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This Defense Intelligence Agency reference document, dated 7 January 2010 and prepared under the Acquisition Threat Support series, surveys biomaterials used in medicine. It covers biocompatibility, biosensor membranes, silicones, Teflon, biodegradable polymers, hydrogels, titanium, bioceramics, tissue constructs, cardiovascular stents, contact lenses, drug delivery and dialysis. It concludes that biomaterial performance underlies many medical devices, that the industry is slow to adopt new materials because of testing costs, and that innovation mainly involves new applications of established materials.
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SILICONE CHEMISTRY
Silicone is actually a common name
for the chemical compound
polydimethylsiloxane (PDMS), a class
of synthetic polymers with repeating
units of silicon and oxygen. Figure 5
shows .the polymeric repeating
structure of medical silicones. Various
functional groups-often methyl-can
be attached to that backbone to
change the,material properties.
Silicone polymerS can easily be
transformed into linear or cross-
linking tn~terials without using any
toxic plasticizers. The resulting
materials are elastic at body
temperature. CH3
The simultaneous presence of Figures. Silicone C6emica.1 Groups
different groups attached to the
silicon-oxygen backbone gives silicones a range of vi_scous and mechanical properties
that allow their use as fluids, emulsions, compounds: resins, and elastomersjn
numerous applications. Thus, silicone Is a versatile polymer/although its use is often •
limited by its relatively poor mechanical strength; However, this limitation can be
overcome by reinforcing silicone with a silica filler or by chemically modifying the
backbone.
The stability, lack of toxicity, and excellent biocompatibility of PDMS make these
materials well suited for use in personal care, pharmaceutical, and medical device
applications. Silicone Is easily molded and cast using room temperature curing (known
as RlV) or through the use of an organic catalyst.
SILICONE IN BIOMEDICAL PRODUCTS
Silicone membranes are made by casting the silicone liquid precursor into thin sheets.
Such membranes are often used in;oxygen and carbon dioxide blood biosensors
because 'membranes made of this material are highly transmissive to these gases while
they block most other chemical substances present in the blood stream. In addition,
silicone's resistance to protein adhesion and its excellent overall biocompatibility make
it one of ttie most commonly used materials for encapsulating biosensors for tissue or
blood contact.
Recent formulations of silicone can· be patterned with ultraviolet light and, thus, lend
themselves to manufacture:with bi6sensors made by photolithography.
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 32 pages are in the text index: search them above, or from the library's search.