Contemporary approaches in aerosolized drug delivery to the lung

Impact of dispersion media and carrier type on spray-dried proliposome powder formulations loaded with beclomethasone dipropionate for their pulmonary drug delivery via a next generation impactor

Drug delivery via aerosolization for localized and systemic effect is a non-invasive approach to achieving pulmonary targeting. The aim of this study was to prepare spray-dried proliposome (SDP) powder formulations to produce carrier particles for superior aerosolization performance, assessed via a next generation impactor (NGI) in combination with a dry powder inhaler. SDP powder formulations (F1-F10) were prepared using a spray dryer, employing five different types of lactose carriers (Lactose monohydrate (LMH), lactose microfine (LMF), lactose 003, lactose 220 and lactose 300) and two different dispersion media. The first dispersion medium was comprised of water and ethanol (50:50% v/v ratio), and the second dispersion medium comprised wholly of ethanol (100%). In the first dispersion medium, the lipid phase (consisting of Soya phosphatidylcholine (SPC as phospholipid) and Beclomethasone dipropionate (BDP; model drug) were dissolved in ethanol and the lactose carrier in water, followed by spray drying. Whereas in second dispersion medium, the lipid phase and lactose carrier were dispersed in ethanol only, post spray drying. SDP powder formulations (F1-F5) possessed significantly smaller particles (2.89 ± 1.24-4.48 ± 1.20 μm), when compared to SDP F6-F10 formulations (10.63 ± 3.71-19.27 ± 4.98 μm), irrespective of lactose carrier type via SEM (scanning electron microscopy). Crystallinity of the F6-F10 and amorphicity of F1-F15 formulations were confirmed by XRD (X-ray diffraction). Differences in size and crystallinity were further reflected in production yield, where significantly higher production yield was obtained for F1-F5 (74.87 ± 4.28-87.32 ± 2.42%) then F6-F10 formulations (40.08 ± 5.714-54.98 ± 5.82%), irrespective of carrier type. Negligible differences were noted in terms of entrapment efficiency, when comparing F1-F5 SDP formulations (94.67 ± 8.41-96.35 ± 7.93) to F6-F10 formulations (78.16 ± 9.35-82.95 ± 9.62). Moreover, formulations F1-F5 demonstrated significantly higher fine particle fraction (FPF), fine particle dose (FPD) and respirable fraction (RF) (on average of 30.35%, 890.12 μg and 85.90%) when compared to counterpart SDP powder formulations (F6-F10). This study has demonstrated that when a combination of water and ethanol was employed as dispersion medium (formulations F1-F5), superior formulation properties for pulmonary drug delivery were observed, irrespective of carrier type employed.

Phenotypic characteristics and protective efficacy of an attenuated Mycoplasma hyopneumoniae vaccine by aerosol administration

With the improvement of large-scale breeding in pig farms, conventional head-by-head immunization has disadvantages with low efficiency and high cost. Considering that most pathogens leading to pulmonary diseases circulate from the respiratory mucosa, immunization through the respiratory tract route has been a highly attractive vaccine delivery strategy. In this study, to develop an effective Mycoplasma hyopneumoniae (Mhp) aerosol vaccine, a customized ultrasonic atomizer was developed. The aerodynamic diameter, activity, and content of the Mhp aerosol vaccine were measured. In addition, piglets were immunized with the Mhp aerosol vaccine, and the immunity of the animal challenge protection test was evaluated. At the end of nebulization, the mass median aerodynamic diameters (MMAD) and geometric standard deviation (GSD) of the aerosol were 2.98 ± 0.02 μm and 1.51 ± 0.02, respectively. Moreover, 10 min after nebulization, the MMAD and GSD of the aerosol were 2.76 ± 0.02 μm and 1.51 ± 0.01, respectively, which were hardly changed. Compared with theoretical value, the actual titer of aerosol vaccines presented in 50% color changing unit (CCU₅₀) after nebulization decreased 0.6. The shape, size, and uniformity of collected aerosols are relatively stable. The proportion of Mhp in aerosol produced by vaccine stock solution and 10 times diluted vaccine solution was 76.52% and 58.82%, respectively, and the average number of Mhp in a single aerosol was 3.06 and 1.51, respectively. In addition, the aerosol vaccine antigen particles could be transported to the lower respiratory tract, a local mucosal immune response was induced in piglets. The vaccine colonized the respiratory tract and significantly decline the lung lesion index after aerosol vaccination. In conclusion, an effective aerosol vaccine against Mhp infection was developed. And this is the first effective assessment for Mhp live vaccine with aerosolization against infection in piglets.

