Interfacial Adsorption and Stabilization of Nanopolysaccharides in Multifunctional Emulsion Systems

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School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2024-06-10
Degree programme
65 + app. 65
Aalto University publication series DOCTORAL THESES, 127/2024
This thesis explores the roles of biobased polysaccharide nanoparticles, including cellulose nanofibrils (CNF), cellulose II nanospheres (NPcats) and chitin nanofibrils (NCh), as stabilizers of emulsion systems. We demonstrate the potential application of these emulsions in the development of advanced materials. The thesis discusses phenomena relevant to colloidal behaviors and adsorption of nanopolysaccharides at oil/water and water/water interfaces, in the form of Pickering emulsions. Variables relevant to the emulsion behaviors, including the particle's interfacial wetting properties, hydrophilicity, functional groups, electrostatic charge, axial aspect ratio and entanglement were evaluated by complementary characterization platforms. The complexation of two oppositely charged nanopolysaccharides, CNF and NCh, were demonstrated to effectively stabilize oil-in-water Pickering emulsions with adjustable droplet size and stability against creaming and oiling-off, imparting long-term stability and remarkable environmental tolerance. Likewise, driven by electrostatic interactions, tuning the mass and charge ratio of NPcat and bovine serum albumin (BSA), the formation of a soft and dense NPcat/BSA layer, is shown to enable the formation of dense NPcat/BSA interfacial layers, stabilizing water-in-water emulsions. Furthermore, NCh was used to formulate high internal phase Pickering emulsions (HIPPEs) through pre-emulsification followed by continuous oil feeding that facilitated a "scaffold" with high elasticity, which arrested droplet mobility and coarsening, achieving edible oil-in-water emulsions with a high internal phase volume fraction (as high as 88%). These green Pickering emulsions offer potential in applications relevant to foodstuff, pharmaceutical, and cosmetic formulations. Direct ink writing (DIW) was applied as a platform to engineer biobased Pickering emulsions to extend their applications. The HIPPEs were easily textured by leveraging their elastic behavior and resilience to compositional changes, making them suitable for 3D printing edible functional foods via DIW. Additionally, we structured emulsion stabilized by NCh (50% oil fraction) through onestep processing into hierarchically and spatially-controlled porous structures defined by emulsion droplet size, ice templating, and DIW infill density. The obtained scaffolds are demonstrated for their excellent modulation of cell adhesion, proliferation, and differentiation, as tested with mouse dermal fibroblast expressing green fluorescent proteins. Taken together, the findings in this thesis are of interest in developing and understanding fundamental emulsion stabilization mechanisms and advancing practical applications. The obtained green Pickering emulsion systems are expected to have an important role in food emulsions, encapsulation, pharmaceuticals, (bio)catalysis, and advanced synthetic cell mimetics.
Supervising professor
Rojas, Orlando, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
Thesis advisor
Rojas, Orlando, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
Bai, Long, Dr., Aalto University, Finland
Siqi, Huan, Dr., Aalto University, Finland
cellulose, chitin, pickering emulsion, interfacial adsorption, direct ink writing
Other note
  • [Publication 1]: Siqi Huan, Ya Zhu, Wenyang Xu, David Julian McClements, Long Bai, Orlando J. Rojas: Pickering Emulsions via Interfacial Nanoparticle Complexation of Oppositely Charged Nanopolysaccharides. ACS Applied Materials & Interfaces, 2021, 13, 12581-12593.
    DOI: 10.1021/acsami.0c22560 View at publisher
  • [Publication 2]: Ya Zhu, Marco Beaumont, Katariina Solin, Panagiotis Spiliopoulos, Bin Zhao, Han Tao, Eero Kontturi, Long Bai, Orlando J. Rojas. Interfacial membranization of regenerated cellulose nanoparticles and a protein renders stable water-in-water emulsion. Submitted to Small, under review, 2024.
  • [Publication 3]: Ya Zhu, Siqi Huan, Long Bai, Annika Ketola, Xuetong Shi, Xiao Zhang, Jukka A. Ketoja, Orlando J. Rojas. High Internal Phase Oil-in-Water Pickering Emulsions Stabilized by Chitin Nanofibrils: 3D Structuring and Solid Foam. ACS Applied Materials & Interfaces, 2020, 12, 11240-11251.
    DOI: 10.1021/acsami.9b23430 View at publisher
  • [Publication 4]: Ya Zhu, Esko Kankuri, Xue Zhang, Zhangmin Wan, Xin Wang, Siqi Huan, Long Bai, Shouxin Liu, Orlando J. Rojas. Layer-by-layer deposition of low-solid nanochitin emulsions create porous structures for high cell attachment and proliferation. ACS Applied Materials & Interfaces, 2023, 22, 27316-27326.
    DOI: 10.1021/acsami.3c03421 View at publisher