Effect of Amphiphilic Polymers on the Activity of Rose Bengal during the Photooxidation of Tryptophan in an Aqueous Medium

A study is performed of the effect such amphiphilic polymers (APs) as pluronics F-127 and F-108, poly-N-vinylpirrolidone (PVP), and polyethylene glycol (PEG) have on the photocatalytic activity of Rose Bengal, a xanthene dye, in the photooxidation of tryptophan in water. Rose Bengal (RB) is an efficient photosensitizer (PS) in the regeneration of singlet 1О2 oxygen and is present in a solution in the form of associates. It is shown that all of the above APs raise the effective rate constant of tryptophan photooxidation, which is usually explained by the partial disaggregation of such associates. The strongest effect is in this case observed when using pluronic F-108. When using APs, the electron absorption and fluorescence spectra of the xanthene dye is transformed somewhat. A bathochromic shift (5–15 nm) of the dye absorption bands and an increase in RB photoluminescence (2–5 times) are observed. RB fluorescence is the strongest strongest when PVP is added. Dynamic light scattering shows that the size of RB particles is reduced 1.3–1.5 times when using pluronic F-108 and PVP. The observed patterns indicate there is interaction between the xanthene dye and APs. Such RB–AP based systems are promising for use as preparations for theranostics (i.e., visualizing fluorescence and treating oncological and nononcological tumors by means of photodynamic therapy).