A magnetoimpedance biosensor microfluidic platform for detection of glial fibrillary acidic protein in blood for acute stroke classification

Upconversion nanoparticle-based optical biosensor for early diagnosis of stroke

Over 17 million people experience a stroke episode annually, with 5.9 million deaths. Stroke is diagnosed by physical tests and neuroimaging which need to be performed quickly to determine if the stroke is caused by ischaemia or haemorrhage. Neuroimaging can reliably confirm bleeding, but many patients with suspected ischaemic stroke (up to 40%) are subsequently confirmed to have alternative pathologies e.g., migraine or seizures (stroke mimics) delaying the transfer of stroke patients to an acute stroke unit for early intervention and treatment. Thus, a simple complimentary blood biomarker test to differentiate stroke patients from non-stroke patients with similar clinical symptoms is essential in prehospital and emergency settings for efficient stroke management and prompt treatment. The current 'Gold Standard' technique for detecting protein biomarkers is complex, time-consuming, and requires automated equipment. In this study, we have developed a proof-of-concept of lanthanide-doped upconversion nanoparticle (UCNP)-based optical biosensor platform for detecting glial fibrillary acidic protein (GFAP), a potential stroke biomarker, in human blood serum. The results show a linear response in photoluminescence quenching of UCNP conjugated GFAP antibody with the increasing concentration of GFAP biomarker in human blood serum. This approach can be used in the ambulance and Emergency Department to quickly diagnose a stroke. In the longer term, such techniques can be integrated into a self-assessment kit to monitor those patients who are at risk after strokes.

Biosensors for early stroke detection

This article aims to provide a comprehensive review of the latest advances in biosensor technology for early stroke diagnosis. Analyzing current research from authoritative databases highlights the significance of biosensors in improving stroke detection and treatment outcomes, discusses their diagnostic capabilities, and addresses the challenges that must be overcome for broader clinical application. This review utilizes updated information and valid research from ISI, Google Scholar, Science Direct, Scopus, and PubMed to examine recent developments in biosensors applicable to early stroke diagnosis. The results indicate that biosensors are crucial for the early detection of strokes, and enhance treatment efficacy. The biosensors studied in this research serve as rapid and non-intrusive diagnostic instruments with exceptional precision and detection capabilities. Cutting-edge biosensors can identify distinct stroke-related biomarkers, offering rapid and non-invasive diagnostic solutions to improve stroke care outcomes. Despite these advancements, significant challenges remain regarding the sensitivity, specificity, and reliability of biosensors. These issues must be resolved to facilitate their widespread implementation in clinical settings.

An integrated magnetoimpedance biosensor microfluidic magnetic platform for the evaluation of the cardiac marker cTnI

An integrated magnetoimpedance (MI) biosensor microfluidic magnetic platform was proposed for the evaluation of the cardiac marker, cardiac troponin I (cTnI). This bioanalyte evaluation platform mainly comprised three external permanent magnets (PMs), one MI element, two peelable SiO2 film units and a microfluidic chip (MFC). The MI element was made of micro-electro-mechanical system (MEMS)-based multilayered [Ti (6 nm)/FeNi (100 nm)]5/Cu (400 nm)/[Ti (6 nm)/FeNi (100 nm)]5 thin films and designed as meander structures with closed magnetic flux. The MFC was fabricated using 3D printing and inverted molding techniques, designed with a solution by mixing the reaction region, magnetic separation region and detection region. Peelable SiO2 film units with the same size as the MI sensing element were used as the immunoreactivity interface of the bioanalytes. Two large PMs were placed directly below the MI sensing unit to provide a bias magnetic field, and the smaller PM was embedded in MCF for magnetic separation function. Different concentrations of the biological target (cTnI antigen)-, PBS buffer-, and Dynabeads-labeled polyclonal cTnI antibody solution were injected sequentially into the MCF. After immunoreactivity and magnetic separation, a classical sandwich immunoreaction process occurred on the surface of the monoclonal antibody-modified SiO2 film via self-assembling process in the reaction region of the MFC. The fundamental principle for evaluation of cTnI was based on variations of the MI signal under different concentrations of the biological target coupled with different numbers of Dynabeads. It was demonstrated that the mentioned MI-based magnetic platform could perform quantitative detection analyses over a range of cTnI concentrations (lowest concentration = 0.1 ng mL-1 and highest concentration = 100 ng mL-1). The proposed MI-based magnetic platform provides a sensitive, reliable, stable and reusable bioanalytical platform, and it has potential in future biomedical applications.

