Microencapsulated Isoniazid-Loaded Metal-Organic Frameworks for Pulmonary Administration of Antituberculosis Drugs.

Tuberculosis (TB) is an infectious disease that causes a great number of deaths in the world (1.5 million people per year). This disease is currently treated by administering high doses of various oral anti-TB drugs for prolonged periods (up to 2 years). While this regimen is normally effective when taken as prescribed, many people with TB experience difficulties in complying with their medication schedule. Furthermore, the oral administration of standard anti-TB drugs causes severe side effects and widespread resistances. Recently, we proposed an original platform for pulmonary TB treatment consisting of mannitol microspheres (Ma MS) containing iron (III) trimesate metal-organic framework (MOF) MIL-100 nanoparticles (NPs). In the present work, we loaded this system with the first-line anti-TB drug isoniazid (INH) and evaluated both the viability and safety of the drug vehicle components, as well as the cell internalization of the formulation in alveolar A549 cells. Results show that INH-loaded MOF (INH@MIL-100) NPs were efficiently microencapsulated in Ma MS, which displayed suitable aerodynamic characteristics for pulmonary administration and non-toxicity. MIL-100 and INH@MIL-100 NPs were efficiently internalized by A549 cells, mainly localized in the cytoplasm. In conclusion, the proposed micro-nanosystem is a good candidate for the pulmonary administration of anti-TB drugs.

Microencapsulated Solid Lipid Nanoparticles as a Hybrid Platform for Pulmonary Antibiotic Delivery.

Solid lipid nanoparticles (SLN) containing rifabutin (RFB), with pulmonary administration purposes, were developed through a technique that avoids the use of organic solvents or sonication. To facilitate their pulmonary delivery, the RFB-loaded SLN were included in microspheres of appropriate size using suitable excipients (mannitol and trehalose) through a spray-drying technique. Confocal analysis microscopy showed that microspheres are spherical and that SLN are efficiently microencapsulated and homogeneously distributed throughout the microsphere matrices. The aerodynamic diameters observed an optimal distribution for reaching the alveolar region. The dry powder's performance during aerosolization and the in vitro drug deposition were tested using a twin-impinger approach, which confirmed that the microspheres can reach the deep lung. Isothermal titration calorimetry revealed that SLN have higher affinity for mannitol than for trehalose. Upon microsphere dissolution in aqueous media, SLN were readily recovered, maintaining their physicochemical properties. When these dry powders reach the deep lung, microspheres are expected to readily dissolve, delivering the SLN which, in turn, will release RFB. The in vivo biodistribution of microencapsulated RFB-SLN demonstrated that the antibiotic achieved the tested organs 15 and 30 min post pulmonary administration. Their antimycobacterial activity was also evaluated in a murine model of infection with a Mycobacterium tuberculosis strain H37Rv resulting in an enhancement of activity against M. tuberculosis infection compared to nontreated animals. These results suggest that RFB-SLN microencapsulation is a promising approach for the treatment of tuberculosis.

Development of PLGA-mannosamine nanoparticles as oral protein carriers.

Here we report the development of polymeric nanoparticles, made of poly(lactide-co-glycolide) (PLGA) chemically modified with mannosamine (MN), intended to specifically interact with the intestinal mucosa and facilitate the intestinal transport of proteins. PLGA-MN nanoparticles displayed nanometric size and a negative zeta potential, which was lower than that of the PLGA nanoparticles. This correlate well with the preferential location of the MN group on the nanoparticles surface obtained by X-ray photoelectron spectroscope (XPS). The presence of MN groups in the polymer chain led to a different surface morphology noted by SEM, an increase of the encapsulation of model proteins, and to help stabilizing the nanoparticles in simulated intestinal fluids. Furthermore, the MN modification significantly enhanced the nanoparticle's interaction with the epithelial cells in human intestinal follicle-associated epithelium cell culture model. Overall, the MN modification significantly modifies the properties of PLGA nanoparticles making them more suitable as nanocarriers for oral protein delivery.

Design and in vitro assessment of chitosan nanocapsules for the pulmonary delivery of rifabutin.

