Influence of PEI as a core modifying agent on PLGA microspheres of PGE₁, a pulmonary selective vasodilator

New Insights on the Burst Release Kinetics of Spray-Dried PLGA Microspheres

Spray drying is one of the leading manufacturing methods for active pharmaceutical ingredients (APIs) owing to its rapid, single-step, and cost-effective nature. It also has the capacity to generate microspheres capable of controlled release of APIs including biomolecules and vaccines. However, one of the key challenges of spray-dried formulations especially with poly(lactic-co-glycolic acid) (PLGA)-based controlled-release injectables is burst release, where a significant fraction of the API is released prematurely within a short period of time following administration, leading to detrimental impact on the performance and quality of end products. This study uses a model API, bovine serum albumin (BSA) protein, to identify the sources of burst release that may affect the kinetics and performance of long-acting injectable microsphere formulations. Spray-dried microspheres with various formulations (i.e., variable BSA/PLGA ratios) were characterized in terms of their morphology, particle size, surface area, thermal properties, moisture content, as well as chemical compositions and their distributions to investigate the impact of spray drying on the burst release phenomenon. The results suggest that a relatively high initial release (85%) observed is mainly attributed to the protein distribution close to the particle surface. Morphology analysis provided evidence that the microspheres retained their spherical structure during the burst release phase. X-ray photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and argon cluster sputtering-assisted time-of-flight secondary ion mass spectrometry analysis suggest an enrichment of PLGA on particle surfaces with buried BSA protein. The statistically significant difference in particle size and surface area between three different formulations may be responsible for an initial variation in release but did not seem to alter the overall burst release profile. Considering the suggested source of burst release, the two-fluid spray-drying method, characterized by a single liquid feed delivering a preprepared emulsion, generated matrix-type microspheres with a surface layer of PLGA, as evidenced by surface analysis. The PLGA surface layer proved to be prone to degradation and pore formation, allowing for faster diffusion of BSA out of the microspheres, resulting in a burst release. Increasing the polymer concentration did not seem to halt this process.

Continuously producible aztreonam-loaded inhalable lipid nanoparticles for cystic fibrosis-associated Pseudomonas aeruginosa infections - Development and in-vitro characterization

Cystic fibrosis (CF) is a genetic disorder affecting nearly 105,000 patients worldwide and is characterized by poor respiratory function due to accumulation of thick mucus in the lungs, which not just acts as a physical barrier, but also provides a breeding ground for bacterial infections. These infections can be controlled with the help of antibiotics which can be delivered directly into the lungs for amplifying the local anti-bacterial effect. More than 50 % of CF patients are associated with Pseudomonas aeruginosa infection in their lungs which requires antibiotics such as Aztreonam (AZT). In this study, we prepared inhalable AZT-loaded lipid nanoparticles using Hot-melt extrusion (HME) coupled with probe sonication to target Pseudomonas aeruginosa infection in the lungs. The optimized nanoparticles were tested for physicochemical properties, stability profile, in-vitro aerosolization, and antimicrobial activity against Pseudomonas aeruginosa. The optimized nanoparticles with a PEI concentration of 0.1 % demonstrated a uniform particle size of <50 nm, a spherical shape observed under a transmission electron microscope, and >70 % drug entrapment. Incorporating cationic polymer, PEI, resulted in sustained drug release from the lipid nanoparticles. The in-vitro aerosolization studies exhibited a mass median aerodynamic diameter (MMAD) of <4.3 μm, suggesting deposition of the nanoparticles in the respirable airway. The antimicrobial activity against Pseudomonas aeruginosa showed the minimum inhibitory concentration of the formulation is 2-fold lower than plain AZT. Stability profile showed the formulations are stable after exposure to accelerated conditions. In conclusion, hot-melt extrusion in combination with probe sonication can be used as a potential method for the continuous production of AZT-loaded lipid nanoparticles with enhanced anti-bacterial activity.

Chitosan/bovine serum albumin layer-by-layer assembled particles for non-invasive inhaled drug delivery to the lungs

Layer-by-Layer (LbL) assembly of polyelectrolytes on a solid core particle is a well-established technique used to deliver drugs, proteins, regenerative medicines, combinatorial therapy, etc. It is a multifunctional delivery system which can be engineered using various core template particles and coating polymers. This study reports the development and in-vitro evaluation of LbL assembled particles for non-invasive inhaled delivery to the lungs. The LbL assembled particles were prepared by successively coating polyelectrolyte macromolecules, glycol chitosan and bovine serum albumin on 0.5- and 4.5-μm polystyrene particles. The LbL assembly of polyelectrolytes was confirmed by reversible change in zeta potential and sequential increase in the particle size after accumulation of the layer. The prepared LbL particles were further assessed for aerodynamic properties using two distinct nebulizers, and toxicity assessment in normal lung cells. The in-vitro aerosolization study performed using next generation impactor coupled with Pari LC Plus and Aeroeclipse nebulizer showed that both the LbL assembled 0.5 and 4.5-μm particles had MMAD <5 μm confirming suitable aerodynamic properties for non-invasive lung delivery. The in-vitro cytotoxicity, and TEER integrity following treatment with the LbL assembled particles in normal lung epithelial and fibroblasts showed no significant cytotoxicity rendering the LbL assembled particles safe. This study extends the efficiency of LbL assembled particles for novel applications towards delivery of small and large molecules into the lungs.

Inhalable Nitric Oxide Delivery Systems for Pulmonary Arterial Hypertension Treatment

Pulmonary arterial hypertension (PAH) is a severe medical condition characterized by elevated blood pressure in the pulmonary arteries. Nitric oxide (NO) is a gaseous signaling molecule with potent vasodilator effects; however, inhaled NO is limited in clinical practice because of the need for tracheal intubation and the toxicity of high NO concentrations. In this study, inhalable NO-releasing microspheres (NO inhalers) are fabricated to deliver nanomolar NO through a nebulizer. Two NO inhalers with distinct porous structures are prepared depending on the molecular weights of NO donors. It is confirmed that pore formation can be controlled by regulating the migration of water molecules from the external aqueous phase to the internal aqueous phase. Notably, open porous NO inhalers (OPNIs) can deliver NO deep into the lungs through a nebulizer. Furthermore, OPNIs exhibit vasodilatory and anti-inflammatory effects via sustained NO release. In conclusion, the findings suggest that OPNIs with highly porous structures have the potential to serve as tools for PAH treatment.

