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Anuschek M, Bawuah P, Zeitler JA. Terahertz time-domain spectroscopy for powder compact porosity and pore shape measurements: An error analysis of the anisotropic bruggeman model. Int J Pharm X 2021; 3:100079. [PMID: 34027385 PMCID: PMC8120941 DOI: 10.1016/j.ijpx.2021.100079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 04/19/2021] [Indexed: 11/21/2022] Open
Abstract
Terahertz time-domain spectroscopy (THz-TDS) is a novel technique which has been applied for pore structure analysis and porosity measurements. For this, mainly the anisotropic Bruggeman (AB-EMA) model is applied to correlate the effective refractive index (n eff) of a tablet and the porosity as well as to evaluate the pore shape based on the depolarisation factor L. This paper investigates possible error sources of the AB-EMA for THz-TDS based tablet analysis. The effect of absorption and tablet anisotropy - changes of pore shape with porosity and density distribution - have been investigated. The results suggest that high tablet absorption has a negligible effect on the accuracy of the AB-EMA. In regards of tablet anisotropy the accuracy of the porosity determination is not impaired significantly. However, density distribution and variations in the pore shape with porosity resulted in an unreliable extraction of the tablet pore shape. As an extension of the AB-EMA a new concept was introduced to convert the model into bounds for L. This new approach was found useful to investigate tablet pore shape but also the applicability of the AB-EMA for an unknown set of data.
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Key Words
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ϵ
˜
eff
, Effective complex dielectric permittivity
-
ϵ
˜
s
, Complex dielectric permittivity of the solid fract
-
n
˜
, Complex refractive index
- AB-EMA, Anisotropic Bruggemen model
- API, Active pharmaceutical ingredient
- Anisotropy
- Bruggeman model
- D, Tablet diameter
- Density distribution
- H, Tablet thickness
- Ibu, Ibuprofen formulation
- L, Depolarisation factor
- L1, Depolarisation factor at the lowest porosity
- Lac, Lactose
- Lfit, Estimation of the depolarisation factor based on a fitting model
- Ll/u, Lower/upper bound of the depolarisation factor
- Lmax/min, Maximal/minimal depolarisation factor in the simulation of a tablet set
- M, Tablet mass
- MCC, Microcrystalline cellulose
- Pharmaceutical tablet
- Pore structure
- RMSE, Root-mean squared error
- THz-TDS, Terahertz time-domain spectroscopy
- Terahertz
- a1, Gradient of the depolarisation factor as a function of porosity
- a2, Y-intercept of the depolarisation factor as a function of porosity
- c, Speed of light
- f, Porosity
- f1, Lowest porosity in a set of tablets
- n, Refractive index
- neff, 1, Effective refractive index at the lowest porosity
- neff, Effective refractive index
- neff, l/u, Lower/upper Wiener bound for neff
- neff, l/u, Lower/upper margin for ns
- ns, Intrinsic refractive index of the solid fraction
- ns, c, ns estimated with accounting for absorption
- ns, fit, Estimation of the intrinsic refractive index based on a fitting model
- p, Polar axis of a spheroid, parallel to the wavevector
- q, r, Equatorial axes of a spheroid, perpendicular to the wavevector
- tablename Str, Starch
- αeff, Effective absorption coefficient
- κ, Extinction coefficient
- κeff, Effective extinction coefficient
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Affiliation(s)
- Moritz Anuschek
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
- Department of Pharmacy, Pharmaceutical Technology and Biopharmaceutics, Ludwig-Maximilians-University, Butenandtstraße, Munich, Germany
| | - Prince Bawuah
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
| | - J. Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
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Lu X, Sun H, Chang T, Zhang J, Cui H. Terahertz detection of porosity and porous microstructure in pharmaceutical tablets: A review. Int J Pharm 2020; 591:120006. [DOI: 10.1016/j.ijpharm.2020.120006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 10/15/2020] [Accepted: 10/18/2020] [Indexed: 12/14/2022]
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Measuring Open Porosity of Porous Materials Using THz-TDS and an Index-Matching Medium. SENSORS 2020; 20:s20113120. [PMID: 32486451 PMCID: PMC7309058 DOI: 10.3390/s20113120] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 05/29/2020] [Accepted: 05/29/2020] [Indexed: 11/17/2022]
Abstract
The porosity of porous materials is a critical quality attribute of many products ranging from catalysis and separation technologies to porous paper and pharmaceutical tablets. The open porosity in particular, which reflects the pore space accessible from the surface, is crucial for applications where a fluid needs to access the pores in order to fulfil the functionality of the product. This study presents a methodology that uses terahertz time-domain spectroscopy (THz-TDS) coupled with an index-matching medium to measure the open porosity and analyze scattering losses of powder compacts. The open porosity can be evaluated without the knowledge of the refractive index of the fully dense material. This method is demonstrated for pellets compressed of pharmaceutical-grade lactose powder. Powder was compressed at four different pressures and measured by THz-TDS before and after they were soaked in an index-matching medium, i.e., paraffin. Determining the change in refractive index of the dry and soaked samples enabled the calculation of the open porosity. The results reveal that the open porosity is consistently lower than the total porosity and it decreases with increasing compression pressure. The scattering losses reduce significantly for the soaked samples and the scattering centers (particle and/or pore sizes) are of the order of or somewhat smaller than the terahertz wavelength. This new method facilitates the development of a better understanding of the links between material properties (particles size), pellet properties (open porosity) and performance-related properties, e.g., disintegration and dissolution performance of pharmaceutical tablets.
