Nano-oncology: drug delivery, imaging, and sensing

Nanoparticle detection of respiratory infection

Respiratory viruses are a constant concern for all demographics. Examples include established viruses such as respiratory syncytial virus (RSV), the leading cause of respiratory infection in infants and young children, and emerging viruses such as severe acute respiratory syndrome (SARS), which reached near pandemic levels in 2003, or H1N1 (swine) influenza. Despite this prevalence, traditional methods of virus detection are typically labor intensive and require several days to successfully confirm infection. Recently, however, nanoparticle‐based detection strategies have been employed in an effort to develop detection assays that are both sensitive and expedient. Each of these platforms capitalizes on the unique properties of nanoparticles for the detection of respiratory viruses. In this article, several nanoparticle‐based scaffolds are discussed.Gold nanoparticles (AuNPs) have been functionalized with virus specific antibodies or oligonucleotides. In each of these constructs, AuNPs act as both an easily conjugated scaffolding system for biological molecules and a powerful fluorescence quencher. AuNPs have also been immobilized and used as electrochemical transducers. They efficiently serve as a conducting interface of electrocatalyic activity making them a powerful tool in this application. Quantum dots (QDs) posses unique fluorescence properties that have also been explored for their application to virus detection when combined with direct antibody conjugation or streptavidin‐biotin binding systems. QDs have an advantage over many traditional fluorophores because their fluorescence properties can be finely tuned and they are resistant to photobleaching. The development of these nanoparticle‐based detection strategies holds the potential to be a powerful method to quickly and easily confirm respiratory virus infection. WIREs Nanomed Nanobiotechnol 2010 2 277–290

This article is categorized under: 1

Diagnostic Tools > In Vitro Nanoparticle-Based Sensing

2

Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease

What is cancer nanotechnology?

Cancer nanotechnology has the potential to dramatically improve current approaches to cancer detection, diagnosis, imaging, and therapy while reducing toxicity associated with traditional cancer therapy (1, 2). In this overview, we will define cancer nanotechnology, consider issues related to application of nanotechnology for cancer imaging and therapy, and broadly consider implications for continued development in nanotechnology for the future of clinical cancer care. These considerations will place in perspective the methodological approaches in cancer nanotechnology and subject reviews outlined in this volume.

Computational methods to predict the reactivity of nanoparticles through structure-property relationships

IMPORTANCE OF THE FIELD

Innovative biomedical techniques operational at the nanoscale level are being developed in therapeutics, including advanced drug delivery systems and targeted nanotherapy. Given the large number of nanoparticles that are being developed for possible biomedical use, the use of computational methods in the assessment of their properties is of key importance.

AREAS COVERED IN THIS REVIEW

Among the in silico methods, quantum mechanics is still used rarely in the study of nanostructured particles. This review provides an overview of some of the main quantum mechanics methods that are already used in the assessment of chemicals. Furthermore, classical tools used in the chemistry field are described, to show their potential also in the pharmacological field.

WHAT THE READER WILL GAIN

The current status of computational methods in terms of availability and applicability to nanoparticles, and recommendations for further research are highlighted.

TAKE HOME MESSAGE

The in silico modelling of nanoparticles can assist in targeting and filling gaps in knowledge on the effects of these particular particles. Computational models of the behaviour of nanoparticles in biological systems, including simulation models for predicting intermolecular interactions and harmful side effects, can be highly valuable in screening candidate particles for potential biomedical use in diagnostics, imaging and drug delivery.

Viral nanoparticles as platforms for next-generation therapeutics and imaging devices

Nanomaterials have been developed for potential applications in biomedicine, such as tissue-specific imaging and drug delivery. There are many different platforms under development, each with advantages and disadvantages, but viral nanoparticles (VNPs) are particularly attractive because they are naturally occurring nanomaterials, and as such they are both biocompatible and biodegradable. VNPs can be designed and engineered using both genetic and chemical protocols. The use of VNPs has evolved rapidly since their introduction 20 years ago, encompassing numerous chemistries and modification strategies that allow the functionalization of VNPs with imaging reagents, targeting ligands, and therapeutic molecules. This review discusses recent advances in the design of "smart" targeted VNPs for therapeutic and imaging applications.

FROM THE CLINICAL EDITOR

This review focuses on viral nanoparticles, which are considered attractive naturally occurring nanomaterials due to their inherent biocompatibility and biodegradability. These can be used as imaging reagents, targeting ligands and therapeutic molecules.

