Browsing by Author "Leskinen, Timo"

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Adsorption of Proteins on Colloidal Lignin Particles for Advanced Biomaterials
(2017-09-11) Leskinen, Timo; Witos, Joanna; Valle-Delgado, Juan José; Lintinen, Kalle; Kostiainen, Mauri; Wiedmer, Susanne K.; Österberg, Monika; Mattinen, Maija Liisa
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Coating of colloidal lignin particles (CLPs), or lignin nanoparticles (LNPs), with proteins was evaluated in order to establish a safe, self-assembly mediated modification technique to tune their surface chemistry. Gelatin and poly- l-lysine formed the most pronounced protein corona on the CLP surface, as determined by dynamic light scattering (DLS) and zeta potential measurements. Spherical morphology of individual protein coated CLPs was confirmed by transmission electron (TEM) and atomic force (AFM) microscopy. A mechanistic adsorption study with several random coiled and globular model proteins was carried out using quartz crystal microbalance with dissipation monitoring (QCM-D). The three-dimensional (3D) protein fold structure and certain amino acid interactions were decisive for the protein adsorption on the lignin surface. The main driving forces for protein adsorption were electrostatic, hydrophobic, and van der Waals interactions, and hydrogen bonding. The relative contributions of these interactions were highly dependent on the ionic strength of the surrounding medium. Capillary electrophoresis (CE) and Fourier transform infrared spectroscopy (FTIR) provided further evidence of the adsorption-enhancing role of specific amino acid residues such as serine and proline. These results have high impact on the utilization of lignin as colloidal particles in biomedicine and biodegradable materials, as the protein corona enables tailoring of the CLP surface chemistry for intended applications.
All-lignin approach to prepare cationic colloidal lignin particles: Stabilization of durable Pickering emulsions
(2017) Sipponen, Mika; Smyth, Matthew; Leskinen, Timo; Johansson, Leena-Sisko; Österberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Surface modification of colloidal lignin particles (CLPs), which are obtained from renewable resources, is a plausible route towards novel biomaterials. Here we show that adsorption of cationic lignin onto spherical CLPs produces positively charged particles with tailored properties for the stabilization of Pickering emulsions. The threshold dosing of cationic lignin needed to achieve colloidally stable cationic dispersions was 4% relative to the dry weight of CLPs. Compared to irregular kraft lignin particles or regular CLPs, cationic CLPs stabilized a broader array of durable Pickering emulsions. This all-lignin adsorption process to prepare cationic CLPs is advantageous because it minimizes the consumption of synthetic polymers, and opens new application opportunities for structurally defined nano- and microscale lignin particles.
Closed cycle production of concentrated and dry redispersible colloidal lignin particles with a three solvent polarity exchange method
(2018) Lintinen, Kalle; Xiao, Yao; Bangalore Ashok, Rahul; Leskinen, Timo; Sakarinen, Ekaterina; Sipponen, Mika; Muhammad, Farooq; Oinas, Pekka; Österberg, Monika; Kostiainen, Mauri
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Lignin, an aromatic biopolymer, is the main by-product of pulp manufacture, and has been under intense study, as it offers great promise as an alternative for petrochemical polymers. However due to its heterogeneity, the applications where lignin can be used have been limited, leading to the vast majority of it being burned for fuel. Colloidal lignin particles (CLPs) offer a means to disperse lignin homogenously into both water and other media, such as polymers. However, no means thus far have been presented that would allow for a large-scale production of CLPs. Herein we show an industrially scalable closed cycle process of CLP production. In the process, a concentrated solution of lignin in tetrahydrofuran (THF) and ethanol (EtOH) is added into the non-solvent water, instantaneously forming CLPs through self-assembly. The organic solvents are recovered and reused in the process. The aqueous CLPs are concentrated by ultrafiltration and the concentrated particles are spray dried, leading to redispersible microclusters. CLPs can be used in multiple applications, such as Pickering emulsions and composite materials. A significant portion of the 50 million tons of lignin produced by the pulp industry could be made into CLPs with this low cost process, which would open a whole new class of materials for industrial applications.
