5.4. Electrosensitive hydrogels
Hydrogel swells in response to an electrical stimulus with a mechanism very similar to pH, experiences shrinkage, and bending. The major difference between electrical and pH stimulations is that the electric field moves mobile ions in order to regulate an ion concentration gradient through the hydrogel and the solution [54,55]. Polymeric networks containing ionizable groups can have important electrical behavior under an electric field. The electrosensitive hydrogels experience shrinkage or swelling in the presence of an applied electric field. In some certain cases, hydrogels swell on one side and deswell on the other side that result in bending or even deformation of hydrogels [92,93]. Electrosensitivity of …show more content…
Such a directional migration causes nonuniform ion concentration inside and outside the gel, which causes the difference in osmotic pressure and the deformation of the gel. Directional migration of free ions also causes non-uniform pH in the gel system and more different ionization state in the polyelectrolyte. This, in turn, alters the structure of the gel, and finally the gel is deformed [94]. So far, many synthetic polymers such as poly (vinyl alcohol)/poly (sodium acrylate-co-sodium maleate) [95], acrylic acid/vinyl sulfonic acid copolymer [96] and sulfonated poly styrene [97] have been used for the synthesis of electrosensitive hydrogels. In addition, some natural electrolytes have been combined with synthetic polymers to produce this type of hydrogels. For example, alignate/poly (methacrylic acid), chitosan/polyaniline, and hyaluronic acid/poly …show more content…
A lot of hydrogels, especially smart or intelligent hydrogels have been studied for use in drug delivery systems for delivery of various drugs from small molecular weight drugs to macromolecular drugs such as peptides, growth factors and insulin [86]. Also, in recent years, extensive efforts have been performed to develop new drug delivery systems [118,120]. Hydrogels can trap drug and protect it against hostile environments for slow release via diffusion or erosion depending on the state of hydration. They can also control rate of drug delivery through changing the structure in response to environmental stimuli such as temperature, pH, electrical and magnetic fields, solvent composition, light, ions, etc. [121]. Research on drug delivery systems has mainly focused on hydrogels because hydrogels not only reduce common problems associated with drug dosage but also new drug delivery systems based on hydrogels provide stable and compatible drug release [122]. Hydrogels are less likely to absorb proteins from body fluids because of their low
Hydrogel swells in response to an electrical stimulus with a mechanism very similar to pH, experiences shrinkage, and bending. The major difference between electrical and pH stimulations is that the electric field moves mobile ions in order to regulate an ion concentration gradient through the hydrogel and the solution [54,55]. Polymeric networks containing ionizable groups can have important electrical behavior under an electric field. The electrosensitive hydrogels experience shrinkage or swelling in the presence of an applied electric field. In some certain cases, hydrogels swell on one side and deswell on the other side that result in bending or even deformation of hydrogels [92,93]. Electrosensitivity of …show more content…
Such a directional migration causes nonuniform ion concentration inside and outside the gel, which causes the difference in osmotic pressure and the deformation of the gel. Directional migration of free ions also causes non-uniform pH in the gel system and more different ionization state in the polyelectrolyte. This, in turn, alters the structure of the gel, and finally the gel is deformed [94]. So far, many synthetic polymers such as poly (vinyl alcohol)/poly (sodium acrylate-co-sodium maleate) [95], acrylic acid/vinyl sulfonic acid copolymer [96] and sulfonated poly styrene [97] have been used for the synthesis of electrosensitive hydrogels. In addition, some natural electrolytes have been combined with synthetic polymers to produce this type of hydrogels. For example, alignate/poly (methacrylic acid), chitosan/polyaniline, and hyaluronic acid/poly …show more content…
A lot of hydrogels, especially smart or intelligent hydrogels have been studied for use in drug delivery systems for delivery of various drugs from small molecular weight drugs to macromolecular drugs such as peptides, growth factors and insulin [86]. Also, in recent years, extensive efforts have been performed to develop new drug delivery systems [118,120]. Hydrogels can trap drug and protect it against hostile environments for slow release via diffusion or erosion depending on the state of hydration. They can also control rate of drug delivery through changing the structure in response to environmental stimuli such as temperature, pH, electrical and magnetic fields, solvent composition, light, ions, etc. [121]. Research on drug delivery systems has mainly focused on hydrogels because hydrogels not only reduce common problems associated with drug dosage but also new drug delivery systems based on hydrogels provide stable and compatible drug release [122]. Hydrogels are less likely to absorb proteins from body fluids because of their low