Ultrasensitive and point-of-care detection of plasma phosphorylated tau in Alzheimer's disease using colorimetric and surface-enhanced Raman scattering dual-readout lateral flow assay

PCA-assisted direct diagnosis of Aβ proteins for Alzheimer's disease using non-metallic SERS platform of graphitic carbon nitride@metal-organic framework

Here, we explored a non-metallic surface enhanced Raman scattering (SERS) platform based on graphitic carbon nitride@metal-organic framework (g-C3N4@MOF) for the sensitive direct diagnosis of Aβ proteins, assisted by principal component analysis (PCA). By systematically optimizing the deposition voltage and time, we successfully achieved a uniform coating of g-C3N4 nanosheets over a large-area copper foil during the initial electrodeposition step. Subsequently, a homogeneous layer of flower-like MOF structures was deposited onto the g-C3N4 nanosheets through a secondary electrodeposition process. This cooperation of g-C3N4 nanosheets and flower-like MOF not only significantly enlarged the effective area for molecular enrichment but also promoted charge transfer through energy-level matching between the two materials. The characteristic SERS spectra of Aβ40 and Aβ42, enhanced by the g-C3N4@MOF composite substrate, were recorded and classified using PCA to extract informative features of these important biomarkers. This research exploits a new avenue for the clinical assay of neurodegenerative diseases by extracting informative features of key biomarkers.

A dual mode biosensor based on self-enhanced polyfluorene nanomaterial for fluorescence and electrochemiluminescence detection of Tau protein

Dual mode detection can overcome the poor anti-interference ability of single-mode detection, and greatly improve the detection accuracy. Fluorescence/electrochemiluminescence (FL/ECL) dual mode detection combines the advantages of FL and ECL, and has a promising application in bioanalysis. Common FL/ECL dual mode detection used different signal probes. Multiple signal probes inevitably have complex operation and uncontrollable differences between the two modes. In this work, poly [9,9-dioctylfluorenyl-2,7-diyl]-End-capped with 2,5-diphenyl-1,2,4-oxadiazole (PFO) was functionalized by sodium dodecyl sulfate (SDS) and polyethylenimine (PEI), and the resulting PFO-SDS-PEI nanoparticles (PSP NPs) exhibited excellent FL and ECL performance at the same time, so were creatively developed as mono-luminophore-based signal probe for FL/ECL dual-mode detection. The functional reagent SDS can significantly improve the water dispersion of luminophores, and PEI can not only provide amino functional groups for assembling biomolecules, but also significantly enhance the FL and ECL signals of the luminophores. Self-enhanced PSP NPs coupled strand displacement reaction (SDR) mediated by exonuclease Ⅲ (Exo Ⅲ) to achieve FL/ECL dual-mode detection of Tau protein, a biomarker of Alzheimer's disease (AD). The linear ranges for FL and ECL detection were 0.001-500 pg/mL and 0.00001-1.0 pg/mL and the limit of detections were 549.16 ag/mL and 5.45 ag/mL, respectively, showing good application potential. Self-enhanced PSP NPs provided an ideal mono-luminophore-based signal probe for FL/ECL dual-mode detection, and built a new method for detecting AD biomarker.

Using Machine Learning to Design a FeMOF Bidirectional Regulator for Electrochemiluminescence Sensing of Tau Protein

The single-luminophore-based ratiometric electrochemiluminescence (ECL) sensor coupling bidirectional regulator has become a research hotspot in the detection field because of its simplicity and accuracy. However, the limited bidirectional regulator hinders its further development. In this study, by leveraging the robust predictive capabilities of machine learning, we prepared an Fe-based metal-organic framework (FeMOF) as a bidirectional regulator for modulating the dual-emission ECL signals of a single luminophore for the first time. The proof of concept was demonstrated by applying FeMOF to the classical luminophore Ru(bpy)32+, and the results showed its ability to enhance the cathode ECL signal (Ecathode) and inhibit the anode ECL signal (Eanode). As an example, a ratiometric ECL sensor for Tau protein (Tau) detection utilizing the FeMOF/Ru(bpy)32+ system was developed. The incorporation of a bidirectional regulator in the ECL system effectively mitigated erratic fluctuations or minor discrepancies between the two signals and showed a stronger correlation and stability of Ecathode/Eanode than before regulation. As a result, the ECL sensor showed good analytical performance with a detection limit as low as 3.38 fg mL-1 (S/N = 3). Moreover, it was not only comparable in test results to the commercially available ELISA kit but also could well distinguish between normal and Alzheimer's disease (AD) patients (80% specificity and 90% sensitivity). Thus, the proposed strategy is promising to be extended to other ECL luminophores or MOFs, providing a new path for ratiometric ECL sensors.

