New insights into the chemical and isotopic composition of human-body biominerals. I: Cholesterol gallstones from England and Greece

We have analyzed gallstones from four patients of Europe and particularly from England (including samples from a mother and a daughter) and Greece. According to the XRD, FTIR, NMR and laser micro-Raman results the studied materials correspond to typical cholesterol monohydrate (ChM). The micro-morphology of cholesterol microcrystals was investigated by means of SEM–EDS. The XRF results revealed that Ca is the dominant non-organic metal in all gallstones (up to ∼1.95 wt.%) together with Fe, Cu, Pb and Ni (up to ∼19 ppm for each metal). Gallstones from England contain additional Mn (up to ∼87 ppm) and Zn (up to ∼6 ppm) while the sample of the mother contains negligible Zn and Mn, compared to that of her daughter, but significant As (∼4.5 ppm). All cholesterol gallstones examined are well enriched in potentially toxic metals (Pb, as well as Ni in one case) and metalloids (As also in one case) as compared to the global average. The position of Zn, which is a characteristic biometal, in the structure of cholesterol, was investigated by molecular simulation using the Accelrys Materials Studio® software. On the basis of IRMS results, all gallstones examined exhibit a very light δ13C signature (average δ13C ∼−24‰ PDB). Gamma-ray spectrometry measurements indicate the presence of 214Pb and 214Bi natural radionuclides due to the 238U series as well as an additional amount of 40K.