Brain targeting of nerve growth factor using poly(butyl cyanoacrylate) nanoparticles

Nanoneuromedicines for degenerative, inflammatory, and infectious nervous system diseases

Interest in nanoneuromedicine has grown rapidly due to the immediate need for improved biomarkers and therapies for psychiatric, developmental, traumatic, inflammatory, infectious and degenerative nervous system disorders. These, in whole or in part, are a significant societal burden due to growth in numbers of affected people and in disease severity. Lost productivity of the patient and his or her caregiver, and the emotional and financial burden cannot be overstated. The need for improved health care, treatment and diagnostics is immediate. A means to such an end is nanotechnology. Indeed, recent developments of health-care enabling nanotechnologies and nanomedicines range from biomarker discovery including neuroimaging to therapeutic applications for degenerative, inflammatory and infectious disorders of the nervous system. This review focuses on the current and future potential of the field to positively affect clinical outcomes. From the clinical editor: Many nervous system disorders remain unresolved clinical problems. In many cases, drug agents simply cannot cross the blood-brain barrier (BBB) into the nervous system. The advent of nanomedicines can enhance the delivery of biologically active molecules for targeted therapy and imaging. This review focused on the use of nanotechnology for degenerative, inflammatory, and infectious diseases in the nervous system.

Nanotoxicity of poly(n-butylcyano-acrylate) nanoparticles at the blood-brain barrier, in human whole blood and in vivo

Therapy of diseases of the central nervous system is a major challenge since drugs have to overcome the blood-brain barrier (BBB). A powerful strategy to enhance cerebral drug concentration is administration of drug-loaded poly(n-butylcyano-acrylate) (PBCA) nanoparticles coated with polysorbate 80 (PS80). This study evaluates the toxicity of PBCA-nanoparticles at the BBB, representing the target organ, the inflammatory response in human whole blood, as the site of administration and in a rat model in vivo. PBCA-nanoparticles were prepared by a mini-emulsion method and characterized concerning size, surface charge, shape and PS80-adsorption. The influence on metabolic activity, cell viability and integrity of the BBB was analyzed in an in vitro model of the BBB. In ex vivo experiments in human whole blood the release of 12 inflammatory cytokines was investigated. In addition, the inflammatory response was studied in vivo in rats and complemented with the analysis of different organ toxicity parameters. PBCA-nanoparticles showed time- and concentration-dependent effects on metabolic activity, cell viability and BBB integrity. No cell death or loss of metabolic activity was observed for nanoparticle-concentrations ≤500μg/ml up to 3h of treatment. Within 12 tested inflammatory cytokines, only interleukin-8 displayed a significant release after nanoparticle exposure in human blood. No severe inflammatory processes or organ damages were identified in rats in vivo. Thus, PBCA-nanoparticles are a promising drug delivery system to overcome the BBB since they showed hardly any cytotoxic or inflammatory effect at therapeutic concentrations and incubation times.

Protective effects of poly (butyl) cyanoacrylate nanoparticles containing vasoactive intestinal peptide against 6-hydroxydopamine-induced neurotoxicity in vitro

The present study investigated brain delivery system of vasoactive intestinal peptide (VIP) adsorbed on poly (butyl cyanoacrylate) nanoparticles coated with polysorbate 80 (P80-poly (butyl) cyanoacrylate (PBCA)-nanoparticles (NPs)) and the neuroprotective effects on the formulation in the model of 6-hydroxydopamine (6-OHDA)-induced Parkinsonian dysfunction in the human neuroblastoma cell line SH-SY5Y. Drug-loaded nanoparticles were prepared by emulsion polymerization method using VIP and PBCA and then stirring with polysorbate 80. The resulting nanoparticles possessed high entrapment efficiency and favorable stability against CaCl2 or fetal bovine serum (FBS)-induced aggregation. Use of fluorescein isothiocyanate (FITC)-conjugated polysorbate 80-PBCA nanoparticles in confocal microscopy revealed that nanoparticles are located inside, while the FITC solution could not penetrate into the cells. The blank nanoparticles showed no significant effects on cell viability, indicating that they had no role in protection; however, polysorbate 80-modified VIP-loading PBCA nanoparticles showed enhanced cell viability compared to free VIP in 6-OHDA-mimic cellular model of Parkinson's disease. In addition, the nanoparticles strikingly increased the anti-apoptosis activity and restored the loss of mitochondrial membrane potential (MMP) significantly after the treatment of 6-OHDA. These results demonstrated that the activity of VIP was enhanced by polysorbate 80-PBCA nanoparticles compared to control solutions, suggesting that PBCA nanoparticles coated with polysorbate 80 could be an effective carrier system for VIP.

