Synthesis of thermo-responsive glycopolymersviacopper catalysed azide–alkyne ‘click’ chemistry for inhibition of ricin: the effect of spacer between polymer backbone and galactose

Abstract

Block copolymers poly(diethylene glycol methyl ether methacrylate)-block-poly(2-hydroxy ethyl methacrylate) (PDEGMA-b-PHEMA) and poly(diethylene glycol methyl ether methacrylate)-block-poly(ethylene glycol methyl ether methacrylate) PDEGMA-b-PPEGMA as well as homopolymers of PPEGMA and PHEMA were generated via Reversible Addition–Fragmentation chain Transfer (RAFT)polymerisation. The terminal hydroxyl moieties on the HEMA and PEGMA blocks were alkyne functionalised and conjugated to azide functionalised galactoseviaCuAAC leading to the glycopolymers PDEGMA-b-P(HEMA-Gal) and PDEGMA-b-P(PEGMA-Gal). Both dynamic light scattering (DLS) and transmission electron microscopy (TEM) prove the thermo-responsive characteristics of the polymers, due to the PDEGMA blocks, with the formation of polymeric micelles above a temperature of 40 °C. These glycopolymers were tested for their binding efficiency to ricin, a dangerous plant toxin reportedly weaponised by terrorist organisations. The binding experiments establish an order of ricin inhibition of P(HEMA-Gal) < P(PEGMA-Gal) < PDEGMA-b-P(HEMA-Gal) ≤ PDEGMA-b-P(PEGMA-Gal) showing that micelles are advantageous, but also that the introduction of a flexible spacer between polymer and galactose can enhance binding to a certain extent.