Browsing by Subject "DISSOLUTION"

Sort by: Order: Results:

Now showing items 1-20 of 22
  • Poller, Bettina; Strachan, Clare; Broadbent, Roland; Walker, Greg F. (2017)
    The purpose of this study was to evaluate electrospun drug loaded nanofibers as a new matrix for mini tablets. Prednisone, a poorly water-soluble drug, was loaded into povidone (polyvinylpyrrolidone, PVP) nanofibers using the process of electrospinning. The drug-loaded nanofiber mat was compressed into minitablets with a 2 mm diameter and a height of 2.63 0.04 mm. SEM analysis of the minitablet identified a nano-web structure with a nanofiber diameter in the range of 400-500 nm. The minitablets met the requirements of the US Pharmacopeia with respect to content uniformity and friability. DSC and XRPD analysis of the minitablet indicated that the drug-polymer mixture was a one-phase amorphous system. XRPD analysis of the drug loaded nanofiber mat after 10-months of storage at ambient temperature showed no evidence of recrystallization of the drug. Solubility and dissolution properties of the drug formulated into a nanofiber mat and minitablet were evaluated. These results show that electrospun nanofibers may provide a useful matrix for the further development of minitablets. (C) 2017 Elsevier B.V. All rights reserved.
  • Reyes, Guillermo; Lundahl, Meri; Alejandro-Martin, Serguei; Arteaga-Perez, Luis; Oviedo, Claudia; King, Alistair; Rojas, Orlando J. (2020)
    Hydrogels of TEMPO-oxidized nanocellulose were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO2Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSFs) that were tough and flexible with an average dry (and wet) toughness of similar to 11 (2) MJ.m(-3) and elongation of similar to 9 (14) %. The CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide-angle X-ray scattering, and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.
  • Ma, Hao; Zhou, Bo; Li, Yiqun; Argyropoulos, Dimitris S. (2012)
  • Rico del Cerro, Daniel; Koso, Tetyana V.; Kakko, Tia; King, Alistair W. T.; Kilpeläinen, Ilkka (2020)
    Herein, we demonstrate the activation of commercial chemical cellulose pulps towards chemical modification by a pre-treatment step with tetrabutylphosphonium acetate ([P-4444][OAc]). A heterogeneous (non-dissolving) pre-treatment was applied allowing for a significant reduction in crystallinity, without concomitant formation of the thermodynamically stable cellulose II. An increase in chemical reactivity was demonstrated using two model reactions; (1) acetylation (organic swelling conditions), where high degrees of substitution (DS) were obtained without the need for a catalyst, and (2) 4-acetamido-TEMPO oxidation (aqueous swelling conditions), where significant degrees of oxidation (DO) were obtained, beyond those for the untreated pulps. In both tests a notable improvement in cellulose reactivity was observed. Regioselectivity of acetylation was assessed using 2D NMR for one low and one high DS sample. The low DS showed a small degree of acetylation of the 6-OH, whereas, the high DS from the pre-treated sample showed mainly mixtures of triacetate and diacetates. Important mechanistic information is attained for future development of aqueous and organic-based reactions involving this ionic liquid pre-treatment.
  • Stukelj, Jernej; Svanback, Sami; Agopov, Mikael; Lobmann, Korbinian; Strachan, Clare J.; Rades, Thomas; Yliruusi, Jouko (2019)
    Amorphous materials exhibit distinct physicochemical properties compared to their respective crystalline counterparts. One of these properties, the increased solubility of amorphous materials, is exploited in the pharmaceutical industry as a way of increasing bioavailability of poorly water-soluble drugs. Despite the increasing interest in drug amorphization, the analytical physicochemical toolbox is lacking a reliable method for direct amorphous solubility assessment. Here, we show, for the first time, a direct approach to measure the amorphous solubility of diverse drugs by combining optics with fluidics, the single particle analysis (SPA) method. Moreover, a comparison was made to a theoretical estimation based on thermal analysis and to a standardized supersaturation and precipitation method. We have found a good level of agreement between the three methods. Importantly, the SPA method allowed for the first experimental measurement of the amorphous solubility for griseofulvin, a fast crystallizing drug, without the use of a crystallization inhibitor. In conclusion, the SPA approach enables rapid and straightforward determination of the supersaturation potential for amorphous materials of less than 0.1 mg, which could prove highly beneficial in the fields of materials science, analytical chemistry, physical chemistry, food science, pharmaceutical science, and others.
