Pharmaceutical Nanotechnology - Volume 1, Issue 3, 2013

Gene therapy is a promising approach for disease prevention and therapy. Efficient gene delivery is an important factor limiting gene delivery. Due to the poor stability of nucleotide molecules in vivo, they require an association with delivery systems to overcome extracellular and intracellular barriers and allow access to the site of action. In this review, we discuss the challenges currently encountered in the delivery of DNA and RNAi-based therapies using the most common cationic polymer assemblies including polylysines, chitosan, polyethylenimines, dendrimers, cyclodextrins and illustrate with examples how chemical modification of cationic assemblies may contribute to their successful application in the clinic.

Anticancer drugs are typically distributed non-specifically in the body, where they affect both cancerous and normal cells. This limits the drug level achievable within the tumor, compromising the therapeutic efficacy, and results in potential toxic effects on normal tissues. Targeted delivery of chemotherapeutics exclusively to cancer cells is the focus of intensive research for improvement of anticancer therapy. Various drug delivery systems have been investigated for this purpose, with therapeutic-carrying polymeric nanoparticulate systems designed for specific targeting of tumor cells receiving special interest. Chitosan, a natural polymer derived from crustacean shells, has attracted particular attention as a drug carrier. The simple and mild preparation methods, low toxicity, good stability, controlled drug release and the ability to overcome biological barriers have made chitosan-based nanoparticles popular in drug and gene delivery applications. Chitosan nanoparticles have been fabricated with optimal size and surface characteristics in order to tailor the behavior within the biological system, including circulation time, as well as passive and active cancer targeting. Folic acid is widely employed as a ligand targeting cancerous cells as its receptor which ‘shuttles’ folic acid into the cells via endocytosis is over-expressed on the surface of many human epithelial cancer cells. Incorporating folic acid into chitosan-based drug and gene delivery formulations renders the systems with an efficient targeting capacity. Furthermore, it is possible to formulate chitosan nanocarriers that display multiple useful characteristics extending beyond targeted delivery. The versatility of these systems is also being exploited in nanotheranostics.

The present work explores the preparation and characterization of chitosan/lecithin nanoparticles loaded with arteether (ART) and arteether entrapped in cyclodextrins (ART-β CD) to boost its anti-malarial activity. Arteether, an antimalarial drug was chosen by the Steering Committee of the Scientific Working Group on Malaria Chemotherapy of the WHO (CHEMAL) for treatment of cerebral malaria. Unfortunately, ART is water-insoluble drug (17 μg/ml at room temp.) and its therapeutic efficacy is greatly hampered due to poor bioavailability (∼40%, degradation in stomach acids). Moreover, Arteether have short plasma half-life which requires frequent administration. Formation of nanoparticles of ART can be a suitable solution to improve their Biopharmaceutical properties. The nanoparticles prepared using modified solvent evaporation method depicted a particle size in the range of 299-354 nm for arteether and 157-212 nm for ART-β CD loaded nanoparticles. 100 mg loaded ART and ART-β CD formulations showed maximum drug entrapment efficiency. Prepared nanoparticles reflected spherical shape inTEM images. Disappearance of decomposition endotherm in DSC scans of nanoparticles revealed the increased physical stability. FT-IR spectra showed small changes in major peaks of drug negating any chemical change in the drug when entrapped in the nanoparticle formulation. In vitro drug release studies suggested the controlled release as well as improved pattern. Enhanced antimalarial activity was observed in ART and ART-β CD containing nanoparticles.

