Human serum albumin nanoparticles modified with apolipoprotein A-I cross the blood-brain barrier and enter the rodent brain

Blood-Nanoparticle Interactions Create a Brain Delivery Superhighway for Doxorubicin

Purpose

This study investigated the brain targeting mechanism of doxorubicin-loaded polybutyl cyanoacrylate (PBCA) nanoparticles, particularly their interactions with the blood-brain barrier (BBB). The BBB protects the brain from drugs in the bloodstream and represents a crucial obstacle in the treatment of brain cancer.

Methods

An advanced computer model analyzed the brain delivery of two distinct formulations, Doxil® and surfactant-coated PBCA nanoparticles. Computational learning was combined with in vitro release and cell interaction studies to comprehend the underlying brain delivery pathways.

Results

Our analysis yielded a surprising discovery regarding the brain delivery mechanism of PBCA nanoparticles. While Doxil® exhibited the expected behavior, accumulating in the brain through extravasation in tumor tissue, PBCA nanoparticles employed a unique and previously uncharacterized mechanism. They underwent cell hitchhiking, resulting in a remarkable more than 1000-fold increase in brain permeation rate compared to Doxil® (2.59 × 10-4 vs 0.32 h-1).

Conclusion

The nonspecific binding to blood cells facilitated and intensified interactions of surfactant-coated PBCA nanoparticles with the vascular endothelium, leading to enhanced transcytosis. Consequently, the significant increase in circulation time in the bloodstream, coupled with improved receptor interactions, contributes to this remarkable uptake of doxorubicin into the brain.

Impact of protein coronas on nanoparticle interactions with tissues and targeted delivery

A major challenge in advancing nanoparticle (NP)-based delivery systems stems from the intricate interactions between NPs and biological systems. These interactions are largely determined by the formation of the NP-protein corona (PC), in which proteins spontaneously adsorb to the surface of NPs. The PC endows the NPs with a new biological identity, capable of altering the interactions of NPs with targeting organs and subsequent biological fate. This review discusses the mechanisms behind PC-mediated effects on tissue distribution of NPs, aiming to provide insights into the role of PC and its potential applications in NP-based drug delivery.

Bioinspired Approaches for Central Nervous System Targeted Gene Delivery

Disorders of the central nervous system (CNS) which include a wide range of neurodegenerative and neurological conditions have become a serious global issue. The presence of CNS barriers poses a significant challenge to the progress of designing effective therapeutic delivery systems, limiting the effectiveness of drugs, genes, and other therapeutic agents. Natural nanocarriers present in biological systems have inspired researchers to design unique delivery systems through biomimicry. As natural resource derived delivery systems are more biocompatible, current research has been focused on the development of delivery systems inspired by bacteria, viruses, fungi, and mammalian cells. Despite their structural potential and extensive physiological function, making them an excellent choice for biomaterial engineering, the delivery of nucleic acids remains challenging due to their instability in biological systems. Similarly, the efficient delivery of genetic material within the tissues of interest remains a hurdle due to a lack of selectivity and targeting ability. Considering that gene therapies are the holy grail for intervention in diseases, including neurodegenerative disorders such as Alzheimer's disease, Parkinson's Disease, and Huntington's disease, this review centers around recent advances in bioinspired approaches to gene delivery for the prevention of CNS disorders.

The role of protein corona on nanodrugs for organ-targeting and its prospects of application

Nowadays, nanodrugs become a hotspot in the high-end medical field. They have the ability to deliver drugs to reach their destination more effectively due to their unique properties and flexible functionalization. However, the fate of nanodrugs in vivo is not the same as those presented in vitro, which indeed influenced their therapeutic efficacy in vivo. When entering the biological organism, nanodrugs will first come into contact with biological fluids and then be covered by some biomacromolecules, especially proteins. The proteins adsorbed on the surface of nanodrugs are known as protein corona (PC), which causes the loss of prospective organ-targeting abilities. Fortunately, the reasonable utilization of PC may determine the organ-targeting efficiency of systemically administered nanodrugs based on the diverse expression of receptors on cells in different organs. In addition, the nanodrugs for local administration targeting diverse lesion sites will also form unique PC, which plays an important role in the therapeutic effect of nanodrugs. This article introduced the formation of PC on the surface of nanodrugs and summarized the recent studies about the roles of diversified proteins adsorbed on nanodrugs and relevant protein for organ-targeting receptor through different administration pathways, which may deepen our understanding of the role that PC played on organ-targeting and improve the therapeutic efficacy of nanodrugs to promote their clinical translation.

Intracellular Localization during Blood-Brain Barrier Crossing Influences Extracellular Release and Uptake of Fluorescent Nanoprobes

To improve the efficacy of nanoparticles (NPs) and boost their theragnostic potential for brain diseases, it is key to understand the mechanisms controlling blood-brain barrier (BBB) crossing. Here, the capability of 100 nm carboxylated polystyrene NPs, used as a nanoprobe model, to cross the human brain endothelial hCMEC/D3 cell layer, as well as to be consequently internalized by human brain tumor U87 cells, is investigated as a function of NPs' different intracellular localization. We compared NPs confined in the endo-lysosomal compartment, delivered to the cells through endocytosis, with free NPs in the cytoplasm, delivered by the gene gun method. The results indicate that the intracellular behavior of NPs changed as a function of their entrance mechanism. Moreover, by bypassing endo-lysosomal accumulation, free NPs were released from cells more efficiently than endocytosed NPs. Most importantly, once excreted by the endothelial cells, free NPs were released in the cell culture medium as aggregates smaller than endocytosed NPs and, consequently, they entered the human glioblastoma U87 cells more efficiently. These findings prove that intracellular localization influences NPs' long-term fate, improving their cellular release and consequent cellular uptake once in the brain parenchyma. This study represents a step forward in designing nanomaterials that are able to reach the brain effectively.

