Treating metastatic cancer with nanotechnology

Antibody-functionalized nanoparticles for imaging cancer: influence of conjugation to gold nanoparticles on the biodistribution of 89Zr-labeled cetuximab in mice

Antibody-labeled gold nanoparticles represent a promising novel tool regarding cancer imaging and therapy. Nevertheless, the characterization of biodistribution of such immunonanocarriers has been poorly documented. In this study, the biodistribution of (89)Zr-labeled cetuximab before and after the coupling reaction to gold nanoparticles (AuNPs) was compared and the quantitative imaging performance of (89)Zr immuno-PET was evaluated. Cetuximab was functionalized with the desferal moiety and labeled with (89)Zr ((89)Zr-Df-Bz-NCS-cetuximab). AuNPs with a mean diameter of 5 nm were synthesized according a new method developed in the laboratory, and conjugated to (89)Zr-Df-Bz-NCS-cetuximab using carbodiimide chemistry (AuNPs-PPAA-cetuximab-(89)Zr). The two tracers were injected in A431 xenograft-bearing mice. Tumor and liver uptakes were assessed at different times after injection using quantitative PET imaging. The in vivo specificity of the binding was investigated using a saturating dose of unlabeled cetuximab. Radiolabeled cetuximab was conjugated to AuNPs with a coupling reaction yield >75%. All conjugates were stable in vitro and to a lesser extent in plasma. In vivo distribution studies revealed no significant difference in tumor uptake for cetuximab conjugated to nanoparticles up to 72 h after injection, compared with unconjugated cetuximab. Immuno-PET studies showed that AuNPs-PPAA-cetuximab-(89)Zr provided high tumor-to-background ratio. The liver uptake of AuNPs-PPAA-cetuximab-(89)Zr was higher, compared with (89)Zr-Df-Bz-NCS-cetuximab. In vivo blocking experiments demonstrated selective tumor targeting after coupling reaction. This study showed that the conjugation of AuNPs to cetuximab did not affect its tumor accumulation and that the efficacy of EGFR-targeted nanoparticles was unaltered. The (89)Zr-labeled cetuximab-targeted gold nanoparticles could be a valuable tool for theranostic purposes.

Hypoxia-sensitive bis(2-(2'-benzothienyl)pyridinato-N,C(3'))iridium[poly(n-butyl cyanoacrylate]/chitosan nanoparticles and their phosphorescence tumor imaging in vitro and in vivo

A new hypoxia-sensitive coordination compound, bis(2-(2'-benzothienyl)pyridinato-N,C(3'))iridium[poly(n-butyl cyanoacrylate)], hereafter denoted as (btp)2Ir(PBCA), is synthesized and characterized by (13)C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). (btp)2Ir(PBCA)/chitosan [(btp)2Ir(PBCA)/CS] nanoparticles (NPs) with a core-shell structure are prepared by a two-step fabrication process. The size distributions of these NPs are measured with a Malvern size analyzer, and their morphology is observed by transmission electron microscopy (TEM). The functional groups on the surface are confirmed by FTIR. Phosphorescence spectra are obtained and lifetimes are determined with a spectrophotofluorometer and a time-correlated single photon counting (TCSPC) apparatus, respectively. HeLa and CT26 cell lines are used to examine the cytotoxicity by the MTT assay, as well as to determine the imaging capability of the samples in air and nitrogen atmospheres, respectively. Tumor-bearing mouse models of colon adenocarcinoma are used for tumor imaging in vivo, and the imaging effect is evaluated with a Maestro 2 fluorescence imaging system. Compared with the hypoxia-associated probe bis(2-(2'-benzothienyl)pyridinato-N,C(3'))iridium(acetylacetonate) (BTP), the phosphorescence lifetime of (btp)2Ir(PBCA)/CS NPs significantly decreases, but the hypoxia-sensitivity increases after preparation of NPs. Apart from the significantly lower cytotoxicity, (btp)2Ir(PBCA)/CS NPs also enhance the tumor imaging effect by more than 10 times, maintaining the phosphorescence signal in tumor tissue for over 24 h and significantly decreasing the phosphorescence signal in normal tissue in vivo compared with the BTP probe.

Stimuli-responsive biodegradable poly(methacrylic acid) based nanocapsules for ultrasound traced and triggered drug delivery system

Ultrasound contrast agents (UCAs) have been investigated for echogenic intravenous drug delivery system. Due to the traditional UCAs with overlarge size (micro-scale), their reluctant accumulation in target organs and the instability have presented severe obstacles to the accurate response to the ultrasound and severely limited their further clinical application. Furthermore, elimination of drug carriers from the biologic system after their carrying out the diagnostic or therapeutic functions is one important aspect to be considered. The drug carriers with large sizes, avoiding renal filtration, will lead to increasing toxicity. In this present paper, we design and develop a new type of triple-stimuli responsive (ultrasound/pH/GSH) biodegradable nanocapsules, in which fill up with perfluorohexane, and the DOX-loaded PMAA with disulfide crosslinking forms the wall. These soft nanocapsules with uniform size of 300 nm can easily enter the tumor tissues via EPR effects. The PMAA shell has high DOX-loading content (36 wt%) and great drug loading efficiency (93.5%), the PFH filled can effectively enhance US imaging signal through acoustic droplet vaporization (ADV), ensuring diagnostic and image-guided therapeutic applications. What is more, the disulfide-crosslinked PMAA shell is biodegradable and thus safe for normal organisms. These merits enabled us optimize the balance of diagnostic, therapeutic and biodegradable functionalities in a multifunctional theranostic nanoplatform.

