Functionalization with PEG/Angiopep-2 peptide to improve the delivery of gold nanoprisms to central nervous system: in vitro and in vivo studies

Tau- and α-synuclein-targeted gold nanoparticles: applications, opportunities, and future outlooks in the diagnosis and therapy of neurodegenerative diseases

The use of nanomaterials in medicine offers multiple opportunities to address neurodegenerative disorders such as Alzheimer's and Parkinson's disease. These diseases are a significant burden for society and the health system, affecting millions of people worldwide without sensitive and selective diagnostic methodologies or effective treatments to stop their progression. In this sense, the use of gold nanoparticles is a promising tool due to their unique properties at the nanometric level. They can be functionalized with specific molecules to selectively target pathological proteins such as Tau and α-synuclein for Alzheimer's and Parkinson's disease, respectively. Additionally, these proteins are used as diagnostic biomarkers, wherein gold nanoparticles play a key role in enhancing their signal, even at the low concentrations present in biological samples such as blood or cerebrospinal fluid, thus enabling an early and accurate diagnosis. On the other hand, gold nanoparticles act as drug delivery platforms, bringing therapeutic agents directly into the brain, improving treatment efficiency and precision, and reducing side effects in healthy tissues. However, despite the exciting potential of gold nanoparticles, it is crucial to address the challenges and issues associated with their use in the medical field before they can be widely applied in clinical settings. It is critical to ensure the safety and biocompatibility of these nanomaterials in the context of the central nervous system. Therefore, rigorous preclinical and clinical studies are needed to assess the efficacy and feasibility of these strategies in patients. Since there is scarce and sometimes contradictory literature about their use in this context, the main aim of this review is to discuss and analyze the current state-of-the-art of gold nanoparticles in relation to delivery, diagnosis, and therapy for Alzheimer's and Parkinson's disease, as well as recent research about their use in preclinical, clinical, and emerging research areas.

Molecularly Targeted Lanthanide Nanoparticles for Cancer Theranostic Applications

Injectable colloidal solutions of lanthanide oxides (nanoparticles between 10 and 100 nm in size) have demonstrated high biocompatibility and no toxicity when the nanoparticulate units are functionalized with specific biomolecules that molecularly target various proteins in the tumor microenvironment. Among the proteins successfully targeted by functionalized lanthanide nanoparticles are folic receptors, fibroblast activation protein (FAP), gastrin-releasing peptide receptor (GRP-R), prostate-specific membrane antigen (PSMA), and integrins associated with tumor neovasculature. Lutetium, samarium, europium, holmium, and terbium, either as lanthanide oxide nanoparticles or as nanoparticles doped with lanthanide ions, have demonstrated their theranostic potential through their ability to generate molecular images by magnetic resonance, nuclear, optical, or computed tomography imaging. Likewise, photodynamic therapy, targeted radiotherapy (neutron-activated nanoparticles), drug delivery guidance, and image-guided tumor therapy are some examples of their potential therapeutic applications. This review provides an overview of cancer theranostics based on lanthanide nanoparticles coated with specific peptides, ligands, and proteins targeting the tumor microenvironment.

Differential Detection of Amyloid Aggregates in Old Animals Using Gold Nanorods by Computerized Tomography: A Pharmacokinetic and Bioaccumulation Study

Introduction

The development of new materials and tools for radiology is key to the implementation of this diagnostic technique in clinics. In this work, we evaluated the differential accumulation of peptide-functionalized GNRs in a transgenic animal model (APPswe/PSENd1E9) of Alzheimer's disease (AD) by computed tomography (CT) and measured the pharmacokinetic parameters and bioaccumulation of the nanosystem.

Methods

The GNRs were functionalized with two peptides, Ang2 and D1, which conferred on them the properties of crossing the blood-brain barrier and binding to amyloid aggregates, respectively, thus making them a diagnostic tool with great potential for AD. The nanosystem was administered intravenously in APPswe/PSEN1dE9 model mice of 4-, 8- and 18-months of age, and the accumulation of gold nanoparticles was observed by computed tomography (CT). The gold accumulation and biodistribution were determined by atomic absorption.

