Pulmonary delivery of liposomes

Research Progress on Liposome Pulmonary Delivery of Mycobacterium tuberculosis Nucleic Acid Vaccine and Its Mechanism of Action

Traditional vaccines have played an important role in the prevention and treatment of infectious diseases, but they still have problems such as low immunogenicity, poor stability, and difficulty in inducing lasting immune responses. In recent years, the nucleic acid vaccine has emerged as a relatively cheap and safe new vaccine. Compared with traditional vaccines, nucleic acid vaccine has some unique advantages, such as easy production and storage, scalability, and consistency between batches. However, the direct administration of naked nucleic acid vaccine is not ideal, and safer and more effective vaccine delivery systems are needed. With the rapid development of nanocarrier technology, the combination of gene therapy and nanodelivery systems has broadened the therapeutic application of molecular biology and the medical application of biological nanomaterials. Nanoparticles can be used as potential drug-delivery vehicles for the treatment of hereditary and infectious diseases. In addition, due to the advantages of lung immunity, such as rapid onset of action, good efficacy, and reduced adverse reactions, pulmonary delivery of nucleic acid vaccine has become a hot spot in the field of research. In recent years, lipid nanocarriers have become safe, efficient, and ideal materials for vaccine delivery due to their unique physical and chemical properties, which can effectively reduce the toxic side effects of drugs and achieve the effect of slow release and controlled release, and there have been a large number of studies using lipid nanocarriers to efficiently deliver target components into the body. Based on the delivery of tuberculosis (TB) nucleic acid vaccine by lipid carrier, this article systematically reviews the advantages and mechanism of liposomes as a nucleic acid vaccine delivery carrier, so as to lay a solid foundation for the faster and more effective development of new anti-TB vaccine delivery systems in the future.

Liposomal Forms of Fluoroquinolones and Antifibrotics Decorated with Mannosylated Chitosan for Inhalation Drug Delivery

The severe course of COVID-19 leads to the long-terming pulmonary diseases, such as bacterial pneumonia and post-COVID-19 pulmonary fibrosis. Thus, the essential task of biomedicine is a design of new effective drug formulations, including those for inhalation administration. In this work, we propose an approach to the creation of lipid–polymer delivery systems for fluoroquinolones and pirfenidone based on liposomes of various compositions decorated with mucoadhesive mannosylated chitosan. A generalizing study on the physicochemical patterns of the interactions of drugs with bilayers of various compositions was carried out, and the main binding sites were identified. The role of the polymer shell in the stabilization of vesicles and the delayed release of the contents has been demonstrated. For the liquid–polymer formulation of moxifloxacin, a prolonged accumulation of the drug in lung tissues was found after a single endotracheal administration to mice, significantly exceeding the control intravenous and endotracheal administration of the drug.

Aspects of Nanotechnology for COVID-19 Vaccine Development and Its Delivery Applications

Coronavirus, a causative agent of the common cold to a much more complicated disease such as "severe acute respiratory syndrome (SARS-CoV-2), Middle East Respiratory Syndrome (MERS-CoV-2), and Coronavirus Disease 2019 (COVID-19)", is a member of the coronaviridae family and contains a positive-sense single-stranded RNA of 26-32 kilobase pairs. COVID-19 has shown very high mortality and morbidity and imparted a significantly impacted socioeconomic status. There are many variants of SARS-CoV-2 that have originated from the mutation of the genetic material of the original coronavirus. This has raised the demand for efficient treatment/therapy to manage newly emerged SARS-CoV-2 infections successfully. However, different types of vaccines have been developed and administered to patients but need more attention because COVID-19 is not under complete control. In this article, currently developed nanotechnology-based vaccines are explored, such as inactivated virus vaccines, mRNA-based vaccines, DNA-based vaccines, S-protein-based vaccines, virus-vectored vaccines, etc. One of the important aspects of vaccines is their administration inside the host body wherein nanotechnology can play a very crucial role. Currently, more than 26 nanotechnology-based COVID-19 vaccine candidates are in various phases of clinical trials. Nanotechnology is one of the growing fields in drug discovery and drug delivery that can also be used for the tackling of coronavirus. Nanotechnology can be used in various ways to design and develop tools and strategies for detection, diagnosis, and therapeutic and vaccine development to protect against COVID-19. The design of instruments for speedy, precise, and sensitive diagnosis, the fabrication of potent sanitizers, the delivery of extracellular antigenic components or mRNA-based vaccines into human tissues, and the administration of antiretroviral medicines into the organism are nanotechnology-based strategies for COVID-19 management. Herein, we discuss the application of nanotechnology in COVID-19 vaccine development and the challenges and opportunities in this approach.

The Optimized Delivery of Triterpenes by Liposomal Nanoformulations: Overcoming the Challenges

The last decade has witnessed a sustained increase in the research development of modern-day chemo-therapeutics, especially for those used for high mortality rate pathologies. However, the therapeutic landscape is continuously changing as a result of the currently existing toxic side effects induced by a substantial range of drug classes. One growing research direction driven to mitigate such inconveniences has converged towards the study of natural molecules for their promising therapeutic potential. Triterpenes are one such class of compounds, intensively investigated for their therapeutic versatility. Although the pharmacological effects reported for several representatives of this class has come as a well-deserved encouragement, the pharmacokinetic profile of these molecules has turned out to be an unwelcomed disappointment. Nevertheless, the light at the end of the tunnel arrived with the development of nanotechnology, more specifically, the use of liposomes as drug delivery systems. Liposomes are easily synthesizable phospholipid-based vesicles, with highly tunable surfaces, that have the ability to transport both hydrophilic and lipophilic structures ensuring superior drug bioavailability at the action site as well as an increased selectivity. This study aims to report the results related to the development of different types of liposomes, used as targeted vectors for the delivery of various triterpenes of high pharmacological interest.