Amrubicin encapsulated PLGA NPs inhibits the PI3K/AKT signaling pathway by activating PTEN and inducing apoptosis in TMZ-resistant Glioma

Glioblastoma (GBM) remains a challenging malignancy due to its aggressive nature and the lack of efficacious therapeutic interventions. Nanotechnology-based approaches exhibit promise in GBM treatment; however, the successful translation of these strategies from preclinical models to clinical settings is hindered by inefficient nanoparticle clearance from vital organs. Addressing this concern, we investigated the therapeutic potential of amrubicin (AMR) encapsulated within poly (lactic-co-glycolic acid) nanoparticles (AMR-PLGA-NPs) in combating temozolomide (TMZ) resistant GBM. The study demonstrated that AMR-PLGA-NPs exerted a pronounced inhibitory effect on the cellular viability and migratory capacity of TMZ-resistant GBM cells. Furthermore, these nanoparticles exhibited considerable efficacy in downregulating the PI3K/AKT signaling pathway, thereby inducing apoptosis specifically in TMZ-resistant glioma cells and glioma stem-like cells through the activation of PTEN. Notably,in vivoexperimentation revealed the ability of AMR-PLGA-NPs to traverse biological barriers within murine models. Collectively, these findings underscore the potential therapeutic utility of AMR-PLGA-NPs as a versatile nanoplatform for addressing the formidable challenges posed by GBM, particularly in mitigating drug resistance mechanisms. The study substantiates the stability and safety profile of AMR-PLGA-NPs, positioning them as a promising avenue for combating drug resistance in GBM therapeutics.

A DUSP6 inhibitor suppresses inflammatory cardiac remodeling and improves heart function after myocardial infarction

Acute myocardial infarction (MI) results in loss of cardiomyocytes and abnormal cardiac remodeling with severe inflammation and fibrosis. However, how cardiac repair can be achieved by timely resolution of inflammation and cardiac fibrosis remains incompletely understood. Our previous findings have shown that dual-specificity phosphatase 6 (DUSP6) is a regeneration repressor from zebrafish to rats. In this study, we found that intravenous administration of the DUSP6 inhibitor (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI) improved heart function and reduced cardiac fibrosis in MI rats. Mechanistic analysis revealed that BCI attenuated macrophage inflammation through NF-κB and p38 signaling, independent of DUSP6 inhibition, leading to the downregulation of various cytokines and chemokines. In addition, BCI suppressed differentiation-related signaling pathways and decreased bone-marrow cell differentiation into macrophages through inhibiting DUSP6. Furthermore, intramyocardial injection of poly (D, L-lactic-co-glycolic acid)-loaded BCI after MI had a notable effect on cardiac repair. In summary, BCI improves heart function and reduces abnormal cardiac remodeling by inhibiting macrophage formation and inflammation post-MI, thus providing a promising pro-drug candidate for the treatment of MI and related heart diseases. This article has an associated First Person interview with the first author of the paper.

Application of PLGA as a Biodegradable and Biocompatible Polymer for Pulmonary Delivery of Drugs

Pulmonary administration of biodegradable polymeric formulation is beneficial in the treatment of various respiratory diseases. For respiratory delivery, the polymer must be non-toxic, biodegradable, biocompatible, and stable. Poly D, L-lactic-co-glycolic acid (PLGA) is a widely used polymer for inhalable formulations because of its attractive mechanical and processing characteristics which give great opportunities to pharmaceutical industries to formulate novel inhalable products. PLGA has many pharmaceutical applications and its biocompatible nature produces non-toxic degradation products. The degradation of PLGA takes place through the non-enzymatic hydrolytic breakdown of ester bonds to produce free lactic acid and glycolic acid. The biodegradation products of PLGA are eliminated in the form of carbon dioxide (CO₂) and water (H₂O) by the Krebs cycle. The biocompatible properties of PLGA are investigated in various in vivo and in vitro studies. The high structural integrity of PLGA particles provides better stability, excellent drug loading, and sustained drug release. This review provides detailed information about PLGA as an inhalable grade polymer, its synthesis, advantages, physicochemical properties, biodegradability, and biocompatible characteristics. The important formulation aspects that must be considered during the manufacturing of inhalable PLGA formulations and the toxicity of PLGA in the lungs are also discussed in this paper. Additionally, a thorough overview is given on the application of PLGA as a particulate carrier in the treatment of major respiratory diseases, such as cystic fibrosis, lung cancer, tuberculosis, asthma, and pulmonary hypertension.

Comprehensive Review on Novel Targets and Emerging Therapeutic Modalities for Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is the progressive increase in mean pulmonary arterial pressure (mPAP) (≥ 20 mmHg at rest). Current treatment strategies include the drugs targeting at nitric oxide pathway, endothelin receptors, prostaglandin receptors, thromboxane receptors and phosphodiesterase inhibitors, which provides the symptomatic relief. Despite of these treatments, the mortality amongst the PAH patients remains high due to non-reversal of the condition. This review primarily covers the introduction of PAH and the current treatments of the disease. This is followed by the newer disease targets expressed in the pathobiology of the disease like Rho Kinase Pathway, Vasoactive Intestinal Peptide Pathway, Receptor Tyrosine Kinases, Serotonin signalling pathway, Voltage-gated potassium (Kv) channel pathway. Newer formulation strategies for targeting at these specific receptors were covered and includes nano formulations like liposomes, Micelles, Polymeric Nanoparticles, Solid Lipid Nanoparticles (SLN), Bioresorbable stents, NONOates, Cell-Based Therapies, miRNA therapy for PAH. Novel targets were identified for their role in the pathogenesis of the PAH and needs to be targeted with new molecules or existing molecules effectively. Nanosystems have shown their potential as alternative carriers on the virtue of their better performance than traditional drug delivery systems.

