2/2010

Bioactive glass heals - and disappears

Heimo Ylanen

According to Professor Heimo Ylänen, A combination
of bioactive glass and bone harvested elsewhere from a patient's
body has proved as durable as the patient's own bone.

Bone implants, dental prostheses, even missing cranial bones - bioactive glass has many uses in bone and plastic surgery. The glass replaces missing bone tissue and is gradually replaced by the patient's own tissue.

Physically, bioactive glass resembles window glass but its chemical composition is different. It is much more reactive to extracellular fluid than conventional glass. As a result of the reactions, bioactive glass bonds to bone.

The glass gradually releases substances inside the human body that are perfectly biocompatible but activate a mechanism that promotes new bone growth. Over time, the glass dissolves completely and is replaced by bone tissue. Bioactive glass is therefore an optimal filler material, because instead of leaving a cavity in the body as it dissolves, the glass is progressively replaced by the patient's own tissue.

"The process continues until the glass has been completely replaced by new bone. Glass is an optimal biomaterial: it does the job and disappears. It also eliminates the need for implant-removal surgery", says Professor Heimo Ylänen from at the Department of Biomedical Engineering at TUT.

Fibre, granules and microspheres

Bioactive glass was initially developed 30 years ago to treat soldiers who suffered bone injuries in the Vietnam War. The first glass materials could not be used to manufacture technically demanding products, such as fibre, because they crystallized during thermal treatment.

In the 1980s, Finnish researchers started developing bioactive glass that could be used in a more diverse range of applications. The current glass types can be shaped into almost any form, such as fibre and tiny microspheres. Along the way, Finland has become a hotspot for research into bioactive glass.

ESB2010: Spare parts for humans

Bioaktiivinen lasi


One of the leading international conferences on biomaterials and tissue engineering, ESB 2010, was held for the first time in Finland on 11 - 15 September 2010. National societies for biomaterials take turns arranging the ESB conference. This year, the conference was hosted by the Finnish Society for Biomaterials. The conference brought together 800 professionals in the field of biomaterials, tissue engineering, chemistry and modeling. ESB2010 had a strong multidisciplinary focus.

"Scientific communities conduct, and are required to conduct, extensive multidisciplinary research in order to develop new biomaterials and grow new organs to replace damaged ones", states Professor Heimo Ylänen, who serves as the President of the Finnish Society for Biomaterials.

In the last few years, tissue engineering has emerged as a valid alternative for treating, for example, bone deficiency. Recent years have seen a flurry of research activity into biomaterials that react to changes in the immediate environment, or so-called stimuli-sensitive biomaterials, which are believed to hold great potential for medical use.

One of the Plenary Lectures of the conference was Professor Tadashi Kokubo, a renowned pioneer in the field of biomaterials research. He presented the clinical results of a new method concerning the attachment of hip prostheses to patients own bone.

Hundreds of people are employed in Tampere in the field of biomedicine and biomedical engineering. Ylänen says that professionals in the field have engaged in unique, multidisciplinary collaboration in Tampere. Their combined knowledge enables globally top-quality research.

"Tampere has become a major research hub for biomaterials, processing technologies and tissue engineering in Finland."

www.esb2010.org

Strong expertise in the field of composite materials

At the moment, TUT and Åbo Akademi University are collaborating to develop glass materials that could be weaved, either by themselves or by adding biodegradable polymer fibres, into bioactive fabric. TUT brings to the project its expertise in composite materials and Åbo Akademi University its knowledge of synthetic chemistry.

"When using bioactive glass, we need to take into account the shape of the product, the speed of the required reaction, and the physiological conditions of the implant. The conditions in the hip joint are different from those in the frontal sinus. Other products need to react slowly and others rapidly in the human body", says Ylänen.

Plaster to keep wounds clean

In the near future, a load-bearing scaffold could be fabricated from bioactive glass and polymer to replace, for example, a broken vertebra. The development of porous implants that stimulate healing is also well underway.

Since some types of bioactive glass are antimicrobial - they kill or inhibit the growth or reproduction of micro-organisms - another potential application area is a plaster that accelerates the healing process and keeps the wound clean. The upper layer of the plaster could be made of a less reactive material that would, for example, protect a burn injury from fluid loss.

Sensors to predict cancer spread

"In the future, biomaterials will be used, for example, to monitor the health status of high-risk groups. Sensors implanted within the human body could even predict the spread of cancer."

A collaboration project with the Chinese Zhongshan Hospital supports the research. The largest hospital in Asia has experience of using biomaterials and the collaboration enables Finnish researchers to benefit from this knowledge.

"At the moment, we're looking into the possibility of launching similar collaboration with partners from India and Indonesia", says Ylänen.

Text: Katri Syvärinen
Photo: Sami Helenius

 

 

 

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