ABSTRACT
Amphiphilic polyelectrolyte based on curdlan derivative containing quaternary ammonium groups with a degree of substitution up to 0.4 was synthesized and characterized. The chemical structure of the amphiphilic curdlan derivative was confirmed by FTIR, 13C and 1H NMR spectroscopy. The 2D NMR homo- and heteronuclear correlations were used to attribute the ambiguous 1D NMR signals from 1H and 13C spectra. The hydrodynamic properties of this new derivative were studied by capillary viscometry. The non-linear Wolf equation was used to determine the intrinsic viscosity and the scaling theory was used to delimitate the concentration domains. The self-aggregation of the amphiphilic derivative was studied by fluorescence spectroscopy using pyrene and N-phenylnaphthylamine as micropolarity sensitive probes, and by surface tension measurements. The results obtained from the antibacterial and antifungal tests performed on E. coli, P. aeruginosa bacteria, and C. albicans fungi recommend this new amphiphilic derivative to be used either as a soluble biopolymer or as a precursor for the preparation of new biomaterials with antimicrobial properties.
ABSTRACT
In this work, we study the adhesion forces between atomic force microscopy (AFM) tips and superficial dentin etched with phosphoric acid. Initially, we quantitatively analyze the effect of acid etching on the surface heterogeneity and the surface roughness, two parameters that play a key role in the adhesion phenomenon. From a statistical study of the force-distance curves, we determine the average adhesion forces on the processed substrates. Our results show that the average adhesion forces, measured in water, increase linearly with the acid exposure time. The highest values of such forces are ascribed to the high density of collagen fibers on the etched surfaces. The individual contribution of exposed collagen fibrils to the adhesion force is highlighted. We also discuss in this paper the influence of the environmental medium (water/air) in the adhesion measurements. We show that the weak forces involved require working in the aqueous medium.