Agile delivery of protein therapeutics to CNS

A variety of therapeutic proteins have shown potential to treat central nervous system (CNS) disorders. Challenge to deliver these protein molecules to the brain is well known. Proteins administered through parenteral routes are often excluded from the brain because of their poor bioavailability and the existence of the blood-brain barrier (BBB). Barriers also exist to proteins administered through non-parenteral routes that bypass the BBB. Several strategies have shown promise in delivering proteins to the brain. This review, first, describes the physiology and pathology of the BBB that underscore the rationale and needs of each strategy to be applied. Second, major classes of protein therapeutics along with some key factors that affect their delivery outcomes are presented. Third, different routes of protein administration (parenteral, central intracerebroventricular and intraparenchymal, intranasal and intrathecal) are discussed along with key barriers to CNS delivery associated with each route. Finally, current delivery strategies involving chemical modification of proteins and use of particle-based carriers are overviewed using examples from literature and our own work. Whereas most of these studies are in the early stage, some provide proof of mechanism of increased protein delivery to the brain in relevant models of CNS diseases, while in few cases proof of concept had been attained in clinical studies. This review will be useful to broad audience of students, academicians and industry professionals who consider critical issues of protein delivery to the brain and aim developing and studying effective brain delivery systems for protein therapeutics.

Drug delivery to the central nervous system by polymeric nanoparticles: what do we know?

Nanoparticles enable the delivery of a great variety of drugs including anticancer drugs, analgesics, anti-Alzheimer's drugs, cardiovascular drugs, protease inhibitors, and several macromolecules into the brain after intravenous injection of animals. The mechanism of the nanoparticle-mediated drug transport across the BBB appears to be receptor-mediated endocytosis followed by transcytosis into the brain or by drug release within the endothelial cells. Modification of the nanoparticle surface with covalently attached targeting ligands or by coating with certain surfactants that lead to the adsorption of specific plasma proteins after injection is necessary for this receptor-mediated uptake. A very critical and important requirement for nanoparticulate brain delivery is that the employed nanoparticles are biocompatible and, moreover, rapidly biodegradable, i.e. over a time frame of a few days. In addition to enabling drug delivery to the brain, nanoparticles, as with doxorubicin, may importantly reduce the drug's toxicity and adverse effects due to an alteration of the body distribution. Because of the possibility to treat severe CNS diseases such as brain tumours and to even transport proteins and other macromolecules across the blood-brain barrier, this technology holds great promise for a non-invasive therapy of these diseases.

Precision nanomedicine in neurodegenerative diseases

The treatment of neurodegenerative diseases remains a tremendous challenge due to the limited access of molecules across the blood-brain barrier, especially large molecules such as peptides and proteins. As a result, at most, a small percentage of a drug that is administered systemically will reach the central nervous system in its active form. Currently, research in the field focuses on developing safer and more effective approaches to deliver peptides and proteins into the central nervous system. Multiple strategies have been developed for this purpose. However, noninvasive approaches, such as nanostructured protein delivery carriers and intranasal administration, seem to be the most promising strategies for the treatment of chronic diseases, which require long-term interventions. These approaches are both target-specific and able to rapidly bypass the blood-brain barrier. In this Perspective, we detail some of these strategies and discuss some of the potential pitfalls and opportunities in this field. The next generation strategies will most likely be more cell-type-specific. Devising these strategies to target the brain may ultimately become a novel therapeutic modality to treat neurodegenerative diseases.

Transport of glial cell line-derived neurotrophic factor into liposomes across the blood-brain barrier: in vitro and in vivo studies

Glial cell line-derived neurotrophic factor (GDNF) was encapsulated into liposomes in order to protect it from enzyme degradation in vivo and promote its permeability across the blood-brain barrier (BBB). In this study, GDNF conventional liposomes (GDNF-L) and GDNF target sterically stabilized liposomes (GDNF-SSL-T) were prepared. The average size of liposomes was below 90 nm. A primary model of BBB was established and evaluated by transendothelial electrical resistance (TEER) and permeability. This BBB model was employed to study the permeability of GDNF liposomes in vitro. The results indicated that the liposomes could enhance transport of GDNF across the BBB and GDNF-SSL-T had achieved the best transport efficacy. The distribution of GDNF liposomes was studied in vivo. Free GDNF and GDNF-L were eliminated rapidly in the circulation. GDNF-SSL-T has a prolonged circulation time in the blood and favorable brain delivery. The values of the area under the curve (AUC_{(0–1 h)}) in the brain of GDNF-SSL-T was 8.1 times and 6.8 times more than that of free GDNF and GDNF-L, respectively. These results showed that GDNF-SSL-T realized the aim of targeted delivery of therapeutic proteins to central nervous system.

Nanoscale drug delivery systems and the blood-brain barrier

The protective properties of the blood–brain barrier (BBB) are conferred by the intricate architecture of its endothelium coupled with multiple specific transport systems expressed on the surface of endothelial cells (ECs) in the brain’s vasculature. When the stringent control of the BBB is disrupted, such as following EC damage, substances that are safe for peripheral tissues but toxic to neurons have easier access to the central nervous system (CNS). As a consequence, CNS disorders, including degenerative diseases, can occur independently of an individual’s age. Although the BBB is crucial in regulating the biochemical environment that is essential for maintaining neuronal integrity, it limits drug delivery to the CNS. This makes it difficult to deliver beneficial drugs across the BBB while preventing the passage of potential neurotoxins. Available options include transport of drugs across the ECs through traversing occludins and claudins in the tight junctions or by attaching drugs to one of the existing transport systems. Either way, access must specifically allow only the passage of a particular drug. In general, the BBB allows small molecules to enter the CNS; however, most drugs with the potential to treat neurological disorders other than infections have large structures. Several mechanisms, such as modifications of the built-in pumping-out system of drugs and utilization of nanocarriers and liposomes, are among the drug-delivery systems that have been tested; however, each has its limitations and constraints. This review comprehensively discusses the functional morphology of the BBB and the challenges that must be overcome by drug-delivery systems and elaborates on the potential targets, mechanisms, and formulations to improve drug delivery to the CNS.

