Current Drug Delivery - Volume 2, Issue 3, 2005

Photo-cation generatable water-soluble polymers (Mw: approximately 1 x 10 5) were prepared by radical copolymerization of N,N-dimethylacrylamide and vinyl monomer of triphenylmethane leucohydroxide (malachite green), which generate a cation upon ultraviolet light (UV) irradiation at wavelengths of between 290 and 410 nm. The malachite green contents of the copolymers were 3.6 (0.4 mol %), 7.9 (0.7 mol %), and 15.0 (2.7 mol %) per molecule. When an aqueous solution of the photo-cationized copolymers generated by UV irradiation was mixed with a Tris-HCl buffer (pH 7.4) of DNA (pGL3-control plasmid), dynamic light scattering (DLS) measurements showed the formation of polyplexes between the cationic copolymers and anionic DNA by non-specific electrostatic interaction, which was visualized with a confocal laser scanning microscopy (CLMS). Their mean cumulant diameter was about 150 nm with low polydispersity irrespective of the malachite green content in the copolymers. In the copolymer with the lowest malachite green content, almost all of the amount of the polyplexes was maintained by repeated UV irradiation, but the amount gradually decreased in the dark at 37°C due to dissociation of the polyplexes, synchronized with the neutralization of the cation form of malachite green. The photo-cation generatable copolymers designed here can undergo photo-induced formation of the polyplexes with DNA and thermal polyplex dissociation, which may be used as a model for a novel photo-induced gene delivery system into cells.

The glycosyltransferase enzyme LgtA, derived from the bacterial pathogen Neisseria meningitidis, was utilised in the chemo-enzymatic synthesis of a trisaccharide-linked endomorphin peptide drug candidate.

The aim of the present study was to prepare and characterize novel vesicular carrier elastic liposomes, of most commonly used non-steroidal anti-inflammatory agent diclofenac for its sustained and targeted delivery. Elastic liposomes of diclofenac were prepared and characterized in vitro and in vivo. The effect of different formulation variables like type of surfactant, concentration of surfactant and dose of drug on transdermal flux, amount of drug deposited into the skin, muscle and plasma concentration was investigated. The biological activity of optimized formulation was evaluated using carrageenan induced rat paw edema model and results were compared with commercial hydrogel formulation. The elastic liposomal formulations achieved muscle drug concentration between 2.2 ± 0.14 to 5.3 ± 0.22 μg/g at 12hr. The same dose of commercial hydrogel formulation produced drug levels between 0.41 ± 0.07 to 1.1 ± 0.09 μg/g in the muscle. Plasma concentration study showed regiospecificity of elastic liposomal formulation. The results of in vivo study revealed that incorporation of diclofenac in elastic liposomes increased its biological activity two fold as compared to commercial hydrogel formulation. The results of the present study demonstrated greater effectiveness of dermaly applied diclofenac elastic liposomal formulation in comparison to conventional delivery system. The optimized elastic liposomal formulation offers a promising means for the non-invasive treatment of local pain and inflammation by topical application.

The objective of the present study was to develop chitosan-based mucoadhesive microspheres of clarithromycin to provide prolonged contact time for drug delivery of antibiotics to treat stomach ulcers. Microspheres based mucoadhesive formulation were extensively evaluated and characterized for in vitro performance followed by investigation of in vivo pharmacokinetics in rats. Microspheres were prepared by emulsification technique using glutaraldehyde as a crosslinking agent. Formulation conditions were optimized for percent drug entrapment and mucoadhesion, by varying different formulation and process parameters like drug to polymer ratio, concentration of crosslinking agent and time of crosslinking. Prepared microspheres were evaluated extensively for particle size, percent drug entrapment, swelling kinetics, in vitro mucoadhesion using rat stomach membrane and in vitro drug release studies. In vitro permeation studies across rat stomach membrane were carried out to determine diffusion parameters and drug retention in the stomach membrane of the formulation and the plain drug. Finally in vivo performance of microsphere formulation in comparison to plain drug was evaluated by pharmacokinetic studies in albino rats. Drug entrapment upto 74% was obtained. Swelling studies indicated that with an increase in cross-linking, the swelling ability decreased. The in vitro drug release and in vitro mucoadhesion studies showed a dependence on the extent of cross-linking and concentration of chitosan. Extent of cross-linking exhibited an inverse relation to drug release rate as well as mucoadhesion, whereas polymer concentration exhibited an inverse correlation with drug release while linear relationship with mucoadhesion (up to 86%). In vitro permeation studies across stomach tissue showed higher accumulation of drug in the stomach tissue with microspheres formulation as compared to that of free drug. This is evident from higher value of K (partition coefficient) and Qm/Csf values for microspheres (68.34 and 106.42 X 10 3, respectively) as compared to that of free drug (1.86 and 173.00, respectively). These findings when analyzed showed an increase in the bioavailability of clarithromycin from microsphere formulation as compared to plain drug suspension in vivo, with AUC 0→α being 91.7 (μg h/ml)and 24.9 (μg h/ml) respectively. Results of the study demonstrated good mucoadhesion of the microspheres with the stomach mucosa as well as higher accumulation of drug in the stomach membrane. Microspheres also exhibited sustained release of drug. Thus chitosan microspheres appear, technically, promising mucoadhesive drug delivery systems for delivering clarithromycin to treat stomach ulcers.

