Bioaffinity-based interaction

Bioaffinity chromatography means that solute components which have a very specific and selective interaction with the adsorbent are separated into fractions with a high purity. Sometimes this selective bonding is based on a steric effect (key-lock-interaction) but also an equilibrium or kinetic effect can be applied for separation. As a mle also a specific eluent is necessary for regeneration. 

DNA-based biosensors possess specificity of response, which is typical for biosensors taking advantage of the bioaffinity properties of DNA. Compared with enzyme sensors and immunosensors, DNA biosensors are mostly used for the investigation of DNA interactions rather than for conventional determination of the concentration of an anal3 e. They exhibit typical biosensor selec-tivity/specificity to the anal3d e (e.g., nucleotide bases sequence. 

Bioaffinity recognition is based on non-catalytic complementary interaction with the analyte. The specificity of the complementary recognition process is mainly determined by the binding constant of the complex-formation reaction. The analyte quantification is usually done at equilibrium (when no further consumption of the analyte takes place) using a suitable transduction process modulated by the complementary recognition reaction. 

Specific bioaffinity assays are always accompanied with nonspecific binding interactions and this has been seen as an obstacle in assay development. However, nonspecific binding in combination with core—shell europium(III) and europium (in)-dyed polymeric nanoparticles has been recently exploited in FRET-based assays for total protein concentration measiuement [137, 138], The method was based on the competitive adsorption of sample proteins and acceptor-labeled proteins to polymeric Eu(Ill) nanoparticles. High sensitivity and low, subnanomolar limit of detection was partially reached due to a short Forster s radius as the acceptor label was brought in direct contact with the surface. 

A urea sensor has conventionally consisted of a urease-immobilized membrane and electrode for the determination of the metabolites electrodes for ammonium ion (20), pH (27), ammonia gas (22), and carbon dioxide (23) have been used. These sensors were all potentiometric ones to give Nernstian responses, the linear concentration range of which was typically between 10" and 10 M of urea. If one wishes to detect urea with using the ion- or gas-selective electrodes, urease is indispensable not only for the specific recognition based on the bioaffinity interaction but also for chemical conversion of urea to detectable species, since urea is essentially electro-inactive. On the contrary, the polymer-modified electrode described here does not rely upon enzymes the concentration of urea can be determined directly. 

Katz E, Heleg-Shabtai V, Bardea A, Willner I, Rau HK, Haehnel W. Fully integrated biocatalytic electrodes based on bioaffinity interactions. Biosens Bioelectron 1998 13 741-756. 

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