B 290

Initially, equimolar amounts of LEV and ARG (resulting in a mass ratio of 67.4% LEV and 32.6% ARG) were dissolved in 100 mL of water. In the later course of the study, LEV and ARG were dissolved in 100 mL of a 30% ethanol/water mixture (v/v). The solid concentration was 10 mg/mL. SD was performed using a Büchi B-290 spray dryer (Büchi Labortechnik AG, Flawil, Switzerland), which was equipped with an inert loop B-295 (Büchi Labortechnik AG) when ethanol was used as a solvent. A 0.7 mm two-fluid nozzle was used. To investigate the influence of the process parameters on the outcome, samples were produced at varying inlet temperatures and feed rates in a design of experiments (DoE) set-ups. The drying air flow and the atomising air flow rate were kept constant at 40 m³/h (nitrogen) and 667 l/h, respectively.

ChS microparticles were prepared by spray-drying, either unloaded or containing an association of the antitubercular drugs INH and RFB. ChS was used at 2% (w/v) in all cases and the drug-loaded microparticles were produced at ChS/INH/RFB mass ratio of 10/1/0.5. While INH was solubilised in water, the hydrophobic character of RFB required the use of co-solvents. Ethanol 70% (v/v) and HCl 0.01 M were tested for this end and the obtained RFB solution was then added to the previously formed ChS/INH solution. When ethanol was used, the final water/ethanol ratio of 80/20 (v/v) was applied in the spraying solution, while HCl was used at a final concentration of 0.002 M.
Microparticles were produced from both solutions using a laboratory mini spray-dryer (Büchi B-290, Büchi Labortechnik AG, Flawil, Switzerland) operating in open mode and equipped with a high-performance cyclone. The operating parameters were: inlet temperature: 175 ± 2 °C; aspirator setting: 90%; feed rate: 0.7 ± 0.1 mL/min; and spray flow rate: 473 L/h. These conditions resulted in an outlet temperature of 110 ± 2 °C. After spray-drying, microparticles were collected, placed in a dark flask and stored inside a desiccator until further use.
The spray-drying yield was calculated by gravimetry, comparing the total amount of solids initially added with the resultant weight of collected microspheres.

Drug–clay aqueous dispersions, 100 mL in volume, at drug–clay w/w ratios used in the intercalation solution technique were spray dried using a Mini Spray Dryer (BÜCHI^® B-290; Massó Analítica S.A., El Prat de Llobregat, Barcelona, Spain) with a nozzle of 0.7 mm diameter aperture. The feed rate was 9 mL/min and the nozzle air pressure was 6 bar. The inlet temperature was set at 200 °C, resulting in an outlet temperature of 130 °C. The airflow rate and the aspirator were 439 L/h and 40 m³/h (100%), respectively. The efficiency of the process, determined from the amount of solid actually recovered versus the theoretical amount of solid to be obtained by atomization of the aqueous phase, was always ≥ 50%.

CS solution was prepared by dissolving 2 g CS in 25 mL of 3% citric acid aqueous solution. The obtained solution was slowly added into 25 mL of above prepared liquid cubosomes under magnetic stirring at 200 rpm at 25 °C. After stirring for 10 min, 0.4 or 0.8 mL of glutaraldehyde solution (6.25%, w/v) was then added into the mixture to initiate the cross-linking reaction between CS and glutaraldehyde. The reaction was allowed to continue for 4 h.^{24 (link)}After cross-linking reaction, 2 g of mannitol as scaffolds was dissolved in the obtained reaction mixture by stirring, followed by spray dryer (Büchi B-290: Büchi Labortechnik AG, Switzerland). The spray drying was carried out using a 0.7 mm nozzle with the inlet temperature of 110 °C, aspirator setting of 40 m³ h⁻¹, spray flow rate of 600 L h⁻¹, pump setting of 2.72 mL min⁻¹. The spray-dried chito-cubosomes solid was collected and stored in desiccators at 25 °C for further characterizations.

Flaxseed oil emulsions powders were obtained by spray-drying, using a lab-scale spray dryer (Büchi B-290, Büchi Labortechnik AGT, Flawill, Switzerland). The drying air inlet temperature of 180 °C was chosen, based on the results described in previous study [12 (link)]. The air flow was 40 m³/h. The drying air outlet temperature was maintained at 55 ± 5 °C. Dried powders were collected in a collection vessel and stored in darkness at 4 °C. The yield of the spray drying process was calculated according to the Formula (1): $\mathrm{Yield} (\%)=\frac{\mathrm{mas} \mathrm{of} \mathrm{powder} \left(\mathrm{g}\right)}{\mathrm{dry} \mathrm{matter} \mathrm{of} \mathrm{emulsion} \left(\mathrm{g}\right)}\times 100\%$