Viscosizer TD: a new automated tool for biophysical characterization

Viscosizer TD: a new automated tool for biophysical characterization.

TDA is a microcapillary flow-based technique that enables the sizing of small molecules, peptides and proteins, and samples containing mixtures of these species. Measurements of hydrodynamic size in different solution conditions are a critical element of screening and formulation studies because they give insight into the conformational stability and self-association behavior of a candidate drug. However, such measurements can be challenging because of the limited availability of target proteins at the candidate validation stage. Into early stage formulation development, candidate molecules are further worked up into complex buffer and excipient backgrounds, and can be present at a concentration – either high or low - that complicates analysis.

The Viscosizer TD uses TDA with UV-absorbance detection to directly address these issues and deliver hydrodynamic sizing in the range 0.2 to 50 nm radius. Target molecule detection is selective on the basis of the UV wavelength used in the measurement. In addition, the ability to baseline the system against a matched sample buffer offers novel measurement capabilities for label-free analysis of biomolecules in complex formulations. TDA can be used to monitor stability and self-association of target molecules in mixtures of excipients and surfactants for example, without measurement interference. Furthermore, measurements are not adversely affected by the presence of low levels of aggregates so samples can be run without dilution of filtration. The capability to work in biologically-relevant solutions makes TDA highly complementary to established tools such as Dynamic Light Scattering (DLS) and Size Exclusion Chromatography (SEC).

The Viscosizer TD also allows relative viscosity measurements, via a microcapillary flow-based methodology, using Poiseuille''s law. A unique dual pass timing approach enables high resolution viscosity measurements with high reproducibility, particularly in the low concentration and low viscosity regime. These measurements are highly complementary to TDA sizing, and used in combination as an early developability screen for candidates, provide crucial data for stability and formulation using a minimal amount of sample. Triplicate measurements of both size and relative viscosity are accessible with a total sample volume of around 35 microliters. Allied with automated measurement protocols, the new Viscosizer TD system is well-suited to a multiple sample screening environment.