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Bioactive glass in bone tissue engineering

A small introduction to bioactive glass

‘Bioactive glasses are surface-reactive glass-ceramic biomaterials.’ These remarkable materials, composed of silicon dioxide, calcium oxide, sodium oxide and phosphorus pentoxide, have been extensively investigated as implants in the human body, to help repair or replace damaged or diseased bone. This could, in the near future, eradicate the use of autogenous bone grafts, bone allografts and growth factors, all of which come attached with several problems.

An autogenous bone graft is when bone is removed from the patient’s own body and used to regenerate bone at the site of damage/disease. Unfortunately this means that there’s a limited supply, and problems could arise at the donor site ( the area where the bone was removed). Bone allografts are similar to autogenous bone grafts, with the difference that bone is removed from someone other than the patient. This also has its risks, such a possible transmission of disease and an immune reaction triggered by the foreign bone material. Growth factors encourage new bone to form by stimulating the growth and activity of osteoblasts, but unfortunately, this method is expensive, and recent studies have showed there may be possible connection between high usage of growth factors and cancer.

These numerous problems give us to reason to believe that the use of bioactive glass will significantly reduce surgical complications, thus proving a less detrimental, safer and cheaper option.

So how do bioactive glasses work?

A bioactive material is defined as: ‘ a material that elicits a specific biological response at the interface of the material, which results in the formation of a bond between the tissues and the material.’ Bioactive glasses do just this, as they are able to react with fluids in the human body to form hydroxyapatite (HA) and hydroxycarbonate apatite (HCA) layers. These bonding layers are almost identical structurally and chemically to our bone, and in addition, HA is the main mineral constituent of bone, so this allows strong bonds to form between the biomaterial and bone. Bioactive glasses also release silica and calcium ions, which are thought to stimulate osteoprogenitor (osteoblast) cells that help in the processes of growth and repair of bone. A study was conducted using soluble silica and human osteoblast-like cells. What was found was that when the cells were exposed to the silica, the DNA synthesis rate increased, as well as the rate of mitosis of the cells, which supports the aforementioned hypothesis of the effect of silica ions.

The use of bioactive glasses in regenerative medicine is fairly new, but what we can see from its clinical history is that is has proven to be successful when utilized, and has most importantly shown to produce no adverse effects in the human body.

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