Cracking cholesterol from a phase transition at body temperatures

The microstructure of cholesterol crystals grown from gallstone melt have been studied using hot-stage microscopy. The microstructure is comprised of needle-shaped crystals growing radially from a unique nucleation center. The growth direction has been found to be [001] using X-ray diffraction methods. The radial growth rate has been reported over a range of temperatures. The growth kinetic curve and the microstructural evidence clearly suggest that cholesterol grows by a spherulitic mechanism. The phase transitions in cholesterol have been studied using differential scanning calorimetry. Anhydrous cholesterol has a phase change a few degrees below body temperature. Optical microscopy establishes that this phase transformation cracks the spherulitic crystals perpendicular to the fast growth direction. Thermal expansion measurements demonstrate that upon cooling across this phase boundary large shrinkage is induced in the growth direction with an expansion in the perpendicular direction. This phase transition and repeated cracking may prove to be useful in destroying natural gallstones, while suppressing this transformation and its associated cracking might aid in securing other cholesterol deposits within the human body.