Optimized preparation of biodegradable polymer particles encapsulating low-molecular-weight hydrophilic drugs

In the present paper, the conditions required to improve the drug loading efficiency in biodegradable polymer particles prepared using the particular technique of freezing the inner water phase of the primary emulsion before preparation of the secondary emulsion were successfully optimized. The optimal freezing temperature for the inner water phase in the primary (w1/(o1 + o2)) emulsion, amount of oil soluble surfactant added to the outer o3 phase, and stirring rate and preparation time for the secondary (w1/(o1 + o2)/o3) emulsion, were determined to be −15 °C, 1.00 g, 400 rpm, and 10 s, respectively. PLGA particles with a smooth spherical morphology were achieved using a sub-zero temperature of −15 °C to freeze the inner water phase in the primary w1/(o1 + o2) emulsion. By utilizing this procedure, PLGA particles with a drug loading efficiency of approximately 60% were prepared in the liquid–liquid system, even though a low-molecular-weight hydrophilic drug (Mw = 137), isoniazid, was used.