Nanoparticle therapeutics: an emerging treatment modality for cancer

Metal-organic frameworks as potential drug carriers

Nanoparticle-based therapeutics have received increasing attention, as these systems can alleviate many drawbacks of conventional therapy. Metal-organic frameworks (MOFs), a new class of hybrid materials composed of metal ions and organic bridging ligands, have emerged as a promising platform for drug delivery, owing to their high drug loadings, biodegradability, and versatile functionality. The bulk MOF materials can absorb and release large amounts of therapeutics including ibuprofen, procainamide, and nitric oxide. Scale-down of MOFs to the nanoregime yields nanoscale metal-organic frameworks (NMOFs) that are more applicable as delivery vehicles, such as selective delivery of cisplatin prodrugs. Although progress has been made in utilizing NMOFs for drug delivery, many improvements must occur before they can become viable nanotherapeutics.

Polymers for drug delivery systems

Polymers have played an integral role in the advancement of drug delivery technology by providing controlled release of therapeutic agents in constant doses over long periods, cyclic dosage, and tunable release of both hydrophilic and hydrophobic drugs. From early beginnings using off-the-shelf materials, the field has grown tremendously, driven in part by the innovations of chemical engineers. Modern advances in drug delivery are now predicated upon the rational design of polymers tailored for specific cargo and engineered to exert distinct biological functions. In this review, we highlight the fundamental drug delivery systems and their mathematical foundations and discuss the physiological barriers to drug delivery. We review the origins and applications of stimuli-responsive polymer systems and polymer therapeutics such as polymer-protein and polymer-drug conjugates. The latest developments in polymers capable of molecular recognition or directing intracellular delivery are surveyed to illustrate areas of research advancing the frontiers of drug delivery.

Controlled synthesis of camptothecin-polylactide conjugates and nanoconjugates

We report here a unique method of formulating camptothecin-polylactide (CPT-PLA) conjugate nanoparticles, termed nanoconjugates (NCs), through CPT/(BDI)ZnN(TMS)(2) [(BDI) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-bisalkyl)-imino)-2-pentene] mediated polymerization of lactide (LA) followed by nanoprecipitation. When CPT was used as the initiator to polymerize LA in the presence of (BDI)ZnN(TMS)(2), the polymerization was completed within hours with nearly 100% CPT loading efficiency and 100% LA conversion. CPT loading as high as 19.5% can be achieved for the CPT-polylactide (CPT-PLA) conjugate prepared at a LA/CPT ratio of 10. The steric bulk of the chelating ligands and the type of metals used had a dramatic effect on the initiation of the LA polymerization and the tendency of the ring-opening of the CPT lactone. The CPT/(BDI)ZnN(TMS)(2)-mediated LA polymerization yielded CPT-PLA conjugates with well-controlled molecular weights and narrow molecular weight distributions (1.02-1.18). The nanoprecipitation of CPT-PLA led to the formation of NCs around 100 nm in size with narrow particle size distributions. Sustained release of CPT from CPT-PLA NCs was achieved without burst release. CPT-PLA NCs were toxic to PC-3 cells with tunable IC(50) possible by adjusting the drug loading of the CPT-PLA NCs.

Design considerations for tumour-targeted nanoparticles

Inorganic/organic hybrid nanoparticles are potentially useful in biomedicine, but to avoid non-specific background fluorescence and long-term toxicity, they need to be cleared from the body within a reasonable timescale. Previously, we have shown that rigid spherical nanoparticles such as quantum dots can be cleared by the kidneys if they have a hydrodynamic diameter of approximately 5.5 nm and a zwitterionic surface charge. Here, we show that quantum dots functionalized with high-affinity small-molecule ligands that target tumours can also be cleared by the kidneys if their hydrodynamic diameter is less than this value, which sets an upper limit of 5-10 ligands per quantum dot for renal clearance. Animal models of prostate cancer and melanoma show receptor-specific imaging and renal clearance within 4 h post-injection. This study suggests a set of design rules for the clinical translation of targeted nanoparticles that can be eliminated through the kidneys.

