Light-activated decellularized extracellular matrix-based bioinks for enhanced mechanical integrity

Abstract

Decellularized extracellular matrix (dECM)-based bioinks have emerged as key materials in tissue engineering and 3D bioprinting technologies due to their ability to closely mimic the biochemical composition and structural organization of native extracellular matrices. These bioinks facilitate critical cellular behaviors, such as adhesion, proliferation, and lineage-specific differentiation, which makes them invaluable for constructing tissue analogs for applications in regenerative medicine, organ transplantation, and disease modeling. Despite their transformative promise, dECM bioinks face persistent challenges, including limited mechanical robustness, delayed gelation kinetics, and suboptimal printability, all of which constrain their translational utility. The advent of photocrosslinking technologies marks a paradigm shift, with light-activated functional groups such as methacrylates, thiol-enes, and phenols substantially improving the gelation efficiency, mechanical properties, and spatial fidelity of the printed constructs. The present review critically examines the state-of-the-art advancements in light-mediated dECM-based bioink crosslinking strategies, with a focus on innovations in bioink and photoinitiator design along with optimized crosslinking kinetics to address inherent limitations such as cytotoxicity and structural variability. Further, the review highlights the necessity of standardized dECM processing protocols and scalable biofabrication techniques to ensure reproducibility and clinical translation. By overcoming these challenges, dECM-based bioinks can enable the production of high-resolution, volumetric tissue constructs, thereby paving the way for transformative advances in regenerative medicine and translational biomedical applications.

Keywords: 3D bioprinting technology; Bioinks; Decellularized extracellular matrix (dECM); Photocrosslinking; Tissue engineering.

Graphical abstract

Fig. 1

Overview of dECM benefits, challenges, and the breakthrough of photocrosslinking.

Fig. 2

Conventional crosslinking strategies of decellularized extracellular matrix bioinks. (A) Shear thinning behavior and a wide range of complex modulus of dECM hydrogel, supporting their suitability for extrusion-based bioprinting applications. Reproduced with permission from Ref. [23]. Copyright 2014 Springer Nature. (B) Shear recovery properties of dECM hydrogel, enabling their use as a supportive hydrogel bath for embedded bioprinting. Reproduced with permission from Ref. [47]. Copyright 2020 Wiley-VCH GmbH. (C) Thermal crosslinking of dECM hydrogels through self-assembly of collagen fibers (scale bar: 5 mm). Reproduced with permission from Ref. [23]. Copyright 2014 Springer Nature. (D) Silk-composite dECM bioink facilitating beta crystalline formation via self-assembly. Reproduced with permission from Ref. [73].Copyright 2024 Elsevier Ltd. (E) Chemical crosslinking of dECM bioink using tannic acid for enhanced mechanical stability. Reproduced with permission from Ref. [91]. Copyright 2020 Ivyspring International Publisher. (F) Ionic crosslinking of dECM bioink through the incorporation of alginate, improving structural fidelity. Reproduced with permission from Ref. [104]. Copyright 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Fig. 3

Photocrosslinkable functional groups commonly used dECM-based hydrogels. (A) Mechanism of free-radical chain polymerization. Reproduced with permission from Ref. [19]. Copyright 2020 American Chemical Society. (B) Crosslinking between methacrylate groups under light exposure. (C) Mechanism of radical-mediated thiol-ene photocrosslinking. Reproduced with permission from Ref. [19]. Copyright 2020 American Chemical Society. (D) Crosslinking of thiol and alkene groups under light exposure. (E) Mechanism of photomediated redox polymerization. Reproduced with permission from Ref. [19]. Copyright 2020 American Chemical Society. (F) Dityrosine bond formation under light exposure.

Fig. 4

Methacrylate-mediated photocrosslinking utilizing dECM hydrogel. (A) Blending with synthetic polymers containing methacrylates for versatile bioprinting (scale bar: 1 cm). Reproduced with permission from Ref. [111]. Copyright 2020 Acta Materialia Inc. (B) Gelatin methacrylate composite dECM hydrogel mimicking tissue-specific architectures (scale bar; i: 250 μm, ii: (left) 500 μm, (right) 250 μm, iii: 1 mm, iv: 200 μm). Reproduced with permission from Ref. [115]. Copyright 2018 Elsevier Ltd. (C) Chemical modification of methacrylated dECM enabling photocrosslinking without blending with other hydrogels (scale bar; i: 5 mm, ii: 10 mm). Reproduced with permission from Ref. [171]. Copyright 2020 Acta Materialia Inc. (D) dECM-MA crosslinking electrospun fibers to improve structural stability and enable uniaxial cell alignment. Reproduced with permission from Ref. [120]. Copyright 2019 American Chemical Society.

Fig. 5

Thiol-ene chemistry mediated photocrosslinking utilizing dECM hydrogel. (A) Incorporation of diverse functional groups within thiol-ene click chemistry for tunable stiffness in printed constructs. Reproduced with permission from Ref. [126]. Copyright 2015 Acta Materialia Inc. (B) Thiolated dECM undergoing thiol-Michael addition crosslinking, followed by a light-activated click reactions for hydrogel stiffness regulation. Reproduced with permission from Ref. [128]. Copyright 2023 American Chemical Society. (C) Norbornene-conjugated dECM applied in diverse light-activated printing techniques for fabricating various structures. Reproduced with permission from Ref. [129]. Copyright 2024 Wiley‐VCH GmbH.

Fig. 6

Phenol-mediated photocrosslinking within dECM-based bioinks. (A) Ruthenium-based photoinitiator mediating the crosslinking of intrinsic phenol groups within dECM for high shape fidelity. Reproduced with permission from Ref. [12]. Copyright 2021 Wiley‐VCH GmbH. (B) Versatile fabrication of complex structures using dECM bioinks supplemented with Ru/SPS through volumetric printing techniques. Reproduced with permission from Ref. [16]. Copyright 2024 Wiley‐VCH GmbH. (C) Triple crosslinking strategies utilizing dECM and its gelatinized derivatives for printed structures with high shape fidelity, toughness, and resilience (scale bar; i: 0.5 cm, ii: 1 cm). Reproduced with permission from Ref. [13]. Copyright 2024 Royal Society of Chemistry.

Fig. 7

Photoinitiators utilized for photopolymerization of dECM bioinks. (A) Type I and II photoiniaitors and their activation wavelength. (B) Mechanism of Type I photoinitiator photopolymerization process. (C) Mechanism of Type II photoinitiator photopolymerization process.