An analytical method for analyzing binding and elution of the viruses over a surface mimicking the ion-exchange matrix was developed by iBET scientists. A sorption rate model capable of quantitatively describing binding and elution of the recombinant baculoviruses and major impurities from dilute to overloaded conditions within a broad range of salt concentrations was subsequently validated (Figure 2A–2B).
A comparison of the adsorption of the major components of the baculovirus bulk onto an anion-exchange surface was conducted with this methodology. SPR operated as a pseudo-chromatographic tool utilized 1,200-fold less material (Figure 2C) than an analytical membrane adsorber unit for the estimation of adsorption isotherms.
Determination of the zeta-potential (a measure of the electrostatic equilibria) further elucidated the contribution of the different virus components to the interaction phenomenon during the ion-exchange process. The main species, product (infective virus particle) and product-derived impurities (dsDNA-, glycoprotein-, and envelope-deprived baculovirus particles), were isolated and correspondent zeta-potentials were measured through DLS.
The overall particle electrostatic interaction energy profile based on a fine-tuned electrokinetic model was able to distinguish the electrostatic properties of the infective virus particle from the major virus-related impurities. Scenarios such as Figure 2D allowed for prediction of the best operating conditions for promoting process selectivity.
Analytical tools based on SPR and DLS combined with in silico models grounded on fundamental knowledge can serve as relevant process predictors/scale-down models for addressing the useful design space more efficiently. The sensible selection of advanced downstream processes allied with rational design streamlines process development of such viruses and potentially other challenging biopharmaceuticals.