Tuberculosis (TB) is a life-threatening disease and a main cause of death worldwide. It mainly affects the lungs, and it is attributed to the infection with Mycobacterium tuberculosis (MTB). Current treatments consist of the oral administration of combinations of antibiotics including rifabutin, in high doses and for long periods of time. These therapeutic regimens are associated with many side effects and high rates of drug resistance. To overcome these problems, this study aims at developing a nanosystem for the improved delivery of antibiotics, with potential application in pulmonary delivery. Chitosan-based nanomaterials are widely used in biomedical applications, due to their biodegradability and biocompatibility, as well as their potential antimicrobial effects and lack of toxicity. In addition, this polymer is particularly attractive for mucosal delivery due to its bioadhesive properties. Therefore, the structure of the proposed nanocarrier consists of a chitosan shell and a lipid core with a combination of different oils and surfactants to allow optimal association of the hydrophobic drug rifabutin. These nanocapsules were characterized in terms of size, polydispersity index, surface charge, morphology, encapsulation efficiency and biological stability. The release kinetics of the drug-loaded nanostructures was evaluated in simulated lung media. Moreover, in vitro studies in different cell models (A549 and Raw 264.7 cells) demonstrated the safety of the nanocapsules as well as their efficient internalization. An antimicrobial susceptibility test was performed to evaluate the efficacy of the rifabutin-loaded nanocapsules against Mycobacterium phlei. This study indicated complete inhibition for antibiotic concentrations within the expected susceptibility range of Mycobacterium (≤ 0.25-16 mg/L).

A Traffic Light System to Maximize Carbohydrate Cryoprotectants' Effectivity in Nanostructured Lipid Carriers' Lyophilization.

Lyophilization is often employed to transform nanoparticle suspensions to stable solid forms. This work proposed Neurofuzzy Logic (NFL) to better understand the lyophilization process of Nanostructured Lipid Carriers' (NLCs) dispersions and the carbohydrate cryoprotectants' (CPs) performance in these processes. NLCs were produced by hot homogenization, frozen at different speeds, and lyophilized using several CPs at variable concentrations. NLCs were characterized, and results were expressed as increase in particle size (Δ size), polydispersity (Δ PdI), and zeta potential (Δ ZP) of lyophilized powders (LP) regarding initial dispersions. CPs were classified according to their molecular weights (MW), and the osmolarities (Π) of CPs solutions were also determined. Databases obtained were finally modelled through FormRules® (Intelligensys Ltd., Kirkwall, Scotland, UK), an NFL software. NFL models revealed that CPs' MW determines the optimal freezing conditions and CPs' proportions. The knowledge generated allowed the establishment of a traffic light system intended to successfully select and apply sugars for nanoparticles lyophilization.

Microencapsulated Chitosan-Based Nanocapsules: A New Platform for Pulmonary Gene Delivery.

In this work, we propose chitosan (CS)-based nanocapsules (NCs) for pulmonary gene delivery. Hyaluronic acid (HA) was incorporated in the NCs composition (HA/CS NCs) aiming to promote gene transfection in the lung epithelium. NCs were loaded with a model plasmid (pCMV-ßGal) to easily evaluate their transfection capacity. The plasmid encapsulation efficiencies were of approx. 90%. To facilitate their administration to the lungs, the plasmid-loaded NCs were microencapsulated in mannitol (Ma) microspheres (MS) using a simple spray-drying technique, obtaining dry powders of adequate properties. In vivo, the MS reached the deep lung, where the plasmid-loaded CS-based NCs were released and transfected the alveolar cells more homogeneously than the control formulation of plasmid directly microencapsulated in Ma MS. The HA-containing formulation achieved the highest transfection efficiency, in a more extended area and more homogeneously distributed than the rest of tested formulations. The new micro-nanostructured platform proposed in this work represents an efficient strategy for the delivery of genetic material to the lung, with great potential for the treatment of genetic lung diseases.

Metal-Organic Framework Microsphere Formulation for Pulmonary Administration.

Although nanoscaled metal-organic frameworks (nanoMOFs) are promising drug carriers, their appropriate formulation remains almost unexplored and basically restricted to intravenous routes. Lungs, beneficiating from a large absorption surface and low enzymatic presence, are a very attractive target for both local and systemic delivery. However, pulmonary nanoMOF formulation is a pending and defying task. Thus, we propose a pioneer nanoMOF-based microsphere system as a potential platform for pulmonary administration. A biocompatible nanoMOF was successfully encapsulated in mannitol by a simple and continuous spray-drying technique. Upon intratracheal administration to rats, the resulting formulation, exhibiting optimal properties (i.e., homogeneity, size, density, and spray-drying process yield), was able to release the intact nanoMOF carrier uniformly along the lungs, reaching the bronchioles and alveoli.

