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Risedronate sodium (RS) is a potent nitrogen-containing bisphosphonate which is known to induce osteoclast apoptosis. As a drug repurposing approach, the current work explored the potential of nebulizable RS-chitosan (CS) microspheres to induce alveolar macrophage apoptosis. RS-CS microspheres were assessed for lung deposition, cytotoxicity, and cellular uptake percentage in Calu-3 cells. The potential of nebulizable microspheres for treating elastase-induced emphysema in rats was investigated, compared to RS marketed oral tablets®, with respect to histopathological, immunohistochemical, and flow cytometric studies. The in vitro lung deposition pattern suggested deep alveolar deposition of RS microspheres, with respect to high FPF% and suitable MMAD (66% and 1.506 μm, respectively, at a flow rate of 28.3 L min -1 ). No apparent cytotoxicity was observed, with a cell viability > 90%. The inhalation of RS-CS microspheres was suggested to inhibit airspace enlargement and lung rarefaction after elastase instillation and reduce the macrophage accumulation in alveolar parenchyma. Immunohistochemical and cytometric analyses revealed significant low expression levels of CD68 and CD11b surface markers, respectively, with significantly (P < 0.05) lower detected numbers of intact alveolar macrophages following inhalation of RS-CS microspheres. The nebulization of RS-CS microspheres could induce apoptosis in alveolar macrophages and be promisingly adopted for attenuation of pulmonary emphysema.

Risedronate sodium (RS) is a potent inhibitor of bone resorption, having an extreme poor permeability and limited oral bioavailability (0.62%). RS should be orally administered under fasting conditions while keeping in an upright posture for at least 30 min to diminish common gastroesophageal injuries. To surmount such limitations, novel risedronate-chitosan (RS-CS) crosslinker-free nebulizable microspheres were developed adopting the quality by design (QbD) approach and risk assessment (RA) thinking. RS:CS ratio, surfactant (Pluronic® F127) concentration, homogenization duration, speed, and temperature were identified using Ishikawa diagrams as the highest formulation and process risk factors affecting the critical quality attributes (CQAs), average particle size (PS), and entrapment efficiency (EE%). The risk factors were screened using the Plackett-Burman design, and the levels of the most significant factors were optimized using a multilevel factorial design to explore the optimized system with the least PS, maximum EE%, and a prolonged drug release profile. The optimized system (B6) was developed at a RS:CS ratio of 1:7, a surfactant concentration of 2% (w/v), and a homogenization speed of 14,000 rpm. It revealed good correlation with QbD theoretical prediction, where positively charged (47.9 ± 3.39 mV) discrete, spherical microspheres (3.47 ± 0.16 μm) having a high EE% (94.58 ± 0.19%) and prolonged RS release over 12 h (Q 12 h , 89.70 ± 0.64%) were achieved. In vivo lung deposition after intratracheal instillation of B6 confirmed the delivery of high RS percentage to rat lung tissues (87 ± 3.54%) and its persistence for 24 h. This investigation demonstrated the effectiveness of QbD philosophy in developing RS-CS crosslinker-free nebulizable microspheres.

The performance of dioctyl sodium sulfosuccinate (aerosol OT) in the development of a pharmaceutically acceptable, stable, self-emulsifying water continuous microemulsion with high dilution efficiency was assessed. A pseudoternary microemulsion system was constructed using aerosol OT/medium-chain triglycerides with oleic acid/glycerol monooleate and water. The model microemulsion was characterized with regard to its electroconductive behavior, eosin sodium absorption, interfacial tension, and droplet size measurements after dilution with water. The percolation transition law, which makes it possible to determine the percolation threshold and to identify bicontinuous structures, was applied to the system. The interfacial tension changes associated with the microemulsion formation revealed ultralow values up to 30% oil at a surfactant/cosurfactant ratio of 3:1. Moreover, the investigated particle size and polydispersity using photon correlation spectroscopy after dilution with excess of the continuous phase proved the efficiency of the microemulsion system as a drug carrier that ensures an infinitely dilutable, homogeneous, and thermodynamically stable system.

The influence of the vehicle on the release and permeation of fluconazole, a topical antifungal drug dissolved in Jojoba oil was evaluated. Series of Cutina lipogels (Cutina CPA [cetyl palmitate], CBS [mixture of glyceryl stearate, cetearyl alcohol, cetyl palmitate, and cocoglycerides], MD [glyceryl stearate], and GMS [glyceryl monostearate]) in different concentrations as well as gel microemulsion were prepared. In-vitro drug release in Sorensen's citrate buffer (pH 5.5) and permeation through the excised skin of hairless mice, using a modified Franz diffusion cell, were performed. The rheological behavior and the apparent viscosity values for different gel bases were measured before and after storage under freezing conditions at -4 degrees C and were taken as measures for stability of network structure. Candida albicans was used as a model fungus to evaluate the antifungal activity of the best formula achieved. The results of in vitro drug release and its percutaneous absorption showed that the highest values from gel microemulsion were assured. The rheological behavior of the prepared systems showed pseudoplastic (shear-thinning) flow indicating structural breakdown of the existing intermolecular interactions between polymeric chains. Moreover, the stability study revealed no significant difference between viscosity before and after storage for different formulae except for CPA Cutina lipogel (using analysis of variance [ANOVA] test at level of significance.05). The antifungal activity of fluconazole showed the widest zone of inhibition with gel microemulsion. The gel microemulsion is an excellent vehicle for fluconazole topical drug delivery.