Cellulose controlled release polymers

Chang, R. K., Price, J., and Whitworth, C. W., Control of drug release rate by use of mixtures of polycaprolactone and cellulose acetate butyrate polymers. Drug Dev. Ind. Pharm.,... 

Fig. 2. Swelling behavior of cellulose ether gels synthesized from different polymer types. The gel transition temperature is near the linear polymer LCST a lower LOST indicates a more hydro-phobic polymer. At comparable crosslink densities, this means a reduction in swelling degree (HPC is less crosslinked than the other gels). Lines added are to guide the eye. Reprinted from the Journal of Controlled Release (1991) 17 175 by permission of the publishers, Elsevier Science Publishers BV [52]...

Suzuki, Y., and Makino, Y. (1999), Mucosal drug delivery using cellulose derivatives as a functional polymer, /. Controlled Release, 62,101-107. 

Velasco, M. V., and Ford, J. L., Rowe, R, and Rajabi-Siahhoomi, A. R. (1999), Influence of drug Hydroxypropyl methyl cellulose ratio, drug and polymer particle size and compression force on the release of diclofenac sodium from HPMC tablets, J. Controlled Release, 57, 75-85. 

The controlled release of various types of herbicides have been studied by many workers and has been summarized elsewhere (4-6, 23). Less Is known, however, about the controlled release of herbicides for land plants than for aquatic plants. Previous studies by other research groups have reported that Isocyanate modified polymers, made from chltln, cellulose or poly(vlnyl alcohol), hydrolyze slowly In aqueous media to release the corresponding aniline derivative (17,24,25). No data appears to be currently available on how effective these agents are as herbicides. 

Amylopectins. — The effects of acrylamide graft copolymerization on the solution properties of amylopectin have been discussed. Amylopectin has been dyed with DyAmyl-L and used in this form as a substrate for the assay of a-amylase. Amylopectin has been treated with isocyanate derivatives of 4-amino-( 1,1-dimethyl ethyl)-3-(methylthio)-l,2,4-triazin-5(4/f)-one ( metribuzin ) or acid chloride derivatives of 2,4-dichlorophenoxyacetic acid ( 2,4-D ) and 2,2-dichloropropionic acid ( dalapon ), to produce controlled-release polymeric pesticide systems. The solvent system utilized for these reactions, a lithium chloride or bromide salt in AW-dimethylacetamide, allows dissolution of the reactant salt and facilitates analysis of the polymer product by such techniques as i.r., U.V., and n.m.r. spectroscopies and gel permeation chromatography. Derivatives of other naturally occurring polysaccharides, including amylopectin, cellulose, chitin, and dextran, were also prepared. 

Young et al. in 2002 successfully prepared controlled release spherical pellets of theophylline by HME and spheronization process. A Randcastle extruder was used to extrude the mixture of anhydrous theophylline, Eudragit 4135F, microcrystalline cellulose, and PEG 8000. Hot-melt extruded rods were cut into symmetrical pellets and then these pellets were spheronized at an elevated temperature. The dissolution profile of the spherical pellets was dependent on the matrix polymer solubility in the media. 

Hydroxypropylmethyl cellulose Hydroxypropyhnethyl cellulose (HPMC) (Figure 28.2) is water-soluble cellulose ether and it can be used as hydrophilic polymer for the preparation of controlled-release tablets. Water penetrates the matrix and hydrates the polymer chains, which eventually disentangle from the matrix. Drug release from HPMC matrices follows two mechanisms, drug diffusion through the swelling gel layer and release by matrix erosion of the swollen layer. " ... 

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