Coupling microdialysis with flow-injection chemiluminescence detection for a protein-drug interaction study

The interaction of metronidazole (MTZ) and human serum albumin (HSA) was studied using the coupling system of on-line microdialysis sampling with flow-injection chemiluminescence detection (FI-MD-CL). The interested drug and HSA were mixed in different molar ratios in 0.067 mol L(-1) phosphate buffer (pH 7.4) and incubated at 37 degrees C in a water-bath. Then the microdialysis probe was put into the MTZ-HSA mixed solution and sampled at a perfusion rate of 5 microL min(-1). The microdialysates was determined using flow-injection chemiluminescence. In vitro recovery (R) of MTZ under experimental conditions was approximately 25.2% with a R.S.D. of about 3.2%. The values estimated for the binding constant (K) and the number of the binding sites (n) were found to be 1.50 x 10(3)L mol(-1) and 1.89, respectively. The values of nK obtained using Scatchard analysis and Klotz plot were found to be quite similar. The method provided a reliable and simple technique for the study of drug-protein interaction.