Inhaled pyrazinamide proliposome for targeting alveolar macrophages

Inhalable solid lipid nanoparticles of levofloxacin for potential tuberculosis treatment

Delivering novel antimycobacterial agents through the pulmonary route using nanoparticle-based systems shows promise for treating diseases like tuberculosis. However, creating dry powder inhaler (DPI) with suitable aerodynamic characteristics while preserving nanostructure integrity and maintaining bioactivity until the active ingredient travels deeply into the lungs is a difficult challenge. We developed DPI formulations containing levofloxacin-loaded solid lipid nanoparticles (SLNs) via spray-drying technique with tailored aerosolization characteristics for effective inhalation therapy. A range of biophysical techniques, including transmission electron microscopy, confocal microscopy, and scanning electron microscopy were used to measure the morphologies and sizes of the spray-dried microparticles that explored both the geometric and aerodynamic properties. Spray drying substantially reduced the particle sizes of the SLNs while preserving their nanostructural integrity and enhancing aerosol dispersion with efficient mucus penetration. Despite a slower uptake rate compared to plain SLNs, the polyethylene glycol modified formulations exhibited enhanced cellular uptake in both A549 and NR8383 cell lines. The percent viability of Mycobacterium bovis had dropped to nearly 0 % by day 5 for both types of SLNs. Interestingly, the levofloxacin-loaded SLNs demonstrated a lower minimum bactericidal concentration (0.25 µg/mL) compared with pure levofloxacin (1 µg/mL), which indicated the formulations have potential as effective treatments for tuberculosis.

Evaluating the biomolecular interaction between delamanid/formulations and human serum albumin by fluorescence, CD spectroscopy and SPR: Effects on protein conformation, kinetic and thermodynamic parameters

Delamanid is an anti-tuberculosis drug used for the treatment of drug-resistant tuberculosis. Since delamanid has a high protein bound potential, even patients with low albumin levels should experience high and rapid delamanid clearance. However, the interaction between delamanid and albumin should be better controlled to optimize drug efficacy. This study was designed to evaluate the binding characteristics of delamanid to human serum albumin (HSA) using various methods: fluorescence spectroscopy, circular dichroism (CD), surface plasmon resonance (SPR), and molecular docking simulation. The fluorescence emission band without any shift indicated the interaction was not affected by the polarity of the fluorophore microenvironment. The reduction of fluorescence intensity at 344 nm was proportional to the increment of delamanid concentration as a fluorescence quencher. UV-absorbance measurement at the maximum wavelength (λmax, 280 nm) was evaluated using inner filter effect correction. The HSA conformation change was explained by the intermolecular energy transfer between delamanid and HSA during complex formation. The study, which was conducted at temperatures of 298 K, 303 K, and 310 K, revealed a static quenching mechanism that correlated with a decreased of bimolecular quenching rate constant (kq) and binding constant (Ka) at increased temperatures. The Ka was 1.75-3.16 × 104 M-1 with a specific binding site with stoichiometry 1:1. The negative enthalpy change, negative entropy change, and negative Gibbs free energy change demonstrated an exothermic-spontaneous reaction while van der Waals forces and hydrogen bonds played a vital role in the binding. The molecular displacement approach and molecular docking confirmed that the binding occurred mainly in subdomain IIA, which is a hydrophobic pocket of HSA, with a theoretical binding free energy of -9.33 kcal/mol. SPR exhibited a real time negative sensorgram that resulted from deviation of the reflex angle due to ligand delamanid-HSA complex forming. The binding occurred spontaneously after delamanid was presented to the HSA surface. The SPR mathematical fitting model revealed that the association rate constant (kon) was 2.62 × 108 s-1M-1 and the dissociation rate constant (koff) was 5.65 × 10-3 s-1. The complexes were performed with an association constant (KA) of 4.64 × 1010 M-1 and the dissociation constant (KD) of 2.15 × 10-11 M. The binding constant indicated high binding affinity and high stability of the complex in an equilibrium. Modified CD spectra revealed that conformation of the HSA structure was altered by the presence of delamanid during preparation of the proliposomes that led to the reduction of secondary structure stabilization. This was indicated by the percentage decrease of α-helix. These findings are beneficial to understanding delamanid-HSA binding characteristics as well as the drug administration regimen.

Liposomes for Inhalation

Inhalation of liposomes formulated with phospholipids similar to endogenous lung surfactants and lipids offers biocompatibility and versatility within the pulmonary medicine field to treat a range of diseases such as lung cancer, cystic fibrosis and lung infections. Manipulation of the physicochemical properties of liposomes enables innovative design of the carrier to meet specific delivery, release and targeting requirements. This delivery system offers several benefits: improved pharmacokinetics with reduced toxicity, enhanced therapeutic efficacy, increased delivery of poorly soluble drugs, taste masking, biopharmaceutics degradation protection and targeted cellular therapy. This section provides an overview of liposomal formulation and delivery, together with their applications for different disease states in the lung.