Treatment of cancer micrometastasis using a multicomponent chain-like nanoparticle

While potent cytotoxic agents are available to oncologists, the clinical utility of these agents is limited due to their non-specific distribution in the body and toxicity to normal tissues leading to use of suboptimal doses for eradication of metastatic disease. Furthermore, treatment of micrometastases is impeded by several biobarriers, including their small size and high dispersion to organs, making them nearly inaccessible to drugs. To circumvent these limitations in treating metastatic disease, we developed a multicomponent, flexible chain-like nanoparticle (termed nanochain) that possesses a unique ability to gain access to and be deposited at micrometastatic sites. Moreover, coupling nanochain particles to radiofrequency (RF)-triggered cargo delivery facilitated widespread delivery of drug into hard-to-reach cancer cells. Collectively, these features synergistically facilitate effective treatment and ultimately eradication of micrometastatic disease using a low dose of a cytotoxic drug.

Biotechnological approaches toward nanoparticle biofunctionalization

Nanomedicine has emerged in the past decade as a promising tool for several therapeutic and diagnostic applications. The development of nanoconjugates containing bioactive ligands specific for targeting cancer cell receptors has become a primary objective of modern nanotechnology. The design of ideal nanoconjugates requires optimization of fundamental parameters including size, shape, ligand shell composition, and reduction in nonspecific protein adsorption. Of great importance is the choice of bioconjugation approach, given that it affects the orientation, accessibility, and bioactivity of the targeting molecule. We provide an overview of recent advances in the immobilization of targeting proteins, focusing on methods to control ligand orientation and density, and highlight criteria for nanoparticle design and development required to achieve enhanced receptor-targeting efficiency.

Recent developments in liposome-based veterinary therapeutics

Recent advances in nanomedicine have been studied in the veterinary field and have found a wide variety of applications. The past decade has witnessed a massive surge of research interest in liposomes for delivery of therapeutic substances in animals. Liposomes are nanosized phospholipid vesicles that can serve as delivery platforms for a wide range of substances. Liposomes are easily formulated, highly modifiable, and easily administered delivery platforms. They are biodegradable and nontoxic and have long in vivo circulation time. This review focuses on recent and ongoing research that may have relevance for veterinary medicine. By examining the recent developments in liposome-based therapeutics in animal cancers, vaccines, and analgesia, this review depicts the current significance and future directions of liposome-based delivery in veterinary medicine.

Tissue distribution and efficacy of gold nanorods coupled with laser induced photoplasmonic therapy in ehrlich carcinoma solid tumor model

Gold nanorods (GNR) within tumor microregions are characterized by their ability to absorb near IR light and emit heat in what is called photoplasmonic effect. Yet, the efficacy of nanoparticles is limited due to intratumoral tissue distribution reasons. In addition, distribution of GNRs to normal tissue might result in non specific toxicity. In the current study, we are assessing the intratumoral and tissue distribution of PEGylated GNRs on the top of its antitumor characteristics when given intravenously or intratumoral to solid tumor bearing mice and coupled with laser photoplasmonic sessions. PEGylated GNRs with a longitudinal size of less than 100 nm were prepared with aspect ratio of 4.6 showing strong surface plasmon absorption at wavelength 800 nm. Pharmacokinetics of GNR after single I.V. administration (0.1 mg/kg) showed very short systemic circulating time (less than 3 h). On the other hand, tissue distribution of I.V. GNR (0.1 mg/kg) to normal animals showed preferential deposition in spleen tissue. Repeated administration of I.V. GNR resulted in preferential accumulation in both liver and spleen tissues. In addition, I.V. administration of GNR to Ehrlich carcinoma tumor bearing mice resulted in similar tissue distribution; tumor accumulation and anti-tumor effect compared to intratumoral administration. In conclusion, the concentration of GNR achieved within tumors microregions after I.V. administration was comparable to I.T. administration and sufficient to elicit tumoral growth arrest when coupled with laser-aided photoplasmonic treatment.

Molecular mechanisms of ETS transcription factor-mediated tumorigenesis

The E26 transformation-specific (ETS) family of transcription factors is critical for development, differentiation, proliferation and also has a role in apoptosis and tissue remodeling. Changes in expression of ETS proteins therefore have a significant impact on normal physiology of the cell. Transcriptional consequences of ETS protein deregulation by overexpression, gene fusion, and modulation by RAS/MAPK signaling are linked to alterations in normal cell functions, and lead to unlimited increased proliferation, sustained angiogenesis, invasion and metastasis. Existing data show that ETS proteins control pathways in epithelial cells as well as stromal compartments, and the crosstalk between the two is essential for normal development and cancer. In this review, we have focused on ETS factors with a known contribution in cancer development. Instead of focusing on a prototype, we address cancer associated ETS proteins and have highlighted the diverse mechanisms by which they affect carcinogenesis. Finally, we discuss strategies for ETS factor targeting as a potential means for cancer therapeutics.

Validation of tumour models for use in anticancer nanomedicine evaluation: the EPR effect and cathepsin B-mediated drug release rate

Purpose

Intravenously (i.v.) administered nanomedicines have the potential for tumour targeting due to the enhanced permeability and retention (EPR) effect, but in vivo tumour models are rarely calibrated with respect to functional vascular permeability and/or mechanisms controlling intratumoural drug release. Here the effect of tumour type and tumour size on EPR-mediated tumour localisation and cathepsin B-mediated drug release was studied.

