NA-based logical circuits for cellular applications. A) Illustration and truth table showing how this aptamer-based nanorobot works (reprinted by permission from reference [30], copyright 2012, AAAS). B) Hybridization chain reaction mechanism (from reference [35a], reprinted with permission from Macmillan Publishers Ltd., Nat. Biotechnol., copyright 2010). C) Scheme of DNA-based logical circuit operating on a target B cell with a C45+CD20+ phenotype and on a nontarget cell with a CD45+CD20− phenotype (e.g., a T cell) (reference [32], reprinted by permission from Macmillan Publishers Ltd., Nat. Nanotechnol., copyright 2013). D) Schematic representation of a HeLa-specific classifier circuit operation (from reference [36], reprinted with permission from AAAS).