Polysorbate 80

Commercial guava leaf extract was purchased from Specialty Natural Products Co., Ltd., Chonburi, Thailand (Lot No. HE-EL41-PSG) and quantified for the total phenolic and flavonoid contents at the Faculty of Pharmaceutical Sciences, Chulalongkorn University (Bangkok, Thailand). The GMT formulation contains 20% v/v of guava leaf extract, 1% w/v of menthol (1381709 USP, Sigma-Aldrich Pte. Ltd., Singapore), aluminium chlorohydrate (ICL performance products Ltd., China), ethanol (RCI Labscan Ltd., Thailand), Polysorbate 80 (Spectrum chemical Mfg., Corp., USA), perfumes, and purified water. The placebo formulation (PCB) composes the same toner base without the actives (i.e., guava leaf extract and menthol). All chemicals are either pharmaceutical or cosmetic grade. The studied preparations were prepared and evaluated for physical and chemical stabilities at the compounding laboratory, the Faculty of Pharmaceutical Sciences, Chulalongkorn University (Bangkok, Thailand).

A stock solution of S2534 (Fc3/FH*) (8.39 mg/mL) in buffer consisting of 77 mM sodium chloride, 15 mM potassium acetate, and 5 mM glycine was thawed, and used to prepare three formulation solutions (A, B, and C) as described in Table 2. The solids composition for all three formulation solutions was ~ 1% (w/w). Trehalose and polysorbate 80 were obtained from Spectrum Chemical (Gardena, CA) in NF grade and used as received. The S2534 formulation solutions were filter sterilized (0.2 μm membrane filter) prior to lyophilization or spray drying. A 0.2 mL aliquot of each formulation in a microfuge tube was pre-frozen by plunging in liquid N₂ and dried by lyophilization (Freezemobile 12SL, SP VirTis, Warminster, PA) to yield ~ 1.8 mg of a voluminous white solid containing 0.84 mg S2534 (Fc3/FH*). A 4 mL aliquot of each formulation was spray dried using a B-90 Nano Spray Dryer (Buchi, New Castle, DE) in the long cylinder configuration and the following conditions: medium nebulizer orifice (4 μm); gas flow rate = 130-135 L/min; inlet temperature = 100°C; outlet temperature = 35-39°C; spray rate = 45% (100 kHz); pressure = 45-50 mbar; sample pump rate = 30%.