Welcome to the Glass Age

53 ions, glass ionomer cements also release fluoride and help to prevent caries. Glass ionomer cements are used regularly by dentists, and most of us have this material somewhere in our teeth. One great advantage of these glass ionomer cements is that for setting they do not require special equipment such as UV light. So, they can be used easily even in rural areas of developing countries, helping dentists to bring dental care even to remote spots. Therapeutic nanoparticles While not really considered a bioactive glass, radioactive glass spheres are used to treat liver cancer, whereby they are injected into the blood stream, become lodged in the liver and emit radiation from inside the liver to destroy the tumour. They are used when externally applied radiation is not effective. There are many experimental cancer treatments that use nano-porous glass nanospheres (Figure 3.10) that aim to deliver chemotherapy drugs only to the cells that are targeted. It is well known that conventional chemotherapy has drastic side effects, which is due to it killing useful cells at the same time that it kills the cancer cells. Silica nanoparticles can carry the drug inside the pores and the particles are small enough that they can be made to pass by cells without interacting with them so they only interact with the target cancer cells [15]. Then, the cancer cells take them in and when they are inside, they release their cargo. Once the efficacy of the targeting is perfected, these strategies are likely to revolutionise cancer therapy. While targeted chemotherapy is challenging to deliver, bioactive glass nanoparticles could also deliver therapeutic ions, for example nanoparticles delivering zinc ions were found to kill breast cancer cells without killing healthy equivalent cells [16]. Therapeutic benefits may extend beyond cancer. A disease that affects most of us as we age is osteoporosis, where the cells that take our bone away are working faster than the cells laying down new bone, resulting in loss of bone density. Figure 3.11 shows bone marrow stem cells that have internalised bioactive glass nanospheres that are delivering strontium ions inside the cells. The combination of silica, calcium and strontium promoted stem cell differentiation down a bone pathway, whereas those that were given nanospheres without the strontium remained as stem cells [17]. The possibilities for bioactive glasses seem endless, but medical device companies have to prove every new device is safe and effective for each individual clinical application before they can used. Summary Biomedical glasses are key contributors to the Glass Age. Strong, corrosion resistant glasses enable storage and delivery of life saving medicines, Figure 3.10. Transmission electron microscope image of nanoporous silica nanospheres that can be loaded with chemotherapy drugs and functionalised with molecules that can target specific cancer cells. Source: Modified from Chen et al . [16].