Targeting of nanoparticles in cancer: drug delivery and diagnostics. Anticancer Drugs. 2011;22:949-962. [PMID: 21970851 DOI: 10.1097/cad.0b013e32834a4554]

Fabrication and modification of composite silica nano test tubes for targeted drug delivery

Drug containing composite silica nano test tubes were fabricated within alumina template membranes, and upon liberation, modified with targeting moieties to specifically kill cancer cells.

Targeted transferrin-modified polymeric micelles: enhanced efficacy in vitro and in vivo in ovarian carcinoma

In this study, transferrin (Tf)-modified poly(ethylene glycol)-phosphatidylethanolamine (mPEG-PE) micelles loaded with the poorly water-soluble drug, R547 (a potent and selective ATP-competitive cyclin-dependent kinase (CDK) inhibitor), were prepared and evaluated for their targeting efficiency and cytotoxicity in vitro and in vivo to A2780 ovarian carcinoma cells, which overexpress transferrin receptors (TfR). At 10 mM lipid concentration, both Tf-modified and plain micelles solubilized 800 μg of R547. Tf-modified micelles showed enhanced interaction with A2780 ovarian carcinoma cells in vitro. The involvement of TfR in endocytosis of Tf-modified micelles was confirmed by colocalization studies of micelle-treated cells with the endosomal marker Tf-Alexa488. We confirmed endocytosis of micelles in an intact form with micelles loaded with a fluorescent dye and additionally labeled with fluorescent lipid. The in vitro cytotoxicity and in vivo tumor growth inhibition studies in A2780-tumor bearing mice confirmed the enhanced efficacy of Tf-modified R547-loaded micelles compared to free drug solution and to nonmodified micelles. The results of this study demonstrate the potential application of Tf-conjugated polymeric micelles in the treatment of tumors overexpressing TfR.

Cytotoxicity and DNA cleavage with core-shell nanocomposites functionalized by a KH domain DNA binding peptide

A nanoconjugate was composed of metal oxide nanoparticles decorated with peptides and fluorescent dye and tested for DNA cleavage following UV light activation. The peptide design was based on a DNA binding domain, the so called KH domain of the hnRNPK protein. This "KH peptide" enabled cellular uptake of nanoconjugates and their entry into cell nuclei. The control nanoconjugate carried no peptide; it consisted only of the metal oxide nanoparticle prepared as Fe3O4@TiO2 nanocomposite and the fluorescent dye alizarin red S. These components of either construct are responsible for nanoconjugate activation by UV light and the resultant production of reactive oxygen species (ROS). Production of ROS at different subcellular locations causes damage to different components of cells: only nanoconjugates inside cell nuclei can be expected to cause DNA cleavage. Degradation of cellular DNA with KH peptide decorated nanoconjugates exceeded the DNA damage obtained from control, no-peptide nanoconjugate counterparts. Moreover, caspase activation and cell death were more extensive in the same cells.

Non-invasive in vivo imaging of near infrared-labeled transferrin in breast cancer cells and tumors using fluorescence lifetime FRET

The conjugation of anti-cancer drugs to endogenous ligands has proven to be an effective strategy to enhance their pharmacological selectivity and delivery towards neoplasic tissues. Since cell proliferation has a strong requirement for iron, cancer cells express high levels of transferrin receptors (TfnR), making its ligand, transferrin (Tfn), of great interest as a delivery agent for therapeutics. However, a critical gap exists in the ability to non-invasively determine whether drugs conjugated to Tfn are internalized into target cells in vivo. Due to the enhanced permeability and retention (EPR) effect, it remains unknown whether these Tfn-conjugated drugs are specifically internalized into cancer cells or are localized non-specifically as a result of a generalized accumulation of macromolecules near tumors. By exploiting the dimeric nature of the TfnR that binds two molecules of Tfn in close proximity, we utilized a Förster Resonance Energy Transfer (FRET) based technique that can discriminate bound and internalized Tfn from free, soluble Tfn. In order to non-invasively visualize intracellular amounts of Tfn in tumors through live animal tissues, we developed a novel near infrared (NIR) fluorescence lifetime FRET imaging technique that uses an active wide-field time gated illumination platform. In summary, we report that the NIR fluorescence lifetime FRET technique is capable of non-invasively detecting bound and internalized forms of Tfn in cancer cells and tumors within a live small animal model, and that our results are quantitatively consistent when compared to well-established intensity-based FRET microscopy methods used in in vitro experiments.

