Nanopharmaceuticals as Drug-Delivery Systems

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Nanopharmaceuticals as Drug-Delivery Systems: For, Against, and Current Applications

4

Sema C¸alı¸s, Kıvılcım O¨ztu¨rk Atar, Fatma B. Arslan, Hakan Eroglu, Yılmaz C¸apan Hacettepe University, Ankara, Turkey

1. INTRODUCTION Nanomedicine is a top area of focus for many research groups. Mainly, nanotechnology is combined with pharmaceuticals and biomedical sciences. Nanopharmaceuticals, which are the products of this combination, are defined as a combination of active molecules or biological substances prepared for the purpose of enhancing drug therapies by targeting, attenuating toxicity profiles and safety concerns, or in vivo imaging. The increased particle surface area as a result of decreased particle size provides nanopharmaceuticals with totally different characteristics with respect to the original bulk forms. These may include biochemical, optical, magnetic, and electronic characteristics [1e6]. Although the dosage forms are generally administered via the oral or intravenous route, examples comprising transdermal application also exist (e.g., Estrasorb). The life cycle of nanopharmaceuticals requires the regulatory approval process, as for drug approvals, including preclinical and clinical evaluation [7]. This chapter is mainly focused on a broad point of view of the range of materials that have been used in the formulation of FDA-approved nanopharmaceuticals, including all steps of the pipeline. It is very fascinating that within the past decade, the number of clinical trials of nanocomponents multiplied by six times and the trend seems to be increasing for the next years [8].

2. HISTORY OF NANOTECHNOLOGY AND NANO DEFINITIONS The term “nanotechnology” was introduced and defined by Norio Taniguchi in 1974 by referring to materials with a dimension in the nanoscale. Before progressing deeper into the world of nanopharmaceuticals, some definitions concerning the “nano world” will be given in the following section. Initially, it will be logical to define nanoscience as the phenomena dealing with materials at the nanoscale. Nanocarriers for Drug Delivery. https://doi.org/10.1016/B978-0-12-814033-8.00004-7 Copyright © 2019 Elsevier Inc. All rights reserved.

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Regarding this basic concept, nanotechnology may be broadly defined as the multidisciplinary field of all nanoscale applications, which includes characterization and production, but keeping in mind that shape and size must be kept in nanoscale. The application of nano terminology in the field of medicine is grouped under the term “nanomedicine,” which is the submicrometer delivery systems intended to be used for prevention, diagnosis, imaging, and finally treatment of various disorders in the living cells. The application of nano in pharmacy is a combination of nanotechnology with the aforementioned purposes, resulting in novel drug delivery, imaging, diagnostics, and sensor targets [9]. The reflection of nanoscience in the field of medicine can be identified by both of the terms nanomedicine and nanopharmaceuticals, the definitions of which may be considered interchangeable [10]. In this chapter, these concepts are discussed in detail in the following section. Conventional application of drugs is hindered by limited efficacy, poor biodistribution, and lack of selectivity for the intended site of action. These boundaries and drawbacks can be overcome by controlling drug-delivery concept. The adverse or side effects of the drugs on healthy tissues may be minimized by directly or passively targeting the drug-delivery system to the site of action. At this point the reflection of nano in the field of pharmaceutics may provide numerous advantages from the perspective of formulation design with respect to conventional opportunities. Nanoparticle delivery systems improve the efficacy of drugs, attenuate the toxicity outcomes, and have favorable biodistribution characteristics with increased patient compliance. In general, the dose of drug in nanopharmaceuticals is very much lower compared with the conventional alternatives; however, with the aid of targeting, increased concentrations are maintained at the targeted site of action [11]. In addition, by the formulation of multifunctional nano-drug-delivery systems having both imaging and treatment capabilities, patient compliance may be significantly improved [12]. In general, size reduction is the fundamental unit operation having important applications in pharmacy. Size reduction in the delivery systems may also provide some advantages such as (1) increased dissolution rate as a result of increased surface area; (2) improved solubility of the active ingredient; (3) enhanced stability; (4) improved absorbance for insoluble active ingredients; (5) attenuation of the required dose for treatment, therefore better toxicity profile; (6) rapid onset of action; and (7) decreased interpatient and fed/fasted state variability. Another advantage of nanopharmaceuticals is being similar in size to biomolecules like receptors, antibodies, and nucleic acids. Therefore, they may be functionalized with these molecules, which makes them suitable candidates for targeting purposes essentially required for cancer drugs. Novel physical properties make these systems, such as nanorods, attractive from the perspective of bioimaging [13].

