Monitoring amyloid-β 42 conformational change using a spray-printed graphene electrode

Up to now, the reproducibility and stability of graphene-based electrochemical sensors have represented an obstacle to the development of practical biosensing techniques. In this paper we report a cost-effective and highly reproducible graphene-based electrochemical sensing platform to monitor the kinetic conformational change of amyloidogenic proteins. The sensor surface is spray-printed with a graphene oxide layer and then electrochemically reduced to achieve excellent sensitivity to the redox current. The reproducibility of these sensors in terms of redox peak position, intensity and electroactive area has been proved to be high. These sensors are used to monitor the conformational changes of amyloid-β 42 via the change in the oxidation current of tyrosine, which is caused by different electrochemical accessibility during the aggregation process. The aggregation process detected at these graphene electrochemical sensors shows a good correlation with the fluorescence assay. The proposed platform provides a complementary technique to aid understanding of the detailed process of amyloidogenic protein aggregation and the mechanism of neurodegenerative diseases as well as helping to promote the development of disease-prevention strategies

Mind the gap: State-of-the-art technologies and applications for EEG-based brain-computer interfaces

Brain–computer interfaces (BCIs) provide bidirectional communication between the brain and output devices that translate user intent into function. Among the different brain imaging techniques used to operate BCIs, electroencephalography (EEG) constitutes the preferred method of choice, owing to its relative low cost, ease of use, high temporal resolution, and noninvasiveness. In recent years, significant progress in wearable technologies and computational intelligence has greatly enhanced the performance and capabilities of EEG-based BCIs (eBCIs) and propelled their migration out of the laboratory and into real-world environments. This rapid translation constitutes a paradigm shift in human–machine interaction that will deeply transform different industries in the near future, including healthcare and wellbeing, entertainment, security, education, and marketing. In this contribution, the state-of-the-art in wearable biosensing is reviewed, focusing on the development of novel electrode interfaces for long term and noninvasive EEG monitoring. Commercially available EEG platforms are surveyed, and a comparative analysis is presented based on the benefits and limitations they provide for eBCI development. Emerging applications in neuroscientific research and future trends related to the widespread implementation of eBCIs for medical and nonmedical uses are discussed. Finally, a commentary on the ethical, social, and legal concerns associated with this increasingly ubiquitous technology is provided, as well as general recommendations to address key issues related to mainstream consumer adoption

A novel Aβ40 assembly at physiological concentration

Aggregates of amyloid-β (Aβ) are characteristic of Alzheimer’s disease, but there is no consensus as to either the nature of the toxic molecular complex or the mechanism by which toxic aggregates are produced. We report on a novel feature of amyloid-lipid interactions where discontinuities in the lipid continuum can serve as catalytic centers for a previously unseen microscale aggregation phenomenon. We show that specific lipid membrane conditions rapidly produce long contours of lipid-bound peptide, even at sub-physiological concentrations of Aβ. Using single molecule fluorescence, time-lapse TIRF microscopy and AFM imaging we characterize this phenomenon and identify some exceptional properties of the aggregation pathway which make it a likely contributor to early oligomer and fibril formation, and thus a potential critical mechanism in the etiology of AD. We infer that these amyloidogenic events occur only at areas of high membrane curvature, which suggests a range of possible mechanisms by which accumulated physiological changes may lead to their inception. The speed of the formation is in hours to days, even at 1 nM peptide concentrations. Lipid features of this type may act like an assembly line for monomeric and small oligomeric subunits of Aβ to increase their aggregation states. We conclude that under lipid environmental conditions, where catalytic centers of the observed type are common, key pathological features of AD may arise on a very short timescale under physiological concentration

