Browsing by Author "Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland"

Now showing 1 - 8 of 8
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    Advanced Structures and Compositions for 3D Forming of Cellulosic Fibers
    (Aalto University, 2017) Khakalo, Alexey; Filpponen, Ilari, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials (BiCMat); Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    The objective of this thesis was to systematically investigate strategies to endow fiber-based materials with toughness and formability. Bio-based polymers and green treatments were applied to develop 3D packaging structures. Formability, the material's ability for three-dimensional shaping, was achieved by plastic deformations in paper structures that were defect-free in terms of appearance and functionality. A set of methods to improve paper toughness was explored, including: (a) combined mechanical treatment of fibers in aqueous dispersions of high- and low-solids content, (b) in-plane compression of paper webs followed by unrestrained drying and (c) chemical modification of fiber joints by protein spraying. The mechanical treatment of fiber suspensions at elevated temperature and high solids content induced permanent fiber deformations, including kinks and curls, which are associated with the formation of microcompressions and dislocations. In turn, they increased the extensibility but compromised the axial stiffness of single fibers. Simultaneously, shrinkage of fibers and paper webs were promoted. In contrast, the low-consistency treatment straightened the fibers while their deformations were partly preserved. Fiber bonding was promoted by fibrillation. The application of gelatin affected the strength of fiber joints and improved their deformation ability, making strong fiber webs. The drying shrinkage was also increased. The fiber network was subjected to in-plane compressive treatment and drying shrinkage, which led to fiber buckling and network compression. The role of proteins as compatibilizers and eco-friendly dispersants in composites comprising cellulose nanofibrils (CNF) and thermoformable polylactide (PLA) was also investigated. The combination of mechanical and protein treatment of fibers and their structures improved paper extensibility, from 5% to 29%. Moreover, tray-like shapes were possible with a level of out-of-plane deformation that has not been recorded before for thermoforming with a fixed blank. Overall, this thesis provides fundamental and practical knowledge about the role of several factors contributing to paper toughness and formability. The suggested modification strategies to improve paper toughness are compatible with modern papermaking and conversion processes and can be implemented easily and economically.
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    Control of Silver Nano-particle Nucleation and Synthesis with Nanocelluloses: Applications in Paper-based Sensing and Anti-microbial Activity
    (Aalto University, 2018) Uddin, Khan Mohammad Ahsan; Orelma, Hannes, Dr., VTT Technical Research Centre of Finland, Finland; Lokanathan, Arcot R., Dr., Achira Labs Pvt. Ltd., India; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials (BiCMat); Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    The synthesis of silver nanoparticles (AgNPs) has drawn significant research interest due to their unique and well-defined physical-chemical properties. Developing a feasible chemical method to synthesize silver nanoparticles using sustainable, renewable, and environmentally friendly materials is very important for environmental safely. In this work, a new route for the synthesis of silver nanoparticles (AgNPs) by using sustainable, renewable and environmentally friendly cellulose nanocrystals (CNCs) is described. Moreover, in this study the utilization of cellulose-AgNPs materials in sensing and antibacterial applications was investigated. The influence of the surface charge of cellulose nanocrystals on the rate of nucleation, growth, stabilization and size distribution of AgNPs was investigated. CNCs produced by sulfuric acid hydrolysis followed by partial desulfation and CNC produced by hydrochloric acid (HCl) hydrolysis followed by different levels of carboxylation by TEMPO-mediated oxidation were used to elucidate the effects of sulfate ester and of carboxyl groups on the silver nanoparticle synthesis process. The results shed light on the mechanistic aspects related to synthesis, control of nucleation, and stabilization of AgNP in a sustainable way, and highlight the potential of CNCs in metal nanoparticle synthesis. The fundamental knowledge of controlled nucleation of plasmonic silver nanoparticles by cellulose was applied to demonstrate a new plasmonic sensing mechanism for qualitative detection of proteins on paper. In contrast to conventional paper-based diagnostic devices that use the cellulosic component as a support structure, the proposed method takes advantage of cellulose as a nucleation controller during silver nanoparticle formation. Reduction of silver ions interacting competitively with the nucleation controlling cellulosic surface and the suppressing effect of protiens on reduction (via complexation) resulted in silver nanoparticles whose size–shape dependent plasmonic properties quantitatively reflected the concentration of protein on paper. In addition, aerogels prepared from aqueous dispersions of anionic and cationic cellulose nanofibrils (CNFs) were investigated as solid supports for enzymes and silver nanoparticles to elicit a sustained antibacterial effect. The antibacterial activity of CNF aerogels loaded with silver nanoparticles (AgNP) after in situ synthesis via UV reduction was tested against gram-negative and gram-positive bacteria. The results were compared with CNFs aerogels carrying antibacterial lysozyme.
