Enhanced blood-brain barrier transmigration using a novel transferrin embedded fluorescent magneto-liposome nanoformulation

A review on the role of nanoparticles for targeted brain drug delivery: synthesis, characterization, and applications

Unfortunately, nowadays, brain disorders, which include both neurological and mental disorders, are the main cause of years spent living with a disability worldwide. There are serious diseases with a high prevalence and a high mortality rate. However, the outmoded technical infrastructure makes their treatment difficult. The blood-brain barrier (BBB) serves as a protective mechanism for the central nervous system (CNS) and regulates its homeostatic processes. The brain is protected against injury and illness by an extremely complex system that precisely regulates the flow of ions, very few tiny molecules, and an even smaller number of macromolecules from the blood to the brain. Nevertheless, the BBB also considerably inhibits the delivery of medications to the brain, making it impossible to treat a variety of neurological diseases. Several strategies are now being studied to enhance the transport of drugs over the BBB. According to this research, nanoparticles are one of the most promising agents for brain disease treatment while many conventional drugs are also capable of crossing this barrier but there are amazing facts about nanoparticles in brain drug delivery. For example, 1. Precision Targeting: Through mechanisms such as receptor-mediated transport, ligand attachment, or the use of external stimuli (e.g., magnetic or thermal guidance), nanoparticles can deliver drugs specifically to diseased areas of the brain while minimizing exposure to healthy tissues. This targeted approach reduces side effects and enhances therapeutic outcomes. 2. Improved Drug Stability: Drugs can be encapsulated by nanoparticles, which keeps them stable and shields them from deterioration while being transported to the brain. 3. Therapeutic Payload: Nanoparticles possess a high surface-area-to-volume ratio, enabling them to encapsulate a substantial quantity of therapeutic agents relative to their size. This allows for enhanced drug delivery efficiency, maximizing therapeutic outcomes while potentially reducing the required dosage to achieve the desired effect. 4. Imaging Properties: Certain nanoparticles can also act as contrast agents for magnetic resonance imaging (MRI), allowing for the real-time visualization of drug distribution and administration in the brain. 5. Combination Therapy Possibility: Nanoparticles can be designed to co-deliver multiple medications or therapeutic agents, which could enhance synergistic effects. There have been in vivo studies where nanoparticles were successfully used for combination therapies, demonstrating potential for personalized treatments. One notable example is in cancer treatment, where nanoparticles have been designed to co-deliver multiple chemotherapeutic agents. In general, brain medication delivery by nanoparticles is a novel strategy that has the potential to revolutionize neurological disease therapy and enhance patient outcomes. The study furthermore includes a concise depiction of the structural and physiological characteristics of the BBB, and it also provides an overview of the nanoparticles that are most often used in medicine. A brief overview of the structural and physiochemical characteristics of the NPs, as well as the most popular nanoparticles used in medicine, is also included in the review.

Borneol and lactoferrin dual-modified crocetin-loaded nanoliposomes enhance neuroprotection in HT22 cells and brain targeting in mice

Crocetin (CCT), a natural bioactive compound extracted and purified from the traditional Chinese medicinal herb saffron, has been shown to play a role in neurodegenerative diseases, particularly depression. However, due to challenges with solubility, targeting, and bioavailability, formulation development and clinical use of CCT are severely limited. In this study, we used the emulsification-reverse volatilization method to prepare CCT-loaded nanoliposomes (CN). We further developed a borneol (Bor) and lactoferrin (Lf) dual-modified CCT-loaded nanoliposome (BLCN) for brain-targeted delivery of CCT. The results of transmission electron microscope (TEM) and particle size analysis indicated that the size of BLCN (∼140 nm) was suitable for transcellular transport across olfactory axons (∼200 nm), potentially paving a direct path to the brain. Studies on lipid solubility, micropolarity, and hydrophobicity showed that BLCN had a relatively high Lf grafting rate (81.11 ± 1.33 %) and CCT entrapment efficiency (83.60 ± 1.04 %) compared to other liposomes, likely due to Bor improving the lipid solubility of Lf, and the combination promoting the orderly arrangement of liposome membrane molecules. Microplate reader and fluorescence microscopy analysis showed that BLCN efficiently promoted the endocytosis of fluorescent coumarin 6 into HT22 cells with a maximal fluorescence intensity of (13.48 ± 0.80 %), which was significantly higher than that of CCT (5.73 ± 1.17 %) and CN (12.13 ± 1.01 %). BLCN also exhibited sustained function, remaining effective for more than 12 h after reaching a peak at 1 h in cells, while CN showed a significant decrease after 4 h. The uptake mechanisms of BLCN in HT22 cells mainly involve energy-dependent, caveolae-mediated, and microtubule-mediated endocytosis, as well as micropinocytosis. Furthermore, BLCN displayed a significant neuroprotective effect on HT22 cells in glutamate-, corticosterone-, and H2O2-induced models. Tissue fluorescence image analysis of mice showed that BLCN exhibited substantial retention of fluorescent DiR in the brain after nasal administration for 12 h. These findings suggest that CCT has the potential for cellular uptake, neuroprotection, and targeted delivery to the brain following intranasal administration when encapsulated in Bor and Lf dual-modified nanoliposomes.

Blood-Brain Barrier-Targeting Nanoparticles: Biomaterial Properties and Biomedical Applications in Translational Neuroscience

Overcoming the blood-brain barrier (BBB) remains a significant hurdle in effective drug delivery to the brain. While the BBB serves as a crucial protective barrier, it poses challenges in delivering therapeutic agents to their intended targets within the brain parenchyma. To enhance drug delivery for the treatment of neurological diseases, several delivery technologies to circumvent the BBB have been developed in the last few years. Among them, nanoparticles (NPs) are one of the most versatile and promising tools. Here, we summarize the characteristics of NPs that facilitate BBB penetration, including their size, shape, chemical composition, surface charge, and importantly, their conjugation with various biological or synthetic molecules such as glucose, transferrin, insulin, polyethylene glycol, peptides, and aptamers. Additionally, we discuss the coating of NPs with surfactants. A comprehensive overview of the common in vitro and in vivo models of the BBB for NP penetration studies is also provided. The discussion extends to discussing BBB impairment under pathological conditions and leveraging BBB alterations under pathological conditions to enhance drug delivery. Emphasizing the need for future studies to uncover the inherent therapeutic properties of NPs, the review advocates for their role beyond delivery systems and calls for efforts translating NPs to the clinic as therapeutics. Overall, NPs stand out as a highly promising therapeutic strategy for precise BBB targeting and drug delivery in neurological disorders.

Magnetic hybrid nanovesicles for the precise diagnosis and treatment of central nervous system disorders

INTRODUCTION

Central nervous system (CNS)-related disorders are increasingly being recognized as a global health challenge worldwide. There are significant challenges for effective diagnosis and treatment due to the presence of the CNS barriers which impede the management of neurological diseases. Combination of nanovesicles (NVs) and magnetic nanoparticles (MNPs), referred to as magnetic nanovesicles (MNVs), is now well suggested as a potential theranostic option for improving the management of neurological disorders with increased targeting efficiency and minimized side effects.

AREAS COVERED

This review provides a summary of major CNS disorders and the physical barriers limiting the access of imaging/therapeutic agents to the CNS environment. A special focus on the unique features of MNPs and NV is discussed which make them attractive candidates for neuro-nanomedicine. Furthermore, a deeper understanding of MNVs as a promising combined strategy for diagnostic and/or therapeutic purposes in neurological disorders is provided.

EXPERT OPINION

The multifunctionality of MNVs offers the ability to overcome the CNS barriers and can be used to monitor the effectiveness of treatment. The insights provided will guide future research toward better outcomes and facilitate the development of next-generation, innovative treatments for CNS disorders.

