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Development of hot-melt extrusion as a novel technique for the ...

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patterns were identified after energy optimisation at <strong>the</strong> B3LYP 6-31G* level using Gaussian09. In all <strong>of</strong> <strong>the</strong> drug/polymers combinations primarily two different H bonding were detectedwith up to 2 °A distance. All possible H bondings were shown in d<strong>as</strong>h line in <strong>the</strong>constructed figures.2.8 X-ray p<strong>hot</strong>oelectron spectroscopy (XPS) analysisX-ray p<strong>hot</strong>oelectron spectra (XPS) were me<strong>as</strong>ured on a Kratos Axis Ultra-DLD usinga monochromatic Al K X-ray source (120 W) and an analyser p<strong>as</strong>s energy <strong>of</strong> 160 eV (surveyscans) or 20 eV (high resolution scans); <strong>the</strong> pressure during analysis w<strong>as</strong> 1×10 -9 Torr. Alldata were referenced to <strong>the</strong> C (1s) signal at 285.0 eV attributable to unsaturated C-C/C-Hbonds [16] . Quantification and curve fitting w<strong>as</strong> per<strong>for</strong>med in C<strong>as</strong>aXPS TM (Version 2.3.15)using elemental sensitivity factors supplied by <strong>the</strong> manufacturer.2.9 Nuclear magnetic resonance (NMR) studiesNMR spectra were recorded on a Jeol ECA 500 NMR spectrometer, incorporating a5mm inverse probe (The 1 H operating frequency w<strong>as</strong> 500 MHz). 1 H NMR spectra <strong>of</strong> <strong>the</strong>drugs, polymers and drug/polymer <strong>for</strong>mulations were recorded using <strong>the</strong> standard Jeol pulsesequence. All samples were dissolved in CD 3 OD, deg<strong>as</strong>sed and <strong>the</strong>n maintained at 25 o Cduring data acquisition. Samples were referenced with respect to <strong>the</strong> solvent. The solutionconcentration <strong>of</strong> <strong>the</strong> drugs w<strong>as</strong> 2 mg/ml, <strong>the</strong> polymer w<strong>as</strong>18mg/ml, and <strong>the</strong> drug/polymer<strong>for</strong>mulation w<strong>as</strong> 20 mg/ml (<strong>the</strong> overall drug content in <strong>the</strong> <strong>for</strong>mulations w<strong>as</strong> 10%).1 H T 1relaxation experiments were recorded <strong>for</strong> all samples using a standard inverse recoveryexperiment. Recovery delays () were investigated between 10 ms and 20 s. The relaxationdelay w<strong>as</strong> set to be > 5T 1. T 1 s were calculated from curve fitting, peak intensities, obtainedfrom <strong>the</strong> spectra recorded <strong>for</strong> different recovery delays. Jeol, curve fitting s<strong>of</strong>tware w<strong>as</strong>utilised during this process.3. Results and discussion3.1 Determination <strong>of</strong> drug-polymer miscibility by Hansen solubility parameters ()To predict <strong>the</strong> miscibility <strong>of</strong> <strong>the</strong> active substances and <strong>the</strong> polymeric carriers <strong>the</strong>Hansen solubility parameter w<strong>as</strong> used [14, 17, 18] . According to <strong>the</strong> Vankrevelen/ H<strong>of</strong>tyzerequation <strong>the</strong> calculated solubility parameters <strong>for</strong> PRP and DPD are 21.94 MPa 1/2 and 17.75MPa 1/2 , respectively where<strong>as</strong> <strong>the</strong> solubility parameters <strong>for</strong> L100 and L100-55 are 22.75MPa 1/2and 21.65 MPa 1/2 , respectively. Since <strong>the</strong> determined difference in solubility109 | P a g e

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