Monitoring the Interaction Between Solid Lipid Nanoparticles and Alveolar Macrophages Via the Label-Free Technique

Macrophages are employed as targets for delivering genes, drugs, or lipid nanoparticles into tumors or other specific sites. Studying the interaction between solid lipid nanoparticles (SLNs) and macrophages is essential for assessing nanotoxicity and advancing the development of nanomedicines. However, limited data are currently available on the membrane microstructure and biochemical changes that occur when macrophages interact with SLNs. We conducted a label-free morphological and biochemical investigation of NR8383 macrophages using optical diffraction tomography (ODT), which validated the efficiency of the SLNs as a drug delivery system. ODT provided intracellular holotomography to characterize the macrophages and fluorescence imaging to analyze delivery efficiency. ODT analysis revealed the responses of phagocytic macrophages. Additionally, a quantitative analysis of lipid droplets using refractive indices revealed that, compared with incubation with normal cells, incubation with SLNs significantly increased the lipid droplet volume and surface area. The uptake of SLNs into macrophages resulted in increased cell volume, surface area, and concentration, which indicated greater morphological and biochemical variability in the treated cells than in the control cells. The results suggest that ODT imaging is promising for understanding the intracellular distribution of SLNs and useful for validating the efficacy of delivery of SLNs to macrophages.

Optimization, characterization, and cytotoxicity studies of novel anti-tubercular agent-loaded liposomal vesicles

The treatment of tuberculosis is still a challenging process due to the widespread of pathogen strains resistant to antibacterial drugs, as well as the undesirable effects of anti-tuberculosis therapy. Hence, the development of safe and effective new anti-antitubercular agents, in addition to suitable nanocarrier systems, has become of utmost importance and necessity. Our research aims to develop liposomal vesicles that contain newly synthesized compounds with antimycobacterial action. The compound being studied is a derivative of imidazo-tetrazine named 3-(3,5-dimethylpyrazole-1-yl)-6-(isopropylthio) imidazo [1,2-b] [1,2,4,5] tetrazine compound. Several factors that affect liposomal characteristics were studied. The maximum encapsulation efficiency was 53.62 ± 0.09. The selected liposomal formulation T8* possessed a mean particle size of about 205.3 ± 3.94 nm with PDI 0.282, and zeta potential was + 36.37 ± 0.49 mv. The results of the in vitro release study indicated that the solubility of compound I was increased by its incorporation in liposomes. The free compound and liposomal preparation showed antimycobacterial activity against Mycobacterium tuberculosis H37Rv (ATCC 27294) at MIC value 0.94-1.88 μg/ml. We predict that the liposomes may be a good candidate for delivering new antitubercular drugs.

Mannose-Functionalized Isoniazid-Loaded Nanostructured Lipid Carriers for Pulmonary Delivery: In Vitro Prospects and In Vivo Therapeutic Efficacy Assessment

Resistance to isoniazid (INH) is common and increases the possibility of acquiring multidrug-resistant tuberculosis. For this study, isoniazid-loaded nanostructured lipid carriers (INH-NLCs) were developed and effectively functionalized with mannose (Man) to enhance the residence time of the drug within the lungs via specific delivery and increase the therapeutic efficacy of the formulation. The mannose-functionalized isoniazid-loaded nanostructured lipid carrier (Man-INH-NLC) formulation was evaluated with respect to various formulation parameters, namely, encapsulation efficiency (EE), drug loading (DL), average particle size (PS), zeta potential (ZP), polydispersity index (PDI), in vitro drug release (DR), and release kinetics. The in vitro inhalation behavior of the developed formulation after nebulization was investigated using an Andersen cascade impactor via the estimation of the mass median aerosolized diameter (MMAD) and geometric aerodynamic diameter (GAD) and subsequently found to be suitable for effective lung delivery. An in vivo pharmacokinetic study was carried out in a guinea pig animal model, and it was demonstrated that Man-INH-NLC has a longer residence time in the lungs with improved pharmacokinetics when compared with unfunctionalized INH-NLC, indicating the enhanced therapeutic efficacy of the Man-INH-NLC formulation. Histopathological analysis led us to determine that the extent of tissue damage was more severe in the case of the pure drug solution of isoniazid compared to the Man-INH-NLC formulation after nebulization. Thus, the nebulization of Man-INH-NLC was found to be safe, forming a sound basis for enhancing the therapeutic efficacy of the drug for improved management in the treatment of pulmonary tuberculosis.

Factors Affecting Drug Exposure after Inhalation

Administration of drugs by inhalation is mainly used to treat lung diseases and is being investigated as a possible route for systemic drug delivery. It offers several benefits, but it is also fraught with many difficulties. The lung is a complex organ with complicated physiology and specific pharmacokinetic processes. Therefore, the exposure and subsequently efficacy of a drug after inhalation is affected by a number of factors. In this review, we summarize the main variables that may affect drug fate after inhalation delivery, such as physicochemical properties of the drug, pulmonary clearance and metabolism, pathophysiological factors and inhalation device. Factors that have impact on pharmacokinetic processes need to be considered during development as their correct setting can lead to new effective inhaled drugs.

