Crystallisation in Confinement - A Biological Perspective

The organisation and function of biological systems is based on compartmentalisation, where processes occur within small volumes rather in bulk solution. A simple example of a biological compartment is a cell, which itself can contain many smaller compartments. It is becoming increasingly obvious that confining reactions in this way can dramatically affect the mechanisms and products of biological and chemical reactions by changing the way that molecules interact with each other and their environment.This project will focus on one very important category of biological processes - biomineralisation - which is the formation of mineral-based structures such as seashells, bones and teeth. There is considerable interest in understanding how Nature controls crystallisation to produce materials of this type. Although biominerals are produced under mild reaction conditions, they often exhibit properties which can not only equal but actually surpass those of engineering materials such as concrete. The research in this proposal will investigate how confinement affects crystallisation, and how Nature exploits this to produce such remarkable materials. To-date, research directed towards understanding how Nature controls the formation of minerals has concentrated on the role of organic macromolecules. Further, although biomineralisation invariably occurs within restricted volumes, experiments aiming to mimic these processes are typically carried out in bulk solution. While organic molecules are certainly important, it is very likely that confinement also has a significant affect on these crystallisation processes. Indeed, there are many biogenic crystallisation phenomena, such as the precipitation of calcium phosphate crystals in collagen fibres during bone formation, which cannot be adequately described in terms of crystallisation from bulk solution. Initial work will focus on the precipitation of calcium carbonate and calcium phosphate in small volumes. The research programme will then be extended to investigate the effect of confinement on the crystallisation of a range of other minerals. While it is clear that confinement over a wide range of length scales can strongly affect crystal nucleation and growth, with the exception of freezing phenomena, these effects are poorly understood and as yet unpredictable. The research conducted will lead to a greater understanding of crystallisation in restricted volumes, and will therefore enable us to use confinement to control crystallisation, and to profit from it in synthetic systems. Indeed, there are many technological applications which rely upon crystal growth within constrained volumes such as the fabrication of nano-materials including nanowires and nanotube arrays, general templating processes, drug delivery systems and implants. Crystallisation in confinement is also widespread in Nature, and in addition to biomineralisation processes, includes events such as weathering and frost heave - which occur with great cost to civil engineering the environment and technology. The proposed research is clearly of great relevance to both fundamental research and technology across many disciplines.