Nano-oncology: drug delivery, imaging, and sensing

LED light source for fluorescence endoscopy using quantum dots

We present an LED light source for use with standard clinical endoscopes to enable visualization of tissues labeled with quantum dots (QDs). QD-assisted endoscopy may improve the outcome of surgical endoscopic procedures by identifying specific tissue types. QDs offer several advantages over current fluorescent stains due to their high target selectivity, long-lasting fluorescence, large excitation and narrow emission bands, and multiplexing capabilities. The prototype presented is compact, modular in design, and was built at low cost making it competitive with commercially available light sources. The device's efficiency is evaluated by measuring light intensity at discreet locations and by successfully illuminating a chicken tissue sample non-specifically labeled with a 250nM or 500nM QD solution. Ultimately, this device serves as a step towards incorporating QDs into real time, image-guided surgical procedures.

Potential implications of nanoparticle characterization on in vitro and in vivo gene delivery

Nanoparticles are rapidly emerging as therapeutic delivery vectors defined by size-dependent properties. They offer several advantages over the traditional drug-delivery systems and medical diagnostics but also pose considerable challenges for systemic applications. Gene delivery is one of the important applications of nanotechnology. Usually, the nanoparticles employed for gene delivery are either formed by condensation of DNA with preformed cationic polymers or by polymerization of monomeric units thereby entrapping DNA in it. The physicochemical properties such as size, shape, surface morphology have been found to have significant influence on the gene-delivery efficacy of nanoparticles. Furthermore, when administered in vitro and in vivo, the efficiency of nanoparticles depends on a wide variety of other parameters, that is, transfection conditions, time of exposure, cell type and so forth. In this review, the potential role of characterization of nanoparticles physicochemical properties on the in vitro and in vivo gene delivery efficacy of nanoparticles is discussed.

Functionalized carbon nanotubes: biomedical applications

Carbon nanotubes (CNTs) are emerging as novel nanomaterials for various biomedical applications. CNTs can be used to deliver a variety of therapeutic agents, including biomolecules, to the target disease sites. In addition, their unparalleled optical and electrical properties make them excellent candidates for bioimaging and other biomedical applications. However, the high cytotoxicity of CNTs limits their use in humans and many biological systems. The biocompatibility and low cytotoxicity of CNTs are attributed to size, dose, duration, testing systems, and surface functionalization. The functionalization of CNTs improves their solubility and biocompatibility and alters their cellular interaction pathways, resulting in much-reduced cytotoxic effects. Functionalized CNTs are promising novel materials for a variety of biomedical applications. These potential applications are particularly enhanced by their ability to penetrate biological membranes with relatively low cytotoxicity. This review is directed towards the overview of CNTs and their functionalization for biomedical applications with minimal cytotoxicity.

The effects of luminescent ruthenium(II) polypyridyl functionalized selenium nanoparticles on bFGF-induced angiogenesis and AKT/ERK signaling

Anti-angiogenesis is an effective strategy for cancer treatment because uncontrolled tumor growth depends on tumor angiogenesis and sufficient blood supply. Thus, blocking angiogenesis could be a strategy to arrest tumor growth. The function and mechanism of luminescent ruthenium-modified selenium nanoparticles (Ru-SeNPs) in angiogenesis have not been elucidated to date. Here, we found that Ru-SeNPs significantly inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, migration and tube formation. Ru-SeNPs was also tested in vivo in the chicken chorioallantoic membrane (CAM) assay and found to inhibit bFGF-treated CAMs development like suramin. Moreover, we showed that Ru-SeNPs inhibited the activations of FGFR1 and its downstream protein kinases, such ErK and AKT. Furthermore, by using fluorescence confocal microscopy and TEM imaging studies, we have demonstrated their cellular uptake and localization within the cytoplasm of HepG2 and HUVEC cells. These findings indicate that Ru-SeNPs inhibits angiogenesis and may be a viable drug candidate in anti-angiogenesis and anticancer therapies.

In vitro and in vivo investigations of upconversion and NIR emitting Gd₂O₃:Er³⁺,Yb³⁺ nanostructures for biomedical applications

The use of an "over 1000-nm near-infrared (NIR) in vivo fluorescence bioimaging" system based on lanthanide containing inorganic nanostructures emitting in the visible and NIR range under 980-nm excitation is proposed. It may overcome problems of currently used biomarkers including color fading, phototoxicity and scattering. Gd(2)O(3):Er(3+),Yb(3+) nanoparticles and nanorods showing upconversion and NIR emission are synthesized and their cytotoxic behavior is investigated by incubation with B-cell hybridomas and macrophages. Surface modification with PEG-b-PAAc provides the necessary chemical durability reducing the release of toxic Gd(3+) ions. NIR fluorescence microscopy is used to investigate the suitability of the nanostructures as NIR-NIR biomarkers. The in vitro uptake of bare and modified nanostructures by macrophages is investigated by confocal laser scanning microscopy. In vivo investigations revealed nanostructures in liver, lung, kidneys and spleen a few hours after injection into mice, while most of the nanostructures have been removed from the body after 24 h.