Nebulizer systems: a new frontier for therapeutics and targeted delivery

Drug delivery via the pulmonary route is a cornerstone in the pharmaceutical sector as an alternative to oral and parenteral administration. Nebulizer inhalation treatment offers multiple drug administration, easily employed with tidal breathing, suitable for children and elderly, can be adapted for severe patients and visible spray ensures patient satisfaction. This review discusses the operational and mechanical characteristics of nebulizer delivery devices in terms of aerosol production processes, their usage, benefits and drawbacks that are currently shaping the contemporary landscape of inhaled drug delivery. With the advent of particle engineering, novel inhaled nanosystems can be successfully developed to increase lung deposition and decrease pulmonary clearance. The above-mentioned advances might pave the path for treating a life-threatening disorder like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is also discussed in the current state of the art.

Functionalized Dendrimer Platforms as a New Forefront Arsenal Targeting SARS-CoV-2: An Opportunity

The novel human coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) has caused a pandemic. There are currently several marketed vaccines and many in clinical trials targeting SARS-CoV-2. Another strategy is to repurpose approved drugs to decrease the burden of the COVID-19 (official name for the coronavirus disease) pandemic. as the FDA (U.S. Food and Drug Administration) approved antiviral drugs and anti-inflammatory drugs to arrest the cytokine storm, inducing the production of pro-inflammatory cytokines. Another view to solve these unprecedented challenges is to analyze the diverse nanotechnological approaches which are able to improve the COVID-19 pandemic. In this original minireview, as promising candidates we analyze the opportunity to develop biocompatible dendrimers as drugs themselves or as nanocarriers against COVID-19 disease. From the standpoint of COVID-19, we suggest developing dendrimers as shields against COVID-19 infection based on their capacity to be incorporated in several environments outside the patients and as important means to stop transmission of SARS-CoV-2.

Status of inhalable antimicrobial agents for lung infection: progress and prospects

Introduction: Available parenteral and oral administration of antimicrobial agents (AMAs) in respiratory infections often show less penetration into the lung parenchyma. Due to inappropriate dose availability, the rate of antibiotic resistance is increasing gradually. Inhaled antibiotics intensely improve the availability of drugs at the site of respiratory infections. This targeted delivery minimizes systemic exposure and associated toxicity.Area covers: This review was performed by searching in the scientific database like PubMed and several trusted government sites like fda.gov, cdc.gov, ClinicalTrials.gov, etc. For better understanding, AMAs are classified in different stages of approval. Mechanism and characterization of pulmonary drug deposition section helps to understand the effective delivery of AMAs to the respiratory tract. There is a need for proper adoption of delivery devices for inhalable AMAs. Thus, delivery devices are extensively explained. Inspiratory flow has a remarkable impact on the delivery device that has been explained in detail.Expert opinion: Pulmonary delivery restricts the bulk administration of drugs in comparison with other routes. Therefore, novel AMAs with higher bactericidal activity at lower concentrations need to be synthesized. Extensive research is indeed in developing innovative delivery devices that would able to deliver higher doses of AMAs through the pulmonary route.

Application of Nanotechnology in the COVID-19 Pandemic

COVID-19, caused by SARS-CoV-2 infection, has been prevalent worldwide for almost a year. In early 2000, there was an outbreak of SARS-CoV, and in early 2010, a similar dissemination of infection by MERS-CoV occurred. However, no clear explanation for the spread of SARS-CoV-2 and a massive increase in the number of infections has yet been proposed. The best solution to overcome this pandemic is the development of suitable and effective vaccines and therapeutics. Fortunately, for SARS-CoV-2, the genome sequence and protein structure have been published in a short period, making research and development for prevention and treatment relatively easy. In addition, intranasal drug delivery has proven to be an effective method of administration for treating viral lung diseases. In recent years, nanotechnology-based drug delivery systems have been applied to intranasal drug delivery to overcome various limitations that occur during mucosal administration, and advances have been made to the stage where effective drug delivery is possible. This review describes the accumulated knowledge of the previous SARS-CoV and MERS-CoV infections and aims to help understand the newly emerged SARS-CoV-2 infection. Furthermore, it elucidates the achievements in developing COVID-19 vaccines and therapeutics to date through existing approaches. Finally, the applicable nanotechnology approach is described in detail, and vaccines and therapeutic drugs developed based on nanomedicine, which are currently undergoing clinical trials, have presented the potential to become innovative alternatives for overcoming COVID-19.

Inhalation of sustained release microparticles for the targeted treatment of respiratory diseases

Delivering drugs through inhalation for systemic and local applications has been in practice since several decades to treat various diseases. In recent times, inhalation drug delivery is becoming one of the highly focused areas of research in the pharmaceutical industry. It is being considered as one of the major portals for delivering drugs because of its wide range of advantages like requirement of low concentrations of drug to reach therapeutic efficacy, surpassing first pass metabolism and a very low incidence of side effects as compared to conventional delivery of drugs. Owing to these favorable characteristics of pulmonary drug delivery, diverse pharmaceutical formulations like liposomes, nanoparticles, and microparticles are developed through consistent efforts for delivery drugs to lungs in suitable form. However, drug-loaded microparticles have displayed various advantages over the other pharmaceutical dosage forms which give a cutting edge over other inhalational drug delivery systems. Assuring results with respect to sustained release through inhalational delivery of drug-loaded microparticles from pre-clinical studies are anticipative of similar benefits in the clinical settings. This review centralizes partly on the advantages of inhalational microparticles over other inhalational dosage forms and largely on the therapeutic applications and future perspectives of inhalable microparticle drug delivery systems.