Methods

Evans Blue (10 mg/kg) and an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer–doxorubicin (Dox) conjugate (FCE28068) (5 mg/kg Dox-equiv) were used as probes and tumour levels (and Dox release) measured at 1 h after i.v. administration in a panel of murine and human xenograft tumours.

Results

Evans Blue and FCE28068 displayed similar tumour levels in the range of 2–18 % dose/g at 1 h for B16F10 and L1210. Approximately half of the tumour models evaluated exhibited tumour size-dependent accumulation of FCE28068; smaller tumours had the highest accumulation. Administration of free Dox (5 mg/kg) produced tumour levels of <2.5 % dose/g independent of tumour size. Whereas the degree of EPR-mediated targeting showed ~12-fold difference across the tumour models evaluated, Dox release from FCE28068 at 1 h displayed ~200-fold variation.

Conclusions

Marked heterogeneity was seen in terms of EPR effect and Dox release rate, underlining the need to carefully calibrate tumour models used to benchmark nanomedicines against known relevant standard agents and for optimal development of strategies for late pre-clinical and clinical development.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-013-2209-7) contains supplementary material, which is available to authorized users.

Nanometre-scale thermometry in a living cell

Sensitive probing of temperature variations on nanometre scales is an outstanding challenge in many areas of modern science and technology. In particular, a thermometer capable of subdegree temperature resolution over a large range of temperatures as well as integration within a living system could provide a powerful new tool in many areas of biological, physical and chemical research. Possibilities range from the temperature-induced control of gene expression and tumour metabolism to the cell-selective treatment of disease and the study of heat dissipation in integrated circuits. By combining local light-induced heat sources with sensitive nanoscale thermometry, it may also be possible to engineer biological processes at the subcellular level. Here we demonstrate a new approach to nanoscale thermometry that uses coherent manipulation of the electronic spin associated with nitrogen-vacancy colour centres in diamond. Our technique makes it possible to detect temperature variations as small as 1.8 mK (a sensitivity of 9 mK Hz(-1/2)) in an ultrapure bulk diamond sample. Using nitrogen-vacancy centres in diamond nanocrystals (nanodiamonds), we directly measure the local thermal environment on length scales as short as 200 nanometres. Finally, by introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, we demonstrate temperature-gradient control and mapping at the subcellular level, enabling unique potential applications in life sciences.

In vitro cytotoxicity of silver nanoparticles in primary rat hepatic stellate cells

The number of studies concerning silver nanoparticles (AgNPs) has increased, due in part to their potential uses for biomedical applications. These particles have been demonstrated in the elimination of the hepatitis B virus and the inhibition of the proliferation of various cancer cells in vivo and in vitro. Thus, studies on AgNPs may lead to a more efficacious and safer therapeutic approach for chronic liver injury. Hepatic stellate cells (HSCs) are essential interstitial cells in the liver and are the predominant therapeutic target in hepatic fibrosis and liver cirrhosis; however, the intracellular effects of AgNPs on HSCs remain to be elucidated. The aim of the present study was to investigate the effects of AgNPs on the function and metabolism of HSCs. Various concentrations of AgNPs, with a diameter of 10 or 30‑50 nm, were incubated with HSCs. Transmission electron microscopy, flow cytometry, enzyme‑linked immunosorbent assays, and apoptosis and proliferation detection kits were used to analyze the effects of AgNPs on cell proliferation and metabolism. These studies demonstrated that AgNPs inhibited the proliferation of HSCs and induced their apoptosis in a size- and dose‑dependent manner.

Nanodiamonds-mediated doxorubicin nuclear delivery to inhibit lung metastasis of breast cancer

Lung metastasis is one of the greatest challenges for breast cancer treatment. Here, a nanodiamonds (NDs)-mediated doxorubicin (DOX) delivery system was first designed to inhibit the lung metastasis of breast cancer effectively. DOX was non-covalently bound to NDs via physical adsorption in an aqueous solution, then DSPE-PEG 2K was coated to the NDs-DOX complex (NDX) to increase the dispersibility and prolong the circulation time. DSPE-PEG 2K coating NDX (DNX) displayed high drug loading and excellent ability to deliver DOX to the nucleus, thereby significantly enhancing cytotoxicity and inducing cell apoptosis. Furthermore, DNX showed good histocompatibility and could improve drug accumulation in lung, as a result, markedly inhibited the lung metastasis of breast cancer. The high anti-metastasis efficacy with the decreased systemic toxicity suggested that DNX could be a promising drug delivery system for the therapy of lung metastasis of breast cancer.

One-pot synthesis of iron oxide nanoparticles with functional silane shells: a versatile general precursor for conjugations and biomedical applications

Iron oxide nanoparticles (IONPs) and their surface modifications with therapeutic or diagnostic (theranostic, TN) agents are of great interest. Here we present a novel one-pot synthesis of a versatile general TN precursor (aminosilane-coated IONPs [IONP-Sil(NH2)]) with surface amine groups. Surface functional group conversion to carboxylic acid was accomplished by conjugating poly(ethylene glycol) diacid to IONP-Sil(NH2). The NPs were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy. Biocompatibility and cell uptake profile of the nanoparticles were evaluated in-vitro using cultured liver cells (HepG2). Oleylamine (hydrophobic) and bovine serum albumin (BSA) as model drugs were attached to IONP-Sil-PEG(COOH). The ability of IONP-Sil(NH2) to bind small interfering RNA (siRNA) is also shown.

