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

Advanced materials and processing for drug delivery: the past and the future

Design and synthesis of efficient drug delivery systems are of vital importance for medicine and healthcare. Materials innovation and nanotechnology have synergistically fueled the advancement of drug delivery. Innovation in material chemistry allows the generation of biodegradable, biocompatible, environment-responsive, and targeted delivery systems. Nanotechnology enables control over size, shape and multi-functionality of particulate drug delivery systems. In this review, we focus on the materials innovation and processing of drug delivery systems and how these advances have shaped the past and may influence the future of drug delivery.

Paclitaxel Nano-Delivery Systems: A Comprehensive Review

Paclitaxel is one of the most effective chemotherapeutic drugs ever developed and is active against a broad range of cancers, such as lung, ovarian, and breast cancers. Due to its low water solubility, paclitaxel is formulated in a mixture of Cremophor EL and dehydrated ethanol (50:50, v/v) a combination known as Taxol. However, Taxol has some severe side effects related to Cremophor EL and ethanol. Therefore, there is an urgent need for the development of alternative Taxol formulations. The encapsulation of paclitaxel in biodegradable and non-toxic nano-delivery systems can protect the drug from degradation during circulation and in-turn protect the body from toxic side effects of the drug thereby lowering its toxicity, increasing its circulation half-life, exhibiting improved pharmacokinetic profiles, and demonstrating better patient compliance. Also, nanoparticle-based delivery systems can take advantage of the enhanced permeability and retention (EPR) effect for passive tumor targeting, therefore, they are promising carriers to improve the therapeutic index and decrease the side effects of paclitaxel. To date, paclitaxel albumin-bound nanoparticles (Abraxane®) have been approved by the FDA for the treatment of metastatic breast cancer and non-small cell lung cancer (NSCLC). In addition, there are a number of novel paclitaxel nanoparticle formulations in clinical trials. In this comprehensive review, several types of developed paclitaxel nano-delivery systems will be covered and discussed, such as polymeric nanoparticles, lipid-based formulations, polymer conjugates, inorganic nanoparticles, carbon nanotubes, nanocrystals, and cyclodextrin nanoparticles.

N-acetylgalactosamine functionalized mixed micellar nanoparticles for targeted delivery of siRNA to liver

Due to its efficient and specific gene silencing ability, RNA interference has shown great potential in the treatment of liver diseases. However, achieving in vivo delivery of siRNA to critical liver cells remains the biggest obstacle for this technique to be a real clinic therapeutic modality. Here, we describe a promising liver targeting siRNA delivery system based on N-acetylgalactosamine functionalized mixed micellar nanoparticles (Gal-MNP), which can efficiently deliver siRNA to hepatocytes and silence the target gene expression after systemic administration. The Gal-MNP were assembled in aqueous solution from mixed N-acetylgalactosamine functionalized poly(ethylene glycol)-b-poly(ε-caprolactone) and cationic poly(ε-caprolactone)-b-poly(2-aminoethyl ethylene phosphate) (PCL-b-PPEEA); the properties of nanoparticles, including particle size, zeta potential and the density of poly(ethylene glycol) could be easily regulated. The hepatocyte-targeting effect of Gal-MNP was demonstrated by significant enriching of fluorescent siRNA in primary hepatocytes in vitro and in vivo. Successful down-regulation of liver-specific apolipoprotein B (apoB) expression was achieved in mouse liver, at both the transcriptional and protein level, following intravenous injection of Gal-MNP/siapoB to BALB/c mice. Systemic delivery of Gal-MNP/siRNA did not induce the innate immune response or positive hepatotoxicity. The results of this study suggested therapeutic potential for the Gal-MNP/siRNA system in liver disease.

