Various drug delivery approaches to the central nervous system

A review: oligodendrocytes in neuronal axonal conduction and methods for enhancing their performance

OBJECTIVES

This review explores the vital role of oligodendrocytes in axon myelination and efficient neuronal transmission and the impact of dysfunction resulting from neurotransmitter deficiencies related disorders. Furthermore, the review also provides insight into the potential of bionanotechnology for addressing neurodegenerative diseases by targeting oligodendrocytes.

METHODS

A review of literature in the field was conducted using Google scholar. Systematic searches were performed to identify relevant studies and reviews addressing the role of oligodendrocytes in neural function, the influence of neurotransmitters on oligodendrocyte differentiation, and the potential of nanotechnology-based strategies for targeted therapy of oligodendrocytes.

RESULTS

This review indicates the mechanisms underlying oligodendrocyte differentiation and the influence of neurotransmitters on this process. The importance of action potentials and neurotransmission in neural function and the susceptibility of damaged nerve axons to ischemic or toxic damage is provided in detail. The potential of bionanotechnology for targeting neurodegenerative diseases using nanotechnology-based strategies, including polymeric, lipid-based, inorganic, organic, and biomimetic nanoparticles, suggests better management of neurodegenerative disorders.

CONCLUSION

While nanotechnology-based biomaterials show promise for targeted oligodendrocyte therapy in addressing neurodegenerative disorders linked to oligodendrocyte dysfunction, encapsulating neuroprotective agents within nanoparticles offers additional advantages. Nano-based delivery systems effectively protect drugs from degradation and prolong their therapeutic effects, holding promise in overcoming the blood-brain barrier by facilitating drug transport. However, a multifaceted approach is essential to enhance oligodendrocyte differentiation, promote myelin repair, and facilitate myelin dynamics with reduced toxicity. Further research is needed to elucidate the optimal therapeutic approaches and enhance patient outcomes.

Development and in vivo Evaluation of Hydroxy-α-Sanshool Intranasal Liposomes as a Potential Remedial Treatment for Alzheimer’s Disease

Purpose

Hydroxy-α-sanshool (HAS) improves cognitive dysfunction, but its structural instability has limited its clinical application. The present study was conducted to investigate the optimal formulation of hydroxy-α-sanshool liposomes (HAS-LPs) and its effect on ameliorating learning and memory disorders in an Alzheimer’s disease (AD) model.

Methods

In this study, HAS was prepared as HAS-LP using a thin film dispersion method. After selecting the optimal preparation conditions, HAS-LP was characterized using transmission electron microscopy (TEM) and by measuring the zeta potential, particle size, and in vitro drug release. Next, evaluated the effect of HAS-LP on the rat nasal mucosa and then applied it to AD mice. By performing behaviour experiments, pathological test and related pharmacokinetic parameters, we explored its effect on attenuating learning and memory impairment in mice.

Results

When the mass ratio of HAS:cholesterol:soybean lecithin was 1:4:16 and 15 mL of ultrapure water were added, the highest encapsulation efficiency and drug loading were obtained. HAS-LP had a particle size of 181.77 nm, a polydispersity index of 0.207 and a zeta potential of −53.8 mV, and it remained stable at 25 °C for 1 week and 4 °C for 8 weeks. Moreover, HAS-LP exhibited slow drug release and was highly consistent with the Higuchi release model. HAS-LP was not significantly toxic to the nasal mucosa and effectively alleviated D-galactose-induced learning memory deficits and protected mouse hippocampal neuronal cells. HAS-LP was highly enriched in plasma and brain tissue after administration via the nasal route and obtained some ability to target the brain.

Conclusion

HAS encapsulated in soybean lecithin and cholesterol was successfully developed, suggesting that treatment with the nanoparticles might reverse some AD symptoms. Therefore, these nanoparticles might be used as promising new candidates for the delivery of HAS to treat AD.