Nano-graphene oxide: a potential multifunctional platform for cancer therapy

Nano-GO is a graphene derivative with a 2D atomic layer of sp² bonded carbon atoms in hexagonal conformation together with sp³ domains with carbon atoms linked to oxygen functional groups. The supremacy of nano-GO resides essentially in its own intrinsic chemical and physical structure, which confers an extraordinary chemical versatility, high aspect ratio and unusual physical properties. The chemical versatility of nano-GO arises from the oxygen functional groups on the carbon structure that make possible its relatively easy functionalization, under mild conditions, with organic molecules or biological structures in covalent or non-covalent linkage. The synergistic effects resulting from the assembly of well-defined structures at nano-GO surface, in addition to its intrinsic optical, mechanical and electronic properties, allow the development of new multifunctional hybrid materials with a high potential in multimodal cancer therapy. Herein, a comprehensive review of the fundamental properties of nano-GO requirements for cancer therapy and the first developments of nano-GO as a platform for this purpose is presented.

Triggered Nanoparticles as Therapeutics

Drug delivery systems (DDSs) face several challenges including site-specific delivery, stability, and the programmed release of drugs. Engineered nanoparticle (NP) surfaces with responsive moieties can enhance the efficacy of DDSs for in vitro and in vivo systems. This triggering process can be achieved through both endogenous (biologically controlled release) and exogenous (external stimuli controlled release) activation. In this review, we will highlight recent examples of the use of triggered release strategies of engineered nanomaterials for in vitro and in vivo applications.

Effectively delivering a unique hsp90 inhibitor using star polymers

We report the synthesis of a novel heat shock protein 90 (hsp90) inhibitor conjugated to a star polymer. Using reversible addition-fragmentation chain-transfer (RAFT) polymerization, we prepared star polymers comprised of PEG attached to a predesigned functional core. The stars were cross-linked using disulfide linkers, and a tagged version of our hsp90 inhibitor was conjugated to the polymer core to generate nanoparticles (14 nM). Dynamic light scattering showed that the nanoparticles were stable in cell growth media for 5 days, and HPLC analysis of compound-release at 3 different pH values showed that release was pH dependent. Cell cytotoxicity studies and confocal microscopy verify that our hsp90 inhibitor was delivered to cells using this nanoparticle delivery system. Further, delivery of our hsp90 inhibitor using star polymer induces apoptosis by a caspase 3-dependent pathway. These studies show that we can deliver our hsp90 inhibitor effectively using star polymers, and induce apoptosis by the same pathway as the parent compound.

Using functional nanomaterials to target and regulate the tumor microenvironment: diagnostic and therapeutic applications

Malignant tumors remain a major health burden throughout the world and effective therapeutic strategies are urgently needed. Cancer nanotechnology, as an integrated platform, has the potential to dramatically improve cancer diagnosis, imaging, and therapy, while reducing the toxicity associated with the current approaches. Tumor microenvironment is an ensemble performance of various stromal cells and extracellular matrix. The recent progress in understanding the critical roles and the underlying mechanisms of the tumor microenvironment on tumor progression has resulted in emerging diagnostic and therapeutic nanomaterials designed and engineered specifically targeting the microenvironment components. Meanwhile, the bio-physicochemical differences between tumor and normal tissues have recently been exploited to achieve specific tumor-targeting for cancer diagnosis and treatment. Here, the major players in the tumor microenvironment and their biochemical properties, which can be utilized for the design of multifunctional nanomaterials with the potential to target and regulate this niche, are summarized. The recent progress in engineering intelligent and versatile nanomaterials for targeting and regulating the tumor microenvironment is emphasized. Although further investigations are required to develop robust methods for more specific tumor-targeting and well-controlled nanomaterials, the applications of tumor microenvironment regulation-based nanotechnology for safer and more effective anticancer nanomedicines have been proven successful and will eventually revolutionize the current landscape of cancer therapy.

Reconstructed stem cell nanoghosts: a natural tumor targeting platform

The ultimate goal in cancer therapy is achieving selective targeting of cancer cells. We report a novel delivery platform, based on nanoghosts (NGs) produced from the membranes of mesenchymal stem cells (MSCs). Encompassing MSC surface molecules, the MSC-NGs retained MSC-specific in vitro and in vivo tumor targeting capabilities and were cleared from blood-filtering organs. MSC-NGs were found to be biocompatible. Systemic administration of drug loaded MSC-NGs demonstrated 80% inhibition of human prostate cancer.

pH-responsive delivery of doxorubicin from citrate-apatite nanocrystals with tailored carbonate content

In this work, the efficiency of bioinspired citrate-functionalized nanocrystalline apatites as nanocarriers for delivery of doxorubicin (DOXO) has been assessed. The nanoparticles were synthesized by thermal decomplexing of metastable calcium/citrate/phosphate solutions both in the absence (Ap) and in the presence (cAp) of carbonate ions. The presence of citrate and carbonate ions in the solution allowed us to tailor the size, shape, carbonate content, and surface chemistry of the nanoparticles. The drug-loading efficiency of the two types of apatite was evaluated by means of the adsorption isotherms, which were found to fit a Langmuir-Freundlich behavior. A model describing the interaction between apatite surface and DOXO is proposed from adsorption isotherms and ζ-potential measurements. DOXO is adsorbed as a dimer by means of a positively charged amino group that electrostatically interacts with negatively charged surface groups of nanoparticles. The drug-release profiles were explored at pHs 7.4 and 5.0, mimicking the physiological pH in the blood circulation and the more acidic pH in the endosome-lysosome intracellular compartment, respectively. After 7 days at pH 7.4, cAp-DOXO released around 42% less drug than Ap-DOXO. However, at acidic pH, both nanoassemblies released similar amounts of DOXO. In vitro assays analyzed by confocal microscopy showed that both drug-loaded apatites were internalized within GTL-16 human carcinoma cells and could release DOXO, which accumulated in the nucleus in short times and exerted cytotoxic activity with the same efficiency. cAp are thus expected to be a more promising nanocarrier for experiments in vivo, in situations where intravenous injection of nanoparticles are required to reach the targeted tumor, after circulating in the bloodstream.

