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| 2. |
- Frenning, Göran, et al.
(författare)
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A new method for characterizing the release of drugs from tablets in low liquid surroundings
- 2002
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0022-3549 .- 1520-6017. ; 91:3, s. 776-784
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this article is to introduce a method capable of determining early drug dissolution in small amounts of liquid. The method is based on the measurement of the alternating ionic current through a cell containing the dissolution medium and the substance to be dissolved. Both the initial and more prolonged absorption of liquid into tablets can also be determined by using the same technique. The method has been tested on two tablet formulations containing agglomerated micronized cellulose and NaCl as a model drug. Release of NaCl was delayed from both formulations; the extent of the delay was strongly formulation-dependent only when the surrounding liquid was in short supply. This finding shows that new drug dissolution phenomena may be encountered in small liquid volumes; these phenomena would not have been seen with the large volume methods normally used in in vitro dissolution tests. Hence, for formulations intended for sublingual, buccal, or rectal administration, i.e., in areas where liquid is scarce, in vitro dissolution tests should be performed in small volumes of dissolution medium.
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| 3. |
- Hedenus, P, et al.
(författare)
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Characterisation of instantaneous water absorption properties of pharmaceutical excipients.
- 2000
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Ingår i: International Journal of Pharmaceutics. - 0378-5173 .- 1873-3476. ; 202:1-2, s. 141-9
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Tidskriftsartikel (refereegranskat)abstract
- Powders absorb water by both capillary imbibition and swelling. The capillary process is almost instantaneous but swelling occurs over a period of time. An isothermal transient ionic current technique was used in this study to characterise the instantaneous absorption properties (rate and capacity) of a few selected pharmaceutical excipients. The results indicate that the instantaneous and long term water absorption properties of pharmaceutical powders can differ considerably. The rate of instantaneous water absorption appears to correlate with the total surface area while the absorption capacity correlates more with the porosity of the powder.
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| 4. |
- Heidarian, Mina, et al.
(författare)
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Influence of water-cellulose binding energy on stability of acetylsalicylic acid
- 2006
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 323:1-2, s. 139-145
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate how the energies of water binding in cellulose tabletting excipients influence the availability of moisture to induce hydrolysis of acetylsalisylic acid (ASA). Cellulose powders of varying degree of order, denoted as low-crystallinity cellulose (LCC) and high-crystallinity cellulose (HCC), were produced by treating ordinary microcrystalline cellulose (MCC) in ZnCl2 solutions of varying concentrations. Microcrystalline cellulose (MCC) and lactose monohydrate were used as reference excipients. The samples were then studied by X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry (DSC). Different ratios of each excipient mixed with ASA were stored at 40% RH and 50 degrees C for 35 days to investigate the hydrolytic stability of the mixtures. Stability studies indicated that as concentration of HCC and MCC in binary mixtures with ASA was raised from 1 to 50% (w/w), ASA became increasingly unstable with respect to hydrolysis. Although LCC contained more moisture than the other celluloses, no such trend was observed in the LCC and lactose samples. DSC analysis revealed that each water molecule on the average was bound by more than three hydrogen bonds in the LCC and lactose structures and therefore remained predominantly unavailable to induce hydrolysis. The current study elucidates the necessity of evaluating the energy of water bindings in a pharmaceutical excipient when predicting the excipient's performance in mixtures comprising moisture-sensitive drugs.
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| 5. |
- Keyoumu, Ayiguli, et al.
(författare)
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Continuous Nano- and Ultrafiltration of Kraft Pulping Black Liquor with Ceramic Filters : A method for lowering the load on the recovery boiler while generating valuable side-products
- 2004
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 20:2, s. 143-150
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Tidskriftsartikel (refereegranskat)abstract
- Ceramic membranes coated with ZrO2 were used for the continuous separation of a well-defined low molecular weight lignin from softwood and hardwood kraft black liquors on a pilot scale. The membranes used had M-w cut-offs of 1000, 5000, and 15,000 Da, respectively. The flux (permeate flow) through the different membranes measured as L/(m(2 .)h) was studied by varying the inlet pressure and temperature. The black liquor lignins in the permeate from the filters were isolated and studied with GPC and UV spectroscopy. The low molecular weight lignin fraction was highly phenolic and could be polymerised by one-electron oxidation.
