Investigation into the effect of varying l-leucine concentration on the product characteristics of spray-dried liposome powders

Process development of inhalation powders containing simvastatin loaded liposomes using spray drying technology

The development of an inhalation powder (IP) for cancer therapy is desired to improve the therapeutic response and patient compliance. The latest studies highlighted that statins, a class of drugs used in hypercholesterolemia, can have anticancer and antiinflammatory properties. Therefore, the aim of the study was to develop an IP containing liposomes loaded with simvastatin using spray drying technology, as well as to investigate the influence of formulation factors on the quality attributes of the IP by means of experimental design. Results highlighted that the composition of liposomes, namely type of phospholipid and cholesterol concentration, highly influences the quality attributes of IP, and the use of optimal concentrations of excipients, i.e. D-mannitol and L-leucine, is essential to preserve the characteristics of liposomes throughout the spray drying process. The in vitro characterization of the optimal IP formulation revealed that the total percentage of released drug is higher from the IP formulation compared to the powder of active substance (53.38 vs. 42.76%) over a period of six hours, and 39.67% of dry particles have a size less than 5 µm, making them suitable for inhalation. As a conclusion, spray drying technology can be effectively used in the development and preparation of IP containing liposomes.

Inhaled dry powder liposomal azithromycin for treatment of chronic lower respiratory tract infection

A dry powder inhaled liposomal azithromycin formulation was developed for the treatment of chronic respiratory diseases such as cystic fibrosis and bronchiectasis. Key properties including liposome size, charge and encapsulation efficiency powder size, shape, glass transition temperature (Tg), water content and in vitro respiratory deposition were determined. Antimicrobial activity against cystic fibrosis (CF) respiratory pathogens was determined by MIC, MBC and biofilm assays. Cytotoxicity and cellular uptake studies were performed using A549 cells. The average liposome size was 105 nm, charge was 55 mV and encapsulation efficiency was 75 %. The mean powder particle size d[v,50] of 4.54 µm and Mass Median Aerodynamic Diameter (MMAD) was 5.23 µm with a mean Tg of 76˚C and water content of 2.1 %. These excellent physicochemical characteristics were maintained over one year. Liposomal loaded azithromycin demonstrated enhanced activity against P. aeruginosa clinical isolates grown in biofilm. The formulation was rapidly delivered into bacterial cells with > 75 % uptake in 1 h. Rapid uptake into A549 cells via a cholesterol-dependent endocytosis pathway with no cytotoxic effects apparent. These data demonstrate that this formulation could offer benefits over current treatment regimens for people with chronic respiratory infection.

Inhalable Dry Powder of Bedaquiline for Pulmonary Tuberculosis: In Vitro Physicochemical Characterization, Antimicrobial Activity and Safety Studies

Bedaquiline is a newly developed anti-tuberculosis drug, conditionally approved by the United States Food and Drug Administration (USFDA) for treating drug-resistant tuberculosis in adults. Oral delivery of bedaquiline causes severe side effects such as increased hepatic aminotransferase levels and cardiac arrhythmias (prolongation of QT-interval). This study aimed to develop inhalable dry powder particles of bedaquiline with high aerosolization efficiency to reduce the side-effects of oral bedaquiline. Bedaquiline (with or without l-leucine) powders were prepared using a Buchi Mini Spray-dryer. The powders were characterized for physicochemical properties and for their in vitro aerosolization efficiency using a next-generation impactor (NGI). The formulation with maximum aerosolization efficiency was investigated for physicochemical and aerosolization stability after one-month storage at 20 ± 2 °C/30 ± 2% relative humidity (RH) and 25 ± 2 °C/75% RH in an open Petri dish. The cytotoxicity of the powders on A549 and Calu-3 cell-lines was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The powders were also evaluated for antimicrobial activity against Mycobacterium tuberculosis. The aerodynamic diameter of the l-leucine-containing powder was 2.4 µm, and the powder was amorphous in nature. The aerosolization efficiency (fine-particle fraction) of l-leucine-containing powder (fine-particle fraction (FPF): 74.4%) was higher than the bedaquiline-only powder (FPF: 31.3%). l-leucine containing powder particles were plate-shaped with rough surfaces, but the bedaquiline-only powder was spherical and smooth. The optimized powder was stable at both storage conditions during one-month storage and non-toxic (up to 50 µg/mL) to the respiratory cell-lines. Bedaquiline powders were effective against Mycobacterium tuberculosis and had a minimal inhibitory concentration (MIC) value of 0.1 µg/mL. Improved aerosolization may help to combat pulmonary tuberculosis by potentially reducing the side-effects of oral bedaquiline. Further research is required to understand the safety of the optimized inhalable powder in animal models.

