• Whitley Wichmann posted an update 2 years, 9 months ago

    Mucus secrated continuously by the specialized goblet cells located throughout the GIT plays a cytoprotective role.Bioadhesion is an interfacial phenomenon in which is biological, are held together by means of interfacial forces.The attachment could between an artificial material and biological substrate, such as adhesion between a polymer and a biological membrane.In the case of polymer attached to the mucin layer of a mucosal tissue, the term mucoadhesion is used.The mucosal layer lines a number of regions of the body including the GIT, the ear, nose and eye.These represent potential sites for attachment of bioadhesive system and hence.As a result, the dosage form is retained for a longer period of time.These systems, since they exhibit the tendency to remain longed at the pyloric sphincter.On coming in contact with gastric fluid, the polymer imbibes water and swells.The extensive swelling of these polymers is due to the presence of physicalchemical crosslink in the hydrophilic polymernetwork.A balance between the extent and duration of swelling is maintained by the degree of crosslinking between the polymeric chains.A high degree of crosslinking retards the swelling ability of the system maintaining its physical integrity for prolonged period.On the other hand, a low degree of crosslinking results in the extensive swelling of the system, succeeded by the rapid dissolution of the polymer.A drug can be either contained in a polymeric composition of the gastroretentive systems or included as a separate component.In swelling, polymer in the system absorbs water from the surrounding environment and swells to form a viscous gel. In diffusion, solvent in which the drug and polymer is dissolved or dispersed, diffuse into the surrounding tissues causing the precipitation of the polymer to form gel. Change in temperature causes abrupt change in the solubility of polymer within system and polymerpolymer interaction occurs to form a solvated macromolecule of hydrophobic nature.Polymer with anionic groups leads to increase in swelling with increase in the pH, while polymer with cationic groups shows a decrease in the swelling.By having a system undergoing phase transition as a consequence of dilution with water a higher amount of polymer can be used.Electro sensitive hydrogels undergo shrinking or swelling in the presence of an applied electric field.Chitosan gels as matrices can be used for electrically modulated drug delivery.The object floats better if F is on the higher positive side. It involves formation of double helical junction zones by aggregation of double helical segments to form dimensional network by complexation with cations and hydrogen bonding with water.After release of drug, the residual system is emptied from the stomach besides a minimal gastric content needed to allow the proper achievement of the buoyancy retention principle, a minimal level of floating force is also required to keep the dosage form reliably buoyant on the surface of the meal.To measure the floating force kinetics, a novel apparatus for determination of resultant weight has been in the literature.Drugs delivered in this manner have a lower level of side effect and provide their therapeutic effects without the need for repeated dosage with a low dosage frequency.