Progress in siRNA delivery using multifunctional nanoparticles

Nanoparticles made from synthetic polymers have been developed to deliver small interfering RNA (siRNA). For successful siRNA delivery, these nanoparticles need to efficiently encapsulate siRNA, actively target sites of interest, and release siRNA intracellularly. This chapter reviews recent progress using a multifunctional approach to design and engineer polymeric nanoparticles for siRNA delivery.

Nanoparticle technologies for cancer therapy

Nanoparticles as drug delivery systems enable unique approaches for cancer treatment. Over the last two decades, a large number of nanoparticle delivery systems have been developed for cancer therapy, including organic and inorganic materials. Many liposomal, polymer-drug conjugates, and micellar formulations are part of the state of the art in the clinics, and an even greater number of nanoparticle platforms are currently in the preclinical stages of development. More recently developed nanoparticles are demonstrating the potential sophistication of these delivery systems by incorporating multifunctional capabilities and targeting strategies in an effort to increase the efficacy of these systems against the most difficult cancer challenges, including drug resistance and metastatic disease. In this chapter, we will review the available preclinical and clinical nanoparticle technology platforms and their impact for cancer therapy.

Mechanism of active targeting in solid tumors with transferrin-containing gold nanoparticles

PEGylated gold nanoparticles are decorated with various amounts of human transferrin (Tf) to give a series of Tf-targeted particles with near-constant size and electrokinetic potential. The effects of Tf content on nanoparticle tumor targeting were investigated in mice bearing s.c. Neuro2A tumors. Quantitative biodistributions of the nanoparticles 24 h after i.v. tail-vein injections show that the nanoparticle accumulations in the tumors and other organs are independent of Tf. However, the nanoparticle localizations within a particular organ are influenced by the Tf content. In tumor tissue, the content of targeting ligands significantly influences the number of nanoparticles localized within the cancer cells. In liver tissue, high Tf content leads to small amounts of the nanoparticles residing in hepatocytes, whereas most nanoparticles remain in nonparenchymal cells. These results suggest that targeted nanoparticles can provide greater intracellular delivery of therapeutic agents to the cancer cells within solid tumors than their nontargeted analogs.

Review Article: High-Content Screening: A Decade of Evolution

In the past decade, high-content screening has become a highly developed approach to obtaining richly descriptive quantitative phenotypic data using automated microscopy. From early use in drug screening, the technique has evolved to embrace a diverse range of applications in both academic and industrial sectors and is now widely recognized as providing an efficient and effective approach to large-scale programs investigating cell biology in situ and in context.

The cancer stem cell concept in progression of head and neck cancer

Human head and neck cancer (HNC) is a highly heterogeneous disease. Understanding the biology of HNC progression is necessary for the development of novel approaches to its prevention, early detection, and treatment. A current evolutional progression model has limitations in explaining the heterogeneity observed in a single tumor nest. Accumulating evidence supports the existence of cancer stem cells (CSCs) as small subpopulations in solid tumors, including HNC. These CSCs can be selected by appropriate cell surface markers, which are cancer type specific and have been confirmed by unique in vitro and in vivo assays. Selected CSC populations maintain a self-renewal capability and show aggressive behaviors, such as chemoresistance and metastasis. In addition to introducing the CSC concept in solid tumors, this short review summarizes current publications in HNC CSC and the prospective development and application of the CSC concept to HNC in the clinic.

PEGylated PLGA nanoparticles for the improved delivery of doxorubicin

We hypothesize that the efficacy of doxorubicin (DOX) can be maximized and dose-limiting cardiotoxicity minimized by controlled release from PEGylated nanoparticles. To test this hypothesis, a unique surface modification technique was used to create PEGylated poly(lactic-co-glycolic acid) (PLGA) nanoparticles encapsulating DOX. An avidin-biotin coupling system was used to control poly(ethylene glycol) conjugation to the surface of PLGA nanoparticles, of diameter approximately 130 nm, loaded with DOX to 5% (wt/wt). Encapsulation in nanoparticles did not compromise the efficacy of DOX; drug-loaded nanoparticles were found to be at least as potent as free DOX against A20 murine B-cell lymphoma cells in culture and of comparable efficacy against subcutaneously implanted tumors. Cardiotoxicity in mice as measured by echocardiography, serum creatine phosphokinase (CPK), and histopathology was reduced for DOX-loaded nanoparticles as compared with free DOX. Administration of 18 mg/kg of free DOX induced a sevenfold increase in CPK levels and significant decreases in left ventricular fractional shortening over control animals, whereas nanoparticle-encapsulated DOX produced none of these pathological changes.

