History Development of Hydrogels

WATERTOWN, Mass. - Feb. 20, 2023 - PRLog -- Hydrogels are composed of hydrophilic polymers, whose three-dimensional network structure can not only absorb a large amount of water, but also be used to carry drugs. Hydrogels prepared with suitable materials of high biocompatibility, mechanical and viscoelastic control. Since the term was coined in the late 19th century, hydrogels have been widely used in drug delivery, wound dressing, tissue engineering, and hygiene products. This article mainly introduces the development history of hydrogels. The history of hydrogel can be roughly divided into three generations.

1. First-genaration Hydrogels

The first generation of hydrogels is mainly divided into three categories. The first category is polymers of vinyl monomers induced by free radical chain addition reactions. The main representatives are polyacrylamide (PAM) and polyhydroxyethyl methacrylate. (pHEMA). The second category is covalently cross-linked hydrophilic polymers, mainly represented by polyvinyl alcohol (PVA) and polyethylene glycol (PEG), mainly It is used in tissue engineering. And the third category is cellulose-based hydrogel, which is mainly used as a drug dispersion matrix for drug delivery.

2. Second-generation Hydrogels

The second generation of hydrogels are mainly PEG/ polyester block copolymers. Compared with the first generation, the second generation is characterized by the ability to convert the chemical energy of hydrogels into the mechanical energy of hydrogels to achieve the specified function. Stimulus-response hydrogels can be broadly divided into three categories:

The first type is temperature-sensitive hydrogels responsive to temperature, which can show the phase transition from gel state to sol state from low temperature to high temperature. The main representatives are Pluronics of BASF or Poloxamers of British Imperial Chemical Industry Group.

The second major ph-sensitive hydrogels, these polymers hydrolyze at either high or low pH.

The third is biomolecular sensitive hydrogels that can respond to changes in concentration of specific biomolecules through conformational changes. Such as glucose oxidase hydrogels, which can be used to deliver insulin. The basic principle is that when glucose diffuses in the hydrogel matrix, it will be converted into gluconic acid by the glucose oxidase in the hydrogel, and then the protonation of the amine functional group of the hydrogel will result in the swelling increase, so that insulin can be released from the matrix, forming a set of insulin self-regulating release system.

3. Third-generation Hydrogels

The main feature of the third generation of hydrogels is "crosslinking", which mainly regulates the mechanical properties and degradation properties of hydrogels by means of stereoscopic complexation, inclusion complexes, metal-ligand coordination and synthetic peptide chain.

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