Formulation and physical characterization of large porous particles for inhalation

Feasibility of spray drying bacteriophages into respirable powders to combat pulmonary bacterial infections

The use of bacterial viruses for antibacterial treatment (bacteriophage therapy) is currently being reevaluated. In this study, we analyze the potential of processing bacteriophages in a dry powder formulation, using a laboratory spray dryer. The phages were dried in the presence of lactose, trehalose or dextran 35, serving as an excipient to give the resulting powder the necessary bulk mass and offer protection to the delicate phage structure. Out of the three excipients tested, trehalose was found to be the most efficient in protecting the phages from temperature and shear stress throughout the spray drying process. A low inlet air temperature and atomizing force appeared to be the best parameter conditions for phage survival. Pseudomonas podovirus LUZ19 was remarkably stable, suffering less than 1 logarithmic unit reduction in phage titer. The phage titer of Staphyloccus phage Romulus-containing powders, a member of the Myoviridae family, showed more than 2.5 logarithmic units reduction. On the other hand, Romulus-containing powders showed more favorable characteristics for pulmonary delivery, with a high percentage of dry powder particles in the pulmonary deposition fraction (1-5 μm particle diameter). Even though the parameters were not optimized for spray drying all phages, it was demonstrated that spray drying phages with this industrial relevant and scalable set up was possible. The resulting powders had desirable size ranges for pulmonary delivery of phages with dry powder inhalers (DPIs).

Surfactants: their critical role in enhancing drug delivery to the lungs

For local lung conditions and diseases, pulmonary drug delivery has been widely used for more than 50 years now. A more recent trend involves the pulmonary route as a systemic drug-delivery target. Advantages such as avoidance of the gastrointestinal environment, different enzyme content compared with the intestine, and avoidance of first-pass metabolism make the lung an alternative route for the systemic delivery of actives. However, the lung offers barriers to absorption such as a surfactant layer, epithelial surface lining fluid, epithelial monolayer, interstitium and basement membrane, and capillary endothelium. Many delivery strategies have been developed in order to overcome these limitations. The use of surfactants is one of these approaches and their role in enhancing pulmonary drug delivery is reviewed in this article. A systematic review of the literature relating to the effect of surfactants on formulations for pulmonary delivery was conducted. Specifically, research reporting enhancement of in vivo performance was focused on. The effect of the addition of surfactants such as phospholipids, bile salts, non-ionic, fatty acids, and liposomes as phospholipid-containing carriers on the enhancement of therapeutic outcomes of drugs for pulmonary delivery was compiled. The main use attributed to surfactants in pulmonary drug delivery is as absorption enhancers by mechanisms of action not yet fully understood. Furthermore, surfactants have been used to improve the delivery of inhaled drugs in various additional strategies discussed herein.

Antisolvent crystallisation is a potential technique to prepare engineered lactose with promising aerosolisation properties: effect of saturation degree

Engineered lactose particles were prepared by anti-solvent crystallisation technique using lactose solutions with different saturation degrees. In comparison to commercial lactose, engineered lactose particles exhibited less elongated and more irregular shape (large aggregates composed of smaller sub-units), rougher surface texture, higher specific surface area, and different anomer form. Engineered lactose powders demonstrated smaller bulk density, smaller tap density, and higher porosity than commercial lactose powder. Dry powder inhaler (DPI) formulations containing engineered lactose and salbutamol sulphate as a model drug demonstrated improved drug content homogeneity and higher amounts of drug delivered to lower airway regions. Higher fine particle fraction of drug was obtained in the case of lactose powders with higher porosity, higher specific surface area and higher fine particle content (<5 μm). The results indicated that the higher the saturation degree of lactose solution used during crystallisation the smaller the specific surface area, the higher the amorphous lactose content, and the higher the β-lactose content of engineered lactose particles. Also, lactose powders obtained from lactose solution with higher degree of saturation showed higher bulk and tap densities and smaller porosity. Engineered lactose powders crystallized from lower saturation degree (20% and 30% w/v) deposited higher amounts of drug on lower airway regions. In conclusion, this study demonstrated that it is possible to prepare engineered lactose particles with favourable properties (e.g. higher fine particle fraction and better drug content homogeneity) for DPI formulations by using lactose solutions with lower degree of saturation during crystallisation process.