  • Monden, Christiaan W. S.; Metsa-Simola, Niina; Saarioja, Saska; Martikainen, Pekka (2015)
    Background: There is an average negative mental health effect for individuals who experience divorce. Little is known whether the pattern of such divorce effects varies within couples. We study whether the husband and wife experience similar harmful effects of divorce, whether they experience opposite effects, or whether divorce effects are purely individual. Methods: We use Finnish registry data to compare changes over a period of 5 years in antidepressant use of husbands and wives from 4,558 divorcing couples to 108,637 continuously married pairs aged 40-64, all of whom were healthy at baseline. Results: In the period three years before and after divorce antidepressant use increases substantially. However, the likelihood of uptake of antidepressant medication during this process of divorce by one partner appears to be independent of medication uptake in the other partner. In contrast, among continuously married couples there is a clear pattern of convergence: If one partner starts to use antidepressants this increases the likelihood of uptake of antidepressant medication in the other partner. Conclusions: Our findings suggest that divorce effects on antidepressant use are individual and show no pattern of either convergence or divergence at the level of the couple. The increased incidence of antidepressant use associated with divorce occurs in individuals independent of what happens to their ex-partner.
  • Hyväkkö, Uula; King, Alistair W. T.; Kilpeläinen, Ilkka (2014)
  • Asaadi, Shirin; Kakko, Tia; King, Alistair W. T.; Kilpeläinen, Ilkka; Hummel, Michael; Sixta, Herbert (2018)
    Cellulose acetate is one of the most important cellulose derivatives. Herein we present a method to access cellulose acetate with a low degree of substitution through a homogeneous reaction in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]). This ionic liquid has also been identified as an excellent cellulose solvent for dry-jet wet fiber spinning. Cellulose was dissolved in [DBNH] [OAc] and esterified in situ to be immediately spun into modified cellulose filaments with a degree of substitution (DS) value of 0.05-0.75. The structural properties of the resulting fibers, which are characterized by particularly high tensile strength values (525-750 MPa conditioned and 315-615 MPa wet) and elastic moduli between 10-26 GPa, were investigated by birefringence measurements, wide-angle X-ray scattering, and molar mass distribution techniques while their unique interactions with water have been studied through dynamic vapor sorption. Thus, an understanding of the novel process is gained, and the advantages are demonstrated for producing high-value products such as textiles, biocomposites, filters, and membranes.
  • Kakko, Tia; King, Alistair W. T.; Kilpeläinen, Ilkka (2017)
    Cellulose acetate is widely used in films, filters, textiles, lacquer and cosmetic products. Herein we demonstrate the production of cellulose esters under homogeneous conditions using 1,5-diazabicyclo[4.3.0]non-5-ene acetate ([DBNH][OAc]) as solvent. The reagents have been chosen such that the system is recyclable, i.e. by-products are low boiling and easy to remove. It is demonstrated that cellulose acetate can be synthesized with different degree of substitution (DS) values, and that some commonly used acylation regents, like vinyl carboxylates react well without additional base catalyst. Low to high DS values are possible with good recovery of high purity ionic liquid (IL). A linear correlation method of two separate methods, IR and P-31 NMR, is proposed to reliably assess the DS of the products. The recyclability of the solvent is demonstrated by acetylating cellulose with isopropenyl acetate to high degree and regeneration into water. After regeneration of cellulose acetate from the IL with addition of water, the residual water was entrained using n-butanol to minimize hydrolysis of [DBNH][OAc], to allow for high recovery and high purity of the ionic liquid. Thus, an overall scheme for batch cellulose acetylation and recovery of [DBNH][OAc] from aqueous solutions is proposed.
  • Pena, Carlos A.; Soto, Ana; King, Alistair W. T.; Rodriguez, Hector (2019)
    The improvement of the reactivity of cellulose by means of an efficient pretreatment method is critical for the optimal valorization of this biorenewable polymer within a biorefinery context. In this work, a nondissolving procedure for the pretreatment of cellulose, based on the direct solid liquid contact of cellulose with an ionic liquid, namely tetrabutylphosphonium acetate, or with its mixtures with water or dimethyl sulfoxide, was found to lead to an effective reduction of the cellulose crystallinity. Due to the non dissolving nature of the method, the cellulose thus pretreated can be simply recovered by filtration from the pretreatment fluid. The use of the molecular cosolvents, as compared to the use of the neat ionic liquid, results in a less viscous pretreatment fluid and also in a larger reduction of the cellulose crystallinity. An improvement in the reactivity of the pretreated cellulose was evidenced via the determination of the kinetics of an enzymatic hydrolysis. A relationship between this reaction kinetics and the degree of crystallinity of the cellulose was inferred: the lower the crystallinity, the faster the hydrolysis. The thermal stability and degree of polymerization of the pretreated cellulose samples were comparable or essentially unaltered with respect to the untreated cellulose.
