Biosensing

 The natural biosensing molecules described above are often replaced by synthetic analogues which mimic functionality of the native unit. The synthetic molecules include peptide aptamers, oligonucleotide aptamer, DNA and oligonucleotide analogues, like peptide nucleic acids (PNAs), locked nucleic acids (LNAs), glycol macromolecule (GNA), and threose macromolecule (TNA). A peptide aptamer may be a short peptide with high affinity to the target molecules, which makes them an alternate to an antibody. It's engineered by inserting an oligonucleotide-encoding aptamer into the gene of the supporting protein. Peptide aptamers are used for detection of food contamination, pathogen detection, medical diagnostics, and detection of proteins, e.g., human chorionic gonadotropin. Their ability to acknowledge 3D structure of proteins they will be used rather than antibodies. The length of a typical oligonucleotide aptamer is typically 12–25-mer. Their stability and life-time are increased by chemical modifications of sugar-phosphate backbone.