Rapid and versatile construction of diverse and functional nanostructures derived from a polyphosphoester-based biomimetic block copolymer system

A rapid and efficient approach for the preparation and modification of a versatile class of functional polymer nanoparticles has been developed, for which the entire engineering process from small molecules to polymers to nanoparticles bypasses typical slow and inefficient procedures and rather employs a series of steps that capture fully the "click" chemistry concepts that have greatly facilitated the preparation of complex polymer materials over the past decade. The construction of various nanoparticles with functional complexity from a versatile platform is a challenging aim to provide materials for fundamental studies and also optimization toward a diverse range of applications. In this paper, we demonstrate the rapid and facile preparation of a family of nanoparticles with different surface charges and functionalities based on a biodegradable polyphosphoester block copolymer system. From a retrosynthetic point of view, the nonionic, anionic, cationic, and zwitterionic micelles with hydrodynamic diameters between 13 and 21 nm and great size uniformity were quickly formed by suspending, independently, four amphiphilic diblock polyphosphoesters into water, which were functionalized from the same parental hydrophobic-functional AB diblock polyphosphoester by click-type thiol-yne reactions. The well-defined (PDI < 1.2) hydrophobic-functional AB diblock polyphosphoester was synthesized by an ultrafast (<5 min) organocatalyzed ring-opening polymerization in a two-step, one-pot manner with the quantitative conversions of two kinds of cyclic phospholane monomers. The whole programmable process starting from small molecules to nanoparticles could be completed within 6 h, as the most rapid approach for the anionic and nonionic nanoparticles, although the cationic and zwitterionic nanoparticles required ca. 2 days due to purification by dialysis. The micelles showed high biocompatibility, with even the cationic micelles exhibiting a 6-fold lower cytotoxicity toward RAW 264.7 mouse macrophage cells, as compared to the commercial transfection agent Lipofectamine.

Lipid modified triblock PAMAM-based nanocarriers for siRNA drug co-delivery

RNA interference by small interfering RNA (siRNA) holds promise to attenuate production of specific target proteins but is challenging in practice owing to the barriers for its efficient intracellular delivery. We have synthesized a triblock co-polymeric system, poly(amidoamine) dendrimer (generation 4)-poly(ethylene glycol)-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (G(4)-D-PEG-(2K)-DOPE). G(4)-PAMAM dendrimer was utilized as a cationic source for efficient siRNA condensation; DOPE provided optimum hydrophobicity and compatible cellular interaction for enhanced cell penetration; PEG rendered flexibility to the G(4)-D for easy accessibility of siRNA for condensation; PEG-DOPE system provided stable micellization in a mixed micellar system. G(4)-D-PEG-(2K)-DOPE was incorporated into the self-assembled PEG-(5K)-PE micelles at a 1:1 molar ratio. Our results demonstrate that the modified dendrimer, G(4)-D-PEG-(2K)-DOPE and the micellar nanocarrier form stable polyplexes with siRNA, shows excellent serum stability and a significantly higher cellular uptake of siRNA that results in target protein down-regulation when compared to the G(4)-PAMAM dendrimer. Moreover, the mixed micellar system showed efficient micellization and higher drug (doxorubicin) loading efficiency. The G(4)-D-PEG-(2K)-DOPE has the higher efficacy for siRNA delivery, whereas G(4)-D-PEG-(2K)-DOPE/PEG-(5K)-PE micelles appear to be a promising carrier for drug/siRNA co-delivery, especially useful for the treatment of multi-drug resistant cancers.

Polymer nanoparticulate drug delivery and combination cancer therapy

This review describes the scientific background, current achievement and future perspective of combination therapy using polymer nanoparticle drug carriers in cancer treatment. Nanotechnology-based drug delivery is expected to dramatically change combination cancer therapy by controlling accumulation and distribution patterns of multiple drugs selectively in disease sites. Rationally designed polymer materials can produce functional nanoparticulate drug carriers that can be used in various biomedical applications. In comparison with conventional drug combination approaches, using polymer nanoparticle drug carriers appears to suppress tumor growth more efficiently, potentially overcoming multidrug resistance in many cancers. It also provides versatile combination options for a variety of therapeutic agents, molecular targeting agents and nucleotide drugs.

Hypocrellin-loaded gold nanocages with high two-photon efficiency for photothermal/photodynamic cancer therapy in vitro

A new bioconjugate nanostructure was constructed by using photosensitizer-incorporated mixed lipid-coated gold nanocages for two-photon photothermal/photodynamic cancer therapy in vitro with high efficiency. Scanning electron microscopic and transmission electron microscopic images reveal that the precursors and bioconjugate nanostructure as-prepared are narrowly dispersed and possess uniform morphologies. The relevant energy dispersion X-ray analysis and UV-vis spectra indicate that the bioconjugate nanostructure above was assembled successfully and has a strong absorption in the near-infrared region. Fluorescence and electronic spin resonance results show that the gold nanocage in the bioconjugate nanostructure can dramatically quench the photosensitizer and inhibit the production of singlet oxygen, which is supposed to alleviate the photosensitizers' unwanted side effects originating from their nontargeted distribution. We have demonstrated that as the nanocomplex is internalized by cancer cells, under two-photon illumination, photodynamic anticancer treatment is dramatically enhanced by the photothermal effect.

Co-delivery of siRNA and therapeutic agents using nanocarriers to overcome cancer resistance

There are two main mechanisms by which cells become multidrug resistant (MDR): by increasing drug efflux pumps on the cell membrane and by increasing anti-apoptotic pathways. The use of nanotechnology to develop nanodelivery systems has allowed researchers to overcome limitations of antineoplastic drugs by increasing the solubility of the drug and decreasing the toxicity to healthy tissues. By encapsulating drugs into nanoparticles that bypass the efflux pumps, drug efflux is reduced, hence increasing the intracellular concentration of the drug. siRNA has the ability to disrupt cellular pathways by knocking down genes, opening the door to down regulating anti-apoptotic pathways. The use of nanocarriers to deliver siRNA, prevents both renal clearance and RNase degradation by protecting siRNA chains, increasing their half life in blood. It has been suggested that co-delivering drugs and siRNA together in the same delivery system would be more effective in overcoming resistance of cancer cells than co-treatment of cancer cells with delivery systems carrying either siRNA or drugs. In this study we discuss the progress of nanoscale co-delivery systems in overcoming multidrug cancer resistance.

Advanced materials for co-delivery of drugs and genes in cancer therapy

With cancer being the major cause of mortality worldwide, the continued development of safe and efficacious treatments is warranted. A better understanding of the molecular mechanism and genetic basis of tumor initiation and progression, coupled with advances in chemistry, molecular biology and engineering have led to discovery of a wide range of therapeutic agents for cancer therapy. However, multidrug-resistance, which is mainly caused by malfunction of genes, has become a major problem in chemotherapy. To overcome this problem, the simultaneous delivery of genes to cancer cells has been proposed to correct the malfunctioned genes to sensitize the cells to chemotherapeutics. This progress report summarizes key advances in drug and gene delivery with focus on the development of polymers, peptides, liposomes and inorganic materials as nanocarriers for co-delivery of small molecular drugs and macromolecular genes or proteins. In addition, challenges and future perspectives in the design of nanocarriers for the co-delivery of therapeutic drugs and genes are discussed.

Microfluidic synthesis of multifunctional Janus particles for biomedical applications

Multifunctional Janus particles have a variety of applications in a wide range of fields. However, to achieve many of these applications, high-throughput, low-cost techniques are needed to synthesize these particles with precise control of the various structural/physical/chemical properties. Microfluidics provides a unique platform to fabricate Janus particles using carefully controlled liquid flow in microfluidic channels to form Janus droplets and various types of solidification methods to solidify them into Janus particles. In this Focus article, we summarize the most recent representative works on Janus particle fabrication in microfluidics. The applications of Janus particles in biomedical areas are emphasized. We believe that microfluidics-enabled multifunctional Janus particles could resolve multiple prevalent issues in biomedicine (e.g., disease monitoring at an early stage, high-throughput bioassays, therapeutic delivery) if persistent effort and collaboration are devoted to this direction.

MiR-100 resensitizes docetaxel-resistant human lung adenocarcinoma cells (SPC-A1) to docetaxel by targeting Plk1

MicroRNAs (miRNAs) expression correlates with biological characteristics of both normal cells and cancer cells, but their roles in cancer chemoresistance remain unclear. By microarray analysis, miR-100 was found significantly down-regulated in docetaxel-resistant SPC-A1/DTX cells compared with parental SPC-A1 cells. Ectopic miR-100 expression resensitized SPC-A1/DTX cells to docetaxel by suppression of cell proliferation and induction of cell arrest in G(2)/M phase and apoptosis. Knock-down of Plk1, which was a direct target of miR-100, yielded similar effects as that of ectopic miR-100 expression. The inverse correlation between miR-100 and Plk1 expression was also detected in nude mice SPC-A1/DTX tumor xenografts and clinical lung adenocarcinoma tissues and was proved to be related with the in vivo response to docetaxel. Thus, our results suggested that down-regulation of miR-100 could lead to Plk1 over-expression and eventually to docetaxel chemoresistance of human lung adenocarcinoma.

Concurrent binding and delivery of proteins and lipophilic small molecules using polymeric nanogels

Supramolecular nanoassemblies, which are capable of binding and delivering either lipophilic small molecules or hydrophilic molecules, are of great interest. Concurrently binding and delivering this combination of molecules is cumbersome, because of the opposing supramolecular host requirements. We describe the development of a versatile nanoassembly system that is capable of binding and delivering both, a protein and a lipophilic small molecule, simultaneously inside the cells.

P-glycoprotein silencing with siRNA delivered by DOPE-modified PEI overcomes doxorubicin resistance in breast cancer cells

AIMS

Multidrug resistance (MDR) mediated by overexpression of drug efflux transporters such as P-glycoprotein (P-gp), is a major problem, limiting successful chemotherapy of breast cancer. The use of siRNA to inhibit P-gp expression in MDR tumors is an attractive strategy to improve the effectiveness of anticancer drugs.

METHOD

We have synthesized a novel conjugate between a phospholipid (dioleoylphosphatidylethanolamine) and polyethylenimine (PEI) for siRNA delivery, for the purpose of silencing P-gp to overcome doxorubicin resistance in MCF-7 human breast cancer cells.

RESULTS

The dioleoylphosphatidylethanolamine-PEI conjugate enhanced the transfection efficacy of low-molecular-weight PEI, which was otherwise totally ineffective. In addition, the polyethylene glycol/lipid coating of the new complexes gave rise to small micelle-like nanoparticles with improved biocompatibility properties. Both coated and noncoated formulations delivered P-gp-specific siRNA to MDR cells.

DISCUSSION

The combination of doxorubicin and P-gp silencing formulations led to a twofold increase of doxorubicin uptake and a significant improvement of the therapeutic effect of doxorubicin in resistant cells.

Binary and ternary complexes based on polycaprolactone-graft-poly (N, N-dimethylaminoethyl methacrylate) for targeted siRNA delivery

Small interfering RNA (siRNA) is a powerful gene silencing tool and has promising prospects in basic research and the development of therapeutic reagents. However, the lack of an effective and safe tool for siRNA delivery hampers its application. Here, we introduced binary and ternary complexes that effectively mediated siRNA-targeted gene silencing. Both complexes showed excellent siRNA loading even at the low N/P/C ratio of 3:1:0. FACS and confocal microscopy demonstrated that nearly all cells robustly internalized siRNAs into the cytoplasm, where RNA interference (RNAi) occurred. Luciferase assay and Western blot verified that silencing efficacy reached >80%, and introducing folate onto the ternary complexes further enhanced silencing efficacy by about 10% over those without folate at the same N/P/C ratio. In addition, the coating of PGA-g-mPEG decreased the zeta potential almost to electroneutrality, and the MTT assay showed decreased cytotoxicity. In vivo distribution measurement and histochemical analysis executed in C57BL/6 and Hela tumor-bearing BALB/c nude mice showed that complexes accumulated in the liver, lungs, pancreas and tumors and were released slowly for a long time after intravenous injection. Furthermore, ternary complexes showed higher siRNA fluorescence intensity than binary complexes at the same N/P ratio in tumor tissues, those with folate delivered more siRNAs to tumors than those without folate, and more folate induced more siRNA transport to tumors. In addition, in vivo functional study showed that both binary and ternary complexes mediated down-regulation of ApoB in liver efficiently and consequently blocked the secretion of fatty acids into the blood, resulted in lipid accumulation in liver, liver steatosis and hepatic dysfunction. In conclusion, these complexes provided a powerful means of administration for siRNA-mediated treatment of liver-related diseases and various cancers, especial for pancreatic and cervical cancer.

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.

Multifunctional nanocapsules for simultaneous encapsulation of hydrophilic and hydrophobic compounds and on-demand release

Cocktail therapy by delivering multiple drugs to diseased cells can elicit synergistic therapeutic effects and better modulate the complex cell-signaling network. Besides selection of drug combinations, a difficulty in delivery is how to encapsulate drugs with various solubility into a common vehicle, particularly when both hydrophobic and hydrophilic compounds are involved. Furthermore, it is highly desirable that the drug release profile can be controlled in an on-demand fashion for balanced therapeutic and side effects. On the basis of a simple and scalable double emulsion approach, we report a new class of nanocapsules that can solve these problems simultaneously. Further linking the nanocapsules with peptides targeting cell surface integrins leads to significantly enhanced cell uptake of the nanocapsules. Intracellular drug release triggered by external stimuli has also been achieved without affecting cell viability. Further development of this technology should open exciting opportunities in treating tough diseases such as cancer, cardiovascular diseases, neurological disorders, and infectious diseases.

Facile preparation of a cationic poly(amino acid) vesicle for potential drug and gene co-delivery

A novel pH-responsive poly(amino acid) grafted with oligocation was prepared through the combination of ring-opening polymerization (ROP) and subsequent atom transfer radical polymerization (ATRP). Firstly, poly(γ-2-chloroethyl-L-glutamate) (PCELG) with a pendent 2-chloroethyl group was synthesized through ROP of γ-2-chloroethyl-L-glutamate N-carboxyanhydride (CELG NCA) using n-hexylamine as the initiator. Then, PCELG was used to initiate the ARTP of 2-aminoethyl methacrylate hydrochloride (AMA), yielding poly(L-glutamate)-graft-oligo(2-aminoethyl methacrylate hydrochloride) (PLG-g-OAMA). The pK(a) of PLG-g-OAMA was 7.3 established by the acid-base titration method. The amphiphilic poly(amino acid) could directly self-assemble into a vesicle in PBS. The vesicle was characterized by TEM and DLS. Hydrophilic DOX·HCl was loaded into the hollow core of the vesicle. The in vitro release behavior of DOX·HCl from the vesicle in PBS could be adjusted by the solution pH. In vitro cell experiments revealed that the vesicle could reduce the toxicity of the DOX·HCl. In addition, the preliminary gel retardation assay displayed that PLG-g-OAMA could efficiently bind DNA at a PLG-g-OAMA/DNA weight ratio of 0.3 or above, indicating its potential use as a gene carrier. More in-depth studies of the PLG-g-OAMA vesicle for drug and gene co-delivery in vitro and in vivo are in progress.

Theranostic applications of nanomaterials in cancer: drug delivery, image-guided therapy, and multifunctional platforms

Successful cancer management depends on accurate diagnostics along with specific treatment protocols. Current diagnostic techniques need to be improved to provide earlier detection capabilities, and traditional chemotherapy approaches to cancer treatment are limited by lack of specificity and systemic toxicity. This review highlights advances in nanotechnology that have allowed the development of multifunctional platforms for cancer detection, therapy, and monitoring. Nanomaterials can be used as MRI, optical imaging, and photoacoustic imaging contrast agents. When used as drug carriers, nanoformulations can increase tumor exposure to therapeutic agents and result in improved treatment effects by prolonging circulation times, protecting entrapped drugs from degradation, and enhancing tumor uptake through the enhanced permeability and retention effect as well as receptor-mediated endocytosis. Multiple therapeutic agents such as chemotherapy, antiangiogenic, or gene therapy agents can be simultaneously delivered by nanocarriers to tumor sites to enhance the effectiveness of therapy. Additionally, imaging and therapy agents can be co-delivered to provide seamless integration of diagnostics, therapy, and follow-up, and different therapeutic modalities such as chemotherapy and hyperthermia can be co-administered to take advantage of synergistic effects. Liposomes, metallic nanoparticles, polymeric nanoparticles, dendrimers, carbon nanotubes, and quantum dots are examples of nanoformulations that can be used as multifunctional platforms for cancer theranostics. Nanomedicine approaches in cancer have great potential for clinically translatable advances that can positively impact the overall diagnostic and therapeutic process and result in enhanced quality of life for cancer patients. However, a concerted scientific effort is still necessary to fully explore long-term risks, effects, and precautions for safe human use.

Cationic liposomal co-delivery of small interfering RNA and a MEK inhibitor for enhanced anticancer efficacy

PURPOSE

To test whether co-delivery of anticancer small interfering RNA (siRNA) and a chemical MEK inhibitor using cationic liposomes enhances anticancer activity in vitro and in vivo.

METHOD

MEK inhibitor PD0325901 was encapsulated in lipid layers of N',N''-dioleylglutamide-based cationic liposomes (DGL). Mcl1-specific siRNA (siMcl1) was complexed to DGL or PD0325901-loaded liposomes (PDGL). Efficiency of cellular siRNA delivery was tested using fluorescent double-stranded RNA. Silencing of target proteins was evaluated using Western blotting and real-time quantitative polymerase chain reactions. In vivo anticancer activity was tested using xenografted mice.

RESULTS

Size and zeta potential of PDGL were similar to DGL. PDGL could deliver double-stranded RNA into cells with efficiencies comparable to DGL. Cellular co-delivery of siMcl1 and PD0325901 reduced expression of Mcl1 and pERK1/2 proteins and more effectively reduced tumor cell survival than other treatments. In mice, siMcl1 and PD0325901 co-delivered by PDGL inhibited growth of tumors 79%. Substantial apoptosis of tumor cells was observed following PDGL-mediated co-delivery of siMcl1, but not in other groups.

CONCLUSIONS

PDGL-mediated co-delivery of siMcl1 and MEK inhibitor, PD0325901, could serve as a potential strategy for combination chemogene anticancer therapy.

A double-modulation strategy in cancer treatment with a chemotherapeutic agent and siRNA

5-Fluorouracil (5-FU) is broadly considered the drug of choice for treating human colorectal cancer (CRC). However, 5-FU resistance, mainly caused by the overexpression of antiapoptotic proteins such as Bcl-2, often leads ultimately to treatment failure. We here investigated the effect of Bcl-2 gene silencing, using small interfering RNA (siRNA) (siBcl-2), on the efficacy of 5-FU in CRC. Transfection of siBcl-2 by a Lipofectamine2000/siRNA lipoplex effectively downregulated Bcl-2 expression in the DLD-1 cell line (a CRC), resulting in significant cell growth inhibition in vitro upon treatment with 5-FU. For in vivo treatments, S-1, an oral formulation of Tegafur (TF), a prodrug of 5-FU, was used to mimic 5-FU infusion. The combined treatment of polyethylene glycol (PEG)-coated siBcl-2-lipoplex and S-1 showed superior tumor growth suppression in a DLD-1 xenograft model, compared to each single treatment. Surprisingly, daily S-1 treatment enhanced the accumulation of PEG-coated siBcl-2-lipoplex in tumor tissue. We propose a novel double modulation strategy in cancer treatment, in which chemotherapy enhances intratumoral siRNA delivery and the delivered siRNA enhances the chemosensitivity of tumors. Combination of siRNA-containing nanocarriers with chemotherapy may compensate for the limited delivery of siRNA to tumor tissue. In addition, such modulation strategy may be considered a promising therapeutic approach to successfully managing 5-FU-resistant tumors.