Spray-Dried Proliposome Microparticles for High-Performance Aerosol Delivery Using a Monodose Powder Inhaler

Proliposome formulations containing salbutamol sulphate (SS) were developed using spray drying, and the effects of carrier type (lactose monohydrate (LMH) or mannitol) and lipid to carrier ratio were evaluated. The lipid phase comprised soy phosphatidylcholine (SPC) and cholesterol (1:1), and the ratios of lipid to carrier were 1:2, 1:4, 1:6, 1:8 or 1:10 w/w. X-ray powder diffraction (XRPD) revealed an interaction between the components of the proliposome particles, and scanning electron microscopy (SEM) showed that mannitol-based proliposomes were uniformly sized and spherical, whilst LMH-based proliposomes were irregular and relatively large. Using a two-stage impinger (TSI), fine particle fraction (FPF) values of the proliposomes were higher for mannitol-based formulations, reaching 52.6%, which was attributed to the better flow properties when mannitol was used as carrier. Following hydration of proliposomes, transmission electron microscopy (TEM) demonstrated that vesicles generated from mannitol-based formulations were oligolamellar, whilst LMH-based proliposomes generated 'worm-like' structures and vesicle clusters. Vesicle size decreased upon increasing carrier to lipid ratio, and the zeta potential values were negative. Drug entrapment efficiency (EE) was higher for liposomes generated from LMH-based proliposomes, reaching 37.76% when 1:2 lipid to carrier ratio was used. The in vitro drug release profile was similar for both carriers when 1:6 lipid to carrier ratio was used. This study showed that spray drying can produce inhalable proliposome microparticles that can generate liposomes upon contact with an aqueous phase, and the FPF of proliposomes and the EE offered by liposomes were formulation-dependent.

Nanomaterials in the Prevention, Diagnosis, and Treatment of Mycobacterium Tuberculosis Infections

Despite the tremendous advancements that have been made in biomedical research, Mycobacterium tuberculosis (TB) still remains one of the top 10 causes of death worldwide, outpacing the Human Immunodeficiency Virus as a leading cause of death from an infectious disease. In the light of such significant disease burden, tremendous efforts have been made worldwide to stem this burgeoning spread of disease. The use of nanomaterials in TB management has increased in the past decade, particularly in the areas of early TB detection, prevention, and treatment. Nanomaterials have been proven to be efficacious in the rapid and accurate detection of TB pathogens. Novel nanocarriers have also shown tremendous promise in improving drug delivery, potentially enhancing drug concentrations in target organs while at the same time, reducing treatment frequency. In addition, the engineering of antigen nanocarriers represents an exciting front in TB research, potentially paving the way for the successful development of a new class of effective TB vaccines. This article discusses epidemiology and pathogenesis of TB infections, current TB therapeutics, advanced nanomaterials for anti-TB drug delivery, and TB vaccines. In addition, challenges and future perspectives in developing safe and effective nanomaterials in TB diagnosis and therapy are also presented.

Pulmonary vaccine delivery

This review will discuss developments in the field of pulmonary vaccine delivery. The possibilities of adopting aerosol-generation technology and specific pharmaceutical formulations for the purpose of pulmonary immunization are described. Aerosol-generation systems might offer advantages with respect to vaccine stability and antigenicity. Adjuvants and their inclusion in vaccine-delivery systems are described. Other formulation components, such as surfactants, particulate systems and dispersion of the aerosols are detailed in this paper. The noninvasive, relatively safe and low-cost nature of pulmonary delivery may provide great benefits to the public health vaccination campaign.

Alternatives to conventional suspensions for pulmonary drug delivery by nebulisers: a review

This review discusses the reports of alternative dosage forms to suspension formulations of hydrophobic drugs for nebulisers. Suspensions for nebulisers, although widely used over recent years, have several limitations which have led to pharmaceutical researchers looking for alternative, better performing preparations. Particular attention has been directed towards the use of nanoparticles as carriers of hydrophobic active ingredients. Several nanoformulations have been prepared and compared in vitro and/or in vivo with the corresponding microsuspension formulation. It is also clear that future studies in this field should address the parallel important aspects of safety and economical aspects of nanoparticualte formulations.

