In this research, an extensive series of self-assembled polyhedral coordination cages, with fixed and known geometries, have been externally functionalised with saccharides, to act as luminescent biosensors for lectins.

Amongst this family of cages are the M₄L₆tetrahedral and the M₈L₁₂ cube, that are prepared from the combination of bis(pyrazolyl-pyridine) ligands with labile M²⁺ions (particularly Co²⁺, Zn²⁺, Fe²⁺, Ni²⁺and Cd²⁺). The cubic cage has been previously functionalized with water soluble hydroxyl groupsand alkyne appendages.

By utilising CuAAC ‘click’ chemistry, L^15CC and L^23CC were reacted with 1-azido derivatives of a range of different saccharides (Glc, Gal, Man, LFuc and 3’-SL/6’-SL). These ligands were then combined with M²⁺salts, to afford tetrahedral and cubic cages (Scheme 1) that have been fully characterised by spin-echo paramagnetic ¹H NMR, DOSY NMR, UV-VIS spectroscopy and HR-ES-MS.

Another abstract will describe the results of analytical testing for these cages, against lectin partners such as Soybean agglutinin (SBA), Jacalin, Wheat germ agglutinin (WGA), and Sambucus Nigra - Elderberry Bark (SNA,EBL) through turbidimetry and haemagglutination assays (sheep’s blood in Alsever’s). Current work is focused on testing against cholera toxin lectin (CTxB) and the synthesis of functionalised M₁₂L₁₆ cages. The LFuc and Man variants of the cubic cage are currently being tested in co-crystallisation trials with a colloborator and any results of these trials, and further lectin testing, will be presented.

If time permits, the synthesis and application of cubic cages with different external functionality will also be described.

Scheme 1 (attached image): A) Simplified scheme for the self-assembly of M₄L₆and M₈L₁₂ Co cages with 12 and 24 sialyllactose units on their periphery; B) Crystal structure of the Ni₈ cage - closely represents how these saccharides would extend away from the cubic cage exterior.

Callum L Pritchard

University of Warwick

Appearances