Raman Spectroscopy Study of Skin Biopsies from Patients with Parkinson’s Disease: Trends in Alpha-Synuclein Aggregation from the Amide I Region

Abstract

Parkinson's disease (PD) is one of the most common neurological pathologies with a high prevalence worldwide. PD is characterized by Lewy bodies, whose major component is the aggregates of α-synuclein (αSyn) protein. Interestingly, recent works have demonstrated that skin biopsy studies are a promising diagnostic tool for evaluating α-synucleinopathies. In this sense, this work focuses on the detection of αSyn in skin biopsies employing Raman spectroscopy, using three different approaches: 1) the in vitro Raman spectrum of α-synuclein, 2) the ex vivo Raman spectra of human skin biopsies from healthy and Parkinson's disease patients, and 3) theoretical calculations of the Raman spectra obtained from different model αSyn fragments using Density Functional Theory (DFT). Significant differences in the intensity and location of Raman active frequencies in the Amide I region were found when comparing healthy and PD subjects related to α-synuclein conformational changes and variations in their aggregation behavior. In samples from healthy patients, we identified well-known Raman peaks at 1655, 1664, and 1680 〖cm〗^(-1) associated with the normal state of the protein. In PD subjects, shifted Raman bands and intensity variations were found at 1650, 1670, and 1687 〖cm〗^(-1) associated with aggregated forms of the protein. DFT calculations reveal that the shape of the Amide I Raman peak in model αSyn fragments strongly depends on the degree of aggregation. Sizable frequency shifts and intensity variations are found within the highly relevant 1600—1700 cm-1 domain, revealing the sensitivity of the Amide I Raman band to the changes in the local atomic environment. Interestingly, we obtain that the presence of surrounding waters also affects the structure of the Amide I band, leading to the appearance of new peaks in the low-frequency side and a notable broadening of the Raman spectra. These results strongly suggest that, through Raman spectroscopy, it is possible to infer the presence of aggregated forms of αSyn in skin biopsies, a result that could have important implications for understanding α-synuclein related diseases.

Influence of TiO2 and ZnO Nanoparticles on α-Synuclein and β-Amyloid Aggregation and Formation of Protein Fibrils

“…The deviations of the spectra from the average spectrum are small, which may indicate a more uniform structure of βA at all investigated points of the Ag SERS substrate. It is known that the amide I region is empowered for protein conformational change [ 30 , 31 ]. The Ag SERS substrate is the same in all experiments, ZnO-NPs or the ZnO-Ag combination likely has a stabilizing effect on a certain structure of the protein or the formation of a certain specific structure.…”

Unveiling brain disorders using liquid biopsy and Raman spectroscopy

“…León-Bejarano and colleagues utilized SERS to analyze α-synuclein levels in skin biopsies from PD patients. 189 Their study revealed distinct alterations in the Raman bands of the protein, with shifts observed from 1655, 1664, and 1680 cm −1 to 1650, 1670, and 1687 cm −1 when comparing control subjects to those with PD. These spectral changes were attributed to protein aggregation, suggesting the potential of SERS in detecting aggregated α-synuclein in skin samples.…”

“…188 We would like to note that researchers have utilized diseased cells or tissues in order to diagnose different NDs. 23,189 For instance, in HD, RS has previously been used to study fibroblast from patients. [190][191][192] Wang et al introduced graphene-assisted RS for rapid biomarker sensing of AD.…”

Applications of Raman spectroscopy in the diagnosis and monitoring of neurodegenerative diseases

“…When comparing the control and PD groups, the Raman spectra changed from 1,655, 1,664, and 1,680 cm −1 to 1,650, 1,670, and 1,687 cm −1 , respectively, which are related to protein aggregation. Research has shown that SERS can detect α-synuclein aggregates in the skin and thus this could be used as a minimally invasive tool for detecting the disease (León-Bejarano et al, 2022). Sevgi et al (2021) conducted Raman spectral and microspectral analyses of the olfactory bulb from the brain of human BAC-SNCA transgenic rats and samples of colon muscular and mucosal tissue sections.…”