Abstract
We propose a sensing platform based on graphene oxide/silver nanoparticles arrays (GO/AgNPs) for the detection and discrimination of the native and toxic fibrillar forms of an amyloid-prone protein, lysozyme, by means of a combination of Quartz Crystal Microbalance (QCM) and Surface Enhanced Raman Scattering (SERS) measurements. The GO/AgNPs layer system was obtained by Langmuir-Blodgett assembly of the silver nanoparticles followed by controlled adsorption of GO sheets on the AgNPs array. The adsorption of native and fibrillar lysozyme was followed by means of QCM, the measurements provided the kinetics and the mechanism of adsorption as a function of protein concentration as well as the mass and thickness of the adsorbed protein on both nanoplatforms. The morphology of the protein layer was characterized by Confocal Laser Scanning Microscopy experiments on Thioflavine T-stained samples. SERS experiments performed on arrays of bare AgNPs and of GO coated AgNP after native, or fibrillar, lysozyme adsorption allowed for the discrimination of the native form and toxic fibrillar structure of lysozyme. Results from combined QCM/SERS studies indicate a general construction paradigm for an efficient sensing platform with high selectivity and low detection limit for native and amyloid lysozyme.
Highlights
Neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease are chronic, degenerative pathologies that irreversibly damage the functional capabilities of the affected individuals
The body of the results shows that the combination of Quartz Crystal Microbalance (QCM) and SERS measurements allows for the quantification of a model amyloid-prone protein, lysozyme, providing at the same time a way to discriminate between native conformation and fibrillar amyloid structures
We constructed a powerful capturing metasurface on the QCM sensor by Langmuir-Blodgett assembly of a mixture of AgNC/NS followed by the controlled adsorption of Graphene Oxide (GO) sheets on the AgNC/NS array
Summary
Neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease are chronic, degenerative pathologies that irreversibly damage the functional capabilities of the affected individuals. The common theme for all these pathologies is the neuronal misfunction and death flanked by the progressive loss of cognitive and motor abilities Clinical studies associate these different neuropathies to different precursor proteins, or peptides, malfunctioning sharing a common pattern: the formation of misfolded fibrillar aggregates of protein, or oligomeric species, with high content of β-sheet secondary structure [1,2]. Such fibrillar aggregates eventually evolve in mature bundles of amyloid fibrils detected once the disease has proceeded to irreversibly impair the patient’s functions. Robust and reliable diagnostic methods to detect the occurrence of low concentrations of toxic fibrils are still lacking, extensive scientific efforts have been recently devoted to the identification of suitable detection systems [3,4]
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