Advances in polymeric and inorganic vectors for nonviral nucleic acid delivery

Nonviral systems for nucleic acid delivery offer a host of potential advantages compared with viruses, including reduced toxicity and immunogenicity, increased ease of production and less stringent vector size limitations, but remain far less efficient than their viral counterparts. In this article we review recent advances in the delivery of nucleic acids using polymeric and inorganic vectors. We discuss the wide range of materials being designed and evaluated for these purposes while considering the physical requirements and barriers to entry that these agents face and reviewing recent novel approaches towards improving delivery with respect to each of these barriers. Furthermore, we provide a brief overview of past and ongoing nonviral gene therapy clinical trials. We conclude with a discussion of multifunctional nucleic acid carriers and future directions.

Preferred Position and Orientation of Anticancer Drug Cisplatin During Encapsulation Into Single-Walled Carbon Nanotubes

Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of cancers. However, this anticancer drug has a number of side effects such as kidney and nerve damages, anaphylactic reactions, hearing loss, nausea, and vomiting that strongly restrict its function. In the present study, single-walled carbon nanotubes (SWCNTs) are used as protective drug carriers which can decrease these severe side effects to some extent. Using the hybrid discrete-continuum model in conjunction with Lennard-Jones potential, new semi-analytical expressions in terms of single integrals are given to evaluate van der Waals (vdW) potential energy and interaction force between an offset cisplatin and a SWCNT. In addition, molecular dynamics (MD) simulations are conducted to validate the results of such a hybrid approach. The preferred location and orientation of cisplatin while entering SWCNTs are determined. It is shown that the equilibrium condition of the drug may be affected by the radius of nanotube, the orientation of cisplatin, and the distance between the central molecule of the drug (Pt) and the left end of nanotube. Furthermore, the influence of equilibrium condition on the distributions of vdW interactions is investigated.

Non-invasive radiofrequency ablation of malignancies mediated by quantum dots, gold nanoparticles and carbon nanotubes

Various types of nanoparticles efficiently heat in radiofrequency fields, which can potentially be used to produce cancer cell cytotoxicity within minutes. Multifunctional and targeted nanoparticles have demonstrated effective cancer control in vivo without significant toxicity associated with radiofrequency field exposure. Importantly, animals treated systemically with targeted nanoparticles smaller than 50 nm demonstrate tumor necrosis after radiofrequency field exposure without acute or chronic toxicity to normal tissues. Likewise, the future holds great promise for multifunctional imaging as well as multimodality therapy with chemotherapeutic molecules and ionizing radiation sensitizing agents attached to nanoparticle constructs. However, the appropriate balance of safety and efficacy for diagnosis, therapy, and therapeutic monitoring with these nanoparticles remains to be fully elucidated.

Structural properties of dendrimer-colloid mixtures

We consider binary mixtures of colloidal particles and amphiphilic dendrimers of the second generation by means of Monte Carlo simulations. By using the effective interactions between monomer-resolved dendrimers and colloids, we compare the results of simulations of mixtures stemming from a full monomer-resolved description with the effective two-component description at different densities, composition ratios, colloid diameters and interaction strengths. Additionally, we map the two-component system onto an effective one-component model for the colloids in the presence of the dendrimers. Simulations based on the resulting depletion potentials allow us to extend the comparison to yet another level of coarse graining and to examine under which conditions this two-step approach is valid. In addition, a preliminary outlook into the phase behavior of this system is given.

A novel lipid-based nanomicelle of docetaxel: evaluation of antitumor activity and biodistribution

Purpose

A lipid-based, nanomicelle-loaded docetaxel (M-DOC) was designed and characterized. Optical imaging was employed to evaluate the pharmacokinetics and antitumor efficacy of docetaxel in vivo.

Materials and methods

The M-DOC was prepared using the emulsion-diffusion method. Transmission electron microscopy and dynamic light scattering were used to assess the morphology and particle size of the M-DOC. Critical micelle concentrations, their stability under physiological conditions, and their encapsulation efficiency – as measured by high-performance liquid chromatography – were assessed. Pharmacological features were evaluated in two different animal models by comparing M-DOC treatments with docetaxel injections (I-DOC). Bioluminescence imaging was used to assess antitumor activity and docetaxel distribution in vivo, using nude mice injected with luciferase-expressing MDA-MB-231 human breast tumor cells. In addition, animals injected with B16 melanoma cells were used to measure survival time and docetaxel distribution.

Results

The M-DOC was prepared as round, uniform spheres with an effective diameter of 20.8 nm. The critical micelle concentration of the original emulsion was 0.06%. Satisfactory encapsulation efficiency (87.6% ± 3.0%) and 12-hour stability were achieved. Xenograft results demonstrated that the M-DOC was more effective in inhibiting tumor growth, without significantly changing body weight. Survival was prolonged by 12.6% in the M-DOC group. Tumor growth inhibitory rates in the M-DOC and I-DOC groups were 91.2% and 57.8% in volume and 71.8% and 44.9% in weight, respectively. Optical bioluminescence imaging of tumor growths yielded similar results. Area under the curve_{(0–6 hour)} levels of docetaxel in blood and tumors were significantly higher in the M-DOC group (15.9 ± 3.2 μg/mL⁻¹, 601.1 ± 194.5 μg/g⁻¹) than in the I-DOC group (7.2 ± 1.7 μg/mL⁻¹, 357.8 ± 86.2 μg/g⁻¹). The fluorescent dye 1,1-dioctadecyl-3,3,3,3′-tetramethylindotricarbocyanine iodide mimicked M-DOC in optical imaging, and accumulated more in tumors in comparison with I-DOC.