Targeting the efficacy of a dendrimer-based nanotherapeutic in heterogeneous xenograft tumors in vivo

Our earlier studies have shown the in vitro and in vivo targeting of a generation 5 (G5) dendrimer-based multifunctional conjugate that contained folic acid (FA) as the targeting agent and methotrexate (MTX) as the chemotherapeutic drug. To clinically apply the synthesized G5-FA-MTX nanotherapeutic, it is important that the anticancer conjugate elicits cytotoxicity specifically and consistently. Toward this objective, we evaluated the large-scale synthesis of a G5-FA-MTX conjugate (Lot # 123-34) for its cytotoxic potential and specificity in vitro and in vivo. The cytotoxicity and specificity were tested by using a coculture assay in which FA receptor-expressing and nonexpressing cells (KB and SK-BR-3 cells, respectively) were cultured together and preferential killing was examined. The in-vitro data were compared with the in-vivo data obtained from a heterogeneous xenograft tumor model. The animal model of the artificial heterogeneous xenograft tumor showed that the nanotherapeutic was preferentially cytotoxic to KB cells.

Invitro application of gold nanoprobes in live neurons for phenotypical classification, connectivity assessment, and electrophysiological recording

Thermoregulatory neurons in the preoptic area of the anterior hypothalamus (POA) form synaptic networks, which affect responses that regulate body temperature. To characterize these pathways of activation, projections to effector control areas, like the dorsomedial hypothalamus (DMH), require labeling in live tissue slices. Traditional fluorescent dyes label axon terminals near an injection site, but unfortunately, also that of nearby fibers of passage. Here, we describe a novel methodology for retrograde labeling of neurons in vitro, which will allow for further electrophysiological recording. To determine if POA neurons project to the DMH, we have used nanometer-sized, gold nanoprobes, which provide for specific neuronal entry, via synapses in close proximity to the injection site. Upon neuronal entry, these nanoprobe complexes diffuse to the soma, where they are readily visualized and quantified. We found that conjugation of these gold nanoprobes with VGLUT-2 antibodies and polyethyleneimine (PEI) facilitates neuronal entry and a high level of labeling efficacy. This novel method, adapted from emerging cancer therapy technologies, is highly specific for determining axon terminal projections within particular neuronal populations, while maintaining neuronal viability for targeted live cell electrophysiological recording.

Gold nanocages for cancer imaging and therapy

Gold nanocages are hollow nanostructures with porous walls that can be simply prepared via the galvanic replacement reaction between silver nanocubes and chloroauric acid. Their optical resonance peaks can be precisely tuned into the near-infrared region, in which the adsorption caused by blood or soft tissue is essentially negligible. Significantly, the strong absorption of gold nanocages makes them attractive as a novel class of contrast enhancement and photothermal agents for cancer detection and treatment. The well-established chemistry for gold also allows them to target specific cells by functionalizing their surface with various moieties such as antibodies, peptides, and DNAs. In this chapter, we focus on their use as a photothermal agent for the ablation of cancer cells and as a contrast agent for the in vivo noninvasive photoacoustic imaging of blood vessels and the sentinel lymph nodes in rats.

Review on early technology assessments of nanotechnologies in oncology

Nanotechnology is expected to play an increasingly important role in the diagnostics, prognostics, and management of targeted cancer treatments. While papers have described promising results for nanotechnology in experimental settings, the translation of fundamental research into clinical applications has yet to be widely adopted. In future, policy makers will need to anticipate new developments for clinical implementation and introduce technology assessments. Here we present an overview of the literature on the technology assessments that have already been undertaken on early stage nanotechnology in cancer care, with particular emphasis placed on clinical efficacy, efficiency, logistics, patient-related features and technology dynamics. Owing to the current stage of development of most nanotechnologies, we found only a limited number of publications describing the application of either Health Technology Assessment (HTA) or Constructive Technology Assessment (CTA). In spite of the promising conclusions of most papers concerning the benefits of clinical implementation, actual clinically relevant applications were rarely encountered, and so far only a few publications report application of systematic forms of technology assessment. Most articles consider aspects of environmental safety, regulation and ethics, often mentioning the need to investigate such issues more thoroughly. Evaluation of financial and organizational aspects is often missing. In order to obtain a realistic perspective on the translation and implementation process there is a need for a broad and systematic evaluation of nanotechnologies at early stages of development. Assessment methods taking technology dynamics into account, such as Constructive Technology Assessment (CTA) should be considered for evaluation purposes.