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Stranzinger S, Faulhammer E, Li J, Dong R, Khinast JG, Zeitler JA, Markl D. Measuring bulk density variations in a moving powder bed via terahertz in-line sensing. POWDER TECHNOL 2019. [DOI: 10.1016/j.powtec.2018.11.106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bawuah P, Karttunen AP, Markl D, Ridgway C, Korhonen O, Gane P, Zeitler JA, Ketolainen J, Peiponen KE. Investigating elastic relaxation effects on the optical properties of functionalised calcium carbonate compacts using optics-based Heckel analysis. Int J Pharm 2018; 544:278-284. [PMID: 29689369 DOI: 10.1016/j.ijpharm.2018.04.043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/09/2018] [Accepted: 04/20/2018] [Indexed: 10/17/2022]
Abstract
Heckel analysis is a widely used method for the characterisation of the compression behaviour of pharmaceutical samples during the preparation of solid dosage formulations. The present study introduces an optical version of the Heckel equation that is based on a combination of the conventional Heckel equation together with the linear relationship defined between the effective terahertz (THz) refractive index and the porosity of pharmaceutical tablets. The proposed optical Heckel equation allows us to, firstly, calculate the zero-porosity refractive index, and, secondly, predict the in-die development of the effective refractive index as a function of the compressive pressure during tablet compression. This was demonstrated for five batches of highly porous functionalised calcium carbonate (FCC) excipient compacts. The close match observed between the estimated in-die effective refractive index and the measured/out-of-die effective THz refractive index supports the validity of the proposed form of the equation. By comparing the measured and estimated in-die tablet properties, a clear change in the porosity and hence, the effective refractive index, due to post-compression elastic relaxation of the FCC compacts, has been observed. We have, therefore, proposed a THz-based compaction setup that will permit in-line monitoring of processes during tablet compression. We envisage that this new approach in tracking powder properties introduced in this preliminary study will lead to the onset of further extensive and detailed future studies.
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Affiliation(s)
- Prince Bawuah
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211 Kuopio, Finland.
| | - Anssi-Pekka Karttunen
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211 Kuopio, Finland
| | - Daniel Markl
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, G4 0RE Glasgow, United Kingdom
| | - Cathy Ridgway
- Omya International AG, CH-4665 Oftringen, Switzerland
| | - Ossi Korhonen
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211 Kuopio, Finland
| | - Patrick Gane
- Omya International AG, CH-4665 Oftringen, Switzerland; Aalto University, Chemical Engineering, Bioproducts and Biosystems, FI-00076 Aalto, Helsinki, Finland
| | - J Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, United Kingdom
| | - Jarkko Ketolainen
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211 Kuopio, Finland
| | - Kai-Erik Peiponen
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
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Markl D, Strobel A, Schlossnikl R, Bøtker J, Bawuah P, Ridgway C, Rantanen J, Rades T, Gane P, Peiponen KE, Zeitler JA. Characterisation of pore structures of pharmaceutical tablets: A review. Int J Pharm 2018; 538:188-214. [PMID: 29341913 DOI: 10.1016/j.ijpharm.2018.01.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/03/2018] [Accepted: 01/05/2018] [Indexed: 10/18/2022]
Abstract
Traditionally, the development of a new solid dosage form is formulation-driven and less focus is put on the design of a specific microstructure for the drug delivery system. However, the compaction process particularly impacts the microstructure, or more precisely, the pore architecture in a pharmaceutical tablet. Besides the formulation, the pore structure is a major contributor to the overall performance of oral solid dosage forms as it directly affects the liquid uptake rate, which is the very first step of the dissolution process. In future, additive manufacturing is a potential game changer to design the inner structures and realise a tailor-made pore structure. In pharmaceutical development the pore structure is most commonly only described by the total porosity of the tablet matrix. Yet it is of great importance to consider other parameters to fully resolve the interplay between microstructure and dosage form performance. Specifically, tortuosity, connectivity, as well as pore shape, size and orientation all impact the flow paths and play an important role in describing the fluid flow in a pharmaceutical tablet. This review presents the key properties of the pore structures in solid dosage forms and it discusses how to measure these properties. In particular, the principles, advantages and limitations of helium pycnometry, mercury porosimetry, terahertz time-domain spectroscopy, nuclear magnetic resonance and X-ray computed microtomography are discussed.
