[Optimization of reaction conditions and methodological investigation on microtox-based fast testing system for...

Vibrio fischeri CS234 was used to establish and optimize microtox assay system, laying a foundation for the application of this method in comprehensive acute toxicity test of traditional Chinese medicine (TCM) injections. Firstly, the Plackett-Burman method was carried out to optimize the factors which would affect Vibrio fischeri CS234 luminescence. Secondly, ZnSO4•7H2O was chosen as reference substance to establish its reaction system with quality control samples. The optimal luminescence conditions were achieved as follows: ①At a temperature of (15±1) ℃, Vibrio fischeri CS234 lyophilized powders were balanced for 15 min, then, 1 mL resuscitation fluid was added and blended for 10 min. 100 μL bacteria suspension was taken to measure the initial luminescence intensity, and then 1 mL resuscitation fluid or test sample was immediately added; after reaction for 10 min, corresponding luminescence intensity was measured again. Resuscitation diluent, osmotic pressure regulator and ZnSO4•7H2O stock solution showed no interference to the determination of Vibrio fischeri CS234 luminescence intensity, so this method was of good specificity. The within-and between-batch precisions of quality controls and the lower limit of quantification (LLOQ) samples were <5% and <10% respectively, while the accuracy ranged between 85.8% and 103.2%. The standard curve equation of ZnSO4•7H2O ranged from 3.86 mg•L⁻¹ to 77.22 mg•L⁻¹ (final concentrations) was y=21.78lnx-15.14, R2=0.998; meanwhile, IC₅₀ of ZnSO4•7H2O to Vibrio fischeri CS234 was 19.90 mg•L⁻¹. ZnSO4•7H2O stock solution and its quality controls were continuously investigated for 120 h and 8 h respectively, and their RSD was lower than 2%, indicating stability at room temperature and 4 ℃ storage conditions. Between pH 4.5-8.0, luminescence intensity of Vibrio fischeri CS234 was controlled within ±10%, and such pH value range could meet the testing needs of the vast majority of traditional Chinese medicine injections. The Vibrio fischeri strain CS234 assay system was specific, stable, sensitive, accurate and adaptable after optimization, so it was suitable for the comprehensive acute toxicity assessment of TCM injections.