Nanoparticles as contrast agents for the diagnosis of Alzheimer’s disease: a systematic review

Biocompatibility and proteomic profiling of DMSA-coated iron nanocubes in a human glioblastoma cell line

Background: Superparamagnetic iron core iron oxide shell nanocubes have previously shown superior performance in magnetic resonance imaging T2 contrast enhancement compared with spherical nanoparticles. Methods: Iron core iron oxide shell nanocubes were synthesized, stabilized with dimercaptosuccinic acid (DMSA-NC) and physicochemically characterized. MRI contrast enhancement and biocompatibility were assessed in vitro. Results: DMSA-NC showed a transverse relaxivity of 122.59 mM-1·s-1 Fe. Treatment with DMSA-NC did not induce cytotoxicity or oxidative stress in U-251 cells, and electron microscopy demonstrated DMSA-NC localization within endosomes and lysosomes in cells following internalization. Global proteomics revealed dysregulation of iron storage, transport, transcription and mRNA processing proteins. Conclusion: DMSA-NC is a promising T2 MRI contrast agent which, in this preliminary investigation, demonstrates favorable biocompatibility with an astrocyte cell model.

Self-assembly of Au nanocubes for ultrasensitive detection of Alzheimer's disease biomarkers by SERS

Since presently Alzheimer's disease (AD) is incurable, early diagnosis of AD is crucial. Aβ 1-42 and tau-441 proteins are promising core biomarkers for early diagnosis and early therapeutic intervention in AD. Here we constructed a surface-enhanced Raman spectroscopy (SERS) biosensor for highly sensitive quantitative detection of Aβ 1-42 and tau proteins by preparing gold nanocube (AuNC) superlattices through evaporation self-assembly. The results showed that the method has a wide response range (0.1-10 000 ng mL-1 and 0.01-1000 ng mL-1, respectively) and high sensitivity. The detection limits of Aβ1-42 and tau protein were 0.0416 ng mL-1 and 0.0087 ng mL-1, respectively. In addition, the method was able to rapidly and simultaneously detect the two biomarkers in serum, which showed the feasibility of the method in complex biological environments. The detection of Aβ 1-42 and tau protein has great potential for the accurate prediction and early diagnosis of Alzheimer's disease.

Evaluation of Dimercaptosuccinic Acid-Coated Iron Nanoparticles Immunotargeted to Amyloid Beta as MRI Contrast Agents for the Diagnosis of Alzheimer's Disease

Nanoparticle-based magnetic contrast agents have opened the potential for magnetic resonance imaging (MRI) to be used for early non-invasive diagnosis of Alzheimer's disease (AD). Accumulation of amyloid pathology in the brain has shown association with cognitive decline and tauopathy; hence, it is an effective biomarker for the early detection of AD. The aim of this study was to develop a biocompatible magnetic nanoparticle targeted to amyloid beta (Aβ) plaques to increase the sensitivity of T2-weighted MRI for imaging of amyloid pathology in AD. We presented novel iron core-iron oxide nanoparticles stabilized with a dimercaptosuccinic acid coating and functionalized with an anti-Aβ antibody. Nanoparticle biocompatibility and cellular internalization were evaluated in vitro in U-251 glioblastoma cells using cellular assays, proteomics, and transmission electron microscopy. Iron nanoparticles demonstrated no significant in vitro cytotoxicity, and electron microscopy results showed their movement through the endocytic cycle within the cell over a 24 h period. In addition, immunostaining and bio-layer interferometry confirmed the targeted nanoparticle's binding affinity to amyloid species. The iron nanoparticles demonstrated favourable MRI contrast enhancement; however, the addition of the antibody resulted in a reduction in the relaxivity of the particles. The present work shows promising preliminary results in the development of a targeted non-invasive method of early AD diagnosis using contrast-enhanced MRI.

