Efficient Drug Delivery to Alveolar Macrophages and Lung Epithelial Lining Fluid Following Pulmonary Administration of Liposomal Ciprofloxacin in Rats with Pneumonia and Estimation of its Antibacterial Effects

Ciprofloxacin-Loaded Inhalable Formulations against Lower Respiratory Tract Infections: Challenges, Recent Advances, and Future Perspectives

Inhaled ciprofloxacin (CFX) has been investigated as a treatment for lower respiratory tract infections (LRTIs) associated with cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), and bronchiectasis. The challenges in CFX effectiveness for LRTI treatment include poor aqueous solubility and therapy resistance. CFX dry powder for inhalation (DPI) formulations were well-tolerated, showing a remarkable decline in overall bacterial burden compared to a placebo in bronchiectasis patients. Recent research using an inhalable powder combining Pseudomonas phage PEV20 with CFX exhibited a substantial reduction in bacterial density in mouse lungs infected with clinical P. aeruginosa strains and reduced inflammation. Currently, studies suggest that elevated biosynthesis of fatty acids could serve as a potential biomarker for detecting CFX resistance in LRTIs. Furthermore, inhaled CFX has successfully addressed various challenges associated with traditional CFX, including the incapacity to eliminate the pathogen, the recurrence of colonization, and the development of resistance. However, further exploration is needed to address three key unresolved issues: identifying the right patient group, determining the optimal treatment duration, and accurately assessing the risk of antibiotic resistance, with additional multicenter randomized controlled trials suggested to tackle these challenges. Importantly, future investigations will focus on the effectiveness of CFX DPI in bronchiectasis and COPD, aiming to differentiate prognoses between these two conditions. This review underscores the importance of CFX inhalable formulations against LRTIs in preclinical and clinical sectors, their challenges, recent advancements, and future perspectives.

Meta-Analysis of Drug Delivery Approaches for Treating Intracellular Infections

This meta-analysis aims to evaluate the trend, methodological quality and completeness of studies on intracellular delivery of antimicrobial agents. PubMed, Embase, and reference lists of related reviews were searched to identify original articles that evaluated carrier-mediated intracellular delivery and pharmacodynamics (PD) of antimicrobial therapeutics against intracellular pathogens in vitro and/or in vivo. A total of 99 studies were included in the analysis. The most commonly targeted intracellular pathogens were bacteria (62.6%), followed by viruses (16.2%) and parasites (15.2%). Twenty-one out of 99 (21.2%) studies performed neither microscopic imaging nor flow cytometric analysis to verify that the carrier particles are present in the infected cells. Only 31.3% of studies provided comparative inhibitory concentrations against a free drug control. Approximately 8% of studies, albeit claimed for intracellular delivery of antimicrobial therapeutics, did not provide any experimental data such as microscopic imaging, flow cytometry, and in vitro PD. Future research on intracellular delivery of antimicrobial agents needs to improve the methodological quality and completeness of supporting data in order to facilitate clinical translation of intracellular delivery platforms for antimicrobial therapeutics.

Bioinspired Heteromultivalent Chitosan-α-Fe₂O₃/Gadofullerene Hybrid Composite for Enhanced Antibiotic-Resistant Bacterial Pneumonia

Herein, we have designed and developed a heteromultivalent chitosan base α-Fe₂O₃/Gadofullerene (GdF) hybrid composite through a simple chemical precipitation method. Unlike other methods, the addition of external stabilizing agents to generate GdF nanoparticles (NPs) was not necessary herein. The prepared chitosan-α-Fe₂O₃/GdF hybrid nanocomposites were characterized using UV, FT-IR, XRD and morphological microscopic analyses. The results showed that α-Fe₂O₃ and GdF hybrid nanocomposites were successfully grown on the surface of chitosan. The FT-IR vibration peaks showed the formation of Fe₂O₃ NPs, and the vibration peak for Fe-O was 568 cm^-1. The broad absorption peak observed in the range of 250-350 nm and a sharp absorption peak at 219 nm represents the UV absorption of the synthesized hybrid composites. XRD pattern showed sharp peaks of crystallinity and purity of α-Fe₂O₃ nanoparticles. Finally, the synthesized chitosan-α-Fe₂O₃/GdF hybrid composites were screened for their antibacterial resistance against the Escherichia coli, Pseudomonas aeruginosa, Bacilus subtilis, and Staphylococcus aereus. In addition, in vitro biocompatibility results exhibited that developed hybrid samples have provided high cell compatibility with fibroblast (L929) cell line. The in vivo bio inspired nanotherapeutics have the potential action to effective inhibition ability on antibiotic-resistant P. aeruginosa, which has been main factor of inducing pneumonia. In conclusion, we expect biomimicking systems combined with the effective antibacterial agent could be the suitable next generation therapeutic potential factors for prevention and treatment of antibiotic-resistant pneumonia.

