Tribomechanical Properties of PVA/Nomex® Composite Hydrogels for Articular Cartilage Repair

Due to the increasing prevalence of articular cartilage diseases and limitations faced by current therapeutic methodologies, there is an unmet need for new materials to replace damaged cartilage. In this work, poly(vinyl alcohol) (PVA) hydrogels were reinforced with different amounts of Nomex® (known for its high mechanical toughness, flexibility, and resilience) and sterilized by gamma irradiation. Samples were studied concerning morphology, chemical structure, thermal behavior, water content, wettability, mechanical properties, and rheological and tribological behavior. Overall, it was found that the incorporation of aramid nanostructures improved the hydrogel's mechanical performance, likely due to the reinforcement's intrinsic strength and hydrogen bonding to PVA chains. Additionally, the sterilization of the materials also led to superior mechanical properties, possibly related to the increased crosslinking density through the hydrogen bonding caused by the irradiation. The water content, wettability, and tribological performance of PVA hydrogels were not compromised by either the reinforcement or the sterilization process. The best-performing composite, containing 1.5% wt. of Nomex®, did not induce cytotoxicity in human chondrocytes. Plugs of this hydrogel were inserted in porcine femoral heads and tested in an anatomical hip simulator. No significant changes were observed in the hydrogel or cartilage, demonstrating the material's potential to be used in cartilage replacement.

Microstructurally and mechanically tunable acellular hydrogel scaffold using carboxymethyl cellulose for potential osteochondral tissue engineering

In tissue engineering, scaffold microstructures and mechanical cues play a significant role in regulating stem cell differentiation, proliferation, and infiltration, offering a promising strategy for osteochondral tissue repair. In this present study, we aimed to develop a facile method to fabricate an acellular hydrogel scaffold (AHS) with tunable mechanical stiffness and microstructures using carboxymethyl cellulose (CMC). The impacts of the degree of crosslinking, crosslinker length, and matrix density on the AHS were investigated using different characterization methods, and the in vitro biocompatible of AHS was also examined. Our CMC-based AHS showed tunable mechanical stiffness ranging from 50 kPa to 300 kPa and adjustable microporous size between 50 μm and 200 μm. In addition, the AHS was also proven biocompatible and did not negatively affect rabbit bone marrow stem cells' dual-linage differentiation into osteoblasts and chondrocytes. In conclusion, our approach may present a promising method in osteochondral tissue engineering.

Effects of Non-Conventional Sterilisation Methods on PBO-Reinforced PVA Hydrogels for Cartilage Replacement

Articular cartilage (AC) degradation is a recurrent pathology that affects millions of people worldwide. Polyvinyl alcohol (PVA) hydrogels have been widely explored for AC replacement. However, their mechanical performance is generally inadequate, and these materials need to be reinforced. Moreover, to be used in a clinical setting, such materials must undergo effective sterilisation. In this work, a PVA hydrogel reinforced with poly(p-phenylene-2,6-benzobisoxazole) (PBO) nanofibres was submitted to three non-conventional sterilisation methods: microwave (MW), high hydrostatic pressure (HHP), and plasma (PM), in order to evaluate their impact on the properties of the material. Sterilisation was achieved in all cases. Properties such as water content and hydrophilicity were not affected. FTIR analysis indicated some changes in crystallinity and/or crosslinking in all cases. MW was revealed to be the most suitable method, since, unlike to PM and HHP, it led to a general improvement of the materials' properties: increasing the hardness, stiffness (both in tensile and compression), and shear modulus, and also leading to a decrease in the coefficient of friction against porcine cartilage. Furthermore, the samples remained non-irritant and non-cytotoxic. Moreover, this method allows terminal sterilisation in a short time (3 min) and using accessible equipment.