Some spectroscopic and transport properties of a rare-earth chelate, Tb-PCTMP

A polyazamacrocyclic chelate of Terbium III; 3,6,9-Tris(methyl phosphonic a cid)-3,6,9, 15-tetraazabicyclo[9,3,1]pentadeca-1(15),11,13-triene, Tb-PCTMP , has been shown to exhibit rich spectroscopic properties, tissue selectivi ty [M.P. Houlne et al., Appl. Spectrosc. 10 (1996) 225-244], millisecond fl uorescence lifetimes [D.S. Hubbard, M.P. Houlne, G.E. Kiefer, H.E Janssen, C. Hacker, D.J. Bornhop, Lasers Med. Sci. (13) (1998) 14-21], sharply spike d emission spectra (<15 nm FWHM), large Stokes shifts (>280 nm), high water solubility and good fluorescence quantum yields (similar to 0.24). Expande d investigations of the Tb-PCTMP chelate are presented here that further in dicate Tb-PCTMP can be used for transport investigations, using endoscopy. First we elucidate the spectroscopic sensitivity of the chelate to physiolo gical pH changes. Second we demonstrate a lack of cyctotoxicity using in-vi tro studies. Finally, we show that chelate transport, through a collagen ma trix, can be quantitatively monitored using fluorescence endoscopy. The res ults provide new insights about how solutes, having different chemical stru ctures, move through the interstitial space and show the potential for perf orming such measurements minimally invasively, in-vivo. (C) 1999 Elsevier S cience B.V. All rights reserved.