Polymer applications controlled-release

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. 

Major polymer applications pharmaceutical applications, controlled release drugs,. polyester fibers, unsaturated polyester resins, oil exploration, polyols, surfactants, haircare, switching elements, polymer electrolytes, lithium batteries, nanocomposites... 

One way of classifying polymers in pharmaceutical applications is to divide them into three general categories according to their common uses (1) polymers in conventional dosage forms (2) polymers in controlled release dosage forms and (3) polymers for packaging. 

In terms of pharmaceutical applications, copolymers have been used as drug carriers for controlled release applications. Controlled release polymer vesicles are prepared using hydrolysable block copolymers such as PLAEG, which is poly-lactic acid co-polyethylene glycol, PLAEG (ie, polycaprolactone-co-polyethylene glycol). 

M. Hruby, J. Kucka, O. Lebeda, H. Mackova, M. Babic, M. Kondk, Studenovsk, A. Sikora, J. Kozempel and K. Ulbrich, New bio-erodable thermoresponsive polymers for possible radiotherapeu-tic applications, /. Control. Release, 119,25-33 (2007). 

Applications controlled release drugs, haircare, nanocomposites, oil exploration, pharmaceutical applications, polyester fibers, polyester resins, polymer electrolytes, polyols, surfactants, switching elements, unsaturated lithium batteries ... 

Based on these properties, LDHs are considered as very important layered crystals with potential applications in catalysis,controlled drugs release, gene therapy, improvement of heat stability and flame retardancy of polymer composites,controlled release or adsorption of pesticides, preparation of novel hybrid materials for specific applications, such as visible lumines-cence, UV/photo-stabilization, and magnetic nanoparticle synthesis and wastewater treatment. ... 

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. 

Polylactic acid (PLA) has been produced for many years as a high-value material for use in medical applications such as dissolvable stitches and controlled release devices, because of the high production costs. The very low toxicity and biodegradability within the body made PLA the polymer of choice for such applications. In theory PLA should be relatively simple to produce by simple condensation polymerization of lactic acid. Unfortunately, in practice, a competing depolymerization process takes place to produce the cyclic lactide (Scheme 6.10). As the degree of polymerization increases the rate slows down until the rates of depolymerization and polymerization are the same. This equilibrium is achieved before commercially useful molecular weights of PLA have been formed. 

Initial tests in the rat revealed a high degree of tissue compatibility of Dat-Tyr-Hex derived polymers. More detailed tests are now in progress. In addition, tyrosine derived polymers are currently being evaluated in the formulation of an intracranial controlled release device for the release of dopamine, in the design of an intraarterial stent (to prevent the restenosis of coronary arteries after balloon angioplasty), and in the development of orthopedic implants. The use of tyrosine derived polymers in these applications will provide additional data on the biocompatibility of these polymers. 

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. 

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]. 

---