West J K
Department of Materials Science and Engineering, University of Florida, Gainesville 32611, USA.
J Biomed Mater Res. 1997 Jun 15;35(4):505-11. doi: 10.1002/(sici)1097-4636(19970615)35:4<505::aid-jbm10>3.0.co;2-a.
Silicones (polydimethylsiloxane, PDMS) are the materials currently used in most breast implants. ICP and FTIR analysis of the tissue capsule around aged breast implants and in vitro models show that Si-containing material is leaking from the PDMS implants. In this study, the hydrolysis of PDMS has been theoretically modeled using a semiempirical quantum mechanical method called AM1. The activation barrier for removing a methanol monomer was found to be +82 Kcal/mol while the removal of a methane monomer was +41 Kcal/mol. Using the same AM1 method, hydrolysis of the identical to Si-O-Si identical to bond also has been modeled for pentasilicic acid and, in this study, for 1,1,3,3,-fetramethyldisiloxane-1,3-diol. The barrier to the removal of a silicon-containing tetrahedron for both studies was found to be +27 Kcal/mol. This is approximately one and a half times smaller than the energy of that needed to remove a methyl group. The pentacoordinated silicon-activated transition state for hydrolysis of PDMS may provide an energetically favorable pathway for development of a surface that will enhance chemisorption of charged protein molecules, and such a pathway may show up in NMR studies of the hydrolysis of PDMS.
硅酮（聚二甲基硅氧烷，PDMS）是目前大多数乳房植入物所使用的材料。对老化乳房植入物周围的组织包膜以及体外模型进行电感耦合等离子体质谱（ICP）和傅里叶变换红外光谱（FTIR）分析表明，含硅材料正从PDMS植入物中泄漏出来。在本研究中，已使用一种名为AM1的半经验量子力学方法对PDMS的水解进行了理论建模。发现去除一个甲醇单体的活化能垒为 +82千卡/摩尔，而去除一个甲烷单体的活化能垒为 +41千卡/摩尔。使用相同的AM1方法，还对五硅酸以及本研究中的1,1,3,3 - 四甲基二硅氧烷 - 1,3 - 二醇的与Si - O - Si相同的键的水解进行了建模。两项研究中去除含硅四面体的能垒均为 +27千卡/摩尔。这大约比去除一个甲基所需能量的一半还小。PDMS水解的五配位硅活化过渡态可能为形成一个能增强带电蛋白质分子化学吸附的表面提供一条能量上有利的途径，并且这样的途径可能会在PDMS水解的核磁共振（NMR）研究中显现出来。
