In-Situ Metabolic Profiling of Single Living Cells by Liquid Secondary Ion Mass Spectrometry.

Single-cell mass spectrometry enables label-free and high-throughput molecular analysis of individual cells. However, conventional vacuum-based secondary ion mass spectrometry (SIMS) faces challenges in probing metabolism of single living cells under native physiological conditions. Here, we introduce a liquid SIMS platform coupled with a vacuum-compatible cell-culture device, which allows in-situ metabolomic profiling of single living cells in their native culture environment without any pretreatment. This platform uniquely enables direct nanoscale interfacial characterization, and we report for the first time the determination, via MS depth profiling, of a lipid bilayer with a SiN-equivalent thickness of ∼8.6 nm in a single living human nonsmall cell lung cancer (A549) cell. As a proof of concept, we applied this method to investigate metabolomic changes linked to cisplatin resistance in A549 cells. Our findings indicate upregulation of cholesterol, phosphatidylcholine, and low-unsaturation fatty acids in resistant cells, and we demonstrate that inhibiting cholesterol synthesis effectively reduces drug resistance. This work underscores the potential of liquid SIMS for in-situ metabolic profiling during complex biological processes.