Characterization of Porous Structures of Cellulose Nanofibrils Loaded with Salicylic Acid

Bleached and unbleached pulp fibers were treated with 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) mediated oxidation to obtain cellulose nanofibrils (CNFs). The resulting bleached and unbleached CNFs were mixed with salicylic acid (0, 5, 10, 20 wt%) before casting and freeze-drying or 3D-printing. A series of methods were tested and implemented to characterize the CNF materials and the porous structures loaded with salicylic acid. The CNFs were characterized with atomic force microscopy and laser profilometry, and release of salicylic acid was quantified with UV-visible absorbance spectroscopy, conductivity measurements, and inductive coupled plasma mass spectrometry (ICP-MS). Fourier-transform infrared spectroscopy (FTIR) complemented the analyses. Herein, we show that aerogels of bleached CNFs yield a greater release of salicylic acid, compared to CNF obtained from unbleached pulp. The results suggest that biodegradable constructs of CNFs can be loaded with a plant hormone that is released slowly over time, which may find uses in small scale agricultural applications and for the private home market.publishedVersio

Influence of initial chemical composition and characteristics of pulps on the production and properties of lignocellulosic nanofibers

This work aimed to study the influence of the initial chemical composition (glucans, lignin, xylan, and mannans), intrinsic viscosity, and carboxylate groups of pulps on the production process and final properties of lignocellulosic nanofibers (LCNF). Pulps of pine sawdust, eucalyptus sawdust, and sugarcane bagasse subjected to conventional pulping and highly oxidized processes were the starting materials. The LCNF were obtained by TEMPO mediated oxidation and mechanical fibrillation with a colloidal grinder. The nanofibrillation degree, chemical charge content, rheology, laser profilometry, cristallinity and atomic force microscopy were used to characterize the LCNF. The carboxylate groups, hemicelluloses and lignin of the initial pulps were important factors that affected the production process of LCNF. The results revealed that intrinsic viscosity and carboxylate groups of the initial pulps affected LCNF production process, whereas lignin and hemicelluloses influenced the viscosity of LCNF aqueous suspensions, the roughness of LCNF films, and the carboxylate groups content of LCNF.Fil: Ehman, Nanci Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Lourenço, Ana Filipa. Universidad de Coimbra; PortugalFil: McDonagh, Birgitte Hjelmeland. Rise, Paper And Fibre Research; NoruegaFil: Vallejos, María Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Felissia, Fernando Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Ferreira, Paulo Jorge Tavares. Universidad de Coimbra; PortugalFil: Chinga Carrasco, Gary. Rise, Paper And Fibre Research; NoruegaFil: Area, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin

Aligned multi-walled carbon nanotube-embodied hydrogel via low magnetic field: A strategy for engineering aligned injectable scaffolds

Injectable scaffolds are a promising strategy to restore and regenerate damaged and diseased tissues. They require minimally invasive procedure and allow the formation of an in-situ structure of any shape. However, the formation of 3D in-situ structure with aligned morphologies using a method which could be easily transferred to clinical settings remains a challenge. Herein, the rational design of an aligned injectable hydrogel-based scaffold via remote-induced alignment is reported. Carboxylated multi-walled carbon nanotubes (cMWCNT) are aligned into hydrogel via low magnetic field. The uniform dispersion and alignment of cMWCNT into the hydrogel are clearly demonstrated by small angle neutron scattering. The obtained aligned cMWCNT-embodied hydrogel is stable over 7 days at room temperature and as well at body temperature (i.e. 37 °C). As unique approach, the formation of MWCNT-hydrogel composite is investigated combining rheology with molecular dynamic and quantum mechanical calculations. The increase of MWCNT concentration into the hydrogel decreases the total energy promoting structural stabilization and increase of stiffness. The remote aligning of injectable hydrogel-based scaffold opens up horizons in the engineering of functional tissues which requires specific cell orientation.publishedVersio

