Cellulose has gained attention as a remarkably versatile biomaterial, owing to its desirable physical properties and biocompatibility, for various biomedical applications. TEMPO (2,2,6,6-tetramethyl-piperidinyl-1-oxyl) radicals oxidized cellulose and nanocellulose microfibrils, in particular, have been recently explored as tissue scaffold materials for wound care and tissue regeneration. However, we currently have a poor understanding of the structure-function relationships guiding protein adsorption to cellulose fibrils and its derivatives that can impact the design and performance of such biomedical devices/implants. In the current study, we have used a carbohydrate binding module or CBM from family 3a (CBM-3a), tagged to a green fluorescent protein (GFP), to characterize protein adsorption to TEMPO-oxidized cellulose microfibrils. CBMs are auxiliary protein domains with autonomous folding that target recognition and binding of glycans (like cellulose) through hydrogen bonding with polar residues, van der Waals (CH-pi bonds) interactions with aromatic amino acids, and/or electrostatic interactions with charged/polar residues. We next created a library of oxidized cellulose with varying degrees of carboxylate surface charge densities using TEMPO chemistry to mimic cellulose fibrils surface modifications relevant for biomedical applications. We then used GFP-fluorescence based subtractive mass balance assays to study the impact of pH, oxidized cellulose surface charge, protein concentration, and buffer ionic strength on protein adsorption to TEMPO-oxidized cellulose. It was determined that both pH and cellulose surface charge are strongly correlated to the amount of bound protein. This can be primarily explained in terms of interfacial electrostatic repulsions between the protein and surface of oxidized cellulose. We also hypothesize that the effect of salt concentration on protein adsorption to oxidized cellulose, can be explained by means of electrostatic screening effects. In summary, our results provide insights into protein and cellulose surface properties that can directly impact the performance of various cellulose-derived biomedical devices or implants.

Understanding protein adsorption to TEMPO-oxidized cellulose microfibrils

253rd National Meeting (2017)

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