Natural Product-based Nanomedicine: Recent Advances and Issues for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) affects the elderly and is characterized by progressive neurodegeneration caused by different pathologies. The most significant challenges in treating AD include the inability of medications to reach the brain because of its poor solubility, low bioavailability, and the presence of the blood-brain barrier (BBB). Additionally, current evidence suggests the disruption of BBB plays an important role in the pathogenesis of AD. One of the critical challenges in treating AD is the ineffective treatments and their severe adverse effects. Nanotechnology offers an alternative approach to facilitate the treatment of AD by overcoming the challenges in drug transport across the BBB. Various nanoparticles (NP) loaded with natural products were reported to aid in drug delivery for the treatment of AD. The nano-sized entities of NP are great platforms for incorporating active materials from natural products into formulations that can be delivered effectively to the intended action site without compromising the material's bioactivity. The review highlights the applications of medicinal plants, their derived components, and various nanomedicinebased approaches for the treatment of AD. The combination of medicinal plants and nanotechnology may lead to new theragnostic solutions for the treatment of AD in the future.

Nose-to-brain delivery of borneol modified tanshinone IIA nanoparticles in prevention of cerebral ischemia/reperfusion injury

Targeted treatment of cerebral ischemia/reperfusion injury (CIRI) remains a problem due to the difficulty in drug delivery across the blood–brain barrier (BBB). In this study, we developed Bo-TSA-NP, a novel tanshinone IIA (TSA) loaded nanoparticles modified by borneol, which has long been proved with the ability to enhance other drugs’ transport across the BBB. The Bo-TSA-NP, with a particle size of about 160 nm, drug loading of 3.6%, showed sustained release and P-glycoprotein (P-gp) inhibition property. It demonstrated a significantly higher uptake by 16HBE cells in vitro through the clathrin/caveolae-mediated endocytosis and micropinocytosis. Following intranasal (IN) administration, Bo-TSA-NP significantly improved the preventive effect on a rat model of CIRI with improved neurological scores, decreased cerebral infarction areas and a reduced content of malondialdehyde (MDA) and increased activity of superoxide dismutase (SOD) in rat brain. In conclusion, these results indicate that Bo-TSA-NP is a promising nose-to-brain delivery system that can enhance the prevention effect of TSA on CIRI.

Recent Advances in Nanotherapeutic Interventions for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD), with impairment of learning and memory as the common clinical manifestations, is one of the most challenging diseases affecting individuals, their families and society as a whole. The fact that its prevalence is escalating rapidly, with the total number of AD patients estimated to reach 115.4 million by 2050, has made the disease a very challenging ailment worldwide. Several biological barriers like the bloodbrain barrier (BBB), drug efflux by P-glycoprotein and the blood-cerebrospinal fluid barrier restrict the delivery of conventional AD drugs to the central nervous system (CNS), thereby limiting their effectiveness. In order to overcome the above physiological barriers, the development of nanomedicines has been extensively explored. The present review provides an insight into the pathophysiology of AD and risk factors associated with AD. Besides, various nanoformulations reported in the literature for the diagnosis and treatments of AD have been classified and summarised. The patented nanoformulations for AD and details of nanoformulations which are in clinical trials are also mentioned. The review would be helpful to researchers and scientific community by providing them with information related to the recent advances in nanointerventions for the diagnosis and treatment of AD, which they can further explore for better management of the disease. However, although the nanotherapeutics for managing AD have been extensively explored, the factors which hinder their commercialisation, the toxicity concern being one of them, need to be addressed so that effective nanotherapeutics for AD can be developed for clinical use.

