Evaluation of Aggregation of Vaccines and Proteins
Fig. 1 shows an illustration of measurement results for vaccine and proteins. The vaccine contains primary particles of several hundred nm or smaller, aggregates of approximately several µm and additional contaminating components of 10µm or larger.
It goes without saying that vaccines should have fewer aggregates or contaminating components to ensure that they act effectively and safely. Also, in almost all cases regarding proteins, the suppression of this aggregation is an important issue.
Up till now, dynamic light scattering method instruments have been used for this evaluation of vaccines and proteins. Yet, it is considered that dynamic light scattering method instruments have hardly been unable to measure the existence of aggregates and contaminating components since their measurement upper limit is approximately several µm.
Consequently, instruments using different measurement principles also have been used in conjunction to measure aggregates and contaminating components. However, even in such cases, the component ratio could not be evaluated accurately since measurement is performed separately.
The SALD-7101 Nanoparticle Size Analyzer adopts a laser diffraction/scattering method (static scattering method) as the measurement principle and has a measurement range of 10 nm up to 300 µm. Thus, both primary particles as well as aggregates and contaminating components can be measured simultaneously on a single instrument. As a result, the aggregation state of vaccines and proteins can be evaluated speedily and accurately.
Furthermore, change over time also can be measured in 1-second intervals.
To demonstrate this feature, an experiment was conducted using 90 nm (0.09 µm) and 5 µm particles (polystyrene latex). Figs. 2, 3 and 4 shows the results of this experiment.
In measurement of 90 nm particles (Fig. 2), detection of scattered light starts from the 44th sensor element, whereas in 5 µm particle measurement (Fig. 3), it starts from the 14th sensor element. When a small amount of 5 µm particles is added to 90 nm particles, light intensity distribution data made by overlapping the light intensity distribution data of 90 nm particles on the light intensity distribution data of 5 µm particles at a fixed ratio can be obtained. With the clear difference from the distribution data shape for only 90 nm particles, it can be confirmed that the result contains large particles. This means that the existence of aggregates can be verified even in light intensity distribution data, the raw detected data. In other words, when aggregates or contaminating components exist in particle size distribution data obtained as measurement results, this indicates that the appropriateness of particle size measurement results can be validated by viewing light intensity distribution data.
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