Degradable glycine-based photo-polymerizable polyphosphazenes for use as scaffolds for tissue regeneration.

Photo-polymerizable scaffolds are designed and prepared via short chain poly(organo)phosphazene building blocks bearing glycine allylester moieties. The polyphosphazene was combined with a trifunctional thiol and divinylester in various ratios, followed by thiol-ene photo-polymerization to obtain porous matrices. Degradation studies under aqueous conditions showed increasing rates in correlation with the polyphosphazene content. Preliminary cell studies show the non-cytotoxic nature of the polymers and their degradation products, as well as the cell adhesion and proliferation of adipose-derived stem cells.

In vitro skin irritation: facts and future. State of the art review of mechanisms and models.

The skin is the main target tissue for exogenous noxes, protecting us from harmful environmental hazards, UV-irradiation and endogenous water loss. It is composed of three layers, whereas the outermost epidermis is a squamous epithelium that mainly consists of keratinocytes. These cells execute a terminal differentiation, which finally results in the assembly of the stratum corneum. This layer, consisting of cornified keratinocytes, is an effective barrier against a vast number of substances. Apart of this, keratinocytes play crucial roles in the immune surveillance and the initiation, modulation and regulation of inflammation in the epidermis. Regarding cutaneous inflammatory reactions, skin irritation is one of the most common adverse effect in humans. For reasons of human safety assessment new chemicals are still evaluated for irritant potentials by application to animals followed by visible changes such as erythema and oedema. Testing for skin irritation in animals potentially cause them pain and discomfort. Furthermore, the results are not always predictive for those found in humans. In order to replace animal testing and to improve the prediction of irritants, the cosmetic and toiletry industry, in Europe represented by Colipa, develops and uses several alternative in vitro test systems. In this respect, the use of in vitro reconstructed organotypic skin equivalents are mostly favored, because of their increasingly close resemblance to human skin. Due to ethical and scientific questions and on account of the 7th amendment of the European Council Directive 76/768/EEC, the authors see the requirement to drive the development of alternative tests for irritants. Therefore, this article centres on cosmetic ingredients and provides the readership an overview of the state of art of cellular mechanisms of skin irritation and summarizes the results of the commonly used skin equivalents to evaluate irritation in vitro.

Kiwi fruit (Actinidia chinensis L.) polysaccharides exert stimulating effects on cell proliferation via enhanced growth factor receptors, energy production, and collagen synthesis of human keratinocytes, fibroblasts, and skin equivalents.

Within physiological engineering exogenous carbohydrates were recently confirmed as pharmacologically active compounds. To investigate potential dermatological activity purified polysaccharides from kiwi fruits (Actinidia chinensis L., Actinidiaceae) were characterized concerning monomer composition, linkage types and molecular weights and were tested under in vitro conditions for regulating activities on cell physiology of human keratinocytes, fibroblasts, and skin equivalents. Ten micrograms per milliliter of raw polysaccharide, neutral type-II-arabinogalactans, and acidic arabinorhamnogalacturonans of kiwi fruits stimulated cell proliferation of human keratinocytes (NHK, HaCaT) up to 30% significantly while mitochondrial activity was stimulated for nearly 25% in regard to control cells. Fibroblasts were not as sensitive as keratinocytes but >130 microg/ml kiwi fruit polysaccharides increased proliferation and ATP-synthesis significantly, too. Proliferation-stimulating activity was dependent on terminal 1-alpha-l-arabinose residues since enzymatic release of these sugar moieties caused significantly decreased proliferation of HaCaT and fibroblasts of about 10% in regard to untreated cells. In three dimensional skin equivalents, it was shown that the polysaccharides led to a doubled collagen synthesis of fibroblasts compared to the normally strongly reduced biosynthetic activity.