Nanoparticle-Based and Bioengineered Probes and Sensors to Detect Physiological and Pathological Biomarkers in Neural Cells

Multivalent Display of Erythropoietin on Quantum Dots Enhances Aquaporin-4 Expression and Water Transport in Human Astrocytes In Vitro

In mammalian cells, growth factor-induced intracellular signaling and protein synthesis play a critical role in cellular physiology and homeostasis. In the brain's glymphatic system (GS), the water-conducting activity of aquaporin-4 (AQPN-4) membrane channels (expressed in polarized fashion on astrocyte end-feet) mediates the clearance of wastes through the convective transport of fluid and solutes through the perivascular space. The glycoprotein erythropoietin (EPO) has been shown to induce the astrocyte expression of AQPN-4 via signaling through the EPO receptor and the JAK/STAT signaling pathway. Here, we self-assemble EPO in a multivalent fashion onto the surface of semiconductor quantum dots (QDs) (driven by polyhistidine-based self-assembly) to drive the interaction of the bioconjugates with EPOR on human astrocytes (HA). This results in a 2-fold augmentation of JAK/STAT signaling activity and a 1.8-fold enhancement in the expression of AQPN-4 in cultured primary HA compared to free EPO. This translates into a 2-fold increase in the water transport rate in HA cells as measured by the calcein AM water transport assay. Importantly, EPO-QD-induced augmented AQPN-4 expression does not elicit any deleterious effect on the astrocyte viability. We discuss our results in the context of the implications of EPO-nanoparticle (NP) bioconjugates for use as research tools to understand the GS and their potential as therapeutics for the modulation of GS function. More generally, our results illustrate the utility of NP bioconjugates for the controlled modulation of growth factor-induced intracellular signaling.

Advanced theragnostics for the central nervous system (CNS) and neurological disorders using functional inorganic nanomaterials

Various types of inorganic nanomaterials are capable of diagnostic biomarker detection and the therapeutic delivery of a disease or inflammatory modulating agent. Those multi-functional nanomaterials have been utilized to treat neurodegenerative diseases and central nervous system (CNS) injuries in an effective and personalized manner. Even though many nanomaterials can deliver a payload and detect a biomarker of interest, only a few studies have yet to fully utilize this combined strategy to its full potential. Combining a nanomaterial's ability to facilitate targeted delivery, promote cellular proliferation and differentiation, and carry a large amount of material with various sensing approaches makes it possible to diagnose a patient selectively and sensitively while offering preventative measures or early disease-modifying strategies. By tuning the properties of an inorganic nanomaterial, the dimensionality, hydrophilicity, size, charge, shape, surface chemistry, and many other chemical and physical parameters, different types of cells in the central nervous system can be monitored, modulated, or further studies to elucidate underlying disease mechanisms. Scientists and clinicians have better understood the underlying processes of pathologies for many neurologically related diseases and injuries by implementing multi-dimensional 0D, 1D, and 2D theragnostic nanomaterials. The incorporation of nanomaterials has allowed scientists to better understand how to detect and treat these conditions at an early stage. To this end, having the multi-modal ability to both sense and treat ailments of the central nervous system can lead to favorable outcomes for patients suffering from such injuries and diseases.

Recent technological advances in correlative light and electron microscopy for the comprehensive analysis of neural circuits

Light microscopy (LM) covers a relatively wide area and is suitable for observing the entire neuronal network. However, resolution of LM is insufficient to identify synapses and determine whether neighboring neurons are connected via synapses. In contrast, the resolution of electron microscopy (EM) is sufficiently high to detect synapses and is useful for identifying neuronal connectivity; however, serial images cannot easily show the entire morphology of neurons, as EM covers a relatively narrow region. Thus, covering a large area requires a large dataset. Furthermore, the three-dimensional (3D) reconstruction of neurons by EM requires considerable time and effort, and the segmentation of neurons is laborious. Correlative light and electron microscopy (CLEM) is an approach for correlating images obtained via LM and EM. Because LM and EM are complementary in terms of compensating for their shortcomings, CLEM is a powerful technique for the comprehensive analysis of neural circuits. This review provides an overview of recent advances in CLEM tools and methods, particularly the fluorescent probes available for CLEM and near-infrared branding technique to match LM and EM images. We also discuss the challenges and limitations associated with contemporary CLEM technologies.

