Mid-infrared absorption spectroscopy of protein aggregates using germanium on silicon waveguides

Abstract

Proteins in human samples can be used to detect the onset of a group of neurodegenerative diseases such as Alzheimer’s and Parkinson’s by studying their conformational (shape and structure) changes that can cause cognitive impairment. Proteins form aggregates from normal state (monomers) to disease state (amyloid deposition and fibril formation in central nervous system) that is associated with disease progression. These changes can be diagnosed and monitored using mid-infrared (MIR) absorption spectroscopy by studying line shapes and relative absorbance of amide bands. We have demonstrated MIR spectroscopy of proteins in three stages of aggregation: monomers, oligomers and fibrils of Bovine Serum Albumin (BSA) protein on a germanium on silicon (GOS) waveguide in the MIR wavelength region of 5.2 – 10 μm (1900 – 1000 cm-1). The protein samples were also characterised by atomic force microscopy to confirm their structure.

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Identifiers

ORCID for Vinita Mittal: orcid.org/0000-0003-4836-5327

ORCID for Philip N. Bartlett: orcid.org/0000-0002-7300-6900

ORCID for Harold Chong: orcid.org/0000-0002-7110-5761

ORCID for Sumeet Mahajan: orcid.org/0000-0001-8923-6666

ORCID for James S Wilkinson: orcid.org/0000-0003-4712-1697

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