No abstract

In an attempt to develop drug delivery systems that bypass the blood–brain barrier (BBB) and prevent liver and intestinal degradation, it was concluded that nasal medication meets these criteria and can be used for drugs that have these drawbacks. The aim of this review is to present the influence of the properties of chitosan and its derivatives (mucoadhesion, permeability enhancement, surface tension, and zeta potential) on the development of suitable nasal drug delivery systems and on the nasal bioavailability of various active pharmaceutical ingredients. Interactions between chitosan and proteins, lipids, antigens, and other molecules lead to complexes that have their own applications or to changing characteristics of the substances involved in the bond (conformational changes, increased stability or solubility, etc.). Chitosan and its derivatives have their own actions (antibacterial, antifungal, immunostimulant, antioxidant, etc.) and can be used as such or in combination with other molecules from the same class to achieve a synergistic effect. The applicability of the properties is set out in the second part of the paper, where nasal formulations based on chitosan are described (vaccines, hydrogels, nanoparticles, nanostructured lipid carriers (NLC), powders, emulsions, etc.).

No abstract

No abstract

The aim of this paper is to study the w * -fixed point property for nonexpansive mappings in the duals of separable Lindenstrauss spaces by means of suitable geometrical properties of the dual ball. First we show that a property concerning the behaviour of a class of w * -closed subsets of the dual sphere is equivalent to the w * -fixed point property. Then, the main result of our paper shows an equivalence between another, stronger geometrical property of the dual ball and the stable w * -fixed point property. The last geometrical notion was introduced by Fonf and Veselý as a strengthening of the notion of polyhedrality. In the last section we show that also the first geometrical assumption that we have introduced can be related to a polyhedral concept for the predual space. Indeed, we give a hierarchical structure among various polyhedrality notions in the framework of Lindenstrauss spaces. Finally, as a by-product, we obtain an improvement of an old result about the norm-preserving compact extension of compact operators.2010 Mathematics Subject Classification. 47H10, 46B45, 46B25. Key words and phrases. w * -fixed point property, stability of the w * -fixed point property, Lindenstrauss spaces, Polyhedral spaces, ℓ 1 space, Extension of compact operators.