Biopolymers for Biomedical and Biotechnological Applications. Группа авторов
for a relevant and applicable test system. The implantation test is set up so that the evaluation is conducted by comparing the result of the test site histopathology with the control site. Thus, if the chosen control article is a hard piece of metal or plastic that would not induce interaction with the surrounding tissues, then the comparison with the implant site of the biopolymer would probably not be favorable, leading to a higher tissue reactivity and making it look like the test material is non‐biocompatible. However, if an appropriate control is used, then the histopathological comparison of the test and control article sites can be made with confidence, and a correct understanding of the implantation risk of the material can be drawn.
1.5 Conclusion
Biopolymers occupy a unique and advantageous space as a medical device material. Devices made from these naturally occurring or biomimetic substances have the distinct advantage that the material itself is akin to those tissues the device contacts. From a bulk perspective, there is no concern regarding the material as a foreign body. Biopolymers also have environmental and manufacturing advantages as they are often produced not from petroleum derivatives but by living systems.
In contrast to the major advantages presented by biopolymers within the context of biocompatibility, there are a couple of key concerns that must be addressed. The natural origin of these materials does not mean that they are free from manufacturing residuals. Contact with solvents through manufacturing and purification steps can introduce contamination, as can contact with storage and primary packaging materials. Chemical analysis screening for these compounds can be complicated by the complex organic nature of the device material. Additionally, many biopolymers are degradable or resorbable by the body. While this is, in principle, a positive therapeutic effect, it can be difficult to prove that the safety of the device does not change over the degradation lifetime.
The pallet of materials afforded by biopolymers allows an even broader spectrum of medical devices with huge potential to help mankind. The biocompatibility principles discussed in this chapter can be applied to biopolymers to address concerns with regard to their safety. Use of thoughtful risk‐based testing strategies can conservatively mitigate risk, allowing more of these devices to reach full maturity in development and arrive on the market.
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2 Advanced Microbial Polysaccharides
Filomena Freitas1, Cristiana A.V. Torres1, Diana Araújo1, Inês Farinha1,2, João R. Pereira1, Patrícia Concórdio‐Reis1, and Maria A.M. Reis1
1 UCIBIO‐REQUIMTE, Chemistry Department, Faculty of Sciences and Technology, Universidade Nova de Lisboa, Campus da Caparica, Caparica, 2829‐516, Portugal
2 73100 Lda., Rua Ivone Silva nº6 4ºpiso, 1050‐124 Lisboa, Portugal
2.1 Introduction
Microbial polysaccharides are high molecular weight (Mw) carbohydrate polymers produced by microorganisms, namely, bacteria, fungi, yeast, and microalgae [1,3]. They include intracellular polysaccharides that are accumulated in the cytoplasm of the cells as carbon and energy reserves (e.g. glycogen), cell‐wall polysaccharides that contribute to the cells' structural stability (e.g. chitin), and extracellular polysaccharides that are secreted by the cells, forming either a capsule that remains associated with the cell surface (capsular polysaccharides [CPS]) or a slime that is loosely bound to the cell surface (exopolysaccharides [EPS]) [2,4]. Of the last type, CPS are mostly associated with the pathogenicity of bacteria and virulence‐promoting factors [5], while EPS have been proposed to provide protection against environmental stress, cell adherence to surfaces, and carbon or water storage reserves [6].
Polysaccharides can be used into two main areas of