A curcumin-induced assembly of a transferrin nanocarrier system and its antitumor effect

To increase the solubility and targeting efficiency of curcumin (CCM) to tumors, transferrin (Tf)-CCM nanoparticles (NPs-CCM) with a CCM loading capacity of 5.2% were fabricated by Tf denaturation with hydrochloric acid, a denaturing agent, to open the hydrophobic cavity of Tf. The NPs-CCM were approximately 160 nm in size with a spherical shape. The solubility of the CCM in the nanoparticles was approximately 100,000 times greater than that of CCM alone (11 ng mL^-1 vs 1.11 mg mL^-1, respectively). The changes in the fluorescence spectra of Tf and 1-(anilinon)-aphthalene-8-sulfonic acid (ANS) in the NP-CCM preparation indicated that the polarity of certain hydrophobic and hydrophilic groups of Tf changed. CCM treatment of A549 cells resulted in a decrease in the mitochondrial membrane potential (MMP) and induced apoptosis through mitochondrial dependence. CCM increased the expression of phosphorylated c-Jun N-terminal kinase (JNK), P38, and extracellular signal-regulated kinase (ERK) but had a weak effect on the expression of nonphosphorylated JNK, P38, and ERK, which showed that the mitogen-activated protein kinase signaling (MAPK) transduction pathway is involved in CCM-mediated apoptosis. The half maximal inhibitory concentration (IC₅₀) of NPs-CCM was higher than that of free CCM in A549 (16.41 ± 0.86 vs 12.51 ± 3.9 (μg mL^-1), p = 0.036) and MCF-7 (9.31 ± 0.11 vs 2.44 ± 3.76 (μg mL^-1), p < 0.0037) tumor cells, however the former had a greater tumor-targeting in vivo. Without the side effects of polyoxyethylene castor oil/ethanol as solvent, the hemolysis effect of NPs-CCM (0.05-1 mg mL^-1) was notably lower than that of free CCM (p < 0.05). It was estimated that the half maximal lethal dose (LD₅₀) of NPs-CCM was approximately two times that of CCM (100 mg kg^-1 vs 50 mg kg^-1), and the former had many advantages over that of free CCM in terms of lower toxicity and better targeting; thus, NPs-CCM can be administered at higher doses to acquire better antitumor effects than CCM alone, indicating that NPs-CCM are an effective and safe carrier for CCM delivery.