The use of nanovesicles for enhanced topical/transdermal delivery of therapeutic agents has been extensively explored in recent years. In our previous study, nanovesicles ethosomes based gel formulation for topical delivery of anticancer drug 5-FU was developed for the treatment of actinic keratosis and non melanoma skin cancers. The exact mechanism of better skin permeation and deposition of drugs from ethosomes is not yet fully understood. Therefore, the investigation was aimed to understand the mechanism for better inter and intracellular drug delivery from ethosomes by quantitative estimation of skin lipids and microscopic evaluation of nanovesicles treated skin for lipid perturbation effects. Marketed 5-FU cream and drug solution were used as control for comparison purpose. Results of the biochemical estimation showed that nanovesicles gel formulation produced maximum perturbation of skin lipids as evidenced by highest quantity of cholesterol (30.2±1.7%) and triglycerides (26.4±0.9%) extracted after 24 h from excised rat skin. In comparison, percentage of cholesterol and triglyceride extracted with marketed cream and drug solution was found to be 5.2±0.2%, 2.3±0.3% and 4.4±0.1, 1.9±0.2%, respectively. Microscopic study revealed that nanovesicles gel formulation influenced the ultra structure of the skin. Distinct regions with lamellar stacks derived from vesicles were observed in the intracellular region of deeper skin layers. Results demonstrated that 5-FU nanovesicles gel formulation does not act only on superficial layers of the stratum corneum, but may also induce lipid perturbations in deeper layers of the skin, whereas the marketed 5-FU cream formulation remain fused on the top of stratum corneum causing an additional barrier to diffusion of the drug. The results of the present study demonstrated that the nanovesicles can forge paths in the disordered stratum corneum, change its biochemical constituents and finally release the drug in the deeper layers of the skin.

Polymeric micelles have received considerable interest for their use as drug delivery vehicles for hydrophobic drug solubilisation. Inorganic metallic nanoparticles have already been exploited clinically in diagnostics for their contrast ability, using magnetic resonance imaging. The combination of these two platforms results in a multifunctional drug carrier for image-guided drug delivery. Here we report the synthesis and evaluation of a new class of poly(allylamine) (PAA) polymer grafted with hydrophobic oxadiazole (Ox) pendant group in a 5% molar monomer: pendant ratio. Further, the thiol-containing pendant group facilitated the attachment of hybrid iron oxide-gold nanoparticles (HNPs) via dative covalent bonding. Physicochemical characterisation of both PAA-Ox5 and PAA-Ox5-HNP polymers was carried out using elemental analysis, nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FTIR) and photon correlation spectroscopy (PCS). The drug loading potential of these novel aggregates was investigated, through direct conjugation of hydrophilic and encapsulation of hydrophobic drugs, respectively. The model hydrophobic drugs 2,6- diisopropylphenol (propofol) and (2S,6'R)-7-chloro-2',4,6-trimethoxy-6'-methyl-3H,4'H-spiro[1-benzofuran-2,1'- cyclohex[2]ene]-3,4'-dione (griseofulvin), and the chemotherapeutic agents bisnapthalamidopropyldiaminooctane (BNIPDaoct) and 6-Thioguanine (6-TG) were used. The data showed that the addition of HNPs onto the PAA-Ox5 structure resulted in aggregates of 175 nm in diameter. The PAA-Ox5-HNP nano-aggregates were capable of high drug solubilisation capacities (25.79 mgmL-1, 1.68 mgmL-1 and 0.92 mgmL-1) for propofol, griseofulvin and BNIPDaoct, respectively. 6-TG was also successfully conjugated into the polymer structure (2.8 mgmL-1). In vitro assays on human pancreatic adenocarcinoma cells (BxPC-3) showed increased drug uptake and decreased IC50 values using the novel formulations compared with free drug. This study highlights the potential of PAA-Ox5-HNP as a bi-functional imaging and drug delivery platform.

Quatiepine, an effective atypical anti psychotic administered as fumarate or hemifumarate salts by intravenous injection shows poor brain uptake due to low partitioning and/or Pgp efflux. In order to improve their brain availability, solid lipid nanoparticles (SLN) loaded with Quetiapine fumarate or hemifumarate were prepared using glyceryl monostearate (GMS), poloxamer 407 and hydrogenated soya phosphatidylcholine (HSPC) as stabilizers—using a hot melt emulsification high- pressure homogenization technique. They were characterized for physical characteristics like particle size, polydispersity (PDI), shape and entrapment efficiency (EE). Fomulation and process parameters were optimized based on particle size, PDI and EE. SLNs with a mean particle size of 101.1 nm were obtained for quetiapine fumarate and 93.6 nm for quetiapine hemifumarate. In-vitro drug release study showed the release followed Higuchi kinetics model for both the formulations. In-vivo studies showed a significant increase in the percentage of drug reaching the brain when administered in the form of SLN’s as compared to the respective drug solutions and the increase was greater in case of quetiapine hemifumarate salt.