Formulation and in vivo evaluation of sodium alendronate spray-dried microparticles intended for lung delivery

Modern trends in the formulation of microparticles for lung delivery using porogens: methods, principles and examples

Inhalation drug administration is increasingly used for local pharmacotherapy of lung disorders and as an alternative route for systemic drug delivery. Modern inhalation powder systems aim to target drug deposition in the required site of action. Large porous particles (LPP), characterized by an aerodynamic diameter over 5 μm, density below 0.4 g/cm3, and the ability to avoid protective lung mechanisms, come to the forefront of the research. They are mostly prepared by spray techniques such as spray drying or lyophilization using pore-forming substances (porogens). These substances could be gaseous, solid, or liquid, and their selection depends on their polarity, solubility, and mutual compatibility with the carrier material and the drug. According to the pores-forming mechanism, porogens can be divided into groups, such as osmogens, extractable porogens, and porogens developing gases during decomposition. This review characterizes modern trends in the formulation of solid microparticles for lung delivery; describes the mechanisms of action of the most often used porogens, discusses their applicability in various formulation methods, emphasizes spray techniques; and documents discussed topics by examples from experimental studies.

Co-spray dried inhalable composite powders of ciprofloxacin and alginate oligosaccharide as anti-biofilm therapy

The treatment of chronic respiratory infections caused by biofilm formation are extremely challenging owing to poor drug penetration into the complex biofilm structure and high drug resistance. Local delivery of an antibiotic together with a non-antibiotic adjuvant to the lungs could often enhance the therapeutic responses by targeting different bacterial growth pathways and minimizing drug resistance. In this study, we designed new inhalable dry powders containing ciprofloxacin (CIP) and OligoG (Oli, a low-molecular-weight alginate oligosaccharide impairing the mucoid biofilms by interacting with their cationic ions) to combat respiratory bacterial biofilm infections. The resulting powders were characterized with respect to their morphology, solid-state property, surface chemistry, moisture sorption behavior, and dissolution rate. The aerosol performance and storage stability of the dry powders were also evaluated. The results showed that inhalable dry powders composed of CIP and Oli could be readily accomplished via the wet milling and spray drying process. Upon the storage under 20 ± 2 °C/20 ± 2 % relative humidity (RH) for one month, there was no significant change in the in vitro aerosol performances of the dry powders. In contrast, the dry powders became non-inhalable following the storage at 20 ± 2 °C/53 ± 2 % RH for one month due to the hygroscopic nature of Oli, which could be largely prevented by incorporation of leucine. Collectively, this study suggests that the newly developed co-spray-dried powders composed of CIP and Oli might represent a promising and alternative treatment strategy against respiratory bacterial biofilm infections.

Development of Large Hollow Particles for Pulmonary Delivery of Cyclosporine A

The purpose of this study was to prepare large hollow particles (LHPs) by spray drying for pulmonary delivery of cyclosporine A (CsA), using L-Leucine (LEU) and hydroxypropyl methylcellulose (HPMC) as excipients and ammonium bicarbonate (AB) as a porogen. The prepared LHPs were spherical particles composed of both CsA and LEU on the surface and HPMC on the inner layer. The formulation of CsA-LEU-0.8HPMC-AB as typical LHPs showed excellent in vitro aerodynamic performance with a minimum mass median aerodynamic diameter (MMAD) of 1.15 μm. The solubility of CsA-LEU-0.8HPMC-AB was about 5.5-fold higher than that of raw CsA, and the dissolution of CsA-LEU-0.8HPMC-AB suggested that the drug was released within 1 h. The cell viability of the A549 cell line showed that CsA-LEU-0.8HPMC-AB was safe for delivering CsA to the lungs. In addition, inhalation administration of CsA-LEU-0.8HPMC-AB with the Cmax and AUC0-∞ increasing by about 2-fold and 2.8-fold compared with the oral administration of Neoral® could achieve therapeutic drug concentrations with lower systemic exposure and significantly improve the in vivo bioavailability of CsA. From these findings, the LHPs, with the advantage of avoiding alveolar macrophage clearance, could be a viable choice for delivering CsA by inhalation administration relative to oral administration.

