As controlled-release systems for

K. Aiedeh, E. Gianas, I. Orienti, V. Zecchi, Chitosan microcapsules as controlled release systems for insulin, J. Microencapsulation 14 567-576 (1997). 

Microspheres as Controlled-Release Systems for Parenteral and Nasal Administration... 

The rate of liposome accumulation in alveolar type-II cells is dependent on lipid composition. It is therefore possible to select liposome compositions displaying minimal interaction with these cells and thereby function as controlled-release systems for entrapped solutes. For example, liposomes composed of dipalmitoylphosphatidylcholine and cholesterol and containing entrapped sodium cromoglycate will provide sustained delivery of the drag for over 24 hours. Conversely other liposome compositions could be utilized for enhanced epithelial interaction and transport of the drug (e g. cationic lipids for the cellular delivery of the CFTR gene). 

Risbud, M.V. Hardikar, A.A. Bhat, S.V. Bhonde, R.R. pH-sensitive freeze-dried chitosan-polyvinyl pyrrohdone hydrogels as controlled release system for antibiotic delivery. J. Control. Release 2000, 68, 23-30. 

In the area of controlled release, the preparation of indomethacin sustained-release microparticles from alginic acid (alginate)-gelatin hydrocolloid coacervate systems has been investigated. In addition, as controlled-release systems for liposome-associated macromolecules, microspheres have been produced encapsulating liposomes coated with alginic... 

Phase Separation. Microporous polymer systems consisting of essentially spherical, intercoimected voids, with a narrow range of pore and ceU-size distribution have been produced from a variety of thermoplastic resins by the phase-separation technique (127). If a polyolefin or polystyrene is insoluble in a solvent at low temperature but soluble at high temperatures, the solvent can be used to prepare a microporous polymer. When the solutions, containing 10—70% polymer, are cooled to ambient temperatures, the polymer separates as a second phase. The remaining nonsolvent can then be extracted from the solid material with common organic solvents. These microporous polymers may be useful in microfiltrations or as controlled-release carriers for a variety of chemicals. 

In other applications the pattern of evolution of styrene, butadiene and acrylonitrile as a function of temperature has provided a unique way for classifying different types of ABS. The loss of the antioxidant butylated hydroxytoluene (BHT) was also detected by MS preceding EVA copolymer degradation [165] BHT was identified at a concentration level of 20 ppm. Lehrle and co-workers [52] have described a successful controlled release system for the stabilisation of rubber by encapsulating efficient but rather mobile antioxidants to prevent loss from the host polymer. The performance of the controlled-release of the antioxidant BHT from alginate matrix particles was studied by means of DSC, TG and TG-MS. Polyisoprene rubber is more resistant to oxidation when protected in this way than by the equivalent concentration of unencapsulated antioxidant. 

Soppimath KS, Kulkarni AR, Aminabhavi TM. Development of hollow microspheres as floating controlled-release systems for cardiovascular drugs preparation and release characteristics. Drug Dev Ind Pharm 2001 27(6) 507-515. 

In summary, the studies reported In this review provide 2 Important demonstrations (1) that In vitro release kinetics of macromolecules such as inulln from ethylene-vinyl acetate copolymer matrices are Identical to their In vivo release kinetics, and (2) that zero-order release for macromolecules can be achieved for over 60 days using a hemisphere design. Further experimentation in these areas should provide Information that will be useful In the eventual design of controlled release systems for Insulin and other important bloactlve macromolecules. 

---