Gold nanoparticles as platform for investigating epidermal growth factor receptor activation and intestinal epithelium cell metabolomics
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Gold nanoparticles (Au NPs) exhibit unique optical and electronic properties due to localized surface plasmon resonance (LSPR), which arises from the collective oscillation of conduction electrons on the surface of AuNPs. Plasmon coupling results in the dramatic enhancement and confinement of the electric field. The distance-dependency of the plasmon coupling and local -field enhancement have been exploited for a variety of sensing techniques. Multivalent presentation of ligands on NPs is considered a general strategy for enhancing receptor binding and activation through amplification of ligand-receptor interactions within the footprint of the NPs. To understand the interplay between ligand density and epidermal growth factor receptor (EGFR) clustering in signal amplification, we apply EGF-functionalized NP with known ligand loading as quantifiable and tractable units of EGFR activation and characterize the NP-mediated amplification of EGFR phosphorylation as function of both EGF surface density and NP-EGF. The measurements confirm that NP-EGF-clustering and the associated local enhancement of ligand-receptor interactions are intrinsic components of the multivalent amplification of phosphorylation for the heterogeneously distributed EGFR through NP-EGF. To investigate the potential perturbation of nanoplastics on the protective function of the intestinal membrane, we use unpatterned gold nanoparticles as Surface Enhanced Raman Spectroscopy (SERS) substrate to monitor the composition of the medium in direct contact with the intestinal cells and to detect potential polystyrene NP induced changes in the cellular metabolism. Reactive oxygen species (ROS) generation, cell viability, and intestinal membrane integrity measurements were also performed to detect and quantify PS NP-induced membrane damage under acute exposure conditions. The measurements reveal that PS NPs induce cellular stress and perturb the membrane integrity. The analysis of the SERS spectra through artificial intelligence algorithms and chemometric tools reveals concentration-, exposure time-, and surface chemistry-dependent differences in the cellular metabolism, and identifies increased hypoxanthine (C4H4N4O) levels as a spectroscopic marker for PS NP-induced loss in membrane integrity.