Polyphosphazenes for biomedical devices and other applications

The work described in this thesis deals with the design, synthesis, and characterization of novel polyphosphazene based materials mainly used for biomedical applications. Most of the polymers that were synthesized were tested in vitro and incorporated into a polymeric devices such as biosensors, polymer actuators, nerve guide conduits, artificial bone composites, and microhydrogel arrays. The research described here deals with polyphosphazenes for the following specific applications in the respective chapters. Chapter 2) Artificial bone composites, Chapter 3) Nerve guide conduits, Chapter 4) Microhydrogel arrays, Chapter 5) Cell encapsulation, Chapter 6) Selective cell adhesion, Chapter 7) ToF-SIMS characterization.;Chapter 1 introduces the topic of polyphosphazenes. This chapter begins with the history of the discovery and development of these types of materials. It also talks about the background chemistry that is typically used to prepare such materials. A list and discussion of many applications that this family of materials has been developed for. Chapter 2 describes the synthesis and characterization of alanine based biodegradable polyphosphazenes. These materials were tested to determine the rate of degradation. They were also tested in vitro to determine cell proliferation and effect of enzymatic activity. The materials here were later evaluated for the ability to form hydroxyapatite composites. In Chapter 3, the design and synthesis of lactato-based polyphosphazenes for nerve guide conduits are described. The polymer candidates were tested for degradation rate, in vitro, and in vivo. These materials were also successfully cast into tubes. Chapter 4 discusses the development of UV photocrosslinkable polyphosphazenes, which were incorporated into microhydrogel arrays. The intended use for this system was for microarray biosensors were cells or enzymes could be entrapped. Chapter 5 is an extension of chapter 4 were the cytotoxicity of MEEP and MEEP based hydrogels is explored. The feasibility of entrapping cells or enzymes in the polymers discussed in chapter 4 was explored. Chapter 6 explores the design and synthesis of a series of polyphosphazenes that will either promote (+ polymer) or prevent (- polymer) cellular growth and adhesion. The two types of polymers were microfabricated and cultured with nerve cells to test the cellular selectivity of the materials. These materials were used to fabricate artificial neural networks for biosensor applications. Chapter 7 focuses on the characterization of the polymers discussed in chapter 6 using ToF-SIMS. This was the first time that these polymers were analyzed using this technique and it showed that the polymers could be readily patterned in distinct regions.