A1.2 - Replicae of Antibodies - Robust Mass-Sensitive Sensors for Allergens and Other Bioanalytes

SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
Proceedings SENSOR 2009, Volume I
A1 - Microacoustic Sensors
F. Dickert, R. Schirhagl, P. Lieberzeit, T. Hussain, M. Cichna-Markl - University of Vienna, Vienna, Austria
29 - 33


Food allergies represent a severe health problem in industriatized countries. They affect up to 2 % of the adult population and 8 % of children. Sesame, which affitiates to the family of pedaliaceae, contains one of the most important food allergens. Hulled seeds are dried or roasted and added to various kinds of food. Products as crackers, bread, fast food or sweets contain sesame. The rissing consumption of sesame leads to contamination of other comestibles as well. Sesame seeds comprise of 50 % sesame oil and 25 % sesame protein, which contains at least 10 allergenic proteins, and other compounds. The protein contains 65-70 % a-globulin and 30-35 % ß-globulin and has an isoelectrical point of 4.9 and consists of 12 subunits with masses of 80000-8500O Da resulting in a mass of 250000 Da for the whole protein. The increastng importance of sesame allergy requires accurate, safe, and cost-effective diagnostic techniques.
The common techniques for the detection of sesame are polymerase chain reactions (PCR) of encoding DNA or enzyme linked immuno sorbent assay (ELISA). Natural antibodies as used for ELISA are well estabiished molecular recognition Systems for hazardous chemicals, proteins or viruses. They are known for their selectivity and high affinities to their antigens, which is due to the optimal fit between the binding site and the antigen structure.
However, the generation of immunoglobulin coatings is accompanied by appreciable time consuming efforts. Additionally, for sensor application natural immunoglobulins require a special treatment to break the bond between antigen and antibodies to make the sensor response reversible. Furthermore, natural materials tend to degrade since proteins include oxidizable groups leading to denatunsing.
These problems can be solved when the recognition capabilities of natural antibodies are transferred to organic polymers, which are more stable than biological materials. In this way immunological responses are cast in polymers which are estabiished in a long evolution period. Such materials, which are used as stationaey phases in chromatography or catalysts, can also be used as sensor materials. They allow mass sensitive and label free detection of bioanalytes as proteins, viruses and cells as coatings on quartz crystal microbalances or surface acoustic wave (SAW) resonators. Therefore, beads in the size of 20-600 nm are pre-polymerised and precipitated in presence of natural immunoglobulins. The nanoparticles are washed to remove the antibody leaving holes with imprints of the antibody behind. Finally, these partictes are adhered on a glass plate, dried and pressed into another polymer placed on the surface of a QMB. After removing the stamp polymer with the positive structure of the antibody, the replica is left.