Medicinal Applications of Organic Silicon

Silicic acid esters of cholesterol have been isolated from feathers [606], and galactose silicates have been isolated from the blades of rye [607]. An adequate supply of silicon is essential for the growth of hair and nails in humans, hair, horn and hoofs in mammals, and feathers in birds. Chickens maintained on silicon-free feed have malformed feathers, and their bones remain fragile and thin. For normal growth, chickens require only 0.003 % silicon in their food [608]. 

The simultaneous presence of amino and alkoxy groups in an organosilyl compound sometimes results in extreme toxicity. The skin rapidly absorbs (4 aminobutyl)diethoxymethylsilane, which is a strong poison [613]. 

Methyl, ethyl, ethinyl, chloromethyl and (1-chloroethyl) silatranes are essentially non-toxic (LDjo greater than 2000 mg/kg). However, (3-iodopropyl)silatrane is toxic (LD50 = 29 mg/kg). Aryl and mercaptomethyl silatranes are very toxic (more so than strychnine or hydrocyanic acid). Table 4.2 gives the toxicity of several silatranes [614]. 

Strangely, silatranes are only toxic to warm-blooded animals. They do not poison bacteria, fungi or frogs. 

The convenient properties of liquid and solid dimethylpolysiloxanes (thermal and chemical stability, hydrophobicity, anti-adhesive behavior, etc.) make them suitable for a variety of technical applications in medicine. Especially pure preparations (Silastic ) have been used to construct artificial limbs, gullets, cardiac valves, trachea, etc., and in face-lifting. Silicon rubber breast implants, which are filled with a polysiloxane gel, have been used cosmetically. Synthetic arteries impregnated with silicon do not break or cause coagulation, they are flexible, and they are well tolerated immunologically. Silicones prevent the formation of foam in equipment for artificial blood circulation (heart-lung machines). The surfaces of such equipment, and of the 

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The Physiology, Toxicology and Medicinal Applications of Organic Silicon... 

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