Targeting nanoparticles to cancer

In vitro biocompatibility of solid lipid nanoparticles

This study was undertaken to address the current deficient knowledge of cellular response to solid lipid nanoparticles (SLNs) exposure. We investigated the cytotoxicity of several SLNs formulations in two fibroblast cell lineages, Vero and MDCK. Several methods were used to explore the mechanisms involved in this cytotoxic process, including cell viability assays, flow cytometry and ROS generation assessment. Among nanoparticles tested, two of them (F4 and F5) demonstrated more cytotoxic effects in both cell lineages. The cell viability assays suggested that F4 and F5 interfere in cell mitochondrial metabolism and in lysosomal activity. In addition, F5 decreased the percentage of MDCK cells in G0/G1 and G2/M phases, with a marked increase in the Sub/G1 population, suggesting DNA fragmentation. Regarding F4, although IC(50) was higher (~700 μg/mL), this formulation affected mitochondrial membrane potential for Vero cells. However, the IC(50) of F5 was around 250 μg/mL, suggesting the effect of SDS (sodium dodecyl sulfate) present in the formulation. In summary, the nanoparticles tested here appears to be biocompatible, with the exception of F5. Further studies are required to elucidate the in vivo effects of these nanoscale structures, in order to evaluate or predict the connotation of their increased and widespread use.

Liver cell specific targeting by the preS1 domain of hepatitis B virus surface antigen displayed on protein nanocages

Protein nanocages are self-organized complexes of oligomers whose three-dimensional architecture can been determined in detail. These structures possess nanoscale inner cavities into which a variety of molecules, including therapeutic or diagnostic agents, can be encapsulated. These properties yield these particles suitable for a new class of drug delivery carrier, or as a bioimaging reagent that might respond to biochemical signals in many different cellular processes. We report here the design, synthesis, and biological characterization of a hepatocyte-specific nanocage carrying small heat-shock protein. These nanoscale protein cages, with a targeting peptide composed of a preS1 derivative from the hepatitis B virus on their surfaces, were prepared by genetic engineering techniques. PreS1-carrying nanocages showed lower cytotoxicity and significantly higher specificity for human hepatocyte cell lines than other cell lines in vitro. These results suggested that small heat-shock protein-based nanocages present great potential for the development of effective targeted delivery of various agents to specific cells.

Folate-PEG-superparamagnetic iron oxide nanoparticles for lung cancer imaging

While superparamagnetic iron oxide nanoparticles (SPIONs) have been widely used in biomedical applications, rapid blood clearance, instability and active targeting of the SPIONs limit their availability for clinical trials. This work was aimed at developing stable and lung cancer targeted SPIONs. For this purpose firstly folic acid (FA)-conjugated poly(ethylene glycol) (FA-PEG) was synthesized, and FA-PEG-SPIONs were subsequently prepared by the reaction of FA-PEG with aminosilane-immobilized SPIONs. FA-PEG-SPIONs were labeled with Cy5.5 for optical imaging. The intracellular uptake of FA-PEG-SPIONs-Cy5.5 was evaluated in KB cells and lung cancer model mice to confirm active targeting. The sizes of the FA-PEG-SPIONs were little changed after up to 8 weeks at 4 °C, suggestive of very stable particle sizes. The results of fluorescent flow cytometry and confocal laser scanning microscopy suggest that the intracellular uptake of FA-PEG-SPIONs-Cy5.5 was greatly inhibited by pre-treatment with free folic acid, indicative of receptor-mediated endocytosis. Stronger optical imaging was observed in the lung cancer model mice for FA-PEG-SPIONs-Cy5.5 than PEG-SPIONs-Cy5.5 6 and 24 h post-injection through the tail vein, due to receptor-mediated endocytosis.

Biocompatibility, endocytosis, and intracellular trafficking of mesoporous silica and polystyrene nanoparticles in ovarian cancer cells: effects of size and surface charge groups

Background and methods

Nanoparticles engineered to carry both a chemotherapeutic drug and a sensitive imaging probe are valid tools for early detection of cancer cells and to monitor the cytotoxic effects of anticancer treatment simultaneously. Here we report on the effect of size (10–30 nm versus 50 nm), type of material (mesoporous silica versus polystyrene), and surface charge functionalization (none, amine groups, or carboxyl groups) on biocompatibility, uptake, compartmentalization, and intracellular retention of fluorescently labeled nanoparticles in cultured human ovarian cancer cells. We also investigated the involvement of caveolae in the mechanism of uptake of nanoparticles.

Results

We found that mesoporous silica nanoparticles entered via caveolae-mediated endocytosis and reached the lysosomes; however, while the 50 nm nanoparticles permanently resided within these organelles, the 10 nm nanoparticles soon relocated in the cytoplasm. Naked 10 nm mesoporous silica nanoparticles showed the highest and 50 nm carboxyl-modified mesoporous silica nanoparticles the lowest uptake rates, respectively. Polystyrene nanoparticle uptake also occurred via a caveolae-independent pathway, and was negatively affected by serum. The 30 nm carboxyl-modified polystyrene nanoparticles did not localize in lysosomes and were not toxic, while the 50 nm amine-modified polystyrene nanoparticles accumulated within lysosomes and eventually caused cell death. Ovarian cancer cells expressing caveolin-1 were more likely to endocytose these nanoparticles.