Simulated biological fluids - a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres

The use of simulated biological fluids (SBFs) is a promising in vitro technique to better understand the release mechanisms and possible in vivo behaviour of materials, including fibres, metal-containing particles and nanomaterials. Applications of SBFs in dissolution tests allow a measure of material biopersistence or, conversely, bioaccessibility that in turn can provide a useful inference of a materials biodistribution, its acute and long-term toxicity, as well as its pathogenicity. Given the wide range of SBFs reported in the literature, a review was conducted, with a focus on fluids used to replicate environments that may be encountered upon material inhalation, including extracellular and intracellular compartments. The review aims to identify when a fluid design can replicate realistic biological conditions, demonstrate operation validation, and/or provide robustness and reproducibility. The studies examined highlight simulated lung fluids (SLFs) that have been shown to suitably replicate physiological conditions, and identify specific components that play a pivotal role in dissolution mechanisms and biological activity; including organic molecules, redox-active species and chelating agents. Material dissolution was not always driven by pH, and likewise not only driven by SLF composition; specific materials and formulations correspond to specific dissolution mechanisms. It is recommended that SLF developments focus on biological predictivity and if not practical, on better biological mimicry, as such an approach ensures results are more likely to reflect in vivo behaviour regardless of the material under investigation.

A quantitative approach to predicting lung deposition profiles of pharmaceutical powder aerosols

Dry powder inhalers (DPI) are widely used systems for pulmonary delivery of therapeutics. The inhalation performance of DPIs is influenced by formulation features, inhaler device and inhalation pattern. The current review presents the affecting factors with great focus on powder characteristics which include particle size, shape, surface, density, hygroscopicity and crystallinity. The properties of a formulation are greatly influenced by a number of physicochemical factors of drug and added excipients. Since available particle engineering techniques result in particles with a set of modifications, it is difficult to distinguish the effect of an individual feature on powder deposition behavior. This necessitates developing a predictive model capable of describing all influential factors on dry powder inhaler delivery. Therefore, in the current study, a model was constructed to correlate the inhaler device properties, inhalation flow rate, particle characteristics and drug/excipient physicochemical properties with the resultant fine particle fraction. The r² value of established correlation was 0.74 indicating 86% variability in FPF values is explained by the model with the mean absolute errors of 0.22 for the predicted values. The authors believe that this model is capable of predicting the lung deposition pattern of a formulation with an acceptable precision when the type of inhaler device, inhalation flow rate, physicochemical behavior of active and inactive ingredients and the particle characteristics of DPI formulations are considered.

Formulation and optimization of sildenafil citrate-loaded PLGA large porous microparticles using spray freeze-drying technique: A factorial design and in-vivo pharmacokinetic study

The oral administration of sildenafil citrate (SC) for the treatment of pulmonary arterial hypertension is associated with several drawbacks. The study aimed to design and formulate SC-loaded inhalable poly (lactic-co-glycolic acid) [PLGA] large porous microparticles (LPMs) for pulmonary delivery. A factorial design was used to study the effect of the composition of LPMs on physicochemical properties. The study also evaluated the effect of glucose and L-leucine concentration on the formulation. The developed LPMs demonstrated an acceptable yield% (≤48%), large geometric particle size (>5µm) with a spherical and porous surface, and sustained drug release (up to 48 h). Increasing the concentration of poly(ethyleneimine) from 0.5% to 1% in SC-loaded LPMs led to an increase in entrapment efficiency from ~3.02% to ~94.48%. The optimum LPMs showed adequate aerodynamic properties with a 97.68 ± 1.07% recovery, 25.33 ± 3.32% fine particle fraction, and low cytotoxicity. Intratracheal administration of LPMs demonstrated significantly higher lung deposition, systemic bioavailability, and longer retention time (p < 0.05) compared to orally administered Viagra® tablets. The study concluded that SC-loaded LPMs could provide better therapeutic efficacy, reduced dosing frequency, and enhanced patient compliance.

Newer approaches and novel drugs for inhalational therapy for pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of small pulmonary arteries leading to increased pulmonary arterial pressure. Existing treatments acts to normalize vascular tone via three signaling pathways: the prostacyclin, the endothelin-1, and the nitric oxide. Although over the past 20 years, there has been considerable progress in terms of treatments for PAH, the disease still remains incurable with a disappointing prognosis.Areas covered: This review summarizes the pathophysiology of PAH, the advantages and disadvantages of the inhalation route, and assess the relative advantages various inhaled therapies for PAH. The recent studies concerning the development of controlled-release drug delivery systems loaded with available anti-PAH drugs have also been summarized.Expert opinion: The main obstacles of current pharmacotherapies of PAH are their short half-life, stability, and formulations, resulting in reducing the efficacy and increasing systemic side effects and unknown pathogenesis of PAH. The pulmonary route has been proposed for delivering anti-PAH drugs to overcome the shortcomings. However, the application of approved inhaled anti-PAH drugs is limited. Inhalational delivery of controlled-release nanoformulations can overcome these restrictions. Extensive studies are required to develop safe and effective drug delivery systems for PAH patients.

Inhaled combination of sildenafil and rosiglitazone improves pulmonary hemodynamics, cardiac function, and arterial remodeling

Currently, dual- or triple-drug combinations comprising different vasodilators are the mainstay for the treatment of pulmonary arterial hypertension (PAH). However, the patient outcome continues to be disappointing because the existing combination therapy cannot restrain progression of the disease. Previously, we have shown that when given as a monotherapy, long-acting inhaled formulations of sildenafil (a phosphodiesterase-5 inhibitor) and rosiglitazone (a peroxisome proliferator receptor-γ agonist) ameliorate PAH in rats. Thus, with a goal to develop a new combination therapy, we prepared and characterized poly(lactic-co-glycolic acid) (PLGA)-based long-acting inhalable particles of sildenafil and rosiglitazone. We then assessed the efficacy of the combinations of sildenafil and rosiglitazone, given in plain forms or as PLGA particles, in reducing mean pulmonary arterial pressure (mPAP) and improving pulmonary arterial remodeling and right ventricular hypertrophy (RVH) in Sugen 5416 plus hypoxia-induced PAH rats. After intratracheal administration of the formulations, we catheterized the rats and measured mPAP, cardiac output, total pulmonary resistance, and RVH. We also conducted morphometric studies using lung tissue samples and assessed the degree of muscularization, the arterial medial wall thickening, and the extent of collagen deposition. Compared with the plain drugs, given via the pulmonary or oral route as a single or dual combination, PLGA particles of the drugs, although given at a longer dosing interval compared with the plain drugs, caused more pronounced reduction in mPAP without affecting mean systemic pressure, improved cardiac function, slowed down right heart remodeling, and reduced arterial muscularization. Overall, PLGA particles of sildenafil and rosiglitazone, given as an inhaled combination, could be a viable alternative to currently available vasodilator-based combination therapy for PAH.

