Angelo J. Madonna

Rapid detection of taxonomically important fatty acid methyl ester and steroid biomarkers using in situ thermal hydrolysis/methylation mass spectrometry (THM-MS): implications for bioaerosol detection

Abstract Implications for the rapid interrogation of biological materials collected from the atmosphere using a simple, one step, sample preparation technique was explored. For this purpose, various samples of whole bacteria, fungi, pollen, media contaminated with viruses, and proteins were treated with an aliquot of methanolic tetramethylammonium hydroxide prior to thermal introduction into the ion source of a triple quadrupole mass spectrometer. Molecular and fragment ions, consistent with fatty acid methyl esters (FAMEs) and steroids (non-methylated and methylated), generated during electron ionization (70 eV) of the volatile hydrolysates were subsequently detected. The varying distributions and relative intensities of these ions were used to discriminate between the different biological samples. More specifically, it was found that polyunsaturated FAMEs and steroids could be used to differentiate eukaryotic cells from prokaryotic cells since the latter do not generally synthesize either of these lipid membrane constituents. Further discrimination of the different eukaryotic samples was made based on the detection of ergosterol for fungi, cholesterol for the viral media, and C18:3Me for pollen. Multivariate statistical analysis was employed to evaluate and compare the large set of mass spectra generated during the study and to build a trained model for predicting the class membership of test samples entered as unknowns. Of 132 different samples subjected to the model as unknowns, 131 were correctly classified into their proper biological categories. Moreover, 29 out of 30 bacteria test samples representing five species of pathogenic bacteria were correctly classified at the species level.

Investigation of cell culture media infected with viruses by pyrolysis mass spectrometry: Implications for bioaerosol detection

Mass spectrometry coupled with a pyrolysis inlet system was used to investigate media from cell cultures infected with viruses. Cell culture media is an intricate mixture of numerous chemical constituents and cells that collectively produce complicated mass spectra. Cholesterol and free fatty acids were identified and attributed to lipid sources in the media (blood serum supplement and plasma membranes of host cells). These lipid moieties could be utilized as signature markers for rapidly detecting the cell culture media. Viruses are intracellular parasites and are dependent upon host cells in order to exist. Therefore, it is highly probable that significant quantities of media needed to grow and maintain viable host cells would be present if a viral agent were disseminated as an aerosol into the environment. Cholesterol was also detected from a purified virus sample, further substantiating its use as a target compound for detection. Implications of this research for detection of viral bioaerosols, using a field-portable pyrolysis mass spectrometer, is described.