Magnetic hydrotalcite (HT)-based nanoparticles are unique carriers for anticancer drug delivery due to their two-dimensional layered structure, high biocompatibility, and their ability to respond to an external magnetic. Tannic acid (TA), a natural polyphenol, is a ligand for estrogen receptor (ER). Acquired resistance to oxaliplatin (Oxa) is an inevitable problem and one of the reasons for the failure of colorectal cancer (CRC) therapy. We aimed to explore the ability of functionalized nano-magnetic MgAl HT particles with TA (TA@HT@Fe3O4) as a doxorubicin (DOX) delivery carrier to Oxa-resistant ER-expressing colorectal cancer HCT116 cells. The synthesized TA@HT@Fe3O4 nanoparticles and loaded particles with DOX (DOX/TA@HT@Fe3O4) were characterized by various analytical techniques. The entrapment efficiency (EE%), loading content (LC%), and in vitro release of DOX was measured at various pH values using UV-Vis spectrophotometer. The reduced negative value of the potential zeta of TA@HT@Fe3O4 nanoparticles after DOX loading and FT-IR spectra of DOX/TA@HT@Fe3O4 particles confirmed the successful DOX loading. The EE% and LC% values of TA@HT@Fe3O4 nanoparticles were about 51% and 8%, respectively. The release of DOX from TA@HT@Fe3O4 nanoparticles was pH-dependent with an initial rapid release (within 16 h) followed by a sustained release for 120 h. Hemolysis results revealed the highly biocompatible behavior of TA@HT@Fe3O4 nanoparticles. Oxa-resistant HCT116 colorectal cancer cells were established by the exposure of HCT116 cells to increasing concentrations (0.5-4.3 µM) of Oxa. The exponentially-growing cells in the presence of 4.3 μM Oxa were considered as Oxa-resistant HCT116 cells (HCT116/Oxa4.3). Fluorescence microscopy images and flow cytometry data confirmed the uptake of DOX/TA@HT@Fe3O4 particles by HCT116/Oxa4.3 cells. MTT results showed that the anti-proliferation activity of DOX/TA@HT@Fe3O4 nanoparticles against HCT116/Oxa4.3 cells was in a concentration dependent manner. Conclusion: TA@HT@Fe3O4 nanoparticles is a pH-responsive release system and offers promise as a safe and an effective system for targeted drug delivery to ER-expressing cells.

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