Herein, a new method for the selective detection and facile separation of creatinine is reported. This method is based on the magnetic creatinine molecularly imprinted polymer nanoparticles (MCMIPNs), which were prepared by the polymerization of a methacrylic acid (MAA)/creatinine complex in the presence of magnetic Fe3O4 nanoparticles functionalized with 3-(trimethylsilyl)propyl methacrylate (TMSPMA) and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The polar carboxylic acid groups of MAA were introduced into the molecularly imprinted polymers to increase the interaction of template molecules and functional monomers, which is the key factor in the selectivity. The structure, size, adsorption/desorption process, reusability, selectivity, and magnetic and thermal properties of MCMIPNs were characterized. Moreover, various factors influencing the adsorption capacity (contact time, pH, amount of Fe3O4 nanoparticles, and initial concentration of creatinine) were investigated. The MCMIPN with a size of 25 nm exhibited 99% loading efficiency with a remarkable affinity for creatinine. The pH dependency of MCMIPN was utilized for the highest loading and guest release with nearly quantitative analyte recovery rate. The imprinting efficiency of MCMIPN was evaluated and was compared with that of the corresponding magnetic non-imprinted polymer (MNIP). The MCMIPN indicated excellent recognition and binding affinity, and the selectivity factors of creatinine relative to creatine, N-hydroxysuccinimide (NHS), and L-tyrosine were 4.47, 8.20, and 4.55, respectively.