Conclusion

These data highlight the importance of considering both the physicochemical characteristics (ie, material, size and surface charge on chemical groups) of nanoparticles and the biochemical composition of the cell membrane when choosing the most suitable nanotheranostics for targeting cancer cells.

Biocompatibility, endocytosis, and intracellular trafficking of mesoporous silica and polystyrene nanoparticles in ovarian cancer cells: effects of size and surface charge groups

BACKGROUND AND METHODS

Nanoparticles engineered to carry both a chemotherapeutic drug and a sensitive imaging probe are valid tools for early detection of cancer cells and to monitor the cytotoxic effects of anticancer treatment simultaneously. Here we report on the effect of size (10-30 nm versus 50 nm), type of material (mesoporous silica versus polystyrene), and surface charge functionalization (none, amine groups, or carboxyl groups) on biocompatibility, uptake, compartmentalization, and intracellular retention of fluorescently labeled nanoparticles in cultured human ovarian cancer cells. We also investigated the involvement of caveolae in the mechanism of uptake of nanoparticles.

RESULTS

We found that mesoporous silica nanoparticles entered via caveolae-mediated endocytosis and reached the lysosomes; however, while the 50 nm nanoparticles permanently resided within these organelles, the 10 nm nanoparticles soon relocated in the cytoplasm. Naked 10 nm mesoporous silica nanoparticles showed the highest and 50 nm carboxyl-modified mesoporous silica nanoparticles the lowest uptake rates, respectively. Polystyrene nanoparticle uptake also occurred via a caveolae-independent pathway, and was negatively affected by serum. The 30 nm carboxyl-modified polystyrene nanoparticles did not localize in lysosomes and were not toxic, while the 50 nm amine-modified polystyrene nanoparticles accumulated within lysosomes and eventually caused cell death. Ovarian cancer cells expressing caveolin-1 were more likely to endocytose these nanoparticles.

CONCLUSION

These data highlight the importance of considering both the physicochemical characteristics (ie, material, size and surface charge on chemical groups) of nanoparticles and the biochemical composition of the cell membrane when choosing the most suitable nanotheranostics for targeting cancer cells.

Preparation and characterization of teniposide PLGA nanoparticles and their uptake in human glioblastoma U87MG cells

Many studies have demonstrated the uptake mechanisms of various nanoparticle delivery systems with different physicochemical properties in different cells. In this study, we report for the first time the preparation and characterization of teniposide (VM-26) poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) and their cellular uptake pathways in human glioblastoma U87MG cells. The nanoparticles prepared with oil-in-water (O/W) single-emulsion solvent evaporation method had a small particle size and spherical shape and provided effective protection against degradation of teniposide in PBS solution. Differential scanning calorimeter (DSC) thermograms concluded that VM-26 was dispersed as amorphous or disordered crystalline phase in the PLGA matrix. A cytotoxicity study revealed that, in a 24h period, blank PLGA NPs had no cytotoxicity, whereas teniposide-loaded PLGA NPs (VM-26-NPs) had U87MG cytotoxicity levels similar to free teniposide. Confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) images showed the distribution and degradation processes of nanoparticles in cells. An endocytosis inhibition test indicated that clathrin-mediated endocytosis and macropinocytosis were the primary modes of engulfment involved in the internalization of VM-26-NPs. Our findings suggest that PLGA nanoparticles containing a sustained release formula of teniposide may multiplex the therapeutic effect and ultimately degrade in lysosomal within human glioblastoma U87MG cells.

Glutathione-mediated release of Bodipy® from PEG cofunctionalized gold nanoparticles

Gold nanoparticles synthesized via sodium citrate reduction of chloroauric acid (HAuCl₄) were functionalized with either various concentrations of thiol-terminated Bodipy^® FL L-cystine (0.5, 1.0, 1.5, and 2.0 μg/mL) or Bodipy-poly(ethylene glycol) at concentrations of 0.5–18.75, 1.0–12.50, and 1.5–6.25 μg/mL to form a mixed monolayer of BODIPY-PEG. Thiol-terminated Bodipy, a fluorescing molecule, was used as the model drug, while PEG is widely used in drug-delivery applications to shield nanoparticles from unwanted immune responses. Understanding the influence of PEG-capping on payload release is critical because it is the most widely used type of nanoparticle functionalization in drug delivery studies. It has been previously reported that glutathione can trigger release of thiol-bound payloads from gold nanoparticles. Bodipy release from Bodipy capped and from Bodipy-PEG functionalized gold nanoparticles was studied at typical intracellular glutathione levels. It was observed that the addition of PEG capping inhibits the initial burst release observed in gold nanoparticles functionalized only with Bodipy and inhibits nanoparticle aggregation. Efficient and controlled payload release was observed in gold nanoparticles cofunctionalized with only a limited amount of PEG, thus enabling the coattachment of large amounts of drug, targeting groups or other payloads.