Evaluation of liposomal ciprofloxacin formulations in a murine model of anthrax

The in vivo efficacy of liposomal encapsulated ciprofloxacin in two formulations, lipoquin and apulmiq, were evaluated against the causative agent of anthrax, Bacillus anthracis. Liposomal encapsulated ciprofloxacin is attractive as a therapy since it allows for once daily dosing and achieves higher concentrations of the antibiotic at the site of initial mucosal entry but lower systemic drug concentrations. The in vivo efficacy of lipoquin and apulmiq delivered by intranasal instillation was studied at different doses and schedules in both a post exposure prophylaxis (PEP) therapy model and in a delayed treatment model of murine inhalational anthrax. In the mouse model of infection, the survival curves for all treatment cohorts differed significantly from the vehicle control. Ciprofloxacin, lipoquin and apulmiq provided a high level of protection (87-90%) after 7 days of therapy when administered within 24 hours of exposure. Reducing therapy to only three days still provided protection of 60-87%, if therapy was provided within 24 hours of exposure. If treatment was initiated 48 hours after exposure the survival rate was reduced to 46-65%. These studies suggest that lipoquin and apulmiq may be attractive therapies as PEP and as part of a treatment cocktail for B. anthracis.

In vitro lung epithelial cell transport and anti-interleukin-8 releasing activity of liposomal ciprofloxacin

As a promising long-acting inhaled formulation, liposomal ciprofloxacin (Lipo-CPFX) was characterized in the in vitro human lung epithelial Calu-3 cell monolayer system, compared to ciprofloxacin in solution (CPFX). Its modulated absorptive transport and uptake, and sustained inhibitory activity against induced pro-inflammatory interleukin-8 (IL-8) release were examined. The absorptive transport and uptake kinetics for Lipo-CPFX and CPFX were determined at 0.1-50 mg/ml in the Transwell system. The Lipo-CPFX transport was then challenged for mechanistic exploration via cell energy depletion, a reduced temperature, endocytosis and/or lipid fusion inhibition, and addition of excess non-loaded liposomes. The inhibitory activities of Lipo-CPFX and CPFX against lipopolysaccharide (LPS)-induced IL-8 release were assessed in a co-incubation or pre-incubation mode. In the tight Calu-3 cell monolayers, Lipo-CPFX yielded 15-times slower ciprofloxacin flux of absorptive transport and 5-times lower cellular drug uptake than CPFX. Its transport appeared to be transcellular; kinetically linear, proportional to encapsulated ciprofloxacin concentration; and consistent with the cell energy-independent lipid bilayer fusion mechanism. Lipo-CPFX was equipotent to CPFX in the anti-IL-8 releasing activity upon 24 h co-incubation with LPS. Additionally, Lipo-CPFX, but not CPFX, retained the anti-IL-8 releasing activity even 24 h after pre-incubation. In conclusion, Lipo-CPFX enabled slower absorptive lung epithelial cell transport and uptake of ciprofloxacin, apparently via the lipid bilayer fusion mechanism, and the sustained inhibitory activity against LPS-induced IL-8 release, compared to CPFX.

