Quantifying the interactions of micellar drug delivery system components with albumin using time-resolved fluorescent methods.

Abstract

The least requirement for the bioavailability of an active pharmaceutical ingredient (API) is its solubility in aqueous media. The solubilization of poorly soluble drugs is one of the key challenges of drug formulation development. Micellar drug delivery systems (MM-DDS) are efficient in solubilizing such APIs, are well tolerated by patients upon administration, are cost efficient and easy to produce. However, the number of marketed drugs is very limited. One problem identified by a reflection paper on this topic by the European Medicines Agency (EMA) is the number of different transformations of MM-DDS upon dilution by intravenous administration. The release of an API from MM-DDS and its subsequent binding to plasma proteins such as human serum albumin (HSA) determines the fate of the API in a human body. Tracking and characterization of such binding processes in a multicomponent system opens the door to understanding the drug - blood-components interaction. In this project we develop a label free time-resolved fluorescence tracking method to investigate the interaction of small molecules (API, MM-DDS components) with albumin. In detail, the data is collected using a time-correlated single-photon counting (TCSPC) technique at 280-nm excitation. Quenching of tryptophan fluorescence through Förster resonance energy transfer (FRET) to an API reveals information about the binding process. Affinity constants and stoichiometry can be obtained by global fitting of the titration curves and confirmed by the means of support plane analysis.