Example 2
<Preparation of Solution B>
Polylactic acid-glycolic acid copolymer (product name: PLGA-5010, obtained from Wako Pure Chemical Industries, Ltd.) (4 parts by mass), acetone (obtained from Wako Pure Chemical Industries, Ltd.) (76.8 parts by mass), and methanol (obtained from Wako Pure Chemical Industries, Ltd.) (19.2 parts by mass) were mixed under stirring using a stirrer (device name: magnetic stirrer, obtained from AS ONE Corporation) for 1 hour at 1,000 rpm, followed by passing the resultant through a 1 μm-filtration filter (product name: Millex SLFA05010, obtained from Merck), to prepare solution B.