FROM THE CLINICAL EDITOR

The efficacy of doxorubicin (DOX) may be maximized and dose-limiting cardiotoxicity minimized by controlled release from PEGylated nanoparticles. Administration of 18 mg/kg of free DOX induced a sevenfold increase in CPK levels and significant decreases in left ventricular fractional shortening in mice, whereas nanoparticle-encapsulated DOX produced none of these pathological changes.

Silk nanospheres and microspheres from silk/pva blend films for drug delivery

Silk fibroin protein-based micro- and nanospheres provide new options for drug delivery due to their biocompatibility, biodegradability and their tunable drug loading and release properties. In the present study, we report a new aqueous-based preparation method for silk spheres with controllable sphere size and shape. The preparation was based on phase separation between silk fibroin and polyvinyl alcohol (PVA) at a weight ratio of 1/1 and 1/4. Water-insoluble silk spheres were easily obtained from the blend in a three step process: (1) air-drying the blend solution into a film, (2) film dissolution in water and (3) removal of residual PVA by subsequent centrifugation. In both cases, the spheres had approximately 30% beta-sheet content and less than 5% residual PVA. Spindle-shaped silk particles, as opposed to the spherical particles formed above, were obtained by stretching the blend films before dissolving in water. Compared to the 1/1 ratio sample, the silk spheres prepared from the 1/4 ratio sample showed a more homogeneous size distribution ranging from 300 nm up to 20 microm. Further studies showed that sphere size and polydispersity could be controlled either by changing the concentration of silk and PVA or by applying ultrasonication on the blend solution. Drug loading was achieved by mixing model drugs in the original silk solution. The distribution and loading efficiency of the drug molecules in silk spheres depended on their hydrophobicity and charge, resulting in different drug release profiles. The entire fabrication procedure could be completed within one day. The only chemical used in the preparation except water was PVA, an FDA-approved ingredient in drug formulations. Silk micro- and nanospheres reported have potential as drug delivery carriers in a variety of biomedical applications.

Targeting the tumor microenvironment with anti-neu/anti-CD40 conjugated nanoparticles for the induction of antitumor immune responses

Clinical and preclinical data indicate that immunotherapeutic interventions could induce immune responses capable of controlling or retard the tumor growth. However, immunotherapies need to be further optimized. We hypothesized that a more effective strategy for tumor eradication is to directly target the tumor microenvironment in order to generate a proinflammatory response and induce a localized antitumor immune response capable of eliminating the tumor cells. Nanoparticles have been proven to be an effective delivery system. In these studies we evaluated conjugated anti-RNEU and anti-CD40 antibodies onto PLA-(poly dl-lactic acid)-biodegradable nanoparticles (PLA-NP) for the induction of antitumor immune responses. The anti-neu/anti-CD40-NP were functional in vitro recognizing RNEU(+) tumors and activating dendritic cells. The delivery of anti-neu/anti-CD40-NP but not anti-neu-NP or anti-CD40-NP induced an antitumor response resulting in complete tumor elimination and generation of protective memory responses. The anti-neu/anti-CD40-NP specifically activated an antitumor response against RNEU(+) tumors but not against RNEU(-) tumors. The antitumor immune responses correlate with the induction of a Th1-proinflammatory response, reduction in the number of Tregs within the tumor and activation of a specific cytotoxic response. These results indicate that anti-neu/anti-CD40-NP with immunomodulatory properties are safe and can be used effectively as cancer vaccines strategy for the specific induction of antitumor immune responses.

