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

Functionalized and Theranostic Lipidic and Tocosomal Drug Delivery Systems: Potentials and Limitations in Cancer Photodynamic Therapy

Photodynamic therapy (PDT) is a multidisciplinary area, which involves photophysics and photochemical sciences and plays an important role in cancer diagnosis and treatment. PDT involves a photo-activable drug called photosensitizer (PS), a specific wavelength of light and cellular compounds to produce toxic oxygen species in a much-localized way to destroy malignant tumors. Despite the various benefits of PDT, some PS-related limitations hinder its use as an ideal treatment option for cancer. To address these limitations (e.g., poor bioavailability, weak permeability, hydrophobicity, and aggregation), lipid-based and vesicular drug delivery systems have been employed. These carrier systems possess the ability to enhance the bioavailability, permeability, and solubility of the drug. Furthermore, they tend to load hydrophobic and lipophilic compounds and can be employed for an efficient and targeted drug delivery. The purpose of this review is to highlight the precise idea of PDT, the limitations of PDT related to PS, and the application of lipidic and tocosomal carriers in PDT for the treatment of various types of cancers. Liposomes, nanoliposomes, solid lipid nanoparticles, vesicular phospholipid gels, exosomes, transferosomes, and tocosomes are presented as commonly-employed vesicular drug carriers. Moreover, the amalgamation of cell-based drug delivery systems (CBDDS) with PDT holds considerable potential as an encouraging avenue in cancer treatment, especially in the context of immunotherapy.

Pulmonary delivery of icariin-phospholipid complex prolongs lung retention and improves therapeutic efficacy in mice with acute lung injury/ARDS

Icariin has been shown the promising therapeutic potential to treat inflammatory airway diseases, yet its poor lung distribution and retention restrict the clinical applications. To this end, this work aimed to prepare an icariin-phospholipid complex (IPC) formulation for sustained nebulization delivery that enabled excellent inhalability, improved lung exposure and prolonged duration of action. Icariin was found to react with soybean phospholipid to form supramolecular IPC, which was able to self-assemble into nanoparticle suspension. The suspension was stable during steam sterilization and nebulization processes, and its aerosols generated by a commercial nebulizer exhibited excellent aerodynamic properties and delivery efficiency. In vitro studies showed that the formation of complex sustained drug release, enhanced lung affinity and slowed lung clearance. The drug distribution in lung epithelial lining fluid (ELF) also demonstrated in vivo sustained release after intratracheal administration to mice. In addition, compared to free icariin, IPC improved the drug exposure to lung tissues and immune cells in the ELF by 4.61-fold and 39.5-fold, respectively. This resulted in improved and prolonged local anti-inflammatory effects up to 24 h in mice with lipopolysaccharide (LPS)-induced acute lung injury. Moreover, IPC improved survival rate of mice with acute respiratory distress syndrome (ARDS). Overall, the present phospholipid complex represented a promising formulation of icariin for the treatment of acute lung injury/ARDS by nebulization delivery.

Lipid sulfoxide polymers as potential inhalable drug delivery platforms with differential albumin binding affinity

Inhalable nanomedicines are increasingly being developed to optimise the pharmaceutical treatment of respiratory diseases. Large lipid-based nanosystems at the forefront of the inhalable nanomedicines development pipeline, though, have a number of limitations. The objective of this study was, therefore, to investigate the utility of novel small lipidated sulfoxide polymers based on poly(2-(methylsulfinyl)ethyl acrylate) (PMSEA) as inhalable drug delivery platforms with tuneable membrane permeability imparted by differential albumin binding kinetics. Linear PMSEA (5 kDa) was used as a hydrophilic polymer backbone with excellent anti-fouling and stealth properties compared to poly(ethylene glycol). Terminal lipids comprising single (1C2, 1C12) or double (2C12) chain diglycerides were installed to provide differing affinities for albumin and, by extension, albumin trafficking pathways in the lungs. Albumin binding kinetics, cytotoxicity, lung mucus penetration and cellular uptake and permeability through key cellular barriers in the lungs were examined in vitro. The polymers showed good mucus penetration and no cytotoxicity over 24 h at up to 1 mg ml-1. While 1C2-showed no interaction with albumin, 1C12-PMSEA and 2C12-PMSEA bound albumin with KD values of approximately 76 and 10 μM, respectively. Despite binding to albumin, 2C12-PMSEA showed reduced cell uptake and membrane permeability compared to the smaller polymers and the presence of albumin had little effect on cell uptake and membrane permeability. While PMSEA strongly shielded these lipids from albumin, the data suggest that there is scope to tune the lipid component of these systems to control membrane permeability and cellular interactions in the lungs to tailor drug disposition in the lungs.

Inhalable spray-dried porous microparticles containing dehydroandrographolide succinate phospholipid complex capable of improving and prolonging pulmonary anti-inflammatory efficacy in mice

Due to the unique physiological barriers within the lungs, there are considerable challenges in developing drug delivery systems enabling prolonged drug exposure to respiratory epithelial cells. Here, we report a PulmoSphere-based dry powder technology that incorporates a drug-phospholipid complex to promote intracellular retention of dehydroandrographolide succinate (DAS) in respiratory epithelial cells following pulmonary delivery. The DAS-phospholipid complex has the ability to self-assemble into nanoparticles. After spray-drying to produce PulmoSphere microparticles loaded with the drug-phospholipid complex, the rehydrated microparticles discharge the phospholipid complex without altering its physicochemical properties. The microparticles containing the DAS-phospholipid complex exhibit remarkable aerodynamic properties with a fine particle fraction of ∼ 60% and a mass median aerodynamic diameter of ∼ 2.3 μm. These properties facilitate deposition in the alveolar region. In vitro cell culture and lung tissue explants experiments reveal that the drug-phospholipid complex prolongs intracellular residence time and lung tissue retention due to the slow intracellular disassociation of drug from the complex. Once deposited in the lungs, the DAS-phospholipid complex loaded microparticles increase and extend drug exposure to the lung tissues and the immune cells compared to the free DAS counterpart. The improved drug exposure to airway epithelial cells, but not immune cells, is related to a prolonged duration of pulmonary anti-inflammation at decreased doses in a mouse model of acute lung injury induced by lipopolysaccharide. Overall, the phospholipid complex loaded microparticles present a promising approach for improved treatment of respiratory diseases, e.g. pneumonia and acute respiratory distress syndrome.

