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Label-free biosensors are ideally suited for the direct monitoring of binding events without the need for additional labeling substances; however, their application in the field of serodiagnosis is not trivial. The major problem is the unspecific adsorption of blood serum components to the sensor surface.
A surface plasmon resonance (SPR) sensor has been used for the direct detection of
Lyme borreliosis specific antibodies in blood serum. The combination of an optimal dilution factor with the addition of suitable detergents minimizes the unspecific adsorption. Serum samples from healthy donors and infected patients have been analyzed and the results were compared with a certified immunoassay and a western blot.
A serum dilution of 1:20 in HBS-buffer with 0.05% Tween20 and 1 mg/mL carboxymethyl dextran reduces unspecific adsorption significantly and enables the identification of antibodies against the OspC/pepC10 antigen pair with a sensitivity of 92% and that against the VlsE/C6 pair with 81% sensitivity; the specificities are 82% and 86% respectively. Positive hits in the western blot could also be determined in the SPR-assay with a correlation of 96.5%.
The presented optical label-free technique has the potential for a precise and fast identification of pathogen-specific antibodies without the need for a secondary labeling antibody.