Multivalent Heparin Binding and Sensing

Heparin therapy involves the clinical use of heparin as an anti-coagulant, for example, during surgery. At the conclusion of treatment, systemic heparin levels must be quantified to allow accurate dosing of a heparin antidote. This thesis details work towards a better sensing methodology and an improved antidote. A synthetically-simple arginine-functionalized dye – Mallard Blue (MalB) – was synthesised and shown able to detect heparin across a clinically relevant concentration range in biological media such as human serum. The heparin binding of MalB is selective over structurally related glycosaminoglycans and is highly tolerant of electrolytic competition. Indeed, the performance of MalB is comparable with the best heparin sensors currently known and makes it the new best-in-class thionine dye. Mallard Blue was developed into a straightforward competition assay able to report on the relative heparin binding efficiencies of candidate molecules in competitive media, including human serum. Using this assay in conjunction with molecular dynamics modelling techniques, fundamental insights into the binding of poly(amidoamine) (PAMAM) dendrimers to heparin were gained. Interestingly, the medium sized (G2-G4) dendrimers achieved the most charge-efficient heparin binding. Comparisons against derivatives modified with poly(phenylenevinylene) cores revealed native PAMAMs to be exponents of adaptive multivalency, in contrast to the more rigid derivatives’ shape-persistent multivalency. The performance of self-assembled multivalent (SAMul) heparin binder C22G1DAPMA was studied in different biological media and shown to be more charge-efficient than the currently used heparin antidote under competitive conditions. Also, C22G1DAPMA was able to reverse anti-coagulation in heparinized human plasma and degrade on a clinically interesting timescale. Structural modifications afforded two new families of SAMul binders, which unveiled fundamental differences in the chiral preferences of heparin and DNA, along with probing the effects of nanoscale morphology on heparin binding ability and aggregate-stability in serum.