Authors: D.A. Chernoff
Affilation: Advanced Surface Microscopy, Inc., United States
Pages: 700 - 703
Keywords: particle morphology, amorphous, crystalline, collagen, DNA, AFM, SPM
AFM is a valuable tool for a wide range of materials and device analysis. AFM images of particles and biopolymers are valued because direct visualization and measurement of individual objects complements the average measures obtained from bulk analysis techniques such as chromatography, spectroscopy and light scattering. The FDA encourages the use of AFM along with those techniques. Working with microspheres composed of an active drug compound dispersed in a polymer matrix, the maker found that particle flowability varied from lot to lot. AFM showed variations in the morphology of small drug particles on the microsphere surface. Lactose particles, long regarded as inert chemically and physically stable, may show changes in handling characteristics as they age. AFM showed molecular diffusion on the surface of a lactose single crystal, giving a mechanism for aggregate formation. AFM analyzes the molecular weight and conformation of collagen monomers by direct imaging of each molecule. Evaluating the length of individual collagen monomers and classifying the oligomers helps optimize the digestion and purification of collagen from animal tissue for subsequent use as a medical biomaterial. AFM images demonstrated a DNA-peptide complex which appears to be a key molecular player in psoriasis.