Multifunctional Nanoparticles for Bioimaging

Bioimaging is a broad term that covers all processes in which biological tissues are imaged. It can range from single-cell visualization with fluorescence microscopy, to imaging of brain structures in living human beings with magnetic resonance imaging. As such, the term is not only interesting from a researcher’s point of view, but also to existing medical technologies. Imaging living organisms is mainly based on existing tissue densities between blood, brain, cartilage, and bone. However, in some cases these differences are not sufficient to separate e.g pathological tissue from healthy tissue. In these instances, a contrast agent may be administered to alter the contrast in the region of interest. Bioimaging of excised tissue usually involve staining with a dye that binds specifically to a cellular organelle or membrane, making it easier to separate intracellular structures from each other. Bioimaging of living and excised tissue both involves an external probe that enhances the available information in the image. Such probes must be synthesized from materials that are likely to improve the acquisition of the image, and must also have few toxic side-effects. Nanomaterials are in the size-range of molecules and proteins, and can potentially traverse cellular membranes as well as being systemically administered. Nanoparticles are described as multifunctional because they can show a range of optical responses, carry drugs and vibrate in response to heat. The nanomaterials in this thesis were chosen based on their plasmonic and magnetic properties, as well as their biocompatibility. The aim of this thesis is twofold. The first aim is to fully characterize and synthesize plasmonic nanomaterials of gold with biomineralization from proteins and from chemical synthesis. The second aim is synthesis and characterization of magnetic nanomaterials of iron and manganese. Characterization in this sense refers not only to physical description of the nanoparticles or nanoconstructs, but involves describing how these nanomaterials interact with biological tissues in vitro or in vivo, to assess their potential for bioimaging, hyperthermia and drug delivery. A plethora of methods have been used to characterize the nanomaterials synthesized in this thesis. The nanomaterials of gold synthesized from proteins were described with a range of optical techniques such as UV-visible and steady state spectroscopy, and time-correlated single-photon counting. Size and shape was assessed with dynamic light scattering, scanning transmission electron microscopy and high resolution transmission electron microscopy. The surface charge was determined with zeta potential measurements. The crystalinity and composition of nanoparticles were characterized with X-ray diffraction spectroscopy, and surface composition was described with X-ray photoelectron spectroscopy. Interactions between protein-stabilized nanomaterials and model membranes were described with Langmuir-trough studies and atomic force microscopy. Magnetic nanomaterials were characterized with magnetic resonance imaging and zero field cooling. Further, nanomaterials were co-incubated with human cancer and/or rodent cells to assess their in vitro uptake or cytotoxicity. The methods for in vitro assays involved fluorescence microscopy and a cytotoxicity assay. Finally, ultramicrotome sectioning and scanning transmission electron microscopy was used to describe cellular uptake as a function of time. The main findings in the first part of this thesis are that fluorescent protein-gold nanoconstructs show membrane interactions radically different from the native protein. We also describe how protein-directed self-assembly of fluorescent gold nanoclusters and plasmonic nanoparticles can be tuned to yield different optical gold nanostructures. In the second part of this thesis, the main findings are size, - and shape-dependent uptake of novel plasmonic and magnetic nanoparticles in vitro, as well as cell actuation in a magnetic field. The final part of this thesis culminates in synthesis of a nanoparticle system that can give dual contrast in magnetic resonance imaging while at the same time release a drug