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    Controlled Self-Assembly of Biobased Materials at Aqueous Interfaces
    (Aalto University, 2022) Greca, Luiz G.; Tardy, Blaise L. , Dr., Aalto University, Finland; Tamminen, Tarja, Dr., VTT, Finland; Rojas, Orlando J., Prof., Aalto University, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biobased Colloids and Materials (BiCMat); Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    The self-assembly of biobased materials in water is a fundamental pillar of life, with natural molecules and biocolloids assembling into well-organized structures displaying a myriad of functions. Wetting forces and geometry of the associated interfaces often guide the interfacial interactions and consequent structure formation of these natural materials. Therefore, this thesis aims at using non-wetting and highly wetting surfaces to form new hierarchical assemblies from some of the most important biocolloids available. First, nanocellulose-producing bacteria were used to form robust 3D biofilms, where hydrophobic particles and superhydrophobic moulds guided the aerobic biofabrication at the air-water interface.The resulting 3D objects were hollow, seamless constructs of varied morphologies. Gradients of thickness and topographical features were tethered to biofabrication time and hydrostatic pressure, respectively, while nanocellulose fibres were observed to be aligned at the lower sections of objects and at a parallel orientation to the gradient of hydrostatic pressure and oxygen availability. These well-controlled morphological features may find important applications in tissue engineering and other biomedical applications. We demonstrated that this approach can also be used for the encapsulation of functional particles, for the formation of multicompartmentalized structures, and for a self-healing functionality. Similarly, highly wetting interfaces also generated hierarchical self-assembly of biocolloids. By drying cellulose nanocrystals (CNC) and chitin nanocrystals (ChNC) suspensions between glass substrates, lamellar structures were formed at the vicinity of the edges of the bond. The anisotropic particles were well-aligned within the lamellae in a parallel orientation. This arrangement, mostly driven by capillary flow, resulted in high lap-shear strengths (ca. 300 N with only 0.8 mg of the adhesive). Suspensions of hen egg white lysozyme (HEWL) amyloids and short amyloids, however, were more affected by Marangoni flow and did not generate well-ordered structures and high adhesive strengths. When mixed with ChNC, however, the lamellar structure was maintained up to ca. 1:10 HEWL amyloids to ChNC ratio, and a synergistic interaction generated ultimate lap-shear loads ca. 25% higher than that of the strongest individual building block. These adhesives also displayed high anisotropy, with an out of plane adhesion ca.10 to 100 times lower than the in plane. This anisotropy is reminiscent of gecko feet, and may find applications e.g. in green adhesives that provide robust adhesion, easy disassembling, and full biodegradability. Overall, via biofabrication and biopolymeric assembly, non- and highly-wetting interfaces can serve as important guides for the fabrication of well-ordered hierarchical assemblies displaying a unique set of properties and functionalities. Micro-structured substrates, with controlled wetting states and topographical features, are expected to have an important role in the fabrication of the sustainable materials of the future.