Advanced spray dried proliposomes of amphotericin B lung surfactant-mimic phospholipid microparticles/nanoparticles as dry powder inhalers for targeted pulmonary drug delivery

The purpose of this study was to design, develop and characterize inhalable proliposomal microparticles/nanoparticles of Amphotericin B (AmB) with synthetic phospholipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) which are lung surfactant-mimic phospholipids. Organic solutions of AmB and phospholipids, were co-spray dried using an advanced closed-mode system and a high performance cyclone. Scanning electron microscopy (SEM) was employed to visualize the surface structure, morphology, and particles size. The residual water content of the proliposomes was quantified by Karl Fisher coulometric titration (KFT). Degree of crystallinity/non-crystallinity was measured by X-ray powder diffraction (XRPD). Phase behavior was measured by differential scanning calorimetry. The chemical composition by molecular fingerprinting was established using attenuated total reflectance (ATR)-Fourier-transform infrared (FTIR) spectroscopy. The amount of AmB loaded into the proliposomes was quantified using UV-VIS spectroscopy. The in vitro aerosol dispersion performance was conducted using the Next Generation Impactor (NGI) and the human dry powder inhaler (DPI) (Handihaler®) that is FDA-approved. Different human lung cell lines were employed to demonstrate in vitro safety as a function of dose and formulation. Smooth, spherical microparticles/nanoparticles were formed at medium and high spray drying pump rates and had low residual water content. A characteristic peak in the XRPD diffraction pattern as well as an endotherm in DSC confirmed the presence of the lipid bilayer structure characteristic in the DPPC/DPPG proliposomal systems. Superior in vitro aerosol performance was achieved with engineered microparticles/nanoparticles demonstrating suitability for targeted pulmonary drug delivery as inhalable dry powders. The in vitro cellular studies demonstrated that the formulated proliposomes are safe. These AmB proliposomes can be a better option for targeted treatment of severe pulmonary fungal infections.

Optimization of inhalable liposomal powder formulations and evaluation of their in vitro drug delivery behavior in Calu-3 human lung epithelial cells

Inhalation therapy has advantages for the treatment of multidrug resistant bacterial lung infections with high drug concentrations at the infection sites in the airways and reduced systemic exposure. We have developed liposomal formulations for pulmonary delivery of synergistic ciprofloxacin (Cipro) and colistin (Col) as the potential candidate for treatment of lung infections caused by multidrug resistant Gram-negative bacteria. This study aims to: (1) further optimize the powder formulation by adding drying stabilizers (polyvinyl pyrrolidone or poloxamer) to protect the liposomes during spray-freeze-drying; (2) evaluate the transport and cellular uptake of drugs in a human lung epithelial Calu-3 cell model. The liposomal powder formulations were produced using the ultrasonic spray-freeze-drying technique. The optimal formulation (F5) used mannitol (8% w/v) and sucrose (2% w/v) as the internal lyoprotectants. Adding external lyoprotectants/aerosolization enhancers (i.e. 8% w/v mannitol, 2% w/v sucrose and 1%, w/w PVP 10) produced the superior rehydrated EE values of ciprofloxacin and colistin (50.2 ± 0.9% for Cipro and 37.8 ± 1.2% for Col) as well as satisfactory aerosol performance (FPF: 34.2 ± 0.8% for Cipro and 33.6 ± 0.9% for Col). The cytotoxicity study indicated that F5 with the colistin concentration at 50 μg/mL and ciprofloxacin at 200 μg/mL was not cytotoxic to human lung epithelial Calu-3 cells. The intracellular uptake of ciprofloxacin was concentration-dependent in Calu-3 cells and the uptake of A-B was more than that of B-A for all samples (p < 0.05). This study demonstrates that co-delivery of ciprofloxacin and colistin in a single liposome can lower the transport capability of both drugs across the Calu-3 cell monolayer and their accumulation in the cells. These findings indicate that co-loaded liposomal powder of ciprofloxacin and colistin is a promising potential treatment for respiratory infections caused by multidrug resistant Gram-negative bacteria.

Synthetic macromolecules as therapeutics that overcome resistance in cancer and microbial infection

Synthetic macromolecular antimicrobials have shown efficacy in the treatment of multidrug resistant (MDR) pathogens. These synthetic macromolecules, inspired by Nature's antimicrobial peptides (AMPs), mitigate resistance by disrupting microbial cell membrane or targeting multiple intracellular proteins or genes. Unlike AMPs, these polymers are less prone to degradation by proteases and are easier to synthesize on a large scale. Recently, various studies have revealed that cancer cell membrane, like that of microbes, is negatively charged, and AMPs can be used as anticancer agents. Nevertheless, efforts in developing polymers as anticancer agents has remained limited. This review highlights the recent advancement in the development of synthetic biodegradable antimicrobial polymers (e.g. polycarbonates, polyesters and polypeptides) and anticancer macromolecules including peptides and polymers. Additionally, strategies to improve their in vivo bioavailability and selectivity towards bacteria and cancer cells are examined. Lastly, future perspectives, including use of artificial intelligence or machine learning, in the development of antimicrobial and anticancer macromolecules are discussed.

DNA biodots based targeted theranostic nanomedicine for the imaging and treatment of non-small cell lung cancer

The light absorption and emission characteristics of DNA biodots (DNA-BD), along with biocompatibility, give them a high potential for use in various medical applications, particularly in diagnostic purpose. DNA, under high pressure and temperature, condenses to form luminescent biodots. The objective of this research is to develop DNA-biodots (BD) loaded and cetuximab conjugated targeted theranostic liposomes of etoposide for lung cancer imaging and therapy. Theranostic liposomes were prepared by using the solvent injection method and characterized for their particle size, polydispersity, zeta potential, encapsulation efficiency, and pH-dependent in-vitro release, SEM, TEM AFM, EDX, and XRD. The t₅₀% (time at which 50% of the drug releases from the preparation) of the formulations was pH-dependent, with a significant increase in the release at lower pH (5.5). To kill A549 adenocarcinoma cells, the etoposide (control) required significantly (p < 0.05) higher drug concentrations in comparison to non-targeted and; the non-targeted formulation required more concentrations in comparison to targeted liposomes. The in-vivo results demonstrated that CTX-TPGS decorated theranostic liposomes could be a promising carrier for lung theranostics due to their nano-size and selectivity towards EGFR overexpressed cells which provided an improved NSCLC targeted delivery of ETP in comparison to the non-targeted and control formulations.