Lipidated brush-PEG polymers as low molecular weight pulmonary drug delivery platforms

OBJECTIVES

Nanomedicines are being actively developed as inhalable drug delivery systems. However, there is a distinct utility in developing smaller polymeric systems that can bind albumin in the lungs. We therefore examined the pulmonary pharmacokinetic behavior of a series of lipidated brush-PEG (5 kDa) polymers conjugated to 1C2, 1C12 lipid or 2C12 lipids.

METHODS

The pulmonary pharmacokinetics, patterns of lung clearance and safety of polymers were examined in rats. Permeability through monolayers of primary human alveolar epithelia, small airway epithelia and lung microvascular endothelium were also investigated, along with lung mucus penetration and cell uptake.

RESULTS

Polymers showed similar pulmonary pharmacokinetic behavior and patterns of lung clearance, irrespective of lipid molecular weight and albumin binding capacity, with up to 30% of the dose absorbed from the lungs over 24 h. 1C12-PEG showed the greatest safety in the lungs. Based on its larger size, 2C12-PEG also showed the lowest mucus and cell membrane permeability of the three polymers. While albumin had no significant effect on membrane transport, the cell uptake of C12-conjugated PEGs were increased in alveolar epithelial cells.

CONCLUSION

Lipidated brush-PEG polymers composed of 1C12 lipid may provide a useful and novel alternative to large nanomaterials as inhalable drug delivery systems.

PK-PD Evaluation of Inhaled Microparticles loaded with Ciprofloxacin-Copper complex in a Rat Model of Chronic Pseudomonas aeruginosa Lung Infection

The potential gain in efficacy of pulmonary administration over IV administration of some antibiotics such as ciprofloxacin (CIP) may be limited by the short residence time of the drug at the site of infection after nebulization. Complexation of CIP with copper reduced its apparent permeability in vitro through a Calu-3 cell monolayer and greatly increased its pulmonary residence time after aerosolisation in healthy rats. Chronic P. aeruginosa lung infections in cystic fibrosis patients result in airway and alveolar inflammation that may increase the permeability of inhaled antibiotics and alter their fate in the lung after inhalation compared to what was seen in healthy conditions. The objective of this study was to compare the pharmacokinetics and efficacy of CIP-Cu²⁺ complex-loaded microparticles administered by pulmonary route with a CIP solution administered by IV to model rats with chronic lung infection. After a single pulmonary administration of microparticles loaded with CIP-Cu²⁺ complex, pulmonary exposure to CIP was increased 2077-fold compared to IV administration of CIP solution. This single lung administration significantly reduced the lung burden of P. aeruginosa expressed as CFU/lung measured 24 h after administration by 10-fold while IV administration of the same dose of CIP was ineffective compared to the untreated control. This better efficacy of inhaled microparticles loaded with CIP-Cu²⁺ complex compared with CIP solution can be attributed to the higher pulmonary exposure to CIP obtained with inhaled CIP-Cu²⁺ complex-loaded microparticles than that obtained with IV solution.

QbD driven targeted pulmonary delivery of dexamethasone-loaded chitosan microspheres: Biodistribution and pharmacokinetic study

Inhaling drugs, on the other hand, is limited mainly by the natural mechanisms of the respiratory system, which push drug particles out of the lungs or make them inefficient once they are there. Because of this, many ways have been found to work around the problems with drug transport through the lungs. Researchers have made polymeric microparticles (MP) and nanoparticles as a possible way to get drugs into the lungs. They showed that the drug could be trapped in large amounts and retained in the lungs for a long time, with as little contact as possible with the bloodstream. MP were formulated in this study to get dexamethasone (DMC) into the pulmonary area. The Box-Behnken design optimized microspheres preparation to meet the pulmonary delivery prerequisites. Optimized formulation was figured out based on the desirability approach. The mass median aerodynamic diameter (MMAD) of the optimized formula (O-DMC-MP) was 8.46 ± 1.45 µm, and the fine particle fraction (FPF) was 77.69 ± 1.26%. This showed that it made suitable drug delivery system, which could make it possible for MP to settle deeply in the lung space after being breathed in. With the first burst of drug release, it was seen that drug release could last up to 16 h. Also, there was no clear sign that the optimized formulation was toxic to the alveoli basal epithelial cells in the lungs, as supported by cytotoxic studies in HUVEC, A549, and H1299 cell lines. Most importantly, loading DMC inside MP cuts the amount of drug into the bloodstream compared to plain DMC, as evident from biodistribution studies. Stability tests have shown that the product can stay the same over time at both the storage conditions. Using chitosan DMC-MP can be a better therapeutic formulation to treat acute respiratory distress syndrome (ARDS).

Inhaled lipid nanocarriers for pulmonary delivery of glucocorticoids: previous strategies, recent advances and key factors description

In view of the strong anti-inflammatory activity of glucocorticoids (GC) they are used in the treatment of almost all inflammatory lung diseases. In particular, inhaled GC (IGC) allow high drug concentrations to be deposited in the lung and may reduce the incidence of adverse effects associated with systemic administration. However, rapid absorption through the highly absorbent surface of the lung epithelium may limit the success of localized therapy. Therefore, inhalation of GC incorporated into nanocarriers is a possible approach to overcome this drawback. In particular, lipid nanocarriers, which showed high pulmonary biocompatibility and are well known in the pharmaceutical industry, have the best prospects for pulmonary delivery of GC by inhalation. This review provides an overview of the pre-clinical applications of inhaled GC-lipid nanocarriers based on several key factors that will determine the efficiency of local pulmonary GC delivery: 1) stability to nebulization, 2) deposition profile in the lungs, 3) mucociliary clearance, 4) selective accumulation in target cells, 5) residence time in the lung and systemic absorption and 6) biocompatibility. Finally, novel preclinical pulmonary models for inflammatory lung diseases are also discussed.