Multimodality PET/MRI agents targeted to activated macrophages

The recent emergence of multimodality imaging, particularly the combination of PET and MRI, has led to excitement over the prospect of improving detection of disease. Iron oxide nanoparticles have become a popular platform for the fabrication of PET/MRI probes owing to their advantages of high MRI detection sensitivity, biocompatibility, and biodegradability. In this article, we report the synthesis of dextran-coated iron oxide nanoparticles (DIO) labeled with the positron emitter (64)Cu to generate a PET/MRI probe, and modified with maleic anhydride to increase the negative surface charge. The modified nanoparticulate PET/MRI probe (MDIO-(64)Cu-DOTA) bears repetitive anionic charges on the surface that facilitate recognition by scavenger receptor type A (SR-A), a ligand receptor found on activated macrophages but not on normal vessel walls. MDIO-(64)Cu-DOTA has an average iron oxide core size of 7-8 nm, an average hydrodynamic diameter of 62.7 nm, an r1 relaxivity of 16.8 mM(-1) s(-1), and an r 2 relaxivity of 83.9 mM(-1) s(-1) (37 °C, 1.4 T). Cell studies confirmed that the probe was nontoxic and was specifically taken up by macrophages via SR-A. In comparison with the nonmodified analog, the accumulation of MDIO in macrophages was substantially improved. These characteristics demonstrate the promise of MDIO-(64)Cu-DOTA for identification of vulnerable atherosclerotic plaques via the targeting of macrophages.

Recombinant lipoproteins reinforce cytotoxicity of doxorubicin to hepatocellular carcinoma

Cancer nanotherapeutics are changing the landscape of tumor treatment and used to circumvent limitations of conventional chemotherapy, such as non-specificity and low bioavailability. Reconstituted high density lipoproteins (rHDL) system is one of the most promising targeting delivery systems of chemotherapeutic drugs toward tumors. Here, we developed recombined high-density lipoprotein which can be functionalized to deliver doxorubicin intracellular with a higher efficiency. The cellular viability assay showed that the rHDL/Dox nanovectors had an enhanced efficiency in inhibiting the cell viability of hepatocellular carcinoma cell lines HepG2 and SMMC-7721. FACS and confocal microscopy was used to observe the doxorubicin delivery into cancer cells. Intracellular drug accumulation analysis confirmed that treatment of rHDL/Dox nanovectors resulted in higher intracellular doxorubicin concentration to the levels exceeding that of free drug. On the premise of efficient drug delivery, rHDL/Dox nanovectors have been preliminarily demonstrated effective inducing of cytotoxic effect and cell apoptosis to both of the cell lines in vitro. Tissue distribution experiment showed that rHDL/Dox nanovectors could also deliver doxorubicin to liver effectively. So, we proposed that this lipoprotein-based strategy holds promise for a safer and more efficient delivery of chemotherapeutic agents in the treatment of hepatocellular carcinoma.

Multifunctional and multitargeted nanoparticles for drug delivery to overcome barriers of drug resistance in human cancers

The recurrence and metastatic spread of cancer are major drawbacks in cancer treatment. Although chemotherapy is one of the most effective methods for the treatment of metastatic cancers, it is nonspecific and causes significant toxic damage. The development of drug resistance to chemotherapeutic agents through various mechanisms also limits their therapeutic potential. However, as we discuss here, the use of nanodelivery systems that are a combination of diagnostics and therapeutics (theranostics) is as relatively novel concept in the treatment of cancer. Such systems are likely to improve the therapeutic benefits of encapsulated drugs and can transit to the desired site, maintaining their pharmaceutical properties. The specific targeting of malignant cells using multifunctional nanoparticles exploits theranostics as an improved agent for delivering anticancer drugs and as a new solution for overriding drug resistance.

Current trends in the use of liposomes for tumor targeting

The use of liposomes for drug delivery began early in the history of pharmaceutical nanocarriers. These nanosized, lipid bilayered vesicles have become popular as drug delivery systems owing to their efficiency, biocompatibility, nonimmunogenicity, enhanced solubility of chemotherapeutic agents and their ability to encapsulate a wide array of drugs. Passive and ligand-mediated active targeting promote tumor specificity with diminished adverse off-target effects. The current field of liposomes focuses on both clinical and diagnostic applications. Recent efforts have concentrated on the development of multifunctional liposomes that target cells and cellular organelles with a single delivery system. This review discusses the recent advances in liposome research in tumor targeting.

