Emerging implications of nanotechnology on cancer diagnostics and therapeutics

Semiconductor quantum dots as fluorescent probes for in vitro and in vivo bio-molecular and cellular imaging

Over the years, biological imaging has seen many advances, allowing scientists to unfold many of the mysteries surrounding biological processes. The ideal imaging resolution would be in nanometres, as most biological processes occur at this scale. Nanotechnology has made this possible with functionalised nanoparticles that can bind to specific targets and trace processes at the cellular and molecular level. Quantum dots (QDs) or semiconductor nanocrystals are luminescent particles that have the potential to be the next generation fluorophores. This paper is an overview of the basics of QDs and their role as fluorescent probes for various biological imaging applications. Their potential clinical applications and the limitations that need to be overcome have also been discussed.

Surface-enhanced Raman scattering detection and tracking of nanoprobes: enhanced uptake and nuclear targeting in single cells

We describe the development and application of a co-functionalized nanoprobe and biodelivery platform combining a nuclear targeting peptide (NTP) for improved cellular uptake and intracellular targeting with p-mercaptobenzoic acid (pMBA) as a surface-enhanced Raman scattering (SERS) reporter for tracking and imaging. The nuclear targeting peptide, an HIV-1 protein-derived TAT sequence, has been previously shown to aid entry of cargo through the cell membrane via normal cellular processes, and furthermore, to localize small cargo to the nucleus of the cell. Previous work in our lab has verified cell uptake and distribution of the nanoprobes in clinically relevant mouse and human cell lines. In this work, two-dimensional SERS mapping was used to track the spatial and temporal progress of nanoparticle uptake in PC-3 human prostate cells and to characterize localization at various time points, demonstrating the potential for an intracellularly targeted multiplexed nanobiosensing system with excellent sensitivity and specificity. Silver nanoparticles co-functionalized with the TAT peptide showed greatly enhanced cellular uptake over the control nanoparticles lacking the targeting moiety. The ability to detect and monitor nanoprobe trafficking using SERS spectroscopy offers an improved alternative over previous tracking and detection methods such as light microscopy and fluorescence methods. The development of multifunctional nanoconstructs for intracellular delivery has potential clinical applications in early detection and selective treatment of disease in affected cells. Other applications include use in basic research aimed at understanding the inner workings of living cells and how they respond to chemical and biological stimuli.

Tailored porous silicon microparticles: fabrication and properties

The use of mesoporous silicon particles for drug delivery has been widely explored thanks to their biodegradability and biocompatibility. The ability to tailor the physicochemical properties of porous silicon at the micro- and nanoscale confers versatility to this material. A method for the fabrication of highly reproducible, monodisperse, mesoporous silicon particles with controlled physical characteristics through electrochemical etching of patterned silicon trenches is presented. The particle size is tailored in the micrometer range and pore size in the nanometer range, the shape from tubular to discoidal to hemispherical, and the porosity from 46 to over 80%. In addition, the properties of the porous matrix are correlated with the loading of model nanoparticles (quantum dots) and their three-dimensional arrangement within the matrix is observed by transmission electron microscopy tomography. The methods developed in this study provide effective means to fabricate mesoporous silicon particles according to the principles of rational design for therapeutic vectors and to characterize the distribution of nanoparticles within the porous matrix.

Gold nanoparticles as radiation sensitizers in cancer therapy

Among other nanoparticle systems, gold nanoparticles have been explored as radiosensitizers. While most of the research in this area has focused on either gold nanoparticles with diameters of less than 2 nm or particles with micrometer dimensions, it has been shown that nanoparticles 50 nm in diameter have the highest cellular uptake. We present the results of in vitro studies that focus on the radiosensitization properties of nanoparticles in the size range from 14-74 nm. Radiosensitization was dependent on the number of gold nanoparticles internalized within the cells. Gold nanoparticles 50-nm in diameter showed the highest radiosensitization enhancement factor (REF) (1.43 at 220 kVp) compared to gold nanoparticles of 14 and 74 nm (1.20 and 1.26, respectively). Using 50-nm gold nanoparticles, the REF for lower- (105 kVp) and higher- (6 MVp) energy photons was 1.66 and 1.17, respectively. DNA double-strand breaks were quantified using radiation-induced foci of gamma-H2AX and 53BP1, and a modest increase in the number of foci per nucleus was observed in irradiated cell populations with internalized gold nanoparticles. The outcome of this research will enable the optimization of gold nanoparticle-based sensitizers for use in therapy.