The Potential of the Nose-to-Brain Delivery of PACAP for the Treatment of Neuronal Disease

Research on the neuroprotective effect of pituitary adenylate cyclase-activating polypeptide (PACAP) and its use as a therapeutic agent has grown over the past 30 years. Both in vitro and in vivo experiments have shown that PACAP exerts a strong neuroprotective effect in many central and peripheral neuronal diseases. Various delivery routes have been employed from intravenous (IV) injections to intracerebroventricular (ICV) administration, leading either to systemic or topical delivery of the peptide. Over the last decade, a growing interest in the use of intranasal (IN) administration of PACAP and other therapeutic agents has emerged as an alternative delivery route to target the brain. The aim of this review is to summarize the findings on the neuroprotective effect of PACAP and to discuss how the IN administration of PACAP could contribute to target the effects of this pleiotropic peptide.

Adhesion to the Brain Endothelium Selects Breast Cancer Cells with Brain Metastasis Potential

Tumor cells metastasize from a primary lesion to distant organs mainly through hematogenous dissemination, in which tumor cell re-adhesion to the endothelium is essential before extravasating into the target site. We thus hypothesize that tumor cells with the ability to adhere to the endothelium of a specific organ exhibit enhanced metastatic tropism to this target organ. This study tested this hypothesis and developed an in vitro model to mimic the adhesion between tumor cells and brain endothelium under fluid shear stress, which selected a subpopulation of tumor cells with enhanced adhesion strength. The selected cells up-regulated the genes related to brain metastasis and exhibited an enhanced ability to transmigrate through the blood-brain barrier. In the soft microenvironments that mimicked brain tissue, these cells had elevated adhesion and survival ability. Further, tumor cells selected by brain endothelium adhesion expressed higher levels of MUC1, VCAM1, and VLA-4, which were relevant to breast cancer brain metastasis. In summary, this study provides the first piece of evidence to support that the adhesion of circulating tumor cells to the brain endothelium selects the cells with enhanced brain metastasis potential.

Access to the CNS: Strategies to overcome the BBB

The blood-brain barrier (BBB) limits the access of substances to the central nervous system (CNS) which hinders the treatment of pathologies affecting the brain and the spinal cord. Nowadays, research is focus on new strategies to overcome the BBB and can treat the pathologies affecting the CNS are needed. In this review, the different strategies that allow and increase the access of substances to the CNS are analysed and extended commented, not only invasive strategies but also non-invasive ones. The invasive techniques include the direct injection into the brain parenchyma or the CSF and the therapeutic opening of the BBB, while the non-invasive techniques include the use of alternative routes of administration (nose-to-brain route), the inhibition of efflux transporters (as it is important to prevent the drug efflux from the brain and enhance the therapeutic efficiency), the chemical modification of the molecules (prodrugs and chemical drug delivery systems (CDDS)) and the use of nanocarriers. In the future, knowledge about nanocarriers to treat CNS diseases will continue to increase, but the use of other strategies such as drug repurposing or drug reprofiling, which are cheaper and less time consuming, may limit its transfer to society. The main conclusion is that the combination of different strategies may be the most interesting approach to increase the access of substances to the CNS.

Transmigration of magnetite nanoparticles across the blood-brain barrier in a rodent model: influence of external and alternating magnetic fields

Despite advances in neurology, drug delivery to the central nervous system is considered a challenge due to the presence of the blood brain barrier (BBB). In this study, the role of magnetic hyperthermia induced by exposure of magnetic nanoparticles (MNPs) to an alternating magnetic field (AMF) in synergy with an external magnetic field (EMF) was investigated to transiently increase the permeability of the MNPs across the BBB. A dual magnetic targeting approach was employed by first dragging the MNPs by an EMF for an intended enhanced cellular association with the brain endothelial cells and then activating the MNPs by an AMF for the temporary disruption of the tight junctions of BBB. The efficacy of the BBB permeability for the MNPs under the influence of dual magnetic targeting was evaluated in vitro using transwell models developed by co-culturing murine brain endothelial cells with astrocytes, as well as in vivo in mouse models. The in vitro results revealed that the exposure to AMF transiently opened the tight junctions at the BBB, which, after 3 h of treatment, were observed to recover back to their comparable control levels. A biodistribution analysis of nanoparticles confirmed targeted accumulation of MNPs in the brain following dual targeting. This dual targeting approach was observed to open the tight junctions, thus increasing the transport of MNPs into the brain with higher specificity as compared to using EMF targeting alone, suggesting that a dual magnetic targeting-induced transport of MNPs across the BBB is an effective measure for delivery of therapeutics.

In Vivo Targeting of the Neurovascular Unit: Challenges and Advancements

The blood-brain barrier (BBB) is essential for the homeostasis of the central nervous system (CNS). Functions of the BBB are performed by the neurovascular unit (NVU), which consists of endothelial cells, pericytes, astrocytes, microglia, basement membrane, and neurons. NVU cells interact closely and together are responsible for neurovascular coupling, BBB integrity, and transendothelial fluid transport. Studies have shown that NVU dysfunction is implicated in several acute and chronic neurological diseases, including Alzheimer's disease, multiple sclerosis, and stroke. The mechanisms of NVU disruption remain poorly understood, partially due to difficulties in selective targeting of NVU cells. In this review, we discuss the relative merits of available protein markers and drivers of the NVU along with recent advancements that have been made in the field to increase efficiency and specificity of NVU research.

Bio-polymeric transferrin-targeted temozolomide nanoparticles in gel for synergistic post-surgical GBM therapy

Spatiotemporal targeting of anti-glioma drugs remains a pressing issue in glioblastoma (GBM) treatment. We challenge this issue by developing a minimally invasive in situ implantable hydrogel implant comprising transferrin-targeted temozolomide-miltefosine nanovesicles in the surgically resected GBM cavity (tumour bed). Injection of the "nanovesicle in hydrogel system" in orthotopic GBM-bearing mice improved drug penetration into the peri-cavitary region (∼4.5 mm in depth) with the potential to act as a bridge therapy in the immediate postoperative period, before the initiation of adjuvant radiotherapy. The controlled and sustained release of temozolomide over a month in the surgical cavity eradicated the microscopic GBM cells present within the tumour bed, thereby augmenting the efficacy of adjuvant therapy. The drug (temozolomide and miltefosine) combination was tolerable and efficiently inhibited tumour growth, causing significant prolongation of the survival of tumour-bearing mice compared to that with the free drug. Direct implantation at the target site in the brain resulted in spatiotemporal anti-glioma activity with minimal extracranial and systemic distribution. Nanovesicle in flexible hydrogel systems can be used as potential platforms for the post-surgical management of GBM before initiating adjuvant radiation therapy.

Preparation of layering-structured magnetic fluorescent liposomes and labeling of HepG2 cells

BACKGROUND

At present, surgical resection and chemotherapy are still the main treatments for hepatocellular carcinoma and other cancers, but the curative effect and survival rate are not ideal.

OBJECTIVE

In this study, we aim to prepare a carrier with low toxicity, high biocompatibility and targeted transport for the treatment of hepatocellular carcinoma.

METHODS

CdSe quantum dots (QDs) modified with oleic acid were synthesized. Then hydrophobic CdSe QDs and hydrophilic super-paramagnetic Fe3O4 particles were encapsulated into different layers of liposomes to form magnetic fluorescent liposomes (MFLs). MFLs in the aqueous would quickly drift towards the external magnet and the entire process was clearly observed with fluorescence microscope. The fluorescence spectra revealed that the fluorescence properties of MFLs were similar to that of CdSe QDs.

RESULTS

QDs had an average size of 3.32 nm with good fluorescence properties. The size of MFLs was about 100 nm (transmission electron microscopy (TEM) analysis showed the average size of MFLs was about 82.8 nm and dynamic light scattering (DLS) detection showed 111.9 nm). After being cultured with MFLs for 8 h, HepG2 cells were labeled by MFLs and good fluorescence images were obtained. MTT analysis also expressed their good biocompatibility.

