BIOMEDICAL POLYMERS

Biomedical Polymers

Biomedical Polymers

Abstract

Today's revolution in biomedical science has raised new hope for the prevention, treatment, and cure of serious illnesses. However, there is growing concern that many of the new basic science discoveries that have been made in recent years may not quickly yield more effective, more affordable, and safe medical products for patients. This is because the current medical product1 development path is becoming increasingly challenging, inefficient, and costly. During the last several years, the number of new drug and biologic applications submitted to FDA has declined significantly; the number of innovative medical device applications has also decreased. The costs of product development have soared over the last decade. Because of rising costs, innovators concentrate their efforts on products with potentially high market return. Developing products targeted for important public health needs (e.g., counterterrorism), less common diseases, prevalent third world diseases, prevention indications, or individualized therapy is becoming increasingly challenging. In fact, with rising health care costs, there is now concern about how the nation can continue to pay even for existing therapies. If the costs and difficulties of medical product development continue to climb, innovation will continue to stagnate or decline, and the biomedical revolution may not deliver on its promise of better health.

Hydrogels, i.e. materials consisting of a permanent, three-dimensional network of hydrophilic polymers and water filling the space between the polymer chains, have a number of biomedical applications, such as wound care products, dental and ophthalmic materials, drug delivery systems, elements of implants, constituents of hybrid-type organs, as well as stimuli-sensitive systems. Among various methods applied for the production of hydrogels, the radiation technique has many advantages, as a simple, efficient, clean and environment-friendly process. It usually allows combining the synthesis and sterilization in a single technological step, thus reducing costs and production time. Efficient application and further development of this method requires broadening of the basic knowledge on the underlying radiation chemistry of polymer systems. Some selected aspects of radiation chemistry of polymers in aqueous solution are presented in this work. The experimental techniques used for studying the radiation-induced processes in polymer solutions are described with special emphasizing of determination of radiation yield of crosslinking by various methods. Also, pulse radiolysis method with different detection methods is briefly described. Selected results of our studies concerning the early stages of polymerization of water-soluble monomers are described together with the studies of mechanisms of radiation-induced crosslinking of polymers in aqueous solution. Separate section of the presentation is devoted to the radiation-induced crosslinking and degradation of polyelectrolytes (i.e. poly (poly (acrylic acid), poly (poly (methacrylic acid)) and biologically important polysaccharide, chitosan. Additionally, special attention is paid to the differences between intra- and intermolecular crosslinking. The irradiation method of changing the proportion between these two processes at the expense on intramolecular crosslinking is described. This leads to the synthesis of internally crosslinked polymeric single coils, i.e. nanogels. The selected properties of such materials are described. Some expectations as to the further research directions in the field of radiation-synthesized ...