Microcalorimetric Investigation of Toxic Effects of Three Injectable Solubilizing Excipients on Tetrahymena thermophila BF5 Growth

Using microcalorimetry, thermal metabolic curves of Tetrahymena thermophila BF₅ (T. thermophila BF₅) growth at 28°C affected by three injectable solubilizing excipients (ISE) including tween 80, hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) and poloxamer 188 were measured. Meanwhile, the toxicities of three ISE were evaluated by dynamic parameters of thermal metabolic curves. In addition, the irritative effects of the ISE on myoblast L₆ cells were investigated to show their cytotoxicities by biochemical method. The results indicated that the effects of the ISE on T. thermophila BF₅ varied for different ISE. 5% inhibition concentration values (IC₅) of the ISE were 1.33, 1.83 and 1.64 mg/mL for tween 80, HP‐β‐CD and poloxamer 188, respectively. By the principal component analysis (PCA), the total quantity of heat (Q), growth rate constant (k) and second maximum power (P₂) were selected as the main characteristic parameters to present their toxicities, there were good linear relationships between Q, k, P₂ and concentrations c, suggesting that the toxicities of the ISE on T. thermophila BF₅ were closely linked to their concentrations. The results of creatine kinase (CK) bioassay of myoblast L₆ cells indicated that the sequence of irritative effects of the ISE was HP‐β‐CD