Miniaturised Bioanalytical Chemistry in Acoustically Levitated Droplets

Sammanfattning: Fuelled by the current demands of the biological sciences, there is today a growing interest in microscale analysis. Miniaturisation of analytical instruments has become a long-standing trend. Miniaturisation offers several advantages, including rapid separation times, high performance and throughput, reduced costs, etc. But the increased surface area to volume ratio can sometimes be a disadvantage and result in analyte adsorption to walls and interfaces. To circumvent the use of solid container walls and yet enable miniaturised bioanalysis, the airborne analytical system described in this thesis was developed. The system consists of an acoustic levitator where a liquid droplet in the 100 nl-2 ?l volume range can be levitated in a nodal point of a standing ultrasonic wave. The levitator is combined with specially designed pl flow-through dispensers to enable additions to the levitated droplet in the pl volume range. To date, several remote detection systems have been fitted with the system. Combined with fluorescence imaging detection, the system has been used for single cell analysis of adipocyte lipolysis and for cell-cell communication studies of adipocytes and pancreatic ?-cells; the two key cell types in fat metabolism and thus with high impact in diabetes. Coupled with right angle light scattering detection, the airborne system has been developed for use in precipitation screening of proteins to establish nucleation conditions for application in protein crystallisation. Equipped with Raman spectroscopy detection, the system showed useful for the study of crystal polymorphs. The levitated droplet approach has also been successfully explored for miniaturised two-phase extractions and for use in affinity partitioning of liposomes. The airborne analytical system offers several benefits. The diversity of applications possible, the proven biological compatibility, the small volumes, and the absence of contacting surfaces are all important features. The results strongly speak to recommend the further use and development of this new approach in bioanalytical chemistry.