“…By the immobilization of aptamers on appropriate transducers, numerous electrochemical [ 16 , 17 , 18 , 19 ], photoelectrochemical [ 20 , 21 , 22 , 23 ], surface plasmon resonance (SPR) [ 24 , 25 , 26 ], microgravimetric quartz-crystal-microbalance (QCM) [ 27 , 28 , 29 , 30 ], magnetic [ 31 , 32 , 33 ] and acoustic [ 34 , 35 , 36 ] sensors were demonstrated. Different target analytes were sensed by aptamers, including low-molecular-weight compounds, such as cocaine [ 37 , 38 , 39 , 40 ], explosives [ 41 , 42 , 43 ], pesticides [ 44 , 45 ], toxins [ 46 ] and antibiotics [ 47 , 48 , 49 ], and macromolecules such as protein [ 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ] and biopolymers [ 58 , 59 , 60 ]. The specific recognition of metal ions by aptamers, e.g., Mg 2+ , Zn 2+ and Ni 2+ led to the assembly of catalytic nucleic acids, DNAzymes [ 61 , 62 , 63 ], capable of cleaving oligonucleotides or ligating nucleic acids.…”