Abstract
Microalgae are gaining increasing attention globally for their diverse uses, predominantly for their high lipid and protein contents. However, the methods used to quantify these cellular components in microalgae are complex and time-consuming. This thesis contributed to a larger project focused on the design of a sensor system for the rapid analysis of cellular lipid, protein, and carbohydrate content based on fluorescence microscopy. The major contribution of this thesis involved the chemical design and testing of the system, specifically the mechanism by which the fluorescent dyes were stored and delivered to the sample.
The device was designed to provide all the required reagents in a single sample well in which all chemical and imaging processes would occur. To begin, the properties of the selected fluorescent lipid and protein dyes were investigated, directing the choice of appropriate filters for fluorescence microscopy. The predetermined design of the system and the chemical properties of the dyes defined the criteria for the optimal function of the dye delivery system. A wide range of mechanisms were considered and the suitability of several options was tested. A dissolving layer based on a water-soluble synthetic polymer which incorporated the dyes and requisite additives was deemed most suitable. Next, the chemical attributes of the dissolvable layer formulation were explored, including its stability, drying method, and compatibility with a range of microalgal mediums. The dissolvable layer was found to perform well on all accounts.
The dissolution rate of the base formulation was optimised while maintaining the core properties of the layer. Alongside this work, several additives for the promotion of cell staining and settling were incorporated into the dissolvable layer in various formulations. The most effective of these were assessed based on their morphology, dissolution characteristics, interactions with the lipid and protein dyes, and modification of the layer solution’s chemical properties.
Finally, two lipid validation studies were done using the model alga Chlamydomonas reinhardtii to assess the overall performance of the sensor system in lipid quantification. The system successfully provided relative measurements of cell counts, non-polar lipid content, and biovolume, although an upgrade of the filter configuration was required before polar lipid content could be quantified. The system was able to detect significant changes in the culture within 24 hours of a treatment, and was demonstrated to effectively track changes in culture properties in a grower-relevant context. Overall, the development of the dye delivery mechanism for the sensor system was successful, with future work already underway by other contributors on the calibration, further validation, and optimisation of the system.