Name: a package of established analytical tools to investigate the solid-state alteration of lipid-based excipients
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1. Differential scanning calorimetry (DSC)
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	<li>Instrument preparation
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		<li>Use a differential scanning calorimeter equipped with an intracooler, an autosampler, and the software for instrument control and data analysis.</li>
		<li>Switch on the nitrogen gas supply and set the pressure between 0.2&#8211;0.5 bar and power up the DSC instrument and the automatic sample changer.</li>
		<li>Open the software and activate the standby mode by clicking on the Yes button. Allow equ...

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	<li>Sato, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystallization+behaviour+of+fats+and+lipids+a+review.">Crystallization behaviour of fats and lipids a review.</a> Chemical Engineering Science. 56 (7), 2255-2265 (2001).</li><li>Becker, K., Salar-Behzadi, S., Zimmer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solvent-free+melting+techniques+for+the+preparation+of+lipid-based+solid+oral+formulations.">Solvent-free melting techniques for the preparation of lipid-based solid oral formulations.</a> Pharmaceutical Research. 32 (5), 1519-1545 (2015).</li><li>Rosiaux, Y., Jannin, V., Hughes, S., Marchaud, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+lipid+excipients+-+Matrix+agents+for+sustained+drug+delivery.">Solid lipid excipients - Matrix agents for sustained drug delivery.</a> Journal of Controlled Release. 188, 18-30 (2014).</li><li>Siepmann, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipids+and+polymers+in+pharmaceutical+technology:+lifelong+companions.">Lipids and polymers in pharmaceutical technology: lifelong companions.</a> International Journal of Pharmaceutics. 558, 128-142 (2019).</li><li>Lopes, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microphase+separation+in+solid+lipid+dosage+forms+as+the+cause+of+drug+release+instability.">Microphase separation in solid lipid dosage forms as the cause of drug release instability.</a> International Journal of Pharmaceutics. 517 (1-2), 403-412 (2017).</li><li>Reitz, C., Kleinebudde, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+lipid+extrusion+of+sustained+release+dosage+forms.">Solid lipid extrusion of sustained release dosage forms.</a> European Journal of Pharmaceutics and Biopharmaceutics. 67 (2), 440-448 (2007).</li><li>Salar-Behzadi, S., Corzo, C., Schaden, L., Laggner, P., Zimmer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+between+the+solid+state+of+lipid+coating+and+release+profile+of+API+from+hot+melt+coated+microcapsules.">Correlation between the solid state of lipid coating and release profile of API from hot melt coated microcapsules.</a> International Journal of Pharmaceutics. 565, 569-578 (2019).</li><li>Windbergs, M., Gueres, S., Strachan, C. J., Kleinebudde, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-step+solid+lipid+extrusion+as+a+process+to+modify+dissolution+behavior.">Two-step solid lipid extrusion as a process to modify dissolution behavior.</a> AAPS PharmSciTech. 11 (1), 2-8 (2010).</li><li>Schertel, S., Salar-Behzadi, S., Zimmer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+surface+properties+of+core+material+on+the+stability+of+hot+melt-coated+multiparticulate+systems.">Impact of surface properties of core material on the stability of hot melt-coated multiparticulate systems.</a> Pharmaceutics. 13 (3), 366 (2021).</li><li>Tang, D., Marangoni, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microstructure+and+fractal+analysis+of+fat+crystal+networks.">Microstructure and fractal analysis of fat crystal networks.</a> Journal of the American Oil Chemists' Society. 83, 377-388 (2006).</li><li>Corzo, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipid-microparticles+for+pulmonary+delivery+of+active+pharmaceutical+ingredients:+Impact+of+lipid+crystallization+on+spray-drying+processability.">Lipid-microparticles for pulmonary delivery of active pharmaceutical ingredients: Impact of lipid crystallization on spray-drying processability.