Spatially resolved chemical analysis of cicada wings using laser-ablation electrospray ionization (LAESI) imaging mass spectrometry (IMS)

Abstract

Laser-ablation electrospray ionization (LAESI) imaging mass spectrometry (IMS) is an emerging bioanalytical tool for direct imaging and analysis of biological tissues. Performing ionization in an ambient environment, this technique requires little sample preparation and no additional matrix, and can be performed on natural, uneven surfaces. When combined with optical microscopy, the investigation of biological samples by LAESI allows for spatially resolved compositional analysis. We demonstrate here the applicability of LAESI-IMS for the chemical analysis of thin, desiccated biological samples, specifically Neotibicen pruinosus cicada wings. Positive-ion LAESI-IMS accurate ion-map data was acquired from several wing cells and superimposed onto optical images allowing for compositional comparisons across areas of the wing. Various putative chemical identifications were made indicating the presence of hydrocarbons, lipids/esters, amines/amides, and sulfonated/phosphorylated compounds. With the spatial resolution capability, surprising chemical distribution patterns were observed across the cicada wing, which may assist in correlating trends in surface properties with chemical distribution. Observed ions were either (1) equally dispersed across the wing, (2) more concentrated closer to the body of the insect (proximal end), or (3) more concentrated toward the tip of the wing (distal end). These findings demonstrate LAESI-IMS as a tool for the acquisition of spatially resolved chemical information from fragile, dried insect wings. This LAESI-IMS technique has important implications for the study of functional biomaterials, where understanding the correlation between chemical composition, physical structure, and biological function is critical. Graphical abstract Positive-ion laser-ablation electrospray ionization mass spectrometry coupled with optical imaging provides a powerful tool for the spatially resolved chemical analysis of cicada wings.

Molecular and Topographical Organization: Influence on Cicada Wing Wettability and Bactericidal Properties

“…Many animal and plant surfaces have functionalities that would be desirable on engineered substrates and have become the focus of intense research. Insect wings are examples of surfaces that have evolved to exhibit a range of properties, including superhydrophobicity, [ 1–3 ] self‐cleaning, [ 4–6 ] droplet jumping, [ 1,4,7,8 ] optical reflectivity, [ 7,9 ] antifogging, [ 6 ] and antimicrobial activity. [ 10,11 ] These properties have been observed on the wings of cicadas, [ 1,2,7,12,13 ] butterflies, [ 14 ] dragonflies, [ 5,15 ] and damselflies.…”

Laser Desorption/Ablation Postionization Mass Spectrometry: Recent Progress in Bioanalytical Applications

“…Advantageously, laser desorption/ablation ambient postionization enables sample detection under ambient environment and provides highly efficient desorption with a lateral resolution ranging from hundreds to a few microns. These merits have made ambient postionization methods superior in mass spectrometric imaging (MSI) (Shelley, Ray & Hieftje, 2008; Wu et al, 2012; O'Brien, Williams, & Holman, 2015; Chen et al, 2017b; Román et al, 2018).…”

“…Laser desorption/ablation postionization (LD/API) techniques are now at hand for mapping target compounds directly in raw biological materials. Considerable inroads have been made in some aspects of biological, clinical, forensic, and environmental health science dealing with toxics, drugs, peptides, lipids, and a wide range of biometabolites (Gasper et al, 2010; Perez et al, 2013; O'Brien, Williams, & Holman, 2015; Lee et al, 2016; Chen et al, 2017b; Román et al, 2018). A general depiction for bioapplication areas of each LD/API techniques is shown in Table 3.…”

Direct analysis of surface chemicals using vibrating sharp‐edge spray ionization mass spectrometry

“…30 Easy sonic spray-assisted ionization using pressurized gas to generate liquid droplets shares a similar workflow to DESI without the need for a high voltage supply. 31,32 Laser ablation electrospray ionization (LAESI) reported by Vertes et al is another surface analysis method using MS. 33 LAESI is especially useful for studying single cells because of its high spatial resolution and compatibility with aqueous solutions. 34 Another example is atmospheric pressure matrix-assisted laser desorption ionization (APMALDI), which eliminates the need for extensive sample preparation and the vacuum requirements of conventional matrixassisted laser desorption ionization.…”

“…Easy sonic spray‐assisted ionization using pressurized gas to generate liquid droplets shares a similar workflow to DESI without the need for a high voltage supply 31,32 . Laser ablation electrospray ionization (LAESI) reported by Vertes et al is another surface analysis method using MS 33 . LAESI is especially useful for studying single cells because of its high spatial resolution and compatibility with aqueous solutions 34 .…”