Development, characterization and stability evaluation of ciprofloxacin-loaded parenteral nutrition nanoemulsions.

In this study, two licensed total parenteral nanoemulsion formulations (Clinoleic® and Intralipid®) were loaded with ciprofloxacin (CP). The physicochemical characteristics and stability profiles of the formulations were investigated using a range of drug concentrations. Furthermore, formulation stability was evaluated over a period of six months at room temperature (RT) or 4 °C. Loading CP into nanoemulsions resulted in no significant differences in their measured droplet size, polydispersity index (PI), zeta potential, and pH. Drug entrapment efficiency (EE) was relatively high for all formulations, regardless of nanoemulsion type, and the drug release was sustained over 24 h. Stability studies of all formulations were performed at 4 °C and RT for 180 and 60 days, respectively. At 4 °C for 180 days, both Clinoleic® and Intralipid® formulations at a range of drug concentrations (1-10 mg/ml) showed high stabilities measured periodically by the average droplet sizes, PI, pH, and zeta potential values. Similar results, but pH values, were shown when the formulations for both nanoemulsion stored at RT for 60 days. Overall, this study has shown that CP was successfully loaded into clinically licensed TPN lipid nanoemulsions. The resultant CP-loaded nanoemulsion formulations demonstrated desirable physicochemical properties and were stable upon storage at 4 °C for up to six months.

Development of Injectable PEGylated Liposome Encapsulating Disulfiram for Colorectal Cancer Treatment.

Disulfiram (DS), an anti-alcoholism medicine, shows strong anti-cancer activity in the laboratory, but the application in clinics for anti-cancer therapy has been limited by its prompt metabolism. Conventional liposomes have shown limited ability to protect DS. Therefore, the aim of this study is to develop PEGylated liposomes of DS for enhanced bio-stability and prolonged circulation. PEGylated liposomes were prepared using ethanol-based proliposome methods. Various ratios of phospholipids, namely: hydrogenated soya phosphatidylcholine (HSPC) or dipalmitoyl phosphatidylcholine (DPPC) and N-(Carbonyl-methoxypolyethylenglycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-PEG2000) with cholesterol were used. DS was dissolved in the alcoholic solution in different lipid mol% ratios. The size of the resulting multilamellar liposomes was reduced by high-pressure homogenization. Liposomal formulations were characterized by size analysis, zeta potential, drug loading efficiency and stability in horse serum. Small unilamellar vesicles (SUVs; nanoliposomes) were generated with a size of approximately 80 to 120 nm with a polydispersity index (PDI) in the range of 0.1 to 0.3. Zeta potential values of all vesicles were negative, and the negative surface charge intensity tended to increase by PEGylation. PEGylated liposomes had a smaller size (80-90 nm) and a significantly lower PDI. All liposomes showed similar loading efficiencies regardless of lipid type (HSPC or DPPC) or PEGylations. PEGylated liposomes provided the highest drug biostability amongst all formulations in horse serum. PEGylated DPPC liposomes had t1/2 =77.3 ± 9.6 min compared to 9.7 ± 2.3 min for free DS. In vitro cytotoxicity on wild type and resistant colorectal cancer cell lines was evaluated by MTT assay. All liposomal formulations of DS were cytotoxic to both the wild type and resistant colorectal cancer cell lines and were able to reverse chemoresistance at low nanomolar concentrations. In conclusion, PEGylated liposomes have a greater potential to be used as an anticancer carrier for disulfiram.

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.

Studies of the precipitation pattern of paclitaxel in intravenous infusions and rat plasma using laser nephelometry.