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.

Nanochemoprevention by bioactive food components: a perspective

Chemoprevention through the use of bioactive food components is a practical approach for cancer control. Despite abundant efficacy data under preclinical settings, this strategy has resulted in limited success for human cancer control. Amongst many reasons, inefficient systemic delivery and bioavailability of promising chemopreventive agents are considered to significantly contribute to such a disconnect. We recently introduced a novel concept in which we utilized nanotechnology for enhancing the outcome of chemoprevention (Cancer Res. 2009; 69:1712-6) and termed it nanochemoprevention. To establish the proof-of-principle of nanotechnology for cancer management, we determined the efficacy of a well-known chemopreventive agent epigallocatechin-3-gallate (EGCG) encapsulated in polylactic acid (PLA)-polyethylene glycol (PEG) nanoparticles in preclinical settings and observed that, compared to non-encapsulated EGCG, nano-EGCG retained its biological efficacy with over 10-fold dose advantage both in cell culture system and in vivo settings in athymic nude mice implanted with human prostate cancer cells. This study laid the foundation of nanochemoprevention by bioactive food components. Since oral consumption is the most desirable and acceptable form of delivery of bioactive food components, it will be important to develop nanoparticles containing bioactive food components that are suitable for oral consumption for which experiments are underway in this laboratory.

Fabrication of gold nanoparticles for targeted therapy in pancreatic cancer

The targeted delivery of a drug should result in enhanced therapeutic efficacy with low to minimal side effects. This is a widely accepted concept, but limited in application due to lack of available technologies and process of validation. Biomedical nanotechnology can play an important role in this respect. Biomedical nanotechnology is a burgeoning field with myriads of opportunities and possibilities for advancing medical science and disease treatment. Cancer nanotechnology (1-100 nm size range) is expected to change the very foundations of cancer treatment, diagnosis and detection. Nanomaterials, especially gold nanoparticles (AuNPs) have unique physico-chemical properties, such as ultra small size, large surface area to mass ratio, and high surface reactivity, presence of surface plasmon resonance (SPR) bands, biocompatibility and ease of surface functionalization. In this review, we will discuss how the unique physico-chemical properties of gold nanoparticles may be utilized for targeted drug delivery in pancreatic cancer leading to increased efficacy of traditional chemotherapeutics.

Multifunctional nanoscale platforms for targeting of the cancer cell immortality spectrum

In the post-genomic era, "omics" platforms and cancer systems biology are greatly advancing our knowledge of the molecular and cellular underpinnings of cancer. In this article, we begin by outlining the factors governing the development of cancer (tumorigenesis) and use this framework to motivate the need for systems-approaches to cancer diagnostics and therapeutics. We review recent efforts to tap into the remarkable potential of nanotechnology for (i) systems-surveillance (or "sensing") of the molecular signatures of tumorigenesis, and (ii) spatiotemporally-regulated delivery (or "targeting") of combination therapeutics to cancer cells. Specifically, we highlight the salient role of polymeric biomaterials and describe the physicochemical characteristics that render them attractive for the design of such nanoscale platforms. We conclude with discussions on the emerging role of macromolecular biophysics and computational nanotechnology in engineering spatiotemporally-regulated anti-cancer systems.

Gold nanorods: multifunctional agents for cancer imaging and therapy

Gold nanorods (GNRs) are strongly absorbing at near-infrared (NIR) frequencies and can be employed as multifunctional agents for biological imaging and theragnostics. GNRs can support nonlinear optical microscopies based on two-photon-excited luminescence and can enhance the contrast of biomedical imaging modalities such as optical coherence tomography and photoacoustic tomography. GNRs are also efficient at mediating the conversion of NIR light energy into heat and can generate localized photothermal effects. However, future clinical applications will require the rigorous removal of CTAB, a micellar surfactant used in GNR synthesis, and reliable methods of surface functionalization for cell-selective targeting and for minimizing nonspecific uptake into cells. This can be accomplished by using polystyrenesulfonate (PSS) as a sorbent for removing CTAB, and in situ dithiocarbamate formation for introducing chemisorptive ligands onto GNR surfaces.