Rifabutin-Loaded Nanostructured Lipid Carriers as a Tool in Oral Anti-Mycobacterial Treatment of Crohn's Disease.

Oral anti-mycobacterial treatment of Crohn's disease (CD) is limited by the low aqueous solubility of drugs, along with the altered gut conditions of patients, making uncommon their clinical use. Hence, the aim of the present work is focused on the in vitro evaluation of rifabutin (RFB)-loaded Nanostructured lipid carriers (NLC), in order to solve limitations associated to this therapeutic approach. RFB-loaded NLC were prepared by hot homogenization and characterized in terms of size, polydispersity, surface charge, morphology, thermal stability, and drug payload and release. Permeability across Caco-2 cell monolayers and cytotoxicity and uptake in human macrophages was also determined. NLC obtained were nano-sized, monodisperse, negatively charged, and spheroidal-shaped, showing a suitable drug payload and thermal stability. Furthermore, the permeability profile, macrophage uptake and selective intracellular release of RFB-loaded NLC, guarantee an effective drug dose administration to cells. Outcomes suggest that rifabutin-loaded NLC constitute a promising strategy to improve oral anti-mycobacterial therapy in Crohn's disease.

New generation of hybrid poly/oligosaccharide nanoparticles as carriers for the nasal delivery of macromolecules.

We have recently reported a new generation of polysaccharide nanoparticles consisting of chitosan (CS) and cyclodextrin (CD) derivatives, which exhibit a number of advantages when compared to the classical CS nanoparticles. In the present work our goal was to explore the potential of these hybrid CS/CD nanoparticles as carriers for the nasal delivery of macromolecules. First, we evaluated the effect of the amount and type of CD (sulfobutylether-beta-CD or carboximethyl-beta-CD) on the physicochemical properties of the nanocarriers. Second, we investigated the interaction of CS/CD nanoparticles with the nasal epithelium by studying their ability to modulate the tight junctions between epithelial cells (Calu-3 cell model) as well as their capacity to overcome mucosal barriers (nasal epithelium of rats). Finally, we loaded two selected nanocarriers with insulin and studied their potential for enhancing the nasal transport of insulin in rabbits. The results showed that CS/CD nanoparticles caused a reversible reduction in the transepithelial resistance of the cell monolayer, thus increasing the membrane permeability. Moreover, the results obtained following the in vivo administration of fluorescent CS/CD nanoparticles to rats evidenced their capability to overcome the nasal mucosal barrier. Finally, the in vivo evaluation in conscious rabbits revealed that insulin-loaded nanoparticles (association efficiencies > 88%) were able to significantly decrease plasma glucose levels (more than 35% reduction). Overall, these results suggest that these new nanoparticles work as nasal carriers and, therefore, have a potential for enhancing the transport of complex molecules across the nasal barrier.

Chitosan-alginate blended nanoparticles as carriers for the transmucosal delivery of macromolecules.

Nanoparticles intended for use in the transmucosal delivery of macromolecules were prepared by the ionic gelation of chitosan (CS) hydrochloride with pentasodium tripolyphosphate (TPP) and concomitant complexation with sodium alginate (ALG). The incorporation of a small proportion of ALG of increasing molecular weight (M(w); from 4 to 74 kDa) into the nanoparticles led to a monotonic increase in colloidal size from ∼260 to ∼525 nm. This increase in size was regarded as a consequence of the formation of gradually more expanded structures. Insulin, taken as a model peptide, was associated to CS-TPP-ALG nanoparticles with efficiencies in the range of ∼41 to ∼52%, irrespective of the M(w) of the ALG incorporated in the formulation. These CS-TPP-ALG nanoparticles exhibited a capacity to enhance the systemic absorption of insulin after nasal administration to conscious rabbits. Interestingly, it was observed that the duration of the hypoglycaemic response was affected by the ALG's M(w). Briefly, this work describes a new nanoparticulate composition of potential value for increasing nasal insulin absorption.

