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  • Hautala, Jaana; Kääriäinen, Tommi; Hoppu, Pekka; Kemell, Marianna; Heinämäki, Jyrki; Cameron, David; George, Steven; Juppo, Anne Mari (2017)
    We introduce atomic layer deposition (ALD) as a novel method for the ultrathin coating (nanolayering) of minitablets. The effects of ALD coating on the tablet characteristics and taste masking were investigated and compared with the established coating method. Minitablets containing bitter tasting denatonium benzoate were coated by ALD using three different TiO2 nanolayer thicknesses (number of deposition cycles). The established coating of minitablets was performed in a laboratory-scale fluidized-bed apparatus using four concentration levels of aqueous Eudragit (R) E coating polymer. The coated minitablets were studied with respect to the surface morphology, taste masking capacity, in vitro disintegration and dissolution, mechanical properties, and uniformity of content. The ALD thin coating resulted in minimal increase in the dimensions and weight of minitablets in comparison to original tablet cores. Surprisingly, ALD coating with TiO2 nanolayers decreased the mechanical strength, and accelerated the in vitro disintegration of minitablets. Unlike previous studies, the studied levels of TiO2 nanolayers on tablets were also inadequate for effective taste masking. In summary, ALD permits a simple and rapid method for the ultrathin coating (nanolayering) of minitablets, and provides nanoscale-range TiO2 coatings on porous minitablets. More research, however, is needed to clarify its potential in tablet taste masking applications. (C) 2017 Elsevier B.V. All rights reserved.
  • Lovikka, Ville A.; Rautkari, Lauri; Maloney, Thaddeus C. (2018)
    Details on how cellulosic surfaces change under changing moisture are incomplete and even existing results are occasionally neglected. Unlike sometimes reported, water adsorption is unsuitable for surface area measurements. However, water can be utilized for assessing surface dynamics. Hygroscopic changes of pulp and bacterial cellulose were studied by dehydrating the samples in a low polarity solvent and then introducing them into a moist atmosphere in a dynamic vapor sorption (DVS) apparatus at 0-93% relative humidity (RH). The DVS treatment caused hygroscopicity loss near applied RH maxima, however, the hygroscopicity increased at RH values > 10-20% units lower. Additionally, the hygroscopic changes were partially reversible near the RH maximum. Therefore the hygroscopicity of cellulose could be controlled by tailoring the exposure history of the sample. Hornification reduced these changes. The observations support reported molecular simulations where cellulose was shown to restructure its surface depending on the polarity of its environment.
  • Ahvenainen, Patrik; Kontro, Inkeri; Svedström, Kirsi (2016)
    Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger () and more varied collection of samples than previous studies have presented is used. In particular, samples () with low crystallinity and small crystallite sizes are included. A good linear correlation () between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity.
  • Tanner, Timo; Antikainen, Osmo; Ehlers, Henrik; Blanco, David; Yliruusi, Jouko (2018)
    The compression physics of powders must be considered when developing a suitable tablet formulation. In the present study, the gravitation-based high-velocity method was utilized to analyze mechanical properties of eight common pharmaceutical excipients: two grades of lactose, anhydrous glucose, anhydrous calcium hydrogen phosphate, three grades of microcrystalline cellulose and starch. Samples were compressed five times consecutively with varying pressure and speed so that Setup A produced higher pressure and longer contact time than Setup B. The important parameters obtained from samples were porosity profiles, compaction pressure, contact time, internal energy change and the amount of elastic recovery. All acquired data was only based on distance-time profile of the compression event. Lactose and glucose fragmented effectively while calcium hydrogen phosphate remained in rearrangement phase, due to its hardness and insufficient pressure applied. Microcrystalline cellulose samples showed plastic behaviour and starch was most elastic of all the samples. By utilizing the method, examined excipients could be categorized according to their compression behaviour in an accurate and cost-efficient manner.
  • Tanner, Timo; Antikainen, Osmo; Ehlers, Henrik; Yliruusi, Jouko (2017)
    With modern tableting machines large amounts of tablets are produced with high output. Consequently, methods to examine powder compression in a high-velocity setting are in demand. In the present study, a novel gravitation-based method was developed to examine powder compression. A steel bar is dropped on a punch to compress microcrystalline cellulose and starch samples inside the die. The distance of the bar is being read by a high-accuracy laser displacement sensor which provides a reliable distance-time plot for the bar movement. In-die height and density of the compact can be seen directly from this data, which can be examined further to obtain information on velocity, acceleration and energy distribution during compression. The energy consumed in compact formation could also be seen. Despite the high vertical compression speed, the method was proven to be cost-efficient, accurate and reproducible. (C) 2017 Elsevier B.V. All rights reserved.
