Grayscale mask-assisted photochemical crosslinking for a dense collagen construct with stiffness gradient

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Biophysics

Background:

• Collagen constructs with stiffness gradients are valuable for studying cell-extracellular matrix (ECM) interactions and mimicking in vivo tissue interfaces.
• Limited development exists due to collagen's inherently low and poorly controllable mechanical properties.

Purpose of the Study:

• To propose and validate a novel fabrication process, COSDIENT, for creating compressed collagen constructs with a controlled stiffness gradient.
• To achieve high stiffness levels (~1 MPa) while preserving native ECM-like dense collagen fibrillar structures.

Main Methods:

• Fabrication involved collagen compression to increase stiffness, followed by grayscale mask-assisted UV-riboflavin crosslinking to induce a stiffness gradient.
• Collagen compression significantly enhanced stiffness from kPa to MPa range via physical compaction.
• UV-riboflavin crosslinking with a grayscale mask modulated crosslinking density, creating a continuous stiffness gradient.

Main Results:

• The COSDIENT process successfully produced compressed collagen constructs with stiffness ranging from 1.16 to 4.38 MPa.
• Collagen compression increased stiffness from ~1-10 kPa to ~1 MPa, maintaining dense fibrillar structures.
• Grayscale mask-assisted crosslinking induced gradual chemical bond changes without altering physical or optical properties.

Conclusions:

• COSDIENT offers a robust method for fabricating stiffness-gradient collagen constructs at MPa levels.
• The technique preserves ECM-like structures and allows for precise control over mechanical properties.
• Demonstrated application in a skin wound healing assay highlights its potential for studying cell behavior in response to stiffness gradients.