PLGA-PEI nanoparticles for gene delivery to pulmonary epithelium

A one-step process in preparation of cationic nanoparticles with poly(lactide-co-glycolide)-containing polyethylenimine gives efficient gene delivery

A one-step preparation of nanoparticles with poly(lactide-co-glycolide) (PLGA) pre-modified with polyethylenimine (PEI) is better in requirements for DNA delivery compared to those prepared in a two-step process (preformed PLGA nanoparticles and subsequently coated with PEI). The particles were prepared by emulsification of PLGA/ethyl acetate in an aqueous solution of PVA and PEI. DLS, AFM and SEM were used for the size characteristics. The cytotoxicity of PLGA/PEI nanoparticles was detected by MTT assay. The transfection activity of the particles was measured using pEGFP and pβ-gal plasmid DNA. Results showed that the PLGA/PEI nanoparticles were spherical and non-porous with a size of about 0.2 μm and a small size distribution. These particles had a positive zeta potential demonstrating that PEI was attached. Interestingly, the zeta potential of the particles (from one-step procedure) was substantially higher than that of two-step process and is ascribed to the conjugation of PEI to PLGA via aminolysis. The PLGA/PEI nanoparticles were able to bind DNA and the formed complexes had a substantially lower cytotoxicity and a higher transfection activity than PEI polyplexes. In conclusion, given their small size, stability, low cytotoxicity and good transfection activity, PLGA/PEI-DNA complexes are attractive gene delivery systems.

Low molecular weight chitosan nanoparticulate system at low N:P ratio for nontoxic polynucleotide delivery

Chitosan, a natural polymer, is a promising system for the therapeutic delivery of both plasmid DNA and synthetic small interfering RNA. Reports attempting to identify the optimal parameters of chitosan for synthetic small interfering RNA delivery were inconclusive with high molecular weight at high amine-to-phosphate (N:P) ratios apparently required for efficient transfection. Here we show, for the first time, that low molecular weight chitosan (LMW-CS) formulations at low N:P ratios are suitable for the in vitro delivery of small interfering RNA. LMW-CS nanoparticles at low N:P ratios were positively charged (ζ-potential ~20 mV) with an average size below 100 nm as demonstrated by dynamic light scattering and environmental scanning electron microscopy, respectively. Nanoparticles were spherical, a shape promoting decreased cytotoxicity and enhanced cellular uptake. Nanoparticle stability was effective for at least 20 hours at N:P ratios above two in a slightly acidic pH of 6.5. At a higher basic pH of 8, these nanoparticles were unravelled due to chitosan neutralization, exposing their polynucleotide cargo. Cellular uptake ranged from 50% to 95% in six different cell lines as measured by cytometry. Increasing chitosan molecular weight improved nanoparticle stability as well as the ability of nanoparticles to protect the oligonucleotide cargo from nucleases at supraphysiological concentrations. The highest knockdown efficiency was obtained with the specific formulation 92-10-5 that combines sufficient nuclease protection with effective intracellular release. This system attained >70% knockdown of the messenger RNA, similar to commercially available lipoplexes, without apparent cytotoxicity. Contrary to previous reports, our data demonstrate that LMW-CS at low N:P ratios are efficient and nontoxic polynucleotide delivery systems capable of transfecting a plethora of cell lines.

PLGA Nanoparticles for Ultrasound-Mediated Gene Delivery to Solid Tumors

This paper focuses on novel approaches in the field of nanotechnology-based carriers utilizing ultrasound stimuli as a means to spatially target gene delivery in vivo, using nanoparticles made with either poly(lactic-co-glycolic acid) (PLGA) or other polymers. We specifically discuss the potential for gene delivery by particles that are echogenic (amenable to destruction by ultrasound) composed either of polymers (PLGA, polystyrene) or other contrast agent materials (Optison, SonoVue microbubbles). The use of ultrasound is an efficient tool to further enhance gene delivery by PLGA or other echogenic particles in vivo. Echogenic PLGA nanoparticles are an attractive strategy for ultrasound-mediated gene delivery since this polymer is currently approved by the US Food and Drug Administration for drug delivery and diagnostics in cancer, cardiovascular disease, and also other applications such as vaccines and tissue engineering. This paper will review recent successes and the potential of applying PLGA nanoparticles for gene delivery, which include (a) echogenic PLGA used with ultrasound to enhance local gene delivery in tumors or muscle and (b) PLGA nanoparticles currently under development, which could benefit in the future from ultrasound-enhanced tumor targeted gene delivery.

Crosslinked chitosan nanoparticle formulations for delivery from pressurized metered dose inhalers

Crosslinked chitosan nanoparticles, prepared using ionic gelation, have been successfully formulated into pressurized metered dose inhalers (pMDIs) with potential for deep lung delivery of therapeutic agents. Nanoparticles were prepared from crosslinked chitosan alone and incorporating PEG 600, PEG 1000 and PEG 5000 for dispersion in aerosol propellant, hydrofuoroalkane (HFA) 227. Spherical, smooth-surfaced, cationic particles of mean size less than 230 nm were produced. Nanoparticles were positively charged and non-aggregated at the pH of the airways. Crosslinked chitosan-PEG 1000 nanoparticles demonstrated greatest dispersibility and physical stability in HFA-227, whereas other formulations readily either creamed or sedimented. Following actuation from pMDIs, the fine particle fraction (FPF) for crosslinked chitosan-PEG 1000 nanoparticles, determined using a next generation impactor, was 34.0±1.4% with a mass median aerodynamic diameter of 4.92±0.3 μm. The FPFs of crosslinked chitosan, crosslinked chitosan-PEG 600 and crosslinked chitosan-PEG 5000 nanoparticles were 5.7±0.9%, 11.8±2.7% and 17.0±2.1%, respectively. These results indicate that crosslinked chitosan-PEG 1000-based nanoparticles are promising candidates for delivering therapeutic agents, particularly biopharmaceuticals, using pMDIs.

