Polysorbate
(PS) is a widely used polymeric excipient in biotherapeutic
formulations to stabilize and protect protein drugs. Commercial PS
is a highly heterogeneous mixture of structurally related components.
PS composition can impact the stabilizer performance of PS in formulated
protein drugs. Characterization of PS heterogeneity is, however, analytically
challenging. In this work, a high-throughput screening protocol is
presented for the profiling of the PS-80 polysorbate form using high
resolution mass spectrometry (HRMS) coupled with a rapid hydrogen/deuterium
(H/D) exchange in deuterated methanol. The protocol takes advantage
of accurate mass measurements from HRMS analysis and utilizes H/D
exchange-induced mass shifts that are characteristic to structures
(particularly the number of terminal hydroxyl groups) of PS molecules
to definitively identify species. In particular, mass shifts caused
by deuterium uptake were used (1) to confirm molecular identities
assigned by accurate mass measurements (which adds an extra level
of identification confidence) and (2) to differentiate isomers that
have an identical mass (thus, undistinguishable by high mass accuracy),
but differ in the number of terminal hydroxyls. These data were input
to an automated searching algorithm against a molecular mass database
covering over 17000 potential PS-80 molecular species. The identified
species were then visualized with Kendrick Mass Defect plots. The
analysis protocol identified and profiled over 180 species from PS-80
samples in a high-throughput fashion without requiring chromatographic
separation to reduce complexity of mixtures or tandem mass spectrometric
analysis to conduct structural elucidation.
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