CONCLUSION

The prepared MFLs had multi-function and could be used as ideal drug carriers.

Crossroads of Drug Abuse and HIV Infection: Neurotoxicity and CNS Reservoir

Drug abuse is a common comorbidity in people infected with HIV. HIV-infected individuals who abuse drugs are a key population who frequently experience suboptimal outcomes along the HIV continuum of care. A modest proportion of HIV-infected individuals develop HIV-associated neurocognitive issues, the severity of which further increases with drug abuse. Moreover, the tendency of the virus to go into latency in certain cellular reservoirs again complicates the elimination of HIV and HIV-associated illnesses. Antiretroviral therapy (ART) successfully decreased the overall viral load in infected people, yet it does not effectively eliminate the virus from all latent reservoirs. Although ART increased the life expectancy of infected individuals, it showed inconsistent improvement in CNS functioning, thus decreasing the quality of life. Research efforts have been dedicated to identifying common mechanisms through which HIV and drug abuse lead to neurotoxicity and CNS dysfunction. Therefore, in order to develop an effective treatment regimen to treat neurocognitive and related symptoms in HIV-infected patients, it is crucial to understand the involved mechanisms of neurotoxicity. Eventually, those mechanisms could lead the way to design and develop novel therapeutic strategies addressing both CNS HIV reservoir and illicit drug use by HIV patients.

An Overview of Nanotechnologies for Drug Delivery to the Brain

Drug delivery to the brain has been one of the toughest challenges researchers have faced to develop effective treatments for brain diseases. Owing to the blood–brain barrier (BBB), only a small portion of administered drug can reach the brain. A consequence of that is the need to administer a higher dose of the drug, which, expectedly, leads to a variety of unwanted side effects. Research in a variety of different fields has been underway for the past couple of decades to address this very serious and frequently lethal problem. One area of research that has produced optimistic results in recent years is nanomedicine. Nanomedicine is the science birthed by fusing the fields of nanotechnology, chemistry and medicine into one. Many different types of nanomedicine-based drug-delivery systems are currently being studied for the sole purpose of improved drug delivery to the brain. This review puts together and briefly summarizes some of the major breakthroughs in this crusade. Inorganic nanoparticle-based drug-delivery systems, such as gold nanoparticles and magnetic nanoparticles, are discussed, as well as some organic nanoparticulate systems. Amongst the organic drug-delivery nanosystems, polymeric micelles and dendrimers are discussed briefly and solid polymeric nanoparticles are explored in detail.

In vitro blood brain barrier models: An overview

Understanding the composition and function of the blood brain barrier (BBB) enables the development of novel, innovative techniques for administering central nervous system (CNS) medications and technologies for improving the existing models. Scientific and methodological interest in the pathology of the BBB resulted in the formation of numerous in vitro BBB models. Once successfully studied and modelled, it would be a valuable tool for elucidating the mechanism of action of the CNS disorders prior to their manifestation and the pathogenic factors. Understanding the rationale behind the selection of the models as well as their working may enable the development of state-of-the-art drugs for treating and managing neurological diseases. Hence, to have realistic simulation of the BBB and test its drug permeability the microfluidics-based BBB-on-Chip model has been developed. To summarise, we aim to evaluate the advanced, newly developed and frequently used in vitro BBB models, thereby providing a brief overview of the components essential for in vitro BBB formation, the methods of chip fabrication and cell culturing, its applications and the recent advances in this technological field. This will be critical for developing CNS treatments with improved BBB penetrability and pharmacokinetic properties.

Nanomaterials‐Mediated Structural and Physiological Modulation of Blood Brain Barrier for Therapeutic Purposes

Blood brain barrier (BBB) protects homeostasis and sensitive environment of brain from several toxic substances coming from the systemic circulation. This barrier along with those substances also prevents therapeutic chemicals to reach brain tissues for several brain diseases. BBB consists of a number of cell types and junctions that help maintain its intricate structure and physiology. To open BBB for therapeutic purposes, researchers are keen to explore the use of nanomaterials as therapeutic agents. Nanomaterials have unique physio‐chemical properties such as, increased surface area to mass ratio, superior adsorption capacity, and a wide variety of functionalization possibilities in contrast to bulk materials, making them sought‐after for research pertaining to brain delivery of therapeutic substances. Both organic and inorganic nanomaterials have been researched in this regard with numerous interesting functionalizations, and their toxicity and distribution profiles have been well assessed. Different pathways taken up by nanomaterials to cross BBB like adsorptive‐mediated transcytosis, inhibition of active efflux pumps, receptor‐mediated transport, and cell‐mediated endocytosis have also been investigated. This review summarizes the structural and physiological properties and the modulation techniques of BBB for delivery of adsorbed/functionalized nano delivery platforms and imaging nanomaterials across.

Tumor microenvironment and nanotherapeutics: intruding the tumor fort

Over recent years, advancements in nanomedicine have allowed new approaches to diagnose and treat tumors. Nano drug delivery systems exploit the enhanced permeability and retention (EPR) effect and enter the tumor tissue's interstitial space. However, tumor barriers play a crucial role, and cause inefficient EPR or the homing effect. Mounting evidence supports the hypothesis that the components of the tumor microenvironment, such as the extracellular matrix, and cellular and physiological components collectively or cooperatively hinder entry and distribution of drugs, and therefore, limit the theragnostic applications of cancer nanomedicine. This abnormal tumor microenvironment plays a pivotal role in cancer nanomedicine and was recently recognized as a promising target for improving nano-drug delivery and their therapeutic outcomes. Strategies like passive or active targeting, stimuli-triggered nanocarriers, and the modulation of immune components have shown promising results in achieving anticancer efficacy. The present review focuses on the tumor microenvironment and nanoparticle-based strategies (polymeric, inorganic and organic nanoparticles) for intruding the tumor barrier and improving therapeutic effects.

Mechanisms Involved in Microglial-Interceded Alzheimer's Disease and Nanocarrier-Based Treatment Approaches

Alzheimer's disease (AD) is a common neurodegenerative disorder accountable for dementia and cognitive dysfunction. The etiology of AD is complex and multifactorial in origin. The formation and deposition of amyloid-beta (Aβ), hyperphosphorylated tau protein, neuroinflammation, persistent oxidative stress, and alteration in signaling pathways have been extensively explored among the various etiological hallmarks. However, more recently, the immunogenic regulation of AD has been identified, and macroglial activation is considered a limiting factor in its etiological cascade. Macroglial activation causes neuroinflammation via modulation of the NLRP3/NF-kB/p38 MAPKs pathway and is also involved in tau pathology via modulation of the GSK-3β/p38 MAPK pathways. Additionally, microglial activation contributes to the discrete release of neurotransmitters and an altered neuronal synaptic plasticity. Therefore, activated microglial cells appear to be an emerging target for managing and treating AD. This review article discussed the pathology of microglial activation in AD and the role of various nanocarrier-based anti-Alzeihmenr's therapeutic approaches that can either reverse or inhibit this activation. Thus, as a targeted drug delivery system, nanocarrier approaches could emerge as a novel means to overcome existing AD therapy limitations.