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Affiliation(s)
- Daniel Markl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK.
| | - Alexa Strobel
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
| | - Rüdiger Schlossnikl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
| | - Johan Bøtker
- Department of Pharmacy, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Prince Bawuah
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211 Kuopio, Finland
| | - Cathy Ridgway
- Omya International AG, CH-4665 Oftringen, Switzerland
| | - Jukka Rantanen
- Department of Pharmacy, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Thomas Rades
- Department of Pharmacy, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Patrick Gane
- Omya International AG, CH-4665 Oftringen, Switzerland; School of Chemical Technology, Department of Bioproducts and Biosystems, Aalto University, FI-00076 Aalto, Helsinki, Finland
| | - Kai-Erik Peiponen
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - J Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
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Markl D, Bawuah P, Ridgway C, van den Ban S, Goodwin DJ, Ketolainen J, Gane P, Peiponen KE, Zeitler JA. Fast and non-destructive pore structure analysis using terahertz time-domain spectroscopy. Int J Pharm 2017; 537:102-110. [PMID: 29247699 DOI: 10.1016/j.ijpharm.2017.12.029] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Accepted: 12/12/2017] [Indexed: 10/18/2022]
Abstract
Pharmaceutical tablets are typically manufactured by the uni-axial compaction of powder that is confined radially by a rigid die. The directional nature of the compaction process yields not only anisotropic mechanical properties (e.g. tensile strength) but also directional properties of the pore structure in the porous compact. This study derives a new quantitative parameter, Sa, to describe the anisotropy in pore structure of pharmaceutical tablets based on terahertz time-domain spectroscopy measurements. The Sa parameter analysis was applied to three different data sets including tablets with only one excipient (functionalised calcium carbonate), samples with one excipient (microcrystalline cellulose) and one drug (indomethacin), and a complex formulation (granulated product comprising several excipients and one drug). The overall porosity, tablet thickness, initial particle size distribution as well as the granule density were all found to affect the significant structural anisotropies that were observed in all investigated tablets. The Sa parameter provides new insights into the microstructure of a tablet and its potential was particularly demonstrated for the analysis of formulations comprising several components. The results clearly indicate that material attributes, such as particle size and granule density, cause a change of the pore structure, which, therefore, directly impacts the liquid imbibition that is part of the disintegration process. We show, for the first time, how the granule density impacts the pore structure, which will also affect the performance of the tablet. It is thus of great importance to gain a better understanding of the relationship of the physical properties of material attributes (e.g. intragranular porosity, particle shape), the compaction process and the microstructure of the finished product.
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Affiliation(s)
- Daniel Markl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK.