Conclusion

These results suggest that the lipid-based nanomicelle system was effective in inhibiting tumor growth, with little toxicity. Moreover, we have developed a noninvasive optical imaging method for antitumor drug evaluation, which merits further analysis for potential clinical applications.

Self-assembling peptide-based nanoparticles enhance anticancer effect of ellipticine in vitro and in vivo

BACKGROUND AND METHODS

Applications of the anticancer agent, ellipticine, have been limited by its hydrophobicity and toxicity. An efficient delivery system is required to exploit the enormous potential of this compound. Recently, EAK16-II, an ionic-complementary, self-assembling peptide, has been found to stabilize ellipticine in aqueous solution. Here, the anticancer activity of ellipticine encapsulated in EAK16-II (EAK-EPT) was evaluated in vitro and in vivo.

RESULTS

Our cellular uptake, toxicity, and apoptosis results in an A549 human lung carcinoma cell line indicate that EAK-EPT complexes are significantly more effective than treatment with EAK16-II or ellipticine alone. This is due to the ability of EAK16-II to stabilize ellipticine in a protonated state in well formed nanostructures approximately 200 nm in size. In vivo observations in an A549 nude mouse tumor model show higher antitumor activity and lower cytotoxicity of EAK-EPT complexes than in the control group treated with ellipticine alone. Tumor growth in animals was significantly inhibited after treatment with EAK-EPT complexes, and without any apparent side effects.

CONCLUSION

The anticancer activity observed in this study coupled with minimal side effects encourages further development of peptide-mediated delivery of anticancer drugs, ellipticine in the present case, for clinical application.

Modeling of the major gas vesicle protein, GvpA: from protein sequence to vesicle wall structure

The structure and assembly process of gas vesicles have received significant attention in recent decades, although relatively little is still known. This work combines state-of-the-art computational methods to develop a model for the major gas vesicle protein, GvpA, and explore its structure within the assembled vesicle. Elucidating this protein's structure has been challenging due to its adherent and aggregative nature, which has so far precluded in-depth biochemical analyses. Moreover, GvpA has extremely low similarity with any known protein structure, which renders homology modeling methods ineffective. Thus, alternate approaches were used to model its tertiary structure. Starting with the sequence from haloarchaeon Halobacterium sp. NRC-1, we performed ab initio modeling and threading to acquire a multitude of structure decoys, which were equilibrated and ranked using molecular dynamics and mechanics, respectively. The highest ranked predictions exhibited an α-β-β-α secondary structure in agreement with earlier experimental findings, as well as with our own secondary structure predictions. Afterwards, GvpA subunits were docked in a quasi-periodic arrangement to investigate the assembly of the vesicle wall and to conduct simulations of contact-mode atomic force microscopy imaging, which allowed us to reconcile the structure predictions with the available experimental data. Finally, the GvpA structure for two representative organisms, Anabaena flos-aquae and Calothrix sp. PCC 7601, was also predicted, which reproduced the major features of our GvpA model, supporting the expectation that homologous GvpA sequences synthesized by different organisms should exhibit similar structures.

Surface conjugation of triphenylphosphonium to target poly(amidoamine) dendrimers to mitochondria

Dendrimers have emerged as promising carriers for the delivery of a wide variety of pay-loads including therapeutic drugs, imaging agents and nucleic acid materials into biological systems. The current work aimed to develop a novel mitochondria-targeted generation 5 poly(amidoamine) (PAMAM) dendrimer (G(5)-D). To achieve this goal, a known mitochondriotropic ligand triphenylphosphonium (TPP) was conjugated on the surface of the dendrimer. A fraction of the cationic surface charge of G(5)-D was neutralized by partial acetylation of the primary amine groups. Next, the mitochondria-targeted dendrimer was synthesized via the acid-amine-coupling conjugation reaction between the acid group of (3-carboxypropyl)triphenyl-phosphonium bromide and the primary amines of the acetylated dendrimer (G(5)-D-Ac). These dendrimers were fluorescently labeled with fluorescein isothiocyanate (FITC) to quantify cell association by flow cytometry and for visualization under confocal laser scanning microscopy to assess the mitochondrial targeting in vitro. The newly developed TPP-anchored dendrimer (G(5)-D-Ac-TPP) was efficiently taken up by the cells and demonstrated good mitochondrial targeting. In vitro cytotoxicity experiments carried out on normal mouse fibroblast cells (NIH-3T3) had greater cell viability in the presence of the G(5)-D-Ac-TPP compared to the parent unmodified G(5)-D. This mitochondria-targeted dendrimer-based nanocarrier could be useful for imaging as well as for selective delivery of bio-actives to the mitochondria for the treatment of diseases associated with mitochondrial dysfunction.