Biomaterials and biotechnology: from the discovery of the first angiogenesis inhibitors to the development of controlled drug delivery systems and the foundation of tissue engineering

This paper describes the discovery of the first inhibitors of angiogenesis; the discoveries that led to the development of the first biocompatible controlled release systems for macromolecules, and findings that helped to create the field of tissue engineering. In addition, new paradigms for creating biomaterials, early work on nanotechnology in medicine and intelligent drug delivery systems are discussed.

Targeted nanoparticles in imaging: paving the way for personalized medicine in the battle against cancer

The way we view cancer has advanced greatly in the past few decades from simplistic approaches to finely honed systems. This transition has been made possible because of advancements on two fronts: the first is the rapidly expanding knowledge base of the mechanisms and characteristics of cancer; the second is innovation in imaging agent design. Rapid advancements in imaging and therapeutic agents are being made through the evolution from one-dimensional molecules to multi-functional nanoparticles. Powerful new agents that have high specificity and minimal toxicity are being developed for in vivo imaging. Here we detail the unique characteristics of cancer that allow differentiation from normal tissue and how they are exploited in nanoparticle imaging development. Firstly, genetic alterations, either endogenous or induced through gene therapy, are one such class of characteristics. Proteomic differences such as overexpressed surface receptors is another targetable feature used for enhanced nanoparticle retention. Increased need for nutrients and specific growth signals to sustain proliferation and angiogenesis are further examples of how cancer can be targeted. Lastly, migration and invasion through a unique microenvironment are two additional traits that are exploitable, due to differences in metalloproteinase concentrations and other factors. These differences are guiding current nanoparticle design to better target, image and treat cancer.

Clinically-translated silica nanoparticles as dual-modality cancer-targeted probes for image-guided surgery and interventions

Early diagnosis and treatment of melanoma are essential to minimizing morbidity and mortality. The presence of lymph node metastases is a vital prognostic predictor, and accurate identification by imaging has important implications for disease staging, prognosis, and clinical outcome. Sentinel lymph node (SLN) mapping procedures are limited by a lack of intraoperative visualization tools that can aid accurate determination of disease spread and delineate nodes from adjacent critical neural and vascular structures. Newer methods for circumventing these issues can exploit a variety of imaging tools, including biocompatible particle-based platforms coupled with portable device technologies for use with image-guided surgical and interventional procedures. We describe herein a clinically-translated, integrin-targeting platform for use with both PET and optical imaging that meets a number of key design criteria for improving SLN tissue localization and retention, target-to-background ratios, and clearance from the site of injection and the body. The use of such agents for selectively probing critical cancer targets may elucidate important insights into cellular and molecular processes that govern metastatic disease spread. Coupled with portable, real-time optical camera systems, we show that pre-operative PET imaging findings for mapping metastatic disease in clinically-relevant larger-animal models can be readily translated into the intraoperative setting for direct visualization of the draining tumor lymphatics and fluorescent SLN/s with histologic correlation. The specificity of this platform, relative to the standard-of-care radiotracer, (18)F-FDG, for potentially discriminating metastatic disease from inflammatory processes is also discussed in the setting of surgically-based or interventionally-driven therapies.

Casein-coated iron oxide nanoparticles for high MRI contrast enhancement and efficient cell targeting

Surface properties, as well as inherent physicochemical properties, of the engineered nanomaterials play important roles in their interactions with the biological systems, which eventually affect their efficiency in diagnostic and therapeutic applications. Here we report a new class of MRI contrast agent based on milk casein protein-coated iron oxide nanoparticles (CNIOs) with a core size of 15 nm and hydrodynamic diameter ~30 nm. These CNIOs exhibited excellent water-solubility, colloidal stability, and biocompatibility. Importantly, CNIOs exhibited prominent T2 enhancing capability with a transverse relaxivity r2 of 273 mM(-1) s(-1) at 3 tesla. The transverse relaxivity is ~2.5-fold higher than that of iron oxide nanoparticles with the same core but an amphiphilic polymer coating. CNIOs showed pH-responsive properties, formed loose and soluble aggregates near the pI (pH ~4.0). The aggregates could be dissociated reversibly when the solution pH was adjusted away from the pI. The transverse relaxation property and MRI contrast enhancing effect of CNIOs remained unchanged in the pH range of 2.0-8.0. Further functionalization of CNIOs can be achieved via surface modification of the protein coating. Bioaffinitive ligands, such as a single chain fragment from the antibody of epidermal growth factor receptor (ScFvEGFR), could be readily conjugated onto the protein coating, enabling specific targeting to MDA-MB-231 breast cancer cells overexpressing EGFR. T2-weighted MRI of mice intravenously administered with CNIOs demonstrated strong contrast enhancement in the liver and spleen. These favorable properties suggest CNIOs as a class of biomarker targeted magnetic nanoparticles for MRI contrast enhancement and related biomedical applications.