Microfluidics for Multiphase Mixing and Liposomal Encapsulation of Nanobioconjugates: Passive vs. Acoustic Systems

One of the main routes to ensure that biomolecules or bioactive agents remain active as they are incorporated into products with applications in different industries is by their encapsulation. Liposomes are attractive platforms for encapsulation due to their ease of synthesis and manipulation and the potential to fuse with cell membranes when they are intended for drug delivery applications. We propose encapsulating our recently developed cell-penetrating nanobioconjugates based on magnetite interfaced with translocating proteins and peptides with the purpose of potentiating their cell internalization capabilities even further. To prepare the encapsulates (also known as magnetoliposomes (MLPs)), we introduced a low-cost microfluidic device equipped with a serpentine microchannel to favor the interaction between the liposomes and the nanobioconjugates. The encapsulation performance of the device, operated either passively or in the presence of ultrasound, was evaluated both in silico and experimentally. The in silico analysis was implemented through multiphysics simulations with the software COMSOL Multiphysics 5.5® (COMSOL Inc., Stockholm, Sweden) via both a Eulerian model and a transport of diluted species model. The encapsulation efficiency was determined experimentally, aided by spectrofluorimetry. Encapsulation efficiencies obtained experimentally and in silico approached 80% for the highest flow rate ratios (FRRs). Compared with the passive mixer, the in silico results of the device under acoustic waves led to higher discrepancies with respect to those obtained experimentally. This was attributed to the complexity of the process in such a situation. The obtained MLPs demonstrated successful encapsulation of the nanobioconjugates by both methods with a 36% reduction in size for the ones obtained in the presence of ultrasound. These findings suggest that the proposed serpentine micromixers are well suited to produce MLPs very efficiently and with homogeneous key physichochemical properties.

Glutathione Liposomes Carrying Ceftriaxone, FK506, and Nilotinib to Control Overexpressed Dopamine Markers and Apoptotic Factors in Neurons

Advances in liposomal formulation carrying multiple neuroprotective drugs, such as ceftriaxone (CEF), FK506, and nilotinib, can point toward an approach to obviating the difficulties in Parkinson's disease (PD) treatment. We prepared functionalized liposomes decorated with glutathione (GSH) to penetrate the blood-brain barrier (BBB) and cardiolipin (CL) to link up apoptotic neurons. Further, the effect of CEF-FK506-nilotinib-GSH-CL-liposomes on a PD model established by SH-SY5Y cells with 1-methyl-4-phenylpyridinium-induced neurotoxicity was investigated. An increment of the mole percentage of dihexadecyl phosphate and CL increased the particle size and the absolute value of ζ potential, improved the entrapment efficiency of CEF, FK506, and nilotinib, and reduced the drug-releasing rate. The toxicity studies revealed that CEF, FK506, and nilotinib-encapsulated liposomes could enhance the survival of SH-SY5Y cells. Western blot and immunofluorescence revealed that incorporation of CL in a lipid bilayer ameliorated the docking of CEF-FK506-nilotinib-GSH-CL-liposomes at α-synuclein (α-syn), indicating a better targeting capability of the liposomes to degenerated neurons. Treatment with CEF-FK506-nilotinib-GSH-CL-liposomes reduced the expression of Bax and α-syn and promoted the expression of Bcl-2, tyrosine hydroxylase, and the dopamine transporter. GSH- and CL-conjugated liposomes showed combined activity of targeting the BBB and α-syn and augmented the efficiency of the three drugs in rescuing dopaminergic neurons for neurodegenerative therapy.

Crossing the blood-brain barrier: A review on drug delivery strategies using colloidal carrier systems

The blood-brain barrier represents the major challenge for delivering drugs to the central nervous system (CNS). It separates the blood circulation from the brain tissue, thereby protecting the CNS and maintaining its ion homeostasis. Unfortunately, most drugs are not able to cross this barrier in vivo despite promising in vitro results. One approach to solve this problem is the delivery of drugs via surface modified nanocarrier systems. This review will give an overview on currently tested systems, mainly liposomes and solid nanoparticles and inform about new developments.

Use of Super Paramagnetic Iron Oxide Nanoparticles as Drug Carriers in Brain and Ear: State of the Art and Challenges

Drug delivery and distribution in the central nervous system (CNS) and the inner ear represent a challenge for the medical and scientific world, especially because of the blood-brain and the blood-perilymph barriers. Solutions are being studied to circumvent or to facilitate drug diffusion across these structures. Using superparamagnetic iron oxide nanoparticles (SPIONs), which can be coated to change their properties and ensure biocompatibility, represents a promising tool as a drug carrier. They can act as nanocarriers and can be driven with precision by magnetic forces. The aim of this study was to systematically review the use of SPIONs in the CNS and the inner ear. A systematic PubMed search between 1999 and 2019 yielded 97 studies. In this review, we describe the applications of the SPIONS, their design, their administration, their pharmacokinetic, their toxicity and the methods used for targeted delivery of drugs into the ear and the CNS.

Evaluation of Physicochemical Properties of Amphiphilic 1,4-Dihydropyridines and Preparation of Magnetoliposomes

This study was focused on the estimation of the targeted modification of 1,4-DHP core with (1) different alkyl chain lengths at 3,5-ester moieties of 1,4-DHP (C₁₂, C₁₄ and C₁₆); (2) N-substituent at position 1 of 1,4-DHP (N-H or N-CH₃); (3) substituents of pyridinium moieties at positions 2 and 6 of 1,4-DHP (H, 4-CN and 3-Ph); (4) substituent at position 4 of 1,4-DHP (phenyl and napthyl) on physicochemical properties of the entire molecules and on the characteristics of the obtained magnetoliposomes formed by them. It was shown that thermal behavior of the tested 1,4-DHP amphiphiles was related to the alkyl chains length, the elongation of which decreased their transition temperatures. The properties of 1,4-DHP amphiphile monolayers and their polar head areas were determined. The packing parameters of amphiphiles were in the 0.43–0.55 range. It was demonstrated that the structure of 1,4-DHPs affected the physicochemical properties of compounds. “Empty” liposomes and magnetoliposomes were prepared from selected 1,4-DHP amphiphiles. It was shown that the variation of alkyl chains length or the change of substituents at positions 4 of 1,4-DHP did not show a significant influence on properties of liposomes.

Use of leptin-conjugated phosphatidic acid liposomes with resveratrol and epigallocatechin gallate to protect dopaminergic neurons against apoptosis for Parkinson's disease therapy

Complex liposomes were assembled with 1,2-distearoyl-sn-glycero-3-phosphocholine, dihexadecyl phosphate (DHDP), cholesterol and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphate (PA) to act as drug carriers for resveratrol (RES) and epigallocatechin gallate (EGCG). The liposomes were modified with leptin (Lep) on the surface to cross the blood-brain barrier (BBB) and to rescue degenerated dopaminergic neurons. The activity of RES and EGCG against neurotoxicity was investigated using an in vitro neurodegenerative model established by SH-SY5Y cells with an insult of 1-methyl-4-phenylpyridinium (MPP⁺). The results indicated that increasing the mole percentage of DHDP and PA increased the particle size and absolute zeta potential value, and improved the entrapment efficiency of RES and EGCG; however, this increase reduced the release rate of RES and EGCG and the grafting efficiency of Lep. The ability of Lep/RES-EGCG-PA-liposomes to cross the BBB was found to be higher than that of non-modified liposomes. Further, the addition of PA and Lep into liposomes enhanced cell viability and target efficiency. The immunofluorescence results demonstrated that the conjugation of Lep with liposomes enabled the docking of HBMECs and SH-SY5Y cells via Lep receptor, and enhanced their ability to permeate the BBB and cellular uptake. Immunofluorescence and western blot analysis also revealed that RES and EGCG encapsulated into liposomes could be a neural defensive strategy by reducing the apoptosis promotor protein Bcl-2 associated X protein and α-synuclein, and enhancement in the apoptosis inhibitor protein B cell lymphoma 2, tyrosine hydroxylase, and the dopamine transporter. Hence, Lep-PA-liposomes can be an excellent choice of potential delivery system for PD treatment.