Improved brain delivery of pueraria flavones via intranasal administration of borneol-modified solid lipid nanoparticles

Aim: To improve the drug delivery to the brain with borneol (Bo)-modified solid lipid nanoparticles (SLNs) of pueraria flavones (PTF) via intranasal administration. Materials & methods: PTF-loaded SLNs were modified with Bo by physical and chemical methods to synthesize PTF-Bo-SA-SLNs and PTF-Bo-SLNs. The prepared SLNs were characterized and their brain delivery effects were evaluated in vitro and in vivo. Results: There was a more pronounced accumulation of PTF-Bo-SA-SLNs in Caco-2 cells. Following intranasal administration, more coumarin-6 was found in the rat brain carried by Bo-SA-SLNs. Brain area under the curve and C_max of PTF-Bo-SA-SLN were 7.31- and 7.29-times higher than those of PTF-SLN, respectively. Conclusion: PTF-Bo-SA-SLNs are a promising therapeutic carrier for brain disease after intranasal administration.

A window into the brain: Tools to assess pre-clinical efficacy of biomaterials-based therapies on central nervous system disorders

Therapeutic conveyance into the brain is a cardinal requirement for treatment of diverse central nervous system (CNS) disorders and associated pathophysiology. Effectual shielding of the brain by the blood-brain barrier (BBB) sieves out major proportion of therapeutics with the exception of small lipophilic molecules. Various nano-delivery systems (NDS) provide an effective solution around this obstacle owing to their small size and targeting properties. To date, these systems have been used for several pre-clinical disease models including glioma, neurodegenerative diseases and psychotic disorders. An efficacy screen for these systems involves a test battery designed to probe into the multiple facets of therapeutic delivery. Despite their wide application in redressing various disease targets, the efficacy evaluation strategies for all can be broadly grouped into four modalities, namely: histological, bio-imaging, molecular and behavioural. This review presents a comprehensive insight into all of these modalities along with their strengths and weaknesses as well as perspectives on an ideal design for a panel of tests to screen brain nano-delivery systems.

Nanotechnology Based Theranostic Approaches in Alzheimer's Disease Management: Current Status and Future Perspective

BACKGROUND

Alzheimer's disease (AD), a cognitive dysfunction/dementia state amongst the elders is characterized by irreversible neurodegeneration due to varied pathophysiology. Up till now, anti-AD drugs having different pharmacology have been developed and used in clinic. Yet, these medications are not curative and only lowering the AD associated symptoms. Improvement in treatment outcome required drug targeting across the blood-brain barrier (BBB) to the central nervous system (CNS) in optimal therapeutic concentration. Nanotechnology based diagnostic tools, drug carriers and theranostics offer highly sensitive molecular detection, effective drug targeting and their combination. Over the past decade, significant works have been done in this area and we have seen very remarkable outocome in AD therapy. Various nanoparticles from organic and inorganic nanomaterial category have successfully been investigated against AD.

CONCLUSION

This paper discussed the role of nanoparticles in early detection of AD, effective drug targeting to brain and theranostic (diagnosis and therapy) approaches in AD's management.

Plasma and cerebrospinal fluid pharmacokinetics of select chemotherapeutic agents following intranasal delivery in a non-human primate model