The use of shear stress for targeted drug delivery

Stenosed segments of arteries significantly alter the blood flow known from healthy vessels. In particular, the wall shear stress at critically stenosed arteries is at least an order of magnitude higher than in healthy situations. This alteration represents a change in physical force and might be used as a trigger signal for drug delivery. Mechano-sensitive drug delivery systems that preferentially release their payload under increased shear stress are discussed. Therefore, besides biological or chemical markers, physical triggers are a further principle approach for targeted drug delivery. We hypothesize that such a physical trigger is much more powerful to release drugs for vasodilation, plaque stabilization, or clot lysis at stenosed arteries than any known biological or chemical ones.

Near-infrared fluorescent silica-coated gold nanoparticle clusters for x-ray computed tomography/optical dual modal imaging of the lymphatic system

Lymph nodes (LNs) are often removed to prevent the spread of cancer because they are frequently the first site of metastases. However, the enucleation of LNs requires difficult operative techniques and lymphedema can result as a complication. Although lymphedema can be cured by anastomosis of a lymph vessel (LV) to a vein, the operative procedure is extremely difficult because LNs and LVs are too small and indistinct to be identified. Therefore, visualization of LNs and LVs is important. The combination of X-ray computed tomography (CT) and fluorescence imaging, CT/fluorescence dual modal imaging, enables the visualization of LNs and LVs before and during surgery. To accomplish this, near-infrared fluorescent silica-coated gold nanoparticle clusters (Au@SiO₂) with a high X-ray absorption coefficient are synthesized. Both fluorescence imaging and CT show that the Au@SiO₂ nanoparticles gradually accumulate in LNs through LVs. CT determines the location and size of the LNs and LVs without dissection, and fluorescence imaging facilitates their identification. The Au@SiO₂ nanoparticles have neither hepatotoxicity nor nephrotoxicity. The results demonstrate that CT/fluorescence dual modal imaging using Au@SiO₂ nanoparticles provides anatomical information, including the location and size of LNs and LVs for determining a surgery plan, and provides intraoperative visualization of LNs and LVs to facilitate the operation.

Overcoming pharmacologic sanctuaries

PURPOSE OF REVIEW

Current antiretroviral treatment regimens represent significant improvements in the management of HIV-1 infection; however, these regimens have not achieved a functional or sterilizing cure. One barrier to achieving a cure may be suboptimal antiretroviral concentrations in sanctuary sites throughout the body, including the central nervous system, gut-associated lymphoid tissue, lymph nodes, and tissue macrophages. This review will focus on the problems associated with achieving effective concentrations in these restricted sanctuary sites, and potential strategies to overcome these barriers.

RECENT FINDINGS

Sufficient data exist to conclude that antiretroviral drug distribution is not uniform throughout the body. Low tissue/reservoir concentrations may be associated with viral replication. Multiple means to increase drug concentrations in sanctuary sites are being investigated, including modification of currently utilized drugs, blockade of transporters and enzymes that affect drug metabolism and pharmacokinetics, and local drug administration. Accumulating data suggest these methods increase antiretroviral concentrations in reservoirs of viral replication. No method has yet resulted in the complete clearance of HIV.

SUMMARY

New strategies for increasing antiretroviral concentrations in predominant sites of viral replication may provide more effective means for elimination of viral sanctuaries. Additional research is necessary to optimize antiretroviral tissue distribution in order to inhibit virus replication fully, and avoid resistance and replenishment of viral reservoirs that may persist in the face of antiretroviral therapy.

Multifunctional nanoparticles for drug delivery and molecular imaging

Recent advances in nanotechnology and growing needs in biomedical applications have driven the development of multifunctional nanoparticles. These nanoparticles, through nanocrystalline synthesis, advanced polymer processing, and coating and functionalization strategies, have the potential to integrate various functionalities, simultaneously providing (a) contrast for different imaging modalities, (b) targeted delivery of drug/gene, and (c) thermal therapies. Although still in its infancy, the field of multifunctional nanoparticles has shown great promise in emerging medical fields such as multimodal imaging, theranostics, and image-guided therapies. In this review, we summarize the techniques used in the synthesis of complex nanostructures, review the major forms of multifunctional nanoparticles that have emerged over the past few years, and provide a perceptual vision of this important field of nanomedicine.

Harnessing nanomedicine for mucosal theranostics--a silver bullet at last?

Inflammatory bowel disease (IBD) has been extensively studied in the last four decades both in animal models and humans. The treatment options remain disappointing, nonspecific, and associated with multiple systemic adverse effects. In this Perspective, we highlight issues related to emerging nanotechnologies designed particularly for treatment and disease management of IBD and discuss potential therapeutic target options with novel molecular imaging modalities.

The failures and challenges of bone metastases research in radiation oncology

Bone metastases affect a large portion of the cancer population. As treatment options continue to evolve, many added failures and challenges arise. This narrative review details such in palliative radiation therapy for bone metastases. We begin by describing the incidence rates of bone metastases in the cancer population, the current standards of practice in recent literature and clinical trial data. Inconsistencies in end point definitions along with difficulties in measuring response to treatment and controversial areas are outlined. Current literature suggests that there is a discrepancy in physician and patient perspective on treatment options as well as quality of life. The added challenges of treatment side effects are addressed and a review of recent trials is given. Stereotactic radiation therapy is a relatively new treatment option for patients with bone metastases. Therefore, a review of the safety and efficacy of this treatment is provided. Other new areas of bone metastases treatment and research such as high intensity focused ultrasound and nanoparticles are discussed. Physicians need to prevent unwanted side effects of treatment in addition to determining how to integrate many new upcoming treatment options for patients with bone metastases. A continued reluctance to practice evidence based medicine needs to be addressed.