3. NANOMEDICINES AND BIOLOGICAL ENVIRONMENT Nanomedicines are exposed to some complex interactions with the components of the biological environment upon administration. The properties of the

4. Characterization of Nanomaterials

nanomedicines are dependent, which means they may be controlled to obtain desired properties; however, the biological environmental characteristics are completely independent in nature. Therefore, the nanomedicine’s dependent variables, particle size distribution, surface charge, and morphological characteristics, determine its biological performance. Interactions of nanomedicines with their biological surroundings (at the level of molecules, cells, organs, etc.) are dependent on a complex interplay between the particles and the biological media. While properties of nanoparticles are controllable, those of biological surroundings are not. Particle size, shape, and surface chemistry are critical factors determining the performance and interaction potential of nanomedicines with the surrounding media. The three major interactions of nanomedicines are biodistribution characteristics, cellular uptake to show efficacy, and finally clearance from the tissues. At this point the size properties take the role of determining factor in how these systems will be cleared from the body. Particles having a size of less than 10 nm are cleared through the kidneys; on the other hand, particles with size larger than 10 nm are eliminated through the liver and mononuclearephagocyte system [14e16]. The design of nanoparticles may be outlined according to the mechanism of clearance. In cases where minimal background signal is desirable, especially for molecular imaging agents, actively targeted small particles are preferred because they are not taken up by the target organ after first-pass metabolism. After nanomedicines are exposed to the systemic circulation, the adsorption of protein molecules forms an outer shell around the particles. The formation of this outer layer seems to be practically fatal; however, the composition of this layer may be somewhat modified by low-fouling coatings such as poly(ethylene glycol) (PEG) [17]. The main problem in this protein coat formation is the denaturation of these proteins at later times, resulting in aggregation and/or being suitable candidates for macrophages. This cascade finally affects the biodistribution, pharmacokinetics, and efficacy of the nanomedicine within the body.

4. CHARACTERIZATION OF NANOMATERIALS Detailed characterization of nanopharmaceuticals plays an important role and is at the heart of guidance documents published by the US FDA. As mentioned earlier, the physicochemical properties of the active materials may be significantly altered by the process of nanosizing, and full characterization of nanosized formulations must be totally identified for approval of the efficacy and safety of these delivery systems. After the total identification of these characteristics, an Investigational New Drug application may be filed for regulatory registration. As for the regular drug development process, this identification period may be divided into four major phases: • •

phase I: drug dosing, toxicity, and excretion in healthy subjects are investigated; phase II: safety and efficacy studies on patients who are experiencing the disease are performed;

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• •

phase III: multicenter placebo-controlled randomized clinical trials; phase IV: after marketing approval from the regulatory authority, these studies are generally requested to address questions regarding the phase III studies [18].

Nanoparticle characterization may be executed using various analytical methods. One of the most important attributes of particles is the size. The size distribution determination of the nanopharmaceutical is basically done by the major method, which is photon correlation spectroscopy (PCS), or dynamic light scattering. In PCS, the basic principle is the determination of the size of nanoparticles having Brownian motion in terms of hydrodynamic diameter. The measurement may go down to 1 nm with this method and the size distribution of the nanoparticles is determined. In addition, the fate of the nanopharmaceutical is also determined by the molecular weight, density, z potential, and hydrophobicity characteristics. Surface investigations of nanopharmaceuticals are carried out by either scanning electron microscopy or atomic force microscopy. Thermal characterization of nanopharmaceuticals may be investigated by differential scanning calorimetry and thermogravimetric analysis [19]. These techniques are summarized in Table 4.1 [19]. Nanopharmaceuticals that are intended to be used for therapeutic or diagnostic purposes are generally classified as inorganic or organic nanoparticles. As of this writing, inorganic particles are mainly used in clinical studies for imaging purposes during surgery, such as intraoperative sentinel lymph node imaging and thermal ablation of tumors; and some of them have been already approved for imaging applications and anemia treatment [20e22]. In addition, organic nanoparticles have found a place for themselves in clinics for the purposes of vaccination, sustained drug-delivery purposes, or locally effective controlled-release delivery for skin disorders [23e25].

5. NANOPARTICLE TYPES, APPLICATIONS, ADVANTAGES, AND POTENTIAL Nanomedicine is one of the pioneer research areas that have a significant potential to radically reform the health of the population within the next century. The golden factor that underlies this fact is the unique characteristics and phenomena that nanoparticles manifest due to their small size [26]. Engineering materials on this scale (usually accepted as 1e100 nm) allows for novel medical therapies such as designing nanoparticle-based drugs that target cells with improved specificity, resulting in decreased side effects for patients [27]. Other advances are being made in medical devices and instrumentation for use in surgical procedures that are less invasive, leading to shorter recovery times and decreased risk of postoperative infections or other complications. Such innovations will improve the quality of life and extend life expectancies, and could reduce the overall cost of health care [28]. The brief and general explanation of pharmaceutical nanosystems is as follows: pharmaceutical nanotechnology is divided into two basic types of nanotools, viz.

