Swelling release

Thermal Thermoresponsive hydrogel Change in temperature, change in polymer-polymer and water-polymer interactions, change in swelling, release of drug... 

Thus, both the permeabilization of the outer mitochondrial membrane by Bax and Bak and the rupture of the outer membrane from MPT and matrix swelling release mitochondrial cytochrome c and cause cell death. 

Methylene chloiide formulas are the most common organic chemical removers. The low molar volume of methylene chloride allows it to rapidly penetrate the finish by entering the microvoids of the finish. When the solvent teaches the substrate, the remover releases the adhesive bond between the finish and the substrate and causes the finish to swell. The result is a bhstering effect and an efficient rapid lifting action. Larger molecule solvents generally cannot... 

Hydrogels. Controlled swelling of hydrophilic polymers, derived from the glossy/mbbery properties of polymers, is used to control the rate of dmg release from matrices. In the mbbery state, accompHshed by lowering the polymer s glass-transition temperature to an appropriate level, the dispersed dmg diffuses as the polymer swells in the presence of water. 

Exxon products appear to release via a unique mechanism. Like other polymer-coated technologies, the penetration of water iato the granule is purely by diffusion. However, as water enters the particle, an osmotic pressure is created as the fertilizer is solubilized. This pressure causes an expansion of the elastomeric coating and the particle swells to many times its original diameter. As the particle swells, the coating becomes increasingly thinner to the point where it caimot contain the internal pressure and the nutrient is released. 

ControUed release dmg dehvery systems include those that ate diffusion controUed, chemically controUed, swelling controUed, and extemahy controUed. Osmoticahy controUed systems ate a subset of diffusion controUed systems and ate often classified separately. 

In swelling-controlled systems, glassy hydrogels ia particular, the release process is a combination of the diffusion of water iato the system and dmg from the system. Empirically, release from these systems may be expressed as (83) ... 

The vapor vent valves are connected to the tank vapor control valve, and ultimately to the carbon canister by tubing that is resistant to swelling in the presence of fuel vapors. The tubing material must also have a low HC permeation rate, so that the evaporative emissions are not increased due to release of HC molecules. The tank vapor control valve connects the carbon canister to two fuel tank vapor sources the vapor vent valve lines and a refueling vent tube. 

Yamamoto and Minamizaki [159] disclose the use of a curable silicone based release agent blended with resin particles which swell or are soluble in organic solvent. Coatings made with such blends can be written on with solvent based inks. For example, an addition cure silicone network containing 20 wt% 0.1 p,m diameter PMMA particles exhibited both good writeability (no ink dewetting and smear free) and a low release force of 10 g/cm for a PSA tape. 

The optimum conditions for polyion complex formation between chitosan and hyaluronate were identified fhe compression exerfed fo manufacture the implant had no role to play in the release kinetics [28,92]. Various authors published data confirming fhaf fhe combinafion of chifosan and hyaluronic acid is always suscepfible fo swelling, even in fhe presence of cross-hnking. 

A simple example of gel formation is provided by chitosan tripolyphosphate and chitosan polyphosphate gel beads the pH-responsive swelling abihty, drug-release characteristics, and morphology of the gel bead depend on polyelectrolyte complexation mechanism and the molecular weight. The chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution by ionotropic cross-hnking or interpolymer complexation, respectively. 

Initial work with poly (ortho esters) focused on norethindrone and the use of water-soluble excipients such as Na2C03, NaCl, and Na2S04 (27). As described by Fedors (28), the inclusion of such water-soluble salts leads to an osmotically driven water intake into the polymer. This water intake leads to polymer swelling with consequent release of the incorporated norethindrone. The effect of incorporated NaCl and Na2C03 on erosion rate as compared to the... 

Because swelling and consequent bulk erosion induced by the water-soluble salt is not desirable, use of the low-water-solubility, sUghtly acidic salt calcium lactate was investigated (30). By using this excipient it was hoped that a lowering of the pH within the surface layers of the device would take place and release of the drug would be controlled by polymer erosion confined to the surface layers of the device. In these experiments norethindrone was replaced by the currently favored steroid levonorgestrel. 

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