Proteins, controlled release, polymer

Keywords Proteins Controlled release Polymers Liposomes Microcrystals Pulmonary... 

Ethylene vinyl acetate has also found major applications in drug delivery. These copolymers used in drug release normally contain 30-50 wt% of vinyl acetate. They have been commercialized by the Alza Corporation for the delivery of pilocarpine over a one-week period (Ocusert) and the delivery of progesterone for over one year in the form of an intrauterine device (Progestasert). Ethylene vinyl acetate has also been evaluated for the release of macromolecules such as proteins. The release of proteins form these polymers is by a porous diffusion and the pore structure can be used to control the rate of release (3). Similar nonbiodegradable polymers such as the polyurethanes, polyethylenes, polytetrafluoroethylene and poly(methyl methacrylate) have also been used to deliver a variety of different pharmaceutical agents usually as implants or removal devices. 

DW Urry, CM Harris, CX Luan, CH Luan, C Gowda, TM Parker, SQ Peng, J Xu. Transductional protein-based polymers as new controlled-release vehicles. In K Park, ed. Controlled Drug Delivery Challenges and Strategies. Washington, DC ACS, 1997, pp 405-437. 

Panyam J, Dali MM, Sahoo SK et al (2003) Polymer degradation and in vitro release of a model protein from poly(D, L-lactide-co-glycolide) nano- and microparticles. J Control Release 92 173-187... 

Self-assembly of polymers in the bulk Polymer micelles, polymero-somes, gelled macromole-cules, nano-tubes, protein fibres/tapes produced by aggregation at low pH, controlled release vehicles, smart delivery systems 50-500 nm Forster and Konrad, 2003 Sanguansri and Augustin, 2006 Dickinson 2006a Graveland-Bikker and de Kruif, 2006 van der Linden, 2006... 

Cappello, J., Crissman, J. W., Crissman, M., Ferrari, F. A., Textor, G., Wallis, O., Whidedge, J. R., Zhou, X., Burman, D., Aukerman, L., and Stedronsky, E. R. (1998). In-situ self-assembling protein polymer gel systems for administration, delivery, and release of drugs. /. Control. Release 53, 105-117. 

Bernkop-Schnurch A (1998) The use of inhibitory agents to overcome the enzymatic barrier to perorally administered therapeutic peptides and proteins. J Control Release 52(1-2) 1-16. Bernkop-Schnurch A, Krajicek ME (1998) Mucoadhesive polymers as platforms for peroral peptide delivery and absorption synthesis and evaluation of different chitosan-EDTA conjugates. J Control Rel 50 215-223... 

A sustained drug release is favourable for drugs with short elimination half-life. It can be controlled by hydration and diffusion mechanisms or ionic interactions between the drug and the polymeric carrier. In the case of diffusion control the stability of the carrier system is essential, as its disintegration leads to a burst release. Therefore, the cohesiveness of the polymer network plays a crucial role in order to control the release over several hours. Due to the formation of disulphide bonds within the network thiomers offer adequate cohesive stability. Almost zero-order release kinetics could be shown for insulin embedded in thiolated polycarbophil matrices (Clausen and Bernkop-Schnurch 2001). In the case of peptide and protein drugs release can be controlled via ionic interactions. An anionic or cationic polymer has to be chosen depending... 

Park,T. G., Lu, W., and Crotts, G. (1995), Importance of in vitro experimental conditions on protein release kinetics, stability and polymer degradation in protein encapsulated poly(D,L-lactic acid-co-glycolic acid) microspheres,/. Controlled Release, 33,211-222. 

Bittner, B., Witt, C., Mader, K., and Kissel, T. (1999), Degradation and protein release properties of microspheres prepared from biodegradable poly(lactide-co-glycolide) and ABA triblock copolymers Influence of buffer media on polymer erosion and bovine serum albumin release, J. Controlled Release, 60, 297-309. 

Determan, A. S., Wilson, J. H., Kipper, M. J., Wannemuehler, M. J., and Narasimhan, B. (2006), Protein stability in the presence of polymer degradation products Consequences for controlled release formulations, Biomaterials, 27, 3312-3320. 

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