Hydrophobic drug particles adopt a complex biomolecular corona in ex vivo gastrointestinal fluids

The adsorption of proteins and other biomolecules onto particles at the blood-particle interface, resulting in the formation of a biomolecular corona, is an established research area and can form the basis for a formulation concept to modify the in vivo behavior of particles. In contrast, the analogous formation of a gastrointestinal (GI) biomolecular corona on particles has only recently gained growing attention. Hydrophobic drugs are ingested in particle form, or may precipitate in the GI tract to form particles upon which a biomolecular corona may form. This study aimed to elucidate the composition of the GI biomolecular corona on drug particles in ex vivo porcine gastric, intestinal and colonic fluids (PGF, PIF & PCF) and its dependence on drug identity and solid-state form. Using LC-MS/MS proteomics, the results show that the composition of the GI corona formed on clotrimazole (CMZ) particles were luminal compartment specific, with the PGF corona showing the highest number of identified proteins. Notably, the composition of the PIF corona rapidly reached equilibrium and displayed no time-dependency at the tested time-points (10, 60 and 120 min). Sequential exposure of CMZ particles to the GI fluids from sequential compartments (mimicking the transit of particles through the GI tract), i.e. PGF-PIF and PGF-PIF-PCF, resulted in corona compositions highly similar to that formed in PIF alone, indicating that PIF proteins form the dominant corona. Furthermore, the PIF corona was drug-particle specific, with distinct compositions observed between CMZ and ritonavir (RTV) (both weak bases with logP values above 5) compared to the corona composition on crystalline indomethacin (IND). Further, amorphous IND exhibited a more diverse corona than crystalline IND, containing 153 unique proteins that were absent from the corona of crystalline IND. All investigated corona compositions showed enrichment of low-abundance proteins not detectable in the original GI fluid. In conclusion, this study provides insights into the issue of how the identity and solid state of drug particles influences the adsorption of biomolecules onto drug particles in ex vivo GI fluids, and that exposure to the different fluids reveals that certain protein components specific to intestinal fluids can dominate the composition of the corona after sequential exposure.