Nanoparticulate systems as drug carriers: the need

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

Controlled pulmonary drug and gene delivery using polymeric nano-carriers

Pulmonary drug and gene delivery to the lung represents a non-invasive avenue for local and systemic therapies. However, the respiratory tract provides substantial barriers that need to be overcome for successful pulmonary application. In this regard, micro- and nano-sized particles offer novel concepts for the development of optimized therapeutic tools in pulmonary research. Polymeric nano-carriers are generally preferred as controlled pulmonary delivery systems due to prolonged retention in the lung. Specific manipulation of nano-carrier characteristics enables the design of "intelligent" carriers specific for modulation of the duration and intensity of pharmacological effects. New formulations should be tested for pulmonary absorption and distribution using more advanced ex vivo and in vivo models. The delivery of nano-carriers to the air-space enables a detailed characterization of the interaction between the carrier vehicle and the natural pulmonary environment. In summary, polymeric nanoparticles seem to be especially promising as controlled delivery systems and represent a solid basis for future advancement for pulmonary delivery applications.

Curcumin-containing chitosan nanoparticles as a potential mucoadhesive delivery system to the colon

In the present study, we investigate the mucoadhesive characteristics and release of the anticancer agent curcumin, contained in chitosan nanoparticles (CS-NPs). Such a system has potential therapeutic benefits in the treatment of colon cancer through prolonged retention and delivery. The CS-NPs were ionically gelled with tripolyphosphate (TPP) and registered an isoelectric pH of 6.2 (z-average diameter of 214 nm ± 1.0 nm). pH variations around the isoelectric point caused a reduction in CS-NPs electrical charge which correspondingly increased the z-average due to agglomeration. Curcumin release from CS-NPs was slowest at chitosan to TPP weight ratio of 3:1, with a significant retention (36%) at the end of 6 h. Adsorption isotherms of mucin on CS-NPs fitted both the Freundlich and Langmuir models, suggesting a monolayer-limited adsorption on heterogeneous sites with varied affinities. Encapsulated curcumin exerted an influence on the adsorption of mucin due to H-bonding as well as π-π interactions between the phenolic moieties of curcumin and mucin.

A potential nanomedicine consisting of heparin-loaded polysaccharide nanocarriers for the treatment of asthma

A new nanomedicine consisting of chitosan/carboxymethyl-β-cyclodextrin loaded with unfractioned or low-molecular-weight heparin is described and its potential in asthma treatment is evaluated. The nanoparticles are prepared by ionotropic gelation showing a size that between 221 and 729 nm with a positive zeta potential. The drug association efficiency is higher than 70%. Developed nanosystems are stable in Hank's balanced salt solution at pH = 6.4, releasing the drug slowly. Ex vivo assays show that nanocarriers lead to an improvement of heparin preventing mast cell degranulation. These results agree with the effective cellular internalization of the fluorescently labeled nanocarriers, and suggest these nanomedicines as promising formulations for asthma treatment.

Pulmonary gene delivery using polymeric nonviral vectors

Pulmonary delivery provides an easy and well tolerated means of access for the administration of biomacromolecules to the pulmonary epithelium and could therefore be an attractive approach for local and systemic therapies. A growing number of reports, which are summarized in this review, mirror the viability of pulmonary gene delivery. Special attention has been paid to the biological barriers in the lung that must be overcome for successful delivery, and which can be divided into anatomic, physical, immunologic, and metabolic barriers. In light of these barriers, successful nonviral polymer-based formulations of therapeutic genes are presented depending on the chemical nature of the polymer. In addition to polyethyleneimine-based nonviral vectors, which have been most intensively studied for pulmonary gene delivery in the past, other polymeric, dendritic, and targeted materials are also described here, including novel and biodegradable polymers. As new materials need in vitro or ex vivo testing before in vivo application, sophisticated models for all three approaches have been illustrated. Although pulmonary siRNA delivery enjoys popularity in clinical trials, pulmonary gene delivery has so far not been translated into clinical applications. With this review, potential hurdles are demonstrated, but novel approaches that may lead to optimized systems are described as well.

Synthesis and properties of a novel biodegradable poly(ester amine) copolymer based on poly(L-lactide) and low molecular weight polyethylenimine for gene delivery

BACKGROUND

Gene therapy is a promising approach to the treatment of a wide range of diseases. The development of efficient and adequate gene delivery systems could be one of the most important factors. Polyethyleneimine, a cationic polymer, is one of the most successful and widely used vectors for nonviral transfection in vitro and in vivo.

METHODS

A novel biodegradable poly(ester amine) copolymer (PEA) was successfully prepared from low molecular weight polyethylenimine (PEI, 2000 Da) and poly(L-lactide) copolymers.

RESULTS

According to the results of agarose gel electrophoresis, particle size and zeta potential measurement, and transfection efficiency, the PEA copolymers showed a good ability to condense plasmid DNA effectively into nanocomplexes with a small particle size (≤150 nm) and moderate zeta potential (≥10 mV) at an appropriate polymeric carrier/DNA weight ratio. Compared with high molecular weight PEI (25kDa), the PEA obtained showed relatively high gene transfection efficiency as well as low cytotoxicity in vitro.