Viruses and their potential in bioimaging and biosensing applications

Successful development of ultrasensitive constructs for bioimaging and biosensing is a challenging task. Recently, viruses have drawn increasing attention due to their exquisite three-dimensional structures and unique properties, including multivalency, orthogonal reactivities, and responsiveness to genetic modifications. With such well-characterized structures, functional units, such as imaging and binding motifs, can be engineered on the surface of viruses in a programmable, polyvalent manner, which leads to novel nanosized sensing/imaging systems with enhanced signaling and targeting performance. This review highlights some recent progress in the applications of viruses in bioimaging and biosensing.

TSPO targeted dendrimer imaging agent: synthesis, characterization, and cellular internalization

While it has become common practice for dendrimers to deliver imaging and therapeutic agents, there are few reported examples of cellular internalization of dendrimers. Moreover, targeting of dendrimers to the mitochondria in cells has not yet been reported. Previously, we have delivered small molecule imaging agents into glioma and breast cancer cells by targeting the translocator protein (TSPO; formerly known as the peripheral benzodiazepine receptor or PBR) with a family of high-affinity conjugable ligands. The 18 kDa multimeric TSPO is expressed in steroid-producing cells, primarily on the outer mitochondrial membrane. This protein is a prime candidate for molecular targeting because tumors and other disease-related cells contain high densities of TSPO. Here, we present the synthesis, characterization, and cellular internalization into C6 rat glioma cells of a TSPO targeted dendrimer imaging agent.

Silver nanoparticles inhibit VEGF-and IL-1beta-induced vascular permeability via Src dependent pathway in porcine retinal endothelial cells

The aim of this study is to determine the effects of silver nanoparticles (Ag-NP) on vascular endothelial growth factor (VEGF)-and interleukin-1 beta (IL-1β)-induced vascular permeability, and to detect the underlying signaling mechanisms involved in endothelial cells. Porcine retinal endothelial cells (PRECs) were exposed to VEGF, IL-1β and Ag-NP at different combinations and endothelial cell permeability was analyzed by measuring the flux of RITC-dextran across the PRECs monolayer. We found that VEGF and IL-1β increase flux of dextran across a PRECs monolayer, and Ag-NP block solute flux induced by both VEGF and IL-1β. To explore the signalling pathway involved VEGF- and IL-1β-induced endothelial alteration, PRECs were treated with Src inhibitor PP2 prior to VEGF and IL-1β treatment, and the effects were recorded. Further, to clarify the possible involvement of the Src pathways in endothelial cell permeability, plasmid encoding dominant negative(DN) and constitutively active(CA) form of Src kinases were transfected into PRECs, 24 h prior to VEGF and IL-1β exposure and the effects were recorded. Overexpression of DN Src blocked both VEGF-and IL-1β-induced permeability, while overexpression of CA Src rescues the inhibitory action of Ag-NP in the presence or absence of VEGF and IL-1β. Further, an in vitro kinase assay was performed to identify the presence of the Src phosphorylation at Y419. We report that VEGF and IL-1β-stimulate endothelial permeability via Src dependent pathway by increasing the Src phosphorylation and Ag-NP block the VEGF-and IL-1β-induced Src phosphorylation at Y419. These results demonstrate that Ag-NP may inhibit the VEGF-and IL-1β-induced permeability through inactivation of Src kinase pathway and this pathway may represent a potential therapeutic target to inhibit the ocular diseases such as diabetic retinopathy.

AFM imaging of functionalized carbon nanotubes on biological membranes

Multifunctional carbon nanotubes are promising for biomedical applications as their nano-size, together with their physical stability, gives access into the cell and various cellular compartments including the nucleus. However, the direct and label-free detection of carbon nanotube uptake into cells is a challenging task. The atomic force microscope (AFM) is capable of resolving details of cellular surfaces at the nanometer scale and thus allows following of the docking of carbon nanotubes to biological membranes. Here we present topographical AFM images of non-covalently functionalized single walled (SWNT) and double walled carbon nanotubes (DWNT) immobilized on different biological membranes, such as plasma membranes and nuclear envelopes, as well as on a monolayer of avidin molecules. We were able to visualize DWNT on the nuclear membrane while at the same time resolving individual nuclear pore complexes. Furthermore, we succeeded in localizing individual SWNT at the border of incubated cells and in identifying bundles of DWNT on cell surfaces by AFM imaging.