Transfection of pulmonary cells by stable pDNA-polycationic hybrid nanostructured particles.

AIM: Cationically modified solid lipid nanoparticles (SLN) were investigated as plasmid DNA (pDNA) carriers and transfection agents for the pulmonary route. MATERIALS & METHODS: pDNA-loaded SLN were produced using glyceryl dibehenate or tristearate as matrix lipids and chitosan as surface charge modifier, and encapsulated by spray-drying in mannitol and trehalose microspheres. RESULTS: Nanoparticles of 200 nm, and zeta potential around +15 mV were produced. Electrophorectic analysis confirmed plasmid stability and integrity. The pDNA-loaded SLN were able to transfect the Calu-3 and A549 pulmonary cell lines, while showing low cytotoxicity. Microencapsulation of SLN yielded dry powders suitable for inhalation that protected pDNA from degradation. CONCLUSION: Microencapsulated SLN are a promising safe and effective carrier system for pulmonary gene delivery following pulmonary administration.

Microspheres containing lipid/chitosan nanoparticles complexes for pulmonary delivery of therapeutic proteins.

Chitosan/tripolyphosphate nanoparticles have already been demonstrated to promote peptide absorption through several mucosal surfaces. We have recently developed a new drug delivery system consisting of complexes formed between preformed chitosan/tripolyphosphate nanoparticles and phospholipids, named as lipid/chitosan nanoparticles (L/CS-NP) complexes. The aim of this work was to microencapsulate these protein-loaded L/CS-NP complexes by spray-drying, using mannitol as excipient to produce microspheres with adequate properties for pulmonary delivery. Results show that the obtained microspheres are spherical and present appropriate aerodynamic characteristics for lung delivery (aerodynamic diameters around 2-3 microm and low apparent tap density of 0.4-0.5 g/cm3). The physicochemical properties of the L/CS-NP complexes are affected by the phospholipids composition. Phospholipids provide a controlled release of the encapsulated protein (insulin), which was successfully associated to the system (68%). The complexes can be easily recovered from the mannitol microspheres upon incubation in aqueous medium, maintaining their morphology and physicochemical characteristics. Therefore, this work demonstrates that protein-loaded L/CS-NP complexes can be efficiently microencapsulated, resulting in microspheres with adequate properties to provide a deep inhalation pattern. Furthermore, they are expected to release their payload (the complexes and, consequently, the encapsulated macromolecule) after contacting with the lung aqueous environment.

Surface characterization of lipid/chitosan nanoparticles assemblies, using X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry.

Chitosan/tripolyphosphate nanoparticles are promising drug delivery systems, which show excellent capacity for protein entrapment and improvement of mucosal peptide absorption. We have recently developed a new drug delivery system consisting of assemblies formed between preformed chitosan nanoparticles and phospholipids (dipalmitoylphosphatidylcholine and dimiristoylphosphatidylglycerol) which are endogenous to the lung. These assemblies are prepared by lipid film hydration with a nanoparticles suspension. The aim of this work was to elucidate the architecture of these structures using sensitive surface analysis techniques such as X-ray photoelectron spectroscopy and static time-of-flight secondary ion mass spectrometry, as well as to determine their physicochemical characteristics. The combination of zeta potential measurements with the results obtained by X-ray photoelectron spectroscopy and static time-of-flight secondary ion mass spectrometry, demonstrated that a complete lipid coating of the nanoparticles can be achieved using a lipid film formed by both dipalmitoylphosphatidylcholine and dimiristoylphosphatidylglycerol, this way conferring to the lipid film a strong negative charge, which favors the interaction with the positively charged nanoparticles. Therefore, the major role of electrostatic interactions as driving forces to control the organisation of the lipid/nanoparticles assemblies was clearly evident. The implications of these findings for the structural organisation of the assemblies, for their in vitro behaviour, as well as for their mechanism of formation are discussed.

Micro/nanostructured inhalable formulation based on polysaccharides: Effect of a thermoprotectant on powder properties and protein integrity.

Combined micro- and nanosystems are appealing for pulmonary protein delivery, fulfilling the specific physiological requirements for efficient outcomes in-vivo. However, fabrication of protein formulations may impose stresses perturbing protein conformational stability and, hence, biological activity. Herein, a protein, insulin (INS), was nanoencapsulated inside chitosan nanoparticles (CS NPs) by ionic gelation. By spray drying, the resultant protein-loaded NPs were further encapsulated with a thermoprotectant into powders bearing adequate aerodynamic properties for lung delivery. Structural modifications and interactions of the protein/carrier system were investigated following processing, with special emphasis on protein integrity. Accordingly, physicochemical, elemental, structural and thermal experiments were performed. The analyses revealed the localization of a proportion of the protein on the NPs' surface following nanoencapsulation, and the involved molecular interactions between the NPs and thermoprotectant after microencapsulation. Protein integrity was conserved throughout the preparation processes. This highlights the non-invasiveness of the fabrication techniques, particularly spray drying, for preparing micro-nanosystems for effective administration of inhalable macromolecules.

Delimiting the knowledge space and the design space of nanostructured lipid carriers through Artificial Intelligence tools.

Nanostructured lipid carriers (NLC) are biocompatible and biodegradable nanoscale systems with extensive application for controlled drug release. However, the development of optimal nanosystems along with a reproducible manufacturing process is still challenging. In this study, a two-step experimental design was performed and databases were successfully modelled using Artificial Intelligence techniques as an innovative method to get optimal, reproducible and stable NLC. The initial approach, including a wide range of values for the different variables, was followed by a second set of experiments with variable values in a narrower range, more suited to the characteristics of the system. NLC loaded with rifabutin, a hydrophobic drug model, were produced by hot homogenization and fully characterized in terms of particle size, size distribution, zeta potential, encapsulation efficiency and drug loading. The use of Artificial Intelligence tools has allowed to elucidate the key parameters that modulate each formulation property. Stable nanoparticles with low sizes and polydispersions, negative zeta potentials and high drug loadings were obtained when the proportion of lipid components, drug, surfactants and stirring speed were optimized by FormRules® and INForm®. The successful application of Artificial Intelligence tools on NLC formulation optimization constitutes a pioneer approach in the field of lipid nanoparticles.

Chitosan nanoparticles are compatible with respiratory epithelial cells in vitro.

The aim of this work was to evaluate the biocompatibility of novel respirable powder formulations of nanoparticles (NP) entrapped in mannitol microspheres using human respiratory epithelial cell lines. Microspheres formulated at NP:mannitol ratios of 10:90, 20:80 and 40:60 were evaluated using the Calu-3 and A549 cell lines. The MTT cell viability assay revealed an absence of overt toxicity to Calu-3 or A549 cells following exposure to the formulations containing <1.3mg NP/ml (equivalent to 0.87 mg NP/cm(2)) for up to 48 h. Transepithelial electrical resistance (TER) and solute permeability in Calu-3 cell layers were determined following exposure of the cells to the NP:mannitol 20:80 formulation. After administration of the formulation dissolved in serum-free cell culture medium (1.3mg/ml NP suspension) to the cells, neither TER nor permeability were altered compared to untreated cell layers. Confocal microscopy did not reveal any NP internalisation under the conditions used in this study, although evidence of mucoadhesion was observed. All the data presented are encouraging with respect to the development of chitosan NP-containing microspheres for the pulmonary administration of therapeutic macromolecules. Not only do the formulations possess suitable aerodynamic characteristics and the capacity to encapsulate proteins as shown previously; they have now been shown to exhibit in vitro biocompatibility.

Freeze-dried cylinders carrying chitosan nanoparticles for vaginal peptide delivery.

Recently nanoparticle-based vaginal drug delivery formulations have been acquiring great attention for the administration of peptide based-vaccines or microbicides to prevent or treat sexually transmitted diseases. In this work, a straightforward and efficient strategy for the vaginal application and release of peptide-loaded mucoadhesive nanoparticles was developed. This essentially consists of chitosan nanoparticles encapsulated in suitable hydrophilic freeze-dried cylinders. Chitosan nanoparticles are responsible for carrying the peptide drug and allowing adhesion to the vaginal mucosal epithelium. Hydrophilic freeze-dried cylinders facilitate the application and quick release of the nanoparticles to the vaginal zone. Upon contact with the aqueous vaginal medium, the excipients constituting these sponge-like systems are quickly dissolved enabling the release of their content. In vitro release studies showed the ability of the sponge-like systems and chitosan nanoparticles to deliver the mucoadhesive nanoparticles and peptide respectively. CLSM micrographs proved the nanoparticles ability promoting the peptide penetration inside the vaginal mucosa.