5. Nanoparticle Types, Applications, Advantages, and Potential

Table 4.1 The Common Techniques for Characterization of Nanosystems [19] Property

Commonly Used Technique

Morphology Size (primary particle) Size (primary/aggregate/agglomerate) Size distribution Molecular weight Structure/shape Stability (3D structure)

TEM, SEM, AFM, XRD TEM, SEM, AFM, DLS, FFF, AUC, CHDF, XDC, HPLC, DMA EM, SEM, AFM, DLS, AUC, FFF, HPLC, SMA SLS, AUC, GPC TEM, SEM, AFM, NMR DLS, AUC, FFF, SEM, TEM

Surface Surface area Surface charge z potential Surface coating composition Surface coating coverage Surface reactivity Surfaceecore interaction Topology

BET SPM, GE, titration methods LDE, ESA, PALS SPM, XPS, MS, RS, FTIR, NMR AFM, AUC, TGA Varies with nanomaterial SPM, RS, ITC, AUC, GE SEM, SPM, MS

Chemical Chemical composition (core, surface) Purity Stability (chemical) Solubility (chemical) Structure (chemical) Crystallinity Catalytic activity

XPS, MS, AAS, ICPeMS, RS, FTIR, NMR ICPeMS, AAS, AUC, HPLC, DSC MS, HPLC, RS, FTIR Varies with nanomaterial NMR, XRD XRD, DSC Varies with nanomaterial

Other Drug loading Drug potency/functionality In vitro release (detection) Deformability

MS, HPLC, UVeVis, varies with nanomaterial Varies with nanomaterial UVeVis, MS, HPLC, varies with nanomaterial AFM, DMA

AAS, atomic absorption spectroscopy; AFM, atomic force microscopy; AUC, area under the curve; BET, BrunauereEmmetteTeller; DLS, dynamic light scattering; DMA, differential mobility analysis; DSC, differential scanning calorimetry; EM, electron microscopy; ESA, excited-state absorption; FFF, field-flow fractionation; FTIR, Fourier transform infrared spectroscopy; GPC, gel permeation chromatography; HPLC, high-performance liquid chromatography; ICPeMS, inductively coupled plasmaemass spectrometry; ITC, isothermal titration calorimetry; LDE, laser Doppler electrophoresis; MS, mass spectrometry; NMR, nuclear magnetic resonance; PALS, phase analysis light scattering; RS, Raman spectroscopy; SEM, scanning electron microscopy; SLS, static light scattering; SPM, scanning probe microscopy; TEM, transmission electron microscopy; TGA, thermogravimetric analysis; UVeVis ultravioletevisible; XDC, X-ray disk centrifugation; XPS, X-ray photoelectron spectroscopy; XRD, X-ray diffraction.

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Functionalized nanoparticle

• Nanoparticle with a surface modified with organic molecules or polymers

• Tree-like synthetic and polymeric structures • Size: Up to 10 nm

• Size: 100-1000 nm Dendrimer

• Improves the therapeutic efficacy of the drug by augmenting the circulation half-life and stability

• Usually in solid lipid nanoparticle form • Submicrometer-sized lipid Solid nanoparticles emulsions (Drug encapsulated or dispersed)

Antibody-polymer conjugate conj n ugate

• Oil nanodroplets dispersed within aqueous continous phase suitable for entrrapment of hydrophobic drugs Nanoemulsions

Polymeric micelles

• Size: 20-200 nm • Supramolecular aggregates composed of amphiphilic block copolymers that self-assemble into aqueous media. Inner core typically serves as a container for hydrophobic drugs • Size: 20-80 nm

Liposome

•

Vesicles composed of one or more concentric bilayers of lipid molecules (entrapping hydrophobic drugs) enclosing one or more aqueous compartments (entrapping hydrophilic drugs)

•

Size: >20 nm

•

Cylindrical carbon-based nanostructures

•

A member of fullerene structural family

PEGylated carbon • nanotube

Size: >20 nm

FIGURE 4.1 Nanomedicines for drug delivery. Modified from Tinkle S, et al. Nanomedicines: addressing the scientific and regulatory gap. Ann Rep 2014; 1313:35e56; Hafner A, et al. Nanotherapeutics in the EU: an overview on current state and future directions. Int J Nanomed 2014;9:1005e23.

nanomaterials and nanodevices. These materials can be subclassified into nanocrystalline and nanostructured materials. Nanoparticles, liposomes, dendrimers, micelles, and drug conjugates are some of the most known examples of nanostructures (Fig. 4.1).

5.1 POLYMERIC NANOPARTICLES Nanoparticles, as one of the well-known examples of nanoparticulate delivery systems, are subnanosized structures, containing a certain amount of drug or biologic molecule in their structure within a certain size range and exhibiting various morphologies (amorphous, crystalline, spherical, needles, etc.). Polymeric nanoparticles, which are a subtype of nanoparticles, are the most applicable and efficient group for nanomedicine applications depending on their

6. Manufacturing Prospects

fast and simple preparation techniques and a widespread application portfolio. In 2013, the two best-selling products were Copaxone and Neulasta among the polymeric drugs [30]. Polymeric nanomedicines usually fall into one of two categories: (1) polymeredrug conjugates for increased drug half-life and bioavailability and (2) degradable polymeric structures for controlled-release applications [18].

