Protein coated colloidal lignin nanoparticles for gluing biological matrixes

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Kemian tekniikan korkeakoulu | Master's thesis
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Fiber and polymer engineering
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Master's Programme in Chemical, Biochemical and Materials Engineering
54 + 2
Lignin is an aromatic, renewable, and biodegradable biopolymer that can be used as a substituent of the oil-based products. Colloidal lignin nanoparticles (CLPs) are a nano-biomaterials that can be prepared from isolated lignin using different techniques. This thesis aims to study the feasibility to use lignin as nano-sized particles as adhesive for gluing leather as a model of biological protein matrix. β-casein was applied to coat CLPs in order to improve the affinity of the modified particles to the selected protein material. Crystal microbalance with dissipation monitoring (QCM-D) examined the optimum pH for β-casein coating. Then transglutaminase (Tgase) was used to stabilize the protein coating CLPs via covalent cross-linking reactions. The average size and zeta potential values of the particles were measured using dynamic light scattering measurement, and analysis light scattering (PALS), respectively. Transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to image the CLPs, thus provide a deeper understanding of the structure of CLPs. Finally, all tailored CLPs including the references were used as adhesive to adhere two leather pieces. The failure force needed to separate the pieces was measured by tensile tester typically used for paper testing. These numerical values indicate of adhesion performance of CLPs. The mixture of commercial glue with uncross-linked/β-casein coated CLPs or cross-linked/β-casein coated CLPs have carried out the same experiment. The average size and zeta potential of fabricated CLPs were ca. 323 nm, and -32.7 mV. The optimum pH for β-casein coating was at pH 3. The β-casein CLP ratio (0.1g/g) lignin was sufficient for the coating of the nanoparticles. The stability of protein coated CLPs at pH 3 and pH 7 was at least 25 days. The optimum enzyme activity to crosslink the β-casein layer around lignin nanoparticles surface was 1333 nkat/mg protein. The elasticity of β-casein layer was increasing after crosslinking. The application of the articles for gluing showed that both unmodified CLPs and modified CLPs have excellent adhesion properties towards protein matrix. The protein coating of CLPs was indeed performing better than uncoated lignin nanoparticles. Furthermore, it was shown that both unmodified and modified lignin nanoparticles could significantly enhance the adhesion properties of a commercial glue. The mixture of glue and β-casein coated lignin nanoparticles has the maximum growth value, which is 5 folds than the reference.
Österberg, Monika
Thesis advisor
Mattinen, Maija-Liisa
lignin nanoparticles, protein coating, gluing test, transglutaminase
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