Real-time insights into the effect of cellulose nanocrystals on the trypsin hydrolysis of bovine serum albumin using interferometric spectroscopy.

Cellulose nanocrystals (CNCs) possess the characteristic of biodegradability and are utilized in the construction of biological matrix materials. Negatively charged CNCs were prepared by hydrolyzing microcrystalline cellulose (MCC) with sulfuric acid. Taking bovine serum albumin (BSA) as an example, the real-time interaction between CNCs and BSA and the effect of CNCs on the hydrolysis of BSA by model enzymes (trypsin) were tracked. A three-dimensional silica colloidal crystal (SCC) film was selected as the interference layer to establish an ordered porous layer interferometry (OPLI) system. The real-time interaction process between CNCs and proteins was monitored by converting the migration of the interference spectra in the OPLI system into real-time changes in the optical thickness (ΔOT). Compared to the direct hydrolysis of BSA by 0.5 mg mL-1 trypsin, the addition of CNCs caused OT to change from a decrease of 1.5 ± 0.4 nm to an increase of 1.3 ± 0.6 nm. The effects of CNCs on BSA adsorption and trypsin-mediated BSA degradation were analyzed by monitoring in real-time ΔOT. Analysis of absorption spectroscopy, zeta potential, and particle size distribution data indicates that CNCs inhibit BSA degradation by trypsin. This work reveals the interactions between nanocellulose and macromolecules at the microscopic level.