Inhaled Antibiotic Therapy in Chronic Respiratory Diseases

The management of patients with chronic respiratory diseases affected by difficult to treat infections has become a challenge in clinical practice. Conditions such as cystic fibrosis (CF) and non-CF bronchiectasis require extensive treatment strategies to deal with multidrug resistant pathogens that include Pseudomonas aeruginosa, Methicillin-resistant Staphylococcus aureus, Burkholderia species and non-tuberculous Mycobacteria (NTM). These challenges prompted scientists to deliver antimicrobial agents through the pulmonary system by using inhaled, aerosolized or nebulized antibiotics. Subsequent research advances focused on the development of antibiotic agents able to achieve high tissue concentrations capable of reducing the bacterial load of difficult-to-treat organisms in hosts with chronic respiratory conditions. In this review, we focus on the evidence regarding the use of antibiotic therapies administered through the respiratory system via inhalation, nebulization or aerosolization, specifically in patients with chronic respiratory diseases that include CF, non-CF bronchiectasis and NTM. However, further research is required to address the potential benefits, mechanisms of action and applications of inhaled antibiotics for the management of difficult-to-treat infections in patients with chronic respiratory diseases.

Inhaled Liposomal Ciprofloxacin Protects against a Lethal Infection in a Murine Model of Pneumonic Plague

Inhalation of Yersinia pestis can lead to pneumonic plague, which without treatment is inevitably fatal. Two novel formulations of liposome-encapsulated ciprofloxacin, ‘ciprofloxacin for inhalation’ (CFI, Lipoquin^®) and ‘dual release ciprofloxacin for inhalation’ (DRCFI, Pulmaquin^®) containing CFI and ciprofloxacin solution, are in development. These were evaluated as potential therapies for infection with Y. pestis. In a murine model of pneumonic plague, human-like doses of aerosolized CFI, aerosolized DRCFI or intraperitoneal (i.p.) ciprofloxacin were administered at 24 h (representing prophylaxis) or 42 h (representing treatment) post-challenge. All three therapies provided a high level of protection when administered 24 h post-challenge. A single dose of CFI, but not DRCFI, significantly improved survival compared to a single dose of ciprofloxacin. Furthermore, single doses of CFI and DRCFI reduced bacterial burden in lungs and spleens to below the detectable limit at 60 h post-challenge. When therapy was delayed until 42 h post-challenge, a single dose of CFI or DRCFI offered minimal protection. However, single doses of CFI or DRCFI were able to significantly reduce the bacterial burden in the spleen compared to empty liposomes. A three-day treatment regimen of ciprofloxacin, CFI, or DRCFI resulted in high levels of protection (90–100% survival). This study suggests that CFI and DRCFI may be useful therapies for Y. pestis infection, both as prophylaxis and for the treatment of plague.

Enhanced intracellular delivery and antibacterial efficacy of enrofloxacin-loaded docosanoic acid solid lipid nanoparticles against intracellular Salmonella

Enrofloxacin-loaded docosanoic acid solid lipid nanoparticles (SLNs) with different physicochemical properties were developed to enhance activity against intracellular Salmonella. Their cellular uptake, intracellular elimination and antibacterial activity were studied in RAW 264.7 cells. During the experimental period, SLN-encapsulated enrofloxacin accumulated in the cells approximately 27.06-37.71 times more efficiently than free drugs at the same extracellular concentration. After incubation for 0.5 h, the intracellular enrofloxacin was enhanced from 0.336 to 1.147 μg/mg of protein as the sizes of nanoparticles were increased from 150 to 605 nm, and from 0.960 to 1.147 μg/mg of protein when the charge was improved from -8.1 to -24.9 mv. The cellular uptake was more significantly influenced by the size than it was by the charge, and was not affected by whether the charge was positive or negative. The elimination of optimal SLN-encapsulated enrofloxacin from the cells was significantly slower than that of free enrofloxacin after removing extracellular drug. The inhibition effect against intracellular Salmonella CVCC541 of 0.24 and 0.06 μg/mL encapsulated enrofloxacin was stronger than 0.6 μg/mL free drug after all of the incubation periods and at 48 h, respectively. Docosanoic acid SLNs are thus considered as a promising carrier for intracellular bacterial treatment.

