GASTROINTESTINAL PATCHES FOR ORAL DRUG DELIVERY -Part 2

3. Microsphere patch
This patch system also contains three layers (i) mucoadhesive layer (ii)a layer of drug loaded microspheres partially immersed in the mucoadhesive layer (iii) an impermeable membrane encompassing microspheres. To fabricate the patches. The microspheres are spread uniformily and partially pressed into a mucoadhesive layer made of Carbopol and pectin which is then covered with an ethyl cellulose layer. A significant enhancement in transport across the intestinal wall is observed in this patch as it provides a high gradient for delivery and the maintenance of unidirectional diffusion towards the intestinal wall.

4. Insulin patch for oral delivery
A bilayered intestinal patch is designed for the oral delivery of insulin. These patches are fabricated using a mucoadhesive matrix of Carbopol, pectin and sodium carboxymethyl cellulose and loaded with bovine insulin as the drug. The main application of the gastrointestinal patches is concerned with the delivery of insulin.

5. Gated hydrogel patch
This system is using a bilayered self folding pH sensitive hydrogel gate. The main device consists of two parts, a poly (hydroxyl methacrylate (P (HEMA)) based drug reservoir with targeting function and a hydrogel gate. Drug release from the device is controlled by the pH dependent swelling properties of the bilayered gate.

6. Micropatches
In this system particles of size 50-200µm and thickness 2-25µm fabricated in three different substrates (silicon dioxide, porous silicon and poly methyl methacrylate (PMMA) are used.

There are two broad classes of mucoadhesive polymers used in gastro intestinal patches; hydrophilic polymers and hydrogels. Hydrophilic polymers contain carboxylic group exhibit the mucoadhesive properties, poly vinyl pyrrolidone, Methyl Cellulose, Sodium carboxy methyl cellulose, hydroxypropyl cellulose and other derivatives.
Hydrogels are the class of polymeric biomaterials that swell by absorbing water and interacting by means of adhesion with the mucous that covers epithelia. Carbopol, chitosan and eudragit are some of the examples for hydrogels.

The polymers used in the preparation of patches should have some peculiar characteristics. They should be non toxic and non absorbable from the GI tract. They should preferably form a strong non-covalent bond with mucin-epithelial cell surface and non irritable to the mucous membrane. These polymers should allow easy incorporation of drug and offer no hindrance to its release. The cost of the polymer must be not high so that the prepared dosage form remains competitive.
Lectin is polymer which will bind specifically and reversibly to mucosa made up of proteins and glycoprpteins.