Masculinization of Red Tilapia (Oreochromis spp.) Using 17α-Methyltestosterone-Loaded Alkyl Polyglucosides Integrated into Nanostructured Lipid Carriers

The aim of the present study was to optimize a masculinization platform for the production of all-male red tilapia fry by oral administration of 30 and 60 ppm of MT and alkyl polyglucoside nanostructured lipid carriers (APG-NLC) loaded with MT, respectively, for 14 and 21 days. The characterization, encapsulation efficiency and release kinetics of MT in lipid-based nanoparticles were assessed in vitro. The results showed that the MT-loaded nanoparticles were spherical, ranging from 80 to 125 nm in size, and had a negative charge with a narrow particle distribution. The APG-NLC loaded with MT provided higher physical stability and encapsulation efficacy than the NLC. The release rate constants of MT from MT-NLC and MT-APG-NLC were higher than those of free MT, which is insoluble in aqueous media. There was no significant difference in survival between the fish administered MT or the those fed orally with MT-APG-NLC fish. According to the logistic regression analysis, the sex reversal efficacy of MT-APG-NLC (30 ppm) and MT (60 ppm), resulted in significantly higher numbers of males after 21 days of treatment compared with the controls. The production cost of MT-APG-NLC (30 ppm) after 21 days of treatment was reduced by 32.9% compared with the conventional MT treatment group (60 ppm). In all the treatments, the length-weight relationship (LWR) showed negatively allomeric growth behavior (b < 3), with a relative condition factor (K_n) of more than 1. Therefore, MT-APG-NLC (30 ppm) would seem to be a promising, cost-effective way to reduce the dose of MT used for the masculinization of farmed red tilapia.

Protein adsorption determines pulmonary cell uptake of lipid-based nanoparticles

The inhalable administration of lipid nanoparticles is an effective strategy for localised delivery of therapeutics against various lung diseases. Of this, improved intracellular delivery of pharmaceuticals for infectious disease and cancer management is of high significance. However, the influence of lipid nanoparticle composition and structure on uptake in pulmonary cell lines, especially in the presence of biologically relevant media is poorly understood. Here, the uptake of lamellar (liposomes) versus non-lamellar (cubosomes) lipid nanoparticles in macrophages and lung epithelial cells was quantified and the influence of bronchoalveolar lavage fluid (BALF), containing native pulmonary protein and surfactant molecules is determined. Cubosome uptake in both macrophages and epithelial cells was strongly mediated by a high percentage of molecular function regulatory and binding proteins present within the protein corona. In contrast, the protein corona did not influence the uptake of liposomes in epithelial cells. In macrophages, the proteins mediated a rapid internalisation, followed by exocytosis of liposomes after 6 h incubation. These findings on the influence of biological fluid in regulating lipid nanoparticle uptake mechanisms may guide future development of optimal intracellular delivery systems for therapeutics via the pulmonary route.

Inhalable microparticles as drug delivery systems to the lungs in a dry powder formulations

Inhalation-administrated drugs remain an interesting possibility of addressing pulmonary diseases. Direct drug delivery to the lungs allows one to obtain high concentration in the site of action with limited systemic distribution, leading to a more effective therapy with reduced required doses and side effects. On the other hand, there are several difficulties in obtaining a formulation that would meet all the criteria related to physicochemical, aerodynamic and biological properties, which is the reason why only very few of the investigated systems can reach the clinical trial phase and proceed to everyday use as a result. Therefore, we focused on powders consisting of polysaccharides, lipids, proteins or natural and synthetic polymers in the form of microparticles that are delivered by inhalation to the lungs as drug carriers. We summarized the most common trends in research today to provide the best dry powders in the right fraction for inhalation that would be able to release the drug before being removed by natural mechanisms. This review article addresses the most common manufacturing methods with novel modifications, pros and cons of different materials, drug loading capacities with release profiles, and biological properties such as cytocompatibility, bactericidal or anticancer properties.

Emerging strategies in nanotechnology to treat respiratory tract infections: realizing current trends for future clinical perspectives

A boom in respiratory tract infection cases has inflicted a socio-economic burden on the healthcare system worldwide, especially in developing countries. Limited alternative therapeutic options have posed a major threat to human health. Nanotechnology has brought an immense breakthrough in the pharmaceutical industry in a jiffy. The vast applications of nanotechnology ranging from early diagnosis to treatment strategies are employed for respiratory tract infections. The research avenues explored a multitude of nanosystems for effective drug delivery to the target site and combating the issues laid through multidrug resistance and protective niches of the bacteria. In this review a brief introduction to respiratory diseases and multifaceted barriers imposed by bacterial infections are enlightened. The manuscript reviewed different nanosystems, i.e. liposomes, solid lipid nanoparticles, polymeric nanoparticles, dendrimers, nanogels, and metallic (gold and silver) which enhanced bactericidal effects, prevented biofilm formation, improved mucus penetration, and site-specific delivery. Moreover, most of the nanotechnology-based recent research is in a preclinical and clinical experimental stage and safety assessment is still challenging.

Dissolution and Absorption of Inhaled Drug Particles in the Lungs

Dry powder inhalation therapy has been effective in treating localized lung diseases such asthma, chronic obstructive pulmonary diseases (COPD), cystic fibrosis and lung infections. In vitro characterization of dry powder formulations includes the determination of physicochemical nature and aerosol performance of powder particles. The relationship between particle properties (size, shape, surface morphology, porosity, solid state nature, and surface hydrophobicity) and aerosol performance of an inhalable dry powder formulation has been well established. However, unlike oral formulations, there is no standard dissolution method for evaluating the dissolution behavior of the inhalable dry powder particles in the lungs. This review focuses on various dissolution systems and absorption models, which have been developed to evaluate dry powder formulations. It covers a summary of airway epithelium, hurdles to developing an in vitro dissolution method for the inhaled dry powder particles, fine particle dose collection methods, various in vitro dissolution testing methods developed for dry powder particles, and models commonly used to study absorption of inhaled drug.