Colloidal lignin particles as adhesives for soft materials
(2018-12-01) Mattinen, Maija Liisa; Riviere, Guillaume; Henn, Alexander; Nugroho, Robertus Wahyu N.; Leskinen, Timo; Nivala, Outi; Valle-Delgado, Juan José; Kostiainen, Mauri A.; Österberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Lignin has interesting functionalities to be exploited in adhesives for medicine, foods and textiles. Nanoparticles (NPs) < 100 nm coated with poly (L-lysine), PL and poly(L-glutamic acid) PGA were prepared from the laccase treated lignin to coat nanocellulose fibrils (CNF) with heat. NPs ca. 300 nm were prepared, β-casein coated and cross-linked with transglutaminase (Tgase) to agglutinate chamois. Size exclusion chromatography (SEC) and Fourier-transform infrared (FTIR) spectroscopy were used to characterize polymerized lignin, while zeta potential and dynamic light scattering (DLS) to ensure coating of colloidal lignin particles (CLPs). Protein adsorption on lignin was studied by quartz crystal microbalance (QCM). Atomic force microscopy (AFM) was exploited to examine interactions between different polymers and to image NPs with transmission electron microscopy (TEM). Tensile testing showed, when using CLPs for the adhesion, the stress improved ca. 10 and strain ca. 6 times compared to unmodified Kraft. For the β-casein NPs, the values were 20 and 8, respectively, and for the β-casein coated CLPs between these two cases. When NPs were dispersed in adhesive formulation, the increased Young’s moduli confirmed significant improvement in the stiffness of the joints over the adhesive alone. Exploitation of lignin in nanoparticulate morphology is a potential method to prepare bionanomaterials for advanced applications.
Colloidal lignin particles for weathering protection in wood coatings
(2017-10-03) Smyth, Matt
Kemian tekniikan korkeakoulu | Master's thesis
Earth’s changing climate and the better understanding of harmful impacts caused by humans has increased the demand for more sustainable products. Lignin is a material that offers renewability, is safe for humans and the environment and is already a by-product of industry. This work uses a recently developed technique for preparing colloidal lignin particles (CLPs) and deploying them into water based industrial wood stain as a UV protectant. The initially transparent stains with added CLPs took on the dark brown color of lignin, with concentration of CLPs having only minor effect. The dispersions remained stable after CLP addition however, viscosity was drastically decreased with a strong correlation with CLP concentration. Siberian larch and spruce wood were coated with the standard commercial stains and stains with 1:1, 1:1.5, and 1:2 ratios of commercial UV absorber to CLP concentrations. Coated wood samples were then exposed to simulated sunlight for 92 hours. Changes in color and UV reflectance spectra were recorded, as well as periodic photographs during exposure. The CLP coated samples go through a more drastic magnitude of color change compared to uncoated (NAT) and standard (STD) samples, however the change in relation to initial color is much less. Additionally, the color after 92 hours of exposure is much closer to the initial color in CLP samples due to an almost cyclical change. Reflectance spectroscopy revealed further differences between CLP samples and both the STD and NAT samples. CLP samples showed a large decrease in absorption in the UVA region but little change in the UVB region. NAT samples showed a similar decrease in the UVA region but with a shifted peak, but also had strong decreases in absorption in the UVB region. The STD samples experienced a more uniform decrease in absorption, with some regions having higher and others lower changes in absorption compared to CLP samples. The overall effectiveness of CLPs remains somewhat uncertain due to the inability to remove the coatings from the wood beneath and see the color. This work did reveal however, some positive outcomes that indicate CLPs could be used effectively in industrial wood coatings. There were strong differences in the color and absorption changes between CLP samples and the NAT and STD samples. This indicates that the CLPs were changing instead of the wood beneath. Although the extent of protection is still uncertain, it can be concluded here that CLPs have potential for use as UV protectants in wood coatings.
