Rapid Growth Cone Uptake and Dynein-Mediated Axonal Retrograde Transport of Negatively Charged Nanoparticles in Neurons Is Dependent on Size and Cell Type

Neural Tracing Protein-Functionalized Nanoparticles Capable of Fast Retrograde Axonal Transport in Live Neurons

Neural tracing proteins like horseradish peroxidase-conjugated wheat germ agglutinin (WGA-HRP) can target the central nervous system (CNS) through anatomic retrograde transport without crossing the blood-brain barrier (BBB). Conjugating WGA-HRP to nanoparticles may enable the creation of BBB-bypassing nanomedicine. Microfluidics and two-photon confocal microscopy is applied to screen nanocarriers for transport efficacy and gain mechanistic insights into their interactions with neurons. Protein modification of gold nanoparticles alters their cellular uptake at the axonal terminal and activates fast retrograde transport. Trajectory analysis of individual endosomes carrying the nanoparticles reveals a run-and-pause pattern along the axon with endosomes carrying WGA-HRP-conjugated gold nanoparticles exhibiting longer run duration and faster instantaneous velocity than those carrying nonconjugated nanoparticles. The results offer a mechanistic explanation of the different axonal transport dynamics as well as a cell-based functional assay of neuron-targeted nanoparticles with the goal of developing BBB-bypassing nanomedicine for the treatment of nervous system disorders.

Nano-pulling stimulates axon regeneration in dorsal root ganglia by inducing stabilization of axonal microtubules and activation of local translation

Introduction

Axonal plasticity is strongly related to neuronal development as well as regeneration. It was recently demonstrated that active mechanical tension, intended as an extrinsic factor, is a valid contribution to the modulation of axonal plasticity.

Methods

In previous publications, our team validated a the "nano-pulling" method used to apply mechanical forces to developing axons of isolated primary neurons using magnetic nanoparticles (MNP) actuated by static magnetic fields. This method was found to promote axon growth and synaptic maturation. Here, we explore the use of nano-pulling as an extrinsic factor to promote axon regeneration in a neuronal tissue explant.

Results

Whole dorsal root ganglia (DRG) were thus dissected from a mouse spinal cord, incubated with MNPs, and then stretched. We found that particles were able to penetrate the ganglion and thus become localised both in the somas and in sprouting axons. Our results highlight that nano-pulling doubles the regeneration rate, and this is accompanied by an increase in the arborizing capacity of axons, an accumulation of cellular organelles related to mass addition (endoplasmic reticulum and mitochondria) and pre-synaptic proteins with respect to spontaneous regeneration. In line with the previous results on isolated hippocampal neurons, we observed that this process is coupled to an increase in the density of stable microtubules and activation of local translation.

Discussion

Our data demonstrate that nano-pulling enhances axon regeneration in whole spinal ganglia exposed to MNPs and external magnetic fields. These preliminary data represent an encouraging starting point for proposing nano-pulling as a biophysical tool for the design of novel therapies based on the use of force as an extrinsic factor for promoting nerve regeneration.

A Multisystemic Approach Revealed Aminated Polystyrene Nanoparticles-Induced Neurotoxicity

Exposure to plastic nanoparticles has dramatically increased in the last 50 years, and there is evidence that plastic nanoparticles can be absorbed by organisms and cross the blood-brain-barrier (BBB). However, their toxic effects, especially on the nervous system, have not yet been extensively investigated, and most of the knowledge is based on studies using different conditions and systems, thus hard to compare. In this work, physicochemical properties of non-modified polystyrene (PS) and amine-functionalized PS (PS-NH2 ) nanoparticles are initially characterized. Advantage of a multisystemic approach is then taken to compare plastic nanoparticles effects in vitro, through cytotoxic readouts in mammalian cell culture, and in vivo, through behavioral readouts in the nematode Caenorhabditis elegans (C. elegans), a powerful 3R-complying model organism for toxicology studies. In vitro experiments in neuroblastoma cells indicate a specific cytotoxic effect of PS-NH2 particles, including a decreased neuronal differentiation and an increased Amyloid β (Aβ) secretion, a sensitive readout correlating with Alzheimer's disease pathology. In parallel, only in vivo treatments with PS-NH2 particles affect C. elegans development, decrease lifespan, and reveal higher sensitivity of animals expressing human Aβ compared to wild-type animals. In summary, the multisystemic approach discloses a neurotoxic effect induced by aminated polystyrene nanoparticles.