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    Covalent Modification of Nanocellulose Towards Advanced Functional Materials
    (Aalto University, 2017) Guo, Jiaqi; Filpponen, Ilari, Dr., Auburn University, USA and Aalto University, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bio-based Colloids & Materials (BiCMat); Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Nanocelluloses including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF) and bacterial cellulose (BNC) display properties that make them suitable for the development of new, advanced materials. They are expected to play key roles in the future bioeconomy, where sustainability and biomass valorization are important concepts. This thesis work mainly focused on proposing and testing effective chemical modification strategies to endow nanocelluloses with new properties and, developing novel hybrid materials. CNF and BNC as well as Carboxymethylated CNF (CM-CNF), TEMPO-oxidized CNF (TO-CNF) and TEMPO-oxidized CNC (TO-CNC) were studied with different microscopies including Atomic Force Microscopy, spectroscopic techniques such as X-ray photoelectron spectroscopy and Fourier Transform-Infrared Spectroscopy and other surface, thermo-mechanical and magnetic instrumentation. In order to prepare the hybrid materials, nanoparticles including gold nanoparticles (Au NP), carbon quantum dots (CQD) and magnetic nanoparticles (Fe3O4 NP) were synthesized. The binding of the respective NP with nanocellulose was accomplished by using Ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) and Azide-alkyne Huisgen cycloaddition (CuAAC click coupling). In turn, the NP assemblies that were installed on the surface made the nanocelluloses truly functional. Significantly, the aforementioned reactions were performed in aqueous media under relatively mild reaction conditions. Several applications of the synthesized nanoparticle-nanocellulose hybrids were demonstrated. For instance, CQD-functionalized nanocellulose was utilized for preparing luminescent nanopaper and as cytocompatible probes for bio-imaging. Magnetically responsive hybrids were designed for protein separation and an impressive separation capacity was realized for isolation of lysozyme from egg white. As very important forms of nanocellulose networks, films and nanopapers were developed as alternatives to plastics made from non-renewable carbon sources. To this end, the change of the inherent hydrophilic character of the cellulosic materials was addressed by using different strategies. For example, photo-induced (thiol-ene and thiol-yne) click reactions were demonstrated to tailor the surface wettability of films and nanopapers. The reactions were shown to be scalable and effective and can be completed within ten minutes. The developed approaches facilitated the generation of properties that are otherwise not possible for unmodified nanocelluloses. For example, CNF films with patterned surface designs and super-slippery properties were developed, making them suitable for applications relevant to drug screening, cell culture, diagnostics, anti-fouling, etc. Overall, this thesis demonstrates a body of work that expands the possible utilization of nanocelluloses in advanced materials.
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    Engineering Nanocellulose Biointerfaces Toward Bioactivity and Strength
    (Aalto University, 2017) Vuoriluoto, Maija; Orelma, Hannes, Dr., VTT Technical Research Centre of Finland, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials; Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    This work was focused on developing bioactive materials from cellulose, mainly in the form of nanofibrils (CNF). The main efforts involved modifications to adjust the surface behavior (adsorption and fouling) and wet strength of CNF in various structures. In addition to other surface analytical techniques, ultrathin films of CNF were investigated by surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D). Additionally, CNF nanopapers and wet-spun filaments were prepared and modified with functional properties, including bioactivity. The effect of molecular architecture of block and random copolymers of poly(2-(dimethylamino)ethyl methacrylate) (PDMEAMA) and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) on adsorption on substrates with low, medium and high density of electrostatic charges, namely, regenerated cellulose, CNF and