Conclusion
Assays based on turbidity and SEC can be used to evaluate protein sensitivity to tungsten in order to optimize formulations
for the packaging of biologics in glass prefilled syringes. Ionic strength and pH are important elements in the aggregation
of proteins by tungstate polyoxyanions. An acidic pH is necessary for the generation of tungstate polyoxyanions and aggregation
may be blocked by increasing the ionic strength of the formulation. This suggests that the interaction of polyoxometalates
with proteins is primarily electrostatic. Some proteins precipitate with tungstate more readily than others, but a net positive
charge is essential. Although protein size does not appear to be important, other factors related to a protein's structure
may play a role in determining binding and aggregation by tungstate polyoxyanions. Syringes made of plastic, which are free
of both silicone oil and tungsten, should be considered for use with sensitive biomolecules.
Vinod Vilivalam*, PhD, is director of strategic market and technical development, Lloyd Waxman is a principal scientist, West Analytical Labs, Tadd Steeley is a senior chemist, all at West Pharmaceutical Services, 101 Gordon Drive, Lionville, PA 1934, tel: 610.594.3147, vinod.vilivalam@westpharma.com
.
*To whom all correspondence should be addressed.
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