Sustainability or CO2 footprint do not play any part at all,’ according to Knetsch. ‘These materials are assessed purely on their properties and role in the treatment process.’
One property is the above-mentioned degradability, even though there are fossil plastics which can degrade, such as PBS. Degradability in the human body is not the only priority of biomedical materials, however. Knetsch names ‘biocompatibility’ as a distinguishing property which is relevant in regenerative medicine especially. In this discipline, cells, tissues and organs are regenerated. Examples are bone and cartilage repair, pressure sores and burns and many kinds of organ disorders. ‘The materials used for this purpose function as tools for the body to tackle the healing process. It is important that this material is not rejected by the body and does not cause complications in surrounding tissues. That is where biobased materials are preferable: to start with, they can be biodegradable and they are of organic origin, which reduces the risk of complications.’ The literature also mentions the porosity of biobased materials. This property makes it possible to develop 3D scaffolds which can facilitate the growth of new cells. These cells gradually replace this artificial framework (thanks to the porosity), after which the framework eventually dissolves.
Unwanted side effects
The degradability of biopolymers in the human body should not be taken lightly. Some constituents that dissolve in nature can possibly cause problems in the body. Knetsch mentions lactic acid, a residual product of PLA, which can result in tissue necrosis (editor’s note: the dying off of cell tissue). This unwanted side effect can be avoided by adjusting the formula. Whatever the case, every blend based on biodegradable biopolymers will have to be investigated for its effects on the human body. This means that the development process of new materials and/or material combinations is lengthy and expensive. ‘These materials do have to offer considerable advantages to justify the investment risk for the often smaller-sized companies. The medical profession generally does not switch to new materials or treatment methods that easily. Indeed, why should it if it already has something that works and is reliable.’
Price plays no part
Another hurdle, price, is less relevant in biomedical materials, according to Knetsch. Material costs generally form only a fraction of the total treatment. Employee costs are the largest cost item. So if biobased biomedical materials accelerate the treatment or prevent a post operation (to remove materials), these would even turn out to be cheaper. Is there no chance at all for biobased materials in healthcare? Far from it. There are already successful products (see box) which are at an advanced stage in the pipeline. Knetsch sees opportunities – as indicated earlier – mainly in regenerative medicine. ‘The trend is that biomedical materials have to offer several functionalities – degradability, biocompatibility, regenerative capacity, etc. Biobased materials and plastics have the potential to meet this ‘need’. Yes, the development will take time, and that is why an initiative like AMIBM is essential to do the much-needed groundwork. This knowledge base can then serve as the foundation for developing specific applications.’
The AMIBM (Aachen Maastricht Institute for Biobased Materials) is investigating wound treatment among other things, examining the potential of the nettle. Not only the fibres of nettles are interesting, but also their bio-active components which prevent infections and aid the healing process. The AMIBM is currently investigating the extent to which these bio-active components can be extracted and purified so they can then be used in an application.