5.2 LIPOSOMES Liposome formulations are named for the group of nanopharmaceuticals that contain an aqueous core, which is surrounded by different numbers of lipid layers depending on the formulation type. This property makes liposomes suitable for the encapsulation of both hydrophilic and hydrophobic drugs. The aqueous core makes them suitable for hydrophilic drug delivery; and on the other hand the lipid layer(s) provides a suitable reservoir for hydrophobic molecules. The maintenance of liposomes in the systemic circulation may be manipulated by surface modifications, especially with PEG, thus resulting in the controlled delivery of active moiety for a longer period of time [31].

6. MANUFACTURING PROSPECTS FOR NANO DRUGS, NANOADDITIVES, AND NANOCARRIERS Nanoscale materials and devices can be fabricated using two different manufacturing approaches: “bottomeup” or “topedown” techniques. In bottomeup methods, the basic principle is the formation of nanomaterials starting from the atoms or molecules by means of self-assembly. On the other hand, microtechnologies that are defined as topedown methods, including photolithography, nanomolding, dip-pen lithography, and nanofluidics, may be used for the preparation of nanomaterials [32]. There exist many prospects for the manipulation of drug release kinetics by coating nanomaterials with a polymer, such as diffusion though a polymer layer and surface degradation resulting in the release of a core material [33]. Therapeutic agents on the nanoscale are individually complex in terms of components, function, and performance. The six components that dictate the function and performance of nanoparticulate drug-delivery systems include the following: 1. the presence and concentration of the active ingredient (small or large molecular weight); 2. surface properties of the drug, additive, or carrier; 3. chemical composition of the drug, additive, or carrier; 4. presumed targeting moieties (subcellular or cellular); 5. physical formulation (solid or liquid); 6. route of administration [34]. In general, design space development requires consideration of the critical quality attributes of the product, usually related to composition, structure, and

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FIGURE 4.2 Attributes to consider at all scales of research and development in nanotechnology. Modified from Hickey AJ, Misra A, Fourie PB. Dry powder antibiotic aerosol product development: inhaled therapy for tuberculosis. J Pharmaceut Sci 2013;102(11):3900e07; Hickey AJ. Back to the future: inhaled drug products. J Pharm Sci 2013;102(4):1165e72; Xu Z, Mansour HM, Hickey AJ. Particle interactions in dry powder inhaler unit processes: a review. J Adhes Sci Technol 2011;25(4e5):451e82.

stability, in the context of the target product profile as illustrated in Fig. 4.2. The illustration shows the critical quality attributes that should be evaluated carefully to reach the desired target product profile and performance criteria. These considerations are familiar to most pharmaceutical scientists. The principle of experimental design employed for product optimization can be illustrated from the literature, where a potential asthma therapy, consisting of nanoscale ipratropium bromide poly(lactide-co-glycolide) constructs as spray-dried particles, was developed through a particle engineering approach to achieve optimal particle morphology and physicochemical, dissolution, and aerodynamic characteristics to extend the duration of bronchodilation in an animal model [35]. A data structure that was suggested by the Nanomaterial Registry allows the examination of trends or identification of information that may not have been easily accessible before the data were integrated. Ideally, this approach will allow decision-making and risk management strategies to be developed as increasing amounts of data are curated. It is evident that nanoparticles exist in large populations and are found in a variety of environments and conditions. As a consequence,

8. Scale-Up of Nanomedicines

the way in which data are collected and expressed depends on the following considerations: 1. 2. 3. 4.

physicochemical property being measured; the manner in which the property is reported; measurement technique and the instrument employed; the record in which the sample is collected and prepared for examination [34].

7. REGULATORY PERSPECTIVE ON THE DEVELOPMENT OF NANOMEDICINES Because specific protocols and regulatory considerations for the development and characterization of nanomaterials are lacking, these products are not able to reach their full potential in biomedical applications and the clinic. Although there exists an awareness of the need for identified and defined procedures for the registration of nanopharmaceuticals, global regulatory views are not clearly and exactly stated as of this writing, despite attempts made since 2013. In the development and characterization of these materials, protocols and regulatory policies for conventional dosage forms were frequently taken into consideration as an alternate approach. From a regulator’s perspective, the active principal ingredient is the main factor that determines the tests to be conducted on the nanopharmaceutical. If the active substance is a biological material, such as a protein, peptide, or antibody, the regulatory processes that should be followed are those defined for biological medicinal products and new chemical entities. The interaction of nanopharmaceuticals is the major concern that needs to be investigated properly, because of the interaction potential of nanopharmaceuticals with the immune cells. The major steps of critical importance are biocompatibility and immunotoxicity (Table 4.2), which need to be identified during preclinical studies. The route of administration, dosage of the active moiety, and effects on the targeted tissue must be well identified and documented [39].