Protein corona: Friend or foe? Co-opting serum proteins for nanoparticle delivery

For systemically delivered nanoparticles to reach target tissues, they must first circulate long enough to reach the target and extravasate there. A challenge is that the particles end up engaging with serum proteins and undergo immune cell recognition and premature clearance. The serum protein binding, also known as protein corona formation, is difficult to prevent, even with artificial protection via "stealth" coating. Protein corona may be problematic as it can interfere with the interaction of targeting ligands with tissue-specific receptors and abrogate the so-called active targeting process, hence, the efficiency of drug delivery. However, recent studies show that serum protein binding to circulating nanoparticles may be actively exploited to enhance their downstream delivery. This review summarizes known issues of protein corona and traditional strategies to control the corona, such as avoiding or overriding its formation, as well as emerging efforts to enhance drug delivery to target organs via nanoparticles. It concludes with a discussion of prevailing challenges in exploiting protein corona for nanoparticle development.

The protein corona modulates the inflammation inhibition by cationic nanoparticles via cell-free DNA scavenging

A central paradigm in nanomedicine is that when synthetic nanoparticles (NPs) enter the body, they are immediately cloaked by a corona of macromolecules (mostly proteins) that mediates the role of the physico-chemical properties in the NP biological functions (the “coronation paradigm”). In this work, we focused on the assessment of the “coronation paradigm” for cationic NPs (cNPs) used as rheumatoid arthritis (RA) drugs due to their ability to scavenge cell-free DNA (cfDNA). We fabricated series of cNPs uniformly coated with single or di-hydroxyl groups and different types of amino groups and showed that hydroxylated nanoparticles displayed a prolonged retention in inflamed joints and greater anti-inflammatory effect in collagen-induced arthritis (CIA) rats than the non-hydroxylated analogues. Especially, the cNPs with secondary amines and a di-hydroxyl shell showed the best performance among the tested cNPs. Proteomic analysis showed that the cNPs with a di-hydroxyl shell adsorbed less opsonin proteins than the cNPs carrying mono hydroxyl groups and non-hydroxylated ones, which may provide a mechanistic explanation for the different biodistribution profiles of cNPs. Thus, this study suggests that the protein corona mediates the effects of the surface chemistry on the fate and functions of cNPs as anti-RA drugs.

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cNPs with hydroxyl shell decreased side-effects to cells and CIA rats without decreasing the ability to scavenge cfDNA.

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Hydroxyl shell reduced the adsorption of proteins, thus prolonged the circulation and site accumulation of cNPs.

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The composition of the protein corona formed onto the cNPs in the serum can be modulated by their synthetic identity.

Design of Smart Nanomedicines for Effective Cancer Treatment

Nanomedicine is a novel field of study that involves the use of nanomaterials to address challenges and issues that are associated with conventional therapeutics for cancer treatment including, but not limited to, low bioavailability, low water-solubility, narrow therapeutic window, nonspecific distribution, and multiple side effects of the drugs. Multiple strategies have been exploited to reduce the nonspecific distribution, and thus the side effect of the active pharmaceutical ingredients (API), including active and passive targeting strategies and externally controllable release of the therapeutic cargo. Site-specific release of the drug prevents it from impacting healthy cells, thereby significantly reducing side effects. API release triggers can be either externally applied, as in ultrasound-mediated activation, or induced by the tumor. To rationally design such nanomedicines, a thorough understanding of the differences between the tumor microenvironment versus that of healthy tissues must be pared with extensive knowledge of stimuli-responsive biomaterials. Herein, we describe the characteristics that differentiate tumor tissues from normal tissues. Then, we introduce smart materials that are commonly used for the development of smart nanomedicines to be triggered by stimuli such as changes in pH, temperature, and enzymatic activity. The most recent advances and their impact on the field of cancer therapy are further discussed.

Nanocarrier mediated drug delivery as an impeccable therapeutic approach against Alzheimer's disease

For the past several years, dementia, is one of the predominantly observed groups of symptoms in a geriatric population. Alzheimer's disease (AD) is a progressive memory related neurodegenerative disease, for which the current Food and drug administration approved therapeutics are only meant for a symptomatic management rather than targeting the root cause of AD. These therapeutics belong to two classes, Acetylcholine Esterase inhibitors and N-methyl D-aspartate antagonist. Furthermore, to facilitate neuroprotective action in AD, the drugs are majorly expected to reach the specific target area in the brain for the desired efficacy. Thus, there is a huge requirement for drug discovery and development for facilitating the entry of drugs more in brain to exert a specific action. The very first line of defense and the major limitation for the entry of drugs into the brain is the Blood Brain Barrier, followed by Blood-Cerebrospinal Fluid Barrier. More than a barrier, these mainly act as selectively permeable membranes, which allows entry of specific molecules into the brain. Furthermore, specific enzymes result in the degradation of xenobiotics. All these mechanisms pose as hurdles in the way of effective drug delivery in the brain. Thus, novel techniques need to be harbored for the facilitation of the delivery of such drugs into the brain. Nanocarriers are advantageous for facilitating the specific targeted drug treatment in AD. As nanomedicines are one of the novels and most useful approaches for AD, thus the present review mainly focuses on understanding the advanced use of nanocarriers for targeted drug delivery in the management of AD.

