Subcellular localization of boron in cultured melanoma cells by electron energy-loss spectroscopy of freeze-dried cryosections

Boron neutron capture therapy (BNCT) is based on the ability of the non‐radioactive isotope ¹⁰B to capture thermal neutrons and to disintegrate instantaneously. This reaction opens a way to selectively destroy tumour cells after specific uptake of ¹⁰B. In this paper, a method based on electron energy‐loss spectroscopy is presented for detecting and quantifying boron in freeze‐dried cryosections of human melanoma cells. A practical detection limit of around 6 mmol kg^?1 in 0.1‐µm² areas is estimated using specimens prepared from standard boron solutions. Preliminary results of boron mapping in the spectrum‐imaging acquisition mode reveal boron penetration and probably spot‐like accumulation within melanoma cells when exposed to culture medium containing sodium borocaptate.