An ongoing challenge for pharmaceutical manufacturers is consistently producing tablets with uniform distribution of the active compounds. This is crucial given how some drugs are taken as cut tablets, and how they are digested over time. One method to observe the distribution during development phases is to incorporate a model drug that fluoresces against a background of non-fluorescent excipient. Researchers at Queen’s University Belfast took advantage of the natural fluorescence of Tetracycline as their model drug in a process to use a blend of lignin and cellulose as the excipient (reference and link at end of article). For visualization, they used the NIGHTSEA Model SFA Stereomicroscope Fluorescence Adapter with the Royal Blue excitation/emission combination on their Leica EZ4 D stereomicroscope.
As the photos below show, the fluorescence of the Tetracycline clearly shows the distribution of the active ingredient in the test tablets.
(Click image for larger view)
Images courtesy Dr. Eneko Larrañeta, Queen’s University Belfast
Domínguez-Robles, J., Stewart, S. A., Rendl, A., González, Z., Donnelly, R. F., & Larrañeta, E. (2019). Lignin and Cellulose Blends as Pharmaceutical Excipient for Tablet Manufacturing via Direct Compression. Biomolecules, 9(9), 423. doi:10.3390/biom9090423. Available for free download.