Mini spray dryer model b 290

Briefly, the enteric microparticles (MP) were prepared using Eudragit^® L100 to S100 (Rohm Pharma GmbH, Darmstadt, Germany) at a ratio of 1:2, with the addition EC (30% w/w, ETHOCEL std. 7, Dow Chemical Company, Milan, Italy), as described in [22 (link)]. 3-IAld (Sigma-Aldrich, Milan, Italy) and the polymers were dissolved in ethanol at a feedstock concentration of 3% w/v, and spray-dried at an inlet temperature of 75 °C, using a Mini Spray-dryer model B-290 (Büchi, Milan, Italy) in the co-current mode, equipped with a two-fluid nozzle with a 0.7 mm nozzle tip and a 1.5 mm diameter nozzle cap. The aspirator capacity was maintained at 20 m³/h, the airflow rate was 301 L/h, and the feed rate 2.4 mL/min. The obtained dried MP were recovered by using a high-performance cyclone (Büchi, Milan, Italy).

Three binary AZM/RIF combinations, 1:1, 2:1 and 1:2, were transformed into MP formulations by spray-drying technology. AZM MP and RIF MP spray-dried powders were prepared independently for comparison. The method is a one step process that allow to obtain dry powders with improved morphological and dimensional characteristics. The microparticles were produced by a Mini Spray-Dryer Model B-290 (Büchi, Milan, Italy) starting from excipient-free drug solutions at a final concentration of 2% w/v in acetonitrile. The spray-drying parameters were set up as follows: inlet temperature 75 °C, air flow rate 357 L/h, feed rate 2.5 mL/min and aspirator rate 20 m³/h.

In this study, the first-line drugs AZM and RIF were tested alone and in combination to investigate their MIC against planktonic R. equi and anti-biofilm properties. To increase the drug water solubility and powder dispersibility, commercial antibiotic powders were transformed in microparticle formulations by spray-drying. The drugs were tested alone and in the exact drug molar ratio 2:1 for the AZM/RIF combination which, in a previous study [26 (link)], demonstrated a synergistic bactericidal effect against planktonic R. equi and long-term activity against a R. equi-infected intracellular model. The microparticle dry powders were produced using a Mini Spray-Dryer Model B-290 (Büchi, Milan, Italy) starting from excipient-free drug solutions at a final concentration of 2% w/v in acetonitrile and adopting the following conditions: inlet temperature 75 °C, air flow rate 357 L/h, feed rate 2.5 mL/min, and aspirator rate 20 m³/h. The quantification of each antibiotic in the AZM/RIF combination was performed by a previously reported HPLC method [26 (link)].

NR latex containing 60 wt.% of solid content was diluted to 20 wt.% of solid content with distilled water, followed by the addition of each acrylate coagent with different amounts in the range of 1 to 11 phr. The mixtures were stirred for 15 min, followed by radiation vulcanization using an electron beam accelerator module MB 10–50, facilitated by the Thailand Institute of Nuclear Technology, with 10 meV and 50 kW of output power. The radiation dose was varied in the range of 250 to 400 kGy. Then, the radiated samples were dried by using a Buchi Mini Spray Dryer Model B-290 (Flawil, Switzerland) with an inlet temperature of 150 °C. The flow meter valve was set to 667 L/h. The pump output was set to 4.5 mL/min of feed flow pumping into the nozzle. The UFPNR was obtained at the bottom part of the cyclone unit.

The spray drying encapsulation process was performed according to the method described by Radulović et al. [23 (link)]. Overnight cultures (300 mL) were centrifuged (4500× g, 15 min, 15 °C), the pellet was washed twice in 50 mM K₂HPO₄ (pH 6.5), re-suspended in 300 mL of sterilised reconstituted skim milk (20% w/v) and spray-dried with a laboratory scale spray-dryer (Büchi mini spray dryer model B-290, Flawil, Switzerland) using the constant inlet air temperature of 170 °C and the outlet temperature of 80 °C.