PEG-Based Hydrogels for Meniscus Replacement: Advancing Scaffold Fabrication Flexibility through a Customized Injection Molding Setup

Meniscal injuries are one of the most frequent orthopedic injuries and often lead to joint degeneration and osteoarthritis if left untreated. Current meniscus prostheses are limited by inadequate mechanical properties and poor integration with native tissue, leading to high failure rates and limited long-term success. The field of meniscus replacement aims to develop scaffolds that mimic the native meniscus's complex structure and mechanical properties while promoting tissue regeneration and integration (when targeting a tissue-engineered meniscus). However, traditional fabrication methods, such as fused deposition modeling (FDM) 3D printing, are limited by the narrow range of compatible materials and insufficient resolution for producing highly porous and biocompatible scaffolds. To overcome these challenges, this study introduces a novel injection molding setup designed to fabricate scaffolds using hydrogel building blocks, AUP4K DA and AUP4K HA, specifically engineered for meniscus replacement applications. The scaffolds were characterized to assess their suitability for meniscus replacement. Microscopic analysis and SEM analysis revealed an interconnected porous network with uniform pore distribution and the absence of traces of the applied negative mold used to fabricate the scaffold. Swelling degree and gel fraction were evaluated to confirm the high hydrogels' water retention and cross-linking efficiency, respectively. Mechanical properties were analyzed through compression testing and texture profile analysis (TPA), demonstrating that the scaffolds exhibit compressive strength and viscoelastic behavior in the range of native human meniscal tissue. By addressing the material and structural limitations of FDM printing, the injection molding setup presents a versatile platform for fabricating hydrogel-based scaffolds with a large range of mechanical properties. This study thus provides a promising solution for meniscus replacement, paving the way for the development of hydrogel scaffolds that mimic the native meniscal tissue.