IgG1 Aggregation and Particle Formation Induced by Silicone–water Interfaces on Siliconized Borosilicate Glass Beads: A Model for Siliconized Primary Containers

Understanding and mitigating particle formation in prefilled syringes are critical for ensuring stability of therapeutic proteins. In the current study, siliconized beads were used as a model for the silicone–water interface to evaluate subvisible particle formation and aggregation of a monoclonal antibody (IgG1). Agitation with siliconized beads greatly accelerated the formation of protein aggregates and particles, an effect that was enhanced at pH 7.4 relative to pH 5 and in the presence of 0.5 M sucrose or 150 mM NaCl. Aggregation and particle formation were minimal in samples agitated without siliconized beads or in quiescent samples with siliconized beads. At pH 5, 0.01% (w/v) polysorbate 20 substantially inhibited aggregation during agitation with siliconized beads, but had minimal protective effect at pH 7.4. Transient exposure of IgG₁ formulations to the silicone–water interface by flowing formulations through a column packed with siliconized beads led to the formation of subvisible particles, with increased levels observed at pH 7.4 compared to pH 5. Agitation of protein formulations in the presence of siliconized glass beads provides a model for baked-on silicone oil–water interface in prefilled syringes and a means by which to evaluate particle formation and aggregation during formulation screening. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:852–865, 2013     

Protein Aggregation and Particle Formation in Prefilled Glass Syringes

The stability of therapeutic proteins formulated in prefilled syringes (PFS) may be negatively impacted by the exposure of protein molecules to silicone oil–water interfaces and air–water interfaces. In addition, agitation, such as that experienced during transportation, may increase the detrimental effects (i.e., protein aggregation and particle formation) of protein interactions with interfaces. In this study, surfactant-free formulations containing either a monoclonal antibody or lysozyme were incubated in PFS, where they were exposed to silicone oil–water interfaces (siliconized syringe walls), air–water interfaces (air bubbles), and agitation stress (occurring during end-over-end rotation). Using flow microscopy, particles (≥2 μm diameter) were detected under all conditions. The highest particle concentrations were found in agitated, siliconized syringes containing an air bubble. The particles formed in this condition consisted of silicone oil droplets and aggregated protein, as well as agglomerates of protein aggregates and silicone oil. We propose an interfacial mechanism of particle generation in PFS in which capillary forces at the three-phase (silicone oil–water–air) contact line remove silicone oil and gelled protein aggregates from the interface and transport them into the bulk. This mechanism explains the synergistic effects of silicone oil–water interfaces, air–water interfaces, and agitation in the generation of particles in protein formulations. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1601–1612, 2014     

Albinterferon α2b Adsorption to Silicone Oil–Water Interfaces: Effects on Protein Conformation,Aggregation, and Subvisible Particle Formation

Silicone oil used as a lubricant in prefilled syringes has the potential to induce formation of particles in protein formulations. In the current study, we used a therapeutic fusion protein, albinterferon α_2b, to evaluate protein aggregation and particle formation in the presence of silicone oil microdroplets or immobilized silicone interfaces. Tertiary structure of albinterferon α_2b adsorbed on silicone oil microdroplets was perturbed in a formulation containing only buffer. In contrast, native-like tertiary structure was retained for albinterferon α_2b adsorbed on silicone oil microdroplets in 300 mM sodium chloride or 300 mM sucrose formulations. Agitation of albinterferon α_2b samples in the presence of silicone oil droplets or siliconized beads, respectively, caused albinterferon α_2b aggregation and subvisible particle formation in formulations containing buffer or 300 mM sucrose. Adsorption of albinterferon α_2b onto silicone oil was inhibited by addition of 0.01% (w/v) polysorbate 80, and this excipient prevented aggregation during agitation in the presence of silicone oil microdroplets. Aggregation was also reduced in the presence of 300 mM sodium chloride during agitation at least in part because of the increased conformational stability of the protein.     

