Templated polymers enable selective capture and release of lysophosphatidic acid in human plasma via optimization of non-covalent binding to functional monomers

Abstract

The first solid phase extraction materials for selective lysophosphatidic acid (LPA) enrichment from human plasma are described. Molecularly imprinted polymers were designed, synthesized and evaluated as cartridge fillings. They enabled a relatively rapid and simple extraction protocol for LPA without any need for multiple liquid-liquid extraction steps. The five major subspecies of lysophosphatidic acid are readily separated from all other native plasma phospholipids, including those well-known to interfere with LPA quantitation, such as phosphatidylcholine and lysophosphatidylcholine. Outstanding LPA purity is obtained via these solid phase materials in a tandem extraction setup.

Fig. 1

Structures of major LPA subspecies. Non-native LPA 17:0 is used as an internal standard.

Fig. 2

Energy-minimized structure of the complex of a tris-urea scaffold and LPA 18:1. Atom colors: carbon=gray, hydrogen=white, oxygen=red, nitrogen=blue, phosphorus=cyan. Only polar hydrogens are shown for clarity.

Fig. 3

Structures of guest (OPA), functional monomers chosen (2-VP, 4-VP, 1-VIM, 1-allylthiourea and MAA) and crosslinking monomer (EGDMA).

Fig. 4

¹H NMR titration of monomer 1 using OPA as the guest.

Fig. 5

LC-ESI/MS traces. Left: 10 μM standard mixtures of LPAs. Right: plasma sample. Column: Luna^™ C-8 (50 × 2 mm, 3 μm) at 40 °C. Injection volume: 10 μL. Mobile phase: 9:1 MeOH–HCOOH (pH 2.5). Flow rate: 0.6 mL/min. Ions are detected in negative ion mode. Sprayer voltage: 3.0 kV and capillary temperature: 300 °C.

Scheme 1

Synthesis of monomer 1.