Transferrin coated nanoparticles: study of the bionano interface in human plasma

It is now well established that the surface of nanoparticles (NPs) in a biological environment is immediately modified by the adsorption of biomolecules with the formation of a protein corona and it is also accepted that the protein corona, rather than the original nanoparticle surface, defines a new biological identity. Consequently, a methodology to effectively study the interaction between nanomaterials and the biological corona encountered within an organism is a key objective in nanoscience for understanding the impact of the nanoparticle-protein interactions on the biological response in vitro and in vivo. Here, we outline an integrated methodology to address the different aspects governing the formation and the function of the protein corona of polystyrene nanoparticles coated with Transferrin by different strategies. Protein-NP complexes are studied both in situ (in human plasma, full corona FC) and after washing (hard corona, HC) in terms of structural properties, composition and second-order interactions with protein microarrays. Human protein microarrays are used to effectively study NP-corona/proteins interactions addressing the growing demand to advance investigations of the extrinsic function of corona complexes. Our data highlight the importance of this methodology as an analysis to be used in advance of the application of engineered NPs in biological environments.

Nitric oxide release: part I. Macromolecular scaffolds

The roles of nitric oxide (NO) in physiology and pathophysiology merit the use of NO as a therapeutic for certain biomedical applications. Unfortunately, limited NO payloads, too rapid NO release, and the lack of targeted NO delivery have hindered the clinical utility of NO gas and low molecular weight NO donor compounds. A wide-variety of NO-releasing macromolecular scaffolds has thus been developed to improve NO's pharmacological potential. In this tutorial review, we provide an overview of the most promising NO release scaffolds including protein, organic, inorganic, and hybrid organic-inorganic systems. The NO release vehicles selected for discussion were chosen based on their enhanced NO storage, tunable NO release characteristics, and potential as therapeutics.

Dendrimer pharmacokinetics: the effect of size, structure and surface characteristics on ADME properties

Dendrimers show increasing promise as drug-delivery vectors and can be generated with a wide range of scaffold structures, sizes and surface functionalities. To this point, the majority of studies of dendrimer-based drug-delivery systems have detailed pharmacodynamic outcomes, or have followed the pharmacokinetics of a solubilized or conjugated drug. By contrast, detailed commentary on the in vivo fate of the dendrimer carrier is less evident, even though the pharmacokinetics of the carrier will likely dictate both pharmacodynamic and toxicokinetic outcomes. In the current article, the influence of size, structure and surface functionality on the absorption, distribution, metabolism and elimination (ADME) properties of dendrimers have been examined and the implications of these findings for delivery system design are discussed.

Doxorubicin and MBO-asGCS oligonucleotide loaded lipid nanoparticles overcome multidrug resistance in adriamycin resistant ovarian cancer cells (NCI/ADR-RES)

The objective of this study was to increase the potency of doxorubicin against adriamycin-resistant NCI/ADR-RES cells by concurrent treatment with doxorubicin and MBO-asGCS loaded solid-lipid nanoparticles (SLN). Loading doxorubicin as ion-pair complex with deoxytaurocholate into cationic and neutral SLN was investigated. Fast release and poor entrapment were observed in cationic nanoparticles, which were corrected by entrapping the complex in neutral polyoxyethylene (20) stearyl ether (Brij(®) 78)/VitE-TPGS nanoparticles. Slow doxorubicin release confirmed the influence of charge and electrolytes on the dissociation of ion-pair complexes. To evaluate antitumor activity, NCI/ADR-RES cells were treated with separate SLN: one loaded with doxorubicin and another carrying MBO-asGCS oligonucleotide. The viability of cells treated with 5 μM doxorubicin was reduced to 17.2% whereas viability was reduced to 2.5% for cells treated with both 5 μM doxorubicin SLN and 100 nM MBO-asGCS SLN. This suggested enhanced apoptosis due to sensitization and effective intracellular delivery of MBO-asGCS and doxorubicin by SLN.

Targeting of nanoparticles in cancer: drug delivery and diagnostics

Anticancer agents continue to be a preferred therapeutic option for several malignancies. Despite their effectiveness, oncologists are continually looking for tumor-specific anticancer agents to prevent adverse effects in patients. Targeting of imaging agents to cancerous tissue is another area that is enthusiastically explored to circumvent some of the drawbacks that current imaging agents possess, including the inability to target small tumor cells, inadequate imaging period, and the risk of renal damage. Formulation scientists have explored nanotechnology-based delivery systems for targeting anticancer agents and tumor-imaging agents to cancer tissue. Targeting with nanotechnology-based delivery systems has been investigated by both passive and active mechanisms with significant clinical success. This review presents a discussion on targeting strategies used for the delivery of nanoparticles by passive and active mechanisms, focusing more specifically on active targeting of nanoparticles using albumin, folic acid, transferrin, and aptamers as targeting ligands.

"Targeting" nanoparticles: the constraints of physical laws and physical barriers

In comparison to the complexities of the body, its organs, its normal and aberrant cells, many nanoparticles will appear to be relatively simple objects. This view is deceptive because the physicochemical properties of nanosystems, although quite well understood on the basis of material science, surface science and colloid theory, are far from simple in practice. While their properties are largely controllable in vitro, often purportedly "designed", their administration by any route changing environments conspires to produce additional layers of complexity. Some of the key physical laws and physicochemical parameters governing the fate of nanoparticles on their journey from point of intravenous administration to desired destinations such as tumors are discussed. Much of the science relevant to nanocarrier based targeting has been elaborated in studying purely physical phenomena, but there can be found therein many analogies with biological systems. These include factors that impede quantitative targeting: diffusion in complex media, aggregation and flocculation, hindered behavior of particles in confined spaces, jamming and dispersion in flow. All of these have the ability to influence fate and destination. Most of the critical processes are particle size dependent but not always linearly so. Virtually all processes in vivo involve an element of probability. Particle size and properties can be controlled to a large extent, but stochastic processes cannot by definition. Progress has been made, but the quantitative delivery of a nanocarrier to defined sites in tumors is neither inevitable nor yet predictable.