Small peptide-modified nanostructured lipid carriers distribution and targeting to EGFR-overexpressing tumor in vivo

Ala-Glu-Tyr-Leu-Arg (AEYLR) was identified as a small peptide ligand targeting epidermal growth factor receptors (EGFR) in vitro in our previous study. The in vivo targeting ability of AEYLR and AEYLR-conjugated nanostructured lipid carriers (NLC) was studied in this paper. Near-infrared fluorescent (NIFR) dye 1,1'-dioctadecyltetramethyl indotricarbocyanine iodide (DiR)-loaded and AEYLR-modified NLC (A-D-NLC) were prepared. The average diameter, zeta potential, coupling efficiency between AEYLR and NLC and the amount of DiR released from A-D-NLC were used to evaluate their in vivo characteristics. AEYLR was labeled by Cy7 and A549 xenograft tumor-bearing mice model were establish. The in vivo distribution in tumor-bearing mice of A-D-NLC and Cy7-AEYLR was examined using NIRF imaging experiments at different times post-injection. AEYLR and AEYLR-conjugated NLC showed obvious targeting to A549 xenograft tumor compared with the control group. These results suggested that AEYLR-modified NLC could be considered as a promising targeted delivery system for combination cancer chemotherapy to improve therapeutic efficacy and to minimize adverse effects.

Development of PIK-75 nanosuspension formulation with enhanced delivery efficiency and cytotoxicity for targeted anti-cancer therapy

PIK-75 is a phosphatidylinositol 3-kinase (PI3K) inhibitor that shows selectivity toward p110-α over the other PI3K class Ia isoforms p110-β and p110-δ, but it lacks solubility, stability and other kinase selectivity. The purpose of this study was to develop folate-targeted PIK-75 nanosuspension for tumor targeted delivery and to improve therapeutic efficacy in human ovarian cancer model. High pressure homogenization was used to prepare the non-targeted and targeted PIK-75 nanosuspensions which were characterized for size, zeta potential, entrapment efficiency, morphology, saturation solubility and dissolution velocity. In vitro analysis of drug uptake, cell viability and cell survival was conducted in SKOV-3 cells. Drug pharmacokinetics and pAkt expression were determined in SKOV-3 tumor bearing mice. PIK-75 nanosuspensions showed an improvement in dissolution velocity and an 11-fold increase in saturation solubility over pre-milled PIK-75. In vitro studies in SKOV-3 cells indicated a 2-fold improvement in drug uptake and 0.4-fold decrease in IC50 value of PIK-75 following treatment with targeted nanosuspension compared to non-targeted nanosuspension. The improvement in cytotoxicity was attributed to an increase in caspase 3/7 and hROS activity. In vivo studies indicated a 5-10-fold increased PIK-75 accumulation in the tumor with both the nanosuspension formulations compared to PIK-75 suspension. The targeted nanosuspension showed an enhanced downregulation of pAkt compared to non-targeted formulation system. These results illustrate the opportunity to formulate PIK-75 as a targeted nanosuspension to enhance uptake and cytotoxicity of the drug in tumor.

A novel small peptide as an epidermal growth factor receptor targeting ligand for nanodelivery in vitro

The epidermal growth factor receptor (EGFR) serves an important function in the proliferation of tumors in humans and is an effective target for the treatment of cancer. In this paper, we studied the targeting characteristics of small peptides (AEYLR, EYINQ, and PDYQQD) that were derived from three major autophosphorylation sites of the EGFR C-terminus domain in vitro. These small peptides were labeled with fluorescein isothiocyanate (FITC) and used the peptide LARLLT as a positive control, which bound to putative EGFR selected from a virtual peptide library by computer-aided design, and the independent peptide RALEL as a negative control. Analyses with flow cytometry and an internalization assay using NCI-H1299 and K562 with high EGFR and no EGFR expression, respectively, indicated that FITC-AEYLR had high EGFR targeting activity. Biotin-AEYLR that was specifically bound to human EGFR proteins demonstrated a high affinity for human non-small-cell lung tumors. We found that AEYLR peptide-conjugated, nanostructured lipid carriers enhanced specific cellular uptake in vitro during a process that was apparently mediated by tumor cells with high-expression EGFR. Analysis of the MTT assay indicated that the AEYLR peptide did not significantly stimulate or inhibit the growth activity of the cells. These findings suggest that, when mediated by EGFR, AEYLR may be a potentially safe and efficient delivery ligand for targeted chemotherapy, radiotherapy, and gene therapy.