A brain glioma gene delivery strategy by angiopep-2 and TAT-modified magnetic lipid-polymer hybrid nanoparticles

Owing to the existence of the blood-brain barrier (BBB), most treatments cannot achieve significant effects on gliomas. In this study, synergistic multitarget Ang-TAT-Fe3O4-pDNA-(ss)373 lipid-polymer hybrid nanoparticles (LPNPs) were designed to penetrate the BBB and deliver therapeutic genes to glioma cells. The basic material of the nanoparticles was PCL3750-ss-PEG7500-ss-PCL3750, and is called (ss)373 herein. (ss)373 NPs, Fe3O4 magnetic nanoparticles (MNPs), DOTAP, and DSPE-PEG-MAL formed the basic structure of LPNPs by self-assembly. The Fe3O4 MNPs were wrapped in (ss)373 NPs to implement magnetic targeting. Then, the Angiopep-2 peptide (Ang) and transactivator of transcription (TAT) were coupled with DSPE-PEG-MAL. Both can enhance BBB penetration and tumor targeting. Finally, the pDNA was compressed on DOTAP to form the complete gene delivery system. The results indicated that the Ang-TAT-Fe3O4-pDNA-(ss)373 LPNPs were 302.33 nm in size. In addition, their zeta potential was 4.66 mV, and they had good biocompatibility. The optimal nanoparticles/pDNA ratio was 5 : 1, as shown by gel retardation assay. In this characterization, compared with other LPNPs, the modified single Ang or without the addition of the Fe3O4 MNPs, the penetration efficiency of the BBB model formed by hCMEC/D3 cells, and the transfection efficiency of C6 cells using pEGFP-C1 as the reporter gene were significantly improved with Ang-TAT-Fe3O4-pDNA-(ss)373 LPNPs in the magnetic field.

Microglia-targeting nanotherapeutics for neurodegenerative diseases

Advances in nanotechnology have enabled the design of nanotherapeutic platforms that could address the challenges of targeted delivery of active therapeutic agents to the central nervous system (CNS). While the majority of previous research studies on CNS nanotherapeutics have focused on neurons and endothelial cells, the predominant resident immune cells of the CNS, microglia, are also emerging as a promising cellular target for neurodegeneration considering their prominent role in neuroinflammation. Under normal physiological conditions, microglia protect neurons by removing pathological agents. However, long-term exposure of microglia to stimulants will cause sustained activation and lead to neuronal damage due to the release of pro-inflammatory agents, resulting in neuroinflammation and neurodegeneration. This Perspective highlights criteria to be considered when designing microglia-targeting nanotherapeutics for the treatment of neurodegenerative disorders. These criteria include conjugating specific microglial receptor-targeting ligands or peptides to the nanoparticle surface to achieve targeted delivery, leveraging microglial phagocytic properties, and utilizing biocompatible and biodegradable nanomaterials with low immune reactivity and neurotoxicity. In addition, certain therapeutic agents for the controlled inhibition of toxic protein aggregation and for modulation of microglial activation pathways can also be incorporated within the nanoparticle structure without compromising stability. Overall, considering the multifaceted disease mechanisms of neurodegeneration, microglia-targeted nanodrugs and nanotherapeutic particles may have the potential to resolve multiple pathological determinants of the disease and to guide a shift in the microglial phenotype spectrum toward a more neuroprotective state.

Application of Iron Oxide Nanoparticles in the Diagnosis and Treatment of Neurodegenerative Diseases With Emphasis on Alzheimer's Disease

Neurodegenerative diseases are characterized by chronic progressive degeneration of the structure and function of the nervous system, which brings an enormous burden on patients, their families, and society. It is difficult to make early diagnosis, resulting from the insidious onset and progressive development of neurodegenerative diseases. The drugs on the market cannot cross the blood-brain barrier (BBB) effectively, which leads to unfavorable prognosis and less effective treatments. Therefore, there is an urgent demand to develop a novel detection method and therapeutic strategies. Recently, nanomedicine has aroused considerable attention for diagnosis and therapy of central nervous system (CNS) diseases. Nanoparticles integrate targeting, imaging, and therapy in one system and facilitate the entry of drug molecules across the blood-brain barrier, offering new hope to patients. In this review, we summarize the application of iron oxide nanoparticles (IONPs) in the diagnosis and treatment of neurodegenerative disease, including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). We focus on IONPs as magnetic resonance imaging (MRI) contrast agents (CAs) and drug carriers in AD. What most neurodegenerative diseases have in common is that hall marker lesions are represented by protein aggregates (Soto and Pritzkow, 2018). These diseases are of unknown etiology and unfavorable prognosis, and the treatments toward them are less effective (Soto and Pritzkow, 2018). Such diseases usually develop in aged people, and early clinical manifestations are atypical, resulting in difficulty in early diagnosis. Recently, nanomedicine has aroused considerable attention for therapy and diagnosis of CNS diseases because it integrates targeting, imaging, and therapy in one system (Gupta et al., 2019). In this review article, we first introduce the neurodegenerative diseases and commonly used MRI CAs. Then we review the application of IONPs in the diagnosis and treatment of neurodegenerative diseases with the purpose of assisting early theranostics (therapy and diagnosis).

Mechanisms of Blood-Retinal Barrier Disruption by HIV-1

It has been found that human immunodeficiency virus (HIV)-1 RNA or antigens can be detected in the intraocular tissues of HIV-1 patients even under effective highly active anti-retroviral therapy (HAART). In vivo, blood-retinal barrier (BRB) establishes a critical, physiological guardian against microbial invasion of the eye, but may be compromised in the presence of HIV-1. The envelope glycoprotein gp120 is exposed on the surface of the HIV envelope, essential for virus entry into cells by the attachment to specific cell surface receptors. The BRB disruption by glycoprotein gp120 has been widely recognized, which is toxic to human retinal epithelial cells (RPE) and umbilical vein endothelial cells (HUVEC). The present review elaborates on various mechanisms of BRB disruption induced by HIV gp120, which may represent potential targets for the prevention of ocular HIV complications in the future.

Novel approaches for the delivery of therapeutics in ischemic stroke

Here, we review novel approaches to deliver neuroprotective drugs to salvageable penumbral brain areas of stroke injury with the goals of offsetting ischemic brain injury and enhancing recovery.

Evaluation of Targeted Delivery to the Brain Using Magnetic Immunoliposomes and Magnetic Force

Magnetic nanoparticles have great prospects for drug delivery purposes, as they can be designed with various surface coatings and conjugated with drugs and targeting moieties. They also have a unique potential for precise delivery when guided by magnetic force. The blood-brain barrier (BBB) denotes the interface between the blood and brain parenchyma and hinders the majority of drugs from entering the brain. Red fluorescent magnetic nanoparticles were encapsulated in liposomes and conjugated to antibodies targeting the rat transferrin receptor (OX26) to form magnetic immunoliposomes. These magnetic immunoliposomes enhanced the uptake by rat brain capillary endothelial cells (BCECs) in vitro. In situ brain perfusion in young rats high in the endogenous expression of transferrin receptors by BCECs, revealed enhanced uptake of magnetic immunoliposomes when compared to naked magnetic nanoparticles or non-targeted magnetic liposomes. When applying the external magnetic force, the magnetic nanoparticles were detected in the brain parenchyma, suggesting transport across the BBB. Ultrastructural examination of the immunoliposomes, unfortunately, was unable to confirm a complete encapsulation of all naked nanoparticles within the liposomes, suggesting that the data on the brain could derive from particles being released from the liposomes under influence of external magnetic force; hence hypothesizes on external magnetic force as a qualifier for dragging targeted magnetic immunoliposomes through the BBB. In conclusion, our results suggest that transport of magnetic nanoparticles present in BCECs by targeted delivery to the transferrin receptor may undergo further transport into the brain when applying magnetic force. While magnetic immunoliposomes are targetable to BCECs, their design to enable further transport across the BBB when applying external magnetic force needs further improvement.

