Electrochemical and atomic force microscopy study of the enzymatic degradation of cellulose thin films

Electrochemistry and atomic force microscopy have been combined to characterize native cellulose thin films on Au(111) and to monitor its in situ degradation by bacterial endoglucanase, CenA from Cellomonas fimi. Using the Langmuir-Blodgett technique, cellulose films were transferred onto Au(111) from cellulose dispersions. The electrochemical results showed successful film transfers and the importance of drying for film stabilization. The optimal conditions for film preparation was with cellulose from A. xylinum in a dispersion of 2 mg mL-1 and transferred at 5 mN m-1. The gold was modified using self assembled monolayers of thioglycerol to improve adhesion. Under these conditions it was possible to produce high resolution images of cellulose fibers 20--200 nm in diameter and microfibrils 2--7 nm in diameter. The results were reproduced with a cellulose film that had never been dried and imaged using MAC mode atomic force microscopy. Finally, the in situ degradation of the model thin film was monitored using atomic force microscopy. It was shown that digestion begins 3 minutes after the addition of the enzyme and after 3 hours the majority of the fibers have been digested or loosened from the gold surface.