TEMPO-oxidized CNF (TOCNF) was investigated. Polymer adsorption was mainly driven by electrostatic interactions between anionic groups of the cellulosic materials and cationic segments of the copolymers. Charge neutralization upon adsorption of block copolymers onto TOCNF was accompanied with significant water expulsion from the interface. The copolymers were highly efficient in producing antifouling TOCNF surfaces by reducing non-specific human IgG adsorption. The blocking efficiency was determined to be between 84-100%, depending on the polymer architecture. Remarkably, the copolymer passivation did not impair the selectivity and sensitivity of the TOCNF biointerfaces toward anti-human IgG after complementary bioactive molecules were installed by EDC/NHS coupling. The copolymer passivation reduced the otherwise nine-fold false response by the biointerface. Water-resistant CNF was prepared by TEMPO-oxidation and EDC/NHS coupling of aminobenzophenone to CNF (BP-CNF). Nanopapers and wet-spun filaments with superior wet strength (230-fold increase) were prepared from BP-CNF upon UV-activated crosslinking. The BP-CNF material was suitable for a secondary activation cycle with EDC/NHS to introduce bioactivity without significant interference from the BP functionalization. An anti-hemoglobin biointerface prepared on BP-CNF presented excellent affinity with hemoglobin, yet minimal non-specific adsorption as probed with human serum albumin. The results point to the possibility of tuning the systems' sensitivity and selectivity by passivation with random copolymers. Additionally, the BP-CNF filaments exhibiting anti-hemoglobin biointerfaces were employed successfully in testing of hemoglobin with fluorescence-labelled secondary antibodies. Overall, the work presented a method to adjust the material properties of cellulosic nanomaterials to allow their adoption in biomedical applications and biosensor development, without compromising the potential of the material for bioactivation.
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    Fractionation of Milk Fat Globule Membranes in butter processing
    (Aalto University, 2019) Jukkola, Annamari; Partanen, Riitta, Dr., Valio Ltd, Finland; Heino, Antti, Dr., Valio Ltd, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bio-Based Colloids and Materials (BiCMat); Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Bovine milk contains components that are significant to human nutrition and most beneficial if present in infant formulas. Such components are mainly associated with the biological membrane surrounding the milk fat globules, the Milk Fat Globule Membrane (MFGM). MFGM, one of the most complex fractions in milk, contains proteins and polar lipids that form a trilayer structure. Compared to its native form, MFGM structure is disrupted during milk processing, leading to the release of valuable components and affecting associated structural and functional properties. Therefore, novel methods are demanded for the isolation, fractionation and deployment of MFGM. In this thesis, we apply concepts relevant to colloid and surface chemistry to establish new processing methods aimed to maximizing the nutritional and technological value of MFGM components. We propose cream microfiltration prior to the traditional buttermaking to separate fat globules from other dairy constituents, such as proteins, lactose and minerals. Filtered cream fractions were churned, upon which phase inversion facilitated the production of butter (termed here as "ideal butter") and buttermilk, the latter of which was enriched with MFGM fragments but depleted of other dairy components. The microfiltration resulted in a protein separation efficiency of 93% and the filtered cream was found suitable for buttermaking, without affecting negatively the process. MFGM damage was observed under intense processing conditions, leading to losses in polar lipids (up to 20%). Moreover, the pH drastically effected filtration performance given its roles in modulating the electrostatic interactions and in fouling the filtration membrane. The optimisation of the process in relation to shearing forces and other factors, was found critical in defining the structure and possible losses of fat globules and MFGM. MFGM-rich ideal buttermilk powder was surface-active and capable of forming relatively stable food emulsions. Such material is proposed for the formulation of nutraceutical and infant formulas.
