The most commonly used materials in the manufacture of urological devices are discussed with respect to their application to urinary catheters, penile implants, testicular implants, artificial urinary sphincters, and urological stents. The manufacturing, physical properties, and general chemical and biological behavior of these materials are reviewed. Attention is paid to future research trends and the general condition of the field of urological device materials.

A method to measure gel bleed from intact silicone gel-filled breast implants was developed. This nondestructive technique permits accurate and reproducible serial measurements of silicone bleed from smooth wall breast implants (n = 10) under simulated physiologic conditions in vitro. Gel bleed rates from new low bleed gel-filled implants and intact explants (unbarriered, low bleed, double lumen) were determined. These results demonstrate the reliability of this method to quantify silicone gel bleed and may permit a meaningful comparison of bleed rates from implants in the future.

Silicone (polydimethylsiloxane, PDMS) is generally a very stable polymer. Because of this, it is used in a wide variety of adverse environments such as those with high temperature or as electrical insulation. However, a great deal of this stability derives from the fact that hydrolysis reactions which occur are reversible and the polymer essentially heals itself. It is likely that such reversibility would not occur in the surface region where high concentrations of other components, such as water, can exist. Because of the significant concern about the fate of silicone released from breast implants in particular, it is important to understand the types of chemical changes which may occur in silicone upon exposure to physiological environments so that the data on various silicon-containing species can be correlated with other physiological studies on known compounds. Accordingly, this chapter will focus on the known silicone degradation reactions which occur within normal physiological ranges (37° and mixed aqueous environment). Various other studies will be drawn upon to evaluate the possible changes since the literature on silicone modification under physiological situations is sparse at this time. Three main reactions discussed are hydrolysis, oxidation, and addition.

The aim of our research was to study if cholesterol feeding might affect the ischemic changes in the vessels surrounding infarction foci in Sephadex G-75-induced cerebral ischemia model (SG-75). One hundred-twenty-four rabbits were divided as follows: group I was given standard food for 5 weeks; group II: as group I and then injected with SG-75; group III: standard food plus 1% cholesterol for 5 weeks; and group IV: as group III and then injected with SG-75. Rabbits were sacrificed 3 h, 6 h and 2, 5 and 7 days after ischemia had occurred. Vessels surrounding infarction foci (SIF) were identified by using a 6% carbon perfusion. Samples were examined by light microscopy and transmission electron microscopy (TEM). The occurrence of hemorrhagic infarction (HI) showed a clear time/course increase in group II whereas a decrease after 2 days in group IV was observed. The rate of HI was 40% and 20% in group II and IV, respectively. SIF vessels showed red blood cells leakage in group II, whereas multiple platelet thrombi appeared in group IV. This phenomenon caused a more extensive ischemic damage, when compared to group II. By making use of a widely employed model of high cholesterol diet and of a more physiological model of cerebral ischemia devised by us, we have provided the evidence that the hypercholesterolemia-induced changes in the SIF vessels strongly affect the pattern and progression of cerebral ischemia.