Intranasal therapeutic strategies for management of Alzheimer's disease

Alzheimer's disease (AD) is a chronic and progressive age-related irreversible neurodegenerative disorder that represents 70% of all dementia with 35 million cases worldwide. Successful treatment strategies for AD have so far been limited, and present therapy is based on cholinergic replacement therapy and inhibiting glutamate excitotoxicity. In this context, role of neuroprotective drugs has generated considerable interest in management of AD. Recently, direct intranasal (IN) delivery of drug moieties to the central nervous system (CNS) has emerged as a therapeutically viable alternative to oral and parenteral routes. IN delivery bypasses the blood-brain barrier by delivering and targeting drugs to the CNS along the olfactory and trigeminal neural pathways which are in direct contact with both the environment and the CNS. In an attempt to understand how neurotherapeutics/nanoparticulate delivery systems can be transported from the nose to the CNS, the present review sets out to discuss the mechanism of transport from nose to brain. The aim of this review is to discuss and summarize the latest findings of some of the major studies on IN drug delivery in AD models, with a focus on the potential efficacy of neuroprotective treatments.

NANOMATERIALS FOR PROTEIN MEDIATED THERAPY AND DELIVERY

There has been a significant amount of research done on liposomes and nanoparticles as drug carriers for protein drugs. Proteins and enzymes have been used both as targeting moieties and for their therapeutic potential. High specificity and rapid reaction rates make proteins and enzymes excellent candidates for therapeutic treatment, but some limitations exist. Many of these limitations can be addressed by a well studied nanotechnology based delivery system. Such a system can provide a medium for delivery, stabilization of the drugs, and enable site specific accumulation of drugs. Nanomedicines such as these have great potential to revolutionize the pharmaceutical industry and improve healthcare worldwide.

Nanomedicine in cerebral palsy

Cerebral palsy is a chronic childhood disorder that can have diverse etiologies. Injury to the developing brain that occurs either in utero or soon after birth can result in the motor, sensory, and cognitive deficits seen in cerebral palsy. Although the etiologies for cerebral palsy are variable, neuroinflammation plays a key role in the pathophysiology of the brain injury irrespective of the etiology. Currently, there is no effective cure for cerebral palsy. Nanomedicine offers a new frontier in the development of therapies for prevention and treatment of brain injury resulting in cerebral palsy. Nanomaterials such as dendrimers provide opportunities for the targeted delivery of multiple drugs that can mitigate several pathways involved in injury and can be delivered specifically to the cells that are responsible for neuroinflammation and injury. These materials also offer the opportunity to deliver agents that would promote repair and regeneration in the brain, resulting not only in attenuation of injury, but also enabling normal growth. In this review, the current advances in nanotechnology for treatment of brain injury are discussed with specific relevance to cerebral palsy. Future directions that would facilitate clinical translation in neonates and children are also addressed.

Neurotrophin delivery using nanotechnology

Deficits or overexpression of neurotrophins cause neurodegenerative diseases and psychiatric disorders. These proteins are required for the maintenance of the function, plasticity and survival of neurons in the central (CNS) and peripheral nervous systems. Significant efforts have been devoted to developing therapeutic delivery systems that enable control of neurotrophin dosage in the brain. Here, we suggest that nanoparticulate carriers favoring targeted delivery in specific brain areas and minimizing biodistribution to the systemic circulation should be developed toward clinical benefits of neuroregeneration. We also provide examples of improved targeted neurotrophin delivery to localized areas in the CNS.

Drug development in Parkinson's disease: from emerging molecules to innovative drug delivery systems

Current treatments for Parkinson's disease (PD) are aimed at addressing motor symptoms but there is no therapy focused on modifying the course of the disease. Successful treatment strategies have been so far limited and brain drug delivery remains a major challenge that restricts its treatment. This review provides an overview of the most promising emerging agents in the field of PD drug discovery, discussing improvements that have been made in brain drug delivery for PD. It will be shown that new approaches able to extend the length of the treatment, to release the drug in a continuous manner or to cross the blood-brain barrier and target a specific region are still needed. Overall, the results reviewed here show that there is an urgent need to develop both symptomatic and disease-modifying treatments, giving priority to neuroprotective treatments. Promising perspectives are being provided in this field by rasagiline and by neurotrophic factors like glial cell line-derived neurotrophic factor. The identification of disease-relevant genes has also encouraged the search for disease-modifying therapies that function by identifying molecularly targeted drugs. The advent of new molecular and cellular targets like α-synuclein, leucine-rich repeat serine/threonine protein kinase 2 or parkin, among others, will require innovative delivery therapies. In this regard, drug delivery systems (DDS) have shown great potential for improving the efficacy of conventional and new PD therapy and reducing its side effects. The new DDS discussed here, which include microparticles, nanoparticles and hydrogels among others, will probably open up possibilities that extend beyond symptomatic relief. However, further work needs to be done before DDS become a therapeutic option for PD patients.

