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  • 1.
    Badal Tejedor, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Swede.
    Nordgren, N.
    Schuleit, M.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Swede.
    Millqvist-Fureby, A.
    Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure2015In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 486, no 1-2, p. 315-323Article in journal (Refereed)
    Abstract [en]

    Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.

  • 2.
    Badal Tejedor, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Intitutes of Sweden.
    Pazesh, Samaneh
    Nordgren, Niklas
    Schuleit, Michael
    Rutland, Mark W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Intitutes of Sweden.
    Alderborn, Göran
    Millqvist-Fureby, Anna
    Milling induced amorphisation andrecrystallization of α-lactose monohydrate2018In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 537, no 1-2, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the alpha-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed alpha-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between un-processed a-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spraydried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition.

  • 3. Bannow, J.
    et al.
    Benjamins, J. -W
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Löbmann, K.
    Svagan, Anna J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Solid nanofoams based on cellulose nanofibers and indomethacin—the effect of processing parameters and drug content on material structure2017In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 526, no 1-2, p. 291-299Article in journal (Refereed)
    Abstract [en]

    The unique colloidal properties of cellulose nanofibers (CNF), makes CNF a very interesting new excipient in pharmaceutical formulations, as CNF in combination with some poorly-soluble drugs can create nanofoams with closed cells. Previous nanofoams, created with the model drug indomethacin, demonstrated a prolonged release compared to films, owing to the tortuous diffusion path that the drug needs to take around the intact air-bubbles. However, the nanofoam was only obtained at a relatively low drug content of 21 wt% using fixed processing parameters. Herein, the effect of indomethacin content and processing parameters on the foaming properties was analysed. Results demonstrate that a certain amount of dissolved drug is needed to stabilize air-bubbles. At the same time, larger fractions of dissolved drug promote coarsening/collapse of the wet foam. The pendant drop/bubble profile tensiometry was used to verify the wet-foam stability at different pHs. The pH influenced the amount of solubilized drug and the processing-window was very narrow at high drug loadings. The results were compared to real foaming-experiments and solid state analysis of the final cellular solids. The parameters were assembled into a processing chart, highlighting the importance of the right combination of processing parameters (pH and time-point of pH adjustment) in order to successfully prepare cellular solid materials with up to 46 wt% drug loading.

  • 4. Fichtner, F.
    et al.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Alderborn, G.
    Particle size distribution and evolution in tablet structure during and after compaction2005In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 292, no 02-jan, p. 211-225Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to investigate the effect of the distribution in size of free-flowing particles for the evolution in tablet structure and tablet strength. For sucrose and sodium chloride, three powders of different size distributions were prepared by mixing predetermined quantities of particle size fractions. For paracetamol, three batches with varying particle size distributions were prepared by crystallisation. The powders were formed into tablets. Tablet porosity and tensile strength were determined directly after compaction and after short-term storage at two different relative humidities. Tablets were also formed after admixture of a lubricant (magnesium stearate) and the tablet tensile strength was determined. For the test materials used in this study, the spread in particle size had no influence on the evolution in tablet porosity and tensile strength during compression. However, the spread in particle size had a significant and complex influence on the short-term post-compaction increase in tablet tensile strength. The effect of the spread was related to the instability mechanism and the presence of lubricant. It is concluded that the distribution in size of free-flowing particles is not critical for the tablet porosity but may give significant effects on tablet tensile strength due to a post-compaction reaction.

  • 5. Fichtner, Frauke
    et al.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Alander, Eva M.
    Alderborn, Goran
    Effect of preparation method on compactability of paracetamol granules and agglomerates2007In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 336, no 1, p. 148-158Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to investigate the effect of fracture strength of paracetamol particles on their compactability. For this purpose two series of paracetamol particles were prepared by crystal agglomeration and by granulation using different solvents. A free flowing particle size fraction of all types of particles was characterized with respect to their shape, degree of agglomeration and single fracture strength. The powders were compressed to tablets and the compression mechanism of the particles and the evolution in tablet micro-structure were assessed by compression parameters derived from the Heckel and Kawakita equations and by a tablet permeabililty coefficient. Tablet tensile strength and porosity were determined. The degree of deformation and fragmentation during compression varied between agglomerates and granules and was dependent on their failure strength. The granules varied in compactability with particle failure strength while the agglomerates showed limited variation. It is proposed that, the dominant mechanism of compression for the granules was permanent deformation while for the agglomerates it was fragmentation. It was thus found that the compression mechanism of the particles was dependent on both the degree of agglomeration and the particle failure strength.

