Responsive hydrogels

In summary, the advantages of our approach to studying gastric retention are twofold. First, hydrogel response to the gastric environment can be noninvasively visualized in real-time. Second, a more efficient and justifiable approach to the development of long-term oral drug delivery systems can be achieved. 

Thus, apart from pH of initial and complete precipitation of hydrogels responsible for growing of particles, the formation of the structure of specimens is also affected by sorption capacities of individual components, which do not affect the gel structure formation mechanism, but distort the shape of the Vg -composition curve and to some extent, create illusive impression of effective growth of the particle size and Vg of the sample in the process of co-precipitation of hydroxides. 

The reversible nature of DNA hybridization in response to an external stimulus causes this type of DNA-polymer hydrogels to have special properties, such as sol-gel phase transition and responsive releasing capability [93]. Thus, potential applications of these materials as label-free DNA sensing device or for controlled drug delivery have been discussed. Just a small portion of DNA is needed to achieve hydrogel responsiveness. 

Cationic Polymeric Hydrogels Responsive to Carbon Dioxide... 

P-CD Alkyl triphenyl phosphonium bromide Hydrogels Responsive delivery [64]... 

Several studies on hydrogels responsive to electric stimulation have been made. For example, De Rossi et al. reported that PVA-PAA composite films shrink because of the electrode reaction in aqueous NaCl solution [61]. Grodzinsky et al. also studied the kinetics of oscillatory tensile forces generated by sinusoidal electric fields in a collagen membrane [62]. A comparison of the experimental and theoretical data suggested that electrodiffusion is the dominant rate-limiting process in this electromechanochemical transduction. 

Another group of effects consists in blocking the channels of losing water from the soil layer, i.e., the hydraulic conductivity responsible for the gravitational flow, and of physical evaporation. All these effects provide an increase of the water content of the soil and, consequently, improve the water supply of plants, which is reflected in the three last columns in Table 8. According to the data of various authors, an increase in the soil water content (AW) in sandy soils lies in the range of 10-35% at doses up to 0.2% in a number of cases [10, 11, 58, 131-133] the dependencies of AW on the doses of the hydrogels added have been studied. 

Poly[(4-carboxylatophenoxy)(methoxyethoxyethoxy)phosphazene] copolymers of variable compositions were synthesized by Allcock [645] in 1996. These polymers were found to be soluble in alkaline solutions. When crosslinked (by y-rays or by addition of CaCl2 to the polymer solution) the resulting hydrogels were found able to contract or expand as a function of the pH of the solution and their utilization as pH-responsive materials for drug delivery systems could be envisaged. 

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