Nano-Infrared Imaging of Primary Neurons

Raul O Freitas,Tomas Deierborg,Ferenc Borondics,Agnes Paulus,Christelle N Prinz,Elke Hebisch,João E Levandoski,Gunnar Keppler Gouras,Adrian Cernescu,Christophe Sandt,Isak Martinsson,Oxana Klementieva,Anders Engdahl

doi:10.3390/cells10102559

Abstract

Alzheimer’s disease (AD) accounts for about 70% of neurodegenerative diseases and is a cause of cognitive decline and death for one-third of seniors. AD is currently underdiagnosed, and it cannot be effectively prevented. Aggregation of amyloid-β (Aβ) proteins has been linked to the development of AD, and it has been established that, under pathological conditions, Aβ proteins undergo structural changes to form β-sheet structures that are considered neurotoxic. Numerous intensive in vitro studies have provided detailed information about amyloid polymorphs; however, little is known on how amyloid β-sheet-enriched aggregates can cause neurotoxicity in relevant settings. We used scattering-type scanning near-field optical microscopy (s-SNOM) to study amyloid structures at the nanoscale, in individual neurons. Specifically, we show that in well-validated systems, s-SNOM can detect amyloid β-sheet structures with nanometer spatial resolution in individual neurons. This is a proof-of-concept study to demonstrate that s-SNOM can be used to detect Aβ-sheet structures on cell surfaces at the nanoscale. Furthermore, this study is intended to raise neurobiologists’ awareness of the potential of s-SNOM as a tool for analyzing amyloid β-sheet structures at the nanoscale in neurons without the need for immunolabeling.

Highlights

Alzheimer’s disease is often regarded as part of natural aging, it is a progressive pathology in which a patient’s cognition worsens over time [1]
To detect β-sheet structures related to Alzheimer’s disease (AD), we used cultured primary neurons carrying a human AD mutant amyloid precursor protein (APP) gene
50–150 nm in diameter, we investigated whether scattering-type scanning near-field optical microscopy (s-SNOM) can be used for the characterization of exosomes isolated from AD and wild-type neurons

Summary

Introduction

Alzheimer’s disease is often regarded as part of natural aging, it is a progressive pathology in which a patient’s cognition worsens over time [1]. The “amyloid hypothesis” states that, based on observations, AD patients have amyloid plaques in their brains. Amyloid plaques are the buildup of β-sheet folded amyloid-β (Aβ) proteins that cause neurotoxicity. Aβ is processed from an amyloid precursor protein (APP) that is physiologically expressed in human nervous tissue; certain amounts of Aβ are always physiologically present. Aβ undergoes structural changes and can form amyloid aggregates [4]. Immunolabeling-based techniques are not always suitable for structural analysis since antibody generation requires prior knowledge of the targeted epitope structure; few structure-sensitive antibodies are available, and this limits the ability of immunolabeling to discriminate between different amyloid polymorphs that may be present in neurons [7,8,9]

Methods

Results

Conclusion