Pulmonary immunization using antigen 85-B polymeric microparticles to boost tuberculosis immunity

This study aims to evaluate immunization with polymeric microparticles containing recombinant antigen 85B (rAg85B) delivered directly to the lungs to protect against tuberculosis. rAg85B was expressed in Escherichia coli and encapsulated in poly(lactic-co-glycolic acid) microparticles (P-rAg85B). These were delivered as dry powders to the lungs of guinea pigs in single or multiple doses of homologous and heterologous antigens. Bacille Calmette-Guérin (BCG) delivered subcutaneously was employed as the positive control and as part of immunization strategies. Immunized animals were challenged with a low-dose aerosol of Mycobacterium tuberculosis (MTB) H37Rv to assess the extent of protection measured as reduction in bacterial burden (CFU) in the lungs and spleens of guinea pigs. Histopathological examination and morphometric analysis of these tissues were also performed. The heterologous strategy of BCG prime-P-rAg85B aerosol boosts appeared to enhance protection from bacterial infection, as indicated by a reduction in CFU in both the lungs and spleens compared with untreated controls. Although the CFU data were not statistically different from the BCG and BCG-BCG groups, the histopathological and morphometric analyses indicated the positive effect of BCG-P-rAg85B in terms of differences in area of tissue affected and number and size of granulomas observed in tissues. P-rAg85B microparticles appeared to be effective in boosting a primary BCG immunization against MTB infection, as indicated by histopathology and morphometric analysis. These encouraging observations are relevant to boosting adults previously immunized with BCG or exposed to MTB, commonly the case in the developing world, and should be followed by further assessment of an appropriate immunization protocol for maximum protection.

PLGA microparticles in respirable sizes enhance an in vitro T cell response to recombinant Mycobacterium tuberculosis antigen TB10.4-Ag85B

PURPOSE

To study the use of poly (lactide-co-glycolide) (PLGA) microparticles in respirable sizes as carriers for recombinant tuberculosis (TB) antigen, TB10.4-Ag85B, with the ultimate goal of pulmonary delivery as vaccine for the prevention of TB.

MATERIALS AND METHODS

Recombinant TB antigens were purified from E. coli by FPLC and encapsulated into PLGA microparticles by emulsion/spray-drying. Spray-drying condition was optimized by half-factorial design. Microparticles encapsulating TB antigens were assessed for their ability to deliver antigens to macrophages for subsequent presentation by employing an in vitro antigen presentation assay specific to an Ag85B epitope.

RESULTS

Spray-drying condition was optimized to prepare PLGA microparticles suitable for pulmonary delivery (aerodynamic diameter of 3.3 microm). Antigen release from particles exhibited an initial burst release followed by sustained release up to 10 days. Antigens encapsulated into PLGA microparticles induced much stronger interleukin-2 secretion in a T-lymphocyte assay compared to antigen solutions for three particle formulations. Macrophages pulsed with PLGA-MDP-TB10.4-Ag85B demonstrated extended epitope presentation.

CONCLUSION

PLGA microparticles in respirable sizes were effective in delivering recombinant TB10.4-Ag85B in an immunologically relevant manner to macrophages. These results set the foundation for further investigation into the potential use of PLGA particles for pulmonary delivery of vaccines to prevent Mycobacterium tuberculosis infection.

Solid lipid nanoparticles for pulmonary delivery of insulin

Growing attention has been given to the potential of pulmonary route as an alternative for non-invasive systemic delivery of therapeutic agents. In this study, novel nebulizer-compatible solid lipid nanoparticles (SLNs) for pulmonary drug delivery of insulin were developed by reverse micelle-double emulsion method. The influences of the amount of sodium cholate (SC) and soybean phosphatidylcholine (SPC) on the deposition properties of the nanoparticles were investigated. Under optimal conditions, the entrapment delivery (ED), respirable fraction (RF) and nebulization efficiency (NE) of SLNs could reach 96.53, 82.11 and 63.28%, respectively, and Ins-SLNs remained stable during nebulization. Fasting plasma glucose level was reduced to 39.41% and insulin level was increased to approximately 170 microIU/ml 4h after pulmonary administration of 20 IU/kg Ins-SLNs. A pharmacological bioavailability of 24.33% and a relative bioavailability of 22.33% were obtained using subcutaneous injection as a reference. Incorporating fluorescent-labelled insulin into SLNs, we found that the SLNs were effectively and homogeneously distributed in the lung alveoli. These findings suggested that SLNs could be used as a potential carrier for pulmonary delivery of insulin by improving both in vitro and in vivo stability as well as prolonging hypoglycemic effect, which inevitably resulted in enhanced bioavailability.