Formulation, Characterization, and Cytotoxicity Evaluation of Lactoferrin Functionalized Lipid Nanoparticles for Riluzole Delivery to the Brain

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with a very poor prognosis. Its treatment is hindered by a lack of new therapeutic alternatives and the existence of the blood-brain barrier (BBB), which restricts the access of drugs commonly used in ALS, such as riluzole, to the brain. To overcome these limitations and increase brain targeting, riluzole-loaded nanostructured lipid carriers (NLC) were prepared and functionalized with lactoferrin (Lf), facilitating transport across the BBB by interacting with Lf receptors expressed in the brain endothelium. NLC were characterized with respect to their physicochemical properties (size, zeta potential, polydispersity index) as well as their stability, encapsulation efficiency, morphology, in vitro release profile, and biocompatibility. Moreover, crystallinity and melting behavior were assessed by DSC and PXRD. Nanoparticles exhibited initial mean diameters between 180 and 220 nm and a polydispersity index below 0.3, indicating a narrow size distribution. NLC remained stable over at least 3 months. Riluzole encapsulation efficiency was very high, around 94-98%. FTIR and protein quantification studies confirmed the conjugation of Lf on the surface of the nanocarriers, with TEM images showing that the functionalized NLC presented a smooth surface and uniform spherical shape. An MTT assay revealed that the nanocarriers developed in this study did not cause a substantial reduction in the viability of NSC-34 and hCMEC/D3 cells at a riluzole concentration up to 10 μM, being therefore biocompatible. The results suggest that Lf-functionalized NLC are a suitable and promising delivery system to target riluzole to the brain.

Nanocarriers for Delivery of Oligonucleotides to the CNS

Nanoparticles with oligonucleotides bound to the outside or incorporated into the matrix can be used for gene editing or to modulate gene expression in the CNS. These nanocarriers are usually optimised for transfection of neurons or glia. They can also facilitate transcytosis across the brain endothelium to circumvent the blood-brain barrier. This review examines the different formulations of nanocarriers and their oligonucleotide cargoes, in relation to their ability to enter the brain and modulate gene expression or disease. The size of the nanocarrier is critical in determining the rate of clearance from the plasma as well as the intracellular routes of endothelial transcytosis. The surface charge is important in determining how it interacts with the endothelium and the target cell. The structure of the oligonucleotide affects its stability and rate of degradation, while the chemical formulation of the nanocarrier primarily controls the location and rate of cargo release. Due to the major anatomical differences between humans and animal models of disease, successful gene therapy with oligonucleotides in humans has required intrathecal injection. In animal models, some progress has been made with intraventricular or intravenous injection of oligonucleotides on nanocarriers. However, getting significant amounts of nanocarriers across the blood-brain barrier in humans will likely require targeting endothelial solute carriers or vesicular transport systems.

Advances in receptor modulation strategies for flexible, efficient, and enhanced antitumor efficacy

Tumor-sensitivity, effective transport, and precise delivery to tumor cells of nano drug delivery systems (NDDs) have been great challenges to cancer therapy in recent years. The conventional targeting approach involves actively installing the corresponding ligand on the nanocarriers, which is prone to recognize the antigen blasts overexpressed on the surface of tumor cells. However, there are some probable limitations for the active tumor-targeting systems in vivo as follows: a. the limited ligand amount of modifications; b. possible steric hindrance, which was likely to prevent ligand-receptor interaction during the delivery process. c. the restrained antigen saturation highly expressed on the cell membrane, will definitely decrease the specificity and often lead to "off-target" effects of NDDs; and d. water insolubility of nanocarriers due to excess of ligands modification. Obviously, any regulation of receptors on surface of tumor cells exerted an important influence on the delivery of targeting systems. Herein, receptor upregulation was mostly desired for enhancing targeted therapy from the cellular level. This technique with the amplification of receptors has the potential to enhance tumor sensitivity towards corresponding ligand-modified nanoparticles, and thereby increasing the effective therapeutic concentration as well as improving the efficacy of chemotherapy. The enhancement of positively expressed receptors on tumor cells and receptor-dependent therapeutic agents or NDDs with an assembled "self-promoting" effect contributes to increasing cell sensitivity to NPs, and will provide a basic platform for clinical therapeutic practice. In this review, we highlight the significance of modulating various receptors on different types of cancer cells for drug delivery and therapeutic benefits.

