Biodegradation of Crystalline Cellulose Nanofibers by Means of Enzyme Immobilized-Alginate Beads and Microparticles

Abstract

<jats:p>Recent advances in nanocellulose technology have revealed the potential of crystalline cellulose nanofibers to reinforce materials which are useful for tissue engineering, among other functions. However, the low biodegradability of nanocellulose can possess some problems in biomedical applications. In this work, alginate particles with encapsulated enzyme cellulase extracted from Trichoderma reesei were prepared for the biodegradation of crystalline cellulose nanofibers, which carrier system could be incorporated in tissue engineering biomaterials to degrade the crystalline cellulose nanoreinforcement in situ and on-demand during tissue regeneration. Both alginate beads and microparticles were processed by extrusion-dropping and inkjet-based methods, respectively. Processing parameters like the alginate concentration, concentration of ionic crosslinker Ca2+, hardening time, and ionic strength of the medium were varied. The hydrolytic activity of the free and encapsulated enzyme was evaluated for unmodified (CNFs) and TEMPO-oxidized cellulose nanofibers (TOCNFs) in suspension (heterogeneous conditions); in comparison to solubilized cellulose derivatives (homogeneous conditions). The enzymatic activity was evaluated for temperatures between 25–75 °C, pH range from 3.5 to 8.0 and incubation times until 21 d. Encapsulated cellulase in general displayed higher activity compared to the free enzyme over wider temperature and pH ranges and for longer incubation times. A statistical design allowed optimizing the processing parameters for the preparation of enzyme-encapsulated alginate particles presenting the highest enzymatic activity and sphericity. The statistical analysis yielded the optimum particles characteristics and properties by using a formulation of 2% (w/v) alginate, a coagulation bath of 0.2 M CaCl2 and a hardening time of 1 h. In homogeneous conditions the highest catalytic activity was obtained at 55 °C and pH 4.8. These temperature and pH values were considered to study the biodegradation of the crystalline cellulose nanofibers in suspension. The encapsulated cellulase preserved its activity for several weeks over that of the free enzyme, which latter considerably decreased and practically showed deactivation after just 10 d. The alginate microparticles with their high surface area-to-volume ratio effectively allowed the controlled release of the encapsulated enzyme and thereby the sustained hydrolysis of the cellulose nanofibers. The relative activity of cellulase encapsulated in the microparticles leveled-off at around 60% after one day and practically remained at that value for three weeks.</jats:p>

Development of Bioinspired Functional Chitosan/Cellulose Nanofiber 3D Hydrogel Constructs by 3D Printing for Application in the Engineering of Mechanically Demanding Tissues

“…Finally, mechanical properties of CHI hydrogels could be improved by reinforcing with the CNFs. The enhanced properties are due to the CNFs nanoscale (large specific surface area), high Young's modulus, and aspect ratio typical of nanofibrillated cellulose [21,22,42,43,56]. In the hydrogel composites, an efficient matrix/reinforcement interaction should contribute to the stress transfer from the CHI matrix to the nanofibers, thereby yielding higher stiffness and strength.…”

“…Low toxicity has been reported, according to ecotoxicological, cytotoxicity and proinflammatory response studies [50][51][52]. Cellulose nanofibers have also been proposed for drug delivery systems [53], reinforcement for biomaterials [21,22,[54][55][56], protein immobilization [57], etc. In hydrogel biomaterials, the use of CNFs is promising-in addition to their mechanical performance, CNFs form a network with high water retention, they are biocompatible and can yield transparent biomaterials [21,22,54,58].…”

Nanoparticles and Colloidal Hydrogels of Chitosan–Caseinate Polyelectrolyte Complexes for Drug-Controlled Release Applications

“…They can substantially improve drug performance by providing better drug shielding, enhancing the specificity of the delivery, promoting its sustained release and tissue healing, regeneration, etc. [ 4 , 5 , 6 ].…”

Cellulosic/Polyvinyl Alcohol Composite Hydrogel: Synthesis, Characterization and Applications in Tissue Engineering

“…Cellulosic materials can persist in the crystalline form up to 5 months after implantation [ 78 ]. To overcome such vivo stability and to reinforce cellulose fibres usage as a biomaterial for tissue engineering, the degradation of cellulose may bee modulated by incorporating cellulase into the material [ 79 ].…”