Tracing cellulose elements adsorbed on composite cellulose biomaterials by a new labeling method

In view of tracing the fate of cellulose fine elements added to a suspension of cellulose fibers, a novel method for specific labeling of polysaccharides in a composite material was developed. The purpose was to visualize a given cellulose material within a cellulose mixture. The method consists of generating aldehyde groups in the chain by mild periodic acid oxidation followed by biotinylation of the carbonyls. Once added to the composite, the biotinylated molecules are labeled with streptavidin conjugated to a fluorescent probe for confocal microscopy, or streptavidin-gold for electron microscopy observations. In the present work, the fate of fresh fines (never-dried) and dead fines (dried) when they were added to a purified suspension of fibers was followed by observation of the labeling in confocal and electron microscopy. The differential mode of interaction of fresh fines and dead fines with the fibers was correlated to the mechanical characteristics measured on the corresponding papers. The versatility of the new labeling method and its possible generalization to other polysaccharides incorporated to a polysaccharide or nonpolysaccharide material should be of potential interest for the study of composite microstructure.