  • Driver, Gordon W.; Kilpelainen, Ilkka A. (2020)
    Knowledge of solution thermodynamics is fundamental for solution control and solvent selection processes. Herein, experimentally determined thermodynamic quantities for solutions of wood pulp (hardwood dissolving pulp, i.e. cellulose) in [m-TBDH][AcO] are presented. Model-free activities (a(i,j)) and associated mass fraction (w(i,j)) activity coefficients (omega(i,j)), are determined to quantify inherent solution non-ideality. Access to the Gibbs energy of mixing, G(mix), in combination with associated partial molar thermodynamic quantities, reveal strong enthalpically favourable (exothermic) interactions due to solvent-j and solute-i contact-encounters. Onset of an entropy driven phase instability appears at increased temperatures as excess entropic contributions dominate solvation character of the irregular solutions formed.
  • Singhal, Mayank; Baumgartner, Ana; Turunen, Elina; van Veen, Bert; Hirvonen, Jouni; Peltonen, Leena (2020)
    Aqueous solubility of a drug substance is an important attribute affecting oral bioavailability. Nanonization, particle size reduction to submicron level, is an elegant approach to improve drug solubility and dissolution by increasing the surface energy, which in turn necessitates the use of stabilizers. The purpose of this study was to develop a nanosuspension of a practically water-insoluble investigational molecule by nanomilling approach using wet media milling. A variety of polymeric and surface active excipients were tested for their wettability. A combination of hydroxypropyl methylcellulose and sodium lauryl sulfate (SLS) were selected as stabilizers on the bases of compatibility studies and efficient wettability behaviour in contact angle measurements (≈80˚). A factorial design set-up was used to study the effect of milling bead diameter and stabilizer concentration on the efficiency of particle size reduction. Nanonization outcome was different when milling beads of 0.5 mm and 1 mm diameter were used at different concentrations of the stabilizers, which demonstrated the complex nature of the whole system. Storage of the nanosuspensions under different temperature conditions resulted only in minor changes of the particle size fractions.
  • Kyllönen, Lasse; Parviainen, Arno; Deb, Somdatta; Lawoko, Martin; Gorlov, Mikhail; Kilpeläinen, Ilkka; King, Alistair W. T. (2013)
  • Elsayed, Sherif; Hellsten, Sanna; Guizani, Chamseddine; Witos, Joanna; Rissanen, Marja; Rantamäki, Antti H.; Varis, Pauliina; Wiedmer, Susanne K.; Sixta, Herbert (2020)
    Ioncell is a Lyocell based technology for the production of manmade cellulose fibers. This technology exploits the intrinsic dissolution power of superbase-based ionic liquids (ILs) toward cellulose and the ability to form spinnable cellulose solutions. The regenerated fibers are produced via a dry-jet wet spinning process in which the cellulose filaments are stretched in an air gap before regenerating in an aqueous coagulation medium. For the commercialization of this process, it is essential to demonstrate the quantitative recovery of the solvent from the coagulation bath without impairing its solvation power. This study reports on the spinnability and recyclability of the IL 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium acetate ([mTBDH][OAc]) over five cycles in comparison to 1,5-diaza-bicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]). The aqueous IL solutions were recovered from the coagulation bath by successive thermal treatments under reduced pressure. Accordingly, the recycled ILs were utilized to dissolve 13 wt % cellulose pulp in each cycle without the addition of make-up IL. While using [mTBDH][OAc], the pulp was completely dissolved and processed into easily spinnable cellulose solutions during all five cycles, whereas the ability to dissolve pulp was completely lost after the first recovery cycle when using [DBNH][OAc]. The composition of the recovered ILs and extent of side-products generated in the adopted process was analyzed in detail. This includes characterization of the rheological properties of the solutions as well as the macromolecular and mechanical properties of the regenerated fibers. In addition, we review the toxicity of both solvents using Vibrio fischeri bacteria. Finally, the spun fibers from all [mTBDH][OAc] spinning trials were combined to produce a demonstration dress (Paju), designed and sewn by Marimekko Design House in Finland.
  • Soengen, Hagen; Reischl, Bernhard; Miyata, Kazuki; Bechstein, Ralf; Raiteri, Paolo; Rohl, Andrew L.; Gale, Julian D.; Fukuma, Takeshi; Kuehnle, Angelika (2018)
    It seems natural to assume that defects at mineral surfaces critically influence interfacial processes such as the dissolution and growth of minerals in water. The experimental verification of this claim, however, is challenging and requires real-space methods with utmost spatial resolution, such as atomic force microscopy (AFM). While defects at mineral-water interfaces have been resolved in 2D AFM images before, the perturbation of the surrounding hydration structure has not yet been analyzed experimentally. In this Letter, we demonstrate that point defects on the most stable and naturally abundant calcite (10.4) surface can be resolved using high-resolution 3D AFM-even within the fifth hydration layer. Our analysis of the hydration structure surrounding the point defect shows a perturbation of the hydration with a lateral extent of approximately one unit cell. These experimental results are corroborated by molecular dynamics simulations.
