Focus On. .. Biodegradable Polymers

This chapter focuses on biodegradable polymers used in the health domain. Some examples of biodegradable and bioerodible polymers are presented in Table 4.1, and some of their thermomechanical properties are given in Table 4.2. 

The programme showed a special focus on biodegradable polymers as an important resource for reducing environmental contamination and waste. 

Although most of the polymers listed in Table I can be used to make microsphere formulations, each polymer requires different processing conditions. For the more hydrophobic polymers, such as polylactides and polyanhydrides, similar processes are utilized to make microsphere formulations. Since the polylactides are the only commercially approved biodegradable polymers for human use, the discussion herein of the engineering aspects of producing microsphere formulations will focus on these polymers. 

In this connection the 7 World Conference on Biodegradable Polymers Plastics held in Tirrenia (Pisa) - Italy in June 2002, as renamed continuation of the series of six former International Scientific Woricshops on Biodegradable Polymers and Plastics started in 1989, was focused on the following topics and issues comprising ... 

Nowadays, a strategic area of research is the development of polymers based on carbohydrates due to the worldwide focus on sustainable materials. Since the necessary multi-step synthesis of carbohydrate-based polymers is not economical for the production of commodity plastics, functionalization of synthetic polymers by carbohydrates has become a current subject of research. This aims to prepare new bioactive and biocompatible polymers capable of exerting a temporary therapeutic function. The large variety of methods of anchoring carbohydrates onto polymers as well as the current and potential applications of the functionalized polymers has been discussed recently in a critical review [171]. Of importance is that such modification renders not only functionality but also biodegradability to the synthetic polymers. 

Since the purpose of this book is to describe applications of biodegradable polymers to drug delivery systems, particularly from the perspective of the materials employed, the approach taken in this chapter has been to focus on the natural biodegradable polymers which have been used most extensively as matrices for the delivery of drugs. Consideration was also given to the fact that collagen has not been the subject of any recent reviews. 

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. 

Recently, many studies have focused on self-assembled biodegradable nanoparticles for biomedical and pharmaceutical applications. Nanoparticles fabricated by the self-assembly of amphiphilic block copolymers or hydrophobically modified polymers have been explored as drug carrier systems. In general, these amphiphilic copolymers consisting of hydrophilic and hydrophobic segments are capable of forming polymeric structures in aqueous solutions via hydrophobic interactions. These self-assembled nanoparticles are composed of an inner core of hydrophobic moieties and an outer shell of hydrophilic groups [35, 36]. 

As shown in Table I, the plastic component of MSW has increased dramatically. Past development of synthetic plastic formulations has focused on reducing the photo, chemical, and biological degradation of the plastic polymers. However, the persistence of plastics in the environment as litter, potential marine hazard, and with concern for global carbon cycling 1,6) has focused recent attention on the recycling of plastics or development of new biodegradable plastic formulations. 

Wherever possible we will therefore focus on degradation studies with pure polymers. The degree of biodegradation of PVAc and PVA depends on characteristics that are intrinsically related to the physical and chemical properties of the polymer. As many of these factors can differ to some extent depending on the... 

This book is a companion volume to Pharmaceutical Technology Controlled Drug Release, Volume 1, edited by M.H.Rubinstein and published in 1987. It focused on the different types of polymeric materials used in controlled release. This book extends these concepts to include drug properties, design and optimization, coating, the effect of food and pharmacokinetics. It also reflects the growing interest in biodegradable polymers in oral and topical formulations and the use of sterile implants. 

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