In vivo nano-imaging of membrane dynamics in metastatic tumor cells using quantum dots

Changes in membrane morphology and membrane protein dynamics based on its fluidity are critical for cancer metastasis. However, this subject has remained unclear, because the spatial precision of previous in vivo imaging has been limited to the micrometer level and single molecule imaging is impossible. Here, we have imaged the membrane dynamics of tumor cells in mice with a spatial precision of 7-9 nm under a confocal microscope. A metastasis-promoting factor on the cell membrane, protease-activated receptor 1 (PAR1), was labeled with quantum dots conjugated with an anti-PAR1 antibody. Movements of cancer cells and PAR1 during metastasis were clearly observed in vivo. Images used to assess PAR1 dynamics were taken of representative cells for four stages of metastasis; i.e. cancer cells far from blood vessels in tumor, near the vessel, in the bloodstream, and adherent to the inner vascular surface in the normal tissues near tumor were photographed. The diffusion constant of PAR1 in static cells far from tumor blood vessels was smaller than in moving cells near the vessels and in the bloodstream. The diffusion constant of cells adhering to the inner vascular surface in the normal tissues was also very small. Cells formed membrane protrusion during migration. The PAR1 diffusion constant on these pseudopodia was greater than in other membrane regions in the same cell. Thus, the dynamics of PAR1 movement showed that membrane fluidity increases during intravasation, reaches a peak in the vessel, decreases during extravasation, and is also higher at locally formed pseudopodia.

Design and development of IT-101, a cyclodextrin-containing polymer conjugate of camptothecin

IT-101 (Insert Therapeutics-101) is a linear, cyclodextrin-containing polymer conjugate of camptothecin (CPT). When formulated properly, the polymer conjugate self-assembles into nanoparticles of ca. 30 nm diameter and near neutral zeta potential. The nanoparticles show long circulation half-lives in animals and humans and localize in tumors. The nanoparticles enter the tumor cells and slowly release the CPT causing them to disassemble into individual polymer chains that are sufficiently small to be cleared renally. IT-101 is currently being investigated in human clinical trials. Here, the design and development of IT-101 is described with emphasis on features distinguishing it from other polymer-containing therapeutics.

Morphological study of acoustic liposomes using transmission electron microscopy

Sonoporation is achieved by ultrasound-mediated destruction of ultrasound contrast agents (UCA) microbubbles. For this, UCAs must be tissue specific and have good echogenicity and also function as drug carriers. Previous studies have developed acoustic liposomes (ALs), liposomes that encapsulate phosphate buffer solution and perfluoropropane (C(3)F(8)) gas and function as both UCAs and drug carriers. Few studies have examined the co-existence of gas and liquid in ALs. This study aims to elucidate AL structure using TEM. The size, zeta potential and structure of ALs were compared with those of two other UCAs, human albumin shell bubbles (ABs; Optison) and lipid bubbles (LBs). ABs and LBs encapsulate the C(3)F(8) gas. Particle size was measured by dynamic light scattering. The zeta potential was determined by the Smoluchowski equation. UCA structure was investigated by TEM. ALs were approximately 200 nm in size, smaller than LBs and ABs. ALs and LBs had almost neutral zeta potentials whereas AB values were strongly negative. The negative or double staining TEM images revealed that approximately 20% of ALs contained both liquid and gas, while approximately 80% contained liquid alone (i.e. nonacoustic). Negative staining AB images indicated electron beam scattering near the shell surface, and albumin was detected in filament form. These findings suggest that AL is capable of carrying drugs and high-molecular-weight, low-solubility gases.

Paclitaxel-loaded poly(N-vinylpyrrolidone)-b-poly(epsilon-caprolactone) nanoparticles: preparation and antitumor activity in vivo

Paclitaxel (PTX)-loaded poly(N-vinylpyrrolidone)-b-poly(epsilon-caprolactone) (PVP-b-PCL) nanoparticles with high drug payload were successfully prepared by a modified nano-precipitation method and characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and zeta potential. The satisfactory drug loading content (>25%) and high encapsulation efficiency (>85%) were achieved. The in vivo real-time biodistribution of PTX-loaded nanoparticles was investigated using near-infrared fluorescence (NIRF) imaging. The antitumor effect of PTX-loaded nanoparticles was evaluated, both, in vitro on three different cancer cell lines and in vivo on hepatic H22 tumor bearing mice model via intravenous administration (i.v.). It is found that PTX-loaded nanoparticles exhibit significant superior in vivo antitumor effect than the commercially available Taxol formulation by combining the tumor volumes and survival rates measurement, intravital positron emission tomography and computed tomography (PET/CT) imaging.