Engineering an Ionic Aggregation-Induced Luminescence-Labeled Fluorescence Lateral Flow Immunoassay for C-Reactive Protein in Human Plasma

The surge of lateral flow immunoassays (LFAs) stimulates researchers to explore the novel vibrant aggregation-induced emission luminogen (AIEgen)-doped nanoparticles to improve the accuracy and reliability of LFAs. However, the loading amount of AIEgens currently used for the LFA in microspheres is limited due to their symmetrical large conjugated skeleton structure, which significantly reduces the fluorescence brightness of the signal reporter in the LFA. Herein, an ionic AIEgens with a donor-acceptor type was developed as the signal reporter of the LFA for C-reactive protein (CRP). Ionic AIEgens are unable to enter the hydrophobic cavity of polystyrene nanoparticles (PS) because of their low hydrophobic nature. By altering ionic AIEgens with extended alkyl chains, it is possible to increase their hydrophobicity, thereby potentially increasing the loading capacity within PS. Notably, the fluorescent nanoparticles (denoted as AIETPANPs) formed by embedding (E)-4-(4-(diphenylamino)styryl)-1-octadecylpyridin-1-ium iodide (TPA) in PS showed orange-red fluorescence emission and have high fluorescence quantum yield. Anti-CRP antibody (mAb1) could be effectively conjugated to the surface of AIETPANPs by an amino-carboxyl reaction, resulting in AIETPANPs-mAb1. The AIETPANPs-mAb1 exhibited a fluorescence emission at 613 nm, a point detectable by the naked eye with minimal background interference. The entire analysis was accomplished in just 10 min, achieving a limit of detection of 4.06 ng/mL for CRP. The AIETPANPs-mAb1-based LFA demonstrates excellent stability and specificity and fully meets the requirements for clinical diagnosis.

MXene Bimetallic Coating Synergistic Enhanced Colorimetric-Raman Dual Signal-Based Immunochromatographic Assay for Advancing Detection Performance

Herein, a three-dimensional thin film-like multifunctional MXene bimetallic coating material (Ti3C2@Au-Ag) with strong color intensity, high surface-enhanced Raman scattering (SERS) activity, and strong antibody affinity (1.00 × 108 M-1) was prepared. It was the first time that Ti3C2@Au-Ag-based colorimetric-SERS dual-signal immunochromatographic assay (ICA) was developed for the detection of dexamethasone, achieving the limits of detection of 0.0089, 0.14, and 0.084 μg/kg for milk, beef, and pork in colorimetric mode and 0.0015, 0.060, and 0.075 μg/kg in SERS mode. It was up to 200-fold more sensitive than the reported ICAs. The recoveries were 82.0%-112.6%, and the coefficients of variation were 1.4%-13.7%. The Ti3C2@Au-Ag-ICA was verified by LC-MS/MS in the application on 30 real samples with a correlation coefficient greater than 0.98. This study can provide efficient theoretical and practical value for the development of a colorimetric-SERS dual-signal immunoassay platform.

Highly sensitive blood-based biomarkers detection of beta-amyloid and phosphorylated-tau181 for Alzheimer's disease

Background

Plasma biomarker has the potential to be the reliable and propagable approach in the early stage diagnosis of Alzheimer's disease (AD). However, conventional methods appear powerless in the detection of these biomarkers at low concentrations in plasma. Here, we determined plasma biomarker concentrations of patients across the AD spectrum by an improved digital enzyme-linked immunosorbent assay (ELISA) technique. Confirms the predictive and diagnostic value of this method for AD patients and study the relationships between these biomarkers and cognitive status.

Methods

Plasma concentrations of amyloid-beta 40 (Aβ40), amyloid-beta 42 (Aβ42) and plasma phosphorylated tau at threonine 181 (p-tau181) were determined in 43 AD patients, 33 mild cognitive impairment (MCI) patients and 40 normal cognition (NC) subjects as healthy controls using the improved digital ELISA technique. In addition, all subjects were required to receive neuropsychological assessments.

Results

Plasma p-tau181 level showed certain discrepancies between NC and MCI (p < 0.05), AD (p < 0.01) groups. The level of plasma Aβ42 (p < 0.05) and Aβ40 (p < 0.01) was significantly different between AD and NC group. The p-tau181 level was able to distinguish AD (AUC = 0.8768) and MCI (AUC = 0.7932) from NC with higher accuracy than Aβ42/Aβ40 ratio (AUC = 0.8343, AUC = 0.6569). Both p-tau181 (CDR: r = 0.388 p < 0.001; MMSE: r = -0.394 p < 0.001) and Aβ42/Aβ40 ratio (CDR: r = -0.413 p < 0.001; MMSE: r = 0.358 p < 0.001) showed stronger positive correlation with clinical dementia rating (CDR) and mini mental state examination (MMSE) scores than Aβ42 (CDR: r = -0.280 p = 0.003; MMSE: r = 0.266 p = 0.005) or Aβ40 (CDR: r = 0.373 p < 0.001; MMSE: r = -0.288 p = 0.002) alone.