Gold nanorods: from synthesis and properties to biological and biomedical applications

Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields.

Nanoparticle-mediated gene delivery

Nonviral gene delivery has been gaining considerable attention recently. Although the efficacy of DNA transfection, which is a major concern, is low in nonviral vector-mediated gene transfer compared with viral ones, nonviral vectors are relatively easy to prepare, less immunogenic and oncogenic, and have no potential of virus recombination and no limitation on the size of a transferred gene. The ability to incorporate genetic materials such as plasmid DNA, RNA, and siRNA into functionalized nanoparticles with little toxicity demonstrates a new era in pharmacotherapy for delivering genes selectively to tissues and cells. In this chapter, we highlight the basic concepts and applications of nonviral gene delivery using super paramagnetic iron oxide nanoparticles and functionalized silica nanoparticles. The experimental protocols related to these topics are described in the chapter.

Gold nanoparticles as a contrast agent for in vivo tumor imaging with photoacoustic tomography

Photoacoustic tomography (PAT) is a rapidly emerging non-invasive imaging technology that integrates the merits of high optical contrast with high ultrasound resolution. The ability to quantitatively and non-invasively image nanoparticles has important implications for the development of nanoparticles as in vivo cancer diagnostic and therapeutic agents. In this study, the ability of systemically administered poly(ethylene glycol)-coated (PEGylated) gold nanoparticles as a contrast agent for in vivo tumor imaging with PAT has been evaluated. We demonstrate that gold nanoparticles (20 and 50 nm) have high photoacoustic contrast as compared to mouse tissue ex vivo. Gold nanoparticles can be visualized in mice in vivo following subcutaneous administration using PAT. Following intravenous administration of PEGylated gold nanoparticles to tumor-bearing mice, accumulation of gold nanoparticles in tumors can be effectively imaged with PAT. With gold nanoparticles as a contrast agent, PAT has important potential applications in the image guided therapy of superficial tumors such as breast cancer, melanoma and Merkel cell carcinoma.

Gyromagnetic imaging: dynamic optical contrast using gold nanostars with magnetic cores

Plasmon-resonant nanoparticles with optical scattering in the near-infrared (NIR) are valuable contrast agents for biophotonic imaging and may be detected at the single-particle limit against a dark background, but their contrast is often limited in environments with high noise. Here we consider gyromagnetic imaging as a dynamic mode of optical contrast, using gold nanostars with superparamagnetic cores. The nanostars exhibit polarization-sensitive NIR scattering and can produce a frequency-modulated signal in response to a rotating magnetic field gradient. This periodic "twinkling" can be converted into Fourier-domain images with a dramatic reduction in background. We demonstrate gyromagnetic imaging of nanostars inside of tumor cells, using broadband excitation: while their time-domain signals are obscured by incoherent scattering, their Fourier-domain signals can be clearly resolved in less than a second. The gyromagnetically active nanostars do not cause a loss in viability, and can even have a mild stimulatory effect on cell growth.

Gold nanoparticles for molecular diagnostics

Gold nanoparticles (AuNPs) exhibit a unique phenomenon, known as surface plasmon resonance, which is responsible for their large absorption and scattering cross-sections, which are four to five orders of magnitude larger than those of conventional dyes. In addition, their optical properties can be controlled by varying their sizes, shapes and compositions. AuNPs can be easily synthesized and functionalized with different biomolecules including oligonucleotides. Numerous methods have been utilized for detecting AuNPs such as colorimetric, scanometric, fluorescence, surface-enhanced Raman scattering and electrochemical techniques. These unique aspects have permitted the development of novel AuNP-based assays for molecular diagnostics which promise increased sensitivity and specificity, multiplexing capability, and short turnaround times. AuNP-based colorimetric assays in particular show great potential in point-of-care testing assays. This review discusses properties of AuNPs and their utilization for the development of novel molecular assays.

