Formation of hydrogels

In this section, the important concepts related to the formation of hydrogels by free radical copolymerization/cross-linking are examined. Greater depth beyond the scope of this chapter can be obtained from textbooks on polymer chemistry and the papers cited herein. As stated earlier, almost all gels produced from monomers for pharmaceutical applications are synthesized by free radical chain polymerizations. 

Hu BH, Messersmith PB (2003) Rational design of transglutaminase substrate peptides for rapid enzymatic formation of hydrogels. J Am Chem Soc 125 14298-14299... 

Title Methods for the Formation of Hydrogels Using Thiosulfonate Compositions and Uses Thereof... 

Cross-linking can be achieved by physical interactions and chemical reactions. Concentrated solutions of low molecular weight dextran (Mw 6000 gmoR1) lead to the formation of hydrogels by crystallisation [51]. Cross-linking with epichlorhydrin gives commercial products known as Sephadex... 

Fig. 20 Synthesis of dextran methacrylate usable for the formation of hydrogels after photo-initiated cross-linking [175]...

Jin R, Hiemstra C, Zhong Z et al (2007) Enzyme-mediated fast in situ formation of hydrogels from dextran-tyramine conjugates. Biomaterials 28 2791-2800... 

The crosslinking of starch at the droplet interface in inverse miniemulsion leads to the formation of hydrogels. The formulation process for the preparation of crosslinked starch capsules in inverse miniemulsion is schematically shown in Fig. 10. The influence of different parameters such as the amount of starch, surfactant P(E/B-fe-EO), and crosslinker (2,4-toluene diisocyanate, TDI) on the capsule size and stability of the system were studied. The obtained capsules were in a size range of 320-920 nm. Higher amounts of starch and surfactant result in a smaller capsule size. The TEM images of crosslinked starch capsules prepared with different amount of crosslinker (TDI) are presented in Fig. 11. The nanocapsules can be employed as nanocontainers for the encapsulation of dsDNA molecules with different lengths [114] and for the encapsulation of magnetite nanoparticles. 

In order to understand the porous structure formation of adsorbents co-precipitated from both three and four-component systems, succession of formation of hydrogels and... 

Deming et al. [53-55] also described the formation of hydrogels from di-and triblock copolypeptides based on PLLeuio-4o and PLLysgo-sso (hydrobromide) gelation occurred at a polymer concentration as low as 0.25 wt %. It is thought that the scaffold of the hydrogel is built of twisted fibril assemblies with a core of closely packed poly(L-leucine) a-helices and a corona of cationic poly(L-lysine) chains. 

ROSIAK, JANUSZ M. Radiation Formation of Hydrogels for Biomedical Applications. International Atomic Agency Report (2002). 

The cyclic G-quartet structure was first identified in 1962 as the basic building block for formation of hydrogels by 5 -GMP I. Using fiber... 

Earlier, we reported that complexes of lithium bromide (LiBr) with copolyether-urethane-ureas led to the formation of hydrogels (6). The water absorption curves for these hydrogels indicated the existence of two modes of absorption an initial water absorption that depended on the concentration ratio of LiBr to the urethane-urea segment (hard segment) of the block copolymer, and the water uptake at higher salt concentration which was attributed to the formation of voids in the film. 

Formation of Hydrogel Scaffolds with Controlled Architecture (Microfabrication Techniques)... 

FIGURE 5.25 Simplified schematic illustrations of the hierarchical self-assembly processes involved in the formation of hydrogels from peptide molecules. Source Dasgupta et al. [55]. Reproduced with permission from the Royal Society of Chemistry. 

Abe K, Yano H (2011) Formation of hydrogels from cellulose nanofibers. Carbohydr Polym... 

The cross-linking behavior of chitosan derivatives can be evalnated by calcnlating some important valnes related to the formation of hydrogels, snch as D, according to Charlesby-Rosiak eqnation (Olejniczak et al. 1991) ... 

Rosiak, J.M., Ulanski, I.P., Pajewski, L.A., Yoshii, F., Makuuchi, K. Radiation formation of hydrogel for biomedical purposes. Some remarks and comments. Radiat. Phys. Chem. 46, 161-168 (1995)... 

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