Inhalable Microparticle Platform Based on a Novel Shell-Forming Lipid Excipient and its Feasibility for Respirable Delivery of Biologics

Administration of biologics such as proteins, vaccines, and phages via the respiratory route is becoming increasingly popular. Inhalable powder formulations for the successful delivery of biologics must first ensure both powder dispersibility and physicochemical stability. A lipid-based inhalable microparticle platform combining the stability advantages offered by dry powder formulations and high dispersibility afforded by a rugose morphology was spray dried and tested. A new simplified spray drying method requiring no organic solvents or complicated feedstock preparation processes was introduced for the manufacture of the microparticles. Trehalose was selected to form the amorphous particle core, because of its well-known ability to stabilize biologics, and also because of its ability to serve as a surrogate for small molecule actives. Phospholipid distearoyl phosphatidylcholine (DSPC), the lipid component in this formulation, was used as a shell former to improve powder dispersibility. Effectiveness of the lipid excipient in modifying trehalose particle morphology and enhancing powder dispersibility was evaluated at different lipid mass fractions (5%, 10%, 25%, 50%) and compared with that of several previously published shell-forming excipients at their effective mass fractions, i.e., 5% trileucine, 20% leucine, and 40% pullulan. A strong dependence of particle morphology on the lipid mass fraction was observed. Particles transitioned from typical smooth spherical trehalose particles without lipid to highly rugose microparticles at higher lipid mass fractions (> 5%). In vitro aerosol performance testing demonstrated a significant improvement of powder dispersibility even at lipid mass fractions as low as 5%. Powder formulations with excellent aerosol performance comparable to those modified with leucine and trileucine were achieved at higher lipid mass fractions (> 25%). A model biologic-containing formulation with 35% myoglobin, 35% glass stabilizer (trehalose), and 30% lipid shell former was shown to produce highly rugose particle structure as designed and excellent aerosol performance for efficient pulmonary delivery. A short-term stability at 40 °C proved that this protein-containing formulation had good thermal stability as designed. The results demonstrated great potential for the new lipid microparticle as a platform for the delivery of both small-molecule APIs and large-molecule biologics to the lung.

Spray Dried Rugose Lipid Particle Platform for Respiratory Drug Delivery

PURPOSE

To develop a new lipid-based particle formulation platform for respiratory drug delivery applications. To find processing conditions for high surface rugosity and manufacturability. To assess the applicability of the new formulation method to different lipids.

METHODS

A new spray drying method with a simplified aqueous suspension feedstock preparation process was developed for the manufacture of rugose lipid particles of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). A study covering a wide range of feedstock temperatures and outlet temperatures was conducted to optimize the processing conditions. Aerosol performance was characterized in vitro and in silico to assess the feasibility of their use in respiratory drug delivery applications. The applicability of the new spray drying method to longer-chain phospholipids with adjusted spray drying temperatures was also evaluated.

RESULTS

Highly rugose DSPC lipid particles were produced via spray drying with good manufacturability. A feedstock temperature close to, and an outlet temperature lower than, the main phase transition were identified as critical in producing particles with highly rugose surface features. High emitted dose and total lung dose showed promising aerosol performance of the produced particles for use as a drug loading platform for respiratory drug delivery. Two types of longer-chain lipid particles with higher main phase transition temperatures, 1,2-diarachidoyl-sn-glycero-3-phosphocholine (DAPC) and 1,2-dibehenoyl-sn-glycero-3-phosphocholine (22:0 PC), yielded similar rugose morphologies when spray dried at correspondingly higher processing temperatures.

CONCLUSIONS

Rugose lipid particles produced via spray drying from an aqueous suspension feedstock are promising as a formulation platform for respiratory drug delivery applications. The new technique can potentially produce rugose particles using various other lipids.

Strategies to Overcome Biological Barriers Associated with Pulmonary Drug Delivery

While the inhalation route has been used for millennia for pharmacologic effect, the biological barriers to treating lung disease created real challenges for the pharmaceutical industry until sophisticated device and formulation technologies emerged over the past fifty years. There are now several inhaled device technologies that enable delivery of therapeutics at high efficiency to the lung and avoid excessive deposition in the oropharyngeal region. Chemistry and formulation technologies have also emerged to prolong retention of drug at the active site by overcoming degradation and clearance mechanisms, or by reducing the rate of systemic absorption. These technologies have also been utilized to improve tolerability or to facilitate uptake within cells when there are intracellular targets. This paper describes the biological barriers and provides recent examples utilizing formulation technologies or drug chemistry modifications to overcome those barriers.

Inhaled Medicines: Past, Present, and Future

The purpose of this review is to summarize essential pharmacological, pharmaceutical, and clinical aspects in the field of orally inhaled therapies that may help scientists seeking to develop new products. After general comments on the rationale for inhaled therapies for respiratory disease, the focus is on products approved approximately over the last half a century. The organization of these sections reflects the key pharmacological categories. Products for asthma and chronic obstructive pulmonary disease include β -2 receptor agonists, muscarinic acetylcholine receptor antagonists, glucocorticosteroids, and cromones as well as their combinations. The antiviral and antibacterial inhaled products to treat respiratory tract infections are then presented. Two "mucoactive" products-dornase α and mannitol, which are both approved for patients with cystic fibrosis-are reviewed. These are followed by sections on inhaled prostacyclins for pulmonary arterial hypertension and the challenging field of aerosol surfactant inhalation delivery, especially for prematurely born infants on ventilation support. The approved products for systemic delivery via the lungs for diseases of the central nervous system and insulin for diabetes are also discussed. New technologies for drug delivery by inhalation are analyzed, with the emphasis on those that would likely yield significant improvements over the technologies in current use or would expand the range of drugs and diseases treatable by this route of administration. SIGNIFICANCE STATEMENT: This review of the key aspects of approved orally inhaled drug products for a variety of respiratory diseases and for systemic administration should be helpful in making judicious decisions about the development of new or improved inhaled drugs. These aspects include the choices of the active ingredients, formulations, delivery systems suitable for the target patient populations, and, to some extent, meaningful safety and efficacy endpoints in clinical trials.

Nanomedicine to advance the treatment of bacteria-induced acute lung injury

Bacteria-induced acute lung injury (ALI) is associated with a high mortality rate due to the lack of an effective treatment. Patients often rely on supportive care such as low tidal volume ventilation to alleviate the symptoms. Nanomedicine has recently received much attention owing to its premium benefits of delivering drugs in a sustainable and controllable manner while minimizing the potential side effects. It can effectively improve the prognosis of bacteria-induced ALI through targeted delivery of drugs, regulation of multiple inflammatory pathways, and combating antibiotic resistance. Hence, in this review, we first discuss the pathogenesis of ALI and its potential therapeutics. In particular, the state-of-the-art nanomedicines for the treatment of bacteria-induced ALI are highlighted, including their administration routes, in vivo distribution, and clearance. Furthermore, the available bacteria-induced ALI animal models are also summarized. In the end, future perspectives of nanomedicine for ALI treatment are proposed.

