A novel fluorescent silica tracer for biological silicification studies

Background: Biological silica production has drawn intense attention and several molecules involved in biosilicification have been identified. Cellular mechanisms, however, remain unknown mainly due to the lack of probes required for obtaining information on live specimens. Results: The fluorescence spectra of the compound 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)- phenyl)oxazole (PDMPO) are affected by the presence of > 3.2 mM silicic acid. Increase in intensity and shift in the fluorescence coincide with the polymerization of Si. The unique PDMPO -silica fluorescence is explored here to visualize Si deposition in living diatoms. The fluorophore is selectively incorporated and co-deposited with Si into the newly synthesized frustules (the outer silica shells) showing an intense green fluorescence. Conclusions: We suggest that a fluorescence shift is due to an interaction between PDMPO and polymeric silicic acid. PDMPO is an excellent probe for imaging newly deposited silica in living cells and has also a potential for a wide range of applications in various Si-related disciplines, including biology of living organisms as diatoms, sponges, and higher plants, clinical research (e.g. lung fibrosis and cancer, bone development, artificial bone implantation), and chemistry and physics of materials research. (C) 2001 Elsevier Science Ltd. All rights reserved.