8. SCALE-UP OF NANOMEDICINES: PREPARATIVE METHODS AND THEIR CHALLENGES As in conventional drug-delivery systems, nanopharmaceutical scale-up requires methodology and knowledge transfer from the bench scale to industrial manufacturing. At this step, sensitive and precise methods of nanopharmaceutical preparation may result in failure due to the limitations in the preparation steps. Therefore, scale-up steps must be well organized, documented, and performed to maintain the quality of the final product. A few reports indicating the scale-up process for emulsion-based and nanoprecipitation methods exist in the literature, in which the process is defined from the lab scale to industrial manufacturing [40,41]. The effects of scale-up

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Table 4.2 Parameters for Quality and Safety Evaluation of NanotechnologyBased Medicinal Products for Biomedical Use Specific Goals Regarding the Parameter

Parameter Physicochemical properties

Production process Microbiology

Microbial contamination Endotoxin levels Viral/mycoplasma levels

Immunology

Cytokine production

Cytotoxicity of NK cells Macrophage uptake Complement activation Plasma protein binding Leukocyte proliferation

In vivo immune response

Hematology

Coagulation time Platelet aggregation

Characterization of: average size, particle size distribution, and aggregation; morphology; surface charge; crystalline structures; rigidity/deformability; chemical and molecular structure Control of critical points Sterility test To assess the presence of pyrogens Nitrous oxide quantification Sterility test Identification and quantification of induced cytokines Evaluation of: the effect on NK cell main functions (recognize and destroy); phagocytosis of the nanoparticle delivery system; the effect on the complement cascade; surface charge and hydrophobicity; the influence on leukocyte responses Function of NK cells Production of cytokines Immunoglobulins T and B cell proliferation Assessment of: the effect on coagulation factors;

9. Nanotechnology Clinical Applications

Table 4.2 Parameters for Quality and Safety Evaluation of Nanotechnology-Based Medicinal Products for Biomedical Usedcont’d Specific Goals Regarding the Parameter

Parameter Hemolysis

the influence on the coagulation cascade; the effect on red blood cells

In vivo single-dose toxicity study

Toxicity to different organs/cells

Biodistribution studies

Pharmacokinetics and pharmacodynamics

NK, natural killer. Modified from Sainz V, et al. Regulatory aspects on nanomedicines. Biochem Biophys Res Commun 2015;468(3):504e10.

are mainly reported to be observed on the particle size distribution of the product, encapsulation efficiency, residual content of the formulation, surface characteristics, and stability. In a study by Colombo et al., it was reported that after a scale-up process of approximately 33-fold, the encapsulation efficiency was not affected. On the other hand, increasing the impeller speed as well as the agitation resulted in a decrease in the particle size distribution. A similar decrease in the particle size was observed after the decrease in polymer amount [42]. In a scale-up study for an emulsion-based method (25 times scale-up) the elevation of the stirring rate significantly decreased the particle size of the dosage forms [40], thus leading to reduced drug loading of nanoparticles [43].

9. NANOTECHNOLOGY CLINICAL APPLICATIONS The impact of nanomedicines is rapidly growing, especially on health care demands. Nanomedicine has been defined by Colombo et al. as the new way of intervention for detection, treatment, and prevention of disease [42]. Among the most prominent developments is the availability of a broad range of engineered and functional nanoparticles for site-specific targeting of therapeutic agents to the diseased area, whether it be in the vasculature structure or the organs and tissues. Significant outcomes in clinical investigations have been recorded, especially for some types of cancer and microbial infection treatments [44]. In addition to the earlier discussed typical advantages of nanocarriers, the drug-induced reverse effects may be significantly altered depending on the proper targeting and reduced dosing of the active moiety. In addition, by the encapsulation and targeting concepts, drugs that are proven to be effective but have been discarded because of their toxicity may be gaining new consideration for the treatment of certain diseases. The pharmacokinetics and drug release pattern of nanopharmaceuticals

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have been well identified [45] and their properties may be tailored according to the intended purpose of administration [46]. Nanopharmaceuticals are being used as medicinal products for a certain number of disorders as of this writing, despite the complexity of their structural properties (Table 4.3) [10]. In clinical use, the most commonly available form of nanopharmaceuticals is the liposome type of formulation. The first approved liposomal formulation entered the market in the 1990s; it encapsulated the anticancer drug doxorubicin (Doxil/ Caelyx [Janssen Pharmaceutica NV, Beerse, Belgium] or Myocet [GP Pharm SA, Barcelona, Spain/Teva Pharmaceutical Industries Ltd., Krakow, Poland]) [48e50]. The first indication for this liposomal formulation was refractory Kaposi’s sarcoma and, in addition, it is also approved for ovarian and recurrent breast cancers [31]. With this formulation, increased half-life, improved tumor-specific delivery, and reduced cardiotoxicity with respect to free doxorubicin have been achieved [51,52]. DaunoXome (Gilead Sciences Ltd., Cork, Ireland), which is also a liposomal carrier incorporating daunorubicin, was formulated again for the purpose of risk reduction for acute and cumulative cardiotoxicity common to all anthracyclines [53e55]. Another liposome-based therapeutic, AmBisome (Gilead Sciences Ltd.), has been approved for prevention of side effects such as infusion-related reactions and nephrotoxicity, which are the two major problems of amphotericin B in clinical use [56]. In addition, the relatively small size and negative surface charge of this liposomal formulation prevent recognition that is followed by uptake by the reticuloendothelial system. Compared with the conventional dosage form, a higher plasma peak concentration and elevated area under the curve were achieved by the liposomal formulation of amphotericin B. In patients receiving the liposomal formulation of amphotericin B, the highest tissue concentration was determined in liver and spleen, with the lowest in kidneys and lungs [57]. A drug formulation exploiting DepoFoam technology (Fig. 4.3), which is defined as a specific multivesicular liposome technology (Pacira Pharmaceuticals, Inc.), is DepoDur (Almac Pharma Services Ltd.). It contains morphine, which is encapsulated in a liposomal formulation and indicated for the pain that is experienced after major surgery. DepoFoam technology consists of liposomes, which are multivesicular in structure and have multiple aqueous chambers inside a single bilayer. This structural conformation provides higher encapsulation efficiency with an efficient stability and a desired sustained-release profile. Compared with epidural administration of an intravenous opioid, the maintenance of pain control is much more successful with this formulation [58].

