Pharmaceutical studies using AFM-Part I

Pharmaceutical studies using AFM-Part I
Microscopic evaluation is important for the design and evaluation of a pharmaceutical product after the steps in the drug formulation process. Efficient investigation of surface structure at nanometer to subangstorm resolution in ambient and liquid environments AFM has been routinely used over two decades in many scientific fields. Pharmaceutical research often consists of a combination of many scientific branches, made a unique viable place for the application of AFM. High resolution three dimensional surface structures, sample conductivity make it a powerful complement to other common analytical techniques currently available. Studies of drug crystal growth, particle Characterization, and tablet coatings in the manufacture of solid dosage forms.

Introduction-AFM
The Atomic Force Microscope was developed to overcome a basic drawback with STM - that it can only image conducting or semi conducting surfaces. The AFM, however, has the advantage of imaging almost any type of surface, including polymers, ceramics, composites, glass, and biological samples. Binnig, Quate, and Gerber invented the Atomic Force Microscope in 1985. Their original AFM consisted of a diamond shard attached to a strip of gold foil. The diamond tip contacted the surface directly, with the interatomic van der Waals forces providing the interaction mechanism. Detection of the cantilever’s vertical movement was done with a second tip - an STM placed above the cantilever.

Methods Used for Pharmaceutical Research
AFM is performed by scanning a sharp tip on the end of a flexible cantilever across a sample surface, while maintaining a small, constant force. Tip types vary depending on application requirements, but they typically have an end radius of 5 to 10 nanometers. In a basic AFM setup, a piezoelectric tube scanner scans the tip in a raster pattern over the sample. Tip-sample interaction is monitored by reflecting a laser off the back of the cantilever onto a split photodiode detector. Over the past several decades, a variety of scanning modes have been developed to control how the tip scans the sample. The modes of operations are

1. Contact / static mode
2. Non-contact mode and
3. Tapping mode

References
1.Using AFM in Pharmaceutical Studies of Drug Crystal Growth,Particles, and Coatings By: John T. Thornton.Veeco Group.
2.www.usbyte.com/common/AFM_storage.htm