Changes in the Porosity and Permeability of a Molecularly ImprintedMembrane Induced by the Adsorption of a Trace Quantity of Template

摘要

It is known that the diffusive permeability of solutes within a thin layer of molecularly imprinted polymer(MIP) may be affected by specific binding of the MIP with its template molecule. This phenomenon, termed the gateeffect, shows promise for the development of novel biomimetic sensors. However, the mechanism underlying this effect isstill unclear; although the relationship between the specific adsorption of a template and the corresponding porosity andpermeability of the polymeric film or membrane is very important, this association has not yet been examined in detail.We therefore studied this relationship using a molecularly imprinted self-supporting membrane (MISSM) possessingchiral specificity, specially developed as a tool for investigating the gate effect. Both the diffusive permeability andvolume porosity of the MISSM were sensitive to the presence of the template compounds (D and L-phenylalanine) atconcentrations as low as 5 μM, while, at the same time, insensitive to the enantiomer of the template. The relationshipbetween the amount of adsorbed template and the equilibrium template concentration followed the expected Langmuirisotherm pattern, which indicates the thermodynamic homogeneity of binding sites in the MISSM. This study alsodemonstrated that the relative concentration of the adsorbed template in the membrane was only 3 ppm and relative siteoccupation was only 1% following exposure to a 5 μM concentration of the template. These results show that the gateeffect may be advantageously exploited during application of MIPs in amplifiers or sensors offering high sensitivity.