Nanoparticle-mediated delivery of anticancer agents to tumor angiogenic vessels

Nanoparticle-mediated drug delivery systems targeting tumor angiogenic vessels have been studied for antineovascular cancer therapy achieved by induction of apoptosis of angiogenic endothelial cells. Nanoparticles such as liposomes are considered to accumulate in tumors due to the enhanced permeability and retention effect. The delivery efficiency of this system appears to be affected by the density of tumor angiogenic vessels regardless of modification with tumor-targeting ligands on the surface of nanoparticles. It remains a challenging problem to deliver sufficient amounts of anticancer drugs to hypovascular tumors using nanoparticles. On the other hand, the strategy of angiogenic vessel-targeting is theoretically different from that of tumor cell-targeting since target angiogenic endothelial cells face the circulating blood. In addition, this strategy is expected to cause indirect tumor regression by disrupting angiogenic vessels. In this review, our recent studies are summarized to show the actual efficacy of angiogenic vessel-targeting delivery. We have developed various angiogenic vessel-targeted liposomes and evaluated them in experimental cancer models such as drug-resistant and hypovascular tumors. Our data indicate that increased apoptosis of angiogenic endothelial cells can be achieved by the targeted liposomes encapsulating cytotoxic drugs, resulting in enhanced anticancer effects. The advantages of angiogenic vessel-targeting are discussed based on our recent findings to provide an insight into why angiogenic vessels are a promising target for advanced cancer therapy.

Multifunctional Polymer-Coated Carbon Nanotubes for Safe Drug Delivery

Though progress in the use carbon nanotubes in medicine has been most encouraging for therapeutic and diagnostic applications, any translational success must involve overcoming the toxicological and surface functionalization challenges inherent in the use of such nanotubes. Ideally, a carbon nanotube-based drug delivery system would exhibit low toxicity, sustained drug release, and persist in circulation without aggregation. We report a carbon nanotube (CNT) coated with a biocompatible block-co-polymer composed of poly(lactide)-poly(ethylene glycol) (PLA-PEG) to reduce short-term and long-term toxicity, sustain drug release of paclitaxel (PTX), and prevent aggregation. The copolymer coating on the surface of CNTs significantly reduces in vitro toxicity in human umbilical vein endothelial cells (HUVEC) and U-87 glioblastoma cells. Moreover, coating reduces in vitro inflammatory response in rat lung epithelial cells. Compared to non-coated CNTs, in vivo studies show no long-term inflammatory response with CNT coated with PLA-PEG (CLP) and the surface coating significantly decreases acute toxicity by doubling the maximum tolerated dose in mice. Using polymer coatings, we can encapsulate PTX and release over one week to increase the therapeutic efficacy compared to free drugs. In vivo biodistribution and histology studies suggests a lower degree of aggregation in tissues in that CLP accumulate more in the brain and less in the spleen than the CNT-PLA (CL) formulation.

Metabolism of nanomaterials in vivo: blood circulation and organ clearance

Before researchers apply nanomaterials (NMs) in biomedicine, they need to understand the blood circulation and clearance profile of these materials in vivo. These qualities determine the balance between nanomaterial-induced activity and unwanted toxicity. NMs have heterogeneous characteristics: they combine the bulk properties of solids with the mobility of molecules, and their highly active contact interfaces exhibit diverse functionalities. Any new and unexpected circulation features and clearance patterns are of great concern in toxicological studies and pharmaceutical screens. A number of studies have reported that NMs can enter the bloodstream directly during their application or indirectly via inhalation, ingestion, and dermal exposure. Due to the small size of NMs, the blood can then transport them throughout the circulation and to many organs where they can be stored. In this Account, we discuss the blood circulation and organ clearance patterns of NMs in the lung, liver, and kidney. The circulation of NMs in bloodstream is critical for delivery of inhalable NMs to extrapulmonary organs, the delivery of injectable NMs, the dynamics of tissue redistribution, and the overall targeting of drug carriers to specific cells and organs. The lung, liver, and kidney are the major distribution sites and target organs for NMs exposure, and the clearance patterns of NMs in these organs are critical for understanding the in vivo fate of NMs. Current studies suggest that multiple factors control the circulation and organ clearance of NMs. The size, shape, surface charge, surface functional groups, and aspect ratio of NMs as well as tissue microstructures strongly influence the circulation of NMs in bloodstream, their site-specific extravasation, and their clearance profiles within organs. Therefore structure design and surface modification can improve biocompatibility, regulate the in vivo metabolism, and reduce the toxicity of NMs. The biophysicochemical interactions occurring between NMs and between NMs and the biological milieu after the introduction of NMs into living systems may further influence the blood circulation and clearance profiles of NMs. These interactions can alter properties such as agglomeration, phase transformations, dissolution, degradation, protein adsorption, and surface reactivity. The physicochemical properties of NMs change dynamically in vivo thereby making the metabolism of NMs complex and difficult to predict. The development of in situ, real-time, and quantitative techniques, in vitro assays, and the adaptation of physiologically-based pharmacokinetic (PBPK) and quantitative structure-activity relationship (QNSAR) modeling for NMs will streamline future in vivo studies.

