Crossing the blood-brain barrier: Glutathione-conjugated poly(ethylene imine) for gene delivery

New Trends in Brain Shuttle Peptides

The pharmacological treatment of central nervous system diseases faces significant challenges due to the presence of the blood-brain barrier (BBB). This barrier naturally protects the brain and prevents therapeutics from reaching their targets efficiently. However, the BBB allows the passage of nutrients and other molecules that guarantee brain homeostasis through selective transport mechanisms present at the BBB. These mechanisms provide an opportunity for delivering therapeutic agents into the central nervous system using brain shuttles. Here we review the progress of brain shuttle peptide development from 2015 until 2025. We highlight the most utilized peptides and describe trends in strategies to develop new shuttles and enhance their transport efficiency. Additionally, we compared them with other types of brain shuttles and emphasize the progress of peptide shuttles toward clinical translation.

Unraveling brain diseases: The promise of brain-on-a-chip models

Brain disorders, encompassing a wide spectrum of neurological and psychiatric conditions, present a formidable challenge in modern medicine. Despite decades of research, the intricate complexity of the human brain still eludes comprehensive understanding, impeding the development of effective treatments. Recent advancements in microfluidics and tissue engineering have led to the development of innovative platforms known as "Brain-on-a-Chip" (BoC) i.e., advanced in vitro systems that aim to replicate the microenvironment of the brain with the highest possible fidelity. This technology offers a promising test-bed for studying brain disorders at the cellular and network levels, providing insights into disease mechanisms, drug screening, and, in perspective, the development of personalized therapeutic strategies. In this review, we provide an overview of the BoC models developed over the years to model and understand the onset and progression of some of the most severe neurological disorders in terms of incidence and debilitation (stroke, Parkinson's, Alzheimer's, and epilepsy). We also report some of the cutting-edge therapeutic approaches whose effects were evaluated by means of these technologies. Finally, we discuss potential challenges, and future perspectives of the BoC models.

Focused ultrasound-mediated cerium-based nanoreactor against Parkinson's disease via ROS regulation and microglia polarization

Neuronal damage caused by oxidative stress and inflammatory microenvironment dominated by microglia are the main obstacles in the treatment of Parkinson's disease (PD). In this study, we developed an integrated nanoreactor Q@CeBG by encapsulating CeO2 nanozyme and quercetin (Que) into glutathione-modified bovine serum albumin, and then selected focused ultrasound (FUS) to temporarily open the blood-brain barrier (BBB) to enhance the accumulation level of Q@CeBG in the brain. Q@CeBG exhibited superior multi-ROS scavenging activity. Under the assistance of FUS, Q@CeBG nanoreactor can penetrate the BBB and act on neurons as well as microglia, reducing the neuron's oxidative stress level and polarizing microglia's phenotype from proinflammatory M1 to anti-inflammatory M2. In vitro and In vivo experiments demonstrated that Q@CeBG nanoreactor with good biocompatibility exhibit outstanding neuroprotection and immunomodulatory effects. In short, this dual synergetic nanoreactor will become a reliable platform against PD.

How Precise are Nanomedicines in Overcoming the Blood-Brain Barrier? A Comprehensive Review of the Literature

New nanotechnology strategies for enhancing drug delivery in brain disorders have recently received increasing attention from drug designers. The treatment of neurological conditions, including brain tumors, stroke, Parkinson's Disease (PD), and Alzheimer's disease (AD), may be greatly influenced by nanotechnology. Numerous studies on neurodegeneration have demonstrated the effective application of nanomaterials in the treatment of brain illnesses. Nanocarriers (NCs) have made it easier to deliver drugs precisely to where they are needed. Thus, the most effective use of nanomaterials is in the treatment of various brain diseases, as this amplifies the overall impact of medication and emphasizes the significance of nanotherapeutics through gene therapy, enzyme replacement therapy, and blood-barrier mechanisms. Recent advances in nanotechnology have led to the development of multifunctional nanotherapeutic agents, a promising treatment for brain disorders. This novel method reduces the side effects and improves treatment outcomes. This review critically assesses efficient nano-based systems in light of obstacles and outstanding achievements. Nanocarriers that transfer medications across the blood-brain barrier and nano-assisted therapies, including nano-immunotherapy, nano-gene therapy, nano enzyme replacement therapy, scaffolds, and 3D to 6D printing, have been widely explored for the treatment of brain disorders. This study aimed to evaluate existing literature regarding the use of nanotechnology in the development of drug delivery systems that can penetrate the blood-brain barrier (BBB) and deliver therapeutic agents to treat various brain disorders.