Microencapsulated SLN: An innovative strategy for pulmonary protein delivery.

Associating protein with nanoparticles is an interesting strategy to improve their bioavailability and biological activity. Solid lipid nanoparticles (SLN) have been sought as carriers for therapeutic proteins transport to the lung epithelium. Nevertheless, because of their low inertia, nanoparticles intended for pulmonary application usually escape from lung deposition. To overcome this problem, the production of spray-dried powders containing nanoparticles has been recently reported. Herein we developed new hybrid microencapsulated SLN for pulmonary administration, containing a model protein (papain, PAP). PAP was adsorbed onto glyceryl dibehenate and glyceryl tristearate SLN. Physical characterization using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) confirmed the interaction between PAP and SLN corroborating that the protein was efficiently adsorbed at SLN's surface. PAP adsorption onto SLN (PAP-SLN) slightly increased particle size, while decreasing the SLN negative surface charge. The adsorption process followed a Freundlich type of adsorption isotherm. Nanoformulations were then spray-dried, originating spherical microparticles with suitable aerodynamic characteristics. Full characterization of microparticles was performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and isothermal titration calorimetry (ITC). PAP was released from dry powders in a higher extent when compared with non spray-dried SLN. Nevertheless, protein stability was kept throughout microsphere production, as assessed by SDS-PAGE.

Ionotropic cross-linked chitosan microspheres for controlled release of ampicillin.

The solubility of non cross-linked chitosan in weak acid solutions restricts its utility in microspheres for drug delivery. The primary aim of this study was to produce pentasodium tripolyphosphate cross-linked chitosan microspheres with higher acid resistance for controlled release of ampicillin. The microspheres were prepared by two different microencapsulation procedures (by emulsification and by spray-drying) and characterized by their particle size, surface morphology, stability, drug entrapment efficiency and drug release. The size of the microspheres was <10 microm with a narrow size distribution. The entrapment of ampicillin in the microspheres was more than 80%. Stability of uncross-linked and cross-linked microspheres was affected by the pH of simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.5). The inclusion of the enzymes pepsin and pancreatin did not affect the stability of the microspheres. The inclusion of lysozyme in phosphate buffer saline resulted in increased solubilization. The release of the drug was affected by cross-linking of microspheres with tripolyphosphate (TPP). The cross-linked microspheres were more stable in simulated gastric fluid and showed slower but sustained release of ampicillin. The antimicrobial activity of the released ampicillin was confirmed by Staphylococcus aureus bioassay.

Rifabutin-loaded solid lipid nanoparticles for inhaled antitubercular therapy: Physicochemical and in vitro studies.

Systemic administration of antitubercular drugs can be complicated by off-target toxicity to cells and tissues that are not infected by Mycobacterium tuberculosis . Delivery of antitubercular drugs via nanoparticles directly to the infected cells has the potential to maximize efficacy and minimize toxicity. The present work demonstrates the potential of solid lipid nanoparticles (SLN) as a delivery platform for rifabutin (RFB). Two different RFB-containing SLN formulations were produced using glyceryl dibehenate or glyceryl tristearate as lipid components. Full characterization was performed in terms of particle size, encapsulation and loading efficiency, morphology by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) studies. Physical stability was evaluated when formulations were stored at 5 ± 3°C and in the freeze-dried form. Formulations were stable throughout lyophilization without significant variations on physicochemical properties and RFB losses. The SLN showed to be able to endure harsh temperature conditions as demonstrated by dynamic light scattering (DLS). Release studies revealed that RFB was almost completely released from SLN. In vitro studies with THP1 cells differentiated in macrophages showing a nanoparticle uptake of 46 ± 3% and 26 ± 9% for glyceryl dibehenate and glyceryl tristearate SLN, respectively. Cell viability studies using relevant lung cell lines (A549 and Calu-3) revealed low cytotoxicity for the SLN, suggesting these could be new potential vehicles for pulmonary delivery of antitubercular drugs.