Tailoring Materials for Epilepsy Imaging: From Biomarkers to Imaging Probes

Excising epileptic foci (EF) is the most efficient approach for treating drug-resistant epilepsy (DRE). However, owing to the vast heterogeneity of epilepsies, EF in one-third of patients cannot be accurately located, even after exhausting all current diagnostic strategies. Therefore, identifying biomarkers that truly represent the status of epilepsy and fabricating probes with high targeting specificity are prerequisites for identifying the "concealed" EF. However, no systematic summary of this topic has been published. Herein, the potential biomarkers of EF are first summarized and classified into three categories: functional, molecular, and structural aberrances during epileptogenesis, a procedure of nonepileptic brain biasing toward epileptic tissue. The materials used to fabricate these imaging probes and their performance in defining the EF in preclinical and clinical studies are highlighted. Finally, perspectives for developing the next generation of probes and their challenges in clinical translation are discussed. In general, this review can be helpful in guiding the development of imaging probes defining EF with improved accuracy and holds promise for increasing the number of DRE patients who are eligible for surgical intervention.

Recent progress in plasmonic nanoparticle-based biomarker detection and cytometry for the study of central nervous system disorders

Neurological disorders affect hundreds of millions of people around the world, are often life-threatening, untreatable, and can result in debilitating symptoms. The high prevalence of these disorders, which feature biochemical or structural abnormalities in neuronal systems, has spurned innovations in both rapid and early detection to assist in the selection of appropriate treatment strategies to improve the patients' quality of life. Plasmonic nanoparticles (PNPs), a versatile and promising class of nanomaterials, are widely utilized in numerous imaging techniques, drug delivery systems, and biomarker detection methods. Recently, PNP-based nanoprobes have attracted considerable attention for the early diagnosis of neurological disorders. Gold nanoparticles (AuNPs), with high local surface plasmon resonance (LSPR) signals, have been particularly well exploited as probes for dynamic biomarker detection, with quantification sensitivity demonstrated down to the single-molecule level. In this review, we will discuss the possibilities of PNPs in the methodological development for rapid neurological disease identification. In addition, we will also describe a new digital cytometry method that combines dark-field imaging and machine learning for precise biomarker enumeration on single cells. The aim of this review is to attract researchers working on the future development of new plasmonic nanoprobe-based strategies for the diagnosis of neurological disorders.

Multifunctional Nanoprobe for the Delivery of Therapeutic siRNA and Real-Time Molecular Imaging of Parkinson's Disease Biomarkers

Parkinson's disease (PD) has been recently associated with the excessive expression of matrix metalloproteinase 3 (MMP3). One of the major challenges in treating PD is to effectively detect and inhibit the early MMP3 activities to relieve the neural stress and inflammation responses. Previously, numerous upconversion nanoparticle (UCNP)-based nanoprobes have been designed for the detection of biomarkers in neurodegenerative diseases. To further improve the performance of the conventional nanoprobes, we introduced novel reporting units and integrated the therapeutic reagents to fabricate a theragnostic platform for PD and other neurodegenerative diseases. Here, we designed a multifunctional UCNP/aggregation-induced emission luminogen (AIEgen)-based nanoprobe to effectively detect the time-lapse MMP3 activities in the inflammatory catecholaminergic SH-SY5Y cells and simultaneously deliver the MMP3-siRNA into the stressed catecholaminergic SH-SY5Y cells, inhibiting the MMP3-induced inflammatory neural responses. The unique features of our UCNP/AIEgen-based nanoprobe platform shed light on the development of a novel theragnostic probe for the early diagnosis and cure of neurodegenerative diseases.

