Nanostructured biomaterials: investigating hierarchical calcite crystal formation

点击翻译按钮获取中文摘要

Living organisms are well known to produce complex mineralised structures that are used for a wide variety of functions, such as navigation, support and protection of soft parts of the body, among others. The formation of such mineralised tissues requires an intricate biological machinery that controls all steps involved in mineralization, from controlling the transport of ions to the mineralisation site to controlling crystal nucleation, growth and morphology and the formation of micron- and macro-sized mineralized tissues. To date, no study could address how all these factors are integrated during the biomineralisation process. As such, what is missing is a fundamental understanding on how cells control processes occurring at different stages and lengths scales, going from the transport of ions to the mineralisation site to crystal nucleation, growth and assembly of the crystals into a hierarchical multi-crystalline mineralised tissue. This issue in the long term, will provide biologists and chemists with new tools to design and synthesise advanced materials with potential applications for biomedical, industrial and technological applications.The aim of this project is to understand how cells control the formation of mineralized tissue, from the first crystals that are formed at the nano-scale, to the mature mineral that is composed of crystals organised in a higher-order structure. For this, we will investigate the formation of coccolith scales made of calcite that are produced by the unicellular marine algae Emiliana huxleyi and Coccolithus pelagicus. These unicellular provide unique models in which all stages in mineralisation, occurring at all length scales - from the onset of mineral formation to the mature mineral - can be investigated in a single system and in a time-resolved manner to elucidate how they contribute to the formation and overall properties of the biomineral.To achieve this aim, we will combine confocal microscopy, cryo-scanning electron microscopy and cryo-transmission electron microscopy. These techniques will provide detailed structural and morphological information on all stages of mineral formation. We will focus on the following aspects:1- Understand the mechanisms of transport of CaCO3 to the coccolith vesicle, which is the mineralisation site. We will combine live-cell imaging and cryo-scanning electron microscopy, to visualise the transport of calcium ions to the mineralization site during mineral formation;2- Elucidate the mechanisms of control over crystal nucleation, growth and morphology. We will address how oriented nucleation is controlled by an organic template, and how crystal morphology is shaped during coccolith formation. This objective will be achieved using cryo-transmission electron microscopy (cryoTEM) to characterize the different stages of coccolithogenesis in situ;3- Understand the nature of the initially deposited mineral. We hypothesise that the mineral is initially deposited as a non-crystalline precursor which later crystallises into calcite. We intend to characterise this initial mineral phase and understand its role in the formation of coccolith structures. This objective will be achieved combining cryoTEM with Raman spectroscopy to characterise the initially deposited mineral phase, and follow the development of crystallinity.Taken together, this study will be the first time in which all stages in biomineral formation will be visualized in a single system. It will reveal unprecedented information on how living organisms control and tailor the size, morphology and construction of complex mineralized structures at all length scales. In the long term, these results will lead to new strategies for the synthesis of novel materials with controllable size, structure and material properties for several industrial and technological applications.