In-vitro blood-brain barrier models for drug screening and permeation studies: an overview

The blood-brain barrier (BBB) is comprised of brain microvascular endothelial central nervous system (CNS) cells, which communicate with other CNS cells (astrocytes, pericytes) and behave according to the state of the CNS, by responding against pathological environments and modulating disease progression. The BBB plays a crucial role in maintaining homeostasis in the CNS by maintaining restricted transport of toxic or harmful molecules, transport of nutrients, and removal of metabolites from the brain. Neurological disorders, such as NeuroHIV, cerebral stroke, brain tumors, and other neurodegenerative diseases increase the permeability of the BBB. While on the other hand, semipermeable nature of BBB restricts the movement of bigger molecules i.e. drugs or proteins (>500 kDa) across it, leading to minimal bioavailability of drugs in the CNS. This poses the most significant shortcoming in the development of therapeutics for CNS neurodegenerative disorders. Although the complexity of the BBB (dynamic and adaptable barrier) affects approaches of CNS drug delivery and promotes disease progression, understanding the composition and functions of BBB provides a platform for novel innovative approaches towards drug delivery to CNS. The methodical and scientific interests in the physiology and pathology of the BBB led to the development and the advancement of numerous in vitro models of the BBB. This review discusses the fundamentals of BBB structure, permeation mechanisms, an overview of all the different in-vitro BBB models with their advantages and disadvantages, and rationale of selecting penetration prediction methods towards the critical role in the development of the CNS therapeutics.

Receptor-Mediated Delivery of Astaxanthin-Loaded Nanoparticles to Neurons: An Enhanced Potential for Subarachnoid Hemorrhage Treatment

Astaxanthin (ATX) is a carotenoid that exerts strong anti-oxidant and anti-inflammatory property deriving from its highly unsaturated molecular structures. However, the low stability and solubility of ATX results in poor bioavailability, which markedly hampers its application as therapeutic agent in clinic advancement. This study investigated a promising way of transferrin conjugated to poly (ethylene glycol) (PEG)-encapsulated ATX nanoparticles (ATX-NPs) on targeted delivery and evaluated the possible mechanism underlying neuroprotection capability. As a result, the ATX integrated into nanocarrier presented both well water-dispersible and biocompatible, primely conquering its limitations. More than that, the transferrin-containing ATX-NPs exhibited enhanced cellular uptake efficiency than that of ATX-NPs without transferrin conjugated in primary cortical neurons. Additionally, compared to free ATX, transferrin-containing ATX-NPs with lower ATX concentration showed powerful neuroprotective effects on OxyHb-induced neuronal damage. Taken together, the improved bioavailability and enhanced neuroprotective effects enabled ATX-NPs as favorable candidates for targeted delivery and absorption of ATX. We believe that these in vitro findings will provide insights for advancement of subarachnoid hemorrhage therapy.

gH625-liposomes as tool for pituitary adenylate cyclase-activating polypeptide brain delivery

The blood-brain barrier (BBB) regulates the traffic of molecules into the central nervous system (CNS) and also limits the drug delivery. Due to their flexible properties, liposomes are an attractive tool to deliver drugs across the BBB. We previously characterized gH625, a peptide derived from Herpes simplex virus 1. The present study investigates the efficiency of liposomes functionalized on their surface with gH625 to promote the brain uptake of neuroprotective peptide PACAP (pituitary adenylate cyclase-activating polypeptide). Using a rat in vitro BBB model, we showed that the liposomes preparations were non-toxic for the endothelial cells, as assessed by analysis of tight junction protein ZO1 organization and barrier integrity. Next, we found that gH625 improves the transfer of liposomes across endothelial cell monolayers, resulting in both low cellular uptake and increased transport of PACAP. Finally, in vivo results demonstrated that gH625 ameliorates the efficiency of liposomes to deliver PACAP to the mouse brain after intravenous administration. gH625-liposomes improve both PACAP reaching and crossing the BBB, as showed by the higher number of brain cells labelled with PACAP. gH625-liposomes represent a promising strategy to deliver therapeutic agents to CNS and to provide an effective imaging and diagnostic tool for the brain.

Brain and bone cancer targeting by a ferrofluid composed of superparamagnetic iron-oxide/silica/carbon nanoparticles (earthicles)

Despite the advances in molecularly targeted therapies, delivery across the blood-brain barrier (BBB) and the targeting of brain tumors remains a challenge. Like brain, bone is a common site of metastasis and requires therapies capable of discerning the tumor from its healthy cellular milieu. To tackle these challenges, we made a variation on the previously proposed concept of the earthicle and fabricated an aqueous, surfactant-free ferrofluid containing superparamagnetic iron oxide nanoparticles (SPIONs) coated with silicate mesolayers and carbon shells, having 13 nm in size on average. Nanoparticles were synthesized hydrothermally and characterized using a range of spectroscopic, diffractometric, hydrodynamic and electron microscopy techniques. The double coating on SPIONs affected a number of physicochemical and biological properties, including colloidal stability and cancer targeting efficacy. Nanoparticles decreased the viability of glioblastoma and osteosarcoma cells and tumors more than that of their primary and non-transformed analogues. They showed a greater preference for cancer cells because of a higher rate of uptake by these cells and a pronounced adherence to cancer cell membrane. Even in an ultralow alternate magnetic field, nanoparticles generated sufficient heat to cause tumor death. Nanoparticles in MDCK-MDR1 BBB model caused mislocalization of claudin-1 at the tight junctions, underexpression of ZO-1 and no effect on occludin-1 and transepithelial resistance. Nanoparticles were detected in the basolateral compartments and examination of LAMP1 demonstrated that nanoparticles escaped the lysosome, traversed the BBB transcellularly and localized to the optic lobes of the third instar larval brains of Drosophila melanogaster. The passage was noninvasive and caused no adverse systemic effects to the animals. In conclusion, these nanoparticulate ferrofluids preferentially bind to cancer cells and, hence, exhibit a greater toxicity in these cells compared to the primary cells. They are also effective against solid tumors in vitro, can cross the BBB in Drosophila, and are nontoxic based on the developmental studies of flies raised in ferrofluid-infused media. STATEMENT OF SIGNIFICANCE: We demonstrate that a novel, hydrothermally synthesized composite nanoparticle-based ferrofluid is effective in reducing the viability of osteosarcoma and glioblastoma cells in vitro, while having minimal effects on primary cell lines. In 3D tumor spheroids, nanoparticles greatly reduced the metastatic migration of cancer cells, while the tumor viability was reduced compared to the control group by applying magnetic hyperthermia to nanoparticle-treated spheroids. Both in vitro and in vivo models of the blood-brain barrier evidence the ability of nanoparticles to cross the barrier and localize to the brain tissue. These composite nanoparticles show great promise as an anticancer biomaterial for the treatment of different types of cancer and may serve as an alternative or addendum to traditional chemotherapies.

Transferrin receptors-targeting nanocarriers for efficient targeted delivery and transcytosis of drugs into the brain tumors: a review of recent advancements and emerging trends

Treatment of glioblastoma multiforme (GBM) is a predominant challenge in chemotherapy due to the existence of blood-brain barrier (BBB) which restricts delivery of chemotherapeutic agents to the brain together with the problem of drug penetration through hard parenchyma of the GBM. With the structural and mechanistic elucidation of the BBB under both physiological and pathological conditions, it is now viable to target central nervous system (CNS) disorders utilizing the presence of transferrin (Tf) receptors (TfRs). However, overexpression of these TfRs on the GBM cell surface can also help to avoid restrictions of GBM cells to deliver chemotherapeutic agents within the tumor. Therefore, targeting of TfR-mediated delivery could counteract drug delivery issues in GBM and create a delivery system that could cross the BBB effectively to utilize ligand-conjugated drug complexes through receptor-mediated transcytosis. Hence, approach towards successful delivery of antitumor agents to the gliomas has been making possible through targeting these overexpressed TfRs within the CNS and glioma cells. This review article presents a thorough analysis of current understanding on Tf-conjugated nanocarriers as efficient drug delivery system.