Prevention of carbon nanohorn agglomeration using a conjugate composed of comb-shaped polyethylene glycol and a peptide aptamer

Assured dispersibility is a prerequisite for clinical application of nanomaterials. Carbon nanomaterials have hydrophobic surfaces and thus readily agglomerate under aqueous conditions. Various conjugates composed of a carbon surface-binding moiety and polyethylene glycol (PEG) have been examined as dispersants for carbon nanomaterials. Here we synthesized a conjugate composed of a comb-shaped PEG (cPEG) and carbon nanomaterial-binding peptide (NHBP-1). The resultant cPEG-NHBP3 conjugate displayed multiple units (2.4 on average) of NHBP-1 on a single cPEG molecule whose average molecular weight was 15-20 kDa. cPEG-NHBP3 endowed single-walled carbon nanohorns (SWNHs) with good dispersibility in vitro, which could not be achieved with 20PEG-NHBP, a conjugate composed of linear 20 kDa PEG and a single NHBP-1 peptide. Notably, cPEG-NHBP1, which was similar to 20PEG-NHBP but had a comb-shaped PEG backbone, functioned better as a dispersant than 20PEG-NHBP, suggesting a graft-type PEG formula is better-suited for dispersing nanomaterials. Finally, cPEG-NHBP3 treatment substantially suppressed formation of SWNH agglomerates in mouse lung, suggesting the potential utility of SWNHs as a carrier in drug delivery systems.

Targeting cancer with 'smart bombs': equipping plant virus nanoparticles for a 'seek and destroy' mission

This article discusses plant virus nanoparticles as a weapon in the war on cancer. The successes and failures of numerous nanoparticle strategies are discussed as a background to consideration of the plant virus nanoparticle approach. To have therapeutic benefit, the advantages of the targeted nanoparticle must outweigh the problems of colloidal stability, uptake by the reticuloendothelial system as well as the requirement for clearance from the body. Biodegradable nanoparticles are considered to have the most promise to address these complex phenomena. After justifying the choice of biodegradable particles, the article focuses on comparison of micelles, liposomes, polymers and modified plant viruses. The structural uniformity, cargo capacity, responsive behavior and ease of manufacturing of plant virus nanoparticles are unique properties that suggest they have a wider role to play in targeted therapy. The loading of chemotherapeutic cargo is discussed, with specific reference to the advantage of reversible transitions of the capsid of Red clover necrotic mosaic virus. These features will be contrasted and compared with other biodegradable 'smart bombs' that target cancer cells.

Antiangiogenic properties of silver nanoparticles

Angiogenesis is an important phenomenon involved in normal growth and wound healing processes. An imbalance of the growth factors involved in this process, however, causes the acceleration of several diseases including malignant, ocular, and inflammatory diseases. Inhibiting angiogenesis through interfering in its pathway is a promising methodology to hinder the progression of these diseases. The function and mechanism of silver nanoparticles (Ag-NPs) in angiogenesis have not been elucidated to date. PEDF is suggested to be a potent anti-angiogenic agent. In this study, we postulated that Ag-NPs might have the ability to inhibit angiogenesis, the pivotal step in tumor growth, invasiveness, and metastasis. We have demonstrated that Ag-NPs could also inhibit vascular endothelial growth factor (VEGF) induced cell proliferation, migration, and capillary-like tube formation of bovine retinal endothelial cells like PEDF. In addition, Ag-NPs effectively inhibited the formation of new blood microvessels induced by VEGF in the mouse Matrigel plug assay. To understand the underlying mechanism of Ag-NPs on the inhibitory effect of angiogenesis, we showed that Ag-NPs could inhibit the activation of PI3K/Akt. Together, our results indicate that Ag-NPs can act as an anti-angiogenic molecule by targeting the activation of PI3K/Akt signaling pathways.

