Comparative Evaluation of Drug Incorporation and Release Profiles in Six Specific Porous Vaterite CaCO3 Formulations.

Background: Vaterite calcium carbonate (CaCO3) particles are promising pH-sensitive carriers for oral drug delivery, but the influence of drug hydrophilicity on loading and release is still not well defined. In this study, we evaluate the encapsulation and release profiles of six specific formulations utilizing metformin and meloxicam across distinct CaCO3 carrier variants and loading methodologies. Methods: We prepared vaterite CaCO3 particles as native (and PVP-stabilized) carriers and utilized co-precipitation, post-loading (adsorption), and sonication-assisted loading techniques. We subsequently evaluated carrier morphology, phase stability, encapsulation efficiency, surface adsorption capacity, and in vitro drug release in simulated gastric (pH 1.2) and intestinal (pH 6.8) media. Results: Quantitative image analysis confirmed that porous vaterite particles formed primarily in the micron range, with PVP stabilization significantly reducing the mean particle diameter compared to native carriers (0.966 µm versus 1.189 µm). Furthermore, extended exposure to aqueous media induced partial transformation to calcite. The highest encapsulation efficiency for metformin (93.0 ± 1.5%) was achieved using co-precipitation, whereas for meloxicam (79.6 ± 1.9%), it was optimized through sonication-assisted adsorption on the PVP-modified carriers. In vitro release showed a clear pH-dependent behavior; the fast dissolution of the vaterite through gastric pH was associated with the fast release of metformin, especially in the calcite-containing formulation that produced the greatest release (98.0 ± 3.3%) in 15 min. At intestinal pH, metformin and meloxicam exhibited sustained release as in the Korsmeyer-Peppas model. Conclusions: The evaluated carrier compositions and loading methodologies distinctly influenced the encapsulation and release profiles of the six prepared formulations. These specific formulation comparisons highlight practical considerations for utilizing vaterite carriers for varied release targets.