  • Tanner, Timo; Antikainen, Osmo; Pollet, Arne; Räikönen, Heikki; Ehlers, Henrik; Juppo, Anne; Yliruusi, Jouko (2019)
    In the present study, a model was developed to estimate tablet tensile strength utilizing the gravitation-based high-velocity (G-HVC) method introduced earlier. Three different formulations consisting of microcrystalline cellulose (MCC), dicalcium phosphate dihydrate (DCP), hydroxypropyl methylcellulose (HPMC), theophylline and magnesium stearate were prepared. The formulations were granulated using fluid bed granulation and the granules were compacted with the G-HVC method and an eccentric tableting machine. Compaction energy values defined from G-HVC data predicted tensile strength of the tablets surprisingly well. It was also shown, that fluid bed granulation improved the compaction energy intake of the granules in comparison to respective physical mixtures. In addition, general mechanical properties and elastic recovery were also examined for all samples. In this study it was finally concluded, that the data obtained by the method was of practical relevance in pharmaceutical formulation development.
  • Ojarinta, Rami; Saarinen, Jukka; Strachan, Clare J.; Korhonen, Ossi; Laitinen, Riikka (2018)
    Co-amorphous mixtures have rarely been formulated as oral dosage forms, even though they have been shown to stabilize amorphous drugs in the solid state and enhance the dissolution properties of poorly soluble drugs. In the present study we formulated tablets consisting of either spray dried co-amorphous ibuprofen-arginine or indomethacin-arginine, mannitol or xylitol and polyvinylpyrrolidone K30 (PVP). Experimental design was used for the selection of tablet compositions, and the effect of tablet composition on tablet characteristics was modelled. Multimodal non-linear imaging, including coherent anti-Stokes Raman scattering (CARS) and sum frequency/second harmonic generation (SFG/SHG) microscopies, as well as scanning electron microscopy, X-ray diffractometry and Fourier-transform infrared spectroscopy were utilized to characterize the tablets. The tablets possessed sufficient strength, but modelling produced no clear evidence about the compaction characteristics of co-amorphous salts. However, co-amorphous drug-arginine mixtures resulted in enhanced dissolution behaviour, and the PVP in the tableting mixture stabilized the supersaturation. The co-amorphous mixtures were physically stable during compaction, but the excipient selection affected the long term stability of the ibuprofen-arginine mixture. CARS and SFG/SHG proved feasible techniques in imaging the component distribution on the tablet surfaces, but possibly due to the limited imaging area, recrystallization detected with xray diffraction was not detected.
  • Mikkonen, Kirsi S. (2020)
    Wood biomass is an abundant renewable source of materials, but due to the accelerating depletion of natural resources, it is important to explore new ways to use it in a more sustainable manner. Modern technologies enable the recovery and valorization of the main components of wood—namely, cellulose, lignin, and hemicelluloses—contributing to sustainability. However, the method of isolation and resulting structure and purity of lignocellulosic materials determine their functionality and applicability. This review discusses the properties of all three main wood-based compounds that can stabilize emulsions, a class of industrial dispersions that are widely used in life science applications and chemicals. Due to the multi-billion-dollar annual market for hydrocolloids, the food, pharmaceutical, cosmetic, coating, and paint industries are actively seeking new sustainable emulsion stabilizers that fulfill the demanding requirements regarding safety and functionality. Wood-derived stabilizers facilitate various mechanisms involved in emulsion stabilization: (1) development of amphiphilic structures that decrease interfacial tension, (2) stabilization of interfaces by particles according to the Pickering theory, and (3) increase in the viscosity of emulsions’ continuous phase. This review presents pathways for treating cellulose, lignin, and hemicelluloses to achieve efficient stabilization and provides suggestions for their broad use in emulsions.
  • Buffiere, Jean; Ahvenainen, Patrik; Borrega, Marc; Svedström, Kirsi; Sixta, Herbert (2016)
    This work discusses the suitability of supercritical water treatment (SCWT) for depolymerising microcrystalline cellulose in a controlled way. The SCWT partially hydrolysed cellulose down to a mixture of three valuable products: water-insoluble low-molecular-weight cellulose (WI-LMWC) precipitate, water-soluble low-molecular-weight cellulose (WS-LMWC) oligomers, and glucose. The conditions under which the energy demand for obtaining these products is minimised were identified by adjusting the reaction time inside the continuous reactor and the temperature around the critical point. The optimum conditions were 370 degrees C and 0.4 seconds for producing WI-LMWC and 360 degrees C and 0.5 seconds for producing WS-LMWC, with maximum yields of 19 wt% and 50 wt%, respectively. This work also shows that the water-insoluble product precipitates into crystalline cellulose II arrangements. This precipitation phenomenon enabled isolation of cellulose chains of different lengths according to their respective solubilities in ambient water. The results show that SCWT is a relevant process for producing narrowly distributed fractions of low-molecular-weight cellulose using water and heat only.
  • 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.