| | - Prince Bawuah
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, 70211 Kuopio, Finland
| | | | | | - Daniel J Goodwin
- GSK Research and Development, New Frontiers Science Park, 3rd Avenue, CM19 5AW Harlow, UK
| | - Jarkko Ketolainen
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, 70211 Kuopio, Finland
| | - Patrick Gane
- Omya International AG, 4665 Oftringen Switzerland; School of Chemical Engineering, Department of Bioproducts and Biosystems, Aalto University, 00076 Aalto, Helsinki, Finland
| | - Kai-Erik Peiponen
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland
| | - J Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS Cambridge, UK
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Esteban J, Moxon TE, Simons TAH, Bakalis S, Fryer PJ. Understanding and Modeling the Liquid Uptake in Porous Compacted Powder Preparations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:7015-7027. [PMID: 28657754 DOI: 10.1021/acs.langmuir.7b01334] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Porous solid materials commonly undergo coating processes during their manufacture, where liquids are put in contact with solids for different purposes. The study of liquid penetration in porous substrates is a process of high relevance in activities in several industries. In particular, powder detergents are subject to coating with surfactants that will boost their performance, although this may affect the flowability and even cause caking of the particulate material, which can be detrimental to consumer acceptance. Here we present a methodology to make compacted preparations of powders relevant to detergent making and evaluate the internal structure of such porous substrates by means of X-ray microcomputed tomography. Liquid penetration in the preparation and the total mass uptake of fluid were monitored by a gravimetric technique based on a modified Wilhelmy plate method consisting of consecutive cycles. Taking into account the geometry of the system, two models were proposed to describe the liquid uptake based on the process being driven by mass (model 1) or pressure (model 2) gradients. A comparison between both from statistical and physical points of view led to the conclusion that the latter was more appropriate for describing the process and retrieving values of the permeability of the solid between 0.03 × 10-12 and 0.95 × 10-12 m2. Finally, with the parameters retrieved from model 2, the force balance observed throughout the experiment was simulated satisfactorily.
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Affiliation(s)
- Jesús Esteban
- School of Chemical Engineering, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Thomas E Moxon
- School of Chemical Engineering, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Tom A H Simons
- School of Chemical Engineering, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Serafim Bakalis
- School of Chemical Engineering, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Peter J Fryer
- School of Chemical Engineering, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom
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Ridgway C, Bawuah P, Markl D, Zeitler JA, Ketolainen J, Peiponen KE, Gane P. On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC as sole excipient. Int J Pharm 2017; 526:321-331. [PMID: 28432018 DOI: 10.1016/j.ijpharm.2017.04.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 04/03/2017] [Accepted: 04/17/2017] [Indexed: 11/26/2022]
Abstract
The physical properties and mechanical integrity of pharmaceutical tablets are of major importance when loading with active pharmaceutical ingredient(s) (API) in order to ensure ease of processing, control of dosage and stability during transportation and handling prior to patient consumption. The interaction between API and excipient, acting as functional extender and binder, however, is little understood in this context. The API indomethacin is combined in this study with microcrystalline cellulose (MCC) at increasing loading levels. Tablets from the defined API/MCC ratios are made under conditions of controlled porosity and tablet thickness, resulting from different compression conditions, and thus compaction levels. Mercury intrusion porosimetry is used to establish the accessible pore volume, pore size distribution and, adopting the observed region of elastic intrusion-extrusion at high pressure, an elastic bulk modulus of the skeletal material is recorded. Porosity values are compared to previously published values derived from terahertz (THz) refractive index data obtained from exactly the same tablet sample sets. It is shown that the elastic bulk modulus is dependent on API wt% loading under constant tablet preparation conditions delivering equal dimensions and porosity. The findings are considered of novel value in respect to establishing consistency of tablet production and optimisation of physical properties.
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Affiliation(s)
- Cathy Ridgway
- Omya International AG, CH-4665 Oftringen, Switzerland.
| | - Prince Bawuah
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Daniel Markl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA, United Kingdom
| | - J Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA, United Kingdom
| | - Jarkko Ketolainen
- School of Pharmacy, Promis Centre, University of Eastern Finland, P.O. Box 1617, FI-70211, Kuopio, Finland
| | - Kai-Erik Peiponen
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Patrick Gane
- Omya International AG, CH-4665 Oftringen, Switzerland; Aalto University, Chemical Engineering, Bioproducts and Biosystems, FI-00076 Aalto, Helsinki, Finland
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Chakraborty M, Ridgway C, Bawuah P, Markl D, Gane PAC, Ketolainen J, Zeitler JA, Peiponen KE. Optics-based compressibility parameter for pharmaceutical tablets obtained with the aid of the terahertz refractive index. Int J Pharm 2017; 525:85-91. [PMID: 28377315 DOI: 10.1016/j.ijpharm.2017.03.093] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 03/30/2017] [Accepted: 03/31/2017] [Indexed: 11/28/2022]
Abstract
The objective of this study is to propose a novel optical compressibility parameter for porous pharmaceutical tablets. This parameter is defined with the aid of the effective refractive index of a tablet that is obtained from non-destructive and contactless terahertz (THz) time-delay transmission measurement. The optical compressibility parameter of two training sets of pharmaceutical tablets with a priori known porosity and mass fraction of a drug was investigated. Both pharmaceutical sets were compressed with one of the most commonly used excipients, namely microcrystalline cellulose (MCC) and drug Indomethacin. The optical compressibility clearly correlates with the skeletal bulk modulus determined by mercury porosimetry and the recently proposed terahertz lumped structural parameter calculated from terahertz measurements. This lumped structural parameter can be used to analyse the pattern of arrangement of excipient and drug particles in porous pharmaceutical tablets. Therefore, we propose that the optical compressibility can serve as a quality parameter of a pharmaceutical tablet corresponding with the skeletal bulk modulus of the porous tablet, which is related to structural arrangement of the powder particles in the tablet.
