Synthesis, functionalization, characterization, and: In vitro evaluation of robust pH-sensitive CFNs-PA-CaCO₃

The preparation, characterization, and application of Papain (PA) conjugated CaCO₃-coated cobalt ferrite nanoparticles (CFNs-PA-CaCO₃) is reported. Papain was covalently attached onto silanized cobalt ferrite nanoparticles (CFNs-APS) and then coated with robust pH sensitive CaCO₃. It was characterized by FTIR, XRD, TEM, FESEM, and TGA. The release behaviour of PA from functionalized nanoparticles in acidic and physiological pH was investigated. However, the rate of PA release was slow and enhanced with time at physiological pH; the results illustrate that acidic conditions disassembles the coating, which caused a rapid release of PA. The biocompatibility evaluation of CFNs/CFNs-CaCO₃ and the cytotoxicity of free PA/CFNs-PA was carried out in vitro on human breast cancer cells (MDA-MB-231) and human skin fibroblast cells (HSF 1184) by performing an MTT assay. An improved cytotoxic effect was obtained for PA conjugated cobalt ferrites in comparison with free PA. The synthesized delivery system was perfectly tolerable to the blood and cells in concentrations below 200 μg mL^-1. Investigations were followed out to measure the time and dose dependent cellular uptake of functionalized nanoparticles via the Prussian blue staining method under an inverted microscope, which indicated that functionalized nanoparticles showed internalization properties. The results conveyed that the synthesized system is a promising biomaterial for future biomedical applications, mainly cancer therapy. The present in vitro findings require comparison with those of in vivo studies.