Biomimetic chromatography-A novel application of the chromatographic principles

Abstract

Biomimetic chromatography is the name of the High Performance Liquid Chromatography (HPLC) methods that apply stationary phases containing proteins and phospholipids that can mimic the biological environment where drug molecules distribute. The applied mobile phases are aqueous organic with a pH of 7.4 to imitate physiological conditions that would be encountered in the human body. The calibrated retention of molecules on biomimetic stationary phases reveals a compound's affinity to proteins and phospholipids, which can be used to model the biological and environmental fate of molecules. This technology, when standardised, enables the prediction of in vivo partition and distribution behaviour of compounds and aids the selection of the best compounds for further studies to become a drug molecule. Applying biomimetic chromatographic measurements helps reduce the number of animal experiments during the drug discovery process. New biomimetic stationary phases, such as sphingomyelin and phosphatidylethanolamine, widen the application to the modelling of blood-brain barrier distribution and lung tissue binding. Recently, the measured properties have also been used to predict toxicity, such as phospholipidosis and cardiotoxicity. The aquatic toxicity of drugs and pesticides can be predicted using biomimetic chromatographic data. Biomimetic chromatographic separation methods may also be extended in the future to predict protein and receptor binding kinetics. The development of new biomimetic stationary phases and new prediction models will further accelerate the widespread application of this analytical method.

Keywords: biomimetic stationary phases; lipophilicity; phospholipid binding; protein binding; toxicity.

FIGURE 1

Commercially available biomimetic stationary phases using immobilised human serum albumin (HSA) and α‐1‐acid glycoproteins (AGP) and phosphatidylcholine are ChiralPak‐HSA, ChiralPak‐AGP and immobilised artificial membrane (IAM) column with phosphatidylcholine, drug discovery

FIGURE 2

The concept of using an IAM stationary phase to predict drug‐induced phospholipidosis. Drug‐induced phospholipidosis occurs when the drug molecule binds strongly to phospholipids and disturbs its metabolism in the cell, resulting in the accumulation of phospholipid vesicles. This can be detected by Nil‐red staining of the cells. It was found that IAM retention (CHI IAM), which measures compound affinity to phospholipids, correlated very well with the staining

FIGURE 3

The chromatogram of marketed drugs with known plasma protein binding data that are used to calibrate the retention times on an albumin column. Column: ChiralPack‐HSA 50 × 3 mm, mobile phases: (A) 50 mM ammonium acetate pH 7.4, (B) 2‐propanol. Flow rate: 1.2 ml/min, gradient profile: 0 to 3 min, 0% to 30% 2‐propanol, 3 to 9 min 30% 2‐propanol, 9 to 10 min, 30% to 0% 2‐propanol

FIGURE 4

The model to predict human ether‐à‐go‐go‐related gene (hERG) inhibition by IAM and AGP biomimetic chromatography (from reference with permission). The hERG receptor is located inside the membrane and has similar funnel‐like shape (right) as the immobilised AGP on the stationary phase. Both AGP and the hERG channel have negative charges at the narrow end of the funnel shape. The compound that interacts with the hERG channel has to go through the membrane that is modelled by the IAM retention, while the hERG channel binding is modelled by the AGP binding