Multifunctional Lipid-Based Nanoparticles for Codelivery of Anticancer Drugs and siRNA for Treatment of Non-Small Cell Lung Cancer with Different Level of Resistance and EGFR Mutations

Resistance to chemotherapy, enhanced proliferation, invasion, angiogenesis, and metastasis (RPIAM) represent major obstacles that limit the efficacy of cancer treatment especially in advanced stages of cancer. Overcoming or suppressing RPIAM can dramatically improve the treatment outcome. Non-small cell lung cancer (NSCLC) is frequently diagnosed in an advanced stage and often possesses intrinsic resistance to chemotherapy accompanied by the fast development of acquired resistance during the treatment. Oncogenic receptor tyrosine kinases (TKs), specifically epidermal growth factor (EGF) TKs, play an important role in the activation of MAPK/PI3K/Akt/STAT pathways, finally leading to the development of RPIAM. However, the suppression of EGF-TK by different drugs is limited by various defensive mechanisms and mutations. In order to effectively prevent the development of RPIAM in NSCLC, we formulated and tested a multicomponent and multifunctional cancer targeted delivery system containing Nanostructured Lipid Carriers (NLCs) as vehicles, luteinizing hormone release hormone (LHRH) as a cancer targeting moiety, EFG-TK inhibitor gefitinib and/or paclitaxel as anticancer drug(s), siRNA targeted to EGF receptor (EGFR) mRNA as a suppressor of EGF receptors, and an imaging agent (rhodamine) for the visualization of cancer cells. Experimental data obtained show that this complex delivery system possesses significantly enhanced anticancer activity that cannot be achieved by individual components applied separately.

Mycobacterium abscessus biofilms have viscoelastic properties which may contribute to their recalcitrance in chronic pulmonary infections

Mycobacterium abscessus is emerging as a cause of recalcitrant chronic pulmonary infections, particularly in people with cystic fibrosis (CF). Biofilm formation has been implicated in the pathology of this organism, however the role of biofilm formation in infection is unclear. Two colony-variants of M. abscessus are routinely isolated from CF samples, smooth (MaSm) and rough (MaRg). These two variants display distinct colony morphologies due to the presence (MaSm) or absence (MaRg) of cell wall glycopeptidolipids (GPLs). We hypothesized that MaSm and MaRg variant biofilms might have different mechanical properties. To test this hypothesis, we performed uniaxial mechanical indentation, and shear rheometry on MaSm and MaRg colony-biofilms. We identified that MaRg biofilms were significantly stiffer than MaSm under a normal force, while MaSm biofilms were more pliant compared to MaRg, under both normal and shear forces. Furthermore, using theoretical indices of mucociliary and cough clearance, we identified that M. abscessus biofilms may be more resistant to mechanical forms of clearance from the lung, compared to another common pulmonary pathogen, Pseudomonas aeruginosa. Thus, the mechanical properties of M. abscessus biofilms may contribute to the persistent nature of pulmonary infections caused by this organism.

Development of solid lipid microparticles by melt-emulsification/spray-drying processes as carriers for pulmonary drug delivery

The aim of this study was to optimize the parameters of the complex melt-emulsification process coupled with the spray-drying, in order to maintain the balance between solid lipid microparticles (SLMs) powders aerodynamic performance and salbutamol sulfate release rate. Quality target product profile was identified and risk management and principal component analysis were used to guide formulation development. Obtained dry powders for inhalation (DPIs) were evaluated in terms of SLMs size distribution, morphology, true density, drug content, solid state characterization studies, in vitro aerosol performance and in vitro drug release. SLMs micrographs indicated spherical, porous particles. Selected powders showed satisfactory aerosol performance with a mean mass aerodynamic diameter of around 3 μm and acceptable fine particle fraction (FPF). Addition of trehalose positively affected SLMs aerodynamic properties. The results of in vitro dissolution testing indicated that salbutamol sulfate release from the tested SLMs formulations was modified, in comparison to the raw drug release. In conclusion, SLMs in a form of DPIs were successfully developed and numerous factors that affects SLMs properties were identified in this study. Further research is required for full understanding of each factor's influence on SLMs properties and optimization of DPIs with maximized FPFs.

Lipid-based Nanoplatforms in Cancer Therapy: Recent Advances and Applications

Though modern available cancer therapies are effective, they possess major adverse effects, causing non-compliance to patients. Furthermore, the majority of the polymeric-based medication platforms are certainly not universally acceptable, due to their several restrictions. With this juxtaposition, lipid-based medication delivery systems have appeared as promising drug nanocarriers to replace the majority of the polymer-based products because they are in a position to reverse polymer as well as, drug-associated restrictions. Furthermore, the amalgamation of the basic principle of nanotechnology in designing lipid nanocarriers, which are the latest form of lipid carriers, has tremendous chemotherapeutic possibilities as tumor-targeted drug-delivery pertaining to tumor therapy. Apart from this, it is reported that nearly 40% of the modern medication entities are lipophilic. Moreover, research continues to be efficient in attaining a significant understanding of the absorption and bioavailability of the developed lipids systems.

Spray Drying for the Preparation of Nanoparticle-Based Drug Formulations as Dry Powders for Inhalation

Nanoparticle-based therapeutics have been used in pulmonary formulations to enhance delivery of poorly water-soluble drugs, protect drugs against degradation and achieve modified release and drug targeting. This review focuses on the use of spray drying as a solidification technique to produce microparticles containing nanoparticles (i.e., nanoparticle (NP) agglomerates) with suitable properties as dry powders for inhalation. The review covers the general aspects of pulmonary drug delivery with emphasis on nanoparticle-based dry powders for inhalation and the principles of spray drying as a method for the conversion of nanosuspensions to microparticles. The production and therapeutic applications of the following types of NP agglomerates are presented: nanoporous microparticles, nanocrystalline agglomerates, lipid-based and polymeric formulations. The use of alternative spray-drying techniques, namely nano spray drying, and supercritical CO2-assisted spray drying is also discussed as a way to produce inhalable NP agglomerates.

