Novel superparamagnetic core-shell molecular imprinting microspheres towards high selective sensing

Novel superparamagnetic core-shell imprinting microspheres (MCSIMs) were synthesized using magnetite microspheres with 350 nm diameter and 70 nm thickness silica gel to form core-shell Fe3O4/SiO2 composite for template phenylephrine (Phen) recognition and high efficiency separation. Compared to the previous imprinting recognition, the main advantage of this strategy lies in two aspects: one is the high stability and monodispersity of the MCSIMs structure, the other is the use of superparamagnetic Fe3O4/SiO2 microspheres as an immobilization matrix and separation tool, thus greatly simplifying time-consuming washing steps. The affinity and selectivity of the MCSIMs were monitored by QCM and electrochemistry measurements. Imprinting microspheres have a remarkable affinity to Phen over that of structurally related molecules, including DA, EP, Phe and Tyr. The relative binding selectivity for different analytes estimated from amperometric signals was Phen : DA : EP = 40 : 5 : 1. The MCSIMs sensor showed a high sensitivity (400 mu A mM(-1)), short response time (reaching 98% within 10 s), and broad linear response range from 1 mu M to 0.1 mM and low detection limit (0.1 mM). Additionally, the results of control experiments showed that only negligible signal was obtained for non-imprinting microspheres. This could be reasonably attributed to the unique surface pores, charges and especially the nature of the functional groups inside MCSIMs cavities.