Method for quantifying the PEGylation of gelatin nanoparticle drug carrier systems using asymmetrical flow field-flow fractionation and refractive index detection.

The PEGylation of colloidal drug carrier systems protects them from a rapid clearance from the blood stream and therefore prolongs their plasma half-lives. This fundamental concept is nowadays widely applied whereas the analytical description, i.e., the quantification of the PEGylation process, is still challenging due to the poor spectrophotometrical properties of PEG. The aim of this work is to quantify the PEGylation process of gelatin nanoparticles by utilizing the combination of asymmetrical flow field-flow fractionation (AF4) and refractive index (RI) detection and to demonstrate the potential of AF4 in the work with colloidal drug carrier systems. An AF4 separation mechanism of gelatin nanoparticles and PEG was developed without further sample preparation. After separation, the PEGylation could be directly quantified from the respective RI data and a threshold of a maximum amount of PEG that can be bound onto the surface of the nanoparticles could be determined. The PEGylation could be further visualized by atomic force microscopy (AFM). In sum, the presented results show the successful application of AF4 in the field of colloidal drug carrier systems, and in combination with AFM, both techniques can be stated as promising tools for the future analysis of colloidal drug carrier systems.