Particle Toxicology - Chapter 21 docx

21 Nanoparticles in Medicine Paul J. A. Borm Centre of ExpertiseinLife Sciences, Hogeschool Zuyd Detlef Mu ¨ ller-Schulte Magnamedics GmbH CONTENTS 21.1 Introduction 387 21.2 Particles in Nanomedicine: Health Benefitsand Perspectives 388 21.2.1 Imaging and Diagnostic Tools 388 21.2.1.1 Magnetic Particles 388 21.2.1.2 Fluorescent Nanoparticles 390 21.2.1.3 Quantum Dots 391 21.2.2 Nanomaterials and Nanodevices 392 21.2.3 Drug Delivery Tools 393 21.2.3.1 Liposomes 394 21.2.3.2 Magnetoliposomes 395 21.2.3.3 Dendrimers 397 21.2.3.4 Fullerenes 398 21.2.3.5 Polymer Carriers 398 21.2.3.6 Magnetic Nanocarriers 399 21.3 Hazardsand Risks of Nanoparticles 401 21.3.1 GeneralConcepts 401 21.3.2 Toxicological Effects of Nanoparticles 402 21.3.2.1 Effects on Blood and Cardiovascular System 402 21.3.2.2 Uptake and Effects of Nanoparticles in the Brain 402 21.3.3 Current Data on the Toxicology of EngineeredNanoparticles 403 21.3.3.1 Quantum Dots 403 21.3.3.2 Carbon Nanotubes 403 21.3.3.3 Fullerenes 404 21.3.3.4 Dendrimers 404 21.3.3.5 Wear Particles from Implants 404 21.3.4 Nanomaterials in Medicine: FutureToxicologicalNeeds 405 References 406 21.1 INTRODUCTION Recent yearshave witnessed unprecedented growth of researchand applications in the area of nanoscience and nanotechnology.There is increasing optimism that nanotechnology, as applied to medicine, will bring significant advances in the diagnosisand treatment of disease.Anticipated 387 © 2007 by Taylor & Francis Group, LLC applicationsinmedicine includedrugdelivery,diagnostics,nutraceuticals, andproductionof biocompatiblematerials (ESF 2005; Ferrari 2005;Vision Paper 2005). Engineered nanoparticles ( ! 100 nm) or nanostructured materials (NSM) are important tools to realize theseapplications. The reason why thesenanoparticles (NP) are attractive for such purposes is based on their important anduniquefeatures, such as theirsurface to mass ratio that is much largerthanthat of other particles, their quantum properties,and theirability to adsorband carry other compounds. NP have alarge (functional) surface that is able to bind, adsorb, and carry other compounds such as drugs,probes, and proteins. However, manychallenges must be overcome if the application of nanotechnology is to realize the anticipated improved understandingofthe patho-physiological basis of disease,bring moresophisticated diagnostic opportunities, and yield improved therapies. One of the mostchallengingproblems that nanotechnology is facing is posed by research data with combustion-derived nanoparticles (CDNP),such as diesel exhaustparticles (DEP). Research has demonstrated thatexposuretoCDNPisassociated with awidevariety of effects(review: Donaldsonetal. 2005) includingpulmonary inflammation, immune adjuvant effects(Granum andLovik 2002),and systemic effects including bloodcoagulationand cardiovascular effects (review: Borm and Kreyling 2004; Oberdo ¨ rster, Oberdo ¨ rster, and Oberdo ¨ rster 2005a; Oberdo ¨ rster et al. 2005b). Since cut-offsizefor their definition (100 nm) is the same, now both terms are used as equivalent. The meeting of the worlds of nanoscience and engineered nanoparticles alongwith Particle Toxicology and its know-how of ultrafines, has led to an impressive series of workshops over the past years. However, little exchange of methods and concepts has taken placeand therefore the aim of this chapter is to discuss applications of nanoscale materials in nanomedicine alongwith their toxicological properties. 21.2 PARTICLES IN NANOMEDICINE:HEALTH BENEFITS AND PERSPECTIVES Nanomedicine uses nano-sized toolsfor the diagnosis, prevention, andtreatmentofdisease to increaseunderstandingofthe underlying complexpathophysiological mechanisms. The ultimate goal is to improvequality of life. The aim of nanomedicine may be broadly defined as the compre- hensivemonitoring, control, construction, repair, defense,and improvement of all human biological systems, workingfrom the molecular level using engineered devices and nanostructures to ultimately achieve medicalbenefit. In this context, nanoscale should be takentoinclude active components or objects in the size range from one nanometre to hundreds of nanometres. They may be includedinamicro-device (that might have amacro-interface) or abiological environment. The focus,however, is always on nano interactions within aframework of alarger device or biologi- cally, within asub-cellular (or cellular)system. These definitions originate from aworking group initiated in early 2003 by the European Science Foundation (ESF 2005). 