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Surface modification of biomaterials with polymer chains has attracted great attention because of their ability to control biointerfacial interactions such as protein adsorption, cell attachment and bacterial biofilm formation. The aim of this study was to control the immobilisation of biomolecules on silicon wafers using poly(ethylene glycol)(PEG) chains by a "grafting to" technique. In particular, to control the polymer chain graft density in order to capture proteins and preserve their activity in cell culture as well as find the optimal density that would totally prevent bacterial attachment. The PEG graft density was varied by changing the polymer solubility using an increasing salt concentration. The silicon substrates were initially modified with aminopropyl-triethoxysilane (APTES), where the surface density of amine groups was optimised using different concentrations. The results showed under specific conditions, the PEG density was highest with grafting under "cloud point" conditions. The modified surfaces were characterised with X-ray photoelectron spectroscopy (XPS), ellipsometry, atomic force microscopy (AFM) and water contact angle measurements. In addition, all modified surfaces were tested with protein solutions and in cell (mesenchymal stem cells and MG63 osteoblast-like cells) and bacterial (Pseudomonas aeruginosa) attachment assays. Overall, the lowest protein adsorption was observed on the highest polymer graft density, bacterial adhesion was very low on all modified surfaces, and it can be seen that the attachment of mammalian cells gradually increased as the PEG grafting density decreased, reaching the maximum attachment at medium PEG densities. The results demonstrate that, at certain PEG surface coverages, mammalian cell attachment can be tuned with the potential to optimise their behaviour with controlled serum protein adsorption. [ABSTRACT FROM AUTHOR]

Colloidal self-assembly into highly ordered binary systems represents a versatile and inexpensive approach to generate well defined surface topographical features with submicron resolution. In addition, the use of surface-functionalized particles where each particle bears a different surface functionality enables the generation of highly resolved surface chemical patterns. Such topographical, as well as chemical features, are of great interest in biomaterials science particularly in the context of investigating and controlling the cellular response. While colloidal crystals have been used to generate a wide range of surface patterns, it has not been possible until now to quantitatively describe the degree of uniformity within such systems. In the present work we describe a novel approach to quantitatively assess the uniformity within binary colloidal assemblies based on image processing methods, primarily the Circular Hough Transform and distance calculations. We believe that the methodology presented here will find broad application in the field of colloidal crystals to quantitatively describe the integrity and homogeneity of assemblies. [ABSTRACT FROM AUTHOR]

Ardipusilloside-I (ADS-I) is a triterpenoid saponin extracted from Ardisia pusilla DC, and has been demonstrated to have potent antitumor activity. However, ADS-I metabolism in humans has not been investigated. In this study, we studied the biotransformation of ADS-I in human intestinal bacteria, and examined the in vitro antitumor activity of the major metabolites. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used to detect ADS-I biotransformation products, and their chemical structures were identified by high performance liquid chromatography-nuclear magnetic resonance (HPLC-NMR). The antitumor activity of the major metabolites was determined by the MTT assay. Here, we show that main reaction seen in the metabolism of ADS-I in human intestinal bacteria was deglycosylation, which produced a total of four metabolites. The structures of the two major metabolites M1 and M2 were confirmed by using NMR. MTT assay showed that ADS-I metabolites M1 and M2 have the same levels of inhibitory activities as ADS-I in cultured SMMC-7721 cells and MCF-7 cells. In conclusion, this study demonstrates deglycosylation as a primary pathway of ADS-I metabolism in human intestinal bacteria, and suggests that the pharmacological activity of ADS-I may be mediated, at least in part, by its metabolites. [ABSTRACT FROM AUTHOR]