Macroporous gels prepared at subzero temperatures as novel materials for chromatography of particulate‐containing fluids and cell culture applications

Abstract

Macroporous gels (MGs) with a broad variety of morphologies are prepared using the cryotropic gelation technique, i. e. gelation at subzero temperatures. These highly elastic hydrophilic materials can be produced from practically any gel-forming system with a broad range of porosity extending from elastic and porous gels with pore sizes up to 1.0 microm to elastic and sponge-like gels with pore sizes up to 100 microm. The versatility of the cryogelation technique is demonstrated by use of different chemical reactions (hydrogen bond formation, chemical cross-linking of polymers, free radical polymerization) mainly in an aqueous medium. Appropriate control over solvent crystallization (formation of solvent crystals) and rate of chemical reaction during the cryogelation allows the reproducible preparation of cryogels with tailored properties. Different approaches, such as chemical modification of reactive groups, grafting of the pore surface with an appropriate polymer, or direct copolymerization with functional monomers are used for control of the surface chemistry of MGs. Typically, MGs with pore sizes up to 1.0 microm are produced in the shape of beads and MGs with pore size up to 100 microm are prepared as monoliths, discs, and sheets. The difference in porous structure of MGs defines the main applications of these porous materials. Elastic beaded MGs are mostly used as carriers for cell and enzyme immobilization or for capture of low-molecular weight targets from particulate-containing fluids in expanded-bed mode. However, the elastic and sponge-like MG monoliths with interconnected pores measuring hundreds of mum have been successfully used as monolithic columns for chromatography of particulate-containing fluids (crude cell homogenates, viruses, whole cells, wastewater effluents) and as three-dimensional scaffolds for mammalian cell culture applications.

Supermacroporous chemically cross-linked poly(aspartic acid) hydrogels

“…In the case of hydrogels, it is a well-established technique to create supermacroporous hydrogels below the melting point of the solvent [13]. The major part of the solvent is frozen during cryogelation, while the reaction occurs in the liquid phase, which is a concentrated solution of the polymer [16,17]. The growing crystals of the solvent act as templates for the interconnected pores forming after melting.…”

Removal of endocrine‐disrupting compounds from water using macroporous molecularly imprinted cryogels in a moving‐bed reactor

“…The macroporous cryogels designed as monolithic columns with pores of up to 100 lm in size and bearing different functionalities were shown as effective adsorption media in the bioseparation area especially with processing the particulate containing fluids [14,16]. Recently, the macroporous cryogels prepared in the form of monoliths containing embedded molecularly imprinted polymer (MIP) or non-MIP (NIP) particles were shown to be effective as adsorbents for the removal of E2 from water effluents [17].…”

Imaging the Structure of Macroporous Hydrogels by Two-Photon Fluorescence Microscopy

“…Mercury porosimetry, which is the most widely used technique for the determination of the porous volumes and the pore size distributions has been used for dry macroporous gels [10][11][12] . This method, however, is not suitable for soft materials 19 and cannot be applied to swollen samples. The macroporous structure can be seen using scanning electron microscopy (SEM) in the dried state and environmental scanning electron microscopy (ESEM) in the swollen state (in water) 18,19 .…”

“…This method, however, is not suitable for soft materials 19 and cannot be applied to swollen samples. The macroporous structure can be seen using scanning electron microscopy (SEM) in the dried state and environmental scanning electron microscopy (ESEM) in the swollen state (in water) 18,19 . In most cases, however, SEM and ESEM techniques provide only a qualitative information.…”

“…This techniques probes the macroporous gel structure down to 200 µm below the gel surface. Confocal fluorescence microscopy yields 3-D images of objects stained with a fluorophore, e.g., walls in swollen macroporous gels 19 or of biomedical research specimens 25 . In the most favorable situation, the maximum observable depth is close to 200 µm.…”