Podophyllotoxin-polyacrylic acid conjugate micelles: improved anticancer efficacy against multidrug-resistant breast...

Podophyllotoxin (PPT) is a naturally occurring compound obtained from the roots of Podophyllum species, indicated for a variety of malignant tumors such as breast, lung, and liver tumors. This toxic polyphenol (PPT) exhibited significant activity against P-glycoprotein (P-gp) mediated multidrug-resistant (MDR) cancer cells. However, extremely poor water solubility, a narrow therapeutic window, and high toxicity have greatly restricted the clinical uses of PPT. Therefore, the present research was aimed to synthesize the water-soluble ester prodrug of PPT with polyacrylic acid (PAA), a water-soluble polymer by Steglich esterification reaction, and to screen it for assay, solubility, in vitro hemolysis, in vitro release, and in vitro anticancer activity.

The Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy results revealed the successful synthesis of podophyllotoxin-polyacrylic acid conjugate (PPC). The assay and saturation solubility of the prodrug is found to be 64.01 ± 4.5% and 1.39 ± 0.05 mg/mL (PPT equivalent) respectively. The PPC showed CMC (critical micelle concentration) of 0.430 mg/mL in distilled water at room temperature. The PPC micelles showed a mean particle size of 215 ± 11 nm with polydispersity index (PDI) of 0.193 ± 0.006. Further, the transmission electron microscope (TEM) results confirmed the self-assembling character of PPC into micelles. The PPC caused significantly less hemolysis (18.6 ± 2.9%) than plain PPT solution. Also, it demonstrated significantly (p < 0.01) higher in vitro cytotoxicity against both sensitive as well as resistance human breast cancer cells (MCF-7 and MDA MB-231) after 48 h of treatment.

The obtained study results clearly revealed the notable in vitro anticancer activity of PPT following its esterification with PAA. However, further in vivo studies are needed to ascertain its efficacy against a variety of cancers.