Multi-layered nanoparticles for combination gene and drug delivery to tumors

Drug resistance and toxicity are major obstacles in cancer chemotherapy. Combination therapies can overcome resistance, and synergies can minimize dosing. Polymer nanocarriers are interesting vehicles for cancer therapeutics for their delivery and tumor targeting abilities. We synthesized a multi-layered polymer nanoparticle (MLNP), comprising of poly(lactic-co-glycolic acid) with surface polyethyleneimine and functional peptides, for targeted drug and gene delivery. We confirmed the particle's ability to inhibit tumor growth through synergistic action of the drug and gene product. MLNPs achieved transfection levels similar to lipofectamine, while maintaining minimal cytotoxicity. The particles delivered camptothecin (CPT), and plasmid encoding TNF related apoptosis inducing ligand (pTRAIL) (CT MLNPs), and synergistically inhibited growth of multiple cancer cells in vitro. The synergy of co-delivering CPT and pTRAIL via CT MLNPs was confirmed using the Chou-Talalay method: the combination index (CI) values at 50% inhibition ranged between 0.31 and 0.53 for all cell lines. Further, co-delivery with MLNPs resulted in a 3.1–15 fold reduction in CPT and 4.7–8.0 fold reduction in pTRAIL dosing. CT MLNPs obtained significant HCT116 growth inhibition in vivo compared to monotherapy. These results support our hypothesis that MLNPs can deliver both small molecules and genetic agents towards synergistically inhibiting tumor growth.     

Construction of a PLGA based,targeted siRNA delivery system for treatment of osteoporosis

Osteoporosis, a systemic skeletal disorder, occurs when bone turnover balance is disrupted. With the identification of the genes involved in the pathogenesis of the disease, studies on development of new treatments has intensified. Short interfering RNA (siRNA) is used to knockdown disease related gene expressions. Targeting siRNA in vivo is challenging. The maintenance of therapeutic plasma level is hampered by clearance of siRNA from the body. Targeted systems are useful in increasing the drug concentration at the target site and decreasing side effects. Aim of the present study was to develop an injectable siRNA delivery system to protect siRNA during systemic distribution and target the siRNA to bone tissue using a thermoresponsive, genetically engineered, elastin-like recombinamer (ELR), designed to interact with the mineral component of bone. The delivery system consisted of DNAoligo as a siRNA substitute complexed with the cationic polymer, polyethyleneimine (PEI), at N/P ratio of 20. The complex was encapsulated in poly(lactic acid-co-glycolic acid) (PLGA) nanocapsules. PLGA capsules were characterized by SEM, TEM and XPS. FTIR was used to show the preferential attachment of ELR to HAp. Encapsulation efficiency of the complex in PLGA nanocapsules was 48%. The release kinetics of the complex fits the Higuchi release kinetics.     

Multifunctional,self-assembling anionic peptide-lipid nanocomplexes for targeted siRNA delivery

Formulations of cationic liposomes and polymers readily self-assemble by electrostatic interactions with siRNA to form cationic nanoparticles which achieve efficient transfection and silencing in vitro. However, the utility of cationic formulations in vivo is limited due to rapid clearance from the circulation, due to their association with serum proteins, as well as systemic and cellular toxicity. These problems may be overcome with anionic formulations but they provide challenges of self-assembly and transfection efficiency. We have developed anionic, siRNA nanocomplexes utilizing anionic PEGylated liposomes and cationic targeting peptides that overcome these problems. Biophysical measurements indicated that at optimal ratios of components, anionic PEGylated nanocomplexes formed spherical particles and that, unlike cationic nanocomplexes, were resistant to aggregation in the presence of serum, and achieved significant gene silencing although their non-PEGylated anionic counterparts were less efficient. We have evaluated the utility of anionic nanoparticles for the treatment of neuronal diseases by administration to rat brains of siRNA to BACE1, a key enzyme involved in the formation of amyloid plaques. Silencing of BACE1 was achieved in vivo following a single injection of anionic nanoparticles by convection enhanced delivery and specificity of RNA interference verified by 5′ RACE-PCR and Western blot analysis of protein.     

Targetable micelleplex hydrogel for long-term,effective, and systemic siRNA delivery

We developed a targetable micelleplex hydrogel as a new efficient systemic siRNA delivery material that functions as a targetable gene carrier, and a hydrogel capable of controlled release to overcome drawbacks of multiple administrations of systemic siRNA carriers due to decreased fluctuation of them in the serum. The micelleplexes, complexes between polymeric micelles and siRNAs could turn into gel after subcutaneous injection and be slowly released from the gel. The released micelleplexes selectively accumulated in the tumor and showed anti-tumor effect due to gene silencing for an extended period of time with only one injection in anywhere in vivo model. Moreover, the duration of therapy can be controlled by adjusting the amount and properties of the hydrogel. Therefore, this micelleplex hydrogel is expected to be a new effective siRNA delivery material for systemic long-term gene silencing.     

Cisplatin crosslinked pH-sensitive nanoparticles for efficient delivery of doxorubicin

pH responsive cisplatin prodrug crosslinked polysaccharide-based nanoparticles were developed from succinic acid decorated dextran (Dex-SA) for active loading and triggered intracellular release of doxorubicin (DOX). Nanoparticles with uniform size were formed spontaneously in aqueous medium via electrostatic interaction between anionic Dex-SA and cationic DOX, and subsequently transformed into crosslinked nanoparticles (CL-Nanoparticles) in situ by readily crosslinking the micelles via chelate interactions between the ionic polymeric carrier and the platinum (II) antitumor drug. This strategy eliminated the need of organic solvents and sophisticated processes in the drug loading procedure. The in vitro release studies showed that DOX was released from the CL-Nanoparticles in a controlled and pH-dependent manner. Furthermore, the pharmacokinetics and biodistribution investigations indicated that, as compared to the non-crosslinked nanoparticles (NCL-Nanoparticles) and free DOX, the CL-Nanoparticles significantly prolonged the blood circulation time of drug, decreased accumulation in the normal tissues and enriched drug into the tumors. As a consequence, the DOX-loaded CL-Nanoparticles exhibited enhanced therapeutic efficacy in tumor-bearing mice compared with the NCL-Nanoparticles and free DOX, which were further confirmed by the histological and immunohistochemical analyses. These cisplatin prodrug crosslinked polysaccharide nanoparticles proved to be a promising nanomedicine drug delivery system for tumor-targeted delivery of DOX.     

Effects of hydrophobic core components in amphiphilic PDMAEMA nanoparticles on siRNA delivery

Due to their biodegradable character, polyesters such as polycaprolactone (PCL), poly(d,l-lactide) (PDLLA), and polylactic-co-glycolic acid (PLGA) were widely used as the hydrophobic cores of amphiphilic cationic nanoparticles (NPs) for siRNA delivery. However, fewer researches focused on facilitating siRNA delivery by adjusting the polyester composition of these nanoparticles. Herein, we investigated the contribution of polyester segments in siRNA delivery in vitro by introducing different ratio of DLLA moieties in PCL segments of mPEG-block-PCL-graft-poly(dimethylamino ethyl methacrylate)(PEG-b-PCL-g-PDMAEMA). It was noticed that compared with the other ratios of DLLA moieties, a certain molar ratio (about 70%) of the NPs, named mPEG₄₅-P(CL₂₁-co-DLLA₄₈)-g-(PDMAEMA₂₉)₂ (PECLD-70), showed the highest gene knockdown efficiency but poorest cellular uptake ability in vitro. Further research revealed that NPs with various compositions of the polyester cores showed different physicochemical properties including particle size, zeta potential and stiffness, leading to different endocytosis mechanisms thus influencing the cellular uptake efficiency. Subsequently, we observed that the cells treated by PECLD-70 NPs/Cy5 siRNA complexes exhibited more diffuse Cy5 signal distribution than other NPs by confocal laser scanning microscope, which suggested that siRNA delivered by PECLD-70 NPs/Cy5 siRNA complexes possessed of stronger capabilities in escaping from endosome/lysosome, entering the RNA-induced silencing complex (RISC) and cutting the target mRNA efficiently. The different siRNA release profile was dominated by the degradation rate of polyester segments. Therefore, it could be concluded that the adjustment of hydrophobic core of cationic nanoparticles could significantly affect their transfection behavior and appropriate polyester composition should be concerned in designing of analogous siRNA vectors.     

Sustained local delivery of siRNA from an injectable scaffold

Controlled gene silencing technologies have significant, unrealized potential for use in tissue regeneration applications. The design described herein provides a means to package and protect siRNA within pH-responsive, endosomolytic micellar nanoparticles (si-NPs) that can be incorporated into nontoxic, biodegradable, and injectable polyurethane (PUR) tissue scaffolds. The si-NPs were homogeneously incorporated throughout the porous PUR scaffolds, and they were shown to be released via a diffusion-based mechanism for over three weeks. The siRNA-loaded micelles were larger but retained nanoparticulate morphology of approximately 100 nm diameter following incorporation into and release from the scaffolds. PUR scaffold releasate collected in vitro in PBS at 37 °C for 1-4 days was able to achieve dose-dependent siRNA-mediated silencing with approximately 50% silencing achieved of the model gene GAPDH in NIH3T3 mouse fibroblasts. This promising platform technology provides both a research tool capable of probing the effects of local gene silencing and a potentially high-impact therapeutic approach for sustained, local silencing of deleterious genes within tissue defects.     

Facile route to versatile nanoplatforms for drug delivery by one-pot self-assembly

There is still unmet demand for developing powerful approaches to produce polymeric nanoplatforms with versatile functions and broad applications, which are essential for the successful bench-to-bedside translation of polymeric nanotherapeutics developed in the laboratory. We have discovered a facile, convenient, cost-effective and easily scalable one-pot strategy to assemble various lipophilic therapeutics bearing carboxyl groups into nanomedicines, through which highly effective cargo loading and nanoparticle formation can be achieved simultaneously. Besides dramatically improving water solubility, the assembled nanopharmaceuticals showed significantly higher bioavailability and much better therapeutic activity. These one-pot assemblies may also serve as nanocontainers to effectively accommodate other highly hydrophobic drugs such as paclitaxel (PTX). PTX nanomedicines thus formulated display strikingly enhanced in vitro antitumor activity and can reverse the multidrug resistance of tumor cells to PTX therapy. The special surface chemistry offers these assembled entities the additional capability of efficiently packaging and efficaciously transfecting plasmid DNA, with a transfection efficiency markedly higher than that of commonly used positive controls. Consequently, this one-pot assembly approach provides a facile route to multifunctional nanoplatforms for simultaneous delivery of multiple therapeutics with improved therapeutic significance.     

Oligopeptide-terminated poly(β-amino ester)s for highly efficient gene delivery and intracellular localization

The main limitation of gene therapy towards clinics is the lack of robust, safe and efficient gene delivery vectors. This paper describes new polycations for gene delivery based on poly(β-amino ester)s (pBAE) containing terminal oligopeptides. The authors developed oligopeptide-modified pBAE–pDNA nanoparticles that achieve better cellular viability and higher transfection efficacy than other end-modified pBAE and commercial transfection agents. Gene expression in highly permissive cell lines was remarkably high, but transfection efficiency in less-permissive cell lines was highly dependent on oligopeptide composition and nanoparticle formulation. Moreover, the use of selected oligopeptides in the pBAE formulation led to preferential intracellular localization of the particles. Particle analysis of highly efficient pBAE formulations revealed different particle sizes and charge features, which indicates chemical pseudotyping of the particle surface, related to the oligopeptide chemical nature. In conclusion, chemical modification at the termini of pBAE with amine-rich oligopeptides is a powerful strategy for developing delivery systems for future gene therapy applications.     

Click conjugated polymeric immuno-nanoparticles for targeted siRNA and antisense oligonucleotide delivery

Efficient and targeted cellular delivery of small interfering RNAs (siRNAs) and antisense oligonucleotides (AONs) is a major challenge facing oligonucleotide-based therapeutics. The majority of current delivery strategies employ either conjugated ligands or oligonucleotide encapsulation within delivery vehicles to facilitate cellular uptake. Chemical modification of the oligonucleotides (ONs) can improve potency and duration of activity, usually as a result of improved nuclease resistance. Here we take advantage of innovations in both polymeric delivery vehicles and ON stabilization to achieve receptor-mediated targeted delivery of siRNAs or AONs for gene silencing. Polymeric nanoparticles comprised of poly(lactide-co-2-methyl, 2-carboxytrimethylene carbonate)-g-polyethylene glycol-furan/azide are click-modified with both anti-HER2 antibodies and nucleic acids on the exterior PEG corona. Phosphorothioate (PS), 2′F-ANA, and 2′F-RNA backbone chemical modifications improve siRNA and AON potency and duration of activity. Importantly, delivery of these nucleic acids on the exterior of the polymeric immuno-nanoparticles are as efficient in gene silencing as lipofectamine transfection without the associated potential toxicity of the latter.     