Bringing pathology to nanomedicine: a comparison of in vivo toxicity of polymeric nanoparticle carriers with and without chitosan coating

Over the last years, there has been an increasing number of proposals for the use of nanomaterials in medicine. The safety of novel technologies must be verified, prior to their clinical application. Pathology has much to contribute towards this end. In this study, we compared the in vivo toxicity effects of poly- (lactic-co-glycolic acid) nanoparticles with and without chitosan shell. Both nanoparticle types were loaded with curcumin. The nanoparticles were assessed in vitro for potential cytotoxicity with cell viability studies. For the in vivo test, 36 adult Wistar rats were used, four of which were the control group. The remaining 32 were divided into 2 groups, each of which was administered differentially coated drug carriers: (A) nanoparticles without chitosan coating and (B) nanoparticles with chitosan coating. For both groups, the subcutaneous route was used for administration. Each group was further divided into 2 sub-groups of 8 animals each. The animals of the first sub-groups were sacrificed 24 h after the injection and those of the second on the 7th day. The control group was also divided into 2 subgroups of 2 animals each. At the appointed post-administrative date, the rats were sacrificed, and specimens from the brain, liver, kidneys, heart, stomach, lungs, and from the skin at the injection site were collected and studied histopathologically. The evaluation of both in vitro and in vivo testing shows that nanoparticles with chitosan have significantly less, if any, toxic effects compared to those without chitosan.

Emerging strategies to fabricate polymeric nanocarriers for enhanced drug delivery across blood-brain barrier: An overview

Blood-brain barrier (BBB) serves as an essential interface between central nervous system (CNS) and its periphery, allowing selective permeation of ions, gaseous molecules, and other nutrients to maintain metabolic functions of brain. Concurrently, it restricts passage of unsolicited materials from bloodstream to CNS which could otherwise lead to neurotoxicity. Nevertheless, in the treatment of neurodegenerative diseases such as Parkinson's, Alzheimer's, diffuse intrinsic pontine glioma, and other brain cancers, drugs must reach CNS. Among various materials developed for this purpose, a few judiciously selected polymeric nanocarriers are reported to be highly prospective to facilitate BBB permeation. However, the challenge of transporting drug-loaded nanomaterials across this barrier remains formidable. Herein a concise analysis of recently employed strategies for designing polymeric nanocarriers to deliver therapeutics across BBB is presented. Impacts of 3Ss, namely, size, shape, and surface charge of polymeric nanocarriers on BBB permeation along with different ligands used for nanoparticle surface modification to achieve targeted delivery have been scrutinized. Finally, we elucidated future research directions in the context of designing smart polymeric nanocarriers for BBB permeation. This work aims to guide researchers engaged in polymeric nanocarrier design, helping them navigate where to begin, what challenges to address, and how to proceed effectively.

Polymer-Based mRNA Delivery Strategies for Advanced Therapies

Messenger RNA (mRNA)-based therapies offer great promise for the treatment of a variety of diseases. In 2020, two FDA approvals of mRNA-based vaccines have elevated mRNA vaccines to global recognition. However, the therapeutic capabilities of mRNA extend far beyond vaccines against infectious diseases. They hold potential for cancer vaccines, protein replacement therapies, gene editing therapies, and immunotherapies. For realizing such advanced therapies, it is crucial to develop effective carrier systems. Recent advances in materials science have led to the development of promising nonviral mRNA delivery systems. In comparison to other carriers like lipid nanoparticles, polymer-based delivery systems often receive less attention, despite their unique ability to carefully tune their chemical features to promote mRNA protection, their favorable pharmacokinetics, and their potential for targeting delivery. In this review, the central features of polymer-based systems for mRNA delivery highlighting the molecular design criteria, stability, and biodistribution are discussed. Finally, the role of targeting ligands for the future of RNA therapies is analyzed.

Assessing the interactions between nanoparticles and biological barriers in vitro: a new challenge for microscopy techniques in nanomedicine

Nanoconstructs intended to be used as biomedical tool must be assessed for their capability to cross biological barriers. However, studying in vivo the permeability of biological barriers to nanoparticles is quite difficult due to the many structural and functional factors involved. Therefore, the in vitro modeling of biological barriers -2D cell monocultures, 2D/3D cell co-cultures, microfluidic devices- is gaining more and more relevance in nanomedical research. Microscopy techniques play a crucial role in these studies, as they allow both visualizing nanoparticles inside the biological barrier and evaluating their impact on the barrier components. This paper provides an overview of the various microscopical approaches used to investigate nanoparticle translocation through in vitro biological barrier models. The high number of scientific articles reported highlights the great contribution of the morphological and histochemical approach to the knowledge of the dynamic interactions between nanoconstructs and the living environment.