CONCLUSION

These results indicate that such PEA might have potential application as a gene delivery system.

Comparison of intracellular accumulation and cytotoxicity of free mTHPC and mTHPC-loaded PLGA nanoparticles in human colon carcinoma cells

The second generation photosensitizer mTHPC was approved by the European Medicines Agency (EMA) for the palliative treatment of advanced head and neck cancer in October 2001. It is known that mTHPC possesses a significant phototoxicity against a variety of human cancer cells in vitro but also exhibits dark toxicity and can cause adverse effects (especially skin photosensitization). Due to its poor water solubility, the administration of hydrophobic photosensitizer still presents several difficulties. To overcome the administration problems, the use of nanoparticles as drug carrier systems is much investigated. Nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) have been extensively studied as delivery systems into tumours due to their biocompatibility and biodegradability. The goal of this study was the comparison of free mTHPC and mTHPC-loaded PLGA nanoparticles concerning cytotoxicity and intracellular accumulation in human colon carcinoma cells (HT29). The nanoparticles delivered the photosensitizer to the colon carcinoma cells and enabled drug release without losing its activity. The cytotoxicity assays showed a time- and concentration-dependent decrease in cell proliferation and viability after illumination. However, first and foremost mTHPC lost its dark toxic effects using the PLGA nanoparticles as a drug carrier system. Therefore, PLGA nanoparticles are a promising drug carrier system for the hydrophobic photosensitizer mTHPC.

Evaluating pulmonary toxicity of Shuang-Huang-Lian in vitro and in vivo

ETHNOPHARMAOCOLOGICAL RELEVANCE: Shuang-Huang-Lian (SHL) is a traditional Chinese formula and has been used for the treatment of respiratory tract infections by inhalation. However, the pulmonary toxicity via inhalation is largely uninvestigated.

AIM OF STUDY

To evaluate the pulmonary toxicity of SHL following in vivo intratracheal spray to rats and in vitro exposures to A549 and Calu-3 cells.

METHODS

Calu-3 and A549 cells were exposed to SHL, chlorogenic acid, baicalin and forsythin solutions and in vitro cytotoxicity was evaluated using an MTT assay, whilst rats were subjected to intratracheal administration of SHL solutions and in vivo toxicity was indicated by assaying the LDH activity and total protein content in bronchoalveolar lavage fluid (BALF) and observing the histopathologic changes of the lungs. Secretion of inflammatory mediators, including IL-6, IL-8 and TNF-α, in cell culture media and BALF was quantified by ELISA.

RESULTS

The MTT cell viability data revealed the presence of minor toxicity to Calu-3 or A549 cells following exposure to SHL and its major ingredients for 24h or 48 h. However, the cell cultural media showed no sign of inflammatory responses. The in vivo results showed that exposures to SHL at doses of up to 50mg/kg did not significantly increase the total protein content, the LDH activity and the concentrations of IL-6, IL-8 and TNF-α in BALF. However, although intratracheal sprayed SHL at doses of up to 6 mg/kg for histopathologic study and up to 25mg/kg for cell counts showed no sign of adverse effects, inhaled SHL at elevated doses appeared to induce alveolar fusion in the lung and significant increases in the cell number of monocytes and granulocytes in the BALF.

CONCLUSION

The results demonstrated that the pulmonary safety of inhaled SHL was dependent on the administered dose. Inhalation therapy of SHL may be safely used when the inhaled dose was properly controlled.

Investigation of PEG-PLGA-PEG nanoparticles-based multipolyplexes for IL-18 gene delivery

Nanoparticles were formulated with biodegradable monomethoxy (poly ethylene glycol)-poly(lactide-co-glycolide)-monomethoxy (poly ethylene glycol) of three different proportional (PEG-PLGA-PEG, lactic acid: glycolic acid = 80/20, 70/30, 50/50) and the cytotoxicity of nanoparticle was characterized according to US Pharmacopoeia XXIII recommendations on various cell lines, including L929, Chang's hepatocytes, primary mouse myoblasts, osteoblasts, and renal vascular endothelial cells. mIL-18 gene was first condensed by polycationic peptide polylysine (PLL), and then encapsulated in the PEG-PLGA-PEG NPs as a novel multi-polyplex gene delivery system - Polymer-PLL-DNA. (PPDs) After lyopholization, the morphology, particle size, zeta potential, and the integrity of DNA in the NPs were investigated. The expression of mIL-18 gene on CT-26 cells in vitro were determined by western blot, while in vivo efficacy was evaluated by tumor inhibition rate, histological section, and survival curve in pulmonary metastasis of colon cancer in BALB/c mice model. Results showed that the cytotoxicity of blank nanoparticles was related to the degradation properties of the polymers with different compositions. The NPs with LA:GA = 70/30 (NPs-73) was optimal for intravenous injection due to its low cytotoxicity. Physicochemical properties of the PPDs were not changed during the lyopholization, while mIL-18 was successfully expressed in vitro. The anti-tumor efficacy in vivo of PPDs showed improvement especially combined with chemotherapy of cisplatin, and confirmed the promising application of the PPDs system, which compared with any single treatment.

