Hydrophilic polymeric matrix system

Polymeric matrix systems are the most widely employed for the formulation of oral prolonged release pharmaceutical dosage forms due to their simple and low-cost manufacturing process. There are three main types of pharmaceutical matrices inert, hydrophilic and lipidic matrices, being hydrophilic and inert matrices the most employed ones.. 

The objective of this chapter is to review degradable materials, including polymers, and the resulting delivery systems fabricated from them that are usefid for the delivery of proteins and peptides. Owing to the diverse nature of the subject area, we have chosen to divide the chapter into sections on hydrophobic synthetic polymers, hydrophilic polymeric biomaterials, and hydrophobic nonpolymeric biomaterials. Each section seeks to briefly highlight ftie chemist and characteristics of the polymer or matrix and provide recent examples of their use in the delivery of proteins. 

Soluble as well as insoluble cellulose ethers have been used in hydrophilic polymeric matrices thanks to their hydrophilicity nature and good gel-forming characteristics. Among cellulose ethers, HEC shows the highest swelling ability and hydration rate. However, HPMC enjoys the most common use in hydrophilic matrix applications thanks to its excellent swelling ability, good compressibility and fast hydration characteristics. Mixtures of cellulose ethers with other cellulose ethers or different polymers are used in controlled release systems [28]. 

Most polymer blends, however, are heterogeneous and consist of a polymeric matrix in which the second polymer is embedded. Consequently, the effects on permeability are very dependent on the degree of heterogeneity of the system and therefore on the method of formation. " The nature and type of the polymers used Le. rubbery, glassy, hydrophilic or hydrophobic) is most important. 

A unique method of formulating delivery systems based on starch/ PLA systems was studied (138). In that approach, the goal was to provide a better matrix for delivery of high molecular weight hydrophilic molecules. A hydrophilic material, starch, was combined through graft polymerization to PLA. The carbolactic polymers were then used to entrap bovine serum albumin in microspheres. 

The drug may be incorporated in a slowly eroding matrix of waxy materials, embedded in a plastic matrix, complexed with anion exchange resins or incorporated in a water-insoluble hydrophilic matrix. Drug release from these systems occurs by several mechanisms diffusion, dissolution, ionic exchange or osmotic pressure [1,2], depending on the type of polymeric excipient present and the formulation used. 

Generally, polymer nanocomposites can be obtained through two routes the first one is the polymerization of monomers in contact with the exfoliated clay and the second one uses existing transformation processes to produce nanocomposites, for example, by a reactive extrusion. There are, however, problems present due to the lack of affinity of the clay-polymer system because of the hydrophilic character of the particles. It is then necessary to treat the clay chemically to increase its affinity with the polymer matrix. This constitutes another whole area of research in the nanocomposites production. 

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