Conclusion

Plasma p-tau181 level and Aβ42/Aβ40 ratio showed promising values in diagnosis of AD and MCI. Our results indicate that this improved digital ELISA diagnosis approach can facilitate early recognition and management of AD and pre-AD patients.

Recent advances of biocompatible optical nanobiosensors in liquid biopsy: towards early non-invasive diagnosis

Liquid biopsy is a non-invasive diagnostic method that can reduce the risk of complications and offers exceptional benefits in the dynamic monitoring and acquisition of heterogeneous cell population information. Optical nanomaterials with excellent light absorption, luminescence, and photoelectrochemical properties have accelerated the development of liquid biopsy technologies. Owing to the unique size effect of optical nanomaterials, their improved optical properties enable them to exhibit good sensitivity and specificity for mitigating signal interference from various molecules in body fluids. Nanomaterials with biocompatible and optical sensing properties play a crucial role in advancing the maturity and diversification of liquid biopsy technologies. This article offers a comprehensive review of recent advanced liquid biopsy technologies that utilize novel biocompatible optical nanomaterials, including fluorescence, colorimetric, photoelectrochemical, and Raman broad-spectrum-based biosensors. We focused on liquid biopsy for the most significant early biomarkers in clinical medicine, and specifically reviewed reports on the effectiveness of optical nanosensing technology in the detection of real patient samples, which may provide basic evidence for the transition of optical nanosensing technology from engineering design to clinical practice. Furthermore, we introduced the integration of optical nanosensing-based liquid biopsy with modern devices, such as smartphones, to demonstrate the potential of the technology in portable clinical diagnosis.

Reduced GLP-1R availability in the caudate nucleus with Alzheimer's disease

The glucagon-like peptide-1 receptor (GLP-1R) agonists reduce glycated hemoglobin in patients with type 2 diabetes. Mounting evidence indicates that the potential of GLP-1R agonists, mimicking a 30 amino acid ligand, GLP-1, extends to the treatment of neurodegenerative conditions, with a particular focus on Alzheimer's disease (AD). However, the mechanism that underlies regulation of GLP-1R availability in the brain with AD remains poorly understood. Here, using whole transcriptome RNA-Seq of the human postmortem caudate nucleus with AD and chronic hydrocephalus (CH) in the elderly, we found that GLP-1R and select mRNAs expressed in glucose dysmetabolism and dyslipidemia were significantly altered. Furthermore, we detected human RNA indicating a deficiency in doublecortin (DCX) levels and the presence of ferroptosis in the caudate nucleus impacted by AD. Using the genome data viewer, we assessed mutability of GLP-1R and 39 other genes by two factors associated with high mutation rates in chromosomes of four species. Surprisingly, we identified that nucleotide sizes of GLP-1R transcript exceptionally differed in all four species of humans, chimpanzees, rats, and mice by up to 6-fold. Taken together, the protein network database analysis suggests that reduced GLP-1R in the aged human brain is associated with glucose dysmetabolism, ferroptosis, and reduced DCX+ neurons, that may contribute to AD.

Aβ42 and ROS dual-targeted multifunctional nanocomposite for combination therapy of Alzheimer's disease

Amyloid-β (Aβ) readily misfolds into neurotoxic aggregates, generating high levels of reactive oxygen species (ROS), leading to progressive oxidative damage and ultimately cell death. Therefore, simultaneous inhibition of Aβ aggregation and scavenging of ROS may be a promising therapeutic strategy to alleviate Alzheimer's disease pathology. Based on the previously developed antibody 1F12 that targets all forms of Aβ42, we developed an Aβ42 and ROS dual-targeting nanocomposite using biodegradable mesoporous silica nanoparticles as carriers to load ultra-small cerium oxide nanocrystals (bMSNs@Ce-1F12). By modifying the brain-targeted rabies virus glycoprotein 29 (RVG29-bMSNs@Ce-1F12), this intelligent nanocomposite can efficiently target brain Aβ-rich regions. Combined with peripheral and central nervous system treatments, RVG29-bMSNs@Ce-1F12 can significantly alleviate AD symptoms by inhibiting Aβ42 misfolding, accelerating Aβ42 clearance, and scavenging ROS. Furthermore, this synergistic effect of ROS scavenging and Aβ clearance exhibited by this Aβ42 and ROS dual-targeted strategy also reduced the burden of hyperphosphorylated tau, alleviated glial cell activation, and ultimately improved cognitive function in APP/PS1 mice. Our findings indicate that RVG29-bMSNs@Ce-1F12 is a promising nanodrug that can facilitate multi-target treatment of AD.