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| 6. |
- Ludvigsson, Johnny, 1943-, et al.
(författare)
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Combined vitamin D, ibuprofen and glutamic acid decarboxylase-alum treatment in recent onset Type I diabetes: lessons from the DIABGAD randomized pilot trial.
- 2020
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Ingår i: Future science OA. - London, United Kingdom : Future Science Ltd. - 2056-5623. ; 6:7
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Tidskriftsartikel (refereegranskat)abstract
- Double-blind placebo-controlled intervention using glutamic acid decarboxylase (GAD)-alum, vitamin D and Ibuprofen in recent onset Type I diabetes (T1D).64 patients (T1D since <4months, age 10-17.99, fasting sC-peptide ≥0.12nmol/l, GADA-positive) were randomized intoDay(D) 1-90 400mg/day Ibuprofen, D1-450 vitamin D 2000IU/day, D15, 45 sc. 20μg GAD-alum; as A but placebo instead of Ibuprofen; as B but 40μg GAD-alum D15, 45; placebo.Treatment was safe and tolerable. No C-peptide preservation was observed. We observed a linear correlation of baseline C-peptide, HbA1c and insulin/per kilogram/24h with change in C-peptide AUC at 15months (r=-0.776, p<0.0001).Ibuprofen, vitamin D + GAD-alum did not preserve C-peptide. Treatment efficacy was influenced by baseline clinical and immunological factors and vitamin D concentration. Clinical Trial Registration: NCT01785108 (ClinicalTrials.gov).
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| 7. |
- Mihranyan, Albert, 1978-
(författare)
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Engineering of Native Cellulose Structure for Pharmaceutical Applications : Influence of Cellulose Crystallinity Index, Surface Area and Pore Volume on Sorption Phenomena
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose powders from various sources were manufactured and characterized to investigate the influence of their crystallinity index, surface area, and pore volume on sorption phenomena and the relevant pharmaceutical functionality. The influence of the cellulose crystallinity index on moisture sorption was important at low and intermediate relative humidities. At high relative humidities, properties such as surface area and pore volume took precedence in governing the moisture sorption process.The theory of physical adsorption of gases onto fractal surfaces was useful for understanding the distribution of water in cellulose and the inner nanoscale structure of cellulose particles. It was found that, as a consequence of swelling, moisture induces a fractal nanopore network in cellulose powders that have a low or intermediate degree of crystallinity. On the other hand, no swelling occurs in highly crystalline cellulose powders and moisture sorption is restricted to the walls of the open pores.No correlation was found between the cellulose crystallinity index and the incorporation and release of nicotine in cellulose mixtures. By loading nicotine in highly porous matrices of the Cladophora sp. algae cellulose, higher stability against oxidative degradation, higher loading capacity, and more steady release into an air-stream was achieved than when commercially available microcrystalline cellulose was loaded.It was also shown that, by manipulating the structure of cellulose, the undesired hydrolysis of acetylsalicylic acid in mixtures with cellulose can be avoided. It was suggested that a broad hysteresis loop between the moisture adsorption and desorption curves of isotherms at low relative humidities could be indicative of an improved compatibility between acetylsalicylic acid and cellulose.In all, this thesis demonstrates how the pharmaceutical functionality of microcrystalline cellulose can be improved via engineering of the structure of native cellulose powders.
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| 14. |
- Sjödahl, Ragnar, et al.
(författare)
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The Effect of Sodium Ion Concentration and Dissolved Wood Components in the Kraft Cook of Softwood
- 2004
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 19:3, s. 325-329
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ionic strength and dissolved wood components (DWC) in form of industrial black liquor on the delignification rate and the brightness of the unbleached softwood kraft pulp has been investigated. A technique with a high liquor-to-wood ratio (75 L/kg) a so-called constant composition cook was used to separate the effects of the different parameters. The study showed that an increase in the ionic strength led to a decrease in the rate of delignification and gave a more coloured pulp, where as the presence of DWC gave a more coloured pulp and an increase in the delignification rate.The influence of the ionic strength and DWC on the bleachability of the softwood kraft pulp in an ECF-sequence (D(EOP)DD) was also investigated. The results show that the bleachability i.e. consumption of bleaching chemicals to reach a certain brightness, was not affected by the ionic strength during the cook. The addition of DWC, on the other hand, increased the consumption of bleaching chemicals to reach ISO brightness 89%.