Withaferin A Suppresses Beta Amyloid in APP Expressing Cells: Studies for Tat and Cocaine Associated Neurological Dysfunctions

Neurological disorders are the biggest concern globally. Out of ~36 million human immunodeficiency virus (HIV) positive people, about 30%-60% exhibit neurological disorders, including dementia and Alzheimer's disease (AD) like pathology. In AD or AD like neurological disorders, the pathogenesis is mainly due to the abnormal accumulation of extracellular amyloid beta (Aβ). In this era of antiretroviral therapy, the life span of the HIV-infected individuals has increased leading towards increased neurocognitive dysfunction in nearly 30% of HIV-infected individuals, specifically older people. Deposition of the Aβ plaques in the CNS is one the major phenomenon happening in aging HIV patients. ART suppresses the viral replication, but the neurotoxic protein (Tat) is still produced and results in increased levels of Aβ. Furthermore, drugs of abuse like cocaine (coc) is known to induce the HIV associated neurocognitive disorders as well as the Aβ secretion. To target the Tat and coc induced Aβ secretion, we propose a potent bifunctional molecule Withaferin A (WA) which may act as a neuro-protectant against Aβ neurotoxicity. In this study, we show that WA reduces secreted Aβ and induced neurotoxicity in amyloid precursor protein (APP)-plasmid transfected SH-SY5Y cells (SH-APP). In this study, we show that in SH-APP cells, Aβ secretion is induced in the presence of HIV-1 Tat (neurotoxic) and drug of abuse coc. Our fluorescent microscopy studies show the increased concentration of Aβ40 in Tat (50 ng/ml) and coc (0.1 μM) treated SH-APP cells as compared to control. Our dose optimization study show, lower concentrations (0.5-2 μM) of WA significantly reduce the Aβ40 levels, without inducing cytotoxicity in the SH-APP cells. Additionally, WA reduces the Tat and cocaine induced Aβ levels. Therefore, we propose that Aβ aggregation is induced by the presence of Tat and coc and WA is potent in reducing the secreted Aβ and induced neurotoxicity. Our study provides new opportunities for exploring the pathophysiology and targeting the neurological disorders.

Multifunctional Nanotherapeutics for the Treatment of neuroAIDS in Drug Abusers

HIV and substance abuse plays an important role in infection and disease progression. Further, the presence of persistent viral CNS reservoirs makes the complete eradication difficult. Thus, neutralizing the drug of abuse effect on HIV-1 infectivity and elimination of latently infected cells is a priority. The development of a multi-component [antiretroviral drugs (ARV), latency reactivating agents (LRA) and drug abuse antagonist (AT)] sustained release nanoformulation targeting the CNS can overcome the issues of HIV-1 cure and will help in improving the drug adherence. The novel magneto-liposomal nanoformulation (NF) was developed to load different types of drugs (LRAs, ARVs, and Meth AT) and evaluated for in-vitro and in-vivo BBB transmigration and antiviral efficacy in primary CNS cells. We established the HIV-1 latency model using human astrocyte cells (HA) and optimized the dose of LRA for latency reversal, Meth AT in in-vitro cell culture system. Further, PEGylated magneto-liposomal NF was developed, characterized for size, shape, drug loading and BBB transport in-vitro. Results showed that drug released in a sustained manner up to 10 days and able to reduce the HIV-1 infectivity up to ~40-50% (>200 pg/mL to <100 pg/mL) continuously using single NF treatment ± Meth treatment in-vitro. The magnetic treatment (0.8 T) was able to transport (15.8% ± 5.5%) NF effectively without inducing any toxic effects due to NF presence in the brain. Thus, our approach and result showed a way to eradicate HIV-1 reservoirs from the CNS and possibility to improve the therapeutic adherence to drugs in drug abusing (Meth) population. In conclusion, the developed NF can provide a better approach for the HIV-1 cure and a foundation for future HIV-1 purging strategies from the CNS using nanotechnology platform.

In vitro models of molecular and nano-particle transport across the blood-brain barrier

The blood-brain barrier (BBB) is the tightest endothelial barrier in humans. Characterized by the presence of tight endothelial junctions and adherens junctions, the primary function of the BBB is to maintain brain homeostasis through the control of solute transit across the barrier. The specific features of this barrier make for unique modes of transport of solutes, nanoparticles, and cells across the BBB. Understanding the different routes of traffic adopted by each of these is therefore critical in the development of targeted therapies. In an attempt to move towards controlled experimental assays, multiple groups are now opting for the use of microfluidic systems. A comprehensive understanding of bio-transport processes across the BBB in microfluidic devices is therefore necessary to develop targeted and efficient therapies for a host of diseases ranging from neurological disorders to the spread of metastases in the brain.

Near-infrared biophotonics-based nanodrug release systems and their potential application for neuro-disorders

INTRODUCTION

Near-infrared ray (NIR)-responsive 'smart' nanoagents allow spatial and temporal control over the drug delivery process, noninvasively, without affecting healthy tissues and therefore they possess high potential for on-demand, targeted drug/gene delivery. Various NIR-responsive drug/gene delivery techniques are under investigation for peripheral disorders (especially for cancer). Nonetheless, their potential not been extensively examined for brain biomedical application.

AREAS COVERED

This review focuses on NIR-responsive characteristics of different NIR-nanobiophotonics-based nanoagents and associated drug delivery strategies. Together with their ongoing applications for peripheral drug delivery, we have highlighted the opportunities, challenges and possible solutions of NIR-nanobiophotonics for potential brain drug delivery.

EXPERT OPINION

NIR-nanobiophotonics can be considered superior among all photo-controlled drug/gene delivery approaches. Future work should focus on coupling NIR with biocompatible nanocarriers to determine the physiological compatibility of this approach. Their applications should be extended beyond the peripheral body region to brain region. Transient or intermittent NIR exposure strategies may be more accommodating for brain physiological ambience in order to minimize or avoid the possible deleterious thermal effect. In addition, while most studies are centered around the first NIR spectral window (700-1000 nm), the potential of second (1100-1350 nm) and third (1600-1870 nm) windows must be explored.

Peptide Mediated Brain Delivery of Nano- and Submicroparticles: A Synergistic Approach

The brain is a complex, regulated organ with a highly controlled access mechanism: The Blood-Brain Barrier (BBB). The selectivity of this barrier is a double-edged sword, being both its greatest strength and weakness. This weakness is evident when trying to target therapeutics against diseases within the brain. Diseases such as metastatic brain cancer have extremely poor prognosis due to the poor permeability of many therapeutics across the BBB. Peptides can be designed to target BBB receptors and gain access to the brain by transcytosis. These peptides (known as BBB-shuttles) can carry compounds, usually excluded from the brain, across the BBB. BBB-shuttles are limited by poor loading of therapeutics and degradation of the peptide and cargo. Likewise, nano- submicro- and microparticles can be fine-tuned to limit their degradation and with high loading of therapeutics. However, most nano- and microparticles' core materials completely lack efficient targeting, with a few selected materials able to cross the BBB passively. Combining the selectivity of peptides with the high loading potential of nano-, microparticles offers an exciting strategy to develop novel, targeted therapeutics towards many brain disorders and diseases. Nevertheless, at present the field is diverse, in both scope and nomenclature, often with competing or contradictory names. In this review, we will try to address some of these issues and evaluate the current state of peptide mediated nano,-microparticle transport to the brain, analyzing delivery vehicle type and peptide design, the two key components that must act synergistically for optimal therapeutic impact.

Magnetic Nanoparticles in the Central Nervous System: Targeting Principles, Applications and Safety Issues

One of the most challenging goals in pharmacological research is overcoming the Blood Brain Barrier (BBB) to deliver drugs to the Central Nervous System (CNS). The use of physical means, such as steady and alternating magnetic fields to drive nanocarriers with proper magnetic characteristics may prove to be a useful strategy. The present review aims at providing an up-to-date picture of the applications of magnetic-driven nanotheranostics agents to the CNS. Although well consolidated on physical ground, some of the techniques described herein are still under investigation on in vitro or in silico models, while others have already entered in—or are close to—clinical validation. The review provides a concise overview of the physical principles underlying the behavior of magnetic nanoparticles (MNPs) interacting with an external magnetic field. Thereafter we describe the physiological pathways by which a substance can reach the brain from the bloodstream and then we focus on those MNP applications that aim at a nondestructive crossing of the BBB such as static magnetic fields to facilitate the passage of drugs and alternating magnetic fields to increment BBB permeability by magnetic heating. In conclusion, we briefly cite the most notable biomedical applications of MNPs and some relevant remarks about their safety and potential toxicity.