Hyperbranched PEI with various oligosaccharide architectures: synthesis, characterization, ATP complexation, and cellular uptake properties

We present a rapid synthetic method for the development of hyperbranched PEIs decorated with different oligosaccharide architectures as carrier systems (CS) for drugs and bioactive molecules for in vitro and in vivo experiments. Reductive amination of hyperbranched PEI with readily available oligosaccharides results in sugar functionalized PEI cores with oligosaccharide shells of different densities. These core-shell architectures were characterized by NMR spectroscopy, elemental analysis, SLS, DLS, IR, and polyelectrolyte titration experiments. ATP complexation of theses polycations was examined by isothermal titration calorimetry to evaluate the binding energy and ATP/CS complexation ratios under physiological conditions. In vitro experiments showed an enhanced cellular uptake of ATP/CS complexes compared to those of the free ATP molecules. The results arise to initiate further noncovalent complexation studies of pharmacologically relevant molecules that may lead to the development of therapeutics based on this polymeric delivery platform.

Genetically designed Peptide-based molecular materials

With recent developments of nanoscale engineering in the physical and chemical sciences and advances in molecular biology, molecular biomimetics is combining genetic tools and evolutionary approaches with synthetic nanoscale constructs to create a new hybrid methodology: genetically designed peptide-based molecular materials. Following the fundamental principles of genome-based design, molecular recognition, and self-assembly in nature, we can now use recombinant DNA technologies to design single or multifunctional peptides and peptide-based molecular constructs that can interact with solids and synthetic systems. These solid-binding peptides have made significant impact as inorganic synthesizers, nanoparticle linkers, and molecular assemblers, or simply as molecular building blocks, in a wide range of fields from chemistry to materials science to medicine. As part of the programmatic theme, "Nanoscience: Challenges for the Future", the current developments, challenges, and future prospects of the field were presented during a symposium at the 237th ACS National Meeting held in March 2009. This Nano Focus article presents a synopsis of the work discussed there.

Nanoscale labels: nanoparticles and liposomes in the development of high-performance biosensors

Technology for the detection of biological species has generated considerable interest in a variety of fields including healthcare, defense, food and environmental monitoring. In a biosensor, labeled specific binding partners are used to emit a detectable signal. Owing to their unique properties, nanomaterials have been proposed as a novel label category and have led to the development of new assays and new transduction mechanisms. In this article, the role of three major types of nanoscale labels (metallic, semiconductor and liposome nanoparticles) in the development of a new generation of optical, electrochemical or gravimetric biosensors will be presented. The underlying transduction principles will be briefly explained and assay strategies relying on the use of these ‘nanolabels’ will be described. The contribution to increased assay performance and sensitivity will be highlighted. Approaches towards simple, cost efficient and sensitive assays are essential to meet the demands of a growing number of applications.

Circulation and distribution of gold nanoparticles and induced alterations of tissue morphology at intravenous particle delivery

Kinetics, biodistribution, and histological studies were performed to evaluate the particle-size effects on the distribution of 15 nm and 50 nm PEG-coated colloidal gold (CG) particles and 160 nm silica/gold nanoshells (NSs) in rats and rabbits. The above nanoparticles (NPs) were used as a model because of their importance for current biomedical applications such as photothermal therapy, optical coherence tomography, and resonance-scattering imaging. The dynamics of NPs circulation in vivo was evaluated after intravenous administration of 15 nm CG NPs to rabbit, and the maximal concentrations of gold were observed 15-30 min after injection. Rats were injected in the tail vein with PEG-coated NPs (about 0.3 mg Au/kg rats). 24 h after injection, the accumulation of gold in different organs and blood was determined by atomic absorption spectroscopy. In accordance with the published reports, we observed 15 nm particles in all organs with rather smooth distribution over liver, spleen and blood. By contrast, the larger NSs were accumulated mainly in the liver and spleen. For rabbits, the biodistribution was similar (72 h after intravenous injection). We report also preliminary data on the light microscopy and TEM histological examination that allows evaluation of the changes in biotissues after gold NPs treatment.

Selective uptake of multi-walled carbon nanotubes by tumor macrophages in a murine glioma model

Carbon nantotubes (CNTs) are emerging as a new family of nanovectors for drug and gene delivery into biological systems. To evaluate potential application of this technology for brain tumor therapy, we studied uptake and toxicity of multi-walled CNTs (MWCNTs) in the GL261 murine intracranial glioma model. Within 24 h of a single intratumoral injection of labeled MWCNTs (5 microg), nearly 10-20% of total cells demonstrated CNT internalization. Most CNT uptake, however, occurred by tumor-associated macrophages (MP), which accounted for most (75%) MWCNT-positive cells. Within 24 h of injection, nearly 30% of tumor MP became MWCNT-positive. Despite a transient increase in inflammatory cell infiltration into both normal and tumor-bearing brains following MWCNT injection, no significant toxicity was noted in mice, and minor changes in tumor cytokine expression were observed. This study suggests that MWCNTs could potentially be used as a novel and non-toxic vehicle for targeting MP in brain tumors.

