Surface Plasmon Resonance Assay for Identification of Small Molecules Capable of Inhibiting Aβ Aggregation

Dual sensitivity-enhanced microring resonance-based integrated microfluidic biosensor for Aβ42 detection

Sensitive, accurate, and straightforward biosensors are pivotal in the battle against Alzheimer's disease, particularly in light of the escalating patient population. These biosensors enable early adjunctive diagnosis, thereby facilitating prompt intervention, alleviating socioeconomic burdens, and preserving individual well-being. In this study, we introduce the development of a highly sensitive add-drop dual-microring resonant microfluidic sensing chip boasting a sensitivity of 188.11 nm/RIU, marking a significant 20.7% enhancement over single microring systems. Leveraging ultra-thin Parylene C for streamlined antibody immobilization and non-destructive removal, this platform facilitates the precise quantification of the Alzheimer's disease biomarker Aβ42. Employing an immune sensing strategy that amplifies and captures antigen signals using Au-labeled antibodies, we achieve an exceptional limit of detection of 9.02 pg/mL. The designed microring-based microfluidic biosensor chip exhibits outstanding specificity and sensitivity for Aβ42 in serum samples, offering a promising avenue for the early adjunctive diagnosis of Alzheimer's disease.

Ultrasensitive and Multiple Biomarker Discrimination for Alzheimer's Disease via Plasmonic & Microfluidic Sensing Technologies

As the population ages, the worldwide prevalence of Alzheimer's disease (AD) as the most common dementia in the elderly is increasing dramatically. However, a long-term challenge is to achieve rapid and accurate early diagnosis of AD by detecting hallmarks such as amyloid beta (Aβ42). Here, a multi-channel microfluidic-based plasmonic fiber-optic biosensing platform is established for simultaneous detection and differentiation of multiple AD biomarkers. The platform is based on a gold-coated, highly-tilted fiber Bragg grating (TFBG) and a custom-developed microfluidics. TFBG excites a high-density, narrow-cladding-mode spectral comb that overlaps with the broad absorption of surface plasmons for high-precision interrogation, enabling ultrasensitive monitoring of analytes. In situ detection and in-parallel discrimination of different forms of Aβ42 in cerebrospinal fluid (CSF) are successfully demonstrated with a detection of limit in the range of ≈30-170 pg mL-1, which is one order of magnitude below the clinical cut-off level in AD onset, providing high detection sensitivity for early diagnosis of AD. The integration of the TFBG sensor with multi-channel microfluidics enables simultaneous detection of multiple biomarkers using sub-µL sample volumes, as well as combining initial binding rate and real-time response time to differentiate between multiple biomarkers in terms of binding kinetics. With the advantages of multi-parameter, low consumption, and highly sensitive detection, the sensor represents an urgently needed potentials for large-scale diagnosis of diseases at early stage.

Peptide-antifouling interface for monitoring β-amyloid based on electrochemiluminescence resonance energy transfer

In this study, a novel antifouling electrochemiluminescence (ECL) analytical platform has been developed for the highly sensitive quantification of β-amyloid (Aβ) peptides based on the ECL resonance energy transfer (ECL-RET) mechanism. Specifically, glassy carbon electrodes (GCE) were initially coated with graphite-phase carbon nitride (g-C3N4) nanosheets, followed by the electropolymerization of polyaniline (PANI) onto the electrode surface. Subsequently, a promising peptide motif candidate (COOH-CPPPPDKDKDKDKKLVFF) was immobilized onto the PANI-modified electrode, functioning as a critical component for both antifouling and specific recognition of full-length Aβ peptides. Furthermore, this peptide motif demonstrated inhibitory effects on Aβ aggregation and dissociation. Upon immobilization of the peptide motif, Aβ aptamer-CdS QDs were bound to the electrode surface through peptide-specific interactions with Aβ, thereby facilitating the highly sensitive ECL detection of Aβ. Under the optimal conditions, the proposed biosensor exhibited an Aβ detection range from 0.1 pM to 100 nM with a detection limit of 16.1 fM. As such, this innovative platform offers a straightforward approach to antifouling, quantification, and monitoring of Aβ concentrations in the blood samples.

Sensitive and high laser damage threshold substrates for surface-enhanced Raman scattering based on gold and silver nanoparticles

Surface-enhanced Raman scattering (SERS) is a sensitive and fast technique for sensing applications such as chemical trace analysis. However, a successful, high-throughput practical implementation necessitates the availability of simple-to-use and economical SERS substrates. In this work, we present a robust, reproducible, flexible and yet cost-effective SERS substrate suited for the sensitive detection of analytes at near-infrared (NIR) excitation wavelengths. The fabrication is based on a simple dropcast deposition of silver or gold nanomaterials on an aluminium foil support, making the design suitable for mass production. The fabricated SERS substrates can withstand very high average Raman laser power of up to 400 mW in the NIR wavelength range while maintaining a linear signal response of the analyte. This enables a combined high signal enhancement potential provided by (i) the field enhancement via the localized surface plasmon resonance introduced by the noble metal nanomaterials and (ii) additional enhancement proportional to an increase of the applicable Raman laser power without causing the thermal decomposition of the analyte. The application of the SERS substrates for the trace detection of melamine and rhodamine 6G is demonstrated, which shows limits of detection smaller than 0.1 ppm and analytical enhancement factors on the order of 104 as compared to bare aluminium foil.

Controlling amyloid formation of intrinsically disordered proteins and peptides: slowing down or speeding up?

The pathological assembly of intrinsically disordered proteins/peptides (IDPs) into amyloid fibrils is associated with a range of human pathologies, including neurodegeneration, metabolic diseases and systemic amyloidosis. These debilitating disorders affect hundreds of millions of people worldwide, and the number of people affected is increasing sharply. However, the discovery of therapeutic agents has been immensely challenging largely because of (i) the diverse number of aggregation pathways and the multi-conformational and transient nature of the related proteins or peptides and (ii) the under-development of experimental pipelines for the identification of disease-modifying molecules and their mode-of-action. Here, we describe current approaches used in the search for small-molecule modulators able to control or arrest amyloid formation commencing from IDPs and review recently reported accelerators and inhibitors of amyloid formation for this class of proteins. We compare their targets, mode-of-action and effects on amyloid-associated cytotoxicity. Recent successes in the control of IDP-associated amyloid formation using small molecules highlight exciting possibilities for future intervention in protein-misfolding diseases, despite the challenges of targeting these highly dynamic precursors of amyloid assembly.

Controllable signal molecule release from Au NP-gated MSNs for photocathodic detection of ultralow level AβO

By integrating a target-responsive MSN-based controlled release system with a sensitization-SPR co-enhanced thionine/MoS₂ QDs/Cu NWs photocathode, a highly sensitive split-type PEC aptasensing platform for AβO detection in blood is constructed. Ultralow detection limit (2.1 fM) and high selectivity show great potential in early AD diagnosis.