Nanoalgosomes: Introducing extracellular vesicles produced by microalgae

Cellular, inter-organismal and cross kingdom communication via extracellular vesicles (EVs) is intensively studied in basic science with high expectation for a large variety of bio-technological applications. EVs intrinsically possess many attributes of a drug delivery vehicle. Beyond the implications for basic cell biology, academic and industrial interests in EVs have increased in the last few years. Microalgae constitute sustainable and renewable sources of bioactive compounds with a range of sectoral applications, including the formulation of health supplements, cosmetic products and food ingredients. Here we describe a newly discovered subtype of EVs derived from microalgae, which we named nanoalgosomes. We isolated these extracellular nano-objects from cultures of microalgal strains, including the marine photosynthetic chlorophyte Tetraselmis chuii, using differential ultracentrifugation or tangential flow fractionation and focusing on the nanosized small EVs (sEVs). We explore different biochemical and physical properties and we show that nanoalgosomes are efficiently taken up by mammalian cell lines, confirming the cross kingdom communication potential of EVs. This is the first detailed description of such membranous nanovesicles from microalgae. With respect to EVs isolated from other organisms, nanoalgosomes present several advantages in that microalgae are a renewable and sustainable natural source, which could easily be scalable in terms of nanoalgosome production.

Exploring the Interplay between Drug Release and Targeting of Lipid-Like Polymer Nanoparticles Loaded with Doxorubicin

Targeted delivery of doxorubicin still poses a challenge with regards to the quantities reaching the target site as well as the specificity of the uptake. In the present approach, two colloidal nanocarrier systems, NanoCore-6.4 and NanoCore-7.4, loaded with doxorubicin and characterized by different drug release behaviors were evaluated in vitro and in vivo. The nanoparticles utilize a specific surface design to modulate the lipid corona by attracting blood-borne apolipoproteins involved in the endogenous transport of chylomicrons across the blood–brain barrier. When applying this strategy, the fine balance between drug release and carrier accumulation is responsible for targeted delivery. Drug release experiments in an aqueous medium resulted in a difference in drug release of approximately 20%, while a 10% difference was found in human serum. This difference affected the partitioning of doxorubicin in human blood and was reflected by the outcome of the pharmacokinetic study in rats. For the fast-releasing formulation NanoCore-6.4, the AUC_0→1h was significantly lower (2999.1 ng × h/mL) than the one of NanoCore-7.4 (3589.5 ng × h/mL). A compartmental analysis using the physiologically-based nanocarrier biopharmaceutics model indicated a significant difference in the release behavior and targeting capability. A fraction of approximately 7.310–7.615% of NanoCore-7.4 was available for drug targeting, while for NanoCore-6.4 only 5.740–6.057% of the injected doxorubicin was accumulated. Although the targeting capabilities indicate bioequivalent behavior, they provide evidence for the quality-by-design approach followed in formulation development.

Single Protein Encapsulated Doxorubicin as an Efficacious Anticancer Therapeutic

Small-molecule chemotherapeutics are potent and effective against a variety of malignancies, but common and severe side effects restrict their clinical applications. Nanomedicine approaches represent a major focus for improving chemotherapy, but have met limited success. To overcome the limitations of chemotherapy drugs, we have developed a novel Single Protein Encapsulation (SPE)-based drug formulation and delivery platform and tested its utility in improving doxorubicin (DOX) treatment. Using this methodology, a series of SPEDOX complexes were generated by encapsulating various numbers of DOX molecules into a single human serum albumin (HSA) molecule. UV/fluorescence spectroscopy, membrane dialysis, and dynamic light scattering techniques showed that SPEDOXs are stable and uniform as monomeric HSA and display unique properties distinct from those of DOX and DOX-HSA mixture. Furthermore, detailed procedures to precisely monitor and control both DOX payload and binding strength to HSA were established. Breast cancer xenograft tumor studies revealed that SPEDOX-6 treatment displays improved pharmacokinetic profiles, higher antitumor efficacy, and lower DOX accumulation in the heart tissue compared with unformulated DOX. This SPE technology, which does not involve nanoparticle assembly and modifications to either small-molecule drugs or HSA, may open up a new avenue for developing new drug delivery systems to improve anticancer therapeutics.

Interaction with Human Serum Proteins Reveals Biocompatibility of Phosphocholine-Functionalized SPIONs and Formation of Albumin-Decorated Nanoparticles

Nanoparticles (NPs) are increasingly exploited as diagnostic and therapeutic devices in medicine. Among them, superparamagnetic nanoparticles (SPIONs) represent very promising tools for magnetic resonance imaging, local heaters for hyperthermia, and nanoplatforms for multimodal imaging and theranostics. However, the use of NPs, including SPIONs, in medicine presents several issues: first, the encounter with the biological world and proteins in particular. Indeed, nanoparticles can suffer from protein adsorption, which can affect NP functionality and biocompatibility. In this respect, we have investigated the interaction of small SPIONs covered by an amphiphilic double layer of oleic acid/oleylamine and 1-octadecanoyl-sn-glycero-3-phosphocholine with two abundant human plasma proteins, human serum albumin (HSA) and human transferrin. By means of spectroscopic and scattering techniques, we analyzed the effect of SPIONs on protein structure and the binding affinities, and only found strong binding in the case of HSA. In no case did SPIONs alter the protein structure significantly. We structurally characterized HSA/SPIONs complexes by means of light and neutron scattering, highlighting the formation of a monolayer of protein molecules on the NP surface. Their interaction with lipid bilayers mimicking biological membranes was investigated by means of neutron reflectivity. We show that HSA/SPIONs do not affect lipid bilayer features and could be further exploited as a nanoplatform for future applications. Overall, our findings point toward a high biocompatibility of phosphocholine-decorated SPIONs and support their use in nanomedicine.