The blood-brain barrier (BBB) limits entry of most chemotherapeutic agents into the CNS, resulting in inadequate exposure within CNS tumor tissue. Intranasal administration is a proposed means of delivery that can bypass the BBB, potentially resulting in more effective chemotherapeutic exposure at the tumor site. The objective of this study was to evaluate the feasibility and pharmacokinetics (plasma and CSF) of intranasal delivery using select chemotherapeutic agents in a non-human primate (NHP) model. Three chemotherapeutic agents with known differences in CNS penetration were selected for intranasal administration in a NHP model to determine proof of principle of CNS delivery, assess tolerability and feasibility, and to evaluate whether certain drug characteristics were associated with increased CNS exposure. Intravenous (IV) temozolomide (TMZ), oral (PO) valproic acid, and PO perifosine were administered to adult male rhesus macaques. The animals received a single dose of each agent systemically and intranasally in separate experiments, with each animal acting as his own control. The dose of the agents administered systemically was the human equivalent of a clinically appropriate dose, while the intranasal dose was the maximum achievable dose based on the volume limitation of 1 mL. Multiple serial paired plasma and CSF samples were collected and quantified using a validated uHPLC/tandem mass spectrometry assay after each drug administration. Pharmacokinetic parameters were estimated using non-compartmental analysis. CSF penetration was calculated from the ratio of areas under the concentration-time curves for CSF and plasma (AUC_CSF:plasma). Intranasal administration was feasible and tolerable for all agents with no significant toxicities observed. For TMZ, the degrees of CSF drug penetration after intranasal and IV administration were 36 (32-57) and 22 (20-41)%, respectively. Although maximum TMZ drug concentration in the CSF (C_max) was lower after intranasal delivery compared to IV administration due to the lower dose administered, clinically significant exposure was achieved in the CSF after intranasal administration with the lower doses. This was associated with lower systemic exposure, suggesting increased efficiency and potentially lower toxicities of TMZ after intranasal delivery. For valproic acid and perifosine, CSF penetration after intranasal delivery was similar to systemic administration. Although this study demonstrates feasibility and safety of intranasal drug administration, further agent-specific studies are necessary to optimize agent selection and dosing to achieve clinically-relevant CSF exposures.

Plasmonics-enhanced and optically modulated delivery of gold nanostars into brain tumor

Plasmonics-active gold nanostars exhibiting strong imaging contrast and efficient photothermal transduction were synthesized for a novel pulsed laser-modulated plasmonics-enhanced brain tumor microvascular permeabilization. We demonstrate a selective, optically modulated delivery of nanoprobes into the tumor parenchyma with minimal off-target distribution.

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.

Novel central nervous system drug delivery systems

For decades, biomedical and pharmaceutical researchers have worked to devise new and more effective therapeutics to treat diseases affecting the central nervous system. The blood-brain barrier effectively protects the brain, but poses a profound challenge to drug delivery across this barrier. Many traditional drugs cannot cross the blood-brain barrier in appreciable concentrations, with less than 1% of most drugs reaching the central nervous system, leading to a lack of available treatments for many central nervous system diseases, such as stroke, neurodegenerative disorders, and brain tumors. Due to the ineffective nature of most treatments for central nervous system disorders, the development of novel drug delivery systems is an area of great interest and active research. Multiple novel strategies show promise for effective central nervous system drug delivery, giving potential for more effective and safer therapies in the future. This review outlines several novel drug delivery techniques, including intranasal drug delivery, nanoparticles, drug modifications, convection-enhanced infusion, and ultrasound-mediated drug delivery. It also assesses possible clinical applications, limitations, and examples of current clinical and preclinical research for each of these drug delivery approaches. Improved central nervous system drug delivery is extremely important and will allow for improved treatment of central nervous system diseases, causing improved therapies for those who are affected by central nervous system diseases.

PDE4 as a target for cognition enhancement

INTRODUCTION

The second messengers cAMP and cGMP mediate fundamental aspects of brain function relevant to memory, learning, and cognitive functions. Consequently, cyclic nucleotide phosphodiesterases (PDEs), the enzymes that inactivate the cyclic nucleotides, are promising targets for the development of cognition-enhancing drugs.

AREAS COVERED

PDE4 is the largest of the 11 mammalian PDE families. This review covers the properties and functions of the PDE4 family, highlighting procognitive and memory-enhancing effects associated with their inactivation.

EXPERT OPINION

PAN-selective PDE4 inhibitors exert a number of memory- and cognition-enhancing effects and have neuroprotective and neuroregenerative properties in preclinical models. The major hurdle for their clinical application is to target inhibitors to specific PDE4 isoforms relevant to particular cognitive disorders to realize the therapeutic potential while avoiding side effects, in particular emesis and nausea. The PDE4 family comprises four genes, PDE4A-D, each expressed as multiple variants. Progress to date stems from characterization of rodent models with selective ablation of individual PDE4 subtypes, revealing that individual subtypes exert unique and non-redundant functions in the brain. Thus, targeting specific PDE4 subtypes, as well as splicing variants or conformational states, represents a promising strategy to separate the therapeutic benefits from the side effects of PAN-PDE4 inhibitors.

