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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:50 |
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Conference: Bucharest University Faculty of Physics 2010 Meeting
Section: Polymer Physics
Title:
Microstructural Morphology of Chitosan Hydrogels Using Atomic Force Microscopy
Authors:
V. Tripadus (1), L. Craciun (1), Cristina Ionescu (1), Luminita Tcacenco (2), O. Constantinescu (1)
Affiliation:
(1) National Institute of Physics and Nuclear Engineering, Bucharest, Romania
(2) National Institute for Biological Sciences, Bucharest, Romania
E-mail
tripadus@nipne.ro, cliviu@nipne.ro
Keywords:
chitosan, AFM, polysaccharides
Abstract:
Among other biodegradable polymers, the linear polysaccharide chitosan, has proved to be a good chemical entity for synthesizing hydrogels because of its greater crosslinking ability due to the presence of (NH2) amino groups. Its biodegradability, biocompatibility and other unique properties have been exploited in a medicine, pharmaceutics and tissue engineering amongst others. At high concentration, the chitosan solution is heterogeneous at different length scales and the concentration dependence of zero-shear specific viscosity presents a critical concentration (C*) which corresponds to the beginning of physical contact point of biopolymer molecules. For concentrations grater than C* the chitosan polymer molecules form aggregates whose mechanism of growing are not enough known, therefore estimation of their size as well as water diffusion inside them are the subject of great interest. The formation of submicrometric chain aggregates driven by hydrophobic interactions was evidenced. The control of the solution morphology and more precisely the presence of heterogeneities appear essential in the elaboration of physical hydrogels, the formation of nanoparticles or the processing of solid forms. We carried out an AFM microscopic study on two chitosan hydrogel samples an uncrosslinked and a glutaraldehyde crosslinked sample. Chitosan having an average molecular weight of 10,000 Dalton and a degree of deacetylation higher than 85% was supplied by Sigma Company. The AFM employed in this study is a MultiMode NanoScope IIID Controller(Digital Instruments Veeco Metrology Group, Santa Barbra, CA, USA) that provides high and phase images of different samples regions simultaneously with a very good resolution. The micrographs display a structure at two levels of organization consisting in nanometric particles interconnected or agglomerated into micrometric clusters entrapping the solvent. The aggregates have a spherical form with the diameter comprised between 8 nm and 50 nm. For crosslinked sample we observed a better homogenization of the hydrogel. At the same time the nanoparticles are more uniformly distributed in the system.
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