Ultrathin Silicon Membranes for in Situ Optical Analysis of Nanoparticle Translocation across a Human Blood-Brain Barrier Model

Here we present a blood-brain barrier (BBB) model that enables high-resolution imaging of nanoparticle (NP) interactions with endothelial cells and the capture of rare NP translocation events. The enabling technology is an ultrathin silicon nitride (SiN) membrane (0.5 μm pore size, 20% porosity, 400 nm thickness) integrated into a dual-chamber platform that facilitates imaging at low working distances (∼50 μm). The platform, the μSiM-BBB (microfluidic silicon membrane-BBB), features human brain endothelial cells and primary astrocytes grown on opposite sides of the membrane. The human brain endothelial cells form tight junctions on the ultrathin membranes and exhibit a significantly higher resistance to FITC-dextran diffusion than commercial membranes. The enhanced optical properties of the SiN membrane allow high-resolution live-cell imaging of three types of NPs, namely, 40 nm PS-COOH, 100 nm PS-COOH, and apolipoprotein E-conjugated 100 nm SiO2, interacting with the BBB. Despite the excellent barrier properties of the endothelial layer, we are able to document rare NP translocation events of NPs localized to lysosomal compartments of astrocytes on the "brain side" of the device. Although the translocation is always low, our data suggest that size and targeting ligand are important parameters for NP translocation across the BBB. As a platform that enables the detection of rare transmission across tight BBB layers, the μSiM-BBB is an important tool for the design of nanoparticle-based delivery of drugs to the central nervous system.

Nanotechnology-based Targeting of Neurodegenerative Disorders: A Promising Tool for Efficient Delivery of Neuromedicines

Traditional drug delivery approaches remained ineffective in offering better treatment to various neurodegenerative disorders (NDs). In this context, diverse types of nanocarriers have shown their great potential to cross the blood-brain barrier (BBB) and have emerged as a prominent carrier system in drug delivery. Moreover, nanotechnology-based methods usually involve numerous nanosized carrier platforms, which potentiate the effect of the therapeutic agents in the therapy of NDs especially in diagnosis and drug delivery with negligible side effects. In addition, nanotechnology-based techniques have offered several strategies to cross BBB to intensify the bioavailability of drug moieties in the brain. In the last few years, diverse kinds of nanoparticles (NPs) have been developed by incorporating various biocompatible components (e.g., polysaccharide-based NPs, polymeric NPs, selenium NPs, AuNPs, protein-based NPs, gadolinium NPs, etc.), that showed great therapeutic benefits against NDs. Eventually, this review provides deep insights to explore recent applications of some innovative nanocarriers enclosing active molecules for the efficient treatment of NDs.

Albumin nanoscience: homing nanotechnology enabling targeted drug delivery and therapy

Albumin is a biocompatible, non-immunogenic and versatile drug carrier system. It has been widely used to extend the half-life, enhance stability, provide protection from degradation and allow specific targeting of therapeutic agents to various disease states. Understanding the role of albumin as a drug delivery and distribution system has increased remarkably in the recent years from the development of albumin-binding prodrugs to albumin as a drug carrier system. The extraordinary surface property of albumin makes it possible to bind various endogenous and exogenous molecules. This review succinctly deals with several albumin-drug conjugates and nanoparticles along with their preparation techniques and focuses on surface-modified albumin and targeting of albumin formulation to specific organs and tissues. It also summarizes research efforts on albumin nanoparticles used for delivering drugs to tumor cells and describes their role in permeation through tumor vasculature and in receptor mediated endocytosis, which is also described in this review. The versatility of albumin and ease of preparation makes it a suitable drug carrier system, swhich is the major objective of this review.

Key for crossing the BBB with nanoparticles: the rational design

Central nervous system diseases are a heavy burden on society and health care systems. Hence, the delivery of drugs to the brain has gained more and more interest. The brain is protected by the blood-brain barrier (BBB), a selective barrier formed by the endothelial cells of the cerebral microvessels, which at the same time acts as a bottleneck for drug delivery by preventing the vast majority of drugs to reach the brain. To overcome this obstacle, drugs can be loaded inside nanoparticles that can carry the drug through the BBB. However, not all particles are able to cross the BBB and a multitude of factors needs to be taken into account when developing a carrier system for this purpose. Depending on the chosen pathway to cross the BBB, nanoparticle material, size and surface properties such as functionalization and charge should be tailored to fit the specific route of BBB crossing.

Nanoparticles as carriers for drug delivery of macromolecules across the blood-brain barrier

Introduction: Current therapies of neurodegenerative or neurometabolic diseases are, to a large extent, hampered by the inability of drugs to cross the blood-brain barrier (BBB). This very tight barrier severely restricts the entrance of molecules from the blood into the brain, especially macromolecular substances (i.e. neurotrophic factors, enzymes, proteins, as well as genetic materials). Due to their size, physicochemical properties, and instability, the delivery of these materials is particularly difficult.Areas covered: Recent research showed that biocompatible and biodegradable nanoparticles possessing tailored surface properties can enable a delivery of drugs and specifically of macromolecules across the blood-brain barrier by using carrier systems of the brain capillary endothelium (Trojan Horse strategy). In the present review, the state-of-art of nanoparticle-mediated drug delivery of different macromolecular substances into the brain following intravenous injection is summarized, and different nanomedicines that are used to enable the transport of neurotrophic factors and enzymes across the blood-brain barrier into the CNS are critically analyzed.Expert opinion: Brain delivery of macromolecules by an intravenous application using nanomedicines is now a growing area of interest which could be really translated into clinical application if dedicated effort will be given to industrial scale-up production.

