Low-molecular-weight drug-containing nanoparticles having a negatively charged group of controlled release

Efficiently targeting excellent drug slow release, and to provide a low-molecular-weight drug-containing nanoparticles to reduce side effects by reducing the liver accumulation, metal small molecule drugs with a negatively charged group ion hydrophobized by which poly L- lactic acid or poly (L- lactic acid / glycolic acid) copolymers, and poly DL- or L- lactic acid - polyethylene glycol block copolymer or poly (DL- or L- lactic acid / glycolic acid) - which is a low molecular drug-containing nanoparticles having a negatively charged group obtained by acting with polyethylene glycol block copolymer.