Surface Characterization of Aspirin Crystal Planes by Dynamic Chemical Force Microscopy

Abstract

Tapping mode (TM) atomic force microscopy (AFM) has been applied in a novel fashion to characterize and distinguish the (001) and (100) surfaces of individual aspirin crystals. The surface characterization was achieved by amplitude-phase, distance (a-p,d) measurements employing gold-coated AFM probes functionalized with self-assembled monolayers (SAM). Experiments using model probes coated with -CH3 and -COOH terminated SAMs have been performed on the two aspirin crystal planes (001) and (100). Results indicate that the hydrophobic -CH3 terminated AFM probes had a greater degree of interaction with the crystal plane (001), whereas the -COOH terminated AFM probes had a larger interaction with the crystal plane (100). Interpretation of these data, based upon the chemistries of the probes, correlates with current understanding of the crystal surface chemistry derived from X-ray diffraction data and dissolution rate studies.

Mapping the Surface Characteristics of Polystyrene Microtiter Wells by a Multimode Scanning Force Microscopy Approach

“…2, recorded with a hydrophobic probe. Similar changes in probe-sample interaction were observed in our recent studies of aspirin crystals in which hydrophilic and hydrophobic AFM probes were utilized to characterize the hydrophobicity of individual crystal planes (45). Figures 3b and 3c display example force measurements extracted from the FCM data on the patch and substrate regions indicated.…”

Adhesion at calcium oxalate crystal surfaces and the effect of urinary constituents

“…AFM imaging also has been used to obtain images of kidney stones (26). Surprisingly, the force measurement capability of AFM imaging, which has been used extensively for quantitative measurement of adhesion forces between various molecular and biomolecular surfaces (27,28), has been rather limited with respect to single crystal surfaces (29)(30)(31). To our knowledge, the adhesion properties of different faces of a crystalline material have never been examined.…”

Crystal Surface Adhesion Explains the Pathological Activity of Calcium Oxalate Hydrates in Kidney Stone Formation

“…Both imaging and force measurements can be performed in a liquid medium, making this method ideal for examining biologically relevant processes. The force measurement capability has been used for quantitative measurement of adhesion forces between various molecular and biomolecular surfaces (19,20), but only recently has it been used to diagnose adhesion events at single crystal surfaces (21,22,23,24).…”