Effect of concentration on photobleaching of Hematoporphrin Monomethyl Ether (HMME) in solutions

摘要

To analyze the effect of concentration on the photobleaching of HMME, the loss of HMME absorption in simplex solution (PBS) and complex solution (albumin buffer) was monitored using steady-state absorption spectra during 532nm laser irradiation. Three concentrations (4, 10, 80μmol/L) were set for each type solution. Photobleaching curves at each concentration were drawn according to the concentration and time during irradiation. Photobleaching rate coefficients (k) at each concentration were calculated with a mathematical model for singlet oxygen-mediated photobleaching reaction. Then the photobleaching of HMME under different concentrations were compared using the photobleaching rate coefficients (k) and the slope of photobleaching curves. Finally, the effect of concentration on HMME photobleaching was analyzed combining the existence state of HMME at each concentration. The results showed that in both PBS and albumin buffer, the photobleaching rate coefficient of HMME was the largest at 4umol/L, smaller at l0μmol/L, and the smallest at 80μmol/L. In conclusion, there is a concentration-dependent relationship in the photobleaching rate of HMME, photobleaching will be inhibited when the concentration of HMME increased above certain level at which HMME aggregates formed.