A polarization sensitive light scattering unit for high throughput screening.

A simple, effective light scattering prototype sensitive to both polarized and depolarized scattering was constructed, and its performance was tested on a variety of pure liquids and optically isotropic and anisotropic polymer solutions and colloidal suspensions. The results, performance, and means to further improvement are reported here. Because of its simplicity and low cost, many identical units can be produced to construct a simultaneous multiple sample light scattering platform that can be used to monitor polymer and colloid solution stability, phase changes, aggregation, degradation, etc. Measurable depolarization was found for a variety of organic liquids and suspensions of both polyfluoroethylene and latex spheres. No detectable depolarization was found for various polymers.

Monitoring protein aggregation kinetics with simultaneous multiple sample light scattering.

A simultaneous multiple sample light scattering (SMSLS) prototype instrument was built to simultaneously measure light scattering from many independent monoclonal antibody (mAb) solutions in order to monitor their time-dependent aggregation behavior and to characterize, via absolute Rayleigh scattering ratios, their molecular masses and second, third, and fourth virial coefficients under non-aggregating conditions at concentrations up to 190mg/ml. One stable mAb and another prone to aggregation were studied. Early phase aggregation rates spanned six orders of magnitude over temperatures 30 to 83°C for both mAbs and divided into "Arrhenius" and "Stochastic" regimes. The Arrhenius regimes comprise two thermal regimes whose breakpoint occurs near the first thermal unfolding temperature of the mAb domain structure. The Stochastic regime occurs for T⩽40°C. Rates yielded activation energies and temperature and concentration crossovers among rate-limiting regimes. Virial coefficients were closely related to aggregation kinetics. Hydrodynamic diameter relationship to virial coefficients provided further insight into stability. SMSLS detected as few as three dimerization events among 1000 monomeric proteins. Although early phase aggregation is linear in time and reproducible, aggregation becomes chaotic in later phases. SMSLS dramatically increases protein monitoring throughput, providing continuous monitoring for hours, weeks, and longer. New samples can be changed in and out without affecting other sample measurements in progress.

Simultaneous in-situ monitoring of parallel polymerization reactions using light scattering; a new tool for high-throughput screening.

A recently introduced technique, simultaneous multiple sample light scattering (SMSLS), was used to monitor parallel polymerization reactions in situ. SMSLS is designed for real-time, high-throughput screening and provides a time-dependent light scattering signature for each reaction, which contains both qualitative and semiquantitative information. Qualitatively, the signature immediately indicates whether the reaction occurs or not, whether there is an initial lag period, and how long the reaction takes until it stops. The signature also provides estimates of the reaction rate and weight average molecular mass M(w), and its shape can help identify mechanistic aspects, for example, controlled versus free radical polymerization, presence of impurities, etc. The method is inherently adapted to small sample volumes and requires no special sample preparation or postpolymerization characterization. The demonstration here involved the free radical polymerization of acrylamide under varying conditions and should be readily applicable to a wide variety of other reactions. Results were cross-checked with multi-detector gel permeation chromatography.