The synthesis, photophysical and biological evaluation of glycosylated naphthalimides for medicinal and material applications

Abstract

This thesis entitled ‘Synthesis, Photophysical and Biological Evaluation of Glycosylated Naphthalimides for Medicinal and Materials Applications’ is divided into 8 chapters, in which Chapter 1, the introduction, gives an overview of the importance of carbohydrates in biology and for prodrug development as well as their use to improve site-selectivity and water solubility. It also explains what glycosidase enzymes are and how they have been used for prodrugs development. A short review on the photophysical and biological applications of naphthalimides, and some previous examples of glycosylated naphthalimides that can be found in the literature are also included. In Chapter 2, the synthesis of a family of glycosylated naphthalimides is described and their spectroscopic and biological properties examined. It was demonstrated that these compounds are good substrates for enzymatic (glycosidase) activity, which cleaves the carbohydrate moiety releasing the naphthalimide core. Interestingly, it was found that when the glycosylated compounds were incubated in vitro (in HeLa cells), no cell uptake occurs. However, the successful implementation of the enzymatic reaction (releasing the naphthalimide core) in vitro, allowed naphthalimide core to rapidly into the cells. Thus, Chapter 2 describes the development of a new class of compounds with interesting photophysical properties that via enzymatic release, could be used for the delivery of a probe inside the cells. Chapter 3 exploits the results obtained in Chapter 2 and aims for the use of this enzymatic-dependent release to deliver selectively (inside or outside the cell) a naphthalimide containing an alkyne group that could undergo click chemistry with modified sugars containing an azide group. These modified sugars, previously fed into the cells, can be metabolically incorporated into the cells’ glycome. Interestingly, these compounds (when released by enzymatic exposure) were able to go into the cell nuclei, thus allowing for click chemistry with modified DNA bases as well. In Chapter 4, the enzymatic-dependent delivery is used in order to deliver a known cytotoxic drug (Amonafide). Thus, Chapter 4 comprises the synthesis, photophysical and biological evaluation of two compounds that could act as prodrugs of Amonafide, as an efficient delivery of Amonafide in vitro was demonstrated in three different cell lines as well as the cytotoxicity induced by the delivery of Amonafide. Chapter 5 describes the use of glycosylated naphthalimides as protein-binding probes, and the affinity of two glycosylated naphthalimides, one being a Tröger’s base of the other one, was successfully assessed using the lectin Concanavalin A (Con A). The changes in the fluorescence emission intensity demonstrated that the binding between the glycosylated naphthalimides and the protein was occurring. The binding with similar proteins is also investigated. Chapter 6 gives a brief description of the different self-assembled structures observed for these glycosylated naphthalimides, which range from microspheres to gels, and studies these different morphologies using confocal microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Chapter 6 gives an overview on the material side of these compounds, and how they could be relevant for different medicinal applications. Chapter 7 gives overall conclusions on glycosylated naphthalimides based on the results obtained from the previous chapters. Finally, Chapter 8 comprises the experimental procedures for the synthesis of the glycosylated naphthalimides described in the previous chapters, as well as the methods used for the different techniques employed.