Preface

When speaking of glass, most people think of the silicate material our windows and drinking vessels are made of. Not surprisingly, the field of bioactive glasses also has long been dominated by silicate compositions, while for phosphate materials, crystalline compounds have been the main focus. Still, phosphate glasses for biomaterials applications have been investigated for several decades, and our institutes have been actively involved in this field.

Phosphate and borate glasses offer some unique properties compared to silicate glasses; in particular, the ability to dissolve completely in aqueous media distinguishes them from conventional silicate glasses. While this water solubility constitutes a profound disadvantage for many other applications, in the field of biomaterials it is a key benefit. Together with the compositional flexibility of glasses, allowing for incorporation of many different therapeutic ions in broad range of concentrations, their solubility makes them of interest as controlled-release devices. While glasses, owing to their hardness and brittleness, have long been considered as hard-tissue replacement, cotton-wool-like materials or fibre meshes made from phosphate or borate fibres have generated interest for soft-tissue applications.

The properties of phosphate and borate glasses originate in their atomic structure, which shows a number of peculiarities compared with silicate glasses. Phosphate glasses, for example, show a larger glass-forming range because of their main building unit typically connecting to three neighbours only rather than four, resulting in more structural flexibility. Borate glasses are well known to show non-linear changes in properties with linear compositional variation, known as the boron anomaly. We believe that understanding the chemical structure of these glasses and how it relates to composition and properties is important for tailoring and fine-tuning their properties to meet clinical demands.

We hope that this book will contribute to making phosphate glasses and borate glasses better known, inspiring further research and extending the field of application of these materials. The book is aimed at readers from various backgrounds and different levels of previous knowledge. Introductory chapters cover the basics of phosphate and borate glasses, their structure and fundamental properties, including their reactions with water, for people new to the field. Following chapters address synthesis routes via sol–gel as an alternative to the conventional melt approach or the preparation of coatings. In the remaining chapters, various aspects of applications or potential future applications are addressed, with a particular focus on medical devices and clinical products. Each chapter has been written by international experts and authorities working in the respective fields.

We thank the authors for their great contribution to this informative book. We also would like to acknowledge Prof. Julian R Jones, the editor of the Royal Society of Chemistry's book series Biomaterials Science, for giving us the opportunity to edit this book. Finally, we thank the staff at the Royal Society of Chemistry for their constant support during the preparation, writing and editing of this book.

Delia S. Brauer

Akiko Obata

Toshihiro Kasuga