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Affiliation(s)
- Mousumi Chakraborty
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
| | - Cathy Ridgway
- Omya International AG, CH-4665 Oftringen, Switzerland
| | - Prince Bawuah
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Daniel Markl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, United Kingdom
| | - Patrick A C Gane
- Omya International AG, CH-4665 Oftringen, Switzerland; Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems, FI-00076 Aalto, Helsinki, Finland
| | - Jarkko Ketolainen
- School of Pharmacy, Promis Centre, University of Eastern Finland, P. O. Box 1617, FI-70211, Kuopio, Finland
| | - J Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, United Kingdom
| | - Kai-Erik Peiponen
- Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
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Markl D, Wang P, Ridgway C, Karttunen AP, Chakraborty M, Bawuah P, Pääkkönen P, Gane P, Ketolainen J, Peiponen KE, Zeitler JA. Characterization of the Pore Structure of Functionalized Calcium Carbonate Tablets by Terahertz Time-Domain Spectroscopy and X-Ray Computed Microtomography. J Pharm Sci 2017; 106:1586-1595. [PMID: 28267446 DOI: 10.1016/j.xphs.2017.02.028] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 11/15/2022]
Abstract
Novel excipients are entering the market to enhance the bioavailability of drug particles by having a high porosity and, thus, providing a rapid liquid uptake and disintegration to accelerate subsequent drug dissolution. One example of such a novel excipient is functionalized calcium carbonate, which enables the manufacture of compacts with a bimodal pore size distribution consisting of larger interparticle and fine intraparticle pores. Five sets of functionalized calcium carbonate tablets with a target porosity of 45%-65% were prepared in 5% steps and characterized using terahertz time-domain spectroscopy and X-ray computed microtomography. Terahertz time-domain spectroscopy was used to derive the porosity using effective medium approximations, that is, the traditional and an anisotropic Bruggeman model. The anisotropic Bruggeman model yields the better correlation with the nominal porosity (R2 = 0.995) and it provided additional information about the shape and orientation of the pores within the powder compact. The spheroidal (ellipsoids of revolution) shaped pores have a preferred orientation perpendicular to the compaction direction causing an anisotropic behavior of the dielectric porous medium. The results from X-ray computed microtomography confirmed the nonspherical shape and the orientation of the pores, and it further revealed that the anisotropic behavior is mainly caused by the interparticle pores. The information from both techniques provides a detailed insight into the pore structure of pharmaceutical tablets. This is of great interest to study the impact of tablet microstructure on the disintegration and dissolution performance.
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Affiliation(s)
- Daniel Markl
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
| | - Parry Wang
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
| | | | | | | | - Prince Bawuah
- Institute of Photonics, University of Eastern Finland, Joensuu, Finland
| | - Pertti Pääkkönen
- Institute of Photonics, University of Eastern Finland, Joensuu, Finland
| | - Patrick Gane
- Omya International AG, Oftringen, Switzerland; Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, Aalto, Helsinki, Finland
| | - Jarkko Ketolainen
- School of Pharmacy, Promis Centre, University of Eastern Finland, Kuopio, Finland
| | - Kai-Erik Peiponen
- Institute of Photonics, University of Eastern Finland, Joensuu, Finland
| | - J Axel Zeitler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK.
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Bawuah P, Ervasti T, Tan N, Zeitler JA, Ketolainen J, Peiponen KE. Noninvasive porosity measurement of biconvex tablets using terahertz pulses. Int J Pharm 2016; 509:439-443. [DOI: 10.1016/j.ijpharm.2016.06.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 06/07/2016] [Accepted: 06/07/2016] [Indexed: 11/25/2022]
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