Real-time imaging and quantification of amyloid-beta peptide aggregates by novel quantum-dot nanoprobes

Gazing Beyond the Horizon: A Systematic Review Unveiling the Theranostic Potential of Quantum Dots in Alzheimer's Disease

Alzheimer's disease (AD), a neurodegenerative disorder characterized by cognitive decline, poses a significant healthcare challenge worldwide. The accumulation of amyloid-beta (Aβ) plaques and hyperphosphorylated tau protein drives neuronal degeneration and neuroinflammation, perpetuating disease progression. Despite advancements in understanding the cellular and molecular mechanisms, treatment hurdles persist, emphasizing the need for innovative intervention strategies. Quantum dots (QDs) emerge as promising nanotechnological tools with unique photo-physical properties, offering advantages over conventional imaging modalities. This systematic review endeavors to elucidate the theranostic potential of QDs in AD by synthesizing preclinical and clinical evidence. A comprehensive search across electronic databases yielded 20 eligible studies investigating the diagnostic, therapeutic, or combined theranostic applications of various QDs in AD. The findings unveil the diverse roles of QDs, including inhibiting Aβ and tau aggregation, modulating amyloidogenesis pathways, restoring membrane fluidity, and enabling simultaneous detection of AD biomarkers. The review highlights the potential of QDs in targeting multiple pathological hallmarks, delivering therapeutic payloads across the blood-brain barrier, and facilitating real-time imaging and high-throughput screening. While promising, challenges such as biocompatibility, surface modifications, and clinical translation warrant further investigation. This systematic review provides a comprehensive synthesis of the theranostic potential of QDs in AD, paving the way for translational research and clinical implementation.

Amyloid β interferes with wound healing of brain microvascular endothelial cells by disorganizing the actin cytoskeleton

Cerebral amyloid angiopathy (CAA) is a disease in which amyloid β (Aβ) is deposited in the cerebral blood vessels, reducing compliance, tearing and weakening of vessel walls, leading to cerebral hemorrhage. The mechanisms by which Aβ leads to focal wall fragmentation and intimal damage are not well understood. We analyzed the motility of human brain microvascular endothelial cells (hBMECs) in real-time using a wound-healing assay. We observed the suppression of cell migration by visualizing Aβ aggregation using quantum dot (QD) nanoprobes. In addition, using QD nanoprobes and a SiR-actin probe, we simultaneously observed Aβ aggregation and F-actin organization in real-time for the first time. Aβ began to aggregate at the edge of endothelial cells, reducing cell motility. In addition, Aβ aggregation disorganized the actin cytoskeleton and induced abnormal actin aggregation. Aβ aggregated actively in the anterior group, where cell motility was active. Our findings may be a first step toward explaining the mechanism by which Aβ causes vascular wall fragility, bleeding, and rebleeding in CAA.

APP-C31: An Intracellular Promoter of Both Metal-Free and Metal-Bound Amyloid-β40 Aggregation and Toxicity in Alzheimer's Disease

Intracellular C-terminal cleavage of the amyloid precursor protein (APP) is elevated in the brains of Alzheimer's disease (AD) patients and produces a peptide labeled APP-C31 that is suspected to be involved in the pathology of AD. But details about the role of APP-C31 in the development of the disease are not known. Here, this work reports that APP-C31 directly interacts with the N-terminal and self-recognition regions of amyloid-β40 (Aβ40 ) to form transient adducts, which facilitates the aggregation of both metal-free and metal-bound Aβ40 peptides and aggravates their toxicity. Specifically, APP-C31 increases the perinuclear and intranuclear generation of large Aβ40 deposits and, consequently, damages the nucleus leading to apoptosis. The Aβ40 -induced degeneration of neurites and inflammation are also intensified by APP-C31 in human neurons and murine brains. This study demonstrates a new function of APP-C31 as an intracellular promoter of Aβ40 amyloidogenesis in both metal-free and metal-present environments, and may offer an interesting alternative target for developing treatments for AD that have not been considered thus far.

A critical review on the role of nanotheranostics mediated approaches for targeting β amyloid in Alzheimer's

Alzheimer's is one of the most common neurodegenerative illnesses that affect brain cellular function. In this disease, the neurons in the brain are considered to be decaying steadily but consistently by the accumulation of amyloid mass, particularly the β-amyloids, amyloid proteins, and Tau proteins. The most responsible amyloid-proteins are amyloid-40 and amyloid-42, which have a high probability of accumulating in excess over the brain cell, interfering with normal brain cell function and triggering brain cell death. The advancement of pharmaceutical sciences leads to the development of Nanotheranostics technology, which may be used to diagnose and treat Alzheimer's. They are the colloidal nanoparticles functionalised with the therapeutic moiety as well as a diagnostic moiety. This article discusses the prognosis of Alzheimer's, various nanotheranostics approaches (nanoparticles, quantum dots, aptamers, dendrimers, etc), and their recent advancement in managing Alzheimer's. Also, various in-vitro and in-vivo diagnostic methodologies were discussed with respect to nanotheranostics.

Cultivation Factors That Affect Amyloid-β Aggregation Inhibitory Activity in Perilla frutescens var. crispa

Alzheimer's disease (AD) is thought to be caused by the deposition of amyloid-β (Aβ) in the brain. Aβ begins to aggregate approximately 20 years before the expression of its symptoms. Previously, we developed a microliter-scale high-throughput screening (MSHTS) system for inhibitors against Aβ aggregation using quantum dot nanoprobes. Using this system, we also found that plants in the Lamiaceae, particularly Perilla frutescens var. crispa, have high activity. The cultivation environment has the potential to enhance Aβ aggregation inhibitory activity in plants by changing their metabolism. Here, we report on cultivation factors that affected the activity of P. frutescens var. crispa cultivated in three fields under different cultivation conditions. The results revealed that the activity of P. frutescens var. crispa harvested just before flowering was highest. Interestingly, the activity of wind-shielded plants that were cultivated to prevent exposure to wind, was reduced to 1/5th of plants just before flowering. Furthermore, activity just before flowering increased following appropriate nitrogen fertilization and at least one week of drying from the day before harvest. In addition, we confirmed that the P. frutescens var. crispa leaf extracts suppressed Aβ-induced toxicity in nerve growth factor-differentiated PC12 cells. In this study, we demonstrated that flowering, wind, soil water content, and soil nitrogen content affected Aβ aggregation inhibitory activity, necessary to suppress Aβ neurotoxicity, in P. frutescens var. crispa extracts. This study provides practical cultivation methods for P. frutescens var. crispa with high Aβ aggregation inhibitory activity for the prevention of AD.