Dry powder inhalers: study of the parameters influencing adhesion and dispersion of fluticasone propionate

Interactions between particles are dependent on the physicochemical characteristics of the interacting particles but it is also important to consider the manufacturing process. Blending active pharmaceutical ingredient (API) with carrier is a critical stage that determines the blend homogeneity and is the first step towards obtaining the final quality of the powder blend. The aim of this work was to study parameters that influence the interactions between API and carrier in adhesive mixtures used in DPI and their effect on API dispersion. The study was done with fluticasone propionate blended with lactose 'Lactohale 200'. The study was based on the influence of the operating conditions (speed, mixing time, resting steps during mixing), the size of the carrier and the storage conditions on the blend properties and on the API dispersion. The quality of the blends was examined by analysing the API content uniformity. Adhesion characteristics were evaluated by submitting mixtures to a sieving action by air depression with the Alpine air-jet sieve. Aerodynamic evaluation of fine particle fraction (FPF) was obtained using a Twin Stage Impinger; the FPF being defined as the mass percentage of API below 6.4 μm. For good dispersion and therefore good homogeneity of the API in the carrier particles, speed and powder blending time have to be sufficient, but not too long to prevent the appearance of static electricity, which is not favourable to homogeneity and stability. The FPF increases with the decrease in the carrier size. The storage conditions have also to be taken into consideration. Higher humidity favours the adhesion of API on the carrier and decreases the FPF.

Lactose characteristics and the generation of the aerosol

The delivery efficiency of dry-powder products for inhalation is dependent upon the drug formulation, the inhaler device, and the inhalation technique. Dry powder formulations are generally produced by mixing the micronised drug particles with larger carrier particles. These carrier particles are commonly lactose. The aerosol performance of a powder is highly dependent on the lactose characteristics, such as particle size distribution and shape and surface properties. Because lactose is the main component in these formulations, its selection is a crucial determinant of drug deposition into the lung, as interparticle forces may be affected by the carrier-particle properties. Therefore, the purpose of this article is to review the various grades of lactose, their production, and the methods of their characterisation. The origin of their adhesive and cohesive forces and their influence on aerosol generation are described, and the impact of the physicochemical properties of lactose on carrier-drug dispersion is discussed in detail.

Spray drying from organic solvents to prepare nanoporous/nanoparticulate microparticles of protein: excipient composites designed for oral inhalation

Objectives

The aim of this study was to determine if spray-drying could successfully produce microparticles containing the model protein trypsin in a form suitable for inhalation.

Methods

Trypsin was spray-dried with raffinose from a methanol : n-butyl acetate solvent system (MeOH : BA). The solvent system was then adjusted to include water, and trypsin was co-spray-dried with raffinose, trehalose or hydroxpropyl-β-cyclodextrin. The spray-dried products were characterised by SEM, XRD, DSC, TGA and FTIR. Protein biological activity and in-vitro deposition of trypsin : excipient nanoporous/nanoparticulate microparticles (NPMPs) was also assessed.

Key findings

The inclusion of water in a MeOH : BA solvent system allowed for the successful production of NPMPs of trypsin : excipient by spray-drying. Trypsin formulated as trypsin : excipient NPMPs retained biological activity on processing and showed no deterioration in activity or morphological characteristics when stored with desiccant at either 4 or 25°C. Hydroxpropyl-β-cyclodextrin showed advantages over the sugars in terms of producing powders with appropriate density and with greater physical stability under high-humidity conditions. Fine particle fractions of between 41 and 45% were determined for trypsin : excipient NPMPs.

Conclusions

NPMPs of trypsin : excipient systems can be produced by spray-drying by adjustment of the solvent system to allow for adequate solubility of trypsin.

