Dendrimers as a Carrier for Pulmonary Delivery of Enoxaparin, a Low-Molecular Weight Heparin

PAMAM dendrimers as aerosol drug nanocarriers for pulmonary delivery via nebulization

Polyamidoamine (PAMAM) dendrimers were evaluated as nanocarriers for pulmonary delivery of the model poorly soluble anti-asthma drug beclometasone dipropionate (BDP) using G3, G4 and G4(12) dendrimers. BDP-loaded dendrimers were characterized for drug solubility, in vitro drug release and aerosolization properties using three nebulizers: Pari LC Sprint (air-jet), Aeroneb Pro (actively vibrating-mesh) and Omron MicroAir (passively vibrating-mesh) nebulizers. Solubilization of BDP using dendrimers was increased by increasing the dendrimer generation and by using higher pH media. In vitro release studies showed that BDP when complexed with dendrimers exhibited a sustained release, and for all dendrimer formulations less than 35% of the drug was released after 8h. Nebulization studies revealed that aerosol performance was dependent on nebulizer rather than dendrimer generation. Nebulization output values for the Pari (air-jet) and Aeroneb Pro (active mesh) nebulizers were in the range of 90-92% and 85-89% respectively compared to 57-63% for the Omron (passive mesh) nebulizer. The size of the droplets generated from the jet nebulizer was slightly smaller and aerosol polydispersity was lower compared to both mesh devices. The "fine particle fraction (FPF)" of the aerosols was in the following order: Pari (air-jet)>Aeroneb Pro (active mesh)>Omron (passive mesh). This study demonstrates that BDP-dendrimers have potential for pulmonary inhalation using air-jet and vibrating-mesh nebulizers. Moreover, the aerosol characteristics are influenced by nebulizer design rather than dendrimer generation.

A simple new competition assay for heparin binding in serum applied to multivalent PAMAM dendrimers

We report a competition assay using our recently reported dye Mallard Blue, which allows us to identify synthetic heparin binders in competitive media, including human serum - using this we gain insight into the ability of PAMAM dendrimers to bind heparin, with the interesting result that low-generation G2-PAMAM is the preferred heparin binder.

Expand classical drug administration ways by emerging routes using dendrimer drug delivery systems: a concise overview

Drugs are introduced into the body by numerous routes such as enteral (oral, sublingual and rectum administration), parenteral (intravascular, intramuscular, subcutaneous and inhalation administration), or topical (skin and mucosal membranes). Each route has specific purposes, advantages and disadvantages. Today, the oral route remains the preferred one for different reasons such as ease and compliance by patients. Several nanoformulated drugs have been already approved by the FDA, such as Abelcet®, Doxil®, Abraxane® or Vivagel®(Starpharma) which is an anionic G4-poly(L-lysine)-type dendrimer showing potent topical vaginal microbicide activity. Numerous biochemical studies, as well as biological and pharmacological applications of both dendrimer based products (dendrimers as therapeutic compounds per se, like Vivagel®) and dendrimers as drug carriers (covalent conjugation or noncovalent encapsulation of drugs) were described. It is widely known that due to their outstanding physical and chemical properties, dendrimers afforded improvement of corresponding carried-drugs as dendrimer-drug complexes or conjugates (versus plain drug) such as biodistribution and pharmacokinetic behaviors. The purpose of this manuscript is to review the recent progresses of dendrimers as nanoscale drug delivery systems for the delivery of drugs using enteral, parenteral and topical routes. In particular, we focus our attention on the emerging and promising routes such as oral, transdermal, ocular and transmucosal routes using dendrimers as delivery systems.

