A particulate poly(lactic-co-glycolic) acid (PLGA) is provided. The particulate PLGA comprises a poly(lactic-co-glycolic) acid (PLGA), and has an average volume-based particle diameter of 80 nm or less and a relative span factor (R.S.F.) satisfying the following formula (1):; 0R.S.F.≦1.20 Formula (1);where R.S.F. is defined by (D90−D10)/D50, where D90, D50, and D10 respectively represent particle diameters at cumulative rates of 90%, 50%, and 10% by volume based on a cumulative particle size distribution counted from a small-particle side.
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