Spinal cord injury: a review of current therapy, future treatments, and basic science frontiers

The incidence of acute and chronic spinal cord injury (SCI) in the United States is more than 10,000 per year, resulting in 720 cases per million persons enduring permanent disability each year. The economic impact of SCI is estimated to be more than 4 billion dollars annually. Preclinical studies, case reports, and small clinical trials suggest that early treatment may improve neurological recovery. To date, no proven therapeutic modality exists that has demonstrated a positive effect on neurological outcome. Emerging data from recent preclinical and clinical studies offer hope for this devastating condition. This review gives an overview of current basic research and clinical studies for the treatment of SCI.

The generation of NGF-secreting primary rat monocytes: a comparison of different transfer methods

Nerve growth factor (NGF), a member of the neurotrophin family, is responsible for the maintenance and survival of cholinergic neurons in the basal forebrain. The degeneration of cholinergic neurons and reduced acetycholine levels are hallmarks of Alzheimer's disease (AD) as well as associated with learning and memory deficits. Thus far, NGF has proven the most potent neuroprotective molecule against cholinergic neurodegeneration. However, delivery of this factor into the brain remains difficult. Recent studies have begun to elucidate the potential use of monocytes as vehicles for therapeutic delivery into the brain. In this study, we employed different transfection and transduction methods to generate NGF-secreting primary rat monocytes. Specifically, we compared five methods for generating NGF-secreting monocytes: (1) cationic lipid-mediated transfection (Effectene and FuGene), (2) classical electroporation, (3) nucleofection, (4) protein delivery (Bioporter) and (5) lentiviral vectors. Here, we report that classical transfection methods (lipid-mediated transfection, electroporation, nucleofection) are inefficient tools for proper gene transfer into primary rat monocytes. We demonstrate that lentiviral infection and Bioporter can successfully transduce/load primary rat monocytes and produce effective NGF secretion. Furthermore, our results indicate that NGF is bioactive and that Bioporter-loaded monocytes do not appear to exhibit any functional disruptions (i.e. in their ability to differentiate and phagocytose beta-amyloid). Taken together, our results show that primary monocytes can be effectively loaded or transduced with NGF and provides information on the most effective method for generating NGF-secreting primary rat monocytes. This study also provides a basis for further development of primary monocytes as therapeutic delivery vehicles to the diseased AD brain.

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Monocytes can be easily transduced using Bioporter protein reagent

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Bioporter-loaded monocytes exhibit no functional disruptions

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Lentiviral vectors are by far the most potent tool for monocyte transduction

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Classical transfection methods are not sufficient for primary monocyte gene transfer

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NGF-secreting monocytes may serve as potential therapeutic vehicles in Alzheimer`s disease

From molecular to nanotechnology strategies for delivery of neurotrophins: emphasis on brain-derived neurotrophic factor (BDNF)

Neurodegenerative diseases represent a major public health problem, but beneficial clinical treatment with neurotrophic factors has not been established yet. The therapeutic use of neurotrophins has been restrained by their instability and rapid degradation in biological medium. A variety of strategies has been proposed for the administration of these leading therapeutic candidates, which are essential for the development, survival and function of human neurons. In this review, we describe the existing approaches for delivery of brain-derived neurotrophic factor (BDNF), which is the most abundant neurotrophin in the mammalian central nervous system (CNS). Biomimetic peptides of BDNF have emerged as a promising therapy against neurodegenerative disorders. Polymer-based carriers have provided sustained neurotrophin delivery, whereas lipid-based particles have contributed also to potentiation of the BDNF action. Nanotechnology offers new possibilities for the design of vehicles for neuroprotection and neuroregeneration. Recent developments in nanoscale carriers for encapsulation and transport of BDNF are highlighted.

New and emerging treatments for Alzheimer's disease

Alzheimer's disease (AD) and other dementias represent a significant and increasing clinical challenge. This review highlights current treatment options for AD and the main focusses of therapies currently being evaluated in clinical trials and for future therapeutic development. Existing treatments slow the progression of symptoms of the disease, but their efficacy does not extend to all people with AD, and benefits are not conveyed beyond an average of 6 months. Despite the substantial economic cost and healthcare burden of AD, which is increasing as populations age, there are currently only three therapies being investigated in Phase III clinical trials. This emphasises the substantial caution and underinvestment in treatment development in this area and why it is critical to address the current lack of effective treatments to target the underlying pathology and disease process in Alzheimer's disease.