Pulmonary administration of PEGylated polylysine dendrimers: absorption from the lung versus retention within the lung is highly size-dependent

The systemic delivery of drugs via the inhaled route is an attractive, needle-free means of improving the systemic exposure of molecules such as peptides and proteins that are poorly absorbed after oral administration. Directed delivery into the lungs also provides a means of increasing drug concentrations at the site of action for lung-specific disease states such as pulmonary infections and lung cancer. The current study has examined the potential utility of PEGylated polylysine dendrimers as pulmonary delivery agents and in particular sought to explore the relationship between dendrimer size and absorption of the intact construct (as a potential systemic delivery mechanism) versus retention within the lungs (as a potential pulmonary depot for controlled local release). Dendrimer absorption from the lungs was inversely correlated with molecular weight, with approximately 20-30% of the dose of relatively small (<22 kDa) dendrimers systemically absorbed compared to only 2% absorption for a larger (78 kDa) PEGylated dendrimer. Increasing the molecular weight of the dendrimers led to slower absorption and more prolonged retention in the lung tissue and bronchoalveolar lavage fluid. Oral administration of the two smaller dendrimers confirmed that oral bioavailability of the PEGylated dendrimers was essentially zero and did not contribute to exposure after pulmonary administration. The smaller PEGylated dendrimers were also degraded in the lungs to low molecular weight products that were subsequently absorbed and excreted via the urine, while the larger constructs showed good stability in the lungs. The data suggest first, that small PEGylated dendrimer-based drug delivery systems may be delivered to the blood via inhalation, providing a more attractive alternative to injections, and second that larger PEGylated dendrimers may be retained in the lungs providing the potential for controlled delivery of medications to the blood or lung tissue.

Novel engineered systems for oral, mucosal and transdermal drug delivery

Technological advances in drug discovery have resulted in increasing number of molecules including proteins and peptides as drug candidates. However, how to deliver drugs with satisfactory therapeutic effect, minimal side effects and increased patient compliance is a question posted before researchers, especially for those drugs with poor solubility, large molecular weight or instability. Microfabrication technology, polymer science and bioconjugate chemistry combine to address these problems and generate a number of novel engineered drug delivery systems. Injection routes usually have poor patient compliance due to their invasive nature and potential safety concerns over needle reuse. The alternative non-invasive routes, such as oral, mucosal (pulmonary, nasal, ocular, buccal, rectal, vaginal), and transdermal drug delivery have thus attracted many attentions. Here, we review the applications of the novel engineered systems for oral, mucosal and transdermal drug delivery.

A Serum-Resistant Low-Generation Polyamidoamine with PEI 423 Outer Layer for Gene Delivery Vector

A new derivative of polyamidoamine and polyethylenimine, G2.5-PEI 423 or G1.5-PEI 423, is prepared by an amidation reaction of PAMAM G2.5 or PAMAM G1.5 using PEI 423. The polycations show a great ability to combine with pDNA to form complexes, which protect the pDNA from nuclease degradation. The polymers display stronger buffer capacity and lower cytotoxicity. The complexes have particle sizes of 120-180 nm and zeta potentials of 20-40 mV. The G2.5-PEI 423 complexes display much higher transfection efficiencies than PAMAM G5 and Lipo-2k, and the G1.5-PEI 423 complexes display higher transfection efficiencies than PAMAM G4 and PEI-25k. The complexes possess better serum-resistant capacity. The G2.5-PEI 423 has a great potential to be used as a serum-resistant gene vector.

Comparative studies on chitosan and polylactic-co-glycolic acid incorporated nanoparticles of low molecular weight heparin

