A thermoreversible, photocrosslinkable collagen bio-ink for free-form fabrication of scaffolds for regenerative medicine

Abstract

As a biomaterial, collagen has been used throughout tissue engineering and regenerative medicine. Collagen is native to the body, is highly biocompatible, and naturally promotes cell adhesion and regeneration. However, collagen fibers and the inherent weak mechanical properties of collagen hydrogels interfere with further development of collagen as a bio-ink. Herein, we demonstrate the use of a modified type-I collagen, collagen methacrylamide (CMA), as a fibril-forming bio-ink for free-form fabrication of scaffolds. Like collagen, CMA can self-assemble into a fibrillar hydrogel at physiological conditions. In contrast, CMA is photocrosslinkable and thermoreversible, and photocrosslinking eliminates thermoreversibility. Free-form fabrication of CMA was performed through self-assembly of the CMA hydrogel, photocrosslinking the structure of interest using a photomask, and cooling the entire hydrogel, which results in cold-melting of unphotocrosslinked regions. Printed hydrogels had a resolution on the order of ~350 μm, and can be fabricated with or without cells and maintain viability or be further processed into freeze-dried sponges, all while retaining pattern fidelity. A subcutaneous implant study confirmed the biocompatibility of CMA in comparison to collagen. Free-form fabrication of CMA allows for printing of macroscale, customized scaffolds with good pattern fidelity and can be implemented with relative ease for continued research and development of collagen-based scaffolds in tissue engineering.

Photochemically crosslinked cell‐laden methacrylated collagen hydrogels with high cell viability and functionality

“…Although short‐term culture (i.e., 7 days) using Saos‐2 cells is a good model to assess the biocompatibility of collagen‐based hydrogels, future studies will build upon this work and assess tissue‐specific cellular differentiation of human mesenchymal stem cells using longer term cultures (i.e., up to 4 weeks). CMA hydrogel in combination with I2959 has been used as bio‐ink for 3D bioprinting applications . Based on the outcomes of the current study, we suggest that VA086 can serve as an effective replacement for I2959 for the synthesis of cell‐laden CMA hydrogels and in the development of viable bio‐inks for 3D printing of collagen‐based biomimetic scaffolds for tissue engineering applications.…”

“…CMA hydrogel in combination with I2959 has been used as bio-ink for 3D bioprinting applications. 28 Based on the outcomes of the current study, we suggest that VA086 can serve as an effective replacement for I2959 for the synthesis of cellladen CMA hydrogels and in the development of viable bio-inks for 3D printing of collagen-based biomimetic scaffolds for tissue engineering applications.…”

“…26 Methacrylated collagen (CMA) has been well characterized and shown to possess 80% free amine groups with a denaturation temperature comparable to native collagen (i.e., 42 C). 27 While I2959 has been previously used to crosslink CMA, 28 to the best of our knowledge, the efficiency of VA086 for photochemical crosslinking of CMA hydrogels and its impact on the physical properties of these hydrogels has not yet been investigated. In addition, the cell-based analyses performed in most existing studies are limited to cell viability and little is known about the impact of VA086 on cell functionality (e.g., ability to generate cell specific de novo extracellular matrix).…”

Smart polymers and nanocomposites for 3D and 4D printing

“…Type I Collagen is widely utilized to coat 2D substrates and to construct 3D scaffolds. It holds a gel form at neutral pH and 37℃ and can be dissolved in acidic environment [143]- [146].…”

Additive Biomanufacturing with Collagen Inks

“…Additionally, this functionalised collagen retains the ability to self-assemble into fibrillar structures upon neutralisation. Modified collagen has shown successful 3D photopatterning of hydrogels loaded with human mesenchymal stem cells [134].…”