Dual-strategy modification for three-dimensional-printed silk methacryloyl hydrogels: Nanofiber reinforcement and poly(ethylene oxide)-induced porosity

Abstract

Hydrogels have emerged as promising scaffolds for cartilage tissue engineering due to their structural mimicry of native articular cartilage extracellular matrix. However, conventional hydrogels typically exhibit only nanoscale porosity and poor mechanical properties, which limit nutrient delivery, metabolic waste exchange, and structural fidelity. To address these challenges, we developed an innovative cell-laden porous silk methacryloyl (SilMA) hydrogel system with biomechanical reinforcement using three-dimensional (3D) bioprinting. The porous architecture was created through a water-in-water emulsification strategy employing poly(ethylene oxide) (PEO) as a sacrificial template. This pore-forming process resulted in a remarkable structural modulation, achieving an increase of over 100% in average pore diameter and a 75% enhancement in overall porosity compared to hydrogels without PEO. However, this structural modification compromised the compressive modulus by approximately 50%. Therefore, homogenized electrospun silk fibroin nanofibers (NFs) were incorporated into the bio-ink to improve the mechanical properties and optimize surface topography. The introduction of NFs (1-2 wt%) not only recovered the compressive strength and modulus (close to SilMA hydrogels) but also improved the 3D printability of PEO/SilMA hydrogels. Additionally, the hydrogel demonstrated excellent biocompatibility and markedly upregulated expression of chondrogenic-related genes, including COL2A1, ACAN, and SOX9. Furthermore, the subcutaneous implantation experiments in non-obese diabetic/severe combined immunodeficiency mice further confirmed the potential of PEO/NF/SilMA hydrogels in promoting cartilage formation. Therefore, this study proposes a promising dual-strategy approach for cartilage tissue engineering, integrating NFs reinforcement and PEO-induced porosity.

Keywords

Cartilage regeneration / Electrospun nanofiber / Poly(ethylene oxide) / Silk methacryloyl / Three-dimensional bioprinting

Funding

This research was funded by the National Natural Science Foundation of China (No. 82201034), and partially funded by Hefei Municipal Natural Science Foundation (No. 202348), Anhui Medical University Enhancement Program for Basic and Clinical Collaborative Research (No. 2022xkjT017), Anhui Provincial Institute of Translational Medicine Research Fund Project (No. 2021zhyx-C69), Anhui Medical University Graduate Research and Practice Innovation Program (No. YJS20230160).

Conflict of interest

The authors declare they have no competing interests.

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