Surface-reacted calcium carbonate microparticles as templates for lactoferrin encapsulation.

Microencapsulation helps to improve bioavailability of a functional whey protein, lactoferrin (Lf), in adults. Herein, we report the Lf loading capacity (LC) and retention efficiency (RE) in the microparticles of surface-reacted calcium carbonate (SRCC) of different types and compare them to those of widely used vaterite microparticles. The LCs and REs are analyzed in connection to the total surface area and the volume of intraparticle pores. The best performing SRCC3 demonstrates Lf LC of 11.00 wt% achieved in a single absorption step and 74% RE after two cycles of washing with deionized water. A much larger surface area of SRCC templates and a lower pH required to release Lf do not affect its antitumor activity in MCF-7 assay. Layer-by-Layer assembly of pepsin-tannic acid multilayer shell around Lf-loaded microparticles followed by acidic decomposition of the inorganic core produces microencapsulated Lf with a yield ~36 times higher than from vaterite templates reported earlier, while the scale of encapsulated Lf production is ~12,000 times larger. In vitro digestion tests demonstrate the protection of ~65% of encapsulated Lf from gastric digestion. The developed capsules are prospective candidates for functional foods fortified with Lf.

Effect of capillary element aspect ratio on the dynamic imbibition within porous networks.

The Washburn equation is widely accepted for describing capillary imbibition. It has, however, been shown to be insufficient at very short times due partly to the lack of inertial terms. Bosanquet (C. H. Bosanquet, Philos. Mag. ser. 645, 525 (1923)) applied an inertial term via momentum, Szekely et al. (J. Szekely, A. W. Neumann, and Y. K. Chang, J. Colloid Interface Sci.35, 273 (1971)) examined single capillaries based on a revised boundary-condition model, and Sorbie et al. (K. S. Sorbie, Y. Z. Wu, and S. R. McDougall, J. Colloid Interface Sci. 289 (1995)) reviewed and applied Szekely's work to examine the effects of comparative imbibition into a parallel pore doublet. The study here extends the work of Sorbie et al. by applying the equation of Bosanquet to a three-dimensional network model, Pore-Cor. All authors agree that, with the inclusion of inertial terms at short times, smaller radius capillaries will initially fill faster than larger radius capillaries which disagrees with the Washburn equation. It is shown that the aspect ratio of a capillary, defined as its length divided by its radius, plays an important role, in combination with the capillary radii themselves, in determining the filling rate of individual elements. The distribution of this ratio associated with the capillary throat elements within a network structure is investigated. The result is that a preferred pathway of permeation is observed under supersource imbibition conditions in the case where a broad size distribution of capillary elements occurs within a network structure.

The Effects of Void Geometry and Contact Angle on the Absorption of Liquids into Porous Calcium Carbonate Structures.

The absorption (permeation) of alcohols into porous blocks of calcium carbonate has been studied experimentally and with a computer model. The experimental measurement was of change in apparent weight of a block with time after contact with liquid. The modeling used the previously developed 'Pore-Cor' model, based on unit cells of 1000 cubic pores connected by cylindrical throats. To gain some insight into absorption into voids of complex geometry, and to provide a representation of heterogeneities in surface interaction energy, the cylindrical throats were converted to double cones. Relative to cylinders, such geometries caused hold-ups of the percolation of nonwetting fluids with respect to increasing applied pressure, and a change in the rate of absorption of wetting fluids. Both the measured absorption of the alcohols and the simulated absorption of the alcohols and of water showed significant deviations from that predicted by an effective hydraulic radius approximation. The simulation demonstrated the development of a highly heterogeneous wetting front, and of preferred wetting pathways that were perturbed by inertial retardation. The findings are useful in the design of high-performance, low-waste pigments for paper coatings, and environmentally friendly printing inks, as well as in wider industrial, environmental, and geological contexts. Copyright 2001 Academic Press.