Recent Development of Sandwich Assay Based on the Nanobiotechnologies for Proteins, Nucleic Acids, Small Molecules, and Ions

The detection of proteins, nucleic acids, small molecules, and ions is of great importance in both the study of their fundamental functions and the development of molecular diagnostics. These biological molecules and ions not only are involved in the construction of living organisms, but also carry out most biological functions, including storage and transmission of genetic information, regulating biochemical activities and reactions, storing and transporting energy, and providing mechanical support. With the development of biotechnology, different recognition molecules, such as antibodies, oligonucleotide sequences, and aptamers, have been applied to specifically and selectively recognize protein, DNA, small molecules, and ions. At the same time, the feasibility of modifying the antibody with different signaling markers, such as fluorescein, radionuclides, enzymes, and redox tags, in turn allows for a broader variety of readouts in a sandwich-structured assay.