Optimization and characterization of dry powder of fanhuncaoin for inhalation based on selection of excipients

In this study, dry powder formulations for inhalation of fanhuncaoin, a newly discovered antiinflammatorily active compound isolated from Chinese herb, were designed to optimize the composition and further explore the relationship between the composition, the physical properties and the aerosolization performance. Dry powders were prepared by spray-drying using leucine, chitosan, chitosan oligosaccharide and dipalmitoyl phosphatidylcholine (DPPC) as excipients. Following spray-drying, resultant powders were characterized using scanning electron microscopy, tapped density analysis, laser diffractometry, thermogravimetric analysis and differential scanning calorimetry. The aerosol behaviour of the powders was studied in a Twin Stage Impinger at an airflow rate of 60 l/min using a HandiHaler® inhaler device. Results revealed that the nature and the relative proportion of the excipients greatly influenced the physical characteristics of the powders and their aerodynamic behavior. Among the combinations tested, the composition ratio of fanhuncaoin/leucine/chitosan/chitosan oligosaccharide/DPPC of 10/45/33.75/11.25/0.4 (w/w/w/w/w) prepared in a total solid mass of 1% (w/v) formulation was found to be particularly optimal and exhibited a tapped density of 0.44 g/cm³, an aerodynamic diameter of 2.24 µm and an respirable fraction of 51.29%. In conclusion, optimization of the aerosolization properties of inhalation dry powders could be achieved by appropriately selecting the composition of the particles.

Comparative pharmacoscintigraphic and pharmacokinetic evaluation of two new formulations of inhaled insulin in type 1 diabetic patients

In this open, single-dose study, we compared the lung deposition and bioavailability of two newly developed insulin formulations for pulmonary delivery. Twelve type 1 diabetic patients were administered the two insulin products (2 U/kg b.w.), which had been radiolabelled with (99m)Tc. The formulations were either microparticles of insulin without excipients (F1) or lipid-coated insulin microparticles (F2). Lung deposition was assessed by γ-scintigraphy imaging performed immediately after administration. Bioavailability was evaluated by quantifying serum insulin levels over a period of 6 h. Lung deposition was found to be 50 ± 9% and 24 ± 8% for the F1 and F2 formulations, respectively. The insulin AUC₀₋₃₆₀ ratio of F1/F2 was 188%, which was consistent with scintigraphic imaging. The concordance between imaging and biological results suggests that the lower bioavailability of F2 is due to its lower lung deposition and not to a reduced absorption into the blood stream. Additional in vitro experiments indicated that the lower performance of F2 was most probably related to a lower disaggregation efficiency of the powder when administered at a sub-optimal flow rate. The two formulations showed interesting pharmacokinetic profiles (T(max) of 26 and 16 min for F1 and F2, respectively) that mimic the physiological insulin secretion pattern. The bioavailability of the developed formulations was within the range of other DPI insulin formulations that have reached the final stages of clinical development.

Effect of carrier particle shape on dry powder inhaler performance

The aim of this study was to characterise the aerosolisation properties of salbutamol sulphate (SS) from dry powder inhaler (DPI) formulations containing different carrier products. The difference in the elongation ratio (ER) of the different carriers was highlighted. Different set of carriers, namely commercial mannitol (CM), commercial lactose (CL), cooling crystallised mannitol (CCM), acetone crystallised mannitol (ACM) and ethanol crystallised mannitol (ECM) were used and inspected in terms of size, shape, density, crystal form, flowability, and in vitro aerosolisation performance using Multi Stage Liquid Impinger (MSLI) and Aerolizer inhaler device. Solid-state and morphological characterization showed that CM product was in pure β-form having particles with smaller ER (CM: ER=1.62 ± 0.04) whereas ACM and ECM mannitol particles were in pure α form with higher ER (ACM: ER=4.83 ± 0.18, ECM: ER=5.89 ± 0.19). CCM product crystallised as mixtures of β-form and δ-form and showed the largest variability in terms of particle shape, size, and DPI performance. Linear relationships were established showing that carrier products with higher ER have smaller bulk density (D(b)), smaller tap density (D(t)), higher porosity (P), and poorer flow properties. In vitro aerosolisation assessments showed that the higher the ER of the carrier particles the greater the amounts of SS delivered to lower airway regions indicating enhanced DPI performance. Yet, DPI performance enhancement by increasing carrier ER reached a "limit" as increasing carrier ER from 4.83±0.18 (ACM) to 5.89±0.19 (ECM) did not significantly alter fine particle fraction (FPF) of SS. Also, carrier particles with higher ER were disadvantageous in terms of higher amounts of SS remained in inhaler device (drug loss) and deposited on throat. Linear relationship was established (r(2)=0.87) showing that the higher the carrier ER the lower the drug emission (EM) upon inhalation. Moreover, poorer flowability for carrier products with higher ER is disadvantageous in terms of DPI formulation dose metering and processing on handling scale. In conclusion, despite that using carrier particles with higher ER can considerably increase the amounts of drug delivered to lower airway regions; this enhancement is restricted to certain point. Also, other limitations should be taken into account including higher drug loss and poorer flowability.