Delivery of small interfering RNA by peptide-targeted mesoporous silica nanoparticle-supported lipid bilayers

The therapeutic potential of small interfering RNAs (siRNAs) is severely limited by the availability of delivery platforms that protect siRNA from degradation, deliver it to the target cell with high specificity and efficiency, and promote its endosomal escape and cytosolic dispersion. Here we report that mesoporous silica nanoparticle-supported lipid bilayers (or "protocells") exhibit multiple properties that overcome many of the limitations of existing delivery platforms. Protocells have a 10- to 100-fold greater capacity for siRNA than corresponding lipid nanoparticles and are markedly more stable when incubated under physiological conditions. Protocells loaded with a cocktail of siRNAs bind to cells in a manner dependent on the presence of an appropriate targeting peptide and, through an endocytic pathway followed by endosomal disruption, promote delivery of the silencing nucleotides to the cytoplasm. The expression of each of the genes targeted by the siRNAs was shown to be repressed at the protein level, resulting in a potent induction of growth arrest and apoptosis. Incubation of control cells that lack expression of the antigen recognized by the targeting peptide with siRNA-loaded protocells induced neither repression of protein expression nor apoptosis, indicating the precise specificity of cytotoxic activity. In terms of loading capacity, targeting capabilities, and potency of action, protocells provide unique attributes as a delivery platform for therapeutic oligonucleotides.

PEGylated liposomal doxorubicin targeted to α5β1-expressing MDA-MB-231 breast cancer cells

Targeting drugs selectively to cancer cells can potentially benefit cancer patients by avoiding side effects generally associated with several cancer therapies. One of the attractive approaches to direct the drug cargo to specific sites is to incorporate ligands at the surface of the delivery systems. Integrin α(5)β(1) is overexpressed in tumor vasculature and cancer cells, thus making it an attractive target for use in drug delivery. Our group has developed a fibronectin-mimetic peptide, PR_b, which has been shown to bind specifically to integrin α(5)β(1), thereby providing a tool to target α(5)β(1)-expressing cancer cells in vitro as well as in vivo. Our current work focuses on designing modified stealth liposomes (liposomes functionalized with polyethylene glycol, PEG) for combining the benefits associated with PEGylation, as well as imparting specific targeting properties to the liposomes. We have designed PEGylated liposomes that incorporate in their bilayer the fibronectin-mimetic peptide-amphiphile PR_b that can target several cancer cells that overexpress α(5)β(1), including the MDA-MB-231 breast cancer cells used in this study. We have encapsulated doxorubicin inside the liposomes to enhance its therapeutic potential via PEGylation as well as active targeting to the cancer cells. Our results show that PR_b-functionalized stealth liposomes were able to specifically bind to MDA-MB-231 cells, and the binding could be controlled by varying the peptide concentration. The intracellular trafficking of the doxorubicin liposomes was examined, and within minutes after delivery the majority of them were found to be in the early endosomes, whereas after a longer period of time they had accumulated in the late endosomes and lysosomes. The functionalized liposomes were found to be equally cytotoxic as the free doxorubicin, especially at higher doxorubicin concentrations, and provided higher cytotoxicity than the nontargeted and GRGDSP-functionalized stealth liposomes. Thus, the PR_b-functionalized PEGylated nanoparticles examined in this study offer a promising strategy to deliver their therapeutic payload directly to the breast cancer cells, in an efficient and specific manner.

A realistic utilization of nanotechnology in molecular imaging and targeted radiotherapy of solid tumors

Precise dose delivery to malignant tissue in radiotherapy is of paramount importance for treatment efficacy while minimizing morbidity of surrounding normal tissues. Current conventional imaging techniques, such as magnetic resonance imaging (MRI) and computerized tomography (CT), are used to define the three-dimensional shape and volume of the tumor for radiation therapy. In many cases, these radiographic imaging (RI) techniques are ambiguous or provide limited information with regard to tumor margins and histopathology. Molecular imaging (MI) modalities, such as positron emission tomography (PET) and single photon-emission computed-tomography (SPECT) that can characterize tumor tissue, are rapidly becoming routine in radiation therapy. However, their inherent low spatial resolution impedes tumor delineation for the purposes of radiation treatment planning. This review will focus on applications of nanotechnology to synergize imaging modalities in order to accurately highlight, as well as subsequently target, tumor cells. Furthermore, using such nano-agents for imaging, simultaneous coupling of novel therapeutics including radiosensitizers can be delivered specifically to the tumor to maximize tumor cell killing while sparing normal tissue.

