From Free-Radical to Radical-Free: A Paradigm Shift in Light-Mediated Biofabrication.

Area of Science:

• Biomaterials Science
• Photochemistry
• Biotechnology

Background:

• Light-mediated biofabrication relies on photocrosslinking, often using photoinitiators (PIs).
• PIs generate radicals, raising cytotoxicity concerns for cell-laden bioprinting applications.
• Existing methods require improvement for enhanced biocompatibility and reduced cellular damage.

Purpose of the Study:

• To develop a universal, radical-free (RF) photocrosslinking strategy for light-based biofabrication.
• To create a highly biocompatible photoresin suitable for cell encapsulation.
• To demonstrate the efficacy of the RF strategy in high-resolution bioprinting.

Main Methods:

• Developed an RF photocrosslinking strategy utilizing uncaging mechanisms and Michael addition.
• Employed a coumarin-based group to cage a 4-arm-PEG-thiol (PEG4SH) photocrosslinker.
• Utilized one- and two-photon excitation for photocrosslinking of cell-laden constructs.
• Investigated reactive oxygen species (ROS) levels in RF versus PI-based systems.

Main Results:

• Achieved high biocompatibility in cell-laden constructs photocrosslinked via the RF strategy.
• Demonstrated the stability of the RF photocrosslinker, suggesting potential for off-the-shelf products.
• Observed no detectable ROS in RF photoresins, unlike PI-based systems which showed significant ROS upregulation.
• Successfully utilized the RF photoresin for high-resolution two-photon stereolithography (2P-SL) with low polymer concentration (<1.5%).

Conclusions:

• The developed RF photocrosslinking strategy offers a highly biocompatible alternative to traditional PI-based methods.
• This RF approach minimizes cytotoxicity concerns in bioprinting by eliminating radical generation.
• The successful application in 2P-SL highlights the potential for advancing radical-free light-based bioprinting technologies.