Drug delivery to macrophages: Challenges and opportunities

Macrophages are prevalent in the body and have roles in almost every aspect of human biology. They have often been considered a subject to avoid during drug delivery. However, with recent understanding of their diverse functions in diseases, macrophages have gained increasing interest as important therapeutic targets. To develop drug carriers to macrophages, it is important to understand their biological roles and requirements for efficient targeting. This review provides an overview of representative carriers and various approaches to address challenges in drug delivery to macrophages such as biodistribution, cellular uptake, intracellular trafficking, and drug release.

Toward an optimized treatment of intracellular bacterial infections: input of nanoparticulate drug delivery systems

Intracellular pathogenic bacteria can lead to some of the most life-threatening infections. By evolving a number of ingenious mechanisms, these bacteria have the ability to invade, colonize and survive in the host cells in active or latent forms over prolonged period of time. A variety of nanoparticulate systems have been developed to optimize the delivery of antibiotics. Main advantages of nanoparticulate systems as compared with free drugs are an efficient drug encapsulation, protection from inactivation, targeting infection sites and the possibility to deliver drugs by overcoming cellular barriers. Nevertheless, despite the great progresses in treating intracellular infections using nanoparticulate carriers, some challenges still remain, such as targeting cellular subcompartments with bacteria and delivering synergistic drug combinations. Engineered nanoparticles should allow controlling drug release both inside cells and within the extracellular space before reaching the target cells.

Nano- and micro-based inhaled drug delivery systems for targeting alveolar macrophages

INTRODUCTION

Macrophages are the most versatile cells in the hematopoietic system and are strategically distributed in tissues to fight pathogens or other foreign particles. In the lung, however, for intracellular infections such as tuberculosis, pneumonia and aspergillosis, bacteria and fungi utilize the alveolar macrophage as a breeding ground. This has become a challenge for the treatment of these infections, as most drugs do not effectively reach the macrophages at therapeutic levels. Alveolar macrophages also play an important role to initiative adaptive immunity toward combating inflammation and cancer in the lung.

AREAS COVERED

This review focuses on the development of micro- and nanotechnology-based drug delivery systems to target alveolar macrophages in association with intracellular infections, cancer and lung inflammation. Aspects of nanoparticle and micron-sized particle engineering through exploitation of particles' physicochemical characteristics such as particle size, surface charge and geometry of particles are discussed. In addition, the application of nanocarriers such as liposomes, polymeric nanoparticles and dendrimers are covered with respect to macrophage targeting.

EXPERT OPINION

Drug delivery targeted to alveolar macrophages in the lung is becoming a reality thanks to micro- and nanotechnology breakthrough. The literature review shows that regulation of physicochemical parameters of particles could be a recipe to enhance macrophage targeting and uptake. However, there is still a need to identify more target-specific receptors in order to facilitate drug targeting. Besides that, the toxicity of nanocarriers arising from prolonged residence in the lung should be taken into consideration during formulation.

Antipseudomonal agents exhibit differential pharmacodynamic interactions with human polymorphonuclear leukocytes against established biofilms of Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most common pathogen infecting the lower respiratory tract of cystic fibrosis (CF) patients, where it forms tracheobronchial biofilms. Pseudomonas biofilms are refractory to antibacterials and to phagocytic cells with innate immunity, leading to refractory infection. Little is known about the interaction between antipseudomonal agents and phagocytic cells in eradication of P. aeruginosa biofilms. Herein, we investigated the capacity of three antipseudomonal agents, amikacin (AMK), ceftazidime (CAZ), and ciprofloxacin (CIP), to interact with human polymorphonuclear leukocytes (PMNs) against biofilms and planktonic cells of P. aeruginosa isolates recovered from sputa of CF patients. Three of the isolates were resistant and three were susceptible to each of these antibiotics. The concentrations studied (2, 8, and 32 mg/liter) were subinhibitory for biofilms of resistant isolates, whereas for biofilms of susceptible isolates, they ranged between sub-MIC and 2 × MIC values. The activity of each antibiotic alone or in combination with human PMNs against 48-h mature biofilms or planktonic cells was determined by XTT [2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] assay. All combinations of AMK with PMNs resulted in synergistic or additive effects against planktonic cells and biofilms of P. aeruginosa isolates compared to each component alone. More than 75% of CAZ combinations exhibited additive interactions against biofilms of P. aeruginosa isolates, whereas CIP had mostly antagonistic interaction or no interaction with PMNs against biofilms of P. aeruginosa. Our findings demonstrate a greater positive interaction between AMK with PMNs than that observed for CAZ and especially CIP against isolates of P. aeruginosa from the respiratory tract of CF patients.

