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.
In this study, poly(ethylene-co-vinyl alcohol) (EVOH) as a novel biocompatible polymeric scaffold was surface modified by succinylation to get EVOHS and further pegylated to improve structural properties using methoxypolyethylene glycol (5000 Da) succinate (PEGS) along with targeting with retinoic acid (RA) to get final modified active and passive targeted conjugate (PEGS-EVOHS-RA) to evaluate its ability in carrying and delivery of epirubicin to hepatocellular carcinoma cell lines in response to varying temperatures. In this regard, the PEGS-EVOHS-RA conjugate was prepared through the desired chemical reactions and its structure was confirmed using 1H-NMR and FT-IR spectra. The micelles were prepared from PEGS-EVOHS-RA by dialysis method. The Particle size and zeta potential were measured, and entrapment efficacy along with in vitro release efficiency in different temperatures were also studied. The structural morphology of optimized nanomicelle was studied by transmission electron microscopy micrographs. The desired final micelles were evaluated for their toxicity using MTT assay on HepG2 human hepatocellular carcinoma cell lines at normal (37 °C) and elevated temperature (45 °C). The results revealed that, as the hydrophilicity of micelles increased, all characteristic properties improved. Then, these micelles can be considered as potentially effective thermo responsive delivery systems for targeted delivery of cytotoxic agents to hepatocellular carcinoma.
Despite the wide-spread use of liposomal drug delivery systems, application of these systems for oral purposes is limited due to their large-scale formulation and storage issues. Proliposomes are one of the formulation approaches for achieving solid powders that readily form liposomes upon hydration. In this work, we investigated a dry powder formulation of a model low-soluble drug with phospholipids loaded in porous functionalized calcium carbonate microparticles. We characterized the liposome formation under conditions that mimic the different gastrointestinal stages and studied the factors that influence the dissolution rate of the model drug. The liposomes that formed upon direct contact with the simulated gastric environment had a capacity to directly encapsulate 25% of the drug in situ. The emerged liposomes allowed complete dissolution of the drug within 15 min. We identified a negative correlation between the phospholipid content and the rate of water uptake. This correlation corroborated the results obtained for the rate of dissolution and liposome encapsulation efficiency. This approach allows for the development of solid proliposomal dosage formulations, which can be scaled up with regular processes.
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