Potential of the Bioinspired CaCO 3 Microspheres Loaded with Tetracycline in Inducing Differential Cytotoxic Effects toward Noncancerous and Cancer Cells: A Cytogenetic Toxicity Assessment Using CHO Cells in Vitro.

Calcium carbonate (CaCO ₃ )-based materials as feasible pH-sensitive drug carriers, which can actively dissolve in an acidic microenvironment of cancer cells, are finding increasing importance. This has drawn our interest in the development of a bioinspired polypeptide- mediated method to design calcium carbonate microspheres loaded with tetracycline (CaCO ₃ -TC) with an aim to explore its safe application in cancer therapeutics. Its therapeutic application in cancer patients essentially demands its safety information on the normal cells. Herein our study presents the in vitro genetic toxicological information on CaCO ₃ -TC using noncancerous mammalian CHO cells in comparison to bare TC at three different concentrations (100, 200, and 300 μM) selected based on the cytotoxicity data (MTT). Assessment of various end points like chromosome aberrations, micronucleus, mitotic index and effects on cell cycle distribution after 24 h post-treatment demonstrates a significant reduction in clastogenic ( P < 0.001), aneugenic potential ( P < 0.05), and nonmitotoxic nature of CaCO ₃ -TC than that of bare TC. Noticeably, as inferred from the FACS analysis on cancer cells, G ₂ /M phase accumulation in breast cancer cells (MDA-MB-231), and at G ₁ phase in cervical cancer cells (HeLa) reveal its potential anticancer property. On the other hand, the genotoxicity studies illustrate protective effects of CaCO ₃ -TC on noncancerous cells. While the pH-dependent dissolution property of the CaCO ₃ matrix encasing tetracycline results in higher toxicity on cancer cells, the near neutral pH in the case of normal cells prevents complete dissolution of CaCO ₃ thereby not allowing the encapsulated TC to adequately interact with the cells. Therefore, thus assembled CaCO ₃ spheres not only provide a way for facile encapsulation of tetracycline under mild conditions but also result in an effective matrix for differential toxicity toward normal and cancer cells justifying its clinical development as a novel target-specific drug in therapeutic applications for metastatic cancers.