The nanoscale in pulmonary delivery. Part 2: formulation platforms

This article is the second part of a review on the nanoscale in pulmonary drug delivery. Specifically it summarises and analyses the potential of the different inhalation delivery routes: nebulisers, dry powder inhalers, pressurised metered-dose inhalers, for the delivery of nanoparticles or nanodroplets. Few products and experimental studies have managed to fully exploit the nanoscale in inhalation delivery, although some may unknowingly benefit from it. Nebulisers are the most advanced in using the nanoscale, pressurised metered-dose inhalers require further developments to realise its full potential, and dry powder inhalers are specifically in need of a dry solid nanoparticle generation technique to make it a reality.

Poly (lactide-co-glycolide) microspheres in respirable sizes enhance an in vitro T cell response to recombinant Mycobacterium tuberculosis antigen 85B

PURPOSE

To investigate the use of poly (lactide-co-glycolide) (PLGA) microparticles in respirable sizes as carriers for Antigen 85B (Ag85B), a secreted protein of Mycobacterium tuberculosis, with the ultimate goal of employing them in pulmonary delivery of tuberculosis vaccine.

MATERIALS AND METHODS

Recombinant Ag85B was expressed from two Escherichia coli strains and encapsulated by spray-drying in PLGA microspheres with/without adjuvants. These microspheres containing rAg85B were assessed for their ability to deliver antigen to macrophages for subsequent processing and presentation to the specific CD4 T-hybridoma cells DB-1. DB-1 cells recognize the Ag85B(97-112) epitope presented in the context of MHC class II and secrete IL-2 as the cytokine marker.

RESULTS

Microspheres suitable for aerosol delivery to the lungs (3.4-4.3 microm median diameter) and targeting alveolar macrophages were manufactured. THP-1 macrophage-like cells exposed with PLGA-rAg85B microspheres induced the DB-1 cells to produce IL-2 at a level that was two orders of magnitude larger than the response elicited by soluble rAg85B. This formulation demonstrated extended epitope presentation.

CONCLUSIONS

PLGA microspheres in respirable sizes were effective in delivering rAg85B in an immunologically relevant manner to macrophages. These results are a foundation for further investigation into the potential use of PLGA particles for delivery of vaccines to prevent M. tuberculosis infection.

Applicability of an ultrasonic nebulization system for the airways delivery of beclomethasone dipropionate in a murine model of asthma

PURPOSE

We have assessed the use of an ultrasonic nebulization system (UNS), composed of ultrasonic nebulizer and diffusion dryer filled with charcoal, for the effective delivery of beclomethasone to the airways in a murine asthma model.

METHODS

Solution of beclomethasone in ethanol was aerosolized using an ultrasonic nebulizer. Passage of the aerosol through a drying column containing charcoal and deionizer produced dry beclomethasone particles. Particles were delivered to BALB/c mice placed in a whole-body exposition chamber 1 h before intranasal challenge with ovalbumine. Efficacy of beclomethasone delivery was evaluated by examining bronchoalveolar lavage fluid (BALF) cytology.

RESULTS

Effect of three UNS system parameters on aerosol particle size was investigated. The critical parameter affecting the size of dry particles was beclomethasone concentration in aerosolized solution and solution flow rate while power level of ultrasonic nebulizer generator had no effect. Administration of beclomethasone at calculated dose of 150 microg/kg to mice significantly decreased total cell number and relative eosinophil number in BALF.

CONCLUSIONS

The UNS system produces a monodisperse aerosol that can be used for inhalative delivery of poorly water soluble substances to experimental animals. The UNS system minimizes formulation requirements and allows rapid and relatively simple efficacy and toxicity testing in animals.

Manufacture, characterization, and pharmacodynamic evaluation of engineered ipratropium bromide particles

PURPOSE

The intent of this research was to generate and characterize respirable particles of ipratropium bromide (IPB), a short-acting anticholinergic bronchodilator, to achieve demonstrable sustained-release properties. The value of a long-acting anticholinergic agent is evident in the use of tiotropium for the treatment of chronic obstructive pulmonary disease.

METHODS

Hollow, spherical particles of ipratropium bromide suitable for inhalation were generated using a spray-drying process and characterized by laser diffraction particle size analysis, scanning electron microscopy, dynamic vapor sorption, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and dissolution testing. Experimental design techniques were used to identify critical process parameters and optimize the spray drying process. Pharmacodynamic studies were conducted to determine duration of effect.

RESULTS

Crystalline, stable, respirable particles with a range of dissolution profiles were manufactured by application of polylactic acid (PLA) coatings of 1, 5, 10, 15, 30, and 50% w/w. A novel, robust, modified Type IV dissolution method discriminated between formulations and guided their development. Preliminary studies in guinea pigs indicated an increased duration of bronchodilatory effect for 30% PLA-coated particles (56.3 min) particles compared with IPB powders alone (11.0 min).

