Molecularly Imprinted Membranes: Past, Present, and Future.

More than 80 years ago, artificial materials with molecular recognition sites emerged. The application of molecular imprinting to membrane separation has been studied since 1962. Especially after 1990, such research has been intensively conducted by membranologists and molecular imprinters to understand the advantages of each technique with the aim of constructing an ideal membrane, which is still an active area of research. The present review aims to be a substantial, comprehensive, authoritative, critical, and general-interest review, placed at the cross section of two broad, interconnected, practical, and extremely dynamic fields, namely, the fields of membrane separation and molecularly imprinted polymers. This review describes the recent discoveries that appeared after repeated and fertile collisions between these two fields in the past three years, to which are added the worthy acknowledgments of pioneering discoveries and a look into the future of molecularly imprinted membranes. The review begins with a general introduction in membrane separation, followed by a short theoretical section regarding the basic principles of mass transport through a membrane. Following these general aspects on membrane separation, two principles of obtaining polymeric materials with molecular recognition properties are reviewed, namely, molecular imprinting and alternative molecular imprinting, followed the methods of obtaining and practical applications for the particular case of molecularly imprinted membranes. The review continues with insights into molecularly imprinted nanofiber membranes as a promising, highly optimized type of membrane that could provide a relatively high throughput without a simultaneous unwanted reduction in permselectivity. Finally, potential applications of molecularly imprinted membranes in a variety of fields are highlighted, and a look into the future of membrane separations is offered.

Green polymers from Geobacillus thermodenitrificans DSM465--candidates for molecularly imprinted materials.

Novel molecular recognition materials were prepared from water soluble proteins from thermophile G. thermodenitrificans DSM465 by an alternative molecular imprinting method. Water soluble proteins from G. thermodenitrificans DSM465 were converted into the molecularly imprinted materials by adopting 9-EA as a print molecule. The molecularly imprinted protein membranes recognized As in preference to Gs. The adsorption isotherms led to the conclusion that molecular recognition sites toward As were constructed by the presence of 9-EA during the membrane preparation process. The affinity constant between As and the molecular recognition site thus constructed was determined to be 1.75 x 10(5) mol(-1) dm(3). The results obtained in the present study suggest that water soluble proteins from G. thermodenitrificans DSM465 is one of environmentally-friendly 'green' polymers to be converted into molecular recognition materials by applying an alternative molecular imprinting method.

Polymeric Pseudo-Liquid Membranes from Poly(N-oleylacrylamide).

A polymeric pseudo-liquid membrane (PPLM) was constructed from poly(N-oleylacrylamide) (PC18AAm), which exhibited a rubbery state under membrane transport conditions and used as the membrane matrix. In the present study, dibenzo-18-crown-6 (DB18C6) and dibenzo-21-crown-7 (DB21C7) were adopted as transporters for alkali metal ions. KCl was adopted as a model substrate for DB18C6 and CsCl the latter. Chiral transporter, O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (AAMC) was used as a transporter for chiral separation of a racemic mixture of phenylglycine (Phegly). The l-somer was transported in preference to the antipode. The present study revealed that PPLMs are applicable to membrane transport, such as metal ion transport and chiral separation.

Effect of constituting amino acid residue numbers on molecularly imprinted chiral recognition sites.

In the present study, the effect of constituting amino acid residue numbers of oligopeptide derivatives, which are candidate materials to construct molecular recognition sites, on chiral recognition ability was investigated. Chiral recognition sites were formed from oligopeptide derivatives, of which constituting amino acid residue numbers were three to six, by adopting an alternative molecular imprinting. It was made clear that the number four, in other words, the tetrapeptide derivative, is the best candidate material to form a chiral recognition site.