Analysis of cicada wing surface constituents by comprehensive multidimensional gas chromatography for species differentiation

Abstract

Cicada wings exhibit several intriguing properties that arise from a combination of nanopillar structures and chemical constituents, including superhydrophobicity, as well as antimicrobial, antireflective, and self-cleaning functions. While the physical dimensions of the nanofeatures are relatively simple to characterize through microscopy, the chemicals that cover these pillars are more difficult to characterize due to the variety and complexity of the mixture. Here, we compared the extractable chemicals from the wing surfaces of two different cicada species using both gas chromatography time-of-flight mass spectrometry (GC-TOFMS) and two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS) platforms. Chemical extracts from Neotibicen pruinosus and Magicicada septendecim cicada wings were separated and analyzed. The GC × GC-TOFMS platform was able to isolate and identified roughly three times the number of constituents as the GC-TOFMS platform at a signal-to-noise ratio (SNR) ≥10.0 and spectral similarity ≥800. When comparing the two cicada species wing extracts, the two-dimensional platform was able to expose differences in the chemical composition that were undetectable by the one-dimensional technique. GC × GC-TOFMS revealed nearly four times the number of unique species-specific compounds as compared to the number identified by GC-TOFMS. Further, surface chemicals were identified that are likely xenobiotics and can pinpoint location and contamination from where the cicada was collected. While the advantages of GC × GC-TOFMS over GC-TOFMS have been documented in the past, our work presents a powerful biological application of GC × GC-TOFMS with promise to reveal both organism species-specific biomarkers while providing insight into the environmental conditions of individual organisms.