Immunosensing with artificial antibodies in organic solvents or complex matrices

The detection of analytes in complex matrices without labour intensive sample preparation is an important goal in analytical chemistry. In this article we would like to address this issue by transferring the selectivity of natural antibody in a cheap, robust and reusable polymer, employing a double imprinting protocol. Antibodies with the desired selectivity were used as template to generate imprinted polymer particles. These antibodies were added to a prepolymer and particles were precipitated. After the antibodies were removed from the particles, cavities remained which reproduce size, shape and surface chemistry of the antibodies. In a second imprinting step the particles with cavities were pressed into a second polymer. After the second polymer has cured the particles can be removed leaving positive structures behind that react with the desired antigen. Such a sensitive coating was applied to the surface of a quartz crystal microbalance and incorporated into a microfluidic chip. An immunosensor for estradiol was fabricated having six times higher affinity to its antigen than to structurally related molecules. The measurements can also be performed after an extraction into an organic solvent which improves the detection limit greatly and would not be possible for natural antibodies. The feasibility of the method for complex matrices was shown by detecting viruses in plasma or allergenic protein in bread extract.