Use of macrophages to deliver therapeutic and imaging contrast agents to tumors

Drug targeting to tumors with limited toxicity and enhanced efficacy of drug is one of the important goals for cancer treatment pharmaceutics. Monocytes/macrophages are able to migrate to tumor sites across the blood barriers by acting as Trojan horses carrying drug cargoes. Taking this advantage, we have intended to develop an efficient administration system using a biologically active carrier of mouse peritoneal macrophage bearing liposomal doxorubicin (macrophage-LP-Dox). We expect that this system could improve the cancer therapeutic efficacy through deeper penetration into tumor even hypoxic region behind tumor blood vessel. We first confirmed that macrophages containing iron oxides could migrate and infiltrate into tumors effectively by MR imaging. Next, we showed that doxorubicin (Dox) encapsulated with liposomes (LP-Dox) was successfully loaded into macrophages, in which the biological activity of macrophage and cytotoxicity of Dox against tumor cells were well preserved. Delivery of Dox into tumor tissue by systemic administration of macrophage-LP-Dox was verified in both subcutaneous and metastasis xenograft tumor models. Importantly, the effective inhibition of in vivo tumor growth was proved with this system. Our results provide the feasibility of macrophages-LP-drug as an active biocarrier for the enhancement of therapeutic effects in cancer treatment and open new perspectives for the active delivery of drugs.

Impact of nanotechnology in cancer: emphasis on nanochemoprevention

Since its advent in the field of cancer, nanotechnology has provided researchers with expertise to explore new avenues for diagnosis, prevention, and treatment of the disease. Utilization of nanotechnology has enabled the development of devices in nanometer (nm) sizes which could be designed to encapsulate useful agents that have shown excellent results but otherwise are generally toxic due to the doses intended for extended use. In addition, examples are also available where these devices are easily conjugated with several purposeful moieties for better localization and targeted delivery. We introduced a novel concept in which nanotechnology was utilized for enhancing the outcome of chemoprevention. This idea, which we termed as “nanochemoprevention,” was subsequently exploited by several laboratories worldwide and has now become an advancing field in chemoprevention research. This review examines some of the up and coming applications of nanotechnology for cancer detection, imaging, treatment, and prevention. Further, we detail the current and future utilization of nanochemoprevention for prevention and treatment of cancer.

Silver nanoparticles as potential antiviral agents

Virus infections pose significant global health challenges, especially in view of the fact that the emergence of resistant viral strains and the adverse side effects associated with prolonged use continue to slow down the application of effective antiviral therapies. This makes imperative the need for the development of safe and potent alternatives to conventional antiviral drugs. In the present scenario, nanoscale materials have emerged as novel antiviral agents for the possibilities offered by their unique chemical and physical properties. Silver nanoparticles have mainly been studied for their antimicrobial potential against bacteria, but have also proven to be active against several types of viruses including human imunodeficiency virus, hepatitis B virus, herpes simplex virus, respiratory syncytial virus, and monkey pox virus. The use of metal nanoparticles provides an interesting opportunity for novel antiviral therapies. Since metals may attack a broad range of targets in the virus there is a lower possibility to develop resistance as compared to conventional antivirals. The present review focuses on the development of methods for the production of silver nanoparticles and on their use as antiviral therapeutics against pathogenic viruses.

The controlled display of biomolecules on nanoparticles: a challenge suited to bioorthogonal chemistry

Interest in developing diverse nanoparticle (NP)-biological composite materials continues to grow almost unabated. This is motivated primarily by the desire to simultaneously exploit the properties of both NP and biological components in new hybrid devices or materials that can be applied in areas ranging from energy harvesting and nanoscale electronics to biomedical diagnostics. The utility and effectiveness of these composites will be predicated on the ability to assemble these structures with control over NP/biomolecule ratio, biomolecular orientation, biomolecular activity, and the separation distance within the NP-bioconjugate architecture. This degree of control will be especially critical in creating theranostic NP-bioconjugates that, as a single vector, are capable of multiple functions in vivo, including targeting, image contrast, biosensing, and drug delivery. In this review, a perspective is given on current and developing chemistries that can provide improved control in the preparation of NP-bioconjugates. The nanoscale properties intrinsic to several prominent NP materials are briefly described to highlight the motivation behind their use. NP materials of interest include quantum dots, carbon nanotubes, viral capsids, liposomes, and NPs composed of gold, lanthanides, silica, polymers, or magnetic materials. This review includes a critical discussion on the design considerations for NP-bioconjugates and the unique challenges associated with chemistry at the biological-nanoscale interface-the liabilities of traditional bioconjugation chemistries being particularly prominent therein. Select bioorthogonal chemistries that can address these challenges are reviewed in detail, and include chemoselective ligations (e.g., hydrazone and Staudinger ligation), cycloaddition reactions in click chemistry (e.g., azide-alkyne cyclyoaddition, tetrazine ligation), metal-affinity coordination (e.g., polyhistidine), enzyme driven modifications (e.g., HaloTag, biotin ligase), and other site-specific chemistries. The benefits and liabilities of particular chemistries are discussed by highlighting relevant NP-bioconjugation examples from the literature. Potential chemistries that have not yet been applied to NPs are also discussed, and an outlook on future developments in this field is given.