This study was performed to test the feasibility of chitosan and polylactic-co-glycolic acid (PLGA) incorporated nanoparticles as sustained-release carriers for the delivery of negatively charged low molecular weight heparin (LMWH). Fourier transform infrared (FTIR) spectrometry was used to evaluate the interactions between chitosan and LMWH. The shifts, intensity, and broadening of the characteristic peaks for the functional groups in the FTIR spectra indicated that strong interactions occur between the positively charged chitosans and the negatively charged LMWHs. Three types of LMWH nanoparticles (NP-1, NP-2, and NP-3) were prepared using chitosan with or without PLGA: NP-1 nanoparticles were formed by polyelectrolyte complexation after single mixing, NP-2 nanoparticles were prepared by polyelectrolyte complexation after single emulsion-diffusion-evaporation, and NP-3 nanoparticles were optimized by double emulsion-diffusion-evaporation. NP-3 nanoparticles of LMWH prepared by the emulsion-diffusion-evaporation method showed significant differences in particle morphology, size, zeta potential, and drug release profile compared to NP-1 nanoparticles formed by polyelectrolyte complexation. Another ionic complex of LMWH with chitosan-incorporated PLGA nanoparticles (NP-2) showed lower drug entrapment efficiency than that of NP-1 and NP-3. The drug release rate of NP-3 was slower than the release rates of NP-1 and NP-2, although particle morphology of NP-3 was similar to that of NP-2. Cell viability was not adversely affected when cells were treated with all three types of nanoparticles. The data presented in this study demonstrate that nanoparticles formulated with chitosan-PLGA could be a safe sustained-release carrier for the delivery of LMWH.

Deep vein thrombosis: current status and nanotechnology advances

Deep vein thrombosis (DVT) affects up to 2 million people in the United States, and worldwide incidence is 70 to 113 cases per 100,000 per year. Mortality from DVT is often due to subsequent pulmonary embolism (PE). Precise diagnosis and treatment is thereby essential for the management of DVT. DVT is diagnosed by a thorough history and physical examination followed by laboratory and diagnostic tests. The choice of laboratory and diagnostic test is dependent on clinical pretest probability. Available laboratory and diagnostic techniques mainly involve D-dimer test, ultrasound, venography, and magnetic resonance imaging. The latter two diagnostic tools require high doses of contrast agents including either radioactive or toxic materials. The available treatment options include lifestyle modifications, mechanical compression, anticoagulant therapy, inferior vena cava filter, and thrombolysis/thrombolectomy. All of these medical and surgical treatments have serious side effects including improper clot clearance and increased risk of hemorrhage occurrence. Therefore, research in this field has recently focused on the development of non-invasive and accurate diagnostics, such as ultrasound enhanced techniques and molecular imaging methods, to assess thrombus location and its treatment course. The frontier of nanomedicine also shows high prospects in tackling DVT with efficient targeted drug delivery. This review describes the pathology of DVT along with successive medical problems such as PE and features a detailed listing of various diagnostic and therapeutic modalities that have been in use and are under development.

Strategies for non-invasive delivery of biologics

Macromolecular therapeutics, in particular, many biologics, is the most advancing category of drugs over conventional chemical drugs. The potency and specificity of the biologics for curing certain disease made them to be a leading compound in the pharmaceutical industry. However, due to their intrinsic nature, including high molecular weight, hydrophilicity and instability, they are difficult to be administered via non-invasive route. This is a major quest especially in biologics, as they are frequently used clinically for chronic disorders, which requires long-term administration. Therefore, many efforts have been made to develop formulation for non-invasive administration, in attempt to improve patient compliance and convenience. In this review, strategies for non-invasive delivery, in particular, oral, pulmonary and nasal delivery, that are recently adopted for delivery of biologics are discussed. Insulin, calcitonin and heparin were mainly focused for the discussion as they could represent protein, polypeptide and polysaccharide drugs, respectively. Many recent attempts for non-invasive delivery of biologics are compared to provide an insight of developing successful delivery system.

Liposomes for cardiovascular targeting

Liposome-based pharmaceuticals used within the cardiovascular system are reviewed in this article. The delivery of diagnostic and therapeutic agents by plain liposomes and liposomes with surface-attached targeting antibodies or polyethylene glycol to prolong their circulation time and accumulation at vascular injuries, ischemic zones or sites of thrombi are also discussed. An overview of the advantages and disadvantages of liposome-mediated in vitro, ex vivo and in vivo targeting is presented, including discussion of the targeting of liposomes to pathological sites on the blood vessel wall and a description of liposomes that can be internalized by endothelial cells. Diagnostic liposomes used to target myocardial infarction and the relative importance of liposome size, targetability of immunoliposomes and prolonged circulation time on the efficiency of sealing hypoxia-induced plasma membrane damage to cardiocytes are discussed as a promising approach for therapy. The progress in the use of targeted liposomal plasmids for the transfection of hypoxic cardiomyocytes and myocardium is presented. Stent-mediated liposomal-based drug delivery is also reviewed briefly.

