Immobilization of Paclitaxel on Hydroxyapatite for Breast Cancer Investigations.

A simple method for immobilization of the chemotherapy drug paclitaxel (PTX) on hydroxyapatite nanoparticles (n-HAP) using the biopolymer chitosan as a trapping agent is described focusing on applications involving breast cancer cells. n-HAP with two distinct crystallinity profiles were used: with predominant crystallization along the long axis and with a more homogeneous crystallization in all directions. In the first scenario, the interactions between chitosan and both the OH and PO43- groups on the surface of the nanoparticles are favored and lead to a more efficient attachment of the drug. In this case, PTX is found to remain mostly attached to the n-HAP for at least 24 h, while being dispersed in aqueous solution. During this time, the activity of the drug is inhibited as corroborated by in vitro assays with breast cancer cells. With that, the in vitro experiments revealed distinct effects from the drug-loaded nanoparticles on the cells depending on the experimental conditions. In a short term, that is, in 24 h, the cells exhibit higher viability than those challenged with nonloaded materials. Nevertheless, after 72 h, even a small content of PTX in the presence of n-HAP can reduce the cells' viability via stimulation of the apoptotic phenotype and suppression of survival stimuli.

Maxwell times in higher-order generalized hydrodynamics: Classical fluids, and carriers and phonons in semiconductors.

A family of what can be so-called Maxwell times which arises in the context of higher-order generalized hydrodynamics (HOGH; also called mesoscopic hydrothermodynamics) is evidenced. This is done in the framework of a HOGH built within a statistical formalism in terms of a nonequilibrium statistical ensemble formalism. It consists in a description in terms of the densities of particles and energy and their fluxes of all orders, with the motion described by a set of coupled nonlinear integro-differential equations involving them. These Maxwell times have a fundamental role in determining the type of hydrodynamic motion that the system would display in the given conditions and constraints. They determine a Maxwell viscous force not present in the usual hydrodynamic equations, for example, in Navier-Stokes equation.

Higher-order generalized hydrodynamics: Foundations within a nonequilibrium statistical ensemble formalism.

Construction, in the framework of a nonequilibrium statistical ensemble formalism, of a higher-order generalized hydrodynamics, also referred to as mesoscopic hydrothermodynamics, that is, covering phenomena involving motion of fluids displaying variations short in space and fast in time-unrestricted values of Knudsen numbers, is presented. In that way, an approach is provided enabling the coupling and simultaneous treatment of the kinetics and hydrodynamic levels of descriptions. It is based on a complete thermostatistical approach in terms of the densities of matter and energy and their fluxes of all orders covering systems arbitrarily driven away from equilibrium. The set of coupled nonlinear integrodifferential hydrodynamic equations is derived. They are the evolution equations of the Gradlike moments of all orders, derived from a generalized kinetic equation built in the framework of the nonequilibrium statistical ensemble formalism. For illustration, the case of a system of particles embedded in a fluid acting as a thermal bath is fully described. The resulting enormous set of coupled evolution equations is of unmanageable proportions, thus requiring in practice to introduce an appropriate description using the smallest possible number of variables. We have obtained a hierarchy of Maxwell times, associated to the set of all the higher-order fluxes, which have a particular relevance in the process of providing criteria for establishing the contraction of description.