Aqueous chromatography system using temperature‐responsive polymer‐modified stationary phases

Abstract

Extensive research has been carried out on functional polymers which are currently playing important roles in various fields such as medicine and engineering. Such functional polymers which respond to various kinds of stimuli are termed 'intelligent materials'. Poly(N-isopropylacrylamide) (PNIPAAm), a temperature-responsive polymer, was utilized as a chromatography column matrix modifier for a novel chromatographic approach in which only aqueous media are used as a mobile phase. The ability of the developed temperature-responsive chromatography system to separate solutes without using an organic solvent is advantageous from the point of view of maintaining the structure and activity of bioactive compounds. Recently, we designed and synthesized a new pH- and temperature-responsive copolymer as a representative of such environment-responsive polymers and grafted it onto aminopropyl silica beads. The products were evaluated as HPLC packing materials for separation systems based on a new concept, according to which the properties of the stationary phase surface are altered by external stimuli such as pH and temperature. This chromatography system utilizing the PNIPAAm copolymer is very useful for the separation of bioactive substances, such as proteins and peptides, because separation in the aqueous mobile phase is controlled solely by changing the temperature. This analytical system reduces organic waste because no organic solvent is used to separate the solutes and can therefore be classified as environmentally friendly. Future medical and pharmaceutical applications are expected.

Thermo‐Responsive Polymer Brushes as Intelligent Biointerfaces: Preparation via ATRP and Characterization

“…PIPAAm exhibits a reversible temperature-dependent phase transition in aqueous solutions at its lower critical solution temperature (LCST) of 32 8C. [8] This intrinsic thermo-responsive property is widely used in biomedical applications, such as controlled drug and gene delivery systems, [9,10] bioconjugates, [11,12] microfluidics, [13] bioseparation, [14,15] cell culture substrates, [16][17][18] and tissue engineering for regenerative medicine. [19,20] For preparing useful and effective thermo-responsive surfaces, various types of PIPAAm modification techniques have been developed and utilized.…”

Thermo‐Responsive PNIPAAm Copolymers with Hydrophobic Spacers

“…These materials are currently being used in a variety of applications including cell attachment, drug release, separation membranes and tissue engineering. [3][4][5][6] The LCST transition in PNIPAAm can be triggered using a variety of external stimuli such as temperature, pH and solvent composition. The two main effects responsible for the LCST are hydrophobic and hydrogen-bonding interactions.…”

Analysis of Psychoactive Drugs by Temperature-Responsive Chromatography

“…We have been investigating temperature-responsive chromatography, in which a thermo-responsive polymer such as poly(N-isopropylacrylamide) (PNIPAAm) is used as the stationary phase [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. PNIPAAm exhibits thermally reversible solubility changes in aqueous solutions in response to temperature changes across its lower critical solution temperature (LCST).…”

“…For example, using n-butyl methacrylate (BMA) as a hydrophobic comonomer leads to increased hydrophobicity [8]. Recently, Hiruta et al reported that aromatic amino acids like L-phenylalanine and L-tryptophan were introduced to PNIPAAm as a comonomer and a new separation mode featuring molecular recognition was successfully introduced to the stationary phase, due to π-π interactions and hydrogen bonding [16].…”