Enhancing chondrogenic differentiation of mesenchymal stem cells through synergistic effects of cellulose nanocrystals and plastic compression in collagen-based hydrogel for cartilage formation.

Collagen-based (COL) hydrogels could be a promising treatment option for injuries to the articular cartilage (AC) becuase of their similarity to AC native extra extracellular matrix. However, the high hydration of COL hydrogels poses challenges for AC's mechanical properties. To address this, we developed a hydrogel platform that incorporating cellulose nanocrystals (CNCs) within COL and followed by plastic compression (PC) procedure to expel the excessive fluid out. This approach significantly improved the mechanical properties of the hydrogels and enhanced the chondrogenic differentiation of mesenchymal stem cells (MSCs). Radially confined PC resulted in higher collagen fibrillar densities together with reducing fibril-fibril distances. Compressed hydrogels containing CNCs exhibited the highest compressive modulus and toughness. MSCs encapsulated in these hydrogels were initially affected by PC, but their viability improved after 7 days. Furthermore, the morphology of the cells and their secretion of glycosaminoglycans (GAGs) were positively influenced by the compressed COL-CNC hydrogel. Our findings shed light on the combined effects of PC and CNCs in improving the physical and mechanical properties of COL and their role in promoting chondrogenesis.

Tailoring structural properties, mechanical behavior and cellular performance of collagen hydrogel through incorporation of cellulose nanofibrils and cellulose nanocrystals: A comparative study.

Physically cross-linked collagen hydrogel is a desirable scaffold for tissue engineering applications especially where 3D cell encapsulation is considered. To overcome its shortcomings such as weak mechanical properties and also provide additional benefits, nanofiller reinforcement could be applied. This study was conducted to compare physical properties and cellular performance of physically cross-linked collagen hydrogel reinforced with cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs). Addition of both nanofillers drastically changed the hydrogel properties depending on the type and concentration. As a general trend, both CNCs and CNFs resulted in reduction in gelation time, enhancement in compressive strength, increase in swelling ratio, decrease in weight loss and improvement of injectability. The highest impact for CNCs was achieved when 5 % was applied, while the maximum impact for CNFs was observed for 3 % content (related to the collagen solid weight). By comparing two types of nanocellulose, CNCs showed higher impact on all properties. In-vitro cell compatibility with fibroblasts showed that CNFs did not adversely affected the viability and morphology of the cells while the CNCs improved cell viability and developed more elongated cell morphology.