Gold nanoparticle probes: design and in vitro applications in cancer cell culture

A new architecture has been designed by the conjugation of [(18)F]2-fluoro-2-deoxy-D-glucose ((18)F-FDG), gold nanoparticles (AuNPs), and anti-metadherin (Anti-MTDH) antibody which is specific to the metadherin (MTDH) over-expressed on the surface of breast cancer cells. Mannose triflate molecule is used as a precursor for synthesis of (18)F-FDG by nucleophilic fluorination. For the conjugation of (18)F-FDG and AuNPs, cysteamine was first bound to mannose triflate (Man-CA) before synthesizing of (18)F-FDG which has cysteamine sides ((18)FDG-CA). Then, (18)FDG-CA was reacted with HAuCl(4) to obtain AuNPs and with NaBH(4) for reduction of AuNPs. At the end of this procedure, AuNPs were conjugated to (18)F-FDG via disulphide bonds ((18)FDG-AuNP). For the conjugation of Anti-MTDH, 1,1'-carbonyl diimidazol (CDI) was bound to the (18)FDG-AuNP, and Anti-MTDH was conjugated via CDI ((18)FDG-AuNP-Anti-MTDH). This procedure was also performed by using Na(19)F to obtain non-radioactive conjugates ((19)FDG-AuNP-Anti-MTDH). Scanning electron microscopy (SEM) images demonstrated that synthesized particles were in nano sizes. (18)FDG-AuNP-Anti-MTDH conjugate was characterized and used as a model probe containing both radioactive and optical labels together as well as the biological target. The (18)FDG-AuNP-Anti-MTDH conjugate was applied to MCF7 breast cancer cell line and apoptotic cell ratio was found to be increasing from 2% to 20% following the treatment. Hence, these results have promised an important application potential of this conjugate in cancer research.

Thermoresponsive polymer colloids for drug delivery and cancer therapy

Many difficulties in treating cancer arise from the problems in directing highly cytotoxic agents to the deseased tissues, cells and intracellular compartments. Many drug delivery systems have been devised to address this problem, including those that show a change in properties in response to a temperature stimulus. In particular, colloidal materials based on thermoresponsive polymers offer a means to transport drugs selectively into tumour tissues that are hyperthermic, either intrinsically or through the application of clinical procedures such as localised heating. In this paper, the key attributes of thermoresponsive polymer colloids are considered, a number of important recent examples are discussed and the possible future developments of these materials are evaluated.

Application of near-infrared fluorescence imaging using a polymeric nanoparticle-based probe for the diagnosis and therapeutic monitoring of colon cancer

BACKGROUND

Early and accurate detection of adenomatous colonic polyps is a major concern in the prevention of colon cancer. Near-infrared fluorescence (NIRF) imaging with optical probes targeting specific peptides enables the noninvasive visualization and characterization of lesions. Matrix metalloproteinases (MMPs) are known to play an important role in tumorigenesis and tumor progression.

AIM

To investigate the effectiveness of NIRF imaging, with a novel MMP-activatable probe based on a polymeric nanoparticle platform, in the colon cancer models.

METHODS

We used an azoxymethane (AOM)-induced mouse colon cancer model resembling human sporadic colon cancer and an MMP-positive xenograft tumor model. MMP expression was evaluated by Western blotting, real-time PCR, and immunohistochemical staining. NIRF imaging was performed with a novel MMP-activatable probe, an MMP-inactivatable probe, and saline. In addition, we observed the change of NIRF signal intensity after intratumoral administration of an MMP-inhibitor.

RESULTS

Multiple tumors with various sizes developed in AOM-treated mouse colons, progressing from adenomas to adenocarcinomas, with MMP expression progressively increasing in the normal-adenoma-adenocarcinoma sequence. In mice injected with the MMP-activatable probe, the NIRF signal also increased in this sequence and was highly correlated with MMP expression (p < 0.001). Tumor-background-ratios (TBR) of adenocarcinoma to adjacent normal mucosa by a novel probe were significantly higher than that of adenoma (p < 0.001). In both the AOM and xenograft models, NIRF signals of tumors decreased after treatment with an MMP-inhibitor.

CONCLUSIONS

NIRF imaging using a polymeric nanoparticle-based probe may be useful for detecting early stage disease and for assessing treatment response.

A comparison of implicit- and explicit-solvent simulations of self-assembly in block copolymer and solute systems

We have developed explicit- and implicit-solvent models for the flash nanoprecipitation process, which involves rapid coprecipitation of block copolymers and solutes by changing solvent quality. The explicit-solvent model uses the dissipative particle dynamics (DPD) method and the implicit-solvent model uses the Brownian dynamics (BD) method. Each of the two models was parameterized to match key properties of the diblock copolymer (specifically, critical micelle concentration, diffusion coefficient, polystyrene melt density, and polyethylene glycol radius of gyration) and the hydrophobic solute (aqueous solubility, diffusion coefficient, and solid density). The models were simulated in the limit of instantaneous mixing of solvent with antisolvent. Despite the significant differences in the potentials employed in the implicit- and explicit-solvent models, the polymer-stabilized nanoparticles formed in both sets of simulations are similar in size and structure; however, the dynamic evolution of the two simulations is quite different. Nanoparticles in the BD simulations have diffusion coefficients that follow Rouse behavior (D ∝ M(-1)), whereas those in the DPD simulations have diffusion coefficients that are close to the values predicted by the Stokes-Einstein relation (D ∝ R(-1)). As the nanoparticles become larger, the discrepancy between diffusion coefficients grows. As a consequence, BD simulations produce increasingly slower aggregation dynamics with respect to real time and result in an unphysical evolution of the nanoparticle size distribution. Surface area per polymer of the stable explicit-solvent nanoparticles agrees well with experimental values, whereas the implicit-solvent nanoparticles are stable when the surface area per particle is roughly two to four times larger. We conclude that implicit-solvent models may produce questionable results when simulating nonequilibrium processes in which hydrodynamics play a critical role.