Cremophor EL (CrEL) is commonly used to solubilize paclitaxel (Ptx); a widely established anticancer agent used against many types of cancer. Using laser-based microplate nephelometry, in this work we assessed the precipitation kinetics of Ptx in CrEL-containing formulations upon dilutions with different infusion media or upon introduction into rat plasma. The precipitation profile of Ptx was assessed for a Taxol-like formulation and compared with a preparation with reduced CrEL content. These two formulations were diluted at various ratios in compatible infusion media and with or without rat plasma. The percentages of Ptx precipitated in dilution media and protein-binding in plasma were quantified using HPLC. The findings of turbidity measurements were in good agreement with HPLC. Despite the presence of albumin, it was possible to assess turbidity within infusion solutions and predict Ptx precipitation. Upon addition to plasma, no precipitation in Taxol-like formulation occurred after 2 h. In contrast, precipitation occurred immediately in CrEL-reduced formulation. It is possible that the high percentage of protein-bound Ptx in plasma (98.5-99.2%) has inhibited drug precipitation. Turbidity measurements using laser nephelometry can provide a rapid screening tool when developing intravenous formulations for poorly soluble drugs, such as Ptx and assess its stability upon dilution in animal plasma.

Sugar-based novel niosomal nanocarrier system for enhanced oral bioavailability of levofloxacin.

CONTEXT: Vesicular systems have attracted great attention in drug delivery because of their amphiphilicity, biodegradability, non-toxicity and potential for increasing drug bioavailability. OBJECTIVE: A novel sugar-based double-tailed surfactant containing renewable block was synthesized for preparing niosomal vesicles that could be exploited for Levofloxacin encapsulation, aiming to increase its oral bioavailability. MATERIALS AND METHODS: The surfactant was characterized by 1H NMR, mass spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Its biocompatibility was studied against cell cultures and human blood hemolysis. In vivo acute toxicity was evaluated in mice. The vesicle morphology, size, drug-excipients interaction and entrapment efficiency (EE) were examined using atomic force microscope (AFM), dynamic light scattering (DLS), FT-IR and HPLC. Oral bioavailability studies of Levofloxacin in surfactant-based niosomal formulation were carried out using rabbits and plasma samples were analyzed using HPLC. RESULTS AND DISCUSSION: Vesicles were spherical in shape and the size was 190.31 ± 4.51 nm with a polydispersity index (PDI) of 0.29 ± 0.03. The drug EE in niosomes was 68.28 ± 3.45%. When applied on cell lines, high cell viability was observed even after prolonged exposure at high concentrations. It caused 5.77 ± 1.34% hemolysis at 1000 µg/mL and was found to be safe up to 2000 mg/kg. Elevated Levofloxacin plasma concentration was achieved when delivered with novel vesicles. CONCLUSION: The surfactant was demonstrated to be safe and effective as carrier of Levofloxacin. The study suggests that this sugar-based double-tailed nonionic surfactant could be promising nano-vesicular system for delivery and enhancing oral bioavailability of the hydrophobic Levofloxacin.

Development of a biocompatible creatinine-based niosomal delivery system for enhanced oral bioavailability of clarithromycin.

CONTEXT: Nonionic surfactant vesicles have gained increasing scientific attention for hydrophobic drugs delivery due to their biocompatibility, stability and low cost. OBJECTIVE: The aim of the present study was to synthesize and evaluate a novel creatinine-based nonionic surfactant in terms of its ability to generate biocompatible niosomal system for the delivery of Clarithromycin. MATERIALS AND METHODS: The surfactant was synthesized by reacting creatinine with lauroyl chloride followed by characterization using 1HNMR and MS. The drug-loaded niosomal vesicles of the surfactant were characterized for drug encapsulation efficiency (EE) using LC-MS, vesicle size using dynamic light scattering (DLS) and vesicle shape using atomic force microscopy (AFM). The surfactant was also investigated for blood hemolysis, in vitro cytotoxicity against different cell lines and in vivo acute toxicity in mice. Furthermore, the in vivo bioavailability of Clarithromycin encapsulated in the novel niosomal formulation was investigated using rabbits and quantified through validated LC-MS/MS method. RESULTS AND DISCUSSION: Findings showed that vesicles were able to entrap up to 67.82 ± 1.27% of the drug, and were rounded in shape with a size around 202.73 ± 5.30 nm and low polydispersity. The surfactant caused negligible blood hemolysis, very low cytotoxicity and was found to be safe up to 2500 mg/kg body weight using mice. The niosomal formulation showed twofold enhanced oral bioavailability of Clarithromycin as compared to commercial formulations of the drug. CONCLUSION: The study has shown that the creatinine-based niosomes developed in our laboratory were biocompatible, safe and increased the oral bioavailability of the model hydrophobic Clarithromycin using experimental animals.