Dual functional pullulan-based spray-dried microparticles for controlled pulmonary drug delivery

Two main challenges are associated with current spray-dried microparticles for inhalation, including the enhancement of aerosolization performance of microparticles and the creation of sustained drug release for continuous treatment on-site. For achieving these purposes, pullulan was explored as a novel excipient to prepare spray-dried inhalable microparticles (with salbutamol sulphate, SS, as a model drug), which were further modified by additives of leucine (Leu), ammonium bicarbonate (AB), ethanol and acetone. It was demonstrated that all pullulan-based spray-dried microparticles had improved flowability and enhanced aerosolization behavior, with the fine particle (<4.46µm) fraction of 42.0-68.7% w/w, much higher than 11.4% w/w of lactose-SS. Moreover, all modified microparticles showed augmented emitted fractions of 88.0-96.9% w/w, over 86.5% w/w of pullulan-SS. The pullulan-Leu-SS and pullulan-(AB)-SS microparticles demonstrated further increased fine particle (<1.66µm) doses of 54.7µg and 53.3µg respectively, surpassing that (49.6µg) of pullulan-SS, suggesting an additionally increased drug deposition in the deep lungs. Furthermore, pullulan-based microparticles revealed sustained drug release profiles with elongated time (60mins) over the control (2mins). Clearly, pullulan has a great potential to construct dual functional microparticles for inhalation with improved pulmonary delivery efficiency and sustained drug release on-site.

Porous hydroxyapatite scaffold orchestrated with bioactive coatings for rapid bone repair

Current bioceramic scaffolds for critical-size bone defects are still facing various challenges such as the poor capability of self-resorption, vascularization and osteogenesis. Herein, a composite scaffold (HOD) is fabricated by integrating bioactive coatings of konjac glucomannan (KGM) and deferoxamine (DFO) into porous hydroxyapatite scaffold (HA), where KGM coating induces the self-resorption of HOD after implanting and DFO promoted the vascularization at the defected bone. Porous HA scaffolds with 200-400 μm of pore sizes were prepared and these bioactive coatings were successfully deposited on the scaffold, which was confirmed by SEM. MC3T3-E1 cells could be tightly attached to the pore wall of HOD and the obvious osteogenic differentiation was clearly displayed after 14 days of co-culture. Besides, HOD displayed the potential of promoting the vascularization of HUVECs. Importantly, the accelerated degradation of HOD was observed in a macrophage-associated acidic medium, which led to the self-resorption of HOD in vivo. Micro-CT images showed that HOD was gradually replaced by newly formed bone, achieving a balance between the new bone formation and the scaffold degradation. The rapid bone repairing of the femoral defects in rats was displayed for HOD in comparison to the HA scaffold. Moreover, the therapeutic mechanism of HOD was highly associated with promoted osteogenesis and vascularization. Collectively, the porous ceramic scaffold orchestrated with bioactive coatings may be a promising strategy for repairing of the large bone defect.

Promoted Antitumor Activity of Myricetin against Lung Carcinoma Via Nanoencapsulated Phospholipid Complex in Respirable Microparticles

PURPOSE

Myricetin (MYR) flavonoid is well-recognized for its antioxidant, anti-inflammatory and anti-tumor potential. Introducing nanomedicine was the ultimate resort to solve the imperfections of this nutraceutical, namely solubility, stability and delivery issues. The study, thus, aims at developing inhalable microparticles comprising MYR solid lipid nanoparticles (SLNs) for lung cancer therapy.

METHODS

A two-step preparation procedure starting with complexation of MYR with the phospholipid Lipoid-S100, followed by nanoencapsulation in Gelucire-based, surfactant-free SLNs was developed. SLNs were characterized in terms of physicochemical properties, MYR loading, release behavior as well as anti-tumor potential and cellular uptake. Respirable microparticles were then obtained by spray drying SLNs with carbohydrate carriers. Their size, flowability and pulmonary deposition pattern were assessed.

RESULTS

Optimized SLNs were 75.98 nm in diameter with a zeta-potential of -22.5 mV, and an encapsulation efficiency of 84.5%. Attempts to ameliorate drug loading implicate MYR-phospholipid complexation (MYR-PH-CPX) prior to its entrapment in SLNs, which ensured 5-fold increase in drug loading. Viability assays were modified to guarantee MYR chemical stability. Superior antitumor activity of MYR-phospholipid-complex and 3-fold reduction in IC₅₀ were accomplished with MYR-SLNs. This could be related to enhanced cellular uptake revealed by confocal imaging and doubled fluorescence intensity. SLNs entrapping MYR-PH-CPX were spray-dried with carbohydrate carriers to produce respirable microparticles. The latter ensured MMAD of 2.39 μm and span index of 1.84, in addition to good flowability and > 80% release over 8 h. Deposition experiments revealed MMAD of 2.77 μm, FPF of 81.23 and EF of 93% indicating particle deposition in the targeted bronchial region.

