A few years ago Solid Crystal Suspensions (SCS), made via hot-melt-extrusion, were proposed as sufficient technique to increase the bioavailability of poorly soluble drugs of biopharmaceutic classification system (BCS) Class II. The drug particle size and the dispersity of these systems are crucial properties because they determine the drug release. The nonlinear imaging techniques, Coherent Anti Stokes Raman Scattering (CARS) and Sum Frequency Generation (SFG) microscopy, were used to characterize SCS in order to understand the dissolution behaviour of different formulations. CARS microscopy is based on the detection of molecular vibrations similar to Raman spectroscopy 1-2 . The advantage in comparison with conventional Raman spectroscopy is the detection of a single vibrational resonance allowing for much faster imaging with CARS. The setup consisted of a laser and an optical parametric oscillator. The beams were scanned over the sample by galvano-mirrors and focused by an objective lens into the sample. Compared to the incident beam the generated CARS signal was shifted to a higher frequency. When the sample contained non-centrosymmetric structures the SFG signal was created. The generated signal was created simultaneously with the CARS signal in the sample and detected on a different detector. The SCS consisted of a drug (griseofulvin) and a matrix (mannitol). The matrix was detected with CARS microscopy and the drug with SHG microscopy offering high contrast between the compounds. The nonlinear microscopy images of the SCS showed a homogeneous distribution of the drug particles. There were no agglomerates and the drug distribution in the centre was almost the same as at the surface of the objects. The drug particle size was also investigated and similar results to the ones in laser diffraction were found. The combination of the two nonlinear microscopy techniques, CARS and SFG was identified as a promising tool to characterize drug distribution and drug particle size in this SCS.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.