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    From wood to industrial polymeric biomaterials
    (Aalto University, 2018) Virtanen, Sanna; Vuoti, Sauli, Dr., Merck & Co., Finland; Biotekniikan ja kemian tekniikan laitos; Department of Biotechnology and Chemical Technology; Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Population growth, the dependence on fossil raw materials, and environmental problems caused by oil-based plastics have created a global need to search for alternative materials to replace conventional oil-based materials. Any effort to tackle such challenge, however, needs to meet the principles of sustainable development. Biodegradable and bio-based materials are promising candidates to support related bioeconomy strategies. Here, forest products are key players and, as such, this thesis targets the development of biocomposite materials by utilising wood as renewable source. The introduction of epoxy and silyl functional groups into wood-derived cellulose surface through chemical modification seemed to provide an advantageous route to enhance cellulose nanofibrils (CNF) dispersibility and compatibility with both polyvinyl alcohol (PVA) and polyurethane (PU) polymer matrices. The solution-casted PVA composites were developed by utilising the crosslinking reaction between the hydroxyl groups of PVA and epoxy groups of CNF. Using epoxidised CNF as reinforcement in PVA produced composites with outstanding mechanical properties already at low levels (0.5 to 1.5 wt.%). Additionally, the silylated CNF exhibit potential reinforcing additives already at low loadings in the water- and solvent-based two-component PU coatings by improving their strength, elasticity and abrasion resistance. The adhesion properties of the PU coatings to substrate were still retained when using the silylated CNF as additive. Modified wood-derived CNF provide fundamental improvements to PVA and PU properties, and are not only scientifically interesting but also industrially important. The study also demonstrates that moist, never-dried bleached softwood kraft pulp (BSKP) can be successfully melt compounded with polylactic acid (PLA) without chemical modification, resulting in a composite with enhanced mechanical properties. By using BSKP with relatively high moisture content in feeding, the general drawbacks associated with fibre cutting and degradation of PLA during melt processing were diminished. Also, the expensive and time-consuming stages involved in drying pulp fibres can be curtailed by using this production route. The processability and properties of the PLA/BSKP composites facilitate their future industrialisation and unveil technically and economically feasible applications.
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    Morphometric Study of Bio-Based Particles and Their Interactions
    (Aalto University, 2020) Kämäräinen, Tero; Tardy, Blaise L., Dr., Aalto University, Department of Bioproducts and Biosystems, Finland; Ago, Mariko, Dr., Aalto University, Department of Bioproducts and Biosystems, Finland; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bio-Based Colloids and Materials (BiCMat); Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando J., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Particle morphology plays many important roles in any technological application. This thesis introduces new protocols to prepare bio-based particles (including those based on lignin, tannin and chitin) and explores their morphological parametrization and colloidal interactions. In Paper I, colloidal lignin particles were prepared by using an aerosol flow reactor, which enabled a size-dependent production of particle surfaces encompassing smooth and corrugated morphologies. Three-dimensional particle morphology characterization was carried out using cryo-electron tomography and harmonic analysis to give insights on their frequency domain characteristics, surface area distribution and volume. These descriptions were used in Paper IV to assess the influence of surface corrugation networks present in crumpled particles on the interaction energy, which consisted of van der Waals and electric double layer forces. The results revealed a highly anisotropic interaction energy depending on the local morphological features near the direction of approach. We identified surface regions that acted either stronger or weaker compared to an equivalent-volume, smooth spherical particle with contact area. In Paper II, crystalline polyphenol-based particles were self-assembled using a simple, green method from alkaline aqueous tannic acid. Attained particle morphologies included rod-like, planar and cuboidal shapes. The process condition-morphology relations were unveiled by using principal component analysis, which indicated the main factors that influence the particle formation. For example, increasing the initial pH produced more elongated particles; base strength increased particle yield and increasing base counter cation size diminished particle size. In Paper III, never-dried chitin nanocrystals were isolated from crab exoskeleton residues. The chirality of these particles was analysed using cryo-electron tomography by utilizing a method based on principal component analysis. No dominant chiral handedness was found for the never-dried nanomaterials. Comparison with the results found in the literature allowed us to suggest that the drying history could influence the chiral twist formation. This is hypothesized to take place through the inhibition of hydrogen bonding networks within and across chitin chains. Overall, this thesis sheds light on the complex morphological details of various colloidal particles prepared from bio-based materials, which we considered for their high valorisation potential. Improved understanding of particle morphology and interactions is expected to facilitate the adoption of bio-based materials in a number of applications, including particulate coatings, composites and Pickering emulsions, among many others.