Curcumin-primed and curcumin-loaded exosomes: potential neural therapy

Curcumin: Curcumin is a yellow colored compound found in the rhizomes of Curcuma longa (turmeric), a member of the ginger family (Zingiberaceae). Structurally curcumin is a diarylheptanoid, a tautomeric compound, present in keto form in water and enolic form in the organic solvents. The therapeutic efficacy of curcumin is extensively studied against neurodegenerative diseases as it possesses anti-inflammatory, anti-lipidemic, and anti-oxidative properties (Kalani et al., 2014b, 2015b). Curcumin’s neuroprotective properties led the compound to the Phase I clinical trials; however, it could not proceed further due to its limited bioavailability, poor absorption, quick metabolism and rapid systemic elimination (Kalani et al., 2015b). In order to increase its bioavailability, different investigators have proposed alternative methods for instance, encapsulation of curcumin by synthesizing microcapsule containing self-assembled nanoparticles using poly-l-lysine, trisodium citrate and silica sol (Patra and Sleem, 2013), and encapsulating curcumin in self-assembling peptide hydrogels as injectable drug delivery vehicles (Altunbas et al., 2011). Similarly, we tried to design nano-formulations of curcumin which are more soluble, more stable, less cost-effective and less labor-intensive. The two important formulations are 1) curcumin-primed exosomes (CUR-EXO) and, 2) curcumin-loaded exosomes (exocur). The given nano-formulations were prepared in exosomes and both performed extensively well in different model systems. Cells release curcumin-primed exosomes when treated with curcumin while curcumin-loaded exosomes were prepared by loading curcumin in the exosomes. The choice of exosomes for making these nano-formulations over other available options was made due to several reasons and these include, exosomes size (40–200 nm), preferred binding of curcumin with exosomes, usefulness in different administrative routes, hydrophobic and non-immunogenic nature, and superiority over other delivery agents (Kalani et al., 2013, 2014a; Kalani and Tyagi, 2015).