Development of an Agar Diffusion Method to Measure Elastase Inhibition Activity Using Elastin-Congo Red

The pancreatic and neutrophil elastases are associated with several illnesses including lung and vascular diseases, various cancers, and pancreatitis. The development of a potent and specific inhibitor to the elastases could lead to new therapies. In this study, an agar diffusion method was modified to include a substrate-dye conjugate (Elastin-Congo red) as a substrate of elastase and an indicator of elastase inhibitory activity. The Elastin-Congo red agar plates consisted of 0.1 % Elastin-Congo red and 2.5% agar. The elastase and elastase inhibitors were simultaneously loaded into wells, ultimately resulting in halo formations in which the halo diameter decreased as the concentration of elastase inhibitor increased. The concentration of elastase inhibitor in the samples, therefore, was inversely proportional to the halo diameters. This simplified method provided an excellent correlation with the standard microplate technique, which uses a chromogenic substrate. The concentration of elastase inhibitor obtained from the culture supernatant of a recombinant elastase inhibitor produced by the yeast Pichia pastoris was easily determined. This study has established a simple modified and inexpensive agar diffusion method that is potentially useful for the identification, quantification, and screening of new elastase inhibitors.