Aspects of pulmonary drug delivery strategies for infections in cystic fibrosis--where do we stand?

INTRODUCTION

Cystic fibrosis (CF) is the most common life-shortening hereditary disease among Caucasians and is associated with severe pulmonary damage because of decreased mucociliary clearance and subsequent chronic bacterial infections. Approximately 90% of CF patients die from lung destruction, promoted by pathogens such as Pseudomonas aeruginosa. Consequently, antibiotic treatment is a cornerstone of CF therapy, preventing chronic infection and reducing bacterial load, exacerbation rates and loss of pulmonary function. Many drugs are administered by inhalation to achieve high pulmonary concentration and to lower systemic side effects. However, pulmonary deposition of inhaled drugs is substantially limited by bronchial obstruction with viscous mucus and restrained by intrapulmonary bacterial biofilms.

AREAS COVERED

This review describes challenges in the therapy of CF-associated infections by inhaled antibiotics and summarizes the current state of microtechnology and nanotechnology-based pulmonary antibiotic delivery strategies. Recent and ongoing clinical trials as well as experimental approaches for microparticle/nanoparticle-based antibiotics are presented and their advantages and disadvantages are discussed.

EXPERT OPINION

Rapidly increasing antimicrobial resistance accompanied by the lack of novel antibiotics force targeted and more efficient use of the available drugs. Encapsulation of antimicrobials in nanoparticles or microparticles of organic polymers may have great potential for use in CF therapy.

Liposomal antibiotic formulations for targeting the lungs in the treatment of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative bacterium that causes serious lung infections in cystic fibrosis, non-cystic fibrosis bronchiectasis, immunocompromised, and mechanically ventilated patients. The arsenal of conventional antipseudomonal antibiotic drugs include the extended-spectrum penicillins, cephalosporins, carbapenems, monobactams, polymyxins, fluoroquinolones, and aminoglycosides but their toxicity and/or increasing antibiotic resistance are of particular concern. Improvement of existing therapies against Pseudomonas aeruginosa infections involves the use of liposomes - artificial phospholipid vesicles that are biocompatible, biodegradable, and nontoxic and able to entrap and carry hydrophilic, hydrophobic, and amphiphilic molecules to the site of action. The goal of developing liposomal antibiotic formulations is to improve their therapeutic efficacy by reducing drug toxicity and/or by enhancing the delivery and retention of antibiotics at the site of infection. The focus of this review is to appraise the current progress of the development and application of liposomal antibiotic delivery systems for the treatment pulmonary infections caused by P. aeruginosa.

Infectious Diseases: Need for Targeted Drug Delivery

Infectious diseases are a leading cause of death worldwide, with the constant fear of global epidemics. It is indeed an irony that the reticuloendothelial system (RES), the body’s major defence system, is the primary site for intracellular infections which are more difficult to treat. Pro-inflammatory M1 macrophages play an important role in defence. However, ingenious pathogen survival mechanisms including phagolysosome destruction enable their persistence. Microbial biofilms present additional challenges. Low intracellular drug concentrations, drug efflux by efflux pumps and/or enzymatic degradation, emergence of multi-drug resistance (MDR), are serious limitations of conventional therapy. Targeted delivery using nanocarriers, and passive and active targeting strategies could provide quantum increase in intracellular drug concentration. Receptor mediated endocytosis using appropriate ligands is a viable approach. Liposomes and polymeric/lipidic nanoparticles, dendrimers micelles and micro/nanoemulsions could all be relied upon. Specialised targeting approaches are demonstrated for important diseases like tuberculosis, HIV and Malaria. Application of targeted delivery in the treatment of veterinary infections is exemplified and future possibilities indicated. The chapter thus provides an overview on important aspects of infectious diseases and the challenges therein, while stressing on the promise of targeted drug delivery in augmenting therapy of infectious diseases.