Emerging trends of nanomedicine--an overview

Nanotechnology is an emerging branch of science for designing tools and devices of size 1 to 100 nm with unique function at the cellular, atomic and molecular levels. The concept of using nanotechnology in medical research and clinical practice is known as nanomedicine. Nanoparticles possess some novel properties not seen with the macro molecules and they can be manipulated by attaching therapeutic components to help in diagnosis and treatment. They can also be used to probe cellular movements and molecular changes associated with pathological states. Nanodevices like carbon nanotubes to locate and deliver anticancer drugs at the specific tumour site are under research. Nanotechnology promises construction of artificial cells, enzymes and genes. This will help in the replacement therapy of many disorders which are due to deficiency of enzymes, mutation of genes or any repair in the synthesis of proteins. Currently nanodevices like respirocytes, microbivores and probes encapsulated by biologically localized embedding have a greater application in treatment of anaemia and infections. Thus in the present scenario, nanotechnology is spreading its wings to address the key problems in the field of medicine. Hence this review discusses in detail the applications of nanotechnology in medicine with more emphasis on drug delivery and therapy.

Biodistribution of TNF-alpha-coated gold nanoparticles in an in vivo model system

AIM

In this study, we describe the biodistribution of CYT-6091, a colloidal gold (Au)-based nanomedicine that targets the delivery of TNF-alpha to solid tumors.

MATERIALS & METHODS

A single intravenous injection of CYT-6091 coated with 5 microg TNF-alpha was given to human prostate tumor-bearing or naive (without tumor) nude mice. Tissues were harvested and analyzed at specific time points for Au nanoparticles by atomic emission spectroscopy and TNF-alpha by ELISA.

RESULTS

The two constituents of CYT-6091, TNF-alpha and Au, exhibited different behavior in blood, with TNF-alpha showing a faster decay than the Au nanoparticles. Between 0 and 4 h after injection, TNF-alpha showed a preferential accumulation in the tumor. Au was observed to accumulate preferentially in the liver between 4 and 12 h, and showed some clearance over time (4 months).

CONCLUSION

These data suggest that CYT-6091 delivers TNF-alpha preferentially to the tumor and that upon TNF-alpha degradation, the liver takes up Au, which is cleared slowly over time.

Influence of alternating L-/D-amino acid chiralities and disulfide bond geometry on the capacity of cysteine-containing reversible cyclic peptides to disperse carbon nanotubes

Although single-walled carbon nanotubes (SWNTs) have exciting properties and potential applications, their hydrophobic nature makes them difficult to purify and manipulate. To fully realize the potential of SWNTs, strategies for the effective dispersion, separation, and organization of these materials must be devised. In this article, work involving the recent design and characterization of reversible cyclic peptides (RCPs) and RCP/SWNT composites will be described. The peptides in this work contain alternating L- and D-amino acid sequences, as well as N- and C-terminal cysteine residues (RCP-Cys) that allow for their covalent closure around the circumference of individual SWNTs. When RCPs are oxidized in the presence of SWNTs, dispersions are produced that are stable against dilution by dialysis without the formation of aggregates. The reported studies using Raman spectroscopy and UV/Vis/NIR were focused on answering the questions (1) does the chirality of the disulfide bond impact the capacity of the RCP-Cys to disperse SWNTs, and (2) is the alternating chirality of the amino acids in the RCP-Cys peptides important for SWNT dispersion. It was found that though Cys-containing RCPs are indeed able to disperse SWNTs, the chirality of the Cys residues on the N- and C- termini does not have a significant influence on the dispersed SWNT population. However, there is a large decrease in the dispersability by RCP-Cys when the alternating L/D-chiral pattern of amino acids is replaced with all L-amino acids.

Use of liposomes as drug delivery vehicles for treatment of melanoma

Melanoma is a progressive disease that claims many lives each year due to lack of therapeutics effective for the long-term treatment of patients. Currently, the best treatment option is early detection followed by surgical removal. Better melanoma therapies that are effectively delivered to tumors with minimal toxicity for patients are urgently needed. Nanotechnologies provide one approach to encapsulate therapeutic agents leading to improvements in circulation time, enhanced tumor uptake, avoidance of the reticulo-endothelial system, and minimization of toxicity. Liposomes in particular are a promising nanotechnology that can be used for more effective delivery of therapeutic agents to treat melanoma. Liposomes delivering chemotherapies, siRNA, asODNs, DNA, and radioactive particles are just some of the promising new nanotechnology based therapies under development for the treatment of melanoma that are discussed in this review.

