Characterization of high molecular weight polyethylenes using high temperature asymmetrical flow field-flow fractionation with on-line infrared, light scattering, and viscometry detection

Critical Assessment of the Application of Multidetection SEC and AF4 for the Separation of Single-Chain Nanoparticles

The intramolecular chain collapse of linear precursors with systematic variation of molar mass and ligation group density (5, 15, and 30 mol %) into single-chain nanoparticles (SCNPs) was studied by two different separation approaches. The efficiency of size exclusion chromatography with quadruple detection (SEC-D4) was compared to asymmetrical field flow fractionation hyphenated to quintuple detection (AF4-D5) in organic solvent. The application of the unique combination of advanced detection to different separation principles opens up the opportunity to critically evaluate the determination of molar masses and different types of radii for an in-depth understanding of the structural properties affected by the internal folding process. This is achieved by a detailed comparison of assets, drawbacks, and limitations of these approaches based on the systematical screening of different chain lengths and sizes of the precursors and the SCNPs. Furthermore, an alternative strategy for quantitative determination of intramolecular ligation density by a combination of AF4 and UV detection is introduced.

Asymmetric flow field-flow fractionation in the field of nanomedicine

Asymmetric flow field-flow fractionation (AF4) is a widely used and versatile technique in the family of field-flow fractionations, indicated by a rapidly increasing number of publications. It represents a gentle separation and characterization method, where nonspecific interactions are reduced to a minimum, allows a broad separation range from several nano- up to micrometers and enables a superior characterization of homo- and heterogenic systems. In particular, coupling to multiangle light scattering provides detailed access to sample properties. Information about molar mass, polydispersity, size, shape/conformation, or density can be obtained nearly independent of the used material. In this Perspective, the application and progress of AF4 for (bio)macromolecules and colloids, relevant for "nano" medical and pharmaceutical issues, will be presented. The characterization of different nanosized drug or gene delivery systems, e.g., polymers, nanoparticles, micelles, dendrimers, liposomes, polyplexes, and virus-like-particles (VLP), as well as therapeutic relevant proteins, antibodies, and nanoparticles for diagnostic usage will be discussed. Thereby, the variety of obtained information, the advantages and pitfalls of this emerging technique will be highlighted. Additionally, the influence of different fractionation parameters in the separation process is discussed in detail. Moreover, a comprehensive overview is given, concerning the investigated samples, fractionation parameters as membrane types and buffers used as well as the chosen detectors and the corresponding references. The perspective ends up with an outlook to the future.