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.

Biodegradable nanoparticles for intracellular delivery of antimicrobial agents

Biodegradable nanoparticles have emerged as a promising strategy for ferrying antimicrobial agents into specific cells due to their unique properties. This review discusses the current progress and challenges of biodegradable nanoparticles for intracellular antimicrobial delivery to understand design principles for the development of ideal nanocarriers. The intracellular delivery performances of biodegradable nanoparticles for diverse antimicrobial agents are first summarized. Second, the cellular internalization and intracellular trafficking, degradation and release kinetics of nanoparticles as well as their relation with intracellular delivery of encapsulated antimicrobial agents are provided. Third, the influences of nanoparticle properties on the cellular internalization and intracellular fate of nanoparticles and their payload antimicrobial agents are discussed. Finally, the challenges and perspectives of nanoparticles for intracellular delivery of antimicrobial agents are addressed. The review will be helpful to the scientists who are interested in searching for more efficient nanosystem strategies for intracellular delivery of antimicrobial agents.

[Designs of optimized microbial therapy systems of respiratory infections]

Several respiratory infections are frequently induced by pathogenic microorganisms in lung epithelial lining fluid (ELF) and alveolar macrophages (AM). Then, two studies concerning designs of antimicrobial therapy systems of respiratory infections were carried out; one was the distribution mechanisms of three macrolide and ketolide antibiotics, clarithromycin (CAM), azithromycin (AZM) and telithromycin (TEL) in plasma, ELF and AM, and the other was the efficient drug delivery to AM by pulmonary administration of fluoroquinolone antibiotic, a ciprofloxacin (CPFX) incorporated into liposomes (CPFX-liposome). In the first study, the areas under drug concentration-time curves (AUCs) in ELF following oral administration of three macrolide and ketolide antibiotics to rats were significantly higher than AUCs in plasma, furthermore AUCs in AM significantly higher than AUCs in ELF. The high distribution of these antibiotics to the respiratory infection site is due to the transport from blood to ELF via MDR1 in lung epithelial cells as well as the uptake by AM. These antibiotics were taken up by AM via active transport system and the trapping in organelles. In the second study, drug delivery efficacy of CPFX-liposome to AM was particle size-dependent over the 100-1000 nm and then become constant at over 1000 nm by pulmonary aerosolization to rats. This result indicates that the most effective size is 1000 nm. Furthermore, the drug delivery efficacy of mannosylated CPFX-liposome (particle size: 1000 nm) was highly delivered to AM and antibacterial effects were significantly higher than those of unmodified CPFX-liposome. This review provides useful findings for microbial therapy systems of respiratory infections.

Liposomal antibiotics for the treatment of infectious diseases

INTRODUCTION

Liposomal delivery systems have been utilized in developing effective therapeutics against cancer and targeting microorganisms in and out of host cells and within biofilm community. The most attractive feature of liposome-based drugs are enhancing therapeutic index of the new or existing drugs while minimizing their adverse effects.

AREAS COVERED

This communication provides an overview on several aspects of liposomal antibiotics including the most widely used preparation techniques for encapsulating different agents and the most important characteristic parameters applied for examining shape, size and stability of the spherical vesicles. In addition, the routes of administration, liposome-cell interactions and host parameters affecting the biodistribution of liposomes are highlighted.

EXPERT OPINION

Liposomes are safe and suitable for delivery of variety of molecules and drugs in biomedical research and medicine. They are known to improve the therapeutic index of encapsulated agents and reduce drug toxicity. Recent studies on liposomal formulation of chemotherapeutic and bioactive agents and their targeted delivery show liposomal antibiotics potential in the treatment of microbial infections.