Cross-Linked Silicone Coating: A Novel Prefilled Syringe Technology That Reduces Subvisible Particles and Maintains Compatibility with Biologics

Prefilled syringes (PFSs) offer improvements in the delivery of drugs to patients compared with traditional vial presentations and are becoming necessities in an increasingly competitive biologics market. However, the development of a product in a PFS must take into account potential incompatibilities between the drug and the components of the syringe. One such component is silicone oil, which has previously been suggested to promote protein aggregation, loss of soluble protein, and an increase in the particulate content of injectable formulations. This study evaluated the particulate content in a model buffer system (polysorbate 80/phosphate-buffered saline) after agitation in glass syringes with a novel cross-linked silicone coating. We also evaluated the compatibility of two monoclonal antibodies with these syringes. We report that syringes with this novel coating, compared with standard siliconized syringes, exhibited reduced particle content and enhanced integrity of the lubricant layer as determined by reflectometry, optical microscopy, and time-of-flight secondary ion mass spectrometry measurements, while maintaining the desired functional properties of the syringe and the antibodies’ stability profiles as determined by high-performance size-exclusion chromatography. Enhanced integrity of the lubricant coating led to significantly fewer subvisible particles in the liquid formulations, particularly after agitation stresses introduced by shipping of the syringes. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.     

The Impact of Syringe Age Prior to Filling on Migration of Subvisible Silicone-Oil Particles into Drug Product

Silicone oil is often applied to the inner surface of glass syringes and cartridges to reduce friction between the glass surface and elastomeric plunger stopper. This oil can appear as intrinsic and non-proteinaceous particles in the ejected fluid or drug product. Limited data is available to understand the impact of age (time between syringe manufacture and filling) on silicone oil migration into the drug product. This study compares subvisible particle count and extrusion force of siliconized syringes from two different manufacturers stored at ambient condition for 2-3 (fresh syringes) and 13-14 (aged syringes) months then filled and placed at 40°C for an additional three months. The fresh syringes exhibit a 2.5-fold increase in subvisible particle count compared to those aged ones. Moreover, the fresh syringes exhibit up to a 2-fold increase in extrusion force. These findings suggest the degree and amount of silicone oil migration is influenced by the time in storage of the glass syringe prior to filling. This rapid communication highlights syringe storage time prior to filling as a factor to be considered during development.     

Protein adsorption and excipient effects on kinetic stability of silicone oil emulsions

The effect of silicone oil on the stability of therapeutic protein formulations is of concern in the biopharmaceutical industry as more proteins are stored and delivered in prefilled syringes. Prefilled syringes provide convenience for medical professionals and patients, but prolonged exposure of proteins to silicone oil within prefilled syringes may be problematic. In this study, we characterize systems of silicone oil‐in‐aqueous buffer emulsions and model proteins in formulations containing surfactant, sodium chloride, or sucrose. For each of the formulations studied, silicone oil‐induced loss of soluble protein, likely through protein adsorption onto the silicone oil droplet surface. Excipient addition affected both protein adsorption and emulsion stability. Addition of surfactant stabilized emulsions but decreased protein adsorption to silicone oil microdroplets. In contrast, addition of sodium chloride increased protein adsorption and decreased emulsion stability. Silicone oil droplets with adsorbed lysozyme rapidly agglomerated and creamed out of suspension. This decrease in the kinetic stability of the emulsion is ascribed to surface charge neutralization and a bridging flocculation phenomenon and illustrates the need to investigate not only the effects of silicone oil on protein stability, but also the effects of protein formulation variables on emulsion stability. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1721–1733, 2010     

Silicone-Oil-Based Subvisible Particles: Their Detection,Interactions, and Regulation in Prefilled Container Closure Systems for Biopharmaceuticals