Advances of cancer therapy by nanotechnology

Recent developments in nanotechnology offer researchers opportunities to significantly transform cancer therapeutics. This technology has enabled the manipulation of the biological and physicochemical properties of nanomaterials to facilitate more efficient drug targeting and delivery. Clinical investigations suggest that therapeutic nanoparticles can enhance efficacy and reduced side effects compared with conventional cancer therapeutic drugs. Encouraged by rapid and promising progress in cancer nanotechnology, researchers continue to develop novel and efficacious nanoparticles for drug delivery. The use of therapeutic nanoparticles as unique drug delivery systems will be a significant addition to current cancer therapeutics.

Green Nanotechnology from Tea: Phytochemicals in Tea as Building Blocks for Production of Biocompatible Gold Nanoparticles

Phytochemicals occluded in tea have been extensively used as dietary supplements and as natural pharmaceuticals in the treatment of various diseases including human cancer. Results on the reduction capabilities of phytochemicals present in tea to reduce gold salts to the corresponding gold nanoparticles are presented in this paper. The phytochemicals present in tea serve the dual roles as effective reducing agents to reduce gold and also as stabilizers to provide robust coating on the gold nanoparticles in a single step. The Tea-generated gold nanoparticles (T-AuNPs), have demonstrated remarkable in vitro stability in various buffers including saline, histidine, HSA, and cysteine solutions. T-AuNPs with phytochemical coatings have shown significant affinity toward prostate (PC-3) and breast (MCF-7) cancer cells. Results on the cellular internalization of T-AuNPs through endocytosis into the PC-3 and MCF-7 cells are presented. The generation of T-AuNPs follows all principles of green chemistry and have been found to be non toxic as assessed through MTT assays. No 'man made' chemicals, other than gold salts, are used in this true biogenic green nanotechnological process thus paving excellent opportunities for their applications in molecular imaging and therapy.

Detoxification of gold nanorods by treatment with polystyrenesulfonate

We address an outstanding issue associated with the biocompatibility of gold nanorods (GNRs), a promising agent for biomedical imaging and theragnostics. GNRs are typically prepared in the presence of cetyltrimethylammonium bromide (CTAB), a cationic surfactant whose rigorous removal is necessary due to its cytotoxicity and membrane-compromising properties. CTAB-stabilized GNRs can be partially purified by treatment with polystyrenesulfonate (PSS), an anionic polyelectrolyte often used as a surrogate peptizing agent, followed by chloroform extraction and ultrafiltration with minimal loss of dispersion stability. However, in vitro cytotoxicity assays of PSS-coated GNRs revealed IC(50) values in the low to submicromolar range, with subsequent studies indicating the source of toxicity to be associated with a persistent PSS-CTAB complex. Further exchange of CTAB-laden PSS with fresh polyelectrolyte greatly improves biocompatibility, to the extent that 85 microg/mL of "CTAB-free" GNRs (the highest level evaluated) has comparable toxicity to a standard phosphate buffer solution. Ironically, PSS is not effective by itself at stabilizing GNRs in CTAB-depleted suspensions: while useful as a detergent for GNR detoxification, it should be replaced by more robust coatings for long-term stability under physiological conditions.

The footprints of cancer development: Cancer biomarkers

Diagnostic detection and measurement of cancer disease progression are essential elements for successful cancer disease management. The early stages of cancer development carry the maximum potential for therapeutic interventions. However, these stages are often asymptomatic, leading to delayed diagnosis at the very advanced stages when effective treatments are unavailing. The application of biomarkers to cancer is leading the way because of the unique association of genomic changes in cancer cells with the disease process. They have the potential to not only help identify who will develop cancer but also to predict as to when the event is most likely to occur. In recent years, there has been an enormous effort to develop specific and sensitive biomarkers for precise and accurate screening, diagnosis, prognosis and monitoring of high risk cancer to assist with therapeutic decisions. The present article is a brief review of the emerging trends in the development of biomarkers for early detection and precise evaluation of cancer disease.