CONCLUSIONS

Sustained-release respirable particles of ipratropium bromide were developed using a PLA spray coating approach and a trend for increased duration of effect was demonstrated in guinea pigs.

Nebulization of biodegradable nanoparticles: impact of nebulizer technology and nanoparticle characteristics on aerosol features

Nanoparticles may be effective drug delivery systems for use in various pulmonary therapeutic schemes. This study investigated the effect of nebulization technology and nanoparticle characteristics on the features of aerosol generation. Suspensions of biodegradable nanoparticles consisting of commercially available poly(lactide-co-glycolide) and novel comb polymers were nebulized with a jet, ultrasonic, and piezo-electric crystal nebulizer. The effects of the nanoparticle suspensions on the aerosol droplet size, as well as the nanoparticle size before and after nebulization, were characterized via laser diffraction. While the individual nanoparticle suspensions showed no clinically relevant influence on aerosol droplet size, as compared to control experiments, an enhanced nanoparticle aggregation within the droplets was observed. This aggregation was further characterized by fluorescence and scanning electron microscopy. Dependency of aggregation on nebulizer technology and nanoparticle characteristics was noted. Nanoparticles exhibiting the highest surface hydrophobicity were particularly susceptible to aggregation when nebulized with a jet nebulizer. Aggregation was reduced with nanoparticles exhibiting a more hydrophilic surface or when using ultrasonic nebulizers. We conclude that the biodegradable nanoparticles contained in the suspensions did not affect the aerosol droplet size in a clinically relevant manner; however, both the nanoparticle characteristics and the technique of aerosol generation influence nanoparticle aggregation occurring during aerosolization.

Physiochemical and pharmacological characterization of a Delta(9)-THC aerosol generated by a metered dose inhaler

The goal of the present study was to formulate a Delta(9)-tetrahydrocannabinol (Delta(9)-THC) metered-dose inhaler (MDI) that can be used to provide a systemic dose of Delta(9)-THC via inhalation. Following physiochemical characterization and accelerated stability testing of the aerosol, mice were exposed to the aerosol and evaluated for pharmacological effects indicative of cannabinoid activity, including hypomotilìty, antinociception, catalepsy, and hypothermia. The fine particle dose of Delta(9)-THC was 0.22 +/- 0.03 mg (mean +/- S.D.) or 25% of the emitted dose and was not affected by accelerated stability testing. A 10-min exposure to aerosolized Delta(9)-THC elicited hypomotility, antinociception, catalepsy, and hypothermia. Additionally, Delta(9)-THC concentrations in blood and brain at the antinociceptive ED(50) dose were similar for both inhalation and intravenous routes of administration. Finally, pretreatment with the CB(1) receptor antagonist SR 141716A (10 mg/kg, i.p.) significantly antagonized all of the Delta(9)-THC-induced effects. These results indicate that an MDI is a viable method to deliver a systemic dose of Delta(9)-THC that elicits a full spectrum of cannabinoid pharmacological effects in mice that is mediated via a CB(1) receptor mechanism of action. Further development of a Delta(9)-THC MDI could provide an appropriate delivery device for the therapeutic use of cannabinoids, thereby reducing the need for medicinal marijuana.

Pulmonary peptide delivery: effect of taste-masking excipients on leuprolide suspension metered-dose inhalers

The purpose of this study was to evaluate the effect of taste-masking excipients on in vitro and in vivo performance of a leuprolide metered-dose inhaler (MDI) suspension formulation. Taste-masking excipients (aspartame and menthol) were added to a leuprolide suspension MDI formulation. The leuprolide MDI formulation with the taste-masking excipients was characterized in terms of milling time, particle size distribution, dose delivery and uniformity, and drug absorption in dogs. The data were compared with a formula that did not contain taste-masking excipients. It was found that the longer milling time for the leuprolide suspension with the taste-masking excipients was required to obtain a similar particle size distribution compared with the formula without taste-masking excipients using a fluid energy mill. Although measurable differences in mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were not observed between the two formulations, the percent of particles < or = 5 microns and the actuator retention for the formula with the taste-masking excipients were significantly different from the formula without taste-masking excipients using the Marple-Miller cascade impactor. Taste-masking excipients did not show a significant effect on valve delivery and through-can dose uniformity. However, the mean ex-actuator dose was 150.4 mg for the formula with the taste-masking excipients and 162.2 mg for the reference formula, respectively, indicating a significant difference. In tracheostomized dogs, both formulations showed comparable pharmacokinetic parameters including Cmax, Tmax, AUC0-12 and bioavailability (F%), indicating that the taste-masking excipients do not have an effect on lung absorption of leuprolide acetate. Therefore, inclusion of taste-masking excipients in the leuprolide MDI suspension formulation showed a significant impact on drug micronization, exactuator dose, and particle deposition pattern. Mechanistically, the unfavorable performance of leuprolide MDI in the presence of taste-masking excipients could be due to modification of the properties of the suspension itself and alteration of propellant evaporation following actuation.