Fabrication, characterization and in vitro evaluation of poly(D,L-lactide-co-glycolide) microparticles loaded with polyamidoamine-plasmid DNA dendriplexes for applications in nonviral gene delivery

We report, for the first time, on the preparation, characterization and in vitro testing of poly(D,L-lactide-co-glycolide) (PLGA) microparticles loaded with polyamidoamine (PAMAM)-plasmid DNA (pDNA) dendriplexes. Loading of pDNA into the PLGA microparticles increased by 150% when pDNA was first complexed with PAMAM dendrimers relative to loading of pDNA alone. Scanning electron microscopy (SEM) showed that the presence of PAMAM dendrimers in the PLGA microparticles created porous features and indentations on the surface of the microparticles. Loading PLGA microparticles with PAMAM-pDNA dendriplexes lowered the average PLGA microparticle size and changed the surface charge of the microparticles from negative to positive when compared to PLGA microparticles loaded with pDNA alone. The zetapotential and buffering capacity of the microparticles increased as the generation of the PAMAM dendrimer loaded in the PLGA microparticles increased. Gel electrophoresis assays showed that all the PLGA microparticle formulations were able to entrap the pDNA within the PLGA matrix. There was no significant difference in the cytotoxicity of PLGA microparticles loaded with PAMAM-pDNA dendriplexes when compared to PLGA microparticles loaded with pDNA alone. Furthermore, and in contrast to PAMAM dendrimers alone, the generation of the PAMAM dendrimer loaded in the PLGA microparticles had no significant impact on cytotoxicity or transfection efficiencies in human embryonic kidney (HEK293) or Monkey African green kidney fibroblast-like (COS7) cells. The transfection efficiency of PLGA microparticles loaded with generation 3 (G3) PAMAM-pDNA dendriplexes was significantly higher than PLGA microparticles loaded with pDNA alone in HEK293 and COS7 cells. PLGA microparticles loaded with G3 PAMAM-pDNA dendriplexes generated equivalent transfection efficiencies as (G3 to G6) PAMAM-pDNA dendriplexes alone in COS7 cells when the transfection was carried out in serum containing media. The delivery system developed in this report has low toxicity, high pDNA loading efficiencies and high transfection efficiencies that are not reduced in the presence of serum. A delivery system with these characteristics is expected to have significant potential for translational applications.

Anti-CD8 conjugated nanoparticles to target mammalian cells expressing CD8

This work aimed at the development of targeted drug delivery systems using nanoparticles fused with antibodies. The antibody anti-human CD8 was coupled onto PLGA nanoparticles, and the ability of these particles to specifically target cells expressing CD8 was studied. The obtained particles were found to be of spherical shape exhibiting a size between 350 and 600 nm. In vitro experiments with different cellular cultures (TE671, CHO and HEK293) using unmodified nanoparticles containing rhodamine have shown that particles were present on their surface within 48 h of incubation. In vitro tests using anti-CD8 conjugated nanoparticles in CHO cell cultures indicated that all transfected cells which express CD8 show these particles on their surface within 1h of incubation. These results demonstrated that, in a shorter time, the produced particles can target cells expressing CD8 on their surface which offers the ability to reduce drug side effects. The antibody-coupled nanoparticles represent a promising approach to improve the efficacy of active targeting for lymphoblastic leukaemia therapy.

The development and mechanism studies of cationic chitosan-modified biodegradable PLGA nanoparticles for efficient siRNA drug delivery

PURPOSE

In order to improve siRNA delivery for possible clinical applications, we developed biodegradable chitosan-modified poly(D,L-lactide-co-glycolide) (CHT-PLGA) nanoparticles with positive surface charge, high siRNA loading, high transfection efficiency and low toxicity.

METHODS

CHT-PLGA nanoparticles were prepared, and siRNA was loaded by emulsion evaporation method with poly(vinyl alcohol) (PVA) as emulsifier. siRNA loading efficiency, particle size, and Zeta potential of nanoparticles were measured. Gel retardation and protection assays were conducted to determine the loading and binding of siRNA in the formulation. Cell transfection was performed to study in vitro siRNA silencing efficiency. XTT assay was used to evaluate the cytotoxicity.

RESULTS

It was found that the nanoparticle diameter and positive Zeta potential increase as the chitosan coating concentration increases. CHT-PLGA nanoparticles showed excellent siRNA binding ability and effective protection of oligos from RNase degradation. siRNA-loaded nanoparticles were successfully delivered into the HEK 293 T cell line, and the silencing of green fluorescence protein (GFP) expression was observed using fluorescent microscopy and flow cytometry. In addition, the cytotoxicity assay revealed that CHT-PLGA nanoparticles had relatively low cytotoxicity.

CONCLUSION

This study suggests that biodegradable cationic CHT-PLGA nanoparticles possess great potential for efficient and safer siRNA delivery in future clinical applications.

Superparamagnetic magnetite nanocrystal clusters: a sensitive tool for MR cellular imaging

Silica coated, PEI and citric acid hybrid superparamagnetic magnetite nanocrystal clusters (SMNC) were synthesized using either a mini-emulsion/sol-gel method or a polyol technique. After careful characterization of the size, structure, composition, and magnetic properties, the as-synthesized SMNC were used for cell labeling while the MR detection sensitivity of cells labeled with silica SMNC was performed with a 3 T whole body MR scanner. TEM investigations revealed that the sizes of the SMNC were about 200 nm and the SMNC mainly consisted of magnetite nanoparticles imbedded in a PEI, citric acid or polystyrene scaffold. Silica and citric acid SMNC were highly negatively charged and PEI SMNC were positively charged. Relaxometry measurements revealed that these SMNC possessed a very high MR sensitivity (silica SMNC: r(2) = 299 s(-1) mM(-1), PEI SMNC: r(2) = 124 s(-1) mM(-1)), especially for the citric acid SMNC (r(2) = 360 s(-1) mM(-1)). Furthermore, when used for cell (RAW264.7 cells) labeling, the SMNC had no adverse effect on cell viability, and the cell uptake of the SMNC show a dose- and time-dependent feature. MR imaging of cells labeled with silica SMNC indicated that cells with a concentration as low as 10 x 10(3) cells ml(-1) could be detected with a 3 T MRI scanner. Our study demonstrated that superparamagnetic magnetite nanocrystal clusters are a sensitive tool for cell imaging.

