Peculiar Mechanism of Solubilization of a Sparingly Water Soluble Drug into Polymeric Micelles. Kinetic and Equilibrium Studies

Complementary kinetic and equilibrium studies on the solubilization process of the sparingly water soluble tamoxifen (TAM) drug in polymeric aqueous solutions have been performed by using the spectrophotometric method. In particular, the amphiphilic copolymers obtained by derivatization of polymeric chain of poly(N-2-hydroxyethyl)-DLaspartamide, PHEA, with poly(ethylene glycol)s, PEG (2000 or 5000 Da), and/or hexadecylamine chain, C16, namely PHEA-PEG2000-C16, PHEA-PEG5000-C16, PHEA-C16, have been employed. Preliminary to the kinetic and equilibrium data quantitative treatment, the molar absorption coefficient of TAM in polymeric micelle aqueous solution has been determined. By these studies the solubization sites of TAM into the polymeric micelles have been determined and the solubilization mechanism has been elucidated through a nonconventional approach by considering the TAM partitioned between three pseudophases, i.e., the aqueous pseudophase, the hydrophilic corona, and the hydrophobic core. The simultaneous solution of the rate laws associated with each step of the proposed mechanism allowed the calculation of the rate constants associated with the involved processes, the values of which are independent of both the copolymer concentration and nature, with the exception of the rate of the TAM transfer from the corona to the core. This has been attributed to the steric barrier, represented by the corona, which hampers the solubilization into the core. The binding constant values of the TAM to the hydrophilic corona of the polymeric micelles, calculated through the quantitative analysis of the equilibrium data, depend on the thickness of the hydrophilic headgroup, while those of the hydrophobic core are almost independent of the copolymer type. Further confirmation to the proposed solubilization mechanism has been provided by performing the kinetic and equilibrium measurements in the presence of PHEA-PEG2000 and PHEAPEG5000 copolymers

Family and non-family women on the board of directors:Effects on corporate citizenship behavior in family-controlled fashion firms

Drawing on self-construal theory and the family business literature, we offer theory and evidence on how the presence of women, either family members or not, on the board of directors of family firms affects firm engagement in corporate citizenship behavior. In examining corporate citizenship behavior, we argue that it is important to distinguish between corporate social responsibility and philanthropy as well as between family and non-family women on the board of directors. Using data from the population of 63 family-controlled firms in the global ranking of the top-100 fashion firms, we find support for our hypotheses: female directors are beneficial for corporate social responsibility engagement only if they are not members of the controlling family, while they are beneficial for philanthropic engagement only if they are members of the controlling family

Clay-biosurfactant materials as functional drug delivery systems: Slowing down effect in the in vitro release of cinnamic acid

The main objectives of the present paper were the preparation and characterization of new surfactant-modified clays and the evaluation of their potential applicability as drug delivery systems for the oral administration of the cinnamic acid (CA) drug. The organoclays (OC) were prepared by loading different amounts of the biocompatible nonionic polyoxyethylene sorbitan monolaurate surfactant (Tween20) onto K10 montmorillonite (Mt) clay and characterized through the construction of the adsorption isotherms by means of the spectrophotometric method. The performance of the prepared material was verified by gathering the adsorption isotherms of the cinnamic acid onto the Mt/Tween20 organoclay and by monitoring the release profiles in both simulated gastric (SGF) and intestinal fluids (SIF). The quantitative analysis of the adsorption isotherms revealed that the uptake of the aromatic component onto both the blank and Tween20-loaded Mt was governed by positive cooperative processes and that the presence of the bio-surfactant enhanced the loading efficiency of the clay. By relating the raw montmorillonite uptake capability with that of the OC it was assessed that the presence of the bio-surfactant enhanced about 2 times the loading efficiency of the clay. From the XRD characterization of the obtained complexes, the successful intercalation of the drug into the prepared organoclay was demonstrated. Very useful information was obtained by the in vitro release studies, which showed that the release of the drug from both the clay and organoclay was prolonged in comparison with the pharmacokinetics of the free drug. Besides, the intercalation of the surfactant into the nano-carrier ensured the complete release of the CA after oral drug administration and the kinetics of the release process was strongly dependent on the type of drug formulation used, which means that the CA release can be modulated by properly functionalizing the clay surface