Microcalorimetric Investigation of Toxic Effects of Three Injectable Solubilizing Excipients on Tetrahymena thermophila BF 5 Growth

Using microcalorimetry, thermal metabolic curves of Tetrahymena thermophila BF 5 ( T . thermophila BF 5 ) 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 L 6 cells were investigated to show their cytotoxicities by biochemical method. The results indicated that the effects of the ISE on T . thermophila BF 5 varied for different ISE. 5% inhibition concentration values (IC 5 ) 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 ( P 2 ) were selected as the main characteristic parameters to present their toxicities, there were good linear relationships between Q , k , P 2 and concentrations c , suggesting that the toxicities of the ISE on T . thermophila BF 5 were closely linked to their concentrations. The results of creatine kinase (CK) bioassay of myoblast L 6 cells indicated that the sequence of irritative effects of the ISE was HP‐ β ‐CD

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