Probing synaptic amyloid-beta aggregation promoted by copper release

Whether or not the metal ions released during synaptic transmission induce amyloid-beta oligomer formation in the vicinity of synapses is a central question pertinent to the molecular mechanism of Alzheimer's disease. Recently, through a combination of experimental kinetics studies and coupled reaction-diffusion simulations, we predicted that Cu(II) rather than Zn(II) plays an important role in the very early stages (i.e., dimer formation) of Aβ aggregation in the synapse. Single molecule photobleaching analysis is a powerful tool to determine the stoichiometry of amyloid-beta oligomers which enables us to examine the time course of small amyloid-beta oligomer formation in solution, immobilised to a solid-phase substrate or artificial lipid membrane, and in live neurons in the presence of Cu(II). Preliminary results indicate that small amyloid-beta oligomers can be locked in their oligomeric state without dissociation on a poly-lysine coated surface and that Cu(II) increases the diversity and abundance of amyloid-beta oligomers

The docking of synaptic vesicles on the presynaptic membrane induced by α-synuclein is modulated by lipid composition

α-Synuclein (αS) is a presynaptic disordered protein whose aberrant aggregation is associated with Parkinson’s disease. The functional role of αS is still debated, although it has been involved in the regulation of neurotransmitter release via the interaction with synaptic vesicles (SVs). We report here a detailed characterisation of the conformational properties of αS bound to the inner and outer leaflets of the presynaptic plasma membrane (PM), using small unilamellar vesicles. Our results suggest that αS preferentially binds the inner PM leaflet. On the basis of these studies we characterise in vitro a mechanism by which αS stabilises, in a concentration-dependent manner, the docking of SVs on the PM by establishing a dynamic link between the two membranes. The study then provides evidence that changes in the lipid composition of the PM, typically associated with neurodegenerative diseases, alter the modes of binding of αS, specifically in a segment of the sequence overlapping with the non-amyloid component region. Taken together, these results reveal how lipid composition modulates the interaction of αS with the PM and underlie its functional and pathological behaviours in vitro

The docking of synaptic vesicles on the presynaptic membrane induced by α-synuclein is modulated by lipid composition

α-Synuclein (αS) is a presynaptic disordered protein whose aberrant aggregation is associated with Parkinson’s disease. The functional role of αS is still debated, although it has been involved in the regulation of neurotransmitter release via the interaction with synaptic vesicles (SVs). We report here a detailed characterisation of the conformational properties of αS bound to the inner and outer leaflets of the presynaptic plasma membrane (PM), using small unilamellar vesicles. Our results suggest that αS preferentially binds the inner PM leaflet. On the basis of these studies we characterise in vitro a mechanism by which αS stabilises, in a concentration-dependent manner, the docking of SVs on the PM by establishing a dynamic link between the two membranes. The study then provides evidence that changes in the lipid composition of the PM, typically associated with neurodegenerative diseases, alter the modes of binding of αS, specifically in a segment of the sequence overlapping with the non-amyloid component region. Taken together, these results reveal how lipid composition modulates the interaction of αS with the PM and underlie its functional and pathological behaviours in vitro

Surface electromyography using dry polymeric electrodes.

Conventional wet Ag/AgCl electrodes are widely used in electrocardiography, electromyography (EMG), and electroencephalography (EEG) and are considered the gold standard for biopotential measurements. However, these electrodes require substantial skin preparation, are single use, and cannot be used for continuous monitoring (>24 h). For these reasons, dry electrodes are preferable during surface electromyography (sEMG) due to their convenience, durability, and longevity. Dry conductive elastomers (CEs) combine conductivity, flexibility, and stretchability. In this study, CEs combining poly(3,4-ehtylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) in polyurethane are explored as dry, skin contacting EMG electrodes. This study compares these CE electrodes to commercial wet Ag/AgCl electrodes in five subjects, classifying four movements: open hand, fist, wrist extension, and wrist flexion. Classification accuracy is tested using a backpropagation artificial neural network. The control Ag/AgCl electrodes have a 98.7% classification accuracy, while the dry conductive elastomer electrodes have a classification accuracy of 99.5%. As a conclusion, PEDOT based dry CEs were shown to successfully function as on-skin electrodes for EMG recording, matching the performance of Ag/AgCl electrodes, while addressing the need for minimal skin prep, no gel, and wearable technology

Quantitative comparison of different iron forms in the temporal cortex of Alzheimer patients and control subjects

Quantum Matter and Optic