Cyclosporin A liposome aerosol: Particle size and calculated respiratory deposition

Inhaled lipid nanocarriers for pulmonary delivery of glucocorticoids: previous strategies, recent advances and key factors description

In view of the strong anti-inflammatory activity of glucocorticoids (GC) they are used in the treatment of almost all inflammatory lung diseases. In particular, inhaled GC (IGC) allow high drug concentrations to be deposited in the lung and may reduce the incidence of adverse effects associated with systemic administration. However, rapid absorption through the highly absorbent surface of the lung epithelium may limit the success of localized therapy. Therefore, inhalation of GC incorporated into nanocarriers is a possible approach to overcome this drawback. In particular, lipid nanocarriers, which showed high pulmonary biocompatibility and are well known in the pharmaceutical industry, have the best prospects for pulmonary delivery of GC by inhalation. This review provides an overview of the pre-clinical applications of inhaled GC-lipid nanocarriers based on several key factors that will determine the efficiency of local pulmonary GC delivery: 1) stability to nebulization, 2) deposition profile in the lungs, 3) mucociliary clearance, 4) selective accumulation in target cells, 5) residence time in the lung and systemic absorption and 6) biocompatibility. Finally, novel preclinical pulmonary models for inflammatory lung diseases are also discussed.

Repurpose but also (nano)-reformulate! The potential role of nanomedicine in the battle against SARS-CoV2

The coronavirus disease-19 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has taken the world by surprise. To date, a worldwide approved treatment remains lacking and hence in the context of rapid viral spread and the growing need for rapid action, drug repurposing has emerged as one of the frontline strategies in the battle against SARS-CoV2. Repurposed drugs currently being evaluated against COVID-19 either tackle the replication and spread of SARS-CoV2 or they aim at controlling hyper-inflammation and the rampaged immune response in severe disease. In both cases, the target for such drugs resides in the lungs, at least during the period where treatment could still provide substantial clinical benefit to the patient. Yet, most of these drugs are administered systemically, questioning the percentage of administered drug that actually reaches the lung and as a consequence, the distribution of the remainder of the dose to off target sites. Inhalation therapy should allow higher concentrations of the drug in the lungs and lower concentrations systemically, hence providing a stronger, more localized action, with reduced adverse effects. Therefore, the nano-reformulation of the repurposed drugs for inhalation is a promising approach for targeted drug delivery to lungs. In this review, we critically analyze, what nanomedicine could and ought to do in the battle against SARS-CoV2. We start by a brief description of SARS-CoV2 structure and pathogenicity and move on to discuss the current limitations of repurposed antiviral and immune-modulating drugs that are being clinically investigated against COVID-19. This account focuses on how nanomedicine could address limitations of current therapeutics, enhancing the efficacy, specificity and safety of such drugs. With the appearance of new variants of SARS-CoV2 and the potential implication on the efficacy of vaccines and diagnostics, the presence of an effective therapeutic solution is inevitable and could be potentially achieved via nano-reformulation. The presence of an inhaled nano-platform capable of delivering antiviral or immunomodulatory drugs should be available as part of the repertoire in the fight against current and future outbreaks.

Liposomal formulations for inhalation

No marketed inhaled products currently use sustained release formulations such as liposomes to enhance drug disposition in the lung, but that may soon change. This review focuses on the interaction between liposomal formulations and the inhalation technology used to deliver them as aerosols. There have been a number of dated reviews evaluating nebulization of liposomes. While the information they shared is still accurate, this paper incorporates data from more recent publications to review the factors that affect aerosol performance. Recent reviews have comprehensively covered the development of dry powder liposomes for aerosolization and only the key aspects of those technologies will be summarized. There are now at least two inhaled liposomal products in late-stage clinical development: ARIKACE® (Insmed, NJ, USA), a liposomal amikacin, and Pulmaquin™ (Aradigm Corp., CA, USA), a liposomal ciprofloxacin, both of which treat a variety of patient populations with lung infections. This review also highlights the safety of inhaled liposomes and summarizes the clinical experience with liposomal formulations for pulmonary application.