A Promising Approach: Magnetic Nanosystems for Alzheimer's Disease Theranostics

Among central nervous system (CNS) disorders, Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and a major cause of dementia worldwide. The yet unclear etiology of AD and the high impenetrability of the blood-brain barrier (BBB) limit most therapeutic compounds from reaching the brain. Although many efforts have been made to effectively deliver drugs to the CNS, both invasive and noninvasive strategies employed often come with associated side effects. Nanotechnology-based approaches such as nanoparticles (NPs), which can act as multifunctional platforms in a single system, emerged as a potential solution for current AD theranostics. Among these, magnetic nanoparticles (MNPs) are an appealing strategy since they can act as contrast agents for magnetic resonance imaging (MRI) and as drug delivery systems. The nanocarrier functionalization with specific moieties, such as peptides, proteins, and antibodies, influences the particles' interaction with brain endothelial cell constituents, facilitating transport across the BBB and possibly increasing brain penetration. In this review, we introduce MNP-based systems, combining surface modifications with the particles' physical properties for molecular imaging, as a novel neuro-targeted strategy for AD theranostics. The main goal is to highlight the potential of multifunctional MNPs and their advances as a dual nanotechnological diagnosis and treatment platform for neurodegenerative disorders.

Two-Photon Fluorescent Probes for Amyloid-β Plaques Imaging In Vivo

Amyloid-β (Aβ) peptide deposition, hyperphosphorylated tau proteins, reactive astrocytes, high levels of metal ions, and upregulated monoamine oxidases are considered to be the primary pathological markers of Alzheimer's disease (AD). Among them, Aβ peptide deposition or Aβ plaques, is regarded as the initial factor in the pathogenesis of AD and a critical pathological hallmark in AD. This review highlights recently Aβ-specific fluorescent probes for two-photon imaging of Aβ plaques in vivo. It includes the synthesis and detection mechanism of probes, as well as their application to two-photon imaging of Aβ plaques in vivo.

In vivo targeting and multimodal imaging of cerebral amyloid-β aggregates using hybrid GdF3 nanoparticles

Aim: To propose a new multimodal imaging agent targeting amyloid-β (Aβ) plaques in Alzheimer's disease. Materials & methods: A new generation of hybrid contrast agents, based on gadolinium fluoride nanoparticles grafted with a pentameric luminescent-conjugated polythiophene, was designed, extensively characterized and evaluated in animal models of Alzheimer's disease through MRI, two-photon microscopy and synchrotron x-ray phase-contrast imaging. Results & conclusion: Two different grafting densities of luminescent-conjugated polythiophene were achieved while preserving colloidal stability and fluorescent properties, and without affecting biodistribution. In vivo brain uptake was dependent on the blood-brain barrier status. Nevertheless, multimodal imaging showed successful Aβ targeting in both transgenic mice and Aβ fibril-injected rats.

Drug Discovery and Development Targeting Dementia

Dementia, most often associated with neurodegenerative diseases, affects millions of people worldwide, predominantly the elderly. Unfortunately, no treatment is still available. Therefore, there is an urgent need to address this situation. This review presents the state of the art of drug discovery and developments in targeting dementia. Several approaches are discussed, such as drug repurposing, the use of small molecules, and phosphodiesterase inhibitors. Furthermore, the review also provides insights into clinical trials of these molecules. Emphasis has been placed on small molecules and multi-target-directed ligands, as well as disease-modifying therapies. Finally, attention is drawn to the possibilities of applications of nanotechnology in managing dementia.

