Using Bioglass To Mend Bones
By Eurasia Review — (April 8, 2013)
Shaista Khanum(CORDIS) — Bones have an amazing ability to regenerate after suffering slight damage. Past a certain point however, this natural healing process is really put to the test. When breaks are too big, bones need a helping hand…or a screw or a nail.
Despite huge advances in regenerative medicine, metal inserts are still used to fix broken bones. While these have proved over time to be effective at bridging larger breaks and giving bone redevelopment a boost, a second operation on the affected area is always needed, once the bone is healed, to remove the metal pins or brace.
Ideally, materials and implants which require no second operation would be a better option. The quest to develop such materials has been the central objective of the work carried out by Jose Ramon Sarasua and Aitor Larrañaga, researchers in the materials engineering department of the UPV/EHU-University of the Basque Country.
The two Spanish researchers have been studying new materials or implants – such as polymers and bioglass – which could help mend bones. Much of their research has focused on the need for these materials to meet a number of requirements before they can be used in therapeutic applications.
Among other things, the materials have to be biocompatible; in other words, they must not damage the cells or the organism itself. Biodegradability is another potentially interesting property, which would enable the body to convert material into non-toxic metabolic products. Other factors, such as mechanical robustness and the straightforward nature of the production process, also have to be taken into consideration.
The UPV/EHU researchers are currently synthesising and shaping tailor-made bioimplants based on a biodegradable polymer. This material was chosen for its ability to gradually disappear as the bone occupies its own place. The polymer was found to be too soft, so bioglass was added. Bioglass is a bioactive agent that helps the bone to regenerate, and gives the polymer tough mechanical properties. This means that the biodegradable polymer/bioglass composite system is stiffer and tougher than the polymer alone.
These composite systems can be manufactured by means of thermoplastic processes that use heat. Studying how these materials respond to high temperatures has also therefore been an important part of the study. The UPV/EHU researchers found that the biodegradable polymer/bioglass composite systems have a lower thermal stability compared with the systems without bioglass. An adverse reaction was identified, which degraded the material and affected the end product. More importantly, when the implant was grafted into the body, the reaction encouraged the formation of bi-products that may be harmful to cells.
This is why the UPV/EHU researchers are now focusing a great deal of research on improving the thermal stability of these systems. One such study, which has been published in the journal Polymer Degradation and Stability, proposes that a chemical transformation of the bioglass surface could be made by means of plasma. By creating protective layers for the bioglass particles, the reaction to the polymer is prevented, ensuring that the final product remains undamaged.
“These composites that have a biodegradable polymer base are candidates with a bright future in mending broken bones or in regenerating bone defects,” says Professor Sarasua.
In fact, after the material has temporarily substituted the bone and encouraged it to regenerate, it gradually disappears as the bone returns to its proper place, making a second operation redundant.
My comment: For some reason, this story brings to mind my previous post about Morgellon’s syndrome
Historically the function of biomaterials has been to replace diseased or damaged tissues. First generation biomaterials were selected to be as bio-inert as possible and thereby minimize formation of scar tissue at the interface with host tissues. Bioactive glasses were discovered in 1969 and provided for the first time an alternative; second generation, interfacial bonding of an implant with host tissues. Tissue regeneration and repair using the gene activation properties of Bioglass® provide a third generation of biomaterials. This article reviews the 40 year history of the development of bioactive glasses, with emphasis on the first composition, 45S5 Bioglass®, that has been in clinical use since 1985. The steps of discovery, characterization, in vivo and in vitro evaluation, clinical studies and product development are summarized along with the technology transfer processes.
This review focuses on recent advances in the development and use of bioactive glass for tissue engineering applications. Despite its inherent brittleness, bioactive glass has several appealing characteristics as a scaffold material for bone tissue engineering. New bioactive glasses based on borate and borosilicate compositions have shown the ability to enhance new bone formation when compared to silicate bioactive glass. Borate-based bioactive glasses also have controllable degradation rates, so the degradation of the bioactive glass implant can be more closely matched to the rate of new bone formation. Bioactive glasses can be doped with trace quantities of elements such as Cu, Zn and Sr, which are known to be beneficial for healthy bone growth.[….]