Results

Our findings indicated that 18-month-old animals treated with our nanosystem (GNR-D1/Ang2) displayed noticeable differences in CT signals compared to those treated with a control nanosystem (GNR-Ang2). However, no such distinctions were observed in younger animals. This suggests that our nanosystem holds the potential to effectively detect AD pathology.

Discussion

These results support the future development of gold nanoparticle-based technology as a more effective and accessible alternative for the diagnosis of AD and represent a significant advance in the development of gold nanoparticle applications in disease diagnosis.

Interactions of Nanoscale Self-Assembled Peptide-Based Assemblies with Glioblastoma Cell Models and Spheroids

Peptide nanoassemblies have garnered remarkable importance in the development of novel nanoscale biomaterials for drug delivery into tumor cells. Taking advantage of receptor mediated recognition of two known peptides, angiopep-2 (TFFYGGSRGKRNNFKTEEY) and A-COOP-K (ACGLSGLC10 VAK) that bind to the over-expressed receptors low density lipoprotein (LRP-1) and fatty acid binding protein (FABP3) respectively, we have developed new peptide conjugates by combining the anti-inflammatory, antitumor compound azelaic acid with angiopep-2, which efficiently self-assembled into nanofibers. Those nanofibers were then functionalized with the A-COOP-K sequence and formed supramolecular hierarchical structures that were found to entrap the chemotherapeutic drug doxorubicin efficaciously. Furthermore, the nanoassemblies were found to release the drug in a dose-dependent manner and showed a stepwise increase over a period of 2 weeks under acidic conditions. Two cell lines (U-87-MG and U-138-MG) were utilized as models for glioblastoma cells grown in the presence of serum and under serum-free conditions to mimic the growth conditions of natural tumors. The drug entrapped assemblies were found to inhibit the cell proliferation of both U-87 and U-138MG glioblastoma cells. Three dimensional spheroids of different sizes were grown to mimic the tumors and evaluate the efficacy of drug release and internalization. Our results indicated that the nanoassemblies were found to have higher internalization of DOX and were well-spread throughout the spheroids grown, particularly under serum-free conditions. The nanoassemblies also displayed blood-brain barrier penetration when tested with a multicellular in vitro model. Such self-assembled nanostructures with targeting ability may provide a suitable platform for the development of new peptide-based biomaterials that can provide more insights about the mechanistic approach for drug delivery for not only 2D cell cultures but also 3D tumoroids that mimic the tumor microenvironments.

Mitochondria-targeting nano therapy altering IDH2-mediated EZH2/EZH1 interaction as precise epigenetic regulation in glioblastoma

Glioblastoma (GBM) is a complex brain cancer with frequent relapses and high mortality and still awaits effective treatment. Mitochondria dysfunction is a pathogenic condition in GBM and could be a prime therapeutic target for ceasing GBM progression. Strategies to overcome brain solid tumor barriers and selectively target mitochondria within specific cell types may improve GBM treatment. Here, we present hypericin-conjugated gold nanoparticles (PEG-AuNPs@Hyp) where hypericin is a mitochondrion-targeting agent exhibiting multimodal therapy by critically impacting the IDH2 gene (Isocitrate dehydrogenase) and its interaction with polycomb methyltransferase EZH1/2 for GBM therapy. It significantly localizes in mitochondria by enhanced cellular uptake in the human GBM cell lines/three-dimensional (3D) culture model under red-light exposure. It triggers oxidative stress and changes the mitochondrial potential, with increased Bax/Bcl2 ratio enhancing GBM cell death. The suppressed expression of mutated IDH2 and polycomb group of proteins upon PEG-AuNPs@Hyp/light exposure regulates mitochondria-targeting-mediated GBM metabolism with epigenetic repression of complex machinery function. Polyubiquitination and proteasomal degradation of EZH1 indicate the implication of these polycomb proteins in GBM progression. Chromatin immunoprecipitation reveals the IDH2 and EZH1/EZH2 direct interaction, confirming the role played by IDH2 in modulating the expression of EZH1 and EZH2. In vivo studies further displayed better tumor ablation in a GBM tumor-bearing nude mouse model. The present multimodal nanoformulation compromised the functional dependency of polycomb on mitochondrial IDH2 and established the mechanism of GBM inhibition.

