Synergistically Enhanced Inhibitory Effects of Pullulan Nanoparticle-Mediated Co-Delivery of Lovastatin and Doxorubicin to Triple-Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC) is a subtype of breast cancer that is prone to drug resistance and difficult to treat. In this study, we grafted water-soluble pullulan with lovastatin (LV) to develop a novel amphiphilic conjugate, pullulan-encapsulated LV (PLV). The PLV conjugate was synthesized with three different ratios of pullulan to LV and characterized by Fourier transform infrared (FTIR). The degree of substitution (DS) of LV in terms of molar ratio was 7.87%, 3.58%, and 3.06% for PLV (1/2), PLV (1/3), and PLV (1/4), respectively, by proton NMR analysis. We selected the PLV (1/2) conjugate to prepare doxorubicin (DXR)-loaded PLV nanoparticles (PLV/DXR NPs) because of its superior properties. The average size and zeta potential for PLV (1/2) NPs were 177.6 nm and - 11.66 mV, respectively, determined by dynamic light scattering, and those for PLV/DXR NPs were 225.6 nm and - 10.51 mV, respectively. In vitro drug release profiling showed that PLV/DXR NPs sustainably released DXR within 72 h, which was more robust at pH 5.4 (97.90%) than pH 7.4 (76.15%). In the cytotoxicity study, PLV/DXR NPs showed greater inhibition of proliferation of TNBC MDA-MB-231 than non-TNBC MDA-MB-453 cells (IC50 0.60 vs 11.05 mu M). FITC-loaded PLV/DXR NPs were prepared to investigate cellular uptake: both cell lines showed a time-dependent uptake of NPs, but the number of NPs entering MDA-MB-231 cells was greater than that entering the MDA-MB-453 cells. Pullulan-based NP co-delivery of LV and DXR could efficiently inhibit TNBC cells, which may help in designing a powerful drug delivery system for treating TNBC.