Rod-shaped nanocrystals elicit neuronal activity in vivo

The development of novel nanomaterials has raised great interest in efforts to evaluate their effect on biological systems, ranging from single cells to whole animals. In particular, there exists an open question regarding whether nanoparticles per se can elicit biological responses, which could interfere with the phenomena they are intended to measure. Here it is reported that challenging the small cnidaria Hydra vulgaris in vivo with rod-shaped semiconductor nanoparticles, also known as quantum rods (QRs), results in an unexpected tentacle-writhing behavior, which is Ca(2+) dependent and relies on the presence of tentacle neurons. Due to the absence of surface functionalization of the QRs with specific ligands, and considering that spherical nanoparticles with same composition as the QRs fail to induce any in vivo behavior on the same experimental model, it is suggested that unique shape-tunable electrical properties of the QRs may account for the neuronal stimulation. This model system may represent a widely applicable tool for screening neuronal response to nanoparticles in vivo.

Polymeric amphiphile branching leads to rare nanodisc shaped planar self-assemblies

Self-assembly is fundamental to the biological function of cells and the fabrication of nanomaterials. However, the origin of the shape of various self-assemblies, such as the shape of cells, is not altogether clear. Polymeric, oligomeric, or low molecular weight amphiphiles are a rich source of nanomaterials, and controlling their self-assembly is the route to tailored nanosystems with specific functionalities. Here, we provide direct evidence that a particular molecular architecture, polymeric branching, leads to a rare form of self-assembly, the planar nanodisc. Cholesterol containing self-assemblies formed from amphiphilic linear or branched cetyl poly(ethylenimine) (Mn approximately 1000 Da) or amphiphilic cetyl poly(propylenimine) dendrimer derivatives (Mn approximately 2000 Da) show that branching, by reducing the hydrophilic headgroup area, alters the shape of the self-assemblies transforming closed 60 nm spherical bilayer vesicles to rare 50 nm x 10 nm planar bilayer discs. Increasing the hydrophilic headgroup area, by the inclusion of methoxy poly(ethylene glycol) moieties into the amphiphilic headgroup, transforms the planar discs to 100 nm spherical bilayer vesicles. This study provides insight into the key role played by molecular shape on molecular self-organization into rare nanodiscs.

Effects of combustion-derived ultrafine particles and manufactured nanoparticles on heart cells in vitro

Evidence from epidemiological studies indicates that acute exposure to airborne pollutants is associated with an increased risk of morbidity and mortality attributed to cardiovascular diseases. The present study investigated the effects of combustion-derived ultrafine particles (diesel exhaust particles) as well as engineered nanoparticles (titanium dioxide and single-walled carbon nanotubes) on impulse conduction characteristics, myofibrillar structure and the formation of reactive oxygen species in patterned growth strands of neonatal rat ventricular cardiomyocytes in vitro. Diesel exhaust particles as well as titanium dioxide nanoparticles showed the most pronounced effects. We observed a dose-dependent change in heart cell function, an increase in reactive oxygen species and, for titanium dioxide, we also found a less organized myofibrillar structure. The mildest effects were observed for single-walled carbon nanotubes, for which no clear dose-dependent alterations of theta and dV/dt(max) could be determined. In addition, there was no increase in oxidative stress and no change in the myofibrillar structure. These results suggest that diesel exhaust as well as titanium dioxide particles and to a lesser extent also single-walled carbon nanotubes can directly induce cardiac cell damage and can affect the function of the cells.

Optical imaging for cervical cancer detection: solutions for a continuing global problem

Cervical cancer is the leading cause of cancer death for women in developing countries. Optical technologies can improve the accuracy and availability of cervical cancer screening. For example, battery-powered digital cameras can obtain multi-spectral images of the entire cervix, highlighting suspicious areas, and high-resolution optical technologies can further interrogate such areas, providing in vivo diagnosis with high sensitivity and specificity. In addition, targeted contrast agents can highlight changes in biomarkers of cervical neoplasia. Such advances should provide a much needed global approach to cervical cancer prevention.