Prostaglandin E1 Attenuates Pulmonary Artery Remodeling by Activating Phosphorylation of CREB and the PTEN Signaling Pathway

The depletion of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) and phosphatase and tensin homolog (PTEN) is the critical mediator of pulmonary arterial hypertension (PAH). We hypothesized that the activation of phosphorylated CREB (pCREB) and PTEN could inhibit the AKT signaling pathway to attenuate pulmonary arterial remodeling in rats with monocrotaline-induced PAH. We observed decreased PTEN and pCREB in idiopathic PAH versus control tissue. We reduced PTEN using small interfering RNA in human control pulmonary arterial smooth muscle cells (PASMCs) and observed an increase in pAKT. Consistent with PTEN knockdown in PASMCs, prostaglandin E1 (PGE1) induced pCREB expression to stimulate PTEN protein expression and inhibited pAKT in a time- and dose-dependent manner. The enhanced proliferation and migration of PASMCs following PTEN knockdown were significantly inhibited by PGE1 treatment. The PGE1-induced elevation of PTEN expression in PTEN-depleted PASMCs was decreased by the application of a PKA inhibitor and a CBP-CREB interaction inhibitor. Supplementation with a novel emulsion composition comprising PGE1 in rats with monocrotaline-induced PAH prevented pulmonary arterial remodeling and improved hemodynamics via the induced expression of PTEN. We conclude that PGE1 recruits pCREB/PTEN to decrease the migration and proliferation of PASMCs associated with PAH. This finding elucidates a relevant underlying mechanism of the PGE1/CREB/PTEN signaling pathway to prevent progressive PAH.

Inhaled sildenafil as an alternative to oral sildenafil in the treatment of pulmonary arterial hypertension (PAH)

The practice of treating PAH patients with oral or intravenous sildenafil suffers from the limitations of short dosing intervals, peripheral vasodilation, unwanted side effects, and restricted use in pediatric patients. In this study, we sought to test the hypothesis that inhalable poly(lactic-co-glycolic acid) (PLGA) particles of sildenafil prolong the release of the drug, produce pulmonary specific vasodilation, reduce the systemic exposure of the drug, and may be used as an alternative to oral sildenafil in the treatment of PAH. Thus, we prepared porous PLGA particles of sildenafil using a water-in-oil-in-water double emulsion solvent evaporation method with polyethyleneimine (PEI) as a porosigen and characterized the formulations for surface morphology, respirability, in-vitro drug release, and evaluated for in vivo absorption, alveolar macrophage uptake, and safety. PEI increased the particle porosity, drug entrapment, and produced drug release for 36h. Fluorescent particles showed reduced uptake by alveolar macrophages. The polymeric particles were safe to rat pulmonary arterial smooth muscle cell and to the lungs, as evidenced by the cytotoxicity assay and analyses of the injury markers in the bronchoalveolar lavage fluid, respectively. Intratracheally administered sildenafil particles elicited more pulmonary specific and sustained vasodilation in SUGEN-5416/hypoxia-induced PAH rats than oral, intravenous, or intratracheal plain sildenafil did, when administered at the same dose. Overall, true to the hypothesis, this study shows that inhaled PLGA particles of sildenafil can be administered, as a substitute for oral form of sildenafil, at a reduced dose and longer dosing interval.

Aerosolizable modified-release particles of montelukast improve retention and availability of the drug in the lungs

Montelukast, a cysteinyl leukotriene receptor antagonist available as oral tablets, is used as a second-line therapy in asthma. In this study, we sought to enhance the availability of montelukast in the lungs by encapsulating the drug in poly (lactide-co-glycolic acid)-based (PLGA) respirable large porous particles. We determined the oral and lung specific availability of montelukast by assessing metabolic stability of the drug in the lung and liver homogenates, respectively. We similarly measured the oral and inhalational bioavailability by monitoring the pharmacokinetics and disposition of the drug in live animals. After preparing montelukast-loaded particles with various polymers, in the absence or presence of polyethylenimine (PEI-1), we characterized the particles for physical-chemical properties, entrapment efficiency, in vitro release, uptake by alveolar macrophages, deposition in the lungs, and safety after pulmonary administration. When incubated in lung or liver homogenates, the amount of intact drug in the lung homogenates was greater than that in the liver homogenates. Likewise, the extent of montelukast absorption via the lungs was greater than that via the oral route. Compared with smaller non-porous particles, large porous particles (PEI-1) were taken up by the alveolar macrophages at a lesser extent but deposited in the lungs at a greater extent. The levels of injury markers in the bronchoalveolar lavage fluid (BALF), collected from rat lungs treated with PEI-1, were no different from that in BALF collected from saline treated rats. Overall, the retention time and concentration of montelukast in the lungs can be increased by formulating the drug in large porous particles of PLGA.

Porous microscaffolds for 3D culture of dental pulp mesenchymal stem cells

The collective power of stem cells due to their evident advantages is incessantly investigated in regenerative medicine to be the next generation exceptional remedy for tissue regeneration and treatment of diseases. Stem cells are highly sensitive and a 3D culture environment is a requisite for its successful transplantation and integration with tissues. Porous microscaffolds can create a 3D microenvironment for growing stems cells, controlling their fate both in vitro and in vivo. In the present study, interconnected porous PLGA microscaffolds were fabricated, characterized and employed to propagate human dental pulp mesenchymal stem cells (DPMSCs) in vitro. The porous topography was investigated by scanning electron microscopy and the pore size was controlled by fabrication conditions such as the concentration of porogen. DPMSCs were cultured on microscaffolds and were evaluated for their morphology, attachment, proliferation, cell viability via MTT and molecular expression (RT-PCR). DPMSCs were adequately proliferated and adhered over the microscaffolds forming a 3D cell-microscaffold construct. The average number of DPMSCs grown on PLGA microscaffolds was significantly higher than monolayer 2D culture during 5th and 7th day. Moreover, cell viability and gene expression results together corroborated that microscaffolds maintained the viability, stemness and plasticity of the cultured dental pulp mesenchymal stem cells. The novel porous microscaffold developed acts as promising scaffold for 3D culture and survival and transplantation of stem cells for tissue engineering.

