Smart Nanoformulation Based on Stimuli-Responsive Nanogels and Curcumin: Promising Therapy against Colon Cancer

Curcumin (CUR) has gained much attention for its widely reported anticancer effect; however, its clinical use is restricted due to its low water solubility and, consequently, its poor bioavailability. Here, we report on the use of a nanoformulation of CUR with cationic nanogels for colon cancer therapy. Cationic stimuli-sensitive nanogels were prepared using a scale-up polymerization methodology based on surfactant-free emulsion polymerization of N,N'-diethylaminoethyl methacrylate (DEAEM) and poly(ethyleneglycol) methacrylate (PEGMA). The obtained nanogels showed a homogeneous size distribution (from 51 to 162 nm, polydispersity index (PDI) < 0.138) and exhibited a spherical form and core-shell morphology as confirmed by dynamic light scattering and electron microscopy, respectively. Nanogels were responsive to and degradable by variations of pH, temperature, or the redox environment, depending on the cross-linker used in the synthesis. Nanogels cross-linked with bis(acryloyl)cystamine incubated in a buffer (pH 7.4) containing 3 mM glutathione degraded in 60 min, while nanogels cross-linked with a divinylacetal cross-linker degraded in 10 min (pH ≤ 6). Nanoformulations of nanogels with CUR were stable as tested up to 30 days at physiological conditions. In vitro studies of the human colon cancer cell line (HCT-116) showed a synergistic effect of CUR and the degradable nanogels. Further, in vivo acute cytotoxicity tests of empty nanogels in mice demonstrate their potential as CUR nanocarriers for colon-anticancer therapies.