Development of new peptide vectors for the transport of therapeutic across the blood-brain barrier

The blood-brain barrier (BBB) is formed by the special nature of the endothelial cells of the brain capillaries characterized by tight junctions between cells and a high expression of efflux pumps only allowing the brain access to nutrients necessary for cell survival and function. These properties of the BBB result in the incapacity of small and large therapeutic compounds to reach the brain at therapeutic concentrations. Various strategies are now being developed to enhance the amount and concentration of these compounds in the brain parenchyma. The development of new technologies such as peptide vectors has the potential to achieve the delivery of active agents in therapeutic concentrations across the BBB to treat brain diseases such as brain primary and metastatic cancers and neurodegenerative disorders. In this review, the design of new active peptides and development of new peptide vectors for drug brain delivery using physiological approaches will be addressed. A new chemical entity incorporating angiopep peptide in a small anticancer agent (paclitaxel) is now in clinical trials. It is the first of such designed agents to be validated for the treatment of human brain cancers and opens the door for such approaches.

Polymeric nanocarriers for controlled and enhanced delivery of therapeutic agents to the CNS

Polymeric nanocarriers are versatile structures that can be engineered to obtain high drug loading, good delivery yields and tunable release kinetics. Moreover, the particle surface can be modified for selective targeting of organs or tissues. In particular, polymeric nanocarriers can be conjugated with functional groups promoting translocation through the blood–brain barrier, thus providing a promising system to deliver therapeutic agents and/or diagnostic probes to the brain. Here we review recent literature on the preparation and characterization of polymeric nanoparticles as potential agents for drug delivery to the CNS, with an emphasis on materials chemistry and functionalization strategies for improved selectivity and delivery. Finally, we underline the immunotoxicological aspects of this class of nanostructured materials in view of potential clinical applications.

Mechanism of polymeric nanoparticle-based drug transport across the blood-brain barrier (BBB)

In 1995 it was reported for the first time that nanoparticles could be used for the delivery of drugs across the blood-brain barrier (BBB) following intravenous injection. In vitro and in vivo experiments show that the underlying mechanism is receptor-mediated endocytosis followed by transcytosis. No opening of the tight junctions was observed. Due to the overcoating of the nanoparticles with polysorbate 80 or poloxamers 188, apolipoproteins A-I and/or E are adsorbed from the blood on to the particle surface after injection. These apolipoproteins mediate the interaction with LDL or scavenger receptors on the BBB followed by the above brain uptake processes. Likewise, covalent attachment of these apolipoproteins or of transferrin, insulin or antibodies against the respective receptors also enables a similar nanoparticle-mediated drug transport across the BBB. From these results it can be concluded that the nanoparticles act as "Trojan Horses" taking advantage of physiological receptor-mediated transport processes across the BBB.

Therapeutics, imaging and toxicity of nanomaterials in the central nervous system

Treatment and diagnosis of neurodegenerative diseases and other CNS disorders are nowadays considered some of the most challenging tasks in modern medicine. The development of effective strategies for the prevention, diagnosis and treatment of CNS pathologies require better understanding of neurological disorders that is still lacking. The use of nanomaterials is thought to contribute to our further understanding of the CNS and the development of novel therapeutic and diagnostic modalities for neurological interventions. Even though the application of nanoparticles in neuroscience is still embryonic, this article attempts to illustrate the use of different types of nanomaterials and the way in which they have been used in various CNS applications in an attempt to limit or reverse neuropathological processes.

Neurotrophic factors and neurodegenerative diseases: a delivery issue

Neurotrophic factors (NTFs) represent one of the most stimulating challenge in neurodegenerative diseases, due to their potential in neurorestoring and neuroprotection. Despite the large number of proofs-of-concept and evidences of their activity, most of the clinical trials, mainly regarding Parkinson's disease and Alzheimer's disease, demonstrated several failures of the therapeutic intervention. A large number of researches were conducted on this hot topic of neuroscience, clearly evidencing the advantages of NTF approach, but evidencing the major limitations in its application. The inability in crossing the blood-brain barrier and the lack of selectivity actually represent some of the most highlighted limits of NTFs-based therapy. In this review, beside an overview of NTF activity versus the main neuropathological disorders, a summary of the most relevant approaches, from invasive to noninvasive strategies, applied for improving NTF delivery to the central nervous systems is critically considered and evaluated.

Evaluation of uptake and transport of ultrasmall superparamagnetic iron oxide nanoparticles by human brain-derived endothelial cells

Aim: Ultrasmall superparamagnetic iron oxide nanoparticles (USPIO-NPs) are under development for imaging and drug delivery; however, their interaction with human blood–brain barrier models is not known. Materials & Methods: The uptake, reactive oxygen species production and transport of USPIO-NPs across human brain-derived endothelial cells as models of the blood–brain tumor barrier were evaluated for either uncoated, oleic acid-coated or polyvinylamine-coated USPIO-NPs. Results: Reactive oxygen species production was observed for oleic acid-coated and polyvinylamine-coated USPIO-NPs. The uptake and intracellular localization of the iron oxide core of the USPIO-NPs was confirmed by transmission electron microscopy. However, while the uptake of these USPIO-NPs by cells was observed, they were neither released by nor transported across these cells even in the presence of an external dynamic magnetic field. Conclusion: USPIO-NP-loaded filopodia were observed to invade the polyester membrane, suggesting that they can be transported by migrating angiogenic brain-derived endothelial cells.