Preparation of a Sustained-Release Nebulized Aerosol of R-terbutaline Hydrochloride Liposome and Evaluation of Its Anti-asthmatic Effects via Pulmonary Delivery in Guinea Pigs

An aerosolized liposome formulation for the pulmonary delivery of an anti-asthmatic medication was developed. Asthma treatment usually requires frequent administration of medication for a sustained bronchodilator response. Liposomes are known for their sustained drug release capability and thus would be a suitable delivery system for prolonging the therapeutic effect of anti-asthmatic medication. Liposomes prepared by thin film hydration were loaded with a model drug, R-terbutaline hydrochloride(R-TBH), using an ammonium sulfate-induced transmembrane electrochemical gradient. This technique provided an encapsulation efficiency of up to 71.35% and yielded R-TBH liposomes with a particle size of approximately 145 ± 20 nm. According to stability studies, these R-TBH liposomes should be stored at 4°C before usage. Compared to R-TBH solution, which showed 90.84% release within 8 h, liposomal R-TBH had a cumulative release of 73.53% at 37°C over 192 h. A next generation impactor (NGI) was used to analyze the particle size distribution in the lungs of R-TBH liposome aerosol in vitro at 5°C. The therapeutic efficacy of the nebulized aerosol of the R-TBH liposomes was assessed via pulmonary delivery in guinea pigs. The results showed that, compared to the R-TBH solution group, the R-TBH liposome group had a prolonged anti-asthma effect.

Pulmonary Deposition and Elimination of Liposomal Amikacin for Inhalation and Effect on Macrophage Function after Administration in Rats

Pulmonary nontuberculous mycobacterial (PNTM) infections represent a treatment challenge. Liposomal amikacin for inhalation (LAI) is a novel formulation currently in development for the treatment of PNTM infections. The pulmonary deposition and elimination of LAI and its effect on macrophage function were evaluated in a series of preclinical studies in healthy rats. The pulmonary deposition of LAI was evaluated in female rats (n = 76) treated with LAI by nebulizer at 10 mg/kg of body weight per day or 90 mg/kg per day for 27 days, followed by dosing of dually labeled LAI (LAI with a lipid label plus an amikacin label) on day 28 with subsequent lung histological and amikacin analyses. In a separate study for assessment of alveolar macrophage function, rats (n = 180) received daily treatment with LAI at 90 mg/kg per day or 1.5% saline over three 30-day treatment periods followed by 30-day recovery periods; phagocytic and Saccharomyces cerevisiae (yeast) killing capabilities and inflammatory mediator release were assessed at the end of each period. LAI demonstrated equal dose-dependent deposition across all lung lobes and regions. Lipid and amikacin labels showed diffuse extracellular colocalization, followed by macrophage uptake and gradual amikacin elimination. Macrophages demonstrated accumulation of amikacin during treatment periods and nearly complete elimination during recovery periods. No evidence of an inflammatory response was seen. No differences in microsphere uptake or yeast killing were seen between LAI-treated and control macrophages. Neither LAI-treated nor control macrophages demonstrated constitutive inflammatory mediator release; however, both showed normal mediator release on lipopolysaccharide stimulation. LAI is readily taken up by macrophages in healthy rats without compromising macrophage function.

Electrostatically entrapped colistin liposomes for the treatment of Pseudomonas aeruginosa infection

The potential use of liposomes for the pulmonary delivery of colistin has been hindered by their phospholipid membrane permeability resulting in a very low entrapment of colistin in the liposomes. To increase the entrapment capacity of colistin in liposomes, the anionic lipid sodium cholesteryl sulfate (Chol-SO4^-) was used to enhance the electrostatic attraction between colistin and the lipid membrane. The resulting colistin-entrapped liposomes of Chol-SO4^- (CCL) showed significantly greater entrapment efficiency in comparison with liposomes without Chol-SO4^-. A time-kill kinetics study showed that colistin could redistribute from the liposomes into a new bacterial cell membrane to exert bactericidal activity. After intratracheal instillation, the CCL exhibited prolonged colistin retention in the lung with less colistin being transferred to the bloodstream and kidney, and the improved biodistribution further resulted in the enhanced therapeutic efficacy in a murine pulmonary Pseudomonas aeruginosa infection model compared with the colistin solution. These results highlight the suitability of applying an electrostatic attraction to entrap colistin in liposomes for pulmonary delivery by increasing colistin retention in the lung, while reducing the systemic exposure.

Pulmonary liposomal formulations encapsulated procaterol hydrochloride by a remote loading method achieve sustained release and extended pharmacological effects

Drug inhalation provides localized drug therapy for respiratory diseases. However, the therapeutic efficacy of inhaled drugs is limited by rapid clearance from the lungs. Small hydrophilic compounds have short half-lives to systemic absorption. We developed a liposomal formulation as a sustained-release strategy for pulmonary delivery of procaterol hydrochloride (PRO), a short-acting pulmonary β2-agonist for asthma treatment. After PRO-loaded liposomes were prepared using a pH gradient (remote loading) method, 100-nm liposomes improved residence times of PRO in the lungs. PRO encapsulation efficiency and release profiles were examined by screening several liposomal formulations of lipid, cholesterol, and inner phase. Although PRO loading was not achieved using the conventional hydration method, PRO encapsulation efficiency was >60% using the pH gradient method. PRO release from liposomes was sustained for several hours depending on liposomal composition. The liposomal formulation effects on the PRO behavior in rat lungs were evaluated following pulmonary administration in vivo. Sustained PRO release was achieved using simplified egg phosphatidylcholine (EPC)/cholesterol (8/1) liposome in vitro, and greater PRO remnants were observed in rat lungs following pulmonary administration. Extended pharmacological PRO effects were observed for 120min in a histamine-induced bronchoconstriction guinea pig model. We indicated the simplified EPC/cholesterol liposome potential as a controlled-release PRO carrier for pulmonary administration.

High-Throughput Continuous Flow Production of Nanoscale Liposomes by Microfluidic Vertical Flow Focusing

Liposomes represent a leading class of nanoparticles for drug delivery. While a variety of techniques for liposome synthesis have been reported that take advantage of microfluidic flow elements to achieve precise control over the size and polydispersity of nanoscale liposomes, with important implications for nanomedicine applications, these methods suffer from extremely limited throughput, making them impractical for large-scale nanoparticle synthesis. High aspect ratio microfluidic vertical flow focusing is investigated here as a new approach to overcoming the throughput limits of established microfluidic nanoparticle synthesis techniques. Here the vertical flow focusing technique is utilized to generate populations of small, unilamellar, and nearly monodisperse liposomal nanoparticles with exceptionally high production rates and remarkable sample homogeneity. By leveraging this platform, liposomes with modal diameters ranging from 80 to 200 nm are prepared at production rates as high as 1.6 mg min(-1) in a simple flow-through process.