</a> International Journal of Pharmaceutics. 610, 121259 (2021).</li><li>Acevedo, N. C., Marangoni, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+nanostructure+of+triacylglycerol+crystal+networks.">Characterization of the nanostructure of triacylglycerol crystal networks.</a> Structure-Function Analysis of Edible Fats. , (2012).</li><li>Marangoni, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure-function+analysis+of+edible+fats.">Structure-function analysis of edible fats.</a> Structure-Function Analysis of Edible Fats. , (2018).</li><li>Sato, K., Sato, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystallization+of+lipids.">Crystallization of lipids.</a> Fundamentals and Applications in Food, Cosmetics, and Pharmaceuticals. , (2018).</li><li>Acevedo, N. C., Marangoni, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+nanoscale+engineering+of+triacylglycerol+crystal+networks.">Toward nanoscale engineering of triacylglycerol crystal networks.</a> Crystal Growth and Design. 10 (8), 3334-3339 (2010).</li><li>Lopes, D. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+lipid+blooming+and+crystallite+size+in+the+performance+of+highly+soluble+drug-loaded+microcapsules.">Role of lipid blooming and crystallite size in the performance of highly soluble drug-loaded microcapsules.</a> Journal of Pharmaceutical Sciences. 104 (12), 4257-4265 (2015).</li><li>Salar-Behzadi, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+approach+for+overcoming+the+stability+challenges+of+lipid-based+excipients.+Part+2:+Application+of+polyglycerol+esters+of+fatty+acids+as+hot+melt+coating+excipients.">Novel approach for overcoming the stability challenges of lipid-based excipients. Part 2: Application of polyglycerol esters of fatty acids as hot melt coating excipients.</a> European Journal of Pharmaceutics and Biopharmaceutics. 148, 107-117 (2020).</li><li>Corzo, C., Meindl, C., Lochmann, D., Reyer, S., Salar-Behzadi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+approach+for+overcoming+the+stability+challenges+of+lipid-based+excipients.+Part+3:+Application+of+polyglycerol+esters+of+fatty+acids+for+the+next+generation+of+solid+lipid+nanoparticles.">Novel approach for overcoming the stability challenges of lipid-based excipients. Part 3: Application of polyglycerol esters of fatty acids for the next generation of solid lipid nanoparticles.</a> European Journal of Pharmaceutics and Biopharmaceutics. 152, 44-55 (2020).</li><li>Tylor, A. K., Rowe, R. C., Sheskey, P. J., Quinn, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glyceryl+monostearate.">Glyceryl monostearate.</a> Handbook of Pharmaceutical Excipients. , 290-293 (2009).</li><li>Lutton, R. S., Jackson, F. 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B. 111 (3), 564-571 (2007).</li><li>Maleky, F., Marangoni, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+effects+on+oil+migration+through+triacylglycerol+polycrystalline+colloidal+networks.">Nanoscale effects on oil migration through triacylglycerol polycrystalline colloidal networks.</a> Soft Matter. 7, 6012-6024 (2011).</li><li>Corzo, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+approach+for+overcoming+the+stability+challenges+of+lipid-based+excipients.+Part+1:+Screening+of+solid-state+and+physical+properties+of+polyglycerol+esters+of+fatty+acids+as+advanced+pharmaceutical+excipients.">Novel approach for overcoming the stability challenges of lipid-based excipients. Part 1: Screening of solid-state and physical properties of polyglycerol esters of fatty acids as advanced pharmaceutical excipients.</a> European Journal of Pharmaceutics and Biopharmaceutics. 148, 134-147 (2020).</li><li>Gordillo-Galeano, A., Mora-Huertas, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid+lipid+nanoparticles+and+nanostructured+lipid+carriers:+A+review+emphasizing+on+particle+structure+and+drug+release.">Solid lipid nanoparticles and nanostructured lipid carriers: A review emphasizing on particle structure and drug release.</a> European Journal of Pharmaceutics and Biopharmaceutics. 133, 285-308 (2018).