Potential of fluorescent nanoprobe in diagnosis and treatment of Alzheimer's disease

Alzheimer's disease (AD) is well known for its insidious nature, slow progression and high incidence as a neurodegenerative disease. In the past, diagnosis of AD mainly depended on analysis of a patient's cognitive ability and behavior. Without a unified standard for analysis methods, this is prone to produce incorrect diagnoses. Currently, definitive diagnosis mainly relies on histopathological examination. Because of the advantages of precision, noninvasiveness, low toxicity and high spatiotemporal resolution, fluorescent nanoprobes are suitable for the early diagnosis of AD. This review summarizes the research progress of different kinds of fluorescent nanoprobes for AD diagnosis and therapy in recent years and provides an outlook on the development prospects of fluorescent nanoprobes.

Kinetics of amyloid accumulation in physiological viscosity

Abnormal aggregation and accumulation of misfolded proteins are involved in the development of various forms of amyloidosis. Aggregates that accumulate in organs induce an inflammatory response and cytotoxicity, and lead to organ failure. Although protein accumulation around an affected area in the body is an important stage that is directly linked to the mechanism of pathogenesis, the kinetics of the accumulation of protein that precipitates while assembling is not well understood because 3D tracking of proteins in solution is difficult. Here, we analyzed the process of aggregation and accumulation of amyloid β (Aβ), which causes the development of Alzheimer's disease (AD), by real-time 3D imaging under physiological conditions using a quantum dot nanoprobe that we previously developed. 3D observations demonstrated that Aβ aggregates with a diameter of several μm emerged in phosphate-buffered saline, gathered in a spiral-like step, and exhibited a mesh-like structure. Additionally, we found that the amount and size of aggregates decreased dramatically in 40% glycerol solution, mimicking the viscosity of human blood. We confirmed that fibrils in 40% glycerol exhibited an extremely short and tangled morphology and formed dense aggregates. Furthermore, numerical calculations revealed that several decades are required to fully develop the settling velocity and diameter of Aβ aggregates in physiological conditions. This time span is consistent with the actual symptom progression of AD.

Optical Nanosensor for Intracellular and Intracranial Detection of Amyloid-Beta

Amyloid-beta (Aβ) deposition occurs in the early stages of Alzheimer's disease (AD), but the early detection of Aβ is a persistent challenge. Herein, we engineered a near-infrared optical nanosensor capable of detecting Aβ intracellularly in live cells and intracranially in vivo. The sensor is composed of single-walled carbon nanotubes functionalized with Aβ wherein Aβ-Aβ interactions drive the response. We found that the Aβ nanosensors selectively responded to Aβ via solvatochromic modulation of the near-infrared emission of the nanotube. The sensor tracked Aβ accumulation in live cells and, upon intracranial administration in a genetic model of AD, signaled distinct responses in aged mice. This technology enables the interrogation of molecular mechanisms underlying Aβ neurotoxicity in the development of AD in living systems.

The Need to Pair Molecular Monitoring Devices with Molecular Imaging to Personalize Health

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health.

Amyloid β aggregation induces human brain microvascular endothelial cell death with abnormal actin organization

Cerebral amyloid angiopathy (CAA) is a disease in which amyloid β (Aβ) is deposited on the walls of blood vessels in the brain, making those walls brittle and causing cerebral hemorrhage. However, the mechanism underlying its onset is not well understood. The aggregation and accumulation of Aβ cause the occlusion and fragility of blood vessels due to endothelial cell damage, breakdown of the blood-brain barrier, and replacement with elements constituting the blood vessel wall. In this study, we observed the effect of Aβ on human primary brain microvascular endothelial cells (hBMECs) in real-time using quantum dot nanoprobes to elucidate the mechanism of vascular weakening by Aβ. It was observed that Aβ began to aggregate around hBMECs after the start of incubation and that the cells were covered with aggregates. Aβ aggregates firmly anchored the cells on the plate surface, and eventually suppressed cell motility and caused cell death. Furthermore, Aβ aggregation induced the organization of abnormal actin, resulting in a significant increase in intracellular actin dots over 10 μm². These results suggest that the mechanism by which Aβ forms a fragile vessel wall is as follows: Aβ aggregation around vascular endothelial cells anchors them to the substrate, induces abnormal actin organization, and leads to cell death.

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Amyloid β (Aβ) aggregates anchor human endothelial cells to the substrate.

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Aβ induces abnormal actin organization in human endothelial cells.

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Aβ induces cell death of human endothelial cells.

Nanomedicine against Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's are the two most rampant neurodegenerative disorders worldwide. Existing treatments have a limited effect on the pathophysiology but are unable to fully arrest the progression of the disease. This is due to the inability of these therapeutic molecules to efficiently cross the blood-brain barrier. We discuss how nanotechnology has enabled researchers to develop novel and efficient nano-therapeutics against these diseases. The development of nanotized drug delivery systems has permitted an efficient, site-targeted, and controlled release of drugs in the brain, thereby presenting a revolutionary therapeutic approach. Nanoparticles are also being thoroughly studied and exploited for their role in the efficient and precise diagnosis of neurodegenerative conditions. We summarize the role of different nano-carriers and RNAi-conjugated nanoparticle-based therapeutics for their efficacy in pre-clinical studies. We also discuss the challenges underlying the use of nanomedicine with a focus on their route of administration, concentration, metabolism, and any toxic effects for successful therapeutics in these diseases.