A spoonful of sugar makes the melanoma go: the role of heparan sulfate proteoglycans in melanoma metastasis

Heparan sulfate proteoglycans (HSPGs) have been shown to regulate signaling in many systems and are of increasing interest in cancer. While these are not the only sugars to drive melanoma metastasis, HSPGs play important roles in driving metastatic signaling cascades in melanoma. The ability of these proteins to modulate ligand-receptor interactions in melanoma has been quite understudied. Recent data from several groups indicate the importance of these ligands in modulating key signaling pathways including Wnt and fibroblast growth factor (FGF) signaling. In this review, we summarize the current knowledge regarding the structure and function of these proteoglycans and their role in melanoma. Understanding how HSPGs modulate signaling in melanoma could lead to new therapeutic approaches via the dampening or heightening of key signaling pathways.

Nanoparticles: Emerging carriers for drug delivery

The core objective of nanoparticles is to control and manipulate biomacromolecular constructs and supramolecular assemblies that are critical to living cells in order to improve the quality of human health. By definition, these constructs and assemblies are nanoscale and include entities such as drugs, proteins, DNA/RNA, viruses, cellular lipid bilayers, cellular receptor sites and antibody variable regions critical for immunology and are involved in events of nanoscale proportions. The emergence of such nanotherapeutics/diagnostics will allow a deeper understanding of human longevity and human ills that include cancer, cardiovascular disease and genetic disorders. A technology platform that provides a wide range of synthetic nanostructures that may be controlled as a function of size, shape and surface chemistry and scale to these nanotechnical dimensions will be a critical first step in developing appropriate tools and a scientific basis for understanding nanoparticles.

Paclitaxel loaded PEG(5000)-DSPE micelles as pulmonary delivery platform: formulation characterization, tissue distribution, plasma pharmacokinetics, and toxicological evaluation

The objective of the present study was to evaluate the potential of paclitaxel loaded micelles fabricated from PEG(5000)-DSPE as a sustained release system following pulmonary delivery. PEG(5000)-DSPE micelles containing paclitaxel were prepared by solvent evaporation technique followed by investigation of in vitro release of paclitaxel in lung simulated fluid. Tissue distribution and plasma pharmacokinetics of the PEG-lipid micelles after intratracheal and intravenous administrations were investigated in addition to intratracheally administered taxol. Finally, toxicological profile of PEG(5000)-DSPE was investigated. Paclitaxel was successfully formulated in PEG-lipid micelles with encapsulation efficiency of 95%. The PEG-lipid micelles exhibited a sustained release behavior in the simulated lung fluid. Intratracheally administered polymeric micellar paclitaxel showed highest accumulation of paclitaxel in the lungs with AUC(0-12) in lungs being 45-fold higher than intravenously administered formulation and 3-fold higher than intratracheally delivered taxol. Paclitaxel concentration in other non-targeted tissues and plasma were significantly lower as compared to other groups. Furthermore, toxicity studies showed no significant increase in levels of lung injury markers in PEG(5000)-DSPE treated group as compared to saline-treated group. PEG(5000)-DSPE micelles delivered intratracheally were able to sustain highest paclitaxel concentrations in lungs for long periods of time, thus apprehending their suitability as pulmonary drug carriers.

Self-assembled terplexes for targeted gene delivery with improved transfection

To improve transfection efficiency and to incorporate target ligands to the gene delivery systems, heparin and heparin-biotin were introduced to complexes of polyamidoamine dendrimer and DNA (PAMAM/DNA) via electrostatic interactions to form self-assembled PAMAM/DNA/heparin and PAMAM/DNA/heparin-biotin terplexes, respectively. The self-assembled terplexes were characterized by agarose gel electrophoresis and particle size analysis. The MTT assay indicated that, after incorporation of heparin and heparin-biotin, the terplexes exhibited decreased cytotoxicity. In addition, as compared with PAMAM/DNA and PAMAM/DNA/heparin complexes, the PAMAM/DNA/heparin-biotin complexes exhibited much higher cellular uptake into HeLa cells due to the specific interactions between biotin and biotin receptors on HeLa cells, which led to the enhanced transfection activity. The PAMAM/DNA/heparin-biotin complexes would be a promising targeting gene delivery system.