The current state of engineered nanomaterials in consumer goods and waste streams: the need to develop nanoproperty-quantifiable sensors for monitoring engineered nanomaterials

As nanomaterials are harnessed for medicine and other technological advances, an understanding of the toxicology of these new materials is required to inform our use. This toxicological knowledge will be required to establish the medical and environmental regulations required to protect consumers and those involved in nanomaterial manufacturing. Nanoparticles of titanium oxide, carbon nanotubes, semiconductor quantum dots, gold, and silver represent a high percentage of the nanotechnology currently available or currently poised to reach consumers. For these nanoparticles, this review aims to identify current applications, the current methods used for characterization and quantification, current environmental concentrations (if known), and an introduction to the toxicology research. Continued development of analytical tools for the characterization and quantification of nanomaterials in complex environmental and biological samples will be required for our understanding of the toxicology and environmental impact of nanomaterials. Nearly all materials exhibit toxicity at a high enough concentration. Robust, rapid, and cost effective analytical techniques will be required to determine current background levels of anthropogenic, accidental, and engineered nanoparticles in air, water, and soil. The impact of the growing number of engineered nanoparticles used in consumer goods and medical applications can then be estimated. This will allow toxicological profiles relevant to the demonstrated or predicted environmental concentrations to be determined.

Development of a hybrid scaffold with synthetic biomaterials and hydrogel using solid freeform fabrication technology

Natural biomaterials such as hyaluronic acid, gelatin and collagen provide excellent environments for tissue regeneration. Furthermore, gel-state natural biomaterials are advantageous for encapsulating cells and growth factors. In cell printing technology, hydrogel which contains cells was printed directly to form three-dimensional (3D) structures for tissue or organ regeneration using various types of printers. However, maintaining the 3D shape of the printed structure, which is made only of the hydrogel, is very difficult due to its weak mechanical properties. In this study, we developed a hybrid scaffold consisting of synthetic biomaterials and natural hydrogel using a multi-head deposition system, which is useful in solid freeform fabrication technology. The hydrogel was intentionally infused into the space between the lines of a synthetic biomaterial-based scaffold. The cellular efficacy of the hybrid scaffold was validated using rat primary hepatocytes and a mouse pre-osteoblast MC3T3-E1 cell line. In addition, the collagen hydrogel, which encapsulates cells, was dispensed and the viability of the cells observed. We demonstrated superior effects of the hybrid scaffold on cell adhesion and proliferation and showed the high viability of dispensed cells.

Use of size and a copolymer design feature to improve the biodistribution and the enhanced permeability and retention effect of doxorubicin-loaded mesoporous silica nanoparticles in a murine xenograft tumor model

A key challenge for improving the efficacy of passive drug delivery to tumor sites by a nanocarrier is to limit reticuloendothelial system uptake and to maximize the enhanced permeability and retention effect. We demonstrate that size reduction and surface functionalization of mesoporous silica nanoparticles (MSNP) with a polyethyleneimine-polyethylene glycol copolymer reduces particle opsonization while enhancing the passive delivery of monodispersed, 50 nm doxorubicin-laden MSNP to a human squamous carcinoma xenograft in nude mice after intravenous injection. Using near-infrared fluorescence imaging and elemental Si analysis, we demonstrate passive accumulation of ∼12% of the tail vein-injected particle load at the tumor site, where there is effective cellular uptake and the delivery of doxorubicin to KB-31 cells. This was accompanied by the induction of apoptosis and an enhanced rate of tumor shrinking compared to free doxorubicin. The improved drug delivery was accompanied by a significant reduction in systemic side effects such as animal weight loss as well as reduced liver and renal injury. These results demonstrate that it is possible to achieve effective passive tumor targeting by MSNP size reduction as well as by introducing steric hindrance and electrostatic repulsion through coating with a copolymer. Further endowment of this multifunctional drug delivery platform with targeting ligands and nanovalves may further enhance cell-specific targeting and on-demand release.