Quantum dots as a theranostic approach in Alzheimer's disease: a systematic review

Aim: Quantum dots (QDs) are nanoparticles that have an emerging application as theranostic agents in several neurodegenerative diseases. The advantage of QDs as nanomedicine is due to their unique optical properties that provide high sensitivity, stability and selectivity at a nanoscale range. Objective: To offer renewed insight into current QD research and elucidate its promising application in Alzheimer's disease (AD) diagnosis and therapy. Methods: A comprehensive literature search was conducted in PubMed and Google Scholar databases that included the following search terms: 'quantum dots', 'blood-brain barrier', 'cytotoxicity', 'toxicity' and 'Alzheimer's disease'; PRISMA guidelines were adhered to. Results: Thirty-four publications were selected to evaluate the ability of QDs to cross the blood-brain barrier, potential toxicity and current AD diagnostic and therapeutic applications. Conclusion: QD's unique optical properties and versatility to conjugate to various biomolecules, while maintaining a nanoscale size, render them a promising theranostic tool in AD.

Dendrimer Architectonics to Treat Cancer and Neurodegenerative Diseases with Implications in Theranostics and Personalized Medicine

Integration of diagnostic and therapeutic functions in a single platform namely theranostics has become a cornerstone for personalized medicine. Theranostics platform facilitates noninvasive detection and treatment while allowing the monitoring of disease progression and therapeutic efficacy in case of chronic conditions of cancer and Alzheimer's disease (AD). Theranostic tools function by themselves or with the aid of carrier, viz. liposomes, micelles, polymers, or dendrimers. The dendrimer architectures (DA) are well-characterized molecular nanoobjects with a large number of terminal functional groups to enhance solubility and offer multivalency and multifunctional properties. Various noninvasive diagnostic tools like magnetic resonance imaging (MRI), computed tomography (CT), gamma scintigraphy, and optical techniques have been accomplished utilizing DAs for simultaneous imaging and drug delivery. Obstacles in the formulation design, drug loading, payload delivery, biocompatibility, overcoming cellular membrane and blood-brain barrier (BBB), and systemic circulation remain a bottleneck in translational efforts. This review focuses on the diagnostic, therapeutic and theranostic potential of DA-based nanocarriers in treating cancer and neurodegenerative disorders like AD and Parkinson's disease (PD), among others. In view of the inverse relationship between cancer and AD, designing suitable DA-based theranostic nanodrug with high selectivity has tremendous implications in personalized medicine to treat cancer and neurodegenerative disorders.

A review on advances of treatment modalities for Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease which is mainly characterized by progressive impairment in cognition, emotion, language and memory in older population. Considering the impact of AD, formulations of pharmaceutical drugs and cholinesterase inhibitors have been widely propagated, receiving endorsement by FDA as a form of AD treatment. However, these medications were gradually discovered to be ineffective in removing the root of AD pathogenesis but merely targeting the symptoms so as to improve a patient's cognitive outcome. Hence, a search for better disease-modifying alternatives is put into motion. Having a clear understanding of the neuroprotective mechanisms and diverse properties undertaken by specific genes, antibodies and nanoparticles is central towards designing novel therapeutic agents. In this review, we provide a brief introduction on the background of Alzheimer's disease, the biology of blood-brain barrier, along with the potentials and drawbacks associated with current therapeutic treatment avenues pertaining to gene therapy, immunotherapy and nanotherapy for better diagnosis and management of Alzheimer's disease.

Aggregation of Mouse Serum Amyloid A Protein Was Promoted by Amyloid-Enhancing Factors with the More Genetically Homologous Serum Amyloid A

Amyloid A (AA) amyloidosis is a condition in which amyloid fibrils characterized by a linear morphology and a cross-β structure accumulate and are deposited extracellularly in organs, resulting in chronic inflammatory diseases and infections. The incidence of AA amyloidosis is high in humans and several animal species. Serum amyloid A (SAA) is one of the most important precursor amyloid proteins and plays a vital step in AA amyloidosis. Amyloid enhancing factor (AEF) serves as a seed for fibril formation and shortens the onset of AA amyloidosis sharply. In this study, we examined whether AEFs extracted and purified from five animal species (camel, cat, cattle, goat, and mouse) could promote mouse SAA (mSAA) protein aggregation in vitro using quantum-dot (QD) nanoprobes to visualize the aggregation. The results showed that AEFs shortened and promoted mSAA aggregation. In addition, mouse and cat AEFs showed higher mSAA aggregation-promoting activity than the camel, cattle, and goat AEFs. Interestingly, homology analysis of SAA in these five animal species revealed a more similar amino acid sequence homology between mouse and cat than between other animal species. Furthermore, a detailed comparison of amino acid sequences suggested that it was important to mSAA aggregation-promoting activity that the 48th amino acid was a basic residue (Lys) and the 125th amino acid was an acidic residue (Asp or Glu). These data imply that AA amyloidosis exhibits higher transmission activity among animals carrying genetically homologous SAA gene, and may provide a new understanding of the pathogenesis of amyloidosis.

Challenges in Biomaterial-Based Drug Delivery Approach for the Treatment of Neurodegenerative Diseases: Opportunities for Extracellular Vesicles

Biomaterials have been the subject of numerous studies to pursue potential therapeutic interventions for a wide variety of disorders and diseases. The physical and chemical properties of various materials have been explored to develop natural, synthetic, or semi-synthetic materials with distinct advantages for use as drug delivery systems for the central nervous system (CNS) and non-CNS diseases. In this review, an overview of popular biomaterials as drug delivery systems for neurogenerative diseases is provided, balancing the potential and challenges associated with the CNS drug delivery. As an effective drug delivery system, desired properties of biomaterials are discussed, addressing the persistent challenges such as targeted drug delivery, stimuli responsiveness, and controlled drug release in vivo. Finally, we discuss the prospects and limitations of incorporating extracellular vesicles (EVs) as a drug delivery system and their use for biocompatible, stable, and targeted delivery with limited immunogenicity, as well as their ability to be delivered via a non-invasive approach for the treatment of neurodegenerative diseases.

