Release of Low Molecular Weight Silicones and Platinum from Silicone Breast Implants

Abstract

We have conducted a series of studies addressing the chemical composition of silicone gels from breast implants as well as the diffusion of low molecular weight silicones (LM-silicones) and heavy metals from intact implants into various surrounding media, namely, lipid-rich medium (soy oil), aqueous tissue culture medium (modified Dulbecco's medium, DMEM), or an emulsion consisting of DMEM plus 10% soy oil. LM-silicones in both implants and surrounding media were detected and quantitated using gas chromatography (GC) coupled with atomic emission (GC-AED) as well as mass spectrometric (GC/MS) detectors, which can detect silicones in the nanogram range. Platinum, a catalyst used in the preparation of silicone gels, was detected and quantitated using inductive argon-coupled plasma/mass spectrometry (ICP-MS), which can detect platinum in the parts per trillion range. Our results indicate that GC-detectable low molecular weight silicones contribute approximately 1-2% to the total gel mass and consist predominantly of cyclic and linear poly-(dimethylsiloxanes) ranging from 3 to 20 siloxane [(CH3)2-Si-O] units (molecular weight 200-1500). Platinum can be detected in implant gels at levels of approximately 700 micrograms/kg by ICP-MS. The major component of implant gels appears to be high molecular weight silicone polymers (HM-silicones) too large to be detected by GC. However, these HM-silicones can be converted almost quantitatively (80% by mass) to LM-silicones by heating implant gels at 150-180 degrees C for several hours. We also studied the rates at which LM-silicones and platinum leak through the intact implant outer shell into the surrounding media under a variety of conditions. Leakage of silicones was greatest when the surrounding medium was lipid-rich, and up to 10 mg/day LM-silicones was observed to diffuse into a lipid-rich medium per 250 g of implant at 37 degrees C. This rate of leakage was maintained over a 7-day experimental period. Similarly, platinum was also observed to leak through intact implants into lipid-containing media at rates of approximately 20-25 micrograms/day/250 g of implant at 37 degrees C. The rates at which both LM-silicones and platinum have been observed to leak from intact implants could lead to significant accumulation within lipid-rich tissues and should be investigated more fully in vivo.

Bioavailability of Octamethylcyclotetrasiloxane (D 4 ) after Exposure to Silicones by Inhalation and Implantation

“…PDMS is commonly used in orthopedic and breast implants (5). Although breast implants are composed mostly of stable high molecular weight siloxanes (HMWS), low molecular weight siloxanes (LMWS) still exist in the polymer as impurities (5)(6)(7)(8)(9). LMWS consist of both cyclic and linear molecules with repeating units of dimethylsiloxane, of which D 4 is a major component (47%) (7)(8)(9).…”

“…Although breast implants are composed mostly of stable high molecular weight siloxanes (HMWS), low molecular weight siloxanes (LMWS) still exist in the polymer as impurities (5)(6)(7)(8)(9). LMWS consist of both cyclic and linear molecules with repeating units of dimethylsiloxane, of which D 4 is a major component (47%) (7)(8)(9). Residual LMWS ranged from 0.2 to 2% by weight for the silicone gel and 0.01% to 0.1% for the silicone envelope (1.04-10.4 mg) (5)(6)(7)(8)(9).…”

“…LMWS consist of both cyclic and linear molecules with repeating units of dimethylsiloxane, of which D 4 is a major component (47%) (7)(8)(9). Residual LMWS ranged from 0.2 to 2% by weight for the silicone gel and 0.01% to 0.1% for the silicone envelope (1.04-10.4 mg) (5)(6)(7)(8)(9). Numerous studies have documented the migration of significant amounts of LMWS out of breast implants into surrounding breast tissues and to the liver (8)(9)(10)(11).…”

“…Residual LMWS ranged from 0.2 to 2% by weight for the silicone gel and 0.01% to 0.1% for the silicone envelope (1.04-10.4 mg) (5)(6)(7)(8)(9). Numerous studies have documented the migration of significant amounts of LMWS out of breast implants into surrounding breast tissues and to the liver (8)(9)(10)(11). This would add to the dermal or inhalation exposures from personal care products in a typical woman.…”

Thoracic Wall Siliconoma after Silicone Leaking from a Defective Breast Implant in Patient with Poland Syndrome

“…Within the rare complications that can appear in patients with this type of implant there is the formation of local and peripheral siliconomas, due to the diffusion of the silicone gel contained within the implant, that can appear in case of both damaged and intact implants [1,2].…”