Therapeutic liposomal dry powder inhalation aerosols for targeted lung delivery

Therapeutic liposomal powders (i.e., lipospheres and proliposomes) for dry powder inhalation aerosol delivery, formulated with phospholipids similar to endogenous lung surfactant, offer unique opportunities in pulmonary nanomedicine while offering controlled release and enhanced stability. Many pulmonary diseases such as lung cancer, tuberculosis (TB), cystic fibrosis (CF), bacterial and fungal lung infections, asthma, and chronic obstructive pulmonary disease (COPD) could greatly benefit from this type of pulmonary nanomedicine approach that can be delivered in a targeted manner by dry powder inhalers (DPIs). These delivery systems may require smaller doses for efficacy, exhibit reduced toxicity, fewer side effects, controlled drug release over a prolonged time period, and increased formulation stability as inhaled powders. This state-of-the-art review presents these novel aspects in depth.

Vibrating-mesh nebulization of liposomes generated using an ethanol-based proliposome technology

This is the first study that evaluates the influence of the compartmental design of the micropump Aeroneb Go nebulizer and the viscosity of a proliposome hydration medium on vibrating-mesh aerosolization of liposomes. Ethanol-based proliposomes comprising soya phosphatidylcholine and cholesterol (1:1 mole ratio) were hydrated by using isotonic NaCl (0.9%) or sucrose (9.25%) solutions to generate liposomes that entrapped approximately 61% of the hydrophilic drug, salbutamol sulphate. Liposomes were aerosolized by the nebulizer to a two-stage impinger. For both formulations, the aerosol mass output was higher than the phospholipid output, indicating some accumulation of large liposomes or liposome aggregate within the nebulizer. Using NaCl (0.9%) solution as the dispersion medium, aerosol droplet size was much smaller and aerosol mass and phospholipid outputs were higher. This was attributed to the lower viscosity of the NaCl solution, resulting in a reduced retention of the aerosols in the "trap" of the nebulizer. For the entrapped salbutamol sulphate, although the "fine particle fraction" was relatively high (57.44%), size reduction of the liposomes during nebulization caused marked losses of the drug originally entrapped. Overall, liposomes generated from proliposomes when using this nebulizer showed high nebulization output and small droplet size. However, further work is required to reduce the losses of the originally entrapped drug from liposomes.

Formulations generated from ethanol-based proliposomes for delivery via medical nebulizers

Multilamellar and oligolamellar liposomes were produced from ethanol-based soya phosphatidylcholine proliposome formulations by addition of isotonic sodium chloride or sucrose solutions. The resultant liposomes entrapped up to 62% of available salbutamol sulfate compared with only 1.23% entrapped by conventionally prepared liposomes. Formulations were aerosolized using an air-jet nebulizer (Pari LC Plus) or a vibrating-mesh nebulizer (Aeroneb Pro small mesh, Aeroneb Pro large mesh, or Omron NE U22). All vibrating-mesh nebulizers produced aerosol droplets having larger volume median diameter (VMD) and narrower size distribution than the air-jet nebulizer. The choice of liposome dispersion medium had little effect on the performance of the Pari nebulizer. However, for the Aeroneb Pro small mesh and Omron NE U22, the use of sucrose solution tended to increase droplet VMD, and reduce aerosol mass and phospholipid outputs from the nebulizers. For the Aeroneb Pro large mesh, sucrose solution increased the VMD of nebulized droplets, increased phospholipid output and produced no effect on aerosol mass output. The Omron NE U22 nebulizer produced the highest mass output (approx. 100%) regardless of formulation, and the delivery rates were much higher for the NaCl-dispersed liposomes compared with sucrose-dispersed formulation. Nebulization produced considerable loss of entrapped drug from liposomes and this was accompanied by vesicle size reduction. Drug loss tended to be less for the vibrating-mesh nebulizers than the jet nebulizer. The large aperture size mesh (8μm) Aeroneb Pro nebulizer increased the proportion of entrapped drug delivered to the lower stage of a twin impinger. This study has demonstrated that liposomes generated from proliposome formulations can be aerosolized in small droplets using air-jet or vibrating-mesh nebulizers. In contrast to the jet nebulizer, the performance of the vibrating-mesh nebulizers was greatly dependent on formulation. The high phospholipid output produced by the nebulizers employed suggests that both air-jet and vibrating-mesh nebulization may provide the potential of delivering liposome-entrapped or solubilized hydrophobic drugs to the airways.

Disease guided optimization of the respiratory delivery of microparticulate formulations

BACKGROUND

Inhalation of microparticulate dosage forms can be effectively used in the treatment of respiratory and systemic diseases.

OBJECTIVE

Disease states investigated for treatment by inhalation of microparticles were reviewed along with the drugs' pharmacological, pharmacokinetic and physical chemical properties to identify the advantages of microparticulate inhalation formulations and to identify areas for further improvement.

METHODS

Microbial infections of the lung, asthma, diabetes, lung transplantation and lung cancer were examined, with a focus on those systems intended to provide a sustained release.

CONCLUSION

In developing microparticulate formulations for inhalation in the lung, there is a need to understand the pharmacology of the drug as the key to revealing the optimal concentration time profile, the disease state, and the pharmacokinetic properties of the pure drug as determined by IV administration and inhalation. Finally, in vitro release studies will allow better identification of the best dosing strategy to be used in efficacy and safety studies.

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.

Comparative analysis of methods to measure aerosols generated by a vibrating mesh nebulizer

Different approaches have been employed for in vitro assessment of the aerosol particle size generated by inhalation devices. In this study, aerosols from the Omron MicroAir vibrating mesh (VM) nebulizer were measured by cascade impaction (CI) using the MSP Next Generation Pharmaceutical Impactor (NGI), the ThermoAndersen Cascade Impactor (ACI), and by time-of-flight (TOF) analysis with the TSI 3321 Aerodynamic Particle Sizer Spectrometer (APS). The VM nebulizer was evaluated with sodium fluoride (NaF; 2.5%) and with generic albuterol (0.083%). Aerosol particle size (MMAD), respirable fractions (RF < 5 microm), and fine particle fractions (FPF < 3.3 microm) were determined with each method at room temperature (RT) and 4 degrees C using 50% average relative humidity. By NGI at either RT or 4 degrees C, aerosol particle sizes were similar for both NaF and albuterol (4.3-4.5 microm MMAD) with 55-61% RF and 27-43% FPF. With ACI, the distribution of particles at RT was similar except at the extremes of the dispersion and the MMAD was smaller (3.3 microm MMAD; p = 0.03). At 4 degrees C, particle sizes determined by ACI results were similar to the NGI (MMAD 4.1 microm; p > 0.05). TOF analysis by APS with albuterol gave significantly larger calculated MMAD (cMMAD) than either CI method (7.2 microm; p < 0.001). TOF measurements of nebulized albuterol at RT and 4 degrees C were equivalent. In summary, the results of VM nebulized NaF and albuterol were more consistent and generally equivalent when determined by NGI (at RT and 4 degrees C) and ACI analysis (at 4 degrees C). In contrast, aerosol particle sizes measured by TOF in the APS at both RT and 4 degrees C were larger than results obtained by CI. Differences in aerosol particle distribution obtained by different analysis methods should be considered while evaluating the in vitro performance of VM nebulizers.

Aerosol characterization of nebulized intranasal glucocorticoid formulations

Inhaled glucocorticoids (GCs) are the mainstay of long-term therapy for asthma. The lack of suitable preparations in the United States has induced clinicians to use intranasal (IN) GC formulations as "nebulizer suspensions" for off-label therapy. However, no data are available regarding aerosol production and characteristics. The aim of this study was to characterize drug outputs and aerodynamic profiles of four nebulized IN GC formulations with further analysis of flunisolide (Flu), and to test the influence of different delivery system/formulation combinations. The aerodynamic profiles and drug outputs were determined by impaction and chemical analysis. The solution output was determined by the gravimetric technique. Triamcinole acetonide (TAA), fluticasone propionate (Flut), beclomethasone dipropionate (Bec), and Flu (550, 500, 840, and 250 microg, respectively) diluted to 4 mL with saline solution were tested with the Sidestream (SID) and Aero-Tech II (AT2) nebulizers. Subsequently, Flu was tested with four additional nebulizers (Pari LC + [PARI] Acorn II, Hudson T Up-draft II, and Raindrop). All the aerosols were heterodisperse and had a particle size range optimal for peripheral airway deposition (1.85 to 3.67 microm). Flu had the highest drug output in the respirable range (22.8 and 20.3 microg/min with the AT and SID, respectively). Flu was 5-11 times more efficiently nebulized than the other formulations tested. No differences were detected in the solution outputs (0.25 to 0.3 mL/min). In subsequent testing of Flu, the PARI, AT, and SID showed the best performances. The LC+ achieved the highest drug and solution output (27.4 microg/min and 0.89 mL/min, respectively). In conclusion, Flu showed the best aerosol performance characteristics. These data do not endorse the off-label utilization of nebulized IN GC, but underscores the importance of in vitro testing before selecting any formulation/nebulizer combinations for clinical use.