Recent Advances in Nanotherapeutic Interventions for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD), with impairment of learning and memory as the common clinical manifestations, is one of the most challenging diseases affecting individuals, their families and society as a whole. The fact that its prevalence is escalating rapidly, with the total number of AD patients estimated to reach 115.4 million by 2050, has made the disease a very challenging ailment worldwide. Several biological barriers like the bloodbrain barrier (BBB), drug efflux by P-glycoprotein and the blood-cerebrospinal fluid barrier restrict the delivery of conventional AD drugs to the central nervous system (CNS), thereby limiting their effectiveness. In order to overcome the above physiological barriers, the development of nanomedicines has been extensively explored. The present review provides an insight into the pathophysiology of AD and risk factors associated with AD. Besides, various nanoformulations reported in the literature for the diagnosis and treatments of AD have been classified and summarised. The patented nanoformulations for AD and details of nanoformulations which are in clinical trials are also mentioned. The review would be helpful to researchers and scientific community by providing them with information related to the recent advances in nanointerventions for the diagnosis and treatment of AD, which they can further explore for better management of the disease. However, although the nanotherapeutics for managing AD have been extensively explored, the factors which hinder their commercialisation, the toxicity concern being one of them, need to be addressed so that effective nanotherapeutics for AD can be developed for clinical use.

The Antiaggregative and Antiamyloidogenic Properties of Nanoparticles: A Promising Tool for the Treatment and Diagnostics of Neurodegenerative Diseases

Due to the progressive aging of the society, the prevalence and socioeconomic burden of neurodegenerative diseases are predicted to rise. The most common neurodegenerative disorders nowadays, such as Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis, can be classified as proteinopathies. They can be either synucleinopathies, amyloidopathies, tauopathies, or TDP-43-related proteinopathies; thus, nanoparticles with a potential ability to inhibit pathological protein aggregation and/or degrade already existing aggregates can be a promising approach in the treatment of neurodegenerative diseases. As it turns out, nanoparticles can be a double-edged sword; they can either promote or inhibit protein aggregation, depending on coating, shape, size, surface charge, and concentration. In this review, we aim to emphasize the need of a breakthrough in the treatment of neurodegenerative disorders and draw attention to nanomaterials, as they can also serve as a diagnostic tool for protein aggregates or can be used in a high-throughput screening for novel antiaggregative compounds.

Dietary Intake of Rosmarinic Acid Increases Serum Inhibitory Activity in Amyloid A Aggregation and Suppresses Deposition in the Organs of Mice

Serum amyloid A (SAA) is one of the most important precursor amyloid proteins and plays a vital step in AA amyloidosis, although the underlying aggregation mechanism has not been elucidated. Since SAA aggregation is a key step in this pathogenesis, inhibitors are useful to prevent and treat AA amyloidosis, serving as tools to investigate the pathogenic mechanism. In this study, we showed that rosmarinic acid (RA), which is a well-known inhibitor of the aggregation of amyloid β (Aβ), displayed inhibitory activity against SAA aggregation in vitro using a microliter-scale high-throughput screening (MSHTS) system with quantum-dot nanoprobes. Therefore, we evaluated the amyloid aggregation inhibitory activity of blood and the deposition of SAA in organs by feeding mice with Melissa officinalis extract (ME) containing RA as an active substance. Interestingly, the inhibitory activity of ME-fed mice sera for SAA and Aβ aggregation, measured with the MSHTS system, was higher than that of the control group. The amount of amyloid deposition in the organs of ME-fed mice was lower than that in the control group, suggesting that the SAA aggregation inhibitory activity of serum is associated with SAA deposition. These results suggest that dietary intake of RA-containing ME enhanced amyloid aggregation inhibitory activity of blood and suppressed SAA deposition in organs. This study also demonstrated that the MSHTS system could be applied to in vitro screening and to monitor comprehensive activity of metabolized foods adsorbed by blood.

Evaluation of Amyloid β42 Aggregation Inhibitory Activity of Commercial Dressings by A Microliter-Scale High-Throughput Screening System Using Quantum-Dot Nanoprobes

The aggregation and accumulation of amyloid β (Aβ) in the brain is a trigger of pathogenesis for Alzheimer's disease. Previously, we developed a microliter-scale high-throughput screening (MSHTS) system for Aβ₄₂ aggregation inhibitors using quantum-dot nanoprobes. The MSHTS system is seldom influenced by contaminants in samples and is able to directly evaluate Aβ₄₂ aggregation inhibitory activity of samples containing various compounds. In this study, to elucidate whether the MSHTS system could be applied to the evaluation of processed foods, we examined Aβ₄₂ aggregation inhibitory activity of salad dressings, including soy sauces. We estimated the 50% effective concentration (EC₅₀) from serial diluted dressings. Interestingly, all 19 commercial dressings tested showed Aβ₄₂ aggregation inhibitory activity. It was suggested that EC₅₀ differed by as much as 100 times between the dressings with the most (0.065 ± 0.020 v/v%) and least (6.737 ± 5.054 v/v%) inhibitory activity. The highest activity sample is traditional Japanese dressing, soy sauce. It is known that soy sauce is roughly classified into a heat-treated variety and a non-heat-treated variety. We demonstrated that non-heat-treated raw soy sauce exhibited higher Aβ₄₂ aggregation inhibitory activity than heat-treated soy sauce. Herein, we propose that MSHTS system can be applied to processed foods.

Three-dimensional real time imaging of amyloid β aggregation on living cells

Alzheimer’s disease (AD) is a progressive disorder of the brain that gradually decreases thinking, memory, and language abilities. The aggregation process of amyloid β (Aβ) is a key step in the expression of its neurocytotoxicity and development of AD because Aβ aggregation and accumulation around neuronal cells induces cell death. However, the molecular mechanism underlying the neurocytotoxicity and cell death by Aβ aggregation has not been clearly elucidated. In this study, we successfully visualized real-time process of Aβ₄₂ aggregation around living cells by applying our established QD imaging method. 3D observations using confocal laser microscopy revealed that Aβ₄₂ preferentially started to aggregate at the region where membrane protrusions frequently formed. Furthermore, we found that inhibition of actin polymerization using cytochalasin D reduced aggregation of Aβ₄₂ on the cell surface. These results indicate that actin polymerization-dependent cell motility is responsible for the promotion of Aβ₄₂ aggregation at the cell periphery. 3D observation also revealed that the aggregates around the cell remained in that location even if cell death occurred, implying that amyloid plaques found in the AD brain grew from the debris of dead cells that accumulated Aβ₄₂ aggregates.