Recent increased regulatory scrutiny concerning subvisible particulates (SbVPs) in parenteral formulations of biologics has led to the publication of numerous articles about the sources, characteristics, implications, and approaches to monitoring and detecting SbVPs. Despite varying opinions on the level of associated risks and method of regulation, nearly all industry scientists and regulators agree on the need for monitoring and reporting visible and subvisible particles. As prefillable drug delivery systems have become a prominent packaging option, silicone oil, a common primary packaging lubricant, may play a role in the appearance of particles. The goal of this article is to complement the current SbVP knowledge base with new insights into the evolution of silicone‐oil‐related particulates and their interactions with components in prefillable systems. We propose a “toolbox” for improved silicone‐oil‐related particulate detection and enumeration, and discuss the benefits and limitations of approaches for lowering and controlling silicone oil release in parenterals. Finally, we present surface cross‐linking of silicone as the recommended solution for achieving significant SbVP reduction without negatively affecting functional performance. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:4569–4583, 2012     

Sweeping of Adsorbed Therapeutic Protein on Prefillable Syringes Promotes Micron Aggregate Generation

This study evaluated how differences in the surface properties of prefillable syringe barrels and in-solution sampling methods affect micron aggregates and protein adsorption levels. Three syringe types (glass barrel with silicone oil coating [GLS/SO+], glass barrel without silicone oil coating [GLS/SO?], and cyclo-olefin polymer [COP] barrel syringes) were tested with 3 therapeutic proteins (adalimumab, etanercept, and infliximab) using 2 sampling methods (aspiration or ejection). After quiescent incubation, solutions sampled by aspiration exhibited no significant change in micron aggregate concentration in any syringes, whereas those sampled by ejection exhibited increased micron aggregates in both GLS syringe types. Micron aggregate concentration in ejected solutions generally increased with increasing density of adsorbed proteins. Notably, COP syringes contained the lowest micron aggregate concentrations, which were independent of the sampling method. Correspondingly, the adsorbed protein density on COP syringes was the lowest at 1-2 mg/m², which was much less compared with that on GLS syringes and was calculated to be equivalent to only 1–2 protein layers, as visually confirmed by high-speed atomic force microscopy. These data indicate that low-adsorption prefillable syringes should be used for therapeutic proteins because protein aggregate concentration in the ejected solution is elevated by increased protein adsorption to the syringe surface.     

Impact of Formulation and Processing Parameters on Silicone Extraction from Cyclic Olefin Copolymer (COC) Syringes

The effect of various formulation and process parameters on the extraction of silicone from siliconized cyclic olefin copolymer (COC) syringes is reported. The impact of proprietary silicone curing process on COC syringe barrels was evaluated with respect to the rate and extent of silicone extraction. Similarly, the impact of formulation parameters such as pH, ionic species, and cosolvents on silicone extraction was also evaluated. The rate and extent of silicone extraction into contact solutions was inversely related to the degree of completion of the silicone curing process. The rate and extent of silicone extraction in solution were highest upon exposure to extreme pH solutions. The silicone extraction data indicate that the silicone curing process and formulation parameters have a profound effect on the rate and extent of silicone extraction into solutions. LAY ABSTRACT: Silicone oils are used in medical syringes to provide lubrication. Prefilled medical syringes contain solutions into which silicone oil components may migrate. This study examined the degree to which silicone components migrated into different solution matrices. The impact of different levels of proprietary silicone curing processes on the migration of silicone components in contact solutions was also examined. This study also examined the impact of various formulation parameters (pHionic strength and cosolvents) on the degree to which silicone components migrated into solutions. Solution pH had the greatest effect on silicone migration with higher levels of silicone measured in solutions at the pH extremes. Curing of the silicone (reaction of the silicone with the syringe materials) also had significant impact. High curing levels resulted in less silicone migrating into solution as compared to levels seen with syringes with low curing levels. Thus it was demonstrated that both the nature of the solution stored in the syringe and the degree of silicone curing on the syringe barrel had substantial impact on the amount of silicone that migrated from the syringe components into the solution contained within the syringe.     