Investigation of some commercially available spacer devices for the delivery of glucocorticoid steroids from a pMDI

Five commercially available spacers were investigated to determine their influence on the percentage of drug retained in the spacer device, percentage fine particle fraction (FPF), percentage deposited in the induction port, mass median aerodynamic diameter (MMAD), and geometric standard deviation (GSD). Betamethasone valerate (BMV) and triamcinolone acetonide (TAA) were used as model drugs in the pressurized metered dose inhaler (pMDI) formulations containing the propellant HFA 134a. The BMV was dissolved in an ethanol/HFA 134a system, and the TAA was suspended in HFA 134a using ethanol as a dispersing agent. The metering chamber volume of the valve was either 50 microl or 150 microl. The spacer devices investigated included the ACE, Aerochamber, Azmacort, Easivent, and Ellipse spacers. Each spacer device was attached to an Andersen Cascade Impactor powered by a vacuum pump. Cascade impaction data were used to derive the percentage drug deposited in the induction port, MMAD, GSD, and FPF. The BMV particles emitted from the spacers were finer than the TAA particles because the dissolved drug precipitated as the cosolvent evaporated. The TAA particles had significantly larger MMADs because many undissolved drug particles were contained within each droplet following actuation. After evaporation of the liquid continuous phase, the suspended drug aggregated to form larger agglomerates than those particles precipitated from the BMV pMDI solution droplets. The addition of a spacer device lowered the MMAD to less than 4.7 microm for particles from both the BMV pMDI solution and the TAA pMDI suspension. The addition of a spacer device also lowered the percentage drug deposited in the induction port. The FPF was significantly increased when a spacer device was used. The MMAD significantly decreased when a spacer device was added for the two model drugs when using the 150-microl metering valves, but the difference was not statistically significant when the 50-microl valves were used (P < .05). The GSD was not influenced by the use of a spacer device. The use of a spacer device will enhance pMDI therapy by reducing the amount of drug deposited in the oropharyngeal region, which will lead to fewer instances of local and systemic side effects. In addition, the spacer devices investigated will allow a higher dose of drug to reach the deep lung, which may permit the use of lower dosage regimens with increased therapeutic efficacy.

Supercritical fluid processing of proteins. I: lysozyme precipitation from organic solution

The solution enhanced dispersion by supercritical fluid (SEDS) process was used to evaluate the effect of the processing variables on the biological and physicochemical characteristics of lysozyme protein particles produced from an organic solution of dimethylsulfoxide (DMSO) using an experimental design procedure. The processing variables were temperature, pressure, solution concentration and the flow-rates of supercritical carbon dioxide and a protein solution. Solutions of hen egg lysozyme (0.5-1%, w/v) in DMSO were dispersed using supercritical carbon dioxide as the antisolvent, and particles precipitated in a particle formation vessel. The morphology, particle size and size distribution and biological activity of the protein were determined. The precipitates were also examined with high sensitivity differential scanning calorimetry (HSDSC) and high-performance cation-exchange chromatography. The amount of residual DMSO was determined using headspace gas chromatography. Particle size measurements showed the precipitates to be agglomerates with primary particles of size 1-5 microm, containing <20 ppm of residual solvent. The activity of the precipitates varied between 44 and 100% depending on the experimental conditions. The similarity of HSDSC data for unprocessed and processed samples indicated that the SEDS process does not cause major denaturation of lysozyme when prepared from DMSO solutions. By optimising of working conditions, the SEDS process can produce micron-sized particles of lysozyme with minimal loss of biological activity.

