Dynamic aspects of rhodamine dye photosensitization in vitro with an argon‐ion Laser

Abstract

Phototoxicity in cultured human bladder carcinoma cells treated by 514.5-nm argon-ion laser irradiation plus rhodamine-123 (R123) or tetrabromo-R123 (TBR) was assessed counting total cell number and percent viability at 1, 24, 48, 72, and 96 h after irradiation. TBR was markedly more efficient than R123 at causing both reversible and persistent phototoxic cytostasis. Furthermore, TBR photosensitization caused net cytocidal effects at 0.5 J/cm2, which were not seen with R123 photosensitization at up to 40 J/cm2. The reduced phototoxic efficiency of R123 as compared to TBR appears, in part, to reflect the presence of a fraction of cells refractory to R123 photosensitization.

Ex vivo photodynamic purging in chronic myelogenous leukaemia and other neoplasias with rhodamine derivatives

“…Extra-corporeal photodynamic therapy must take advantage of different thresholds of photosensitization for commitment to death [194]. The mechanisms responsible for the preferential uptake and retention of R123 derivatives by certain cells are not fully understood, but R123 and tetrabromorhodamine 123 (R1BR4) were reported to be variably, but specifically, retained by various neoplasias, including carcinoma [40,42,195], melanoma [196], glioma and leukaemia cells [38][39][40], including CML [26,27,43,44], while minimally affecting normal cells. Interestingly, primitive BM stem cells, with in vitro long-term repopulating potential (LTC-IC) display a very low accumulation of R123 [197,198].…”

Structural and functional alterations in rhodamine-123- and doxycycline-photosensitized cells

“…The response to photosensitization is quite different, however. Rl23 is a relatively inefficient photosensitizer (13,14), requiring more than 10 J/cm2 to cause 90% inhibition of colony-forming ability or proliferation rate, when cells are incubated in 10 zM R123 for 30 mm before irradiation at 514.5 jim. Greater phototoxicity is seen when incubation time is increased, but longer incubation times lead to alterations in mitochondrial morphology and Rl23 localization even in the absence of irradiation (15).…”

“…Our laboratory in recent years has conducted research on several such photosensitizers. We here review our results on photosensitization of carcinoma cells by the use of two different mitochondriotropic agents, doxycycline (DOTC) (8)(9)(10)(11)(12) and rhodamine-l23 (Rl23) (13)(14)(15)(16).…”