Polymers in medicine

As with all branches of science, polymer chemistry is continually advancing. New topics in polymer chemistry which involve new concepts, new polymers or novel uses for existing materials are being studied in research laboratories throughout the world. In this chapter, some of the more important of these developments are described including the use of polymers in medicine, electronically conducting polymers, and polymer liquid crystals. 

Medicine has made major advances in the past 50 or so years partly by the use of devices to improve patient health. These devices include artificial hearts and pacemakers, machines for artificial kidney dialysis, replacement joints for hips, knees, and fingers, and intraocular lenses. These devices need to survive in sustained contact with blood or living tissue. 

In order to be successful as part of a medical device a polymer has to resist both biological rejection by the patient s body and degradation. The human body is an enviromnent which is simultaneously hostile and sensitive, so that materials for application in medicine must be carefully selected. The essential requirement is that these materials are biocompafible with the particular part of the body in which they are placed. The extent to which polymers fulfil this requirement of biocompafibility depends partly on the properties of the polymer and partly on the location in which they are expected to perform. For example the requirements for blood biocompafibility are stringent since blood coagulation may be triggered by a variety of materials. By contrast, the requirements for materials to be used in replacement joints in orthopaedic surgery are less severe and materials as diverse as poly (methyl methacrylate) and stainless steel can be used with minimal adverse reaction from the body. 

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. 

Hip replacement surgery is now routinely used to relieve pain and restore mobility in patients suffering from osteoarthritis. In this condition the surfaces of bone in contact with each other within the joint become worn and the layer of lubricating cartilage disappears. This makes movement of the joint both difficult and painful. By replacing the hip with an artificial joint patients stop experiencing pain and are once again able to move freely. 

Poly(hydroxyethyl methacrylate) Poly(glycolic acid) 

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Heller, J., Control of polymer surface erosion by the use of excipients, in Polymers in Medicine II (E. ChieUni, P. C. Migliaresi, Giusti, and L. Nicolais, eds.). Plenum Press, New York, 1986, pp. 357-368. 

J. E., Synthesis and release of contraceptive steroids from bio-erodible poly(ortho esters), in Polymers in Medicine (E. Chielini and P. Giusti, eds.). Plenum Publishing, New York, 1983, pp. 169-178. 

The most prominent aliphatic polyamides are polyamide 6 and polyamide 6.6. Polyamides are used in a broad range of applications as performance polymers in medicine, textile, and car manufacturing industries. In 2003, the European production ofpolyamides was approximately 3 million tons for technical applications. Of the total polyamide consumption, 94% was polyamide 6 and polyamide 6.6. 

Tamada Y, Ikada Y (1986) Cell attachment to various polymer surfaces. In Chiellini E, Giusti P, Migliaresi C, Nicolais L (eds) Polymers in medicine II. Plenum, New York... 

An important application of polymers in medicine is in advanced drug-delivery systems. These materials control the drug concentration and delivery rate in the body. Hyperbranched polyesters have been suggested for such systems [111]. However, most applications within this field, described in the literature, deal with dendrimers and not with hyperbranched polymers. 

Polymers in Medicine, ed. K. Dusek, Sprlnger-Verleig Press, N.Y. 198V. 

U.Conte, P.Colombo, C.Caramella and A.La Manna, Proc. Symp. on Polymers in Medicine, Plenum, New York, 1983, p. 179. 

The use of synthetic polymers in medicine and biotechnology is a subject of wide interest. Polymers are used in replacement blood vessels, heart valves, blood pumps, dialysis membranes, intraocular lenses, tissue regeneration platforms, surgical sutures, and in a variety of targeted, controlled drug delivery devices. Poly(organosiloxanes) have been used for many years as inert prostheses and heart valves. Biomedical materials based on polyphosphazenes are being considered for nearly all the uses mentioned above. 

Corretge E, Kishida A, Konishi H, Ikada Y (1988) In Migliaresi C (ed) Polymers in medicine III. Elsevier Science, Amsterdam, pp.61-72... 

Klee D, Thissen H, Thelen H, Severich B, Hoffmeister K, Von Dahl J, Hanrath P, Hocker H (1996) Proc International Conference on Polymers in Medicine and Surgery, 1-3 July, Glasgow, UK, The Institute of Materials, pp 87-93... 

J. A. Bakan. Microcapsule drug delivery systems, in R. L. Kronenthal, Z. Oser, and E. Martin (eds.), Polymers in Medicine and Surgery. New York Plenum Press, 1975, pp. 213-235. 

Kronenthal RL (1975) Biodegradable polymers in medicine and surgery. In Kro-nenthal RL, Oser Z, Martin E (eds), Polymers in medicine and surgery. Plenum Press, New York, p 119... 

FIGURE 7.31 Release of hydroxyethyltheophylline in water from a PEO slab (Mw = 0.6 x 106). [Graph reconstructed from data by Apicella et al. in Polymers in Medicine Biomedical and Pharmaceutical Applications, R. M. Ottenbrite and E.M.O. Chiellin (Eds.), Technomic Publishing Co., Lancaster, PA, 1992, p. 23.]... 

D. Klee, H. Thissen, H. Thelen, B. Severich, K. Hoffmeister, J.Yon Dahl, P. Hanrath, and H. Hocker, Proceedings of International Conference on Polymers in Medicine and Surgery 1-3 July, 1996, pp. 87-93. 

The long quest for blood-compatible materials to some extent overshadows the vast number of other applications of polymers in medicine. Development and testing of biocompatible materials have in fact been pursued by a significant number of chemical engineers in collaboration with physicians, with incremental but no revolutionary results to date. Progress is certainly evident, however the Jarvik-7 artificial heart is largely built from polymers [34]. Much attention has been focused on new classes of materials, such... 

PIMS 2000. Proceedings of the Ninth International Conference on Polymers in Medicine and Surgery, held Krems, Austria, llth-13th Sept.2000. 

Kronenthal, R.L. Biodegradable polymers in medicine and surgery. In Polymers in Medicine and Surgery Kronenthal, R.L., Oser, Z., Martin, E., Eds. From Series Polymer Science and Technology Plenum Press New York, 1975 8. 

Bader, H. Ringsdorf, H. Schmidt, B. Water-soluble polymers in medicine. Angew. Makromol. Chem. 1984, 123, 457-485. 

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