Nebulisation of rehydrated freeze-dried beclomethasone dipropionate liposomes

Beclomethasone dipropionate (BDP) liposomes were prepared from various lipids, dilauroyl phosphatidylcholine (DLPC), dimyristoyl phosphatidylcholine (DMPC), dipalmitoyl phosphatidylcholine (DPPC), and hydrogenated soybean phosphatidylcholine (Epikuron 200 SH). A lipid with a low transition temperature (T(m)) (DLPC) incorporated a higher amount of BDP than lipid with a high T(m). The nebulisation of rehydrated freeze-dried BDP liposomes was carried out using a Pari LC Plus nebuliser and the generated aerosol characterised by an Andersen Cascade Impactor operated at 28.3 l/min. The rehydrated BDP-DLPC liposomes showed a higher output (78.3%) and a higher fine particle fraction (FPF) (75.0%) and smaller mass median aerodynamic diameter (MMAD) (3.31 microm) than the other rehydrated liposome preparations. Liposomes containing lipid with a high T(m) (DPPC and Epikuron) underwent aggregation during nebulisation. This was shown by the large increase in size of the DPPC liposomes from 15.78 to 47.51 microm and the Epikuron liposomes from 5.84 to 46.70 microm.

Inhalational interleukin-2 liposomes for pulmonary metastases: a phase I clinical trial

The lung is a common site of both metastases and primary neoplasia. This phase I study was designed to test the feasibility and toxicity of administering interleukin (IL)-2 liposomes by aerosol to patients with pulmonary metastases. The goal was to test whether IL-2 liposomes could be given by aerosol using biologically effective but non-toxic doses in an outpatient setting. Liposomes containing IL-2 or placebo (buffer) were synthesized and mixed to provide a constant lipid dose, and were nebulized using a Puritan twin jet nebulizer and a standard compressor. The liposome-containing mist was inhaled for about 20 min 3 times a day in order to selectively stimulate immune function within the lung and to avoid systemic toxicity. The dose chosen was based on canine efficacy and toxicity studies that used bronchoalveolar lavage to demonstrate increased cell numbers and activation of mononuclear cells after inhalation of nebulized IL-2 liposomes. Nine patients were treated in three cohorts of three patients at 1.5, 3.0 and 6.0 x 10(6) IU of IL-2 3 times a day. No significant toxicity was observed. We conclude that the delivery of IL-2 liposomes by inhalation is well tolerated. Further studies of inhalational IL-2 liposomes to determine efficacy as an anti-cancer therapy are warranted.

Nebulizer-compatible liquid formulations for aerosol pulmonary delivery of hydrophobic drugs: glucocorticoids and cyclosporine

This review discusses pulmonary delivery of glucocorticoids and cyclosporine in pharmaceutically acceptable organic solvents and liposomes, as well as in micellar solutions and microemulsions, by means of liquid aerosols generated by nebulizers. The review points out the importance of a variety of parameters for successful treatment of immunologically mediated lung diseases by inhalation of drug containing aerosols with particular references to physico-chemical properties of formulations, aerosol parameters, pharmacokinetics, and lung deposition in experimental animals and humans. The prospects for the use of these types of formulations for clinical treatment of asthma, lung transplant rejection processes and other lung diseases are summarized.

Pharmacokinetics of liposomal aerosolized cyclosporine A for pulmonary immunosuppression

BACKGROUND

The results of pulmonary transplantation are compromised by acute and chronic rejection. We hypothesized that a liposomal form of aerosolized cyclosporine A (CsA) would be selectively deposited and concentrated in the lungs. The theoretical advantage of this therapy is selective pulmonary immunosuppression with prolonged utilization.

METHODS

Eighteen dogs were endotracheally intubated; aerosolized liposomal CsA was administered for 15 min. CsA levels were measured in whole blood, lung, trachea, heart, kidney, liver, and spleen at various times after treatment.

RESULTS

The lung rapidly absorbs aerosolized liposomal CsA; other organs have much lower concentrations. The retention of pulmonary CsA delivered by liposome aerosol is approximately 120 min in this model.

CONCLUSIONS

Aerosolized liposomal CsA is selectively deposited and concentrated in the lungs; other organs absorb less CsA.

Gene transfer by guanidinium-cholesterol: dioleoylphosphatidyl-ethanolamine liposome-DNA complexes in aerosol

BACKGROUND

A major challenge of gene therapy is the efficient transfer of genes to cell sites where effective transfection can occur. The impact of jet nebulization on DNA structural and functional integrity has been problematic for the aerosol delivery of genes to pulmonary sites and remains a serious concern for this otherwise promising and noninvasive approach.