Soybeans as a phytochemical reservoir for the production and stabilization of biocompatible gold nanoparticles

The present study demonstrates an unprecedented green process for the production of gold nanoparticles by simple treatment of gold salts with soybean extracts. Reduction capabilities of antioxidant phytochemicals present in soybean and their ability to reduce gold salts chemically to nanoparticles with subsequent coating of proteins and a host of other phytochemicals present in soybean on the freshly generated gold nanoparticles are discussed. The new genre of green nanoparticles exhibit remarkable in vitro stability in various buffers including saline, histidine, HSA, and cysteine solutions. MTT assays reveal that the green gold nanoparticles are nontoxic and thus provide excellent opportunities for their applications in nanomedicine for molecular imaging and therapy. The overall strategy described herein for the generation of gold nanoparticles meets all 12 principles of green chemistry, as no "man-made" chemicals, other than the gold salts, are used in the green nanotechnological process.

Noninvasive Raman spectroscopy in living mice for evaluation of tumor targeting with carbon nanotubes

An optimized noninvasive Raman microscope was used to evaluate tumor targeting and localization of single walled carbon nanotubes (SWNTs) in mice. Raman images were acquired in two groups of tumor-bearing mice. The control group received plain-SWNTs, whereas the experimental group received tumor targeting RGD-SWNTs intravenously. Raman imaging commenced over the next 72 h and revealed increased accumulation of RGD-SWNTs in tumor ( p < 0.05) as opposed to plain-SWNTs. These results support the development of a new preclinical Raman imager.

Coating multi-walled carbon nanotubes with rare-earth complexes by an in situ synthetic method

Multi-walled carbon nanotubes (MWCNTs) were coated with rare-earth (RE) (Eu(3+), Tb(3+)) complex layers by a simple in situ synthetic method via noncovalently functionalized MWCNTs with sodium dodecyl sulfate. Extensive characterizations of the resulting nanocomposite materials have been performed using scanning electron microscopy (SEM), FT-IR spectra, x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS). The photoluminescence properties of the RE-complex-modified MWCNTs were also investigated. Under the excitation of UV light, these samples exhibit characteristic emissions of Eu(3+) or Tb(3+) ions. The presence of the MWCNT framework does not quench the lanthanide-centered luminescence originating from the characteristic electronic transitions within the 4f shell of the RE ions. Furthermore, the existence of the nanotube framework can improve the stability of the RE complex under UV irradiation and elongate the fluorescence lifetime of the RE complex.

Quantifying nanoparticle adhesion mediated by specific molecular interactions

Receptor-mediated targeting of nanometric contrast agents or drug carriers holds great potential for treating cardiovascular and vascular-associated diseases. However, predicting the ability of these vectors to adhere to diseased cells under dynamic conditions is complex due to the interplay of transport, hydrodynamic force, and multivalent bond formation dynamics. Therefore, we sought to determine the effects of adhesion molecule density and flow rate on adhesion of 210 nm particles, with the goal of identifying criteria to optimize binding efficiency and selectivity. Our system employed a physiologically relevant ligand, the vascular adhesion molecule ICAM-1, and an ICAM-1 specific antibody tethered to the nanoparticle using avidin-biotin chemistry. We measured binding and dissociation of these particles in a flow chamber as a function of antibody density, ligand density, and flow rate, and using a transport-reaction model we distilled overall kinetic rate constants for adhesion and detachment from the binding data. We demonstrate that both attachment and detachment of 210 nm particles can be correlated with receptor and ligand valency and are minimally affected by shear rate. Furthermore, we uncovered a time-dependent mechanism governing particle detachment, in which the rate of detachment decreases with contact time according to a power law. Finally, we use our results to illustrate how to engineer adhesion selectivity for specific molecular targeting applications. These results establish basic principles dictating nanoparticle adhesion and dissociation and can be used as a framework for the rational design of targeted nanoparticle therapeutics that possess optimum adhesive characteristics.