Fighting fire with fire: poisonous Chinese herbal medicine for cancer therapy

ETHNOPHARMACOLOGICAL RELEVANCE

Following the known principle of "fighting fire with fire", poisonous Chinese herbal medicine (PCHM) has been historically used in cancer therapies by skilled Chinese practitioners for thousands of years. In fact, most of the marketed natural anti-cancer compounds (e.g., camptothecin derivatives, vinca alkaloids, etc.) are often known in traditional Chinese medicine (TCM) and recorded as poisonous herbs as well. Inspired by the encouraging precedents, significant researches into the potential of novel anticancer drugs from other PCHM-derived natural products have been ongoing for several years and PCHM is increasingly being recognized as a gathering place for promising anti-cancer drugs. The present review aimed at giving a rational understanding of the toxicity of PCHM and, especially, providing the most recent developments on PCHM-derived anti-cancer compounds.

MATERIALS AND METHODS

Information on the toxicity and safety control of PCHM, as well as PCHM-derived anti-cancer compounds, was gathered from the articles, books and monographs published in the past 20 years.

RESULTS

Based on an objective introduction to the CHM toxicity, we clarified the general misconceptions about the safety of CHM and summarized the traditional experiences in dealing with the toxicity. Several PCHM-derived compounds, namely gambogic acid, triptolide, arsenic trioxide, and cantharidin, were selected as representatives, and their traditional usage and mechanism of anti-cancer actions were discussed.

CONCLUSIONS

Natural products derived from PCHM are of extreme importance in devising new drugs and providing unique ideas for the war against cancer. To fully exploit the potential of PCHM in cancer therapy, more attentions are advocated to be focused on their safety evaluation and mechanism exploration.

Monosaccharides versus PEG-functionalized NPs: influence in the cellular uptake

Magnetic nanoparticles (NPs) hold great promise for biomedical applications. The core composition and small size of these particles produce superparamagnetic behavior, thus facilitating their use in magnetic resonance imaging and magnetically induced therapeutic hyperthermia. However, the development and control of safe in vivo applications for NPs call for the study of cell-NP interactions and cell viability. Furthermore, as for most biotechnological applications, it is desirable to prevent unspecific cell internalization of these particles. It is also crucial to understand how the surface composition of the NPs affects their internalization capacity. Here, through accurate control over unspecific protein adsorption, size distribution, grafting density, and an extensive physicochemical characterization, we correlated the cytotoxicity and cellular uptake mechanism of 6 nm magnetic NPs coated with several types and various densities of biomolecules, such as glucose, galactose, and poly(ethylene glycol). We found that the density of the grafted molecule was crucial to prevent unspecific uptake of NPs by Vero cells. Surprisingly, the glucose-coated NPs described here showed cellular uptake as a result of lipid raft instead of clathrin-mediated cellular internalization. Moreover, these glucose-functionalized NPs could be one of the first examples of NPs being endocytosed by caveolae that finally end up in the lysosomes. These results reinforce the use of simple carbohydrates as an alternative to PEG molecules for NPs functionalization when cellular uptake is required.

Production and characterization of anisotropic particles from biodegradable materials

In recent years, production and characterization of anisotropic particles has become of interest in a wide range of scientific fields including polymer chemistry, drug delivery, electronics, energy, and nanotechnology. In this work, we demonstrate a novel formulation for production of anisotropic particles via an internal phase separation of biodegradable components. Specifically, binary mixtures of biodegradable polymers poly(lactic-co-glycolic acid), polycaprolactone, and biodegradable lipid Precirol (glyceryl palmitostearate) were dissolved in dichloromethane, emulsified, and prepared into anisotropic particles using a modified solvent evaporation technique. During the slow evaporation process the components self-assembled into anisotropic particles with distinct morphologies. Polymer/polymer formulations resulted in compartmentalized anisotropic heterodimer particles, while polymer/lipid combinations yielded "ice cream cone" shaped particles. It was found that addition of certain active pharmaceuticals resulted in an altered, pox-like segregation at the particle surface of polymer/polymer formulations. The anisotropic nature of the particles was subsequently characterized using optical microscopy, scanning electron microscopy, zeta potential, electrophoresis, and X-ray diffraction. Successful formulations presented here may potentially be employed as multicompartmental drug carriers with staggered drug release rates or alternatively as a colloidal excipient for an arsenal of pharmaceutical applications.

Zinc oxide nanoparticles selectively induce apoptosis in human cancer cells through reactive oxygen species

Background

Zinc oxide nanoparticles (ZnO NPs) have received much attention for their implications in cancer therapy. It has been reported that ZnO NPs induce selective killing of cancer cells. However, the underlying molecular mechanisms behind the anticancer response of ZnO NPs remain unclear.

Methods and results

We investigated the cytotoxicity of ZnO NPs against three types of cancer cells (human hepatocellular carcinoma HepG2, human lung adenocarcinoma A549, and human bronchial epithelial BEAS-2B) and two primary rat cells (astrocytes and hepatocytes). Results showed that ZnO NPs exert distinct effects on mammalian cell viability via killing of all three types of cancer cells while posing no impact on normal rat astrocytes and hepatocytes. The toxicity mechanisms of ZnO NPs were further investigated using human liver cancer HepG2 cells. Both the mRNA and protein levels of tumor suppressor gene p53 and apoptotic gene bax were upregulated while the antiapoptotic gene bcl-2 was downregulated in ZnO NP-treated HepG2 cells. ZnO NPs were also found to induce activity of caspase-3 enzyme, DNA fragmentation, reactive oxygen species generation, and oxidative stress in HepG2 cells.