Mechanisms of burst release from pH-responsive polymeric microparticles

OBJECTIVES

Microencapsulation of drugs into preformed polymers is commonly achieved through solvent evaporation techniques or spray drying. We compared these encapsulation methods in terms of controlled drug release properties of prepared microparticles and investigated the underlying mechanisms responsible for the 'burst release' effect.

METHODS

Using two different pH-responsive polymers with a dissolution threshold of pH 6 (Eudragit L100 and AQOAT AS-MG), hydrocortisone, a model hydrophobic drug, was incorporated into microparticles below and above its solubility within the polymer matrix.

KEY FINDINGS

Although, spray drying was an attractive approach due to rapid particle production and relatively low solvent waste, the oil-in-oil microencapsulation method was superior in terms of controlled drug release properties from the microparticles. Slow solvent evaporation during the oil-in-oil emulsification process allowed adequate time for drug and polymer redistribution in the microparticles and reduced uncontrolled drug burst release. Electron microscopy showed that this slower manufacturing procedure generated nonporous particles whereas thermal analysis and X-ray diffractometry showed that drug loading above the solubility limit of the drug in the polymer generated excess crystalline drug on the surface of the particles. Raman spectral mapping illustrated that drug was homogeneously distributed as a solid solution in the particles when loaded below saturation in the polymer with consequently minimal burst release.

CONCLUSIONS

Both the manufacturing method (which influenced particle porosity and density) and drug:polymer compatibility and loading (which affected drug form and distribution) were responsible for burst release seen from our particles.

Lung vascular targeting through inhalation delivery: insight from filamentous viruses and other shapes

Systemic delivery of therapeutic agents via inhalation of particulates remains an attractive, noninvasive means of administration due to the possibilities of high bioavailability and high patient compliance. Optimization of particle shapes and particle properties for deep lung deposition after inhalation continues to be one of the key challenges. Here, we review several aspects of nanoparticle design for deep lung deposition as well as the nature and extent of translocation through the air-blood barrier for local or systemic vascular targeting. We describe filamentous influenza virus in comparison to worm-like "filomicelle" polymers as one example of a nature inspired design.

Influence of PEI as a core modifying agent on PLGA microspheres of PGE₁, a pulmonary selective vasodilator

This study tests the hypothesis that large porous poly (lactic-co-glycolic acid) (PLGA) microparticles modified with polyethyleneimine (PEI) are viable carriers for pulmonary delivery of prostaglandin E(1) (PGE(1)) used in the treatment of pulmonary arterial hypertension (PAH), a pulmonary vascular disorder. The particles were prepared by a double-emulsion solvent evaporation method with PEI-25 kDa in the internal aqueous phase to produce an osmotic pressure gradient. Polyvinyl alcohol (PVA) was used for external coating of the particles. The particles were examined for morphology, size, aerodynamic diameter, surface area, pore volume and in-vitro release profiles. Particles with optimal properties for inhalation were tested for in-vivo pulmonary absorption, metabolic stability in rat lung homogenates, and acute toxicity in rat bronchoalveolar lavage fluid and respiratory epithelial cells, Calu-3. The micromeritic data indicated that the PEI-modified particles of PGE(1) are optimal for inhalation. Incorporation of PEI in the formulations resulted in an increased entrapment efficiency - 83.26 ± 3.04% for particles with 1% PVA and 95.48 ± 0.46% for particles with 2% PVA. The amount of cumulative drug released into the simulated interstitial lung fluid was between 50.8 ± 0.76% and 55.36 ± 0.06%. A remarkable extension of the circulation half-life up to 6.0-6.5h was observed when the formulations were administered via the lungs. The metabolic stability and toxicity studies showed that the optimized formulations were stable at physiological conditions and relatively safe to the lungs and respiratory epithelium. Overall, this study demonstrates that large porous inhalable polymeric microparticles can be a feasible option for non-invasive and controlled release of PGE(1) for treatment of PAH.