21.2.1 I MAGING AND D IAGNOSTIC T OOLS In thecourse of extending our knowledge in thefield of nanoparticles, the medicalarea has witnessed in the last few years increasing attemptstoexploit the intriguing perspectives nanotech- nologyoffers in medical diagnostics and analytics as well as look for asubstitution or assistant modalities for conventional x-ray analysis. It is realistic to say that nanotechnological tools will be routinely used in diagnosislong before beingapproved for the treatment of diseases. Some tools are already on the market or available on short-term, but many others still need considerable develop- ment(Table 21.1). 21.2.1.1 Magnetic Particles This in particular applies to magnetic nanoparticles and luminescent species that are applied for the detection of pathogeniccells or tissue (Table 21.2). Theprinciple is based on the specific targeting Particle Toxicology388 © 2007 by Taylor & Francis Group, LLC of these nanovectors onto the target tissue or cellwhich can afterwards be monitored either by magnetic resonance imaging (MRI), ultrasound, or optical screening proceduressuch fluorescence molecular tomography (Graves et al. 2005). Due to the enormous know how accumulated in the science area in the last decades, abroad spectrumofvarious nanocarriers have been developed which areabletomeet the medical needsand prerequisites.Thisapplies to (i)the magnetic properties, (ii) size adaptation,and (iii)specific tissue targeting. One of the key aims in modern diagnostics is undoubtedly the improvement and increaseof detection sensitivity, leading ultimately to adetection of neoplastic chances in cancerinthe earliest possiblestage. This aspect certainlyconstitutes the focus of present research and development. The magnetic properties of nanoparticles are primarily exploited in MRI—where the contrastofthe target tissue results from the diverse signal intensities this tissue deliversinresponse to aspecifi- cally applied radio frequencypulse. This response is afunction of the proton density and magnetic relaxation time, which on its part is determined by the biochemical structure, and properties of the TABLE 21.1 Anticipated Time Lines for Nano Based Diagnostic Tools Time IntervalAnticipated Development Particles Used 2005–2010 Cell sorting, on site detection in packaging, cell separation Magnetic or fluorescent beads with specific antibodies 2010–2015 Encapsulation, coating of contrast enhancement agents Magnetic beads, quantum dots, polymers with fluorescent markers 2010–2015 Biomimetic sensors Gels encapsulating antibodies and drugs 2015–2020 Transfection nanodevice, implantable devices, multifunctional cameras Complex multifunctional nanomaterials Source:Modified from ESF, European Science FoundationPolicy Briefing: ESF Scientific Forward Look on Nanomedicine 2005.IREG Strasbourg, France, ISBN, 2-912049-520, 2005. TABLE 21.2 Overview of Particles and Their Medical or Pharmaceutical Applications Particle Class Materials Size (nm) Payload Application Liposomes Lipid-mixtures 50–100 10% volume Drug delivery Magneto- liposomes Lipid mixtures 50–100 Ferrofluids Imaging, diagnostics,separation Dendrimers Branched polymers5–50 Drugs Drug delivery FullerenesCarbon based carriers Photodynamics Polymer carriers Dextrane 50–50,000 Drugs Drug delivery Polylacticacid Polysaccharides Poly(cyano)acrylates Polyethyleinemine Polymer magnetic carriers All above containing ferrofluids 50–50,000 Various Diagnostics, separation Quantum dots CdSe, Zns, Si 2–10 None Diagnostics Latex beads Polystyrene 20–2000 Markers (FITC) Diagnostics Silica-beads Amorphoussilica 20–10,000 Ferrofluids Diagnostics Nanoparticles in Medicine 389 © 2007 by Taylor & Francis Group, LLC tissue. Theeffect of the magneticnanoparticlesonthe relaxation timesistocreate localfield inhomogeneity, which consequently shortens the relaxation times resulting in an enhancement of the image contrast. In practice and especially for in vivo applications, the magnetic nanoparticles are coated with afunctional polymer that fulfils two major prerequisites: † The polymer serves as matrix for attaching disease relevantmoieties such as peptides, antibodies,orothersmall molecules that will bind to the pathologicaltarget. † The coating shouldassist the overall blood compatibility and in particularthe increaseof the blood half-lives, which is acrucial point as such particles are clearedbythe liver and spleen within afew minutes. Areview by Bulteand Brooks (1997) summarizes the diverse approacheswith special focus on varietyofcoatings and type of nanocarrier on the contrastbehavior. Thepotential of superparamagnetic iron oxide particles (SPIO) in MR lymphography using different administrationroutes and the usage of differently modified magnetic liposomes for the specific imaging of an adenocarcinoma in arat modelhave been addressed by Kresse, Wagner, and Taupitz(1997) andPa ¨ user et al. (1997).Likewise, Guimaraes et al.(1994) demonstrated the imaging of hyperplastic and tumorous lymph nodes in rodents using commercial SPIOs. Parallel to the preparation and optimization of the differentnanocarriers andironoxides, respectively, which was subject of diverse research(Tiefenauer, Kuhne, and Andres 1993; Grimmetal. 