Towards a dapivirine and levonorgestrel multipurpose vaginal ring: Investigations into the reaction between levonorgestrel and addition-cure silicone elastomers

With a dapivirine-releasing vaginal ring having successfully completed late-stage clinical testing for HIV prevention and currently undergoing regulatory review, there is now growing interest in next-generation multipurpose prevention technologies that seek to combine antiretroviral and contraceptive drugs within a single product. Here, we focus on ongoing efforts to develop a silicone elastomer vaginal ring releasing both dapivirine and levonorgestrel. Specifically, we evaluate various strategies aimed at both better understanding and reducing the tendency of levonorgestrel to bind with the elastomer, including: (i) formulation and post-manufacturing strategies aimed at reducing the extent of levonorgestrel reaction with addition-cure silicone elastomers; (ii) evaluation of a simple silicone system to model the complex elastomer; (iii) use of model compounds representing the enone and ethinyl moieties of levonorgestrel to probe the mode of addition of levonorgestrel to addition-cure silicone elastomers; and (iv) solution and solid-state ¹³C NMR analysis to probe the structural features of the levonorgestrel-silicone system. The results demonstrate that both the enone and ethinyl groups within levonorgestrel undergo hydrosilylation reactions with the hydrosiloxane groups in the silicone elastomer leading to covalent binding. The results also highlight potential strategies for further optimising the dapivirine + levonorgestrel silicone vaginal ring formulation to ensure that the levonorgestrel is available for release.

Cholesterol modulates the liposome membrane fluidity and permeability for a hydrophilic molecule

The effect of cholesterol (CHOL) content on the permeability and fluidity of dipalmitoylphosphatidylcholine (DPPC) liposome membrane was investigated. Liposomes encapsulating sulforhodamine B (SRB), a fluorescent dye, were prepared by reverse phase evaporation technique (REV) at various DPPC:CHOL molar ratios (from 100:0 to 100:100). The release kinetics of SRB was studied during 48 h in buffer (pH 7.4) containing NaCl at 37 °C. The DPPC:CHOL formulations were also characterized for their size, polydispersity index and morphology. Increasing CHOL concentration induced an increase in the mean liposomes size accompanying with a shape transition from irregular to nanosized, regular and spherical vesicles. The release kinetics of SRB showed a biphasic pattern; the release data was then analyzed using different mathematical models. On the overall, the SRB release was governed by a non-Fickian diffusion during the first period (0-10 h) while it followed a Fickian diffusion between 10 and 48 h. Changes in DPPC liposome membrane fluidity of various batches (CHOL% 0, 10, 20, 30 and 100) were monitored by using 5- and 16 doxyl stearic acids (DSA) as spin labels. CHOL induced a decrease in the bilayer fluidity. Concisely, CHOL represents a critical component in modulating the release of hydrophilic molecules from lipid vesicles.

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.

The effect of polymer coatings on physicochemical properties of spray-dried liposomes for nasal delivery of BSA

This work describes the development of spray dried polymer coated liposomes composed of soy phosphatidylcholine (SPC) and phospholipid dimyristoyl phosphatidylglycerol (DMPG) coated with alginate, chitosan or trimethyl chitosan (TMC), that are able to penetrate through the nasal mucosa and offer enhanced penetration over uncoated liposomes when delivered as a dry powder. All the liposome formulations, loaded with BSA as model antigen, were spray-dried to obtain powder size and liposome size in a suitable range for nasal delivery. Although coating resulted in some reduction in encapsulation efficiency, levels were still maintained between 60% and 69% and the structural integrity of the entrapped protein and its release characteristics were maintained. Coating with TMC gave the best product characteristics in terms of entrapment efficiency, glass transition (T(g)) and mucoadhesive strength, while penetration of nasal mucosal tissue was very encouraging when these liposomes were administered as dispersions although improved results were observed for the dry powders.