Biodegradable Polymer-Curcumin Conjugate Micelles Enhance the Loading and Delivery of Low-Potency Curcumin

To utilize a novel type of polymer-drug conjugate micelle to enhance the delivery of low-potency curcumin. Multiple curcumin molecules were conjugated to poly(lactic acid) (PLA) via tris(hydroxymethyl)aminomethane (Tris) linker producing the hydrophobic drug-binding block; methoxy-poly(ethylene glycol) (mPEG) was employed as the hydrophilic block. Micelles were characterized by size, loading capacity, stability, and critical micelle concentration (CMC). Human hepatocellular carcinoma (HepG2) cells were employed to assess cytotoxicity and intracellular targeting ability of micelles. mPEG-PLA-Tris-Cur micelles were within nanorange (< 100 nm). CMC of such micelles (2.3 +/- 0.4 mu g/mL) was 10 times lower than mPEG-PLA micelles (27.4 +/- 0.8 mu g/mL). Curcumin loading in mPEG-PLA-Tris-Cur micelles reached 18.5 +/- 1.3% (w/w), compared to traditional mPEG-PLA micelles at 3.6 +/- 0.4% (w/w). IC50 of mPEG-PLA-Tris-Cur micelles (similar to 22 mu g/mL at curcumin-equivalent dose) was similar to unmodified curcumin. Placebo and drug-encapsulated conjugate micelles could be efficiently internalized to cytoplasmic compartment of HepG2 cells. Micelle-forming polymer-drug conjugates containing multiple drug molecules were an efficient means to increase loading and intracellular delivery of low-potency curcumin.