Current in vitro methods in nanoparticle risk assessment: limitations and challenges

Nanoparticles are an emerging class of functional materials defined by size-dependent properties. Application fields range from medical imaging, new drug delivery technologies to various industrial products. Due to the expanding use of nanoparticles, the risk of human exposure rapidly increases and reliable toxicity test systems are urgently needed. Currently, nanoparticle cytotoxicity testing is based on in vitro methods established for hazard characterization of chemicals. However, evidence is accumulating that nanoparticles differ largely from these materials and may interfere with commonly used test systems. Here, we present an overview of current in vitro toxicity test methods for nanoparticle risk assessment and focus on their limitations resulting from specific nanoparticle properties. Nanoparticle features such as high adsorption capacity, hydrophobicity, surface charge, optical and magnetic properties, or catalytic activity may interfere with assay components or detection systems, which has to be considered in nanoparticle toxicity studies by characterization of specific particle properties and a careful test system validation. Future studies require well-characterized materials, the use of available reference materials and an extensive characterization of the applicability of the test methods employed. The resulting challenge for nanoparticle toxicity testing is the development of new standardized in vitro methods that cannot be affected by nanoparticle properties.

Exploiting lipid raft transport with membrane targeted nanoparticles: a strategy for cytosolic drug delivery

The ability to specifically deliver therapeutic agents to selected cell types while minimizing systemic toxicity is a principal goal of nanoparticle-based drug delivery approaches. Numerous cellular portals exist for cargo uptake and transport, but after targeting, intact nanoparticles typically are internalized via endocytosis prior to drug release. However, in this work, we show that certain classes of nanoparticles, namely lipid-coated liquid perfluorocarbon emulsions, undergo unique interactions with cells to deliver lipophilic substances to target cells without the need for entire nanoparticle internalization. To define the delivery mechanisms, fluorescently-labeled nanoparticles complexed with alphav beta 3-integrin targeting ligands were incubated with alphav beta 3-integrin expressing cells (C32 melanoma) under selected inhibitory conditions that revealed specific nanoparticle-to-cell interactions. We observed that the predominant mechanism of lipophilic delivery entailed direct delivery of lipophilic substances to the target cell plasma membrane via lipid mixing and subsequent intracellular trafficking through lipid raft-dependent processes. We suggest that local drug delivery to selected cell types could be facilitated by employing targeted nanoparticles designed specifically to utilize alternative membrane transport mechanisms.

Intracellular gold nanoparticles enhance non-invasive radiofrequency thermal destruction of human gastrointestinal cancer cells

Background

Novel approaches to treat human cancer that are effective with minimal toxicity profiles are needed. We evaluated gold nanoparticles (GNPs) in human hepatocellular and pancreatic cancer cells to determine: 1) absence of intrinsic cytotoxicity of the GNPs and 2) external radiofrequency (RF) field-induced heating of intracellular GNPs to produce thermal destruction of malignant cells. GNPs (5 nm diameter) were added to 2 human cancer cell lines (Panc-1, Hep3B). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and propidium iodide-fluorescence associated cell sorting (PI-FACS) assessed cell proliferation and GNP-related cytotoxicity. Other GNP-treated cells were exposed to a 13.56 MHz RF field for 1, 2, or 5 minutes, and then incubated for 24 hours. PI-FACS measured RF-induced cytotoxicity.

Results

GNPs had no impact on cellular proliferation by MTT assay. PI-FACS confirmed that GNPs alone produced no cytotoxicity. A GNP dose-dependent RF-induced cytotoxicity was observed. For Hep3B cells treated with a 67 μM/L dose of GNPs, cytotoxicity at 1, 2 and 5 minutes of RF was 99.0%, 98.5%, and 99.8%. For Panc-1 cells treated at the 67 μM/L dose, cytotoxicity at 1, 2, and 5 minutes of RF was 98.5%, 98.7%, and 96.5%. Lower doses of GNPs were associated with significantly lower rates of RF-induced thermal cytotoxicity for each cell line (P < 0.01). Cells not treated with GNPs but treated with RF for identical time-points had less cytotoxicity (Hep3B: 17.6%, 21%, and 75%; Panc-1: 15.3%, 26.4%, and 39.8%, all P < 0.01).

Conclusion

We demonstrate that GNPs 1) have no intrinsic cytotoxicity or anti-proliferative effects in two human cancer cell lines in vitro and 2) GNPs release heat in a focused external RF field. This RF-induced heat release is lethal to cancer cells bearing intracellular GNPs in vitro.