Metallofullerene-nanoplatform-delivered interstitial brachytherapy improved survival in a murine model of glioblastoma multiforme

Fullerenes are used across scientific disciplines because of their diverse properties gained by altering encapsulated or surface-bound components. In this study, the recently developed theranostic agent based on a radiolabeled functionalized metallofullerene ((177)Lu-DOTA-f-Gd(3)N@C(80)) was synthesized with high radiochemical yield and purity. The efficacy of this agent was demonstrated in two orthotopic xenograft brain tumor models of glioblastoma multiforme (GBM). A dose-dependent improvement in survival was also shown. The in vivo stability of the agent was verified through dual label measurements of biological elimination from the tumor. Overall, these results provide evidence that nanomaterial platforms can be used to deliver effective interstitial brachytherapy.

Peptides: important tools for the treatment of central nervous system disorders

This review shows some classical applications of peptides and suggests there is great promise for the treatment of various central nervous system diseases. Actually, peptides are considered the new generation of biologically active tools because they are key regulators in cellular and intercellular physiological responses, which possess enormous potential for the treatment of various diseases. In spite of their clinical potential, native peptides have seen limited use due to their poor bioavailability and low stability in physiological conditions. Moreover, most peptide or protein pharmaceuticals currently in use are delivered by invasive routes such as via subcutaneous injection. Considerable efforts have been made to design new drugs based on peptides and recent developments in technology and science have provided the means and opportunity to produce a stable as well as controlled-release form of peptide and protein drugs to combat poorly controlled diseases and to increase patients' quality of life. A major challenge in this regard, however, is the delivery of peptides over the blood-brain barrier. This review gives an overview of some strategies used to improve both bioavailability and uptake of peptide drugs for delivery into the brain. Indeed, recent findings suggest that the use of peptides by conjugation to a polymer such as nanoparticles can offer tremendous hope in the treatment of brain disorders. The polymer conjugation improves pharmacokinetics by increasing the molecular mass of proteins and peptides and shielding them from proteolytic enzymes. These new strategies will create new opportunities for the future development of neurotherapeutic drugs. In the present review we have focused our attention on the peptide controlled delivery, summarizing literature reports on the use of peptides and nanotechnology for the treatment and diagnosis of brain disorders.

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.

Metallofullerene-based nanoplatform for brain tumor brachytherapy and longitudinal imaging in a murine orthotopic xenograft model

PURPOSE

To demonstrate in an orthotopic xenograft brain tumor model that a functionalized metallofullerene (f-Gd₃N@C₈₀) can enable longitudinal tumor imaging and, when radiolabeled with lutetium 177 (¹⁷⁷Lu) and tetraazacyclododecane tetraacetic acid (DOTA) (¹⁷⁷Lu-DOTA-f-Gd₃N@C₈₀), provide an anchor to deliver effective brachytherapy.

MATERIALS AND METHODS

All experiments involving the use of mice were carried out in accordance with protocols approved by the institutional animal care and use committee. Human glioblastoma U87MG cells were implanted by using stereotactic procedures into the brains of 37 female athymic nude-Foxn1nu mice and allowed to develop into a tumor for 8 days. T1- and T2-weighted magnetic resonance (MR) imaging was performed in five mice. Biodistribution studies were performed in 12 mice at four time points over 7 days to evaluate gadolinium content. Survival studies involved 20 mice that received infusion of a nanoplatform by means of convection-enhanced delivery (CED) 8 days after tumor implantation. Mice in survival studies were divided into two groups: one comprised untreated mice that received f-Gd₃N@CC₈₀ alone and the other comprised mice treated with brachytherapy that received 1.11 MBq of ¹⁷⁷Lu-DOTA-f-Gd₃N@CC₈₀. Survival data were evaluated by using Kaplan-Meier statistical methods.