Pediatric oncology and the future of oncological imaging

The future of pediatric oncology will be influenced by changes in drug design and treatment strategy, with genomic medicine and molecular-based diagnostics and therapeutics playing increasingly important roles. The role of imaging as a means of measuring response to therapy has also evolved, with the development of new technologies and higher sensitivity means of detecting tumors. Conventional anatomical imaging techniques are being increasingly supplemented with functional techniques, including FDG-PET imaging and diffusion-weighted MR imaging. The risk-adapted treatment regimens of the past, which led to improved event-free and overall survival in many pediatric cancers, have paved the way for new response-based treatment paradigms. Response-based approaches seek to identify patients with a high likelihood of cure, treating them less aggressively, while those not responding to therapy are identified early and redirected into more aggressive therapeutic regimens. These advances will require concurrent development of imaging biomarkers as surrogates of early response to therapy. Incorporating these techniques into new response-directed treatment algorithms will be crucial as personalized medicine and molecular-targeted, tumor-specific therapies gain acceptance for the treatment of children with cancer.

Development of iron-containing multiwalled carbon nanotubes for MR-guided laser-induced thermotherapy

AIMS

To test iron-containing multiwalled carbon nanotubes (MWCNTs) as bifunctional nanomaterials for imaging and thermal ablation of tumors.

MATERIALS & METHODS

MWCNTs entrapping iron were synthesized by chemical vapor deposition. The T2-weighted contrast enhancement properties of MWCNTs containing increasing amounts of iron were determined in vitro. Suspensions of these particles were injected into tumor-bearing mice and tracked longitudinally over 7 days by MRI. Heat-generating abilities of these nanomaterials following exposure to near infrared (NIR) laser irradiation was determined in vitro and in vivo.

RESULTS

The magnetic resonance contrast properties of carbon nanotubes were directly related to their iron content. Iron-containing nanotubes were functional T2-weighted contrast agents in vitro and could be imaged in vivo long-term following injection. Iron content of nanotubes did not affect their ability to generate thermoablative temperatures following exposure to NIR and significant tumor regression was observed in mice treated with MWCNTs and NIR laser irradiation.

CONCLUSION

These data demonstrate that iron-containing MWCNTs are functional T2-weighted contrast agents and efficient mediators of tumor-specific thermal ablation in vivo.

Multi-functional liposomes having temperature-triggered release and magnetic resonance imaging for tumor-specific chemotherapy

For development of tumor-specific chemotherapy, we designed liposomes with temperature-triggered drug release and magnetic resonance imaging (MRI) functions. We prepared multi-functional liposomes by incorporating thermosensitive poly(2-ethoxy(ethoxyethyl)vinyl ether) chains with a lower critical solution temperatures around 40 °C and polyamidoamine G3 dendron-based lipids having Gd(3+) chelate residues into pegylated liposomes. These stable doxorubicin (DOX)-loaded liposomes retained DOX in their interior below physiological temperature but released DOX immediately at temperatures greater than 40 °C. They exhibited excellent ability to shorten the longitudinal proton relaxation time. When administered intravenously into colon 26 tumor-bearing mice, accumulated liposomes in tumors increased with time, reaching a constant level 8 h after administration by following T(1)-weighted MRI signal intensity in tumors. Liposome size affected the liposome accumulation efficiency in tumors: liposomes of about 100 nm diameter were accumulated more efficiently than those with about 50 nm diameter. Tumor size also affected accumulation: more efficient accumulation occurred in larger tumors. Tumor growth was strongly suppressed when liposomes loaded with DOX were administered intravenously into tumor-bearing mice and the tumor was heated mildly at 44 °C for 10 min at 8 h after administration. Multi-functional liposomes having temperature-triggered drug release and MRI functions might engender personalized chemotherapy, providing efficient patient-optimized chemotherapy.

Seed-mediated synthesis of Au nanocages and their electrocatalytic activity towards glucose oxidation

We report a modified seed-mediated approach for the synthesis of uniform Au nanocages (AuNCs). HAuCl(4) was reduced in an aqueous mixture of hexamethylenetetramine (HMT), poly(N-vinyl-2-pyrrolidone) (PVP), and AgNO(3). The nanocages were (54.6+/-13.3) nm in outer-edge length and about 12 nm in wall thickness. The structure of the AuNCs was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Morphological changes associated with the seed-mediated growth of Au nanoparticles (AuNPs) in the absence of HMT or PVP were examined. The results demonstrate that both PVP and HMT play important roles in the formation of the nanocage structure. The function of AgNO(3) was also studied. A possible formation mechanism for the AuNCs was investigated by monitoring TEM images of the Au nanostructures formed at various reaction times. The electrocatalytic activity of the AuNCs towards the oxidation of glucose was explored, and a nonenzymatic glucose sensor with high sensitivity and good stability was further fabricated. To the best of our knowledge, this is the first report of the preparation of AuNCs by a seed-mediated strategy and of the application of AuNCs in the electrocatalytic oxidation of glucose. Our results should facilitate the creation of novel nanomaterials with various morphologies and the exploration of their applications in nanotechnological, optical, catalytic, and materials science fields.