Efficient in vitro and in vivo pulmonary delivery of nucleic acid by carbon dot-based nanocarriers

Cationic carbon dots were fabricated by pyrolysis of citric acid and bPEI25k under microwave radiation. Various nanoparticles were produced in a 20–30% yield through straightforward modifications of the reaction parameters (stoichiometry of the reactants and energy supply regime). Particular attention was paid to the purification of the reaction products to ensure satisfactory elimination of the residual starting polyamine. Intrinsic properties of the particles (size, surface charge, photoluminescence and quantum yield) were measured and their ability to form stable complexes with nucleic acid was determined. Their potential to deliver plasmid DNA or small interfering RNA to various cell lines was investigated and compared to that of bPEI25k. The pDNA in vitro transfection efficiency of these carbon dots was similar to that of the parent PEI, as was their cytotoxicity. The higher cytotoxicity of bPEI25k/siRNA complexes when compared to that of the CD/siRNA complexes however had marked consequences on the gene silencing efficiency of the two carriers. These results are not fully consistent with those in some earlier reports on similar nanoparticles, revealing that toxicity of the carbon dots strongly depends on their protocol of fabrication. Finally, these carriers were evaluated for in vivo gene delivery through the non-invasive pulmonary route in mice. High transgene expression was obtained in the lung that was similar to that obtained with the golden standard formulation GL67A, but was associated with significantly lower toxicity. Post-functionalization of these carbon dots with PEG or targeting moieties should significantly broaden their scope and practical implications in improving their in vivo transfection efficiency and biocompatibility.     

Fabrication of multi-layered biodegradable drug delivery device based on micro-structuring of PLGA polymers

A programmable and biodegradable drug delivery device is desirable when a drug needs to be administered locally. While most local drug delivery devices made of biodegradable polymers relied on the degradation of the polymers, the degradation-based release control is often limited by the property of the polymers. Thus, we propose micro-geometry as an alternative measure of controlling drug release. The proposed devices consist of three functional layers: diffusion control layer via micro-orifices, diffusion layer, and drug reservoir layers. A micro-fabrication technology was used to shape an array of micro-orifices and micro-cavities in 85/15PLGA layers. A thin layer of fast degrading 50/50PLGA was placed as the diffusion layer between the 85/15PLGA layers to prevent any burst-type release. To modulate the release of the devices, the dimension and location of the micro-orifices were varied and the responding in vitro release response of tetracycline was monitored over 2 weeks. The release response to the different micro-geometry was prominent and further analyzed by FEM simulation. Comparison of the experiments to the simulated results identified that the variation of micro-geometry influenced also the volume-dependent degradation rate and induced the osmotic pressure.     

PTX-loaded three-layer PLGA/CS/ALG nanoparticle based on layer-by-layer method for cancer therapy

Poly (lactic-co-glycolic acid) (PLGA) nanoparticles are an ideal paclitaxel (PTX)-carrying system due to its biocompatibility and biodegradability. But it possessed disadvantage of drug burst release. In this research, a layer-by-layer deposition of chitosan (CS) and sodium alginate (ALG) was applied to modify the PLGA nanoparticles. The surface charges and morphology of the PLGA, PLGA/CS and PLGA/CS/ALG particles was measured by capillary electrophoresis and SEM and TEM, respectively. The drug encapsulation and loading efficiency were confirmed by ultraviolet spectrophotometer. The nanoparticles were stable and exhibited controlled drug release performance, with good cytotoxicity to human lung carcinoma cells (HepG 2). Cumulatively, our research suggests that this kind of three-layer nanoparticle with LbL-coated shield has great properties to act as a novel drug-loaded system.     

Polycation-detachable nanoparticles self-assembled from mPEG-PCL-g-SS-PDMAEMA for in vitro and in vivo siRNA delivery

Long circulation, cell internalization, endosomal escape and small interfering RNA (siRNA) release to the cytoplasm are the prerequisite considerations for siRNA delivery vectors. Herein, a kind of sheddable nanoparticles (NPs) with micelle architecture for siRNA delivery were fabricated by using an intracellular-activated polycation-detachable copolymer (PECssD), which was prepared by introducing highly reducing environment-responsive disulfide linkages between PEGylated polycaprolactone (PCL) and the grafted polycation, poly(2-dimethylaminoethyl methacrylate) (PDMAEMA). The architecture of PECssD self-assembled NPs includes a biodegradable hydrophobic PCL core, a PEG shield and a detachable comb-like polycation surface. The stable nanosized complexes of PECssD NPs with siRNA, termed PECssD/siRNA micelleplexes, were formed, which could prolong circulation, improve accumulation and retention in tumor tissue, and be favorable for internalization. In particular, the cleavage of the disulfide linkages in the intracellular microenvironment and the subsequent dissociation of the PDMAEMA/siRNA polyplexes from the PEGylated PCL cores of PECssD/siRNA micelleplexes were also confirmed, which facilitated the endosomal escape and the efficient release of siRNA. As a result, the distribution of siRNA in cytoplasm was enhanced and subsequently promoted the efficiency of siRNA in gene silencing. Furthermore, systemic administration of the NPs carrying siPlk1 (polo-like kinase 1 specific siRNA) induced a tumor-suppressing effect in the HeLa-Luc xenograft murine model. Therefore, the devised strategy of the polycation-detachable copolymer PECssD NPs could address the requirements of the multistep systemic delivery process of siRNA. The hydrophobic core of the PECssD/siRNA micelleplexes is expected to entrap antitumor drugs or other therapeutic agents for combined therapies.     

