Abstract
In this study, we aimed to prepare and characterise hydrogel formulations using cellulose nanocrystals (CNCs), alginate (Alg), and polyethylene glycol diacrylate (PEGDA). The CNC/Alg/PEGDA formulations were formed using a double network crosslinking approach. Firstly, CNC was extracted from oil palm trunk, and the size and morphology of the CNCs were characterised using TEM analysis. Secondly, different formulations were prepared using CNCs, Alg, and PEGDA. The mixtures were crosslinked with Ca2+ ions and manually extruded using a syringe before being subjected to UV irradiation at 365 nm. The shear-thinning properties of the formulations were tested prior to any crosslinking, while the determination of storage and loss modulus was conducted post extrusion after the Ca2+ ion crosslink using a rheometer. For the analysis of swelling behaviour, the constructs treated with UV were immersed in PBS solution (pH 7.4) for 48 h. The morphology of the UV crosslinked construct was analysed using SEM imaging. The extracted CNC exhibited rod-like structures with an average diameter and length of around 7 ± 2.4 and 113 ± 20.7 nm, respectively. Almost all CNC/Alg/PEGDA formulations (pre-gel formulation) displayed shear-thinning behaviour with the power-law index η < 1, and the behaviour was more prominent in the 1% [w/v] Alg formulations. The CNC/Alg/PEGDA with 2.5% and 4% [w/v] Alg displayed a storage modulus dominance over loss modulus (G′ > G″) which suggests good shape fidelity. After the hydrogel constructs were subjected to UV treatment at 365 nm, only the F8 construct [4% CNC: 4% Alg: 40% PEGDA] demonstrated tough and flexible characteristics that possibly mimic the native articular cartilage property due to a similar water content percentage (79.5%). In addition, the small swelling ratio of 4.877 might contribute to a minimal change of the 3D construct’s geometry. The hydrogel revealed a rough and wavy surface, and the pore size ranged from 3 to 20 µm. Overall, the presence of CNCs in the double network hydrogel demonstrated importance and showed positive effects towards the fabrication of a potentially ideal 3D bioprinted scaffold.
Highlights
The articular cartilage is a specialised connective tissue that provides a low-friction, lubricated, and load-bearing surface for efficient joint movement
Calcium sulphate, and polyethylene glycol diacrylate (PEGDA) with a molecular weight of (Mn) 700 g/mol, and phosphate-buffered saline were purchased from Sigma Aldrich
The results revealed that pre-gel formulation without
Summary
The articular cartilage is a specialised connective tissue that provides a low-friction, lubricated, and load-bearing surface for efficient joint movement. Unlike bones, which have the natural ability to heal over time, the articular cartilage, has a limited capacity for self-repair due to the absence of blood vessels, making treatment efforts a challenge [1,3]. Symptomatic treatments are generally prescribed painkillers and non-steroidal anti-inflammatory drugs (NSAIDs) that offer pain relief while restoration treatments utilise surgical approaches which involve reconstructing the damaged articular cartilage and total joint replacement. These treatments require prolonged rehabilitation and complications can arise, such as donor shortage and immunologic response associated with these methods [2,4]
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