Peptides as Pharmacological Carriers to the Brain: Promises, Shortcomings and Challenges

Central nervous system (CNS) diseases are among the most difficult to treat, mainly because the vast majority of the drugs fail to cross the blood-brain barrier (BBB) or to reach the brain at concentrations adequate to exert a pharmacological activity. The obstacle posed by the BBB has led to the in-depth study of strategies allowing the brain delivery of CNS-active drugs. Among the most promising strategies is the use of peptides addressed to the BBB. Peptides are versatile molecules that can be used to decorate nanoparticles or can be conjugated to drugs, with either a stable link or as pro-drugs. They have been used to deliver to the brain both small molecules and proteins, with applications in diverse therapeutic areas such as brain cancers, neurodegenerative diseases and imaging. Peptides can be generally classified as receptor-targeted, recognizing membrane proteins expressed by the BBB microvessels (e.g., Angiopep2, CDX, and iRGD), "cell-penetrating peptides" (CPPs; e.g. TAT_47-57, SynB1/3, and Penetratin), undergoing transcytosis through unspecific mechanisms, or those exploiting a mixed approach. The advantages of peptides have been extensively pointed out, but so far few studies have focused on the potential negative aspects. Indeed, despite having a generally good safety profile, some peptide conjugates may display toxicological characteristics distinct from those of the peptide itself, causing for instance antigenicity, cardiovascular alterations or hemolysis. Other shortcomings are the often brief lifetime in vivo, caused by the presence of peptidases, the vulnerability to endosomal/lysosomal degradation, and the frequently still insufficient attainable increase of brain drug levels, which remain below the therapeutically useful concentrations. The aim of this review is to analyze not only the successful and promising aspects of the use of peptides in brain targeting but also the problems posed by this strategy for drug delivery.

In Vitro Models of Biological Barriers for Nanomedical Research

Nanoconstructs developed for biomedical purposes must overcome diverse biological barriers before reaching the target where playing their therapeutic or diagnostic function. In vivo models are very complex and unsuitable to distinguish the roles plaid by the multiple biological barriers on nanoparticle biodistribution and effect; in addition, they are costly, time-consuming and subject to strict ethical regulation. For these reasons, simplified in vitro models are preferred, at least for the earlier phases of the nanoconstruct development. Many in vitro models have therefore been set up. Each model has its own pros and cons: conventional 2D cell cultures are simple and cost-effective, but the information remains limited to single cells; cell monolayers allow the formation of cell–cell junctions and the assessment of nanoparticle translocation across structured barriers but they lack three-dimensionality; 3D cell culture systems are more appropriate to test in vitro nanoparticle biodistribution but they are static; finally, bioreactors and microfluidic devices can mimicking the physiological flow occurring in vivo thus providing in vitro biological barrier models suitable to reliably assess nanoparticles relocation. In this evolving context, the present review provides an overview of the most representative and performing in vitro models of biological barriers set up for nanomedical research.

New Drug Delivery Systems Developed for Brain Targeting

The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (B_CSF) are two of the most complex and sophisticated concierges that defend the central nervous system (CNS) by numerous mechanisms. While they maintain the neuro-ecological homeostasis through the regulated entry of essential biomolecules, their conservative nature challenges the entry of most of the drugs intended for CNS delivery. Targeted delivery challenges for a diverse spectrum of therapeutic agents/drugs (non-small molecules, small molecules, gene-based therapeutics, protein and peptides, antibodies) are diverse and demand specialized delivery and disease-targeting strategies. This review aims to capture the trends that have shaped the current brain targeting research scenario. This review discusses the physiological, neuropharmacological, and etiological factors that participate in the transportation of various drug delivery cargoes across the BBB/B_CSF and influence their therapeutic intracranial concentrations. Recent research works spanning various invasive, minimally invasive, and non-invasive brain- targeting approaches are discussed. While the pre-clinical outcomes from many of these approaches seem promising, further research is warranted to overcome the translational glitches that prevent their clinical use. Non-invasive approaches like intranasal administration, P-glycoprotein (P-gp) inhibition, pro-drugs, and carrier/targeted nanocarrier-aided delivery systems (alone or often in combination) hold positive clinical prospects for brain targeting if explored further in the right direction.