10. NANOTECHNOLOGY IN THE TREATMENT OF NEURODEGENERATIVE DISORDERS Delivery and targeting of therapeutics, especially of those that are macromolecular, to the central nervous system (CNS) has always been difficult. The bloodebrain

Table 4.3 Intravenous Targeted Nanoparticle Therapies That Have Been Clinically Approved or Are Undergoing Clinical Trials [47] Name (Company)/ ClinicalTrials.gov Identifier

Drug

Particle Type

Targeting Strategy

Indication

Doxil/Caelyx (Janssen)

Doxorubicin

PEGylated liposome

Passive targeting

Abraxane (Celgene)

Paclitaxel

Protein-bound particles

Passive targeting

CPX-351 liposomal formulation of a fixed combination of cytarabine:daunorubicin (Jazz Pharmaceuticals) TKM-080301 lipid nanoparticles containing siRNA against the PLK1 gene product (National Cancer Institute) SNS01-T (Senesco Technologies, Inc.)

Cytarabine:daunorubicin (5:1)

Liposome

Passive targeting

Ovarian cancer (secondary to platinumbased therapies) Advanced non-small-cell lung cancer (surgery or radiation is not an option); metastatic breast cancer (secondary); metastatic pancreatic cancer (primary) High-risk acute myeloid leukemia

siRNA against PLK1

Lipid nanoparticles

Passive targeting

Neuroendocrine tumors, adrenocortical carcinoma, advanced hepatocellular carcinoma

Phase I

siRNA against eIF5A and plasmid expressing eIF5A-K50R

Polyethylenimine nanoparticles

Passive targeting

Phase I/II

Cisplatin

Liposome

Passive targeting

Multiple myeloma, multiple myeloma in relapse, mantle cell lymphoma in relapse, diffuse large B cell lymphoma in relapse, other B cell lymphoma in relapse, plasma cell leukemia Ovarian cancer

Vincristine

Liposome

Passive targeting

SPI-77 STEALTH liposomal cisplatin (New York University School of Medicine) Vincristine liposomes (Onco TCS) (INEX Pharmaceuticals, M.D. Anderson Cancer Center)

Soft tissue sarcoma, lymphoma, leukemia, Wilms’ tumor, osteosarcoma

Approval/ Clinical Trial Phase FDA (1995) EMA (1996) FDA (2005) EMA (2008)

FDA (2017)

Phase II

Phase II

Continued

Table 4.3 Intravenous Targeted Nanoparticle Therapies That Have Been Clinically Approved or Are Undergoing Clinical Trials [47]dcont’d Name (Company)/ ClinicalTrials.gov Identifier NK-105 (Nippon Kayaku) SGT-94 (RB94 gene encapsulated with liposome targeted with anti-transferrin receptor single-chain antibody fragment) (SynerGene Therapeutics) ThermoDox in combination with radiofrequency ablation (Celsion) SGT-53 transferrin receptor-targeting liposome (SynerGene Therapeutics, Inc.) CALAA-01 transferrin receptor-targeting polymeric nanoparticle (Calando Pharmaceuticals) MM-302 HER2targeting liposome (Merrimack) BIND-04 PSMAtargeting docetaxel nanoparticles for injectable suspension (BIND Therapeutics)

Approval/ Clinical Trial Phase

Drug

Particle Type

Targeting Strategy

Indication

Paclitaxel

Polymeric micelle

Passive targeting

RB94 plasmid DNA

Liposome with antitransferrin receptor antibody

Active targeting

Metastatic or recurrent breast cancer Solid tumors

Doxorubicin

Thermally sensitive liposome

Active targeting

Hepatocellular carcinoma

Phase I

Plasmid encoding normal human wild-type p53 DNA

Liposome

Active targeting

Recurrent glioblastoma and metastatic pancreatic cancer

Phase I

siRNA against ribonucleotide reductase M2

Adamantane poly(ethylene glycol) nanoparticle

Active targeting

Solid tumors

Phase I

Doxorubicin

Liposome

Active targeting

HER2-positive breast cancer

Phase II

Docetaxel

Polymeric nanoparticle

Active targeting

Prostate cancer

Phase II

EMA, European Medicines Agency; FDA, US Food and Drug Administration; PSMA, prostate-specific membrane antigen; siRNA, small interfering RNA.