Dry powder inhalers of antitubercular drugs

Despite advancements in the medical and pharmaceutical fields, tuberculosis remains a major health problem globally. Patients do not widely accept the conventional approach to treating tuberculosis (TB) due to prolonged treatment periods with multiple high doses of drugs and associated side effects. A pulmonary route is a non-invasive approach to delivering drugs, hormones, nucleic acid, steroids, proteins, and peptides directly to the lungs, improving the efficacy of the treatment and consequently decreasing the adverse effect of the treatment. This route has been successfully developed for the treatment of various respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), tuberculosis (TB), lung cancer, and other pulmonary infections. The major approaches of inhalation delivery systems include nebulizers, metered-dose inhalers (MDIs), and dry powder inhalers (DPIs). However, dry powder inhalers (DPIs) are more advantageous due to their stability and ability to deliver a high dose of the drug to the lungs. The present review analyzes the modern therapeutic approach of inhaled dry powders, with a special focus on novel drug delivery system (NDDS) based DPIs for the treatment of TB. The article also discussed the challenges of preparing inhalable dry powder formulations for the treatment of TB. The clinical development of inhalable anti-TB drugs is also reviewed.

A drift on liposomes to proliposomes: recent advances and promising approaches

Liposomes are nano-structured vesicles, made up of phospholipids that provide active ingredients at the site of action at a predetermined rate and add the advantage of the sustained-release formulation. Liposomes have stability issues that tend to agglomerate and fuse upon storage, which reflects their drawback. Hence to overcome the aggregation, fusion, hydrolysis, and/or oxidation problems associated with liposomes a new technology named Proliposomes has been introduced. Proliposomes are defined as carbohydrate carriers coated with phospholipids, which upon addition of water generate liposomes. The objective of the review is to cover the concept of proliposomes for pulmonary or alveolar delivery of drugs and compare it with that of liposomes; highlight the methods used for preparations along with the characterization parameters. This is the first systematic review that covers the categorization of liposomes, characteristic methods, and recent examples of drugs from 2015 to 2021, supplied in form of proliposomes to the macrophages as well as others and offers an advantage over the free drug by offering a prolonged drug release and sufficient bioavailability in addition to overcome the stability issues related to liposomes. Since this is a very new technology and many scientists are continuously working in this field to make the drug available for clinical trials and ultimately in the market for the targeted delivery of drugs with better storage life.HIGHLIGHTSProliposomes as an alternative to overwhelm the stability and storage-related issues of liposomes.Anhydrous carbohydrate carriers are utilized for proliposomal preparation.Inhaled delivery of drugs as solid lipid nanoparticles offers a significant impact on pulmonary tract infections, particularly in cystic fibrosis.Size of liposomes attained after proliposome hydrolysis is critical for drug delivery via respiration.

Nanocarrier-Based Approaches for the Efficient Delivery of Anti-Tubercular Drugs and Vaccines for Management of Tuberculosis

Drug-resistant species of tuberculosis (TB), which spread faster than traditiona TB, is a severely infectious disease. The conventional drug therapy used in the management of tuberculosis has several challenges linked with adverse effects. Hence, nanotherapeutics served as an emerging technique to overcome problems associated with current treatment. Nanotherapeutics helps to overcome toxicity and poor solubility issues of several drugs used in the management of tuberculosis. Due to their diameter and surface chemistry, nanocarriers encapsulated with antimicrobial drugs are readily taken up by macrophages. Macrophages play a crucial role as they serve as target sites for active and passive targeting for nanocarriers. The surface of the nanocarriers is coated with ligand-specific receptors, which further enhances drug concentration locally and indicates the therapeutic potential of nanocarriers. This review highlights tuberculosis's current facts, figures, challenges associated with conventional treatment, different nanocarrier-based systems, and its application in vaccine development.

Inhalable nanoparticles delivery targeting alveolar macrophages for the treatment of pulmonary tuberculosis

Pulmonary tuberculosis is a highly prevalent respiratory disease that affects approximately a quarter of the world's population. The drug treatment protocol for tuberculosis is complex because the Mycobacterium tuberculosis (M. tuberculosis) invades macrophages and begins to infect. Thus treatment usually includes combination therapy with several drugs such as rifampicin, pyrazinamide, isoniazid, and ethambutol over a long dosing period. Therefore, drug-delivery technologies have been developed to improve patient compliance with medication, reduce adverse effects, and increase effectiveness of the treatment. In the present review, we have discussed recent inhalable nanopharmaceutical systems for the treatment of pulmonary tuberculosis and investigated their design and effectiveness. We examined the underlying processes and characteristics of spray-drying technology and studied the formulation of a dry carrier using spray-drying method. Moreover, we reviewed various research articles on pulmonary delivery of nanoparticles using these carriers, and studied their alveolar macrophage targeting ability and therapeutic effects. Further, we appraised the effectiveness of nanoparticle inhalation therapy for the treatment of pulmonary tuberculosis and its potential as a treatment strategy for lung diseases.

Efficacy and safety of combined isoniazid-rifampicin-pyrazinamide-levofloxacin dry powder inhaler in treatment of pulmonary tuberculosis: A randomized controlled trial

OBJECTIVE

To determine the efficacy and safety of add-on dry powder for inhalation (DPI) of combined anti-TB agents prepared as a particulate system (study group) compared with placebo DPI (control group) in patients diagnosed with pulmonary TB.

METHODS

This study was a randomized, placebo-controlled, double-blinded parallel design. Subjects were pulmonary TB patients, new or re-treatment, aged 18 years or older. The eligible patients were randomly allocated (1:1) to either the study group or the control group using stratified blocked randomization. The add-on DPI of combined anti-TB therapy (each capsule contained isoniazid 5 mg, rifampicin 2 mg, pyrazinamide 16 mg, and levofloxacin 2 mg) was used throughout the course of the standard oral anti-TB treatment. The primary outcome was Mycobacterium tuberculosis (MTB) sputum culture conversion measured after receiving treatment for eight weeks. Secondary outcomes were clinical signs and symptoms of pulmonary TB and adverse drug reactions (ADRs) related to anti-TB agents. The percentages of patients who achieved the primary outcome were compared (95% confidence interval). All analyses were performed using the modified intention-to-treat principle.

RESULTS

91 patients were randomly allocated: 44 to the study group and 47 to the control group. Important baseline data (%peak expiratory flow rate, chest X-ray findings, resistance to anti-TB agents, renal and liver function tests) were similar between the two groups. Although the percentages of patients who achieved the primary outcome were similar in both groups (34/44 [77.3%] in the study group and (34/47 [72.3%] in the control group; relative risk [RR] 1.07, 95% CI 0.84-1.36; p = 0.589), the study group patients seemed to achieve the primary outcome earlier than the control group (22/44 [50.0%] vs 15/47 [31.9%]; RR 1.57, 95% CI 0.94-2.61; p = 0.079) at the end of week 4. Cough was significantly lower in the study group than in the control group (23/44 [52.3%] vs 43/47 [91.5%]; RR 0.57, 95% CI 0.43-0.77; p < 0.001) at week 4 of treatment. Hemoptysis was found in approximately half of each group at baseline. The percentage of patients having hemoptysis was substantially reduced at week 2 of treatment (5 [11.4%] in the study group and 11 [23.0%] in the control group, p = 0.132). Regarding safety outcomes, no dyspnea or severe ADRs were reported. Adverse events (AEs) related to oral anti-TB agents, (e.g. liver function tests) were in normal ranges in most patients in both groups during the treatment. The incidences of common AEs reported (e.g. anorexia, dizziness, numbness, arthralgia, rash, and itching) were similar between the two groups, while the incidences of nausea and vomiting were significantly lower in the study group than the control group (38.6% vs 74.5%, p = 0.001, and 43.2% vs 66.0%, p = 0.029, respectively).

CONCLUSIONS

Add-on combined anti-TB DPI therapy to the standard oral anti-TB treatment did not increase MTB sputum culture conversion at two months of treatment. However, the percentage of patients having cough in the study group was significantly lower than in the control group at two months after treatment. A reduction in cough might represent adequate response to treatment, and result in a decreased risk of spread of infection. Combined anti-TB DPI therapy was safe. Further study investigated in a larger sample using higher strengths of DPI therapy is required.

Nano-based drug delivery optimization for tuberculosis treatment: A review

Regardless of advanced technology and innovation, infectious diseases continue to be one of the extreme health challenges in modern world. Tuberculosis (TB) is one of the top ten causes of deaths worldwide and the leading cause of death from a single infectious agent. The conventional TB drug therapy requires a long term treatment with frequent and multiple drug dosing with a stiff administration schedule, which results in low patient compliance. This eventually leads to the recurrence of the infection and the emergence of multiple drug resistance. Hence, there is an urgent need to develop more successful and effective strategies to overcome the problems of drug resistance, duration of treatment course and devotion to treatment. Nanotechnology has considerable potential for diagnosis, treatment and prevention of infectious diseases including TB. The main advantages of nanoparticles to be used as drug carriers are their small size, high stability, enhanced delivery of hydrophilic and hydrophobic drugs, intracellular delivery of macromolecules, targeted delivery of drugs to specific cells or tissues, and the feasibility of various drug administration routes. Moreover, these carriers are adapted to facilitate controlled, slow, and persistent drug release from the matrix. Above properties of nanoparticles permit the improvement of drug bioavailability and reduction of dosing frequency and may reduce the toxicity and resolve the problem of low adherence to the prescribed therapy. In this review, various types of nanocarriers have been evaluated as promising drug delivery systems for different administration routes and main research outcomes in this area have been discussed.