Albumin-coated porous hollow poly(lactic-co-glycolic acid) microparticles bound with palmityl-acylated exendin-4 as a long-acting inhalation delivery system for the treatment of diabetes

PURPOSE

To study the development of porous poly(lactic-co-glycolic acid) microparticles (PLGA MPs) coated initially with albumin and then with palmityl-acylated exendin-4 (Pal-Ex4) as an inhalation system for treating diabetes.

METHODS

Porous PLGA MPs were prepared by w/o/w double emulsification using hydroxypropyl-β-cyclodextrin and poly(ethylene-alt-maleic anhydride). Albumin was covalently attached to the MPs using EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide); Pal-Ex4 was then bound on the albumin surface. Albumin-binding degree and aerosolization efficiency were investigated. Deposition of the MPs after insufflations into the lungs of ICR mice was observed by image monitoring, and pulmonary hypoglycemic efficacies were examined in db/db mice. Cytotoxicity and histopathology induced by MPs were examined in Calu-3 and A549 cells and in the lungs of db/db mice, respectively.

RESULTS

Albumin-coating and Pal-Ex4-binding to porous MP were performed with acceptable efficiencies. Pal-Ex4-bound albumin-coated MPs (Pal-Ex4/HSA-PLGA MP) were of high porosity and had appropriate aerodynamic sizes. Furthermore, this MP was efficiently deposited throughout mouse lungs, and exhibited a prolonged hypoglycemia and no significant lung tissue damage in db/db mice.

CONCLUSION

Pal-Ex4/HSA-PLGA MP demonstrated many meaningful pharmaceutical advantages for the treatment of diabetes, in terms of aerosolization efficiency, drug loading, sustained drug-release, and hypoglycemic duration in vivo.

Nanosized rods agglomerates as a new approach for formulation of a dry powder inhaler

Background:

Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs as compared with liquid formulations. However, the respirable particles must have a diameter of 1–5 μm in order to deposit in the lungs. Controlled agglomeration of the nanoparticles increases their geometric particle size so they can deposit easily in the lungs. In the lungs, they fall apart to reform nanoparticles, thus enhancing the dissolution rate of the drugs. Theophylline is a bronchodilator with poor solubility in water.

Methods:

Nanosized theophylline colloids were formed using an amphiphilic surfactant and destabilized using dilute sodium chloride solutions to form the agglomerates.

Results:

The theophylline nanoparticles thus obtained had an average particle size of 290 nm and a zeta potential of −39.5 mV, whereas the agglomerates were 2.47 μm in size with a zeta potential of −28.9 mV. The release profile was found to follow first-order kinetics (r² > 0.96). The aerodynamic characteristics of the agglomerated nanoparticles were determined using a cascade impactor. The behavior of the agglomerate was significantly better than unprocessed raw theophylline powder. In addition, the nanoparticles and agglomerates resulted in a significant improvement in the dissolution of theophylline.

Conclusion:

The results obtained lend support to the hypothesis that controlled agglomeration strategies provide an efficient approach for the delivery of poorly water-soluble drugs into the lungs.