Toxicity of Gold Nanoparticles in Mice due to Nanoparticle/Drug Interaction Induces Acute Kidney Damage

Nanomaterials are innovative materials with many useful properties, but there is concern regarding their many unknown effects on living organisms. Gold nanoparticles are widely used as industrial materials because of their excellent properties. The potential biological hazards of gold nanoparticles are unknown, and thus, here we examined the in vivo effects of gold nanoparticles 10, 50, and 100 nm in diameter (GnP10, GnP50, and GnP100, respectively) and their interactions with drugs in mice to clarify their safety in mammals. Cisplatin, paraquat, and 5-aminosalicylic acid cause side-effect damage to the liver and kidney in mice. No hepatotoxicity or nephrotoxicity was observed when any of the gold nanoparticles alone were administered via the tail vein. In contrast, co-administration of GnP-10 with cisplatin, paraquat, or 5-aminosalicylic acid caused side-effect damage to the kidney. This suggests that gold nanoparticles with a particle size of 10 nm are potentially nephrotoxic due to their interaction with drugs.

Nanotheranostic Applications for Detection and Targeting Neurodegenerative Diseases

Nanotechnology utilizes engineered materials and devices which function with biological systems at the molecular level and could transform the management of neurodegenerative diseases (NDs) by provoking, reacting to, and intermingling with target sites to stimulate physiological responses while minimizing side effects. Blood-brain barrier (BBB) protects the brain from harmful agents, and transporting drugs across the BBB is a major challenge for diagnosis, targeting, and treatment of NDs. The BBB provides severe limitations for diagnosis and treatment of Alzheimer's disease (AD), Parkinson's disease (PD), and various other neurological diseases. Conventional drug delivery systems generally fail to cross the BBB, thus are inefficient in treatment. Although gradual development through research is ensuring the progress of nanotheranostic approaches from animal to human modeling, aspects of translational applicability and safety are a key concern. This demands a deep understanding of the interaction of body systems with nanomaterials. There are various plant-based nanobioactive compounds which are reported to have applicability in the diagnosis and treatment of these NDs. This review article provides an overview of applications of nanotheranostics in AD and PD. The review also discusses nano-enabled drug delivery systems and their current and potential applications for the treatment of various NDs.

Highly sensitive piezoelectric immunosensors employing signal amplification with gold nanoparticles

We present a quartz crystal microbalance (QCM) immunosensor for highly sensitive detection of prostate-specific antigen (PSA) in a human serum immunoassay. In particular, in this study, we employed signal amplification using and enlarging gold nanoparticles. Because QCM measures the change of resonance frequency according to the mass change occurring on the sensor surface, we could quantitatively analyze PSA based on a tremendous increase in mass by sandwich immunoassay using AuNP-conjugated anti-PSA-detecting antibody enhanced with subsequent gold staining. The limit of detection of the PSA immunoassay in human serum without gold staining enhancement was 687 pg ml^-1 but was 48 pg ml^-1 with the gold staining-mediated signal amplification. That is, amplifying the signal resulted in increased sensitivity and reproducibility of immunoassay in a human serum.

Theoretical Analysis for Wireless Magnetothermal Deep Brain Stimulation Using Commercial Nanoparticles

A wireless magnetothermal stimulation (WMS) is suggested as a fast, tetherless, and implanted device-free stimulation method using low-radio frequency (100 kHz to 1 MHz) alternating magnetic fields (AMF). As magnetic nanoparticles (MNPs) can transduce alternating magnetic fields into heat, they are targeted to a region of the brain expressing the temperature-sensitive ion channel (TRPV1). The local temperature of the targeted area is increased up to 44 °C to open the TRPV1 channels and cause an influx of Ca²⁺ sensitive promoter, which can activate individual neurons inside the brain. The WMS has initially succeeded in showing the potential of thermomagnetics for the remote control of neural cell activity with MNPs that are internally targeted to the brain. In this paper, by using the steady-state temperature rise defined by Fourier’s law, the bio-heat equation, and COMSOL Multiphysics software, we investigate most of the basic parameters such as the specific loss power (SLP) of MNPs, the injection volume of magnetic fluid, stimulation and cooling times, and cytotoxic effects at high temperatures (43–44 °C) to provide a realizable design guideline for WMS.