Biomimetic drug-delivery systems for the management of brain diseases

Acting as a double-edged sword, the blood-brain barrier (BBB) is essential for maintaining brain homeostasis by restricting the entry of small molecules and most macromolecules from blood. However, it also largely limits the brain delivery of most drugs. Even if a drug can penetrate the BBB, its accumulation in the intracerebral pathological regions is relatively low. Thus, an optimal drug-delivery system (DDS) for the management of brain diseases needs to display BBB permeability, lesion-targeting capability, and acceptable safety. Biomimetic DDSs, developed by directly utilizing or mimicking the biological structures and processes, provide promising approaches for overcoming the barriers to brain drug delivery. The present review summarizes the biological properties and biomedical applications of the biomimetic DDSs including the cell membrane-based DDS, lipoprotein-based DDS, exosome-based DDS, virus-based DDS, protein template-based DDS and peptide template-based DDS for the management of brain diseases.

Benefits of Nanomedicine for Therapeutic Intervention in Malignant Diseases

Cancer remains one of the most difficult to manage healthcare problems. The last two decades have been considered the golden age of cancer research, with major breakthroughs being announced on a regular basis. However, the major problem regarding cancer treatment is the incapability to selectively target cancer cells, with certain populations of tumors still remaining alive after treatment. The main focus of researchers is to develop treatments that are both effective and selective in targeting malignant cells. In this regard, bioavailability can be increased by overcoming the biological barriers encountered in the active agent’s pathway, creating carrier vehicles that have the ability to target malignant cells and effectively release the active agent. Since its appearance, nanomedicine has provided many answers to these challenges, but still, some expectations were not satisfied. In this review, we focused on the most recent developments in targeted drug delivery. Furthermore, a summary of different types of nanoparticles used to deliver active therapeutic agents in oncology is presented, along with details on the nanodrugs that were clinically approved by the Food and Drug Administration (FDA), until April 2019.

In vivo Evaluation and Alzheimer’s Disease Treatment Outcome of siRNA Loaded Dual Targeting Drug Delivery System

Background:

To deliver drugs to treat Alzheimer’s Disease (AD), nanoparticles should firstly penetrate through blood brain barrier, and then target neurons.

Methods:

Recently, we developed an Apo A-I and NL4 dual modified nanoparticle (ANNP) to deliver beta-amyloid converting enzyme 1 (BACE1) siRNA. Although promising in vitro results were obtained, the in vivo performance was not clear. Therefore, in this study, we further evaluated the in vivo neuroprotective effect and toxicity of the ANNP/siRNA. The ANNP/siRNA was 80.6 nm with good stability when incubated with serum. In vivo, the treatment with ANNP/siRNA significantly improves the spatial learning and memory of APP/PS1 double transgenic mice, as determined by mean escape latency, times of crossing the platform area during the 60 s swimming and the percentage of the distance in the target quadrant.

Results and Conclusion:

After the treatment, BACE1 RNA level of ANNP/siRNA group was greatly reduced, which contributed a good AD treatment outcome. Finally, after repeated administration, the ANNP/siRNA did not lead to significant change as observed by HE staining of main organs, suggesting the good biocompatibility of ANNP/siRNA. These results demonstrated that the ANNP was a good candidate for AD targeting siRNA delivery.

Stimulating brain recovery after stroke using theranostic albumin nanocarriers loaded with nerve growth factor in combination therapy

For many years, delivering drug molecules across the blood brain barrier has been a major challenge. The neuropeptide nerve growth factor is involved in the regulation of growth and differentiation of cholinergic neurons and holds great potential in the treatment of stroke. However, as with many other compounds, the biomolecule is not able to enter the central nervous system. In the present study, nerve growth factor and ultra-small particles of iron oxide were co-encapsulated into a chemically crosslinked albumin nanocarrier matrix which was modified on the surface with apolipoprotein E. These biodegradable nanoparticles with a size of 212 ± 1 nm exhibited monodisperse size distribution and low toxicity. They delivered NGF through an artificial blood brain barrier and were able to induce neurite outgrowth in PC12 cells in vitro. In an animal model of stroke, the infarct size was significantly reduced compared to the vehicle control. The combination therapy of NGF and the small-molecular MEK inhibitor U0126 showed a slight but not significant difference compared to U0126 alone. However, further in vivo evidence suggests that successful delivery of the neuropeptide is possible as well as the synergism between those two treatments.

Prospects and Challenges of Phospholipid-Based Prodrugs

Nowadays, the prodrug approach is used already at the early stages of drug development. Lipidic prodrug approach is a growing field for improving a number of drug properties/delivery/therapy aspects, and can offer solutions for various unmet needs. This approach includes drug moiety bound to the lipid carrier, which can be triglyceride, fatty acids, steroid, or phospholipid (PL). The focus of this article is PL-based prodrugs, which includes a PL carrier covalently bound to the active drug moiety. An overview of relevant physiological lipid processing pathways and absorption barriers is provided, followed by drug delivery/therapeutic application of PL-drug conjugates, as well as computational modeling techniques, and a modern bioinformatics tool that can aid in the optimization of PL conjugates. PL-based prodrugs have increased lipophilicity comparing to the parent drug, and can therefore significantly improve the pharmacokinetic profile and overall bioavailability of the parent drug, join the endogenous lipid processing pathways and therefore accomplish drug targeting, e.g., by lymphatic transport, drug release at specific target site(s), or passing the blood-brain barrier. Moreover, an exciting gateway for treating inflammatory diseases and cancer is presented, by utilizing the PL sn-2 position in the prodrug design, aiming for PLA₂-mediated activation. Overall, a PL-based prodrug approach shows great potential in improving different drug delivery/therapy aspects, and is expected to grow.