Conclusion

Overall, our data demonstrated that ZnO NPs selectively induce apoptosis in cancer cells, which is likely to be mediated by reactive oxygen species via p53 pathway, through which most of the anticancer drugs trigger apoptosis. This study provides preliminary guidance for the development of liver cancer therapy using ZnO NPs.

Multicolor core/shell silica nanoparticles for in vivo and ex vivo imaging

Biocompatible highly bright silica nanoparticles were designed, prepared and tested in small living organisms for both in vivo and ex vivo imaging. The results that we report here demonstrate that they are suitable for optical imaging applications as a possible alternative to commercially available fluorescent materials including quantum dots. Moreover, the tunability of their photophysical properties, which was enhanced by the use of different dyes as doping agents, constitutes a very important added value in the field of medical diagnostics.

PLGA-based nanoparticles: an overview of biomedical applications

Poly(lactic-co-glycolic acid) (PLGA) is one of the most successfully developed biodegradable polymers. Among the different polymers developed to formulate polymeric nanoparticles, PLGA has attracted considerable attention due to its attractive properties: (i) biodegradability and biocompatibility, (ii) FDA and European Medicine Agency approval in drug delivery systems for parenteral administration, (iii) well described formulations and methods of production adapted to various types of drugs e.g. hydrophilic or hydrophobic small molecules or macromolecules, (iv) protection of drug from degradation, (v) possibility of sustained release, (vi) possibility to modify surface properties to provide stealthness and/or better interaction with biological materials and (vii) possibility to target nanoparticles to specific organs or cells. This review presents why PLGA has been chosen to design nanoparticles as drug delivery systems in various biomedical applications such as vaccination, cancer, inflammation and other diseases. This review focuses on the understanding of specific characteristics exploited by PLGA-based nanoparticles to target a specific organ or tissue or specific cells.

Delivery and biodistribution of siRNA for cancer therapy: challenges and future prospects

RNAi-based approaches provide a promising therapeutic modality for the treatment of cancer. The inaccessibility of tumors in different cancer types necessitates the development of safe, specific and efficient systemic delivery systems to meet therapeutic need. The translation of siRNA-based cancer therapeutics to the clinic is hindered by several challenges associated with the cargo (siRNA) and the delivery system, including susceptibility to nucleases; insufficient circulation half-life due to phagocytosis by the reticuloendothelial system, transient and poor biodistribution in the tumor tissue; cellular uptake; inability to escape endosomes and release into the cytosolic compartment for an RNAi-mediated effect; microRNA-like unintended off-target effects; undesirable immune stimulation; and carrier-related toxicity. This review provides an overview of the pharmacokinetic and biodistribution challenges witnessed in the delivery of siRNA when administered systemically. It also describes the current delivery approaches using liposome-, polymer- and peptide-based delivery systems shown to elicit significant gene silencing and tumor growth regression in proof-of-concept studies. As part of future perspectives, delivery agents that showed significant efficacy in preclinical rodent models and clinical trials are also reviewed.

Physico-chemical parameters that govern nanoparticles fate also dictate rules for their molecular evolution

Nanoparticles are efficient to safely deliver therapeutic and imaging contrast agents to tumors for cancer diagnostic and therapy, if they can escape the reticuloendothelial system (RES) and accumulate in tumors either passively due to the enhanced permeability and retention (EPR) effect or actively via a specific ligand. The main hallmark of nanoparticles is their large surface areas, which, depending of their chemical compositions, surface coatings, electric charges, sizes and shapes, will generate complex, extremely dynamic and continuous interactions and exchanges between the nanoparticles and the different molecules present in the blood. Special attention will be paid to explain how the nanoparticles were improved step by step in order to adapt our increasing knowledge on their biophysics. In particular, we will discuss the influence of PEGylation, the difficulties to generate actively targeted particles and finally the actual trends in the manufacturing of "third-generation" smart particles.

Doxorubicin-conjugated PEGylated dendrimers show similar tumoricidal activity but lower systemic toxicity when compared to PEGylated liposome and solution formulations in mouse and rat tumor models

PEGylated polylysine dendrimers show promise as novel drug delivery systems with the potential to direct site specific deposition patterns and to reduce toxicity at nontarget sites. Here the activity and toxicity profiles of a generation 5 polylysine dendrimer with 50% surface conjugation of PEG1100 and 50% surface conjugation of doxorubicin (via an acid labile 4-hydrazinosulfonyl benzoic acid linker) have been compared in a Walker 256 rat tumor model and a human MDA-MB231 xenograft in mice. A direct comparison was also made to a PEGylated liposomal formulation of doxorubicin and a doxorubicin solution. In both rat and mouse breast cancer models, the dendrimer formulation gave equivalent antitumor efficacy when compared to the liposomal or solution doxorubicin formulations and administration of all three doxorubicin formulations resulted in a significant reduction (>75%) in tumor growth in both models at doses ranging from 2 to 10 mg/kg doxorubicin equivalents. The dendrimer formulation, however, was better tolerated by both rats and mice, and approximately 2-fold higher doses were required to induce similar levels of toxicity (as assessed by organ weight, peripheral white cell counts, body weight and survival curves) when compared to administration of the doxorubicin solution or PEGylated liposomal doxorubicin. In rats the appearance of palmar plantar erythematosis (PPE), or hand foot syndrome, was also less evident after administration of dendrimer doxorubicin when compared to the liposome. Finally, even after administration to mice at 2-fold higher doses, dendrimer-doxorubicin resulted in a reduced incidence of cardiotoxicity when compared with a simple solution formulation of doxorubicin. The data suggest that dendrimer-based doxorubicin formulations may provide advantage over solution and liposomal formulations of doxorubicin via a reduction in systemic toxicity.