Real-Time 3D Imaging and Inhibition Analysis of Various Amyloid Aggregations Using Quantum Dots

Amyloidosis refers to aggregates of protein that accumulate and are deposited as amyloid fibrils into plaques. When these are detected in organs, they are the main hallmark of Alzheimer's disease, Parkinson's disease, and other related diseases. Recent medical advances have shown that many precursors and proteins can induce amyloidosis even though the mechanism of amyloid aggregation and the relationship of these proteins to amyloidosis remains mostly unclear. In this study, we report the real-time 3D-imaging and inhibition analysis of amyloid β (Aβ), tau, and α-synuclein aggregation utilizing the affinity between quantum dots (QD) and amyloid aggregates. We successfully visualized these amyloid aggregations in real-time using fluorescence microscopy and confocal microscopy simply by adding commercially available QD. The observation by transmission electron microscopy (TEM) showed that QD particles bound to all amyloid fibrils. The 3D-imaging with QD revealed differences between amyloid aggregates composed of different amyloid peptides that could not be detected by TEM. We were also able to quantify the inhibition activities of these proteins by rosmarinic acid, which has high activity for Aβ aggregation, from fluorescence micrographs as half-maximal effective concentrations. These imaging techniques with QD serve as quick, easy, and powerful tools to understand amyloidosis and to discover drugs for therapies.

Tau-tubulin kinase 1 and amyloid-β peptide induce phosphorylation of collapsin response mediator protein-2 and enhance neurite degeneration in Alzheimer disease mouse models

The accumulation of phosphorylated tau protein (pTau) in the entorhinal cortex (EC) is the earliest tau pathology in Alzheimer’s disease (AD). Tau tubulin kinase-1 (TTBK1) is a neuron-specific tau kinase and expressed in the EC and hippocampal regions in both human and mouse brains. Here we report that collapsin response mediator protein-2 (CRMP2), a critical mediator of growth cone collapse, is a new downstream target of TTBK1 and is accumulated in the EC region of early stage AD brains. TTBK1 transgenic mice show severe axonal degeneration in the perforant path, which is exacerbated by crossing with Tg2576 mice expressing Swedish familial AD mutant of amyloid precursor protein (APP). TTBK1 mice show accumulation of phosphorylated CRMP2 (pCRMP2), in the EC at 10 months of age, whereas age-matched APP/TTBK1 bigenic mice show pCRMP2 accumulation in both the EC and hippocampal regions. Amyloid-β peptide (Aβ) and TTBK1 suppress the kinetics of microtubule polymerization and TTBK1 reduces the neurite length of primary cultured neurons in Rho kinase-dependent manner in vitro. Silencing of TTBK1 or expression of dominant-negative Rho kinase demonstrates that Aβ induces CRMP2 phosphorylation at threonine 514 in a TTBK1-dependent manner, and TTBK1 enhances Aβ-induced CRMP2 phosphorylation in Rho kinase-dependent manner in vitro. Furthermore, TTBK1 expression induces pCRMP2 complex formation with pTau in vitro, which is enhanced upon Aβ stimulation in vitro. Finally, pCRMP2 forms a complex with pTau in the EC tissue of TTBK1 mice in vivo, which is exacerbated in both the EC and hippocampal tissues in APP/TTBK1 mice. These results suggest that TTBK1 and Aβ induce phosphorylation of CRMP2, which may be causative for the neurite degeneration and somal accumulation of pTau in the EC neurons, indicating critical involvement of TTBK1 and pCRMP2 in the early AD pathology.

Quantum Dots as Promising Theranostic Tools Against Amyloidosis: A Review

Amyloids are highly ordered beta sheet rich stable protein aggregates, which have been found to play a significant role in the onset of several degenerative diseases such as Alzheimer's disease, Huntington's disease, Parkinson's disease, Type II diabetes mellitus and so on. Aggregation of proteins leading to amyloid fibril formation via intermediate(s), is thought to be a nucleated condensation polymerization process associated with many pathological conditions. There has been extensive research to identify inhibitors of these disease oriented aggregation processes. In recent times, quantum dots, with their unique physico-chemical properties have grabbed the attention of scientific community due to its applications in medical sciences. Quantum dots are nano-particles usually made of semiconductor materials which emit fluorescence upon radiation. The wavelength of fluorescence emission varies with changes in size of quantum dots. Several studies have reported significant inhibitory effects of these quantum dots towards amyloidogenesis, thereby presenting themselves as promising candidates against amyloidosis. Further, studies have also revealed amyloid detection capacity of quantum dots with sensitivity and specificity better than conventional probes. In the current review, we will discuss the various effects of quantum dots on protein aggregation pathways, their mechanism of actions and their potentials as effective therapeutics against amyloidosis.

Nanoparticle technology and stem cell therapy team up against neurodegenerative disorders

The convergence of nanoparticles and stem cell therapy holds great promise for the study, diagnosis, and treatment of neurodegenerative disorders. Researchers aim to harness the power of nanoparticles to regulate cellular microenvironment, improve the efficiency of cell and drug delivery to the brain, and enhance the survival of stem cell transplants. Understanding the various properties of different nanoparticles is key to applying them to clinical therapies; the many distinct types of nanoparticles offer unique capacities for medical imaging, diagnosis, and treatment of neurodegeneration disorders. In this review we introduce the biology of Alzheimer's, Parkinson's Disease, and amyotrophic lateral sclerosis, and discuss the potentials and shortcomings of metal, silica, lipid-based, polymeric, and hydrogel nanoparticles for diagnosis and treatment of neurodegenerative disorders. We then provide an overview of current strategies in stem cell therapies and how they can be combined with nanotechnology to improve clinical outcomes.

An automated microliter-scale high-throughput screening system (MSHTS) for real-time monitoring of protein aggregation using quantum-dot nanoprobes

Protein aggregation is the principal component of numerous protein misfolding pathologies termed proteinopathies, such as Alzheimer’s disease, Parkinson’s disease, prion disease, and AA amyloidosis with unmet treatment needs. Protein aggregation inhibitors have great potential for the prevention and treatment of proteinopathies. Here we report the development of an automated real-time microliter-scale high throughput screening (MSHTS) system for amyloid aggregation inhibitors using quantum-dot nanoprobes. Screening 504 crude extracts and 134 low molecular weight aromatic compounds revealed the relationship of amyloid-β (Aβ) aggregation inhibitory activities of plant extracts using a plant-based classification. Within the eudicots, rosids, Geraniales and Myrtales showed higher activity. Screening low molecular weight aromatic compounds demonstrated that the structure of tropolone endows it with potential Aβ aggregation inhibitory activity. The activity of the most active tropolone derivative was higher than that of rosmarinic acid. MSHTS also identified three chaperone molecules as tau aggregation inhibitors. These results demonstrate that our automated MSHTS system is a novel and robust tool that can be adapted to a wide range of compounds and aggregation-prone polypeptides.

