Development of New Fluorophores for Cellular Imaging

Fluorescence cellular imaging employs compounds—probes—with several important qualities. Primarily, fluorescent probes must possess a high fluorescence quantum yield and large stokes shift to ensure measurements using them can be conducted with high degrees of precision. In addition, high degrees of photostability are important to allow practical use and storage. Arguably of higher importance to a fluorescent probe is its selectivity for sub-cellular compartments. Recently several 3,4-dimethoxy-1,8-naphthalimide compounds have been shown to possess noteworthy fluorescence qualities, as well as a remarkable selectivity for lipid droplets. Recent developments in the methodology for the syntheses of these 3,4-dialkoxy compounds appear to have made this class of compounds much more accessible and in this project a family of novel 3,4-dialkoxy-1,8-naphthalimides was designed with longer alkyl chains at the 3 and 4 positions. These compounds were designed to explore the role of these larger alkyl groups in lipid droplet selectivity during cellular imaging as compared to the original 3,4-dimethoxy analogue. Synthesis of these compounds required alterations to the existing methodology to be made, in particular revised methods of purification had to be explored but the targeted family of compounds were ultimately obtained (characterised by 1H NMR, 13C NMR and HRMS). Cellular imaging assays are yet to be completed but once results are made available will provide useful information on the specific implications of the alterations of each of the synthesised products in relation to their lipid droplet selectivity.