Lipid-functionalized dextran nanosystems to overcome multidrug resistance in cancer: a pilot study

BACKGROUND

The toxicity of anticancer agents and the difficulty in delivering drugs selectively to tumor cells pose a challenge in overcoming multidrug resistance (MDR). Recently, nanotechnology has emerged as a powerful tool in addressing some of the barriers to drug delivery, including MDR in cancer, by utilizing alternate routes of cellular entry and targeted delivery of drugs and genes. However, it is unclear whether doxorubicin (Dox) can be delivered by nanotechnologic approaches.

QUESTIONS/PURPOSES

We asked whether (1) Dox-loaded lipid-functionalized dextran-based biocompatible nanoparticles (Dox/NP) can reverse MDR, (2) Dox/NP has more potent cytotoxic effect on MDR tumors than poly(ethylene glycol)-modified liposomal Dox (PLD), and (3) multidrug resistance protein 1 (MDR1) small interfering RNA loaded in these nanoparticles (siMDR1/NP) can modulate MDR.

METHODS

To create stable Dox/NP and siMDR1/NP, we used two different lipid-modified dextran derivatives. The effect of Dox or Dox/NP was tested on drug-sensitive osteosarcoma (KHOS) and ovarian cancer (SKOV-3) cell cultures in triplicate and their respective MDR counterparts KHOS(R2) and SKOV-3(TR) in triplicate. We determined the effects on drug retention, transfection efficacy of siMDR1/NP, and P-glycoprotein expression and the antiproliferative effect between Dox/NP and PLD in MDR tumor cells.

RESULTS

Fluorescence microscopy revealed efficient uptake of the Dox/NP and fluorescently tagged siMDR1/NP. Dox/NP showed five- to 10-fold higher antiproliferative activity at the 50% inhibitory concentration than free Dox in tumor cells. Dox/NP showed twofold higher activity than PLD in MDR tumor cells. siMDR1/NP (100 nM) suppressed P-glycoprotein expression in KHOS(R2).

CONCLUSIONS

Dextran-lipid nanoparticles are a promising platform for delivering Dox and siRNAs.

CLINICAL RELEVANCE

Biocompatible dextran-based nanoparticles that are directly translatable to clinical medicine may lead to new potential therapeutics for reversing MDR in patients with cancer.

Nanoparticle PET/CT imaging of natriuretic peptide clearance receptor in prostate cancer

Atrial natriuretic peptide has been recently discovered to have anticancer effects via interaction with cell surface natriuretic peptide receptor A (NPRA) and natriuretic peptide clearance receptor (NPRC). In a preclinical model, NPRA expression has been identified during tumor angiogenesis and may serve as a potential prognostic marker and target for prostate cancer (PCa) therapy. However, the presence of NPRC receptor in the PCa model has not yet been assessed. Furthermore, there is still no report using nanoparticle for PCa positron emission tomography (PET) imaging. Herein, an amphiphilic comb-like nanoparticle was synthesized with controlled properties through modular construction containing C-atrial natriuretic factor (CANF) for NPRC receptor targeting and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator for high specific activity Cu-64 radiolabeling. The pharmacokinetics of (64)Cu-CANF-Comb exhibited tuned biodistribution and optimized in vivo profile in contrast to the nontargeted (64)Cu-Comb nanoparticle. PET imaging with (64)Cu-CANF-Comb in CWR22 PCa tumor model showed high blood pool retention, low renal clearance, enhanced tumor uptake, and decreased hepatic burden relative to the nontargeted (64)Cu-Comb. Immunohistochemistry staining confirmed the presence of NPRC receptor in tumor tissue. Competitive PET receptor blocking study demonstrated the targeting specificity of (64)Cu-CANF-Comb to NPRC receptor in vivo. These results establish a new nanoagent for prostate cancer PET imaging.

Targeting cancer cells with controlled release nanocapsules based on a single aptamer

Molecular gates have received considerable attention as drug delivery systems. More recently, aptamer-based gates showed great potential in overcoming major challenges associated with drug delivery by means of nanocapsules. Based on a switchable aptamer nanovalves approach, we herein report the first demonstration of an engineered single molecular gate that directs nanoparticles to cancer cells and subsequently delivers the payload in a controllable fashion.