The binary complex of poly(PEGMA-co-MAA) hydrogel and PLGA nanoparticles as a novel oral drug delivery system for ibuprofen delivery

To improve the bioavailability of ibuprofen (IBU), we developed a novel binary complex of poly(PEGMA-co-MAA) hydrogel and IBU-loaded PLGA nanoparticles (IBU-PLGA NPs@hydrogels) as an oral intestinal targeting drug delivery system (OIDDS). The IBU-loaded PLGA NPs and pH-sensitive hydrogels were obtained via the solvent evaporation method and radical polymerization, respectively. The final OIDDS was obtained by immersing the hydrogel chips in the IBU-loaded PLGA NPs solutions (pH 7.4) for 3 d. The size distribution and morphology of cargo-free NPs were studied by laser granularity analyzer and transmission electron microscope (TEM). The inner structures of the pH-sensitive hydrogel chips were observed with an S-4800 scanning electron microscope (SEM). The distribution states of IBU in the OIDDS were also studied with X-ray diffraction (XRD) and differential scanning calorimetry (DSC). TEM photographs illustrated that the PLGA NPs had a round shape with an average diameter about 100 nm. Fourier transform infrared spectrum (FTIR) confirmed the synthesis of poly(PEGMA-co-MAA) hydrogel. The SEM picture showed that the final hydrogel had 3D net-work structures. Moreover, the poly(PEGMA-co-MAA) hydrogel showed an excellent pH-sensitivity. The XRD and DSC curves suggested that IBU distributed in the OIDDS with an amorphous state. The cumulated release profiles indicated that the final OIDDS could release IBU in alkaline environment (e.g. intestinal tract) at a sustained manner. Therefore, the novel OIDDS could improve the oral bioavailability of IBU, and had a potential application in drug delivery.     

Synthesis and characterization of PLGA nanoparticles

Poly(lactide-co-glycolide) (PLGA) nanoparticles of different physical characteristics (size, size distribution, morphology, zeta potential) can be synthesized by controlling the parameters specific to the synthesis method employed. The aim of this review is to clearly, quantitatively and comprehensively describe the top–down synthesis techniques available for PLGA nanoparticle formation, as well as the techniques commonly used for nanoparticle characterization. Many examples are discussed in detail to provide the reader with an extensive knowledge base on the important parameters specific to the synthesis method described and ways in which these parameters can be manipulated to control the nanoparticle physical characteristics.     

非病毒载体在siRNA体内递送中的应用

RNAi是一种由siRNA触发的特异基因沉默机制。自其发现以来,RNAi技术迅速发展为药物靶标确认和功能基因组学研究的新策略,并有望成为一种疾病基因治疗学方法。然而,由于siRNA体内不稳定的理化性质,递送siRNA成为RNAi发展的最大障碍。因此研发能够保护siRNA、促进细胞吸收、正确细胞定位和包内体逃逸,结合具有高生物相容性与减少非特异沉默和毒性反应的体内递送系统是RNAi成功用于临床治疗的关键。本文就体内非病毒载体方式递送siRNA的研究进展进行综述。     

Hierarchical targeted hepatocyte mitochondrial multifunctional chitosan nanoparticles for anticancer drug delivery

The overwhelming majority of drugs exert their pharmacological effects after reaching their target sites of action, however, these target sites are mainly located in the cytosol or intracellular organelles. Consequently, delivering drugs to the specific organelle is the key to achieve maximum therapeutic effects and minimum side-effects. In the work reported here, we designed, synthesized, and evaluated a novel mitochondrial-targeted multifunctional nanoparticles (MNPs) based on chitosan derivatives according to the physiological environment of the tumor and the requirement of mitochondrial targeting drug delivery. The intelligent chitosan nanoparticles possess various functions such as stealth, hepatocyte targeting, multistage pH-response, lysosomal escape and mitochondrial targeting, which lead to targeted drug release after the progressively shedding of functional groups, thus realize the efficient intracellular delivery and mitochondrial localization, inhibit the growth of tumor, elevate the antitumor efficacy, and reduce the toxicity of anticancer drugs. It provides a safe and efficient nanocarrier platform for mitochondria targeting anticancer drug delivery.