Nanoparticles for biomedical imaging

BACKGROUND

Synthetic nanoparticles are emerging as versatile tools in biomedical applications, particularly in the area of biomedical imaging. Nanoparticles 1 - 100 nm in diameter have dimensions comparable to biological functional units. Diverse surface chemistries, unique magnetic properties, tunable absorption and emission properties, and recent advances in the synthesis and engineering of various nanoparticles suggest their potential as probes for early detection of diseases such as cancer. Surface functionalization has expanded further the potential of nanoparticles as probes for molecular imaging.

OBJECTIVE

To summarize emerging research of nanoparticles for biomedical imaging with increased selectivity and reduced nonspecific uptake with increased spatial resolution containing stabilizers conjugated with targeting ligands.

METHODS

This review summarizes recent technological advances in the synthesis of various nanoparticle probes, and surveys methods to improve the targeting of nanoparticles for their application in biomedical imaging.

CONCLUSION

Structural design of nanomaterials for biomedical imaging continues to expand and diversify. Synthetic methods have aimed to control the size and surface characteristics of nanoparticles to control distribution, half-life and elimination. Although molecular imaging applications using nanoparticles are advancing into clinical applications, challenges such as storage stability and long-term toxicology should continue to be addressed.

HFT-T, a targeting nanoparticle, enhances specific delivery of paclitaxel to folate receptor-positive tumors

Nonspecific distribution of chemotherapeutic drugs (such as paclitaxel) is a major factor contributing to side effects and poor clinical outcomes in the treatment of human head and neck cancer. To develop novel drug delivery systems with enhanced efficacy and minimized adverse effects, we synthesized a ternary conjugate heparin-folic acid-paclitaxel (HFT), loaded with additional paclitaxel (T). The resulting nanoparticle, HFT-T, is expected to retain the antitumor activity of paclitaxel and specifically target folate receptor (FR)-expressing tumors, thereby increasing the bioavailability and efficacy of paclitaxel. In vitro experiments found that HFT-T selectively recognizes FR-positive human head and neck cancer cell line KB-3-1, displaying higher cytotoxicity compared to the free form of paclitaxel. In a subcutaneous KB-3-1 xenograft model, HFT-T administration enhanced the specific delivery of paclitaxel into tumor tissues and remarkably improved antitumor efficacy of paclitaxel. The average tumor volume in the HFT-T treatment group was 92.9 +/- 78.2 mm(3) vs 1670.3 +/- 286.1 mm(3) in the mice treated with free paclitaxel. Furthermore, paclitaxel tumors showed a resurgence of growth after several weeks of treatment, but this was not observed with HFT-T. This indicates that HFT-T could be more effective in preventing tumors from developing drug resistance. No significant acute in vivo toxicity was observed. These results indicate that specific delivery of paclitaxel with a ternary structured nanoparticle (HFT-T) targeting FR-positive tumor is a promising strategy to enhance chemotherapy efficacy and minimize adverse effects.

Therapeutic efficacy and microSPECT/CT imaging of 188Re-DXR-liposome in a C26 murine colon carcinoma solid tumor model