Nanotechnology Based Theranostic Approaches in Alzheimer's Disease Management: Current Status and Future Perspective

BACKGROUND

Alzheimer's disease (AD), a cognitive dysfunction/dementia state amongst the elders is characterized by irreversible neurodegeneration due to varied pathophysiology. Up till now, anti-AD drugs having different pharmacology have been developed and used in clinic. Yet, these medications are not curative and only lowering the AD associated symptoms. Improvement in treatment outcome required drug targeting across the blood-brain barrier (BBB) to the central nervous system (CNS) in optimal therapeutic concentration. Nanotechnology based diagnostic tools, drug carriers and theranostics offer highly sensitive molecular detection, effective drug targeting and their combination. Over the past decade, significant works have been done in this area and we have seen very remarkable outocome in AD therapy. Various nanoparticles from organic and inorganic nanomaterial category have successfully been investigated against AD.

CONCLUSION

This paper discussed the role of nanoparticles in early detection of AD, effective drug targeting to brain and theranostic (diagnosis and therapy) approaches in AD's management.

Nanomedicine applications in women's health: state of the art

State-of-the-art applications of nanomedicine have the potential to revolutionize the diagnosis, prevention, and treatment of a range of conditions and diseases affecting women’s health. In this review, we provide a synopsis of potential applications of nanomedicine in some of the most dominant fields of women’s health: mental health, sexual health, reproductive medicine, oncology, menopause-related conditions and dementia. We explore published studies arising from in vitro and in vivo experiments, and clinical trials where available, to reveal novel and highly promising therapeutic applications of nanomedicine in these fields. For the first time, we summarize the growing body of evidence relating to the use of nanomaterials as experimental tools for the detection, prevention, and treatment of significant diseases and conditions across the life course of a cisgender woman, from puberty to menopause; revealing the far-reaching and desirable theoretical impact of nanomedicine across different medical disciplines. We also present an overview of potential concerns regarding the therapeutic applications of nanomedicine and the factors currently restricting the growth of applied nanomedicine.

Bio-inspired nano tools for neuroscience

Research and treatment in the nervous system is challenged by many physiological barriers posing a major hurdle for neurologists. The CNS is protected by a formidable blood brain barrier (BBB) which limits surgical, therapeutic and diagnostic interventions. The hostile environment created by reactive astrocytes in the CNS along with the limited regeneration capacity of the PNS makes functional recovery after tissue damage difficult and inefficient. Nanomaterials have the unique ability to interface with neural tissue in the nano-scale and are capable of influencing the function of a single neuron. The ability of nanoparticles to transcend the BBB through surface modifications has been exploited in various neuro-imaging techniques and for targeted drug delivery. The tunable topography of nanofibers provides accurate spatio-temporal guidance to regenerating axons. This review is an attempt to comprehend the progress in understanding the obstacles posed by the complex physiology of the nervous system and the innovations in design and fabrication of advanced nanomaterials drawing inspiration from natural phenomenon. We also discuss the development of nanomaterials for use in Neuro-diagnostics, Neuro-therapy and the fabrication of advanced nano-devices for use in opto-electronic and ultrasensitive electrophysiological applications. The energy efficient and parallel computing ability of the human brain has inspired the design of advanced nanotechnology based computational systems. However, extensive use of nanomaterials in neuroscience also raises serious toxicity issues as well as ethical concerns regarding nano implants in the brain. In conclusion we summarize these challenges and provide an insight into the huge potential of nanotechnology platforms in neuroscience.

Ultra rapid in vivo screening for anti-Alzheimer anti-amyloid drugs

More than 46 million people worldwide suffer from Alzheimer’s disease. A large number of potential treatments have been proposed; among these, the inhibition of the aggregation of amyloid β-peptide (Aβ), considered one of the main culprits in Alzheimer’s disease. Limitations in monitoring the aggregation of Aβ in cells and tissues restrict the screening of anti-amyloid drugs to in vitro studies in most cases. We have developed a simple but powerful method to track Aβ aggregation in vivo in real-time, using bacteria as in vivo amyloid reservoir. We use the specific amyloid dye Thioflavin-S (Th-S) to stain bacterial inclusion bodies (IBs), in this case mainly formed of Aβ in amyloid conformation. Th-S binding to amyloids leads to an increment of fluorescence that can be monitored. The quantification of the Th-S fluorescence along the time allows tracking Aβ aggregation and the effect of potential anti-aggregating agents.

[Physico-chemical methods for studing β-amyloid aggregation]

Alzheimer's disease is the most prevalent neurodegenerative pathology. According to the amyloid cascade hypothesis, a key event of the Alzheimer's disease pathogenesis is a transition of the β-amyloid peptide (Аβ) from the monomeric form to the aggregated state. The mechanism of Аβ aggregation is intensively studied in vitro, by means of synthetic peptides and various physico-chemical methods allowing evaluation of size, molecular structure, and morphology of the formed aggregates. The paper reviews both the well-known and recently introduced physico-chemical methods for analysis of Аβ aggregation, including microscopу, optical and fluorescent methods, method of electron paramagnetic resonance, electrochemical and electrophoretic methods, gel-filtration, and mass spectrometric methods. Merits and drawbacks of the methods are discussed. The unique possibility to simultaneously observe Аβ monomers as well oligomers and large aggregates by means of atomic force microscopy or fluorescence correlation spectroscopy is emphasized. The high detection sensitivity of the latter method, monitoring the aggregation process in Аβ solutions at low peptide concentrations is underlined. Among mass spectrometric methods, the ion mobility mass spectrometry is marked out as a method enabling to obtain information about both the spectrum of Аβ oligomers and their structure. It is pointed out that the use of several methods giving the complementary data about Аβ aggregates is the best experimental approach to studying the process of b-amyloid peptide aggregation in vitro.