The holistic 3M modality of drug delivery nanosystems for cancer therapy

Cancer has become the leading cause of human death worldwide. There are many challenges in the treatment of cancer and the rapidly developing area of nanotechnology has shown great potential to open a new era in cancer therapy. This article, rather than being exhaustive, focuses on the striking progress in the drug delivery nanosystems (DDNS) for cancer therapy and selects typical examples to point out the emerging mode of action of DDNS from our perspective. Among the outstanding advances in DDNS for cancer therapy is the development of "multicomponent delivery systems", "multifunctional nanocarriers" and "multistage delivery systems". However, these represent only one aspect of DDNS research. In addition, nature is the best teacher and natural evolution pressure has meant that virions conform to the "multitarget, multistage and multicomponent" (3M) mode of action. Amazingly, traditional Chinese medicine (TCM), used for over 4000 years in China, also displays the same mode of action. Integrating the previous notable progress in nanoparticle technology, learned from the building mode of natural virions and the action concept of TCM, we propose an integrity-based 3M mode DDNS for cancer therapy: multitarget, multistage and multicomponent, which are not fragmented parts but an interconnected integrity. Based on the physiological multitarget and the pharmacokinetic multistage, multicomponent DDNS are rationally designed, where different components with individual specific functions act in a synergistic manner against each target at each disposition stage to maximize the targeted delivery effectiveness. In this article, we introduce each component of 3M DDNS in detail and describe some typical cases to realize the tumor-homing purposes.

Sharka: the past, the present and the future

Members the Potyviridae family belong to a group of plant viruses that are causing devastating plant diseases with a significant impact on agronomy and economics. Plum pox virus (PPV), as a causative agent of sharka disease, is widely discussed. The understanding of the molecular biology of potyviruses including PPV and the function of individual proteins as products of genome expression are quite necessary for the proposal the new antiviral strategies. This review brings to view the members of Potyviridae family with respect to plum pox virus. The genome of potyviruses is discussed with respect to protein products of its expression and their function. Plum pox virus distribution, genome organization, transmission and biochemical changes in infected plants are introduced. In addition, techniques used in PPV detection are accentuated and discussed, especially with respect to new modern techniques of nucleic acids isolation, based on the nanotechnological approach. Finally, perspectives on the future of possibilities for nanotechnology application in PPV determination/identification are outlined.

Nanovectorized radiotherapy: a new strategy to induce anti-tumor immunity

Recent experimental findings show that activation of the host immune system is required for the success of chemo- and radiotherapy. However, clinically apparent tumors have already developed multiple mechanisms to escape anti-tumor immunity. The fact that tumors are able to induce a state of tolerance and immunosuppression is a major obstacle in immunotherapy. Hence, there is an overwhelming need to develop new strategies that overcome this state of immune tolerance and induce an anti-tumor immune response both at primary and metastatic sites. Nanovectorized radiotherapy that combines ionizing radiation and nanodevices, is one strategy that could boost the quality and magnitude of an immune response in a predictable and designable fashion. The potential benefits of this emerging treatment may be based on the unique combination of immunostimulatory properties of nanoparticles with the ability of ionizing radiation to induce immunogenic tumor cell death. In this review, we will discuss available data and propose that the nanovectorized radiotherapy could be a powerful new strategy to induce anti-tumor immunity required for positive patient outcome.

Chondroitin sulfate functionalized mesostructured silica nanoparticles as biocompatible carriers for drug delivery

Mesoporous silica nanoparticles (MSNs) have garnered a great deal of attention as potential carriers for therapeutic payloads. Here, we report a pH-responsive drug-carrier based on chondroitin sulfate functionalized mesostructured silica nanoparticles (NMChS-MSNs) ie, the amidation between NMChS macromer and amino group functionalized MSNs. The prepared nanoparticles were characterized using dynamic light scattering, fourier transform infrared spectroscopy and transmission electron microscopy. The resultant NMChS-MSNs were uniform spherical nanoparticles with a mean diameter of approximately 74 nm. Due to the covalent graft of hydrophilic and pH responsive NMChS, the NMChS-MSNs could be well dispersed in aqueous solution, which is favorable to being utilized as drug carriers to construct a pH-responsive controlled drug delivery system. Doxorubicin hydrochloride (DOX), a well-known anticancer drug, could be effectively loaded into the channels of NMChS-MSNs through electrostatic interactions between drug and matrix. The drug release rate of DOX@NMChS-MSNs was pH dependent and increased with the decrease of pH. The in vitro cytotoxicity test indicated that NMChS-MSNs were highly biocompatible and suitable to use as drug carriers. Our results imply that chondroitin sulfate functionalized nanoparticles are promising platforms to construct the pH-responsive controlled drug delivery systems for cancer therapy.

