Exploring Acoustic Disruption of Lipid Assemblies for Mass Spectrometry

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Theresa Evans-Nguyen and Venkat Bhethanabotla and their groups at the University of South Florida are devising ways to improve analysis of lipid assemblies critical to extracellular signaling. The roles of discrete lipids in these assemblies are not well understood.

Furthermore, because lipids aggregate so readily, it is difficult even to identify and quantitate the individual lipid constituents of such assemblies. Mass spectrometry (MS) offers a powerful analytical tool which could provide a great deal of useful information if aggregation challenges could be overcome. To that end, this project focuses on using controlled acoustic waves to disrupt lipid aggregation, thereby facilitating MS analysis.

The principles developed in this project should be extendable to other non-specific assemblies and amenable to coupling with current MS sampling methodologies. The research involves a cross-disciplinary effort between the fields of chemistry and engineering, and is expected to strengthen STEM recruitment programs through both fields.

At the heart of this research is the use of novel surface acoustic wave (SAW) technologies in the MS workflow. In one modality, SAWs can already lyse extracellular vesicles known as exosomes. Also, as has been previously demonstrated by the team, one can use SAWs to mitigate biofouling from non-specific binding on microfluidic sensors.

By extension, SAWs may be feasibly tuned to not just disrupt but further disintegrate bilayer membranes as model aggregates. In a second modality, SAW nebulization (SAWN) exhibits a distinct ionization capacity for both polar and non-polar lipids. By coupling to corona discharge (CD), the South Florida team has achieved comparable efficiency to electrospray ionization (ESI).

Thus, the employment of SAWN-CD for the simultaneous analysis of non-polar cholesterol and polar phospholipids comprises a specific capability for which ESI falls short. SAWs are known to effect disruption of extracellular vesicles and to mitigate non-specific biofouling. In this work, SAWs are used to disintegrate model bilayer membrane vesicles into individual lipid components and, through SAW nebulization (SAWN), to facilitate MS ionization of both polar and non-polar lipids by coupling to corona discharge (CD).

Specific objectives are: (1) formulation of liposomes as model aggregations to enable a systematic evaluation of SAWs; (2) investigation of SAW disruption parameters to disintegrate lipid assemblies; and 3) investigation SAW nebulization parameters to achieve simultaneous ionization of polar and non-polar species. Thus, through this investigation, the team aims to develop a method that can be applied to extracellular vesicles, allowing them to be directly sampled by mass spectrometry, vastly short-cutting traditional analysis methods for such complex assemblies.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.