Nanocarriers can selectively target cancer sites and carry payloads, thereby improving diagnostic and therapeutic effectiveness and reducing toxicity. The objective of this study was to investigate the therapeutic efficacy of a new co-delivery radiochemotherapeutics of (188)Re-N,N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA)-labeled pegylated liposomal doxorubicin (DXR) ((188)Re-DXR-liposome) in a C26 murine colon carcinoma solid tumor model. To evaluate the targeting and localization of (188)Re-DXR-liposome in C26 murine tumor-bearing mice, biodistribution, microSPECT/CT imaging and pharmacokinetic studies were performed. The antitumor effect of (188)Re-DXR-liposome was assessed by tumor growth inhibition, survival ratio and histopathological hematoxylin-eosin staining. The tumor target and localization of the nanoliposome delivery radiochemotherapeutics of (188)Re-DXR-liposome were demonstrated in the biodistribution, pharmacokinetics and in vivo nuclear imaging studies. In the study on therapeutic efficacy, the tumor-bearing mice treated with bimodality radiochemotherapeutics of (188)Re-DXR-liposome showed better mean tumor growth inhibition rate (MGI) and longer median survival time (MGI=0.048; 74 days) than those treated with radiotherapeutics of (188)Re-liposome (MGI=0.134; 60 days) and chemotherapeutics of Lipo-Dox (MGI=0.413; 38 days). The synergistic tumor regression effect was observed with the combination index (CI) exceeding 1 (CI=1.145) for co-delivery radiochemotherapeutics of (188)Re-DXR-liposome. Two (25%) of the mice treated with radiochemotherapeutics were completely cured after 120 days. The therapeutic efficacy of radiotherapeutics of (188)Re-liposome and the synergistic effect of the combination radiochemotherapeutics of (188)Re-DXR-liposome have been demonstrated in a C26 murine solid tumor animal model, which pointed to the potential benefit and promise of the co-delivery of nanoliposome radiochemotherapeutics for adjuvant cancer treatment on oncology applications.

Multimodal drug delivery using gold nanoparticles

Gold nanoparticles (AuNPs) are promising nanocarriers for therapeutics due to their facile synthesis, ease of functionalization, biocompatibility, and inherent non-toxicity. The unique chemical and physical properties of AuNP monolayers provide versatility in delivery method and tunability of surface properties. Here, we discuss several strategies to utilize the properties of AuNPs for drug delivery.

Molecular imaging and therapy of cancer with radiolabeled nanoparticles

This review summarizes the current state-of-the-art of radiolabeled nanoparticles for molecular imaging and internal radiotherapy applications targeting cancer. With the capacity to provide enormous flexibility, radiolabeled nanoparticles have the potential to profoundly impact disease diagnosis and patient management in the near future. Currently, the major challenges facing the research on radiolabeled nanoparticles are desirable (tumor) targeting efficacy, robust chemistry for both radionuclide encapsulation/incorporation and targeting ligand conjugation, favorable safety profile, as well as certain commercial and regulatory hurdles.

In vitro method to characterize diffusion of dye from polymeric particles: a model for drug release

The release profile of a drug delivery system is a key factor in determining its efficacy. In the case of a polymeric particle based system, the release profile is a function of several parameters including particle diameter and porosity. The effects of these parameters are usually investigated experimentally using UV-spectroscopy. Predicting the drug release profile from particles as a result of the interaction of many parameters is desirable in order to facilitate the design of more efficient drug delivery particles. In this work, a quantitative method of determining the diffusion profile is developed which removes the need for repetitive experimentation. Particles of polymethylsilsesquioxane were prepared using coaxial electrohydrodynamic atomization and collected in solutions containing different concentrations of Evans blue dye (6, 0.6, and 0.06 mg/mL) which was used to simulate a drug. The dye release profile was calculated by solving the unsteady state diffusion equation for parameters used in the experiments. It was demonstrated that the dye release profile from particles with diameters ranging from 400 nm to 9 mum can be calculated using a simple equation without addition of a dissolution term, if the volume ratio of surrounding liquid to particle in the unsteady second order solution is substituted by the surface area of particles to liquid volume ratio. The calculated data are found to be in good agreement with the experimental, indicating that this method can be used to determine the diffusion coefficient as a function of particle diameter and material. This study represents a crucial step toward developing a full drug release model.

Targeting of tumor endothelium by RGD-grafted PLGA-nanoparticles loaded with paclitaxel

Paclitaxel (PTX)-loaded PEGylated PLGA-based nanoparticles (NP) have been previously described as more effective in vitro and in vivo than taxol. The aim of this study was to test the hypothesis that our PEGylated PLGA-based nanoparticles grafted with the RGD peptide or RGD-peptidomimetic (RGDp) would target the tumor endothelium and would further enhance the anti-tumor efficacy of PTX. The ligands were grafted on the PEG chain of PCL-b-PEG included in the nanoparticles. We observed in vitro that RGD-grafted nanoparticles were more associated to human umbilical vein endothelial cells (HUVEC) by binding to alpha(v)beta(3) integrin than non-targeted nanoparticles. Doxorubicin was also used to confirm the findings observed for PTX. In vivo, we demonstrated the targeting of RGD and RGDp-grafted nanoparticles to tumor vessels as well as the effective retardation of TLT tumor growth and prolonged survival times of mice treated by PTX-loaded RGD-nanoparticles when compared to non-targeted nanoparticles. Hence, the targeting of anti-cancer drug to tumor endothelium by RGD-labeled NP is a promising approach.