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.

Analysis of immediate stress mechanisms upon injection of polymeric micelles and related colloidal drug carriers: implications on drug targeting

Polymeric micelles are ideal carriers for solubilization and targeting applications using hydrophobic drugs. Stability of colloidal aggregates upon injection into the bloodstream is mandatory to maintain the drugs' targeting potential and to influence pharmacokinetics. In this review we analyzed and discussed the most relevant stress mechanisms that polymeric micelles and related colloidal carriers encounter upon injection, including (1) dilution, (2) interactions with blood components, and (3) immunological responses of the body. In detail we analyzed the opsonin-dysopsonin hypothesis that points at a connection between a particles' protein-corona and its tissue accumulation by the enhanced permeability and retention (EPR) effect. In the established theory, size is seen as a necessary condition to reach nanoparticle accumulation in disease modified tissue. There is, however, mounting evidence of other sufficient conditions (e.g., particle charge, receptor recognition of proteins adsorbed onto particle surfaces) triggering nanoparticle extravasation by active mechanisms. In conclusion, the analyzed stress mechanisms are directly responsible for in vivo success or failure of the site-specific delivery with colloidal carrier systems.

Targeted polymeric therapeutic nanoparticles: design, development and clinical translation

Polymeric materials have been used in a range of pharmaceutical and biotechnology products for more than 40 years. These materials have evolved from their earlier use as biodegradable products such as resorbable sutures, orthopaedic implants, macroscale and microscale drug delivery systems such as microparticles and wafers used as controlled drug release depots, to multifunctional nanoparticles (NPs) capable of targeting, and controlled release of therapeutic and diagnostic agents. These newer generations of targeted and controlled release polymeric NPs are now engineered to navigate the complex in vivo environment, and incorporate functionalities for achieving target specificity, control of drug concentration and exposure kinetics at the tissue, cell, and subcellular levels. Indeed this optimization of drug pharmacology as aided by careful design of multifunctional NPs can lead to improved drug safety and efficacy, and may be complimentary to drug enhancements that are traditionally achieved by medicinal chemistry. In this regard, polymeric NPs have the potential to result in a highly differentiated new class of therapeutics, distinct from the original active drugs used in their composition, and distinct from first generation NPs that largely facilitated drug formulation. A greater flexibility in the design of drug molecules themselves may also be facilitated following their incorporation into NPs, as drug properties (solubility, metabolism, plasma binding, biodistribution, target tissue accumulation) will no longer be constrained to the same extent by drug chemical composition, but also become in-part the function of the physicochemical properties of the NP. The combination of optimally designed drugs with optimally engineered polymeric NPs opens up the possibility of improved clinical outcomes that may not be achievable with the administration of drugs in their conventional form. In this critical review, we aim to provide insights into the design and development of targeted polymeric NPs and to highlight the challenges associated with the engineering of this novel class of therapeutics, including considerations of NP design optimization, development and biophysicochemical properties. Additionally, we highlight some recent examples from the literature, which demonstrate current trends and novel concepts in both the design and utility of targeted polymeric NPs (444 references).

Potential Use of Polyamidoamine Dendrimer Conjugates with Cyclodextrins as Novel Carriers for siRNA

Cyclodextrin (CyD)-based nanoparticles and polyamidoamine (PAMAM) starburst dendrimers (dendrimers) are used as novel carriers for DNA and RNA. Recently, small interfering RNA (siRNA) complex with β-CyD-containing polycations (CDP) having adamantine-PEG or adamantine-PEG-transferrin underwent a phase I study for treatment of solid tumors. Multifunctional dendrimers can be used for a wide range of biomedical applications, including the interaction and intracellular delivery of DNA and RNA. The present review will address the latest developments in dendrimer conjugates with cyclodextrins for siRNA delivery including the novel sustained release system.