Analysis of protein adsorption to a silicone oil/water interface
Kenneth Olesen PhD Sep 24, ’19 ~ 3 min

Analysis of protein adsorption to a silicone oil/water interface

A common way to store and administer therapeutic protein to patients is via prefilled glass-syringes.  Silicone oil, which is used as a syringe lubricant, could induce protein loss, but the addition of surfactant has been shown to reduce such loss. A study has been made to get a deeper understanding of why this is the case [1]. Here we present a summary of how the protein-silicone oil interaction was analyzed in the presence and absence of surfactant.

Lubricated prefilled glass-syringes, a model system

To be able to analyze the protein interaction with the silicone oil/water interface, a model system that mimics protein formulation in silicone oil lubricated syringes was designed [1]. Glass sensors, spin-coated with silicone oil, were to represent the silicone oil lubricated syringe, and the silicone oil coated sensors were then exposed to the model protein together with different non-ionic surfactants.

The protein-silicone oil surface interaction was analyzed with QSense® QCM-D, a surface-sensitive technology that monitors mass uptake at the surface in real-time. In addition to the mass, QCM-D also senses the structure of the layer adsorbed (or bound) at the surface. The adsorption behavior of the model protein, both in the absence and presence of two different surfactants, PS-80 and Poloxamer, were measured and compared.

Protein adsorption to silicone oil experimental-1

One of the surfactants reduces the amount adsorbed

The time-resolved mass changes, Fig. 1, showed that the total amount adsorbed is smaller when PS-80 is added to the protein solution, compared to when there is no surfactant present. The addition of Poloxamer 188, however, did not alter the amount adsorbed significantly. A possible explanation for this observation, presented by the authors [1], could be that PS-80 shows faster adsorption kinetics onto the oil-water interface than the model protein on its own (data not shown). This would allow PS-80 to form a protective layer at the surface, and thereby be more effective in preventing the protein adsorption, compared to Poloxamer 188, which binds more slowly to the interface.

Protein adsorption to Silicone oil with and without surfactant-1

Figure 1. Time-resolved mass change upon injection of the three samples i) protein, ii) protein with PS-80 and iii) protein with Poloxamer 188.

In summary

It was concluded that the time-resolved QCM-D analysis could provide insight into the protein-surface interaction, and how the protein adsorbs at the silicone oil/water interface. It was also concluded that this kind of data can shed light on how formulation additives impact the protein-surface interaction, information which can help decide which additives to use to minimize loss of product.

Download the case study to read more about protein interaction with surfaces with and without the presence of excipient.

Case study  QCM-D in drug formulation and storage  Download


  1. J. Li, et. al., Mechanistic understanding of protein-silicone oil interactions, Pharm Res. 2012, 29(6):1689-97

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