Nanoparticulate systems as drug carriers: the need

Development of nanoparticles for drug delivery has progressed by leaps and bounds over the last few decades, facilitating the possibility of an efficacious therapy for some fatal diseases. This development has stemmed from either the unsuitable physicochemical characteristics of the existing drug molecules, such as limited solubility and hence poor bioavailability, or the inadequacy of the conventional delivery systems to provide safe and efficient delivery. This chapter focuses on the precise need for the development of these novel nanoparticulate drug carriers and reasons for their popularity with the drug delivery scientists. The text also discusses the various strategies, including different formulation and targeting approaches, which have been adopted to overcome the challenges presented by the inherent properties of the drug molecules. Examples of nanoparticulate drug delivery systems which have already gained market approval have been cited in the discussion, wherever applicable.

Nanocomposites for Neurodegenerative Diseases: Hydrogel-Nanoparticle Combinations for a Challenging Drug Delivery

Neurodegenerative disorders are expected to strike social and health care systems of developed countries heavily in the coming decades. Alzheimer's and Parkinson's diseases (AD/PD) are the most prevalent neurodegenerative pathologies, and currently their available therapy is only symptomatic. However, innovative potential drugs are actively under development, though their efficacy is sometimes limited by poor brain bioavailability and/or sustained peripheral degradation. To partly overcome these constraints, the development of drug delivery devices made by biocompatible and easily administrable materials might be a great adjuvant. In particular, materials science can provide a powerful tool to design hydrogels and nanoparticles as basic components of more complex nanocomposites that might ameliorate drug or cell delivery in AD/PD. This kind of approach is particularly promising for intranasal delivery, which might increase brain targeting of neuroprotective molecules or proteins. Here we review these issues, with a focus on nanoparticles as nanocomponents able to carry and tune drug release in the central nervous system, without ignoring warnings concerning their potential toxicity.

Phase I study of the safety, tolerability and pharmacokinetics of PHA-848125AC, a dual tropomyosin receptor kinase A and cyclin-dependent kinase inhibitor, in patients with advanced solid malignancies

PURPOSE

This phase I trial assessed the safety, maximally tolerated dose (MTD) and pharmacokinetics of TRKA/CDK inhibitor PHA-848125AC in adult patients with advanced/metastatic solid tumors.

PATIENTS AND METHODS

Patients with relapsed or refractory solid tumors, for which no standard therapy existed, were eligible. PHA-848125AC was administered orally in two schedules: daily for 7 consecutive days in 2-week cycles (i.e. 7 days on/7 days off q2wks; S1) or daily for 4 consecutive days a week for 3 weeks in 4-week cycles (i.e. 4 days on/3 days off x 3wks q4wks; S2).

RESULTS

Thirty-seven patients were treated in this study, 22 in S1 and 15 in S2. The recommended phase II dose (RP2D) was 150 mg/day for either schedule. The dose-limiting toxicities (DLTs) in S1 included ataxia (Grade 2-4) and tremors (Grade 2-3). In S2, DLTs included tremors (Grade 2-3), elevated lipase (Grade 3), increased creatinine (Grade 2), and nausea and vomiting (Grade 3). These events were all reversible. In S2, out of 14 patients evaluable for efficacy, 2 patients with thymic carcinoma, showed partial response and stable disease was observed in 3 patients. Stable disease was observed in 6 out 14 patients evaluable for efficacy on S1. Drug pharmacokinetics demonstrated a half-life of approximately 33 h, and dose-proportionality with accumulation by a factor of 3 after repeated administrations.

CONCLUSION

The RP2D of PHA-848125AC was 150 mg/day on both schedules. Based on the responses noted in thymic carcinoma, a phase II study for patients with that disease is currently enrolling.

Nanostructure-based drug delivery systems for brain targeting

CONTEXT

It is well-known fact that blood brain barrier (BBB) hinders the penetrance and access of many pharmacotherapeutic agents to central nervous system (CNS). Many diseases of the CNS remain undertreated and the inability to treat most CNS disorders is not due to the lack of effective CNS drug discovery, rather, it is due to the ineffective CNS delivery. Therefore, a number of nanostructured drug delivery carriers have been developed and explored over the past couple of years to transport the drugs to brain.

OBJECTIVE

The present review will give comprehensive details of extensive research being done in field of nanostructured carriers to transport the drugs through the BBB in a safe and effective manner.

METHODS

The method includes both the polymeric- and lipid-based nanocarriers with emphasis on their utility, methodology, advantages, and the drugs which have been worked on using a particular approach to provide a noninvasive method to improve the drug transport through BBB.