The influence of lactose carrier on the content homogeneity and dispersibility of beclomethasone dipropionate from dry powder aerosols

Dry powder formulations for inhalation usually comprise a mixture of coarse lactose (CL), employed as a carrier, and micronized drug. It was the aim of this study to determine the effects of fine lactose (FL), blended as a tertiary component on the mixing homogeneity and dispersibility of a model hydrophobic drug, beclomethasone dipropionate (BDP). BDP particles (volume median diameter (VMD) 4.6 microm) existed mainly as agglomerates, the majority of which were not dispersed into primary particles after aerosolization at a high shear force (4.7 psi). The resultant particle size distribution of BDP was multi-modal with VMD varying between 4.7 and 30.2 microm. Ternary interactive mixtures were prepared to consist of CL, FL and BDP with a fixed ratio of lactose to BDP of 67.5:1 w/w, but two concentrations of FL, i.e. 2.5 and 5%, w/w. The mixing was carried out using different sequences of adding the three components for two mixing times (15 and 60 min). Binary mixtures composed of CL and BDP were prepared for both mixing times as the controls, and these exhibited a coefficient of variation (COV) in BDP content <= 5%. Addition of FL to the binary formulations greatly reduced the content uniformity of BDP if the final powder were prepared by first mixing CL with FL before mixing with the drug (COV>20%, after mixing for 15 min). However, the mixtures, prepared using other mixing sequences, had a similar uniformity of BDP content to the binary mixtures. All ternary mixtures containing 2.5% FL consistently produced a significantly higher (ANOVA P<0.01) fine particle fraction (FPF, 3.1--6.1%) and fine particle dose (FPD, 13.6--30.1 microg) of BDP than the binary mixtures (FPF, 0.3-0.4%; FPD, 1.6-2.1 microg) after aerosolization at 60 l min(-1) via a Rotahaler into a twin stage liquid impinger. The mixing sequences exerted a significant (P<0.05) effect on the dispersion and deaggregation of BDP from the formulations prepared using a mixing time of 15 min but such an effect disappeared when the mixing time was lengthened to 60 min. The dispersibility of BDP was always higher from the ternary mixtures than from the binary mixtures. BDP delivery from dry powder inhalers was improved markedly by adding FL to the formulation, without substantial reduction in the content uniformity of the drug.

Pulmonary delivery of a dopamine D-1 agonist, ABT-431, in dogs and humans

The purpose of this study was to evaluate the feasibility of intrapulmonary delivery of ABT-431, a selective D1 receptor agonist. Following intratracheal instillation of the drug solution, the lung bioavailability was found to be approximately 75% in dogs. An aerosol suspension formulation was then developed by dispersing the drug in tetrafluoroethane, HFC-134a, with the aid of poloxamer 124 and vitamin E. This ABT-431 MDI aerosol formulation showed about 40% of the particles emitted from the valve and actuator system to be under 5 microm in diameter. Also, the primary package (15 mL aluminum container, DF10/ACT-150 valve, and Micron-4-actuator with the orifice 0.4 mm) was satisfactory for accurate and reproducible dosimetry. Using tracheostomized beagle dogs, the C(max) following tracheal administration of 5 mg aerosolized ABT-431 was found to be 13.3+/-0.9 ng ml(-1) and the AUC(0-24) was estimated at 33.2+/-10.6 h ng ml(-1). The lung bioavailability of the aerosolized drug was 34% compared to intravenous injection in dogs. In humans, results from a single rising dose study demonstrated that rapid absorption of ABT-431 following oral inhalation administration resulted in a dose-dependent increase in the area under the plasma-time curve at dosage levels between 3.3 and 13.2 mg. There is a possibility of up to 25% absorption of the drug from human lung. Thus, pulmonary bioavailability of ABT-431 is significantly greater than that of oral administration. Also, these findings suggest that small and lipophilic compounds, especially with hepatic first pass effect, may be effectively delivered systemically using oral inhalation aerosols.

Activity-stability considerations of trypsinogen during spray drying: effects of sucrose

The preparation and processing of protein pharmaceuticals into powders may impose significant stresses that could perturb and ultimately denature them. In many cases their stabilization through added excipients is necessary to yield native and active proteins. In this study, the effect of spray drying on the structure and activity of a model protein (trypsinogen) was investigated. In the absence of excipients, spray drying resulted in small losses of its enzymatic activity. Protein conformational rearrangements in the solid state (observed via FTIR) and irreversible aggregation (upon reconstitution) constituted the major degradation pathways. The irreversible unfolding in the solid state was also confirmed by solution calorimetric studies that indicated a decreased thermal stability of the spray-dried protein after reconstitution. The presence of sucrose, a thermal and dehydration stress stabilizer, induced a concentration-dependent protective effect. Protein protection was afforded even at low carbohydrate concentrations, while at specific mass ratios (sucrose-to-protein = 1:1) complete activity preservation was achieved. However, at the high end of sucrose concentrations, a small destabilization was evident, indicating that excluded volume effects may be undesirable during preparation of protein microparticles via spray drying. The profile of both the protein conformational changes and thermal stability in the solid state closely followed that of the incurred activity losses, indicating that protein stabilization during dehydration is crucial during processing of these polypeptides.

