Abstract
Accurate analysis of intraparticle distribution of substances within porous drug carriers is important to optimize loading and subsequent processing. Mercury intrusion porosimetry, a common technique used for characterization of porous materials, assumes cylindrical pore geometry, which may lead to misinterpretation. Therefore, imaging techniques such as focused ion beam scanning electron microscopy (FIB-SEM) help to better interpret these results. The purpose of this study was to investigate the differences between mercury intrusion and scanning electron microscopy and to identify the limitations of each method. Porous microparticles, functionalized calcium carbonate, were loaded with bovine serum albumin and dipalmitoylphosphatidylcholine (DPPC) by solvent evaporation and results of the pore size distribution obtained by both methods were compared. The internal structure of the novel pharmaceutical excipient, functionalized calcium carbonate, was revealed for the first time. Our results demonstrated that image analysis provides a closer representation of the material distribution since it was possible to discriminate between blocked and filled pores. The physical nature of the loaded substances is critical for the deposition within the pores of functionalized calcium carbonate. We conclude, that a combination of mercury intrusion porosimetry and focused ion beam scanning electron microscopy allows for a reliable analysis of sub-micron porous structures of particulate drug carriers.
Highlights
Porous microparticles are promising carriers for the delivery of a wide variety of substances
For the mentioned applications [2,17,18,26,27,28,29], we have identified a major problem with drug loading into deep porous regions of investigated microparticles as well as the understanding of the internal structure
functionalized calcium carbonate (FCC) particles were loaded by an established solvent evaporation method [17] using two model compounds: a hydrophilic macromolecule (BSA with a molecular weight of 66 kDa) and Porous microparticles such as FCC can be used as carriers for drugs and other materials
Summary
Porous microparticles are promising carriers for the delivery of a wide variety of substances. Loading drugs into the porous structure of microparticles may increase the dissolution rate and the solubility of poorly soluble active pharmaceutical ingredients (API). This is achieved on one hand by enlarging the surface area, which is exposed to a dissolution medium, and on the other hand by increasing the internal energy of an API due to amorphization, because initial crystallization is inhibited by the restricted space inside the pore [1]. Microparticles can be used to deliver drugs to the site of action, for either systemic uptake or local treatment. Enteral administration of chemically inert and biodegradable drug carriers (such as, for example, calcium carbonate) is considered to be safe [7,8]
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