Thermodynamic Study of the Interaction of Bovine Serum Albumin and Amino Acids with Cellulose Nanocrystals

Abstract

The interaction of bovine serum albumin (BSA) with sulfated, carboxylated, and pyridinium-grafted cellulose nanocrystals (CNCs) was studied as a function of the degree of substitution by determining the adsorption isotherm and by directly measuring the thermodynamics of interaction. The adsorption of BSA onto positively charged pyridinium-grafted cellulose nanocrystals followed Langmuirian adsorption with the maximum amount of adsorbed protein increasing linearly with increasing degree of substitution. The binding mechanism between the positively charged pyridinum-grafted cellulose nanocrystals and BSA was found to be endothermic and based on charge neutralization. A positive entropy of adsorption associated with an increase of the degree of disorder upon addition of BSA compensated for the unfavorable endothermic enthalpy and enabled formation of pyridinium-g-CNC-BSA complexes. The endothermic enthalpy of adsorption was further found to decrease as a function of increasing degree of substitution. Negatively charged cellulose nanocrystals bearing sulfate and/or carboxylic functionalities were found to not interact significantly with the BSA protein. To investigate in more detail the role of single amino acids in the adsorption of proteins onto cellulose nanocrystals, we also studied the interaction of different types of amino acids with CNCs, i.e., charged (lysine, aspartic acid), aromatic (tryptophan, tyrosine), and polar (serine) amino acids. We found that none of the single amino acids bound with CNCs irrespective of surface charge and that therefore the binding of proteins with CNCs appears to require larger amino acid sequences that induce a greater entropic contribution to stabilize binding. Single amino acids are thus not adsorbed onto cellulose nanocrystals.

Reversible pH Responsive Bovine Serum Albumin Hydrogel Sponge Nanolayer

“…Multiple articles have extensively reported on the BSA molecules sorption phenomenon at different interfaces such as gold (Dennison et al, 2017), mica (Fitzpatrick et al, 1992), silicon (Jachimska et al, 2016;Givens et al, 2017), and cellulose (Mohan et al, 2014;Lombardo et al, 2017). The adsorbed BSA molecule's conformation and the topology of the formed layer are strongly affected by pH, ionic strength and temperature.…”

Lectins at Interfaces—An Atomic Force Microscopy and Multi-Parameter-Surface Plasmon Resonance Study

“…This may even lead to denaturation of the protein, if the degree of interaction is very high. It is widely accepted that this process is mainly governed by entropic contributions rather than enthalpy, unless specific interactions come into play [27]. However, it should be noted here, that also non-hydrophobic effects may contribute to entropy, such as changes in low energy vibrational states.…”

Engineered Multilayer Microcapsules Based on Polysaccharides Nanomaterials

“…Systems of polymeric polysaccharide-based microcapsules stabilized by electrostatic interaction, hydrogen bonding, covalent crosslinking, ionic cross-linking, and host–guest interactions, have been reported [ 12 ]. Interactions between opposite charges are of particular interest for polysaccharide nanomaterials, as binding can be controlled by the degree of substitution, and their surface chemistry could be further exploited for controlled attachment of drugs or other species [ 109 , 110 ]. The layer-by-layer approach has been widely used to prepare nanocellulose-based films in combination with oppositely charged polyelectrolytes, [ 111 ] or with other cell wall polysaccharides such as xyloglucan [ 112 ].…”