Phase III Phase I

10. Nanotechnology in the Treatment of Neurodegenerative Disorders

FIGURE 4.3 DepoFoam technology (Pacira Pharmaceuticals, Inc.).

barrier (BBB) is the main obstacle to reaching their targets in the brain that drug-delivery systems encounter. To improve the transport of therapeutics across the BBB and into the CNS much effort has been made, including the use of nanoparticles [59]. Nanoparticles such as dendrimers may have multitasking effects when the mechanism of drug delivery through the BBB is taken into account (Fig. 4.4). Many research groups have been working on the delivery of antineoplastic agents that are encapsulated in nanopharmaceuticals though the BBB to the CNS. Radiolabeled PEG-coated hexadecylcyanoacrylate nanospheres were

FIGURE 4.4 Nanocarriers as targeted a drug-delivery system across the bloodebrain barrier. Modified from Teli MK, Mutalik S, Rajanikant GK. Nanotechnology and nanomedicine: going small means aiming big. Curr Pharm Des 2010;16(16):1882e92.

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targeted and accumulated in a rat gliosarcoma. However, this method is not yet ready for clinical trials as of this writing, since the accumulation of the nanospheres in the surrounding healthy tissue still cannot be avoided [19]. Neurodegenerative disorders (NDs) are still a challenge for the treatment of patients. Because of the long recovery period and the existence of the BBB there is still no efficient therapy option for patients suffering from NDs. The existing prospects include palliative options, and the source of the problem in these disorders cannot be treated effectively. Therefore, nanotechnology has found a great space for itself for ND patients [60]. The superior properties of nanodelivery systems such as targeting and controlled-release characteristics take nanosystems one step forward with respect to the conventional forms. For this purpose, dendrimers, nanogels, nanoemulsions, liposomes, polymeric nanoparticles, solid lipid nanoparticles, and nanosuspensions have been investigated by many research groups for CNS delivery. The transport of these nano-delivery systems has been investigated by a set of methods including in vitro and in vivo BBB models by endocytosis and/or transcytosis, and early preclinical success for the management of CNS conditions such as Alzheimer’s disease, brain tumors, HIV encephalopathy, and acute ischemic stroke has become possible. Using avidinebiotin technology, chitosan nanoparticles conjugated with PEG bearing the OX26 monoclonal antibody have been formulated by Akta¸s et al. The purpose of this study was to deliver Z-DEVD-FMK peptide, which is a specific caspase inhibitor for the purpose of neuroprotection. The molecule itself cannot penetrate the BBB and diffuse into the brain tissue. In this formulation OX26, which is a specific antibody and has great affinity for the transferrin receptor, was used to enhance passage through the BBB. In experimental studies, it was proven that these nanocarriers had the ability to localize in brain tissue rather than the intravascular compartment by the methods of fluorescence labeling and scanning electron microscopy. Therefore, these nanocarriers were classified as promising systems to transport molecules through the BBB for the maintenance of neuroprotection [47]. In a complementary study by Karatas et al., this time Z-DEVD-FMK was encapsulated in anti-mouse transferrin receptor monoclonal antibody-functionalized chitosan nanoparticles, which have the capability of selectively recognizing transferrin type 1 on the cerebral vasculature. In experimental studies, it was demonstrated by intravital microscopy that the nanomedicine was rapidly transported across the BBB without being measurably taken up by the liver and spleen. Brain ischemia was formed by proximal occlusion of the right middle cerebral artery and nanoparticles were administered pre- or posttreatment (2 h) by intravenous injection. It was found that the chitosan nanoparticles significantly reduced infarct volume and neurological deficit in a dose-dependent fashion. In addition, the attenuation of ischemia and caspase-3 activity revealed that chitosan nanoparticles showed the capability of releasing sufficient amount of peptide to inhibit caspase-3 activity, resulting in sufficient neuroprotection [61].

11. Problems With Current Nanotechnology Concepts

It is a clear need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. Although there exist some molecules, such as adenosine, with enough pharmacological activity, their rapid clearance from the plasma and fast metabolization put them out of range for the treatment of neurodegeneration. For this purpose, the neuroprotective effect of squalenoyl adenosine nanoparticles was investigated by Gaudin et al. in a 2014 study. In this study adenosine was conjugated with lipid squalene for the preparation of nanoparticles. The efficacy of the nanoparticles has been investigated in two different animal models that include brain ischemia and spinal cord injury. The nanoparticles provided neuroprotection by improving the neurological deficit score after cerebral ischemia and by providing early motor recovery after spinal cord injury. In addition, it was proven that adenosine circulation was extended as well as the interaction with the neurovascular unit [62].