Inhalable lactose-based dry powder formulations of low molecular weight heparin

BACKGROUND

Currently low molecular weight heparin (LMWH) is administered as subcutaneous injection. This study sought to investigate the feasibility of LMWH as an inhalable dry powder (DPI) formulation and evaluate the interaction of the drug with lactose when used as a carrier. The study also compares the extent of pulmonary absorption of LMWH administered as a dry powder with that administered as an aerosolized aqueous solution.

METHODS

The formulations were prepared by mixing LMWH in an aqueous solution of lactose followed by lyophilization of the resulting solution. The lyophilized preparation was then ground and sieved. Physical characterization of the formulations was performed by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), particle size analysis, and determination of aerodynamic diameter. For in vivo studies, formulations were administered to anesthetized rats, and drug absorption was monitored by measuring plasma antifactor Xa activity.

RESULTS AND CONCLUSIONS

In the FTIR scan, all characteristic peaks of lactose and LMWH were observed, suggesting that there was no strong interaction between lactose and LMWH. Although the aerodynamic diameter of the formulation (DPI-2) that was sieved through 170- and 230-mesh screens was similar to that of the formulation (DPI-1) sieved through 120- and 170-mesh screens, the particle sizes of the two formulations were significantly different. Dry powder formulations of LMWH were better absorbed compared to an inhalable solution of LMWH. One of the dry powder formulations (DPI-2) produced an almost 1.5-fold increase in the relative bioavailability (41.6%) compared to the liquid formulation of LMWH (32.5%). Overall, the data presented here suggest that lactose does not adversely affect the physical-chemical characteristics of the drug, and that lactose can be used as a carrier for pulmonary delivery of LMWH.

Polyamidoamine dendrimers as novel potential absorption enhancers for improving the small intestinal absorption of poorly absorbable drugs in rats

Effects of polyamidoamine (PAMAM) dendrimers on the intestinal absorption of poorly absorbable drugs were examined by an in situ closed loop method in rats. 5(6)-Carboxyfluorescein (CF), fluorescein isothiocyanate-dextrans (FDs) with various molecular weights, calcitonin and insulin were used as model drugs of poorly absorbable drugs. The absorption of CF, FD4 and calcitonin from the rat small intestine was significantly enhanced in the presence of PAMAM dendrimers. The absorption-enhancing effects of PAMAM dendrimers for improving the small intestinal absorption of CF were concentration and generation dependent and a maximal absorption-enhancing effect was observed in the presence of 0.5% (w/v) G2 PAMAM dendrimer. However, G2 PAMAM dendrimer had almost no absorption-enhancing effect on the small intestinal absorption of macromolecular drugs including FD10 and insulin. Overall, the absorption-enhancing effects of G2 PAMAM dendrimer in the small intestine decreased as the molecular weights of drug increased. However, G2 PAMAM dendrimer did not enhance the intestinal absorption of these drugs with different molecular weights in the large intestine. Furthermore, we evaluated the intestinal membrane damage with or without G2 PAMAM dendrimer. G2 PAMAM dendrimer (0.5% (w/v)) significantly increased the activities of lactate dehydrogenase (LDH) and the amounts of protein released from the intestinal membranes, but the activities and amounts of these toxic markers were less than those in the presence of 3% Triton X-100 used as a positive control. Moreover, G2 PAMAM dendrimer at concentrations of 0.05% (w/v) and 0.1% (w/v) did not increase the activities and amounts of these toxic markers. These findings suggested that PAMAM dendrimers at lower concentrations might be potential and safe absorption enhancers for improving absorption of poorly absorbable drugs from the small intestine.

Nanomedicine in pulmonary delivery

The lung is an attractive target for drug delivery due to noninvasive administration via inhalation aerosols, avoidance of first-pass metabolism, direct delivery to the site of action for the treatment of respiratory diseases, and the availability of a huge surface area for local drug action and systemic absorption of drug. Colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery offer many advantages such as the potential to achieve relatively uniform distribution of drug dose among the alveoli, achievement of improved solubility of the drug from its own aqueous solubility, a sustained drug release which consequently reduces dosing frequency, improves patient compliance, decreases incidence of side effects, and the potential of drug internalization by cells. This review focuses on the current status and explores the potential of colloidal carriers (ie, nanocarrier systems) in pulmonary drug delivery with special attention to their pharmaceutical aspects. Manufacturing processes, in vitro/in vivo evaluation methods, and regulatory/toxicity issues of nanomedicines in pulmonary delivery are also discussed.

Dendrimers: emerging polymers for drug-delivery systems

Dendrimers are new class of polymeric materials. It is generally described as a macromolecule, which is characterized by its extensively branched 3D structure that provides a high degree of surface functionality and versatility. The unique properties associated with these dendrimers such as uniform size, high degree of branching, water solubility, multivalency, well-defined molecular weight and available internal cavities make them attractive for biological and drug-delivery applications. Commercialization of dendrimers is now forthcoming. The present review briefly describes about dendrimer synthesis strategies, types of dendrimers with different functionalities, properties which having crucial importance and their potential applications.

Cationic liposomes as carriers for aerosolized formulations of an anionic drug: safety and efficacy study

This study tests the hypothesis that pegylated cationic liposomes are a viable carrier for inhalable formulations of low molecular weight heparin, an anionic drug. Cationic liposomal formulations of low molecular weight heparin were prepared by the hydration method using 1,2-dioleoyl-3-trimethylammonium-propane (chloride salt), cholesterol and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000]. The formulations were characterized for particle size, entrapment efficiency, pulmonary absorption and pharmacological efficacy. For absorption studies, the formulations were administered to anesthetized male Sprague-Dawley rats via the pulmonary route and drug absorption was monitored by measuring plasma anti-factor Xa activity. The pharmacological efficacy of the formulations was studied in rodent models of pulmonary embolism and deep vein thrombosis. The mean particle size of the liposomes was 104.8+/-20.7 nm and the drug entrapment efficiency was 90.3+/-0.1%. The half-life of the cationic liposomal formulation was 10.6+/-0.2h, a 2.2-fold increase compared to low molecular weight heparin formulated in saline, and the relative bioavailability was approximately 73.4+/-19.1% when compared to subcutaneously administered drug. A once-every-other-day inhaled dose of the formulation showed similar efficacy in reducing thrombus weight as a once-daily dose of subcutaneously administered drug. Likewise, cationic liposomal formulations administered via the pulmonary route 6h prior to embolization in the lungs showed a thrombolytic effect comparable to that of low molecular weight heparin administered subcutaneously 2h before embolization. Histological examination of lung tissue and measurement of injury markers in bronchoalveolar lavage fluid suggest that the formulations did not produce extensive damage. The results demonstrate that pegylated cationic liposomes could be a viable carrier for an inhalable formulation of low molecular weight heparin.