Nanoparticle-mediated macrophage targeting-a new inhalation therapy tackling tuberculosis

Despite the potent clinical efficacy of linezolid (LNZ) against drug-resistant tuberculosis, its safety and tolerability remain of major concern. Our objective is to develop antitubercular inhalable LNZ nano-embedded microparticles. In this context, LNZ incorporated in non-structured lipid carriers (NLCs) was characterized in terms of colloidal, morphological, thermal, and release profiles. The potential of LNZ-NLCs to cross mucosal barriers and invade alveolar macrophages (AM, MH-S cells) was appraised. In vivo proof of concept was accomplished via orotracheal administration to mice. Respirable microparticles prepared by spray drying NLCs with diluents were assessed for their size, shape, flowability, aerosolization performance, and lung deposition pattern. NLCs (809-827 nm in size, zeta potential - 37.4 to - 58.9 mV) ensued 19% LNZ loading and pH-independent sustained release. Penetration studies revealed 73% LNZ crossing mucus within 1 h. Meanwhile, viability assay on A549 cells ensured an IC50 of 1.2 and 0.32 mg/mL for plain and LNZ-NLCs, respectively. CLSM confirmed phagocytosis of NLCs by MH-S macrophages, while H&E staining demonstrated NLC accumulation in murine AM in vivo with no signs of histopathological/biochemical changes. Bronchoalveolar lavage showed significantly low levels of LDH and total proteins (TP) for LNZ-NLCs highlighting their superior safety. Respirable microparticles embedding LNZ-NLCs ensured excellent aerosolization (MMAD 2 μm, FPF 93%) denoting perfect alveolar deposition. The developed inhalation therapy provided sustained LNZ release, mucus penetrability, potential safety in therapeutic doses, in vitro and in vivo macrophage targetability, and preferential deposition in the deep lung. Overall positive outcomes rely on reduced dose, dosing frequency, and per se superior safety circumventing systemic-associated life-threatening side effects. Graphical abstract.

Future Trends in Nebulized Therapies for Pulmonary Disease

Aerosol therapy is a key modality for drug delivery to the lungs of respiratory disease patients. Aerosol therapy improves therapeutic effects by directly targeting diseased lung regions for rapid onset of action, requiring smaller doses than oral or intravenous delivery and minimizing systemic side effects. In order to optimize treatment of critically ill patients, the efficacy of aerosol therapy depends on lung morphology, breathing patterns, aerosol droplet characteristics, disease, mechanical ventilation, pharmacokinetics, and the pharmacodynamics of cell-drug interactions. While aerosol characteristics are influenced by drug formulations and device mechanisms, most other factors are reliant on individual patient variables. This has led to increased efforts towards more personalized therapeutic approaches to optimize pulmonary drug delivery and improve selection of effective drug types for individual patients. Vibrating mesh nebulizers (VMN) are the dominant device in clinical trials involving mechanical ventilation and emerging drugs. In this review, we consider the use of VMN during mechanical ventilation in intensive care units. We aim to link VMN fundamentals to applications in mechanically ventilated patients and look to the future use of VMN in emerging personalized therapeutic drugs.

Control of the Lung Residence Time of Highly Permeable Molecules after Nebulization: Example of the Fluoroquinolones

Pulmonary drug delivery is a promising strategy to treat lung infectious disease as it allows for a high local drug concentration and low systemic side effects. This is particularly true for low-permeability drugs, such as tobramycin or colistin, that penetrate the lung at a low rate after systemic administration and greatly benefit from lung administration in terms of the local drug concentration. However, for relatively high-permeable drugs, such as fluoroquinolones (FQs), the rate of absorption is so high that the pulmonary administration has no therapeutic advantage compared to systemic or oral administration. Formulation strategies have thus been developed to decrease the absorption rate and increase FQs’ residence time in the lung after inhalation. In the present review, some of these strategies, which generally consist of either decreasing the lung epithelium permeability or decreasing the release rate of FQs into the epithelial lining fluid after lung deposition, are presented in regards to their clinical aspects.

Comparison of Phospholipid-Based Particles for Sustained Release of Ciprofloxacin Following Pulmonary Administration to Bronchiectasis Patients

The rapid clearance of ciprofloxacin hydrochloride from the lungs following administration as an aerosol leads to poor efficacy in the treatment of pulmonary infections. The development of formulations capable of sustaining ciprofloxacin concentrations in the lungs has the potential to significantly improve antibacterial activity. The present review compares two approaches for sustaining levels of ciprofloxacin in the lungs, a liposomal formulation where ciprofloxacin is encapsulated in small unilamellar vesicles, and a dry powder formulation of the practically insoluble zwitterionic form of the drug. These two formulations recently completed large multicenter, phase 3 clinical studies in bronchiectasis patients. As such, they present a unique opportunity to examine the chemistry, manufacturing, and control of the dosage forms in addition to their tolerability and efficacy in more than 1000 bronchiectasis patients. Both formulations were generally well tolerated with most adverse events found to be mild to moderate in intensity. While the formulations were effective in reducing and/or eradicating infections, this did not lead to reductions in pulmonary exacerbations, the primary endpoint. The failures speak more to the heterogeneous nature of the disease and the difficulty in identifying bronchiectasis patients likely to exacerbate, rather than an inherent limitation of the formulations. While the formulations are similar in many respects, they also present some interesting differences. This review explores the implications of these differences on the treatment of respiratory infections.

Rational particle design to overcome pulmonary barriers for obstructive lung diseases therapy

Pulmonary delivery of active drugs has been applied for the treatment of obstructive lung diseases, including asthma, chronic obstructive pulmonary disease and cystic fibrosis, for several decades and has achieved progress in symptom management by bronchodilator inhalation. However, substantial progress in anti-inflammation, prevention of airway remodeling and disease progression is limited, since the majority of the formulation strategies focus only on particle deposition, which is insufficient for pulmonary delivery of the drugs. The lack of knowledge on lung absorption barriers in obstructive lung diseases and on pathogenesis impedes the development of functional formulations by rational design. In this review, we describe the physiological structure and biological functions of the barriers in various regions of the lung, review the pathogenesis and functional changes of barriers in obstructive lung diseases, and examine the interaction of these barriers with particles to influence drug delivery efficiency. Subsequently, we review rational particle design for overcoming lung barriers based on excipients selection, particle size and surface properties, release properties and targeting ability. Additionally, useful particle fabrication strategies and commonly used drug carriers for pulmonary delivery in obstructive lung diseases are proposed in this article.

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.

