Biodegradable polymers, therapeutic

While this book is focused on drug delivery, the value of biodegradable polymers is not limited to this field. Biodegradable polymers will be useful in other areas of medical therapeutics, such as sutures and bone plates and other types of prostheses. The polymers will also be useful in nonmedical fields, for disposable plastics, bottles, diapers and many other entities. 

More than a dozen biocompatible and biodegradable polymers have been described and studied for their potential use as carriers for therapeutic proteins (Table 13.5). However, some of the monomer building blocks such as acrylamide and its derivatives are neurotoxic. Incomplete polymerization or breakdown of the polymer may result in toxic monomer. Among the biopolymers, poly-lactide cofabricated with glycolide (PLG) is one of the most well studied and has been demonstrated to be both biocompatible and biodegradable [12]. PLG polymers are hydrolyzed in vivo and revert to the monomeric forms of glycolic and lactic acids, which are intermediates in the citric acid metabolic pathway. 

PROGRESS IN DESIGN OF BIODEGRADABLE POLYMER-BASED MICROSPHERES FOR PARENTERAL CONTROLLED DELIVERY OF THERAPEUTIC PEPTIDE/PROTEIN... 

Selected examples of therapeutic peptide and protein including vaccines which have been encapsulated into biodegradable polymer-based microspheres are discussed in this section. Besides what is mentioned below, many other proteins and vaccines have been encapsulated in biodegradable polymers, so a glimpse of ongoing... 

Shunmugaperumal Tamilvanan, University of Antwerp, Antwerp, Belgium, Progress in Design of Biodegradable Polymer-Based Microspheres for Parenteral Controlled Delivery of Therapeutic Peptide/Protein Oil-in-Water Nanosized Emulsions Medical Applications... 

Heller, J. Biodegradable polymers in controlled drug delivery. Critical Reviews in Therapeutic Drug Carrier Systems 1984, 1 (1), 39-90. 

Polymer nanoparticles including nanospheres and nanocapsules (Fig. 1) can be prepared according to numerous methods that have been developed over the last 30 years. The development of these methods occurred in several steps. Historically, the first nanoparticles proposed as carriers for therapeutic applications were made of gelatin and cross-linked albumin. Then, to avoid the use of proteins that may stimulate the immune system and to limit the toxicity of the cross-linking agents, nanoparticles made from synthetic polymers were developed. At first, the nanoparticles were made by emulsion polymerization of acrylamide and by dispersion polymerization of methylmethacry-late.f These nanoparticles were proposed as adjuvants for vaccines. However, since they were made of non-biodegradable polymers, these nanoparticles were rapidly substituted by particles made of biodegradable... 

Similar to fumaric acid, L-malic acid is also a naturally occurring four-carbon dicarboxyhc acid and an intermediate in the TCA cycle. It has been used in many food products, primarily as an acidulant. L-Malic acid is compatible with all sugars with low hygroscopicity and good solubihty. In addition, it has therapeutic value for the treatment of hyperammoemia and liver dysfunction and as a component for amino acid infusion. L-Malic acid has been the subject of interest because of its increased application in the food industry as a citric acid replacement and its potential use as a raw material for the manufacture of biodegradable polymers. 

With poly(PGA), a biodegradable polymer backbone is linked to drugs, used primarily as chemotherapy. Conjugates with pa-clitaxel (Cell Therapeutics Inc./Chugai Pharmaceutical Co. Ltd.) showed good results in pre-clinical studies when administered either alone or combined with radiation [37]. A number of clinical studies are also currently under way to determine efficacy against various types of solid tumor [38- 1],... 

Strasser, J.F., et al. Distribution of l,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) and tracers in the rabbit brain following interstitial delivery by biodegradable polymer implants. Journal of Pharmacology and Experimental Therapeutics, 1995, 275(3), 1647-1655. 

Ionotropic gelation process presents numerous advantages along with few major demerits for controlled protein delivery, where the matrix and membrane formed is not capable of controlling the release rate for a long period of time. It does not matter in cell encapsulation, where the membrane should provide sufficient permeability for the cell products such as therapeutic protein. However, for controlled delivery of protein entities, biodegradable polymers that can produce dense membrane, preferably capable of controlling the release rate, should be incorporated or alternative combinations of polyelectrolytes should be explored to control the permeability of membrane, so that the release rate may be controlled over the desired span. ... 

---