Abstract
In this study, chitosan hydrogels were produced with 0, 2, 4 and 6 wt% of cellulose nanocrystals (CNC) using hexahydrate zinc nitrate (Zn(NO3)2.6H2O) as a catalyst for chitosan crosslinking reaction. CNC´s size was estimated by dynamic light scattering (DLS) and surface charge by zeta potential. Hydrogels were characterized by rotational rheometer, swelling test, uniaxial compression test, in vitro degradation, scanning electron microscopy (SEM) and microtomography. Results showed that zinc nitrate and CNC addition did not influence mechanical properties, degradation, and morphology of the hydrogels. However, zinc nitrate decreased 36.54% of the gel time and 41.37% of the swelling degree, and increased the crosslinking degree of the chitosan hydrogels, proving not only its catalytic effect but also its participation in the crosslinking reaction. Porosity was slightly reduced after addition of zinc nitrate and incorporation of CNC. In the mechanism of crosslinking reaction, a competition between CNC and zinc nitrate was observed.
Highlights
Hydrogels designed for medical applications are inherently biocompatible due to the hydrophilicity and anatomical similarity to humans, so, they can be used as a biomaterial to simulate a bone, cartilage, and others
The zeta potential in deionized water was - 45 mV. This might be considered a stable cellulose nanocrystals (CNC) suspension, because the modulus of the obtained value is greater than 25 mV27. This value of zeta potential is suitable for the production of aqueous chitosan solution, once it will result in a stable colloidal suspension, resulting in a good dispersion of CNC into de hydrogels
This result is in accordance with the rheological analyses, which showed that the addition of zinc nitrate increased the crosslinking degree of chitosan hydrogels
Summary
Hydrogels designed for medical applications are inherently biocompatible due to the hydrophilicity and anatomical similarity to humans, so, they can be used as a biomaterial to simulate a bone, cartilage, and others. Chitosan is a natural polymer of great interest in the production of hydrogels for medicine due to its biocompatibility, biodegradability and bacteriostatic activity It can be used in polymeric scaffolds for tissue engineering, wound healing, microcapsules for drug controlled release and many others medical applications[3,4,5]. CNC possess many desirable properties, such as large surface area, excellent colloidal stability, high tensile strength and stiffness, and hydroxyl groups that have potential for reactions[17] They are needle-shaped nanostructures used in composites as reinforcement to improve essential properties in materials such as thermal stability, water and mechanical resistance[18,19,20,21,22]. CNC, produced by acid hydrolysis and dried by spray dryer, were supplied by CelluForce
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