Colorimetric Detection of Mutant β-Amyloid(1–40) Membrane-Active Aggregation with Biosensing Vesicles

Concentration of Diynoic Acids in Bicellar Mixtures Derived from Those Phase Separation

Bicellar mixtures containing diacetylene molecules, such as diynoic acids, can be used as parent materials for functional membranes. A bicellar mixture consisting of a diynoic acid-10,12-tricosadiynoic acid (TCDA)-, a phospholipid-1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-, and a detergent-3-[(3-cholamidopropyl) dimethylammonio]-2-hydroxypropanesulfonate (CHAPSO)-was evaluated for its morphology and packing of TCDA molecules in its bicellar mixture. A TCDA/DMPC vesicle was prepared at different molar ratios, TCDA/DMPC = 2/8, 5/5, and 8/2; a TCDA/DMPC/CHAPSO bicellar mixture was prepared by mixing a CHAPSO solution with a TCDA/DMPC vesicle solution as a detergent at different composition ratios, x TCDA/DMPC = [TCDA/DMPC]/([TCDA/DMPC]+[CHAPSO]), of 1.0, 0.70, 0.50, and 0.30. A DMPC molecule formed a bilayer membrane structure and was used to suppress its precipitation. The packing density of the TCDA/DMPC/CHAPSO bicellar mixtures was increased by mixing a CHAPSO molecule in x TCDA/DMPC = 1.0 to 0.70 or 0.50. A TEM image of a TCDA/DMPC/CHAPSO bicellar mixture showed many discoidal assemblies at x TCDA/DMPC = 0.5 of TCDA/DMPC = 5/5. Polymerization of the TCDA molecules in the bicellar mixture by UV light suggested an ordered arrangement of TCDA. Polymerization at x TCDA/DMPC = 0.70 and 0.50 correlated with improved packing density.

Consequence of Dementia and Cognitive Impairment by Primary Nucleation Pathway

An acquired loss of cognition in several cognitive domains that is severe enough to interfere with social or professional functioning is called dementia. As well as a moderately in-depth mental status examination by a clinician to identify impairments in memory, language, attention, visuospatial cognition, such as spatial orientation, executive function, and mood, the diagnosis of dementia requires a history evaluating for cognitive decline and impairment in daily activities, with confirmation from a close friend or family member. The start and organization of the cognitive assessment can be helped by short screening tests for cognitive impairment. Clinical presentations show that neurodegenerative diseases are often incurable because patients permanently lose some types of neurons. It has been determined through an assessment that, at best, our understanding of the underlying processes is still rudimentary, which presents exciting new targets for further study as well as the development of diagnostics and drugs. A growing body of research suggests that they also advance our knowledge of the processes that are probably crucial for maintaining the health and functionality of the brain. We concentrate on a number of the animal models of memory problems that have been mentioned in this review article because dementia has numerous etiologies. Serious neurological impairment and neuronal death are the main features of neurodegenerative illnesses, which are also extremely crippling ailments. The most prevalent neurodegenerative disorders are followed by those primary nucleation pathways responsible for cognitive impairment and dementia.

Electrochemiluminescence resonance energy transfer of MnCO3 for ultrasensitive amyloid-β protein detection

A composite material MnCO₃/poly(diallyl dimethyl ammonium chloride) (PDDA)/Ag with excellent electrochemiluminescence (ECL) performance and high biocompatibility was prepared by adding MnCO₃ and PDDA to silver nanoparticles (AgNPs). MnCO₃/PDDA/Ag and Au@SiO₂NPs were used as ECL donors and acceptors, respectively. Thus, an effective ECL-resonance energy transfer (RET) sensing platform was established. In a potassium persulfate (K₂S₂O₈) medium, MnCO₃ exhibited ECL emission with an ECL band appearing at 500-600 nm. In addition, Au@SiO₂ nanoparticles showed a UV-visible absorption at 450-650 nm. The ECL emission spectra of MnCO₃ overlapped with the absorption spectra of Au@SiO₂NPs. The effective ECL quenching resulted in a good response to the concentration of Aβ₄₂ in serum samples. The linear range was 5 fg ⋅ mL^-1 to 100 ng ⋅ mL^-1, and the detection limit was 2 fg ⋅ mL^-1. The recovery ranged from 97.7% to 104%. The high-efficiency ECL-RET immunosensor has potential application in detecting human serum Aβ₄₂ and other biomarkers, and can be used for the early screening of diseases.