Novel Approaches for the Treatment of Pulmonary Tuberculosis

Tuberculosis (TB) is a contagious airborne disease caused by Mycobacterium tuberculosis, which primarily affects human lungs. The progression of drug-susceptible TB to drug-resistant strains, MDR-TB and XDR-TB, has become worldwide challenge in eliminating TB. The limitations of conventional TB treatment including frequent dosing and prolonged treatment, which results in patient’s noncompliance to the treatment because of treatment-related adverse effects. The non-invasive pulmonary drug administration provides the advantages of targeted-site delivery and avoids first-pass metabolism, which reduced the dose requirement and systemic adverse effects of the therapeutics. With the modification of the drugs with advanced carriers, the formulations may possess sustained released property, which helps in reducing the dosing frequency and enhanced patients’ compliances. The dry powder inhaler formulation is easy to handle and storage as it is relatively stable compared to liquids and suspension. This review mainly highlights the aerosolization properties of dry powder inhalable formulations with different anti-TB agents to understand and estimate the deposition manner of the drug in the lungs. Moreover, the safety profile of the novel dry powder inhaler formulations has been discussed. The results of the studies demonstrated that dry powder inhaler formulation has the potential in enhancing treatment efficacy.

A novel multifaceted approach for wound healing: Optimization and in vivo evaluation of spray dried tadalafil loaded pro-nanoliposomal powder

The topical delivery of nanotherapeutics at the injury site for skin regeneration has received increasing attention as a strategy for wound treatment. This study aimed to investigate the preparation of spray dried tadalafil loaded pro-nanoliposomes powder as a novel system to accelerate wound healing process. The optimization was carried out employing 3² factorial design based on phospholipid and cholesterol concentrations. The physicochemical characterizations, in vitro cellular assessment and in vivo performance were evaluated. The results obtained pointed out that phospholipid concentration presented a positive effect on the entrapment efficacy and particle size, while cholesterol hindered the entrapment efficacy yet presented a prominent influence on particle size. Moreover, the optimized formulation showed a sustained release, high zeta potential and uniform spherical particles indicating entrapment of tadalafil in its amorphous state as demonstrated by FTIR and XPRD results. Cell viability and in vitro scratch assay demonstrated no cytotoxicity on human fibroblast cell lines and the ability of the drug and optimized formulation to promote cell migration. In vivo wound healing studies revealed significantly higher wound closure rates for areas treated with optimized loaded-formulation (65.95±6.47%) compared to unloaded formulation (29.78±9.65%), free drug (38.87±11.44%) and sham group (10.22±5.11%). In the in vivo study, histopathological specimens supported the previous results with presentation of cascade of healing elements via the angiogenetic activity of tadalafil. These outcomes provide an insight of a novel and emerging therapeutic drug system for wound treatment in clinical practice.

Characterization, Optimization, In Vitro and In Vivo Evaluation of Simvastatin Proliposomes, as a Drug Delivery

Simvastatin a cholesterol-lowering agent used to treat hypercholesterolemia, coronary heart disease, and dyslipidemia. However, simvastatin (SV) has shown low oral bioavailability in GIT. The main purpose of the work was to develop proliposomal formulations to increase the oral bioavailability of SV. Film deposition on the carrier method has been used to prepare the proliposomes. The proliposomes were assessed for morphology, particulate size, entrapment efficacy, drug-polymer compatibility, in vitro and in vivo studies. FTIR and DSC results revealed no drug-polymer interaction. SEM and XRD analysis conform; proliposomes are spherical, amorphous in nature, so that it enhances the solubility of SV between 15.01 ± 0.026 and 57.80 ± 0.015 μg/mL in pH 7.4 phosphate buffer. The optimised formulation (PL6) shows drug release up to 12 h (99.78 ± 0.067%). The pharmacokinetics of pure SV and SV proliposomes (SVP) in rats were T_max 2 ± 0.5 and 4 ± 0.7 h, C_max 10.4 ± 2.921 and 21.18 ± 12.321 μg/mL, AUC0-∞ 67.124 ± 0.23 and 179.75 ± 1.541 μg/mL h, respectively. Optimised SVP shows a significant improvement in the rate and absorption of SV. The optimised formulation showed enhanced oral bioavailability of SV in Albino Wister rats and offers a new technique to improve the poor water-soluble drug absorption in the gastrointestinal system.

Inhalable nanotherapeutics to improve treatment efficacy for common lung diseases

Respiratory illnesses are prevalent around the world, and inhalation-based therapies provide an attractive, noninvasive means of directly delivering therapeutic agents to their site of action to improve treatment efficacy and limit adverse systemic side effects. Recent trends in medicine and nanoscience have prompted the development of inhalable nanomedicines to further enhance effectiveness, patient compliance, and quality of life for people suffering from lung cancer, chronic pulmonary diseases, and tuberculosis. Herein, we discuss recent advancements in the development of inhalable nanomaterial-based drug delivery systems and analyze several representative systems to illustrate their key design principles that can translate to improved therapeutic efficacy for prevalent respiratory diseases. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease.

Soy Lecithin-Derived Liposomal Delivery Systems: Surface Modification and Current Applications

The development of natural phospholipids for nanostructured drug delivery systems has attracted much attention in the past decades. Lecithin that was derived from naturally occurring in soybeans (SL) has introduced some auspicious accomplishments to the drug carrying aspect, like effectual encapsulation, controlled release, and successful delivery of the curative factors to intracellular regions in which they procure these properties from their flexible physicochemical and biophysical properties, such as large aqueous center and biocompatible lipid, self-assembly, tunable properties, and high loading capacity. Despite the almost perfect properties as a drug carrier, liposome is known to be quite quickly eliminated from the body systems. The surface modification of liposomes has been investigated in many studies to overcome this drawback. In this review, we intensively discussed the surface-modified liposomes that enhancing the targeting, cellular uptake, and therapeutic response. Moreover, the recent applications of soy lecithin-derived liposome, focusing on cancer treatment, brain targeting, and vaccinology, are also summarized.

Novel combination proliposomes containing tobramycin and clarithromycin effective against Pseudomonas aeruginosa biofilms

Tobramycin (TOB) and clarithromycin (CLA) can potentially be used synergistically for the treatment of respiratory infections caused by Pseudomonas aeruginosa (P. aeruginosa) in cystic fibrosis (CF) patients. This study aimed to develop a novel combination proliposome formulation (TOB/CLA-CPROLips) containing both hydrophilic TOB and hydrophobic CLA via a core-carrier approach. The combination proliposomes were produced by spray drying a suspension comprising spray-driedmannitol (SD-MAN, 0.45%) and spray-dried tobramycin (SD-TOB, 0.05%) particles suspended in an ethanolic lipid solution of CLA (0.05%). The lipid layer coated on the surface of the dry proliposome particles conferred moisture protection and sustained drug release properties in comparison to the pure drugs. The optimized TOB/CLA-CPROLips formulation was stable after 3 months of storage at 60% relative humidity (RH) and 25 °C. The combination drug proliposomes showed a synergistic antimicrobial activity against planktonic cells and biofilm cultures of P. aeruginosa. In conclusion, the core-carrier method coupled with spray-drying provided a novel approach for the preparation of combination antibiotics proliposomes.

High dose dry powder inhalers to overcome the challenges of tuberculosis treatment

Tuberculosis (TB) is a major global health burden. The emergence of the human immunodeficiency virus (HIV) epidemic and drug resistance has complicated global TB control. Pulmonary delivery of drugs using dry powder inhalers (DPI) is an emerging approach to treat TB. In comparison with the conventional pulmonary delivery for asthma and chronic obstructive pulmonary disease (COPD), TB requires high dose delivery to the lung. However, high dose delivery depends on the successful design of the inhaler device and the formulation of highly aerosolizable powders. Particle engineering techniques play an important role in the development of high dose dry powder formulations. This review focuses on the development of high dose dry powder formulations for TB treatment with background information on the challenges of the current treatment of TB and the potential for pulmonary delivery. Particle engineering techniques with a particular focus on the spray drying and a summary of the developed dry powder formulations using different techniques are also discussed.

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

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

The Multirole of Liposomes in Therapy and Prevention of Infectious Diseases

Liposomes are closed bilayer structures spontaneously formed by hydrated phospholipids that are widely used as efficient delivery systems for drugs or antigens, due to their capability to encapsulate bioactive hydrophilic, amphipathic, and lipophilic molecules into inner water phase or within lipid leaflets. The efficacy of liposomes as drug or antigen carriers has been improved in the last years to ameliorate pharmacokinetics and capacity to release their cargo in selected target organs or cells. Moreover, different formulations and variations in liposome composition have been often proposed to include immunostimulatory molecules, ligands for specific receptors, or stimuli responsive compounds. Intriguingly, independent research has unveiled the capacity of several phospholipids to play critical roles as intracellular messengers in modulating both innate and adaptive immune responses through various mechanisms, including (i) activation of different antimicrobial enzymatic pathways, (ii) driving the fusion–fission events between endosomes with direct consequences to phagosome maturation and/or to antigen presentation pathway, and (iii) modulation of the inflammatory response. These features can be exploited by including selected bioactive phospholipids in the bilayer scaffold of liposomes. This would represent an important step forward since drug or antigen carrying liposomes could be engineered to simultaneously activate different signal transduction pathways and target specific cells or tissues to induce antigen-specific T and/or B cell response. This lipid-based host-directed strategy can provide a focused antimicrobial innate and adaptive immune response against specific pathogens and offer a novel prophylactic or therapeutic option against chronic, recurrent, or drug-resistant infections.

Factors Affecting Enhanced Permeation of Amphotericin B Across Cell Membranes and Safety of Formulation

The aim of this study was to determine amphotericin B (AmB) permeation across lipid bilayer membranes mounted on Transwell® and to observe the phagocytosis of the AmB and the AmB-lipid formulations by alveolar macrophage (AM) cell lines using a fluorescence microscope. The lipid bilayer membranes were prepared from phospholipid and ergosterol as well as phospholipid and cholesterol in a ratio (67:33 mol%). AmB-lipid formulations were prepared from AmB incorporated with four lipid derivatives during a lyophilization process. In vitro cytotoxicity studies were carried out on kidney cells by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The levels of nitric oxide production by AMs exposed to these AmB-lipid formulations were determined by the Griess reaction. Phagocytosis of the AmB-lipid formulations was carried out using AM cells. The lipid bilayer membranes and AmB-lipid formulations were successfully prepared. In vitro cytotoxicity results showed less toxicity to kidney cells than pure AmB, and a 1,000-fold less production of nitric oxide by NR8383 cell lines was obtained when compared to lipopolysaccharide. Permeation results were two- to fivefold higher than for pure AmB in the ergosterol containing lipid bilayer and two- to fourfold higher than AmB in the cholesterol containing compositions, both of which were enough to kill the fungi according to their MICs and MFCs. AM phagocytosed the AmB-lipid formulations. We suggest that these products especially the AmB-sodium deoxycholate sulfate are potential candidates for targeting AM cells for the treatment of invasive pulmonary aspergillosis.

Sharpening nature's tools for efficient tuberculosis control: A review of the potential role and development of host-directed therapies and strategies for targeted respiratory delivery

Centuries since it was first described, tuberculosis (TB) remains a significant global public health issue. Despite ongoing holistic measures implemented by health authorities and a number of new oral treatments reaching the market, there is still a need for an advanced, efficient TB treatment. An adjunctive, host-directed therapy designed to enhance endogenous pathways and hence compliment current regimens could be the answer. The integration of drug repurposing, including synthetic and naturally occurring compounds, with a targeted drug delivery platform is an attractive development option. In order for a new anti-tubercular treatment to be produced in a timely manner, a multidisciplinary approach should be taken from the outset including stakeholders from academia, the pharmaceutical industry, and regulatory bodies keeping the patient as the key focus. Pre-clinical considerations for the development of a targeted host-directed therapy are discussed here.

Dry powder inhalable formulations for anti-tubercular therapy

Tuberculosis (TB) is an intracellular infectious disease caused by the airborne bacterium, Mycobacterium tuberculosis. Despite considerable research efforts, the treatment of TB continues to be a great challenge in part due to the requirement of prolonged therapy with multiple high-dose drugs and associated side effects. The delivery of pharmacological agents directly to the respiratory system, following the natural route of infection, represents a logical therapeutic approach for treatment or vaccination against TB. Pulmonary delivery is non-invasive, avoids first-pass metabolism in the liver and enables targeting of therapeutic agents to the infection site. Inhaled delivery also potentially reduces the dose requirement and the accompanying side effects. Dry powder is a stable formulation of drug that can be stored without refrigeration compared to liquids and suspensions. The dry powder inhalers are easy to use and suitable for high-dose formulations. This review focuses on the current innovations of inhalable dry powder formulations of drug and vaccine delivery for TB, including the powder production method, preclinical and clinical evaluations of inhaled dry powder over the last decade. Finally, the risks associated with pulmonary therapy are addressed. A novel dry powder formulation with high percentages of respirable particles coupled with a cost effective inhaler device is an appealing platform for TB drug delivery.

Oleic acid derivative of polyethylenimine-functionalized proliposomes for enhancing oral bioavailability of extract of Ginkgo biloba

The present systematic study focused to investigate the oleic acid derivative of branched polyethylenimine (bPEI-OA)-functionalized proliposomes for improving the oral delivery of extract of Ginkgo biloba (GbE). The GbE proliposomes were prepared by a spray drying method at varying ratios of egg yolk phosphatidylcholine and cholesterol, and the optimized formulation was tailored with bPEI-OA to obtain bPEI-OA-functionalized proliposomes. The formulations were characterized for particle size, zeta potential, and entrapment efficiency. The release of GbE from proliposomes exhibited a sustained release. And the release rate was regulated by changing the amount of bPEI-OA on the proliposomes. The physical state characterization studies showed some interactions between GbE and other materials, such as hydrogen bonds and van der Waals forces during the process of preparation of proliposomes. The in situ single-pass perfusion and oral bioavailability studies were performed in rats. The significant increase in absorption constant (Ka) and apparent permeability coefficient (Papp) from bPEI-OA-functionalized proliposomes indicated the importance of positive charge for effective uptake across the gastrointestinal tract. The oral bioavailability of bPEI-OA-functionalized proliposomes was remarkable enhanced in comparison with control and conventional proliposomes. The bPEI-OA-functionalized proliposomes showed great potential of improving oral absorption of GbE as a suitable carrier.

