Self-Aliquoting Microarray Plates for Accurate Quantitative Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Abstract

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a fast analysis tool employed for the detection of a broad range of analytes. However, MALDI-MS has a reputation of not being suitable for quantitative analysis. Inhomogeneous analyte/matrix co-crystallization, spot-to-spot inhomogeneity, as well as a typically low number of replicates are the main contributing factors. Here, we present a novel MALDI sample target for quantitative MALDI-MS applications, which addresses the limitations mentioned above. The platform is based on the recently developed microarray for mass spectrometry (MAMS) technology and contains parallel lanes of hydrophilic reservoirs. Samples are not pipetted manually but deposited by dragging one or several sample droplets with a metal sliding device along these lanes. Sample is rapidly and automatically aliquoted into the sample spots due to the interplay of hydrophilic/hydrophobic interactions. With a few microliters of sample, it is possible to aliquot up to 40 replicates within seconds, each aliquot containing just 10 nL. The analyte droplet dries immediately and homogeneously, and consumption of the whole spot during MALDI-MS analysis is typically accomplished within few seconds. We evaluated these sample targets with respect to their suitability for use with different samples and matrices. Furthermore, we tested their application for generating calibration curves of standard peptides with α-cyano-4-hdydroxycinnamic acid as a matrix. For angiotensin II and [Glu(1)]-fibrinopeptide B we achieved coefficients of determination (r(2)) greater than 0.99 without the use of internal standards.

A Microarray-Matrix-assisted Laser Desorption/Ionization-Mass Spectrometry Approach for Site-specific Protein N-glycosylation Analysis, as Demonstrated for Human Serum Immunoglobulin M (IgM)*

“…Production of Microarray Chips-Microarrays for Mass Spectrometry (MAMS) were fabricated as described in Urban et al, and Kü ster et al (65,66) In brief, a coated ITO-glass slide (12)(13)(14)(15)(16)(17)(18) Ohm/m 2 , Sigma Aldrich) was structured using a laser ablation system to generate a checkerboard-like array of 2800 hydrophilic sample deposition areas of 300 m diameter and ϳ35 m depth each (720 m center-tocenter distance within one row).…”

microMS: A Python Platform for Image-Guided Mass Spectrometry Profiling

“…MS profiling of adhered cells provides advantages in data fusion by simplifying data processing and allowing sequential analysis of the same cell. Microarrays for mass spectrometry [15–17] (MAMS) have demonstrated such capabilities by combining Raman microspectroscopy with MS [18]. As an alternative to MAMS, cells may be randomly seeded on a substrate, greatly relaxing fabrication requirements, but at the expense of a necessarily gentle sample extraction.…”

Mass spectrometry-based characterization of endogenous peptides and metabolites in small volume samples

“…With the proper cell suspension density, it is possible to deposit single cells into wells by pipetting the suspension onto the array, allowing them to sediment, and removing excess liquid. As result, many wells can be quickly and repeatedly loaded for high throughput and quantitative experiments [66]. The number of cells deposited in a well follows a Poisson distribution and can be visualized using a microscope [67].…”

“…A MAMS chip containing (A) 24 or (B) 12 spots per lane can be automatically aliquoted by dragging the sample over each lane (D–F). (Reprinted with permission from reference [66]. Copyright 2013 American Chemical Society).…”