Polymeric Nanoparticles Properties and Brain Delivery

Safe and reliable entry to the brain is essential for successful diagnosis and treatment of diseases, but it still poses major challenges. As a result, many therapeutic approaches to treating disorders associated with the central nervous system (CNS) still only show limited success. Nano-sized systems are being explored as drug carriers and show great improvements in the delivery of many therapeutics. The systemic delivery of nanoparticles (NPs) or nanocarriers (NCs) to the brain involves reaching the neurovascular unit (NVU), being transported across the blood-brain barrier, (BBB) and accumulating in the brain. Each of these steps can benefit from specifically controlled properties of NPs. Here, we discuss how brain delivery by NPs can benefit from careful design of the NP properties. Properties such as size, charge, shape, and ligand functionalization are commonly addressed in the literature; however, properties such as ligand density, linker length, avidity, protein corona, and stiffness are insufficiently discussed. This is unfortunate since they present great value against multiple barriers encountered by the NPs before reaching the brain, particularly the BBB. We further highlight important examples utilizing targeting ligands and how functionalization parameters, e.g., ligand density and ligand properties, can affect the success of the nano-based delivery system.

Potential of Nanocarrier-Based Drug Delivery Systems for Brain Targeting: A Current Review of Literature

The advent of nanotechnologies such as nanocarriers and nanotherapeutics has changed the treatment strategy and developed a more efficacious novel drug delivery system. Various drug delivery systems are focused on drug-targeting of brain cells. However, the manifestation of the brain barrier is the main hurdle for the effective delivery of chemotherapeutics, ultimately causing treatment failure of various drugs. To solve this problem, various nanocarrier-based drug delivery system has been developed for brain targeting. This review outlines nanocarrier-based composites for different brain diseases and highlights nanocarriers for drug targeting towards brain cells. It also summarizes the latest developments in nanocarrier-based delivery systems containing liposomal systems, dendrimers, polymeric micelles, polymeric nanocarriers, quantum dots (QDs), and gold nanoparticles. Besides, the optimal properties of nanocarriers and therapeutic implications for brain targeting have been extensively studied. Finally, the potential applications and research opportunities for nanocarriers in brain targeting are discussed.

Nanoparticles for Targeted Brain Drug Delivery: What Do We Know?

The blood-brain barrier (BBB) is a barrier that separates the blood from the brain tissue and possesses unique characteristics that make the delivery of drugs to the brain a great challenge. To achieve this purpose, it is necessary to design strategies to allow BBB passage, in order to reach the brain and target the desired anatomic region. The use of nanomedicine has great potential to overcome this problem, since one can modify nanoparticles with strategic molecules that can interact with the BBB and induce uptake through the brain endothelial cells and consequently reach the brain tissue. This review addresses the potential of nanomedicines to treat neurological diseases by using nanoparticles specially developed to cross the BBB.

In vitro infection models to study fungal-host interactions

Fungal infections (mycoses) affect over a billion people per year. Approximately, two million of these infections are life-threatening, especially for patients with a compromised immune system. Fungi of the genera Aspergillus, Candida, Histoplasma and Cryptococcus are opportunistic pathogens that contribute to a substantial number of mycoses. To optimize the diagnosis and treatment of mycoses, we need to understand the complex fungal-host interplay during pathogenesis, the fungal attributes causing virulence and how the host resists infection via immunological defenses. In vitro models can be used to mimic fungal infections of various tissues and organs and the corresponding immune responses at near-physiological conditions. Furthermore, models can include fungal interactions with the host-microbiota to mimic the in vivo situation on skin and mucosal surfaces. This article reviews currently used in vitro models of fungal infections ranging from cell monolayers to microfluidic 3D organ-on-chip (OOC) platforms. We also discuss how OOC models can expand the toolbox for investigating interactions of fungi and their human hosts in the future.

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.

Integrating Emerging Polymer Chemistries for the Advancement of Recyclable, Biodegradable, and Biocompatible Electronics

Through advances in molecular design, understanding of processing parameters, and development of non-traditional device fabrication techniques, the field of wearable and implantable skin-inspired devices is rapidly growing interest in the consumer market. Like previous technological advances, economic growth and efficiency is anticipated, as these devices will enable an augmented level of interaction between humans and the environment. However, the parallel growing electronic waste that is yet to be addressed has already left an adverse impact on the environment and human health. Looking forward, it is imperative to develop both human- and environmentally-friendly electronics, which are contingent on emerging recyclable, biodegradable, and biocompatible polymer technologies. This review provides definitions for recyclable, biodegradable, and biocompatible polymers based on reported literature, an overview of the analytical techniques used to characterize mechanical and chemical property changes, and standard policies for real-life applications. Then, various strategies in designing the next-generation of polymers to be recyclable, biodegradable, or biocompatible with enhanced functionalities relative to traditional or commercial polymers are discussed. Finally, electronics that exhibit an element of recyclability, biodegradability, or biocompatibility with new molecular design are highlighted with the anticipation of integrating emerging polymer chemistries into future electronic devices.

Targeted Drug Delivery: Trends and Perspectives

BACKGROUND

Due to various limitations in conventional drug delivery system, it is important to focus on the target-specific drug delivery system where we can deliver the drug without any degradation. Among various challenges faced by a formulation scientist, delivering the drug to its right site, in its right dose, is also an important aim. A focused drug transport aims to extend, localize, target and have a safe drug interaction with the diseased tissue.

