THESIS
2018
xvi, 129 pages : illustrations (some color) ; 30 cm
Abstract
Hydrogels, noted for their biomimetic properties, are the main materials used in
biomedical applications such as drug delivery and stem cell therapy. Traditional
hydrogels made up of either synthetic polymers or natural biomolecules often serve as
passive scaffolds for molecular or cellular species. These features render traditional
hydrogels unable to fully recapitulate biological dynamics. It is, therefore, increasingly
important to design stimuli-responsive, dynamic hydrogels that can accommodate or
mimic the complexity of biological systems. The properties of photoresponsive hydrogels
can be controlled using light with great spatiotemporal precision. Although a great
number of photoreceptors proteins have been discovered and engineered in the past few decades, which has furt...[
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Hydrogels, noted for their biomimetic properties, are the main materials used in
biomedical applications such as drug delivery and stem cell therapy. Traditional
hydrogels made up of either synthetic polymers or natural biomolecules often serve as
passive scaffolds for molecular or cellular species. These features render traditional
hydrogels unable to fully recapitulate biological dynamics. It is, therefore, increasingly
important to design stimuli-responsive, dynamic hydrogels that can accommodate or
mimic the complexity of biological systems. The properties of photoresponsive hydrogels
can be controlled using light with great spatiotemporal precision. Although a great
number of photoreceptors proteins have been discovered and engineered in the past few decades, which has further led to the emergence of powerful optogenetic tools for
numerous biomedical research and applications, most photoresponsive materials still rely
on synthetic chromophores as light-sensing moieties, leaving the diverse protein-based
photoreceptors untapped.
In this thesis, we developed a new category of protein-based photoresponsive hydrogels
by combining the use of recombinant DNA technology, a robust protein assembly
strategy known as SpyTag/SpyCatcher chemistry and the newly discovered protein
photoreceptor CarH. In Chapter 2, we show the synthesis of the entirely protein-based
photoresponsive hydrogels by covalently polymerizing the adenosylcobalamin (AdoB
12)-dependent photoreceptor C-terminal adenosylcobalamin binding domain (CarH
C)
proteins using genetically encoded SpyTag-SpyCatcher chemistry under mild
physiological conditions. Also shown is the resulting hydrogel that exhibited a rapid gel-sol transition on the light exposure. In Chapter 3, we demonstrate that the hydrogel
composed of physically self-assembled CarH
C polymers enabled the light-controlled
facile release/recovery of human mesenchymal stem cells (hMSCs), 3T3 fibroblasts and
PC12 cells from 3D cultures while maintaining their viability. This suggests its great
potential as a powerful platform for 3D cell culturing and release. In Chapter 4, a designed
covalently cross-linked CarH
C hydrogel can be seen to encapsulate and release bulky
globular proteins, such as mCherry, in a light-dependent manner, showing the suitability
of using our material for optically controlled release. In Chapter 5, we further explore the
feasibility of using other photoresponsive proteins to create hydrogels with different light
responsiveness in the hope of gaining insight on some general principles of designing
photoresponsive protein materials.
In summary, the direct assembly of stimuli-responsive proteins into hydrogels represents
a versatile strategy to design dynamically tunable materials, which may open up new
opportunities for materials biology.
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