</li><li>Fan, Y., Marioli, M., Zhang, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+characterization+of+liposomes+and+other+lipid+nanoparticles+for+drug+delivery.">Analytical characterization of liposomes and other lipid nanoparticles for drug delivery.</a> Journal of Pharmaceutical and Biomedical Analysis. 192, 113642 (2021).</li><li>Peyronel, F., Pink, D. A., Marangoni, A. 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Influence of cooling rate.</a> Journal of Dairy Science. 88 (2), 511-526 (2005).</li><li>Kalnin, D., Garnaud, G., Amenitsch, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ollivon.+Monitoring+fat+crystallization+in+aerated+food+emulsions+by+combined+DSC+and+time-resolved+synchrotron+X-ray+diffraction.">Ollivon. Monitoring fat crystallization in aerated food emulsions by combined DSC and time-resolved synchrotron X-ray diffraction.</a> Food Research International. 35 (10), 927-934 (2002).</li><li>Bugeat, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unsaturated+fatty+acid+enriched+vs.+control+milk+triacylglycerols:+Solid+and+liquid+TAG+phases+examined+by+Synchrotron+radian+X-ray+diffraction+coupled+with+DSC.">Unsaturated fatty acid enriched vs. control milk triacylglycerols: Solid and liquid TAG phases examined by Synchrotron radian X-ray diffraction coupled with DSC.</a> Food Research International. 67, 91-101 (2015).</li><li>Brubach, J. 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Powder x-ray diffraction and DSC were described in this manuscript as gold standards for the solid-state analysis of LBEs. Powder x-ray diffraction has the outstanding advantage of processing the measurements in situ, with minimum solid-state manipulation of samples during the measurements. Moreover, the same-filled capillaries can be stored under different conditions after initial measurements to investigate the solid-state alteration during storage. In this work, we focused on the wide- and small-angle regions...

Lipids are a class of materials that contain long-chain aliphatic hydrocarbons and their derivatives. They cover a broad range of chemical structures, including fatty acids, acylglycerols, sterols and sterol esters, waxes, phospholipids, and sphingolipids1. The use of lipids as pharmaceutical excipients started in 1960 for embedding drugs in a wax matrix to provide sustained release formulations2. Since then, lipid-based excipients (LBEs) have gained extensive attention for diverse applications, such as modified drug release, taste-masking, drug encapsulation, and enhanced drug bioavailability. LBEs can be applied in a broad range of pharmaceutical dosage forms via versatile manufacturing processes, namely, hot-melt coating, spray-drying, solid lipid extrusion, 3D printing, tableting, and high-pressure homogenization, among others. Dosage forms such as tablets, orally disintegrating films, multiparticulate systems, nano and microparticles, pellets, and 3D-printed forms are the result2,3,4.
LBEs possess the &#34;General Recognized as Safe&#34; status, low toxicity, good biocompatibility, and improved patient tolerance. Their natural origin and broad availability allow them to empower green and sustainable pharmaceutical manufacturing. Nevertheless, the use of LBEs has been associated with unstable dosage forms. Alterations in the properties of lipid-based products after storage have been widely reported. The solid-state of LBEs and the existence of lipid polymorphism are considered the main reasons for the instability of lipid-based dosage forms5,6,7,8.
The mechanical and physical properties of lipids are closely related to their crystallization properties and the structure of their crystal network, which shows distinct hierarchies of structural organization. When lipids are used in the manufacturing of pharmaceutical products, the crystal structure is affected by the process parameters applied, such as temperature, organic solvents, shear, and mechanical forces, which in turn affects the performance of the pharmaceutical product5,7,9,10,11,12. To understand this structure-function relationship, it is important to know the fundaments of lipid crystallization and crystal structure and analytical methods to screen them.