Synthesis of the first poly(diaminosulfide)s and an investigation of their applications as drug delivery vehicles

This paper reports the first examples of poly(diaminosulfide)s that were synthesized by the reaction of a sulfur transfer reagent and several secondary diamines. The diaminosulfide group has the general structure of R(2)N-S-NR(2) and, although it has been used in the synthesis of small molecules, it has never been utilized in the synthesis of macromolecules until this report. A series of poly(diaminosulfide)s were synthesized at elevated temperatures, and the molecular weights of the polymers were as high as 12,400 g mol(-1) with conversions for the polymerization reaction up to 99%. The rate constants for the transamination reactions that lead to the polymers were measured in several solvents to provide an understanding the reaction conditions necessary to polymerize the monomers. The degradation of diaminosulfides were studied in D(2)O, C(6)D(6), CD(3)OD, CDCl(3), and DMSO-d(6)/D(2)O to demonstrate that they were very stable in organic solvents but degraded within hours under aqueous conditions. These results clearly demonstrated that diaminosulfides are very stable in organic solvents under ambient conditions. Poly(diaminosulfide)s have sufficient stabilities to be useful for many applications. The ability of these polymers to function as drug delivery vehicles were studied by the fabrication of nanoparticles of a water-insoluble poly(diaminosulfide) with a dye. The microparticles were readily absorbed into human embryonic 293 cells and possessed no measureable toxicity towards these same cells.

Gold nanoparticles generated by thermolysis of "all-in-one" gold(I) carboxylate complexes

Consecutive synthesis methodologies for the preparation of the gold(I) carboxylates [(Ph(3)P)AuO(2)CCH(2)(OCH(2)CH(2))(n)OCH(3)] (n = 0-6) (6a-g) are reported, whereby selective mono-alkylation of diols HO(CH(2)CH(2)O)(n)H (n = 0-6), Williamson ether synthesis and metal carboxylate (Ag, Au) formation are the key steps. Single crystal X-ray diffraction studies of 6a (n = 0) and 6b (n = 1) were carried out showing that the P-Au-O unit is essentially linear. These compounds were applied in the formation of gold nanoparticles (NP) by a thermally induced decomposition process and hence the addition of any further stabilizing and reducing reagents, respectively, is not required. The ethylene glycol functionalities, providing multiple donating capabilities, are able to stabilise the encapsulated gold colloids. The dependency of concentration, generation time and ethylene glycol chain lengths on the NP size and size distribution is discussed. Characterisation of the gold colloids was performed by TEM, UV/Vis spectroscopy and electron diffraction studies revealing that Au NP are formed with a size of 3.3 (±0.6) to 6.5 (±0.9) nm in p-xylene with a sharp size distribution. Additionally, a decomposition mechanism determined by TG-MS coupling experiments of the gold(i) precursors is reported showing that 1(st) decarboxylation occurs followed by the cleavage of the Au-PPh(3) bond and finally release of ethylene glycol fragments to give Au-NP and the appropriate organics.

Targeting strategies for multifunctional nanoparticles in cancer imaging and therapy

Nanomaterials offer new opportunities for cancer diagnosis and treatment. Multifunctional nanoparticles harboring various functions including targeting, imaging, therapy, and etc have been intensively studied aiming to overcome limitations associated with conventional cancer diagnosis and therapy. Of various nanoparticles, magnetic iron oxide nanoparticles with superparamagnetic property have shown potential as multifunctional nanoparticles for clinical translation because they have been used asmagnetic resonance imaging (MRI) constrast agents in clinic and their features could be easily tailored by including targeting moieties, fluorescence dyes, or therapeutic agents. This review summarizes targeting strategies for construction of multifunctional nanoparticles including magnetic nanoparticles-based theranostic systems, and the various surface engineering strategies of nanoparticles for in vivo applications.

New developments and opportunities in oral mucosal drug delivery for local and systemic disease

The oral mucosa's accessibility, excellent blood supply, by-pass of hepatic first-pass metabolism, rapid repair and permeability profile make it an attractive site for local and systemic drug delivery. Technological advances in mucoadhesives, sustained drug release, permeability enhancers and drug delivery vectors are increasing the efficient delivery of drugs to treat oral and systemic diseases. When treating oral diseases, these advances result in enhanced therapeutic efficacy, reduced drug wastage and the prospect of using biological agents such as genes, peptides and antibodies. These technologies are also increasing the repertoire of drugs that can be delivered across the oral mucosa to treat systemic diseases. Trans-mucosal delivery is now a favoured route for non-parenteral administration of emergency drugs and agents where a rapid onset of action is required. Furthermore, advances in drug delivery technology are bringing forward the likelihood of transmucosal systemic delivery of biological agents.