Immunomodulation in age-related disorders and nanotechnology interventions

Recently, the aging population has increased exponentially around the globe bringing more challenges to improve quality of life in those populations while reducing the economic burden on healthcare systems. Aging is associated with changes in the immune system culminating in detrimental effects such as immune dysfunction, immunosenescence, and chronic inflammation. Age-related decline of immune functions is associated with various pathologies including cardiovascular, autoimmune, neurodegenerative, and infectious diseases to name a few. Conventional treatment addresses the onset of age-related diseases by early detection of risk factors, administration of vaccines as preventive care, immunomodulatory treatment, and other dietary supplements. However, these approaches often come with systemic side-effects, low bioavailability of therapeutic agents, and poor outcomes seen in the elderly. Recent innovations in nanotechnology have led to the development of novel biomaterials/nanomaterials, which explore targeted drug delivery and immunomodulatory interactions in vivo. Current nanotechnology-based immunomodulatory approaches that have the potential to be used as therapeutic interventions for some prominent age-related diseases are discussed here. Finally, we explore challenges and future aspects of nanotechnology in the treatments of age-related disorders to improve quality of life in the elderly. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Therapeutic nanotechnologies for Alzheimer's disease: a critical analysis of recent trends and findings

Alzheimer's Disease (AD) is an irreversible neurodegenerative disease for which no disease modifying therapies are presently available. Besides the identification of pathological targets, AD presents numerous clinical and pharmacological challenges such as efficient active delivery to the central nervous system, cell targeting, and long-term dosing. Nanoparticles have been explored to overcome some of these challenges as drug delivery vehicles or drugs themselves. However, early promises have failed to materialize as no nanotechnology-based product has been able to reach the market and very few have moved past preclinical stages. In this review, we perform a critical analysis of the past decade's research on nanomedicine-based therapies for AD at the preclinical and clinical stages. The main obstacles to nanotechnology products and the most promising approaches were also identified, including renewed promise with gene editing, gene modulation, and vaccines.

How Could Nanomedicine Improve the Safety of Contrast Agents for MRI during Pregnancy?

Pregnancy is a delicate state, during which timely investigation of possible physiological anomalies is essential to reduce the risk of maternal and fetal complications. Medical imaging encompasses different technologies to image the human body for the diagnosis, course of treatment management, and follow-up of diseases. Ultrasound (US) is currently the imaging system of choice for pregnant patients. However, sonographic evaluations can be non-effective or give ambiguous results. Therefore, magnetic resonance imaging (MRI), due to its excellent tissue penetration, the possibility of acquisition of three-dimensional anatomical information, and its high spatial resolution, is considered a valid diagnostical alternative. Nevertheless, currently employed contrast agents to improve the MRI image quality are harmful to the fetus. Because of their ability to cross the placenta, their use on pregnant patients is avoided. This review will firstly recapitulate the most common non-obstetrical, obstetrical, and fetal indications for magnetic resonance imaging on pregnant women. Fetal safety risks, due to the use of strong magnetic fields and exogenous contrast agents, will be presented. Then, possible advantages of nanostructured contrast agents compared to current molecular ones are explored. Nanosystems’ characteristics affecting contrast efficiency, and their potential for improving contrast-enhanced MRI’s safety in pregnant women, are discussed. Lastly, promising examples of nanoparticles as safer alternatives to current MRI contrast agents in pregnancy are discussed.

Alzheimer's Disease: Pathogenesis and Therapeutic Interventions

BACKGROUND

Alzheimer's Disease (AD) is the most common cause of dementia. Genetics, excessive exposure to environmental pollutants, as well as unhealthy lifestyle practices are often linked to the development of AD. No therapeutic approach has achieved complete success in treating AD; however, early detection and management with appropriate drugs are key to improving prognosis.

INTERVENTIONS

The pathogenesis of AD was extensively discussed in order to understand the reasons for the interventions suggested. The interventions reviewed include the use of different therapeutic agents and approaches, gene therapy, adherence to healthy dietary plans (Mediterranean diet, Okinawan diet and MIND diet), as well as the use of medicinal plants. The potential of nanotechnology as a multidisciplinary and interdisciplinary approach in the design of nano-formulations of AD drugs and the use of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as theranostic tools for early detection of Alzheimer's disease were also discussed.

