Nanocellulose-lysozyme colloidal gels via electrostatic complexation.

Area of Science:

• Materials Science
• Biomaterials Engineering
• Colloid Science

Background:

• Cellulose nanofibrils (CNF) are versatile biomaterials.
• Protein-based materials offer unique functionalities.
• Biohybrid materials combine properties of both components.

Purpose of the Study:

• To fabricate and characterize biohybrid colloids from TEMPO-oxidized cellulose nanofibrils (TO-CNF) and hen egg white lysozyme (HEWL).
• To investigate the influence of HEWL loading and pH on colloidal complex formation, gelation, and rheological properties.
• To explore the potential of these biohybrid systems for tunable material applications.

Main Methods:

• Electrostatic complexation between anionic TO-CNF and cationic HEWL.
• Varying HEWL loading to control colloidal complex formation.
• Zeta-potential measurements to probe charge screening and aggregation.
• Rheological testing to evaluate mechanical properties and stability.
• Thermo-cycling and pH variation to assess material responsiveness.

Main Results:

• Formation of physical colloidal complexes and gels at low TO-CNF concentrations (0.1 wt%).
• Increased HEWL loading enhanced charge screening, leading to TO-CNF aggregation and gelation.
• Mechanical reinforcement of gels achieved by increasing HEWL loading.
• Colloidal gels showed partial destruction under cyclic shear but resisted temperatures up to 90 °C.
• Demonstrated pH responsiveness for tunable gelation based on HEWL's isoelectric point.

Conclusions:

• Electrostatic complexation is a viable method for forming HEWL/TO-CNF hybrid colloids.
• Colloidal morphology and rheology are tunable by adjusting component ratios and pH.
• These biohybrid systems show promise for applications requiring responsive and tunable materials.