CONCLUSIONS

The study highlights the ability of phospholipid-complex on the nanoencapsulation, cellular uptake and antitumor activity of MYR. Formulation of respirable microparticles gives promises of efficacious therapy of lung carcinoma.

Rifampicin-Carbohydrate Spray-Dried Nanocomposite: A Futuristic Multiparticulate Platform For Pulmonary Delivery

Purpose

Rifampicin, a first-line anti-tuberculosis drug, was loaded into a carbohydrate-based spray-dried nanocomposite with the aim to design a dry powder inhalation formulation. This strategy can enable efficient distribution of rifampicin within the lungs, localizing its action, enhancing its bioavailability and reducing its systemic exposure consequently side effects.

Methods

The respirable nanocomposite was developed utilizing spray drying of rifampicin nanosuspension employing a combination of mannitol, maltodextrin and leucine as microparticles matrix formers. Detailed physicochemical characterization and in-vitro inhalation properties of the nanocomposite particles were investigated. Compatibility studies were carried out using differential scanning calorimetry and Infrared spectroscopy techniques. Moreover, pulmonary in-vitro cytotoxicity on alveolar basal epithelial cells was performed and evaluated.

Results

Nanocomposite-based rifampicin-loaded dry inhalable powder containing maltodextrin, mannitol and leucine at a ratio of 2:1:1 was successfully formulated. Rifampicin loading efficiency into the carbohydrate nanocomposite was in the range of 89.3% to 99.2% w/w with a suitable particle size (3.47-6.80 µm) and unimodal size distribution. Inhalation efficiency of the spray-dried nanosuspension was significantly improved after transforming into an inhalable carbohydrate composite. Specifically, mannitol-based powder had higher respirable fraction (49.91%) relative to the corresponding formulation of maltodextrin. Additionally, IC₅₀ value of rifampicin nanocomposite was statistically significantly higher than that of free drug thus providing superior safety profile on lung tissues.

Conclusion

The obtained results suggested that spray drying of rifampicin nanosuspension utilizing carbohydrates as matrix formers can enhance drug inhalation performance and reduce cellular toxicity. Thus, representing an effective safer pulmonary delivery of anti-tuberculosis drugs.

Bioavailability Enhancement of Poorly Soluble Drugs: The Holy Grail in Pharma Industry

Background:

Bioavailability, one of the prime pharmacokinetic properties of a drug, is defined as the fraction of an administered dose of unchanged drug that reaches the systemic circulation and is used to describe the systemic availability of a drug. Bioavailability assessment is imperative in order to demonstrate whether the drug attains the desirable systemic exposure for effective therapy. In recent years, bioavailability has become the subject of importance in drug discovery and development studies.

Methods:

A systematic literature review in the field of bioavailability and the approaches towards its enhancement have been comprehensively done, purely focusing upon recent papers. The data mining was performed using databases like PubMed, Science Direct and general Google searches and the collected data was exhaustively studied and summarized in a generalized manner.

Results:

The main prospect of this review was to generate a comprehensive one-stop summary of the numerous available approaches and their pharmaceutical applications in improving the stability concerns, physicochemical and mechanical properties of the poorly water-soluble drugs which directly or indirectly augment their bioavailability.

Conclusion:

The use of novel methods, including but not limited to, nano-based formulations, bio-enhancers, solid dispersions, lipid-and polymer-based formulations which provide a wide range of applications not only increases the solubility and permeability of the poorly bioavailable drugs but also improves their stability, and targeting efficacy. Although, these methods have drastically changed the pharmaceutical industry demand for the newer potential methods with better outcomes in the field of pharmaceutical science to formulate various dosage forms with adequate systemic availability and improved patient compliance, further research is required.