Efficacy of inhaled ciprofloxacin in the management of non-cystic fibrosis bronchiectasis

Non-cystic fibrosis bronchiectasis (NCFBE), a historically under-recognized chronic respiratory condition, is a significant diagnosis currently experiencing a resurgence of interest in its clinical management. Ciprofloxacin is part of the current armamentarium used in the treatment of the recurrent respiratory tract infections seen in NCFBE. Inhaled ciprofloxacin, a novel method of drug delivery for the fluoroquinolone class, is being actively investigated. The inhaled formulation is designed to enhance drug delivery to the site of infection in the lung while minimizing the risk of systemic toxicity. This review summarizes the pharmacology and pharmacokinetics of ciprofloxacin and the rationale for the development of an inhaled formulation for NCFBE. Preclinical and clinical data regarding current development of inhaled ciprofloxacin formulations is also evaluated. Lastly, the anticipated role of inhaled ciprofloxacin in the management of NCFBE is discussed, including future considerations and potential limitations of therapy.

Ciprofloxacin is actively transported across bronchial lung epithelial cells using a Calu-3 air interface cell model

Ciprofloxacin is a well-established broad-spectrum fluoroquinolone antibiotic that penetrates well into the lung tissues; still, the mechanisms of its transepithelial transport are unknown. The contributions of specific transporters, including multidrug efflux transporters, organic cation transporters, and organic anion-transporting polypeptide transporters, to the uptake of ciprofloxacin were investigated in vitro using an air interface bronchial epithelial model. Our results demonstrate that ciprofloxacin is subject to predominantly active influx and a slight efflux component.

Systemic exposure, tissue distribution, and disease evolution of a high solubility ciprofloxacin-aluminum complex in a murine model of septicemia induced by salmonella enterica serotype Enteritidis

A new pharmaceutical derivative obtained by stoichiometric complexation of ciprofloxacin (CIP) with aluminum (CIP-complex) has been investigated and reported in this study. Such product has high solubility in the gastrointestinal pH range and was successful in the development of optimized formulations while maintaining its antimicrobial potency. The systemic exposure, tissue distribution, and the disease evolution after given CIP-complex were assessed. The systemic exposure and distribution in intestines, lungs, and kidneys after a single intragastric administration of CIP-complex and CIP given alone, used as reference, were performed in Balb-C mice at a dose of 5 mg CIP/kg. For the assessment of the disease evolution assay, mice were infected with a virulent strain of Salmonella enterica serotype Enteritidis and treated intragastrically once or twice daily during 5 consecutive days with solutions of CIP-complex or the reference. Clinical follow up and survival was measured during 15 days post inoculation and health state was scored during this period from 0 to 5. CIP-complex showed a 32% increase in C(max), an earlier T(max), and a smaller AUC(0-12) than the reference. Maximum tissue concentrations (0.5-1 h) were significantly higher in CIP-complex (447% in intestine, 93% in kidney, and 44% in lungs). In the infection model used in this study, survival in CIP-complex versus CIP groups was 40% versus 20% (twice-daily administration) and 30% versus 0% (once-daily administration). Health state of the survivors of CIP-complex group (5/5) was higher than CIP group (3/5). The greater effectiveness of CIP-complex is attributed to the higher levels of CIP in the intestine. Our results supported the fact that CIP-complex is a promising candidate to develop dose-efficient formulations of CIP for oral administration.

Quantitative assessment of the comparative nanoparticle-uptake efficiency of a range of cell lines

