Drug delivery systems poly

Poly[(4-carboxylatophenoxy)(methoxyethoxyethoxy)phosphazene] copolymers of variable compositions were synthesized by Allcock [645] in 1996. These polymers were found to be soluble in alkaline solutions. When crosslinked (by y-rays or by addition of CaCl2 to the polymer solution) the resulting hydrogels were found able to contract or expand as a function of the pH of the solution and their utilization as pH-responsive materials for drug delivery systems could be envisaged. 

T., Katutani, Y., and Kitsugi, T., Release of antibiotics from composites of hydroxyapatite and poly(lactic acid), in Advances in Drug Delivery Systems (J. M. Anderson and S. W. Kim, eds.), Elsevier, New York, 1986, pp. 179-186. 

Pitt, C. G., Jeffcoat, A. R., Zweidinger, R. A., and Schindler, A., Sustained drug delivery systems. I. The permeability of poly(e-caprolactone), poly(DL-lactic acid), and their copolymers, J. Biomed. Mater. Res., 13. 497-507, 1979. 

Sparer, R. V., Chung, S., Ringeisen, C. D., and Himmelstein, K. J., Controlled release from erodible poly(ortho ester) drug delivery systems, J. Control. Rel.. 23-32, 1984. 

Kohn, J., and Langer, R., Non-peptide poly(amino acids) for biodegradable drug delivery systems, in Proceedings of the 12th International Symposium on Controlled Release of Bioactive Materials (N. A. Peppas and R. J. Haluska, eds.). Controlled Release Society, Lincolnshire, IL, 1985, pp. 51-52. 

In this paper, then, the previously developed model (7) is extended to the calculation of erosion characteristics of a well described polymeric delivery system, the acid-catalyzed erosion of poly (ortho ester)s (2-6). This system is chosen as the example system because of the completeness of the data package in the open literature. It is expected that this modelling approach is also useful for other hydrolytically unstable polymeric drug delivery systems. 

New drug delivery systems are of great scientific and commercial interest. Amphiphilic networks composed of about 50/50 hydrophobic PIB and hydrophilic poly(2-(-dimethylamino)ethyl methacrylate) (DMAEMA) polymer segments were found to be biocompatible and to a large extent avascular (7). These PHM-PDMAEMA networks (i, in line with propositions of Weber and Stadler (2), and Sperling (J), denotes PDMAEMA chains linked by PIB chains) gave pH dependent... 

In the previous paper (7) we have described the synthesis, characterization, and certain diffusional characteristics of poly(N V-methylacrylamide)-l -polyisobutylene amphiphilic networks exhibiting a relatively high degree of swelling in both water and n-heptane. It was of interest to prepare further neutral amphiphilic networks of lower water swelling for sustained drug delivery systems. One candidate for this... 

JT Jacob-LaBarre, HE Kaufman. (1990). Investigation of pilocarpine loaded poly-butylcyanoacrylate nanocapsules in collagen shields as a drug delivery system. Invest Ophthalmol Vis Sci 31(Suppl) 485-488. 

Poly-j3-malate is readily degraded completely to L-malic acid under both acid and base conditions [108], and it can also be hydrolyzed by enzymes within the cell [105,106]. Recently, several bacteria were isolated which were able to utilize poly-/i-malate as sole carbon source for growth [109]. Because the polymer is biodegradable and bioadsorbable, it is of considerable interest for pharmaceutical applications, especially in controlled-release drug delivery systems [97,98]. Chemical routes to poly-/ -malate are expected to provide materials with various properties [110]. 

Erdmann et al. (2000) report the fabrication of devices for the localized delivery of salicylic acid from the poly(anhydride-co-ester)s mentioned in Section II.C. A unique feature of this drug delivery system is that the drug compound is part of the polymer backbone. Devices were implanted intraorally and histopathology was reported (Erdmann et al., 2000). Chasin et al. (1990) review fabrication and testing of implantable formulations for other drugs including angiogenesis inhibitors for treatment of carcinomas and bethanechol for the treatment of Alzheimer s disease. 

The failure in increasing residence time of mucoadhesive systems in the human intestinal tract has led scientists to the evaluation of multifunctional mucoadhesive polymers. Research in the area of mucoadhesive drug delivery systems has shed light on other properties of some of the mucoadhesive polymers. One important class of mucoadhesive polymers, poly(acrylic acid) derivatives, has been identified as potent inhibitors of proteolytic enzymes [72-74]. The interaction between various types of mucoadhesive polymers and epithelial cells has a direct influence on the permeability of mucosal epithelia by means of changing the gating properties of the tight jrmctions. More than being only adhesives, some mucoadhesive polymers can therefore be considered as a novel class of multifunctional macromolecules with a number of desirable properties for their use as delivery adjuvants [72,75]. 

Applications of hydrogels include highly absorbent diapers based on poly(sodium acrylate), contact lenses based on poly(2-hydroxyethyl methacrylate) (polyHEMA), and switches based on variations of swelling of the hydrogels. A number of drug delivery systems have also been based on hydrogels. 

A great number of researches have so far been carried on the incorporation of poly(IPAAm) and its copolymers in various biomedical devices, utilizing soluble/insoluble or swelling/deswelling processes in the temperature range of LCST. As overviewed by Okano et al. [44] these include drug delivery system (DDS) solute separation concentration of dilute solutions immobilization of enzymes detachment of cultured cells coupling to biomolecules, and other aspects. 

Merkli, A., Heller, J., Tabatabay, C., and Gumy, R. (1996). Purity and stability assessment of a semi-solid poly(ortho ester) used in drug delivery systems. Biomaterials, 17, 897-902. 

Pitt, C.G. (1990). Poly(e-caprolactone) and its copolymers. In Chasin, M., Langer, R., eds. Biodegradable Polymers as Drug Delivery Systems. Marcel Dekker, New York. 

Vinogradov, S., Batrakova, E. and Kabanov. A. (1999b) Poly(ethylene glycol)-polyethyleneimine NanoGel particles novel drug delivery systems for antisense oligonucleotides. Colloids and Surfaces B Biointerfaces, 16, 291-304. 

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