Monday, September 28, 2009

Picturing Drugs With Raman Microscopes

On Friday, September 25th, Lucinda Buhs, Director, Division of Pharmaceutical Analysis, FDA, delivered a talk on "Raman Microscopic Imaging of Pharmaceuticals" for the Visualization Friday Forum.

Raman microscopic imaging is a spectroscopic technique that utilizes the concept of Raman
scattering of monochromatic light. It is based on the interaction of laser (monochromatic) light with vibrations of the lattice photons.

Using Raman microscope imaging, it is possible to determine the crystal structure of a tablet and determine the configuration of a particular drug in a tablet.

"So why did we select Raman spectroscopy?" asks Lucinda. "Raman spectroscopy exhibits extremely sharp features that are characteristic to a molecular structure. The Raman spectrum gives a series of intensity vs peak numbers(wave numbers) which are unique to each molecule. This way we can tell the difference between two samples. And we can even combine it with a third dimension called chemical spectrum"

Lucinda exhibited the images of a number of drug samples generated using Raman microscopy.

(Image adapted from the research paper: "Raman Chemical Imaging for Ingredient-specific Particle Size Characterization of Aqueous Suspension Nasal Spray Formulations: A Progress Report", by Lucinda Buhse et al.)

"Through this kind of imaging, we look at the distribution of a drug throughout the sample. Specifically, we also use chemical imaging and new infrared to look at the blending effect, i.e, how well do the drugs blend with other chemicals in the sample. We search for a uniform distribution, and if not, we immediately know that the drug wasn't mixed well."

Lucinda Buhse graduated with a PhD in Physical Chemistry from the University of California, Berkeley in 1986. She is also the sister of Rachael Brady, the founding director of the Visualization Technology Group at Duke University.

No comments: