Simultaneous delivery of siRNA and paclitaxel via a "two-in-one" micelleplex promotes synergistic tumor suppression

Triple negative breast cancer therapy with CDK1 siRNA delivered by cationic lipid assisted PEG-PLA nanoparticles

There is no effective clinical therapy yet for triple-negative breast cancer (TNBC) without particular human epidermal growth factor receptor-2, estrogen and progesterone receptor expression. In this study, we report a molecularly targeted and synthetic lethality-based siRNA therapy for TNBC treatment, using cationic lipid assisted poly(ethylene glycol)-b-poly(d,l-lactide) (PEG-PLA) nanoparticles as the siRNA carrier. It is demonstrated that only in c-Myc overexpressed TNBC cells, while not in normal mammary epithelial cells, delivery of siRNA targeting cyclin-dependent kinase 1 (CDK1) with the nanoparticle carrier (NPsiCDK1) induces cell viability decreasing and cell apoptosis through RNAi-mediated CDK1 expression inhibition, indicating the synthetic lethality between c-Myc with CDK1 in TNBC cells. Moreover, systemic delivery of NPsiCDK1 is able to suppress tumor growth in mice bearing SUM149 and BT549 xenograft and cause no systemic toxicity or activate the innate immune response, suggesting the therapeutic promise with such nanoparticles carrying siCDK1 for c-Myc overexpressed triple negative breast cancer.

Co-delivery of doxorubicin and siRNA with reduction and pH dually sensitive nanocarrier for synergistic cancer therapy

Drug resistance is the greatest challenge in clinical cancer chemotherapy. Co-delivery of chemotherapeutic drugs and siRNA to tumor cells is a vital means to silence drug resistant genes during the course of cancer chemotherapy for an improved chemotherapeutic effect. This study aims at effective co-delivery of siRNA and anticancer drugs to tumor cells. A ternary block copolymer PEG-PAsp(AED)-PDPA consisting of pH-sensitive poly(2-(diisopropyl amino)ethyl methacrylate) (PDPA), reduction-sensitive poly(N-(2,2'-dithiobis(ethylamine)) aspartamide) PAsp(AED), and poly(ethylene glycol) (PEG) is synthesized and assembled into a core-shell structural micelle which encapsulated doxorubicin (DOX) in its pH-sensitive core and the siRNA-targeting anti-apoptosis BCL-2 gene (BCL-2 siRNA) in a reduction-sensitive interlayer. At the optimized size and zeta potential, the nanocarriers loaded with DOX and BCL-2 siRNA may effectively accumulate in the tumor site via blood circulation. Moreover, the dual stimuli-responsive design of micellar carriers allows microenviroment-specific rapid release of both DOX and BCL-2 siRNA inside acidic lysosomes with enriched reducing agent, glutathione (GSH, up to 10 mM). Consequently, the expression of anti-apoptotic BCL-2 protein induced by DOX treatment is significantly down-regulated, which results in synergistically enhanced apoptosis of human ovarian cancer SKOV-3 cells and thus dramatically inhibited tumor growth.

MicroRNA modulation combined with sunitinib as a novel therapeutic strategy for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and mortal cancer, characterized by a set of known mutations, invasive features, and aberrant microRNA expression that have been associated with hallmark malignant properties of PDAC. The lack of effective PDAC treatment options prompted us to investigate whether microRNAs would constitute promising therapeutic targets toward the generation of a gene therapy approach with clinical significance for this disease. In this work, we show that the developed human serum albumin–1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine:cholesterol/anti-microRNA oligonucleotides (+/−) (4/1) nanosystem exhibits the ability to efficiently deliver anti-microRNA oligonucleotides targeting the overexpressed microRNAs miR-21, miR-221, miR-222, and miR-10 in PDCA cells, promoting an almost complete abolishment of microRNA expression. Silencing of these microRNAs resulted in a significant increase in the levels of their targets. Moreover, the combination of microRNA silencing, namely miR-21, with low amounts of the chemotherapeutic drug sunitinib resulted in a strong and synergistic antitumor effect, showing that this combined strategy could be of great importance for therapeutic application in PDAC.

Recent advances in nanoparticle-mediated siRNA delivery

Inhibiting specific gene expression by short interfering RNA (siRNA) offers a new therapeutic strategy to tackle many diseases, including cancer, metabolic disorders, and viral infections, at the molecular level. The macromolecular and polar nature of siRNA hinders its cellular access to exert its effect. Nanoparticulate delivery systems can promote efficient intracellular delivery. Despite showing promise in many preclinical studies and potential in some clinical trials, siRNA has poor delivery efficiency, which continues to demand innovations, from carrier design to formulation, in order to overcome transport barriers. Previous findings for optimal plasmid DNA delivery cannot be generalized to siRNA delivery owing to significant discrepancy in size and subtle differences in chain flexibility between the two types of nucleic acids. In this review, we highlight the recent advances in improving the stability of siRNA nanoparticles, understanding their intracellular trafficking and release mechanisms, and applying judiciously the promising formulations to disease models.

Janus nanoparticles: materials, preparation and recent advances in drug delivery

INTRODUCTION

The term Janus particles was used to describe particles that are the combination of two distinct sides with differences in chemical nature and/or polarity on each face. Due to the exponential growth of interest on multifunctional nanotechnologies, such anisotropic nanoparticles are promising tools in the field of drug delivery.

AREAS COVERED

The main preparation processes and the materials used have been described first. Then a specific focus has been done on therapeutic and/or diagnostic applications of Janus particles.

EXPERT OPINION

Janus particles are demonstrated as interesting objects with advanced properties that combine features and functionalities of different materials in one single unit. Due to their dual structure, Janus particles are promising candidates for a variety of high-quality applications dealing with drug delivery purposes. Still, the main challenges for the future lie in the development of the preparation of shape-controlled and nano-sized particles with large-scale production processes and approved pharmaceutical excipients.

Multifunctional polymeric micelles for delivery of drugs and siRNA

Polymeric micelles, self-assembling nano-constructs of amphiphilic copolymers with a core-shell structure have been used as versatile carriers for delivery of drugs as well as nucleic acids. They have gained immense popularity owing to a host of favorable properties including their capacity to effectively solubilize a variety of poorly soluble pharmaceutical agents, biocompatibility, longevity, high stability in vitro and in vivo and the ability to accumulate in pathological areas with compromised vasculature. Moreover, additional functions can be imparted to these micelles by engineering their surface with various ligands and cell-penetrating moieties to allow for specific targeting and intracellular accumulation, respectively, to load them with contrast agents to confer imaging capabilities, and incorporating stimuli-sensitive groups that allow drug release in response to small changes in the environment. Recently, there has been an increasing trend toward designing polymeric micelles which integrate a number of the above functions into a single carrier to give rise to “smart,” multifunctional polymeric micelles. Such multifunctional micelles can be envisaged as key to improving the efficacy of current treatments which have seen a steady increase not only in hydrophobic small molecules, but also in biologics including therapeutic genes, antibodies and small interfering RNA (siRNA). The purpose of this review is to highlight recent advances in the development of multifunctional polymeric micelles specifically for delivery of drugs and siRNA. In spite of the tremendous potential of siRNA, its translation into clinics has been a significant challenge because of physiological barriers to its effective delivery and the lack of safe, effective and clinically suitable vehicles. To that end, we also discuss the potential and suitability of multifunctional polymeric micelles, including lipid-based micelles, as promising vehicles for both siRNA and drugs.

Aptamer-targeted DNA nanostructures for therapeutic delivery

DNA-based nanostructures have been widely used in various applications due to their structural diversity, programmability, and uniform structures. Their intrinsic biocompatibility and biodegradability further motivates the investigation of DNA-based nanostructures as delivery vehicles. Incorporating AS1411 aptamers into DNA pyramids leads to enhanced intracellular uptake and selectively inhibits the growth of cancer cells, achieved without the use of transfection reagents. Furthermore, aptamer-displaying pyramids are found to be substantially more resistant to nuclease degradation than single-stranded aptamers. These findings, along with their modularity, reinforce the potential of DNA-based nanostructures for therapeutic applications.

Tumor-targeting dual peptides-modified cationic liposomes for delivery of siRNA and docetaxel to gliomas

Combinations of drugs promoting anti-angiogenesis and apoptosis effects are meaningful for cancer therapy. In the present study, dual peptides-modified liposomes were designed by attaching two receptor-specific peptides, specifically low-density lipoprotein receptor-related protein receptor (Angiopep-2) and neuropilin-1 receptor (tLyP-1) for brain tumor targeting and tumor penetration. Vascular endothelial growth factor (VEGF) siRNA and chemotherapeutic docetaxel (DTX) were chosen as the two payloads because VEGF is closely associated with angiogenesis, and DTX can kill tumor cells efficiently. Binding to glioma cells, co-delivery of siRNA and DTX in human glioblastoma cells (U87 MG) and murine brain microvascular endothelial cells (BMVEC), VEGF gene silencing, antiproliferation and anti-tumor effects of the dual peptides-modified liposomes were evaluated in vitro and in vivo. The dual peptides-modified liposomes persisted the binding ability to glioma cells, enhanced the internalization via specific receptor mediated endocytosis and tissue penetration, thus the dual peptides-modified liposomes loading VEGF siRNA and DTX possessed stimulative gene silencing and antiproliferation activity compared with non-modified and single peptide-modified liposomes. The co-delivery research revealed different intracellular behavior of hydrophilic large molecular and lipophilic small molecule, the former involves endocytosis and subsequent escape of endosome/lysosomes, while the latter experiences passive diffusion of lipophilic small drugs after its release. Furthermore, the dual peptides-modified liposomes showed superiority in anti-tumor efficacy, combination of anti-angiogenesis by VEGF siRNA and apoptosis effects by DTX, after both intratumor and system application against mice with U87 MG tumors, and the treatment did not activate system-associated toxicity or the innate immune response. Combination with the dual peptides-guided tumor homing and penetration, the dual peptides-modified liposomes provide a strategy for effective targeting delivery of siRNA and DTX into the glioma cell and inhibition of tumor growth in a synergistic manner.

Matrix metalloproteinase 2-sensitive multifunctional polymeric micelles for tumor-specific co-delivery of siRNA and hydrophobic drugs

Co-delivery of hydrophilic siRNA and hydrophobic drugs is one of the major challenges for nanomaterial-based medicine. Here, we present a simple but multifunctional micellar platform constructed by a matrix metalloproteinase 2 (MMP2)-sensitive copolymer (PEG-pp-PEI-PE) via self-assembly for tumor-targeted siRNA and drug co-delivery. The micellar nanocarrier possesses several key features for siRNA and drug delivery, including (i) excellent stability; (ii) efficient siRNA condensation by PEI; (iii) hydrophobic drug solubilization in the lipid "core"; (iv) passive tumor targeting via the enhanced permeability and retention (EPR) effect; (v) tumor targeting triggered by the up-regulated tumoral MMP2; and (vi) enhanced cell internalization after MMP2-activated exposure of the previously hidden PEI. These cooperative functions ensure the improved tumor targetability, enhanced tumor cell internalization, and synergistic antitumor activity of co-loaded siRNA and drug.

Theranostic GO-based nanohybrid for tumor induced imaging and potential combinational tumor therapy

Graphene oxide (GO)-based theranostic nanohybrid is designed for tumor induced imaging and potential combinational tumor therapy. The anti-tumor drug, Doxorubicin (DOX) is chemically conjugated to the poly(ethylenimine)-co-poly(ethylene glycol) (PEI-PEG) grafted GO via a MMP2-cleavable PLGLAG peptide linkage. The therapeutic efficacy of DOX is chemically locked and its intrinsic fluorescence is quenched by GO under normal physiological condition. Once stimulated by the MMP2 enzyme over-expressed in tumor tissues, the resulting peptide cleavage permits the unloading of DOX for tumor therapy and concurrent fluorescence recovery of DOX for in situ tumor cell imaging. Attractively, this PEI-bearing nanohybrid can mediate efficient DNA transfection and shows great potential for combinational drug/gene therapy. This tumor induced imaging and potential combinational therapy will open a window for tumor treatment by offering a unique theranostic approach through merging the diagnostic capability and pathology-responsive therapeutic function.

Synthetic lethal therapy for KRAS mutant non-small-cell lung carcinoma with nanoparticle-mediated CDK4 siRNA delivery

The KRAS mutation is present in ~20% of lung cancers and has not yet been effectively targeted for therapy. This mutation is associated with a poor prognosis in non-small-cell lung carcinomas (NSCLCs) and confers resistance to standard anticancer treatment drugs, including epidermal growth factor receptor tyrosine kinase inhibitors. In this study, we exploited a new therapeutic strategy based on the synthetic lethal interaction between cyclin-dependent kinase 4 (CDK4) downregulation and the KRAS mutation to deliver micellar nanoparticles (MNPs) containing small interfering RNA targeting CDK4 (MNPsiCDK4) for treatment in NSCLCs harboring the oncogenic KRAS mutation. Following MNPsiCDK4 administration, CDK4 expression was decreased, accompanied by inhibited cell proliferation, specifically in KRAS mutant NSCLCs. However, this intervention was harmless to normal KRAS wild-type cells, confirming the proposed mechanism of synthetic lethality. Moreover, systemic delivery of MNPsiCDK4 significantly inhibited tumor growth in an A549 NSCLC xenograft murine model, with depressed expression of CDK4 and mutational KRAS status, suggesting the therapeutic promise of MNPsiCDK4 delivery in KRAS mutant NSCLCs via a synthetic lethal interaction between KRAS and CDK4.

Doxorubicin conjugate of poly(ethylene glycol)-block-polyphosphoester for cancer therapy

Polyphosphoesters with repeating phosphoester linkages in the backbone can be easily functionalized, are biodegradable and potentially biocompatible, and may be potential candidates as polymer carriers of drug conjugates. Here, the efficacy of a polyphosphoester drug conjugate as an anticancer agent in vivo is assessed for the first time. With controlled synthesis, doxorubicin conjugated to poly(ethylene glycol)-block-polyphosphoester (PPEH-DOX) via labile hydrazone bonds form spherical nanoparticles in aqueous solution with an average diameter of ≈60 nm. These nanoparticles are effectively internalized by MDA-MB-231 breast cancer cells and release the conjugated doxorubicin in response to the intracellular pH of endosomes and lysosomes, resulting in significant antiproliferative activity in cancer cells. Compared with free doxorubicin injection, PPEH-DOX injection exhibits much longer circulation behavior in the plasma of mice and leads to enhanced drug accumulation in tumor cells. In an MDA-MB-231 xenograft murine model, inhibition of tumor growth with systemic delivery of PPEH-DOX nanoparticles is more pronounced compared with free doxorubicin injection, suggesting the potential of polyphosphoesters as carriers of drug conjugates in cancer therapy.

Dynamic disordering of liposomal cocktails and the spatio-temporal favorable release of cargoes to circumvent drug resistance

Multidrug resistance (MDR) has been a major impediment to the success of cancer chemotherapy. Extensive efforts have been devoted to the development of drug delivery systems using nanotechnology to reverse MDR in cancer. However, the spontaneous release of drug payloads was always a slow process, which leads to the low intracellular drug concentration resulting in consequent drug insensitivity. To circumvent this limitation, we described a liposomal cocktail (LMDHV) constructed by a pH-responsive molecule (i.e., malachite green carbinol base (MG)) and liposome conjugated with Her-2 antibody for codelivery of doxorubicin (DOX) and verapamil (VER) to suppress drug resistance in Her-2 positive breast cancer. MG inserted in the bilayer as pH responders greatly contributed to the destabilization of the vesicle membrane in low pH, followed by the rapid release of the payloads. LMDHV showed 6-fold reversal efficiency in DOX resistant breast cancer owing to the efficient tumor targeting delivery and rapid burst release of drug intracellularly. Compared to tumor inhibition ratio of treated groups by free DOX (32.4 ± 7.4%), our designed kinetically favorable drug release system exhibited significantly (P < 0.01) enhanced tumor inhibition ratio up to 83.9 ± 12.5%, which is attributed to the remarkably increased drug concentration in cells. The spatio-temporal favorable release of drugs resulted in synergistic inhibition of tumor growth in xenografts. We envision that this new type of liposomal cocktail might be potentially utilized to circumvent drug resistance in the future.

Synthesis of an acid-cleavable and fluorescent amphiphilic block copolymer as a combined delivery vector of DNA and doxorubicin

An acid-cleavable and fluorescent block copolymer with good biocompatibility has been prepared and applied as a co-delivery carrier of DNA and doxorubicin.

Self-assembling doxorubicin-prodrug nanoparticles as siRNA drug delivery system for cancer treatment: in vitro and in vivo

The DOX-prodrug NPs can complex siRNA in pH 3 citrate buffer and have slight negative charges on the surface of NPs in pH 7.4 PBS.

Materials innovation for co-delivery of diverse therapeutic cargos

Co-delivery is a rapidly growing sector of drug delivery that aspires to enhance therapeutic efficacy through controlled delivery of diverse therapeutic cargoes with synergistic activities. It requires the design of carriers capable of simultaneously transporting to and releasing multiple therapeutics at a disease site. Co-delivery has arisen from the emerging trend of combination therapy, where treatment with two or more therapeutics at the same time can succeed where single therapeutics fail. However, conventional combination therapy offers little control over achieving an optimized therapeutic ratio at the target site. Co-delivery via inclusion of multiple therapeutic cargos within the same carrier addresses this issue by not only ensuring delivery of both therapeutics to the same cell, but also offering a platform for control of the delivery process, from loading to release. Co-delivery systems have been formulated using a number of carriers previously developed for single-therapeutic delivery. Liposomes, polymeric micelles, PLGA nanoparticles, and dendrimers have all been adapted for co-delivery. Much of the effort focuses on dealing with drugs having dissimilar properties, increasing loading efficiencies, and controlling loading and release ratios. In this review, we highlight the innovations in carrier designs and formulations to deliver combination cargoes of drug/drug, drug/siRNA, and drug/pDNA toward disease therapy. With rapid advances in mechanistic understanding of interrelating molecular pathways and development of molecular medicine, the future of co-delivery will become increasingly promising and prominent.

Layer-by-layer nanoparticles for systemic codelivery of an anticancer drug and siRNA for potential triple-negative breast cancer treatment

A single nanoparticle platform has been developed through the modular and controlled layer-by-layer process to codeliver siRNA that knocks down a drug-resistance pathway in tumor cells and a chemotherapy drug to challenge a highly aggressive form of triple-negative breast cancer. Layer-by-layer films were formed on nanoparticles by alternately depositing siRNA and poly-l-arginine; a single bilayer on the nanoparticle surface could effectively load up to 3500 siRNA molecules, and the resulting LbL nanoparticles exhibit an extended serum half-life of 28 h. In animal models, one dose via intravenous administration significantly reduced the target gene expression in the tumors by almost 80%. By generating the siRNA-loaded film atop a doxorubicin-loaded liposome, we identified an effective combination therapy with siRNA targeting multidrug resistance protein 1, which significantly enhanced doxorubicin efficacy by 4 fold in vitro and led to up to an 8-fold decrease in tumor volume compared to the control treatments with no observed toxicity. The results indicate that the use of layer-by-layer films to modify a simple liposomal doxorubicin delivery construct with a synergistic siRNA can lead to significant tumor reduction in the cancers that are otherwise nonresponsive to treatment with Doxil or other common chemotherapy drugs. This approach provides a potential strategy to treat aggressive and resistant cancers, and a modular platform for a broad range of controlled multidrug therapies customizable to the cancer type in a singular nanoparticle delivery system.

Supramolecular self-assembly forming a multifunctional synergistic system for targeted co-delivery of gene and drug

For developing a multifunctional bioreducible targeted and synergistic co-delivery system for anticancer drug paclitaxel (PTX) and p53 gene for potential cancer therapy, supramolecular self-assembled inclusion complex was prepared from PTX and star-shaped cationic polymer containing γ-cyclodextrin (γ-CD) and multiple oligoethylenimine (OEI) arms with folic acid (FA) conjugated via a disulfide linker. The inclusion complex, termed as γ-CD-OEI-SS-FA/PTX, was formed between PTX and the hydrophobic cavity of γ-CD core of the star polymer. The γ-CD-OEI-SS-FA/PTX complex further formed polyplexes with pDNA to give positively charged nanoparticles, becoming multifunctional supramolecular self-assembled co-delivery system for PTX and pDNA targeting to cancer cells that overexpress folate receptors (FRs). The results showed that the FA-targeted function induced higher gene transfection efficiency in the FR-positive KB cells. The redox-sensitive disulfide linker in the self-assembly system led to the detachment of the FA groups from the carrier after the FR-mediated endocytosis, which resulted in the release of the bound FRs followed by the recycling of the FRs from the cytosol onto the cell membrane surface, facilitating continuous FR-mediated endocytosis to achieve enhanced gene transfection. In addition, the complexed PTX was co-delivered to the cells with pDNA, which further enhanced the gene transfection even at low N/P ratios in the FR-positive KB cells. Further, the efficient delivery of wild-type p53 gene resulted in large cell population at sub G1 and G2/M phases, inducing significant cell apoptosis. Therefore, the multifunctional γ-CD-OEI-SS-FA/PTX self-assembly system with the synergistic effects of redox-sensitive FA-targeted and PTX-enhanced p53 gene delivery may be promising for cancer therapeutic application.

Nanopreparations to overcome multidrug resistance in cancer

Multidrug resistance is the most widely exploited phenomenon by which cancer eludes chemotherapy. Broad variety of factors, ranging from the cellular ones, such as over-expression of efflux transporters, defective apoptotic machineries, and altered molecular targets, to the physiological factors such as higher interstitial fluid pressure, low extracellular pH, and formation of irregular tumor vasculature are responsible for multidrug resistance. A combination of various undesirable factors associated with biological surroundings together with poor solubility and instability of many potential therapeutic small & large molecules within the biological systems and systemic toxicity of chemotherapeutic agents has necessitated the need for nano-preparations to optimize drug delivery. The physiology of solid tumors presents numerous challenges for successful therapy. However, it also offers unique opportunities for the use of nanotechnology. Nanoparticles, up to 400 nm in size, have shown great promise for carrying, protecting and delivering potential therapeutic molecules with diverse physiological properties. In this review, various factors responsible for the MDR and the use of nanotechnology to overcome the MDR, the use of spheroid culture as well as the current technique of producing microtumor tissues in vitro are discussed in detail.

Enhancing tumor cell response to chemotherapy through nanoparticle-mediated codelivery of siRNA and cisplatin prodrug

Cisplatin and other DNA-damaging chemotherapeutics are widely used to treat a broad spectrum of malignancies. However, their application is limited by both intrinsic and acquired chemoresistance. Most mutations that result from DNA damage are the consequence of error-prone translesion DNA synthesis, which could be responsible for the acquired resistance against DNA-damaging agents. Recent studies have shown that the suppression of crucial gene products (e.g., REV1, REV3L) involved in the error-prone translesion DNA synthesis pathway can sensitize intrinsically resistant tumors to chemotherapy and reduce the frequency of acquired drug resistance of relapsed tumors. In this context, combining conventional DNA-damaging chemotherapy with siRNA-based therapeutics represents a promising strategy for treating patients with malignancies. To this end, we developed a versatile nanoparticle (NP) platform to deliver a cisplatin prodrug and REV1/REV3L-specific siRNAs simultaneously to the same tumor cells. NPs are formulated through self-assembly of a biodegradable poly(lactide-coglycolide)-b-poly(ethylene glycol) diblock copolymer and a self-synthesized cationic lipid. We demonstrated the potency of the siRNA-containing NPs to knock down target genes efficiently both in vitro and in vivo. The therapeutic efficacy of NPs containing both cisplatin prodrug and REV1/REV3L-specific siRNAs was further investigated in vitro and in vivo. Quantitative real-time PCR results showed that the NPs exhibited a significant and sustained suppression of both genes in tumors for up to 3 d after a single dose. Administering these NPs revealed a synergistic effect on tumor inhibition in a human Lymph Node Carcinoma of the Prostate xenograft mouse model that was strikingly more effective than platinum monotherapy.

Determination of key structure-activity relationships in siRNA delivery with a mixed micelle system

Short interfering ribonucleic acids (siRNAs) offer a highly specific and selective form of therapy for diseases with a genetic component; however the poor pharmacokinetic properties of the molecule have impeded its development into a therapeutic for use in vivo. Several different approaches have been taken to develop a successful siRNA delivery system but these systems lack the flexibility for easy optimisation. Here, we propose a polymeric nanoparticle (PNP) system consisting of two amphiphilic diblock copolymers which allow for the rapid determination of structure-activity relationships involving gene knockdown and toxicity. The diblock copolymers self-assemble into monodisperse micelles of defined hydrodynamic diameters ranging from 30 to 100 nm dependent on the copolymer ratio. A luciferase-based high throughput assay varying PNP composition, concentration and siRNA concentration allowed the rapid identification of efficient PNP formulations for adherent and suspension cell lines. Optimised PNPs efficiently knocked down a fusion oncogene in hard to transfect human leukaemic cells raising the possibility of targeting malignant cells in a cancer-specific fashion. This approach allows the optimum PNP formulation to be identified for different cell types and conditions.

Multifunctional nanoparticles for targeted delivery of immune activating and cancer therapeutic agents

Nanoparticles (NPs) have been extensively investigated for applications in both experimental and clinical settings to improve delivery efficiency of therapeutic and diagnostic agents. Most recently, novel multifunctional nanoparticles have attracted much attention because of their ability to carry diverse functionalities to achieve effective synergistic therapeutic treatments. Multifunctional NPs have been designed to co-deliver multiple components, target the delivery of drugs by surface functionalization, and realize therapy and diagnosis simultaneously. In this review, various materials of diverse chemistries for fabricating multifunctional NPs with distinctive architectures are discussed and compared. Recent progress involving multifunctional NPs for immune activation, anticancer drug delivery, and synergistic theranostics is the focus of this review. Overall, this comprehensive review demonstrates that multifunctional NPs have distinctive properties that make them highly suitable for targeted therapeutic delivery in these areas.

Single vehicular delivery of siRNA and small molecules to control stem cell differentiation

Achieving a controlled and reproducible means to direct stem cell differentiation is the single most critical concern scientists have been trying to address since the discovery of stem cells. In this regard, the use of small molecules and RNA interference offers unique advantages by targeting different cellular mechanisms. Our cyclodextrin-modified dendritic polyamine construct (termed DexAM) combines the unique properties of two distinct chemical moieties in a single delivery vehicle. DexAM is a single vehicle that not only solubilizes hydrophobic small molecules in physiological solutions but also forms complexes with siRNA molecules, making it an attractive delivery system for controlling stem cell differentiation. Herein, we report the synthesis and application of DexAM to simultaneously deliver hydrophobic small molecules and siRNA into neural stem cells to significantly enhance their neuronal differentiation.

Reversal of lung cancer multidrug resistance by pH-responsive micelleplexes mediating co-delivery of siRNA and paclitaxel

The recent advances in RNA interference (RNAi) technology provided novel and promising solutions for human cancer treatment. In this study, the application of dual pH-responsive cationic micellar nanoparticles for small interfering RNA (siRNA) and paclitaxel (PTX) co-delivery to overcome cancer multidrug resistance (MDR) is reported. The in vitro siRNA transfection shows that siRNA-luciferase (Luc) loaded micelleplexes efficiently silences Luc expression in various carcinoma cell lines. The Luc knockdown ability of the micelleplexes can be enhanced by choloquine (CQ) co-incubation. However, is abolished by bafilomycin-A1 (Baf-A1) treatment. The micelleplexes are further exploited for co-delivery of siRNA-Bcl-2 and PTX to Bcl-2 overexpressing A549 lung cancer cells (A549-Bcl-2). The experimental results show that the micelleplexes could sensitize A549-Bcl-2 cells to PTX via down-regulation of anti-apoptosis gene of Bcl-2, suggesting that PDMA-b-PDPA micelleplexes are promising nanovectors for siRNA and anti-cancer drug co-delivery to overcome cancer MDR.

Polymeric micelles for multidrug delivery and combination therapy

The use of conventional therapy based on a single therapeutic agent is not optimal to treat human diseases. The concept called "combination therapy", based on simultaneous administration of multiple therapeutics is recognized as a more efficient solution. Interestingly, this concept has been in use since ancient times in traditional herbal remedies with drug combinations, despite mechanisms of these therapeutics not fully comprehended by scientists. This idea has been recently re-enacted in modern scenarios with the introduction of polymeric micelles loaded with several drugs as multidrug nanocarriers. This Concept article presents current research and developments on the application of polymeric micelles for multidrug delivery and combination therapy. The principles of micelle formation, their structure, and the developments and concept of multidrug delivery are introduced, followed by discussion on recent advances of multidrug delivery concepts directed towards targeted drug delivery and cancer, gene, and RNA therapies. The advantages of various polymeric micelles designed for different applications, and new developments combined with diagnostics and imaging are elucidated. A compilation work from our group based on multidrug-loaded micelles as carriers in drug-releasing implants for local delivery systems based on titania nanotubes is summarized. Finally, an overview of recent developments and prospective outlook for future trends in this field is given.

Development and in vivo quantitative magnetic resonance imaging of polymer micelles targeted to the melanocortin 1 receptor

Recent emphasis has focused on the development of rationally designed polymer-based micelle carriers for drug delivery. The current work tests the hypothesis that target specificity can be enhanced by micelles with cancer-specific ligands. In particular, we describe the synthesis and characterization of a new gadolinium texaphyrin (Gd-Tx) complex encapsulated in an IVECT micellar system, stabilized through Fe(III) cross-linking and targeted with multiple copies of a specific ligand for the melanocortin 1 receptor (MC1R), which has been evaluated as a cell-surface marker for melanoma. On the basis of comparative MRI experiments, we have been able to demonstrate that these Gd-Tx micelles are able to target MC1R-expressing xenograft tumors in vitro and in vivo more effectively than various control systems, including untargeted or un-cross-linked Gd-Tx micelles. Taken in concert, the findings reported herein support the conclusion that appropriately designed micelles are able to deliver contrast agent payloads to tumors expressing the MC1R.

Tumor extracellular acidity-activated nanoparticles as drug delivery systems for enhanced cancer therapy

pH-responsive nanoparticles (NPs) are currently under intense development as drug delivery systems for cancer therapy. Among various pH-responsiveness, NPs that are designed to target slightly acidic extracellular pH environment (pHe) of solid tumors provide a new paradigm of tumor targeted drug delivery. Compared to conventional specific surface targeting approaches, the pHe-targeting strategy is considered to be more general due to the common occurrence of acidic microenvironment in solid tumors. This review mainly focuses on the design and applications of pHe-activated NPs, with special emphasis on pHe-activated surface charge reversal NPs, for drug and siRNA delivery to tumors. The novel development of NPs described here offers great potential for achieving better therapeutic effects in cancer treatment.

Nanoparticles for gene delivery

Nanocarriers are a new type of nonviral gene carriers, many of which have demonstrated a broad range of pharmacological and biological properties, such as being biodegradable in the body, stimulus-responsive towards the surrounding environment, and an ability to specifically targeting certain disease sites. By summarizing some main types of nanocarriers, this Concept considers the current status and possible future directions of the potential clinical applications of multifunctional nanocarriers, with primary attention on the combination of such properties as biodegradability, targetability, transfection ability, and stimuli sensitivity.

A review of the current status of siRNA nanomedicines in the treatment of cancer

RNA interference currently offers new opportunities for gene therapy by the specific extinction of targeted gene(s) in cancer diseases. However, the main challenge for nucleic acid delivery still remains its efficacy through intravenous administration. Over the last decade, many delivery systems have been developed and optimized to encapsulate siRNA and to specifically promote their delivery into tumor cells and improve their pharmacokinetics for anti-cancer purposes. This review aims to sum up the potential targets in numerous pathways and the properties of recently optimized siRNA synthetic nanomedicines with their preclinical applications and efficacy. Future perspectives in cancer treatment are discussed including promising concomitant treatment with chemotherapies or other siRNA. The outcomes in human clinical trials are also presented.

Systemic delivery of sticky siRNAs targeting the cell cycle for lung tumor metastasis inhibition

RNA interference allows the design of new inhibitors that target deregulated pathways in cancer. However systemic delivery of siRNA for the treatment of solid tumors still remains an issue. In our study, in order to suppress the progression of lung cancer metastasis in mice, we developed sticky siRNA (ssiRNA) to inhibit survivin and cyclin B1, two candidates involved in cell survival and proliferation. We exploited the linear polyethylenimine (PEI) as potent non-viral carrier to efficiently deliver our inhibitors. As a proof of concept, we have chosen a very aggressive mammary adenocarcinoma model (TSA-Luc cells), which forms lung metastases upon systemic cell injection. We confirmed in vitro, that the ssiRNAs delivered with PEI are not only able to inhibit our target genes at the mRNA and protein levels, but are also able to block the cell cycle and cell proliferation through a mechanism of RNA interference. More importantly, we showed in vivo by luciferase dosage, bioimaging and tissue section, an inhibition of lung tumor metastases after systemic delivery of cyclin B1 and survivin ssiRNA complexed with PEI. Alternating treatment with cisplatin and ssiRNA/PEI showed an additive effect between the two anticancer drugs on lung tumor inhibition leading to a significant increase in animal survival. Moreover a promising window between activity (IC₅₀) and toxicity (LD₅₀), essential for therapeutic application, was observed. Our data show that systemic delivery of ssiRNA/PEI complexes targeting the cell cycle is a valuable strategy for the treatment of lung tumor metastasis and that it can be combined with chemotherapy.

Multifunctional hierarchically assembled nanostructures as complex stage-wise dual-delivery systems for coincidental yet differential trafficking of siRNA and paclitaxel

Development of multifunctional nanostructures that can be tuned to codeliver multiple drugs and diagnostic agents to diseased tissues is of great importance. Hierarchically assembled theranostic (HAT) nanostructures based on anionic cylindrical shell cross-linked nanoparticles and cationic shell cross-linked knedel-like nanoparticles (cSCKs) have recently been developed by our group to deliver siRNA intracellularly and to undergo radiolabeling. In the current study, paclitaxel, a hydrophobic anticancer drug, and siRNA have been successfully loaded into the cylindrical and spherical components of the hierarchical assemblies, respectively. Cytotoxicity, immunotoxicity, and intracellular delivery mechanism of the HAT nanostructures and their individual components have been investigated. Decoration of nanoparticles with F3-tumor homing peptide was shown to enhance the selective cellular uptake of the spherical particles, whereas the HAT nanoassemblies underwent an interesting disassembly process in contact with either OVCAR-3 or RAW 264.7 cell lines. The HAT nanostructures were found to "stick" to the cell membrane and "trigger" the release of spherical cSCKs templated onto their surfaces intracellularly, while retaining the cylindrical part on the cell surface. Combination of paclitaxel and cell-death siRNA (siRNA that induces cell death) into the HAT nanostructures resulted in greater reduction in cell viability than siRNA complexed with Lipofectamine and the assemblies loaded with the individual drugs. In addition, a shape-dependent immunotoxicity was observed for both spherical and cylindrical nanoparticles with the latter being highly immunotoxic. Supramolecular assembly of the two nanoparticles into the HAT nanostructures significantly reduced the immunotoxicity of both cSCKs and cylinders. HAT nanostructures decorated with targeting moieties, loaded with nucleic acids, hydrophobic drugs, radiolabels, and fluorophores, with control over their toxicity, immunotoxicity, and intracellular delivery might have great potential for biomedical delivery applications.

Recent advances in delivery of drug-nucleic acid combinations for cancer treatment

Cancer treatment that uses a combination of approaches with the ability to affect multiple disease pathways has been proven highly effective in the treatment of many cancers. Combination therapy can include multiple chemotherapeutics or combinations of chemotherapeutics with other treatment modalities like surgery or radiation. However, despite the widespread clinical use of combination therapies, relatively little attention has been given to the potential of modern nanocarrier delivery methods, like liposomes, micelles, and nanoparticles, to enhance the efficacy of combination treatments. This lack of knowledge is particularly notable in the limited success of vectors for the delivery of combinations of nucleic acids with traditional small molecule drugs. The delivery of drug-nucleic acid combinations is particularly challenging due to differences in the physicochemical properties of the two types of agents. This review discusses recent advances in the development of delivery methods using combinations of small molecule drugs and nucleic acid therapeutics to treat cancer. This review primarily focuses on the rationale used for selecting appropriate drug-nucleic acid combinations as well as progress in the development of nanocarriers suitable for simultaneous delivery of drug-nucleic acid combinations.

Targeted co-delivery of docetaxel and siPlk1 by herceptin-conjugated vitamin E TPGS based immunomicelles

We developed a drug delivery system of herceptin-conjugated micelles, which consist of vitamin E TPGS and TPGS-siRNA conjugates, for targeted co-delivery of docetaxel and polo-like kinase 1 siRNA to achieve synergistic effects between the anticancer drug and the small interfering RNA responsible for multidrug resistance. The TPGS-siRNA conjugate is made through disulfide bond that could enable a pH-sensitive intracellular release. The load ratio between siPlk1 and docetaxel could be controlled by adjusting the siPlk1-TPGS to TPGS ratio as well as the drug to polymer ratio. NIH3T3, MCF7, and SK-BR-3 cell lines, which are of low, moderate and high HER2 overexpression, were employed to obtain proof-of-concept experimental results for the advantages of such a design. It has been shown that the IC(50), which is the drug concentration needed to kill 50% of the cancer cells in a designated time period, was 1.72, 0.042, 0.0032 and 0.000671 μg/mL for SK-BR-3 cells after 24 h treatment by Taxotere(®), and docetaxel formulated in the TPGS micelles, the TPGS-siPlk1/TPGS micelles and the herceptin-conjugated TPGS-siPlk1/TPGS micelles, respectively.

Optically traceable solid lipid nanoparticles loaded with siRNA and paclitaxel for synergistic chemotherapy with in situ imaging

Here, we report quantum dot-incorporating solid lipid nanoparticles (SLNs) for anticancer theranostics with synergistic therapeutic effects of paclitaxel-siRNA combination. The natural components of a low-density lipoprotein (LDL) are reconstituted to produce LDL-mimetic SLNs having a stable core/shell nanostructure incorporating quantum dots and paclitaxel within the lipid shell while anionic siRNA molecules are electrostatically complexed with the outer surface of SLNs. The produced SLN/siRNA complexes efficiently deliver both of paclitaxel and Bcl-2 targeted siRNA into human lung carcinoma cells and exhibit synergistic anticancer activities by triggering caspase-mediated apoptosis as determined by median effect plot analysis. Moreover, the strong fluorescence from quantum dots within SLNs enables in situ visualization of intracellular translocation of SLNs into cancer cells. Our study suggests that LDL-mimetic SLNs can be utilized as a multifunctional and optically traceable nanocarrier for efficient anticancer theranostics.

Synergistic gene and drug tumor therapy using a chimeric peptide

Co-delivery of gene and drug for synergistic therapy has provided a promising strategy to cure devastating diseases. Here, an amphiphilic chimeric peptide (Fmoc)2KH7-TAT with pH-responsibility for gene and drug delivery was designed and fabricated. As a drug carrier, the micelles self-assembled from the peptide exhibited a much faster doxorubicin (DOX) release rate at pH 5.0 than that at pH 7.4. As a non-viral gene vector, (Fmoc)(2)KH(7)-TAT peptide could satisfactorily mediate transfection of pGL-3 reporter plasmid with or without the existence of serum in both 293T and HeLa cell-lines. Besides, the endosome escape capability of peptide/DNA complexes was investigated by confocal laser scanning microscopy (CLSM). To evaluate the co-delivery efficiency and the synergistic anti-tumor effect of gene and drug, p53 plasmid and DOX were simultaneously loaded in the peptide micelles to form micelleplexes during the self-assembly of the peptide. Cellular uptake and intracellular delivery of gene and drug were studied by CLSM and flow cytometry respectively. And p53 protein expression was determined via Western blot analysis. The in vitro cytotoxicity and in vivo tumor inhibition effect were also studied. Results suggest that the co-delivery of gene and drug from peptide micelles resulted in effective cell growth inhibition in vitro and significant tumor growth restraining in vivo. The chimeric peptide-based gene and drug co-delivery system will find great potential for tumor therapy.

Single-step assembly of DOX/ICG loaded lipid--polymer nanoparticles for highly effective chemo-photothermal combination therapy

A combination of chemotherapy and photothermal therapy has emerged as a promising strategy for cancer therapy. To ensure the chemotherapeutic drug and photothermal agent could be simultaneously delivered to a tumor region to exert their synergistic effect, a safe and efficient delivery system is highly desirable. Herein, we fabricated doxorubicin (DOX) and indocyanine green (ICG) loaded poly(lactic-co-glycolic acid) (PLGA)-lecithin-polyethylene glycol (PEG) nanoparticles (DINPs) using a single-step sonication method. The DINPs exhibited good monodispersity, excellent fluorescence/size stability, and consistent spectra characteristics compared with free ICG or DOX. Moreover, the DINPs showed higher temperature response, faster DOX release under laser irradiation, and longer retention time in tumor. In the meantime, the fluorescence of DOX and ICG in DINPs was also visualized for the process of subcellular location in vitro and metabolic distribution in vivo. In comparison with chemo or photothermal treatment alone, the combined treatment of DINPs with laser irradiation synergistically induced the apoptosis and death of DOX-sensitive MCF-7 and DOX-resistant MCF-7/ADR cells, and suppressed MCF-7 and MCF-7/ADR tumor growth in vivo. Notably, no tumor recurrence was observed after only a single dose of DINPs with laser irradiation. Hence, the well-defined DINPs exhibited great potential in targeting cancer imaging and chemo-photothermal therapy.

Exploring polymeric micelles for improved delivery of anticancer agents: recent developments in preclinical studies

As versatile drug delivery systems, polymeric micelles have demonstrated particular strength in solubilizing hydrophobic anticancer drugs while eliminating the use of toxic organic solvents and surfactants. However, the true promise of polymeric micelles as drug carriers for cancer therapy resides in their potential ability to preferentially elevate drug exposure in the tumor and achieve enhanced anticancer efficacy, which still remains to be fully exploited. Here, we review various micellar constructs that exhibit the enhanced permeation and retention effect in the tumor, the targeting ligands that potentiate the anticancer efficacy of micellar drugs, and the polyplex micelle systems suitable for the delivery of plasmid DNA and small interference RNA. Together, these preclinical studies in animal models help us further explore polymeric micelles as emerging drug carriers for targeted cancer therapy.

