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Biosilicification occurs on a globally vast scale under mild conditions. Although research has progressed in the area of silica biosynthesis, the molecular mechanisms of these interactions are effectively unknown. The natural production of silica in the Tethya aurantia marine sponge, Cylindrotheca fusiformis diatom, and Equisetum telmateia plant appear to be similar. However, the studies were complicated mechanistic queries due to the use of silicic acid analogues. Given these complications, a carefully chosen model study was carried out to test the ability of enzymes to catalyse the formation of molecules with a single siloxane bond during the in vitro hydrolysis and condensation of alkoxysilanes. Our data suggest that homologous lipase and protease enzymes catalyse the formation of siloxane bonds under mild conditions. Non-specific interactions with trypsin promoted the in vitro hydrolysis of alkoxysilanes, while the active site was determined to selectively catalyse the condensation of silanols.

Methods for analyzing for silicon and silicone in biological matrixes were developed. A silicone-specific technique involved microwave digestion of samples in acid solution to rapidly break down the biological matrix while hydrolyzing silicones to monomeric species. The resulting monomeric silanol species were then capped with trimethylsilyl groups, extracted into hexamethyldisiloxane, and analyzed by gas chromatography. In serum, positive identification of silicone species with detection limits below 0.5 microgram of Si/mL are possible with this technique. The technique is compared with a silicone-specific technique, 29Si NMR, and a non-silicone-specific technique, ICP-AES. 29Si NMR was far less sensitive, with a detection limit of only 64 micrograms of Si/mL in serum when analyzing for one compound with a single sharp resonance. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) has potentially lower detection limits, but the technique is not silicone-specific and suffers from species-dependent responses.

What is silicone? Is it the same as silicon? The answer is no, but they are related. Silicones contain silicon as a primary atom in their structure. The recent public debate about the use of silicones in medical devices and recent scientific and medical literature highlights the confusion surrounding the meaning of these terms and how they are related. Published research describing the presence of silicone in terms of measured silicon in a variety of samples such as biopsies and urine can also be difficult to follow. A fundamental understanding of a few definitions can help clinicians and researchers in interpreting and clearly communicating technical information to patients and the public. The definitions and illustrations that follow can be used to achieve this objective. The review that follows is provided in the context of medical applications. More complete information concerning silicon, silicas and the chemistry of silicones are available (Iler R. K. The Chemistry of Silica: Solubility, Polymerization Colloid and Surface Properties, and Biochemistry. New York: Wiley; 1979 [1]; Eborn C. Organosilicon Compounds. London: Butterworth; 1960 [2]).

What is silicone? Is it the same as silicon? The answer is no, but they are related. Silicones contain silicon as a primary atom in their structure. The recent public debate about the use of silicones in medical devices and recent scientific and medical literature highlights the confusion surrounding the meaning of these terms and how they are related. Published research describing the presence of silicone in terms of measured silicon in a variety of samples such as biopsies and urine can also be difficult to follow. A fundamental understanding of a few definitions can help clinicians and researchers in interpreting and clearly communicating technical information to patients and the public. The definitions and illustrations that follow can be used to achieve this objective. The review that follows is provided in the context of medical applications. More complete information concerning silicon, silicas and the chemistry of silicones are available (Iler R. K. The Chemistry of Silica: Solubility, Polymerization Colloid and Surface Properties, and Biochemistry. New York: Wiley; 1979 [1]; Eborn C. Organosilicon Compounds. London: Butterworth; 1960 [2]).

A new device for rapid enzymatic debridement of cutaneous wounds has been developed using a controlled-release, silicone-based, dried emulsion. A dehydrated serine protease of the subtilisin family, previously untested for wound debridement, was incorporated into the emulsion. This device exhibited excellent storage stability. Moisture from the wound triggered an even, reproducible, and complete release of the enzyme within the first 8 hours. The device maintains a moist wound environment that allows the enzyme to achieve nearly complete digestion of the hardened eschar of full-thickness burns in a porcine model after an exposure period of 24 hours. Debridement was faster than in untreated wounds or wounds treated with a currently available enzyme ointment. Following rapid enzymatic debridement, healing appeared to progress normally, with no histological evidence of damage to adjacent healthy tissue.

Immobilized lipase B from Candida antarctica (Novozyme 435) catalyzed the regioselective formation of ester bonds between organosilicon carboxylic diacids and a C1-O-alkylated sugar under mild reaction conditions (i.e., low temperature, neutral pH, solventless). Specifically, the acid-functionalized organosilicones reacted with the primary hydroxyl group at the C6 position of alpha,beta-ethyl glucoside during the regioselective esterification. The pure organosilicon-sugar conjugates were prepared in a one-step reaction without protection-deprotection steps and without activation of the acid groups with the integrity of the siloxane bonds. [reaction: see text]

The paper by Lykissa and Maharaj (Lykissa, E. D.; Maharaj, S. V. M Anal. Chem. 2006, 78, 2925-2933) purports to provide evidence that the urine of women with silicone breast implants contain 60 to over 1700 times more platinum in their urine that the urine of people with no known exposure to platinum. Further, they purport to show evidence that the platinum used in the manufacture of breast implants (Pt0) is converted by a unknown process to yield highly oxidized platinum species, stable in biological matrixes, up to and including Pt6+. This correspondence poses three questions associated with the work and directs the reader's attention to the data, which clearly show that the blood and urine platinum levels in implanted women and their healthy control group were not significantly different from one another.

A novel and convenient method for the apparent liquid phase generation of dimethylsilanone, Me2SiO (D1), based on readily obtainable reactants and employing conventional temperatures (50–150°) is reported herein. Platinum catalyzed hydrosilylation of vinyldimethylcaarbinoxydimethylsilane (I) appears to proceed by an exclusively intramolecular path to produce not only the expected 5-membered heterocyclic, 1,1,3,3-tetramethyl-2-oxa-1 silacyclopentane (V), but also the isomeric and highly unstable 4-membered siloxetane, 1,1,3,3,4-pentamethyl-2-oxa-1-silacyclobutane (IV). The intermediacy of IV is suggested by the products: i.e., 2-methyl-2-butene which is believed to arise along with Me2SiO from fragmentation of IV; D3 and D4 from D1 self-coupling; a 6-membered cyclic derived from insertion of D1 into the Si-O bond of IV, i.e., 1,1,3,3,5,5,6-heptamethyl-2,4-dioxa-1,3-disilacyclohexane (VI); a polymer which upon alkaline cracking produces more 6-ring (VI) but little or no 5-ring (V) suggesting that the polymer arose from copolymerization of D1, D2, and siloxetane (IV). Compound I is also an excellent thermolytic source of D1 as evidenced by the formation of the expected derivatives upon heating in the presence of known silanone traps.