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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.
UNCLASSIFIED/}FOl'il GFFICI ek W&E ,a.IL>< Biomaterials for Biosensors Implantable biosensors for the human body place some of the greatest functional demands on biomaterials. Biosensors monitor the physiologic state of tissues for medical therapeutics or for assessing human performance. Sensors for glucose, oxygen, blood pH, adrenal hormones, nervous activity, heart performance, and blood pressure monitors are all of interest. Blood biochemistry sensors are the most difficult sensors to keep functioning over time primarily because the sensor interface materials provoke low-level foreign-body reactions in tissues. These types of responses are not specifically important to implantable devices that have structural rather than sensing functions1 such as heart valves, but they can completely render a biosensor for blood glucose, for example, useless aher a few days. Chemically sensitive biosensor interfaces to tissue and body environments employ membranes in an effort to protect the biosensor active-sensing surface from possible body reactions. The membrane allows small molecules of interest to pass through its pores while excluding larger proteins, blood-formed elements, and cells like macrophages that would engulf the sensor. The membrane's biomaterial composition, pore size, and long-term physical integrity are critical components in the functioning of the sensor. If the biomaterial chosen retards the adhesion of proteins and does not provoke a biological response, then this improves sensor longevity. Figure 3 shows some representative biomembranes. No one biomaterial is best for all sensor applications, primarily because different biomaterials behave differently relative to the substance being sensed. Membranes that pass glucose, for example, may not pass oxygen that is needed for a sensor to function. Membrane biofouling starts immediately upon contact of the sensor with the body cells. Proteins and other biological components adhere to the sensor surface, and in some cases, impregnate the pores of the material. This process retards diffusion of the molecules of interest to the sensor surface and either slows the sensor's response to changes in concentration or reduces the overall response to the point where the sensor falls out of calibration. --·• •• Figure 3. Biomaterials Such as Polycarbonates, Cellulose, and Silicones Used in Membranes for Sensors, Dialyzers, and Oxygenators The design of sensor membrane materials has been found to be critically dependent on subtle features of the membrane's chemistry, material thickness, and porosity, as well as, more generally, where in the human body the sensor is located. The blood stream is 1 UNCLASSIFIED/ /EPA. QFFilllaS.IE Y81! OHL i
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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.