The combination of chemotherapy with photothermal therapy, which may lead to improved therapeutic efficacies and reduced side effects of conventional chemotherapy, would require safe drug delivery systems (DDSs) with strong near-infrared (NIR) absorbance, efficient drug loading, and effective tumor homing ability. Herein, we fabricate nano-assemblies containing J-aggregates of a NIR dye, IR825, for drug delivery and combined photothermal & chemotherapy of cancer. It is found that IR825 could be complexed with a low-molecular-weight cationic polymer polyethylenimine (PEI), forming IR825@PEI J-aggregates with greatly enhanced NIR absorbance red-shifted to 915 nm. Those nano-assemblies of J-aggregates are further modified with polyethylene glycol (PEG), obtaining IR825@PEI-PEG nano-complex which exhibits great dispersity in physiological solutions, excellent photostability, and is able to efficiently-load chemotherapeutic drug doxorubicin (DOX) via a unique strategy different from drug loading in conventional amphiphilic polymer-based DDSs. In vivo animal experiments uncover that IR825@PEIPEG/DOX upon intravenous injection into tumor-bearing mice shows rather high tumor uptake as illustrated by photoacoustic imaging. In vivo combined photothermal & chemotherapy is then carried out, demonstrating great synergistic anti-tumor therapeutic effect remarkably superior to those achieved by the respective mono-therapies. Hence, we present a novel type of nanoscale DDSs based on nano-assemblies of small molecules without involving amphiphilic polymers, promising for imaging-guided combination cancer therapy. (C) 2015 Elsevier Ltd. All rights reserved.
