# Biomedical Applications of Polymeric Cryogels
## 3 Cryogels in Medical Applications
### Cryogels for Tissue Engineering
#### 3.4.2 Cell Separation  
Cell separation was one of the preliminary applications of supermacroporous monolithic columns including cryogels. The accepted strategy known as fluorescence-activated cell sorting (FACS) was used for investigating cell populations. This method relies on fluorescent labeling, by this way, the cells could be divided into sub-populations. Another alternative approach for cell sorting identified as magnetic-activated cell sorting (MACS) allows separation and capturing of targeted cells from complex media. Apart from these two cell sorting standards, affinity-based cryogels have superior efficiencies with their more portable and cost-effective properties. In addition, cryogel adsorbents provide high surface area for the cell attachment and high liquid flow with low flow resistance [53].  
In a study, microbial cell (histidine tagged _Escherichia coli_) separation have been performed using Cu\({}^{2+}\)-IDA supermacroporous monolithic columns with continuously preserving cell viability [64]. Another example from literature consists of the ligand immobilization to the support matrices offers effective cell separation. 2-(Dimethylamino)ethyl methacrylate (DMAEMA), MBAA and AAm was preferred to synthesize of cryogel matrix using ion-exchange ligands. Amino groups of the ligands show affinity against _E. coli_ cells with a 70-80% recovery ratio after desorption step. SEM photographs of matrices with bound _E. coli_ cells were given in Figure 5[65]. To give an example for virus capturing, streptavidin immobilized monolith was prepared to allow single-step capturing of biotinylated Moloney Murine Leukemia Virus (MoMuLV) from cell cultures. These matrices were synthesized using acrylamide, MBAA, and glycidyl methacrylate via cryopolymerization [66].  
Figure 5: SEM photographs of matrices with bound _E. coli_ cells [65].  
Supermacroporous cryogels make it easy to process human body fluids including blood. These monoliths offer a high flow rate, enabling cells to pass through the porous matrix. In a previous study, bacteriophage immobilized poly(dimethylacrylamide) monoliths were applied for von Willebrand factor (vWF) capturing from blood samples [67].  
Immunoglobulins playing crucial roles in immune system functioning are attractive molecules for the development of affinity-based cryogels. Antibody-affinity-based cryogels have been known as effective matrices for cell separation due to their specificity and variety. The interactions between immunoglobulins and antigens present on the cell surface enable specific cell separation such as T- and B-lymphocytes separation. In a study conducted in our research group, poly(hydroxyethyl methacrylate)/poly(ethylene imine)-Cu(II) (PHEMA/PEI-Cu(II)) cryogels were prepared for IgG purification from human plasma with immobilized metal affinity chromatography [30].  
Separation of mammalian cells considers the availability of appropriate matrices necessary. Cryogels can well serve as adsorbents for the separation of mammalian cells. In a previous study, [PERSON] et al. (2004) prepared PVA cryogel beads and protein A immobilized dimethyl acrylamide (DMAAm) monolithic cryogel to specifically capture human acute myeloid leukemia KG-1 cells and fractionate human blood lymphocytes. The cell capturing capacity of protein A immobilized dimethyl acrylamide (DMAAm) monolithic cryogel was found to be higher (90-95%) than that of cryogel beads (76%). On the other hand, the separation of T- and B-lymphocytes was successfully performed with high yields.