Nano- and microscale control of alginate interactions and assembly
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- Institutt for fysikk 
Hydrogels are materials primarily comprised of water and are extensively applied to mimic the extracellular matrix surrounding the cells in our body. Alginate, a naturally derived biopolymer shows great promise in this regard as the polysaccharide is biocompatible and may form biologically relevant hydrogels under mild conditions. The focus of this work has been to gain fundamental knowledge of the molecular interactions and gelling kinetics of alginates and to apply this knowledge in contemporary bionanotechnology research. Interactions on the single-molecule level between alginate chains and alginate modifying enzymes, mannuronan C-5 epimerases, have been extensively studied with optical tweezers and an atomic force microscope to unveil the importance of the variations within the enzyme family. Knowledge on this matter which was attained through this study may pave the way for tailor making of epimerases that in turn may be utilized to tailor the properties of alginates and the gels they form. Alginate-mucin interactions were also investigated on the molecular level to examine use of alginate, possibly in combination with chitosan, as a mucoadhesion-based drug delivery system. Alginate based hydrogels must meet the requirements set by the biotechnological application in question. Often times, such applications require tunable gelation kinetics in terms of gelation time and strength, under mild and biocompatible conditions. Contemporary methods to gel alginate suffer from lack of control over the transition time from a sol to a gel, or poor cell compatibility due to harsh gelation conditions such as pH triggering, or both. As part of this work, a novel gelation method termed competitive ligand exchange X–linking (CLEX) for ionotropic polymers, including alginate, was discovered and thoroughly characterized. CLEX proved to offer many advantages over existing gelation methods for encapsulation of cells in alginate micro beads and fibers using microfluidics, with the main advantages being clog-free and cell friendly microfluidic operation. Lastly, micro encapsulated bacteria and algae in CLEX produced alginate beads and in water-oil-water emulsions were systematically arranged onto microarrays to improve current biotechnological methods to study single or small colonies of microorganisms. Altogether, this work provides new insight into the fundamental nature of alginate interactions with mannuronan C-5 epimerases and mucins, as well as new means by which alginate hydrogels may be formed to allow for use in emerging biotechnological research.