Bioresorbable polymers materials

To satisfy the requirements of biocompalibility and biodegradability, the materials used in medical and pharmaceutical fields for intravenous injection are generally characterized by polymeric NPs based on polyesters, which are biocompatible and biodegradable. In this chapter, we cover the most common bioresorbable polymer materials that are synthesized. Then, we discuss the methods adopted for the synthesis of NPs made of bioresorbable polymers. Finally, we present the most common applications of bioresorbable polymer NPs in medical and pharmaceutical fields and the hurdles involved in their use. 

A plethora of bioresorbable polymer materials are adopted for medical and pharmaceutical applications. Among them, aliphatic polyesters, polycarbonates, poly (amino acids), and polyphosphoesters are the main representatives. For the synthesis of NPs, aliphatic polyesters are the most adopted materials. Data on a huge number of different polyesters can be found in the literature, but this chapter focuses on the main polyesters poly (lactic acid) (PLA), poly(glycolic acid) (PGA), polycaprolactone (PCL), and their copolymers [4]. 

The growth in polymer-made biomedical devices has in part been made possible thanks to the discovery of a new class of materials bioresorbable polymers. The term bioresorbable has become a common expression, used in order to qualify this type of macromolecules. A scientifically accepted definition for such materials is the following a material for which the degradation is mediated, at least partly, from a biological system (Ottenbiight and Scott, 1992). This statement shows one of the most important features of these materials. Devices made of bioresorbable polymers are subjected to degradation in the human body which means they do not need to be removed. 

Note This chapter was previously published as Chapter 3 Synthetic bioresorbable polymers by R. E. Cameron and A. Kamvari-Moghaddam, originally published in Degradation rate of bioresorbable materials predication and evaluation, ed. F. J. Buchanan, Woodhead Publishing Limited, 2008 ISBN 978-1-84569-329-9. 

Bioresorbable polymers are put to extensive use as medical materials because of their diverse biodegradability, good mechanical properties and biocompatibility. The ability to tailor their chemical structures to control their degradation behaviour and rate is a great advantage when it comes to designing implants with suitable mechanical and degradational properties for their intended use. 

Cameron, R.E., Kamvari-Moghaddam, A., 2008. Synthetic bioresorbable polymers. Degradation Rate of Bioresorbable Materials. Woodhead Pubishing Limited, Cambridge England, pp. 43 6. 

The bioresorbable polymers in medicine represent a diverse family within the field of biomaterials. To understand properly aU the science behind these attractive materials, it is necessary to start with general definitions. 

When designing a medical device based on a bioresorbable polymer, the degradation ability of the material during all the phases from the synthesis to the complete resorption in vivo must be carefully considered. In this regard, synthetic polymers are more versatile compared to natural origin polymers, thereby allowing a finer control of the theoretical degradation rate. However, this rate depends from a number of external factors such as production process conditions (eg, humidity, temperature) and site of implantation (eg, pH, mechanical stress) [13—18]. 

The choice of the right suppliers for raw materials is critical because validation of a bioresorbable polymer includes the characteristics of all the suppliers involved in the production process, ie, their quality systems and certifications. An unreliable supplier represents a possible source of issues when producing a device under regulatory approval. For example, a supplier could fail obliging the company to begin a validation process for the new supplier, the quality of the raw material could be erratic, or the supply of a determined material could be discontinued [20]. Moreover, in the past years the number of suppliers of bioresorbable materials did not increase as expected,... 

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