OBJECTIVE

The aim of targeted drug delivery is to make the required amount of the drug available at its desired site of action. Drug targeting can be accomplished in a number ways that include enzyme mediation, pH-dependent release, use of special vehicles, receptor targeting among other mechanisms. Intelligently designed targeted drug delivery systems also offer the advantages of a low dose of the drug along with reduced side effects which ultimately improves patient compliance. Incidences of dose dumping and dosage form failure are negligible. A focused drug transport aims to have a safe drug interaction with the diseased tissue.

CONCLUSION

This review focuses on the available targeting techniques for delivery to the colon, brain and other sites of interest. Overall, the article should make an excellent read for the researchers in this area. Newer drug targets may be identified and exploited for successful drug targeting.

Development of Polymeric Nanoparticles for Blood-Brain Barrier Transfer-Strategies and Challenges

Neurological disorders such as Alzheimer's disease, stroke, and brain cancers are difficult to treat with current drugs as their delivery efficacy to the brain is severely hampered by the presence of the blood-brain barrier (BBB). Drug delivery systems have been extensively explored in recent decades aiming to circumvent this barrier. In particular, polymeric nanoparticles have shown enormous potentials owing to their unique properties, such as high tunability, ease of synthesis, and control over drug release profile. However, careful analysis of their performance in effective drug transport across the BBB should be performed using clinically relevant testing models. In this review, polymeric nanoparticle systems for drug delivery to the central nervous system are discussed with an emphasis on the effects of particle size, shape, and surface modifications on BBB penetration. Moreover, the authors critically analyze the current in vitro and in vivo models used to evaluate BBB penetration efficacy, including the latest developments in the BBB-on-a-chip models. Finally, the challenges and future perspectives for the development of polymeric nanoparticles to combat neurological disorders are discussed.

2-(2-Cholesteroxyethoxyl)ethyl 3'-S-glutathionylpropionate and its self-assembled micelles for brain delivery: Design, synthesis and evaluation

The blood-brain barrier (BBB) is a barrier that prevents almost all large and most small exogenous molecules from reaching the brain. The barrier is the major cause of treatment failure for most brain diseases. Extensive efforts have been made to facilitate drug molecules to cross the BBB. One of the approaches is to employ an endogenous ligand or ligand analogue that can enter the brain through its transporter or receptor at the BBB as a brain-targeting agent. Glutathione (GSH) transporters are richly expressed at the BBB with limited presence in other tissues except kidneys. 2-(2-Cholesteroxyethoxyl)ethyl 3'-S-glutathionylpropionate (COXP), formed by connecting GSH with cholesterol through a linker, was designed as a GSH transporter-mediated brain targeting molecule. The amphiphilic nature of COXP enables the molecule to self-assemble to form micelles with a CMC value of 3.9 μM. By using DiR as a fluorescence tracking agent and the whole-body fluorescence imaging technique, the brain distribution of DiR delivered by COXP micelles in mice was 20 folds higher when compared with free DiR. Interestingly, the brain targeting effect was further enhanced by co-administration of GSH. The low CMC value and effective brain targeting make COXP micelles a promising drug delivery system to the brain.

Recent Strategies for Targeted Brain Drug Delivery

Because the brain is the most important human organ, many brain disorders can cause severe symptoms. For example, glioma, one type of brain tumor, is progressive and lethal, while neurodegenerative diseases cause severe disability. Nevertheless, medical treatment for brain diseases remains unsatisfactory, and therefore innovative therapies are desired. However, the development of therapies to treat some cerebral diseases is difficult because the blood-brain barrier (BBB) or blood-brain tumor barrier prevents drugs from entering the brain. Hence, drug delivery system (DDS) strategies are required to deliver therapeutic agents to the brain. Recently, brain-targeted DDS have been developed, which increases the quality of therapy for cerebral disorders. This review gives an overview of recent brain-targeting DDS strategies. First, it describes strategies to cross the BBB. This includes BBB-crossing ligand modification or temporal BBB permeabilization. Strategies to avoid the BBB using local administration are also summarized. Intrabrain drug distribution is a crucial factor that directly determines the therapeutic effect, and thus it is important to evaluate drug distribution using optimal methods. We introduce some methods for evaluating drug distribution in the brain. Finally, applications of brain-targeted DDS for the treatment of brain tumors, Alzheimer's disease, Parkinson's disease, and stroke are explained.

