Editing Biosensor (section)

===Affinity binding receptors===
Antibodies have a high [[binding constant]] in excess of 10^8 L/mol, which stands for a nearly irreversible association once the antigen-antibody couple has formed. For certain analyte molecules like [[glucose]] affinity binding proteins exist that bind their ligand with a high [[sensitivity and specificity|specificity]] like an antibody, but with a much smaller binding constant on the order of 10^2 to 10^4 L/mol. The association between analyte and receptor then is of [[reversible process (thermodynamics)|reversible]] nature and next to the couple between both also their free molecules occur in a measurable concentration. In case of glucose, for instance, [[concanavalin A]] may function as affinity receptor exhibiting a binding constant of 4x10^2 L/mol.<ref name= SMG1982>{{cite journal | author = J. S. Schultz | author2 = S. Mansouri | author3 = I. J. Goldstein | title = Affinity sensor: A New Technique for Developing Implantable Sensors for Glucose and Other Metabolites | journal = Diabetes Care| volume = 5 | issue = 3 | pages = 245–253 | year = 1982 | doi=10.2337/diacare.5.3.245| pmid = 6184210 | s2cid = 20186661 }}</ref> The use of affinity binding receptors for purposes of biosensing has been proposed by Schultz and Sims in 1979 <ref name= SSi1979>{{cite journal | author = J. S. Schultz | author2 =  G. Sims | title = Affinity sensors for individual metabolites | journal = Biotechnol. Bioeng. Symp. | volume = 9 | pages = 65–71 | year = 1979 | issue = 9 | pmid = 94999 }}</ref> and was subsequently configured into a fluorescent assay for measuring glucose in the relevant [[blood sugar|physiological range]] between 4.4 and 6.1&nbsp;mmol/L.<ref name= BS2000>{{cite journal | author = R. Ballerstadt | author2 = J. S. Schultz | title = A Fluorescence Affinity Hollow Fiber Sensor for Continuous Transdermal Glucose Monitoring| journal = Anal. Chem. | volume = 72 | issue = 17 | pages = 4185–4192 | year = 2000 | doi = 10.1021/ac000215r | pmid = 10994982 }}</ref> The sensor principle has the advantage that it does not consume the analyte in a chemical reaction as occurs in enzymatic assays.