2000; Lawaczeck and Menzel 2004), the mode of applicability of these particlesisprimarily determined by the targeting possibility. This topic is basically addressed by the coupling of such targeting mediating species that show ahigh specific affinity towards the according target tissue or cell. Zhao et al. (2002) investigated the influence of the HIV-1 Tat peptide derivatized iron oxide nanopar- ticles for the uptake in cells. This peptide, which translocates exogenous molecules intocells, facilitates thecellular uptakeofthe nanoparticlesinanexponentialfashion andresults in a 100-fold increase in cell labeling efficiency. Further approaches addressing this topicpertain to the coating with galactosides(Weisslederetal. 1990)for the targetingofhepatocytes via the asialoglycoprotein receptor, anti-carcinoembryonic antigen CEA coupled magnetic nanoparticles as models for tumor targeting (Tiefenauer, Kuhne, Andres 1993), and antibody coated nanoparticles directed againstthe HT-29surface antigenshowing their basicapplicabilityasrelaxation and targeting agents (Cerdan et al. 1989). Lanza et al. (2004) concisely discuss the diverse aspects of molecularimaging includingthe physical magnetic parameters,the possibilities of active and passive targeting into the diverse organ tissues, ligand coupling strategies with the emphasize on antibodies, avidin and aptamers, and the spectrumofdiverse nanovectors ranging from gadolinium loaded perfluorocarbon-lipidparticles targeted towards fibrin, liposomes, and ab-integrin-targeted nanoparticles specially designed for the detection of angiogenesis. Jaffer andWeissleder(2005) reviewed thedifferent molecular imagingsystems, including MRI, nuclear, andopticalimaging.Theyalsoconducted asurveyabout thediverse imaging agents, their clinical applications with particularemphasis on cancer, atherosclerosis, apoptosis, and inflammatory enzyme activityimaging. Apart from nanocarriers, Mikawaetal. (2001) describe anew approach in MRI contrast enhancement by using water-soluble gadolinium metallofullerenes used for both in vivo and in vitro tests. They could show a20-fold higher relaxivity than that of the commercial MRIcontrast agent Magnevist w . In vivo MRI at lung, liver, spleen, and kidneyofmice corroborated these findings. 21.2.1.2 Fluorescent Nanoparticles Other types of nanoparticles that have attracted much interest in the last few years in the area of diagnostics are the optical markersinthe form of fluorescent nanoparticles.Imaging of cell-surface receptors, antigens, andgeneexpressions usingconventional fluorescentmolecular probes or Particle Toxicology390 © 2007 by Taylor & Francis Group, LLC fluorescent-taggedantibodies to trace tumor cells, apoptosis, and metastases have been described (Graves et al. 2005). Despite their broad usage and successful application, which has resulted in the development of fluorescencemolecular tomography, these probes have generally some disadvan- tages with regard to photo stability and show low in vivo biodegradability of tagged biomolecules, or they show inappropriate bio distribution. Hence, there is an ongoing tendency to use the potential of these fluorescent markersincombination with apolymer carriertoexploit their full potential for molecular imaging in medical diagnostics. The number of fluorescent molecules potentially used as markers in bioscience is underlined by thefactthatthere areanumber of companiesspecializinginthe commercializationofsuch compounds. In this review,wewill focus solely on two issues, namely, dye-doped silicacarriers and quantum dots, as these appeartoprovide the most promising perspectives in this area. Based on the well-known Sto ¨ ber suspension process for the preparation of monodispersesilicananoparticles, several researchershave used this intriguing technology to create fluorescent markers. Because of the pronounced functionality of the silica matrix, isothiocyanate derivatized fluorophores in the form of rhodamine and fluorescein were directly coupled to the matrix. This approach was inten- sively studied by van Blaaderen(2006), aiming to develop the coupling chemistry on derivatized nanoparticles, their fluorescence properties in different solvents, and the diverse physical character- ization using, e.g., lightscatteringand transmission electron microscopy.Analternative route (Santra and Biomoleku ¨ le et al. 2005)uses aW/O micro emulsion of afluorescein-isothiocyanate derivatized silane precursors to obtain dye-doped nanocarriers. To demonstrate the bio imaging potential of thesemarkers, the nanocarriers were modified with the Tat peptide and folic acid. Incubating these carriers with A-549 and lung adenocarcinoma cells revealedanextensive cell labeling. Afurther basic method of preparing dye labeledparticleswas recently described (Graf et al. 1999) usingamulti-step core-shellapproach whoseaim is to protectthe encapsulated fluorophores such as rhodamine B, coumarin, and pyrene with asilane layer. 