Functionalized graphene oxide mediated adriamycin delivery and miR-21 gene silencing to overcome tumor multidrug resistance in vitro

Multidrug resistance (MDR) is a major impediment to successful cancer chemotherapy. Co-delivery of novel MDR-reversing agents and anticancer drugs to cancer cells holds great promise for cancer treatment. MicroRNA-21 (miR-21) overexpression is associated with the development and progression of MDR in breast cancer, and it is emerging as a novel and promising MDR-reversing target. In this study, a multifunctional nanocomplex, composed of polyethylenimine (PEI)/poly(sodium 4-styrenesulfonates) (PSS)/graphene oxide (GO) and termed PPG, was prepared using the layer-by-layer assembly method to evaluate the reversal effects of PPG as a carrier for adriamycin (ADR) along with miR-21 targeted siRNA (anti-miR-21) in cancer drug resistance. ADR was firstly loaded onto the PPG surface (PPG_ADR) by physical mixing and anti-miR-21 was sequentially loaded onto PPG_ADR through electric absorption to form ^anti-miR-21PPG_ADR. Cell experiments showed that PPG significantly enhanced the accumulation of ADR in MCF-7/ADR cells (an ADR resistant breast cancer cell line) and exhibited much higher cytotoxicity than free ADR, suggesting that PPG could effectively reverse ADR resistance of MCF-7/ADR. Furthermore, the enhanced therapeutic efficacy of PPG could be correlated with effective silencing of miR-21 and with increased accumulation of ADR in drug-resistant tumor cells. The endocytosis study confirmed that PPG could effectively carry drug molecules into cells via the caveolae and clathrin-mediated endocytosis pathways. These results suggest that this PPG could be a potential and efficient non-viral vector for reversing MDR, and the strategy of combining anticancer drugs with miRNA therapy to overcome MDR could be an attractive approach in cancer treatment.

Codelivery of an optimal drug/siRNA combination using mesoporous silica nanoparticles to overcome drug resistance in breast cancer in vitro and in vivo

We used a multifunctional mesoporous silica nanoparticle (MSNP) carrier to overcome doxorubicin (Dox) resistance in a multidrug resistant (MDR) human breast cancer xenograft by codelivering Dox and siRNA that targets the P-glycoprotein (Pgp) drug exporter. The Pgp siRNA selection from among a series of drug resistance targets was achieved by performing high throughput screening in a MDR breast cancer cell line, MCF-7/MDR. Following the establishment of a MCF-7/MDR xenograft model in nude mice, we demonstrated that a 50 nm MSNP, functionalized by a polyethyleneimine-polyethylene glycol (PEI-PEG) copolymer, provides protected delivery of stably bound Dox and Pgp siRNA to the tumor site. The effective biodistribution and reduced reticuloendothelial uptake, as a result of our nanocarrier design, allowed us to achieve an 8% enhanced permeability and retention effect at the tumor site. Compared to free Dox or the carrier loaded with either drug or siRNA alone, the dual delivery system resulted in synergistic inhibition of tumor growth in vivo. Analysis of multiple xenograft biopsies demonstrated significant Pgp knockdown at heterogeneous tumor sites that correspond to the regions where Dox was released intracellularly and induced apoptosis. We emphasize that the heterogeneity originates in the tumor microenvironment, which influences the vascular access, rather than heterogeneous Pgp expression in the MDR cells. Taken together, these data provide proof-of-principle testing of the use of a dual drug/siRNA nanocarrier to overcome Dox resistance in a xenograft. The study also provides the first detailed analysis of the impact of heterogeneity in the tumor microenvironment on the efficacy of siRNA delivery in vivo.

Surface-modified HK:siRNA nanoplexes with enhanced pharmacokinetics and tumor growth inhibition

We characterized in this study the pharmacokinetics and antitumor efficacy of histidine-lysine (HK):siRNA nanoplexes modified with PEG and a cyclic RGD (cRGD) ligand targeting αvβ3 and αvβ5 integrins. With noninvasive imaging, systemically administered surface-modified HK:siRNA nanoplexes showed nearly 4-fold greater blood levels, 40% higher accumulation in tumor tissue, and 60% lower luciferase activity than unmodified HK:siRNA nanoplexes. We then determined whether the surface-modified HK:siRNA nanoplex carrier was more effective in reducing MDA-MB-435 tumor growth with an siRNA targeting Raf-1. Repeated systemic administration of the selected surface modified HK:siRNA nanoplexes targeting Raf-1 showed 35% greater inhibition of tumor growth than unmodified HK:siRNA nanoplexes and 60% greater inhibition of tumor growth than untreated mice. The improved blood pharmacokinetic results and tumor localization observed with the integrin-targeting surface modification of HK:siRNA nanoplexes correlated with greater tumor growth inhibition. This investigation reveals that through control of targeting ligand surface display in association with a steric PEG layer, modified HK: siRNA nanoplexes show promise to advance RNAi therapeutics in oncology and potentially other critical diseases.

Dual delivery of chlorhexidine and platelet-derived growth factor-BB for enhanced wound healing and infection control

Wound treatment can require molecules that both enhance healing and control infection. As in many biomedical applications, the options for therapeutic molecules may include both hydrophilic and hydrophobic molecules. The goal of this study was to investigate a polymer system for drug delivery that simultaneously delivers platelet-derived growth factor (PDGF)-BB, a hydrophilic protein known to promote wound healing, and chlorhexidine (CHX), a hydrophobic antimicrobial agent for infection treatment. Poly(lactic-co-glycolic acid) (PLGA) microspheres were prepared using different polymer formulations in a double emulsion process. CHX encapsulation efficiency was 19.6±0.8% and 28.9±1.5% for PLGA 50:50 and 85:15, respectively. The presence of CHX significantly increased PDGF-BB encapsulation efficiency relative to PDGF-BB alone. Both molecules could be released for up to 50 days and exhibited bioactivity for greater than 3 (PLGA 85:15) or 8 (PLGA 50:50) weeks using in vitro bacteria and cellular assays. An infected wound model was used to evaluate the system in vivo. Wounds treated with the dual delivery system showed decreased levels of infection and increased healing. Vascular analysis of wound tissues also showed higher levels of mature vasculature with the delivery of PDGF-BB. In conclusion, we have evaluated a drug delivery system for simultaneous delivery of hydrophobic and hydrophilic molecules and have shown that this system can improve healing and reduce bacteria levels in an infected wound model. This system could be applied to other therapeutic applications where sustained delivery of hydrophobic and hydrophilic molecules is required.