Chitosan nanoparticles as non-viral gene delivery vehicles based on atomic force microscopy study

Chitosan (CS), a biocompatible and biodegradable material, can act as a non-viral delivery vehicle with low toxicity. In this study, plasmid DNA (pDNA) and siRNA were encapsulated in CS nanoparticles (NPs) to prepare CS-DNA and CS-siRNA NPs using a complex coacervation process. The CS-DNA particle size was within the range of 180-370 nm with a surface charge ranging from 0 to 18 mV at pH 5.5. The stability of pDNA in CS-DNA was investigated by pDNA release study and DNase I protection assay. The release of pDNA from NPs was studied in pH 7.4 phosphatebuffered saline at 378C and the CS-DNA NPs could delay the DNA release. Results of DNase I protection assay showed that CS-DNA NPs could protect the encapsulated pDNA from nuclease degradation. In the transfection study, it was found that the transfection efficiency in vitro was dependent on the molecular weight, charge ratio, and DNA concentration of the CS-DNA NP as well as the type of cell transfected. Moreover, the morphology of HeLa cells transfected with CS-siRNA complexes was studied using atomic force microscopy. The results suggest that CS may be more capable than liposome in delivering siRNA to target cells. In summary, our analysis suggests that pDNA and siRNA can be encapsulated in CS NPs without being damaged.

Pulmonary delivery of DNA encoding Mycobacterium tuberculosis latency antigen Rv1733c associated to PLGA-PEI nanoparticles enhances T cell responses in a DNA prime/protein boost vaccination regimen in mice

During persistent infection and hypoxic-stress, Mycobacterium tuberculosis (Mtb) expresses a series of Mtb latency antigens. The aim of this study was to evaluate the immunogenicity of a DNA vaccine encoding the Mtb latency antigen Rv1733c and to explore the effect of pulmonary delivery and co-formulation with poly (d,l-lactide-co-glycolide) (PLGA)-polyethyleneimine (PEI) nanoparticles (np) on host immunity. Characterization studies indicated that PLGA-PEI np kept their nanometer size after concentration and were positively charged. The np were able to mature human dendritic cells and stimulated them to secrete IL-12 and TNF-alpha comparable to levels observed after lipopolysaccharide (LPS) stimulation. Mtb latency antigen Rv1733c DNA prime combined with Rv1733c protein boost enhanced T cell proliferation and IFN-gamma secretion in mice in response to Rv1733c and Mtb hypoxic lysate. Rv1733c DNA adsorbed to PLGA-PEI np and applied to the lungs increased T cell proliferation and IFN-gamma production more potently compared to the same vaccinations given intramuscularly. The strongest immunogenicity was obtained by pulmonary priming with np-adsorbed Rv1733c DNA followed by boosting with Rv1733c protein. These results confirm that PLGA-PEI np are an efficient DNA vaccine delivery system to enhance T cell responses through pulmonary delivery in a DNA prime/protein boost vaccine regimen.

Formulation of polylactide-co-glycolic acid nanospheres for encapsulation and sustained release of poly(ethylene imine)-poly(ethylene glycol) copolymers complexed to oligonucleotides

Antisense oligonucleotides (AOs) have been shown to induce dystrophin expression in muscles cells of patients with Duchenne Muscular Dystrophy (DMD) and in the mdx mouse, the murine model of DMD. However, ineffective delivery of AOs limits their therapeutic potential. Copolymers of cationic poly(ethylene imine) (PEI) and non-ionic poly(ethylene glycol) (PEG) form stable nanoparticles when complexed with AOs, but the positive surface charge on the resultant PEG-PEI-AO nanoparticles limits their biodistribution. We adapted a modified double emulsion procedure for encapsulating PEG-PEI-AO polyplexes into degradable polylactide-co-glycolic acid (PLGA) nanospheres. Formulation parameters were varied including PLGA molecular weight, ester end-capping, and sonication energy/volume. Our results showed successful encapsulation of PEG-PEI-AO within PLGA nanospheres with average diameters ranging from 215 to 240 nm. Encapsulation efficiency ranged from 60 to 100%, and zeta potential measurements confirmed shielding of the PEG-PEI-AO cationic charge. Kinetic measurements of 17 kDa PLGA showed a rapid burst release of about 20% of the PEG-PEI-AO, followed by sustained release of up to 65% over three weeks. To evaluate functionality, PEG-PEI-AO polyplexes were loaded into PLGA nanospheres using an AO that is known to induce dystrophin expression in dystrophic mdx mice. Intramuscular injections of this compound into mdx mice resulted in over 300 dystrophin-positive muscle fibers distributed throughout the muscle cross-sections, approximately 3.4 times greater than for injections of AO alone. We conclude that PLGA nanospheres are effective compounds for the sustained release of PEG-PEI-AO polyplexes in skeletal muscle and concomitant expression of dystrophin, and may have translational potential in treating DMD.