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| 15. |
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| 16. |
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| 17. |
- Sjödahl, Ragnar, et al.
(författare)
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The influence of industrial black liquor on the delignification rate in the kraft cooking
- 2007
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 33:4, s. 240-245
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Tidskriftsartikel (refereegranskat)abstract
- The effect of dissolved wood components in industrial black liquor on the rate of delignification in softwood kraft cooking has been studied The results show that, when industrial black liquor was added, the delignification rate increased significantly during the bulk phase and decreased during the residual phase. A softwood black liquor was fractionated with ceramic membranes with various cut-offs, to see the way the addition of various molecular weight fractions of the black-liquor lignin affected the delignification rate. The results show that the delignification rate is dependent more on the content of phenolic groups than on the size of the lignin fragments. However, a low molecular-weight lignin fraction has a higher content of phenolic groups than a high molecular-weight fraction does. These results may explain one reason for the positive effect of adding industrial black liquor to the bulk phase of a softwood kraft cook.
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| 18. |
- Strömme, Maria, 1970-, et al.
(författare)
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A new method of characterising liquid uptake within particles over short time periods.
- 2000
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Ingår i: International Journal of Pharmaceutics. - 0378-5173 .- 1873-3476. ; 199:2, s. 179-85
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Tidskriftsartikel (refereegranskat)abstract
- A method of measuring both the capacity and rate of absorption of liquid by powders of small particles over short time periods (of the order of a few seconds or less) is presented. The method is based on the measurement of the isothermal transient ionic current in a sample cell containing the absorbant material and the liquid. The method has been tested on solid glass beads, porous glass beads and cellulose agglomerates. Properties such as the instantaneous absorption capacity and rate can be characterised within a few seconds. No other technique is currently able to measure these fast outcomes.
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| 19. |
- Strömme, Maria, et al.
(författare)
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Densification-induced conductivity percolation in high-porosity pharmaceutical microcrystalline cellulose compacts
- 2003
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 82:4, s. 648-650
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Tidskriftsartikel (refereegranskat)abstract
- The percolation theory is established as a useful tool in the field of pharmaceutical materials science.It is shown that percolation theory, developed for analyzing insulator–conductor transitions, can beapplied to describe imperfect dc conduction in pharmaceutical microcrystalline cellulose duringdensification. The system, in fact, exactly reproduces the values of the percolation threshold andexponent estimated for a three-dimensional random continuum. Our data clearly show a crossoverfrom a power-law percolation theory region to a linear effective medium theory region at a celluloseporosity of ;0.7.
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| 20. |
- Strömme, Maria, et al.
(författare)
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Fractal dimension of cellulose powders analyzed by multilayer BET adsorption of water and nitrogen
- 2003
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 107:51, s. 14378-14382
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to show that multilayer fractal Brunauer-Emmett-Teller (mfBET) theory can be used as a tool to obtain information about the distribution of water in cellulose powder particles of varying crystallinity. Microcrystalline cellulose, agglomerated micronized cellulose, low-crystallinity cellulose, and cellulose powders from green and brown algae were characterized by scanning electron microscopy and mfBET analysis on water and nitrogen adsorption isotherms. The distribution of water in the cellulose materials was found to be characterized by a fractal dimension smaller than 1.5 for all powders. The results showed that for highly crystalline cellulose materials, such as Cladophora cellulose, the cellulose-water interactions take place mainly on cellulose fibril surfaces adjacent to open pores without causing any significant swelling of the material. For less ordered celluloses the water interaction was found to take place inside the bulk material and the water uptake process caused the pore volume to swell between 1 and 2 orders in magnitude. For the Cladophora cellulose, the thickness of the adsorbed water layer at the outer cut off of the fractal region was found to coincide very well with the average pore size obtained from nitrogen adsorption measurements. The multilayer fractal BET analysis on nitrogen adsorption isotherms showed that the particles could be characterized by fractal dimensions between 2.13 and 2.50. We conclude that water adsorption has the ability to alter the structure of the studied material and reveal a sorption-induced, "apparent" fractal structure over a relatively narrow length scale interval, while nitrogen adsorption probes the substrate morphology over a wide range of length scales and reveals the "true" fractal structure.