At the molecular level, the smallest unit of a lipid crystal is termed a &#34;unit cell.&#34; A regular three-dimensional repetition of unit cells builds the crystal lattices, with stronger molecular interactions alongside their lateral directions than the longitudinal ones, explaining the layered construction of lipid crystals. The repeated cross-sectional packing of hydrocarbon chains is known as sub-cell1,12,13 (Figure 1). Lamellae are the lateral packing of lipid molecules. In the crystal package, the interfaces between different lamellae are made of methyl end groups, whereas the polar glycerol groups are placed at the interior parts of the lamella14. To differentiate each fatty-acid chain in the lamella, the term leaflet is employed, which represents a sublayer composed of single fatty-acid chains. Acylglycerols can be arranged in double (2L) or triple (3L) leaflet chain lengths14. The surface energy of the lamellae drives them to epitaxially stack to each other, to provide nano-crystallites. Different processing factors such as cooling temperature and rate affect the number of stacked lamellae and thereby, the crystallite thickness (~10-100 nm). Aggregation of crystallites leads to the formation of spherulites in micro-scale, and the aggregation of spherulites provides the crystal network of LBEs with defined macroscopic behavior13.
Solid-state transitions start at the molecular level. The geometrical transition from one sub-cell to another is called polymorphism. Three major polymorphs of &#945;-, &#946;&#39;-, and &#946;-form are usually found in acylglycerols, ordered according to increased stability. Tilting of the lamella with respect to end-groups occurs during polymorphic transitions1,13. Storage and melt-mediated polymorphic transitions are experienced by LBEs. Storage transitions occur when the metastable form is stored below its melting temperature, whereas melt-mediated transitions happen as the temperature rises above the melting point of a metastable form provoking melting and successive crystallization of the more stable form.
Furthermore, phase separation and crystal growth can also occur. Phase separation is driven by initial multiphasic crystallization and growth of one phase or more. Particle-particle interactions, including sintering, molecular interactions, microstructural features, and foreign components, can also trigger crystal growth1,5.
Monitoring the solid-state transitions of LBEs and their impact on the performance of dosage forms is of significant importance. Among others, differential scanning calorimetry (DSC) and x-ray diffraction, specifically simultaneous small and wide-angle X-ray scattering (SWAXS), are two gold standards for assessing lipid solid-state.
DSC is commonly used to measure the enthalpy changes of the material of interest associated with the heat flow as a function of time and temperature. The method is widely used for the screening of thermal behavior of lipids, such as possible pathways of melting and crystallization, corresponding temperature and enthalpy of different polymorphic forms, as well as minor and main fractions of lipid compositions. These data can be used to depict the heterogeneity, multiple phases, and lipid polymorphism5,7,13.
X-ray diffraction techniques are the most powerful methods for structure determination in the solid state. Possessing ordered nanostructure with repeated lamellae, the reflection of x-ray beam from lipid crystals can be investigated using Bragg&#39;s law:
d = &#955;/2sin&#952;&#160; &#160; &#160;(Equation 1)
where &#955; is the x-ray wavelength of 1.542 &#197;, &#952; is the diffraction angle of the scattered beam, and d is the interplanar spacing of repeated layers, defined as lamella length in lipids. The small-angle region of the x-ray can be perfectly used to detect the long-spacing pattern and calculate the lamella length (d). The larger the repeated distance d, the smaller the scattering angle (1-15&#176;, small-angle region) since d is inversely proportional to sin &#952;. The sub-cell arrangement of lipids can be characterized as the short-spacing pattern in the wide-angle region of the x-ray diffraction. Both the long- and short-spacing patterns of lipids (lamella length and sub-cell arrangement) can be used to indicate the monotropic polymorphic transformation. For example, the &#945;-form (hexagonal) can be altered to &#946; (triclinic) due to a change in the angle of tilt of the chains, with alterations in the lamella length (long-spacing pattern, in the small-angle region, 1-15&#176;) and in the cross-sectional packing mode (short-spacing pattern, in the wide-angle region, 16-25&#176;) (Figure 2).