Gold nanostructures: synthesis, properties, and neurological applications

Recent advances in technology are expected to increase our current understanding of neuroscience. Nanotechnology and nanomaterials can alter and control neural functionality in both in vitro and in vivo experimental setups. The intersection between neuroscience and nanoscience may generate long-term neural interfaces adapted at the molecular level. Owing to their intrinsic physicochemical characteristics, gold nanostructures (GNSs) have received much attention in neuroscience, especially for combined diagnostic and therapeutic (theragnostic) purposes. GNSs have been successfully employed to stimulate and monitor neurophysiological signals. Hence, GNSs could provide a promising solution for the regeneration and recovery of neural tissue, novel neuroprotective strategies, and integrated implantable materials. This review covers the broad range of neurological applications of GNS-based materials to improve clinical diagnosis and therapy. Sub-topics include neurotoxicity, targeted delivery of therapeutics to the central nervous system (CNS), neurochemical sensing, neuromodulation, neuroimaging, neurotherapy, tissue engineering, and neural regeneration. It focuses on core concepts of GNSs in neurology, to circumvent the limitations and significant obstacles of innovative approaches in neurobiology and neurochemistry, including theragnostics. We will discuss recent advances in the use of GNSs to overcome current bottlenecks and tackle technical and conceptual challenges.

Angiopep-2-Modified Nanoparticles for Brain-Directed Delivery of Therapeutics: A Review

Nanotechnology has opened up a world of possibilities for the treatment of brain disorders. Nanosystems can be designed to encapsulate, carry, and deliver a variety of therapeutic agents, including drugs and nucleic acids. Nanoparticles may also be formulated to contain photosensitizers or, on their own, serve as photothermal conversion agents for phototherapy. Furthermore, nano-delivery agents can enhance the efficacy of contrast agents for improved brain imaging and diagnostics. However, effective nano-delivery to the brain is seriously hampered by the formidable blood–brain barrier (BBB). Advances in understanding natural transport routes across the BBB have led to receptor-mediated transcytosis being exploited as a possible means of nanoparticle uptake. In this regard, the oligopeptide Angiopep-2, which has high BBB transcytosis capacity, has been utilized as a targeting ligand. Various organic and inorganic nanostructures have been functionalized with Angiopep-2 to direct therapeutic and diagnostic agents to the brain. Not only have these shown great promise in the treatment and diagnosis of brain cancer but they have also been investigated for the treatment of brain injury, stroke, epilepsy, Parkinson’s disease, and Alzheimer’s disease. This review focuses on studies conducted from 2010 to 2021 with Angiopep-2-modified nanoparticles aimed at the treatment and diagnosis of brain disorders.

Cyclodextrin-Modified Nanomaterials for Drug Delivery: Classification and Advances in Controlled Release and Bioavailability

In drug delivery, one widely used way of overcoming the biopharmaceutical problems present in several active pharmaceutical ingredients, such as poor aqueous solubility, early instability, and low bioavailability, is the formation of inclusion compounds with cyclodextrins (CD). In recent years, the use of CD derivatives in combination with nanomaterials has shown to be a promising strategy for formulating new, optimized systems. The goals of this review are to give in-depth knowledge and critical appraisal of the main CD-modified or CD-based nanomaterials for drug delivery, such as lipid-based nanocarriers, natural and synthetic polymeric nanocarriers, nanosponges, graphene derivatives, mesoporous silica nanoparticles, plasmonic and magnetic nanoparticles, quantum dots and other miscellaneous systems such as nanovalves, metal-organic frameworks, Janus nanoparticles, and nanofibers. Special attention is given to nanosystems that achieve controlled drug release and increase their bioavailability during in vivo studies.