Surfen, a small molecule antagonist of heparan sulfate

In a search for small molecule antagonists of heparan sulfate, we examined the activity of bis-2-methyl-4-amino-quinolyl-6-carbamide, also known as surfen. Fluorescence-based titrations indicated that surfen bound to glycosaminoglycans, and the extent of binding increased according to charge density in the order heparin > dermatan sulfate > heparan sulfate > chondroitin sulfate. All charged groups in heparin (N-sulfates, O-sulfates, and carboxyl groups) contributed to binding, consistent with the idea that surfen interacted electrostatically. Surfen neutralized the anticoagulant activity of both unfractionated and low molecular weight heparins and inhibited enzymatic sulfation and degradation reactions in vitro. Addition of surfen to cultured cells blocked FGF2-binding and signaling that depended on cell surface heparan sulfate and prevented both FGF2- and VEGF(165)-mediated sprouting of endothelial cells in Matrigel. Surfen also blocked heparan sulfate-mediated cell adhesion to the Hep-II domain of fibronectin and prevented infection by HSV-1 that depended on glycoprotein D interaction with heparan sulfate. These findings demonstrate the feasibility of identifying small molecule antagonists of heparan sulfate and raise the possibility of developing pharmacological agents to treat disorders that involve glycosaminoglycan-protein interactions.

Inhalable large porous microspheres of low molecular weight heparin: in vitro and in vivo evaluation

This study tests the feasibility of large porous particles as long-acting carriers for pulmonary delivery of low molecular weight heparin (LMWH). Microspheres were prepared with a biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA), by a double-emulsion-solvent-evaporation technique. The drug entrapment efficiencies of the microspheres were increased by modifying them with three different additivespolyethyleneimine (PEI), Span 60 and stearylamine. The resulting microspheres were evaluated for morphology, size, zeta potential, density, in vitro drug-release properties, cytotoxicity, and for pulmonary absorption in vivo. Scanning electron microscopic examination suggests that the porosity of the particles increased with the increase in aqueous volume fraction. The amount of aqueous volume fraction and the type of core-modifying agent added to the aqueous interior had varying degrees of effect on the size, density and aerodynamic diameter of the particles. When PEI was incorporated in the internal aqueous phase, the entrapment efficiency was increased from 16.22+/-1.32% to 54.82+/-2.79%. The amount of drug released in the initial burst phase and the release-rate constant for the core-modified microspheres were greater than those for the plain microspheres. After pulmonary administration, the half-life of the drug from the PEI- and stearylamine-modified microspheres was increased by 5- to 6-fold compared to the drug entrapped in plain microspheres. The viability of Calu-3 cells was not adversely affected when incubated with the microspheres. Overall, the data presented here suggest that the newly developed porous microspheres of LMWH have the potential to be used in a form deliverable by dry-powder inhaler as an alternative to multiple parenteral administrations of LMWH.

Feasibility study of inhaled hepatitis B vaccine formulated with tetradecylmaltoside

This study was designed to test the hypothesis that formulation of hepatitis B vaccine with tetradecyl-beta-maltoside (TDM) enhances the immune response after pulmonary administration in a rodent model. Commercially available recombinant hepatitis B vaccine (rHBV) was formulated with varying concentrations of TDM and administered intratracheally to anesthetized male Sprague-Dawley rats. rHBV administered intramuscularly at doses of 2 and 4 microg served as positive controls. All formulations were administered on days 0 and 14 and the immune response was evaluated for 28 days. Specific antibodies generated to HBsAg were analyzed by ELISA. Safety studies were carried out by measuring the levels of alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-alpha) in bronchoalveolar lavage (BAL) fluid. There was a significant increase in the immune response when the vaccine was administered intramuscularly at a dose of 4 microg. Only a modest increase in the immune response was observed when plain rHBV was administered intratracheally at the same dose. However, a pulmonary formulation of 4 microg rHBV plus 0.5% TDM produced a fourfold increase in the immune response compared to plain rHBV administered via the pulmonary route. No increase in immune response was observed for formulations containing rHBV plus 0.125% or 0.25% TDM. The levels of ALP and LDH in the BAL fluid suggest that the hepatitis B vaccine plus TDM formulations cause some injury to the lungs after the first intratracheal instillation of the formulation; however, the enzyme levels tended to be lower after the second instillation. The level of TNF-alpha in the BAL fluid of TDM-treated rats was substantially lower than that in rats treated with the positive control substance, sodium dodecyl sulfate. Overall, rHBV formulated with TDM increases the immune response after pulmonary administration, and pulmonary formulation of rHBV plus TDM could be used as an alternative to needle-based delivery of hepatitis B vaccine.