The information obtained from the SAXS region can further be used to investigate the crystal growth by measuring its thickness (D) via the Scherrer equation15:
D = K&#955;/FWHMcos&#952;&#160; &#160; &#160;(Equation 2)
Where, FWHM is the width in radians of the diffraction maximum measured at a half-way height between the background and the peak, generally known as full-width at half-maximum (FWHM); &#952; is the diffraction angle; &#955; is the X-ray wavelength (1.542 &#197;) and K (Scherrer constant) is a dimensionless number that provides information about the shape of the crystal (in case of the absence of detailed shape information K = 0.9 is a good approximation). Please note that the Scherrer equation can be used to estimate mean crystal sizes of up to about 100 nm since the peak broadening is inversely proportional to the crystallite size. Therefore, its application is useful for determining the thickness of nanoplatelets and, indirectly, the number of aggregated lamellae. Examples of using this well-known approach for screening the crystal properties of lipids in the pharmaceutical formulation development and the corresponding instability in product performance can be found in5,12,16,17,18.
Monitoring the solid-state of LBEs within each developmental stage through well-established analytical techniques provide an effective strategy for designing high-performance manufacturing processes and stable lipid-based pharmaceutical products.
This publication presents the critical application of a comprehensive solid-state analysis of LBEs for monitoring the changes in solid-state and its correlation to the alteration in the release profile of active pharmaceutical ingredient (API) from the pharmaceutical dosage form. Multiparticulate systems based on lipid-coated API crystals via hot-melt coating, and nano-lipid suspensions produced via high-pressure homogenization are taken as case studies. The focus of this publication is the application of powder x-ray diffraction and DSC as analytical tools. The first two examples show the effect of polymorphic transformation and crystal growth, respectively, on the alteration in API release from coated samples. The last example reveals the correlation between the stable solid-state of lipid and the stable performance of the pharmaceutical product in lipid-coated multiparticulate systems and in nano-lipid suspensions.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>CaCl2&#183;2H2O</td>
			<td>Sigma-Aldrich</td>
			<td>223506</td>
			<td></td>
		</tr>
		<tr>
			<td>Cassettes with a cellulose membrane bag with a cut-off of 7000 Da, Thermo Scientific Slide-A-Lyzer 7K</td>
			<td>Fisher Scientific Inco, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Control software of x-ray system</td>
			<td>HECUS dedicated house equipment</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Control unit of x-ray system</td>
			<td>HECUS dedicated house equipment</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Differential scanning calorimeter (DSC) aluminum crucibles and lids</td>
			<td>Netzsch, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Differential scanning calorimeter DSC 204 F1 Phoenix (NETZSCH, Germany).</td>
			<td>Netzsch, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dipalmitoylphosphatidylcholine (DPPC)</td>
			<td>Sigma-Aldrich</td>
			<td>850355P</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissolution paddle apparatus II, Erweka DT 828 LH</td>
			<td>Erweka GmbH, Langen, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dynasan 116</td>
			<td>IOI OLEO</td>
			<td></td>
			<td>Tripalmitin</td>
		</tr>
		<tr>
			<td>Geleol</td>
			<td>Gattefosse</td>
			<td></td>
			<td>Glyceryl monosterarate&#160;</td>
		</tr>
		<tr>
			<td>KCl&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>529552</td>
			<td></td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>P0662</td>
			<td></td>
		</tr>
		<tr>
			<td>Kolliphor P 188</td>
			<td>BASF Chem Trade</td>
			<td></td>
			<td>Poloxamer 188&#160;</td>
		</tr>
		<tr>
			<td>MgCl2&#183;6H2O</td>
			<td>Sigma-Aldrich</td>
			<td>M2670</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2HPO4&#183;2H2O</td>
			<td>Sigma-Aldrich</td>
			<td>S9763</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich</td>
			<td>S9888</td>