  • 6. Fonteyne, Margot
    et al.
    Correia, Ana
    De Plecker, Sofie
    Vercruysse, Jurgen
    Ilic, Ilija
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience.
    Veryaet, Chris
    Remon, Jean Paul
    Onofre, Fernanda
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    De Beer, Thomas
    Impact of microcrystalline cellulose material attributes: A case study on continuous twin screw granulation2015In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 478, no 2, p. 705-717Article in journal (Refereed)
    Abstract [en]

    The International Conference on Harmonisation (ICH) states in its Q8 'Pharmaceutical Development' guideline that the manufacturer of pharmaceuticals should have an enhanced knowledge of the product performance over a range of material attributes, manufacturing process options and process parameters. The present case study evaluates the effect of unspecified variability of raw material properties upon the quality attributes of granules; produced using a continuous from-powder-to-tablet wet granulation line (ConsiGma (TM) 25). The impact of different material attributes of six samples of microcrystalline cellulose (MCC) was investigated. During a blind study the different samples of MCC were used separately and the resulting granules were evaluated in order to identify the differences between the six samples. Variation in size distribution due to varying water binding capacity of the MCC samples was observed. The cause of this different water binding capacity was investigated and was caused by a different degree of crystallinity. Afterwards, an experimental design was conducted in order to evaluate the effect of both product and process variability upon the granule size distribution. This model was used in order to calculate the required process parameters to obtain a preset granule size distribution regardless of the type of MCC used. The difference in water binding capacity and its effect on granular properties was still present when combining the MCC grades with different binders.

  • 7.
    Katta, Jyothi
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Spherical Crystallization of benzoic acid2008In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 348, no 1-2, p. 61-69Article in journal (Refereed)
    Abstract [en]

    This paper deals with the development of a method for spherical crystallization of benzoic acid. Benzoic acid is dissolved in ethanol, water is used as anti-solvent and chloroform is used as bridging liquid. After an introductory screening of different methods, the influence of the amount of the bridging liquid, the solute concentration and the stirring rate is investigated. The product particle characterization includes the particle size distribution, morphology and strength. The mechanical strength of single agglomerates has been determined by compression in a materials testing machine, using a 10 N load cell. It is found that favourable properties are obtained if the bridging liquid is added during the crystallization. Larger and stronger well-shaped agglomerates are formed. The stress-strain curves are J-shaped with no clear fracturing of the particles, and are well correlated by an exponential-polynomial equation.

  • 8. Lobmann, Korbinian
    et al.
    Svagan, Anna J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Cellulose nanofibers as excipient for the delivery of poorly soluble drugs2017In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 533, no 1, p. 285-297Article in journal (Refereed)
    Abstract [en]

    Poor aqueous solubility of drugs is becoming an increasingly pronounced challenge in the formulation and development of drug delivery systems. To overcome the limitations associated with these problematic drugs, formulation scientists are required to use enabling strategies which often demands the use of new excipients. Cellulose nanofibers (CNFs) is such an excipient and it has only recently been described in the pharmaceutical field. In this review, the use of CNF in drug formulation with a focus on poorly soluble drugs is featured. In particular, the aim is to describe and discuss the many unique properties of CNFs, which make CNFs attractive as excipients in pharmaceutical sciences. Furthermore, the use of CNF as stabilizers for crystalline drug nanoparticles, as a matrix former to obtain a long-lasting sustained drug release over several weeks and as a film former with immediate release properties for poorly soluble drug are reported. Finally, the preparation of pharmaceutical CNF foams together with poorly soluble drugs is highlighted; foams, which offer a sustained drug delivery system with positive buoyancy.