PLGA nano/micro particles encapsulated with pertussis toxoid (PTd) enhances Th1/Th17 immune response in a murine model

Poly(lactic-co-glycolic acid) (PLGA) based nano/micro particles were investigated as a potential vaccine platform for pertussis antigen. Presentation of pertussis toxoid as nano/micro particles (NP/MP) gave similar antigen-specific IgG responses in mice compared to soluble antigen. Notably, in cell line based assays, it was found that PLGA based nano/micro particles enhanced the phagocytosis of fluorescent antigen-nano/micro particles by J774.2 murine monocyte/macrophage cells compared to soluble antigen. More importantly, when mice were immunised with the antigen-nano/micro particles they significantly increased antigen-specific Th1 cytokines INF-γ and IL-17 secretion in splenocytes after in vitro re-stimulation with heat killed Bordetalla pertussis, indicating the induction of a Th1/Th17 response. Also, presentation of pertussis antigen in a NP/MP formulation is able to provide protection against respiratory infection in a murine model. Thus, the NP/MP formulation may provide an alternative to conventional acellular vaccines to achieve a more balanced Th1/Th2 immune response.

Polydopamine-Coated Porous Microspheres Conjugated with Immune Stimulators for Enhanced Cytokine Induction in Macrophages

Polydopamine-coated porous microsphere (PPM) is investigated as a simple and versatile immobilization strategy for immune-stimulating biomolecules to enhance delivery efficiency and immune-stimulating effects such as cytokine induction in macrophages. The PPMs, with diameters of about 2 μm, exhibit simultaneous and efficient incorporation of biomolecules (nucleotides and proteins), which is comparable to that achieved using microspheres carrying biomolecules internally by virtue of their porous structure. Ovalbumin-conjugated PPMs are internalized into macrophages efficiently and selectively via the phagocytic pathway, without any noticeable toxicity. Internalized CpG oligodeoxynucleotide (ODN)-conjugated PPMs (PPM-CpG) greatly enhance the induction of selected cytokines (TNF-α and IL-6) in RAW 264.7 cells compared to that by the soluble CpG ODN and ionic complexes. Therefore, PPMs generated in this study may serve as effective carriers of immune-stimulating biomolecules such as diverse toll-like receptor agonists.

Liposomal Aerosols of Nitric Oxide (NO) Donor as a Long-Acting Substitute for the Ultra-Short-Acting Inhaled NO in the Treatment of PAH

PURPOSE

This study seeks to develop a liposomal formulation of diethylenetriamine NONOate (DN), a long acting nitric oxide (NO) donor, with a goal to replace inhaled NO (iNO) in the treatment of pulmonary arterial hypertension (PAH).

METHODS

Liposomal formulations were prepared by a lipid film hydration method and modified with a cell penetrating peptide, CAR. The particles were characterized for size, polydispersity index (PDI), zeta potential, entrapment efficiency, storage and nebulization stability, and in-vitro release profiles. The cellular uptake and transport were assessed in rat alveolar macrophages (NR8383) and transforming growth factor β (TGF-β) activated rat pulmonary arterial smooth muscle cells (PASMCs). The fraction of the formulation that enters the systemic circulation, after intratracheal administration, was determined in an Isolated Perfused Rat Lung (IPRL) model. The safety of the formulations were assessed using an MTT assay and by measuring injury markers in the bronchoalveolar lavage (BAL) fluid; the pharmacological efficacy was evaluated by monitoring the changes in the mean pulmonary arterial (mPAP) and systemic pressure (mSAP) in a monocrotaline (MCT) induced-PAH rat model

RESULTS

Liposome size, zeta potential, and entrapment efficiency were 171 ± 4 nm, -37 ± 3 mV, and 46 ± 5%, respectively. The liposomes released 70 ± 5% of the drug in 8 h and were stable when stored at 4°C. CAR-conjugated-liposomes were taken up more efficiently by PASMCs than liposomes-without-CAR; the uptake of the formulations by rat alveolar macrophages was minimal. DN-liposomes did not increase lung weight, protein quantity, and levels of injury markers in the BAL fluid. Intratracheal CAR-liposomes reduced the entry of liposomes from the lung to blood; the formulations produced a 40% reduction in mPAP for 180 minutes.

CONCLUSION

This study establishes the proof-of-concept that peptide modified liposomal formulations of long-acting NO donor can be an alternative to short-acting iNO.

Large Porous Particles for Sustained Release of a Decoy Oligonucelotide and Poly(ethylenimine): Potential for Combined Therapy of Chronic Pseudomonas aeruginosa Lung Infections

We have recently demonstrated that the specific inhibition of nuclear factor-κB by a decoy oligonucleotide (dec-ODN) delivered through inhalable large porous particles (LPP) made of poly(lactic-co-glycolic acid) (PLGA) may be highly beneficial for long-term treatment of lung inflammation. Nevertheless, besides chronic inflammation, multifunctional systems aimed to control also infection are required in chronic lung diseases, such as cystic fibrosis (CF). In this work, we tested the hypothesis that engineering PLGA-based LPP with branched poly(ethylenimine) (PEI) may improve LPP properties for pulmonary delivery of dec-ODN, with particular regard to the treatment of Pseudomonas aeruginosa lung infections. After getting insight into the role of PEI on the technological properties of PLGA-based LPP for delivery of dec-ODN, the putative synergistic effect of PEI free or PEI released from LPP on in vitro antimicrobial activity of tobramycin (Tb) and aztreonam (AZT) against P. aeruginosa was elucidated. Meanwhile, cytotoxicity studies on A549 cells were carried out. Results clearly demonstrate that the dry powders have promising aerosolization properties and afford a prolonged in vitro release of both dec-ODN and PEI. The encapsulation of PEI into LPP results in a 2-fold reduction of the minimum inhibitory concentration of AZT, while reducing the cytotoxic effect of PEI. Of note, the developed ODN/PLGA/PEI LPP persisted at lung at least for 14 days after intratracheal administration in rats where they can provide sustained and combined release of dec-ODN and PEI. dec-ODN will likely act as an anti-inflammatory drug, while PEI may enhance the therapeutic activity of inhaled antibiotics, which are commonly employed for the treatment of concomitant lung infections.

Polymeric micro/nanoparticles: Particle design and potential vaccine delivery applications

Particle based adjuvant showed promising signs on delivering antigen to immune cells and acting as stimulators to elicit preventive or therapeutic response. Nevertheless, the wide size distribution of available polymeric particles has so far obscured the immunostimulative effects of particle adjuvant, and compromised the progress in pharmacological researches. To conquer this hurdle, our research group has carried out a series of researches regarding the particulate vaccine, by taking advantage of the successful fabrication of polymeric particles with uniform size. In this review, we highlight the insight and practical progress focused on the effects of physiochemical property (e.g. particle size, charge, hydrophobicity, surface chemical group, and particle shape) and antigen loading mode on the resultant biological/immunological outcome. The underlying mechanisms of how the particles-based vaccine functioned in the immune system are also discussed. Based on the knowledge, particles with high antigen payload and optimized attributes could be designed for expected adjuvant purpose, leading to the development of high efficient vaccine candidates.

