Protein release behavior from porous microparticle with lysozyme/hyaluronate ionic complex

Porous microparticles (PMs) with a low density (<0.4 g/cm³) for pulmonary protein delivery were prepared by the water-in-oil-in-water (W₁/O/W₂) multi-emulsion method using a cyclodextrin derivative as a porogen. The complexation of positively charged lysozyme (Lys) and negative-charged hyaluronate (HA) was investigated for long-term protein release from PMs. The interaction of Lys and HA not only increased protein encapsulation efficiency but also stabilized Lys against a denaturing organic solvent (dichloromethane). Furthermore, PMs with Lys/HA complexes increased the Lys release period up to 7 days, as opposed to a 4 h Lys release time from PMs without Lys/HA complexes. In particular, PMs containing 10 mg of HA and 50 mg of Lys showed almost zero-order Lys release kinetic for 7 days and preserved the bioactivity of Lys more than 98% during its entire release period. This result suggests that PMs with Lys/HA complexes may be applied in long-term pulmonary administration of protein or peptide drugs, including those that require particles to arrive at a deep lung epithelium with the help of low density (high porosity) of PMs.