METHODS

This study examined effects of cationic liposome-DNA formulation on both transfection efficiency (in vitro and in vivo) and jet nebulizer stability. The effects of nebulization and sonication on liposome-DNA particle size characteristics were examined. Electron microscopy of promising formulations was performed using several fixation methods.

RESULTS

The cationic lipid bis-guanidinium-tren-cholesterol (BGTC), in combination with the neutral co-lipid dioleoylphosphatidylethanolamine (DOPE), was found to have a degree of stability adequate to permit effective gene delivery by the aerosol route. Optimal ratios of lipids and plasmid DNA were identified. Particle size analysis and ultrastructural studies revealed a remarkably homogeneous population of distinctly liposomal structures correlating with the highest levels of transfection efficiency and nebulizer stability.

CONCLUSIONS

Optimizing gene delivery vectors for pulmonary aerosol delivery to respiratory sites must take into account factors other than transfection efficiency in vitro. Effects of liposome-DNA formulation on liposomal morphology (i.e. particle size, multilamellar structure) appear to be relevant to stability during aerosolization. These studies have allowed us to identify formulations that hold promise for successful clinical application of aerosol gene delivery.

Four hours of continuous albuterol nebulization

BACKGROUND AND OBJECTIVES

Continuous albuterol nebulization (CAN) is a therapeutic modality available to treat status asthmaticus. Currently, CAN may be administered using a large-volume nebulizer (LVN) or a small-volume nebulizer attached to an infusion pump or refilled as needed. Few data are available regarding the reproducibility of aerosol characteristics during CAN. In this study, we determined the aerodynamic profile, drug output (DO), DO in respirable range (RD), solution output (SO), and changes in reservoir's albuterol concentration (AR) hourly during 4 hours of CAN.

DESIGN

A modified Puritan-Bennett 1600 jet nebulizer was tested with a large reservoir (LR; 250 mL), medium reservoir (MR; 45 mL), and small reservoir with infusion pump (SRP; 18 mL). We used 100-, 40-, and 4-mL initial fill volumes (with 10-mL/h infusion for SRP) of 1 mg/mL albuterol solution for the LR, MR, and SRP, respectively. Particle size distribution and DO consistency were determined by impaction and spectrophotometric analysis (275 nm). We also determined albuterol mass output. The SO was determined by gravimetric technique.

RESULTS

The PBsj produced a heterodisperse aerosol with a median mass aerodynamic diameter range of 1.8 to 2.2 microm. DO and RD paralleled SO. The LR had the highest SO, DO, and RD (8.03+/-2.36 vs 5.73+/-2.48 and 5.85+/-0.51 mg/h for MR and SRP, respectively). The AR showed no statistically significant changes.

CONCLUSIONS

The PBsj demonstrated consistent and adequate aerosol production during 4 hours of CAN. These bench data support the widespread use of a LVN for CAN.

Tolerance of volunteers to cyclosporine A-dilauroylphosphatidylcholine liposome aerosol

Cyclosporine A (CsA) in liposomes of dilauroylphosphatidylcholine (DLPC), containing 118 micrograms of CsA/L of aerosol with a particle size of 1.6 to 1.7 micron diameter, was inhaled by 10 nonsmoking, normal volunteers each for 45 min. Aerosol was administered through an Aerotech II nebulizer (CIS-US, Inc., Bedford, MA) mouthpiece. Eight of the 10 volunteers had tracheal irritation and intermittent coughing following exposure. FEV1 and FVC values were mildly reduced, but returned to normal in 1 h. Blood chemical and hematologic values were unchanged at any time point after as opposed to before inhalation. Nine of the 10 volunteers later inhaled DLPC only, administered through the nebulizer mouthpiece. There was no change in FEV1 or FVC values, and there was no coughing or tracheal irritation. Subsequently, five of the volunteers who had previously had respiratory reactions inhaled CsA-DLPC liposome aerosol for 45-min, but through a mouth-only face mask. There was no tracheal irritation, coughing, or changes in spirometric measures. Blood concentrations of CsA at 15 min after the 45-min inhalation with a face mask averaged 83 +/- 42 ng/ml (mean +/- SD). At 24 h after treatment, CsA was undetectable in blood of the initial 10 volunteers. These studies indicate that CsA-DLPC liposome aerosol can be safely explored as a treatment for patients with moderately severe asthma.

