Nonaqueous Emulsion Polymerization: A Practical Synthetic Route for the Production of Molecularly Imprinted Nanospheres

Monodisperse, molecularly imprinted nanospheres were synthesized by nonaqueous (mini)emulsion polymerization using a standard monomer mixture of methacrylic acid and ethylene dimethacrylate containing the drug propranolol as a template. The preparation conditions (solvent, amount of surfactant, and amount of employed template) were extensively varied in order to assess their effect on the properties of the resulting polymer nanoparticles. The molecular recognition capability of the nanospheres was evaluated in batch rebinding experiments, and the effect of the nanosphere preparation conditions as well as of the reaction conditions was investigated. In this way, optimal preparation protocols for molecularly imprinted nanoparticles under nonaqueous conditions with the use of a nonionic emulsifier were identified, which lead to nanospheres with a diameter of around 100 nm having an enhanced capacity of specific template rebinding compared to both nonimprinted nanospheres and to particles obtained by emulsion polymerization in water. Best results were obtained with nanospheres prepared in N,N-dimethylformamide/ n-hexane with a high functional monomer to template ratio. The enantioselectivity of the rebinding process was also demonstrated.