Thermoresponsive Glycopolypeptide Containing Block Copolymers, Particle Formation, and Lectin Interaction

Amphiphilic block copolymers with a thermoresponsive poly(N-isopropylacrylamide) block and a glycopeptide block are synthesized and particle formation as well as interaction of the glyco-corona with lectins is investigated. The synthetic route comprises the preparation of block copolymers by N-carboxyanhydride polymerization and subsequent deprotection to obtain pH- and thermoresponsive poly(l-glutamic acid)-b-poly(N-isopropylacrylamide) (pGA-b-pNIPAM), which is then further modified with different amino sugars by a versatile coupling method with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholin-4-ium chloride (DMT-MM). The glycosylated pGA-b-pNIPAM block copolymers are investigated with regard to cloud point temperatures (T_cp ), particle size, and stability. The morphology of the particles is visualized using cryo-SEM. Zeta potential measurements are indicating that the saccharide moieties are located on the surface of the particles. This assumption is further substantiated by quantitative lectin interaction assays with nonaggregated and aggregated glycosylated pGA-b-pNIPAM. The interaction of the model lectin ConA with the block copolymers is independent of the degree of substitution in the nonaggregated state at room temperature. However, at 37 °C, when particles of pGA-b-pNIPAM are present, the interaction becomes stronger with increasing degree of substitution. This interaction with lectins can be used for targeting saccharide-modified particles in drug delivery.