Reversible Immuno-Infrared Sensor for the Detection of Alzheimer's Disease Related Biomarkers.

The development of biosensors for medical purposes is a growing field. An immuno-infrared biosensor for the preclinical detection of Alzheimer's disease (AD) in body fluids was developed. The key element of this sensor is an ATR crystal with chemically modified surface to catch the biomarker out of the body fluid. So far, the immuno-infrared sensor can be used only once and requires time-consuming steps of sensor exchange, sensor cleaning, and novel surface functionalization. Here, we developed an immuno-infrared sensor providing a reusable surface and showcase its performance by the detection of the AD biomarker proteins Aβ and Tau in human cerebrospinal fluid (CSF). The sensor surface is covalently coated with the immunoglobulin binding proteins Protein A or Protein G. These were employed for noncovalent immobilization of antibodies and the subsequent immobilization and analysis of their antigens. The reversible antibody immobilization can be repeated several times with the same or different antibodies. Further, the more specific binding of the antibody via its Fc region instead of the conventional NHS coupling leads to a 3-4-fold higher antigen binding capacity of the antibody. Thus, the throughput, sensitivity, and automation capacity of the immuno-infrared biosensor are significantly increased as compared to former immuno-infrared assays. This immuno-sensor can be used with any antibody that binds to Protein A or Protein G.