Welcome to the Glass Age

46 The ions seem to kill some pathogens and actively stimulate wound healing, most likely by accelerating angiogenesis (sprouting of blood vessels). However, the morphology of the fibres is also likely to play a role in accelerating the wound healing process, as the fibres have similar diameters to the collagenous extracellular matrix of skin. They can act as a framework (scaffold) for migration of cells, which may well have been dormant, into the wound bed. When glass composition invented by Larry L. Hench in 1969 [2]. It was a silicate glass of the composition 46.1 mol% (45 wt%) SiO 2 , 24.4 mol% Na 2 O, 26.9 mol% CaO and 2.6 mol% P 2 O 5 , later termed 45S5 Bioglass. This composition was Hench’s first attempt at making a glass that might bond with human bone. Amazingly, it worked. His clinical colleagues tested it in animal studies and found that it bonded to bone so well that it was difficult for them to remove it to be able to study the bonding! This changed the way clinicians thought about biomaterials, as previously biomaterials were selected from materials that were corrosion resistant, such as titanium alloys, high density polymers and alumina-based ceramics. If an inert (and sterile) piece of window glass was implanted next to a patient’s damaged bone, it would be encapsulated by fibrous tissue and sealed off from the rest of the body by the immune system dealing with this foreign object. When a Bioglass implant comes into contact with blood, it undergoes surface dissolution, releasing calcium, the dressing is replaced after a day or two, the fibres will have biodegraded and a new matt of Mirragen ® fibres can be placed into the wound. The concept of a glass’s dissolution ions activating cells was established more than a decade before they were used in wound healing in studies designed to understand the mode of action of the original “Bioglass ® ” in bone regeneration. The name “Bioglass” specifically refers to the first bioactive Figure 3.3. Schematic of Bioglass reactions with water. Source: P. Wiemuth, University of Jena.