  • Rahikainen, Jenni; Anbarasan, Sasikala; Wahlström, Ronny; Parviainen, Arno; King, Alistair W. T.; Puranen, Terhi; Kruus, Kristiina; Kilpeläinen, Ilkka; Turunen, Ossi; Suurnäkki, Anna (2018)
    BACKGROUNDThis study elaborates the possibility to apply combined ionic liquid (IL) and enzyme treatments for pulp fibre modification. The approach involves swelling of fibre surfaces with IL followed by enzymatic modification of the disrupted fibre surface using carbohydrate active enzymes. RESULTSThe capacity of seven cellulose-dissolving or cellulose-swelling ionic liquids to swell pulp fibres was compared. In addition, thirteen cellulases and five xylanases were screened for their IL tolerance, which determines their applicability in combined or sequential IL-enzyme treatments of fibres. Among the studied ionic liquids, 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DMP) and 1,3-dimethylimidazolium dimethylphosphate ([DMIM]DMP) had the strongest effect on fibre swelling. These solvents were also found to be the least inactivating for the studied enzymes. CONCLUSIONEnzyme compatibility and cellulose-dissolving capability are not two conflicting properties of an ionic liquid. (c) 2017 Society of Chemical Industry
  • Holmlund, Maria; Hobbs, Päivi (Emerald Group Publishing Ltd, 2009)
  • Reyes, Guillermo; Borghei, Maryam; King, Alistair W. T.; Lahti, Johanna; Rojas, Orlando J. (2019)
    Cellulose nanofiber films (CNFF) were treated via a welding process using ionic liquids (ILs). Acid base-conjugated ILs derived from 1,5-diazabicyclo[4.3.0]non-5-ene [DBN] and 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) were utilized. The removal efficiency of ILs from welded CNFF was assessed using liquid-state nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The mechanical and physical properties of CNFF indicated surface plasticization of CNFF, which improved transparency. Upon treatment, the average CNFF toughness increased by 27%, and the films reached a Young's modulus of similar to 5.8 GPa. These first attempts for IL "welding" show promise to tune the surfaces of biobased films, expanding the scope of properties for the production of new biobased materials in a green chemistry context. The results of this work are highly relevant to the fabrication of CNFFs using ionic liquids and related solvents.
  • Buffiere, Jean; Abad, Nerea; Ahvenainen, Patrik; Dou, Jinze; Jose Cocero, Maria; Sixta, Herbert (2018)
    This paper discusses the influence of reactor design and initial consistency when partially hydrolyzing microcrystalline cellulose (MCC) in supercritical water. Experiments conducted on two pilot reactors located in Finland and in Spain showed that stopping the reaction using depressurization instead of quenching, combined with a sufficiently high MCC consistency, led to significant change in reaction kinetics. A complete particle size reduction was achieved after 50 ms only due to additional shear induced degradation, with a low-molecular-weight product yield above 50 wt % and an average DP of 25. In addition, gradually increasing the MCC consistency triggered precipitation under higher apparent temperature, which affected both the morphology and structure of the product. A range of particles from ribbon-like cellulose II to shish-kebab structures to lamellar cellulose IVII crystals was obtained. Furthermore, heat requirements as low as 66 kJ.g(-1) of product confirm the high potential and versatility of this process for refining MCC into colloidal low-molecular-weight cellulose with different particle shapes and structural properties.
  • Lehti, Hannu; Erola, Jani; Karhula, Aleksi (2019)
    The literature on the intergenerational effects of unemployment has shown that unemployment has short-term negative effects on children's schooling ambitions, performance and high school dropout rates. The long-term effects on children's educational outcomes, however, are mixed. One potentially important limitation of previous studies has been that they have ignored the heterogeneous effects of parental unemployment on children's education. We study the effects of parental unemployment on children's grade point average, enrollment into general secondary and tertiary education by comparing the effects according to the children's age of exposure and the parental level of education. We use high quality Finnish longitudinal register data and sibling fixed-effect models to obtain causal effects. We find that parental unemployment has negative effects on both children's educational enrollment and performance at the educational transitional periods when children are an adolescent but parental unemployment is not detrimental in early childhood. For general secondary but not for tertiary enrollment, children's poorer school performance due to parental unemployment explains the effect entirely. Parental unemployment is not affecting children general secondary enrollment or school performance among higher educated parents. However, children with a higher educated parent exposed to unemployment are less likely to enroll in tertiary education. The reduced amount of parental economic resources due to unemployment cannot explain any of these effects. This calls for other forms of support for children at crucial periods when educational decisions are made.