Glycoside-based niosomal nanocarrier for enhanced in-vivo performance of Cefixime.

This study aimed to evaluate the potential of a novel glycoside non-ionic surfactant synthesized and characterized in our laboratory for increased oral bioavailability of Cefixime. The surfactant was synthesized by simple etherification of bergenin with bromoundecane and characterized by (1)H NMR and mass spectroscopy (MS). Biocompatibility of the surfactant (BRM-BG) was assessed by in-vitro cytotoxicity against NIH/3T3 cells and human blood hemolysis. In-vivo acute toxicity was evaluated in mices. Cefixime loaded BRM-BG niosomes were investigated for drug entrapment efficiency using HPLC and surface morphology and vesicle size by atomic force microscopy (AFM) and dynamic light scattering (DLS). The in-vivo oral bioavailability and pharmacokinetics studies were carried out using rabbits. Cefixime loaded BRM-BG vesicles were spherical in the size range of 178.66±8.17nm with a polydipersity index (PDI) of 0.20±0.01, offering an entrapment efficiency as high as 78.4±0.83%. When the surfactant was applied on NIH 3T3 tissue culture, as high as 90.77±3.15% and 86.86±3.02%, cell viability at 1000µg/mL concentration after 24 and 48h respectively were observed. The surfactant also caused 5.49±1.62% haemolysis and was found to be safe at a dose up to 2000mg/kg. In-vivo drug plasma concentration (Cmax) was found to be 9.69±1.22µg/mL, much higher than that resulting from the intake of commercial suspension and capsules. BRM-BG demonstrated to be safe and effective as carrier of Cefixime following oral dosing in rabbits. The BRM-BG surfactant delivery nano-system is relatively safe and in animal models it is an appropriate carrier for Cefixime, offering enhanced bioavailability compared to commercially available formulations of the drug.

Novel paclitaxel formulations solubilized by parenteral nutrition nanoemulsions for application against glioma cell lines.

The aim of this study is to investigate using nanoemulsion formulations as drug-delivery vehicles of paclitaxel (PX), a poor water-soluble anticancer drug. Two commercially available nanoemulsion fat formulations (Clinoleic 20% and Intralipid 20%) were loaded with PX and characterised based on their size, zeta potential, pH and loading efficiency. The effect of formulation on the cytotoxicity of PX was also evaluated using MTT assay. The droplet size of the Clinoleic emulsion increased from 254.1nm to 264.7nm when paclitaxel (6mg/ml) was loaded into the formulation, compared to the drug-free formulation. Similarly, the droplet size of Intralipid increased from 283.3 to 294.6nm on inclusion of 6mg/ml paclitaxel. The Polydispersity Indexes (PDIs) of all the nanoemulsion formulations (Clinoleic and Intralipid) were less than 0.2 irrespective of paclitaxel concentration indicating that all nanoemulsion formulations used were homogeneously sized. The pH range for the Clinoleic formulations (7.1-7.5) was slightly higher than that of the Intralipid formulations (6.5-6.9). The zeta potential of linoleic had a greater negative value than that of Intralipid. Loading efficiencies for paclitaxel were 70.4-80.2% and 44.2-57.4% for Clinoleic and Intralipid formulations, respectively. Clinoleic loaded with paclitaxel decreased the viability of U87-MG cell to 6.4±2.3%, compared to Intralipid loaded with paclitaxel (21.29±3.82%). Both nanoemulsions were less toxic to the normal glial cells (SVG-P12), decreasing the cell viability to 25-35%. This study suggests that nanoemulsions are useful and potentially applicable vehicles of paclitaxel for treatment of glioma.

PEGylated graphene oxide for tumor-targeted delivery of paclitaxel.

AIM: The graphene oxide (GO) sheet has been considered one of the most promising carbon derivatives in the field of material science for the past few years and has shown excellent tumor-targeting ability, biocompatibility and low toxicity. We have endeavored to conjugate paclitaxel (PTX) to GO molecule and investigate its anticancer efficacy. MATERIALS & METHODS: We conjugated the anticancer drug PTX to aminated PEG chains on GO sheets through covalent bonds to get GO-PEG-PTX complexes. The tissue distribution and anticancer efficacy of GO-PEG-PTX were then investigated using a B16 melanoma cancer-bearing C57 mice model. RESULTS: The GO-PEG-PTX complexes exhibited excellent water solubility and biocompatibility. Compared with the traditional formulation of PTX (Taxol®), GO-PEG-PTX has shown prolonged blood circulation time as well as high tumor-targeting and -suppressing efficacy. CONCLUSION: PEGylated graphene oxide is an excellent nanocarrier for paclitaxel for cancer targeting.

A comprehensive production method of self-cryoprotected nano-liposome powders.

This study provided a convenient approach for large scale production of hydrogenated soya phosphatidylcholine nano-liposome powders using beclometasone dipropionate as a model drug and sucrose as proliposome carrier. Fluid-bed coating was employed to manufacture proliposomes by coating sucrose with the phospholipid (5%, 10%, 15% and 20% weight gains), followed by hydration, size reduction using high pressure homogenization, and freeze-drying to yield stable nano-vesicles. High pressure homogenization was compared with probe-sonication in terms of liposome size, zeta potential and drug entrapment. Furthermore, the effect of freeze-drying on vesicle properties generated using both size reduction methods was evaluated. Results have shown that high-pressure homogenization followed by freeze-drying and rehydration tended to yield liposomes smaller than the corresponding vesicles downsized via probe-sonication, and all size measurements were in the range of 72.64-152.50 nm, indicating that freeze-drying was appropriate, regardless of the size reduction technique. The liposomes, regardless of size reduction technique and freeze drying had slightly negative zeta potential values or were almost neutral in surface charge. The entrapment efficiency of BDP in homogenized liposomes was found to increase following freeze-drying, hence the drug entrapment efficiency values in rehydrated liposomes were 64.9%, 57%, 69.5% and 64.5% for 5%, 10%, 15% and 20% weight gains respectively. In this study, we have reported a reliable production method of nano-liposomes based on widely applicable industrial technologies such as fluid-bed coating, high pressure homogenization and freeze-drying. Moreover, sucrose played a dual role as a carrier in the proliposome formulations and as a cryoprotectant during freeze-drying.

Thymopentin nanoparticles engineered with high loading efficiency, improved pharmacokinetic properties, and enhanced immunostimulating effect using soybean phospholipid and PHBHHx polymer.

Formulation of protein and peptide drugs with sustained release properties is crucial to enhance their therapeutic effect and minimize administration frequency. In this study, immunomodulating polymeric systems were designed by manufacturing PHBHHx nanoparticles (NPs) containing thymopentin (TP5). The release profile of the drug was studied over a period of 7 days. The PHBHHx NPs containing TP5-phospholipid (PLC) complex (TP5-PLC) displayed a spherical shape with a mean size, zeta potential, and encapsulation efficiency of 238.9 nm, -32.0 mV, and 72.81%, respectively. The cytotoxicity results showed the PHBHHx NPs had a relatively low toxicity in vitro. TP5 entrapped in the NPs could hardly release in vitro, while the NPs had longer than 7 days release duration after a single subcutaneous injection in Wistar rats. The immunodepression rat model was built to evaluate the immunomodulating effects of TP5-PLC-NPs in vivo. The results of T-lymphocyte subsets (CD3(+), CD4(+), CD8(+), and CD4(+)/CD8(+) ratio) analysis and superoxide dismutase (SOD) values suggested that TP5-PLC-NPs had stronger immunoregulation effects than TP5 solution. In conclusion, an applicable approach to markedly enhancing the loading of a water-soluble peptide into a hydrophobic polymer matrix has been introduced. Thus, TP5-PLC-NPs are promising nanomedicine systems for sustained release effects of TP5.

Stability of parenteral nanoemulsions loaded with paclitaxel: the influence of lipid phase composition, drug concentration and storage temperature.

Paclitaxel was loaded into licensed parenteral nutrition nanoemulsions (Clinoleic® and Intralipid®) using bath sonication, and the stability of the formulations was investigated following storage for two weeks at room temperature or at 4 °C. In general, Clinoleic droplets were smaller than Intralipid droplets, being around 255 and 285 nm, respectively, for blank and freshly loaded emulsions. Regardless of storage temperature, the Clinoleic exhibited a very slight or no increase in droplet size upon storage, whilst the droplet size of the Intralipid emulsion increased significantly. The droplet size of both emulsions was minimally affected by paclitaxel concentration within the range of 0, 1, 3 and 6 mg/ml. The pH of both emulsions markedly decreased upon storage at room temperature, which was possibly attributed to the production of fatty acids resulting from phospholipid hydrolysis. However, at 4 °C, the pH of Clinoleic emulsion was unaffected by storage or paclitaxel concentration while the Intralipid emulsion demonstrated a trend for pH reduction. Both nanoemulsions had a negative zeta potential, with the Clinoleic formulations having the highest charge, possibly explaining the better size stability of this emulsion. Overall, this study has shown that paclitaxel was successfully loaded into clinically licensed parenteral emulsions and that Clinoleic showed greater stability than the Intralipid.

Laser diffraction and electron microscopy studies on inhalable liposomes generated from particulate-based proliposomes within a medical nebulizer.

Particulate-based proliposomes were made by coating sucrose carrier particles with egg phosphatidylcholine (EPC), soya phosphatidylcholine (SPC) or soya phosphatidylcholine with an equimole ratio of cholesterol (SPC:Chol, 1:1). Inhalable multilamellar liposomes were generated from proliposomes in situ within a Pari LC Plus nebulizer by addition of aqueous phase, with no need for prior manual shaking. All proliposome formulations produced high aerosol and phospholipid outputs and were delivered in high fractions to the lower stage of a two-stage impinger. The SPC:Chol (1:1) liposomes tended to accumulate more in the nebulizer because of their greater rigidity, which correlated with the larger size measured at the end of nebulization. The size of aerosol droplets as measured by laser diffraction was similar for all formulations, however, at the sputtering period, the SPC:Chol (1:1) formulation produced large droplets with broadened size distribution. This study has demonstrated a simple approach to delivering high outputs of liposomes using a particulate-based proliposome technology and has shown an evidence of liposome generation from proliposomes within a medical nebulizer.

Nebulization of ultradeformable liposomes: the influence of aerosolization mechanism and formulation excipients.

Ultradeformable liposomes are stress-responsive phospholipid vesicles that have been investigated extensively in transdermal delivery. In this study, the suitability of ultradeformable liposomes for pulmonary delivery was investigated. Aerosols of ultradeformable liposomes were generated using air-jet, ultrasonic or vibrating-mesh nebulizers and their stability during aerosol generation was evaluated using salbutamol sulphate as a model hydrophilic drug. Although delivery of ultradeformable liposome aerosols in high fine particle fraction was achievable, the vesicles were very unstable to nebulization so that up to 98% drug losses were demonstrated. Conventional liposomes were relatively less unstable to nebulization. Moreover, ultradeformable liposomes tended to aggregate during nebulization whilst conventional vesicles demonstrated a "size fractionation" behaviour, with smaller liposomes delivered to the lower stage of the impinger and larger vesicles to the upper stage. A release study conducted for 2 h showed that ultradeformable liposomes retained only 30% of the originally entrapped drug, which was increased to 53% by inclusion of cholesterol within the formulations. By contrast, conventional liposomes retained 60-70% of the originally entrapped drug. The differences between ultradeformable liposomes and liposomes were attributed to the presence of ethanol or Tween 80 within the elastic vesicle formulations. Overall, this study demonstrated, contrary to our expectation, that materials included with the aim of making the liposomes more elastic and ultradeformable to enhance delivery from nebulizers were in fact responsible for vesicle instability during nebulization and high leakage rates of the drug.