Differential effects of insufflated, subcutaneous, and intravenous growth hormone on bone growth, cognitive function, and NMDA receptor subunit expression

The objective of this study was to characterize the effect of inhalable growth hormone (GH) delivered by an insufflator to the lungs of hypophysectomized Sprague Dawley rats. In the first cohort, the safety and efficacy of the insufflated GH were evaluated. Three experimental groups (n = 7 per group) were treated with GH for 15 d: One group received sc injection of GH daily at 200 microg/kg (SC200). Two other groups received GH by insufflation daily: 200 microg/kg (INS 200) and 600 microg/kg (INS 600). In the second set of experiments, GH was administered in three routes [SC200, INS200, intravenous (IV200)] (n=10) for 5 d, and escape latency and N-methyl D-aspartate (NMDA) receptor expression were evaluated. In the first cohort, INS200 showed similar bioactivity as SC200 in growth promotion, tibial growth, as well as escape latency on the 12th day of treatment. Insufflated GH was well tolerated without significant inflammatory responses. In the second cohort, expression of the NMDA receptor 1 and 2B in hippocampus measured after 3 or 6 d of daily treatments were significantly higher in INS200 as compared to IV200, consistent with the improvement of the escape latency. In summary, the inhalable form of GH delivered by intratracheal insufflation was safe, and its bioactivity was comparable to sc injection both in promotion of growth and acquisition of learning ability. If applied properly to human, inhalable GH would be effective for growth promotion and possibly for several disorders caused by underexpression of NMDA receptors.

Formation of highly ordered nanostructures by drying micrometer colloidal droplets

Nanoparticles with well-defined chemical compositions can act as building blocks for the construction of functional structures, such as highly ordered aggregates, as well as porous and hollow aggregates. In this work, a spray-drying technique is used to form a crystal-like structure with nanoparticle building blocks. When spray-drying uniform spherical particles, tightly packed aggregates with either simple or broken symmetries (quasicrystalline) were formed. Using polystyrene (PS) particles with varied zeta potentials as templates, it is also possible to form highly ordered porous and hollow aggregates from inorganic colloidal particles. Essential to the production of quasicrystalline structures is the use of monodisperse colloidal particles in spray drying, as the quasicrystalline form is not achievable when two different sizes of colloidal particles are used in the precursor suspension. With varying colloidal particles sizes, smaller colloidal particles fill the spaces formed between the larger particles, resulting in adjustment of colloidal crystallization. A geometric model that considers the tight packing of several spheres into frustrated clusters (quasicrystal form) with short-range icosahedral symmetry is compared to experimentally produced structures and found to quantitatively explain experimental observations.

Engineering gas-foamed large porous particles for efficient local delivery of macromolecules to the lung

Gas-foamed large porous particles (gfLPP) based on poly(lactic-co-glycolic) acid (PLGA) have been recently suggested as potential carriers for pulmonary drug delivery. In this work, we attempt to engineer gfLPP for efficient local delivery of macromolecules in the lungs. Particles were fabricated by the double emulsion-solvent evaporation technique using ammonium bicarbonate as porogen. To improve particle technological properties, two lipid aid excipients, namely dipalmitoylphosphatidylcholine (DPPC) and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), were tested. Preliminary technological studies performed on unloaded gfLPP showed that the addition of an appropriate amount of NH(4)(HCO(3)), which spontaneously produces CO(2) and NH(3) during solvent evaporation, is essential to achieve a homogeneous population of highly porous particles with optimal aerodynamic properties. Then, the effect of the presence of DPPC or DOTAP upon the properties of gfLPP containing a model hydrophilic macromolecule, rhodamine B isothiocyanate-dextran (Rhod-dex), was assessed. We found that in the case of hydrophilic macromolecules unable to interact with PLGA end-groups, such as Rhod-dex, excipient addition is essential to increase the amount of drug entrapped within gfLPP, being as high as 80% only for DPPC- or DOTAP-engineered gfLPP. Also Rhod-dex release profile from gfLPP was strongly affected by excipient addition in the initial formulation, with lipid-engineered gfLPP allowing for a more prolonged release of Rhod-dex as compared to excipient-free gfLPP. A further modulation of Rhod-dex initial release rate could be achieved when DOTAP was used, likely due to the electrostatic interactions occurring between macromolecule and cationic phospholipid. Conceiving the developed gfLPP for drug inhalation, DPPC- and DOTAP-engineered gfLPP displayed optimal MMAD(exp) values falling within the range 6.1-7.6 microm and very low geometric standard deviations (GSD) varying between 1.2 and 1.3. In vivo deposition studies performed after intra-tracheal administration of gfLPP in rats confirmed the ability of the developed dry powders to deposit along bronchia and bronchioles. In perspective, lipid-engineered gfLPP represent a viable alternative to LPP developed so far to achieve local and prolonged release of hydrophilic macromolecules, such as nucleic acids, in the lungs.

