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Oil-filled microcapsules of kraft lignin were synthesized by first creating an oil in water emulsion followed by a high-intensity, ultrasound-assisted cross-linking of lignin at the water/oil interface. The rationale behind our approach is based on promoting documented lignin hydrophobic interactions within the oil phase, followed by locking the resulting spherical microsystems by covalent cross-linking using a high intensity ultrasound treatment. As further evidence in support of our rationale, confocal and optical microscopies demonstrated the uniformly spherical morphology of the created lignin microparticles. The detailed elucidation of the cross-linking processes was carried out using gel permeation chromatography (GPC) and quantitative (31)P NMR analyses. The ability of lignin microcapsules to incorporate and release Coumarin-6 was evaluated in detail. In vitro studies and confocal laser scanning microscopy analysis were carried out to assess the internalization of capsules into Chinese hamster ovary (CHO) cells. This part of our work demonstrated that the lignin microcapsules are not cytotoxic and readily incorporated in the CHO cells.

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This paper reviews our previous studies on the diffusion behavior in polymers clay nanocomposites. A geometric model for predicting the effective diffusivity through this type of systems as a function of clay sheets orientation, volume fraction, polymer clay interaction, and aspect ratio is proposed. Model predictions are compared to the effective diffusivity generated using random walk simulations as well as with predictions obtained from already existing theoretical models. Fair agreement is found between the model prediction and the results of numerical simulations. With respect to the already existing theoretical models, the present mathematical derivation seems more adequate to describe diffusion behavior in conventional nanocomposites systems (i.e. when fillers present very low values of volume to surface ratio). Experimental diffusion tests are discussed and interpreted with the aid of the proposed model. In addition to the aspect ratio and clay concentration, the polymer clay interactions as well as the sheets orientation are the factors controlling the barrier properties of polymer-layered silicate nanocomposites. Good agreement was found in the case of samples containing exfoliated clay, whereas the model fails in the case of micro-composites, in which the inorganic lamellae are agglomerated in clusters.

Nitric oxide plays a central role in controlling arterial thrombosis and in cardiovascular diseases by inhibiting the platelet aggregation process. This process is regulated by giving a deactivating signal for the protein membrane integrins, the major platelet adhesion receptors. The localized production of NO, naturally occurring in arterial vessels, is carried out by the NO synthase enzymatic system. Inhibition of platelets aggregation in the coagulation cascade process is due to the antagonist action of NO toward integrin-fibrinogen induced platelet adhesion. However, sometimes the natural supply of NO is not sufficient to prevent clotting. The design of devices for suitable transport and delivery of NO is therefore important. We are developing a new concept of drug delivery in which NO release can be performed by means of polymer shelled microbubbles. The NO release can theoretically be concentrated in vessels with acute thrombosis by bursting of the microparticles upon insonification. This feature is linked to the structural and mechanical properties of the particles shell and it would make minimally invasive local theraphy of acute vascular disease feasible. In this paper, we present a study on some new structural and mechanical features of this microdevice supporting its NO loading capacity and in vitro efficacy in preventing the formation of a clot by releasing NO.

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The structural characterization and transport properties of blends of a commercial high molecular weight poly(ϵ‐caprolactone) with different amounts of a montmorillonite‐poly(ϵ‐caprolactone) nanocomposite containing 30 wt % clay were studied. Two different vapors were used for the sorption and diffusion analysis—water as a hydrophilic permeant and dichloromethane as anorganic permeant—in the range of vapor activity between 0.2 and 0.8. The blends showed improved mechanical properties in terms of flexibility and drawability as compared with the starting nanocomposites. The permeability (P), calculated as the product of the sorption (S) and the zero‐concentration diffusion coefficient (D0), showed a strong dependence on the clay content in the blends. It greatly decreased on increasing the montmorillonite content for both vapors. This behavior was largely dominated by the diffusion parameters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1118–1124, 2002

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