Homogeneous analysis: label-free and substrate-free aptasensors.

In this Focus Review, we introduce a kind of "label-free" and "substrate-free" (LFSF) aptasensor that carries out the whole sensing process in a homogeneous solution. This means that commonly used covalent label; separation, and immobilization steps in biosensors are successfully avoided, which simplifies the sensing operations to the greatest degree. After brief description about the advantages of aptamers and "LFSF" aptasensors, the main content of the review is divided into fluorescent aptasenors, calorimetric aptasensors, and hemin-aptamer-DNAzyme "LFSF" aptasensors, which are three most widely developed sensing systems in this field. It is hoped that this review can provide an overall scene about how aptamers function as ideal recognition elements in smart analysis.