RESULTS

MR imaging showed extended tumor retention (25.6% ± 1.2 of the infused dose at 52 days, confirmed with biodistribution studies) of the f-Gd₃N@CC₈₀ nanoplatform, which enabled longitudinal imaging. Successful coupling of ¹⁷⁷Lu to the f-Gd₃N@CC₈₀ surface was achieved by using a bifunctional macrocyclic chelator. The extended tumor retention allowed for effective brachytherapy, as indicated by extended survival time (> 2.5 times that of the untreated group) and histologic signs of radiation-induced tumor damage.

CONCLUSION

The authors have developed a multimodal nanoplatform and have demonstrated longitudinal tumor imaging, prolonged intratumoral probe retention, biodistribution, and extended survival in an orthotopic xenograft brain tumor model.

Neuroimmune pharmacology as a sub-discipline of medical neuroscience in the medical school curriculum

The emerging field of neuroimmune pharmacology (NIP) is the confluence of three distinct disciplines: neuroscience, immunology, and pharmacology (Gendelman and Ikezu 2008). NIP was born from the realization that inflammation within the central nervous system (CNS) plays a crucial role in many neurological pathologies and as such offers a rich array of novel pharmacological targets as potential therapeutics. As this field is likely to have a major impact in medical science, educating future physicians on this area will help increase awareness and may potentially inspire them to pursue careers in the field of NIP. However, a key challenge for medical educators, is how best to incorporate new material on emerging fields, such as NIP, into the medical school curriculum, specifically in the context of a medical neuroscience course. We propose the addition of two 50-min lectures plus an additional optional 2-h lab module to the standard first year medical neuroscience class curriculum. Lecture 1 will focus on how the CNS and the immune system inter-communicate with one another with emphasis on neuroanatomical features and chemical signal transduction between the two systems. Lecture 2 provides an introduction to inflammation in the CNS and provides a series of clinical correlates to describe how CNS inflammation contributes to the disease process. The lab module provides detailed visual examples of how CNS inflammation influences disease processes and provides two examples of how application of an immunomodulatory pharmacological agent can modify disease processes.

Advances in using chitosan-based nanoparticles for in vitro and in vivo drug and gene delivery

IMPORTANCE OF THE FIELD

This review aims to provide an overview of state-of-the-art chitosan-based nanosized carriers for the delivery of therapeutic agents. Chitosan nanocarriers are smart delivery systems owing to the possibility of their property alterations with various approaches, which would confer them with the possibility of spatiotemporal delivery features.

AREAS COVERED IN THIS REVIEW

The focus of this review is principally on those aspects that have not often been addressed in other reviews. These include the influence of physicochemical properties of chitosan on delivery mechanisms and chitosan modification with a variety of ligand moieties specific for cell surface receptors to increase recognition and uptake of nanocarriers into cells through receptor-mediated endocytosis. Multiple examples that demonstrate the advantages of chitosan-based nanocarriers over other delivery systems of therapeutic agents are highlighted. Particular emphasis is given to the alteration of material properties by functionalization or combination with other polymers for their specific applications. Finally, structural and experimental parameters influencing transfection efficiency of chitosan-based nanocarriers are presented for both in vitro and in vivo gene delivery.

WHAT THE READER WILL GAIN

The readers will acquire knowledge of parameters influencing the properties of the chitosan-based nanocarriers for delivery of therapeutic agents (genetic material or drugs) in vitro and in vivo. They will get a better idea of the strategies to be adapted to tune the characteristics of chitosan and chitosan derivatives for specific delivery applications.

TAKE HOME MESSAGE

Chitosan is prone to chemical and physical modifications, and is very responsive to environmental stimuli such as temperature and pH. These features make chitosan a smart material with great potential for developing multifunctional nanocarrier systems to deliver large varieties of therapeutic agents administrated in multiple ways with reduced side effects.