Photosensitiser delivery for photodynamic therapy. Part 2: systemic carrier platforms

BACKGROUND

The treatment of solid tumours and angiogenic ocular diseases by photodynamic therapy (PDT) requires the injection of a photosensitiser (PS) to destroy target cells through a combination of visible light irradiation and molecular oxygen. There is currently great interest in the development of efficient and specific carrier delivery platforms for systemic PDT.

OBJECTIVE

This article aims to review recent developments in systemic carrier delivery platforms for PDT, with an emphasis on target specificity.

METHODS

Recent publications, spanning the last five years, concerning delivery carrier platforms for systemic PDT were reviewed, including PS conjugates, dendrimers, micelles, liposomes and nanoparticles.

RESULTS/CONCLUSION

PS conjugates and supramolecular delivery platforms can improve PDT selectivity by exploiting cellular and physiological specificities of the targeted tissue. Overexpression of receptors in cancer and angiogenic endothelial cells allows their targeting by affinity-based moieties for the selective uptake of PS conjugates and encapsulating delivery carriers, while the abnormal tumour neovascularisation induces a specific accumulation of heavy weighted PS carriers by enhanced permeability and retention (EPR) effect. In addition, polymeric prodrug delivery platforms triggered by the acidic nature of the tumour environment or the expression of proteases can be designed. Promising results obtained with recent systemic carrier platforms will, in due course, be translated into the clinic for highly efficient and selective PDT protocols.

Crucial functionalizations of carbon nanotubes for improved drug delivery: a valuable option?

Amidst the myriad of drug delivery systems able to enhance delivery, absorption and intracellular uptake of a bioactive molecule while protecting it from deactivation, Carbon Nanotubes (CNTs) have emerged as a recent and promising option especially in cancer therapy. This is mainly due to their unique properties, which render them extremely versatile through the incorporation of several functional groups and targeting molecules at the same time, while their natural shape allows them to selectively penetrate across biological barriers in a non-invasive way. In this expert review we aim to evaluate whether this innovative material, once chemically-modified with suitable functionalizations, can be considered as a valuable system in comparison to the already existing nanodevices. This will include the estimation of the most recent advances in the field of nanotechnology, together with a cautious evaluation of potential risks and hazards associated with the extensive use of this fascinating, but still unknown, nanomaterial.

Langmuir adsorption study of the interaction of CdSe/ZnS quantum dots with model substrates: influence of substrate surface chemistry and pH

We investigate the utility of Langmuir adsorption measurements for characterizing nanoparticle-substrate interactions. Spherical CdSe/ZnS core-shell nanoparticles were chosen as representative particles because of their widespread use in biological labeling measurements and their relatively monodisperse dimensions. In particular, the quantum dots were functionalized with 11-mercaptoundecanoic acid, and we utilized an amine-terminated self-assembled monolayer (SAM) as a model substrate. SAMs with different end-groups (-CH(3) and -COOH) were also considered to contrast with the adsorption behavior on the amine-terminated SAM substrates. We followed the kinetics of nanoparticle adsorption on the aminosilane layer by quartz crystal microgravimetry (QCM) over a range of particle concentrations and determined the corresponding Langmuir adsorption isotherms. Analysis of both equilibrium adsorption and kinetic adsorption data allowed us to determine a consistent value of the Langmuir adsorption equilibrium constant for the amine-terminated SAM at room temperature (K(L) approximately 2.7 (micromol/L)(-1)), providing a useful characterization of the nanoparticle-substrate interaction. The effect of varying solution pH on Langmuir adsorption was also investigated in order to gain insight into the role of electrostatic interactions on nanoparticle adsorption. The equilibrium extent of adsorption was found to be maximum at about pH 7. These changes of nanoparticle adsorption were further quantified and validated by X-ray photoelectron spectroscopy (XPS) and confocal fluorescence microscopy measurements. We conclude that Langmuir adsorption measurements provide a promising approach for quantifying nanoparticle-substrate interactions.