Inhaled nano- and microparticles for drug delivery

The 21st century has seen a paradigm shift to inhaled therapy, for both systemic and local drug delivery, due to the lung's favourable properties of a large surface area and high permeability. Pulmonary drug delivery possesses many advantages, including non-invasive route of administration, low metabolic activity, control environment for systemic absorption and avoids first bypass metabolism. However, because the lung is one of the major ports of entry, it has multiple clearance mechanisms, which prevent foreign particles from entering the body. Although these clearance mechanisms maintain the sterility of the lung, clearance mechanisms can also act as barriers to the therapeutic effectiveness of inhaled drugs. This effectiveness is also influenced by the deposition site and delivered dose. Particulate-based drug delivery systems have emerged as an innovative and promising alternative to conventional inhaled drugs to circumvent pulmonary clearance mechanisms and provide enhanced therapeutic efficiency and controlled drug release. The principle of multiple pulmonary clearance mechanisms is reviewed, including mucociliary, alveolar macrophages, absorptive, and metabolic degradation. This review also discusses the current approaches and formulations developed to achieve optimal pulmonary drug delivery systems.

Lipid-based carriers for pulmonary products: preclinical development and case studies in humans

A number of lipid-based technologies have been applied to pharmaceuticals to modify their drug release characteristics, and additionally, to improve the drug loading for poorly soluble drugs. These technologies, including solid-state lipid microparticles, many of which are porous in nature, liposomes, solid lipid nanoparticles and nanostructured lipid carriers, are increasingly being developed for inhalation applications. This article provides a review of the rationale for the use of these technologies in the pulmonary delivery of drugs, and summarizes the manufacturing processes and their limitations, the in vitro and in vivo performance of these systems, the safety of these lipid-based systems in the lung, and their promise for commercialization.

Fusogenic pH sensitive liposomal formulation for rapamycin: improvement of antiproliferative effect

CONTEXT

Liposomes are increasingly employed to deliver chemotherapeutic agents, antisense oligonucleotides, and genes to various therapeutic targets.

OBJECTIVE

The present investigation evaluates the ability of fusogenic pH-sensitive liposomes of rapamycin in increasing its antiproliferative effect on human breast adenocarcinoma (MCF-7) cell line.

MATERIALS AND METHODS

Cholesterol (Chol) and dipalmitoylphosphatidylcholine (DPPC) (DPPC:Chol, 7:3) were used to prepare conventional rapamycin liposomes by a modified ethanol injection method. Dioleoylphosphatidylethanolamine (DOPE) was used to produce fusogenic and pH-sensitive properties in liposomes simultaneously (DPPC:Chol:DOPE, 7:3:4.2). The prepared liposomes were characterized by their size, zeta potential, encapsulation efficiency percent (EE%), and chemical stability during 6 months. The antiproliferative effects of both types of rapamycin liposomes (10, 25, and 50 nmol/L) with optimized formulations were assessed on MCF-7 cells, as cancerous cells, and human umbilical vein endothelial cells (HUVEC), as healthy cells, employing the diphenyltetrazolium bromide (MTT) assay for 72 h.

RESULTS AND DISCUSSION

The particle size, zeta potential, and EE% of the liposomes were 165 ± 12.3 and 178 ± 15.4 nm, -39.6 ± 1.3, and -41.2 ± 2.1 mV as well as 76.9 ± 2.6 and 76.9 ± 2.6% in conventional and fusogenic pH-sensitive liposomes, respectively. Physicochemical stability results indicated that both liposome types were relatively stable at 4 °C than 25 °C. In vitro antiproliferative evaluation showed that fusogenic pH-sensitive liposomes had better antiproliferative effects on MCF-7 cells compared to the conventional liposomes. Conversely, fusogenic pH-sensitive liposomes had less cytotoxicity on HUVEC cell line.

Formulation of inhalable lipid-based salbutamol sulfate microparticles by spray drying technique

Background

The aim of this work was to develop dry powder inhaler (DPI) formulations of salbutamol sulfate (SS) by the aid of solid lipid microparticles (SLmPs), composed of biocompatible phospholipids or cholesterol.

Methods

The SLmPs were prepared by using two different solvent systems (ethanol and water-ethanol) and lipid carriers (dipalmitoylphosphatidylcholine (DPPC) and cholesterol) with/without L-leucine in the spray drying process. The spray-dried microparticles were physically-mixed with coarse lactose monohydrate in order to make our final DPI formulations and were investigated in terms of physical characteristics as well as in vitro drug release profile and aerosolization behavior.

Results

We observed significant differences in the sizes, morphologies, and in vitro pulmonary depositions between the formulations. In particular, the SS-containing SLmPs prepared with water-ethanol (30:70 v/v) solution of DPPC and L-leucine which had then been blended with coarse lactose (1:9 w/w) exhibited the highest emitted dose (87.9%) and fine particle fraction (42.7%) among the formulations. In vitro drug release study indicated that despite of having a significant initial burst release for both cholesterol and DPPC-based microparticles, the remained drug released more slowly than the pure drug.

Conclusion

This study demonstrated the potential of using lipid carriers as well as L-leucine in DPI formulations of SS to improve its aerosolization behavior and retard the release profile of the drug.

Inhaled antibiotics to treat lung infection

The development of inhaled antibiotics to treat lung infection is an active field, with four approved products in the USA and more in the late stages of clinical development. The efficacies of TOBI® tobramycin (Novartis) and Cayston® aztreonam lysate (Gilead), the approved inhaled antibiotics for cystic fibrosis (CF) patients colonized with Pseudomonas aeruginosa, have been well documented. Recent approvals for a second-generation tobramycin solution, Bethkis®, and a tobramycin powder formulation in a dry-powder inhaler (DPI), TOBI Podhaler®, indicate that the inhaled antibiotic marketplace in CF is becoming very competitive. Other indications are also receiving interest. While there have been a number of recent reviews from a clinical, technical or regulatory perspective in the field of inhaled antibiotics, as well as others focused on a specific product or data from a recent clinical trial, there have not been any that describe the patent coverage of these products. This review addresses that missing piece.

