Rabbit IgG-imprinted nanoMIPs by solid phase synthesis: Effect of cross-linker on affinity and selectivity

The solid phase synthesis (SPS) of molecularly imprinted nanopolymers (nanoMIPs) represents an innovative method to prepare nanomaterials with tailor-made molecular recognition properties towards peptides and protein. The synthesis of nanoMIPs by SPS usually involves a pre-polymerization formulation where the cross-linker is invariably N,N′-methylen-bis-acrylamide (BIS). To date, the effect on the binding properties of nanoMIPs using other than BIS cross-linkers has never been reported. In this work, in order to investigate the effect of different cross-linkers in protein-imprinted nanoMIPs prepared by SPS, alongside BIS we considered other similar cross-linkers: N,N'-ethylene dimethacrylamide (EDAM), N,O-bis-methacryloylethanolamine (NOBE), ethylene glycol dimethacrilate (EDMA) and glycerol dimethacrylate (GDMA), replacing them for the BIS in pre-polymerization mixtures. Synthetized nanoMIPs were homogeneous, with a polydispersity index of 0.24-0.30 and mean diameter of 129-169 nm in water. The binding properties of the nanoMIPs were measured by equilibrium partition experiments with the template, rabbit IgG (RIgG), and selectivity was evalued with respect to bovine IgG (BIgG), bovine serum albumin (BSA) and hen egg lysozime (LZM). The experimental results show that all the cross-linkers, with the exception of EDMA, gave nanoMIPs with high binding affinities for the template (BIS: 16.0 x 10^6 mol-1 L, EDAM: 8.8 x 10^6 mol-1 L, NOBE: 15.8 x 10^6 mol-1 L, GDMA 12.8 x 10^6 mol-1 L), medium to high imprinting factors (BIS: 12.3, EDAM: 5.5, NOBE: 7.2, GDMA 11.6) and selectivity towards other proteins good but markedly dependent on the structure of the cross-linker, confirming the importance of the latter in the SPS of imprinted nanopolymers