Potential applications of microfluidics based blood brain barrier (BBB)-on-chips for in vitro drug development

The human blood-brain barrier (BBB) is a complex multi-dimensional reticular barrier system composed of cerebral microvascular endothelial cells, pericytes, astrocytes and a variety of neurons. The conventional in vitro cell culture model fails to truly present the dynamic hemodynamics of BBB and the interaction between neurons. And it is even more impossible to explore brain-related multi-organ diseases, which brings huge obstacles to explore diseases of the central nervous system and the interaction between brain-related multi-organs, and evaluate drug efficacy. Miniaturized microfluidics based BBB chips are being commonly used to co-culture a variety of cells on a small-sized chip to construct a three-dimensional (3D) BBB or BBB-related organ disease models. By combining with other electrophysiological, biochemical sensors or equipment and imaging systems, it can in real time and quickly screen disease-related markers and evaluate drug efficacy. This review systematically summarized the research progress of in vitro BBB and BBB-related organ chips, and analyzed the obstacles of BBB models in depth. Parallelly combined with the current research trends and hot spots, we give the further improvement measures of microfluidic BBB chips.

Ferulic Acid Ameliorates MPP+/MPTP-Induced Oxidative Stress via ERK1/2-Dependent Nrf2 Activation: Translational Implications for Parkinson Disease Treatment

Parkinson's disease (PD) is a neurodegenerative disorder closely associated with oxidative stress. The biochemical and cellular alterations that occur after cell and mouse treatment with the parkinsonism-inducing neurotoxin MPP⁺/MPTP are remarkably similar to those observed in idiopathic PD. Previously, we showed that ferulic acid (FA) has antioxidant properties and the ability to activate nuclear factor E2-related factor 2 (Nrf2). The present study tested the hypothesis that FA attenuates MPP⁺/MPTP-induced oxidative stress by regulating crosstalk between sirtuin 2 (SIRT2) and Nrf2 pathways. To test this hypothesis, we performed in vitro and in vivo studies using MPP⁺/MPTP-challenged SH-SY5Y cells or mice treated with or not with FA. FA marginally inhibited SIRT2 in parallel with α-synuclein at levels of transcription and translation in SH-SY5Y cells challenged with MPP⁺. Moreover, FA attenuated MPP⁺-induced oxidative stress, as indicated by reactive oxygen species, lipid hydroperoxides, GSH/GSSG ratio, and NAD⁺/NADH ratio. Mechanistically, FA strongly upregulated the glutamate cysteine ligase catalytic subunit and heme oxygenase-1 expression at the levels of transcription and translation. Interestingly, FA-mediated extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation contributed to nuclear accumulation of Nrf2 via de novo synthesis, which was validated by the use of dominant negative ERK2. Surprisingly, activation of the ERK1/2 and inhibition of SIRT2 by FA are mediated by independent mechanisms. Furthermore, FA ameliorated motor deficits and oxidative stress in the ventral midbrain in MPTP-treated (25 mg/kg, i.p., daily for 5 days) wild-type mice and α-synuclein knockout mice, but not in Nrf2 knockout mice. Collectively, FA exerts antioxidant effects through ERK1/2-mediated activation of the Nrf2 pathway, and these results may have important translational value for the treatment of PD.

Ligand Conjugated Targeted Nanotherapeutics for Treatment of Neurological Disorders

BACKGROUND

Human brain is amongst the most complex organs in human body, and delivery of therapeutic agents across the brain is a tedious task. Existence of blood brain barrier (BBB) protects the brain from invasion of undesirable substances; therefore it hinders the transport of various drugs used for the treatment of different neurological diseases including glioma, Parkinson's disease, Alzheimer's disease, etc. To surmount this barrier, various approaches have been used such as the use of carrier mediated drug delivery; use of intranasal route, to avoid first pass metabolism; and use of ligands (lactoferrin, apolipoprotein) to transport the drug across the BBB. Ligands bind with proteins present on the cell and facilitate the transport of drug across the cell membrane via. receptor mediated, transporter mediated or adsorptive mediated transcytosis.

OBJECTIVE

The main focus of this review article is to illustrate various studies performed using ligands for delivering drug across BBB; it also describes the procedure used by various researchers for conjugating the ligands to the formulation to achieve targeted action.

METHODS

Research articles that focused on the used of ligand conjugation for brain delivery and compared the outcome with unconjugated formulation were collected from various search engines like PubMed, Science Direct and Google Scholar, using keywords like ligands, neurological disorders, conjugation, etc. Results and Conclusion: Ligands have shown great potential in delivering drug across BBB for treatment of various diseases, yet extensive research is required so that the ligands can be used clinically for treating neurological diseases.