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.

Lipid-based carriers: manufacturing and applications for pulmonary route

INTRODUCTION

Recent advances in aerosol therapy have sparked considerable interest in the development of novel drug delivery systems for pulmonary route. Development of colloidal carriers as pharmaceutical drug delivery systems has spurred an exponential growth; the encapsulation of bioactive molecules into relatively inert and non-toxic carriers for in vivo delivery constitutes a promising approach for improving their therapeutic index while reducing the side effects. Extraordinary success has been made toward improving efficacy by developing lipid-based carriers (LBCs); among classical examples are liposomes and solid lipid nanoparticles (SLNs).

AREAS COVERED

The authors review lipid-based colloidal carriers - liposomes and SLNs - as pulmonary drug delivery systems. Conventional methods of liposome preparation and recently developed systems are discussed. Special attention is given to SLNs and their main manufacturing techniques. Finally, a summary of recent scientific publications and important results in the field of pulmonary lipidic carriers are presented. Some practical considerations regarding the toxicological concerns of such systems are briefly cited.

EXPERT OPINION

Despite several scientific investigations, numerous advantages and encouraging results, LBCs for pulmonary route have attained only few great achievements as many challenges still remain. Problems limiting the use of such system seem to be the complexity of the respiratory tract as well as the lack of toxicity assessment risks of colloidal carriers.

Effect of cholesterol on the properties of spray-dried lysozyme-loaded liposomal powders

The influence of cholesterol (Chol) in the liposomal bilayer on the properties of inhalable protein-loaded liposomal powders prepared by spray-drying technique was investigated. Lysozyme (LSZ) was used as a model protein. Feed solution for spray drying was prepared by direct mixing of aqueous solution of LSZ with mannitol solution and empty liposome dispersions composed of hydrogenated phosphatidylcholine and Chol at various molar ratios. The spray-dried powders were characterized with respect to morphology, thermal property, and crystallinity using scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction, respectively. Most formulations gave slightly aggregated, spherical particles, and percentage yields of the spray-dried powders decreased with increasing Chol content. Degree of particle aggregation depended on the powder composition. The powders spontaneously formed liposomes which efficiently entrapped LSZ after reconstitution with HEPES buffered saline (HBS) at 37 degrees C. Lysozyme entrapment efficiency and size distribution of the reconstituted liposomes were evaluated after the powders were reconstituted with HBS. Increasing Chol content resulted in a decrease in size of the reconstituted liposomes and an increase in entrapment efficiency of LSZ. These results correlated with thermal behaviors of the reconstituted liposomes. Biological activity of LSZ was not affected by the spray-drying process. It was also demonstrated that LSZ-loaded liposomal powders could be produced without the need to preload the LSZ into liposomes prior to spray-drying process.

Monitoring safety of liposomes containing rifampicin on respiratory cell lines and in vitro efficacy against Mycobacterium bovis in alveolar macrophages

Rifampicin-encapsulated liposome suspensions were prepared by a chloroform-film method and converted to dry powders by freeze-drying with mannitol as a cryoprotectant. The liposome suspension had multilamellar nanovesicles with 50% rifampicin encapsulation. The liposome dry powder comprised particles with a mass median aerodynamic diameter of 3.4 mum, with 60% present as a fine particle fraction. Rifampicin-encapsulated liposomes were evidently nontoxic to respiratory associated cells, including bronchial epithelial cells, small airway epithelial and alveolar macrophages (AMs). Furthermore, the liposomes did not activate AMs to produce interleukin-1 beta, tumor necrosis factor-alpha, and nitric oxide at a level that would cascade to other inflammatory effects. The minimum inhibitory concentrations against Mycobacterium bovis was 0.2 and 0.8 microM for liposomes containing rifampicin and free rifampicin, respectively. The less negatively charged reconstituted liposome displayed the greatest activity against intracellular growth of M. bovis.

A review on the clinical use of inhaled amphotericin B

BACKGROUND

Despite the systemic toxicity of amphotericin B (AMB), it still has a place in treatment or prophylactic regimes of fungal infections.

METHODS

A strategy for minimizing the potential of systemic side effects is to bring it in direct contact with the body site most likely to be infected, such as the administration of AMB as an aerosol. Nebulized amphotericin has been used in humans since 1959. However, due to a lack of sufficient data regarding efficacy, its use is still not established. Little is known about the optimal dose, frequency, duration of administration, and the pharmacokinetics of inhaled AMB in humans.

RESULTS AND CONCLUSIONS

In this review, published data regarding inhaled AMB are summarized, including available descriptions regarding preparation, dose, efficacy, and toxicity, and its place in therapy is discussed. The results from the studies that were reviewed in this article indicate that inhaled AMB may have a place in the prophylactic regimens of patients with prolonged neutropenia and in lung transplant recipients. Furthermore, nebulized (liposomal) AMB may have a place in the treatment of allergic bronchopulmonary aspergillosis (ABPA) in patients with corticosteroid-dependent ABPA.