Size control of arsenic trioxide nanocrystals grown in nanowells

This paper describes a new strategy to generate nanocrystalline drugs through the precipitation of drug molecules in attoliter nanowells. We controlled the size of arsenic trioxide (ATO) nanocrystals by simply changing the concentration of ATO solution in the nanowells; particles with sizes ranging from 55 to 175 nm were formed. This approach only requires the drugs to be soluble in a solvent and thus can be broadly applicable to produce other drugs in nanocrystalline form.

The first targeted delivery of siRNA in humans via a self-assembling, cyclodextrin polymer-based nanoparticle: from concept to clinic

Experimental therapeutics developed to exploit RNA interference (RNAi) are now in clinical studies. Here, the translation from concept to clinic for the first experimental therapeutic to provide targeted delivery of synthetic, small interfering RNA (siRNA) in humans is described. This targeted, nanoparticle formulation of siRNA, denoted as CALAA-01, consists of a cyclodextrin-containing polymer (CDP), a polythethylene glycol (PEG) steric stabilization agent, and human transferrin (Tf) as a targeting ligand for binding to transferrin receptors (TfR) that are typically upregulated on cancer cells. The four component formulation is self-assembled into nanoparticles in the pharmacy and administered intravenously (iv) to patients. The designed features of this experimental therapeutic are described, and their functions illustrated.

A self-assembling nanoparticle for paclitaxel delivery in ovarian cancer

Paclitaxel (PTX) is one of the most effective chemotherapeutic drugs for the treatment of a variety of cancers. However, it is associated with serious side effects caused by PTX itself and the Cremophor EL emulsifier. In the present study, we report the development of a well-defined amphiphilic linear-dendritic copolymer (named as telodendrimer) composed of polyethylene glycol (PEG), cholic acid (CA, a facial amphiphilic molecule) and lysine, which can form drug-loaded core/shell micelles when mixed with hydrophobic drug, such as PTX, under aqueous condition. We have used PEG(5k)-CA(8), a representive telodendrimer, to prepare paclitaxel-loaded nanoparticles (PTX-PEG(5k)-CA(8) NPs) with high loading capacity (7.3 mg PTX/mL) and a size of 20-60 nm. This novel nanoformulation of PTX was found to exhibit similar in vitro cytotoxic activity against ovarian cancer cells as the free drug (Taxol) or paclitaxel/human serum albumin nanoaggregate (Abraxane). The maximum tolerated doses (MTDs) of PTX-PEG(5k)-CA(8) NPs after single dose and five consecutive daily doses in mice were approximately 75 and 45 mg PTX/kg, respectively, which were 2.5-fold higher than those of Taxol. In both subcutaneous and orthotopic intraperitoneal murine models of ovarian cancer, PTX-PEG(5k)-CA(8) NPs achieved superior toxicity profiles and anti-tumor effects compared to Taxol and Abraxane at equivalent PTX doses, which were attributed to their preferential tumor accumulation, and deep penetration into tumor tissue, as confirmed by near infrared fluorescence (NIRF) imaging.