Development of porous PLGA/PEI1.8k biodegradable microspheres for the delivery of mesenchymal stem cells (MSCs)

Multipotent mesenchymal stem cells (MSCs) promise a therapeutic alternative for many debilitating and incurable diseases. However, one of the major limitations for the therapeutic application of human MSC (hMSC) is the lengthy ex vivo expansion time for preparing a sufficient amount of cells due to the low engraftment rate after transplantation. To solve this conundrum, a porous biodegradable polymeric microsphere was investigated as a potential scaffold for the delivery of MSCs. The modified water/oil/water (W1/O/W2) double emulsion solvent evaporation method was used for the construction of porous microspheres. PEI1.8k was blended with poly(lactic-co-glycolic acid) (PLGA) to enhance electrostatic cellular attachment to the microspheres. The porous PLGA/PEI1.8k (PPP) particles demonstrated an average particle size of 290μm and an average pore size of 14.3μm, providing a micro-carrier for the MSC delivery. PPP particles allowed for better attachment of rMSCs than non-porous PLGA/PEI1.8k (NPP) particles and non-porous (NP) and porous PLGA (PP) microspheres. rMSC successfully grew on the PPP particles for 2weeks in vitro. Next, PPP particles loaded with 3 different amounts of hMSC showed increased in vivo engraftment rates and maintained the stemness characteristics of hMSC compared with hMSCs-alone group in rats 2weeks after intramyocardial administration. These customized PPP particles for MSC delivery are a biodegradable and injectable scaffold that can be used for clinical applications.

Peptide-coated liposomal fasudil enhances site specific vasodilation in pulmonary arterial hypertension

This study sought to develop a liposomal delivery system of fasudil—an investigational drug for the treatment of pulmonary arterial hypertension (PAH)—that will preferentially accumulate in the PAH lungs. Liposomal fasudil was prepared by film-hydration method, and the drug was encapsulated by active loading. The liposome surface was coated with a targeting moiety, CARSKNKDC, a cyclic peptide; the liposomes were characterized for size, polydispersity index, zeta potential, and storage and nebulization stability. The in vitro drug release profiles and uptake by TGF-β activated pulmonary arterial smooth muscle cells (PASMC) and alveolar macrophages were evaluated. The pharmacokinetics were monitored in male Sprague–Dawley rats, and the pulmonary hemodynamics were studied in acute and chronic PAH rats. The size, polydispersity index (PDI), and zeta potential of the liposomes were 206–216 nm, 0.058–0.084, and −20–42.7 mV, respectively. The formulations showed minimal changes in structural integrity when nebulized with a commercial microsprayer. The optimized formulation was stable for >4 weeks when stored at 4 °C. Fasudil was released in a continuous fashion over 120 h with a cumulative release of 76%. Peptide-linked liposomes were taken up at a higher degree by TGF-β activated PASMCs; but alveolar macrophages could not engulf peptide-coated liposomes. The formulations did not injure the lungs; the half-life of liposomal fasudil was 34-fold higher than that of plain fasudil after intravenous administration. Peptide-linked liposomal fasudil, as opposed to plain liposomes, reduced the mean pulmonary arterial pressure by 35–40%, without influencing the mean systemic arterial pressure. This study establishes that CAR-conjugated inhalable liposomal fasudil offers favorable pharmacokinetics and produces pulmonary vasculature specific dilatation.

Delivery strategies for sustained drug release in the lungs

Drug delivery to the lungs by inhalation offers a targeted drug therapy for respiratory diseases. However, the therapeutic efficacy of inhaled drugs is limited by their rapid clearance in the lungs. Carriers providing sustained drug release in the lungs can improve therapeutic outcomes of inhaled medicines because they can retain the drug load within the lungs and progressively release the drug locally at therapeutic levels. This review presents the different formulation strategies developed to control drug release in the lungs including microparticles and the wide array of nanomedicines. Large and porous microparticles offer excellent aerodynamic properties. Their large geometric size reduces their uptake by alveolar macrophages, making them a suitable carrier for sustained drug release in the lungs. Similarly, nanocarriers present significant potential for prolonged drug release in the lungs because they largely escape uptake by lung-surface macrophages and can remain in the pulmonary tissue for weeks. They can be embedded in large and porous microparticles in order to facilitate their delivery to the lungs. Conjugation of drugs to polymers as polyethylene glycol can be particularly beneficial to sustain the release of proteins in the lungs as it allows high protein loading. Drug conjugates can be readily delivered to respiratory airways by any current nebulizer device. Nonetheless, liposomes represent the formulation most advanced in clinical development. Liposomes can be prepared with lipids endogenous to the lungs and are particularly safe. Their composition can be adjusted to modulate drug release and they can encapsulate both hydrophilic and lipophilic compounds with high drug loading.

Dry powders for oral inhalation free of lactose carrier particles

Dry powder inhaler (DPI) products have traditionally comprised a simple formulation of micronised drug mixed with a carrier excipient, typically lactose monohydrate. The presence of the carrier is aimed at overcoming issues of poor flowability and dispersibility, associated with the cohesive nature of small, micronised active pharmaceutical ingredient (API) particles. Both the powder blend and the DPI device must be carefully designed so as to ensure detachment of the micronised drug from the carrier excipient on inhalation. Over the last two decades there has been a significant body of research undertaken on the design of carrier-free formulations for DPI products. Many of these formulations are based on sophisticated particle engineering techniques; a common aim in formulation design of carrier-free products being to reduce the intrinsic cohesion of the particles, while maximising dispersion and delivery from the inhaler. In tandem with the development of alternative formulations has been the development of devices designed to ensure the efficient delivery and dispersion of carrier-free powder on inhalation. In this review we examine approaches to both the powder formulation and inhaler design for carrier-free DPI products.