Colloidal stability as a determinant of nanoparticle behavior in the brain

Drug delivery to the brain is challenging due to a highly regulated blood-brain barrier (BBB) and a complex brain microenvironment. Nanoparticles, due to their tailorability, provide promising platforms to enhance therapeutic delivery and achieve controlled release and disease-specific localization in the brain. However, we have yet to fully understand the complex interactions between nanoparticles and the biological environments in which they operate. It is important to perform a systematic study to characterize nanoparticle behavior as a function of ion composition, concentration, and pH in cerebrospinal fluid (CSF). These could alter nanoparticle biological identity and influence diffusive capability and cellular uptake. In this study, poly(ethylene glycol) (PEG)-coated and carboxyl-coated polystyrene (PS-PEG and PS-COOH respectively) nanoparticles (NPs) were used to evaluate the aggregation kinetics, colloidal stability, and diffusive capability of nanoparticles in conditions relevant to the brain microenvironment. Size, surface charge, and surface coating were varied in a range of CSF ion concentrations and compositions, pH conditions, and temperatures. Small changes in calcium concentration and pH destabilize nanoparticles in CSF. However, PS-PEG NPs remain stable over a wider variety of conditions than PS-COOH NPs, and have higher diffusion capabilities in both agarose gels, an in vitro model of the brain microenvironment, and an organotypic brain tissue slice model. These results demonstrate the need for steric stabilization to maintain nanoparticle colloidal stability in a wide range of conditions. Importantly, colloidal stabilization allows for increased diffusive capability and can be used to predict diffusive behavior in the brain microenvironment.

Interfacing Graphene-Based Materials With Neural Cells

The scientific community has witnessed an exponential increase in the applications of graphene and graphene-based materials in a wide range of fields, from engineering to electronics to biotechnologies and biomedical applications. For what concerns neuroscience, the interest raised by these materials is two-fold. On one side, nanosheets made of graphene or graphene derivatives (graphene oxide, or its reduced form) can be used as carriers for drug delivery. Here, an important aspect is to evaluate their toxicity, which strongly depends on flake composition, chemical functionalization and dimensions. On the other side, graphene can be exploited as a substrate for tissue engineering. In this case, conductivity is probably the most relevant amongst the various properties of the different graphene materials, as it may allow to instruct and interrogate neural networks, as well as to drive neural growth and differentiation, which holds a great potential in regenerative medicine. In this review, we try to give a comprehensive view of the accomplishments and new challenges of the field, as well as which in our view are the most exciting directions to take in the immediate future. These include the need to engineer multifunctional nanoparticles (NPs) able to cross the blood-brain-barrier to reach neural cells, and to achieve on-demand delivery of specific drugs. We describe the state-of-the-art in the use of graphene materials to engineer three-dimensional scaffolds to drive neuronal growth and regeneration in vivo, and the possibility of using graphene as a component of hybrid composites/multi-layer organic electronics devices. Last but not least, we address the need of an accurate theoretical modeling of the interface between graphene and biological material, by modeling the interaction of graphene with proteins and cell membranes at the nanoscale, and describing the physical mechanism(s) of charge transfer by which the various graphene materials can influence the excitability and physiology of neural cells.

Self-assembled amphiphilic core-shell nanocarriers in line with the modern strategies for brain delivery

Disorders of the central nervous system (CNS) represent increasing social and economic problems all over the world which makes the effective transport of drugs to the brain a crucial need. In the last decade, many strategies were introduced to deliver drugs to the brain trying to overcome the challenge of the blood brain barrier (BBB) using both invasive and non-invasive methods. Non-invasive strategy represented in the application of nanocarriers became very common. One of the most hopeful nanoscopic carriers for brain delivery is core-shell nanocarriers or polymeric micelles (PMs). They are more advantageous than other nanocarriers. They offer small size, ease of preparation, ease of sterilization and the possibility of surface modification with various ligands. Hence, the aim of this review is to discuss modern strategies for brain delivery, micelles as a successful delivery system for the brain and how micelles could be modified to act as "magic bullets" for brain delivery.

The novel phospholipid mimetic KPC34 is highly active against preclinical models of Philadelphia chromosome positive acute lymphoblastic leukemia

Philadelphia chromosome positive B cell acute lymphoblastic leukemia (Ph+ ALL) is an aggressive cancer of the bone marrow. The addition of tyrosine kinase inhibitors (TKIs) has improved outcomes but many patients still suffer relapse and novel therapeutic agents are needed. KPC34 is an orally available, novel phospholipid conjugate of gemcitabine, rationally designed to overcome multiple mechanisms of resistance, inhibit the classical and novel isoforms of protein kinase C, is able to cross the blood brain barrier and is orally bioavailable. KPC34 had an IC50 in the nanomolar range against multiple ALL cell lines tested but was lowest for Ph+ lines. In mice bearing either naïve or resistant Ph+ ALL, KPC34 treatment resulted in significantly improved survival compared to cytarabine and gemcitabine. Treatment with KPC34 and doxorubicin was more effective than doxorubicin and cytarabine. Mice with recurrence of their ALL after initial treatment with cytarabine and doxorubicin saw dramatic improvements in hind limb paralysis after treatment with KPC34 demonstrating activity against established CNS disease. Consistent with this KPC34 was better than gemcitabine at reducing CNS leukemic burden. These promising pre-clinical results justify the continued development of KPC34 for the treatment of Ph+ALL.