Quantification of nanoparticle uptake by cells using microscopical and analytical techniques

Quantification of nanoparticles in biological systems (i.e., cells, tissues and organs) is becoming a vital part of nanotoxicological and nanomedical fields. Dose is a key parameter when assessing behavior and any potential risk of nanomaterials. Various techniques for nanoparticle quantification in cells and tissues already exist but will need further development in order to make measurements reliable, reproducible and intercomparable between different techniques. Microscopy allows detection and location of nanoparticles in cells and has been used extensively in recent years to characterize nanoparticles and their pathways in living systems. Besides microscopical techniques (light microscopy and electron microscopy mainly), analytical techniques such as mass spectrometry, an established technique in trace element analysis, have been used in nanoparticle research. Other techniques require ‘labeled’ particles, fluorescently, radioactively or magnetically. However, these techniques lack spatial resolution and subcellular localization is not possible. To date, only electron microscopy offers the resolving power to determine accumulation of nanoparticles in cells due to its ability to image particles individually. So-called super-resolution light microscopy techniques are emerging to provide sufficient resolution on the light microscopy level to image or ‘see’ particles as individual particles. Nevertheless, all microscopy techniques require statistically sound sampling strategies in order to provide quantitative results. Stereology is a well-known sampling technique in various areas and, in combination with electron microscopy, proves highly successful with regard to quantification of nanoparticle uptake by cells.

Light-sensitive lipid-based nanoparticles for drug delivery: design principles and future considerations for biological applications

Radiation-based therapies aided by nanoparticles have been developed for decades, and can be primarily categorized into two main platforms. First, delivery of payload of photo-reactive drugs (photosensitizers) using the conventional nanoparticles, and second, design and development of photo-triggerable nanoparticles (primarily liposomes) to attain light-assisted on-demand drug delivery. The main focus of this review is to provide an update of the history, current status and future applications of photo-triggerable lipid-based nanoparticles (light-sensitive liposomes). We will begin with a brief overview on the applications of liposomes for delivery of photosensitizers, including the choice of photosensitizers for photodynamic therapy, as well as the currently available light sources (lasers) used for these applications. The main segment of this review will encompass the details of strategies used to develop photo-triggerable liposomes for their drug delivery function. The principles underlying the assembly of photoreactive lipids into nanoparticles (liposomes) and photo-triggering mechanisms will be presented. We will also discuss factors that limit the applications of these liposomes for in vivo triggered drug delivery and emerging concepts that may lead to the biologically viable photo-activation strategies. We will conclude with our view point on the future perspectives of light-sensitive liposomes in the clinic.

Quantum dot peptide biosensors for monitoring caspase 3 proteolysis and calcium ions

The nanoscale size and unique optical properties of semiconductor quantum dots (QDs) have made them attractive as central photoluminescent scaffolds for a variety of biosensing platforms. In this report we functionalize QDs with dye-labeled peptides using two different linkage chemistries to yield Förster resonance energy transfer (FRET)-based sensors capable of monitoring either enzymatic activity or ionic presence. The first sensor targets the proteolytic activity of caspase 3, a key downstream effector of apoptosis. This QD conjugate utilized carbodiimide chemistry to covalently link dye-labeled peptide substrates to the terminal carboxyl groups on the QD's surface hydrophilic ligands in a quantitative manner. Caspase 3 cleaved the peptide substrate and disrupted QD donor-dye acceptor FRET providing signal transduction of enzymatic activity and allowing derivation of relevant Michaelis-Menten kinetic descriptors. The second sensor was designed to monitor Ca2+ ions that are ubiquitous in many biological processes. For this sensor, Cu+-catalyzed [3 + 2] azide-alkyne cycloaddition was exploited to attach a recently developed azide-functionalized CalciumRuby-Cl indicator dye to a cognate alkyne group present on the terminus of a modified peptide. The labeled peptide also expressed a polyhistidine sequence, which facilitated its subsequent metal-affinity coordination to the QD surface establishing the final FRET sensing construct. Adding exogenous Ca2+ to the sensor solution increased the dyes fluorescence, altering the donor-acceptor emission ratio and manifested a dissociation constant similar to that of the native dye. These results highlight the potential for combining peptides with QDs using different chemistries to create sensors for monitoring chemical compounds and biological processes.

Human serum albumin nanoparticles as an efficient noscapine drug delivery system for potential use in breast cancer: preparation and in vitro analysis

Drug delivery systems such as nanoparticles can provide enhanced efficacy for anticancer agents. Noscapine, a widely used cough suppressant for decades has recently been shown to cause significant inhibition and regression of tumor volumes without any detectable toxicity in cells or tissues. Nanoparticles made of human serum albumin (HSA) represent promising strategy for targeted drug delivery to tumor cells by enhancing the drug’s bioavailability and distribution, and reducing the body’s response towards drug resistance. In the present study, we report for the first time the incorporation and delivery of noscapine-loaded HSA nanoparticles to tumor cells. The nanoparticles were designed and optimized to achieve a particle size in the range of 150–300 nm with a drug-loading efficiency of 85%–96%. The nanoparticles were evaluated in vitro for their anticancer activity and efficacy on breast cancer cells.

Carbon Nanotubes Filled with Ferromagnetic Materials

Carbon nanotubes (CNT) filled with ferromagnetic metals like iron, cobalt or nickel are new and very interesting nanostructured materials with a number of unique properties. In this paper we give an overview about different chemical vapor deposition (CVD) methods for their synthesis and discuss the influence of selected growth parameters. In addition we evaluate possible growth mechanisms involved in their formation. Moreover we show their identified structural and magnetic properties. On the basis of these properties we present different application possibilities. Some selected examples reveal the high potential of these materials in the field of medicine and nanotechnology.