Effect of preparative variables on small interfering RNA loaded Poly(D,L-lactide-co-glycolide)-chitosan submicron particles prepared by emulsification diffusion method

PLGA nanoparticle preparations by emulsification and nanoprecipitation techniques: effects of formulation parameters

This study presents the influence of the primary formulation parameters on the formation of poly-dl-lactic-co-glycolic nanoparticles by the emulsification-solvent evaporation, and the nanoprecipitation techniques. In the emulsification-solvent evaporation technique, the polymer and tensoactive concentrations, the organic solvent fraction, and the sonication amplitude effects were analyzed. Similarly, in the nanoprecipitation technique the polymer and tensoactive concentrations, the organic solvent fraction and the injection speed were varied. Additionally, the agitation speed during solvent evaporation, the centrifugation speeds and the use of cryoprotectants in the freeze-drying process were analyzed. Nanoparticles were characterized by dynamic light scattering, laser Doppler electrophoresis, and scanning electron microscopy, and the results were evaluated by statistical analysis. Nanoparticle physicochemical characteristics can be adjusted by varying the formulation parameters to obtain specific sizes and stable nanoparticles. Also, by adjusting these parameters, the nanoparticle preparation processes have the potential to be tuned to yield nanoparticles with specific characteristics while maintaining reproducible results.

This study presents the influence of the primary formulation parameters on the formation of poly-dl-lactic-co-glycolic nanoparticles by the emulsification-solvent evaporation, and the nanoprecipitation techniques.

Cell penetrating peptide-modified poly(lactic-co-glycolic acid) nanoparticles with enhanced cell internalization

The surface modification of nanoparticles (NPs) can enhance the intracellular delivery of drugs, proteins, and genetic agents. Here we studied the effect of different surface ligands, including cell penetrating peptides (CPPs), on the cell binding and internalization of poly(lactic-co-glycolic) (PLGA) NPs. Relative to unmodified NPs, we observed that surface-modified NPs greatly enhanced cell internalization. Using one CPP, MPG (unabbreviated notation), that achieved the highest degree of internalization at both low and high surface modification densities, we evaluated the effect of two different NP surface chemistries on cell internalization. After 2h, avidin-MPG NPs enhanced cellular internalization by 5 to 26-fold relative to DSPE-MPG NP formulations. Yet, despite a 5-fold increase in MPG density on DSPE compared to Avidin NPs, both formulations resulted in similar internalization levels (48 and 64-fold, respectively) after 24h. Regardless of surface modification, all NPs were internalized through an energy-dependent, clathrin-mediated process, and became dispersed throughout the cell. Overall both Avidin- and DSPE-CPP modified NPs significantly increased internalization and offer promising delivery options for applications in which internalization presents challenges to efficacious delivery.

Reversal of multidrug resistance in vitro by co-delivery of MDR1 targeting siRNA and doxorubicin using a novel cationic poly(lactide-co-glycolide) nanoformulation

Over expression of drug efflux transporters such as P-glycoprotein (P-gp) cumulatively leading to multidrug resistance (MDR) embodies a major hindrance for successful cancer therapy. A paradigm nanomedicinal approach involving an anticancer drug and modulators of drug resistance within one multifunctional nanocarrier-based delivery system represent an ideal modality for the treatment of MDR. In this regards, we have developed a cationic polymeric nanoparticulate system loaded with MDR1-siRNA and doxorubicin. Results indicated augmented synergistic effect of combinational nanoformulation in overcoming MDR in MCF-7/ADR cells. Therefore, the above regime could be a promising co-delivery system for effective therapy of drug resistant breast cancer.

Anti-epidermal growth factor receptor siRNA carried by chitosan-transacylated lipid nanocapsules increases sensitivity of glioblastoma cells to temozolomide

Epidermal growth factor receptor (EGFR) is a crucial protein that plays an important role in the maintenance and development of glioblastomas. The silencing or knockdown of EGFR is possible by administering a small interfering ribonucleic acid (siRNA). Lipid nanocapsules (LNCs) covered by chitosan were developed in our laboratory by a transacylation process. The resulting nanocapsules have a positive zeta potential that enables electrostatic interactions with the negatively-charged siRNA. Prior to transfection, the cytotoxicity of the nanocapsules by (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) test was performed on the U87MG cell line to determine non-toxic levels of the LNCs to avoid cell mortality. Treatment of the U87MG cells with the chitosan-transacylated LNCs/anti-EGFR siRNA complex resulted in a reduction of EGFR expression by 51.95% ± 6.03% (P ≤ 0.05) after 96 hours of incubation. It also increased the cellular sensitivity to temozolomide in comparison to untreated cells with siRNA. The largest increase in mortality was 62.55% ± 3.55% (P<0.05). This successful knockdown provides proof for the concept of surface grafting of siRNA onto LNCs to modify cell sensitivity to temozolomide. The method could be implemented in future clinical models regarding the experimental treatment of glioblastoma cancer.