			<td></td>
		</tr>
		<tr>
			<td>Netzsch DSC 204F1 Software Version 8.0.1</td>
			<td>Netzsch, Germany</td>
			<td>6.239.2-64.51.00</td>
			<td></td>
		</tr>
		<tr>
			<td>Origin Pro (OriginLab, Northampton, MA) (statistical software</td>
			<td>OriginLab, Northampton, MA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Proteous Analysis Software</td>
			<td>Netzsch, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tween 65</td>
			<td></td>
			<td></td>
			<td>Polysorbate 65</td>
		</tr>
		<tr>
			<td>Witepsol PMF 1683</td>
			<td>IOI OLEO</td>
			<td></td>
			<td>Triglycerol ester of stearatic/palmitic acid (partially esterified)</td>
		</tr>
		<tr>
			<td>Witepsol PMF 282</td>
			<td>IOI OLEO</td>
			<td></td>
			<td>Diglycerol ester of stearic acid&#160;</td>
		</tr>
		<tr>
			<td>X-ray HECUS system composed of a point-focusing camera and two linearly positioned sensitive detectors</td>
			<td>HECUS dedicated house equipment</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a package of established analytical tools to investigate the solid-state alteration of lipid-based excipients

Lipid-based excipients (LBEs) are low-toxic, biocompatible, and natural-based, and their application supports the sustainability of pharmaceutical manufacturing. However, the major challenge is their unstable solid-state, affecting the stability of the pharmaceutical product. Critical physical properties of lipids for their processing-such as melt temperature and viscosity, rheology, etc.-are related to their molecular structure and their crystallinity. Additives, as well as thermal and mechanical stress involved in the manufacturing process, affect the solid-state of lipids and thus the performance of pharmaceutical products thereof. Therefore, understanding the alteration in the solid-state is crucial. In this work, the combination of powder x-ray diffraction and differential scanning calorimetry (DSC) is introduced as the gold standard for the characterization of lipids' solid state. X-ray diffraction is the most efficient method to screen polymorphism and crystal growth. The polymorphic arrangement and the lamella length are characterized in the wide- and small-angle regions of x-ray diffraction, respectively. The small-angle x-ray scattering (SAXS) region can be further used to investigate crystal growth. Phase transition and separation can be indicated. DSC is used to screen the thermal behavior of lipids, estimate the miscibility of additives and/or active pharmaceutical ingredients (API) in the lipid matrix, and provide phase diagrams. Four case studies are presented in which LBEs are either used as a coating material or as an encapsulation matrix to provide lipid-coated multiparticulate systems and lipid nanosuspensions, respectively. The lipid solid-state and its potential alteration during storage are investigated and correlated to the alteration in the API release. Qualitative microscopical methods such as polarized light microscopy and scanning electron microscopy are complementary tools to investigate micro-level crystallization. Further analytical methods should be added based on the selected manufacturing process. The structure-function-processability relationship should be understood carefully to design robust and stable lipid-based pharmaceutical products.

Correlation between polymorphic transition of lipid and API release in lipid-coated API crystals: 
API crystals coated with glycerol monostearate are measured via DSC and x-ray directly after coating and after 3 months of storage under accelerated conditions (40 &#176;C, 75% relative humidity)7. Glyceryl monostearate is a multiphasic system containing 40%-55% monoglycerides, 30%-45% diglycerides, and 5%-15% glycerides, mainly tristearin19. The...

Watch this Scientific Journal Video about A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients at JoVE.com

A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients

This publication shows the application of x-ray diffraction and differential scanning calorimetry as gold standards for investigating the solid-state of lipid-based excipients (LBEs). Understanding the solid-state alteration in LBEs and its effect on the performance of pharmaceutical products thereof is the key factor for manufacturing robust lipid-based dosage forms.