The mechanism(s) of nanoparticle-cell interactions are still not understood. At present there is little knowledge of the relevant length- and timescales for nanoparticle intracellular entry and localization within cells, or the cell-specificity of nanoparticle uptake and localisation. Here, the effect of particle size on the in-vitro intracellular uptake of model fluorescent carboxyl-modified polystyrene nanoparticles is investigated in various cell lines. A range of micro- and nanoparticles of defined sizes (40 nm to 2 μm) are incubated with a series of cell types, including HeLa and A549 epithelial cells, 1321N1 astrocytes, HCMEC D3 endothelial cells, and murine RAW 264.7 macrophages. Techniques such as confocal microscopy and flow cytometry are used to study particle uptake and subcellular localisation, making significant efforts to ensure reproducibility in a semiquantitative approach. The results indicate that internalization of (nano)particles is highly size-dependent for all cell lines studied, and the kinetics of uptake for the same type of nanoparticle varies in the different cell types. Interestingly, even cells not specialized for phagocytosis are able to internalize the larger nanoparticles. Intracellular uptake of all sizes of particles is observed to be highest in RAW 264.7 cells (a specialized phagocytic cell line) and the lowest in the HeLa cells. These results suggest that (nano)particle uptake might not follow commonly defined size limits for uptake processes, and highlight the variability of uptake kinetics for the same material in different cell types. These conclusions have important implications for the assessment of the safety of nanomaterials and for the potential biomedical applications of nanoparticles.

Penetration of anti-infective agents into pulmonary epithelial lining fluid: focus on antibacterial agents

The exposure-response relationship of anti-infective agents at the site of infection is currently being re-examined. Epithelial lining fluid (ELF) has been suggested as the site (compartment) of antimicrobial activity against lung infections caused by extracellular pathogens. There have been an extensive number of studies conducted during the past 20 years to determine drug penetration into ELF and to compare plasma and ELF concentrations of anti-infective agents. The majority of these studies estimated ELF drug concentrations by the method of urea dilution and involved either healthy adult subjects or patients undergoing diagnostic bronchoscopy. Antibacterial agents such as macrolides, ketolides, newer fluoroquinolones and oxazolidinones have ELF to plasma concentration ratios of >1. In comparison, β-lactams, aminoglycosides and glycopeptides have ELF to plasma concentration ratios of ≤1. Potential explanations (e.g. drug transporters, overestimation of the ELF volume, lysis of cells) for why these differences in ELF penetration occur among antibacterial classes need further investigation. The relationship between ELF concentrations and clinical outcomes has been under-studied. In vitro pharmacodynamic models, using simulated ELF and plasma concentrations, have been used to examine the eradication rates of resistant and susceptible pathogens and to explain why selected anti-infective agents (e.g. those with ELF to plasma concentration ratios of >1) are less likely to be associated with clinical treatment failures. Population pharmacokinetic modelling and Monte Carlo simulations have recently been used and permit ELF and plasma concentrations to be evaluated with regard to achievement of target attainment rates. These mathematical modelling techniques have also allowed further examination of drug doses and differences in the time courses of ELF and plasma concentrations as potential explanations for clinical and microbiological effects seen in clinical trials. Further studies are warranted in patients with lower respiratory tract infections to confirm and explore the relationships between ELF concentrations, clinical and microbiological outcomes, and pharmacodynamic parameters.

Challenges in inhaled product development and opportunities for open innovation

Dosimetry, safety and the efficacy of drugs in the lungs are critical factors in the development of inhaled medicines. This article considers the challenges in each of these areas with reference to current industry practices for developing inhaled products, and suggests collaborative scientific approaches to address these challenges. The portfolio of molecules requiring delivery by inhalation has expanded rapidly to include novel drugs for lung disease, combination therapies, biopharmaceuticals and candidates for systemic delivery via the lung. For these drugs to be developed as inhaled medicines, a better understanding of their fate in the lungs and how this might be modified is required. Harmonized approaches based on 'best practice' are advocated for dosimetry and safety studies; this would provide coherent data to help product developers and regulatory agencies differentiate new inhaled drug products. To date, there are limited reports describing full temporal relationships between pharmacokinetic (PK) and pharmacodynamic (PD) measurements. A better understanding of pulmonary PK and PK/PD relationships would help mitigate the risk of not engaging successfully or persistently with the drug target as well as identifying the potential for drug accumulation in the lung or excessive systemic exposure. Recommendations are made for (i) better industry-academia-regulatory co-operation, (ii) sharing of pre-competitive data, and (iii) open innovation through collaborative research in key topics such as lung deposition, drug solubility and dissolution in lung fluid, adaptive responses in safety studies, biomarker development and validation, the role of transporters in pulmonary drug disposition, target localisation within the lung and the determinants of local efficacy following inhaled drug administration.