# Biomedical Applications of Polymeric Cryogels
## 3 Cryogels in Medical Applications
### Capturing of Target Molecules  
Capturing of a target molecule from a complex medium is an important factor in modern biotechnology. The effective separation of the target can be achieved by using supermacroporous materials and longtime physically and chemically stable sorbents. Lower mass transfer resistance and pressure drop properties of cryogels make them useful as sorbents for the separation of target molecules from a complex medium [10]. Traditional gels are delicate and fragile. Whereas, cryogels are elastic, soft, sponge-like materials without deformations. Therefore, these materials can be used in the field of biochromotography. Cryogel matrices are widely used in bioseparation technology such as separation and removal of proteins, peptides, nucleotides and even toxic metals. The removal of dominating proteins such as human serum albumin (HSA) and immunoglobulins from the biological sample is crucial to allow the analysis of less components. The promising cryogels can be used as matrices to make these minor components more accessible. Different technologies such as immunoaffinity, dye affinity, and molecular imprinting can be applied with cryogel-based matrices for the effective separation and removal of target molecules. [PERSON] and co-workers used HEMA and \(N\),\(N\)-bis (2,6-disisopropylphenyl) perylene-3,4,9, 10-tetracarboxylic diimide (DIPPER) monomers for preparation of P(HEMA-DIPPER) monolithic cryogels and used these cryogels for capturing of albumin [27]. The maximum adsorption for albumin was reported 40.9 mg/g. Monolithic cryogels are even more attractive with shorter processing times, and they have better ease use and higher overall ease of capacity. The dominant interaction between matrices and target molecules could be attributed to the hydrophobic interactions due to the hydrophobic character of DIPPER. [PERSON] and co-workers synthesized supermacroporous PHEMA-based cryogel with \(N\)-methacryloyl-(L)-histidine methyl ester (MAH) as the specific ligand for purification of immunoglobulin G (IgG) from human plasma. Supermacroporous cryogels were produced by free-radical polymerization initiated by tetrametiletilendiamin and ammonium persulfate pair in an ice bath. Supermacroporous cryogels with 38.6 m\({}^{2}\)/g surface area and containing 113.7 umol MAH/g were used in the purification of IgG from human plasma. They reported 24.7 mg/g maximum adsorption capacity of IgG. The adsorption capacity of supermacroporous cryogels was significantly improved due to the MAH incorporation into the cryogel. They obtained 97.3 mg/g IgG adsorption capacity from human plasma [28]. Also, 94.6% purity of IgG by SDS-PAGE (sodium dodecyl sulfate-polyacrylamideamide gel electrophoresis) has been indicated in this study. In another study, [PERSON] et al. used immobilized metal affinity-based cryogels for the separation of IgG. They used poly(ethylene imine) (PEI) as the chelating ligand covalently coupled with PHEMA cryogels after activation and then Cu(II) ions were chelated to the PEI bound PHEMA cryogels. The separation was selectively achieved up to 72.28 mg/g cryogel. As a conclusion, they have reported that IgG separation was performed by immobilized metal affinity-based cryogel column successfully and selectively (Figure 3) [29]. In another study, they prepared and characterized two different combinations for the purification of IgG. They synthesized thiophilic PHEMA-based and thiophilic composite cryogel membranes via attachment of 2-mercaptoethanol as an affinity ligand. They reported 27.5 mg/g and 68.7 mg/g maximum adsorption capacities for thiophilic PHEMA and thiophilic composite cryogel membranes, respectively [30]. Besides immobilization-based affinity chromatography, it is also possible to separate biomolecules with molecularly imprinted cryogels and then to use them for the separation of molecules. Molecular imprinting-based cryogels (MIC) are prepared with high affinity and specificity binding sites to the target molecules.