Development of modified polymer dot as stimuli-sensitive and 67Ga radio-carrier, for investigation of in vitro drug delivery, in vivo imaging and drug release kinetic

A polymer dot modified histidine-functionalized graphene quantum dot carrier, PD@His.GQD, was synthesized to investigate the in vitro sunitinib (STB) deliveryvia luminescence spectrometer. The carrier's synthesis, with an average size of 34 nm, was proved by Fourier transform infrared (FTIR), Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS) analyses. In the in vitro, STB delivery investigation showed that for healthy tissue, the STB was loaded at pH  = 7.2 and at 25  = 5.4 at 37 °C with a maximum loading efficiency percentage of 99 % while it was released at pH = 5.4 at 37 °C with a release percentage of 97 %. In the sequel, the STB loaded carrier was labeled with Gallium-67 (⁶⁷Ga-STB.PD@His.GQD) to produce exceedingly transparent radio-carrier for in vivo kidney cancerous mice imaging via the single photon emission computed tomography (SPECT) device. The radiochemical purity of the ⁶⁷Ga-STB.PD@His.GQD was obtained as 95 % by Radio Thin Layer Chromatography (RTLC) and High-Performance Liquid Chromatography (HPLC) analysis. All obtained results affirmed that the synthesized PD@His.GQD is an STB stimuli-sensitive and selective targeting carrier. All cancerous mice in vivo images at 10 and 20 h of ⁶⁷Ga-STB.PD@His.GQD post-injection and its bio-distribution calculations showed its most accumulation in the kidney cancerous tissue. Also, the STB release kinetic was studied via Zero-order, First-order, Higuchi, and Korsmeyer-Peppas models, and the release data were fitted with Korsmeyer-Peppas model that expresses the STB release mechanism is controlled by diffusion.

Plasmonic Nanoparticles as Optical Sensing Probes for the Detection of Alzheimer's Disease

Alzheimer's disease (AD), considered a common type of dementia, is mainly characterized by a progressive loss of memory and cognitive functions. Although its cause is multifactorial, it has been associated with the accumulation of toxic aggregates of the amyloid-β peptide (Aβ) and neurofibrillary tangles (NFTs) of tau protein. At present, the development of highly sensitive, high cost-effective, and non-invasive diagnostic tools for AD remains a challenge. In the last decades, nanomaterials have emerged as an interesting and useful tool in nanomedicine for diagnostics and therapy. In particular, plasmonic nanoparticles are well-known to display unique optical properties derived from their localized surface plasmon resonance (LSPR), allowing their use as transducers in various sensing configurations and enhancing detection sensitivity. Herein, this review focuses on current advances in in vitro sensing techniques such as Surface-enhanced Raman scattering (SERS), Surface-enhanced fluorescence (SEF), colorimetric, and LSPR using plasmonic nanoparticles for improving the sensitivity in the detection of main biomarkers related to AD in body fluids. Additionally, we refer to the use of plasmonic nanoparticles for in vivo imaging studies in AD.

SERS-Based Immunoassay Enhanced with Silver Probe for Selective Separation and Detection of Alzheimer's Disease Biomarkers

Purpose

Developing a sensitive SERS-based method to quantitatively detect serum biomarkers (Aβ1-42 and P-Tau-181) for the early diagnosis of Alzheimer’s disease (AD).

Methods

In this study, a novel SERS-based sandwich immunoassay, which consists of tannin-capped silver nanoparticles and magnetic graphene oxide (Fe₃O₄@GOs), was developed. We firstly applied this method for the detection of protein standards in buffer solution, obtaining the regression equation. Then, its potential value on real serum samples of AD was further explored.

Results

The detection linear range of Aβ1-42 and P-Tau-181 protein standards were observed to range from 100 pg mL⁻¹ to 10 fg mL⁻¹, 100 pg mL⁻¹ to 1 fg mL⁻¹ respectively. We finally explored clinical application of the proposed method in 63 serum samples. As a result, P-tau-181 differentiated AD from non-AD dementia patients (AUC = 0.770), with a more favored ROC than Aβ1-42 (AUC = 0.383).

