Biotinylated MCM-41 channels as a sensing element in planar bilayer lipid membranes

Mesoporous silica MCM-41 and biotinylated MCM-41 (biotin-MCM-41) channels were incorporated into planar bilayer lipid membranes (BLMs). The BLMs containing MCM-41 and biotin-MCM-41 exhibited a marked shift in the chord current, often accompanied by rectangular, channel-like currents, which were ascribable to ion translocation through the pores of MCM-41. The penetration of lipid molecules into the pores of biotin-MCM-41 was indicated by fluorometric measurements with rhodamine B-tagged lipid. The ion transport, through MCM-41 and biotin-MCM-41 channels, was symmetrical with respect to the applied voltage. When biotinylated MCM-41 was incorporated into BLMs, the integrated current decreased with an increase in the concentration of avidin ranging from 2.9 pM to 1.5 nM for the micro BLMs formed by the tip–dip method and from 1.5 to 15 nM for the BLM formed by the folding method. Bovine serum albumin (BSA) did not induce any changes in the integrated currents, showing the selective recognition of avidin by the biotin sites of MCM-41 channels in the BLM. The present results show the potential of biotin-MCM-41 channels as a sensing element that exhibit the on/off gating of ion transport for ion-channel sensors.