Mechanisms of chitosan-coated poly(lactic-co-glycolic acid) nanoparticles for improving oral absorption of 7-ethyl-10-hydroxycamptothecin

Chitosan-modified poly(lactic-co-glycolic acid) nanoparticles (CHI/PLGA NPs) loaded with 7-ethyl-10-hydroxycamptothecin (SN-38), named CHI/PLGA/SN-38 NPs, were successfully prepared using an oil-in-water (O/W) solvent evaporation method. The physicochemical properties of the novel NPs were characterized by DLS, Zeta potential, SEM, DSC, XRD, and FTIR. The encapsulation efficiency and drug loading content were 71.83 (±2.77)% and 6.79 (±0.26)%, respectively. In vitro drug release in the simulated gastric juice was lower than that in the intestinal juice. In situ single-pass intestinal perfusion (SPIP) studies indicated a dramatic improvement of drug absorption as a result of the synergistic effect between CHI and PLGA on P-glycoprotein (Pgp) inhibition. CHI/PLGA NPs showed high cellular uptake and low efflux for drugs in Caco-2 cells. The cytotoxicity studies revealed that CHI/PLGA NPs had a transient effect on the membrane integrity, but did not have an influence on cell viability. Based on the in vitro release studies, SPIP, and intracellular drug accumulation and transport investigations, we speculate rationally that CHI/PLGA NPs were mainly internalized in the form of intact NPs, thus escaping the recognition of enterocyte Pgp and avoiding efflux into the apical part of the enterocytes. After partial release of drugs inside the enterocytes, CHI/PLGA interfered with the microenvironment of Pgp and further weakened the Pgp-mediated efflux. Then, the drug-loaded NPs exited via the exocytose effect from the basal part of the enterocytes and entered the blood circulation. These results showed that CHI/PLGA NPs would be smart oral delivery carriers for antineoplastic agents that are also Pgp substrates.

Low molecular weight chitosan conjugated with folate for siRNA delivery in vitro: optimization studies

The low transfection efficiency of chitosan is one of its drawbacks as a gene delivery carrier. Low molecular weight chitosan may help to form small-sized polymer-DNA or small interfering RNA (siRNA) complexes. Folate conjugation may improve gene transfection efficiency because of the promoted uptake of folate receptor-bearing cells. In the present study, chitosan was conjugated with folate and investigated for its efficacy as a delivery vector for siRNA in vitro. We demonstrate that the molecular weight of chitosan has a major influence on its biological and physicochemical properties, and very low molecular weight chitosan (below 10 kDa) has difficulty in forming stable complexes with siRNA. In this study, chitosan 25 kDa and 50 kDa completely absorbed siRNA and formed nanoparticles (≤220 nm) at a chitosan to siRNA weight ratio of 50:1. The introduction of a folate ligand onto chitosan decreased nanoparticle toxicity. Compared with chitosan-siRNA, folate-chitosan-siRNA nanoparticles improved gene silencing transfection efficiency. Therefore, folate-chitosan shows potential as a viable candidate vector for safe and efficient siRNA delivery.

Design of an inhalable dry powder formulation of DOTAP-modified PLGA nanoparticles loaded with siRNA

Matrix systems based on biocompatible and biodegradable polymers like the United States Food and Drug Administration (FDA)-approved polymer poly(DL-lactide-co-glycolide acid) (PLGA) are promising for the delivery of small interfering RNA (siRNA) due to favorable safety profiles, sustained release properties and improved colloidal stability, as compared to polyplexes. The purpose of this study was to design a dry powder formulation based on cationic lipid-modified PLGA nanoparticles intended for treatment of severe lung diseases by pulmonary delivery of siRNA. The cationic lipid dioleoyltrimethylammoniumpropane (DOTAP) was incorporated into the PLGA matrix to potentiate the gene silencing efficiency. The gene knock-down level in vitro was positively correlated to the weight ratio of DOTAP in the particles, and 73% silencing was achieved in the presence of 10% (v/v) serum at 25% (w/w) DOTAP. Optimal properties were found for nanoparticles modified with 15% (w/w) DOTAP, which reduced the gene expression with 54%. This formulation was spray-dried with mannitol into nanocomposite microparticles of an aerodynamic size appropriate for lung deposition. The spray-drying process did not affect the physicochemical properties of the readily re-dispersible nanoparticles, and most importantly, the in vitro gene silencing activity was preserved during spray-drying. The siRNA content in the powder was similar to the theoretical loading and the siRNA was intact, suggesting that the siRNA is preserved during the spray-drying process. Finally, X-ray powder diffraction analysis demonstrated that mannitol remained in a crystalline state upon spray-drying with PLGA nanoparticles suggesting that the sugar excipient might exert its stabilizing effect by sterical inhibition of the interactions between adjacent nanoparticles. This study demonstrates that spray-drying is an excellent technique for engineering dry powder formulations of siRNA nanoparticles, which might enable the local delivery of biologically active siRNA directly to the lung tissue.

Delivery of siRNA therapeutics: barriers and carriers

RNA interference is a naturally occurring endogenous regulatory process where short double-stranded RNA causes sequence-specific posttranscriptional gene silencing. Small interference RNA (siRNA) represents a promising therapeutic strategy. Clinical evaluations of siRNA therapeutics in locoregional treatment settings began in 2004. Systemic siRNA therapy is hampered by the barriers for siRNA to reach their intended targets in the cytoplasm and to exert their gene silencing activity. The three goals of this review were to provide an overview of (a) the barriers to siRNA delivery, from the perspectives of physicochemical properties of siRNA, pharmacokinetics and biodistribution, and intracellular trafficking; (b) the non-viral siRNA carriers including cell-penetrating peptides, polymers, dendrimers, siRNA bioconjugates, and lipid-based siRNA carriers; and (c) the current status of the clinical trials of siRNA therapeutics.