Supercritical Fluid-Assisted Porous Microspheres for Efficient Delivery of Insulin and Inhalation Therapy of Diabetes

Pulmonary delivery of drugs has attracted increasing attention in healthcare, as the lungs are an easily accessible site for noninvasive systemic delivery of drugs. Although pulmonary inhalation of porous microparticles has been shown to sustain drug delivery, there are limited reports on efficient delivery of insulin and inhalation therapy of diabetes based on supercritical carbon dioxide (SC-CO₂ ) technology. Herein, this study reports the fabrication of insulin-loaded poly-l-lactide porous microspheres (INS-PLLA PMs) by using the SC-CO₂ technology, and their use as an inhalation delivery system potentially for diabetes therapy. Biocompatibility and delivery efficiency of the PLLA PMs in the lungs are investigated. The PLLA PMs show negligible toxicity to lung-derived cells, resulting in no significant reduction in cell viability, as well as levels of various inflammatory mediators such as interleukin (IL)-6, IL-8, and tumor necrosis factor-α, compared with the negative control group. INS-PLLA PMs are further efficiently deposited in the trachea and the bronchi of superior lobes of the lungs, which exhibit pronounced hypoglycemic activity in induced diabetic rats. Together, the results demonstrate that the INS-PLLA PMs have a strong potential as an effective strategy for inhalation treatment of diabetes.

Carrier-free combination dry powder inhaler formulation of ethionamide and moxifloxacin for treating drug-resistant tuberculosis

This study aimed to develop a combination dry powder formulation of ethionamide and moxifloxacin HCl as this combination is synergistic against drug-resistant Mycobacterium tuberculosis (Mtb). L-leucine (20% w/w) was added in the formulations to maximize the process yield. Moxifloxacin HCl and/or ethionamide powders with/without L-leucine were produced using a Buchi Mini Spray-dryer. A next generation impactor was used to determine the in vitro aerosolization efficiency. The powders were also characterized for other physicochemical properties and cytotoxicity. All the spray-dried powders were within the aerodynamic size range of <5.0 µm except ethionamide-only powder (6.0 µm). The combination powders with L-leucine aerosolized better (% fine particle fraction (FPF): 61.3 and 61.1 for ethionamide and moxifloxacin, respectively) than ethionamide-only (%FPF: 9.0) and moxifloxacin-only (%FPF: 30.8) powders. The combination powder particles were collapsed with wrinkled surfaces whereas moxifloxacin-only powders were spherical and smooth and ethionamide-only powders were angular-shaped flakes. The combination powders had low water content (<2.0%). All the powders were physically stable at 15% RH and 25 ± 2 °C during 1-month storage and tolerated by bronchial epithelial cell-lines up to 100 µg/ml. The improved aerosolization of the combination formulation may be helpful for the effective treatment of drug-resistant tuberculosis. Further studies are required to understand the mechanisms for improved aerosolization and test the synergistic activity of the combination powder.

Preparation and Characterization of Doripenem-Loaded Microparticles for Pulmonary Delivery

Background: Pneumonia is a bacterial lower respiratory tract infection that has a high morbidity rate. The gram-negative pathogen Pseudomonas aeruginosa is a significant cause of nosocomial infections and ventilator-associated pneumonias and is mainly treated by carbapenems. Doripenem is a carbapenem drug, which has a broad-spectrum antibacterial activity. The aim of this study was to develop doripenem-loaded chitosan microparticles for pulmonary administration to provide more efficient treatment for pneumonia. Methods: Ionotropic gelation and the spray-drying method were used to obtain doripenem-loaded chitosan microparticles with different lactose, trehalose, and L-leucine concentrations. Physicochemical characteristics, in vitro drug release properties, and aerodynamics properties were investigated and in vitro antimicrobial susceptibility tests of the formulations were performed. Assessment of aerodynamic properties of the powders, including Mass Median Aerodynamic Diameter, size distribution, and fine particle fraction (FPF), were performed using a Next Generation Impactor. Cytotoxicity of the fabricated microparticles was assessed using the Calu-3 cell airway epithelial cell line. Results: Optimum microparticles were produced using a combination of ionotropic gelation and spray-drying methods. Spray-dried microparticle production yield was relatively high (74.03% ± 3.88% to 98.23% ± 1.70%). Lactose, trehalose, and L-leucine were added to the formulation to prevent aggregation produced by the ionotropic gelation spray-drying method. Each formulation's encapsulation efficiency was above 78.98% ± 2.37%. The doripenem-loaded microparticle mean diameter ranged from 3.8 ± 0.110 to 6.9 ± 0.090 μm. Microparticles with 20% (w/w) L-leucine had the highest FPF ratio indicating the best aerosolization properties of the formulations. The efficacy of the formulations as an antibacterial agent was increased by forming doripenem-loaded microparticles compared to blank microparticles. P. aeruginosa showed the same susceptibility to all doripenem-loaded microparticle formulations. Cell viability of microparticles was between 70% ± 0.08% and 90% ± 0.04% at 0.5 and 10 mg/mL concentration, respectively. Conclusions: Doripenem-loaded microparticles, produced using a combination of ionotropic gelation and spray-drying methods, are suitable for pulmonary drug delivery based on their particles size, zeta potential, cytotoxicity and high production yield. To our knowledge, this is the first study that microparticles containing doripenem were produced and characterized.

