<title>Effect of blood plasma on laser-excited singlet oxygen phosphorescence in aqueous buffer solutions of water-soluble porphyrins</title>

Abstract

Preliminary data are reported on time-resolved measurements of photosensitized phosphorescence of singlet molecular oxygen (2 = 1270 nm) excited by pulses of a copper-vapor laser in aqueous buffer solutions (pH 7.4) containing water-soluble porphyrins and bovine blood plasma. Reliable phosphorescence kinetic curves were detected after 100-500 s signal accumulation that corresponded to (1--6) x 106 laser shots. With no plasma and no oxygen purging the phosphorescence kinetics comprised the rise and decay phases with a maximum at 2.5 _ts after a laser shot. Addition of 1% bovine blood plasma (vol/vol) caused ten-fold decrease of the phosphorescence intensity. With higher plasma concentration the phosphorescence was not detected. When oxygen bubbled through the plasma-containing solutions during laser irradiation and the solution flowed at a rate of 1 .5 ml/s through the spectrophotometric cell, the phosphorescence intensity increased and was observed at plasma concentration up to 20%. The phosphorescence intensity of a 20% plasma solution was about eight fold less than that of a porphyrin solution containing no plasma. With 20% plasma the phosphorescence rise-time was in a range of 1--i .5 is, the phosphorescence decay-time was 7--8 ts. Further experiments are in progress in order to optimize our experimental set-up for measurements in whole blood serum and plasma.