Innovative strategies for co-delivering antigens and CpG oligonucleotides

Cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG ODN) is a recent class of immunostimulatory adjuvants that includes unmethylated CpG dinucleotide sequences similar to those commonly found in bacterial DNA. CpG ODN specifically triggers toll like receptor 9 (TLR9), which is found within phagoendosomes of antigen presenting cells (APCs) such as dendritic cells (DCs). CpG ODN triggers activation and maturation of DCs and helps to increase expression of antigens. CpG ODN can be used to induce polarized Th1 type immune responses. Several studies have shown that antigens and CpG ODN must be co-localized in the same APC to generate the most potent therapeutic antigen-specific immune responses. Delivery vehicles can be utilized to ensure co-delivery of antigens and CpG ODN to the same APCs and to significantly increase uptake by APCs. These strategies can result in antigen-specific immune responses that are 5 to 500-fold greater than administration of antigen alone. In this review, we discuss several recent and innovative strategies to co-delivering antigens and CpG ODN adjuvants to APCs. These approaches include the utilization of conjugate molecules, multi-component nanorods, liposomes, biodegradable microparticles, pulsatile release chips and cell-microparticle hybrids.

Silica nanoparticles as a delivery system for nucleic acid-based reagents

The transport of nucleic acid-based reagents is predicated upon developing structurally stable delivery systems that can preferentially bind and protect DNA and RNA, and release their cargo upon reaching their designated sites. Recent advancements in tailoring the size, shape, and external surface functionalization of silica materials have led to increased biocompatibility and efficiency of delivery. In this Feature Article, we highlight recent research progress in the use of silica nanoparticles as a delivery vehicle for nucleic acid-based reagents.

Bio-mimetic surface engineering of plasmid-loaded nanoparticles for active intracellular trafficking by actin comet-tail motility

Intracellular transport after endosomal escape presents one of the major barriers for efficient non-viral gene delivery because plasmid DNA and synthetic nanoparticulate carriers suffer from significantly restricted diffusion in the cytoplasm. We postulate that forces generated by actin polymerization, a mechanism used by several bacterial pathogens such as Listeria monocytogenes, can be harnessed to propel nanoparticles within the cytoplasm and thereby overcome diffusional limitations associated with gene transport in the cell cytoplasm. In this work, we synthesized and characterized plasmid DNA-containing nanoparticles modified with ActA protein, the single protein in L. monocytogenes responsible for activating actin polymerization and initiating actin comet-tail propulsion. The motility of the ActA-modified nanoparticles was assessed in Xenopus laevis cytoplasmic extract supplemented with fluorescently labeled actin. Nanoparticle motility was monitored using multi-color, time-lapse fluorescence microscopy for the formation of actin comet tails attached to the fluorescently labeled vehicle. We observed particle motility with velocities approximately 0.06 microm/s with anionic-charged plasmid carriers formed from either poly(lactic-co-glycolic acid) (PLGA) or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes, but interestingly not with cationic particles assembled by encapsulation of plasmid with either polyethylenimine (PEI) or 1,2-dioleoyl-3-trimethylammonium-propane/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOTAP/DOPE) lipids. Control particles coated with albumin instead of ActA also showed no motility. Taken together, we have demonstrated the feasibility of translating the comet-tail propulsion mechanism to synthetic drug carriers as a potential approach to overcome intracellular transport barriers, and also have identified appropriate gene delivery systems that can be employed for this mechanism.

Preparation of polyethyleneimine incorporated poly(D,L-lactide-co-glycolide) nanoparticles by spontaneous emulsion diffusion method for small interfering RNA delivery

Gene therapy based on small interfering RNA (siRNA) has emerged as an exciting new therapeutic approach. However, insufficient cellular uptake and poor stability have limited its usefulness. Polyethyleneimine (PEI) has been extensively studied as a vector for nucleic acids and incorporation of PEI into poly(d,l-lactide-co-glycolide) (PLGA) particles has been shown to be useful in the development of gene delivery. PEI was incorporated into the PLGA particles by spontaneous modified emulsification diffusion method. Incorporation of PEI into PLGA particles with the PLGA to PEI weight ratio 29:1 was found to produce spherical and positively charged nanoparticles where type of polymer, type and concentration of surfactant could affect their physical properties. Particle size of around 100nm was obtained when 5% (m/v) PVA was used as a stabiliser. PLGA-PEI nanoparticles were able to completely bind siRNA at N/P ratio 20:1 and to provide protection for siRNA against nuclease degradation. In vitro cell culture studies subsequently revealed that PLGA-PEI nanoparticles with adsorbed siRNA could efficiently silence the targeted gene in mammalian cells, better than PEI alone, with acceptable cell viability. PLGA-PEI nanoparticles have been found to be superior to its cationising parent compound; PEI polymer.

Biodegradable polymeric nanocarriers for pulmonary drug delivery

BACKGROUND

Pulmonary drug delivery is attractive for both local and systemic drug delivery as a non-invasive route that provides a large surface area, thin epithelial barrier, high blood flow and the avoidance of first-pass metabolism.

OBJECTIVE

Nanoparticles can be designed to have several advantages for controlled and targeted drug delivery, including controlled deposition, sustained release, reduced dosing frequency, as well as an appropriate size for avoiding alveolar macrophage clearance or promoting transepithelial transport.

METHODS

This review focuses on the development and application of biodegradable polymers to nanocarrier-based strategies for the delivery of drugs, peptides, proteins, genes, siRNA and vaccines by the pulmonary route.

RESULTS/CONCLUSION

The selection of natural or synthetic materials is important in designing particles or nanoparticle clusters with the desired characteristics, such as biocompatibility, size, charge, drug release and polymer degradation rate.