Impact of Ethylene Oxide Sterilization of Polymer-Based Prefilled Syringes on Chemical Degradation of a Model Therapeutic Protein During Storage

Materials from prefilled syringe systems—such as silicone oil, tungsten, glass, and rubber—may enhance therapeutic protein aggregation and particle formation. Also, the sterilization method used for syringes may impact aggregation and chemical degradation of biologics during storage. Syringes are generally sterilized by radiation, ethylene oxide gas (EO), or steam. Among the sterilization methods, EO has the potential to cause chemical degradation by the formation of adducts with susceptible amino acid residues in the protein. In this study, EO- and steam-sterilized syringes were compared to determine the influence of residual EO on human serum albumin (HSA) degradation. Although the amount of residual EO in the EO-sterilized syringes was less than 220 μg/syringe, well below the International Organization for Standardization limit, EO adduction to cysteine (Cys) and methionine (Met) in HSA was observed by liquid chromatography and mass spectrometry analysis. The EO adduct ratio of HSA stored for 2 weeks in EO-sterilized syringes was about 45%. In contrast, no chemical degradation was observed in HSA formulation stored in steam-sterilized syringes. Because of the propensity of EO to readily form adducts with proteins, an alternative to EO sterilization should be used for prefilled syringes that will be used for therapeutic protein products.     

An Assessment of the Ability of Submicron- and Micron-Size Silicone Oil Droplets in Dropped Prefillable Syringes to Invoke Early- and Late-Stage Immune Responses

A number of biopharmaceuticals are available as lyophilized formulations along with a prefilled syringe (PFS) containing water for injection (WFI). Submicron- and micron-size droplets of lubricating silicone oil (SO) applied to the inner surface of the PFS barrel might migrate into the WFI, to which protein pharmaceuticals can adsorb, potentially inducing an immune response. In the present study, we subjected siliconized cyclo-olefin polymer PFSs filled with WFI to dropping stress to simulate actual shipping conditions as well as evaluated the risk associated with the released SO droplets. The results confirmed the undesirable effects of SO on therapeutic proteins, including adsorption to SO droplets and increased secretion of several innate cytokines from human peripheral blood mononuclear cells of a small donor panel. Assessment of immunogenicity in vivo using BALB/c mice revealed a slight increase in the plasma concentrations of antidrug antibodies over 21 days in response to SO-containing antibody samples compared to the absence of SO. These results indicate that SO droplets form complexes with pharmaceutical proteins that can potentially invoke early- and late-stage immune responses. Therefore, the use of SO-free cyclo-olefin polymer PFSs as primary containers for WFI could contribute to the enhanced safety of reconstituted biopharmaceuticals.     

Effect of Various Silicone Oil And Tungsten Levels on the Stability of a Monoclonal Antibody in Nine Commercially Available Prefilled Syringes

Prefilled syringes are widely used as a primary container for therapeutic proteins because they are more convenient than glass vials. The stability of biologic molecules can be affected by different syringe materials and techniques, such as silicone oil levels and coating method, amount of tungsten remaining in the glass barrel after using a tungsten pin to create the needle hole, and end of the syringe, which can be Luer locked or pre-staked with a needle. We investigated the impact of these parameters by using a monoclonal antibody to collect the antibody's stability profile and the prefilled syringes’ functionality data. Silicone oil levels had no impact on aggregation levels, and particle counts were lowest for silicone oil–free syringes. Functionality performance was similar and did not change throughout all stability time points for all syringe configurations. The break-loose force for Ompi syringes was initially lower and increased over time to align with those of the other configurations, all of which remained well below 25 N. Tungsten contaminants and agitation stress from shipping studies did not impact quality attributes. This work can help guide the development of similar products in prefilled syringes to ensure selection of the primary container that provides adequate stability for the protein, as well as maintain the desired functionality features over the shelf life of the drug product.     

Fatty Acids Can Induce the Formation of Proteinaceous Particles in Monoclonal Antibody Formulations

