Virus Isoelectric Point Determination Using Single-Particle Chemical Force Microscopy.

Area of Science:

• * Colloidal science
• * Virology
• * Surface chemistry

Background:

• * Virus colloidal behavior is dictated by surface charge and environmental interactions.
• * Traditional methods for determining virus isoelectric point (pI) use bulk measurements, which do not account for capsid heterogeneity.
• * Single-particle analysis offers a more nuanced understanding of surface charge variations within a viral population.

Purpose of the Study:

• * To introduce and validate chemical force microscopy (CFM) as a single-particle technique for measuring virus isoelectric points (pI).
• * To compare CFM-derived pI values with traditional methods for non-enveloped porcine parvovirus (PPV) and enveloped bovine viral diarrhea virus (BVDV).

Main Methods:

• * Chemical force microscopy (CFM) utilizing functionalized atomic force microscope (AFM) probes to measure adhesion forces with surface-bound viruses.
• * Application of CFM to non-enveloped porcine parvovirus (PPV) and enveloped bovine viral diarrhea virus (BVDV).
• * Validation using bulk measurements, ζ-potential, and aqueous two-phase system (ATPS) cross-partitioning.

Main Results:

• * CFM successfully determined the pI range for PPV as 4.8-5.1, consistent with literature values (pI=5.0).
• * CFM predicted an unknown pI range for BVDV as 4.3-4.5.
• * CFM results showed good agreement with traditional bulk measurement techniques.

Conclusions:

• * Chemical force microscopy (CFM) is a viable single-particle method for characterizing virus surface charge and determining pI.
• * CFM provides valuable insights into the heterogeneity of viral capsids.
• * This technique enables direct comparison of surface charge properties across different virus types.