Cancer gene therapy has been intensively developed using non-viral vectors, among which cationic liposomes and nanoparticles are the most thoroughly investigated. For targeted delivery to tumors, vitamin folic acid has been utilized for folate receptor (FR)-mediated drug delivery, since FR is frequently overexpressed on many types of human tumors. Liposomes conjugated to folate ligand have been used as carriers of chemotherapeutic agents and DNA to receptor- bearing tumor cells in vitro. As an alternative treatment for prostate cancer, suicide gene therapy by local injection using an adenoviral vector has been reported, but not that using non-viral vectors. The folate-linked, lipid-based nanoparticles which we developed could deliver genes extensively to FR-negative LNCaP and PC-3 cells, as well as FRpositive KB and Hela cells. In this review, we outline folate-linked liposomes and nanoparticles, and show the effectiveness of folate-linked, lipid-based nanoparticles as a vector for DNA transfection and for suicide gene therapy, to treat human nasopharyngeal and prostate tumors.

Over the last few years, considerable advances have been made in the field of nanotechnology. The advent of carbon nanotube functionalization has paved the way for their potential application as a delivery system of diverse molecules such as peptides, proteins, plasmid DNA, and synthetic oligodeoxynucleotides. This opens new therapeutic and preventive opportunities to combat diseases. The scope of this review is to summarize our recent work in this rapidly growing field.

Superoxide, hydrogen peroxide, hydroxyl radicals and peroxynitrite are collectively termed reactive oxygen and nitrogen species (RONS). They have been ascribed an important role in oxidative stress contributing to the progression of inflammatory diseases. RONS generating systems include the inflammatory response, enzymatic pathways and as side products of catabolism. Protective enzymes exist for the regulation of RONS such as superoxide dismutase, catalase and glutathione peroxidase. Furthermore, vitamins play a secondary role in deactivating RONS. The redox active metal ions such as ferrous and cuprous ions are released from the storage proteins ferritin and caeruloplasmin by RONS. Redox active metal ions further activate/generate RONS and thus perpetuate their damaging effects. Here we report recent therapies that focus on intervening in the roles of metal ions in oxidative stress. These include: i) chelators which complex labile metal ions to form antioxidant enzyme mimetics, ii) site-specific RONS scavengers, where dual functionality colocalizes the scavenger and chelation centre to direct scavenging, and iii) redox silencing, metal complexation with concomitant stabilization of the metal ion in the oxidized form to prevent further activation of RONS. The rationale for this new therapeutic approach and recent advances will be presented in this review.

The rationale behind this work was that a permeation enhancing carrier could facilitate the transport of antibacterial molecules through the two biological barriers: stratum corneum of the skin and bacterial membrane/cell wall. To this end, erythromycin ethosomes (EE) were designed and characterized, and their antibacterial efficiency was evaluated in vitro and in vivo. TEM, CLSM, DLS, DSC and ultracentrifugation tests indicate that EE are small unilamellar soft vesicles encapsulating 78.6% erythromycin. The compositions were stable for at least one year at room temperature. In live/dead viability/cytotoxicity tests, EE systems were nontoxic to cultured 3T3 dermal fibroblasts. Susceptibility studies conducted on three bacterial strains (B. subtilis ATCC 6633, S. aureus ATCC 29213 and S. aureus clinically resistant to erythromycin) showed significantly larger inhibition zones for EE as compared to erythromycin in hydroethanolic solutions. Moreover, EE reduced erythromycin MIC as compared to control solution: from 2.5 to 1.25μg/ml for S. aureus ATCC 29213 and from 12.5 to 5.0μg/ml for clinically isolated resistant S. aureus strain. Ethosomal erythromycin applied to the skin of ICR mice inoculated with 10 7cfu S. aurues ATCC 29213 resulted in complete inhibition of infection. On the contrary, when hydroethanolic solution of erythromycin was applied, deep dermal and subcutaneous abscesses developed within five days after challenge. On day seven, a similar number of S. aureus colonies (1.06x10 7 vs. 0.90x10 7 cfu/g tissue) were isolated from the untreated wounds or treated with hydroethanolic erythromycin. For these animals, histopathological examination showed necrosis, destroyed skin structures and dense infiltrates of neutrophils and macrophages. These findings show that ethosomes are efficient carriers for erythromycin delivery to bacteria localized within the deep skin strata for eradication of staphylococcal infections.

A review with 93 references. Heparins are high molecular weight, hydrophilic polyanions, which are unstable under acidic conditions; and therefore they exhibit poor oral bioavailability. Consequently they must be administered via the parenteral route which is expensive, inconvenient, and limits use by outpatients. The development of an oral form of heparin is warranted. This review examined the literature, mostly published between January 2000 and January 2005, pertaining to the gastrointestinal absorption of heparin by lipidization or coadministration with penetration enhancers. A lipidization strategy that was examined involved conjugation of low molecular weight heparin with deoxycholic acid. The majority of studies examined the ability of different formulations, typically utilizing penetration enhancers, to improve heparin bioavailability. The penetration enhancers used included fatty acids, Labrasol™, Gelucire 44/14™, polycationic lipophilic-core dendrons, saponins, mono-N-carboxymethyl chitosan, Carbopol® 934P, a combination of thiolated polycarbophil and glutathione, polymeric nanoparticles, polymeric microparticles, sodium N-[8-(2-hydroxybenzoyl) amino]caprylate (SNAC), and sodium N-[10-(2-hydroxybenzoyl)amino]decanoate (SNAD). The variety of models used and doses of heparin/penetration enhancers applied, however, made it difficult to compare the results between studies. Nevertheless, all of the reviewed drug delivery systems showed therapeutic value and confirmation of the promising results obtained from animal studies, by progression to clinical trials, is necessary. Overall, progress has been made in the quest for an oral heparin formulation.

The purpose of this study was to evaluate and compare the effect of glycerides with different fatty acid distributions (e.g. Arlacel 186, Capmul GMO and Captex 350) on Cyclosporine absorption in rat ileum segment using the modified single-pass intestinal perfusion with mesenteric vein cannulation. Drug concentration in the perfusate and blood plasma was analyzed by HPLC; and permeability coefficients were calculated from drug appearance in blood (Pblood) and disappearance from perfusate (Plumen). Particle size was measured using Malvern Zetasaizer 1000HSA. Rheologic properties were measured using Brookfield viscometer. The results show that the average particle sizes after dilution (100 folds) of formulae containing Arlacel 186, Capmul GMO and Captex 350 and containing 0.8 mM CsA were 260± 35.8, 130± 11.4 and 37.5± 6.0 nm, respectively. The polydispersity index was 0.6, 0.7 and 0.108 for formulations with Arlacel 186, Capmul GMO and Captex 350, respectively. CsA permeability coefficients (Pblood) calculated from drug appearance in the blood in presence of Arlacel 186, Capmul GMO and Captex 350 were 0.3x10-6, 1.0x10-6 and 1.7x10-6 cm2/sec, respectively. Phenol red was used as a water marker to determine net water absorption and secretion. Its constant concentration suggested that formulation did not alter intestinal water flux. From the results we can conclude that degree of glyceride esterification has a potential impact on the average particle size distribution and polydispersity of the formed micelles on dilution, which on turn contribute to the interaction between membrane and drug.