Colloidal lignin particles in plywood adhesives
(2018-02-27) Koivula, Nanna
Kemian tekniikan korkeakoulu | Master's thesis
Lignin is a by-product of the pulp production and it is mainly used for energy generation at the pulp mill. Lignin has potential to be used in many more valuable applications, such as in plywood adhesives. Lignin polymer has a phenolic structure and it is a non-toxic natural material, whereas the currently used phenol-formaldehyde (PF) resins in plywood applications are toxic and fossil-based. The goal of this thesis was to produce a lignin-based adhesive without any fossil-based components for plywood applications. The hypothesis was that colloidal lignin particles (CLPs) of lignin fractions would produce a strong adhesive. Also, the effect of a cationic component, such as gelatin and cationic lignin in the adhesion was investigated. Lignoboost lignin was fractionated to ethanol soluble lignin (ESL) and ethanol insoluble lignin (EIL) fractions. These fractions were characterised with Fourier Transform Infrared Spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The colloidal lignin particles were prepared from these fractions for glue tests. Also, cationic lignin was prepared. These were characterised with particle size and zeta potential measurement. CLPs of different lignin fractions, cationic lignin and gelatin were concentrated to ~30% dry matter content. For gluing tests, ice cream sticks were glued with a lap-shear joint applying cold (CP) or hot pressing (HP). The tensile shear strengths of different glues were determined, and they were compared to polyvinyl acetate (PVA) glue. ABES testing was used in order to test lignin in different pressing temperatures and compare the adhesive strength to PF. Also, moisture resistance testing was done and FESEM images were taken of the glued surface. The FT-IR analysis of Lignoboost lignin and different lignin fractions showed that the fractionation has not affected the lignin structure. The DSC analysis showed that the glass transition temperature (Tg) decreased with fractionation. Tg for Lignoboost lignin was 178ºC and for ESL 138°C. EIL showed no clear Tg. Zeta potential was negative for CLP fractions and positive for cationic components. Particle sizes of CLPs varied with different fractions. Cationic lignin showed lowest and gelatin coated lignin the highest particle size. In the lap-shear testing, HP samples showed better results than the CP samples and this was because lignin softened in a higher temperature. HP gelatin showed maximum value of 6.4 MPa, followed by gelatin+EIL CLP, gelatin+CLP and gelatin+ESL CLP. Cationic lignin showed lowest adhesive strength. The PVA glue value (7.7 MPa) was not reached. In Automated Bonding Evaluation System (ABES) testing the PF value was exceeded with birch veneer but not with spruce veneers. Spruce veneers showed decreasing adhesive strength with increasing pressing temperature. Moisture resistance for CLPs+gelatin showed stabile bonding therefore indicating that there might be potential for plywood applications. The lignin glues used in this thesis showed good bonding, but did not reach the adhesive strength of commercial glue or PF.
Enzymatically and chemically oxidized lignin nanoparticles for biomaterial applications
(2018-04-01) Mattinen, Maija Liisa; Valle-Delgado, Juan José; Leskinen, Timo; Anttila, Tuomas; Riviere, Guillaume; Sipponen, Mika; Paananen, Arja; Lintinen, Kalle; Kostiainen, Mauri; Österberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Cross-linked and decolorized lignin nanoparticles (LNPs) were prepared enzymatically and chemically from softwood Kraft lignin. Colloidal lignin particles (CLPs, ca. 200 nm) in a non-malodorous aqueous dispersion could be dried and redispersed in tetrahydrofuran (THF) or in water retaining their stability i.e. spherical shape and size. Two fungal laccases, Trametes hirsuta (ThL) and Melanocarpus albomyces (MaL) were used in the cross-linking reactions. Reactivity of ThL and MaL on Lignoboost™ lignin and LNPs was confirmed by high performance size exclusion chromatography (HPSEC) and oxygen consumption measurements with simultaneous detection of red-brown color due to the formation of quinones. Zeta potential measurements verified oxidation of LNPs via formation of surface-oriented carboxylic acid groups. Dynamic light scattering (DLS) revealed minor changes in the particle size distributions of LNPs after laccase catalyzed radicalization, indicating preferably covalent intraparticular cross-linking over polymerization. Changes in the surface morphology of laccase treated LNPs were imaged by atomic force (AFM) and transmission emission (TEM) microscopy. Furthermore, decolorization of LNPs without degradation was obtained using ultrasonication with H2O2 in alkaline reaction conditions. The research results have high impact for the utilization of Kraft lignin as nanosized colloidal particles in advanced bionanomaterial applications in medicine, foods and cosmetics including different sectors from chemical industry.
