RELEASE OF LOW-MOLECULAR-WEIGHT SILICONES AND PLATINUM FROM SILICONE BREAST IMPLANTS

We have conducted a series of studies addressing the chemical composit ion of silicone gels from breast implants as well as the diffusion of low molecular weight silicones (LM-silicones) and heavy metals from in tact implants into various surrounding media, namely, lipid-rich mediu m (soy oil), aqueous tissue culture medium (modified Dulbecco's medium , DMEM), or an emulsion consisting of DMEM plus 10% soy oil, LM-silico nes in both implants and surrounding media were detected and quantitat ed using gas chromatography (GC) coupled with atomic emission (GC-AED) as well as mass spectrometric (GC/MS) detectors, which can detect sil icones in the nanogram range, Platinum, a catalyst used in the prepara tion of silicone gels, was detected and quantitated using inductive ar gon-coupled plasma/mass spectrometry (TCP-MS), which can detect platin um in the parts per trillion range, Our results indicate that GC-detec table 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] unit s (molecular weight 200-1500). Platinum can be detected in implant gel s at levels of similar to 700 mu g/kg by ICP-MS, The major component o f implant gels appears to be high molecular weight silicone polymers ( HM-HM-silicones) too large to be detected by GC, However, these HM-sil icones can be converted almost quantitatively (80% by mass) to LM-sili cones by heating implant gels at 150-180 degrees C for several hours, We also studied the rates at which LM-silicones and platinum leak thro ugh the intact implant outer shell into the surrounding media under a variety of conditions, Leakage of silicones was greatest when the surr ounding medium was lipid-rich, and up to 10 mg/day LM-silicones was ob served 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 experiment al period, Similarly, platinum was also observed to leak through intac t implants into lipid-containing media at rates of approximately 20-25 mu g/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 implant s could lead to significant accumulation within lipid-rich tissues and should be investigated more fully in vivo.