Pharmacokinetics and tumor dynamics of the nanoparticle IT-101 from PET imaging and tumor histological measurements

IT-101, a cyclodextrin polymer-based nanoparticle containing camptothecin, is in clinical development for the treatment of cancer. Multiorgan pharmacokinetics and accumulation in tumor tissue of IT-101 is investigated by using PET. IT-101 is modified through the attachment of a 1,4,7,10-tetraazacyclododecane-1,4,7-Tris-acetic acid ligand to bind (64)Cu(2+). This modification does not affect the particle size and minimally affects the surface charge of the resulting nanoparticles. PET data from (64)Cu-labeled IT-101 are used to quantify the in vivo biodistribution in mice bearing Neuro2A s.c. tumors. The (64)Cu-labeled IT-101 displays a biphasic plasma elimination. Approximately 8% of the injected dose is rapidly cleared as a low-molecular-weight fraction through the kidneys. The remaining material circulates in plasma with a terminal half-life of 13.3 h. Steadily increasing concentrations, up to 11% injected dose per cm(3), are observed in the tumor over 24 h, higher than any other tissue at that time. A 3-compartment model is used to determine vascular permeability and nanoparticle retention in tumors, and is able to accurately represent the experimental data. The calculated tumor vascular permeability indicates that the majority of nanoparticles stay intact in circulation and do not disassemble into individual polymer strands. A key assumption to modeling the tumor dynamics is that there is a "sink" for the nanoparticles within the tumor. Histological measurements using confocal microscopy show that IT-101 localizes within tumor cells and provides the sink in the tumor for the nanoparticles.

Polymeric nanomedicine for cancer MR imaging and drug delivery

Multifunctional nanomedicine is emerging as a highly integrated platform that allows for molecular diagnosis, targeted drug delivery, and simultaneous monitoring and treatment of cancer. Advances in polymer and materials science are critical for the successful development of these multi-component nanocomposites in one particulate system with such a small size confinement (<200 nm). Currently, several nanoscopic therapeutic and diagnostic systems have been translated into clinical practice. In this feature article, we will provide an up-to-date review on the development and biomedical applications of nanocomposite materials for cancer diagnosis and therapy. An overview of each functional component, i.e. polymer carriers, MR imaging agents, and therapeutic drugs, will be presented. Integration of different functional components will be illustrated in several highlighted examples to demonstrate the synergy of the multifunctional nanomedicine design.

Convergence of biomarkers, bioinformatics and nanotechnology for individualized cancer treatment

Recent advances in biomarker discovery, biocomputing and nanotechnology have raised new opportunities in the emerging fields of personalized medicine (in which disease detection, diagnosis and therapy are tailored to each individual's molecular profile) and predictive medicine (in which genetic and molecular information is used to predict disease development, progression and clinical outcome). Here, we discuss advanced biocomputing tools for cancer biomarker discovery and multiplexed nanoparticle probes for cancer biomarker profiling, in addition to the prospects for and challenges involved in correlating biomolecular signatures with clinical outcome. This bio-nano-info convergence holds great promise for molecular diagnosis and individualized therapy of cancer and other human diseases.

Mediating tumor targeting efficiency of nanoparticles through design

Here we systematically examined the effect of nanoparticle size (10-100 nm) and surface chemistry (i.e., poly(ethylene glycol)) on passive targeting of tumors in vivo. We found that the physical and chemical properties of the nanoparticles influenced their pharmacokinetic behavior, which ultimately determined their tumor accumulation capacity. Interestingly, the permeation of nanoparticles within the tumor is highly dependent on the overall size of the nanoparticle, where larger nanoparticles appear to stay near the vasculature while smaller nanoparticles rapidly diffuse throughout the tumor matrix. Our results provide design parameters for engineering nanoparticles for optimized tumor targeting of contrast agents and therapeutics.

Polymeric micelles from poly(ethylene glycol)-poly(amino acid) block copolymer for drug and gene delivery

Dramatic advances in biological research have revealed the mechanisms underlying many diseases at the molecular level. However, conventional techniques may be inadequate for direct application of this new knowledge to medical treatments. Nanobiotechnology, which integrates biology with the rapidly growing field of nanotechnology, has great potential to overcome many technical problems and lead to the development of effective therapies. The use of nanobiotechnology in drug delivery systems (DDS) is attractive for advanced treatment of conditions such as cancer and genetic diseases. In this review paper for a special issue on biomaterial research in Japan, we discuss the development of DDS based on polymeric micelles mainly in our group for anti-cancer drug and gene delivery, and also address our challenges associated with developing polymeric micelles as super-functionalized nanodevices with intelligent performance.

Advances of cancer therapy by nanotechnology

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