Methods for detecting silicones in biological matrixes

Considerations on the Analysis of E-900 Food Additive: An NMR Perspective

Food additives are in widespread use in the food industry to extend the shelf life of food, improve its organoleptic characteristics or facilitate industrial processing. Their use is not without controversy, which makes regulation and control crucial for food safety and public health. Among food additives, silicone-based antifoaming agents (polysiloxanes or E900) are difficult to analyze and quantify due to their polymeric nature. Currently, there is no official method of quantifying this additive in foods. In this context, nuclear magnetic resonance (NMR) is a quantitative method for speciation analysis of silicon compounds almost without known interferents. In this work, we describe the evolution of the regulation of the E900 additive, discuss different analytic methods quantifying polydimethylsiloxanes (PDMS), and propose a new method based on NMR suitable for analyzing the content of E900 in the form of PDMS in various types of food from dietary oils to marmalades and jellies, among others. The proposed method consists of a previous quantitative concentration of PDMS by liquid–liquid extraction and the monitoring of the quantification using a bis(trimethylsilyl)benzene (BTMSB) standard to control the variability, ranging within 2–7%, depending on the food. This simple, direct, and reproducible procedure for aqueous and lipidic foods may help to monitor and fill a gap in regulatory legislation regarding the E900 additive.

Analysis of Silicone Oil in Prefilled Syringes and Biopharmaceutical Drug Products Using High-Performance Liquid Chromatography

As the packaging of choice for many therapeutic proteins, prefilled syringes have been widely used in biopharmaceutical industry as primary containers, where silicone oil is applied to ensure their proper functionality. Adequate lubrication from sufficient amount of silicone oil and its appropriate distribution across syringe barrels is crucial for successful administration of drug product (DP) from the prefilled syringes; however, silicone oil is also susceptible to leaching from the syringe surface into the formulation with the potential to interact with therapeutic proteins, which could lead to the formation of visible and sub-visible aggregates and/or particles that are potentially immunogenic. Accurate determination and careful control of silicone oil levels in both empty syringes and protein drug products are therefore critical in process development to ensure syringe functionality, drug product quality, and patient safety. On the other hand, analysis of silicone oil can be challenging especially when the analysis is performed on formulated protein drug products, where matrix effects could be significant. It is demonstrated in this study that silicone oil in empty syringes or formulated drug products can be extracted effectively using organic solvents and quantitatively determined using high-performance liquid chromatography (HPLC) coupled with a universal detector. It was also shown that direct extraction of silicone oil from formulated protein drug products can be very challenging, but pretreatment of the protein drug products with pepsin enzymatic digestion facilitated the extraction process, which enabled the analysis of silicone oil in the drug product at low ppm levels.

Quantification of Silicone Oil and Its Degradation Products in Aqueous Pharmaceutical Formulations by 1H-NMR Spectroscopy

During the past years, there has been an increasing focus on the presence of silicone oil as a contaminant in pharmaceutical formulations kept in prefilled syringes (PFSs). As the PFSs are coated on the inner wall with silicone oil (polydimethylsiloxane), there is a potential risk that the oil can migrate from the inner surface of the primary packing material into the aqueous solution. Several studies have demonstrated that presence of silicone oil as droplets in a high-concentrated protein formulation can cause protein aggregation. Hence, because the use of silicone-coated primary packing material for protein formulations are increasing, the call for an easy and quantitative method for determination of silicone oil and its degradation products in pharmaceutical formulations is therefore needed. Several analytical techniques have in the past been developed with the aim of detecting the presence of silicone oil and degradation products hereof. Most of these methods require hydrolyzation, derivatization, and extraction steps followed by, for example, gas chromatography-mass spectrometry analysis. Applying these methods can cause a loss in detection or an overestimation of the hydrolytic degradation products of silicone oil, that is, trimethylsilanol and dimethylsilanediol. The 2 silanols are highly hydrophilic and prefers the aqueous environment. Analysis of an aqueous formulation obtained from a PFS by ¹H-NMR spectroscopy provides data about the content and levels of silicone oil and the 2 silanols even in levels below 10 ppm. The ¹H-NMR method offers an easy and direct, quantitative measurement of samples intended for clinical use and samples kept at elevated temperature for a prolonged time (i.e., stability studies). The result of the study presented here showed dimethylsilanediol to be the main silicone compound present in the aqueous formulation when kept in baked-on PFSs. The degradation product dimethylsilanediol, in full accordance with expected hydrolytic degradation of silicone oil, increased during storage and with elevated temperature. In addition, the method can be applied to aqueous samples where polydimethylsiloxane has been added as, for example, the major constituent of antifoam.