Formulating poly(lactide-co-glycolide) particles for plasmid DNA delivery

Biodegradable poly(lactide-co-glycolide) (PLGA) particles have shown significant potential for sustained and targeted delivery of several pharmaceutical agents, including plasmid DNA (pDNA). Here, we survey current approaches to PLGA particle preparation for pDNA delivery and discuss recent progress on optimizing formulation development.

Polymeric nanoparticles for siRNA delivery and gene silencing

Gene silencing using small interfering RNA (siRNA) has several potential therapeutic applications. In the present study, we investigated nanoparticles formulated using the biodegradable polymer, poly(d,l-lactide-co-glycolide) (PLGA) for siRNA delivery. A cationic polymer, polyethylenimine (PEI), was incorporated in the PLGA matrix to improve siRNA encapsulation in PLGA nanoparticles. PLGA-PEI nanoparticles were formulated using double emulsion-solvent evaporation technique and characterized for siRNA encapsulation and in vitro release. The effectiveness of siRNA-loaded PLGA-PEI nanoparticles in silencing a model gene, fire-fly luciferase, was investigated in cell culture. Presence of PEI in PLGA nanoparticle matrix increased siRNA encapsulation by about 2-fold and also improved the siRNA release profile. PLGA-PEI nanoparticles carrying luciferase-targeted siRNA enabled effective silencing of the gene in cells stably expressing luciferase as well as in cells that could be induced to overexpress the gene. Quantitative studies indicated that presence of PEI in PLGA nanoparticles resulted in 2-fold higher cellular uptake of nanoparticles while fluorescence microscopy studies showed that PLGA-PEI nanoparticles delivered the encapsulated siRNA in the cellular cytoplasm; both higher uptake and greater cytosolic delivery could have contributed to the gene silencing effectiveness of PLGA-PEI nanoparticles. Serum stability and lack of cytotoxicity further add to the potential of PLGA-PEI nanoparticles in gene silencing-based therapeutic applications.

Understanding the adsorption mechanism of chitosan onto poly(lactide-co-glycolide) particles

Polyelectrolyte-coated nanoparticles or microparticles interact with bioactive molecules (peptides, proteins or nucleic acids) and have been proposed as delivery systems for these molecules. However, the mechanism of adsorption of polyelectrolyte onto particles remains unsolved. In this study, cationic poly(lactide-co-glycolide) (PLGA) nanoparticles were fabricated by adsorption of various concentrations of a biodegradable polysaccharide, chitosan (0-2.4g/L), using oil-in-water emulsion and solvent evaporation techniques. The particle diameter, zeta-potential, and chitosan adsorption of chitosan-coated PLGA nanoparticles confirmed the increase of polyelectrolyte adsorption. Five adsorption isotherm models (Langmuir, Freundlich, Halsey, Henderson, and Smith) were applied to the experimental data in order to better understand the mechanism of adsorption. Both particle diameter and chitosan adsorption increased with chitosan concentration during adsorption. A good correlation was obtained between PLGA-chitosan nanoparticle size and adsorbed chitosan on the surface, suggesting that the increased particle size was primarily due to the increased chitosan adsorption. The zeta-potential of chitosan-coated PLGA nanoparticles was positive and increased with chitosan adsorbed until a maximum value (+55mV) was reached at approximately 0.4-0.6g/L; PLGA nanoparticles had a negative zeta-potential (-20mV) prior to chitosan adsorption. Chitosan adsorption on PLGA nanoparticles followed a multilayer adsorption behavior, although the Langmuir monolayer equation held at low concentrations of chitosan. The underlying reasons for adsorption of chitosan on PLGA nanoparticles were thought to be the cationic nature of chitosan, high surface energy and microporous non-uniform surface of PLGA nanoparticles.

Process considerations related to the microencapsulation of plasmid DNA via ultrasonic atomization

An effective means of facilitating DNA vaccine delivery to antigen presenting cells is through biodegradable microspheres. Microspheres offer distinct advantages over other delivery technologies by providing release of DNA vaccine in its bioactive form in a controlled fashion. In this study, biodegradable poly(D,L-lactide-co-glycolide) (PLGA) microspheres containing polyethylenimine (PEI) condensed plasmid DNA (pDNA) were prepared using a 40 kHz ultrasonic atomization system. Process synthesis parameters, which are important to the scale-up of microspheres that are suitable for nasal delivery (i.e., less than 20 microm), were studied. These parameters include polymer concentration; feed flowrate; volumetric ratio of polymer and pDNA-PEI (plasmid DNA-polyethylenimine) complexes; and nitrogen to phosphorous (N/P) ratio. PDNA encapsulation efficiencies were predominantly in the range 82-96%, and the mean sizes of the particle were between 6 and 15 microm. The ultrasonic synthesis method was shown to have excellent reproducibility. PEI affected morphology of the microspheres, as it induced the formation of porous particles that accelerate the release rate of pDNA. The PLGA microspheres displayed an in vitro release of pDNA of 95-99% within 30 days and demonstrated zero order release kinetics without an initial spike of pDNA. Agarose electrophoresis confirmed conservation of the supercoiled form of pDNA throughout the synthesis and in vitro release stages. It was concluded that ultrasonic atomization is an efficient technique to overcome the key obstacles in scaling-up the manufacture of encapsulated vaccine for clinical trials and ultimately, commercial applications.