Perioperative pharmacological management of pulmonary hypertensive crisis during congenital heart surgery

Pulmonary hypertensive crisis is an important cause of morbidity and mortality in patients with pulmonary arterial hypertension secondary to congenital heart disease (PAH-CHD) who require cardiac surgery. At present, prevention and management of perioperative pulmonary hypertensive crisis is aimed at optimizing cardiopulmonary interactions by targeting prostacyclin, endothelin, and nitric oxide signaling pathways within the pulmonary circulation with various pharmacological agents. This review is aimed at familiarizing the practitioner with the current pharmacological treatment for dealing with perioperative pulmonary hypertensive crisis in PAH-CHD patients. Given the life-threatening complications associated with pulmonary hypertensive crisis, proper perioperative planning can help anticipate cardiopulmonary complications and optimize surgical outcomes in this patient population.

Aerosolized montelukast polymeric particles-an alternative to oral montelukast-alleviate symptoms of asthma in a rodent model

PURPOSE

Cysteinyl leukotrienes (CysLTs) propagate inflammatory reactions that result from allergen exposure in asthma. Montelukast, a CysLT type-1 receptor antagonist, disrupts mediator-receptor interactions and minimizes inflammatory response. In this study, we have evaluated anti-asthmatic efficacy of inhalable montelukast-loaded large porous particulate formulations in ovalbumin-induced rat airway inflammation model that mimics asthma.

METHODS

The anti-inflammatory effects of a montelukast-loaded formulation were investigated in rats by measuring the total protein content, levels of injury markers and number of inflammatory cells in the bronchoalveolar lavage fluid (BALF). The histopathological studies assessed the morphological and structural changes that occur in asthmatic lungs. Animals were also challenged with methacholine to examine the airway hyper-reactivity.

RESULTS

Compared with healthy animals, asthmatic animals showed a 3.8- and 4.77-fold increase in the protein content and number of inflammatory cells in BALF, respectively. Intratracheal montelukast particles reduced the protein content by 3.3-fold and the number of inflammatory cells by 2.62-fold. Also, montelukast particles reduced the lactate dehydrogenase (LDH) and myeloperoxidase (MPO) levels by a 4.87- and 6.8-fold in BALF, respectively. Montelukast particles reduced the airway wall thickness by 2.5-fold compared with untreated asthmatic lungs. Further, particulate formulation protected the lungs against methacholine-induced bronchial provocation (p < 0.05).

CONCLUSIONS

Respirable large porous particles containing montelukast alleviated allergen-induced inflammatory response in an animal model and prevented histological changes associated with asthma. Thus montelukast-loaded large porous polylactic acid (PLA) particles could be an aerosolized delivery approach for administration of currently available oral montelukast.

Particles from preformed polymers as carriers for drug delivery

Biodegradable and biocompatible polymers are widely used for the encapsulation of drug molecules. Various particulate carriers with different sizes and characteristics have been prepared by miscellaneous techniques. In this review, we reported the commonly used preformed polymer based techniques for the preparation of micro and nano-structured materials intended for drug encapsulation. A description of polymer-solvent interaction was provided. The most widely used polymers were reported and described and their related research studies were mentioned. Moreover, principles of each technique and its crucial operating conditions were described and discussed. Recent applications of all the reported techniques in drug delivery were also reviewed.

Starch-coated magnetic liposomes as an inhalable carrier for accumulation of fasudil in the pulmonary vasculature

In this study, we tested the feasibility of magnetic liposomes as a carrier for pulmonary preferential accumulation of fasudil, an investigational drug for the treatment of pulmonary arterial hypertension (PAH). To develop an optimal inhalable formulation, various magnetic liposomes were prepared and characterized for physicochemical properties, storage stability and in vitro release profiles. Select formulations were evaluated for uptake by pulmonary arterial smooth muscle cells (PASMCs) - target cells - using fluorescence microscopy and HPLC. The efficacy of the magnetic liposomes in reducing hyperplasia was tested in 5-HT-induced proliferated PASMCs. The drug absorption profiles upon intratracheal administration were monitored in healthy rats. Optimized spherical liposomes - with mean size of 170 nm, zeta potential of -35mV and entrapment efficiency of 85% - exhibited an 80% cumulative drug release over 120 h. Fluorescence microscopic study revealed an enhanced uptake of liposomes by PASMCs under an applied magnetic field: the uptake was 3-fold greater compared with that observed in the absence of magnetic field. PASMC proliferation was reduced by 40% under the influence of the magnetic field. Optimized liposomes appeared to be safe when incubated with PASMCs and bronchial epithelial cells. Compared with plain fasudil, intratracheal magnetic liposomes containing fasudil extended the half-life and area under the curve by 27- and 14-fold, respectively. Magnetic-liposomes could be a viable delivery system for site-specific treatment of PAH.

Hydrogels for controlled pulmonary delivery

A significant number of research articles have focused on pulmonary delivery as an alternative administration route owing to no first-pass metabolism, low protease activity, thin epithelium barrier and large surface area in the lung system. Controlled release in the pulmonary delivery system further reduces loading dose, frequency of dosing and systemic side effects, and also increases duration of action and patient compliance. Compared with other microparticles used in controlled-release pulmonary administration, hydrogels (3D polymeric matrix networks) have recently been investigated due to their swelling and mucoadhesive properties that could help bypass pulmonary delivery barriers. This review introduces controlled-release drug delivery to the lung, followed by a summary of currently available approaches for controlled-release pulmonary drug delivery. Lastly, the origin, advantages, detailed applications and concerns of hydrogels in pulmonary delivery are discussed.

Preparation of methotrexate-loaded, large, highly-porous PLLA microspheres by a high-voltage electrostatic antisolvent process

A high-voltage (10 kV) electrostatic antisolvent process was used to prepare methotrexate (MTX)-loaded, large, highly-porous poly-L-lactide (PLLA) microspheres. MTX solution in dimethyl sulfoxide (DMSO) and PLLA solution in dichloromethane (DCM) were homogeneously mixed, and then ammonium bicarbonate (AB) aqueous solution was added. The mixed solution was emulsified by ultrasonication with Pluronic F127 (PF127) as an emulsion stabilizer. The emulsion was electrosprayed by the specific high-voltage apparatus and dropped into a 100 mL of ethanol, which acted as an antisolvent for the solute and extracted DMSO and DCM, causing the co-precipitation of PLLA and MTX, thus forming microspheres with AB aqueous micro-droplets uniformly inlaid. The obtained MTX-PLLA microspheres were subsequently lyophilized to obtain large, highly-porous MTX-PLLA microspheres, which exhibited an identifiable spherical shape and a rough surface furnished with open pores, with a mean particle size of 25.0 μm, mass median aerodynamic diameter of 3.1 ± 0.2 μm, fine-particle fraction of 57.1 ± 1.6 %, and porosity of 81.8 %; furthermore, they offered a sustained release of MTX. X-ray diffraction and Fourier transform-infrared spectra revealed that no crystallinity or alteration of chemical structure occurred during the high-voltage electrostatic antisolvent process, which in this study was proved to have great potential for preparing highly-porous drug-loaded polymer microspheres for use in pulmonary drug delivery.

