Simultaneous Proton Transfer Reaction-Mass Spectrometry and electronic nose study of the volatile compounds released by Plasmodium falciparum infected red blood cells in vitro

Rosamaria Capuano,Franco Biasioli,Iuliia Khomenko,Roberto Paolesse,Corrado Di Natale,Alexandro Catini,Valeria Messina,Luca Cappellin,Marta Ponzi,Felicia Grasso,Anna Olivieri

doi:10.1038/s41598-019-48732-x

Abstract

The discovery that Volatile Organic Compounds (VOCs) can be biomarkers for several diseases has led to the conception of their possible application as diagnostic tools. In this study, we aimed at defining of diagnostic signatures for the presence of malaria transmissible stages in infected individuals. To do this, we compared VOCs released by asexual and sexual stage cultures of Plasmodium falciparum, the deadliest species of malaria, with those emitted by uninfected red blood cells (RBCs). VOC analysis was carried out with an innovative set-up, where each sample was simultaneously analysed by proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS) and an electronic nose. PTR-Tof-MS results show that sexual stages are characterized by a larger emission of hexanal, compared with uninfected or asexual stage-infected RBCs, which makes them clearly identifiable. PTR-Tof-MS analysis also detected differences in VOC composition between asexual stages and uninfected RBCs. These results have been substantially replicated by the electronic nose analysis and may open the possibility to develop sensitive and easy-to-use devices able to detect sexual parasite stages in infected individuals. This study also demonstrates that the combination of mass spectrometry with electronic noses is a useful tool to identify markers of diseases and to support the development of optimized sensors.

Highlights

Malaria is a serious worldwide health problem, with a total of 216 million cases in 2016 involving 445,000 deaths, most of them in Africa[1]
In order to investigate changes in Volatile Organic Compounds (VOCs) emitted by P. falciparum asexual and sexual stages in vitro, asexual forms were induced to produce fully mature gametocytes in 10–14 days by overgrowth in blood cultures
The gametocytes were selected by supplementation with N-acetylglucosamine (NAG) that is selectively toxic for asexual trophozoites and schizonts, while not affecting gametocytes[17]

Summary

Introduction

Malaria is a serious worldwide health problem, with a total of 216 million cases in 2016 involving 445,000 deaths, most of them in Africa[1]. Parasite carriers often harbour sexual stages at submicroscopic levels, only be detectable by molecular methods In this context, identification and monitoring of gametocyte reservoirs is a fundamental aspect. Identification and monitoring of gametocyte reservoirs is a fundamental aspect To this aim, the development of sensitive, non-invasive, easy-to-use and low-cost devices to detect parasite sexual stages in infected individuals is strategic. Several studies in human malaria showed that Plasmodium-infected individuals are more attractive to mosquitoes than non-infected hosts, when high levels of gametocytes are present[4,5]. It remains unclear whether the increased human attractiveness to mosquitoes is due to infection in general

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