Synthesis and characterization of a cytotoxic cationic polyvinylpyrrolidone-curcumin conjugate

Curcumin has been studied as a potential drug for many diseases including cancer. One of the serious limitations projected on curcumin is its poor water solubility and the substantially low bioavailability. With a view to enhance the aqueous solubility of curcumin, we synthesized polyvinylpyrrolidone-curcumin conjugates. Polyvinylpyrrolidone was used for the conjugation considering its long history of safe usage as a biomaterial for various medical applications. The drug conjugates self-assembled in aqueous solution to form nanosized micellar aggregates. The formation of micellae stabilized curcumin against hydrolytic degradation. Another interesting feature of the conjugate was its cationic nature. The net zeta potential in the pH range from 3 to 7.4 was +25 to +20 mV, reflecting the potential stability of the conjugate micellae at physiological pH. We quantified cytotoxic potential of the conjugate by the MTT assay, using L929 fibroblast cells. The results showed that the conjugate had higher cytotoxicity than that of the free curcumin. It is expected that the relative enhanced cytotoxicities are the result of enhanced aqueous solubility and polymer-mediated drug internalization. The conjugate has the potential to circumvent limitations of curcumin and thereby to extrapolate further its applications as an effective anticancer drug.