In vitro, in vivo and ex vivo models for studying particle deposition and drug absorption of inhaled pharmaceuticals

Delivery of therapeutic agents via the pulmonary route has gained significant attention over the past few decades because this route of administration offers multiple advantages over traditional routes that include localized action, non-invasive nature and favorable lung-to-plasma ratio. However, assessment of post administration behavior of inhaled pharmaceuticals-such as deposition of particles over the respiratory airways, interaction with the respiratory fluid and movement across the air-blood barrier-is challenging because the lung is a very complex organs that is composed of airways with thousands of bifurcations with variable diameters. Thus, much effort has been put forward to develop models that mimic human lungs and allow evaluation of various pharmaceutical and physiological factors that influence the deposition and absorption profiles of inhaled formulations. In this review, we sought to discuss in vitro, in vivo and ex vivo models that have been extensively used to study the behaviors of airborne particles in the lungs and determine the absorption of drugs after pulmonary administration. We have provided a summary of lung cast models, cascade impactors, noninvasive imaging, intact animals, cell culture and isolated perfused lung models as tools to evaluate the distribution and absorption of inhaled particles. We have also outlined the limitations of currently used models and proposed future studies to enhance the reproducibility of these models.

Supercritical fluid technology based large porous celecoxib-PLGA microparticles do not induce pulmonary fibrosis and sustain drug delivery and efficacy for several weeks following a single dose

Although pulmonary dosing of large porous particles has been shown to sustain drug delivery for a few days, there are no reports on safety or long term delivery. In this study we prepared large porous poly(lactide-co-glycolide) (PLGA) microparticles of celecoxib using supercritical fluid pressure-quench technology and demonstrated 4.8-, 15.7-, and 2.1-fold greater drug levels in lung, bronchoalveolar lavage fluid (BAL), and plasma compared to conventional microparticles on day 21 after a single intratracheal dosing of dry powders in A/J mice. Porous particle based delivery was 50.2-, 95.5-, and 7.7-fold higher compared to plain drug in the lung, BAL, and plasma, respectively. Toxicity of the formulations was assessed on day 21 following a fibrosis assessment protocol in A/J mice. There was no significant change in lactate dehydrogenase (LDH), total protein, and total cell counts in the BAL, and soluble collagen levels in the lung tissue following particle or drug treatments. Lung histology indicated no significant hyperplasia, granuloma, or collagen deposition in the treated groups. Chemopreventive potential of celecoxib porous particles was assessed in a benzo[a]pyrene (B[a]P) induced lung cancer model in A/J mice, on day 60 following a single intratracheal dose with or without single intravenous paclitaxel/carboplatin treatment. The combination group was more effective than individual groups, with the inhibition of tumor multiplicity and reduction of vascular endothelial growth factor in the BAL being 70 and 58%, respectively. Thus, large porous celecoxib-PLGA microparticles prepared using supercritical fluid technology exhibited sustained drug delivery and anti-tumor efficacy, without causing any significant toxicity.

Inhaled PLGA particles of prostaglandin E₁ ameliorate symptoms and progression of pulmonary hypertension at a reduced dosing frequency

This study sought to investigate the efficacy of a noninvasive and long acting polymeric particle based formulation of prostaglandin E1 (PGE1), a potent pulmonary vasodilator, in alleviating the signs of pulmonary hypertension (PH) and reversing the biochemical changes that occur in the diseased lungs. PH rats, developed by a single subcutaneous injection of monocrotaline (MCT), were treated with two types of polymeric particles of PGE1, porous and nonporous, and intratracheal or intravenous plain PGE1. For chronic studies, rats received either intratracheal porous poly(lactic-co-glycolic acid) (PLGA) particles, once- or thrice-a-day, or plain PGE1 thrice-a-day for 10 days administered intratracheally or intravenously. The influence of formulations on disease progression was studied by measuring the mean pulmonary arterial pressure (MPAP), evaluating right ventricular hypertrophy and assessing various molecular and cellular makers including the degree of muscularization, platelet aggregation, matrix metalloproteinase-2 (MMP-2), and proliferating cell nuclear antigen (PCNA). Both plain PGE1 and large porous particles of PGE1 reduced MPAP and right ventricular hypertrophy (RVH) in rats that received the treatments for 10 days. Polymeric porous particles of PGE1 produced the same effects at a reduced dosing frequency compared to plain PGE1 and caused minimal off-target effects on systemic hemodynamics. Microscopic and immunohistochemical studies revealed that porous particles of PGE1 also reduced the degree of muscularization, von Willebrand factor (vWF), and PCNA expression in the lungs of PH rats. Overall, our study suggests that PGE1 loaded inhalable particulate formulations improve PH symptoms and arrest the progression of disease at a reduced dosing frequency compared to plain PGE1.

Engineered PLGA nano- and micro-carriers for pulmonary delivery: challenges and promises

Objectives

The aim of this review is to summarize the current state-of-the-art in poly(lactic-co-glycolic acid) (PLGA) carriers for inhalation. It presents the rational of use, the potential and the recent advances in developing PLGA microparticles and nanoparticles for pulmonary delivery. The most promising particle engineering strategies are discussed, highlighting the advantages along with the major challenges for researchers working in this field.

Key findings

Biodegradable polymer carriers, such as PLGA particles, may permit effective protection and long-term delivery of the inhaled drug and, when adequately engineered, its efficient transport to the target. The carrier can be designed for inhalation on the basis of several strategies through the adequate combination of available particle technologies and excipients. In so doing, the properties of PLGA particles can be finely tuned at micro-size and nano-size level to fulfill specific therapeutic needs. This means not only to realize optimal in vitro/in vivo lung deposition of the formulation, which is still crucial, but also to control the fate of the drug in the lung after particle landing.

Summary

Although many challenges still exist, PLGA carriers may be highly beneficial and present a new scenario for patients suffering from chronic lung diseases and for pharmaceutical companies working to develop novel inhaled products.