  • 9. Petrov, O.
    et al.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Schuleit, M.
    Domanig, R.
    Plunkett, M.
    Daicic, J.
    Pore size distributions of biodegradable polymer microparticles in aqueous environments measured by NMR cryoporometry2006In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 309, no 02-jan, p. 157-162Article in journal (Refereed)
    Abstract [en]

    NMR cryoporometry is a unique method permitting the investigation of pores in the microporous and mesoporous regimes for samples in aqueous environments. Here, we apply the technique to porous biodegradable polymer microparticles designed as devices for drug delivery in depot formulations. The results indicate that structural features too small to be captured in surface and fracture images obtained by SEM are able to be accessed using the technique, and that the evolution of pore structure can be studied for several days as the particles swell and degrade in the aqueous environment.

  • 10. Silvander, M.
    et al.
    Hellstrom, A.
    Warnheim, T.
    Claesson, Per M.
    KTH, Superseded Departments, Chemistry.
    Rheological properties of phospholipid-stabilized parenteral oil-in-water emulsions - effects of electrolyte concentration and presence of heparin2003In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 252, no 02-jan, p. 123-132Article in journal (Refereed)
    Abstract [en]

    The rheological properties of the parenteral oil-in-water emulsion Intralipid(TM) were investigated. The viscosity data at different phase volumes correlated well with that obtained via a theoretical model developed by Yaron and Gal-Or. The model also describes the temperature dependence well. The effects of electrolyte addition were also investigated. Monovalent sodium chloride had practically no influence on viscosity. Calcium chloride, on the other hand, had a large impact on viscosity even at low concentrations. It was shown that the obtained maximum in viscosity coincided with the zeta-potential being close to zero. The resulting increase in viscosity is due to flocculation that leads to an increase in apparent phase volume. A similar behaviour was obtained with magnesium chloride with the difference that the maximum in viscosity was shifted to higher electrolyte concentrations. This is interpreted as that because magnesium binds strongly to the hydration water than does calcium. The addition of the negatively charged anti-coagulant heparin causes flocculation in the presence of small amounts of calcium. The amounts of calcium needed for such bridging flocculation is lower than what is needed in order to create a positive potential at the surfaces of the droplets. A fraction of the floes is not broken down even by extensive shear.

  • 11.
    Stjern, Louise
    et al.
    KTH.
    Voittonen, Sandra
    KTH.
    Weldemichel, Rahel
    KTH.
    Thuresson, Sofia
    Agnes, Marco
    Benkovics, Gabor
    Fenyvesi, Eva
    Malanga, Milo
    Yannakopoulou, Konstantina
    Feiler, Adam
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Valetti, Sabrina
    Cyclodextrin-mesoporous silica particle composites for controlled antibiotic release. A proof of concept toward colon targeting2017In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 531, no 2, p. 595-605Article in journal (Refereed)
    Abstract [en]

    Cyclodextrins (CDs) and mesoporous silica particles (MSPs) have been combined as composite carriers for controlled antibiotic release. CDs were employed as "gatekeeper" agents and grafted onto MSPs to retain drug molecules inside the MSP carrier. A variety of CDs (unfunctionalized, positively charged and carboxymethylated) and three different coupling strategies (covalent binding, electrostatic adsorption and inclusion complexation) were systematically investigated for their ability to control the release of two antibiotic drugs, metronidazole and clofazimine. The drugs had significantly different physicochemical properties (metronidazole - small hydrophilic, clofazimine-large hydrophobic). We report for the first time on the encapsulation and characterization of metronidazole-loaded-MSP. Each CD coating strategy reduced the drug release rate in phosphate buffer compared to unmodified MSP (from 20% to 100% retained drug). Covalent binding and inclusion complex approaches were significantly more effective than electrostatically adsorbed CD. In particular, the novel inclusion complex based on host/guest interaction between benzyl-modified silica surface and alpha-CD proved to be very effective (60-100% retained drug amount). Using pharmaceutical manufacturing processes, our study shows that CD-MSP composites can retain both hydrophobic and hydrophilic antibiotic compounds with potential translation to triggered release formulation targeting bacterial infections in the colon and lower intestine.

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