In vivo micro computed tomography detection and decrease in amyloid load by using multifunctionalized gold nanorods: a neurotheranostic platform for Alzheimer's disease

The development and use of nanosystems is an emerging strategy for the diagnosis and treatment of a broad number of diseases, such as Alzheimer's disease (AD). Here, we developed a neurotheranostic nanosystem based on gold nanorods (GNRs) that works as a therapeutic peptide delivery system and can be detected in vivo for microcomputed tomography (micro-CT), being a diagnostic tool. GNRs functionalized with the peptides Ang2 (a shuttle to the Central Nervous System) and D1 (that binds to the Aβ peptide, also inhibiting its aggregation) allowed detecting differences in vivo between wild type and AD mice (APPswe/PSEN1dE9) 15 minutes after a single dose by micro-CT. Moreover, after a recurrent treatment for one month with GNRs-D1/Ang2, we observed a diminution of amyloid load and inflammatory markers in the brain. Thus, this new designed nanosystem exhibits promising properties for neurotheranostics of AD.

β-Cyclodextrin-Based Nanosponges Functionalized with Drugs and Gold Nanoparticles

Drugs are widely used as therapeutic agents; however, they may present some limitations. To overcome some of the therapeutic disadvantages of drugs, the use of β-cyclodextrin-based nanosponges (βCDNS) constitutes a promising strategy. βCDNS are matrices that contain multiple hydrophobic cavities, increasing the loading capacity, association, and stability of the included drugs. On the other hand, gold nanoparticles (AuNPs) are also used as therapeutic and diagnostic agents due to their unique properties and high chemical reactivity. In this work, we developed a new nanomaterial based on βCDNS and two therapeutic agents, drugs and AuNPs. First, the drugs phenylethylamine (PhEA) and 2-amino-4-(4-chlorophenyl)-thiazole (AT) were loaded on βCDNS. Later, the βCDNS-drug supramolecular complexes were functionalized with AuNPs, forming the βCDNS-PhEA-AuNP and βCDNS-AT-AuNP systems. The success of the formation of βCDNS and the loading of PhEA, AT, and AuNPs was demonstrated using different characterization techniques. The loading capacities of PhEA and AT in βCDNS were 90% and 150%, respectively, which is eight times higher than that with native βCD. The functional groups SH and NH2 of the drugs remained exposed and allowed the stabilization of the AuNPs, 85% of which were immobilized. These unique systems can be versatile materials with an efficient loading capacity for potential applications in the transport of therapeutic agents.

Functionalization of Gold Nanostars with Cationic β-Cyclodextrin-Based Polymer for Drug Co-Loading and SERS Monitoring

Gold nanostars (AuNSs) exhibit modulated plasmon resonance and have a high SERS enhancement factor. However, their low colloidal stability limits their biomedical application as a nanomaterial. Cationic β-cyclodextrin-based polymer (CCD/P) has low cytotoxicity, can load and transport drugs more efficiently than the corresponding monomeric form, and has an appropriate cationic group to stabilize gold nanoparticles. In this work, we functionalized AuNSs with CCD/P to load phenylethylamine (PhEA) and piperine (PIP) and evaluated SERS-based applications of the products. PhEA and PIP were included in the polymer and used to functionalize AuNSs, forming a new AuNS-CCD/P-PhEA-PIP nanosystem. The system was characterized by UV–VIS, IR, and NMR spectroscopy, TGA, SPR, DLS, zeta potential analysis, FE-SEM, and TEM. Additionally, Raman optical activity, SERS analysis and complementary theoretical studies were used for characterization. Minor adjustments increased the colloidal stability of AuNSs. The loading capacity of the CCD/P with PhEA-PIP was 95 ± 7%. The physicochemical parameters of the AuNS-CCD/P-PhEA-PIP system, such as size and Z potential, are suitable for potential biomedical applications Raman and SERS studies were used to monitor PhEA and PIP loading and their preferential orientation upon interaction with the surface of AuNSs. This unique nanomaterial could be used for simultaneous drug loading and SERS-based detection.