21.2.1.3 Quantum Dots Compared to conventional organic fluorescent dyes, quantum dots—nanocrystalline semiconduc- tors for bioimaging purposes mainlycomposed of III–V materials, e.g., GaP, GaAs, and INAs or II–VI materials, e.g., CdSe,CdS, ZnSe—represent anovel class of marker systemswith unique optical properties (Figure 21.1). This is first of all reflected by the size- and composition-tunable fluorescence emission from visible to infrared light. By reducing the sizeofthe nanocrystal, we observe ablue shift and vice versainthe emission (Murphy 2002; Parak et al. 2003). Together with thelarge absorptioncoefficientacrossawide spectral range, thehighquantum yield,longer fluorescentdecay timesincomparison to conventional dyes,and pronounced photostability, these nanocrystalsare an idealmarker for bioimaging. However, to applythese nanocrystals for in vivo imaging, two pre-requisites need to be fulfilled: the quantum dots mustbewater dispersible, and, due to the high toxicity of the basicchemical constituents, they have to be coated with a biocompatible matrix.Thispreventsdirectcontactwith thebiologicaltissuethus preventing toxicity (Chenand Yao2004). This is achieved by coatingthe nanocarrierswitharange of diverse polymersand surfactants. Most promising approaches fulfilling the basic purposes are siloxanes, polyethylene glycol, phospholipids,carboxymethyldextran, mercaptoacetic acid, dithio- threitol,glutathione, or synthetic polymers, e.g., in form of ablockcopolymers (Hirai, Okubo, and Komasawa 2001; Winter et al. 2001; Dubertret et al. 2002; Chen, Ji, and Rosensweig 2003; Parak et al. 2003; Gao et al. 2004). Apart from the stabilization, the chemical functionality of the coatings also provides abasis to attachtarget-finding bioligands to the surface that paves away in in vivo imaging. Promisingapproaches in this field include theattachmentofspecific antibodiesor peptides forneurontargeting(Winter), DNA couplingfor thedetection of nucleotide poly- morphism (Parak et al. 2003), and antibody and streptavidin for labeling breast cancer cells (Wu et al. 2003; Gao et al. 2004). Apart from the bioimaging application,quantum dots are also very Nanoparticles in Medicine 391 © 2007 by Taylor & Francis Group, LLC suitable for optical coding in the scope of bioassays. Han et al. (2001) recently described multicolor polystyrene CdSe/ZnS nanocrystals for multiplexed optical coding of biomolecules.The extremely high number of possiblecodeswhenusing multiple wavelengths andmultiple intensities are exemplarily demonstrated in aDNA hybridization assay. We recently described anew approach forhighlyfluorescentmarkersystems. Usinganovelinversesol–gelsuspensiontechnique, quantumdotsand fluorescence dyes canbeeasilyencapsulated in aone-step procedureinto silica nano- andmicrobeads(Mu ¨ ller-Schulte 2004, Mu ¨ ller-Schulteetal. 2005). The intriguing aspectofthis novel technique is that it allowsasynthesisoffluorescent carriers withinafew minutes thus providing asignificant time saving in comparison to established methods, as well as asimultaneous combinatorialencapsulation of diverse fluorescent compounds and magnetic colloids. This opens up novel perspectives for cell screening and bioassays. 21.2.2 N ANOMATERIALS AND N ANODEVICES Nanomaterials and nanodevices are criticalinnanomedicine. On the one hand, the principles of materials science may be employed to identify biological mechanisms and develop medical thera- peutics.Onthe otherhand, theopportunitiesofnanomedicinedependonthe appropriate nanomaterialsand nanodevices to realizetheir potentials. Nanomaterials andnanodevices for nanomedicine are produced largely based on nanoscale assemblies for targeting and ligand display. Thefield of medicalimplants is fast growing since new, light, durable, and biocompatible implants can be constructed on atailor-madebasis. Medical implants are being used in every organ of the humanbody. Ideally, medicalimplants must have biomechanical properties comparable to thoseofautogenous tissues without any adverse effects. In each anatomic site, studies of the long- term effects of medicalimplants must be undertaken to determine accurately the safety and per- formance of the implants. Today, implant surgery has become an interdisciplinary undertaking involving anumber of skilled and gifted specialists. Applications can be identified for each implant site, from orthopaedics, dentistry,tocardiovascular surgery. Artificial hips on one hand need to be fixed steadily in the bone while on the other hand the knob needs to be