Forensic Analysis of Human Autopsy Tissue for the Presence of Polydimethylsiloxane (Silicone) and Volatile Cyclic Siloxanes using Macro FT-IR, FT-IR Spectroscopic Imaging and Headspace GC-MS

This study describes effective and straightforward primary and secondary methods for the detection of silicone in human autopsy tissue. The primary method is polydimethylsiloxane (PDMS) specific and employs either macro-attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy for samples with a high PDMS concentration (relative to that of the matrix) or micro-FT-IR spectroscopic imaging in a reflection/absorption modality for samples with a low PDMS concentration. Although the secondary method is not PDMS specific, it employs headspace gas chromatography with mass spectrometric detection (HS/GC-MS) for the detection of low molecular weight volatile cyclic siloxanes (VCS), which are characteristic marker compounds for PDMS. Overall, the combined results from the primary and secondary analyses provide reliable evidence for the presence of silicone.

Volatile organic silicon compounds in biogases: development of sampling and analytical methods for total silicon quantification by ICP-OES

Current waste management policies favor biogases (digester gases (DGs) and landfill gases (LFGs)) valorization as it becomes a way for energy politics. However, volatile organic silicon compounds (VOSiCs) contained into DGs/LFGs severely damage combustion engines and endanger the conversion into electricity by power plants, resulting in a high purification level requirement. Assessing treatment efficiency is still difficult. No consensus has been reached to provide a standardized sampling and quantification of VOSiCs into gases because of their diversity, their physicochemical properties, and the omnipresence of silicon in analytical chains. Usually, samplings are done by adsorption or absorption and quantification made by gas chromatography-mass spectrometry (GC-MS) or inductively coupled plasma-optical emission spectrometry (ICP-OES). In this objective, this paper presents and discusses the optimization of a patented method consisting in VOSiCs sampling by absorption of 100% ethanol and quantification of total Si by ICP-OES.

Distribution of silicon/e in tissues of mice of different fibrinogen genotypes following intraperitoneal administration of emulsified poly(dimethylsiloxane) [correction of poly(dimethysiloxane)]

Following injection into the abdominal cavity of a C57BL/6 mouse, droplets of emulsified PDMS visible by light microscopy (diameter > or = 1 microm) disseminate to multiple organs of the animal. Because fibrinogen may facilitate dissemination, we compared histologically the accumulation of PDMS droplets in lymph nodes, lungs, spleen, liver, and left kidney of Fib +/+, Fib +/-, and Fib -/- mice of C57BL/6 background 35 and 75 days after intraperitoneal injection of an emulsion of the polymer. We also used ICP-AES to assess the accumulation of silicon in the lymph nodes, livers, and spleens of the animals. The emulsion droplets ranged in diameter from approximately 0.04 to approximately 80 microm. PDMS droplets visible by light microscopy were in all organs of both Fib +/+ mice and Fib +/- mice. In those animals, droplets were invariably either within or adjacent to inflammatory cells, predominantly macrophages. In contrast, PDMS droplets were visible in none of the organs of Fib -/- mice. Despite the absence of visible droplets in them, the lymph nodes, livers, and spleens of Fib -/- mice, like the corresponding organs of Fib +/+ and Fib +/- mice, contained measurable silicon after 35 and 75 days. The amount of silicon, however, was always greater in the organs of Fib +/+ and Fib +/- mice than in the organs of Fib -/- mice. We attribute the presence of silicon in organs that had no histologic evidence of droplets to diffusion of the very smallest droplets/soluble species of PDMS from the abdominal cavity. Taken together, our data and observations implicate a role for fibrinogen in the dissemination of larger PDMS droplets in vivo. We propose this role involves recognition of droplet-bound fibrinogen by macrophages and, perhaps, other inflammatory cells, and the subsequent fibrinogen-facilitated ingestion and/or extracellular movement of the droplets by those cells.

Determination of low molecular weight silicones in plasma and blood of women after exposure to silicone breast implants by GC/MS

A sensitive, one-step sample preparation method for detection of volatile, low molecular weight (LMW) cyclic silicones hexamethylcyclotrisiloxane (D3), octamethyl-cyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in plasma and blood using gas chromatography coupled with mass spectrometry (GC/MS, SIM mode) is presented. In spiked experiments, extraction efficiencies for these siloxanes (100-20 000 ng/mL) were approximately 90% for plasma and approximately 80% for blood; only in the case of D3 was the recovery very low. Plasma and blood of women who are or were exposed to silicone gel-filled implants and of control subjects were analyzed for low molecular weight silicones. D3-D6 were not detectable in control plasma or blood. Although the investigated numbers of patients samples are very limited, and thus, no statistical analysis is possible, our data clearly show a general increase in the amount of LMW cyclic siloxanes in the bodies of women with silicone implants. In particular, several years after ruptured silicone implants were removed, siloxanes could still be found in blood samples from several women. Siloxane compound D3 varied between 6 and 12 ng/mL (plasma) and between 20 and 28 ng/mL (blood), whereas the concentration range of D4 was 14-50 ng/mL (plasma) and 79-92 ng/mL (blood). D5 and D6, with one exception, could not be detected.