Thermo and pH dual-responsive nanoparticles encapsulating an anticancer drug (paclitaxel) were assembled from a diblock copolymer comprised of a hydrophilic poly(N-isopropylacrylamide-co -acrylic acid) block and a hydrophobic polycaprolactone block. These nanoparticles aggregated at body temperature under a slightly acidic pH of 6.9 (see figure), and a faster drug release was found to be associated with higher temperature and lower pH, both of which are advantageous for tumor-targeted anti-caner drug delivery.