Anionic nanoplastic contaminants promote Parkinson's disease-associated α-synuclein aggregation

Recent studies have identified increasing levels of nanoplastic pollution in the environment. Here, we find that anionic nanoplastic contaminants potently precipitate the formation and propagation of α-synuclein protein fibrils through a high-affinity interaction with the amphipathic and non-amyloid component (NAC) domains in α-synuclein. Nanoplastics can internalize in neurons through clathrin-dependent endocytosis, causing a mild lysosomal impairment that slows the degradation of aggregated α-synuclein. In mice, nanoplastics combine with α-synuclein fibrils to exacerbate the spread of α-synuclein pathology across interconnected vulnerable brain regions, including the strong induction of α-synuclein inclusions in dopaminergic neurons in the substantia nigra. These results highlight a potential link for further exploration between nanoplastic pollution and α-synuclein aggregation associated with Parkinson's disease and related dementias.

Neuroprotective effect of nose-to-brain delivery of Asiatic acid in solid lipid nanoparticles and its mechanisms against memory dysfunction induced by Amyloid Beta1-42 in mice

BACKGROUND

Amyloid-β1-42 (Aβ1-42) plays an essential role in the development of the early stage of Alzheimer's disease (AD). Asiatic acid (AA), an active compound in Centella asiatica L, exhibit neuroprotective properties in previous studies. Due to its low bioavailability, the nose-to-brain delivery technique was used to enhance AA penetration in the brain. In this study, AA was also loaded in solid lipid nanoparticles (SLNs) as a strategy to increase its absorption in the nasal cavity.

METHODS

Memory impairment was induced via direct intracerebroventricular injection of Aβ1-42 oligomer into mouse brain. The neuroprotective effect and potential underlying mechanisms were investigated using several memory behavioral examinations and molecular techniques.

RESULTS

The intranasal administration of AA in SLNs attenuated learning and memory impairment induced by Aβ1-42 in Morris water maze and novel object recognition tests. AA significantly inhibited tau hyperphosphorylation of pTau-S396 and pTau-T231 and prevented astrocyte reactivity and microglial activation in the hippocampus of Aβ1-42-treated mice. It is also decreased the high levels of IL-1β, TNF-α, and malondialdehyde (MDA) in mouse brain.

CONCLUSIONS

These results suggested that nose-to-brain delivery of AA in SLNs could be a promising strategy to treat the early stage of AD.

Colloidal Perspective on Targeted Drug Delivery to the Central Nervous System

This article describes a new approach in targeted drug delivery to the central nervous system (CNS) in a significant departure from the predominant systematic drug administration attempting to penetrate the blood-brain barrier (BBB). Nanoparticles chemically conjugated to neural tract tracer proteins are capable of path-specific axonal retrograde transport, transneuronal transport, and anatomical tract flow to bypass the BBB. To celebrate the work by Dr. Bettye Washington Greene on the physical chemistry of colloidal particles, this article focuses on the physiochemical characteristics of the nanoparticles, various colloidal forces that impact the colloidal stability of nanoparticles in biological media, and surface chemistry strategies to avoid nanoparticle aggregation-induced poor therapeutic outcomes. The biological environment for the anatomical retrograde transport of neural tract tracers is examined to directly link factors impacting the colloidal stability of the new class of CNS-targeting nanoconjugates such as nanoconjugate size, shape, surface charge, surface chemistry, ionic strength, pH, and protein adsorption on the nanoparticle. We conclude with opportunities and challenges for future research.

Nanotechnology: A Promising Targeted Drug Delivery System for Brain Tumours and Alzheimer's Disease

Nanotechnology is the process of modulating shape and size at the nanoscale to design and manufacture structures, devices, and systems. Nanotechnology's prospective breakthroughs are incredible, and some cannot even be comprehended right now. The blood-brain barrier, which is a prominent physiological barrier in the brain, limits the adequate elimination of malignant cells by changing the concentration of therapeutic agents at the target tissue. Nanotechnology has sparked interest in recent years as a way to solve these issues and improve drug delivery. Inorganic and organic nanomaterials have been found to be beneficial for bioimaging approaches and controlled drug delivery systems. Brain cancer (BC) and Alzheimer's disease (AD) are two of the prominent disorders of the brain. Even though the pathophysiology and pathways for both disorders are different, nanotechnology with common features can deliver drugs over the BBB, advancing the treatment of both disorders. This innovative technology could provide a foundation for combining diagnostics, treatments, and delivery of targeted drugs to the tumour site, further supervising the response and designing and delivering materials by employing atomic and molecular elements. There is currently limited treatment for Alzheimer's disease, and reversing further progression is difficult. Recently, various nanocarriers have been investigated to improve the bioavailability and efficacy of many AD treatment drugs. Nanotechnology-assisted drugs can penetrate the BBB and reach the target tissue. However, further research is required in this field to ensure the safety and efficacy of drug-loaded nanoparticles. The application of nanotechnology in the diagnosis and treatment of brain tumours and Alzheimer's disease is briefly discussed in this review.