flexible, biocompatible, and not subject to wearing. Thesuccess of total hip replacement dependsinpart on the materials, design, and processing of the materials used in the implant. During surgery, the painful parts of the Cdse QD core-shell (e.g., CdSe/ZnS) Bioactivecoating (e.g., protein, peptide) 5nm Quantum dot ZnS FIGURE 21.1 QDs consist of ametalloid core and acap/shell that shields the core andrenders the QD bioavailable. The further addition of biocompatible coatings or functional groups can give the QD adesired bioactivity. (Reproduced fromHardman, R., Environ. Health. Perspect.,114,165–172,2006. With permission.) Particle Toxicology392 © 2007 by Taylor & Francis Group, LLC damaged hip are replacedwith artificial hip parts, which make up the prosthesis—adevice that substitutes or supplementsajoint.Toduplicate theactionofaball-and-sockethip joint, the prosthesis has three parts (Figure21.2): † The stem, usually made from metal which has to be fixed in the bone † The ball or head, madeofceramic or metal † The shell and accompanying liner, with the shell made of metal and the liner made of cross-linked polyethylene.The liner may also be madeofceramic or metal. 21.2.3 D RUG D ELIVERY T OOLS Drug deliveryand related pharmaceutical development in the context of nanomedicine should be viewed as scienceand technology of nanometresizescale complexsystems (10–1000nm), consistingofatleast twocomponents,one of whichisanactive ingredient(Duncan 2003; Ferrari 2005). Thewholesystemleads to aspecialfunction relatedtotreating,preventing,or diagnosing diseases,sometimescalled smart-drugsortheragnostics (LaVan,McGuire,and Langer 2003). Depending on the origin, the materials employed include synthetic or semi-synthetic polymersand natural materials such as lipids, polymers, and proteins (Aston 2005). The primary goals for researchofnanobiotechnologies in drug deliveryinclude: –Faster development of new safe medicines, –More specific drug deliveryand targeting,and –Greater safety and biocompatibility. Currently, the development of anew drug is estimated at over 700 billion euro, and the number of FDA approvals has been gradually decreasing over the past decade. It is anticipated that with the Acetabular shell Polyethylene liner Femoral head Longevity highly crosslinked polyethylene surface Neck Stem FIGURE 21.2 Schematical depiction of the building parts of an artificial hip, which is probably the most successful medical implant over the past 20 years. Dependent on the material and the wear forces, every step causes the release of asignificant amount of particles (wear debris) into the surrounding tissue. Nanoparticles in Medicine 393 © 2007 by Taylor & Francis Group, LLC help of nanoscience, so-called orphan drugs may be further developed and drugs that were elimi- nated in the development of the process may be reactivated. However, the pharmaceuticalindustry is currently showing little interest and major developments occur in academia. It is therefore quite obvious that the nanomaterialssegment,which includesseveral long-established marketssuch as carbon black rubber filler, catalytic converter materials, and silver nanoparticles used in photo- graphic films and papers, presently accounts for over 97.5% of global nanotechnology sales. By 2008, the nanomaterials shareofthe market will have shrunkto74.7% of total sales (BCC 2004). Nanotools will have increased their share to 4.3% ($1.2 billion), and nanodevices will have estab- lished amajor presence in the market with a21% share($6.0 billion).The Life Science applications are thought to inducethe latter increase. Themain issues in the search for appropriatecarriers as drug delivery systems pertain to the following topics that are basic prerequisites for design of new materials. They comprise (i) biocom- patibility, (ii)biodistribution, (iii) functionality,(vi)targetingand (v)drugincorporationand releaseability. Certainly none of the so far developed carriers fulfill all of these parameters to the full extent; the progress made in nanotechnology,inter alia, emerging from the progress in the polymer-chemistry, however, can provide an intriguing basis to tackle this issueinapromising way.The following paragraphs briefly discuss different particle types currently used in nanome- dicine for drug delivery. 