Nondestructive Metabolic Monitoring of Living Organisms by Water-Droplet Extraction and Contact-Free Electrospray Ionization Mass Spectrometry

We present a novel tool for nondestructive in vivo metabolite analysis, which we call MetaTube. This method utilizes a high voltage to facilitate efficient ionization while maintaining electrical isolation from living tissues that are sampled. MetaTube achieves a 2-3 order of magnitude improvement in metabolite signal intensity, giving MetaTube the capacity to identify 10-fold more metabolites. These capabilities allow us to profile metabolites of human skin surfaces and monitor metabolite fluctuations of growing bacterial colonies. MetaTube offers a promising strategy to understand in vivo metabolic dynamics and evaluate the metabolic state of living tissues in real time.