Unveiling the Behavior of Curcumin in Biocompatible Microemulsion and Its Differential Interaction with Gold and Silver Nanoparticles

The yellow polyphenolic pigment curcumin has many medicinal and therapeutic properties. However, the lack of bioavailability prevents its widespread use as a drug. On the other hand, microemulsion possesses the capability to enhance the bioavailability of the hydrophobic drug curcumin. This molecule undergoes excited state intramolecular proton transfer and is also used as a probe to monitor solvation dynamics. We have performed various dynamical studies of curcumin in a biocompatible microemulsion. This microemulsion is comprised of isopropyl myristate (IPM), poly(oxyethylene) sorbitan monooleate (Tween 80), sorbitan laurate (Span 20), and ionic liquid. Furthermore, we have synthesized silver and gold nanoparticles in this microemulsion and extensively characterized the same employing different spectroscopic and microscopic characterization techniques. We have studied broadly their interactions with curcumin, and we have observed that the excited state photophysics of curcumin in microemulsion is substantially affected by the presence of the nanoparticles. The excited state lifetime of curcumin increases in the presence of silver nanoparticles but decreases in the presence of gold nanoparticles, which indicates that curcumin forms nanoconjugates with silver nanoparticles, whereas it undergoes nanometal surface energy transfer with gold nanoparticles. Therefore, our study may provide detailed insight into the behavior of curcumin in microemulsion and the modulation of its excited state dynamics due to interactions with nanoparticles in microemulsion. Finally, this study may broaden our understanding and widen the scope to use this system for drug delivery and bioimaging applications.