Caffeic acid for the prevention and treatment of Alzheimer's disease: The effect of lipid membranes on the inhibition of aggregation and disruption of Aβ fibrils

The onset of Alzheimer's disease (AD) is triggered by the aggregation of amyloid β (Aβ) peptides which leads to the formation of fibrils. Molecules that are able to inhibit fibrillation and/or disrupt fibrils have aroused interest for AD therapy. Fibrillation is a complex process highly dependent on the surrounding environment. One of the most relevant factors affecting Aβ aggregation is the presence of cellular membranes. Here, the ability of caffeic acid (CA) in preventing the Aβ_1-42 aggregation and disaggregating mature fibrils was evaluated in a membrane-like environment and in a bulk solution for comparison. To this end, liposomes were used as in vitro models of neuronal membranes. CA exhibited strong activity in inhibiting the fibrillation of Aβ_1-42 in the aqueous medium, which remained in the presence of liposomes. Furthermore, CA disrupted instantly preformed fibrils in the aqueous medium. However, the CA's disaggregating activity was disturbed by the presence of lipid membranes. Instead of being immediate, the CA's disaggregating activity increased over time. The moderate affinity of CA for the lipid bilayer may explain the distinct fibrils disaggregation profiles. These findings emphasize the therapeutic potential of CA in preventing and treating AD, thus justifying further investigations in animal models.

The Role of Amyloid β-Biomembrane Interactions in the Pathogenesis of Alzheimer's Disease: Insights from Liposomes as Membrane Models

The aggregation and deposition of amyloid β (Aβ) peptide onto neuronal cells, with consequent cellular membrane perturbation, are central to the pathogenesis of Alzheimer's disease (AD). Substantial evidence reveals that biological membranes play a key role in this process. Thus, elucidating the mechanisms by which Aβ interacts with biomembranes and becomes neurotoxic is fundamental to developing effective therapies for this devastating progressive disease. However, the structural basis behind such interactions is not fully understood, largely due to the complexity of natural membranes. In this context, lipid biomembrane models provide a simplified way to mimic the characteristics and composition of membranes. Aβ-biomembrane interactions have been extensively investigated applying artificial membrane models to elucidate the molecular mechanisms underlying the AD pathogenesis. This review summarizes the latest findings on this field using liposomes as biomembrane model, as they are considered the most promising 3D model. The current challenges and future directions are discussed.

Advances in nanomedicines for diagnosis of central nervous system disorders

In spite of a great improvement in medical health services and an increase in lifespan, we have witnessed a skyrocket increase in the incidence of central nervous system (CNS) disorders including brain tumors, neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease), ischemic stroke, and epilepsy, which have seriously undermined the quality of life and substantially increased economic and societal burdens. Development of diagnostic methods for CNS disorders is still in the early stage, and the clinical outcomes suggest these methods are not ready for the challenges associated with diagnosis of CNS disorders, such as early detection, specific binding, sharp contrast, and continuous monitoring of therapeutic interventions. Another challenge is to overcome various barrier structures during delivery of diagnostic agents, especially the blood-brain barrier (BBB). Fortunately, utilization of nanomaterials has been pursued as a potential and promising strategy to address these challenges. This review will discuss anatomical and functional structures of BBB and transport mechanisms of nanomaterials across the BBB, and special emphases will be placed on the state-of-the-art advances in the development of nanomedicines from a variety of nanomaterials for diagnosis of CNS disorders. Meanwhile, current challenges and future perspectives in this field are also highlighted.