21.2.3.1 Liposomes One of the earliest approachesinthe field of drug deliveryconcerns liposomes that are nanovesicles composed of phospholipids. Starting with the pioneering work by Gregoriadis (1973) and later by Fendler (1977),the cell-like structure of these vectors and their enormous chemical and physical versatility in terms of size, lipid composition, surface charge, fluidity,surface functionality, and drug incorporationability make these carriersthe material of choice when approachingthese subjects. Due to the potential variety of the liposomes,researchershave pursued diverse routes in the development in order to fulfill the above-defined parameters. Bio- and blood compatibility represent the starting prerequisites for acarrierdesign because they directly determine the blood half-lifeand hencethe pathwayand biodistributionofaparticle.Several attemptshavebeen describedtodesign liposomesavoidingthe uptake by theimmunesystem—particularly the reticuloendothelial system (RES), to clear foreign bodies—andtoenhanceblood half-life from generally less than one hour to several hours.Thisobjective has been addressedbymodifying the liposomesurface.Iga et al. (1994) tested various lipid compositions and found that the incorpor- ation of negatively charged polyoxyethylene-stearyl-derivatives revealed the greatest reduction in RESuptake. This is caused by thenegative charge andthe specific chain length of thepoly- oxyethylenes. The mostpromisingapproachinenhancing liposome bloodhalf-life comes from preparations, whichincorporated either monosialogangliosidesorpolyethyleneglycols into the lipid membrane. Several authors (Gabizonetal. 1990; Allenand Hansen 1991;Torchilin et al. 1994)have comprehensivelyaddressedthis issue leading to the concept of so-called stealth lipo- somes.Sphingomyelin–eggphosphatidylcholine–cholesterol-composed liposomes with ahalf-life of over 20 hshow adosage-independence of blood clearance (Allen and Hansen 1991). The reason forthiseffectismainly attributedtothe sterical hindrance of opsonins.Apart from directly influencing theblood-half lives,the compositionand derivatization of thelipids also exert an impact on thetissuedistributionofthe vesicles.Thisand theaspectsconcerning, amongst others,the stability, RESuptake, pharmacokinetics, lipid composition, particles size,surface modification, andsurface charge have been conciselyreviewedbyWoodleand Lasic(1992). Following thedevelopmentofproviding appropriate routes forfundamentally improvingthe biocompatibility and biodistribution, the application of thesenanovectors notably in cancer thera- pies also require functionality,i.e., thepossibilitytoattachtargeting findingmoietiestothe liposomesurface thus enabling tissue targeting.Several researchgroups,whereby mainlytumor Particle Toxicology394 © 2007 by Taylor & Francis Group, LLC antibodies were attached via the functional lipid phosphatidylethanolamine, have addressedthis objective. Jonesand Hudson describeanti-placentalalkaline phosphatase antibodies linked to immunoliposomes that could be effectively targeted to tumor cells. Similarly, specific antibody- linked polyethyleneglycol liposomes containing entrappeddoxorubicin, targeted to KLN-205lung carcinoma cells, were capable of reducing the tumor in amice model significantly (Ahmad et al. 1993). The almost unlimited application potential of the liposometechnology is furthermore under- linedbyresearch done by Flasher, Konopka,and Chamow (1994),who targeted CD4coated liposomes to immunodeficiency virustype 1-infectedcellsopening up novelperspectivesin another highly explosivemedical area. The final parameter to be addressed and which determines the efficacy and applicability of a drug carrier is the incorporation capacity for aspecific drug and its release once the target tissue has been reached (Figure21.3). Several authors (Kim 1993; Allen 2002; Park 2002)have reviewed this issue anddescribeamultitudeofwell-known anti-cancer drugsinliposomeformulations,the targeting aspect, and the medicaltherapeutic background. Based on the amount of publications, liposomebased papers represent by far the biggest portion in this list followed by polymer nano- particles. Despite somedrawbacks of the liposome concept regarding mainly lackofchemical, biological, and physical stability, the commercialization of liposometumor therapeutics amounting to more than $200million US in the year 2003 underlines the promising basis of this technology (Wagner and Wechsler 2004). 21.2.3.2 Magnetoliposomes In the last two decades, there has been an increasing trend to render particle carriers magnetic. While magnetic nano- and microparticles and -beads are already fully established in the area Red blood cell Neovascular endothelum Drug Tumour cell Cytotoxic payload released into targeted cancer cell, leading to cell death Irradation activates nanoparticles Normal cell Blood vessel FIGURE 21.3 ( See color insert)Multi-component targeting strategies using nanoparticles in treating cancer. Nanoparticles extravasate into the tumor stroma through the fenestrations of the angiogenic vasculature, demon- strating targeting by enhanced permeation and retention. The particles carry multiple antibodies, which further target them to epitopes on cancer cells, and direct antitumour action. Nanoparticles are activated and release their cytotoxic action when irradiated by external