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

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

Inhaled powder formulation of naked siRNA using spray drying technology with l-leucine as dispersion enhancer

Pulmonary delivery of short interfering RNA (siRNA) has been widely studied in both animal and clinical studies to treat various respiratory diseases by gene silencing through RNA interference. Some of these studies showed that the administration of naked siRNA (without the use of any delivery vectors) could achieve satisfactory gene silencing effect, a unique feature to pulmonary delivery. Liquid aerosols were mostly used with very limited studies on the use of powder aerosols for siRNA. In this study, siRNA was co-spray dried with mannitol and l-leucine, the latter being a dispersion enhancer. To the best of our knowledge, this is the first time that siRNA in its naked form was formulated into an inhalable dry powder using spray drying technology. The aerosol performance of the powder was evaluated by Next Generation Impactor (NGI). The presence of l-leucine in the formulation could improve the aerosolization of siRNA-containing powders. Results from the X-ray photoelectron spectroscopy (XPS) suggested that l-leucine was enriched on the particle surface and promote powder dispersion. Among the different siRNA formulations being examined, the one that contained 50% w/w of l-leucine exhibited the best aerodynamic performance, with a high emitted fraction (EF) of around 80% and a modest fine particle fraction (FPF) of 45%. Importantly, the integrity of siRNA was successfully retained as evaluated by gel retardation assay and high performance liquid chromatography (HPLC).

Design and Biological Evaluation of Delivery Systems Containing Bisphosphonates

Bisphosphonates have found application in the treatment of reoccurrence of bone diseases, breast cancer, etc. They have also been found to exhibit antimicrobial, anticancer and antimalarial activities. However, they suffer from pharmacological deficiencies such as toxicity, poor bioavailability and low intestinal adsorption. These shortcomings have resulted in several researchers developing delivery systems that can enhance their overall therapeutic effectiveness. This review provides a detailed overview of the published studies on delivery systems designed for the delivery of bisphosphonates and the corresponding in vitro/in vivo results.

An investigation of surface properties, local elastic modulus and interaction with simulated pulmonary surfactant of surface modified inhalable voriconazole dry powders using atomic force microscopy

l-Leucine modified voriconazole spray dried micropartcles.

Development of Novel Chitosan Microcapsules for Pulmonary Delivery of Dapsone: Characterization, Aerosol Performance, and In Vivo Toxicity Evaluation

Pneumocystis carinii pneumonia (PCP) is a major opportunistic infection that affects patients with human immunodeficiency virus. Although orally administered dapsone leads to high hepatic metabolism, decreasing the therapeutic index and causing severe side effects, this drug is an effective alternative for the treatment of PCP. In this context, microencapsulation for pulmonary administration can offer an alternative to increase the bioavailability of dapsone, reducing its adverse effects. The aim of this work was to develop novel dapsone-loaded chitosan microcapsules intended for deep-lung aerosolized drug delivery. The geometric particle size (D 4,3) was approximately 7 μm, the calculated aerodynamic diameter (d aero) was approximately 4.5 μm, and the mass median aerodynamic diameter from an Andersen cascade impactor was 4.7 μm. The in vitro dissolution profile showed an efficient dapsone encapsulation, demonstrating the sustained release of the drug. The in vitro deposition (measured by the Andersen cascade impactor) showed an adequate distribution and a high fine particles fraction (FPF = 50%). Scanning electron microscopy of the pulmonary tissues demonstrated an adequate deposition of these particles in the deepest part of the lung. An in vivo toxicity experiment showed the low toxicity of the drug-loaded microcapsules, indicating a protective effect of the microencapsulation process when the particles are microencapsulated. In conclusion, the pulmonary administration of the novel dapsone-loaded microcapsules could be a promising alternative for PCP treatment.

