It is known that the combination of
laser light and its sensitizer is effective for noninvasive
tumor treatment, referred to as
photodynamic therapy. Using the combination of ultrasound and its sensitizer has also been suggested for a similar kind of
tumor treatment, referred to as sonodynamic
therapy. The purpose of this paper is to obtain such sensitizers accumulating selectively in
tumors. Amphiphilic derivatives of
rose bengal (RB) were synthesized to add a
tumor-accumulating property to RB. One type of the synthesized RB derivatives (RBD3), having an alkyl chain with a branching carboxyl group, was found to be superior in amphiphilicity to the other types.
Tumor tissue distribution of the synthesized derivatives in mice bearing colon 26
carcinoma was evaluated. It was found that RBD3s with
carbon chain lengths of 12, 14, and 16 had higher concentrations in the
tumor tissue than RB by more than 1 order of magnitude, several hours after administration. The concentrations correlated well with their water/
1-octanol partition coefficients. Since RB is known to induce in vitro cell damage in combination with either
laser light or ultrasound, the newly synthesized amphiphilic RB derivatives may be potentially useful as a
tumor-selective sensitizer for both light and ultrasound.