Nebulized interleukin 2 liposomes: aerosol characteristics and biodistribution

Although interleukin 2 (IL-2) has been associated with modest anti-tumour responses in man, treatment-related toxicity has limited its widespread use. The local delivery of liposomal formulations of interleukin 2 to the lung as aerosols has been demonstrated to be non-toxic, biologically active, and associated with regression of spontaneous pulmonary metastases in dogs. This study was undertaken to evaluate the physical and biological characteristics of nebulized interleukin 2 liposomes. The aerosol droplet size distribution and the physical stability of interleukin 2 liposomes were examined in-vitro using an Andersen cascade impactor and studies of liposome entrapment of interleukin 2 before and after nebulization. The biological stability of interleukin 2 liposomes after nebulization was demonstrated using the CTLL-2 bioassay for interleukin 2. In-vivo studies of pulmonary biodistribution and clearance of inhaled technetium (99mTc)-labelled interleukin 2 liposomes were undertaken in a normal dog. Aerosols of free interleukin 2 and of interleukin 2 liposomes were compared in both in-vitro and in-vivo experiments. The mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) of interleukin 2 liposomes were 1.98 microns and 2.02, respectively. Independent analysis of aerosol particle-size distribution using the constitutive components of the interleukin 2 liposomes (interleukin 2: lipid:HSA) demonstrated a close correlation of size distributions (r = 0.9445; P < 0.001). The entrapment of interleukin 2 in liposomes was 93 +/- 4.3% before nebulization and 90 +/- 8.9% after. After delivery to an anaesthetized dog, interleukin 2 liposome aerosols were deposited evenly throughout the lung (mean +/- s.d. central lung-to-peripheral lung deposition was 1.12 +/- 0.03). After approximately 24 h inhalation, interleukin 2 liposomes were retained within the lung and were taken up in part by the spleen. The results of this study are indicative of the stability of this interleukin 2 liposome formulation to nebulization. Such nebulization might be an attractive immunotherapeutic strategy for treatment of pulmonary metastases and primary lung cancers.

Delivery of DNA-cationic liposome complexes by small-particle aerosol

Aerosol delivery of gene therapy for treatment of lung diseases allows topical treatment of the airways with DNA concentrations not obtainable by systemic administration. We have investigated delivery of cationic liposomes complexed to plasmid DNA in a small particle aerosol. Plasmid cDNA-DMRIE/DOPE complexes were nebulized using either an Aerotech II or Puritan-Bennett 1600 (PB1600) nebulizer. Reservoir sampling showed that DNA-DMRIE/DOPE complexes were damaged to a significant degree during nebulization, such that activity of transfected gene was diminished. Of the nebulizers analyzed, DNA-DMRIE/DOPE complexes were more stable in the PB1600. The loss of effective transfection by DNA-DMRIE/DOPE, as detected by decreased reporter gene activity in A549 lung cells, was consistent with denaturation of the DMRIE/DOPE. In contrast, nebulized DNA-DOSPA/DOPE complexes retained complete ability to transfect. Adjustments to flow rate and reservoir volume of the PB1600 allowed a longer period of delivery of active DNA-DMRIE/DOPE particles. DNA-DMRIE/DOPE was radiolabeled with Technetium-99m (99mTc), nebulized, and the output captured in either an Andersen Sampler (AS) (Andersen, 1958) cascade impactor particle size analyzer or an all glass impinger. cDNA-cationic lipid complexes were detected in size ranges of 0.4-10 microns, with most particles found between 1-2 microns. Aerosol output was consistent from 0 to 5 min. These results show the feasibility of aerosol delivery of DNA-cationic lipids for the purposes of gene therapy to the lung.

Operating characteristics of 18 different continuous-flow jet nebulizers with beclomethasone dipropionate liposome aerosol

A study of 18 different commercially available continuous-flow, jet nebulizers was performed with a standard liposomal formulation of beclomethasone dipropionate (Bec-DP) prepared with dilauroyl phosphatidylcholine (Bec-DLPC). The analysis compared the total Bec-DP output from aqueous suspensions of Bec-DLPC containing an initial starting reservoir concentration of 0.5 mg/ml. Aerosols from each nebulizer tested were characterized by the mass median aerodynamic diameter, geometric standard deviation, drug output, and the predicted percentage regional deposition of inhaled Bec-DLPC liposomes within the human respiratory tract. These data can provide a basis for the selection of commercially available jet nebulizers for use with glucocorticoid liposome aerosols for treatment of asthma and other inflammatory lung diseases.