Advantages and challenges of the spray-drying technology for the production of pure drug particles and drug-loaded polymeric carriers

Spray-drying is a rapid, continuous, cost-effective, reproducible and scalable process for the production of dry powders from a fluid material by atomization through an atomizer into a hot drying gas medium, usually air. Often spray-drying is considered only a dehydration process, though it also can be used for the encapsulation of hydrophilic and hydrophobic active compounds within different carriers without substantial thermal degradation, even of heat-sensitive substances due to fast drying (seconds or milliseconds) and relatively short exposure time to heat. The solid particles obtained present relatively narrow size distribution at the submicron-to-micron scale. Generally, the yield% of spray-drying at laboratory scale with conventional spray-dryers is not optimal (20-70%) due to the loss of product in the walls of the drying chamber and the low capacity of the cyclone to separate fine particles (<2 μm). Aiming to overcome this crucial drawback in early development stages, new devices that enable the production of submicron particles with high yield, even for small sample amounts, have been introduced into the market. This review describes the most outstanding advantages and challenges of the spray-drying method for the production of pure drug particles and drug-loaded polymeric particles and discusses the potential of this technique and the more advanced equipment to pave the way toward reproducible and scalable processes that are critical to the bench-to-bedside translation of innovative pharmaceutical products.

Novel drug delivery systems for actinides (uranium and plutonium) decontamination agents

The possibility of accidents in the nuclear industry or of nuclear terrorist attacks makes the development of new decontamination strategies crucial. Among radionuclides, actinides such as uranium and plutonium and their different isotopes are considered as the most dangerous contaminants, plutonium displaying mostly a radiological toxicity whereas uranium exhibits mainly a chemical toxicity. Contamination occurs through ingestion, skin or lung exposure with subsequent absorption and distribution of the radionuclides to different tissues where they induce damaging effects. Different chelating agents have been synthesized but their efficacy is limited by their low tissue specificity and high toxicity. For these reasons, several groups have developed smart delivery systems to increase the local concentration of the chelating agent or to improve its biodistribution. The aim of this review is to highlight these strategies.

Alendronate inhalation ameliorates elastase-induced pulmonary emphysema in mice by induction of apoptosis of alveolar macrophages

Alveolar macrophages play a crucial role in the pathogenesis of emphysema, for which there is currently no effective treatment. Bisphosphonates are widely used to treat osteoclast-mediated bone diseases. Here we show that delivery of the nitrogen-containing bisphosphonate alendronate via aerosol inhalation ameliorates elastase-induced emphysema in mice. Inhaled, but not orally ingested, alendronate inhibits airspace enlargement after elastase instillation, and induces apoptosis of macrophages in bronchoalveolar fluid via caspase-3- and mevalonate-dependent pathways. Cytometric analysis indicates that the F4/80(+)CD11b(high)CD11c(mild) population characterizing inflammatory macrophages, and the F4/80(+)CD11b(mild)CD11c(high) population defining resident alveolar macrophages take up substantial amounts of the bisphosphonate imaging agent OsteoSense680 after aerosol inhalation. We further show that alendronate inhibits macrophage migratory and phagocytotic activities and blunts the inflammatory response of alveolar macrophages by inhibiting nuclear factor-κB signalling. Given that the alendronate inhalation effectively induces apoptosis in both recruited and resident alveolar macrophages, we suggest this strategy may have therapeutic potential for the treatment of emphysema.

Development of biodegradable methylprednisolone microparticles for treatment of articular pathology using a spray-drying technique

In this work, microparticles were prepared by spray-drying using albumin, chondroitin sulfate, and hyaluronic acid as excipients to create a controlled-release methylprednisolone system for use in inflammatory disorders such as arthritis. Scanning electron microscopy demonstrated that these microparticles were almost spherical, with development of surface wrinkling as the methylprednisolone load in the formulation was increased. The methylprednisolone load also had a direct influence on the mean diameter and zeta potential of the microparticles. Interactions between formulation excipients and the active drug were evaluated by x-ray diffraction, differential scanning calorimetry, and thermal gravimetric analysis, showing limited amounts of methylprednisolone in a crystalline state in the loaded microparticles. The encapsulation efficiency of methylprednisolone was approximately 89% in all formulations. The rate of methylprednisolone release from the microparticles depended on the initial drug load in the formulation. In vitro cytotoxic evaluation using THP-1 cells showed that none of the formulations prepared triggered an inflammatory response on release of interleukin-1β, nor did they affect cellular viability, except for the 9.1% methylprednisolone formulation, which was the maximum test concentration used. The microparticles developed in this study have characteristics amenable to a therapeutic role in inflammatory pathology, such as arthritis.