Sensitivity evaluation of an optical microfiber featuring interfaces with various gold nanoparticle morphologies: Application to the GFAP detection

Glial fibrillary acidic protein (GFAP) is a specific blood biomarker for various neurological diseases, including traumatic brain injury (TBI). In this study, we present a cost-effective, portable, and label-free biosensing method for the sensitive and rapid detection of GFAP in body fluids. As the sensitivity of current optical fiber sensors is insufficient to detect the ultralow concentration of GFAP in early body fluids, interfaces of gold nanoparticles with various morphologies were employed to improve the sensitivity of sensor. The optical microfiber sensor with gold nanostar interface demonstrated superior evanescent field enhancement compared to other gold interfaces, thereby enabling the optical microfiber sensor with gold nanostar interface to exhibit higher sensitivity. This sensor detected GFAP at concentrations ranging from 1 aM to 0.1 nM, with a limit of detection (LOD) of 0.09 aM in phosphate buffered saline (PBS) solution, being capable of detecting GFAP molecules at the single-molecule level. The compactness, portability, and high selectivity of the biosensor allow for its use in detecting GFAP in body fluids, such as serum and artificial cerebrospinal fluid (CSF), with LODs of 0.21 aM and 0.1 aM, respectively. This study introduces a valuable tool for the early diagnosis of TBI. The ultra-sensitive detection of GFAP in serum provides information on the severity of TBI in addition to imaging techniques.

Current Trends in Stroke Biomarkers: The Prognostic Role of S100 Calcium-Binding Protein B and Glial Fibrillary Acidic Protein

Stroke is the third leading cause of death in the developed world and a major cause of chronic disability, especially among the elderly population. The major biomarkers of stroke which are the most promising for predicting onset time and independently differentiating ischemic from hemorrhagic and other stroke subtypes are at present limited to a few. This review aims to emphasize on the prognostic role of S100 calcium-binding protein b (S100B), and Glial Fibrillary Acidic Protein (GFAP) in patients with stroke. An electronic search of the published research from January 2000 to February 2024 was conducted using the MEDLINE, Scopus, and Cochrane databases. The implementation of S100B and GFAP in existing clinical scales and imaging modalities may be used to improve diagnostic accuracy and realize the potential of blood biomarkers in clinical practice. The reviewed studies highlight the potential of S100B and GFAP as significant biomarkers in the prognosis and diagnosis of patients with stroke and their ability of predicting long-term neurological deficits. They demonstrate high sensitivity and specificity in differentiating between ischemic and hemorrhagic stroke and they correlate well with stroke severity and outcomes. Several studies also emphasize on the early elevation of these biomarkers post-stroke onset, underscoring their value in early diagnosis and risk stratification. The ongoing research in this field should aim at improving patient outcomes and reducing stroke-related morbidity and mortality by developing a reliable, non-invasive diagnostic tool that can be easily implemented in several healthcare settings, with the ultimate goal of improving stroke management.

Deformed graphene FET biosensor on textured glass coupled with dielectrophoretic trapping for ultrasensitive detection of GFAP

Numerous efforts have been undertaken to mitigate the Debye screening effect of FET biosensors for achieving higher sensitivity. There are few reports that show sub-femtomolar detection of biomolecules by FET mechanisms but they either suffer from significant background noise or lack robust control. In this aspect, deformed/crumpled graphene has been recently deployed by other researchers for various biomolecule detection like DNA, COVID-19 spike proteins and immunity markers like IL-6 at sub-femtomolar levels. However, the chemical vapor deposition (CVD) approach for graphene fabrication suffers from various surface contamination while the transfer process induces structural defects. In this paper, an alternative fabrication methodology has been proposed where glass substrate has been initially texturized by wet chemical etching through the sacrificial layer of synthesized silver nanoparticles, obtained by annealing of thin silver films leading to solid state dewetting. Graphene has been subsequently deposited by thermal reduction technique from graphene oxide solution. The resulting deformed graphene structure exhibits higher sensor response towards glial fibrillary acidic protein (GFAP) detection with respect to flat graphene owing to the combined effect of reduced Debye screening and higher surface area for receptor immobilization. Additionally, another interesting aspect of the reported work lies in the biomolecule capture by dielectrophoretic (DEP) transport on the crests of the convex surfaces of graphene in a coplanar gated topology structure which has resulted in 10 aM and 28 aM detection limits of GFAP in buffer and undiluted plasma respectively, within 15 min of application of analyte. The detection limit in buffer is almost four decades lower than that documented for GFAP using biosensors which is is expected to pave way for advancing graphene FET based sensors towards ultrasensitive point-of-care diagnosis of GFAP, a biomarker for traumatic brain injury.

