Enhanced chemiluminescent assay for measuring the total antioxidant capacity of serum, saliva and crevicular fluid

This paper reports the development of an enhanced chemiluminescent (ECL) assay for measuring the total antioxidant (AO) capacity of serum, saliva and a fluid collectable from the gum margin called gingival crevicular fluid (GCF), The theory behind the assay is explained, and the optimum conditions for the assay, and for storage of reagents and clinical samples is described. Calibration lines were linear (R greater than or equal to 0.99; P<0.0001) and the within batch coefficient of variations for a water soluble vitamin E analogue (Trolox), serum and saliva samples were <5%. In saliva and GCF, a characteristic AO response not seen in serum of the same patients, was identified. Total peripheral (serum) and local (saliva) AO capacities (mu mol/L Trolox) were investigated in patients with (n = 18) and without (n = 16) adult periodontitis. Serum AO status did not differ between groups. Salivary total AO concentrations were lower in the periodontitis (P) group [175 (53) mu mol/L] than in the non-periodontitis (NP) group [254 (110) mu mol/L-1: P<0.01], as were saliva:serum AO ratio's [0.37 (0.11) versus 0.5 (0.18): P<0.01]. Periodontitis patients may have a reduced salivary AO concentration, which could result from, or predispose to, the damaging effects of reactive oxygen species (ROS). The potential for ROS production in the oral and periodontal environment may explain the presence of a specific antioxidant in oral fluids that is not detectable in serum. The ECL assay described provides a rapid, simple and reproducible method of measuring total antioxidant defence in small volumes of biological fluids.