Lipid-based excipients (LBEs) are low-toxic, biocompatible, and natural-based, and their application supports the sustainability of pharmaceutical ...

The combination of differential scanning calorimetry and x-ray diffraction is a gold standard for investigated solid-state alterations of lipid-based pharmaceutical products. The combined methodology is a strong tool for screening the polymorphism, crystal growth and face transition of lipids combined with the screening, the terminal behavior and the visibility of the drug with lipid matrix. This methodology can be used to understand the interaction between the solid state of lipid and the performance of his pharmaceutical product.Such products can be ranged from nano lipid formulations to matrix tablets. The procedure will be performed by Gerfried Luschin-Ebengreuth. Gerfried is a scientist from our lab.To begin switch on the nitrogen gas supply and set the pressure between 0.2 and 0.5 bar. Power up the differential scanning calorimetry or DSC instrument and the automatic sample changer. Open the software and click the yes button to activate the standby mode, and then click on view signals.Allow a calibration of the device for at least one hour. Purge the furnace with nitrogen. Click on the new method icon and go to method definition.When the overview window opens, activate the temperature modulation option. Go to header tab and select the method by clicking on sample. Go to the tab temperature program.Select purge two MFC and protective MFC both at 50 milliliters per minute. Set standby at 20 degree Celsius, heating cycle at five kelvin per minute from 20 degree Celsius to above the melting temperature of lipid isothermal holding at this temperature for five minutes. Cooling cycle to zero degree Celsius at five Kelvin per minute.Set the final emergency reset temperature at a temperature 10 degree Celsius above the highest temperature of the program and final standby temperature at 20 degrees Celsius. Go to the calibration tab and select the appropriate temperature and sensitivity file. Save the method.Weigh three to four milligrams of each sample into aluminum crucibles and record the exact weight loaded into each crucible. Seal the aluminum crucible with a pierced lid. Place the crucibles in the auto sampler tray and activate the auto sampler mode in the software and load related method for each sample.Fill out the sample position, sample name and weight of each sample, and the position of reference crucible in the sample tray view window. Start the measurement. Open the raw data using the software for data analysis and plant the temperature versus heat flow by clicking on the button X time, X temperature.On the popped up window, click on hide isothermal segments. On the left side of the screen, select only the curves that are to be analyzed. Check the thermal behavior of lipids as endothermic and exothermic events of absorbed or released energy in the form of heat respectively as a function of temperature.Click on the curve followed by evaluation and area. To calculate the enthalpy of fusion as the area under the curve of endotherms. Select the integration boundaries by moving the vertical lines around two to three degrees Celsius before and after the onset and endpoint of the peak.Select a linear baseline for the peak integration. The area between the curve and the baseline is proportional to the change in enthalpy. Click on apply to finish the calculation.Similarly, calculate the enthalpy of crystallization as the area under the curve of exotherms. Determine the onset of melting temperature or T-onset by clicking on the curve to be analyzed. And then on evaluation and onset.Select the quantification boundaries by moving the vertical lines to the most straight section of the curve. This is usually around five to 10 degrees Celsius before and after the peak. Then determine the melting temperature or TM by clicking on the curve to be analyzed.Followed by evaluation and peak, the obtained value is the peak maximum. Use an x-ray scattering system composing of a point focusing camera fixed to a sealed tube x-ray generator and equipped with a control unit and related software. Use two linearly positioned sensitive detectors to cover both small and wide angle X-ray scattering regions.Switch on the cooling water system on the control unit, the vacuum pump, the gas valves, and the power and safety control system. Then switch on the voltage control and purging valves for the detectors at a gas flow between 10 to 20 milliliters per minute. Switch on the x-ray tube and standby option and wait approximately 10 minutes.Switch off the standby mode and power up the x-ray tube to full power, which is greater than 50 kilovolts. Wait for at least 30 minutes. Start the control software and click on reset TPF.Then choose Tungsten filter and set position. Go to