Effect of reversible cross-linker, N,N '-bis(acryloyl)cystamine, on calcium ion adsorption by imprinted gels

Imprinted gels incorporating two different breakable cross linkers, a PbMAA (2) complex and a disulfide (S-S) bond, were prepared by radical polymeriza tion. After the lead ions were removed by washing, these gels showed a high affinity for calcium ions. Breakage and subsequent reconnection of the S-S bonds in the absence of Ca2+ decreases the Ca2+ binding affinity of the ge l. This indicates that random reconnection of the S-S bonds produces a frus tration in the adsorption of Ca2+ by the carboxyl groups. However, if the S -S bonds were reconnected in the presence of Ca2+ and the Ca2+ was subseque ntly removed (the post-imprinting technique), the resulting gels showed a h igher binding affinity for Ca2+. This indicates that the post-imprinting te chnique creates a more favorable conformation for Ca2+ binding in the polym er network. We interpret our data to mean that "memory" of target binding s ites was encoded effectively into the polymer network by the initial imprin ting technique and then enhanced by the post-imprinting technique.