Diagnosis of Alzheimer's disease: Towards accuracy and accessibility

Alzheimer's disease (AD) is a serious dementia afflicting aging population and is characterized by cognitive decline, amyloid-β plaques, and neurofibrillary tangles. AD substantially impairs the life quality of the victims and poses a heavy burden on the society at large. The number of people with dementia due to AD, prodromal AD, and preclinical AD is estimated to stand at roughly 3.2, 69, and 315 million worldwide, respectively. Current clinical diagnosis is based on clinical symptoms, and clinical research demonstrated that positron emission tomography (PET) and cerebrospinal fluid (CSF) biomarkers had excellent diagnostic performance. However, the application of CSF biomarker tests and PET are restricted by the invasiveness and high cost. The presence of clinical symptoms means that AD pathology has been progressing for many years, and only a few drugs have been approved for the traetemnt of AD. Therefore, early diagnosis is extremely important for controlling the outcomes caused by AD. In this review, we provided an overview of developing clinical diagnostic criteria, diagnostic strategies under clinical research, developing blood based-biomarker assays, and promising nanotechnologically-based assays.

Recent advances in SERS-based immunochromatographic assay for pathogenic microorganism diagnosis: A review

Infectious diseases caused by bacteria, viruses, fungi, and other pathogenic microorganisms are among the most harmful public health problems in the world, causing tens of millions of deaths and incalculable economic losses every year. The establishment of rapid, simple, and highly sensitive diagnostic methods for pathogenic microorganisms is important for the prevention and control of infectious diseases, guidance of timely treatment, and the reduction of public safety risks. Lateral flow immunoassay (LFA) based on the colorimetric signal of colloidal gold is the most popular point-of-care testing technology at present, but it is limited by poor sensitivity and low throughput and hardly meets the needs of the highly sensitive screening of pathogenic microorganisms. In recent years, the combination of surface-enhanced Raman scattering (SERS) and LFA technology has developed into a novel analytical platform with high sensitivity and multiple detection capabilities and has shown great advantages in the detection of pathogenic microorganisms and infectious diseases. This review summarizes the working principle, design ideas, and application of the existing SERS-based LFA methods in pathogenic microorganism detection and further introduces the effect of new technologies such as Raman signal encoding, magnetic enrichment, novel membrane nanotags, and integrated Raman reading equipment on the performance of SERS-LFA. Finally, the main challenges and the future direction of development in this field of SERS-LFA are discussed.

Advancing Brain Research through Surface-Enhanced Raman Spectroscopy (SERS): Current Applications and Future Prospects

Surface-enhanced Raman spectroscopy (SERS) has recently emerged as a potent analytical technique with significant potential in the field of brain research. This review explores the applications and innovations of SERS in understanding the pathophysiological basis and diagnosis of brain disorders. SERS holds significant advantages over conventional Raman spectroscopy, particularly in terms of sensitivity and stability. The integration of label-free SERS presents promising opportunities for the rapid, reliable, and non-invasive diagnosis of brain-associated diseases, particularly when combined with advanced computational methods such as machine learning. SERS has potential to deepen our understanding of brain diseases, enhancing diagnosis, monitoring, and therapeutic interventions. Such advancements could significantly enhance the accuracy of clinical diagnosis and further our understanding of brain-related processes and diseases. This review assesses the utility of SERS in diagnosing and understanding the pathophysiological basis of brain disorders such as Alzheimer's and Parkinson's diseases, stroke, and brain cancer. Recent technological advances in SERS instrumentation and techniques are discussed, including innovations in nanoparticle design, substrate materials, and imaging technologies. We also explore prospects and emerging trends, offering insights into new technologies, while also addressing various challenges and limitations associated with SERS in brain research.

SERS-Based Optical Nanobiosensors for the Detection of Alzheimer's Disease

Alzheimer's disease (AD) is a leading cause of dementia, impacting millions worldwide. However, its complex neuropathologic features and heterogeneous pathophysiology present significant challenges for diagnosis and treatment. To address the urgent need for early AD diagnosis, this review focuses on surface-enhanced Raman scattering (SERS)-based biosensors, leveraging the excellent optical properties of nanomaterials to enhance detection performance. These highly sensitive and noninvasive biosensors offer opportunities for biomarker-driven clinical diagnostics and precision medicine. The review highlights various types of SERS-based biosensors targeting AD biomarkers, discussing their potential applications and contributions to AD diagnosis. Specific details about nanomaterials and targeted AD biomarkers are provided. Furthermore, the future research directions and challenges for improving AD marker detection using SERS sensors are outlined.

Rapid and simultaneous detection of SARS-CoV-2 and influenza A using vertical flow assay based on AAO and SERS nanotags

A highly sensitive SERS-VFA sensor was developed to determine SARS-CoV-2 or influenza A infection simultaneously, especially during co-pandemics.