Hybrid magneto-plasmonic liposomes for multimodal image-guided and brain-targeted HIV treatment

Image-guided drug delivery is an emerging strategy in the field of nanomedicine. The addition of image guidance to a traditional drug delivery system is expected to achieve highly efficient treatment by tracking the drug carriers in the body and monitoring their effective accumulation in the targeted tissues. In this study, we developed multifunctional magneto-plasmonic liposomes (MPLs), a hybrid system combining liposomes and magneto-plasmonic nanoparticles for a triple-modality image-guided drug delivery. Tenofovir disoproxil fumarate, an antiretroviral drug used to treat human immunodeficiency virus type 1 (HIV-1), was encapsulated into the MPLs to enable the treatment in the brain microenvironment, which is inaccessible to most of the drugs. We found strong negative and positive contrasts originating from the magnetic core of MPLs in magnetic resonance imaging (MRI) and magnetic particle imaging (MPI), respectively. The gold shell of MPLs showed bright positive contrast in X-ray computed tomography (CT). MPLs achieved enhanced transmigration across an in vitro blood-brain barrier (BBB) model by magnetic targeting. Moreover, MPLs provided desired therapeutic effects against HIV infected microglia cells.

Crossing the blood-brain barrier with nanoparticles

The blood-brain barrier (BBB) is one of the most essential protection mechanisms in the central nervous system (CNS). It selectively allows individual molecules such as small lipid-soluble molecules to pass through the capillary endothelial membrane while limiting the passage of pathogens or toxins. However, this protection mechanism is also a major obstacle during disease state since it dramatically hinders the drug delivery. In recent years, various tactics have been applied to assist drugs to cross the BBB including osmotic disruption of the BBB and chemical modification of prodrugs. Additionally, nanoparticles (NPs)-mediated drug delivery is emerging as an effective and non-invasive system to treat cerebral diseases. In this review, we will summarize and analyze the advances in the drug delivery across the BBB using various NPs in the last decade. The NPs will cover both traditional and novel nanocarriers. The traditional nanocarriers consist of poly(butylcyanoacrylate), poly(lactic-co-glycolic acid), poly(lactic acid) NPs, liposomes and inorganic systems. In the meanwhile, novel nanocarriers such as carbon quantum dots with their recent applications in drug delivery will also be introduced. In terms of significance, this review clearly depicts the BBB structure and comprehensively describes various NPs-mediated drug delivery systems according to different NPs species. Also, the BBB penetration mechanisms are concluded in general, emphasized and investigated in each drug delivery system.

Nanocarriers for brain specific delivery of anti-retro viral drugs: challenges and achievements

HIV/AIDS is a global pandemic and the deleterious effects of human immunodeficiency virus in the brain cannot be overlooked. Though the current anti-retro viral therapy is able to reduce the virus load in the peripheral tissues of the body, the inability of the anti-retro viral drugs to cross the blood brain barrier, as such, limits its therapeutic effect in the brain. The development of newer, successful nanoparticulate drug delivery systems to enhance the feasibility of the anti-retro viral drugs to the brain, offers a novel strategy to treat the AIDS-related neuronal degradation. This review summarised the neuropathogenesis of neuroAIDS, the challenges and achievements made in the delivery of therapeutics across the BBB and the use of nanocarriers as a safe and effective way for delivering anti-retro viral drugs to the brain.

Novel nanoformulation to mitigate co-effects of drugs of abuse and HIV-1 infection: towards the treatment of NeuroAIDS

Drug abuse (e.g., methamphetamine-Meth or cocaine-Coc) is one of the major risk factors for becoming infected with HIV-1, and studies show that in combination, drug abuse and HIV-1 lead to significantly greater damage to CNS. To overcome these issues, we have developed a novel nanoformulation (NF) for drug-abusing population infected with HIV-1. In this work, a novel approach was developed for the co-encapsulation of Nelfinavir (Nel) and Rimcazole (Rico) using layer-by-layer (LbL) assembled magnetic nanoformulation for the cure of neuroAIDS. Developed NF was evaluated for blood-brain barrier (BBB) transmigration, cell uptake, cytotoxicity and efficacy (p24 assay) in HIV-1 infected primary astrocyte (HA) in presence or absence of Coc and Meth. Developed magnetic nanoformulation (NF) fabricated using the LbL approach exhibited higher amounts of drug loading (Nel and Rico) with 100% release of both the therapeutic agents in a sustained manner for 8 days. NF efficacy studies indicated a dose-dependent decrease in p24 levels in HIV-1-infected HA (~55%) compared to Coc + Meth treated (~50%). The results showed that Rico significantly subdued the effect of drugs of abuse on HIV infectivity. NF successfully transmigrated (38.8 ± 6.5%) across in vitro BBB model on the application of an external magnetic field and showed >90% of cell viability with efficient cell uptake. In conclusion, our proof of concept study revealed that sustained and concurrent release of sigma σ1 antagonist and anti-HIV drug from the developed novel sustained release NF can overcome the exacerbated effects of drugs of abuse in HIV infection and may solve the issue of medication adherence in the drug-abusing HIV-1 infected population.

A CRISPR/Cas9 guidance RNA screen platform for HIV provirus disruption and HIV/AIDS gene therapy in astrocytes

HIV/AIDS remains a major health threat despite significant advances in the prevention and treatment of HIV infection. The major reason is the inability of existing treatments to eradicate the multiple HIV reservoirs in the human body, including astrocytes in the human brain. CRISPR/Cas9 system is an emerging gene-editing technique with the potential to eliminate or disrupt HIV provirus in HIV reservoir cells, which may lead to a complete cure of HIV/AIDS. The key components of CRISPR/Cas9 are guide RNAs (gRNAs) which determine specific sequence targeting of DNAs. This study established a novel, simple and quick screening method to identify gRNA candidates for targeting HIV provirus in astrocytes. Briefly, stable astrocytes clones with an integrated fluorescent HIV reporter and Cas9 expression gene were generated. Various gRNAs were screened for their efficiencies against HIV provirus in these cells. Moreover, these gRNAs and Cas9 protein were successfully tested on HIV latent astrocytes without Cas9 expression to mimic clinical conditions. HIV provirus gene-editing were confirmed by cell genomic DNA PCR and fluorescent marker expression analysis. In the future, the established transgenic cells can be used for other gene-editing studies and is well-suited for high-throughput screen application.

Current application of CRISPR/Cas9 gene-editing technique to eradication of HIV/AIDS

Human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) remains a major health hazard despite significant advances in prevention and treatment of HIV infection. The major reason for the persistence of HIV/AIDS is the inability of existing treatments to clear or eradicate the multiple HIV reservoirs that exist in the human body. To suppress the virus replication and rebound, HIV/AIDS patients must take life-long antiviral medications. The clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9) system is an emerging gene-editing technique with the potential to eliminate or disrupt HIV-integrated genomes or HIV-infected cells from multiple HIV reservoirs, which could result in the complete cure of HIV/AIDS. Encouraging progress has already been reported for the application of the CRISPR/Cas9 technique to HIV/AIDS treatment and prevention, both in vitro in human patient cells and in vivo in animal model experiments. In this review, we will summarize the most recent progress in the application of the CRISPR/Cas9 gene-editing technique to HIV/AIDS therapy and elimination. Future directions and trends of such applications are also discussed.