RESULTS

Polymeric- and lipid-based nanocarriers enter brain capillaries before reaching the surface of the brain microvascular endothelial cells without the disruption of BBB. These systems are further modified with specific ligands vectors and pegylation aiming to target and enhance their binding with surface receptors of the specific tissues inside brain and increase long circulatory time which favors interaction and penetration into brain endothelial cells.

CONCLUSION

This review would give an insight to the researchers working on neurodegenerative and non-neurodegenerative diseases of the CNS including brain tumor.

Transport of drugs across the blood-brain barrier by nanoparticles

The central nervous system is well protected by the blood-brain barrier (BBB) which maintains its homeostasis. Due to this barrier many potential drugs for the treatment of diseases of the central nervous system (CNS) cannot reach the brain in sufficient concentrations. One possibility to deliver drugs to the CNS is the employment of polymeric nanoparticles. The ability of these carriers to overcome the BBB and to produce biologic effects on the CNS was shown in a number of studies. Over the past few years, progress in understanding of the mechanism of the nanoparticle uptake into the brain was made. This mechanism appears to be receptor-mediated endocytosis in brain capillary endothelial cells. Modification of the nanoparticle surface with covalently attached targeting ligands or by coating with certain surfactants enabling the adsorption of specific plasma proteins are necessary for this receptor-mediated uptake. The delivery of drugs, which usually are not able to cross the BBB, into the brain was confirmed by the biodistribution studies and pharmacological assays in rodents. Furthermore, the presence of nanoparticles in the brain parenchyma was visualized by electron microscopy. The intravenously administered biodegradable polymeric nanoparticles loaded with doxorubicin were successfully used for the treatment of experimental glioblastoma. These data, together with the possibility to employ nanoparticles for delivery of proteins and other macromolecules across the BBB, suggest that this technology holds great promise for non-invasive therapy of the CNS diseases.

Proteins conjugated to poly(butyl cyanoacrylate) nanoparticles as potential neuroprotective agents

Poly(butyl cyanoacrylate) (PBCA) nanoparticles (NPs) can penetrate blood-brain barrier providing the means for drug delivery to the central nervous system. Here, we study attachment of superoxide dismutase (SOD) and anti-glutamate N-methyl D-aspartate receptor 1 (NR1) antibody to PBCA NPs with the ultimate goal to design neuroprotective therapeutics for treatment of secondary spinal cord injury. Synthesis of monodispersed, ∼200 nm-diameter PBCA NPs was performed using polymerization at pH 2.0 with Dextran 70,000 as the stabilizer. Sulfo-HSAB spacers were used to covalently attach SOD and NR1 antibodies to the dextran-coated NPs. The prepared protein-NP conjugates possessed SOD activity and were capable of binding to rat cerebellar neurons. Thus, SOD and NR1 antibodies may be simultaneously attached to PBCA NPs while retaining at least a fraction of enzymatic activity and receptor-binding ability. The conjugates showed neuroprotective efficacy in vitro with rat cerebellar cell cultures challenged by superoxide.

Formulation development and systematic optimization of solid lipid nanoparticles of quercetin for improved brain delivery

Objective

This study aims at formulating solid lipid nanoparticles (SLNs) of quercetin, a natural flavonoid with established antioxidant activity, for intravenous administration in order to improve its permeation across the blood–brain barrier into the CNS, and eventually to improve the therapeutic efficacy of this molecule in Alzheimer's disease.

Methods

The SLNs of quercetin were formulated using Compritol as the lipid and Tween 80 as the surfactant through a microemulsification technique, and optimized employing a 32 central composite design (CCD). Selection of the optimized SLN formulation, using brute-force methodology and overlay plots, was based on its efficiency of entrapping quercetin inside the lipophilic core, particle size, surface charge potential and ability of the SLNs to release the entrapped drug completely. The optimized formulation was subjected to various in-vivo behavioral and biochemical studies in Wistar rats.

Key findings

The optimized formulation exhibited a particle size of less than 200 nm, 85.73% drug entrapment efficiency and a zeta potential of 21.05 mV. In all the in-vivo behavioral and biochemical experiments, the rats treated with SLN-encapsulated quercetin showed markedly better memory-retention vis-à-vis test and pure quercetin-treated rats.

Conclusions

The studies demonstrated successful targeting of the potent natural antioxidant, quercetin, to brain as a novel strategy having significant therapeutic potential to treat Alzheimer's disease.

Drug delivery to the CNS and polymeric nanoparticulate carriers

The delivery of drugs to the CNS is hampered by the existence of the blood–brain barrier (BBB). Nowadays, medicinal chemists follow defined rules for the development of drugs able to cross the BBB. At the same time, the parameters needed in order to gain valuable estimates of brain drug delivery are well defined. Despite the limits in molecular weight that allow drugs to cross the BBB, it was shown that nanotech products, in particular properly functionalized nanoparticles, spherical particles of approximately 200 nm in diameter, are able to cross the BBB after intravenous administration and act as drug carriers for CNS. Moreover, peptides as ligands for receptors present on the brain endothelium, or able to cross the BBB and to act as carriers for CNS drug delivery in the form of conjugates with drugs, have been discovered and started to be studied as targeting moieties for nanoparticulate systems. This article will discuss the results obtained so far in the field of nanoparticle drug carriers for CNS and highlight the parameters needed in order to fully characterize these hitherto largely unknown delivery systems. Even if promising results have been obtained, more studies are needed in order to fully evaluate the clinical potential of this drug-delivery system.