Biomedical applications of bisphosphonates

Since their discovery over 100 years ago, bisphosphonates have been used industrially as corrosion inhibitors and complexing agents. With the discovery of their pharmacological activity in the late 1960s, implicating their high affinity for hydroxyapatite, bisphosphonates have been employed in the treatment of bone diseases and as targeting agents for colloids and drugs. They have notably been investigated for the treatment of Paget's disease, osteoporosis, bone metastases, malignancy-associated hypercalcemia, and pediatric bone diseases. Currently, they are first-line medications for several of these diseases and are taken by millions of patients worldwide, mostly postmenopausal women. A major problem associated with their use is their low oral bioavailability. Several delivery systems have been proposed to improve their absorption and to direct them to sites other than bone tissues. Beyond their important pharmacological role, the medical applications of bisphosphonates are numerous. In addition, their metal-chelating properties have been exploited to coat and stabilize implants, nanoparticulates, and contrast agents. In this contribution, we review the pharmacological and clinical uses of bisphosphonates and highlight their novel applications in the pharmaceutical and biomedical fields.

Drug carriers in osteoporosis: preparation, drug encapsulation and applications

Carriers are largely used to enhance therapy efficiency via the encapsulation of active molecules. The encapsulation enhances the stability of drug molecules, improves the targeting properties and prolongs pharmacological activity via continuous local release of active molecules. The aim of this review is to report the carrier systems used in osteoporosis therapy. This state of the art research has mainly focused on describing all types of carriers used in this area, their elaboration and properties, the drug characteristics used in such specific application, and drug release and efficiency. In this field, various processes have been used in order to obtain well-defined capsules, spheres and more complex carriers. In this exhaustive review, each process is described, illustrated and discussed.

Design, physicochemical characterization, and optimization of organic solution advanced spray-dried inhalable dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine poly(ethylene glycol) (DPPE-PEG) microparticles and nanoparticles for targeted respiratory nanomedicine delivery as dry powder inhalation aerosols

Novel advanced spray-dried and co-spray-dried inhalable lung surfactant-mimic phospholipid and poly(ethylene glycol) (PEG)ylated lipopolymers as microparticulate/nanoparticulate dry powders of biodegradable biocompatible lipopolymers were rationally formulated via an organic solution advanced spray-drying process in closed mode using various phospholipid formulations and rationally chosen spray-drying pump rates. Ratios of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine PEG (DPPE-PEG) with varying PEG lengths were mixed in a dilute methanol solution. Scanning electron microscopy images showed the smooth, spherical particle morphology of the inhalable particles. The size of the particles was statistically analyzed using the scanning electron micrographs and SigmaScan^® software and were determined to be 600 nm to 1.2 μm in diameter, which is optimal for deep-lung alveolar penetration. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) were performed to analyze solid-state transitions and long-range molecular order, respectively, and allowed for the confirmation of the presence of phospholipid bilayers in the solid state of the particles. The residual water content of the particles was very low, as quantified analytically via Karl Fischer titration. The composition of the particles was confirmed using attenuated total-reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and confocal Raman microscopy (CRM), and chemical imaging confirmed the chemical homogeneity of the particles. The dry powder aerosol dispersion properties were evaluated using the Next Generation Impactor™ (NGI™) coupled with the HandiHaler^® dry powder inhaler device, where the mass median aerodynamic diameter from 2.6 to 4.3 μm with excellent aerosol dispersion performance, as exemplified by high values of emitted dose, fine particle fraction, and respirable fraction. Overall, it was determined that the pump rates defined in the spray-drying process had a significant effect on the solid-state particle properties and that a higher pump rate produced the most optimal system. Advanced dry powder inhalers of inhalable lipopolymers for targeted dry powder inhalation delivery were successfully achieved.