Poly(D,L-lactide-co-glycolide) nanoparticle agglomerates as carriers in dry powder aerosol formulation of proteins

A dry powder aerosol drug delivery system was designed with both nano- and microstructure to maximize the protein loading via surface adsorption and to facilitate delivery to the deep lung, respectively. Ovalbumin was employed as a model protein to adsorb to and controllably flocculate DOTAP-coated PLG nanoparticles into "nanoclusters" possessing low density microstructure. The mechanism of nanoparticle flocculation was probed by evaluating the effects of ionic strength, shear force, and protein concentration on the geometric and aerodynamic diameters of the nanoclusters as well as the protein adsorption efficiency. Salt ions were found to compete with ovalbumin adsorption to nanoparticles and facilitate flocculation; therefore, formulation of nanoclusters for inhaled drug delivery may require the lowest possible ionic strength to maximize protein adsorption. Additional factors, such as shear force and total protein-particle concentration can be altered to optimize nanocluster size, suggesting the possibility of regional lung delivery. Immediate release of ovalbumin was observed, and native protein structure upon release was confirmed by circular dichroism and fluorescence spectroscopy studies. Controlled flocculation of nanoparticles may provide a useful alternative to spray drying when formulating dry powders for pulmonary or nasal administration of protein therapeutics or antigens.

Pulmonary applications and toxicity of engineered nanoparticles

Because of their unique physicochemical properties, engineered nanoparticles have the potential to significantly impact respiratory research and medicine by means of improving imaging capability and drug delivery, among other applications. These same properties, however, present potential safety concerns, and there is accumulating evidence to suggest that nanoparticles may exert adverse effects on pulmonary structure and function. The respiratory system is susceptible to injury resulting from inhalation of gases, aerosols, and particles, and also from systemic delivery of drugs, chemicals, and other compounds to the lungs via direct cardiac output to the pulmonary arteries. As such, it is a prime target for the possible toxic effects of engineered nanoparticles. The purpose of this article is to provide an overview of the potential usefulness of nanoparticles and nanotechnology in respiratory research and medicine and to highlight important issues and recent data pertaining to nanoparticle-related pulmonary toxicity.

Surface modification of microspheres with steric stabilizing and cationic polymers for gene delivery

In this paper, we describe surface modification of poly( D,L-lactide- co-glycolide) (PLG) microspheres, intended for DNA vaccine application, with two functionalities: a steric stabilizing component, provided by poly(vinyl alcohol) (PVA) and a cationic component, aimed at subsequent DNA surface loading. The cationic functionality arises from polycations, such as PEI, poly( L-lysine), trimethyl chitosan, and (dimethylamino)ethyl methacrylate, introduced into the water phase of classical oil-in-water (o/w) solvent evaporation method of PLG microsphere fabrication. By systematic evaluation of production variables, a system was produced with balanced properties in terms of microsphere size appropriate for uptake by antigen presenting (e.g., dendritic) cells, colloidal stability, and relatively high DNA loading. The polycation (PEI) molecular weight and preparation concentration were both found to increase the surface polycation content and DNA binding capacity; however, they lead to an increased tendency for aggregation, particularly when the microsphere size was decreased. DNA loading of almost 100% efficiency was achieved under optimized conditions in physiologically acceptable buffers, resulting in a surface DNA loading appropriate for vaccine purposes. A further increase in surface DNA loading was however associated with an increase in the particles negative potential, indicating the surface presence of DNA charges not neutralized by the polycation and hence potentially not protected from in vivo enzymatic degradation. The internalization of surface-loaded DNA into the target cells was confirmed by monitoring fluorescent DNA after the microspheres were endocytosed by the cells in culture.

Progress in developing cationic vectors for non-viral systemic gene therapy against cancer

Initially, gene therapy was viewed as an approach for treating hereditary diseases, but its potential role in the treatment of acquired diseases such as cancer is now widely recognized. The understanding of the molecular mechanisms involved in cancer and the development of nucleic acid delivery systems are two concepts that have led to this development. Systemic gene delivery systems are needed for therapeutic application to cells inaccessible by percutaneous injection and for multi-located tumor sites, i.e. metastases. Non-viral vectors based on the use of cationic lipids or polymers appear to have promising potential, given the problems of safety encountered with viral vectors. Using these non-viral vectors, the current challenge is to obtain a similarly effective transfection to viral ones. Based on the advantages and disadvantages of existing vectors and on the hurdles encountered with these carriers, the aim of this review is to describe the "perfect vector" for systemic gene therapy against cancer.

Poly(L-lactic acid)/polyethylenimine nanoparticles as plasmid DNA carriers

Non-viral vectors such as liposomes, polycations, and nanoparticles have been used as gene delivery systems. In this study, we prepared and characterized biodegradable poly(L-lactic acid) (PLA)/polyethylenimine (PEI) nanoparticles as gene carriers. pCMV/beta-gal and pEGFP-C1 were utilized as model plasmid DNAs (pDNA). Nanoparticles were prepared using a double emulsion-solvent evaporation technique, and their pDNA binding capacity was assessed by agarose gel electrophoresis. Transfection was studied in HEK 293 and HeLa cell lines, and the transfection efficiencies were determined by beta-galactosidase assay or flow cytometry. Three kinds of PLA/PEI systems were studied by varying the molecular weight of PEI. The PLA/PEI 25K system had a higher transfection efficiency than the PLA/PEI 0.8K or PLA/PEI 750K systems. The transfection efficiency was found to be dependent on the ratio of PLA/PEI nanoparticles to pDNA with an optimum ratio of 60:1 (w/w). The cytotoxicity was dependent on the quantity of PLA/PEI nanoparticles used, but it was comparable to that of commercial Lipofectin. These results demonstrate the potential of PLA/PEI nanoparticles as gene carriers.