Evaluation of co-delivery of colistin and ciprofloxacin in liposomes using an in vitro human lung epithelial cell model

Respiratory tract infections caused by multidrug-resistant Gram-negative bacteria are serious burdens to the public. Our previous findings indicated that co-loading of colistin and ciprofloxacin via liposomes improved in vitro antimicrobial activities against multidrug resistant Pseudomonas aeruginosa as compared to the monotherapies. The current study aims to investigate the transport behavior of colistin and ciprofloxacin in liposomes using the in vitro Calu-3 cell monolayer, which is a lung epithelial model cultured under the air-interfaced condition. The cell viability results demonstrated that there was no obvious toxicity of cells exposed to single or co-administered drugs at the concentration ≤500 μg/mL. Transport of ciprofloxacin into the cells was easier than that of colistin, which reached a plateau rapidly. Colistin was less trapped in the mucus or adhered to the apical cell membrane, and less transported across the cell monolayer than ciprofloxacin. The deposition of ciprofloxacin on the apical side increased over time (from 1 to 4 h). There was no drug-drug interaction observed during the transport of ciprofloxacin and colistin across the cell monolayer, when they were dosed together in the solution form. The amount of drug transported across the cell monolayer was decreased in both agents when loaded in liposomes. Both drugs were more trapped in the mucus or more adhered to the apical side cell membrane of the cell monolayer when they were in liposomes. This study demonstrated that co-delivery of colistin and ciprofloxacin in a single liposome can reduce transport capacity of both drugs across the lung epithelial cell monolayer and enhance drug retention on the lung epithelial surfaces; therefore, it is a promising approach to treat the respiratory infections caused by multidrug resistant Pseudomonas aeruginosa.

Ciprofloxacin nanocrystals liposomal powders for controlled drug release via inhalation

This study was conducted to evaluate the feasibility of developing inhalable dry powders of liposomal encapsulated ciprofloxacin nanocrystals (LECN) for controlled drug release. Dry powders of LECN were produced by freeze-thaw followed by spray drying. The formulations contained sucrose as a lyoprotectant in different weight ratios (0.75:1, 1:1 and 2:1 sucrose to lipids), along with 2% magnesium stearate and 5% isoleucine as aerosolization enhancers. The powder physical properties (particle size, morphology, crystallinity, moisture content), in vitro aerosolization performance, drug encapsulation efficiency and in vitro drug release were investigated. The spray dried powders were comprised of spherical particles with a median diameter of ∼1 µm, partially crystalline, with a low water content (∼2% mass) and did not undergo recrystallization at high relative humidity. When dispersed by an Osmohaler® inhaler at 100 L/min, the powders showed a high aerosol performance with a fine particle fraction (% wt. <5 µm) of 66-70%. After reconstitution of the powders in saline, ciprofloxacin nanocrystals were confirmed by cryo-electron microscopy. The drug encapsulation efficiency of the reconstituted liposomes was 71-79% compared with the stock liquid formulation. Of the three formulations, the one containing a sucrose to lipids wt. ratio of 2:1 demonstrated a prolonged release of ciprofloxacin from the liposomes. In conclusion, ciprofloxacin nanocrystal liposomal powders were prepared that were suitable for inhalation aerosol delivery and controlled drug release.

Efficacy of Ciprofloxacin and Its Copper Complex against Pseudomonas aeruginosa Biofilms

A limitation of antibiotic treatments for P. aeruginosa (PA) chronic pulmonary infections is the reduced efficacy due to sub-therapeutic concentrations at the infection site and the development of biofilm. A novel approach to sustain ciprofloxacin (CIP) in the lungs after inhalation is to reduce its pulmonary absorption rate by its complexation with copper (CIP-Cu). This study aimed to evaluate the antimicrobial action of cationic CIP-Cu complex in PA biofilms in terms of drug concentration and time. Two PA strains, PA01 and PA14, were grown to form biofilm layers in equilibrium with planktonic cells. Static parameters such as pyoverdine production by planktonic cells, enzymatic activity within biofilms, and biofilm biomass 24 h after the addition of CIP or CIP-Cu were evaluated. Also, the kinetic effects of CIP and CIP-Cu on biofilms were evaluated by bioluminescence kinetics using transgenic strains. No differences were observed between CIP and CIP-Cu in terms of efficacy against biofilms, validating the potential of using this complex to treat PA biofilms. Interestingly, CIP concentrations slightly below the MIC value against planktonic bacteria stimulated both virulence and biofilm PA01 production. These results support the need to accurately achieve high CIP concentration in the lungs, which can be more easily achieved by pulmonary delivery of advanced CIP formulations (CIP-metal complexes or liposomal CIP) instead of the oral administration of free CIP.

In vitro dissolution testing of respirable size anti-tubercular drug particles using a small volume dissolution apparatus

A dissolution apparatus that uses a small volume of stationary medium (25 μL) has been developed for in vitro dissolution testing of respirable drug particles and used to evaluate the dissolution of two anti-tubercular drugs, moxifloxacin and ethionamide. Solubilities of moxifloxacin and ethionamide in phosphate buffered saline (PBS, pH 7.4) were 17.68 ± 0.85 mg mL^-1 and 0.46 ± 0.02 mg mL^-1 whereas in the presence of lung surfactant (0.4% w/v Curosurf^® in PBS) solubilities were 20.76 ± 0.35 mg mL^-1 and 0.56 ± 0.03 mg mL^-1, respectively. A fine particle dose (∼50 µg) of aerodynamically separated moxifloxacin or ethionamide particles (<6.4 µm) was collected onto a glass coverslip using a modified Twin Stage Impinger. The dissolution behaviour of the fine particle dose was evaluated at various perfusate flow rates (0.2, 0.4 and 0.8 mL min^-1 of PBS), mucus simulant concentrations (1.0, 1.5 and 2.0% w/v polyethylene oxide in PBS), and in the presence of lung surfactant. The dissolution behaviour of the respirable size particles was observed under an optical microscope and the dissolved drug that diffused into the perfusate was quantified by HPLC. The moxifloxacin particles disappeared quickly and showed faster permeation (<30 min) compared to the ethionamide particles at all the dissolution conditions evaluated. This study demonstrated the differences in the dissolution rates of moxifloxacin and ethionamide particles and may be useful to estimate the residence time of the inhaled dry powder particles in the lungs.