In vivo methods to study uptake of nanoparticles into the brain

Several in vivo techniques have been developed to study and measure the uptake of CNS compounds into the brain. With these techniques, various parameters can be determined after drug administration, including the blood-to-brain influx constant (K_in), the permeability-surface area (PS) product, and the brain uptake index (BUI). These techniques have been mostly used for drugs that are expected to enter the brain via transmembrane diffusion or by carrier-mediated transcytosis. Drugs that have limitations in entering the brain via such pathways have been encapsulated in nanoparticles (based on lipids or synthetic polymers) to enhance brain uptake. Nanoparticles are different from CNS compounds in size, composition and uptake mechanisms. This has led to different methods and approaches to study brain uptake in vivo. Here we discuss the techniques generally used to measure nanoparticle uptake in addition to the techniques used for CNS compounds. Techniques include visualization methods, behavioral tests, and quantitative methods.

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

Nanoparticles made of human serum albumin (HSA) and modified with apolipoproteins have previously been shown to transport drugs, which normally do not enter the brain, across the blood-brain barrier (BBB). However the precise mechanism by which nanoparticles with different apolipoproteins on their surface can target to the brain, as yet, has not been totally elucidated. In the present study, HSA nanoparticles with covalently bound apolipoprotein A-I (Apo A-I) as a targetor for brain capillary endothelial cells were injected intravenously into SV 129 mice and Wistar rats. The rodents were sacrificed after 15 or 30 min, and their brains were examined by transmission electron microscopy. Apo A-I nanoparticles could be found inside the endothelial cells of brain capillaries as well as within parenchymal brain tissue of both, mice and rats, whereas control particles without Apo A-I on their surface did not cross the BBB during our experiments. The maintenance of tight junction integrity and barrier function during treatment with nanoparticles was demonstrated by perfusion with a fixative containing lanthanum nitrate as an electron dense marker for the permeability of tight junctions.

Nanoparticle-mediated brain-specific drug delivery, imaging, and diagnosis

Central nervous system (CNS) diseases represent the largest and fastest-growing area of unmet medical need. Nanotechnology plays a unique instrumental role in the revolutionary development of brain-specific drug delivery, imaging, and diagnosis. With the aid of nanoparticles of high specificity and multifunctionality, such as dendrimers and quantum dots, therapeutics, imaging agents, and diagnostic molecules can be delivered to the brain across the blood-brain barrier (BBB), enabling considerable progress in the understanding, diagnosis, and treatment of CNS diseases. Nanoparticles used in the CNS for drug delivery, imaging, and diagnosis are reviewed, as well as their administration routes, toxicity, and routes to cross the BBB. Future directions and major challenges are outlined.

Conference Scene: Nanoneuroprotection and nanoneurotoxicity: recent progress and future perspectives

Recent developments in research related to nanoparticles in neuroscience necessitated the establishment of a new discipline known as ‘nanoneuroscience’. In order to understand the possible role of nanoparticles in the development of neurotoxicity or their potential use in neuroprotection, nine top experts across the world in this newly developing discipline were invited to present their cutting edge research in the 7th annual meeting of the Global College of Neuroprotection & Neuroregeneration in Stockholm, Sweden. The new developments suggest that more research is needed to understand the potential use of nanoparticles in nanomedicine. Highlights of these presentations are summarized in this article.

Nanoparticle-based vaginal drug delivery systems for HIV prevention

IMPORTANCE OF THE FIELD

Several strategies are being investigated for the prevention of heterosexual transmission of HIV. Of these, topical vaginal drug delivery systems, microbicides, are being actively pursued. HIV prevention by means of a topical microbicide has several drug delivery challenges. These challenges include the vaginal mucosal barriers and potential degradation of the drugs in the vaginal lumen due to pH and enzymes present. Also, new drugs being evaluated as microbicides have specific mechanisms of action, which in some cases require drug targeting to a specific site of action. Nanoparticles provide a delivery strategy for targeted or controlled delivery to the vagina which can be applied in the field of HIV prevention.

AREAS COVERED IN THE REVIEW

This review summarizes nanoparticulate systems and their use in mucosal delivery to date. The sexual transmission of HIV along with the various targets to prevent transmission are discussed as well as the potential opportunities, challenges and advantages in using a nanoparticle-based approach for microbicidal drug delivery.

WHAT THE READER WILL GAIN

This review provides a general understanding of vaginal drug delivery, its challenges, and nanoparticulate delivery systems. Additionally, insight will be gained as to the limited existing application of this technology to the field of HIV prevention.

TAKE HOME MESSAGE

To date, few studies have been published that exploit nanoparticle-based microbicidal delivery to the vagina. The use of nanoparticles for vaginal drug delivery provides an approach to overcome the existing barriers to success.