Evaluation of the effects of amyloid β aggregation from seaweed extracts by a microliter-scale high-throughput screening system with a quantum dot nanoprobe

Inhibitors of amyloid β (Aβ) aggregation have the potential to serve as lead compounds for anti-Alzheimer's disease (AD) agents because Aβ aggregation is a key step in AD pathogenesis. Recently, we developed a novel microliter-scale high-throughput screening (MSHTS) system for Aβ aggregation inhibitors that applied fluorescence microscopic analysis with quantum dot nanoprobes, and attempted to comprehensively screen the inhibitors from spices using this system (Ishigaki et al., PLoS One, 8, e72992, 2013). In this study, we tried to evaluate the inhibitory activities of 11 seaweed extracts on Aβ aggregation using the MSHTS system. The half-maximal effective concentration (EC50) of the ethanolic extracts from all seaweeds exceeded 4.9 mg/ml, indicating that the extracts inhibit Aβ aggregation although this activity was significantly lower than that displayed by members of the Lamiaceae, a family of herbal spices that showed highest activity among 52 spices tested in our 2013 study. On the other hand, the EC50 of boiling water extracts was 0.013-0.42 mg/ml which was comparable with the EC50 of the extracts from the Lamiaceae family. These results suggest that the extraction efficiency of the inhibitors by boiling water extraction was higher than that by ethanolic extraction. Moreover, analysis of fluorescence micrographs, which were obtained from the MSHTS system, revealed that the morphology of the Aβ aggregates coincubated with boiling water extracts differed from control aggregates, suggesting that the MSHTS system is also useful for screening substances that affect the morphology of aggregates.

Noninvasive label-free nanoplasmonic optical imaging for real-time monitoring of in vitro amyloid fibrogenesis

It is important to develop a noninvasive label-free detection method to monitor dynamic phenomena in biology and medicine. Here, we utilize nanoplasmonic optical imaging as the noninvasive and label-free method in order to monitor in vitro amyloid fibrogenesis in real-time, which is considered as the primary pathological mechanism of Alzheimer's disease. Using Rayleigh scattering of gold nanoplasmonic probes (GNPs), which have an enhanced scattering optical cross-section due to the surface plasmon resonance, we accomplished efficient tracking of the random movements of the GNPs in Aβ solution, and quantified the kinetics of the fibrogenesis. We expect that this noninvasive and label-free in vitro method can be utilized in monitoring in a wide range of other research fields as well. As future applications, we can envision long-term monitoring in neuronal cells to elucidate the mechanism of amyloid growth and NIR-based in vivo imaging with nanoplasmonic optical antennas for gene delivery, photonic gene circuits, and monitoring toward the theranostics of neurodegenerative diseases.

Peptide detection of fungal functional amyloids in infected tissue

Many fungal cell adhesion proteins form functional amyloid patches on the surface of adhering cells. The Candida albicansAgglutinin-like sequence (Als) adhesins are exemplars for this phenomenon, and have amyloid forming sequences that are conserved between family members. The Als5p amyloid sequence mediates amyloid fibril formation and is critical for cell adhesion and biofilm formation, and is also present in the related adhesins Als1p and Als3p. We have developed a fluorescent peptide probe containing the conserved Als amyloid-forming sequence. This peptide bound specifically to yeast expressing Als5p, but not to cells lacking the adhesin. The probe bound to both yeast and hyphal forms of C. albicans. Δals1/Δals3 single and double deletion strains exhibited reduced fluorescence, indicating that probe binding required expression of these proteins. Additionally, the Als peptide specifically stained fungal cells in abscesses in autopsy sections. Counterstaining with calcofluor white showed colocalization with the amyloid peptide. In addition, fungi in autopsy sections derived from the gastrointestinal tract showed colocalization of the amyloid-specific dye thioflavin T and the fluorescent peptide. Collectively, our data demonstrate that we can exploit amyloid sequence specificity for detection of functional amyloids in situ.

A microliter-scale high-throughput screening system with quantum-dot nanoprobes for amyloid-β aggregation inhibitors

The aggregation of amyloid β protein (Aβ) is a key step in the pathogenesis of Alzheimer’s disease (AD), and therefore inhibitory substances for Aβ aggregation may have preventive and/or therapeutic potential for AD. Here we report a novel microliter-scale high-throughput screening system for Aβ aggregation inhibitors based on fluorescence microscopy-imaging technology with quantum-dot Nanoprobes. This screening system could be analyzed with a 5-µl sample volume when a 1536-well plate was used, and the inhibitory activity could be estimated as half-maximal effective concentrations (EC₅₀). We attempted to comprehensively screen Aβ aggregation inhibitors from 52 spices using this system to assess whether this novel screening system is actually useful for screening inhibitors. Screening results indicate that approximately 90% of the ethanolic extracts from the spices showed inhibitory activity for Aβ aggregation. Interestingly, spices belonging to the Lamiaceae, the mint family, showed significantly higher activity than the average of tested spices. Furthermore, we tried to isolate the main inhibitory compound from Saturejahortensis, summer savory, a member of the Lamiaceae, using this system, and revealed that the main active compound was rosmarinic acid. These results demonstrate that this novel microliter-scale high-throughput screening system could be applied to the actual screening of Aβ aggregation inhibitors. Since this system can analyze at a microscopic scale, it is likely that further minimization of the system would easily be possible such as protein microarray technology.

Nanomaterials for reducing amyloid cytotoxicity

This review is intended to reflect the recent progress on therapeutic applications of nanomaterials in amyloid diseases. The progress on anti-amyloid functions of various nanomaterials including inorganic nanoparticles, polymeric nanoparticles, carbon nanomaterials and biomolecular aggregates, is reviewed and discussed. The main functionalization strategies for general nanoparticle modifications are reviewed for potential applications of targeted therapeutics. The interaction mechanisms between amyloid peptides and nanomaterials are discussed from the perspectives of dominant interactions and kinetics. The encapsulation of anti-amyloid drugs, targeted drug delivery, controlled drug release and drug delivery crossing blood brain barrier by application of nanomaterials would also improve the therapeutics of amyloid diseases.

