Investigation of the use of sodium dodecyl sulfate for reducing leakage of bovine serum albumin from ethyl cellulose microcapsules

Phenylketonuria (PKU) is an inborn metabolic disorder where an inability to metabolize phenylalanine (Phe) results in its toxic accumulation in blood and brain. Our laboratory proposes using microencapsulated phenylalanine ammonia lyase (PAL) as an oral therapy for managing PKU. Encapsulated in semipermeable, non-digestible ethylcellulose (EC), PAL will metabolize Phe in the gastrointestinal tract and lower Phe absorption . Using bovine serum albumin (BSA) as a model protein we are determining the best method for manufacturing microcapsules. We investigated the effectiveness of spray drying a BSA-EC suspension and found rapid leakage of protein, which is undesirable. We then complexed BSA with surfactants, hypothesizing that their amphipathic nature would increase hydrophilic BSA's affinity for the hydrophobic EC capsule. These microcapsules also exhibited rapid protein leakage. We suggest that the differences in viscosities and spray radii of the solid and oil phases prevented proper encapsulation of BSA via spray drying. We are now investigating solvent evaporation from a solid/oil/water emulsion: first with BSA alone, then with BSA-surfactant complexes. We expect the slower precipitation of EC around BSA particles to produce more complete encapsulation and reduce leakage.