Carbon nanotubes in cancer therapy and drug delivery.

Carbon nanotubes (CNTs) have been introduced recently as a novel carrier system for both small and large therapeutic molecules. CNTs can be functionalized (i.e., surface engineered) with certain functional groups in order to manipulate their physical or biological properties. In addition to the ability of CNTs to act as carriers for a wide range of therapeutic molecules, their large surface area and possibility to manipulate their surfaces and physical dimensions have been exploited for use in the photothermal destruction of cancer cells. This paper paper will discuss the therapeutic applications of CNTs with a major focus on their applications for the treatment of cancer.

Predicting the physical properties of tablets from ATR-FTIR spectra using partial least squares regression.

CONTEXT: The formulation of a new tablet is a time-consuming activity involving the preparation and testing of many different formulations with the aim of identifying one with the desired properties. In complex formulations it may not be clear which excipient is responsible for eliciting a particular property. OBJECTIVE: To investigate partial least squares (PLS) regression analysis of ATR-FTIR spectra of tablets as a predictive and investigative tool in the formulation of novel tablet formulations. MATERIALS: Magnesium stearate, lactose, acetylsalicylic acid and Ac-Di-Sol. RESULTS AND DISCUSSION: ATR-FTIR spectra of a simple aspirin tablet formulation with varying amounts of the lubricant magnesium stearate were obtained. PLS models were built using the spectral data as the multivariate variable and various physical properties of the tablets as the univariate variables. PLS models that allowed good predications to be made for samples not included in the training set were obtained for tablet hardness and disintegration time. It was clear from PLS model regression coefficients that magnesium stearate was responsible for the variation in the tablets' physical properties. CONCLUSION: PLS regression in combination with ATR-FTIR spectroscopy has been shown to be a useful approach for the prediction of the physical properties of tablets.

The influence of fluid physicochemical properties on vibrating-mesh nebulization.

In this study, the effect of fluid physicochemical properties and the vibrating-mesh mechanism on the aerosols generated from vibrating-mesh nebulizers have been evaluated using fluids having a range of viscosity, surface tension and ion concentration. Two nebulizers were investigated: the Omron MicroAir NE-U22 (passively vibrating) and the Aeroneb Pro (actively vibrating) mesh nebulizers. For both devices, the total aerosol output was generally unaffected by fluid properties. Increased viscosity or ion concentration resulted in a decrease in droplet volume median diameter (VMD) and an increase in fine particle fraction (FPF). Moreover, increased viscosity resulted in prolonged nebulization and reduced output rate, particularly for the Omron nebulizer. Both nebulizers were unsuitable for delivery of viscous fluids since nebulization was intermittent or completely ceased at >1.92cP. The presence of ions reduced variability particularly for the Aeroneb Pro nebulizer. No clear effect of surface tension was observed on the performance of nebulizers employing a vibrating-mesh technology. However, when viscosity was low, reduced surface tension seemed advantageous in shortening the nebulization time and increasing the output rate, but for the Omron nebulizer this also increased the droplet VMD and decreased the FPF. This study has shown that vibrating-mesh nebulization was highly dependent on fluid characteristics and nebulizer mechanism of operation.

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

Multilamellar and oligolamellar liposomes were produced from ethanol-based soya phosphatidyl-choline 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 (8 mum) 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.