Nanomedicine as a promising approach for the treatment and diagnosis of brain diseases: the example of Alzheimer's disease

Targeting of the central nervous system (CNS) in order to treat disorders is actually challenging due to the necessity to cross the blood brain barrier (BBB). This review aims to show how nanomedicine can propose new approach for the treatment and the diagnosis of CNS diseases focusing on Alzheimer's disease (AD). AD is a neurodegenerative disorder prevalent in the senile population. It is characterized by severe neuronal loss and proliferation of plaques composed of β-amyloid peptide (Aβ) and Tau protein deposites. An imbalance between production and clearance leading to the aggregation of Aβ peptides especially in neurotoxic forms, may be the initiating factor in AD. The absence of an effective therapeutic approach nowadays could be, in part, due to the bad knowledge of AD physiopathology and the lack of early diagnosis. Many drawbacks such as poor bioavailability or limited BBB arising of tested molecules in the current or new therapeutic strategies explain their failure but can be resolved by the use of nanotechnology. Examples of recently published works using nanoparticles for improving diagnosis and therapy of AD are presented. Ideal nanocarriers for this aim must be able to pass through the BBB and to interact with an AD marker as soluble extracellular Aβ forms which are known as the most toxic ones. These first results, even if many ones were obtained in vitro, brought to light the potential of nanoparticles for this challenging issue.

A simple method of labeling amyloid β with quantum dots and ingestion of the labeled amyloid β by astrocytes

Steady labeling of amyloid beta (Aβ) is crucial for studying the ingestion and degradation of Aβ by astrocytes and unraveling a relevant regulation mechanism. Quantum dots (QDs) are an optimum labeling reagent for this because of their strong and steady fluorescence properties. In this paper, Aβ was labeled with QDs by a simple mixed incubation strategy, with a QD labeled Aβ complex (QDs-Aβ) being obtained. In the complex, QDs efficiently restrained the formation of β-folding and fibrils of Aβ, while the graininess, dispersivity and fluorescence properties of the QDs hardly changed. The fluorescence microscopy imaging results showed that the astrocytes could ingest the QDs-Aβ. The QDs and Aβ did not separate from each other during the ingestion process, and the Aβ could be degraded subsequently.

Experimental inhibition of peptide fibrillogenesis by synthetic peptides, carbohydrates and drugs

Peptide fibrillogenesis generally begins by the transformation of normally soluble proteins into elongated aggregates which are called as amyloid. These fibrils mainly consist of ß-sheets. They share certain common characteristics such as a cross-ß x-ray diffraction pattern, association with other common proteins and typical staining by the dye Congo Red. The individual form of the deposit consists of a disease-specific peptide/protein. The disease-specific protein serves as the basis for the classification of the amyloids. The association of fibril-forming peptides/proteins with diseases makes them primary disease-targets. Understanding the molecular interactions involved in the fibril formation becomes the foremost requirement to characterize the target. Interference with these interactions of ß-sheets in vitro prevents and sometimes reverses the fibril assembly. A small molecule capable of interfering with the formation of fibril could have therapeutic applications in these diseases. This anti-aggregation approach appears to be a viable treatment option. A search for such a molecule is pursued actively world over. All types of compounds and approaches to slow down or prevent the aggregation process have been described in the literature. These efforts are reviewed in this chapter.

FGF2 gene transfer restores hippocampal functions in mouse models of Alzheimer's disease and has therapeutic implications for neurocognitive disorders

The adult hippocampus plays a central role in memory formation, synaptic plasticity, and neurogenesis. The subgranular zone of the dentate gyrus contains neural progenitor cells with self-renewal and multilineage potency. Transgene expression of familial Alzheimer's disease-linked mutants of β-amyloid precursor protein (APP) and presenilin-1 leads to a significant inhibition of neurogenesis, which is potentially linked to age-dependent memory loss. To investigate the effect of neurogenesis on cognitive function in a relevant disease model, FGF2 gene is delivered bilaterally to the hippocampi of APP+presenilin-1 bigenic mice via an adenoassociated virus serotype 2/1 hybrid (AAV2/1-FGF2). Animals injected with AAV2/1-FGF2 at a pre- or postsymptomatic stage show significantly improved spatial learning in the radial arm water maze test. A neuropathological investigation demonstrates that AAV2/1-FGF2 injection enhances the number of doublecortin, BrdU/NeuN, and c-fos-positive cells in the dentate gyrus, and the clearance of fibrillar amyloid-β peptide (Aβ) in the hippocampus. AAV2/1-FGF2 injection also enhances long-term potentiation in another APP mouse model (J20) compared with control AAV2/1-GFP-injected littermates. An in vitro study confirmed the enhanced neurogenesis of mouse neural stem cells by direct AAV2/1-FGF2 infection in an Aβ oligomer-sensitive manner. Further, FGF2 enhances Aβ phagocytosis in primary cultured microglia, and reduces Aβ production from primary cultured neurons after AAV2/1-FGF2 infection. Thus, our data indicate that virus-mediated FGF2 gene delivery has potential as an alternative therapy of Alzheimer's disease and possibly other neurocognitive disorders.

Nanotechnologies for Alzheimer's disease: diagnosis, therapy, and safety issues

Alzheimer's disease (AD) represents the most common form of dementia worldwide, affecting more than 35 million people. Advances in nanotechnology are beginning to exert a significant impact in neurology. These approaches, which are often based on the design and engineering of a plethora of nanoparticulate entities with high specificity for brain capillary endothelial cells, are currently being applied to early AD diagnosis and treatment. In addition, nanoparticles (NPs) with high affinity for the circulating amyloid-β (Aβ) forms may induce "sink effect" and improve the AD condition. There are also developments in relation to in vitro diagnostics for AD, including ultrasensitive NP-based bio-barcodes, immunosensors, as well as scanning tunneling microscopy procedures capable of detecting Aβ(1-40) and Aβ(1-42). However, there are concerns regarding the initiation of possible NP-mediated adverse events in AD, thus demanding the use of precisely assembled nanoconstructs from biocompatible materials. Key advances and safety issues are reviewed and discussed.