Polymers in Medical and Biomedical Applications

The aim of this chapter is to give a brief selective overview of typical biomedical areas where cationic polymers can be employed. The use of cationic polymers in tissue engineering is a high priority topic in this chapter and several aspects on this phenomenon are given related to this is the potential of cationic hydrogels for medical and pharmaceutical applications. The importance of cationic polymers and copolymers as non-viral vectors in gene therapy is described, as well as how micelles and vesicles based on cationic polypeptides can form nanostructures by self-assembly. The potential of cationic polymers for drug delivery applications is also elucidated. 

Over the past decades, CHNCs have been widely studied and used in various chemical and biomedical applications, such as polymer/CHNC nanocomposites, tissue engineering scaffolds, hydrogels, and medical wound dressings. In the following sections, the structure, preparation, characterization, and applications of CHNCs in the biomedical area will be briefly reviewed. 

Although there are a large number of polymer blends available, only those blends that contain biodegradable polymers and/or natural components are applicable in the biomedical engineering, particularly in tissue engineering. The use of biodegradable polymer blends has opened a wide area of study. Different combination of blends has led to obtain different mechanical properties, which are indeed very meritorious in medical and other engineering applications. 

Shape memory PU and polymers in general have tremendous applications in biology and medicine [104, 105] especially for biomedical devices which may permit new medical procedures. Because of the ability to memorise a permanent shape that can be substantially different from an initial temporary phase, a bulky device could be introduced into the body in a temporary shape (e.g., string) that could go through a small laparoscopic hole and then be expanded on demand into a permanent shape at body temperature. 

Green plastics comprise only a very small part (less than 1%) of today s plastics. They do, however, make up a significant part of some specialty, niche markets starch-based loose-fill packaging now constitutes 30% of the loose-fill packaging market. The plastics described here are those currently commercially available, and are limited mainly to those available in the United States. Manufacturers are named only for illustrative purposes the list is not intended to be comprehensive. The plastics materials are described generically, with respect to the major polymer constituent(s) for each generic type there are likely to be many specific formulations. Brief mention is made, at the end, of some materials that have been studied in the laboratory. Biomedical applications are described separately (see Biodegradable Polymers, Medical Applications). 

The biological and biomedical applications of polymeric materials have increased greatly in the past few years. This book will detail some, but not all, of these recent developments. There would not be enough space in this book to cover, even lightly, all of the major advances that have occurred. Some earlier books and summaries are available by two of this book s Editors (Gebelein Carraher) and these should be consulted for additional information. The books are "Bioactive Polymeric Systems" (Plenum, 1986) "Polymeric Materials In Medication" (Plenum, 1986) "Biological Activities of Polymers" (American Chemical Society, 1982). Of these three, "Bioactive Polymeric Systems" should be the most useful to a person who is new to this field because it only contains review articles written at an introductory level. The present book primarily consists of recent research results and applications, with only a few review or summary articles. 

The use of metal and organometallic containing polymers in medical applications is widespread focusing on siloxane polymers and to a lesser degree on polyphosphazenes (for instance 1). This work is focused on the use of these polymers as medical materials in applications such as biomedical implants in catheters, blood pumps and breasts. 

Biomedical Applications. In the area of biomedical polymers and materials, two types of appHcations have been envisioned and explored. The first is the use of polyphosphazenes as bioinert materials for implantation in the body either as housing for medical devices or as stmctural materials for heart valves, artificial blood vessels, and catheters. A number of fluoroalkoxy-, aryloxy-, and arylamino-substituted polyphosphazenes have been tested by actual implantation ia rats and found to generate Httle tissue response (18). 

An idea of the range of materials and applications for polymers in medicine can be gained from the information in Table 10.1. As can be seen from this table a number of polymers are used in medical applications. One particular such polymer is poly (methyl methacrylate), PMMA. Early on it was used as the material for fabricating dentures later other biomedical applications developed. For example, PMMA is now used as the cement in the majority of hip replacement operations worldwide. 

Polyvinyl alcohol (PVA), which is a water soluble polyhidroxy polymer, is one of the widely used synthetic polymers for a variety of medical applications [197] because of easy preparation, excellent chemical resistance, and physical properties. [198] But it has poor stability in water because of its highly hydrophilic character. Therefore, to overcome this problem PVA should be insolubilized by copolymerization [43], grafting [199], crosslinking [200], and blending [201], These processes may lead a decrease in the hydrophilic character of PVA. Because of this reason these processes should be carried out in the presence of hydrophilic polymers. Polyfyinyl pyrrolidone), PVP, is one of the hydrophilic, biocompatible polymer and it is used in many biomedical applications [202] and separation processes to increase the hydrophilic character of the blended polymeric materials [203,204], An important factor in the development of new materials based on polymeric blends is the miscibility between the polymers in the mixture, because the degree of miscibility is directly related to the final properties of polymeric blends [205],... 

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