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| 21. |
- Strömme, Maria, et al.
(författare)
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What do we do with all these algae?
- 2002
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Ingår i: Materials letters (General ed.). - 0167-577X .- 1873-4979. ; 57:3, s. 569-572
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Tidskriftsartikel (refereegranskat)abstract
- The severe eutrophication of coastal areas is considered to be one of the most serious environmental threats of our time S. Nixon, Ambio 19 (1990) 101. Even if the nutrient outlet is curtailed, carpets of green algae filaments will remain for a long time as the algae life cycle feeds itself S. Naeem, D.R. Hahn, G. Schuurman, Nature 403 (2002) 762. One way to master this ecological problem is to remove algae from the cycle O. Jousson, J. Pawlowski, L. Zaninetti, F.W. Zechman, F. Dini, G. Di Guiseppe, R. Woodfield, A. Millar, A. Meinensz, Nature 408 (2000) 157. Hence, the necessity of finding some relevant use for green algae is obvious. It has been shown that cellulose powder from green algae sources has a higher level of crystallinity and a relatively larger surface area than higher plant cellulose R. Ek, C. Gustafsson, A. Nutt, T. Iversen, C, Nyström, J. Mol. Recognit. 11 (1998) 263. Could these properties possibly be advantageous in pharmaceutical tablet manufacturing? Here, we show that green algae filaments provide an alternative raw material source for the production of microcrystalline cellulose with a hitherto unobserved combination of properties desirable for a tableting excipient.
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| 22. |
- Welch, Ken, et al.
(författare)
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Comparative Drug Release Measurements in Limited Amounts of Liquid : A Suppository Formulation Study
- 2006
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Ingår i: Current Drug Delivery. - : Bentham Science Publishers Ltd.. - 1567-2018 .- 1875-5704. ; 3:3, s. 299-306(8)
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for the investigation of drug formulations in limited liquid volumes is presented. The experimental setup consists of a measurement cell containing an absorbent sponge cloth placed between two parallel electrodes. Conductivity measurements are used to monitor the drug release from the dosage form. By varying the amount of water contained in the absorbent cloth surrounding the dosage form, it is possible to measure the drug release performance of the dosage form in very limited amounts of water. The method was employed to test four different tablet formulations consisting of the model drug NaCl incorporated in excipient matrices of hard fat, polyethylene glycol, microcrystalline cellulose and a mixture of microcrystalline cellulose and croscarmellose sodium (Ac-Di-Sol). The drug release rates of the different formulations in limited water volumes differed markedly from the release rates in an excess of water. Whereas the release rates from all tablet types in an excess of water showed only minor differences among the tablet types, the release rates from the tablets formulated with disintegrating e
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| 23. |
- Welch, Ken, 1968-
(författare)
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Electrodynamic and Mechanical Spectroscopy Method Development and Analysis Relating to Materials with Biotechnological Applications
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Materials with biotechnological applications and materials that interact with the biological environment play an ever increasing role in our lives and society. In order to be able to tailor specific properties of these materials to suit their intended applications, it is important to gain a deeper understanding of the relationship between the material structure and its function. This thesis contributes to the goal of achieving a better understanding of the functional properties of materials through the development of novel characterizing methods as well as the analysis of such materials. Electrodynamic and mechanical spectroscopy methods are developed or employed in the characterization of three classes of materials, namely, pharmaceutical, biomedical and biological materials. Two electrodynamic methods utilizing conductivity measurements were developed for the investigation of drug release from pharmaceutical dosage forms, particularly in low liquid volumes. Furthermore, a mechanical spectroscopy method based on the split Hopkinson pressure bar setup was developed for the viscoelastic characterization of pharmaceutical compacts. It was shown that this method is a valuable complement to other methods of characterization. Dielectric spectroscopy was integrated with microfabrication techniques to create a method for bacteria detection in a biotechnological application. As well, dielectric spectroscopy was used in the characterization of a novel biomimetic ionomer and was demonstrated to be a powerful tool for studying the bulk molecular dynamics of this functional material. The work presented in this thesis not only provides an enhanced understanding of materials and their functional properties, but also presents new methods that should be useful for the future characterization of such materials.
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