Inhaled drug treatment for tuberculosis: Past progress and future prospects

Since the 1990s the rising incidence of multiple drug resistant TB, particularly in the context of human immunodeficiency virus co-infected patients, has threatened global TB control. At that time funding agencies began to support formal investigation of aerosol therapy which until then had been the subject of case reports of individual investigators. Over the last decade, proponents of aerosol therapy have increased in number within the TB research community as the incidence of multiple and extremely drug resistant TB has increased dramatically around the world. Aerosol therapy offers the potential to deliver drug at target concentrations directly into the lungs, use the alveolar-capillary interface to achieve systemic levels, while reducing the risk of systemic toxicity seen with parentally administered doses. In addition, there are insufficient new drugs in the pipeline to anticipate the appearance of a new regimen in time to assure future control of drug resistance. Consequently, alternative strategies are critical to achieving global TB control, and inhaled therapies should be considered as one such strategy.

Preclinical safety and efficacy models for pulmonary drug delivery of antimicrobials with focus on in vitro models

New pharmaceutical formulations must be proven as safe and effective before entering clinical trials. Also in the context of pulmonary drug delivery, preclinical models allow testing of novel antimicrobials, reducing risks and costs during their development. Such models allow reducing the complexity of the human lung, but still need to reflect relevant (patho-) physiological features. This review focuses on preclinical pulmonary models, mainly in vitro models, to assess drug safety and efficacy of antimicrobials. Furthermore, approaches to investigate common infectious diseases of the respiratory tract, are emphasized. Pneumonia, tuberculosis and infections occurring due to cystic fibrosis are in focus of this review. We conclude that especially in vitro models offer the chance of an efficient and detailed analysis of new antimicrobials, but also draw attention to the advantages and limitations of such currently available models and critically discuss the necessary steps for their future development.

Pulmonary drug delivery systems for tuberculosis treatment

Tuberculosis (TB) remains a major global health problem as it is the second leading cause of death from an infectious disease worldwide, after the human immunodeficiency virus (HIV). Conventional treatments fail either because of poor patient compliance to the drug regimen or due to the emergence of multidrug-resistant tuberculosis. The aim of this review is to give an update on the information available on tuberculosis, its pathogenesis and current antitubercular chemotherapies. Direct lung delivery of anti-TB drugs using pulmonary delivery systems is then reviewed since it appears as an interesting strategy to improve first and second line drugs. A particular focus is place on research performed on inhalable dry powder formulations of antitubercular drugs to target alveolar macrophages where the bacteria develop. Numerous studies show that anti-TB drugs can be incorporated into liposomes, microparticles or nanoparticles which can be delivered as dry powders to the deep lungs for instantaneous, targeted and/or controlled release. Treatments of infected animals show a significant reduction of the number of viable bacteria as well as a decrease in tissue damage. These new formulations appear as interesting alternatives to deliver directly drugs to the lungs and favor efficient TB treatment.

Novel drugs against tuberculosis: a clinician's perspective

The United Nations Millennium Development Goal of reversing the global spread of tuberculosis by 2015 has been offset by the rampant re-emergence of drug-resistant tuberculosis, in particular fluoroquinolone-resistant multidrug-resistant and extensively drug-resistant tuberculosis. After decades of quiescence in the development of antituberculosis medications, bedaquiline and delamanid have been conditionally approved for the treatment of drug-resistant tuberculosis, while several other novel compounds (AZD5847, PA-824, SQ109 and sutezolid) have been evaluated in phase II clinical trials. Before novel drugs can find their place in the battle against drug-resistant tuberculosis, linezolid has been compassionately used with success in the treatment of fluoroquinolone-resistant multidrug-resistant tuberculosis. This review largely discusses six novel drugs that have been evaluated in phase II and III clinical trials, with focus on the clinical evidence for efficacy and safety, potential drug interactions, and prospect for using multiple novel drugs in new regimens.

Respirable nanocarriers as a promising strategy for antitubercular drug delivery

Tuberculosis is considered a fatal respiratory infectious disease that represents a global threat, which must be faced. Despite the availability of oral conventional anti-tuberculosis therapy, the disease is characterized by high progression. The leading causes are poor patient compliance and failure to adhere to the drug regimen primarily due to systemic toxicity. In this context, inhalation therapy as a non-invasive route of administration is capable of increasing local drug concentrations in lung tissues, the primary infection side, by passive targeting as well as reducing the risk of systemic toxicity and hence improving the patient compliance. Nanotechnology represents a promising strategy in the development of inhaled drug delivery systems. Nanocarriers can improve the drug effectiveness and decrease the expected side effects as consequences of their ability to target the drug to the infected area as well as sustain its release in a prolonged manner. The current review summarizes the state-of-the-art in the development of inhaled nanotechnological carriers confined currently available anti-tuberculosis drugs (anti TB) for local and targeting drug delivery specifically, polymeric nanoparticles, solid lipid nanoparticles, nanoliposomes and nanomicelles. Moreover, complexes and ion pairs are also reported. The impact and progress of nanotechnology on the therapeutic effectiveness and patient adherence to anti TB regimen are addressed.