Evaluation of antitubercular drug-loaded surfactants as inhalable drug-delivery systems for pulmonary tuberculosis

Pulmonary tuberculosis is associated with a year-long chemotherapy, poor alveolar drug levels, drug-related systemic toxicity, and patient noncompliance. In this study, exogenous pulmonary surfactant is proposed as a drug carrier for antitubercular drugs. Dipalmitoylphosphatidylcholine (DPPC), the major lung-surfactant lipid, has been combined with antitubercular drugs isoniazid (INH), rifampicin (RFM), and ethambutol (ETH) in 1:1 ratio by weight, in which drugs had a ratio of 1:2:3 by weight. At 37 degrees C, the formulation had better surfactant function with quicker reduction of surface tension on adsorption (32.71 +/- 0.65 mN/m) than DPPC liposomes (44.67 +/- 0.57 mN/m) and maintained 100% airway patency in a capillary surfactometer. Drug-loaded surfactant liposomes were about 2 microm and had entrapment efficiency of 30.04% +/- 2.05%, 18.85% +/- 2.92%, and 61.47% +/- 3.32% for INH, RFM, and ETH, respectively. Sustained release of the drugs from surfactants was observed over 24 h. In vitro alveolar deposition efficiency using the twin impinger showed 12.06% +/- 1.87% of INH, 43.30% +/- 0.87% of RFM, and 22.07% +/- 2.02% of ETH deposited in the alveolar chamber upon nebulization for a minute using a jet nebulizer. The formulation was biocompatible and stable with physicochemical properties being retained even after storage for a month at 4 degrees C. Antitubercular drug-loaded surfactants developed could serve dual purposes of alveolar stabilization due to surfactant action and better reach of these drugs to the alveoli due to antiatelectatic effect of the surfactant.

Development of alpha-tocopherol acetate nanoparticles: influence of preparative processes

We studied different methods of preparing alpha-tocopherol acetate (ATA) nanoparticles, which are to be used in targeting the lungs as aerosols in order to prevent cigarette smoke toxicity. Poly-(lactide) nanoparticles were prepared using nanoprecipitation and solvent evaporation techniques, which produced, respectively, too small and too large nanoparticles to be aerosolized. The emulsification-diffusion method produced 2 months stable nanoparticles with a size between (500-700 nm). Increasing ATA concentration (1-7 mg/mL) induced a decrease in the association rate (97-93%) and in the adsorbed ATA rate (7-4.5%), which was associated with variations of Zeta potentials (-27.5 to -24.3 mV) and decrease in polymeric wall thickness and density.

Nebulization of Liposomal rh-Cu/Zn–SOD with a Novel Vibrating Membrane Nebulizer

Liposomes are potential drug carriers for pulmonary drug delivery: They can be prepared from phospholipids, which are endogenous to the respiratory tract as a component of pulmonary surfactant, and at an appropriate dose liposomes do not pose a toxicological risk to this organ. Among the various categories of drug that benefit from liposomal entrapment is the anti-inflammatory enzyme superoxide dismutase, thus prolonging its biological half-life. The delivery of liposomes by nebulization is hampered by stability problems, like physical and chemical changes that may lead to chemical degradation and leakage of the encapsulated drug. Here we present data of liposomes aerosolized with a novel electronic nebulizer based on a vibrating membrane technology (PARI eFlow), which amends drawbacks like liposomes degradation and product release. The data acquisition included aerosol properties such as aerodynamic particle size, nebulization efficiency, and liposome leakage upon nebulization. In conclusion, this study shows the ability of the PARI eFlow to nebulize high amounts of liposomal recombinant human superoxide dismutase with reduced vesicle disruption tested in an enclosing experimental protocol.

Enhanced anti-inflammation of inhaled dexamethasone palmitate using mannosylated liposomes in an endotoxin-induced lung inflammation model

Inhalation of bacterial endotoxin induces pulmonary inflammation by activation of nuclear factor kappaB (NFkappaB), production of cytokines and chemokines, and neutrophil activation. Although glucocorticoids are the drugs of choice, administration of free drugs results in adverse effects as a result of a lack of selectivity for the inflammatory effector cells. Because alveolar macrophages play a key role in the inflammatory response in the lung, selective targeting of glucocorticoids to alveolar macrophages offers efficacious pharmacological intervention with minimal side effects. We have demonstrated previously the selective targeting of mannosylated liposomes to alveolar macrophages via mannose receptor-mediated endocytosis after intratracheal administration. In this study, the anti-inflammatory effects of dexamethasone palmitate incorporated in mannosylated liposomes (DPML) at 0.5 mg/kg via intratracheal administration were investigated in lipopolysaccharide-induced lung inflammation in rats. DPML significantly inhibited tumor necrosis factor alpha, interleukin-1beta, and cytokine-induced neutrophil chemoattractant-1 levels, suppressed neutrophil infiltration and myeloperoxidase activity, and inhibited NFkappaB and p38 mitogen-activated protein kinase activation in the lung. These results prove the value of inhaled mannosylated liposomes as powerful targeting systems for the delivery of anti-inflammatory drugs to alveolar macrophages to improve their efficacy against lung inflammation.

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 microparticles as a sustained release system for pulmonary drug delivery

The controlled release of drugs for pulmonary delivery is a research field which has been so far rather unexploited but is currently becoming increasingly attractive. The introduction part of this research article first details the potential advantages of solid lipid microparticles (SLMs) as drug carrier compared to liposomes and polymeric microspheres. The aim of this work is to use SLMs to impart a sustained release profile to a model drug, salbutamol acetonide (SA). SA was synthesized from salbutamol in order to increase the lipophilicity of this molecule and thereby to increase its incorporation efficiency into SLMs. SA-loaded SLMs were then produced by a hot emulsion technique followed by high-shear homogenisation and the manufacturing parameters were optimized using the experimental design methodology in order to reach a suitable particle size for pulmonary administration. Scanning electron micrographs showed that SLMs are spherical, have a smooth surface and that SA crystallizes outside of the particles when the drug loading is higher than 20%. This was confirmed by X-ray diffraction. SA in vitro release study from SLMs showed that the release rate increased with SA loading but remained in every case lower than the dissolution rate of pure SA.