Apoptosis of A549 cells by small interfering RNA targeting survivin delivery using poly-β-amino ester/guanidinylated O-carboxymethyl chitosan nanoparticles

Gene-based therapeutics has emerged as a promising approach for human cancer therapy. Among a variety of non-viral vectors, polymer vectors are particularly attractive due to their safety and multivalent groups on their surface. This study focuses on guanidinylated O-carboxymethyl chitosan (GOCMCS) along with poly-β-amino ester(PBAE) for siRNA delivery. Binding efficiency of PBAE/siRNA/GOCMCS nanoparticles were characterized by gel electrophoresis. The siRNA-loaded nanoparticles were found to be stable in the presence of RNase A, serum and BALF respectively. Fine particle fraction (FPF) which was determined by a two-stage impinger (TSI) was 57.8% ± 2.6%. The particle size and zeta potential of the nanoparticles were 153.8 ± 12.54 nm and + 12.2 ± 4.94 mV. In vitro cell transfection studies were carried out with A549 cells. The cellular uptake was significantly increased. When the cells were incubated with siSurvivin-loaded nanoparticles, it could induce 26.83% ± 0.59% apoptosis of A549 cells and the gene silencing level of survivin expression in A549 cells were 30.93% ± 2.27%. The results suggested that PBAE/GOCMCS nanoparticle was a very promising gene delivery carrier.

Nanostructured lipid carriers: A potential use for skin drug delivery systems

Skin application of pharmaceutical products is one of the methods used for drug administration. The problem of limited drug penetration via topical application makes searching for safe drug carriers that will provide an expected therapeutic effect of utmost importance. Research into safe drug carriers began with liposome structures, paving the way for work with nanocarriers, which currently play a large role as drug vehicles. Nanostructured lipid carriers (NLC) consist of blended solid and liquid lipids (oils) dispersed in an aqueous solution containing a surfactant. These carriers have many advantages: good biocompatibility, low cytotoxicity, high drug content; they enhance a drug's stability and have many possibilities of application (oral, intravenous, pulmonary, ocular, dermal). The following article presents properties, methods of preparation and tests to assess the quality and toxicity of NLC. This analysis indicates the possibility of using NLC for dermal and transdermal drug application.

Co-Delivery of Ciprofloxacin and Colistin in Liposomal Formulations with Enhanced In Vitro Antimicrobial Activities against Multidrug Resistant Pseudomonas aeruginosa

PURPOSE

This study aims to develop liposomal formulations containing synergistic antibiotics of colistin and ciprofloxacin for the treatment of infections caused by multidrug-resistant Pseudomonas aeruginosa.

METHODS

Colistin (Col) and ciprofloxacin (Cip) were co-encapsulated in anionic liposomes by ammonium sulfate gradient. Particle size, encapsulation efficiency, in vitro drug release and in vitro antibiotic activities were evaluated.

RESULTS

The optimized liposomal formulation has uniform sizes of approximately 100 nm, with encapsulation efficiency of 67.0% (for colistin) and 85.2% (for ciprofloxacin). Incorporation of anionic lipid (DMPG) markedly increased encapsulation efficiency of colistin (from 5.4 to 67.0%); however, the encapsulation efficiency of ciprofloxacin was independent of DMPG ratio. Incorporation of colistin significantly accelerated the release of ciprofloxacin from the DMPG anionic liposomes. In vitro release of ciprofloxacin and colistin in the bovine serum for 2 h were above 70 and 50%. The cytotoxicity study using A549 cells showed the liposomal formulation is as non-toxic as the drug solutions. Liposomal formulations of combinations had enhanced in vitro antimicrobial activities against multidrug resistant P. aeruginosa than the monotherapies.

CONCLUSIONS

Liposomal formulations of two synergistic antibiotics was promising against multidrug resistant P. aeruginosa infections.

Catan-ionic hybrid lipidic nano-carriers for enhanced bioavailability and anti-tumor efficacy of chemodrugs

To date there has not been any report on catan-ionic hybrid lipidic nano-carriers, let alone a report on applying them to deliver insoluble anti-tumor drugs. Catan-ionic hybrid lipidic nano-carriers containing curcumin (CUR-C-HLN) inherit the merits of catan-ionic systems, hybrid lipidic systems and nano-structured carriers (the second-generation substitute of solid lipidic nano-systems). Catan-ionic surfactants increased microvesicle stabilization by producing unordered isometric clusters, enhanced absorptive amount as an inhibitor of enzyme and protein, improved tumor accumulation by cellular endocytosis and membranous fusion; hybrid lipids helped to obtain high drug content and low leakage by forming a less-organized matrix arrangement. CUR-C-HLN favorably changed absorptive and pharmacokinetic properties after oral and/or intravenous administrations; improved cell growth inhibition, apoptotic inducing and anti-invasion effects; enhanced antitumor efficiency and reduced cancerous growth. Catan-ionic hybrid lipidic nano-carriers provide an alternative good choice for effective delivery of anticancerous chemodrugs.

A comparison of the lung clearance kinetics of solid lipid nanoparticles and liposomes by following the 3H-labelled structural lipids after pulmonary delivery in rats

The utility of biodegradable nanosized drug carriers for the local and controlled delivery of therapeutics to the lungs has prompted significant interest in the development of inhalable nanomedicines. Still, little is known about how these systems are cleared from the lungs, including the kinetics of the structural lipids. Most preclinical and clinical studies to date have evaluated the lung clearance of loaded drugs, which in many cases poorly reflects the kinetics of the nanocarrier, or the bulk-labelled particles. This study therefore aimed to describe and compare the pulmonary pharmacokinetic behaviour and patterns of lung clearance of two commonly explored inhalable nanocarriers (anionic ∼150 nm liposomes and solid lipid nanoparticles [SLNs]) in rats by following the ³H-labelled structural lipids (phosphatidylcholine and tristearin respectively). The data showed that SLNs and liposomes were cleared from the lungs at similar rates, despite SLNs being deposited after intratracheal instillation in the upper respiratory track, and primarily via the mucociliary escalator, but this process was more pronounced for SLNs. Structural lipids were mainly associated with plasma proteins rather than nanocarrier in plasma. The lipids also exhibit prolonged lung exposure and are associated with the lung tissue (rather than BALF) over 2 weeks.

Solid lipid nanoparticles and nanostructured lipid carriers as novel drug delivery systems: applications, advantages and disadvantages

During the recent years, more attentions have been focused on lipid base drug delivery system to overcome some limitations of conventional formulations. Among these delivery systems solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) are promising delivery systems due to the ease of manufacturing processes, scale up capability, biocompatibility, and also biodegradability of formulation constituents and many other advantages which could be related to specific route of administration or nature of the materials are to be loaded to these delivery systems. The aim of this article is to review the advantages and limitations of these delivery systems based on the route of administration and to emphasis the effectiveness of such formulations.