Periodic Reporting for period 1 - AMORPREBIO (Amorphous Precursors in Biomineralization.)
Okres sprawozdawczy: 2018-09-01 do 2020-08-31
Calcium carbonate is an inorganic compound ubiquitous in nature present as minerals and biominerals (produced by organisms), with great environmental importance and extensive industrial applications. Carbonates are important biominerals building blocks of biological bodies, making up the skeletal structure of invertebrate organisms in the marine, freshwater, and terrestrial realm. Calcium carbonate is also a key compound for atmospheric CO2 sequestration through mineral trapping regulating CO2 emission levels. Therefore, due to its ubiquity and broad applications understanding the mechanisms of the CaCO3 formation and its governing parameters is of great importance.
Recently, many studies have revealed that calcification, the process of CaCO3 formation, involves the precipitation of an amorphous precursor, which acts as an intermediate in the formation of the final CaCO3 crystalline mineral (e.g. calcite, vaterite or aragonite). Therefore, the main goal of this project was to understand the role of the amorphous calcium carbonate (ACC) in the (bio)mineralization process. With this aim, in this project, we characterized the amorphous precursor phase and the crystalline mineral and investigate which factors (e.g. water, presence of organic molecules) affect the transformation kinetics of the amorphous precursor into the crystalline phase (Fig. 1) using a wide range of traditional and advanced techniques. These advanced techniques, which included synchrotron (X-ray Photon Correlation Spectroscopy (XPCS)) and neutron techniques (Incoherent Inelastic Neutron Scattering (INS)), are more sensitive to small structural changes than other traditional characterization techniques and their use makes the results and outcomes of the AMORPREBIO project very original and innovative.
Recently, many studies have revealed that calcification, the process of CaCO3 formation, involves the precipitation of an amorphous precursor, which acts as an intermediate in the formation of the final CaCO3 crystalline mineral (e.g. calcite, vaterite or aragonite). Therefore, the main goal of this project was to understand the role of the amorphous calcium carbonate (ACC) in the (bio)mineralization process. With this aim, in this project, we characterized the amorphous precursor phase and the crystalline mineral and investigate which factors (e.g. water, presence of organic molecules) affect the transformation kinetics of the amorphous precursor into the crystalline phase (Fig. 1) using a wide range of traditional and advanced techniques. These advanced techniques, which included synchrotron (X-ray Photon Correlation Spectroscopy (XPCS)) and neutron techniques (Incoherent Inelastic Neutron Scattering (INS)), are more sensitive to small structural changes than other traditional characterization techniques and their use makes the results and outcomes of the AMORPREBIO project very original and innovative.
With the aforementioned aim, pure ACC and ACC doped with aspartic acid, polyaspartic acid (pAsp) and polystyrene sulfonate (PSS) crystallization experiments were performed under conditions of controlled humidity. These conditions mimic the low water activities present during crystallization in biomineralization systems, where the amorphous phase is enclosed in a membrane or compartment with a limited amount of water. The microscopic dynamics of ACC with and without the presence of different organic molecules such as those present in biogenic carbonates, and at different hydration states were studied. Through the research, we have confirmed that large changes in the dynamics can be caused by very small structural changes. In addition, the study carried out shed light into the dynamic behavior of ACC and the influence of different additives (e.g. proteins, as pAsp) and water (ACC with different hydration levels) on the crystallization kinetics. The X-ray photon correlation spectroscopy (XPCS) experiments revealed that the amount of adsorbed water has a strong control on its diffusive dynamics and they showed an unexpected reversible behavior of the dynamics upon dehydration and rehydration cycles (in pure ACC and ACC doped with pAsp) that has not been reported previously. Results of crystallization experiments under conditions of controlled humidity indicated that the adsorbed water is enough to spark crystallization of calcite and a direct proportionality was found between the relative humidity of the environment and the final calcite crystal size (Fig. 2). Control of the water activity and water content is, therefore, a possible way to regulate biomineral crystallinity both in nature and for the design of functional biomimetic materials.
During the development of the project, several dissemination activities were carried out to contribute to making science more accessible and interesting to students, teachers and the general public. Among the activities, the results were presented in several seminars for academic staff, undergraduates, postgraduates and postdoctoral researchers. Public dissemination was carried out by the website of the project, which explains the importance, main aims of the project, and its innovative aspects as well as the research team involved. The dissemination to the scientific community has been performed through the publication of the results in scientific articles (1 published, 2 under review, and 1 in preparation) and through the participation in the Goldschmidt conferences hold in Barcelona in 2019.
During the development of the project, several dissemination activities were carried out to contribute to making science more accessible and interesting to students, teachers and the general public. Among the activities, the results were presented in several seminars for academic staff, undergraduates, postgraduates and postdoctoral researchers. Public dissemination was carried out by the website of the project, which explains the importance, main aims of the project, and its innovative aspects as well as the research team involved. The dissemination to the scientific community has been performed through the publication of the results in scientific articles (1 published, 2 under review, and 1 in preparation) and through the participation in the Goldschmidt conferences hold in Barcelona in 2019.
The AMORPREBIO project has provided new insights about the strategies for controlled biomineralization routes, relevant not only to human health (bones, teeth) but also to other applications related to the environment, such as CO2 sequestration via mineral trapping. Moreover, the advance beyond the state-of-the-art of the knowledge of how the amorphous calcium carbonate precipitates under laboratory conditions could have a huge impact on the competitiveness of the European industry decreasing the costs associated with the CO2 mitigation systems or using the biomineralization mechanisms studied for the development of novel biomimetic materials.