energy. Not shown: nanoparticles might preferentially adhere to cancer neovasculature and cause it to collapse, providing anti-angiogenic therapy. The red blood cells are not shown to scale; the volume occupied by ared blood cell would suffice to host 1–10 million nanoparticles of 10 nm diameter. (Reproduced from Ferrari, M., Nat. Rev.,5,161–171, 2005. With permission.) Nanoparticles in Medicine 395 © 2007 by Taylor & Francis Group, LLC of molecule and cellseparation, this concept is just beginningtopenetrate the medical area. The intriguing perspectives are: (i) to maneuver or target these carriers into special locations or tissues using ahand or aelectromagnet and (ii) to inductively heat up these magnetic particlesinanhighfrequencymagnetic field (induction coil)withinthe scope of tumor hyperthermia. De Cuyper and his group conducted pioneering work for the synthesis and modification of magnetoliposomes. This technique comprises adialysis procedure of preformed lipid vesicles in the presence of lauric acid-coatedmagnetite nanoparticles (DeCuyper and Joniau 1988; De Cuyper 1996). Hodenius et al. (2002) described the modification of the magnetoliposomes with biotinylated lipids for streptavidin targeting. Viroonchatapan et al. (1995) presented thermosensitive dextran magnetite-incorporated liposomes with varying magnetite contentsfor application in hyperthermia and for potential cancertreatments. Ito et al. (2004) described real-life applications of magnetic immunoliposomes for tumor treatment. Anti-HER2 antibodies were attached to the vesicles and showed 60% incorporation into SKBr3 cells. Subsequent exposure of the cells to 42.58 Cusingan alternatingmagneticfieldresultedinastrong cytotoxic effect. Shinkaietal. (1994) prepared magnetoliposomes for hyperthermia treatment of cancerbycoating aspecial lipid composition onto magnetite particles. The nanovectors carrying antibodies directed to the surface antigensof humancolonic cancercells BM314 and glioma cells U251-SP showed a12times more efficient cell uptakethancontrol cells.Zhang et al.(2005)investigatedthe potential of negatively charged paclitaxel magneticliposomes as carriersfor breast carcinomavia parenteral administration. Their studies demonstrated that these magnetoliposomes could be delivered to tumors more effec- tivelythan conventional vesicles, resulting in ahigher potency on the therapy of breast cancerthan otherformulations. Anew potential approach using surface modified magnetoliposomes (MP) in HIV-infection was described by Mu ¨ ller-Schulte et al. (1997),asshowninFigure 21.4.Due to the dramatic development of this infection worldwide, the lack of effectivedrugs,aswell as adisappointing perspectivefor vaccination treatments, newtherapeuticmeasuresare highly desirable. The approach described exploits the heat sensitivity of HIV-virusesthat are known to be irreversibly inactivated at 508 C–60 8 C. Thus heat treatment is applied in this method: magnetoliposomes with asizeof50–100 nm are injected into the patient. To direct the MP to the site of the infection, one can exploit the same biochemical mechanism that HIVuses to infect the target cells (mainly T4 helper/inducer cellsand macrophages). This initial infectionisbrought aboutbythe interaction of the HIVenvelope proteingp120 with the CD4 receptorofthe T4 helper cell. This leads to the incorporation of the virus in the target cell, which then triggers all the required steps for virus proliferation. To target the liposomes, theseCD4 receptors are chemically bound to the vesicles. With this receptor, the MP imitatethe target cells and can hence bind to the gp120 envelope proteinofHIV, as well as the HIV infected cells which also contain the gp120 ligand. The concomitant presence of the gp120 envelope protein on the infected cells is aresult of the infection andproliferationprocess respectively (budding process). This opensupthe exiting perspectivetosimultaneously target the MP to the HIV infected cells. After MP are administered and attached to the target organs(HIV and infected cells), the magnetic liposomes are inductively heated up to the appropriate temperatures of 508 C–60 8 Cusinganexternal high frequent alternating magnetic field (induction heating). Such induction devices are state-of-the- art. Thespecial technique makes it possiblefor only the viruses and infected cells to be heated up, not theresidualtissue. This is achieved by selecting specificfrequencies that abrogate couplingofthe tissue so that allthe energyisadsorbedbythe liposomes. This selective heatingalsoallows theapplicationofhighertemperatures ( O 508 C),thus shorteningthe overall duration of treatment to afew minutes. The courseofthe disease can be monitored after each treatment by using, e.g., the T4 count.Depending on infection status,anadditional treatment can be applied any time. Particle Toxicology396 © 2007 by Taylor & Francis Group, LLC [...]