Precipitation of proteins in supercritical carbon dioxide

Supercritical CO2 was used as an antisolvent to form protein particles that exhibited minimal loss of activity upon reconstitution. Organic protein solutions were sprayed under a variety of operating conditions into the supercritical fluid, causing precipitation of dry, microparticulate (1-5 microns) protein powders. Three proteins were studied: trypsin, lysozyme, and insulin. Amide I band Raman spectra were used to estimate the alpha-helix and beta-sheet structural contents of native and precipitate powders of each protein. Analysis of the Raman spectral revealed minimal (lysozyme), intermediate (trypsin), and appreciable (insulin) changes in secondary structure with respect to the commercial starting materials. The perturbations in secondary structure suggest that the most significant event during supercritical fluid-induced precipitation involved the formation of beta-sheet structures with concomitant decreases of alpha-helix. Amide I band Raman and Fourier-transform infrared (FTIR) spectra indicate that higher operating temperatures and pressures lead to more extensive beta-sheet-mediated intermolecular interactions in the precipitates. Raman and FTIR spectra of redissolved precipitates are similar to those of aqueous commercial proteins, indicating that conformational changes were reversible upon reconstitution. These results suggest that protein precipitation in supercritical fluids can be used to form particles suitable for controlled release, direct aerosol delivery to the lungs, and long-term storage at ambient conditions.

Dry-powder inhalers: evaluation of testing methodology and effect of inhaler design

We have previously developed a spray dried formulation of a model protein (beta-galactosidase) of a size suitable for evaluation in dry powder inhaler devices. In this study, we wished to evaluate the roles of various methods available for the laboratory testing of dry powders for inhalation (cascade impactor, twin impinger, aerodynamic time of flight and image analysis). Secondly we wished to compare different inhaler devices using formulations with and without a carrier. Both the cascade impactor and twin impinger were appropriate methods for the testing of dry powder inhalers, and gave comparable estimates of respirable fraction. Image analysis and aerodynamic time of flight were suitable methods for determining the particle size of the dry powders, although the former was considerably more time consuming than the latter. The four inhalers evaluated differed greatly in terms of in vitro deposition properties. The presence of a carrier significantly improved respirable fraction with the poorer inhalers, but was less critical to the performance of the more efficient devices.

Liposomes in pulmonary applications: physicochemical considerations, pulmonary distribution and antioxidant delivery

The application of liposomes for improved drug delivery to the lung is promising. Liposome-mediated pulmonary drug delivery promotes an increase in drug retention-time in the lung and more importantly, a reduction in extrapulmonary side-effects, invariably resulting in enhanced therapeutic efficacies. The engineering of an effective liposomal drug formulation for inhalation therapy must take into consideration the leakage problem associated with the nebulization process; vesicle stability and release kinetics within the pulmonary milieu; and, the altered pharmacokinetics of the entrapped drug. The delivery of liposome-entrapped antioxidants via the tracheobronchial route has been found to be very useful in increasing the half-times of the administered agents, thus providing a sustained release effect for prolonged drug action. The entrapment in liposomes of alpha-tocopherol, an extremely insoluble but highly effective antioxidant, has been shown to be very effective in ameliorating oxidant-induced injuries in the lung. The use of bifunctional liposomes containing two antioxidants have been determined to provide excellent resistance to an oxidative challenge and appears to hold promise for improved clinical applications in antioxidant therapy.

In vivo evaluation of dosage forms: application of gamma scintigraphy to non-enteral routes of administration

The trend to deliver drugs to defined areas of the body involves sophisticated carriers systems. In addition to the in vitro drug release profile one must be aware of the in vivo behaviour of the dosage form and the drug. Gamma scintigraphy is an elegant way to gain insights of the actual in vivo distribution pattern of dosage forms. This technique relies on the use of radioactive tracers included into the medicament and selected so as to enable an optimum detection by a gamma ray camera. The choice of a convenient label enables the in vivo determination of the targeting of the formulation administered through a large number of routes. The present paper reviews applications of gamma scintigraphy for the evaluation of dosage forms administered by the parenteral, rectal, buccal, nasal, pulmonary, and ophthalmic routes.