Self-assembling Pd₂L₄ cages as carbohydrate receptors

Carbohydrates are one of nature's most abundant and versatile molecules. Several diseases have been linked to processes involving carbohydrates (e.g. diabetes, infection, and cancer metastasis). Many other regular processes are also mediated by carbohydrate molecules, including hormonal activities, immune surveillance and inflammatory responses. Understanding these processes is therefore of great interest as intervening can be exploited in the context of medicinal therapies and biomedical research in general. Such technologies are often limited due the low availability of molecules that can selectively bind and/or detect a certain carbohydrate.
This dissertation describes the use of self-assembling Pd₂L₄ cages as carbohydrate receptors to expand molecular systems that can selectively bind carbohydrates. Therefore, literature described Pd₂L₄ cages were modified to be better soluble in apolar organic or aqueous media. Subsequent titration of carbohydrates revealed that the modified cages can be used as receptors for carbohydrates. In particular, it was found that most of the self-assembling systems have a preference for equatorial carbohydrates similar as covalent cages described in literature. Interestingly, when urea moieties were used instead of the traditional amide moieties, the selectivity went to carbohydrates with axial hydroxyl groups. Similar change of selectivity was observed when a palladium centre with a vacant site was incorporated in the receptor. Lastly, the water soluble Pd₂L₄ cage was titrated with other biomedical relevant molecules, showing good selectivity for medical imaging relevant compounds compared with biological common molecules. All in all, this dissertation paves the way for generalised designs of polar bis-pyridyl ligands as carbohydrates receptors.