A Montmorillonite-Based Pickering Nanoemulsion for the Integration of Photothermal Therapy and NIR-Responsive Drug Delivery

Chemo/photothermal combination therapy is a promising and practical approach for cancer treatment which calls for certain nanovehicles to achieve the spatiotemporal co-occurrence of photothermal conversion and drug delivery. Herein, we developed a montmorillonite-based Pickering emulsion equipped with a near-infrared photothermal agent (indocyanine green, ICG) and anticarcinogen (paclitaxel, PTX). With both montmorillonite and ICG functioning as interfacial stabilizers, the Pickering emulsion showed good stability and nanoscale droplet size, which were favored for cellular applications. Due to the vast oil-water interface, where the majority of amphiphilic ICG was prone to distribute, the Pickering nanoemulsion could achieve a higher local concentration of ICG than the aqueous solution, therefore leading to a higher local photothermal performance under near-infrared irradiation. The Pickering nanoemulsion exhibited fast cell penetration, which promoted the photothermal therapeutic effect of ICG. Moreover, the inner phase of the Pickering nanoemulsion also facilitated the loading of PTX, further improving its killing efficacy against cancer cells under near-infrared irradiation, because the photothermal conversion of the Pickering nanoemulsion could not only cause heat damage by itself but also promote the loaded PTX to diffuse out and induce cell death. Therefore, this clay-based Pickering nanoemulsion as a nanovehicle could realize the synergy of chemo- and photothermal therapy.