11. PROBLEMS WITH CURRENT NANOTECHNOLOGY CONCEPTS 11.1 DRUG LOADING One of the most important parameters in developing nanoparticle delivery systems is the encapsulation efficiency, which is the indicator of loading efficiency of the drug. Compared with the conventional drug-delivery systems, the size of the reservoir in which the drug molecule is loaded is extremely small. Depending on this small capacity, the drug molecules interact with the polymeric structure to a certain degree. In micellar nanoparticles, the maximum capacity of the drug that can be encapsulated is around 20%e30% with respect to the polymer amount. The reason for that is the limited capacity of interaction between the hydrophobic drug and the hydrophobic polymer. Hydrotropic polymers are under investigation to overcome this problem [63].

11.2 STABILITY AND STORAGE Depending on the polymeric structure of the drug-delivery system, a certain amount of water may be absorbed by the polymer under storage conditions. This absorption can further lead to the initiation of the degradation process of the polymeric structure. As a result of this cascade, a set of changes including physicochemical properties and in vivo performance may take place. The existence of impurities such as residual monomers and solvent and polymerization catalysts can also have effects on the shelf life of the drug product. As in all pharmaceutical products, storage conditions must be carefully defined and the product must be stored under appropriate inert conditions for maintaining the shelf life [64]. In an interesting study by Schroeder et al., the stability of nanosuspensions that were prepared using poly(butylcyanoacrylate)

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was investigated over the particle size distribution measurements for a certain period of time under three different conditions. The storage conditions were determined as hydrochloric acid, phosphate-buffered saline (PBS), and human blood serum. At certain time intervals, it was found that storage in PBS resulted in elevated polydispersity index values due to agglomeration; storage in human blood serum resulted in stable particle size distribution for at least 5 days, and finally, in acidic medium, the nanosuspensions maintained their stability for more than 2 months. The results of this study showed that acidic storage conditions might be an alternative to lyophilization and overcome the problems that are associated with reconstitution in some cases [65].

11.3 COMPLEXITY OF NANOCARRIERS The studies done on the manufacture of multifunctional, targeted, and more efficient nanoparticle delivery systems rendered them more complicated. The combination of many components in nanosized drug-delivery systems demands the collaboration of a number of disciplines. Because this complexity results in low yield of production, the cost of nanosystems is much higher with respect to that of conventional forms. Complex systems also have more variables in their physicochemical properties, which make it more difficult to predict the fate and action mechanism of the systems after they are administered into the human body.

11.4 TOXICITY ISSUES Although nanomaterials are highly promising platforms, many of their features may have a negative impact on the environment and human health [66]. Their unique properties are also a major cause of concern, because their effects on biological systems are still not known to the fullest. There exist concerns not only about the use of these nanopharmaceutical products, but also about the occupational and environmental risks that are associated with their production and disposal. Clear identification of the environmental and toxicity issues of nanomedicines is a rapidly growing concern that researchers nowadays are focused on [66]. Despite the clear fact that nanomedicines do provide clear benefits and advantages, the modification of the physicochemical properties of the components may lead to unidentified constraints. One significant example for this situation is the increased clearance time with respect to the increased circulation time and the fate of this prolonged existence within the body is not fully identified yet. As Singh et al. highlighted, in the cases of nanomaterials such as metal nanoparticles, metal oxide nanoparticles, quantum dots, fullerenes, and fibrous nanomaterials, which were found to induce chromosomal fragmentation, DNA strand breakages, point mutations, oxidative DNA adducts, and alterations in gene expression, safety especially becomes a major concern [67]. The aforementioned properties of nanopharmaceuticals make nanotoxicology inseparable from the multidisciplinary science of nanotechnology. Their fate, safety, and toxicity profiles must be fully identified, which keeps the position unresolved [19].

References

12. CONCLUSIONS As in all fields of science, nanotechnology brings new insights to conventional perspectives. Modification to the scale of nano provides new advantages and improvements that provide more efficient and useful touches for human life. Nanotechnology has started to gain importance in the field of medicine for drug delivery, gene therapy, imaging applications, biomarkers, biotechnology, and bioengineering science. The continuous evolution of the pharma industry has ingested the use of nanoscience especially for biotech products and targeting applications. Early diagnosis of crucial diseases and targeted delivery applications that provide lower dose treatments with fewer side effects have become the pioneer applications of nano in medical sciences. Drugs that are effective but unusable because of toxicity issues have started to gain much more importance with the encapsulation concept in nanodosage forms. In addition, delivery of two or more molecules in a single targeted nanosystem either for treatment or for imaging purposes has provided more effective medical options for patients. The search for these ideal nanosized drug-delivery systems, which can reduce the required dose, improve absorption and bioavailability, provide better compliance, target the drug to the desired area, and reduce or eliminate altogether the side effects, still continues. Despite these numerous advantages, considerable obstacles in technology transfer from the lab scale to manufacturing and in financial issues remain a challenge for the application of nanotechnology in our daily lives. As accepted worldwide, the regulatory authorities visualize all of the aspects of nanomedicines from bench to market, including the changes in the characteristics of the materials and safety issues. As a result, it is a clear fact that nanomedicine will continue to gain importance and many issues additionally need to be evaluated in this field. Proper methods with proper identification technologies are still needed to provide complete trust in the nano concept.

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