Proteins covered with aldehyde-dextran have been used as carrier molecules to detect the immuno-response against an aminated hapten. These conjugates were used in immunodetection after immobilization on ELISA plates and compared to hapten-protein conjugates produced by the same chemistry that was used to induce the immuno-response (by carbodiimide coupling method). It has been found that the use of dextran-protein carriers conjugates avoid the high cross-reaction found using the carbodiimide routes. The modification degree of the dextran by aminated haptens depended on the pH (the best results were achieved at alkaline pH values) and presence of organic solvents (the presence of dioxane improved the modification). (C) 2004 Elsevier Inc. All rights reserved.