Polymers drug carrier

The ultimate fate of drugs and their metabolites is a major concern. If they are not cleared in a reasonable time, they could promote undesirable side effects. Polymer drug carriers are usually nonbiodegradable, and if their size is greater than 40,000 daltons, they could accumulate in the host with the potential of future unwanted effects. 

Wise, D. Fellmann, T. Sanderson, J. Wentwotrth, R. In Lactic/Glycolic Acid Polymers, Drug Carriers in Biology and Medicine Academic Press London, 1976 pp 237-270. 

Fig. 4 Schematic picture of EPR effect. Tumor targeting of long-circulating polymer drug carrier occurs passively by the enhanced permeability and retention (EPR) effect. The inset is the chemical structure of folic acid...

Poly(ethylene glycol) (PEG) is a nondegradable synthetic polymer that has been extensively studied as a polymer-drug carrier. PEG is hydrophilic and is well tolerated in human. The main disadvantage of PEG is that the polymer backbone is not biodegradable in vivo. PEG has been used to conjugate anticancer drugs such as doxorubicin [311], camptothecin... 

Akashi, M. Kishida, A. Sakuma, S. Kikuchi, H. Granular polymer drug carriers for water-insoluble drugs. PCX Int. Appl. WO 9730730, 1997 Chem. Abstr. 1997,127, 210387. 

Figure 1.24. Basic structures of polymer drug carriers with biodegradable polymer backbone poly[N -(2-hydroxyethyl)-L-glutamine] (a), poly(amido amine)s (b) and polyacetals (c).

V. Chytry and K. Ulbrich, Conjugate of doxorubicin with thermosensitive polymer drug carrier, /. Bioactive Compat. Polym., 16, 427-439 (2001). 

Duncan, R. and Kopecek, J. Soluble Synthetic Polymers as Potential Drug Carriers. Vol. 57, pp. 51 —10 . 

Polymeric microparticles have been studied and developed for several years. Their contribution in the pharmacy field is of utmost importance in order to improve the efficiency of oral delivery of drugs. As drug carriers, polymer-based microparticles may avoid the early degradation of active molecules in undesirable sites of the gastrointestinal tract, mask unpleasant taste of drugs, reduce doses and side effects and improve bioavailability. Also, they allow the production of site-specific drug targeting, which consists of a suitable approach for the delivery of active molecules into desired tissues or cells in order to increase their efficiency. 

The aim of this chapter is to summarize some of the research findings on xylan, a natural polymer extracted from corn cobs, which presents a promising application in the development of colon-specific drug carriers. Physicochemical characterization of the polymer regarding particle size and morphology, composition, rheology, thermal behavior, and crystallinity will be provided. Additionally, research data on its extraction and the development of microparticles based on xylan and prepared by different methods will also be presented and discussed. 

Heller, J., Biodegradable polymers in controlled drug delivery, CRC Crit. Rev. Ther. Drug Carrier Syst.. 1, 39-90, 1984. 

Numerous experimental therapeutics have shown potency in vitro however, when they are tested in vivo, they often lack significant efficacy. This is often attributed to unfavorable pharmacokinetic properties and systemic toxicity, which limit the maximum tolerated dose. These limitations can be overcome by use of drug carriers. Two general types of carrier systems have been designed drug conjugation to macromolecular carriers, such as polymers and proteins and drug encapsulation in nanocarriers, such as liposomes, polymersomes and micelles. 

Probably the most promising polymeric drug carrier system involves polysaccharide molecules. These are natural polymers and are often biodegradable to products that are useful to the host or easily eliminated by the host. Dextrans have been the most extensively used polysaccharide for macromolecular prodrug preparations (79). These materials are biocompatible and the in vivo fate is directly related to their molecular weight. Moreover these macromolecules can be easily targetted to the hepatocytes with D-mannose or L-fucose (20). 

Polymers, being macromolecules of considerable size and weight, have many limitations when used either as drugs or as drug carriers (1). One of the most serious limitations is the existence of epithelial or endothelial barriers (2). However, macromolecules can be transported by a vesicular process known as transcytosis (3,4). In transcytosis, a polymer can be shuttled across an epithelial cell by first... 

E. Tomlinson and J. J. Burger, Monolithic albumin particles as drug carriers, in Polymers in Controlled Drug Delivery (L. Ilium and S. S. Davis, eds.), Wright, Bristol, 1987, p. 25. 

J. B. Lloyd, Soluble polymers as targetable drug carriers, in Drug Delivery Systems. Fundamental and Techniques (P. Johnson and J. G. Llyod, eds.), Ellis Horwood and VCH Verlagsgesellschaft, Chichester and Weinheim, 1987, p. 95. 

R Duncan, M Bhakoo, PA Flanagan, D Sgouras. Evaluation of the biocompatibihty of soluble synthetic polymers designed as drug carriers. Proc Int Symp Controlled Release Bioact Mater 15 121-122, 1988. 

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