Optimalised Carbodiimide Chemistry for RGD-coupled Alginate

Alginate is a naturally ocurring polyanion of (1→4)linked β-d-mannuronic acid (M)and its C-5 epimer α-l guluronic acid (G). The polyanion, and particularly longstretches of guluronic acids, chelates and form hydrogels in the presence of divalentcations such as Ca2+ . Chelation occur at physiological conditions and the formed hy-drogels are biocompatible and stable. These properties nominates alginate hydrogelsas promising biomaterials in tissue engineering applications. Encapsulation of cells inalginate beads is easily prepared by mixing cells with high molecular weight alginate,and dripping the solution into a CaCl2 solution. When alginate comes into contactwith Ca2+ ions, alginate beads are immediately formed and the cells are captured ina three dimensional alginate matrix. Once inside the alginate capsule, the cells canbe transplanted into a host deficient in the particular cells. The alginate protectsthe cells against the immune system of the host, opening for allograf transplantationwithout immunosuppressiva. The pores in the alginate network are big enough toenable diffusion of waste and nutrition through the membrane, which is importantfor cell survival.Alginate is in itself not cell adhesive. However, alginate can be tailored into a celladhesive biomaterial by attachement of cell adhesive peptides, such as the RGDmotif found in extracellular matrix molecules such as fibronectin. Coupling of celladhesive peptides increase cell survival in three dimensional alginate matrices. Inthis study, RGD-alginate is tailored with a chemoenzymatic approach that ensuresRGD-coupling to non-gelling residues. This procedure starts with non-gelling man-nuronan that is chemically modified by attachement of the cell adhesive peptideGRGDYP by carbodiimide chemistry. Gelling residues are introduced to peptidecoupled mannuronan by a two step epimerisation catalyzed by the epimerases AlgE4and AlgE6.In this study, the carbodiimide chemsitry used for coupling GRGDYP to mannuro-nan is optimalised to create alginate with more than 0.2% bound peptide. Themodel molecules fluoresceinamine, 4-aminophenol and L-tyrosine-methyl ester areused for optimalisation, and the latter model molecule was found to give the bestrepresentation of peptide coupling to mannuronan. The carbodiimide mediated cou-pling to mannuronan is investigated by varying the pH, temperature and reactantconcentrations. The degrees of coupling for each intervention is assessed by 1 H NMRand UV/vis spectroscopy. The presence of covalently bound by-products, namedN-acylurea adducts, to mannuronan is assessed by 1 H NMR spectroscopy and acontrolled reduction of these unwanted compounds is attempted. The results from the optimalisation indicates that coupling of Me-O-Tyr and GRGDYP to mannuro-nan is concentration-dependent, as an increase in coupling was observed when theGRGDYP and Me-O-Tyr concentrations was increased. The highest peptide incor-poration described in this study was 3.4% GRGDYP coupled to mannuronan, whichis higher compared to similar studies.The optimalised carbodiimide chemistry is applied to a large scale batch of RGD-coupled alginate that is to be used for cell encapsulation of olfactory ensheating cellsfrom neonatal rat brain.High molecular weight alginate was coupled with 0.45% GRGDYP and filtratedwith active coal before cell encapsulation. The coal filtration removed a substantialamount of the unwanted N-acylurea adducts but also removed peptides, resultingin a GRGDYP coupling of 0.1% calculated from UV/vis spectroscopy, and 0.4%calculated from 1 H NMR spectroscopy. This indicates that peptides are associatedwith N-acylurea adducts and that active coal filtration is necessary to remove them.Encapsulation of olfactory ensheating cells to RGD-coupled alginate gave no mor-phology changes or enhanced cell viability compared to non-peptide coupled alginate.It is believed that the low enzymatic action of the AlgE6 epimerase, a low concen-tration of peptides or a combination of both, have influenced the cell viability andlack of morphology changes. Enhanced peptide incorporation can be achieved byincreasing the reactant concentrations of the peptides, but this would lead to a moreexpensive procedure. Increased efficacy, meaning a higher peptide coupling withlower adduct formation, at lower peptide concentrations was not achieved. However,the use of sodium borohydride in combination with periodate oxidised alginates forpeptide coupling should be assessed as a novel approach for increased peptide yieldsat lower peptide concentrations

Characterization of Porous Structures of Cellulose Nanofibrils Loaded with Salicylic Acid