Flying squirrel and area planning
(2010) Kaksonen, Simo
School of Engineering | Master's thesis
Hemiselluloosapohjaisten hydrogeelien valmistus ja sovellukset
(2016-05-08) Äkräs, Laura
Kemiantekniikan korkeakoulu | Bachelor's thesis
Ligniinin käyttö nanokomposiiteissa ja hybridimateriaaleissa
(2016-05-08) Tamminen, Juho
Kemiantekniikan korkeakoulu | Bachelor's thesis
Scaling up production of colloidal lignin particles
(2017) Leskinen, Timo; Smyth, Matthew; Xiao, Yao; Lintinen, Kalle; Mattinen, Maija-Liisa; Kostiainen, Mauri A.; Oinas, Pekka; Osterberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Fundamentals of nanoprecipitation process to form colloidal lignin particles (CLPs) from tetrahydrofuran (THF)-water solvent system were studied, and applied in establishment of a robust reactor design for scaled-up CLP production. Spherical lignin particles with an average diameter of 220 nm could be produced by the new reactor design. Evaporation was applied for removal of THF, concentration of the CLP dispersions, and finally for drying of the CLPs into flake like dry form. The dried CLPs could be re-dispersed in water to restore their colloidal form by applying short physical agitation. Salt triggered sedimentation of the particles was also investigated as a way for reducing the energy consumption related to water evaporation from the CLP dispersions. Aqueous thermal post-treatments were demonstrated to yield structural reinforcement of the CLP structure against solvation in various lignin solvents. In summary, the presented work pushes forward the conceptual design of large-scale CLP production, and addresses some of the foreseen technical challenges.
Structural changes of lignin in biorefinery pretreatments and consequences to enzyme-lignin interactions
(2017) Sipponen, Mika; Rahikainen, Jenni; Leskinen, Timo; Pihlajaniemi, Ville; Mattinen, Maija-Liisa; Lange, Heiko; Crestini, Claudia; Österberg, Monika
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The main target of a biorefinery pretreatment process is to break down the lignin-reinforced plant cell wall structure prior to enzymatic hydrolysis of polysaccharides to fermentable sugars. Various physico-chemical alterations occur in lignin during the biomass pretreatment, but effects of those structural changes on subsequent enzymatic hydrolysis have remained ambiguous. We review the reinforcing and detrimental lignin-enzyme interactions and their underlying mechanisms, and use this structure-function information to assess critical features of current and emerging pretreatment technologies. Our perspective is that truly multidisciplinary research is needed to develop pretreatments that render lignin non-inhibiting to enzymes and with high potential for further valorisation.
The using of virtual environment for studying occupational safety and ergonomics and the plan for measurement of sense of presence
(2005) Turunen, Antti
Helsinki University of Technology | Master's thesis
There have been three main goals in this thesis. One of them has been to create a comprehensive theoretical part, which can be used as familiarization material for all the users of the virtual space at Finnish Institute of Occupational Health (FIOH). Another goal has been to explain by means of literature survey, how the virtual space of FIOH could be used for studying occupational safety and ergonomics. The third goal has been to find a suitable method by which the sense of presence can be measured, and to make a plan for research and realization. In the first part of the thesis the concepts connected to virtual space are explained, the most important senses (sense of sight, hearing, touch and balance) from the point of view of virtual space are presented and there are also introduced various machineries and techniques, which enable the production of stimuli as well as moving and interaction in the virtual environment. The machinery of the virtual space of FIOH and the circumstances of health and safety are also presented in the first part of thesis. Special attention has been paid to what kind of influence the use of various machines and techniques have on the sense of presence. The utilization of virtual environment for examination of occupational safety and ergonomics are presented in so far as information is available. Three different ways to apply the virtual space to research of occupational safety and ergonomics are introduced and the applicability of them in the virtual space of FIOH is considered. In the final part of thesis the significance of the sense of presence and the measurement of it are discussed as well as there are presented the various methods, which have been developed for measurement of the sense of presence. Finally the plan for measuring the sense of presence in the virtual space of the department of occupational safety is introduced. The study shows that virtual environments give new possibilities in the virtual studying of occupational safety and ergonomics. Among others the examinations that could inflict high risks on testers when implemented in real environment, can be implemented in virtual environment. For example the examination of working in high circumstances can be implemented safely in virtual environment. It also makes possible the efficient planning of the ergonomics of products. With this kind of planning new variations can be produced and tested rapidly. Additionally infrequently encountered real life situations connected to occupational safety, which would be very expensive to simulate, can be simulated with this virtual environment cheaply. However the literature survey shows that virtual environments are still rarely used for the examination of occupational safety and ergonomics.