Polyacrylic Acid Functionalized Co0.85Se Nanoparticles: An Ultrasmall pH-Responsive Nanocarrier for Synergistic Photothermal-Chemo Treatment of Cancer

To surmount the challenges of limited drug penetration and therapeutic resistance in solid tumors, stimuli responsive nanocarrier-based drug delivery systems (DDSs) with relatively small sizes are inherently favorable for combined treatment of cancerous cells. In this work, poly(acrylic acid) (PAA) functionalized Co0.85Se nanoparticles (PAA-Co0.85Se NPs) were synthesized through an ambient aqueous precipitating approach for synergistic photothermal-chemo treatment of cancer. The obtained PAA-Co0.85Se NPs possess ultrasmall size (8.2 +/- 2.6 nm), considerable near-infrared (NIR) light absorption, high photothermal transforming efficiency (45.2%) and low cytotoxicity, all of which are beneficial for localized photothermal ablation of cancer cells. Doxorubicin hydrochloride (DOX center dot HCL) was then successfully loaded on PAA-Co0.85Se NPs with a loading capacity up to 8.3% to form PAA-Co0.85Se-DOX composites, which exhibited an exciting acidic pH responsive drug release property due to the protonation of amino groups in DOX and carboxyl groups in PAA molecules. As expected, when HeLa cells were treated with PAA-Co0.85Se-DOX NPs as well as NIR laser irradiation, a significant synergistic cell -killing effect was observed, greatly improving the treatment efficiency. Thus, this work presents novel insight into the design of ultrasmall stimuli-responsive nanocarrier-based DDSs for synergistic photothermal-chemo treatment of cancer cells.