Prediction of micelle/water and liposome/water partition coefficients based on molecular dynamics simulations, COSMO-RS, and COSMOmic

Liposomes and micelles find various applications as potential solubilizers in extraction processes or in drug delivery systems. Thermodynamic and transport processes governing the interactions of different kinds of solutes in liposomes or micelles can be analyzed regarding the free energy profiles of the solutes in the system. However, free energy profiles in heterogeneous systems such as micelles are experimentally almost not accessible. Therefore, the development of predictive methods is desirable. Molecular dynamics (MD) simulations reliably simulate the structure and dynamics of lipid membranes and micelles, whereas COSMO-RS accurately reproduces solvation free energies in different solvents. For the first time, free energy profiles in micellar systems, as well as mixed lipid bilayers, are investigated, taking advantage of both methods: MD simulations and COSMO-RS, referred to as COSMOmic (Klamt, A.; Huniar, U.; Spycher, S.; Keldenich, J. COSMOmic: A Mechanistic Approach to the Calculation of Membrane-Water Partition Coefficients and Internal Distributions within Membranes and Micelles. J. Phys. Chem. B 2008, 112, 12148-12157). All-atom molecular dynamics simulations of the system SDS/water and CTAB/water have been applied in order to retrieve representative micelle structures for further analysis with COSMOmic. For the system CTAB/water, different surfactant concentrations were considered, which results in different micelle sizes. Free energy profiles of more than 200 solutes were predicted and validated by means of experimental partition coefficients. To our knowledge, these are the first quantitative predictions of micelle/water partition coefficients, which are based on whole free energy profiles from molecular methods. Further, the partitioning in lipid bilayer systems containing different hydrophobic tail groups (DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine), SOPC (stearoyl-oleoylphosphatidylcholine), DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine)) as well as mixed bilayers was calculated. Experimental partition coefficients (log P) were reproduced with a root-mean-square error (RMSE) of 0.62. To determine the influence of cholesterol as an important component of cellular membranes, free energy profiles in the presence of cholesterol were calculated and shown to be in good agreement with experimental data.

Synergistic antitumor activity from two-stage delivery of targeted toxins and endosome-disrupting nanoparticles

Plant-derived Type I toxins are candidate anticancer therapeutics requiring cytosolic delivery into tumor cells. We tested a concept for two-stage delivery, whereby tumor cells precoated with an antibody-targeted gelonin toxin were killed by exposure to endosome-disrupting polymer nanoparticles. Co-internalization of particles and tumor cell-bound gelonin led to cytosolic delivery and >50-fold enhancement of toxin efficacy. This approach allows the extreme potency of gelonin to be focused on tumors with significantly reduced potential for off-target toxicity.

A platelet-mimetic paradigm for metastasis-targeted nanomedicine platforms

There is compelling evidence that, beyond their traditional role in hemostasis and thrombosis, platelets play a significant role in mediating hematologic mechanisms of tumor metastasis by directly and indirectly interacting with pro-metastatic cancer cells. With this rationale, we hypothesized that platelets can be an effective paradigm to develop nanomedicine platforms that utilize platelet-mimetic interaction mechanisms for targeted diagnosis and therapy of metastatic cancer cells. Here we report on our investigation of the development of nanoconstructs that interact with metastatic cancer cells via platelet-mimetic heteromultivalent ligand-receptor pathways. For our studies, pro-metastatic human breast cancer cell line MDA-MB-231 was studied for its surface expression of platelet-interactive receptors, in comparison to another low-metastatic human breast cancer cell line, MCF-7. Certain platelet-interactive receptors were found to be significantly overexpressed on the MDA-MB-231 cells, and these cells showed significantly enhanced binding interactions with active platelets compared to MCF-7 cells. Based upon these observations, two specific receptor interactions were selected, and corresponding ligands were engineered onto the surface of liposomes as model nanoconstructs, to enable platelet-mimetic binding to the cancer cells. Our model platelet-mimetic liposomal constructs showed enhanced targeting and attachment of MDA-MB-231 cells compared to the MCF-7 cells. These results demonstrate the promise of utilizing platelet-mimetic constructs in modifying nanovehicle constructs for metastasis-targeted drug as well as modifying surfaces for ex-vivo cell enrichment diagnostic technologies.

Doxorubicin-conjugated dendrimer/collagen hybrid gels for metastasis-associated drug delivery systems

Metastasis is a characteristic property of cancer cells, which degrade extracellular matrix containing collagen. We prepared a polymer prodrug-embedded collagen gel for metastasis-associated drug delivery. A collagen peptide-modified dendrimer that attached doxorubicin (Dox) via a pH-degradable linkage was synthesized as a polymer prodrug. Compared with free Dox, the diffusion of the dendrimer prodrug from the collagen gel was suppressed. Highly invasive MDA-MB-231 cells were more sensitive to the prodrug-hybrid collagen gel than poorly invasive MCF-7 cells, even though the cytotoxicity of the dendrimer prodrug by itself against these cells was almost identical. The cytotoxicity against MDA-MB-231 cells decreased in the presence of a matrix metalloproteinase (MMP) inhibitor, suggesting that the dendrimer prodrug/collagen hybrid gel was affected by MMP activity. The dendrimer prodrug/collagen hybrid gel not only suppressed tumor growth but also attenuated metastatic activity in vivo. Therefore, the dendrimer prodrug-embedded collagen gel is useful for cancer chemotherapy.

Nanotechnology-based photodynamic therapy

According to recent advances in nanotechnology, various nano-sized formulations have been designed for the application in biomedical fields, including diagnosis, drug delivery, and therapeutics. The nanotechnology-based formulations have a great merit in the design of multifunctional platform for the biomedical applications. Therefore, recent trends in nanotechnology are moving onto the combination of nanotechnology and conventional therapeutic. Typically, photodynamic therapy (PDT) is one of promising techniques for the combination with nanotechnology owing to its less invasiveness. In this paper, we are going to briefly review recent advances in nanotechnology-based PDT, including selective delivery and excitation of photosensitizers, combination therapy, and multifunctional PDT.