Budesonide nanoparticle agglomerates as dry powder aerosols with rapid dissolution

Nanoparticle technology represents an attractive approach for formulating poorly water-soluble pulmonary medicines. Unfortunately, nanoparticle suspensions used in nebulizers or metered dose inhalers often suffer from physical instability in the form of uncontrolled agglomeration or Ostwald ripening. In addition, processing such suspensions into dry powders can yield broad particle size distributions. To address these encumbrances, a controlled nanoparticle flocculation process has been developed. Nanosuspensions of the poorly water-soluble drug budesonide were prepared by dissolving the drug in organic solvent containing surfactants followed by rapid solvent extraction in water. Different surfactants were employed to control the size and surface charge of the precipitated nanoparticles. Nanosuspensions were flocculated using leucine and lyophilized. Selected budesonide nanoparticle suspensions exhibited an average particle size ranging from approximately 160 to 230 nm, high yield and high drug content. Flocculated nanosuspensions produced micron-sized agglomerates. Freeze-drying the nanoparticle agglomerates yielded dry powders with desirable aerodynamic properties for inhalation therapy. In addition, the dissolution rates of dried nanoparticle agglomerate formulations were significantly faster than that of stock budesonide. The results of this study suggest that nanoparticle agglomerates possess the microstructure desired for lung deposition and the nanostructure to facilitate rapid dissolution of poorly water-soluble drugs.

Dry powdered aerosols of diatrizoic acid nanoparticle agglomerates as a lung contrast agent

Aerosolized contrast agents may improve the resolution of biomedical imaging modalities and enable more accurate diagnosis of lung diseases. Many iodinated compounds, such as diatrizoic acid, have been shown to be safe and useful for radiographic examination of the airways. Formulations of such compounds must be improved in order to allow imaging of the smallest airways. Here, diatrizoic acid nanoparticle agglomerates were created by assembling nanoparticles into inhalable microparticles that may augment deposition in the lung periphery. Nanoparticle agglomerates were fully characterized and safety was determined in vivo. After dry powder insufflation to rats, no acute alveolar tissue damage was observed 2h post-dose. Diatrizoic acid nanoparticle agglomerates possess the characteristics of an efficient and safe inhalable lung contrast agent.

Respiratory delivery of theophylline by size-targeted starch microspheres for treatment of asthma

Asthma is considered as the most relevant pulmonary disease which is located at bronchial airways and oral theophylline is one of the most prescribed drugs for its treatment as it is inexpensive. However, the frequency of theophylline side-effects has recently reduced its usage. Inhaled theophylline has not been successful either, mostly due to the lack of retention in the airways and irritation. In this study, theophylline was encapsulated in mucoadhesive starch microspheres using an inverse emulsion method. Glutaraldehyde was applied as the cross-linker for some of starch-derived microspheres. Cross-linking reaction was studied by means of the FTIR. A central composite face (CFC) design was used to optimize manufacturing conditions in order to obtain the highest drug entrapment yield and ideal aerodynamic diameter range of 5-11 microm at which bronchial deposition is maximum. Optimized microspheres were successfully reproduced using the model provided by CFC design and their experimental aerodynamic diameter and drug entrapment yield were in good correlation with predicted values. Drug release of optimized microspheres was measured in phosphate buffer solution. Both cross-linked and uncross-linked microspheres showed biphasic Fickian type drug release (Higuchi Model). These new formulations may recover the role of this valuable drug in asthma management.