The presence of subvisible or visible particles in mAb formulations can pose significant challenges to pharmaceutical development as it can lead to reduced shelf life, batch rejection, and recalls. Among all type of particles, proteinaceous particles are the most concerning due to their potential role in immunogenicity. Nevertheless, the underlying mechanism for protein particle formation remains poorly understood. Past research highlighted the importance of interfaces and mechanical agitation in causing protein particle formation. Current research suggests that fatty acids, as impurities present in excipients or as a result of polysorbate degradation, can also induce protein assembly and promote particle formation. In this work, we assessed oleic and lauric acid for their impact on particle formation as each represents the main hydrolysis product of PS80 or PS20, respectively. It was found that co-existence of either fatty acids with 10 mg/mL mAb A can cause protein particles, with a similar morphology to those observed previously in mAb formulations. FTIR spectra showed that the particles are proteinaceous, heterogeneous in its composition, but contain corresponding fatty acids. Interestingly, it was found that oleic acid is significantly more effective in causing protein particles than lauric acid in these experiments. This suggests that PS20 containing formulations might have a lower likelihood to have protein particles compared to PS80 containing mAb formulations if hydrolysis of polysorbate were to occur. Lastly, the presence of 0.01% polysorbate in the mAb A formulation was able to fully mitigate the effect of fatty acids and reduce the protein particles significantly, suggesting a potential mechanism where interfacial action is involved. The present study can help to understand the root cause for protein particles in a mAb formulation where fatty acids are introduced because of polysorbate hydrolysis. With further work, it will help to shed light into product control strategy as well as design approaches for robust mAb products.     

Differentiation of Subvisible Silicone Oil Droplets from Irregular Standard Dust Particles

New methods are being applied to distinguish silicone oil droplets from subvisible particles in therapeutic protein formulations. The need to standardize these methods and compare them to established methods is critical to increase the understanding of the risks from protein aggregation and other subvisible particulate matter. We present the use of medium test dust (MTD) as a stable subvisible particle standard that can be distinguished from silicone oil by flow imaging methodology and the combination of light obscuration and microscopic methods. We further present the use of binary classification techniques to characterize the ability of flow imaging to distinguish between particle types (i.e., silicone vs. protein, silicone vs. standard, etc.) as a function of particle size. For the differentiation of silicone oil and MTD, the aspect ratio attribute was as good as or better than any other characteristic or combination of two characteristics applied to distinguish this particle population. However, the value of the discrimination by flow imaging was limited to particles larger than 5 μm. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1696-1700, 2013     

Direct visualization of protein adsorption to primary containers by gold nanoparticles

Adsorption of proteins to primary containers can result in protein loss, protein denaturation, or aggregation. We report a simple and effective method to directly detect and visualize adsorption of proteins to container surfaces by staining adsorbed proteins with gold nanoparticles, which bind proteins nonspecifically. The gold nanoparticle staining method was applied to study adsorption to siliconized glass prefilled syringes (PFSs) of a therapeutic protein in a liquid formulation. The protein was found to preferentially adsorb to glass surfaces over siliconized surfaces in PFSs. The presence of adsorbed proteins on glass surfaces was confirmed by in situ Raman spectroscopy. Gold nanoparticle staining patterns revealed that adsorption of proteins to hydrophobic cyclic olefin polymer plastic vials was minimized compared with hydrophilic type I glass vials. Bovine serum albumin (BSA) also preferentially adsorbed to glass surfaces compared with siliconized surfaces as revealed by the gold staining patterns in PFS incubated with BSA, supporting the use of albumin to minimize loss of proteins in glass containers. The method is particularly valuable for high-concentration protein formulations in which adsorption of proteins to containers cannot be easily detected by other methods.     

Effects of Product Handling Parameters on Particle Levels in a Commercial Factor VIII Product: Impacts and Mitigation

To reduce the risk of immunogenicity that may be caused by therapeutic protein products, it is important to properly characterize subvisible particles and to develop strategies to reduce the levels of particles delivered to patients. In the present study, by using state-of-the-art methods to quantify particle levels, we found that the factor VIII product, Kogenate FS, contained relatively high levels of protein particles and silicone oil droplets, the vast majority of which were submicron in size. In a test of effects of product mishandling, the Kogenate FS vial was shaken instead of swirled during reconstitution. Levels of silicone oil droplets and protein particles were increased. In contrast, these levels were greatly reduced by 2 mitigation strategies tested, using a nonsiliconized syringe for the diluent container or using submicron pore size syringe filters during simulated infusion. Thus, to avoid potential adverse effects due to mishandling-induced increases in particle levels, it is important to educate end-users about proper product handling. Furthermore, effective particle mitigation and reduction strategies should be developed for factor VIII, and other therapeutic protein products. Such efforts could lead to clinically useful approaches to reduce the levels of particles delivered to patients and to an associated reduction in adverse immunogenicity.     

