Functionalized calcium carbonate microparticles for the delivery of proteins.

The recently introduced functionalized calcium carbonate (FCC), a porous microparticle with a nano-structured, lamellar surface, shows promising properties in the field of oral drug delivery. In this work, FCC was loaded with biomolecules e.g. lysozyme (Lys) and bovine serum albumin (BSA) in order to investigate its suitability to deliver protein based drugs. Loading efficiency for our model proteins was >90% and enzyme activity was preserved as demonstrated by Michaelis-Menten enzyme kinetic experiments. Circular dichroism analysis confirmed, that neither the structure of both model substances, nor the activity of Lys was affected by the loading process or the interaction with the surface of FCC. Electron microscopy (SEM) and mercury porosimetry were indicative of protein deposition on the particle surface as well as within the particle pores. Release properties were investigated in a customized flow cell, which simulates the conditions in the oral cavity. Depending on the isoelectric point of the investigated proteins, complete release was obtained within 1.5 h. This work shows, that FCC is a suitable pharmaceutical excipient for delivery of proteins.