Biomedical Engineering Reference
In-Depth Information
There will be more about this in Chapter 3. One is not restricted to
simple glasses - multicomponent glasses can also be made. There are
several other advantages to sol-gel processing aside from being able to
obtain high-purity glasses, but two chief advantages are: (i) it is possible
to engineer porosity (from nanoscale to microscale) in the glass; and
(ii) since the glass does not have to be taken to a high temperature to
solidify, one can incorporate temperature-sensitive molecules.
1.6 EXOTIC GLASS
In the glass world, the term ''exotic glasses'' usually refers to glasses
that are not common silicates, but it can also mean glasses that have a
novel application. In theory, one can make a glass from any element or
compound if one cools it fast enough. There are many inorganic glasses
that have found applications in biotechnology or medicine. Phosphate
glasses are safely soluble in the body and are discussed in Chapter 4.
Glasses such as borosilicates (Pyrex) are known for their chemical stabil-
ity. However, silica-free glasses made from borate networks are soluble
and have shown great potential in tissue regeneration, particularly in
wound healing, such as healing diabetic ulcers. Deemed exotic even
though they are a silicate are Bioglass
®
type compositions, which are
explained in Chapters 2, 3, 5, 6, 8, 9, 11, and 12. There is a whole class
of glasses made from fluoride compounds that can transmit infrared
light of longer wavelength than can the silicates. Chalcogenide glasses
made from combinations of elements from group 16 of the Periodic
Table, such as arsenic, antimony, tellurium, selenium, and sulfur, also
can transmit infrared light at longer wavelengths than the fluorides. The
applications for these glasses in medicine have mostly been associated
with their role as a conduit for infrared laser light. Not widely used
yet, but likely to have a huge impact on medicine and biotechnology
in the near future, are amorphous metals, which have interesting mag-
netic properties and outstanding mechanical properties and corrosion
resistance.
1.7 SUMMARY
The take-home message for biotechnologists and practitioners of
medicine from this introductory chapter should be that a glass is not
a glass is not a glass. By this I mean that there is no one material
''glass'' and that care has to be taken to characterize what glass one has.