Physicochemical Characterization of Phthalocyanine-Functionalized Quantum Dots by Capillary Electrophoresis Coupled to a LED Fluorescence Detector

Capillary zone electrophoresis (CZE) complemented with Taylor Dispersion Analysis-CE (TDA-CE) was developed to physicochemically characterize phthalocyanine-capped core/shell/shell quantum dots (QDs) at various pH and ionic strengths. An LED-induced fluorescence detector was used to specifically detect the QDs. The electropherograms and taylorgrams allowed calculating the phthalocyanine-QDs (Pc-QDs) ζ-potential and size, respectively, and determining the experimental conditions for colloidal stability. This methodology allowed evidencing either a colloidal stability or an aggregation state according to the background electrolytes nature. The calculated ζ-potential values of Pc-QDs decreased when ionic strength increased, being well correlated with the aggregation of the nanoconjugates at elevated salt concentrations. For the same reason, the hydrodynamic diameter of Pc-QDs increased with increasing background electrolyte ionic strength. The use of electrokinetic methodologies has provided insights into the colloidal stability of the photosensitizer-functionalized QDs in physiologically relevant solutions and, thereby, its usefulness for improving their design and applications for photodynamic therapy.

Advances in Intravital Non-Linear Optical Imaging of the Central Nervous System in Rodents

Purpose of review: Highly coordinated cellular interactions occur in the healthy or pathologic adult rodent central nervous system (CNS). Until recently, technical challenges have restricted the analysis of these events to largely static modes of study such as immuno-fluorescence and electron microscopy on fixed tissues. The development of intravital imaging with subcellular resolution is required to probe the dynamics of these events in their natural context, the living brain. Recent findings: This review focuses on the recently developed live non-linear optical imaging modalities, the core principles involved, the identified technical challenges that limit their use and the scope of their applications. We highlight some practical applications for these modalities with a specific attention given to Experimental Autoimmune Encephalomyelitis (EAE), a rodent model of a chronic inflammatory disease of the CNS characterized by the formation of disseminated demyelinating lesions accompanied by axonal degeneration. Summary: We conclude that label-free nonlinear optical imaging combined to two photon imaging will continue to contribute richly to comprehend brain function and pathogenesis and to develop effective therapeutic strategies.

Nutritional and Nanotechnological Modulators of Microglia

Microglia are the essential responders to alimentary, pharmacological, and nanotechnological immunomodulators. These neural cells play multiple roles as surveyors, sculptors, and guardians of essential parts of complex neural circuitries. Microglia can play dual roles in the central nervous system; they can be deleterious and/or protective. The immunomodulatory effects of alimentary components, gut microbiota, and nanotechnological products have been investigated in microglia at the single-cell level and in vivo using intravital imaging approaches, and different biochemical assays. This review highlights some of the emerging questions and topics from studies involving alimentation, microbiota, nanotechnological products, and associated problems in this area of research. Some of the advantages and limitations of in vitro and in vivo models used to study the neuromodulatory effects of these factors, as well as the merits and pitfalls of intravital imaging modalities employed are presented.

Tunable ultraviolet and blue light generation from Nd:YAB random laser bolstered by second-order nonlinear processes

Ultraviolet and blue light were obtained by nonlinear frequency conversion in a random laser (RL) based on Nd0.10Y0.90Al3(BO3)4 nanocrystalline powder. RL operation at 1062 nm, due to the (4)F3/2 → (4)I11/2 transition of neodymium ions (Nd(3+)), was achieved by exciting the Nd(3+) with a tunable beam from 680 to 920 nm covering the ground state absorption transitions to the (4)F9/2, ((4)F7/2,(4)S3/2), ((4)F5/2,(2)H9/2), and (4)F3/2 states. Light from 340 to 460 nm was obtained via the second-harmonic generation of the excitation beam while tunable blue light, from 417 to 486 nm, was generated by self-sum-frequency mixing between the excitation beam and the RL emission.