Sustained release of vascular endothelial growth factor A and basic fibroblast growth factor from nanofiber membranes reduces oxygen/glucose deprivation-induced injury to neurovascular units

Upregulation of vascular endothelial growth factor A/basic fibroblast growth factor (VEGFA/bFGF) expression in the penumbra of cerebral ischemia can increase vascular volume, reduce lesion volume, and enhance neural cell proliferation and differentiation, thereby exerting neuroprotective effects. However, the beneficial effects of endogenous VEGFA/bFGF are limited as their expression is only transiently increased. In this study, we generated multilayered nanofiber membranes loaded with VEGFA/bFGF using layer-by-layer self-assembly and electrospinning techniques. We found that a membrane containing 10 layers had an ideal ultrastructure and could efficiently and stably release growth factors for more than 1 month. This 10-layered nanofiber membrane promoted brain microvascular endothelial cell tube formation and proliferation, inhibited neuronal apoptosis, upregulated the expression of tight junction proteins, and improved the viability of various cellular components of neurovascular units under conditions of oxygen/glucose deprivation. Furthermore, this nanofiber membrane decreased the expression of Janus kinase-2/signal transducer and activator of transcription-3 (JAK2/STAT3), Bax/Bcl-2, and cleaved caspase-3. Therefore, this nanofiber membrane exhibits a neuroprotective effect on oxygen/glucose-deprived neurovascular units by inhibiting the JAK2/STAT3 pathway.

Giant Magnetoimpedance Effect of Multilayered Thin Film Meanders Formed on Flexible Substrates

The giant magnetoimpedance effect of multilayered thin films under stress has great application prospects in magnetic sensing, but related studies are rarely reported. Therefore, the giant magnetoimpedance effects in multilayered thin film meanders under different stresses were thoroughly investigated. Firstly, multilayered FeNi/Cu/FeNi thin film meanders with the same thickness were manufactured on polyimide (PI) and polyester (PET) substrates by DC magnetron sputtering and MEMS technology. The characterization of meanders was analyzed by SEM, AFM, XRD, and VSM. The results show that multilayered thin film meanders on flexible substrates also have the advantages of good density, high crystallinity, and excellent soft magnetic properties. Then, we observed the giant magnetoimpedance effect under tensile and compressive stresses. The results show that the application of longitudinal compressive stress increases the transverse anisotropy and enhances the GMI effect of multilayered thin film meanders, while the application of longitudinal tensile stress yields the opposite result. The results provide novel solutions for the fabrication of more stable and flexible giant magnetoimpedance sensors, as well as for the development of stress sensors.

Ultrasensitive Determination of Glial-Fibrillary-Acidic-Protein (GFAP) in Human Serum-Matrix with a Label-Free Impedimetric Immunosensor

In this work, immobilizing anti-GFAP antibodies via covalent attachment onto L-cysteine/gold nanoparticles that were modified with screen-printed carbon electrodes (Anti-GFAP/L-cys/AuNps/SPCE) resulted in the development of a sensitive label-free impedance immunosensor for the detection of Glial Fibrillary Acidic Protein (GFAP). The immunosensor's stepwise construction was studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). L-cysteine was chosen as the linker between GFAP antibodies and Au NPs/SPCE because it enables the guided and stable immobilization of GFAP antibodies, thus resulting in increased immunosensor sensitivity. As a redox probe, 5 mM of [Fe(CN)6]3-/4- was used to measure the electron-transfer resistance (Ret), which was raised by the binding of antigens to the immobilized anti-GFAP on the surface of the modified electrode. A linear correlation between Rct and GFAP concentration was achieved under optimum conditions in the range of 1.0-1000.0 pg/mL, with an extraordinarily low detection limit of 51.0 fg/mL. The suggested immunosensor was successfully used to detect the presence of GFAP in human blood serum samples, yielding good findings. As a result, the proposed platform may be utilized to monitor central nervous system injuries.

Expression pattern and clinical value of Key RNA methylation modification regulators in ischemic stroke

Ischemic stroke (IS) is one of the major causes of death and disability worldwide, and effective diagnosis and treatment methods are lacking. RNA methylation, a common epigenetic modification, plays an important role in disease progression. However, little is known about the role of RNA methylation modification in the regulation of IS. The aim of this study was to investigate RNA methylation modification patterns and immune infiltration characteristics in IS through bioinformatics analysis. We downloaded gene expression profiles of control and IS model rat brain tissues from the Gene Expression Omnibus database. IS profiles were divided into two subtypes based on RNA methylation regulators, and functional enrichment analyses were conducted to determine the differentially expressed genes (DEGs) between the subtypes. Weighted gene co-expression network analysis was used to explore co-expression modules and genes based on DEGs. The IS clinical diagnosis model was successfully constructed and four IS characteristic genes (GFAP, GPNMB, FKBP9, and CHMP5) were identified, which were significantly upregulated in IS samples. Characteristic genes were verified by receiver operating characteristic curve and real-time quantitative PCR analyses. The correlation between characteristic genes and infiltrating immune cells was determined by correlation analysis. Furthermore, GPNMB was screened using the protein-protein interaction network, and its regulatory network and the potential therapeutic drug chloroquine were predicted. Our finding describes the expression pattern and clinical value of key RNA methylation modification regulators in IS and novel diagnostic and therapeutic targets of IS from a new perspective.