Construction of bio-layer interferometry biosensors via cell-free synthesized proteins for fishing bioactive compounds from Chinese herbs

Abstract

The application of Bio-Layer Interferometry (BLI) is contingent upon the immobilization of highly purified target proteins onto the sensor. The cumbersome and time-consuming nature of traditional protein expression and purification processes restricts the application of BLI in high-throughput screening of traditional Chinese medicine (TCM). This study aims to develop a rapid and efficient BLI-based platform for screening bioactive components in TCM. An integrated platform combining cell-free protein synthesis (CFPS), BLI, and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) was established for efficient TCM bioactive compound discovery. Functional C-X-C chemokine receptor 4 (CXCR4) was synthesized in vitro using a CFPS system, which were then validated by surface plasmon resonance (SPR) and western blotting. Immobilized CXCR4 on NTA biosensors enabled BLI-based high-throughput screening of TCM extracts, followed by target-specific compound recovery and characterized via mass spectrometry. Three bioactive TCM constituents were successfully fished and identified as coptisine, ligustilide, and senkyunolide A. All of them exhibited negligible cytotoxicity at concentrations ranging from 6.25 to 100 μM). Furthermore, ligustilide and senkyunolide A demonstrated certain affinity for CXCR4 with K_D of 69.86 μM and 14.7 μM, respectively, and significantly inhibited cell migration. This study is the first identification of ligustilide and senkyunolide A as functional ligands of CXCR4. The established CFPS-BLI-UHPLC-QTOF/MS platform enables efficient discovery of low-toxicity, high-affinity CXCR4-targeting therapeutics from TCM.