Development of a respirable, sustained release microcarrier for 5-fluorouracil I: In vitro assessment of liposomes, microspheres, and lipid coated nanoparticles

The release rate of 5-fluorouracil (5-FU) from liposomes, microspheres, and lipid-coated nanoparticles (LNPs) was determined by microdialysis to investigate their use as a respirable delivery system for adjuvant (postsurgery) therapy of lung cancer. 5-FU was incorporated into liposomes using thin film hydration and into microspheres and LNPs by spray drying. Primary particle size distributions were measured by dynamic light scattering. Liposomes released 5-FU in 4-10 h (k(1) = 0.44-2.31/h, first-order release model). Extruded vesicles with diameters less than one micron released 5-FU more quickly than nonextruded vesicles. With poly-(lactide) (PLA) and Poly-(lactide-co-glycolide) (PLGA) microspheres, slower release rates were observed (k(1) = 0.067-0.202/h). Increasing the lactide:glycolide ratio (50:50-100:0) resulted in a progressive decrease in the release rate of 5-FU. poly-(lactide-co-caprolactone) (PLCL) microspheres released 5-FU more rapidly compared to PLGA systems (k(1) = 0.254-0.259/h). LNPs formulated with polymeric core excipients had lower release rates compared to monomeric excipients (k(1) = 0.043-0.105/h vs. k(1) = 0.192-0.345/h). Changing the lipid chain length of the shell lipid components had a relatively minor effect (k(1) = 0.043-0.129/h). Overall, these systems yielded a wide range of delivery durations that may be suitable for use as an inhalation delivery system for adjuvant therapy of lung cancer.

Liposomal dry powders as aerosols for pulmonary delivery of proteins

The purpose of this research was to develop liposomal dry powder aerosols for protein delivery. The delivery of stable protein formulations is essential for protein subunit vaccine delivery, which requires local delivery to macrophages in the lungs. Beta-glucuronidase (GUS) was used as a model protein to evaluate dry powder liposomes as inhaled delivery vehicles. Dimyristoyl phosphatylcholine:cholesterol (7:3) was selected as the liposome composition. The lyophilization of liposomes, micronization of the powders, aerosolization using a dry powder inhaler (DPI), and in vitro aerodynamic fine particle fraction upon collection in a twin-stage liquid impinger were evaluated. After lyophilization and jet-milling, the total amount of GUS and its activity, representing encapsulation efficiency and stability, were evaluated. The GUS amount and activity were measured and compared with freshly-prepared liposomes in the presence of mannitol, 43% of initial GUS amount, 29% of GUS activity after lyophilization and 36% of GUS amount, 22% of activity after micronization were obtained. Emitted doses from dry powder inhaler were 53%, 58%, 66%, and 73% for liposome powder:mannitol carrier ratios of 1:0, 1:4, 1:9, and 1:19. Fifteen percent of the liposome particles were less than 6.4 mum in aerodynamic diameter. The results demonstrate that milled liposome powders containing protein molecules can be aerosolized effectively at a fixed flow rate. Influences of different cryoprotectants on lyophilization of protein liposome formulations are reported. The feasibility of using liposomal dry powder aerosols for protein delivery has been demonstrated but further optimization is required in the context of specific therapeutic proteins.

Unilamellar vesicles as potential capreomycin sulfate carriers: preparation and physicochemical characterization

The aim of this work was to evaluate unilamellar liposomes as new potential capreomycin sulfate (CS) delivery systems for future pulmonary targeting by aerosol administration. Dipalmitoylphosphatidylcholine, hydrogenated phosphatidylcholine, and distearoylphosphatidylcholine were used for liposome preparation. Peptide-membrane interaction was investigated by differential scanning calorimetry (DSC) and attenuated total internal reflection Fourier-transform infrared spectroscopy (ATIR-FTIR). Peptide entrapment, size, and morphology were evaluated by UV spectrophotometry, photocorrelation spectroscopy, and transmission electron microscopy, respectively. Interaction between CS and the outer region of the bilayer was revealed by DSC and ATIR-FTIR. DSPC liposomes showed enhanced interdigitation when the CS molar fraction was increased. Formation of a second phase on the bilayer surface was observed. From kinetic and permeability studies, CS loaded DSPC liposomes resulted more stable if compared to DPPC and HPC over the period of time investigated. The amount of entrapped peptide oscillated between 10% and 13%. Vesicles showed a narrow size distribution, from 138 to 166 nm, and a good morphology. These systems, in particular DSPC liposomes, could represent promising carriers for this peptide.

Preparation and in vivo toxicity study of solid lipid microparticles as carrier for pulmonary administration

The purpose of this research was to investigate the effects of processing conditions on the characteristics of solid lipid microparticles (SLM) with a potential application as carriers for pulmonary administration. Compritol (5.0% wt/wt) SLM dispersions were prepared by rotor-stator homogenization, at different surfactant concentrations and emulsification times. The SLM were characterized, in terms of morphology and size, after lyophilization and sterilization by autoclaving process. In vivo assessment was carried out in rats by intratracheal instillation of either placebo or SLM dispersion, and by bronchoalveolar lavage for cytological analysis. Mean particle size of 4 to 5 microm was achieved using 0.3% and 0.4% (wt/wt) of emulsifier (Poloxamer 188) and emulsification times of 2 and 5 minutes. The particles showed spherical shape and smooth surface. The morphology of microparticles, the size, and the size distribution were not substantially modified after lyophilization and sterilization. Total cell counts showed no significant differences between placebo and SLM 0.5% or 2.5% groups. Regarding cytology, percentage of polymorphonuclear neutrophils and macrophages did not significantly differ between groups. These results suggest that a single intratracheal administration of the SLMs does not induce a significant inflammatory airway response in rats and that the SLMs might be a potential carrier for encapsulated drug via the pulmonary route.

Pulmonary drug delivery. Part II: the role of inhalant delivery devices and drug formulations in therapeutic effectiveness of aerosolized medications

Research in the area of pulmonary drug delivery has gathered momentum in the last several years, with increased interest in using the lung as a means of delivering drugs systemically. Advances in device technology have led to the development of more efficient delivery systems capable of delivering larger doses and finer particles into the lung. As more efficient pulmonary delivery devices and sophisticated formulations become available, physicians and health professionals will have a choice of a wide variety of device and formulation combinations that will target specific cells or regions of the lung, avoid the lung's clearance mechanisms and be retained within the lung for longer periods. It is now recognized that it is not enough just to have inhalation therapy available for prescribing; physicians and other healthcare providers need a basic understanding of aerosol science, inhaled formulations, delivery devices, and bioequivalence of products to prescribe these therapies optimally.