Inhaled colistin is used to treat pneumonia and respiratory infections through nebulization or dry powder inhalers. Nevertheless, the development of a metered-dose inhaler (MDI) for colistin, which could enhance patient convenience and treatment efficacy, has not yet been developed. Colistin is known for its ability to induce cellular toxicity. Gold nanoparticles (AuNPs) can potentially mitigate colistin toxicity. Therefore, this study aimed to evaluate the antimicrobial effectiveness of colistin conjugated with chitosan-capped gold nanoparticles (Col-CS-AuNPs) and their potential formulation for use with MDIs to deliver the aerosol directly to the deep lung. Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and elemental analysis were used to characterize the synthesized Col-CS-AuNPs. Drug release profiles fitted with the most suitable release kinetic model were evaluated. An MDI formulation containing 100 µg of colistin per puff was prepared. The aerosol properties used to determine the MDI performance included the fine particle fraction, mass median aerodynamic diameter, and geometric standard deviation, which were evaluated using the Andersen Cascade Impactor. The delivered dose uniformity was also determined. The antimicrobial efficacy of the Col-CS-AuNP formulation in the MDI was assessed. The chitosan-capped gold nanoparticles (CS-AuNPs) and Col-CS-AuNPs had particle sizes of 44.34 ± 1.02 and 174.50 ± 4.46 nm, respectively. CS-AuNPs effectively entrapped 76.4% of colistin. Col-CS-AuNPs exhibited an initial burst release of up to 60% colistin within the first 6 h. The release mechanism was accurately described by the Korsmeyer–Peppas model, with an R² > 0.95. The aerosol properties of the Col-CS-AuNP formulation in the MDI revealed a high fine particle fraction of 61.08%, mass median aerodynamic diameter of 2.34 µm, and geometric standard deviation of 0.21, with a delivered dose uniformity within 75–125% of the labeled claim. The Col-CS-AuNP MDI formulation completely killed Escherichia coli at 5× and 10× minimum inhibitory concentrations after 6 and 12 h of incubation, respectively. The toxicity of CS-AuNP and Col-CS-AuNP MDI formulations in upper and lower respiratory tract cell lines was lower than that of free colistin. The stability of the Col-CS-AuNP MDI formulation was maintained for at least 3 months. The Col-CS-AuNP MDI formulation effectively eradicated bacteria over a 12-h period, showing promise for advancing lung infection treatments.

BrSPR-20-P1 antimicrobial peptide (P1-AMP) is a novel antimicrobial peptide isolated from Brevibacillus sp. SPR-20 and has been developed as a liposomal in chitosan hydrogel. It has potential to be used as a topical antimicrobial agent.

The cashew apple (Anacardium occidentale L.) is rich in antioxidant bioactive constituents that have anti-aging and wound healing properties. The objective of this study is to evaluate the biological activities of cashew apple extract (CAE) and to improve the issue involving the instability of ascorbic acid, the principal active compound, by encapsulating the extract in liposomes in order to enhance its stability and skin permeation for cosmetic applications. CAE was obtained from fresh cashew apple via ethanol maceration, solvent evaporation, and freeze-drying. Ascorbic acid content, total phenolic content (TPC), total flavonoid content (TFC), and total caffeoylquinic acid content (TCQAC) were determined. The ascorbic acid content and its tautomer in the extract were quantified using the LC-MS/MS method. Biological activities, including antioxidant, anti-tyrosinase, fibroblast collagen synthesis, cytoprotection against oxidative stress, wound healing, and cytotoxicity, were assessed. CAE was encapsulated in liposomes to enhance the stability of its inherent ascorbic acid and improve its skin in comparison to free-CAE. The CAE and liposomal-CAE were incorporated and formulated into a solution, and their physicochemical stability was assessed after storage. CAE appeared as a brown, viscous liquid with a characteristic sweet, fruity scent. Each gram of CAE contained 0.90 ± 0.05 mg of ascorbic acid, TPC, 81.40 ± 7.14 mg of gallic acid equivalents (GAE), TFC, 3.73 ± 0.30 mg of rutin equivalents (RE), and TCQAC, 4.48 ± 0.05 mg of chlorogenic acid equivalents (CGAE). CAE exhibited antioxidant properties (IC₅₀ = 282.19 ± 11.16 and 963.66 ± 3.95 µg/mL for DPPH and ABTS assay, respectively) and weak anti-tyrosinase activity (IC₅₀ = 4213.77 ± 138.97 µg/mL). It was non-cytotoxic to fibroblast and monocyte cells at a concentration of less than 1 mg/mL. In vitro wound healing assays demonstrated that CAE stimulated collagen production in a dose-dependent manner at CAE concentrations above 250 µg/mL. Additionally, CAE exhibited cytoprotective effects against H₂O₂-induced oxidative stress and did not induce inflammatory responses in immune cells. The liposomal formulation containing CAE achieved high encapsulation efficiency (79.75–84.55%) based on ascorbic acid content. In skin permeation studies, CAE-loaded liposomes demonstrated an enhancement ratio approximately two-fold greater than that of free-CAE. Stability testing over 3 months showed that the ascorbic acid content in CAE-loaded liposomes remained significantly higher than that in the free-CAE under both refrigerated and long-term conditions (30 °C/75% RH). CAE demonstrated potential anti-aging properties for improving aging skin. Liposomal incorporation markedly improved ascorbic acid stability and skin permeability.

Hydroxypropyl methylcellulose (HPMC)-based formulations are commonly used in nasal sprays due to their gelling and viscosity-enhancing properties. However, data on in vitro studies that mimic patient use remain limited. This study investigated two commercial HPMC-based aqueous formulations and HPMC-based powder formulations to provide an understanding of the relationship between the physical properties, their performance, and the stability of nasal products. Physical properties, quality tests focused on shot mass and shot volume were assessed. The coverage area within the nasal cavity was examined at various angles of actuation (15°, 30°, 45°, and 80°) using a simulated inhalation model. The 45° spray angle exhibited the highest coverage area (%) within the nasal cavity. Devices containing liquid formulations demonstrated more reproducible shot mass and shot volume compared to dry powder preparations. These findings provide valuable insights for patients and manufacturers, leading to a better understanding of optimal usage and formulation effectiveness.