Towards new functional nanostructures for medical imaging

Nanostructures represent a promising new type of contrast agent for clinical medical imaging modalities, including magnetic resonance imaging, x-ray computed tomography, ultrasound, and nuclear imaging. Currently, most nanostructures are simple, single-purpose imaging agents based on spherical constructs (e.g., liposomes, micelles, nanoemulsions, macromolecules, dendrimers, and solid nanoparticle structures). In the next decade, new clinical imaging nanostructures will be designed as multi-functional constructs, to both amplify imaging signals at disease sites and deliver localized therapy. Proposals for nanostructures to fulfill these new functions will be outlined. New functional nanostructures are expected to develop in five main directions: Modular nanostructures with additive functionality; cooperative nanostructures with synergistic functionality; nanostructures activated by their in vivo environment; nanostructures activated by sources outside the patient; and novel, nonspherical nanostructures and components. The development and clinical translation of next-generation nanostructures will be facilitated by a combination of improved clarity of the in vivo imaging and biological challenges and the requirements to successfully overcome them; development of standardized characterization and validation systems tailored for the preclinical assessment of nanostructure agents; and development of streamlined commercialization strategies and pipelines tailored for nanostructure-based agents for their efficient translation to the clinic.

Synthesis and Optical Properties of Cubic Gold Nanoframes

This paper describes a facile method of preparing cubic Au nanoframes with open structures via the galvanic replacement reaction between Ag nanocubes and AuCl(2) (-). A mechanistic study of the reaction revealed that the formation of Au nanoframes relies on the diffusion of both Au and Ag atoms. The effect of the edge length and ridge thickness of the nanoframes on the localized surface plasmon resonance peak was explored by a combination of discrete dipole approximation calculations and single nanoparticle spectroscopy. With their hollow and open structures, the Au nanoframes represent a novel class of substrates for applications including surface plasmonics and surface-enhanced Raman scattering.

Hapten-derivatized nanoparticle targeting and imaging of gene expression by multimodality imaging systems

Non-invasive gene monitoring is important for most gene therapy applications to ensure selective gene transfer to specific cells or tissues. We developed a non-invasive imaging system to assess the location and persistence of gene expression by anchoring an anti-dansyl (DNS) single-chain antibody (DNS receptor) on the cell surface to trap DNS-derivatized imaging probes. DNS hapten was covalently attached to cross-linked iron oxide (CLIO) to form a 39+/-0.5 nm DNS-CLIO nanoparticle imaging probe. DNS-CLIO specifically bound to DNS receptors but not to a control single-chain antibody receptor. DNS-CLIO (100 microM Fe) was non-toxic to both B16/DNS (DNS receptor positive) and B16/phOx (control receptor positive) cells. Magnetic resonance (MR) imaging could detect as few as 10% B16/DNS cells in a mixture in vitro. Importantly, DNS-CLIO specifically bound to a B16/DNS tumor, which markedly reduced signal intensity. Similar results were also shown with DNS quantum dots, which specifically targeted CT26/DNS cells but not control CT26/phOx cells both in vitro and in vivo. These results demonstrate that DNS nanoparticles can systemically monitor the expression of DNS receptor in vivo by feasible imaging systems. This targeting strategy may provide a valuable tool to estimate the efficacy and specificity of different gene delivery systems and optimize gene therapy protocols in the clinic.

Nanovehicular intracellular delivery systems

This article provides an overview of principles and barriers relevant to intracellular drug and gene transport, accumulation and retention (collectively called as drug delivery) by means of nanovehicles (NV). The aim is to deliver a cargo to a particular intracellular site, if possible, to exert a local action. Some of the principles discussed in this article apply to noncolloidal drugs that are not permeable to the plasma membrane or to the blood-brain barrier. NV are defined as a wide range of nanosized particles leading to colloidal objects which are capable of entering cells and tissues and delivering a cargo intracelullarly. Different localization and targeting means are discussed. Limited discussion on pharmacokinetics and pharmacodynamics is also presented. NVs are contrasted to micro-delivery and current nanotechnologies which are already in commercial use. Newer developments in NV technologies are outlined and future applications are stressed. We also briefly review the existing modeling tools and approaches to quantitatively describe the behavior of targeted NV within the vascular and tumor compartments, an area of particular importance. While we list "elementary" phenomena related to different level of complexity of delivery to cancer, we also stress importance of multi-scale modeling and bottom-up systems biology approach.