Blood-Brain Delivery Methods Using Nanotechnology

Pathologies of the brain, of which brain cancer, Alzheimer's disease, Parkinson's disease, stroke, and multiple sclerosis, are some of the most prevalent, and that presently are poorly treated due to the difficulties associated with drug development, administration, and targeting to the brain. The existence of the blood-brain barrier, a selective permeability system which acts as a local gateway against circulating foreign substances, represents the key challenge for the delivery of therapeutic agents to the brain. However, the development of nanotechnology-based approaches for brain delivery, such as nanoparticles, liposomes, dendrimers, micelles, and carbon nanotubes, might be the solution for improved brain therapies.

Would antioxidant-loaded nanoparticles present an effective treatment for ischemic stroke?

Ischemic stroke is a leading cause of death and disability worldwide and is in urgent need of new treatment options. The only approved treatment for stroke restores blood flow to the brain, but much of the tissue damage occurs during the subsequent reperfusion. Antioxidant therapies that directly address ischemia-reperfusion injury have shown promise in preclinical results. In this review, we discuss that reformulating antioxidant therapies as nanomedicine can potentially overcome the barriers that have kept these therapies from succeeding in the clinic. We begin by reviewing the pathophysiology of ischemic stroke with a focus on the effects of reperfusion injury. Next, we review nanotherapeutic systems designed to treat the disease with a focus on those addressing reperfusion injury. Mechanisms of passive and active transport required to traverse a blood–brain barrier are discussed. Finally, we conclude by outlining design parameters for potentially successful nanomedicines as front-line therapeutics for ischemic stroke.

The Power of Shielding: Low Toxicity and High Transfection Performance of Cationic Graft Copolymers Containing Poly(2-oxazoline) Side Chains

We show the potential of oligo(2-ethyl-2-oxazoline) (Ox_n)-shielded graft copolymers of (2-aminoethyl)-methacrylate and N-methyl-(2-aminoethyl)-methacrylate for pDNA delivery in HEK cells. For the effect of grafting density and side chain length concerning improved transfection properties through the concept of shielding to be investigated, copolymers were synthesized via the macromonomer method using a combination of cationic ring opening polymerization and reversible addition-fragmentation chain transfer polymerization to vary the degree of grafting (DG = 10 and 30%) as well as the side chain degree of polymerization (DP = 5 and 20). Investigations of the polyplex formation, in vitro flow cytometry, and confocal laser scanning microscopy measurements on the copolymer library revealed classical shielding properties of the Ox side chains, including highly reduced cytotoxicity and a partial decrease in transfection efficiency, as also reported for polyethylene glycol shielding. In terms of the transfection efficiency, the best performing copolymers (A- g-Ox₅(10) and M- g-Ox₅(10)) revealed equal or better performances compared to those of the corresponding homopolymers. In particular, the graft copolymers with low DG and side chain DP transfected well with over 10-fold higher IC₅₀ values. In contrast, a DG of 30% resulted in a loss of transfection efficiency due to missing ability for endosomal release, and a side chain DP of 20 hampered the cellular uptake.

Glutathione: Antioxidant Properties Dedicated to Nanotechnologies

Which scientist has never heard of glutathione (GSH)? This well-known low-molecular-weight tripeptide is perhaps the most famous natural antioxidant. However, the interest in GSH should not be restricted to its redox properties. This multidisciplinary review aims to bring out some lesser-known aspects of GSH, for example, as an emerging tool in nanotechnologies to achieve targeted drug delivery. After recalling the biochemistry of GSH, including its metabolism pathways and redox properties, its involvement in cellular redox homeostasis and signaling is described. Analytical methods for the dosage and localization of GSH or glutathiolated proteins are also covered. Finally, the various therapeutic strategies to replenish GSH stocks are discussed, in parallel with its use as an addressing molecule in drug delivery.

Gastrodin and Isorhynchophylline Synergistically Inhibit MPP+-Induced Oxidative Stress in SH-SY5Y Cells by Targeting ERK1/2 and GSK-3β Pathways: Involvement of Nrf2 Nuclear Translocation

