Polyacrylonitrile hydrogel

Gohin YP, Vinuela F, et al. (2000) Embolization with radiopaque microheads of polyacrylonitrile hydrogel evaluation in swine. Radiology 214 113-119... 

Fig. 5. Scanning electron micrographs of hoUow fiber dialysis membranes. Membranes in left panels are prepared from regenerated cellulose (Cuprophan) and those on the right from a copolymer of polyacrylonitrile. The ceUulosic materials are hydrogels and the synthetic thermoplastic forms a microreticulated open cell foam with a tight skin on the inner wall. Pictures at top are membrane cross sections those below are of the wall region. Dimensions as indicated.

Production of hydrogels by chemical conversion uses chemical reactions to convert one type of gel to another. This can involve the conversion of a nonhydrogel to a hydrogel or the conversion of one type of hydrogel to another. Examples of the former include the hydrolysis of polyacrylonitrile to polyacrylamide or of poly(vinyl acetate) to poly(vinyl alcohol) an example of the latter... 

Link et al. (35) proposed the use of tantalum and tungsten to add radiopacity to hydrogel embolic agents for embolotherapy and studied the emboli formed by coagulation under high pressure of a 1 1 or 2 1 mixture of tungsten particles (1-10 jam) and a liquid hydrogel (polyacrylonitrile copolymer) in a rabbit model. 

Polyacrylamides are also suitable for a variety of biomedical uses the structure of polyacrylamide is shown in Fig. IG, although the use of acrylamides in copolymers is much more common. Polyvinylpyrrolidinone has also found use as a biocompatible coating material (Fig. IH). Polyacrylonitrile, though not suitable in itself, can be hydrolyzed to form some hydrophilic polymers such as the Hypan (Hymedix Inc.) series of hydrogels. 

S.J. Kim, S.R. Shin, YM. Lee, and S.I. Kim, Swelling characterizations of chitosan and polyacrylonitrile semi-interpenetrating polymer network hydrogels. Journal of Applied Polymer Science, 87 (12), 2011-2015,2003. 

Radiopaque microbeads made of polyacrylonitrile (PAN) hydrogel have also been evaluated in vitro and in vivo for transcatheter embolization on a swine model showing potential for future use [23[. 

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