... mediators (IL-1, IL-6, TNF-a, GM-CSF, PGE2) and bone resorbing activity (review: Ingham and Fisher 2005) Induction of bone resorbing activity in particle- stimulated macrophage supernatants has been shown to be dependent upon particle size and particle concentration Particles with a mean size of 0.24 mm stimulated bone resorption at a ratio of 10 mm3/cell Larger particles failed to stimulate bone-resorbing... to cytokine production, particles in the 0.1–1.0 mm-sized range at a volumetric concentration of 10–100 mm3 of particles per cell are the most biologically reactive In vitro studies have indicated that, of the numerous cytokines, TNF-a is a key osteolytic cytokine generated by particle- stimulated macrophages Algan, Purdon, and Horowitz (1996) showed that addition of anti-TNF-a antibody was able to... Morales, M D., Veintemillas-Verdaguer, S., Gonzalez-Carreno, T., and Serna, C J., The preparation of magnetic nanoparticles for applications in biomedicine, J Phys D: Appl Phys., 36 (13), R182–R197, 2003 Tiefenauer, L X., Kuhne, G., Andres, and R Y., Antibody magnetite nanoparticles—in-vitro characterization of a potential tumor-specific contrast agent for magnetic-resonance-imaging, Bioconj Chem., 4(5),... nanoparticles: a nonviral vector for in vivo gene delivery and expression in the brain, Proc Natl Acad Sci., 32, 11539–11544, 2005 Borm, P J A., Particle toxicology: from coal mining to nanotechnology, Inhal Toxicol., 14, 311–324, 2002 Borm, P J A and Kreyling, W., Toxicological hazards of inhaled nanoparticles-potential implications for drug delivery, J Nanosci Nanotechnol., 4, 521 531, 2004 Brannon-Peppas,... ultra-high molecular weight polyethylene particles, J Biomed Mater Res Appl Biomater., 53, 490–497, 2000 © 2007 by Taylor & Francis Group, LLC 408 Particle Toxicology Gregoriadis, G., Drug entrapment in liposomes, FEBS Lett., 36, 292–296, 1973 Grimm, J., Karger, N., Lusse, S., Winoto-Morbach, S., Krisch, B., Muller-Hulsbeck, S., and Heller, M., Characterization of ultrasmall paramagnetic magnetite particles... Application DE 4412651, 1995 ¨ Muller-Schulte, D., Separating, detecting or quantifying biological materials using magnetic cross-linked polyvinyl alcohol, US-Patent 6,514,688, 2003 ¨ Muller-Schulte, D., Luminescent, spherical, non-autofluorescent silica gel particles with changeable emision intensities and emission frequencies, Eur Patent Application PCT/EP 03/03163, 2004 ¨ ¨ Muller-Schulte, D., Fussl, F., Lueken,... source of particles and nanoparticles These particles consist of micro- and nanoparticles and may invoke immune and other responses Particulate debris can be generated following total joint replacement as a result of either wear or corrosion Wear of the polyethylene (PE) acetabular cup articulating against the hard metal or ceramic femoral head (see Figure 21. 1) leads to the generation of PE particles... pathways Such tests are not routine in protocol toxicology of medical devices and need to be discussed 3 Effects of combustion derived nanoparticles in environmentally exposed populations mainly occur in diseased individuals (see also Chapter 14 and Chapter 15) Typical pre-clinical screening is almost always done in healthy animals and volunteers and risks of particles may therefore be detected at a very... Group, LLC 402 21. 3.2 TOXICOLOGICAL EFFECTS Particle Toxicology OF NANOPARTICLES As already discussed in other chapters of this book, NP exert some very special properties that are very relevant in the further design of toxicity testing of engineered nanomaterials The first issue is that of cardiovascular effects and the second is of penetration and effects in the central nervous system 21. 3.2.1 Effects... http://www.bccreserach.com/editors/RGB-290.html Bell, J., Tipper, J L., Ingham, E., Stone, M H., Wroblewski, B M., and Fisher, J., Quantitative analysis of UHMWPE wear debris isolated from the periprosthetic femoral tissues from a series of Charnley total hip arthroplasties, Bio-med Mater Eng., 12, 189–201, 2002 ¨ ¨ Bergemann, C., Muller-Schulte, D., Oster, J., Brassard, L., and Lubbe, A S., Magnetic ion-exchange nano- and microparticles . 402 21. 3.3 Current Data on the Toxicology of EngineeredNanoparticles 403 21. 3.3.1 Quantum Dots 403 21. 3.3.2 Carbon Nanotubes 403 21. 3.3.3 Fullerenes 404 21. 3.3.4 Dendrimers 404 21. 3.3.5 Wear Particles. Perspectives 388 21. 2.1 Imaging and Diagnostic Tools 388 21. 2.1.1 Magnetic Particles 388 21. 2.1.2 Fluorescent Nanoparticles 390 21. 2.1.3 Quantum Dots 391 21. 2.2 Nanomaterials and Nanodevices 392 21. 2.3. Nanoparticles 401 21. 3.1 GeneralConcepts 401 21. 3.2 Toxicological Effects of Nanoparticles 402 21. 3.2.1 Effects on Blood and Cardiovascular System 402 21. 3.2.2 Uptake and Effects of Nanoparticles