Conventional approaches in ND (neurodegenerative disease) diagnosis and challenges in clinical routine testing are addressed in order to understand the context of how molecular-based diagnosis techniques can perform in real, in vivo sampling and bioassays for early ND diagnosis.
Clinical Examples | Advantages | Disadvantages | Current Use | |
---|---|---|---|---|
Imaging techniques | Magnetic resonance imaging (MRI) | Label based Reliable High resolution Wide collection of fluorophores or contrast agents |
Incapable of differential diagnosis due to chemical contrast limitations Current need for tissue-specific labeling Toxicity due to dye usage |
In vivo |
Optical coherence tomography (OCT) | In vivo | |||
Two-photon excited fluorescence (TPEF) | In vivo (limited) |
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Photoacoustic imaging | High sensitivity Specificity Rapid output |
Costs due to specific labels Specific absorption limitations of dyes in practice Toxicity due to dye usage |
In vivo | |
Confocal fluorescence microscopy | ||||
Spectroscopic techniques | IR microscopy | Label free Provides chemical contrast due to molecular vibrations specific selectivity |
Long wavelength → low spatial resolution Interference of water absorption specific to biological samples Tissue depth penetration is limited |
Ex vivo |
Raman scattering | Label free Complex matrices as samples with minimal preparation required (biofluids, cells, tissues, etc.) No interference from water (intrinsic to samples) Selective tool for NDs differential diagnostics Imaging of (bio-)molecular distribution Specific molecular fingerprinting spectral output Clinical adapted portable setups: optical fibers with possibility to integrate with cannulas, endoscopes, catheters |
Time consuming when using mapping technique of large tissular areas Low efficiency of the scattering process translated into inherently weak Raman signals Potentially destructive to the sample due to long laser exposure times |
In vivo | |
Hyperspectral Raman imaging | Able to show the amyloid plaques, neuritic plaques, or neurofibrillary tangles and is able to distinguish tissue components for margin determinations | |||
Surface-enhanced Raman scattering | Label free No need for staining High chemical specificity Combined with cryo-sampling of brain tissue |
Signal enhancement is local, mainly due to the molecules in close contact with the metallic nanostructures | In vivo | |
Label based When combined with spatially offset (SORS) the detection is possible within the skull Bio-barcode assays for differential PD diagnosis Reduced time Multiplexing capacity |
Silver nanoparticles (AgNPs) are shown to alter neurotransmitters in in vivo conditions (rats) Reliant on costly antibodies specific to NDs |
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Molecular Biology techniques | ELISA/Western blot | Label based High accuracy Suitable for routine protocols (predictive and diagnosis screening) |
Costly due to highly specific reagents required, invasive, and laboratory dependent Time consuming when including bioinformatics protocols |
Ex vivo |
Immunohistochemistry | ||||
Genomics (PCR, RT-PCR, DNA sequencing, (epi)transcriptomics) |
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Clinical Examples | Advantages | Disadvantages | Current Use | |
Imaging techniques | Magnetic resonance imaging (MRI) | Label based Reliable High resolution Wide collection of fluorophores or contrast agents |
Incapable of differential diagnosis due to chemical contrast limitations Current need for tissue-specific labeling Toxicity due to dye usage |
In vivo |
Optical coherence tomography (OCT) | In vivo | |||
Two-photon excited fluorescence (TPEF) | In vivo (limited) |
|||
Photoacoustic imaging | High sensitivity Specificity Rapid output |
Costs due to specific labels Specific absorption limitations of dyes in practice Toxicity due to dye usage |
In vivo | |
Confocal fluorescence microscopy | ||||
Spectroscopic techniques | IR microscopy | Label free Provides chemical contrast due to molecular vibrations specific selectivity |
Long wavelength → low spatial resolution Interference of water absorption specific to biological samples Tissue depth penetration is limited |
Ex vivo |
Raman scattering | Label free Complex matrices as samples with minimal preparation required (biofluids, cells, tissues, etc.) No interference from water (intrinsic to samples) Selective tool for NDs differential diagnostics Imaging of (bio-)molecular distribution Specific molecular fingerprinting spectral output Clinical adapted portable setups: optical fibers with possibility to integrate with cannulas, endoscopes, catheters |
Time consuming when using mapping technique of large tissular areas Low efficiency of the scattering process translated into inherently weak Raman signals Potentially destructive to the sample due to long laser exposure times |
In vivo | |
Hyperspectral Raman imaging | Able to show the amyloid plaques, neuritic plaques, or neurofibrillary tangles and is able to distinguish tissue components for margin determinations | |||
Surface-enhanced Raman scattering | Label free No need for staining High chemical specificity Combined with cryo-sampling of brain tissue |
Signal enhancement is local, mainly due to the molecules in close contact with the metallic nanostructures | In vivo | |
Label based When combined with spatially offset (SORS) the detection is possible within the skull Bio-barcode assays for differential PD diagnosis Reduced time Multiplexing capacity |
Silver nanoparticles (AgNPs) are shown to alter neurotransmitters in in vivo conditions (rats) Reliant on costly antibodies specific to NDs |
|||
Molecular Biology techniques | ELISA/Western blot | Label based High accuracy Suitable for routine protocols (predictive and diagnosis screening) |
Costly due to highly specific reagents required, invasive, and laboratory dependent Time consuming when including bioinformatics protocols |
Ex vivo |
Immunohistochemistry | ||||
Genomics (PCR, RT-PCR, DNA sequencing, (epi)transcriptomics) |