Micro–Flow Imaging and Resonant Mass Measurement (Archimedes) – Complementary Methods to Quantitatively Differentiate Protein Particles and Silicone Oil Droplets

Our study aimed to comparatively evaluate Micro–Flow Imaging (MFI) and the recently introduced technique of resonant mass measurement (Archimedes, RMM) as orthogonal methods for the quantitative differentiation of silicone oil droplets and protein particles. This distinction in the submicron and micron size range is highly relevant for the development of biopharmaceuticals, in particular for products in prefilled syringes. Samples of artificially generated silicone oil droplets and protein particles were quantified individually and in defined mixtures to assess the performance of the two techniques. The built-in MFI software solution proved to be suitable to discriminate between droplets and particles for sizes above 2 μm at moderate droplet/particle ratios (70:30–30:70). A customized filter developed specifically for this study greatly improved the results and enabled reliable discrimination also for more extreme mixing ratios (95:5–15:85). RMM showed highly accurate discrimination in the size range of about 0.5–2 μm independent of the ratio, provided that a sufficient number of particles (>50 counted particles) were counted. We recommend applying both techniques for a comprehensive analysis of biotherapeutics potentially containing silicone oil droplets and protein particles in the submicron and micron size range. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2152–2165, 2013     

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.     

折光率对微流成像法检测蛋白制剂不溶性微粒的影响

目的：蛋白制剂中不溶性微粒的含量是衡量样品质量的重要指标之一,为了更为准确地检测不溶性微粒的含量和粒径,本研究探讨了溶液折光率对于微流成像系统检测不溶性微粒的影响。方法：本研究以牛血清白蛋白（BSA）为例,通过常见的外界刺激条件（冷冻-解冻）制备高浓度的蛋白质不溶性微粒,并将此微粒稀释至不同折光率的溶液（由PEG1000、海藻糖制备）中,利用微流成像系统检测不溶性微粒的含量。结果：当溶液的折光率接近蛋白质不溶性微粒折光率时,利用微流成像技术检测的不溶性微粒含量低于实际的微粒含量。此外,随着溶液折光率的增加,采用微流成像技术检测出的不溶性微粒的粒径也随之减小。结论：蛋白质溶液的折光率发生改变,会影响利用微流成像技术检测不溶性微粒的准确性。因此,利用微流成像技术检测蛋白制剂中不溶性微粒时,需要考虑到制剂处方的折光率对于检测不溶性微粒的影响,必要时可以采用稀释的方法降低折光率对蛋白质颗粒的屏蔽作用。     

Demonstrating the stability of albinterferon alfa-2b in the presence of silicone oil

Silicone oil is often used to decrease glide forces in prefilled syringes and cartridges, common primary container closures for biopharmaceutical products. Silicone oil has been linked to inducing protein aggregation (Diabet Med 1989;6:278; Diabet Care 1987;10:786-790), leading to patient safety and immunogenicity concerns. Because of the silicone oil application process (Biotech Adv 2007;25:318-324), silicone oil levels tend to vary between individual container closures. Various silicone oil levels were applied to a container closure prior to filling and lyophilization of an albumin and interferon alfa-2b fusion protein (albinterferon alfa-2b). Data demonstrated that high silicone oil levels in combination with intended and stress storage conditions had no impact on protein purity, higher order structure, stability trajectory, or biological activity. Subvisible particulate analysis (1-10 μm range) from active and placebo samples from siliconized glass barrels showed similar particle counts. Increases in solution turbidity readings for both active and placebo samples correlated well with increases in silicone oil levels, suggesting that the particles in solution are related to the presence of silicone oil and not large protein aggregates. Results from this study demonstrate that silicone oil is not always detrimental to proteins; nevertheless, assessing the impact of silicone oil on a product case-by-case basis is still recommended.