Bio-inspired Magnetite Mineralization in Gelatin Hydrogels : A Small Angle Scattering Investigation

235 Pages·2016·13.89 MB·English

by  Baohu Wu

Bio-inspired Magnetite Mineralization in
Gelatin Hydrogels: A Small Angle Scattering Investigation
Dissertation
zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften
“doctor rerum naturalium“
(Dr. rer. nat.)

vorgelegt von
Baohu Wu

an der

Mathematisch – Naturwissenschaftliche Sektion
– Fachbereich Chemie –
Tag der mündlichen Prüfung: 21. Juni. 2016

1. Referent: Prof. Dr. Helmut Cölfen
2. Referent: Prof. Dr. Alexander Wittemann
Konstanzer Online-Publikations-System (KOPS)
URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-0-377350

Preamble

This work was financed by the German Research Foundation (Deutsche Forschungsge-
meinschaft, DFG) through the priority project SPP 1569 “Generation of multifunctional
inorganic materials by molecular bionics”. The research for this thesis was carried out at
Jülich Centre for Neutron Science, Forschungszentrum Jülich, jointly with the Depart-
ment of Chemistry, University of Konstanz. At the Forschungszentrum Jülich, Dr. Vi-
taliy Pipich and Dr. Dietmar Schwahn supervised the project and provided assistance to
design, prepare and conduct the Experiments.

Acknowledgment
Foremost, I would like to express my deepest appreciation to my thesis supervisor Prof.
Dr. Helmut Cölfen and Prof. Dr. Andreas Zumbusch from University of Konstanz, Dr.
Vitaliy Pipich and Dr. Dietmar Schwahn from Forschungszentrum Jülich for their great
support of my Ph.D. study and research during the last three years. Their guidance
helped me in all the time of research and writing of this thesis. Without their assistance
and inspiration this thesis would not have been possible.
Throughout the three years of my thesis work, important guidance came from Dr. Vi-
taliy Pipich. I truly benefited from his considerable expertise in small angle neutron
scattering and his assistance. He helped me to carry out and prepare the various neutron
scattering experiments at the JCNS, which constitute the fundament of this thesis.
I would like to express my sincere gratitude to Dr. Dietmar Schwahn, who helped me to
understand the technique of small-angle scattering and the physics behind the biominer-
alization.
Acknowledgment is given to Maria Siglreitmeier, Christian Debus, Tina Kollmann, Dr.
Damien Faivre, Prof. Dr. Dirk Zahn for the good collaboration throughout the DFG pri-
ority project 1569 “Generation of multifunctional inorganic materials by molecular bi-
onics”. In this context, I owe my deepest gratitude to Maria Siglreitmeier who was per-
forming many project related experiments in Konstanz.
My sincere gratitude to Dr. Zhengyu Di, Dr. Marie-Sousai Appavou, Dr. Artem Feok-
tystov, Dr. Zhengdong Fu, Dr. Sabine Pütter, Dr. Emmanuel Kentzinger and all other
staff in JCNS who assisted me to collect an essential part of my data at the KWS1,
KWS3 neutron spectrometers, AFM and SAXS. Moreover, I particularly thank Armin
Kriele from HZG-TUM he has assisted me for a lot of SAXS, DSC, AFM and XRD
experiments.
Last but not least, I am deeply thankful to my wife Yan Li and my family who gave me
the support and the encouragement I needed throughout the period of Ph.D. research. I
am grateful to the JCNS for the allocation of beamtime. The work was financed by the
DFG priority project 1569.

Zusammenfassung

In vielen Fällen stellt Biomineralisation ein komplexes Verfahren für die Bildung von
hochgeordneten hierarchischen Mineralstrukturen im Zusammenspiel mit lebenden
Organismen dar. Biomineralisierung findet unter strenger biologischer Kontrolle durch
speziell gestaltete Biomakromoleküle statt. Mineralisationsmechanismen, die eine solch
ausgeklügelte Kontrolle erlauben, beinhalten meist die Interaktion zwischen dem
anorganischen Mineral und der Oberfläche einer organischen Matrix. Ein tiefes
Verständnis dieser Mechanismen erlaubt die Erkundung neuer Strategien für die
Herstellung von Materialien mit verbesserten chemischen und physikalischen
Eigenschaften. Die Strategie der Natur, Biomoleküle zur Herstellung von Materialien zu
verwenden, soll uns als Inspirationsquelle dienen. Diese Mineralisationsprozesse sollen
in situ untersucht werden, um die mechanistischen Aspekte ihrer Kontrolle näher zu
beleuchten. Das Ziel dieser Arbeit ist es, den Mechanismus der bio-inspirierten
Magnetit-Mineralisierung in einer organischen Matrix und die resultierenden organisch-
anorganischen Hybridstrukturen mittels Kleinwinkel-Neutronen- und Röntgenstreuung
zu untersuchen. Die Untersuchungen konzentrieren sich auf Nukleation und Wachstum
des Magnetit in Gelatine-Hydrogelen, die bioinspirierte Hybridmaterialien aus drei
natürlichen Biomineralen sind. SANS-Kontrastvariation wurde genutzt, um die
einzelnen Komponenten der Struktur durch Variation der H O / D O-Konzentration zu
2 2
analysieren. Diese Ergebnisse lieferten in-situ-Strukturinformationen zum Verständnis
des Mechanismus der Magnetit-Mineralisierung. Um die Funktion der organischen
Matrix zu erklären, wurden mehrere Hyopthesen aufgestellt. Die Eigenschaften der
Struktur und des Mineralisationsmechanismus wurden mit den biologischen Proben
verglichen. Diese vergleichenden Untersuchungen der strukturellen Merkmale werden
die Optimierung der Materialstruktur unterstützen, um verbesserte mechanische
Eigenschaften zu erreichen.
Stichwort: Biomineralisation, Magnetit, Gelatine, Hydrogele, SANS, VSANS, SAXS

Abstract

Biomineralization represents a sophisticated process of forming a highly hierarchically
ordered mineral structure by a living organism. The process is carried out under strict
biological control of specially designed biomacromolecules. Mineralization mechanisms
permitting such sophistication control typically involve interaction between an inorgan-
ic mineral and an organic matrix interface. A clear understanding of the mechanisms of
this process may pave way for exploration of new material design strategies and genera-
tion of materials with improved mechanical, chemical and physical properties. We thus
attempt to follow nature‟s fabrication strategy of using biomolecules and study the min-
eralization process in-situ which might shed light on the mechanistic aspects of control-
ling the process.
The aim of this work is to investigate, understand and probably control the mechanism
of bio-inspired magnetite mineralization in organic matrices and the organic-inorganic
hybrid structures by Small Angle Neutron and X-ray Scattering methods. The studies
focus on the nucleation and growth of the magnetite particles in the gelatin hydrogel
matrix by employing biomineralization strategies from three natural bio-minerals. The
SANS contrast matching method was used by the variation of heavy water content in
the H O/D O mixture in order to emphasize the structure of the individual components
2 2
of the complex material on the different stages of biomineralization process. These re-
sults have provided structural information and understanding of the mechanisms of
magnetite mineralization as well as in-situ. Several hypotheses have been introduced to
explain functionality of the organic matrix in magnetite biomineralization. These struc-
tural and mineralization mechanisms were compared with the biological samples. The
comparative studies of the structural features will help to optimize the structure of mate-
rials for improved mechanical properties.
Keywords: Biomineralization, Magnetite, Gelatin, Hydrogels, SANS, VSANS,
SAXS