Colorimetric　sensors　based　on　assembly　or　disassembly　of　isotropic　gold　nanoparticle　(AuNP)　aggregates　have　been　frequently　reported.　Herein　we　demonstrate　the　first　colorimetric　aptasensor　for　sensitive　detection　of　ochratoxin　A,　one　of　the　most　abundant　food-contaminating　mycotoxins,　based　on　disassembly　of　aggregates　of　oriented　AuNP　dimers.