The potential of cellulose nanocrystal-modified polyhydroxybutyrate/chitosan scaffolds in cartilage regeneration

• Affect the network density, bulk porosity, and fiber diameter (from 422 to 370 nm). • Increase surface roughness (Ra from 203.4 to 288.9 nm) • Enhance hydrophilicity (water contact angle from 62° to 55°) • Increase thermal degradation temperature (from 245 to 252 °C) • Improve the tensile strength of the scaffold (up to 4.52 MPa) • Change both the crystal size and crystallization degree (from 44% to 52%) • Provide a significant improvement in chondrocyte viability (41.04% compared to the unmodified) • Improve biological responses of this 3D ECM-like structure for cartilage tissue. Electrospun scaffolds are widely used in tissue engineering due to their ability to replicate the extracellular matrix (ECM) architecture, featuring a highly porous fibrous network similar to open-cell foams. This study presents an innovative modeling approach to predict the mechanical properties of nanocomposite electrospun scaffolds prior to their 3D network formation, aimed at cartilage tissue engineering applications. Scaffolds were fabricated from polyhydroxybutyrate (PHB) and chitosan (CHT) reinforced with 1, 3, and 5 wt% cellulose nanocrystals (CNCs). The modulus of the matrix and dispersed phases were first measured via AFM nanoindentation. Using these inputs, the Halpin-Tsai model predicted the modulus of individual composite nanofibers with over 90 % accuracy, which was then integrated into foam mechanical models to estimate 3D-scaffold properties. The outputs indicated that the predicted modulus values are within the physiological range suitable for skeletal tissues. Moreover, incorporation of CNCs influenced network density and bulk porosity, yielding finer fibers and enhancing scaffold characteristics, including an increase in surface roughness (300.2 to 350.1 nm), decreased water contact angle (62.64° to 55.12°), improved thermal stability (245 °C to 252 °C), and increased tensile strength (up to 4.52 MPa). Ultimately, biological evaluations demonstrated that the nanocomposite scaffolds significantly promoted cell adhesion and proliferation, as evidenced by SEM observations and a 41.04 % increase in chondrocyte viability compared to unmodified scaffolds. These findings suggest that the developed nanocomposite electrospun scaffolds offer a mechanically and biologically favorable 3D ECM-like environment, making them promising candidates for cartilage tissue regeneration