position to fix the position of the Tungsten filter. Fill the samples into special glass capillaries with an external diameter of approximately two millimeters avoiding any air entrapment in the capillaries.Seal the glass capillary with wax and place it carefully into the capillary holder. Switch on the motor for sample rotation and close the vacuum valve and wait until the pressure is beneath five millibars. In the software, select a position resolution of 1024 for both detectors and set the exposure time to 1, 200 seconds.Click on the tap tools to set up the energy limits, then click on set energy limits and resolutions and restart. Set up the energy limits to a suitable range between 400 to 900. Open the safety shutter and start the measurement.Ensure that the measurement window shows a maximum of 80 counts per second. If this is not given, adapt the filter position. Export the data as P00 files.The data consists of the intensity of transmission and absorption versus the channel number. Transfer the data for evaluation to a statistical software and correct the data by normalizing the intensities using the scattering mass measured with the Tungsten filter. Create a plot of normalized intensity versus two times the diffraction angle.Use the function of screen reader to find diffraction peaks in both small angle x-ray scattering or SAXS and wide range x-ray scattering or WAXS regions. Apply brags equation to compute the diffraction peaks for which the maximum intensity was reached into interplay or spacings. Calculate the ratios of the peak position of the SAXS region to find out the crystal symmetry of the lipids and use the main diffraction peak of the SAXS region to quantify the crystallite thickness.Fit the peak into a Gaussian function via classical leased squares and obtain the full width at half maximum by clicking on analysis peaks and baselines, peak analyzer, open dialogue. On the popped up window, select the option Fit Peaks Pro. Select a constant baseline with Y equal zero.Select the main diffraction peak of the SAXS region. Click on fit control to select the peak fit parameters. Choose the Gauss Amp function.Set the parameters Y zero XC1 and A1 as fixed and fit the data. Obtain the full width at half maximum from the fit. Finally, use the surer equation to compute the crystalline thickness.The tune fork and chair configurations of a Triacylglycerol molecule, the sub cell, the Lamella, and the crystalline platelet are shown here. The representative image shows the short spacing and long spacing patterns of the alpha form of Tripalmitin and WAXS and SAXS regions. The same for the beta form is shown in this image.The active pharmaceutical ingredient or API crystals coded with glycerol monostearate are measured via DSC and x-ray directly after coating and after three months of storage under accelerated conditions. DSC data of samples after three months of storage under accelerated show an endotherm at T-onset equals 55.7 degrees Celsius with two overlapped events at 60.2 degrees Celsius for the melting of remaining alpha form and at TM equals 63.8 degrees Celsius as the main event for the melting of beta form. The polymorphic transition is confirmed with the x-ray data by detecting the short D spacings typical for the beta form combined with the reduction in the Lamella thickness due to the molecular tilting.Significant alteration in the release profiles was also observed which can be explained by the evident polymorphic transformation of alpha form to beta form with a denser sub cell arrangement resulting in a water repellent surface. DSC data, X-ray data, and an API release profile of API Crystals coded with PG13C16C18 partial directly after coding and after three months of storage under accelerated conditions are shown here. DSC analysis of stored samples revealed unchanged thermograms, which depict no polymorphism and no phase separation.The stable solid state of PG3C16C18 partial was confirmed by the x-ray patterns. The WAXS region shows a peak corresponding to a short spacing of D equals 4.15 angstrom and T0 in stored samples associated with the alpha form. The SAXS region revealed an unaltered main peak at a long D spacing of D equals 63.7 angstrom corresponding to a lamella structure with two L configuration.The stable solid-state of the lipid matrix results in the stable release profile of API from coding. To provide high quality x-ray data, it is important to avoid entrapment between particles when filling the capillaries. Also to select an exposure time that is based on the type of sample and the available equipment.During the development of novel pharmaceutical products, screening the solid-state of lipids and their interaction with the API is used to select the suitable manufacturing process and to predict the product stability.

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