Bleached and unbleached pulp fibers were treated with 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) mediated oxidation to obtain cellulose nanofibrils (CNFs). The resulting bleached and unbleached CNFs were mixed with salicylic acid (0, 5, 10, 20 wt%) before casting and freeze-drying or 3D-printing. A series of methods were tested and implemented to characterize the CNF materials and the porous structures loaded with salicylic acid. The CNFs were characterized with atomic force microscopy and laser profilometry, and release of salicylic acid was quantified with UV-visible absorbance spectroscopy, conductivity measurements, and inductive coupled plasma mass spectrometry (ICP-MS). Fourier-transform infrared spectroscopy (FTIR) complemented the analyses. Herein, we show that aerogels of bleached CNFs yield a greater release of salicylic acid, compared to CNF obtained from unbleached pulp. The results suggest that biodegradable constructs of CNFs can be loaded with a plant hormone that is released slowly over time, which may find uses in small scale agricultural applications and for the private home market

Incorporation of Fe@Au nanoparticles into multiresponsive pNIPAM-AAc colloidal gels modulates drug uptake and release

Here, a synthetic method has been optimized for the synthesis of thermoresponsive and pH-responsive poly(N-isopropylacrylamide-co-acrylic acid) nanogels which are subsequently loaded with cytochrome C by using a modified breathing-in mechanism. Physico-chemical properties mapped by using dynamic light scattering (DLS) and differential scanning calorimetry (DSC) confirm the swelling/deswelling kinetics as reversible with a volume phase transition temperature (VPTT) of ~39 °C. Fe@Au nanoparticles were incorporated inside the nanogel networks by using two different methods: coating and in situ growth. The latter bears closer resemblance to the nanogels only, while the former follows the trend of bare Fe@Au nanoparticles. High loading (~96 %) and encapsulation (500 μg/mg of nanogels) of cytochrome C were obtained. Release experiments performed by using a dialysis set-up and monitored by using UV-vis spectroscopy show the highest release at 40 °C and pH 3.2 (high temperature, low pH), with maximum release from the Fe@Au-coated nanogels that also show a reverse swelling-collapse trend. The location of the drug, the incorporation and presence of Fe@Au nanoparticles and the drug incorporation method are found to control both the drug release mechanism and kinetics.Incorporation of Fe@Au nanoparticles into multiresponsive pNIPAM-AAc colloidal gels modulates drug uptake and releaseacceptedVersio

L-DOPA-Coated Manganese Oxide Nanoparticles as Dual MRI Contrast Agents and Drug-Delivery Vehicles

Manganese oxide nanoparticles (MONPs) are capable of time‐dependent magnetic resonance imaging contrast switching as well as releasing a surface‐bound drug. MONPs give T2/T2* contrast, but dissolve and release T1‐active Mn2+ and L‐3,4‐dihydroxyphenylalanine. Complementary images are acquired with a single contrast agent, and applications toward Parkinson's disease are suggested

Nanoparticle-stabilized microbubbles for multimodal imaging and drug delivery

Microbubbles (MBs) are routinely used as contrast agents for ultrasound imaging. The use of ultrasound in combination with MBs has also attracted attention as a method to enhance drug delivery. We have developed a technology platform incorporating multiple functionalities, including imaging and therapy in a single system consisting of MBs stabilized by polyethylene glycol (PEG)-coated polymeric nanoparticles (NPs). The NPs, containing lipophilic drugs and/or contrast agents, are composed of the widely used poly(butyl cyanoacrylate) (PBCA) polymer and prepared in a single step. MBs stabilized by these NPs are subsequently prepared by self-assembly of NPs at the MB air–liquid interface. Here we show that these MBs can act as contrast agents for conventional ultrasound imaging. Successful encapsulation of iron oxide NPs inside the PBCA NPs is demonstrated, potentially enabling the NP–MBs to be used as magnetic resonance imaging (MRI) and/or molecular ultrasound imaging contrast agents. By precise tuning of the applied ultrasound pulse, the MBs burst and the NPs constituting the shell are released. This could result in increased local deposit of NPs into target tissue, providing improved therapy and imaging contrast compared with freely distributed NPs. Copyright © 2015 John Wiley & Sons, Ltd