Single Emulsion Manufacturing Method for Encapsulation of Low Molecular Weight Chemokines

For decades, poly(lactic-co-glycolic acid) (PLGA) has been a widely utilized FDA-approved polymer due to its biodegradability and biocompatibility. PLGA is often utilized in the development of a variety of different drug delivery systems, such as microparticles. These PLGA microparticles (MPs) are often used to encapsulate hydrophobic small molecule and peptide-based drugs to enable sustained drug release and are manufactured using a single emulsion solvent evaporation method. More recently, there is growing interest in expanding the use of PLGA to encapsulate biologic drugs, such as proteins, to increase their bioavailability and protect them from degradation. It has previously been demonstrated that local, sustained delivery of CCL22, a chemokine known to recruit regulatory T cells, promotes immune homeostasis in various inflammatory disease models. However, encapsulating biologics typically requires a more complex double emulsion technique, which limits scalability and clinical translation. This study explored the feasibility of using a single emulsion technique to encapsulate CCL22, aiming to develop a more streamlined process for large-scale production.

PLGA with varying end caps was used in a single emulsion water-in-oil evaporation method to encapsulate CCL22 into MPs. CCL22 was dissolved in DMSO and combined with PLGA in dichloromethane to create a discrete phase, which was then added to an aqueous continuous phase containing PVA and homogenized to form an emulsion. After solvent evaporation through continuous stirring, the MPs were washed, flash-frozen, and lyophilized. The MPs were characterized for size, morphology, and release kinetics using Coulter Counter measurements, scanning electron microscopy (SEM), and in vitro release assays. Encapsulation with 10 kDa acid-terminated PLGA was successful but resulted in a significant lag phase in drug release. Changing to 10kDa hydroxyl-terminated PLGA improved the magnitude of the initial burst release; however, following the burst a lag phase was still seen. These findings suggest that low molecular weight chemokines, like CCL22, can be effectively encapsulated using a single emulsion technique. To further enable translational potential, CCL22 MPs were also manufactured using a continuous microfluidic process. Taken together, this study suggests that a single emulsion encapsulation technique, through homogenization or microfluidics, may be a viable option for low molecular weight biologics, thus expanding the therapeutic potential of PLGA delivery systems.