The pathogenesis of Parkinson's disease (PD) is multifactorial event. Combination therapies might be more effective in controlling the disease. Thus, the studies reported were designed to test the hypothesis that gastrodin (GAS)-induced de novo synthesis of nuclear factor E2-related factor 2 (Nrf2) and isorhynchophylline (IRN) inhibition of Nrf2 nuclear export contribute to their additive or synergistic neuroprotective effect. Here, we have demonstrated that the combination of GAS and IRN (GAS/IRN) protects SH-SY5Y cells against 1-methyl-4-phenylpyridinium (MPP⁺) toxicity in a synergistic manner. Concomitantly, GAS/IRN led to a statistically significant reduction of oxidative stress, as assessed by reactive oxygen species (ROS) and lipid hydroperoxides (LPO), and enhancement of both glutathione (GSH) and thioredoxin (Trx) systems compared with treatment with either agent alone in MPP⁺-challenged SH-SY5Y cells. Interestingly, GAS but not IRN activated extracellular signal-regulated kinases 1 and 2 (ERK1/2), leading to a increase in de novo synthesis of Nrf2 and nuclear import of Nrf2. Simultaneously, IRN but not GAS suppressed both constitutive glycogen synthase kinase (GSK)-3β and Fyn activation, which inhibited nuclear export of Nrf2. Importantly, simultaneous inhibition of GSK-3β pathway by IRN and activation of ERK1/2 pathway by GAS synergistically induced accumulation of Nrf2 in the nucleus in SH-SY5Y cells challenged with MPP⁺. Furthermore, the activation of the ERK1/2 pathway and inhibition of GSK-3β pathway by GAS/IRN are mediated by independent mechanisms. Collectively, these novel findings suggest an in vitro model of synergism between IRN and GAS in the induction of neuroprotection warrant further investigations in vivo.

Full and partial hydrolysis of poly(2-oxazoline)s and the subsequent post-polymerization modification of the resulting polyethylenimine (co)polymers

This review discusses the full and partial hydrolysis of poly(2-oxazoline)s as well as the synthetic methods that have been reported to modify the resulting secondary amine groups.

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.

Drug Delivery to the Brain across the Blood-Brain Barrier Using Nanomaterials

A major obstacle facing brain diseases such as Alzheimer's disease, multiple sclerosis, brain tumors, and strokes is the blood-brain barrier (BBB). The BBB prevents the passage of certain molecules and pathogens from the circulatory system into the brain. Therefore, it is nearly impossible for therapeutic drugs to target the diseased cells without the assistance of carriers. Nanotechnology is an area of growing public interest; nanocarriers, such as polymer-based, lipid-based, and inorganic-based nanoparticles can be engineered in different sizes, shapes, and surface charges, and they can be modified with functional groups to enhance their penetration and targeting capabilities. Hence, understanding the interaction between nanomaterials and the BBB is crucial. In this Review, the components and properties of the BBB are revisited and the types of nanocarriers that are most commonly used for brain drug delivery are discussed. The properties of the nanocarriers and the factors that affect drug delivery across the BBB are elaborated upon in this review. Additionally, the most recent developments of nanoformulations and nonconventional drug delivery strategies are highlighted. Finally, challenges and considerations for the development of brain targeting nanomedicines are discussed. The overall objective is to broaden the understanding of the design and to develop nanomedicines for the treatment of brain diseases.

Delivery of siRNA silencing P-gp in peptide-functionalized nanoparticles causes efflux modulation at the blood–brain barrier

Aim: Explore the use of transferrin-receptor peptide-functionalized nanoparticles (NPs) targeting blood–brain barrier (BBB) as siRNA carriers to silence P-glycoprotein (P-gp). Materials & methods: Permeability experiments were assessed through a developed BBB cell-based model; P-gp mRNA expression was evaluated in vitro; rhodamine 123 permeability was assessed after cell monolayer treatment with siRNA NPs. Results: Beyond their ability to improve siRNA permeability through the BBB by twofold, 96-h post-transfection, functionalized polymeric NPs successfully reduced P-gp mRNA expression up to 52%, compared with nonfunctionalized systems. Subsequently, the permeability of rhodamine 123 through the human BBB model increased up to 27%. Conclusion: Developed BBB-targeted NPs induced P-gp downregulation and consequent increase on P-gp substrate permeability, revealing their ability to modulate drug efflux at the BBB.

d-Fructose-Decorated Poly(ethylene imine) for Human Breast Cancer Cell Targeting

The high affinity of GLUT5 transporter for d-fructose in breast cancer cells has been discussed intensely. In this contribution, high molar mass linear poly(ethylene imine) (LPEI) is functionalized with d-fructose moieties to combine the selectivity for the GLUT5 transporter with the delivery potential of PEI for genetic material. The four-step synthesis of a thiol-group bearing d-fructose enables the decoration of a cationic polymer backbone with d-fructose via thiol-ene photoaddition. The functionalization of LPEI is confirmed by 2D NMR techniques, elemental analysis, and size exclusion chromatography. Importantly, a d-fructose decoration of 16% renders the polymers water-soluble and eliminates the cytotoxicity of PEI in noncancer L929 cells, accompanied by a reduced unspecific cellular uptake of the genetic material. In contrast, the cytotoxicity as well as the cell specific uptake is increased for triple negative MDA-MB-231 breast cancer cells. Therefore, the introduction of d-fructose shows superior potential for cell targeting, which can be assumed to be GLUT5 dependent.