Polymers for Controlled Release

Growth factor administration may also be a useful treatment for neurodegenerative diseases, such as Alzheimer s disease or Parkinson s disease, which are characterized by the degeneration of neuronal cell populations. It was found that the NGF promoted nerve regeneration within conduits at an early stage, but the effect did not last after one month. This was attributed to the rapid decline in NGF concentrations in the conduit due to degradation in aqueous media and leakage from the 

To provide for prolonged, site-specific delivery of NGF to the tissue in a convenient manner without affecting the properties of the conduit, biodegradable polymer microspheres of poly(L-lactide)co-glycolide 

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Kohn, J., and Langer, R., A new approach to the development of bioerodible polymers for controlled release applications employing naturally occurring amino acids, in Proceeding of the ACS Division of Polymeric Materials. Science and Engineering. American Chemical Society, 1984, Vol. 51, pp. 119-121. 

HB Rosen, J Kohn, K Leong, R Langer. Bioerodible polymers for controlled release systems. In DST Hsieh, ed. Controlled Release Systems Fabrication Technology, Vol n. Boca Raton, FL CRC Press, 1988, pp 83-110. 

R. J. Linhard, Biodegradable Polymers for Controlled Release of Drugs, in P. Roshoff (ed), Controlled Release of Drugs. Polymers and Aggregate Systems, New York, VCH, 1989. 

J. Kohn, R. Danger, A New Approach to the Development of Bio-erodible Polymers for Controlled Release Apphcations Employing Naturally Occurring Amino Acids, American Chemical Society, Washington, DC, 1984. 

Y. Wang, H. Morinaga, A. Sudo, T. Endo, Synthesis of amphijdiilic polyacetal by polycondensation of aldehyde and polyethylene glycol as an acid-labile polymer for controlled release of aldehyde, J. Polym. Sd. A Polym. Chem. 49 (2011) 596-602. 

Vert, M., 1987, Design and synthesis of biorestxhable polymers for controlled release of... 

FP is being pursued along three directions. The first direction is to use it to make new types of polymers or existing polymers more easily. For example, FP has been used for the preparation of amphihc gels [69], polymers for controlled release [70], and porous polyacrylamide hydrogels [71]. 

The ability of a new biodegradable polymer, polyurethane triethylene glycol 1,6-hexa-methylene diisocyanate PU(TEG-HMDI), to act as matrix-forming polymer for controlled release tablets has been studied and its percolation threshold in a matrix system has been estimated [112]. The hydrophilic polyurethane PU(TEG-HMDI) was successfully synthesized by reaction of 1,6-hexamethylene diisocyanate (HMDI) and triethylene glycol (TEG) (Scheme 4.1). The diol monomer (TEG) was chosen to enhance the hydrophilic nature and swelling properties of the new material. These properties contribute to the degradability of the polyurethane. 

M. Abdouss, E. Asadi, S. Azodi-Deilami, N. Beik-mohammadi and S.A. Aslanzadeh, Development and characterization of molecularly imprinted polymers for controlled release of citalopram, J. Mater. Sci. Mater. M., 22 (10) 2273-2281, 2011. 

For many drug delivery applications, the preferred method of delivery of the dosage form is by injection. For controlled release applications, the most frequently used approach to allow this method of administration is to prepare microspheres of the polymer containing the drug to be delivered. Several different techniques have been developed for the preparation of microspheres from polyanhydrides. 

Saltzman, W. M., Pasternak, S. H., and Langer, R., Micro-structural models for diffusive transport in porous polymers, in Controlled-Release Technology, ACS Symposium Series 348... 

Robert Langer, Polymer Systems for Controlled Release of Macromolecules, Immobilized Enzyme Medical Bioreactors, and Tissue Engineering J. J. Linderman, P. A. Mahama, K. E. Forsten, and D, A. Lauffenburger, Diffusion and Probability in Receptor Binding and Signaling Rakesh K. Jain, Transport Phenomena in Tumors... 

The use of polymers for biomedical applications has been widely accepted since the 1960 s (7), and specifically for controlled release applications since the 1970 s (2). The primary goal of this research was to create a controlled release matrix from polymers with pre-existing Food and Drug Administration (FDA) histories, which would be capable of releasing insoluble active agents, and upon exhaustion of the device, leave a stable, inert, removable skeleton. The application of such a matrix would be as an intracervical device which would prevent both conception and ascending infection. 

A novel polymerized vesicular system for controlled release, which contains a cyclic a-alkoxyacrylate as the polymerizable group on the amphiphilic structure, has been developed. These lipids can be easily polymerized through a free radical process. It has been shown that polymerization improves the stabilities of the synthetic vesicles. In the aqueous system the cyclic acrylate group, which connects the polymerized chain and the amphiphilic structure, can be slowly hydrolyzed to separate the polymer chain and the vesicular system and generate a water-soluble biodegradable polymer. Furthermore, in order to retain the fluidity and to prepare the polymerized vesicles directly from prev lymerized lipids, a hydrophilic spacer has been introduced. 

IC Kwon, YH Bae, SW Kim. Electrically erodible polymer gel for controlled release of drugs. Nature 354 291-293, 1991. 

Concerning drug delivery, electrically erodible polymer gels for controlled release of drugs have been prepared, and a measured release rate of insulin has been observed under electrical stimulus [69]. A suspension of zinc insulin in a mixed solution of poly(ethyloxazoline) and PMAA was formed into a gel by decreasing the pH of the suspension. The obtained complex gel with 0.5 wt% of insulin was attached to a woven platinum wire cathode which was 1 cm away from the anode and immersed in 0.9% saline solution. When a stepped function of electrical current of 5 mA was applied to the insulin-loaded gel matrix, insulin was released in a stepwise manner up to a release of 70%. The insulin rate measured was 0.10 mg/h. 

Langer, R. 1994. Polymer systems for controlled release of macromolecnles, immohilized enzyme medical hioreactors, and tissne engineering. In Advances in Chemical Engineering, vol. 19. San Diego Academic Press 1-50. 

Langer, R. and N. Peppas. 1983. Chemical and physical stmctnre of polymers as carriers for controlled release of hioactive agents a review. Journal of Macromolecular Science Reviews in Macromolecular Chemistry and Physics C23 61-126. 

Robert Langer, Polymer Systems for Controlled Release of Macromolecules, Immobilized Enzyme Medical Bioreactors, and Tissue Engineering... 

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