The Imprinted PARAFILM as a New Carrier Material for Dried Plasma Spots (DPSs) Utilizing Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) in Phospholipidomics

Abstract

The application of desorption electrospray ionization mass spectrometry (DESI-MS) and dried blood spot (DBS) sampling has been successfully implemented several times. However, the difficulty of combining DBS sampling with DESI-MS is still the carrier material used for the blood samples. In this study, a new, easily obtained, and cost-effective carrier substrate for dried plasma spot (DPS) sampling and DESI-MS analysis and its application in phospholipidomics studies was described. First, the effects of several carrier materials, including cellulose-based materials (31 ET paper and filter paper) and non-cellulose-based materials (PARAFILM and its shape-modified material, PTFE-printed glass slide and polyvinylidene fluoride film), were tested. Second, a method combining DPS sampling with DESI-MS for phospholipidomics analysis was established, and parameters affecting compound signal intensities, such as sample volume and sprayer solvent system, were optimized. In conclusion, the total signal intensity obtained from shape-modified PARAFILM was the strongest. The suitable plasma sample volume deposited on PARAFILM carriers was 5 μl, and acetonitrile (ACN) was recommended as the optimal spray solvent for phospholipid (PL) profiling. Repeatability (87.5% of compounds with CV < 30%) and stability for data acquisition (48 h) were confirmed. Finally, the developed method was applied in phospholipidomics analysis of schistosomiasis, and a distinguished classification between control mice and infected mice was observed by using multivariate pattern recognition analysis, confirming the practical application of this new carrier material for DPS sampling and DESI-MS analysis. Compared with a previously reported method, the rapid metabolomics screening approach based on the implementation of DPS sampling coupled with the DESI-MS instrument developed in this study has increased analyte sensitivity, which may promote its further application in clinical studies.

Customized Surface Design to Increase Throughput of Ambient Ionization Mass Spectrometry Lipidomics

“…As such, one goal of this study is to establish a customizable surface for small molecule detection suitable for ionizing a wide range of chemical species from biological samples via DESI-MS. We have attempted to use commonly available tools, such as 3D printing technology, open-source software, and low-cost robotics, to ensure wide-reaching accessibility to the platform. An important aspect of this workflow is the use of “PARAFILM” to create custom ionization surfaces via an imprinting process. PARAFILM is a wax film that is pliable, cost-effective, and commonly found in laboratories .…”

“…A critical piece in ambient ionization workflows is the ionization surface chosen for analyses. Previous studies have shown that a range of surfaces are suitable for the detection of metabolites, lipids, or drugs using DESI-MS: selected phospholipids (imprinted PARAFILM), 4 choline (PTFE-glass slides), 5 verapamil, sitamaquine, prazosin, and terfenadine (31ETF paper). 6 In these previous reports, investigators have tested a relatively narrow range of compounds for detection and targeted analysis (e.g., choline, verapamil, sitamaquine, etc.).…”

“…A distinct advantage of ambient ionization is the potential for multiplex assays of up to several thousand samples in a relatively short time. For example, the Cooks lab has established an impressive approach for rapid reaction screening via DESI-MS 3 capable of monitoring >10 4 reactions per hour. In many cases, this extreme level of throughput is not required, but some intermediate compromise between the benefits of automation and throughput would be beneficial to move translational research forward.…”

“…These circular divots may reduce the risk that a dried sample is "washed off" from the surface once the nebulizing gas of a DESI source is applied to the sample. 4 Therefore, we present a method for divot creation to efficiently produce imprinted PARAFILM plates with customizable divot dimensions. Automated aliquoting via liquid handling has also been shown to be highly effective for preparation of reactions for DESI-MS analysis.…”

“…Previous work has shown improved detection of six phospholipids from dried biological sample spots when this film is “imprinted” with circular divots. These circular divots may reduce the risk that a dried sample is “washed off” from the surface once the nebulizing gas of a DESI source is applied to the sample . Therefore, we present a method for divot creation to efficiently produce imprinted PARAFILM plates with customizable divot dimensions.…”