Protein formulations for therapeutic medicine have been extensively used in recent years, especially in oncology, autoimmune diseases, and hematology. Delivery of such medicine requires the use of syringes where silicone oil is often applied due to its lubricating properties. Unfortunately, adsorption of proteins at the silicone oil-water interface is thought to cause conformational changes in protein secondary structures, producing surface-induced protein aggregation in prefilled glass syringes. Interactions at the silicone oil and protein interface reduced the efficiency of the therapeutic and caused safety concerns. It is of great importance to characterize and understand the conformational changes in a protein at an interface in situ. In this study, we are applying sum frequency generation (SFG) spectroscopy, a surface specific nonlinear optical technique, to characterize the interface between silicone oil and solution of Immunoglobulin G (IgG) from bovine serum, fibrinogen and bovine serum albumin (BSA) in situ. Time-dependent SFG study showed an increase in the SFG signal when fibrinogen was introduced, proving the protein was adsorbed at the silicone oil interface and ordered. SFG spectra of BSA and IgG suggested that protein was not adsorbed at the interface as no significant increase was observed in the time-dependent nor any peaks in the amide region. The effect of polysorbate-80 in the aqueous layer on protein adsorption to silicone oil will be analyzed. Our work demonstrated the potential of SFG for providing a molecular level understanding of protein conformation at buried silicone oil interface, which would enable the risk assessment of the therapeutic protein.

Probing macromolecular protein interactions in situ via sum frequency generation (SFG) vibrational spectroscopy

2019 Spring National Meeting

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