Disclosed is a novel means whereby cyanoacrylate polymer particles that are more useful than conventional product as an antimicrobial agent, antitumor agent, or the like can be provided. This method for manufacturing cyanoacrylate polymer particles includes anionically polymerizing cyanoacrylate monomer in the presence of at least one type of compound selected from the group consisting of an amino acid, a derivative thereof, and an oligomer and polymer thereof, and substantially in the absence of a saccharide or polysorbate. Cyanoacrylate nanoparticles conjugated with amino acid molecules demonstrate cytotoxic activity by specifically adhering to cells, and effectively suppress the proliferation of cancer cells and bacteria. Manufacturing nanoparticles using this novel manufacturing method makes it possible to enhance the cytotoxic activity of the particles.