Nanotransducers for Wireless Neuromodulation

Understanding the signal transmission and processing within the central nervous system (CNS) is a grand challenge in neuroscience. The past decade has witnessed significant advances in the development of new tools to address this challenge. Development of these new tools draws diverse expertise from genetics, materials science, electrical engineering, photonics and other disciplines. Among these tools, nanomaterials have emerged as a unique class of neural interfaces due to their small size, remote coupling and conversion of different energy modalities, various delivery methods, and mitigated chronic immune responses. In this review, we will discuss recent advances in nanotransducers to modulate and interface with the neural system without physical wires. Nanotransducers work collectively to modulate brain activity through optogenetic, mechanical, thermal, electrical and chemical modalities. We will compare important parameters among these techniques including the invasiveness, spatiotemporal precision, cell-type specificity, brain penetration, and translation to large animals and humans. Important areas for future research include a better understanding of the nanomaterials-brain interface, integration of sensing capability for bidirectional closed-loop neuromodulation, and genetically engineered functional materials for cell-type specific neuromodulation.

Neuronal delivery of nanoparticles via nerve fibres in the skin

Accessing the peripheral nervous system (PNS) by topically applied nanoparticles is a simple and novel approach with clinical applications in several PNS disorders. Skin is richly innervated by long peripheral axons that arise from cell bodies located distally within ganglia. In this study we attempt to target dorsal root ganglia (DRG) neurons, via their axons by topical application of lectin-functionalized gold nanoparticles (IB4-AuNP). In vitro, 140.2 ± 1.9 nm IB4-AuNP were found to bind both axons and cell bodies of DRG neurons, and AuNP applied at the axonal terminals were found to translocate to the cell bodies. Topical application of IB4-AuNP on rat hind-paw resulted in accumulation of three to fourfold higher AuNP in lumbar DRG than in contralateral control DRGs. Results from this study clearly suggest that topically applied nanoparticles with neurotropic targeting ligands can be utilized for delivering nanoparticles to neuronal cell bodies via axonal transport mechanisms.

Governing Transport Principles for Nanotherapeutic Application in the Brain

Neurological diseases account for a significant portion of the global disease burden. While research efforts have identified potential drugs or drug targets for neurological diseases, most therapeutic platforms are still ineffective at reaching the target location selectively and with high yield. Restricted transport, including passage across the blood-brain barrier, through the brain parenchyma, and into specific cells, is a major cause of ineffective therapeutic delivery. However, nanotechnology is a promising, tailorable platform for overcoming these transport barriers and improving therapeutic delivery to the brain. We provide a transport-oriented analysis of nanotechnology's ability to navigate these transport barriers in the brain. We also provide an opinion on the need for technology development for increasing our capacity to characterize and quantify nanoparticle passage through each transport barrier. Finally, we highlight the importance of incorporating the effect of disease, metabolic state, and regional dependencies to better understand transport of nanotherapeutics in the brain.

CURATE.AI: Optimizing Personalized Medicine with Artificial Intelligence

The clinical team attending to a patient upon a diagnosis is faced with two main questions: what treatment, and at what dose? Clinical trials' results provide the basis for guidance and support for official protocols that clinicians use to base their decisions upon. However, individuals rarely demonstrate the reported response from relevant clinical trials, often the average from a group representing a population or subpopulation. The decision complexity increases with combination treatments where drugs administered together can interact with each other, which is often the case. Additionally, the individual's response to the treatment varies over time with the changes in his or her condition, whether via the indication or physiology. In practice, the drug and the dose selection depend greatly on the medical protocol of the healthcare provider and the medical team's experience. As such, the results are inherently varied and often suboptimal. Big data approaches have emerged as an excellent decision-making support tool, but their application is limited by multiple challenges, the main one being the availability of sufficiently big datasets with good quality, representative information. An alternative approach-phenotypic personalized medicine (PPM)-finds an appropriate drug combination (quadratic phenotypic optimization platform [QPOP]) and an appropriate dosing strategy over time (CURATE.AI) based on small data collected exclusively from the treated individual. PPM-based approaches have demonstrated superior results over the current standard of care. The side effects are limited while the desired output is maximized, which directly translates into improving the length and quality of individuals' lives.