Conclusion

The developed SERS-based immunoassay is successfully applied to the determination of Aβ1-42 and P-Tau-181 in human serum specimens, which provides a promising tool for the early diagnosis of AD.

Applications of magnetic particle imaging in the dementias

PURPOSE OF REVIEW

This review discusses recent developments in the application of magnetic particle imaging (MPI) to dementia research.

RECENT FINDINGS

MPI is a tracer method that is currently in the preclinical development stage. It provides high sensitivity for the detection and localization of magnetic nanoparticles with very high spatial and temporal resolution and a similar application spectrum as PET. Unlike MRI, the MPI signal is not contaminated by background signal from tissues and is highly quantifiable in terms of local tracer concentrations. These properties make the technology ideally suited for localization of specific targets or quantification of vascular parameters. MPI uses magnetic nanoparticles which can be modified by various coatings, and by adding ligands (i.e. peptides or antibodies) for specific targeting. This makes MPI an attractive tool for the potential detection of abnormal protein deposits, such as Aβ plaques, with greater specificity than MRI. Neural stem cells can also be labelled with these nanoparticles ex vivo to monitor their migration in vivo.

SUMMARY

The capabilities of MPI opens the potential for several applications of MPI in neurocognitive disorders, including vascular imaging, detection of amyloid plaques and potentially other pathological hallmarks of Alzheimer's disease and stem-cell tracking.

Advances in fluorescent probes for detection and imaging of amyloid-β peptides in Alzheimer's disease

Amyloid plaques generated from the accumulation of amyloid-β peptides (Aβ) fibrils in the brain is one of the main hallmarks of Alzheimer's disease (AD), a most common neurodegenerative disorder. Aβ aggregation can produce neurotoxic oligomers and fibrils, which has been widely accepted as the causative factor in AD pathogenesis. Accordingly, both soluble oligomers and insoluble fibrils have been considered as diagnostic biomarkers for AD. Among the existing analytical methods, fluorometry using fluorescent probes has exhibited promising potential in quantitative detection and imaging of both soluble and insoluble Aβ species, providing a valuable approach for the diagnosis and drug development of AD. In this review, the most recent advances in the fluorescent probes for soluble or insoluble Aβ aggregates are discussed in terms of design strategy, probing mechanism, and potential applications. In the end, future research directions of fluorescent probes for Aβ species are also proposed.

Functional nanoassemblies for the diagnosis and therapy of Alzheimer's diseases

Alzheimer's disease (AD) is a progressive neurodegenerative disease that affects populations around the world. Many therapeutics have been investigated for AD diagnosis and/or therapy, but the efficacy is largely limited by the poor bioavailability of drugs and by the presence of the blood-brain barrier. Recently, the development of nanomedicines enables efficient drug delivery to the brain, but the complex pathological mechanism of AD prevents them from successful treatment. As a type of advanced nanomedicine, multifunctional nanoassemblies self-assembled from nanoscale imaging or therapeutic agents can simultaneously target multiple pathological factors, showing great potential in the diagnosis and therapy of AD. To help readers better understand this emerging field, in this review, we first introduce the pathological mechanisms and the potential drug candidates of AD, as well as the design strategies of nanoassemblies for improving AD targeting efficiency. Moreover, the progress of dynamic nanoassemblies that can diagnose and/or treat AD in response to the endogenous or exogenous stimuli will be described. Finally, we conclude with our perspectives on the future development in this field. The objective of this review is to outline the latest progress of using nanoassemblies to overcome the complex pathological environment of AD for improved diagnosis and therapy, in hopes of accelerating the future development of intelligent AD nanomedicines. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Diagnostic Tools > in vivo Nanodiagnostics and Imaging.