Assessment of enhancing curcumin's solubility versus uptake on its anti-cancer efficacy

Curcumin (CUR) exhibits anti-inflammatory and anti-cancer activities. However, its poor solubility and bioavailability limit its therapeutic applications. Several CUR nano-formulations have been developed to enhance its solubility and uptake, thereby improving its anti-cancer activity. Despite this, studies comparing the effect of enhanced CUR solubility versus cellular uptake on its anti-cancer efficacy are lacking. Therefore, CUR nanofibers (CUR NF) were synthesized by electrospinning using a water-soluble polymer to enhance CUR solubility. While CUR nanoparticles (CUR NP) were synthesized by nanoprecipitation method using a water-insoluble polymer to enhance CUR cellular uptake. Both nano-formulations aim to improve CUR cellular concentration and anti-cancer activity against various cancer cells. CUR NF and CUR NP were successfully synthesized at drug load (DL%) of 10 %, 20 %, and 40 % w/w. Both nano-formulations were characterized, and CUR dissolution, release, cytotoxicity, IC50, and cellular uptake were assessed. A gradual increase in NF diameter and NP size was observed as the drug load% increased compared to the placebo. NF showed a rapid CUR release and increased solubility by 16–38 fold. In contrast, NP sustained CUR release and resulted in only a 2-fold increase in solubility. Both formulations significantly reduced cell viability and IC50 compared to free CUR. However, CUR NP demonstrated higher cell toxicity (70–80 %) than CUR NF (60 %) and reduced IC50 up to 4 μM compared to 11 μM for NF. Enhancing CUR solubility or uptake can significantly increase its cellular concentration and anti-cancer activity. However, enhancing CUR cellular uptake by NP demonstrated superior anti-cancer effect compared to enhancing its solubility by NF.