Throughput optimized immuno‐infrared‐assay for Alzheimer’s disease diagnosis

• Published in: Alzheimer's & dementia Vol. 16
• Main Authors: Budde, Brian, Mann, Marvin, Woitzik, Nathalie, Güldenhaupt, Jörn, Kötting, Carsten, Gerwert, Klaus Bernhard
• Format: Journal Article
• Language: English
• Published: 01.12.2020
• ISSN: 1552-5260; 1552-5279
• DOI: 10.1002/alz.043093

Background It is believed, that one of the first events in the progression of Alzheimer’s Disease is the misfolding of the Amyloid Beta (Aβ) Peptide. This event takes place up to 20 years before the clinical onset of the disease. Therefore, biosensors detecting the misfolding of Aβ are especially useful for the early and specific detection of Alzheimer’s Disease. In recent studies, our biosensor based on ATR‐FTIR spectroscopy performed with an overall accuracy of 86% [1,2,3]. This system is robust and reliable but the user input required is very high because each sensor can only be used once. To overcome these issues and increase the automation capacity, a regenerative system is urgently needed. Method To achieve higher throughput of this system, we introduced immunoglobulin binding proteins (Protein A and Protein G) as capture for antibody immobilization. Protein A and Protein G are able to recognize and bind the constant region of different IgG antibodies in a non‐covlant manner. This allows multiple measurements within the same system by performing multiple binding and elution cycles. Result Protein A and Protein G can be attached covalently to the sensor without losing its ability to bind IgG antibodies [4]. The antibody binding and elution is monitored by ATR‐FTIR spectroscopy and validated using fluorescence spectroscopy. It is possible to perform at least 35 cycles of antibody binding and elution over 7 days without loss in diagnostic accuracy. The sensor is still able to extract different biomarkers like Aβ and the Tau Protein from CSF with highly comparable results compared to the recently used system. Conclusion The development of a regenerative immuno‐infrared‐sensor is crucial to reduce the user input and to increase the throughput of this method. Compared to assays where the capture antibody is covalently immobilized, the regenerative system has a factor 6 increased thoughput. References: (1) Nabers, A. et al. (2016) J. Biophotonics, 9. 224‐234. (2) Nabers, A. et al. (2018) EMBO Mol. Med. 10, e8763. (3) Nabers, A et al. (2019) Alzheimer’s Dement. Diagnosis, Assess. Dis. Monit., 11, 257‐263. (4) Budde, B. et al. (2019) ACS Sens. 4, 1851‐1856.