Development of a Molecular Recognition Ion Gating Membrane and Estimation of Its Pore Size Control

Abstract

We have fabricated a molecular recognition ion gating membrane. This synthetic membrane spontaneously opens and closes its pores in response to specific solvated ions. In addition to this switching function, we found that this membrane could control its pore size in response to a known concentration of a specific ion. The membrane was prepared by plasma graft copolymerization, which filled the pores of porous polyethylene film with a copolymer of NIPAM (N-isopropylacrylamide) and BCAm (benzo[18]crown-6-acrylamide). NIPAM is well-known to have an LCST (lower critical solution temperature), at which its volume changes dramatically in water. The crown receptor of the BCAm traps a specific ion, and causes a shift in the LCST. Therefore, selectively responding to either K(+) or Ba(2+), the grafted copolymer swelled and shrank in the pores at a constant temperature between two LCSTs. The solution flux in the absence of Ba(2+) decreased by about 2 orders of magnitude over a solution flux containing Ba(2+). The pore size was estimated by the filtration of aqueous dextran solutions with various solute sizes. This revealed that the membrane changed its pore size between 5 and 27 nm in response to the Ba(2+) concentration changes. No such change was observed for Ca(2+) solutions. Furthermore, this pore size change occurred uniformly in all pores, as a clear cut-off value for a solute size that could pass through pores was always present. This membrane may be useful not only as a molecular recognition ion gate, but also as a device for spontaneously controlling the permeation flux and solute size.

Fabrication of Functional Membrane with Activated Ester via Plasma-Induced Graft Polymerization

“…Filling ratio Φ [cm 3 3 ] and was assumed to be 1.0 [8]. In the porous PE substrate, surface area of outer surface is about 10 4 times smaller than that of pore surface, thus the amount of grafted polymer on the outer surface was ignored.…”

“…PIGP also has favorable features that can modify only the pore surface throughout membrane thickness and cause little damage to the substrate. Via PIGP, several fascinating membranes such as pervaporation membrane having high performance [1], ion gating membrane and biomolecular recognition gating membrane whose permeability can be finely controlled by specific ion and biomolecular signal [3,4], protein refolding assisting membrane having zwitterionic sulfobetaine group [5], and proton exchange membrane for fuel cell [6] have been exploited up until now.…”

Fabrication of Precursor Membrane with Reactive Groups via Plasma-Induced Graft Polymerization

“…The porous substrate having many nano to micron-sized pores inside is an essential material that is widely used in filtration [1], separator [2], substrate for pore-filling membrane [3], gating membrane [4], membrane chromatography [5], and so on. The convective mass transfer through the pores plays an important role for little pressure loss and energy conservation, using it in filtration or membrane chromatography purposes.…”

Synthesis of thermoresponsive polymeric micelles of PNIPAAm‐b‐OMMA as a drug carrier for loading and controlled release of prednisolone

“…This property of hydrophobically modified PNIPAAm gel has been investigated in many fields. 6,23,[31][32][33][34][35] Because the polymers possess high drug loading capacity of inner core as well as unique disposition characteristics in the body, they are used as novel drug carriers in the field of drug targeting. 36,37 The advantageous properties of polymeric micelles as drug carriers are associated with solubilization of low-solubility drugs and potentials for tumor targeting and controlled drug release.…”