Effect of the Protein Corona on Antibody-Antigen Binding in Nanoparticle Sandwich Immunoassays

We investigated the effect of the protein corona on the function of nanoparticle (NP) antibody (Ab) conjugates in dipstick sandwich immunoassays. Ab specific for Zika virus nonstructural protein 1 (NS1) were conjugated to gold NPs, and another anti-NS1 Ab was immobilized onto the nitrocellulose membrane. Sandwich immunoassay formation was influenced by whether the strip was run in corona forming conditions, i.e., in human serum. Strips run in buffer or pure solutions of bovine serum albumin exhibited false positives, but those run in human serum did not. Serum pretreatment of the nitrocellulose also eliminated false positives. Corona formation around the NP-Ab in serum was faster than the immunoassay time scale. Langmuir binding analysis determined how the immobilized Ab affinity for the NP-Ab/NS1 was impacted by corona formation conditions, quantified as an effective dissociation constant, K_D^eff. Results show that corona formation mediates the specificity and sensitivity of the antibody-antigen interaction of Zika biomarkers in immunoassays, and plays a critical but beneficial role.

Transport of Gold Nanoparticles by Vascular Endothelium from Different Human Tissues

The selective entry of nanoparticles into target tissues is the key factor which determines their tissue distribution. Entry is primarily controlled by microvascular endothelial cells, which have tissue-specific properties. This study investigated the cellular properties involved in selective transport of gold nanoparticles (<5 nm) coated with PEG-amine/galactose in two different human vascular endothelia. Kidney endothelium (ciGENC) showed higher uptake of these nanoparticles than brain endothelium (hCMEC/D3), reflecting their biodistribution in vivo. Nanoparticle uptake and subcellular localisation was quantified by transmission electron microscopy. The rate of internalisation was approximately 4x higher in kidney endothelium than brain endothelium. Vesicular endocytosis was approximately 4x greater than cytosolic uptake in both cell types, and endocytosis was blocked by metabolic inhibition, whereas cytosolic uptake was energy-independent. The cellular basis for the different rates of internalisation was investigated. Morphologically, both endothelia had similar profiles of vesicles and cell volumes. However, the rate of endocytosis was higher in kidney endothelium. Moreover, the glycocalyces of the endothelia differed, as determined by lectin-binding, and partial removal of the glycocalyx reduced nanoparticle uptake by kidney endothelium, but not brain endothelium. This study identifies tissue-specific properties of vascular endothelium that affects their interaction with nanoparticles and rate of transport.

Biodegradable Nanoparticles for Delivery of Therapeutics in CNS Infection

Despite the significant advances in neurological medicine, it remains difficult to treat ailments directly involving the brain. The blood brain barrier (BBB) is a tightly regulated, selectively permeable barrier that restricts access from the blood into the brain extracellular fluid (BEF). Many conditions such as tumors or infections in the brain are difficult to treat due to the fact that drugs and other therapeutic agents are unable to easily pass through this relatively impermeable barrier. Human Immunodeficiency Virus (HIV) presents a particular problem as it is able to remain dormant in the brain for years protected from antiretroviral drugs by the BBB. The development of nanoscale carriers over the past few decades has made possible the delivery of therapies with the potential to overcome membrane barriers and provide specific, targeted delivery. This review seeks to provide a comprehensive overview of the various aspects of nanoparticle formulation and their applications in improving the delivery efficiency of drugs, specifically antiretroviral therapeutics to the brain to treat HIV.

Progress and perspectives on targeting nanoparticles for brain drug delivery

Due to the ability of the blood-brain barrier (BBB) to prevent the entry of drugs into the brain, it is a challenge to treat central nervous system disorders pharmacologically. The development of nanotechnology provides potential to overcome this problem. In this review, the barriers to brain-targeted drug delivery are reviewed, including the BBB, blood-brain tumor barrier (BBTB), and nose-to-brain barrier. Delivery strategies are focused on overcoming the BBB, directly targeting diseased cells in the brain, and dual-targeted delivery. The major concerns and perspectives on constructing brain-targeted delivery systems are discussed.

Quantitative analysis of nanoparticle transport through in vitro blood-brain barrier models

Nanoparticle transport through the blood-brain barrier has received much attention of late, both from the point of view of nano-enabled drug delivery, as well as due to concerns about unintended exposure of nanomaterials to humans and other organisms. In vitro models play a lead role in efforts to understand the extent of transport through the blood-brain barrier, but unique features of the nanoscale challenge their direct adaptation. Here we highlight some of the differences compared to molecular species when utilizing in vitro blood-brain barrier models for nanoparticle studies. Issues that may arise with transwell systems are discussed, together with some potential alternative methodologies. We also briefly review the biomolecular corona concept and its importance for how nanoparticles interact with the blood-brain barrier. We end with considering future directions, including indirect effects and application of shear and fluidics-technologies.