Single cell-asymmetrical flow field-flow fractionation/ICP-time of flight-mass spectrometry (sc-AF4/ICP-ToF-MS): an efficient alternative for the cleaning and multielemental analysis of individual cells

Abstract

One of the greatest challenges in the analysis of single cells, quite often is the severe ionic background their samples exhibit. With that in mind, Asymmetrical Flow Field-Flow Fractionation (AF4), as a cleaning technique, was combined on-line with the multielemental analytical capabilities of an Inductively Coupled Plasma-Time of Flight-Mass Spectrometer (ICP-ToF-MS). In that manner, the heavy ionic matrix effect of untreated cells' samples can be significantly reduced. As a proof of concept, commercial baker's yeast cells were analysed. Their metal content can be determined on a single cell level, for multiple elements at a time. The combination yielded promising results, with the system exhibiting the ability to effectively limit the effect of matrices as severe as 3 × 10⁵ mg per L sodium chloride (NaCl) or 50 mg per L ionic phosphorus (P). In the meantime, no hampering in the analysis of the cells was observed, due to clogging or otherwise equipment related issues. Furthermore, cells grown in heavy metal medium (lead, Pb, 0.1–10 mg L⁻¹) were also analysed without prior cleaning, highlighting the ability for fast analysis without previous manual and/or laborious cleaning procedures. That fact, coupled with the ability of the ToF to detect the single cells' content for both the event related element (P) and the spiked element (Pb), on the same event, highlighted the potential of the further development and optimization of this fast, robust, and effective coupling and its future applicability to numerous life-science related applications. In addition, new and versatile data treatment tools were developed, and their performance was tested against established methods.