Nanoparticulate systems as drug carriers: the need

Development of nanoparticles for drug delivery has progressed by leaps and bounds over the last few decades, facilitating the possibility of an efficacious therapy for some fatal diseases. This development has stemmed from either the unsuitable physicochemical characteristics of the existing drug molecules, such as limited solubility and hence poor bioavailability, or the inadequacy of the conventional delivery systems to provide safe and efficient delivery. This chapter focuses on the precise need for the development of these novel nanoparticulate drug carriers and reasons for their popularity with the drug delivery scientists. The text also discusses the various strategies, including different formulation and targeting approaches, which have been adopted to overcome the challenges presented by the inherent properties of the drug molecules. Examples of nanoparticulate drug delivery systems which have already gained market approval have been cited in the discussion, wherever applicable.

Nanomedicine as an emerging approach against intracellular pathogens

Diseases such as tuberculosis, hepatitis, and HIV/AIDS are caused by intracellular pathogens and are a major burden to the global medical community. Conventional treatments for these diseases typically consist of long-term therapy with a combination of drugs, which may lead to side effects and contribute to low patient compliance. The pathogens reside within intracellular compartments of the cell, which provide additional barriers to effective treatment. Therefore, there is a need for improved and more effective therapies for such intracellular diseases. This review will summarize, for the first time, the intracellular compartments in which pathogens can reside and discuss how nanomedicine has the potential to improve intracellular disease therapy by offering properties such as targeting, sustained drug release, and drug delivery to the pathogen’s intracellular location. The characteristics of nanomedicine may prove advantageous in developing improved or alternative therapies for intracellular diseases.

Spacer length effects on in vitro imaging and surface accessibility of fluorescent inhibitors of prostate specific membrane antigen

Prostate-specific membrane antigen (PSMA), a type II transmembrane protein, has been becoming an active target for imaging and therapeutic applications for prostate cancer. Recently, the development of its various chemical inhibitor scaffolds has been explored to serve as carriers for therapeutic or diagnostic payloads targeted to PSMA-positive tumor cells. However, there have been few efforts to definitively determine the optimal length of linker between PSMA inhibitor cores and their payload molecules with regard to the affinity to PSMA and in vitro performance. In our present model study, three spacer-length varied fluorescent inhibitors (FAM-CTT-54, FAM-X-CTT-54 and FAM-PEG(8)-CTT-54) were synthesized, and further enzymatic inhibition studies displayed linker length-dependent changes in: inhibitory potency (IC(50)=0.41 nM, 0.35 nM, 1.93 nM), modes of binding (reversible, slowly reversible, irreversible), respectively. Furthermore, cell-labeling imaging revealed the spacer length-related change of fluorescence intensity (FAM-X-CTT-54>FAM-PEG(8)-CTT-54>FAM-CTT-54). These results suggest that selection of linkers and their lengths will be important considerations in the development of next-generation prostate tumor-targeted imaging probes and therapeutic agents that specifically home to PSMA on tumor cells.

Polyethylene glycol-conjugated hyaluronic acid-ceramide self-assembled nanoparticles for targeted delivery of doxorubicin

Polyethylene glycol (PEG)-conjugated hyaluronic acid-ceramide (HACE) was synthesized for the preparation of doxorubicin (DOX)-loaded HACE-PEG-based nanoparticles, 160 nm in mean diameter with a negative surface charge. Greater uptake of DOX from these HACE-PEG-based nanoparticles was observed in the CD44 receptor highly expressed SCC7 cell line, compared to results from the CD44-negative cell line, NIH3T3. A strong fluorescent signal was detected in the tumor region upon intravenous injection of cyanine 5.5-labeled nanoparticles into the SCC7 tumor xenograft mice; the extended circulation time of the HACE-PEG-based nanoparticle was also observed. Pharmacokinetic study in rats showed a 73.0% reduction of the in vivo clearance of DOX compared to the control group. The antitumor efficacy of the DOX-loaded HACE-PEG-based nanoparticles was also verified in a tumor xenograft mouse model. DOX was efficiently delivered to the tumor site by active targeting via HA and CD44 receptor interaction and by passive targeting due to its small mean diameter (<200 nm). Moreover, PEGylation resulted in prolonged nanoparticle circulation and reduced DOX clearance rate in an in vivo model. These results therefore indicate that PEGylated HACE nanoparticles represent a promising anticancer drug delivery system for cancer diagnosis and therapy.

Role of cell cycle on the cellular uptake and dilution of nanoparticles in a cell population

Nanoparticles are considered a primary vehicle for targeted therapies because they can pass biological barriers and enter and distribute within cells by energy-dependent pathways. So far, most studies have shown that nanoparticle properties, such as size and surface, can influence how cells internalize nanoparticles. Here, we show that uptake of nanoparticles by cells is also influenced by their cell cycle phase. Although cells in different phases of the cell cycle were found to internalize nanoparticles at similar rates, after 24 h the concentration of nanoparticles in the cells could be ranked according to the different phases: G2/M > S > G0/G1. Nanoparticles that are internalized by cells are not exported from cells but are split between daughter cells when the parent cell divides. Our results suggest that future studies on nanoparticle uptake should consider the cell cycle, because, in a cell population, the dose of internalized nanoparticles in each cell varies as the cell advances through the cell cycle.